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The Performance of a reactor using photocatalysis to degrade a mixture of organic contaminants in aqueous solution

University of Florida Institutional Repository
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THE PERFORMANCE OF A REACTOR USING PHOTOCATALYSIS TO DEGRADE A MIXTURE OF OR GANIC CONTAMINANTS IN AQUEOUS SOLUTION By FREDERICK ROLAND HOLMES A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ENGINEERING UNIVERSITY OF FLORIDA 2003

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This document is dedicated to my wife Apr il and all of the people who have helped me along the way.

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iii ACKNOWLEDGMENTS I would like to begin by tha nking my professor and advisor Dr. Paul A. Chadik. His help in this research and my other educa tion has been invaluable. I would also like to extend my appreciation to the other member s of my committee, Dr. David Mazyck and Dr. Chang-Yu Wu. I would like to thank the me mbers of the Photocatalysis Seminar, especially Dr. Powers, for their knowledge and suggestions on th is research. I am also thankful for all of the guidance and time Dr. Booth provided to this research in perf orming the analyses. Additionally, I would like to thank NASA for provi ding the funding and support for this research. I thank Jack Drwiega for putting together the reactor support and I would like to thank Danielle Londere for pr oviding the formula used in creation of the silica/titania photocatalyst. Lastly, I would like to thank my famil y, Stanley, Patricia, Vincent, and Shannon Holmes. Most importantly, I would like to than k God and my wife April. Without either of them I could not accomplis h the things that I have.

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iv TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iii LIST OF TABLES.............................................................................................................vi LIST OF FIGURES.........................................................................................................viii ABSTRACT....................................................................................................................... ..x CHAPTER 1 INTRODUCTION........................................................................................................1 2 LITERATURE REVIEW.............................................................................................4 Photolysis and Photocatalysis.......................................................................................4 Factors Affecting Photocatalysis..................................................................................6 Reactor Type.........................................................................................................7 pH..........................................................................................................................7 Dissolved Oxygen (DO)........................................................................................8 Intermediates.........................................................................................................9 Bicarbonate Alkalinity...........................................................................................9 Light Intensity.....................................................................................................10 Temperature.........................................................................................................11 Other Factors.......................................................................................................11 Enhancements to the Phot ocatalyst and Solution.......................................................12 H2O2.....................................................................................................................12 TiO2 Supports......................................................................................................13 Activated carbon..........................................................................................13 Glass beads and filters..................................................................................13 Silica gel.......................................................................................................14 SiO2/TiO2.....................................................................................................15 Sol-gel structure...........................................................................................15 Degradable Compounds..............................................................................................16 Reaction Kinetics........................................................................................................17 Summary.....................................................................................................................18 3 METHODS.................................................................................................................20 Making of the Silica-Titania Pellets...........................................................................20

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v Pellet Composition..............................................................................................20 Aging...................................................................................................................23 The Reactor.................................................................................................................24 Design of the Reactor..........................................................................................24 The Reactor System.............................................................................................27 Reactor Hydrodynamics......................................................................................30 Sample Collection.......................................................................................................33 Sample Analysis.........................................................................................................33 Performing Experiments.............................................................................................35 Initial Degradation...............................................................................................35 Determining Effects of Volatility........................................................................37 Adsorption Experiment.......................................................................................40 Desorption Experiments......................................................................................42 Oxygen as an Electron Acceptor.........................................................................43 Photocatalytic Oxidation Experiments................................................................45 Effects of UV radiation intensity.................................................................45 Effects of contact time..................................................................................45 Experiments including indole and butyl alcohol..........................................46 4 RESULTS...................................................................................................................48 Effects of UV Radiation Intensity..............................................................................48 Effects of Empty Bed Contact Time...........................................................................52 Extended Duration Experiment..................................................................................59 Removal of Butyl Alcohol and Indole........................................................................59 5 SUMMARY AND CONCLUSIONS.........................................................................62 Summary.....................................................................................................................62 Conclusions.................................................................................................................62 APPENDIX A CHEMICAL INFORMATION..................................................................................64 B REACTOR INFORMATION.....................................................................................73 C RAW DATA...............................................................................................................77 REFERENCES..................................................................................................................87 BIOGRAPHICAL SKETCH.............................................................................................92

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vi LIST OF TABLES Table page 1 Target Analytes..........................................................................................................2 2 Researched Compounds...........................................................................................17 3 Key Statistics from the Tracer Analysis...................................................................32 4 Average %RSDs for the Analyses in this Research.................................................35 5 Important data gathered from the tr end lines shown in Figures 25 and 26..............58 6 Results of the extended duration test performed for 23 hours.................................59 7 Table of Target Analytes..........................................................................................64 8 Molecular Weight of Target Analytes......................................................................65 9 Henry’s Constants and Pa rtitioning Coefficients.....................................................65 10 Melting Points/Boiling Points..................................................................................65 11 Sources of Contaminant...........................................................................................66 12 Contaminant Generation in the ALS........................................................................66 13 Water Quality Requirements....................................................................................67 14 Spacecraft Trace Contaminant Generation Rates.....................................................67 15 Spacecraft Maximum Allowable Concentrations....................................................72 16 Predicted Retention Time Calculations....................................................................73 17 System Volume Calculation.....................................................................................74 18 KCl Conductivities for Testing Probe Accuracy......................................................74 19 Calculation of Flow Regime in the Reactor.............................................................75 20 Calculation of UV Energy at Reactor Surface.........................................................76

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vii 21 Initial Raw Data Test (1/6/3)....................................................................................77 22 Volatility Test Raw Data (2/6/3)..............................................................................77 23 Adsorption Test Raw Data (3/8/3)...........................................................................77 24 UV Optimization (3 Lamps) Raw Data (3/12/3)......................................................77 25 UV Optimization (2 Lamps) Raw Data (3/13/3)......................................................78 26 UV Optimization (1 Lamp) Raw Data (3/14/3).......................................................78 27 UV Optimization (2 Lamp Duplicate) Raw Data (3/17/3).......................................78 28 11-Hour Adsorption Experiment Raw Data (4/3/3).................................................79 29 60 mL/min Flow Test (Series 2) Raw Data (4/6/3)..................................................79 30 20 mL/min Flow Test (Series 2) Raw Data (4/9/3)..................................................80 31 10 mL/min Flow Test (Series 2) Raw Data (4/7/3)..................................................80 32 23-Hour Test Raw Data (4/16/3)..............................................................................80 33 60 mL/min Flow Test (Ser ies 3) Raw Data (4/28/3)................................................81 34 20 mL/min Flow Test (Ser ies 3) Raw Data (4/25/3)................................................81 35 10 mL/min Flow Test (Ser ies 3) Raw Data (4/27/3)................................................81 36 1st Desorption Test Raw Data (5/13/3).....................................................................82 37 2nd Desorption Test Raw Data (5/16/3)....................................................................82 38 SPME 1st Test Raw Data (5/28/3)............................................................................83 39 SPME 2nd Test Raw Data (5/29/3)...........................................................................83 40 SPME 3rd Test Raw Data (6/7/3)..............................................................................83 41 SPME 4th Test Raw Data (6/14/3)............................................................................84 42 SPME 5th Test Raw Data (6/15/3)............................................................................84

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viii LIST OF FIGURES Figure page 1 Figure demonstrating the elevation of an electron from one energy state to another due to UV radiation.......................................................................................6 2 A curve showing a series of experiment s that were modeled using the LangmuirHinshelwood equation..............................................................................................18 3 Picture showing an example of the 8 oz. jars, sitting on mixers and filled with the silica-titania suspension, going through the gelling process..............................22 4 Suspension being transferred from the 8 oz. gelling to the assay plates used for creating the pellet shape...........................................................................................23 5 Diagram showing the aging process for the pellets. The dashed line is used for the 500o F to indicate that not all gels required this treatment.................................24 6 UV transmittance curve for the quartz materi al used in constructing the reactor....25 7 Diagram showing the plans for the dimensions and shape of the reactor used for containing the pellets................................................................................................26 8 Picture of the reactor on its support stand and connected to the system used for the testing.................................................................................................................28 9 Diagram of the system setup used fo r testing the reactors capabilities..................28 10 A picture of the 4 L source tank used in reactor system for this research................29 11 E curve generated using the data from a tracer analysis performed on the reactor used in this research.................................................................................................33 12 Target analyte degradation seen as a result of recycling the spiked solution through the system...................................................................................................37 13 Diagram demonstrating the setup used fo r estimating volatile losses of analytes in the system.............................................................................................................39 14 Volatile losses in the system over an 8hour period without the reactor in place....39 15 Diagram showing the setup used fo r saturating the cat alyst pellets.........................40

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ix 16 Loss of toluene and chlorobenzene as a re sult of adsorption in the reactor system..41 17 Results of desorption experiments performed..........................................................43 18 Degradation of 5 NASA target analytes...................................................................49 19 Degradation of 5 NASA target analytes...................................................................49 20 Degradation of 5 NASA target analytes...................................................................50 21 Average normalized degradation seen in the two experiments performed with 2 UV lamps and a 1-liter source tank.......................................................................50 22 Removal of chlorobenzene is shown over the course of time as a function of the contaminant remaining divided by the in itial concentration introduced to the reactor displayed as a percent...................................................................................51 23 Average results of two flow optimization experiments...........................................52 24 Degradation of five target analytes in the reactor using three UV lamps and operating the system in a single-pass m ode after adsorption for five hours in a circulation mode had taken place.............................................................................54 25 Trend lines produced for each target analyte...........................................................57 26 Trend lines produced for each target analyte...........................................................58 27 Results showing the degradation of butyl alcohol and indole as a result of 6 hours of exposure to UV radiation...........................................................................60 28 Data showing the ratio of each chemical ’s concentration in the sample from Port 2 versus the sample from Port 1.......................................................................61 29 Concentration of NaCl in deionized wa ter solution versus the conductivity read on a Fisher Scientific conductivity probe.................................................................75 30 Normalized removal of toluene over the course of 6 hours.....................................84 31 Normalized removal of methyl meth acrylate over the course of 6 hours................85 32 Normalized removal of carbon disu lfide over the course of 6 hours.......................85 33 Normalized removal of ethyl acet ate over the course of 6 hours.............................86

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x Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Engineering THE PERFORMANCE OF A REACTOR USING PHOTOCATALYSIS TO DEGRADE A MIXTURE OF OR GANIC CONTAMINANTS IN AQUEOUS SOLUTION By Frederick Roland Holmes August 2003 Chair: Dr. Paul A. Chadik Major Department: Environmental Engineering Sciences A study was performed to investigate the use of an annular reactor filled with photocatalyst pellets (sili ca gel support doped with De gussa P25 titanium dioxide) arranged in a packed-bed-style to oxidize selected organic chemicals in aqueous solution. The annular reactor had a volume of 436 mL with 327 mL of that being interparticle space. The reactor was configured to a system setup which included a source tank, the reactor, a PTFE (polytetrafluor oethylene) tubing pump head with modular speed drive, a dampener for controlling flow, 2 sampling ports and a test stand to hold the reactor with slots for four 8-watt UV lamps. Eight target analytes (acet one, butyl alcohol, carbon disulf ide, chlorobenzene, ethyl acetate, indole, methyl methacrylate, and tolu ene) were tested for degradability in a mixed solution within the reactor system. Volatile losses were assessed as many of these chemicals are classified as VOCs.

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xi The photocatalyst pellets were found to be capable of adsorbing target analytes when exposed to solution containing the ta rget analytes. When exposed to solution devoid of the target analytes, however, desorption of the analytes from the silica-titania pellets occurred. Optimization was investigated with resp ect to UV radiation intensity and empty bed contact time (EBCT). One UV lamp resu lted in the same level of degradation of contaminant as three UV lamps. An in creased EBCT was found to increase the photocatalytic degradation observed in the reactor. All 8 of the target analytes were show n capable of complete oxidation using the reactor system. Degradation rate constants (k values) of .019 min-1, .065 min-1, .057 min1, .059 min-1, and .128 min-1 were found for acetone, chlorobenzene, ethyl acetate, methyl methacrylate, and toluene respectively. Thes e rate constants are comparable to those experienced by other researchers working with a slurry of TiO2.

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1 CHAPTER 1 INTRODUCTION The goal of the research discu ssed in this thesis is to pr ovide a finishing process for treating the wastewater produ ced by NASA in their Advanced Life Support System (ALS). NASA is in the planning stages of a manned space trip to Mars (Lane and Behrend, 1999). The ALS is to provide the su pport system allowing astronauts to travel the estimated 266 days to complete the missi on. Fresh water that meets the requirements set forth in the Requirements De finition and Design Consideration (Lange and Lin, 1998) is an important part of the ALS. These re quirements are displayed in Table 13 (Appendix A). High-energy costs are incurred to move mass in NASA space missions. As a result, NASA desires to minimize the amount of mass required for space transport. This means that in addition to treating the wastewater the finishing process must do so while minimizing space and energy requirements. Wastewater will be collected through two different sources in the space module. One source of wastewater is from the crew in the module. Shower water, wash water, urine, and wastewater from the solid waste processor are among the contributors to the wastewater stream. Machinery within the AL S will be the second source of wastewater. Condensate on the walls, panels, and instrument s will be collected for treatment. A list of all organic contaminants expected in the ALS wastewater is found in NASA documentation, provided in Table 14 (Appendix A). The rate that this water is expected to be produced is 28 L/person/day based on an assumed number of six astronauts.

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2 Collected wastewater from the ALS will be treated through a series of treatment processes. Those processes include biological removal, i on exchange, reverse osmosis, and chemical disinfection. These processe s remove many water contaminants; however, there remain some organic chemicals and microbial constituents in the water that are not expected to be removable by the aforemen tioned treatment processes. Of those remaining chemicals, the 8 shown in Table 1 were chosen as target analytes for this research. This thesis focuses on a finish ing process to remove these chemicals. Table 1. Target Analytes Acetone Butyl Alcohol Carbon Disulfide Chlorobenzene Ethyl Acetate Indole Methyl Methacrylate Toluene The process chosen for study as a potential NASA finishing process is photocatalytic oxidation. Photocatalysis wa s chosen as a viable option due to its potentially small mass, space, and energy requirement. In addition, photocatalysis has been shown to be effective for the removal of organic compounds, inorganic compounds, and microbes. This thesis will only consider the removal of the organic chemicals shown in Table 1. Included in the compounds that have proven removable are three among the target contaminants for this research chlorobenzene (Rohrbacher, 2001), acetone (Hingorani et al., 2000), and toluene (Vijayaraghavan, 2000; Luo and Ollis, 1996). This research was performed in a 436 mL flow-through annular reactor designed for the purpose of maximizing exposure of the p hotocatalyst to the ultr aviolet (UV) light. A previously designed silica-titania com posite (Londeree, 2002) was used as the

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3 photocatalyst in the reactor. The photocatalyst was formed into a pellet of approximately 3 mm diameter. These pellets were then pack ed within the annular reactor. Solutions containing the target analytes were subjected to photocatalytic oxida tion treatment within the reactor, and the product waters were analyzed using gas chromatography / mass spectrometry (GC/MS) and gas chromatography / flame ionization detection (GF/FID) to asses the efficiency of the treatment process. The hypothesis for this research was that an annular reacto r, filled with a titania/silica composite, and arranged in a packed bed formation could be used to photocatalytically oxidize the ei ght target analytes listed in Table 1. Several objectives were set forth in this research to acco mplish the proving of this hypothesis. Demonstrate the reactor’s ability to degrad e the 8 target analytes (acetone, butyl alcohol, carbon disulfide, chlorobenzene, ethyl acetate, indole, methyl methacrylate, and toluene). Determine the reactor’s optimal degradation performance with respect to UV intensity and flow rate (contact time). Quantify reaction rate constants for removal of the organic chemicals. Assess the reactor’s effluent conductivit y, dissolved oxygen concentration, pH, and temperature.

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4 CHAPTER 2 LITERATURE REVIEW Photolysis and Photocatalysis The degradation of both organic and inorga nic constituents with light has been well established. The words degradation and photocat alytic oxidation used in this thesis will always refer to the disappearance of the initial compound or tran sformation of that compound into another. The words do not mean that the contaminant has been completely oxidized or entirely removed. De gradation has been achieved using two main methods important to the current res earch, photolysis a nd photocatalysis. Photolysis is a process th at involves the use of lig ht to degrade molecular compounds toward their base constituents often carbon dioxide and water. During photolysis a direct photochemical transforma tion takes place where energy from light attacks the bonds within a molecular compound, thereby degrading the compound. Unfortunately, not all compounds can be de graded in this manner. Specifically, chlorobenzene cannot be degraded photolytic ally (Nishida and O hgaki, 1994). For this reason, photocatalysis becomes necessary. Photocatalytic oxidation uses light energy to react with a molecule leading to the formation of radicals in the solution. Se veral different molecules have been shown capable of promoting photocatalysis, from methylene blue (Cooper and Goswami, 1999), to ZnO (Sakthivel et al. 2002), to TiO2 (Goswami et al., 1997). The radicals can be formed from the molecule itself or from constituents in the solution containing the molecule. These radicals are then capa ble of oxidizing or reducing and thereby

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5 destroying the target contaminants. There are three known highly reactive intermediates formed by the process of photocatalysis, 1O2 (oxygen singlets), OH (hydroxyl radicals), and H2O2 (hydrogen peroxide). Research suggests that the OH is the prominent player in photocatalysis (Turchi and Ollis, 1990). The hydroxyl radical’s ability to degrade contaminants comes from its high level of oxi dation power, which is more than twice as strong as chlorine (Goswami and Blake, 1996). The hydroxyl radical breaks down chemicals through a series of steps. The exact steps by which the degradation process takes place are not known, but the generally accepted hypothesis is that hydrogen atoms are removed and oxygen atoms are added. It is also known that the process is preferential to attacking double bonds as opposed to single (Emanuel, 1984). Heterogeneous photocatalysis has been us ed to enhance the general process of photocatalysis. Heterogeneous photocatalysis us es a metal or dye, which is not the target of degradation, to absorb the electromagnetic energy and create the hydroxyl radicals. Titanium dioxide (TiO2) has been the most popular choice as a catalyst for use in heterogeneous photocatalysis, because TiO2 is inert under most conditions and therefore unlikely to react directly with the target compounds. TiO2 has been shown by many researchers to be very effective as a photo catalyst (Chen et al., 1995; D’Oliveira et al., 1990). UV radiation at approxima tely 388 nm strikes the TiO2 particle exciting an electron from the ground state to an excited state (388 nm is the chosen wavelength of light because it provides the necessary energy to excite the electron). At this point an

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6 (Blake et al., 1991) Figure 1: Figure demonstrating the elevation of an electron from one energy state to another due to UV radiation. Several possible electron donors (O2, H2O2) and H2O) are then shown adding their elec tron to the hole and producing their products. electron acceptor, typically oxygen, accepts the excited electron leaving an electron hole on the surface of the TiO2 (Turchi and Ollis, 1990). This hole is then available to accept electrons from OHions, oxygen, or water to create th e hydroxyl radicals. Those radicals then oxidize the pollutants in the water. Th e following equations de scribe the process of using OHas the precursor for the radicals and th en the effects of the radical formation (Blake et al., 1991). OH+ TiO2 + hv TiO2 + OH (Eq.1) TiO2 + O2 + H+ TiO2 + HO2 (Eq.2) 2HO2 H2O2 + O2 (Eq.3) TiO2 + H2O2 + H+ TiO2 + H2O + OH (Eq.4) Pollutant + OH POH (Eq.5) POH + (O2, H2O2, OH ) nCO2 + mH2O (Eq.6) Factors Affecting Photocatalysis As previously discussed, there are several steps required in carry ing out the process of photocatalytic oxidation. Any of those step s have the potential to limit the rate of

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7 pollutant degradation. The following sections will discuss factors th at play a part in enhancing or retarding th e photocatalytic process. Reactor Type TiO2 has been studied through two different modes of contact with contaminated waste streams. One method is to introduce slurry of TiO2 to the wastewater. The other method involves fixing the TiO2 to a surface, often a filter or the outside of a tube and then moving the water over the surface of the TiO2. Both methods have their limitations. When using a TiO2 slurry degradation of the target pol lutants is often highly efficient; however, the complication comes from the in ability to effectively remove the TiO2 from the effluent water. The aver age size of Degussa P25 TiO2 (the brand used in this research) is only 21 nm in diameter, and ther efore expensive filtration systems would be required to remove the TiO2 rendering the entire process not viable for space missions. Fixing the TiO2 to a surface solves the issue of TiO2 in the effluent but yields other disadvantages. Scouring of TiO2 from the fixed surfaces has been observed (Butterfield et al., 1997). The more pressing concern is that the short life of the OH can lead to situations where the contaminant may not come into contact with the TiO2 surface and thus never be degraded. “The convenience of catalyst immobilizat ion is bought at the price of diffusion distance from pollutant to cat alyst surface” (Ollis et al., 1991). This led to the concept of immobilization of the TiO2 on particles creating slurry that would later be easily removable due to its larger size (f or this research approximately 3 mm in diameter). pH One of the most problematic factors affec ting the use of photocat alysis as a viable means of water treatment is pH. Understandi ng the effect of pH is difficult due to the

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8 mixed results obtained during experimentati on. The effect of pH on the removal of distillery effluent (Zaidi and Goswami, 1995) and 3-Ch lorophenol (D’Oliveira et al., 1990) was found to be minimal, while the eff ect of pH on the removal of toluene was found to be significant (Vijayaraghava n, 2000). Highly acidic solutions (pH 3) have been found to assist in the de gradation of some molecules such as chlorobenzene that were found to have an optimum pH of 3.5 (Kawaguchi, Furuya, 1990). A high pH (pH 10) has also been found to help in the oxida tion of ammonia and trace organics (Bonsen et al., 1997; Chen et al., 1995). Low pH prefer ence has been explained as the ability of the H2O2 to make more OH (Chen et al., 1995). A high pH has been credited with providing enough of the necessary hydroxyl ions for making the hydroxyl radicals (D’Oliveira et al., 1990; Chen et al., 1995). The research indicates pH will be an important factor to assess in the analysis of photocatalysis as an effective means of treatment for the ALS. Dissolved Oxygen (DO) Dissolved oxygen (DO) in sufficient amounts has been found by multiple researchers to be a necessity to the photocat alytic process. Hand et al. (1995) found that below 2.0 mg/L the rate of degradation fo r disinfection byproducts was significantly decreased. Vijayaraghavan (2000) found that wh en sodium sulfite was used to remove oxygen from water that was then contaminat ed with toluene, the rate of toluene degradation was significantly decreased. Other researchers have made statements about the importance of DO in the photocatalytic oxidation proces s (Zaidi and Goswami, 1995; Ollis et al., 1991). “Several researchers ha ve observed that oxygen adsorbed on the titanium dioxide surface prevents the recomb ination of hole/electron pairs by trapping

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9 electrons and therefore, play s an important role in semiconductor mediated reactions” (Vidal, 1998). It does stand to reason th at a replacement electron acceptor could be found, such as H2O2 (Ollis et al., 1991). However, it is likely that oxygen will prove to be the cheapest and safest electron acceptor for use in the space missions, and for this reason oxygen will be the electron ac ceptor used in this research. Intermediates Formation of oxidation intermediates in th e photocatalytic reaction is a concern in water treatment because some intermediates ha ve the potential to be more toxic than the original contaminants (Torimoto et al., 1996) Intermediates also occupy sites on the surface of the TiO2 where the photocatalytic reactions with target compounds are meant to occur (Chen et al., 1995). Several intermediates have been detected in a variety of degradation processes. Cat echols, hydroquinones, biphenyls, formaldehyde, and glyoxal, are a few of the intermediates that have been detected during the photocatalytic degradation of hydrocarbons and aromatic s (Kawaguchi and Furuya, 1990; Denisov, 1977). One series of experiment s claims that the use of TiO2 on the surface of activated carbon suppressed the amount of intermedia tes in the solution by trapping the intermediates until they were fully degraded by photocatalysis (Torimoto et al., 1996). Bicarbonate Alkalinity Alkalinity in the water has been shown to significantly decrease the rate of photocatalytic oxidation in several cases. On e researcher observed as much as a 67% decrease in the photocatalytic degradation rate of chlo robenzene when 500 mg/L of HCO3 was added to the water (Blake et al., 1991). Bekblet (1996) observed a significant decrease in the degrad ation of humic acids. He attr ibuted the decreased rate to bicarbonate ions scavenging the hydroxyl radicals that are ne cessary for photocatalysis.

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10 Equation 7 describes the reacti on whereby bicarbonate ions a nd hydroxyl radicals react to form water and the significantly less powerful oxidant, the carbonate radical. HCO3 + OH CO3 + H2O (Eq.7) Light Intensity Illumination of the photocatalyst at an a ppropriate intensity is essential to the photocatalysis process. Some observations have suggested that photocatalysis may even be impossible for water with high turbidity le vels capable of bloc king out light (Anheden et al., 1996). Most research appears to agr ee that there is a balance to be found with increasing or decreasing the light intensit y. One study suggests that a decrease in UV intensity decreased the energy consumption and yet increasing UV intensity decreased the efficiency of energy use (Klausner and Goswami, 1993). Light intensity application is a balance between capital co st and operating costs. A higher light intensity will increase the rate of the reaction meaning a sma ller reactor size will be required leading to a lower capital cost and a hi gher operating cost. A decreas e in light intensity will decrease the operating costs, but increase the size of the reactor re quired to achieve a specified level of photodegradati on. There is a limit at which an increase in UV intensity no longer increases the photocat alysis rate as some other step in photocatalysis will become rate limiting. Ollis et al. (1991) repor ted that at low intensities the degradation rate is linearly dependent upon intensity. In some (not quant itatively defined) intermediate range there is a square root dependence on intens ity (I) where the rate varies as I0.5. Finally there comes a poi nt at high UV intensities wh ere the rate no longer has any dependence on UV radiation. UV intensity is also based on the refraction of light caused by the TiO2 itself and the contaminants within the wastewater to be treated. This

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11 is due to the scattering of the light photons required for exciting the TiO2’s electrons (Chen et al., 1995; D’Ol iveira et al., 1990). Temperature The effects of temperature on photocatalysis are mixed in the research literature. One study found a linear increase in the degrad ation rate of toluene with increasing temperature up to 90 C (Vijayaraghavan, 2000). It would appear that with regards to diffusion of OH from the surface of the TiO2 to the pollutant a hi gher temperature would increase the photocatalytic re action rate. Higher temperat ures may have a negative effect, however, on the concentration of di ssolved oxygen in the solution. Dissolved oxygen levels below a certain point may allo w for electron-hole re combination at the surface of the TiO2. Electron-hole recombination is dominant unless there is an electron acceptor such as oxygen available to absorb the excited electron. Other Factors There are many other factors that can a ffect photocatalysis. Common acids and anions have been shown to affect photocatalysis. The effect of HCO3 has already been mentioned for its effects as alkalinity. The rate of mineralization of targeted contaminants has also been shown to decr ease in the presence of the following acids: HCl, H3PO4, H2SO4, HNO3, and perchloric acid in the orde r shown at the top of page 18 (Ollis et al., 1991). HCl > H3PO4 > H2SO4 > HNO3 > perchloric acid Inorganic substances and salts have also been found to decrease the reaction rates (Block et al., 1997; Vidal, 1998), because they take up sites on the TiO2 preventing the OHfrom reacting with holes on the TiO2 surface. Additionally, some of these substances have the possibility of reacting with the hydroxyl radical after it forms.

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12 Enhancements to the Photocatalyst and Solution Several different methods may be used to enhance the process of photocatalysis. Possible additives to the photocatalyst are pl atinum, tungsten, palladium, peroxydisulfate, silver, and ferrioxalate (Goswami, 1995; Goswam i, 1999; Ollis et al., 1991; Crittenden et al., 1997). The addition of hydr ogen peroxide to the contam inated solution is another enhancement method that has been intensely st udied. Varying the pollutant concentration has also been found to affect the photocatal ytic rate (Anheden et al., 1996). Various supports for the photocatalyst have also been tr ied. The advantages and disadvantages to each of these enhancement possibilities ar e discussed in the following sections. H2O2 Hydrogen peroxide is a potential additive to the photocatalytic process that has been studied in depth. Addition of H2O2 has produced widely different results under varying circumstances. Hydrogen peroxide has been shown to increase the rate of mineralization of target compounds eleven fold (Lichtin et al., 1992). However, it has also been shown to decrease the rate of photocat alysis (Bekblet and Baleioglu, 1996). This wide variance is not surprising based on Equations 8-10 (Be kblet and Baleioglu, 1996). e+ H2O2 + H+ H2O + OH (Eq. 8) H2O2 + OH H2O + HO2 (Eq.9) HO2 + OH H2O + O2 (Eq.10) Equation 8 shows hydrogen peroxide as an electron acceptor similar to that of oxygen. Research has found that the use of H2O2 can help make up for a l ack of oxygen (Ollis et al., 1991). Equation 8 also shows the producti on of a hydroxyl radical, which is also a benefit to the photocatalytic process. Equations 9 and 10 demonstrate the problem with

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13 hydrogen peroxide; it will consume hydroxyl ra dicals meant for attacking the target pollutants. One researcher (Bekblet, 1996) said that, “it could be seen that the degradation of humic acid firs t increased when hydrogen peroxide increased and reached a maximum beyond which they appeared to decline at high H2O2 doses.” TiO2 Supports In an attempt to overcome the issues surrounding the method of contact between the solution and the photocatalyst, many suppor ts have been tried. Silica, activated carbon, glass beads, and filters represent the bulk of the research into support structures for TiO2. Each support has its particular be nefits and detriments. For the NASA research, a silica gel support was chosen due to its transparency to UV radiation and possible adsorption capability for the contaminants. Activated carbon Activated carbon offers the advantage of added surface area to adsorb pollutants and intermediates, holding them near the s ite of hydroxyl radical formation. Activated carbon is, however, opaque and so will have a negative impact on the amount of UV energy reaching the TiO2 particles. For this reason ac tivated carbon was not used as a support structure in this research. Glass beads and filters Both glass beads and filters have been st udied in past resear ch as possible support structures for TiO2 (Ollis and Al-Ekabi, 1993). Although both have demonstrated minor efficiency in degrading specific target com pounds, there are concerns with both methods. One concern is that the TiO2 may be scoured off of either surface (Bideau et al., 1995). A second problem is that adsorption of contam inants and intermediate s to these surfaces

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14 is not probable. For these reasons neither of these supports was chosen for use in this research. Silica gel The use of SiO2 as a support offers several benef its. Pore structure, surface area, and hydroxyl groups that encourage the adsorpti on of pollutants to its surface (Yu and Wang, 2000; Liu, Cheng, 1995; Gao and Wach s, 1999) are among the advantages to using a silica gel matrix as th e support structure for the TiO2. Importantly, it offers these benefits without compromising the ability of the light energy to strike the TiO2 particles (Matsuda et al., 2000). Having noted the benefits pointed out in th e literature it is im portant to recognize that there is research that indicates disadvant ages to using silica gel as a photocatalyst support. Matthews (1998) performed an expe riment using a reactor similar to the one built for this current NASA research. A silica gel matrix was used as an adsorbent support for TiO2, and this system achieved excell ent degradation of the target compounds. However, in a later article (O llis and Al-Ekabi, 1993), Matthews reported that the degradation of the initial compounds was promisi ng, but the byproduct formation rendered the process not viable for treatment Matthews went on to state the reason as being due to the byproducts becoming trapped in pores of the silica gel that do not receive contact from hydroxyl radicals pr oduced near other pores on the silica gel surface. The main difference between the rese arch of Matthews and that being reported in this thesis is the concentration of TiO2 in the silica gel. The pellets created by Matthews (.15 g TiO2 per 80 g SiO2) contained two orders of magnitude less titanium dioxide than that of the ones designed by L onderee (2002) for this research. Presumably, this increased ratio of TiO2 to SiO2 will allow for photocatalysis over the entire surface of

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15 the silica gel preventing intermediates from escaping into solution without exposure to photocatalysis. SiO2/TiO2 The process of creating a TiO2/SiO2 catalyst can be carrie d out in different ways and no one way has currently been proven to be the superior me thod. The types of TiO2/SiO2 catalysts are classified as two general types. There are the structures where the TiO2 is contained within the pore s and within the gel as TiO2 (Londeree, 2002). In this particular case there is no chemical combination of the SiO2 with the TiO2. The SiO2 gel physically contains the TiO2 particles. In the second cas e there are actual chemical bonds formed between the Ti element and the Si element. The presence of Si-O-Si bonds, Ti-O-Ti bonds, and Si-O-Ti bonds have been studied and c onfirmed (Nawrocki, 1997; Liu and Cheng, 1995; Matsuda et al., 2000 ; Gao and Wachs, 1999). Currently, the process being used in the NASA rese arch is a method of doping the SiO2 sol-gel while it is being created with solid TiO2 particles. This would be counted under the first classification of catalyst described where the particles are physically trapped within the silica gel, but not chemically bonded. Sol-gel structure The structure of the sol-gel is very important to the benefits received from it. The hydroxyl concentrations on the SiO2/TiO2 surface contribute to the ability of the catalyst to adsorb pollutants. Adsorption of the pollu tants directly to the catalyst decreases the distance the hydroxyl radical has to travel in order to degr ade the pollutant. This is important considering the shor t life of the hydroxyl radical in solution. Nawrocki (1997) gave these 10 facts about the surf ace structure of the silica gel.

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16 The hydroxyl concentration on the surface of the SiO2 (silanol groups) is accepted to be approximately 8.0 1.0 mol/m2. These hydroxyl sites come in three different types, isolated, geminal, and vicinal. The isolated sites involve a hydroxide ion attached to a silicon atom on the outer edge of the gel. Geminal sites are characterized by two hydroxi de ions attached to the gel at the same point. Vicinal sites have two hydroxyl groups joined to the gel at two different sites, but a hydrogen group from one is also bonded to the oxygen group from the other. Isolated and geminal silanol groups are the most effective at adsorbing pollutants, particularly organics. The difficulty lie s in obtaining the isolated hydroxyl groups on the surface of the gel. Rehydroxylation and dehydroxylatio n are the two methods fo r controlling the type of silanol groups. Rehydroxylation is achieved through exposing th e gel to water. As the silica gel is rehydroxylated the number of vicinal groups increases. This means less isolated and geminal groups are available for the attachment of pollutants. The gel is treated at high temperatur es to remove the silanol groups during dehydroxylation. Heating the ge l initially removes water th at is attached to the silanols. It will then remove the bonded si lanol groups leading to a slight increase in the number of isolated and geminal sites. Lastly, all of th e silanol groups are removed, leaving a surface of just oxygen. Achieving a balance between rehydroxylat ion and dehydroxylation would create the ideal gel, as it would provide for the maximum possible number of isolated and geminal sites on the gel surface. This is important since these sites are the ones capable of enhancing adsorption. Unfortuna tely, without the addition of organics to the surface of a silica gel during gel formation, it is not possible to maintain a balance in solution. This is due to the ra pid rehydroxylation that occurs in aqueous solution. Degradable Compounds The ability for TiO2 to degrade many different compounds with or without the help of SiO2 and other additives is an area that has be en the focus of many researchers. Table 2 (Blake, 1999) lists a numb er of compounds that have been researched and shown

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17 capable of being mineralized; however ther e is a lack of studies reported on TiO2 photocatalysis in solutions involving a mixtur e of chemicals. In this NASA project an aqueous mixture of 8 chemicals will be investig ated. It’s expected that one hindrance to the photocatalytic reaction rate caused by the use of a mixt ure will result from the availability of sites on the TiO2 particles. This is the same problem experienced in a solution with just one pollutant. The possibi lity also exists for an increase in the obstruction of light from th e photocatalyst. One importa nt and unpredictable problem lies with the production of intermediates. Because there are so many intermediate combinations possible with the compounds be ing tested. There are a multitude of reactions and interactions that could then occur between those formed intermediates. Table 2: Researched Compounds Degradable CompoundsResearcher Bacteria and Viruses(Goswami et al., 1997) B-TEX(Srinivasan et al., 1997) Chlorinated Hydrocarbon s(Crittenden et al., 1997) Organics(Matthews, 1987) Monoand DiChlorobenzene( Kawaguchi and Furuya, 1990) Non-Degradable Co mpoundsResearcher Carbon Tetrachloride(Ollis, 1983) Reaction Kinetics The Langmuir-Hinshelwood (LH) equation ha s been shown by Klausner (1994) to appropriately model the kinetic reaction rates of photocatalysis. dC/dt = -k1KC/(1+KC) (Eq.11) where C is the bulk concentration of contaminant in the solution, k1 is the reaction rate constant and K represents the equilibrium adsorption constant for a particular contaminant to the photocatal yst (Turchi, Ollis, 1989).

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18 It is important to note that the use of the LH equation to describe photocatalytic kinetics makes an assumption that adso rption of the contaminant to the TiO2 surface is the rate limiting step. At low bulk con centration values, the LH equation becomes equivalent to a first order reaction equation, as the TiO2 will not be saturated at the surface. Since all of the con centrations used in this research will be at or below 300 g/L, the first order reaction will likely be applicable; however this also relies on low K values. Figure 2 depicts a Langmuir-Hinshelwood curve. From this curve, it can be seen that the lower concentrations appear to have a first order reaction rate while the higher concentrations move away from the first order model. (Davis and Hao, 1991) Figure 2. A curve showing a series of e xperiments that were modeled using the Langmuir-Hinshelwood equation. Summary Photocatalysis is a complex process of in teractions between the photocatalyst, the reactants, and light. Literature comes to no valid consensus on some of the parameters’

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19 effects on the process. pH data provides mi xed results, temperature is inconclusive, and the use of hydrogen peroxide as an aid has been proven and dispr oved. However, other parameters have been shown to have definiti ve effects. UV radia tion intensity has been shown to directly affect photocat alytic oxidation rates to a poin t. It has also been shown that the rate of flow thr ough a reactor using fixed TiO2 can have an impact on the amount of degradation due to the short life span of OH. This thesis investigates the effect some of these parameters have on this specific reactor using the photocatalysis process.

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20 CHAPTER 3 METHODS Assessing of the reactor’s capabilities fo r degrading NASA’s 8 target analytes required several steps. First, the photocatalyst was created. This was done in accordance with a predetermined method (Londeree, 2002). Secondly, a suitable reactor was designed for the process. UV transmission and the ability for the reactor to be included into a system that would allow for testi ng of the reactor were important factors considered in the making of this reactor. Many of the target analytes were volatile organic compounds (VOCs). The tendency for th e target analytes to volatilize required that the system for testing th e reactor be airtight. All sa mpling methods and analytical procedures were also focused around this im portant issue of preventing volatile loss of the analytes. Several tests were performed during the cour se of this research with the goal of understanding the reactor’s cap abilities and the process of photocatalytic oxidation. Tracer analyses were performed to unde rstand the hydrodynamics of the reactor. Adsorption and desorption of the 8 target compounds on the photocatalyst was also examined. UV intensity, empty bed contact time (EBCT), and total oxidation of the contaminants in their original state were considered. Making of the Silica-Titania Pellets Pellet Composition To create the photocatalyst a silica ge l matrix was impregnated with TiO2. The titanium dioxide was contained both inside the gel itself and in the pores of the gel. This

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21 silica/titania gel was made into a pellet form measuring 3 mm in diameter were fixed in a reactor (packed bed style) allowing solutions to pass through the packed bed. The pellets were designed according to the formula chosen in the research conducted by Danielle Londeree (2002). Etha nol, hydrofluoric acid (HF), nitric acid (HNO3), Degussa P25 titanium dioxide, water, and tetra-ethyl-orthosil icate (TEOS) make up the list of necessary chemicals for this formula. First, 4.2 grams of TiO2 were placed in a polymethylpentene jar. Next, an 8 oz. pl astic jar was put on a mixer with a magnetic stir bar to keep the solution thoroughly mixed as the contents were added in the following order: 25 mL deionized (DI) water; 50 mL ethanol; 35 mL TEOS; 4 mL HNO3; 4 mL HF; 4.2 grams TiO2. All acids were reagent grade. The TiO2 used in this research was Degussa P25. TEOS and water are the two co mponents that actually make up the silica gel matrix. TEOS, a silicon alkoxide is a spec ific type of silica precursor. The ethanol allows the TEOS and the water to combine. Nitr ic acid and hydrofluoric acid are used to speed up the reactions that creat e the gel. In addition the tw o acids can be used to alter the pore size and structure within the gel. The water, ethanol, and TEOS were measured using 10 mL graduated glass pi pettes and then the acids were introduced through 10 mL graduated plastic pipettes. Figure 3 shows the jars and mixers where the solution gelled for approximately 1 hour before the proce ss of creating the pellet forms was begun.

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22 Figure 3. Picture showing an example of the 8 oz. jars, sitting on mixers and filled with the silica-titania suspension, going through the gelling process. To obtain the pellet shape, the suspension was pipetted using an automatic pipetter into 96-well assay plates. Figure 4 shows a pi cture of this process. Each batch of chemicals created approximately 4 assay plates worth of pellets. Each batch of assay

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23 plates was then stacked into groups of 4, capped with an assay lid, and wrapped in aluminum foil and duct tape. Figure 4. Suspension being transferred from th e 8 oz. gelling to the assay plates used for creating the pellet shape. Aging After putting the solution into assay pl ates, the pellets underwent the “aging” process. This is where the fluid is dried from the inside of the pell ets, leaving behind the structure that holds the gel toge ther. The aging process used in this research consisted of first leaving the assay plates at room temperature for 48 hours and then moving the pellets to an oven preheated at 66 C. Fo r 48 hours the gel aged in the 66 C oven. Pellets were then removed from the assay tr ays and put into an 8 ounce Teflon jar with a hole in the top for equalizing pressure between the inside and outside of the jar. The jar

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24 was put into a programmable oven that gradually increased the temperature from 25 C to 103 C at a rate of 2 C/min. The jar stay ed at the 103 C temperature for 18 hours. After the 18 hours, the temperatur e was then increased from 1 03 C at the same rate as before to the temperature of 180 C where it remained for 6 hours before gradually decreasing the temperature back down to 25 C. The pellets were then removed and placed in plastic jars for storage. A major ity of the pellets came out of the oven with a slight brown color. To remove the color, the pellets were put into a ceramic dish and heated in an oven at 500 degr ees Fahrenheit for approximately 1 hour. This removed the brownish tinge almost comple tely. It was also found th at over time the brown color would slowly dissipate without the addition of heat. Figu re 5 shows a diagram that displays the overall aging process used fo r creating the photocatalyst used in this research. Figure 5. Diagram showing the aging process for the pellets. The dashed line is used for the 500o F to indicate that not a ll gels required this treatment. The Reactor Design of the Reactor The bench-scale reactor was designed and constructed in order to contain the pellets and provide effective oxidation of organic compounds and inactivation of pathogenic microorganisms. It was necessary to develop a reactor that would be well 25 oC 48 hrs 66 oC 48 hrs 103 oC 18 hrs 6 hrs 180 oC 500 oF 1 hr 25 oC

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25 suited for photocatalysis and for testing the pellets. One important issue was the transmission of ultraviolet light. Quartz was chosen for its ability to transmit UV radiation energy, as demonstrated by the tr ansmittance of energy at the wavelength of 388 nm shown in Figure 6 (http://www.quartz.com, 2003). Figure 6. UV transmittance curve for the quartz material used in constructing the reactor. The reactor shape (Figure 7) was chosen to optimize the exposure of the pellets to the light. By building the reac tor in a cylindrical shape to surround the lamps, most of the UV energy produced would be used. It was al so important that, should the need arise, the pellets could be easily removed from th e reactor. For this reason alternate configurations such as a co il were avoided. The thickness of the reactor (10.5 cm) was chosen to give every pellet inside the ability to react with UV radia tion. A thicker reactor would have hid some pellets behind others, thereby creating a waste of catalyst. The Fused Q uartz Avera g e Transmittance Curves Wavelength Micrometers PercentTransmitt ance

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26 schematic shown in Figure 7 gives the dimensi ons and shape of the reactor used in this NASA research. Figure 7. Diagram showing the plans for the dimensions and shape of the reactor used for containing the pellets. The entrance and exit were each given threaded ends to allow for O-Ring connectors. This was done to provide connections for the PTFE tubing used in the system. A frit was placed in the exit port to prevent the pellets from flowing out of the reactor with the solution. The entire reactor was made of quartz w ith the exception of one end where a glass frit was placed to keep the pe llets from flowing out of the reactor. The reactor had a volume of 436 mL with the pellets taking up 109 mL of that space (the pellets filled the reactor completely, but the remaining 327 mL was interparticle space. The bed porosity was estimated by filling a graduated cylinder with 24 mL of pellets and then adding nanopure water (NPW) until the water was at th e same level as the pellets. 18 mL of NPW were added in all. This led to the conclusion of 75% bed porosity within the reactor. Figure 8 shows the re actor in place on its support. Exit for Effluent 1.0 cm in Annular Space for Solution 1.0 cm in 14.0 cm 8.5 cm in 10.5 cm in C y lindrical Hole for UV Entrance for Influent Place for UV Lamps

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27 The Reactor System A system was designed for testing the reacto r’s capabilities for degrading the target analytes. That system included the reacto r and reactor support, two sampling ports, a source tank, a pump, and a flow dampener. Fi gure 9 shows a schematic of the entire system setup. The reactor was placed on a wooden support in the horizontal position to limit the influence of gravity on the flow. Since NASA specifications require the reactor to work in a micro gravity situation, it was necessary to keep gravity from enhancing the results of the experiments. Connections were made available for 4 UV lamps to be used in the center of the reactor. The lamps were 12-inch, 8-watt lamps that each provided approximately 4.44 W of available UV energy (wavelength near 365 nm) to the inner surface of the reactor (Table 20). The support also included a cover that could be placed over the reactor and UV lamps to prev ent exposure to laboratory personnel. All of the tubing used was PTFE tubing to prevent adsorptio n or desorption of organic compounds during experime ntation. Several of the targ et analytes fall into the category of volatile organic compounds (VOCs). Therefore, all connections were sealed with PTFE tape to ensure an airtight system

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28 Figure 8. Picture of the reacto r on its support stand and connected to the system used for the testing. Figure 9. Diagram of the system setup used for testing the reactor’s capabilities. The diagram does not show the magnetic stir plate under the source tank. It also does not show the wooden support stand for the reactor. However, that support is depicted in Figure 8. Since each sample taken from the system was 40 mL, a source tank was necessary to prevent pockets of air from forming in the tubing or in the reacto r. A 1 L Erlenmeyer Pump Reactor Source Tank Flow Dampener First Sampling Port Second Sampling Port

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29 Figure 10. A picture of the 4 L source tank us ed in reactor system for this research. flask was initially used to fill this role. Late r in the research the size of the source tank was increased to a 4 L Erlenmeyer flask to further reduce the effects of sampling. Glass rods placed through a rubber stopper on top of the source tank carried solution in and out of the flask. The rubber was covered in Tefl on tape to preclude reactions between the stopper and the test solution. One glass tube through the stopper allo wed a small air leak to prevent a vacuum situation within the sy stem when samples were taken. This did result in a necessary 14.5 mL of headspace at the top of the flask to keep from losing solution out of that tube. A picture of the source tank is shown in Figure 10. The total volume of the system was a little over 1.5 L ( 4.5 L with the change in source tank) with 1.3 L (4.3 L) coming from the flask and the reactor. The pump used was a L/S PTFE-

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30 Tubing Pump Head powered by a L/S Variable -Speed Modular Drive. A polyethylene pulse dampener was used to ensure a steady flow rate in the system. Reactor Hydrodynamics All real reactors behave, from a hydrodynami c perspective, in a range between two ideal reactor types. Those two ideal types are known as a continuously stirred reactor (CSTR) and a plug flow reactor (PFR). A CS TR represents the ideality where the entire reactor is completely mixed and the concentratio n in all locations within the reactor is the same as the effluent concentration. A PFR allows for no axial mixing (mixing in the direction of flow) and therefor e a concentration gradient exists from the influent to the effluent of the reactor. The PFR is repres entative of an infinite number of CSTRs in series. No working reactor can ever operate co mpletely as one of these ideal reactors, but every reactor behaves somewher e between these two ideals. The goal was to design a reacto r that would simulate a PFR as closely as possible. A PFR was desired to maximize the reactor’ s performance as a PFR provides the greatest transformation for all positive order reactions This would lead to a predictable and reliable reaction rate and a minimum size for the reactor to achieve a selected degree of oxidation or disinfection. In order to determine the hydrodynamic behavi or of the reactor, a tracer analysis was performed. Sodium chloride (NaCl) wa s chosen for the tracer to prevent any possibility of staining the pell ets or the inside of the react or, which may have led to a reduced transmittance of UV radiation. Also, NaCl was not expected to react with the pellets in the reactor system.

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31 The chosen flow-rate for the tracer anal ysis was 10 mL/min since this was the design flow for the reactor. With a reactor volume of 436 mL and 109 mL of that composed of pellets, the mean residence time of the reactor was predicted to be 32.7 min. The tracer analysis was conducted by fi rst maintaining a steady flow through the system of DI water at 10 mL /min. A solution of 2 mg NaC l/mL was put into a gas-tight luer-lock syringe. An aliquot of 5 mL of that solution was then introduced through a luer-lock connection into the tubing. The tubing leading from the sampling port to the reactor created about 3.7 min of plug flow time prior to entering the reactor. The concentration of NaCl in the effluent was measured using a Fisher Scientific conductivity probe. The probe constant, as determined in a calibration procedure (Standard Methods, 2000), was 0.866. This was calculated by prepar ing concentrations of potassium chloride, which were known to ha ve specific conductivity (Table 18). Then the readings of the probe were compared agai nst those standard values. 3 readings were taken and from those readings an average di fference between the ac tual conductivity and the real conductivity was calculated. That average difference was then divided by the actual conductivity to determine the probes ce ll constant of .866. This means that any conductivity reading on the probe actually corresponded with 0.866 mmhos/cm of that reading. A linear correlation was found between th e conductivity reading on the probe and the concentration of sodium ch loride in solution from 0 to 576 mg/L. This was done by measuring known concentrations of sodium chloride and comparing them with the reading on the probe. This showed that each mmho on the probe represented 0.562 mg/L of NaCl in the solution (Figure 29).

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32 Using this information, data from the tracer analysis were collect ed in the form of conductivity in the reactor effluent over ti me. The conductivity was then changed to a concentration of NaCl. Samples were taken of the reactor effluent prior to injection of NaCl in order to determine the natural conductivity in the effluent. The average conductivity was subtracted out so that only conductivity cau sed by the tracer analysis impulse was considered. The mean residenc e time in minutes, variance, and tanks in series were calculated. These numbers are displayed in Table 3. The residence time represents the average amount of time sodium chloride rema ined in the reactor. Variance describes the difference in times over which the contaminant left the reactor. Also calculated, was the number of CMFRs in seri es. This shows how many CMFRs in a row it would take to create a residence time distri bution like the one seen by the reactor. An infinite number of CMFRs in series represents a plug flow reactor. Table 3. Key Statistics from the Tracer Analysis Mean Residence Time42.07 Variance458.94 Number of CMFRs in Series3.86 E-curves (residence time distributions) were generated, based on the data, to graphically demonstrate the results of the tr acer analysis. The Tanks in Series (TIS) model was used due to its abil ity to accurately model the r eactor. Figure 11 shows the Ecurve produced. The ability of the TIS model to simulate the flow in the reactor is key to the calculation of reactor kinetics discussed later in the results s ection of this thesis.

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33 E Curve 0.0 5.0 10.0 15.0 20.0 25.0 0.0020.0040.0060.0080.00100.00120.00 t* (min)E* (min-1)*103 Data Model Figure 11. E curve generated using the data from a tracer analysis performed on the reactor used in this research. The data represent the E-curve actually generated by the reactor. The model curve is the E-curve generated by the TIS model. Sample Collection Samples (with the exception of those in th e desorption experiments) were collected using a gas tight, luer-lock sy ringe. Samples were taken fr om one of the two three-way luer-lock sampling ports provided in the system Volatile Organic Analysis (VOA) vials were used to collect the samples and keep th em airtight. Each vial was 40 mL. These vials were stored in refrigerators at 4o C until they could be analyzed. Each sample was viable for up to two weeks at that temperature. Sample Analysis Samples were analyzed using two diffe rent methods, one for acetone, carbon disulfide, chlorobenzene, ethyl acetate, met hyl methacrylate, and to luene, and a second method for butyl alcohol and indole.

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34 The first method of analyses was performed using a GCQ gas chromatograph/ mass spectrometer with a Tekmar 3100 purge and tr ap extraction system. Analyses were performed in accordance with the USEPA method 524.2, Methods for the Determination of Organic Compounds in Dri nking Water: Supplement 2 (USEPA, 1992). Samples were purged at room temperature fo r 11 minutes at 35 mL/min with helium. They were then dry purged for 2 minutes to remove water. Th e Supelco k-trap was then back flushed and heated to 250 C for desorpti on to the column. The column used was a DB-VRX column from J&W Scientific. It was a 75-meter l ong column with a 0.45 mm inner diameter, and a 2.55m-film thickness. Desorption to the colu mn lasted for 6 minutes at the 250 C and the trap was then baked at 270 C for 10 minutes. The column was taken from a 25 C start temperature and ramped to 220 C at a rate of 6 C/min. An initial hold was done at 35 C for 6 minutes. The mass spectr ometer used is an ion trap that looks between 34 amu and 280 amu with 0.6 seconds/scan. The second method of analysis (for butyl alcohol and i ndole) was performed using a Hewlett Packard 5890 GC/FID with a solid phase micro extraction (SPME) process using a StableFlex Divinylbenzene/Carboxen/PD MS fiber. Analyses were performed in accordance with an alternative of AWWA Method 6040D, Analysis of Taste and Odor Compounds by SPME Samples were adsorbed to the fiber for 15 minutes at 100 C. They were then desorbed to the column by increasing the temperature from 45 C where it was held for 5 minutes to 220 C where it remained for 7 minutes. The rate of temperature increase was 15 /min.

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35 The reliability of the testing was verified using the % Relative Standard Deviation (%RSD). %RSD is based on the Response Fact or (RF) of a chemical. The RF and %RSD are calculated using Equations 12 and 13. Response Factor (RF) = (Areaanalyte*Amountinternal standard)/(Areainternal standard*Amountanalyte) (Eq.12) % Relative Standard Deviation (%RSD) = 100 (SRF / RFAVE) (Eq.13) The USEPA method requires a %RSD of le ss than 30, but strongly recommends a %RSD of less than 20. Table 4 give s the average %RSDs for the analyses performed for this research. Table 4: Average %RSDs for the Analyses in this Research ChemicalAverage %RSD Acetone32.5 Carbon Disulfide23.8 Chlorobenzene13.9 Ethyl Acetate13.1 Methyl Methacrylate 11.4 Toluene18.6 Performing Experiments Initial Degradation An initial test was performed to determ ine if the reactor would demonstrate the capability for removing the target compounds. This experiment was performed using the system in the configuration shown in Figure 9. The only difference was that at this time the second sampling port did not exist. That was added later in the research. A solution containing the 8 target analytes (acetone, butyl alcohol, carbon disulfide, chlorobenzene, ethyl acetate, indole, methyl methacrylate, and toluene) was prepared using the following steps: 1-2 L of each of the 8 neat chemicals were added to a 50 mL volumetricflask.

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36 The volumetric flask was inverted five times for mixing. 20 mL of solution from the 50 mL flask was added to a 2 L volumetric flask already containing 2 L of deionized (DI) water. This larger flask was then inverted 5 times for mixing purposes. The prepared solution was then carefully poured into the source tank used in the system to minimize volatilization. Solution wa s pumped through the system until all of the tubing and reactor were filled. The source tank was then refilled back to the top and the stopper replaced. 12-inch, 8-watt UV lamps were then placed in the center of the reactor. They could not be placed prior to filling because the react or had to be tilted in order to ensure it would fill completely. The lamps were shielded using aluminum foil and turned on to warm-up. A support cover was used to prev ent the exposure of la boratory personnel to UV radiation. For the rest of the experiment the contam inated solution was circulated through the system at a rate of 10 mL/min. After thirty minutes of time allowed for the lamps to come to full intensity, the fo il shield was removed to allo w photocatalysis to begin. A sample was taken here representi ng the initial (t = 0) concentration for the analytes before any photocatalysis took place. Samples were then taken every 2 hours for the next 6 hours. After the 6 hours the lamps were turned off and the system drained. Figure 12 displays the results of this initia l degradation experiment. The results of the experiment show removal of contamin ants from the solution. All 3 of the contaminants shown in Figure 12 demonstrat ed a better than a 90% removal over the course of the 6-hour run. The capability for the reactor to remove NASA’s target analytes was demonstrated in this experiment.

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37 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 Stock02.04.05.8 Time (hrs)Concentration ( g/L) Carbon Disulfide Toluene Chlorobenzene Figure 12. Target analyte degradation seen as a result of recycling the spiked solution through the system. 3 of the 8 target anal ytes are displayed in this figure. The data represented in the “Stock” bars represents the initial concentration prepared in the 2-liter volumetric flask. The “0” data is the concentration measured after the system containi ng the 1-liter source tank was filled. Determining Effects of Volatility Three sources of loss were anticipated in th e experiments. Work indicated that in this experiment some loss was probable due to volatilization, some to adsorption on the pellets, and the rest due to phot ocatalysis. Many measures were taken to reduce volatility losses in the system. Teflon tubing, stainless steel connector s, and Teflon tape at each junction were all used in an effort to redu ce this loss. Other m easures of protection against volatility included the use of gas-ti ght syringes, luer-lock sampling ports, and keeping the headspace in the s ource tank at a minimum.

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38 Losses due to adsorption were expected and encouraged. Adsorption loss was considered a viable means of contaminant removal for the NASA analytes. However, adsorption losses had to be accounted for, because adsorption removal was finite and could not be relied upon for an entire space mi ssion to Mars (the eventual goal of this reactor). It had to be prove n that after the pellets adso rption capacity was exhausted, photocatalysis alone would have the capabil ity of sufficiently removing the analytes. An experiment was performed to ensure th at losses of analytes were not due to volatility. For this experiment the reactor was taken out of the system setup. A schematic of this setup is shown in Figure 13. The solution for testing was prepared in accordance with the same method described for the initial degradation experime nt. Solution was then added to the source tank and pumped through the system to fill up the tubing. As before, the source tank was filled to the top and capped w ith the rubber stopper. For 8 hours, the contaminated solution was allowed to circulate through the system at a constant flow rate of 10 mL/min. Samples were taken every two hour s for analysis. The results of this experiment are shown in Figure 14.

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39 Figure 13. Diagram demonstrating the setup used for estimating volatile losses of analytes in the system. Only one sampling port is shown in the diagram because only the first sampling port was online during this experiment. 0 20 40 60 80 100 120 140 02468 Time (hrs)Concentration ( g/L) toluene chlorobenzene Figure 14. Volatile losses in the system ove r an 8-hour period without the reactor in place. Samples were taken every 2 hours from the 1st port in the system. This run was performed with a 1-liter sour ce tank, making the entire volume a little over 1.1 liters. Pump Sam p lin g Port Source Tank Dampener

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40 Figure 14 shows small volatile losses for bot h chlorobenzene and toluene (16% and 18% respectively) over the 8-hour period of the experiment. The results of analyses for the 6-hour sample appeared to be anomalous and may have been affected by reloading the feed tank at about this sampling time Discounting the 6-hour sample, volatility losses over an 8-hour period were 16% a nd 18% for toluene and chlorobenzene, respectively. After this experiment certain measures were taken to try to further reduce volatility. This included reduction in head space for the feed tank and a more secure wrapping of PTFE tape around the rubber stoppe r. Based on this experiment and the further measures taken, volatile losses were assumed to be negligible in future experiments. Adsorption Experiment Following the volatility test, adsorption becam e the next source of loss to isolate. The system was reconfigured to that shown in Figure 15. Figure 15. Diagram showing the setup us ed for saturating the catalyst pellets. Dam p ene r Sam p lin g Ports Waste Reactor Feed tank Pump

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41 Using the setup shown in Figure 15, 8 liters of contaminated solution at approximately 200 g/L was put through the re actor with the lights o ff. This was done to ensure that adsorption would not be a cause for loss of analytes in the rest of the research. To assess losses by adsorpti on, an experiment was run with the setup in the configuration shown in Figure 15. Solution wa s prepared and introduced to the system using the method described in Initial Degrad ation section. The solution was circulated through the system at 10 mL/min for 5 hours. The lamps were left on but shielded during this experiment to keep the conditions si milar to what the reactor would typically experience. Samples were taken every hour over the 5-hour period to determine the rate at which the concentration changed. The resu lts of this experiment are shown in Figure 16. 0 20 40 60 80 100 120 140 0123.94.9 Time (hrs)Concentration ( g/L) Toluene Chlorobenzene Figure 16. Loss of toluene and chlorobenzene as a result of adsorption in the reactor system. The source tank was excluded from the experiment as any adsorption there was predicted to be minimal. The “0” sample represents the concentration after addition of cont aminated solution to the system.

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42 This graph shows that some loss is still being experienced in the absence of photocatalysis. However, it can be seen that the loss becomes minimal as the concentrations begin to level out by the fifth hour. Based on this experiment, the decision was made to operate future experime nts by letting the system run for five hours prior to beginning the photocatal ysis experiments. At this point all losses would be considered due to photocatalysis only. Desorption Experiments Experiments were conducted to study deso rption of the target analytes from the catalyst pellets occurring in th e reactor. Contaminated so lution was prepared according to the method described in the Initial Degrad ation section. The reactor system was then filled with solution and allowed to circulate at 10 mL/min for 5 hours. This was done to saturate the gels with respect to adsorption. At the end of the 5 hours a sample was taken and the system was drained. 300 mL of nanopu re water was then put through the system to rinse the extraparticular space within the r eactor. This rinse water was then analyzed to determine the concentration rinsed. Na nopure water was then put into the entire system, with the source tank excluded, to allow for possible desorption. The period of exposure chosen was 45 minutes. After exposur e to the nanopure water for this duration, the system was drained into a 500-mL volumet ric flask and the flask was inverted to provide mixing (excess solution from the syst em was wasted). Two samples were taken from the 500-mL flask for analysis. In a s econd test the solution wa s allowed to remain for another 23 hours and 15 minutes after the 45-minute sample. The system was then drained and a sample was taken to represent 24 hours of desorption. The data in Figure 17, representing the resu lts of the two desorption experiments, led to two important conclusions. The firs t conclusion was that the contaminants do

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43 desorb from the silica/titania gels pellets. This means that when low-level concentrations (lower than those seen in Fi gure 17) are seen in future ex periments the photocatalysis has to degrade contaminants in the feed solution as well as the contaminants that are desorbed from the silica gel-titania composite. 0.0 20.0 40.0 60.0 80.0 100.0 120.0 Rinse (AVG)45 min (AVG)24-hourConcentration ( g/L) Toluene Chlorobenzene Acetone Carbon Disulfide Ethyl Acetate Methyl Methacrylate Figure 17. Results of desorption experiment s performed. The Rinse (AVG) columns represent the average concentration in the rinse solution sample over two experiments. The 45 min (AVG) column s represent the average concentration of contaminant in the NPW solution after 45 minutes of contact with the reactor. The 24-hour columns represen t the average concen tration after 24 hours of circulating through the system. Error bars are representative not of the error in 1 experiment, but the rang e of data in the 2 separate runs. Oxygen as an Electron Acceptor Photocatalysis requires the continual pres ence of an electron acceptor. When UV radiation comes in contact with the TiO2 surface it creates an ex cited electron and a hole left behind by the electron. In the absence of an electron acceptor the excited electron would simply recombine with the hole leav ing no ability for h ydroxyl radicals to be

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44 formed. Oxygen is the most prominent accepto r available and also the cheapest available to fill the position in the NASA research. To demonstrate the availability of oxyge n for use as an electron acceptor in the NASA reactor, an experiment was performed. The setup was configured to that shown in Figure 8. The method outlined in the Initia l Degradation section was then followed for this experiment, with a small exception. Be fore the lamps were turned on, the solution was allowed to circulate for five hours in order to let adsorption effects take place. From then on the lamps were turned on for 6 hours. For this case, samples were only taken of the oxygen concentration in the influent soluti on and of the final solution at the end of photocatalysis. The results of the samples showed no cha nge in the dissolved oxygen level of the solution from the stock solution to the final sample. In both cases the dissolved oxygen level was 5.4 mg/L. This sugge sts that the concentration of pollutants being degraded in the NASA research is too low to cause a measurable effect on the dissolved oxygen concentration in the system. Based on these results, addition of oxygen or other electron acceptors for wastewater degradation in this research may not be necessary if the dissolved oxygen concentration in the influent contains appreciable levels of dissolved oxygen, as the same level of degradation wi ll be achieved with th e currently available electron acceptor concentration. However, tests would actually be necessary with NASA’s wastewater from within their process treatment train in order to determine if oxygen would be limiting at very low levels of dissolved oxygen.

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45 Photocatalytic Oxidation Experiments Effects of UV radiation intensity Experiments were performed to determine the impact of incr easing the amount of UV radiation on degradation of the analytes. Each experiment was performed using the setup shown in Figure 9. Solu tions containing between 70 and 200 g/L were prepared using the method described in the Initial Degrad ation section. The system was then filled with solution and allowed to circulate at 10 mL/min. Initially, the lamps were left off. Based on results from the adsorption experime nt, the solution was circulated for 5 hours before allowing exposure to UV radiation. The lamps were turned on with shields in place at 4.5 hours to provide 30 minutes for the lamps to come to full intensity. At this point, the system was run for 6 hours with the lamps on to allow photocatalysis to occur. Samples were taken every 2 hours for analysis. This experiment was performed four separa te times; once with 3 lamps, once with 1 UV lamp, and twice with 2 UV lamps to a ssess precision of the data. Table 20 shows the calculations performed to find the amount of energy provided to the reactor by 1 UV lamp. Measurements were made using a Fisher Traceable UV Light Meter. Those measurements contained a possible 2% error on the part of the meter. Effects of contact time Experiments were performed to investig ate the impact of flow rate on the degradation of the target anal ytes. Three different flow ra tes were tested; 10 mL/min, 20 mL/min, and 60 mL/min. Solution for these experiments was created using the method described in the Initial Degrada tion section. The system was then configured to the setup shown in Figure 8 and loaded with the soluti on. For 5 hours the solution was circulated to allow adsorption to take place. After 4.5 of the 5 hours, the lamps were turned on and

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46 shielded to allow them to warm up. Thirty minutes later the shields were removed and the system setup was reconfigured to that s hown in Figure 11. Flow in the system was changed to 10 mL/min, 20 mL/min, or 60 mL /min for the each of the three different experiments. One liter of solution was put through the reactor at the experimental flow rate. At the end of that time, samples were collected for analysis from the port before and the port after the reactor. All three of the flow rates tested were w ithin the laminar region of flow as shown in Table 19. This was acceptable since th e flow rate NASA predicted of 116 mL/min also lies within the laminar flow regime (L ange and Lin, 1998). So, turbulent versus laminar flow did not have an effect on the flow optimization experiments. Experiments including i ndole and butyl alcohol All of the previously described expe riments, the flow optimization, UV optimization, 23-hour experiments, and deso rption tests were performed with only acetone, carbon disulfide, chlorobenzene, ethyl acetate, methyl methacrylate, and toluene as the analytes. Tests had to be performed using indole and butyl alcohol as well. These tests required a different method of analysis in addition to the typi cal GC/MS with purge and trap extraction. Indole and butyl alcohol were analyzed using the GC/FID with solid phase micro extraction (SPME). Samples were collected for analysis of the butyl alcohol and indole using the same protocol as with those collected for the other contaminants, however, the same vial of solution could not be used for both analyses. Therefore, two sample vials were filled at each sampling time. These experiments were performed in two different ways. The first three were performed in the same manner as the UV optimization experiment using 3 UV lamps and a recycle mode system. The only differen ce was that indole and butyl alcohol were

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47 included in the stock solution. Two separate experiments were also performed using a similar method to that used in the flow optimization experiments. Five hours of adsorption circulation was performed and then the system was reconfigured to the singlepass system. After 1 L of solution flowed th rough the reactor, two samples were taken at each port.

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48 CHAPTER 4 RESULTS This chapter will discuss the results of experimentation to determine the photocatalytic capabilities of the reactor. Th e effects of UV radiati on intensity and empty bed contact time (EBCT) will be considered. It will be proven through the data that all of the target analytes used in this research (acetone, butyl alc ohol, carbon disulfide, chlorobenzene, ethyl acetate, indole, methyl methacrylate, and indole) are capable of undergoing photocatalytic oxidation. Rates fo r the process of oxidation will also be considered based on data from the tests studying the effects of EBCT. Effects of UV Radiation Intensity Experiments were performed to investigat e the improvement in degradation as the number of lamps was increased. Four expe riments were performed using 1 UV lamp, 2 UV lamps, 3 UV lamps and a duplicate for the run using 2 UV lamps. The details of the experimental method are discussed in the Methods chapter (Eff ects of UV radiation intensity). Figures 18-21 show the results from the UV optimization experiments. The results from these four experiment s demonstrated several important points about the capabilities of the reactor. First, they proved th e ability of the reactor to photocatalytically degrade each of the 5 comp ounds (carbon disulfide, chlorobenzene, ethyl acetate, methyl methacrylate, toluene) s hown in the figures. In all cases, at least 80% destruction of the initial contaminant concentration was achieved. Second, the destruction did not appear linear over time, but rather appeared to approach the 10 g/L

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49 0 10 20 30 40 50 60 70 80 90 0.02.04.06.08.0 Time (hrs)Concentration ( g/L) Toluene Chlorobenzene Carbon Disulfide Ethyl Acetate Methyl Methacrylate Figure 18. Degradation of 5 NASA target an alytes. This loss is due solely to photocatalytic destruction. 3 UV lamps were turned on during this experiment and the experiment was performed in a circulation mode w ith a 1-liter source tank. 0 10 20 30 40 50 60 70 80 90 02468 Time (hrs)Concentration ( g/L) Toluene Chlorobenzene Carbon Disulfide Ethyl Acetate Methyl Methacrylate Figure 19. Degradation of 5 NASA target an alytes. This loss is due solely to photocatalytic destruction. 2 UV lamps were turned on during this experiment and the experiment was performed in a circulation mode w ith a 1-liter source tank.

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50 0 20 40 60 80 100 120 140 0.02.04.06.08.0 Time (hrs)Concentration ( g/L) Toluene Chlorobenzene Carbon Disulfide Ethyl Acetate Methyl Methacrylate Figure 20. Degradation of 5 NASA target an alytes. This loss is due solely to photocatalytic destruction. 1 UV lamp was turned on during this experiment and the experiment was performed in a circulation mode w ith a 1-liter source tank. 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 246 Time (hrs)C/Co Toluene Chlorobenzene Carbon Disulfide Ethyl Acetate Methyl Methacrylate Figure 21. Average normalized degradation seen in the two experiments performed with 2 UV lamps and a 1-liter source tank. E rror bars show the range of data for two experiments. There are no error bars present in the 2-hour sample results due to analytical errors in the 1st of the 2 experiments.

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51 concentrations for all of the tests and contam inants. This suggested that the reaction was limited by the ability of the hydroxyl radicals to contact the contam inants, as suggested by the Langmuir-Hinshelwood equation. Figure 22 shows the normalized curve fo r chlorobenzene. This curve is representative of the norma lized graph for all compounds. The graphs for the other compounds can be found in Figures 29-32. The graph shows all 4 of the UV optimization tests degrading the chlorobenzene at virtually the same rate and magnitude. These data were important to the NASA res earch because it showed that UV radiation energy was not a limiting factor in the degradation of the target analytes beyond the use of 1 UV lamp. The lower the energy requirement s, the more practical the process is for NASA. 0 10 20 30 40 50 60 70 80 90 100 0.02.04.06.08.0 Time (hrs)C/Co (%) 3 Lamps 2 Lamps 1 Lamp 2 Lamp (duplicate) Figure 22. Removal of chlorobenzene is show n over the course of time as a function of the contaminant remaining divided by th e initial concentration introduced to the reactor displayed as a percent. It is important to note that the time displayed on the bottom represents time in the overall system rather than just time in the reactor.

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52 Effects of Empty Bed Contact Time In order to determine the possibility of flow rate and therefore residence time influencing the reactor’s performance, a seri es of experiments were performed. The reactor was studied at three empty bed cont act times (EBCT), 7.27 min, 21.8 min, and 43.6 min. These empty bed contact times were achieved by varying the flow rate at 60 mL/min, 20 mL/min, and 10 mL/min respectively. The method used for performing these experiments has been previously desc ribed in the Methods chapter (Effects of empty bed contact time). Experiments were pe rformed twice at each of the flow rates. Figure 23 shows the percent of selected cont aminants that remain after a single pass through the reactor with the chosen EBCTs. The bars in Figure 23 represent the average value of the two replicates and the error bars represent the ra nge of the data. All of the series raw data can be found in Tables 21-42. 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00Tol u e ne C hl o rob e n z ene Ac e tone E t hy l Ace t ate M eth y l Me t h a c r yl a t eC/Co (%) 10 mL/min 20 mL/min 60 mL/min Figure 23. Average results of two flow optimiza tion experiments. The y-axis is given as the concentration remaining in the effluent solution divided by the concentration present in the influent, di splayed as a percent. Therefore the smaller columns represent a greater per centage of contaminant removed. % RSDs for acetone were outside of th e acceptable range, which explains the large error bars.

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53 The EBCT for solution in the reactor wa s decreased from 43.6 minutes to 21.8 minutes to 7.27 minutes. A decreased reten tion time available for photocatalysis should have logically led to a poor er degradation. This hypothe sis is proven by the data in Figure 23 where the greater degrad ation is consistently seen in the tests performed at the slower flow rate. Not only do the data reported in Figure 23 gi ve insight into the effect of flow rate on the reactor’s capability to degrade the target analytes, but they al so show the reactor’s capability for destroying the analytes in a single pass. Unlike the UV optimization experiments, the flow experiments studied the reactor’s performa nce in a single-pass situation. The results demonstrate the ability of the reactor to re move between 85% and 95% of target analytes in a single pass with the longer E BCT. Importantly, both toluene and chlorobenzene were removed to 10 g/L and 13 g/L respectively. This is far below the USEPA National Primary Dr inking Water Standards of 1000 g/L for toluene and 100 g/L for chlorobenzene. The USEPA does not have Primary Drinking Water Standards for the other target analytes in this study. Figure 24 displays the data in a different manner. This graph shows the normalized removal of the contaminants with respect to the length of EBCT (empty bed contact time) in the reactor. The tendency for the reactor to quickly re move the contaminants to a certain concentration and then level off in degr adation rate is clearly visible in Figure 24. The data from Figures 23 and 24 were used to assess the reaction rate constants of the five target analytes shown in these figur es. As discussed in the literature review chapter, the Langmuir-Hinshelwood (LH) e quation has been shown by many researchers

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54 to model the degradation rates in photocatalytic oxidation. The LH equation is shown in Equation 14. 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 01020304050 EBCT (min)C/Co (%) Toluene Chlorobenzene Acetone Ethyl Acetate Methyl Methacrylate Figure 24. Degradation of five target analyt es in the reactor using three UV lamps and operating the system in a single-pass m ode after adsorption for five hours in a circulation mode had taken place. EBCT stands for Empty Bed Contact Time. rate = kK1C/(1+K1C) (Eq.14) where the rate is the actual rate of photocat alysis, k, is a rate constant, C is the bulk concentration of contaminan t in the solution, and K1 is an adsorption equilibrium constant based on the tendency for the contaminant to adsorb to the photocatalyst surface. As the term K1C becomes smaller (1>>K1C) the right hand side of Equation 14 reduces to Equation 15. Equation 15 is a si mplified version of the LH equation and is recognized as a first-order rate equation. rate = dC/dt = kK1C = k’C (Eq.15) where k’ is used to represent the combination of the k and K1 terms. During this research the concentrations were kept low (100 – 300 g/L) because NASA needs to remove

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55 contaminants that will be at this approximate concentration level. The K1 term was not studied in this research. Theref ore, it was not determinable if K1C could be considered minimal compared to 1. However, for the ease of modeling an attempt was made to model the oxidation kinetics in the reactor us ing first-order kinetics. After performing the analysis, it will be shown how accurately the reactions for the contaminants behaved as approximately first order. In the Methods chapter (Reactor hydrodynami cs) it is shown that through a tracer analyses the reactor performe d as 3.9 CMFRs in series. The first order equation for 1 CMFR is shown in Equation 16. C/Co = (1+k tbar)-1 (Eq.16) where C is the effluent concentration, Co is the influent concentration, k is the reaction rate constant, and tbar represents the mean residence time through the reactor. To obtain the equation for 3.9 CMFRs in series, Equation 15 is used around each CMFR. By using Equation 15, the effluent to the first CMFR is found, and then the second, and this is continued until the number of CMFRs to be represented has been accomplished. A simplification to this process is Equation 17. C/Co = (1 + k tbar/n)-n (Eq.17) where n represents the number of CMFRs in seri es. In this analysis, the k’ being solved for can be inserted in place of the k shown in Equation 17. This is shown in Equation 18. C/Co = (1 + k’ tbar/n)-n (Eq.18) In order to determine k’ for the target anal ytes in this research, it was necessary to rearrange Equation 18. Equation 18 was rearra nged algebraically to form Equation 19. n ((Co/C)1/n 1) = k’ tbar (Eq.19)

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56 Equation 19 was then used to graphically dete rmine the k’ constant for each of the five compounds studied in the Effect s of Empty Bed Contact Time section. This was done by graphing the left-hand side of E quation 19 on the y-axis versus tbar on the x-axis. The resulting graphs, Figures 25 and 26, have trend lines with slopes equal to the k’ for each specific contaminant. If the volume within the reactor were composed entirely of solution, then the slopes would represent the actual first order rate constant. The reactor, however, is composed of volume occupied by 75% solution and 25% pellets, therefore porosity must be accounted for. To do this, Equation 20 was used. kobserved = k’ / (Eq. 20) where kobserved is the first order reaction rate cons tant found reported for this system and is the porosity of the reactor (0.75). The r eal first order rate c onstants, determined by using the slopes from Figures 25 and 26 in Equation 20, are shown in Table 5. To assess how well a contaminant was mode led using the first order rate equation the following facts were considered. A higher R2 (>0.8) represents a contaminant that more closely resembles a first-order reaction rate. The lower R2 (<0.8) for acetone and methyl methacrylate suggest that a first-orde r reaction rate is probably not an acceptable assumption for these contaminants. Of additional importance is the intercept of the equations. Ideally, these intercepts would be zero. The presence of a y-intercept emphasizes the fact that there is a fast ini tial period of contaminant transformation after which the rate of removal becomes more linear with respect to EBCT.

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57 Chlorobenzene y = 0.065x + 0.4485 R2 = 0.8349 Ethyl Acetate y = 0.0565x + 0.2009 R2 = 0.9285 Toluene y = 0.1278x + 0.3515 R2 = 0.9409 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 010203040 tbar (min)n((Co/C)1/n-1) Chlorobenzene Ethyl Acetate Toluene Li Figure 25. The slope of the trend lines produ ced for each target analyte represents the kinetic rate for that contaminant base d on the assumption that its degradation is first-order in nature. These data are based on information from Figure 24. This figure only shows the compounds with higher R2 values (values > 0.8). The observed reaction rate cons tants predicted in Table 5 are very similar to those seen by other researchers for TiO2 slurry. Kawaguchi (1990) reported a first order rate constant of 0.065 min-1 for chlorobenzene degradation at a pH of 3.5. The pH in the effluent of the reactor used in this re search was approximately 3.8. In 2000, Vijayaraghavan reported a first order ra te constant for toluene of 1.272 min-1 at a pH of 4.0. Although, the first order rate constants for each compound are similar, the form of the photocatalyst, TiO2, is significantly different. Both of these prior researchers used TiO2 in a slurry form in order to achieve photocat alytic oxidation. In this research similar kinetic rates were achieved in a packed bed configuration using sili ca gel as a support for

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58 the TiO2. Comparisons of these reaction rate co nstants are complicated by the different TiO2 loadings, UV energy, pH, and reaction temper ature, which likely were different in each case reported in the literature; however, the results show that the silica gel doped with TiO2 was capable of degrading these target or ganic analytes with rates that compare well with TiO2 slurries. Methyl Methacrylate y = 0.0592x + 0.5601 R2 = 0.7175 Acetone y = 0.0191x + 0.1567 R2 = 0.6979 0.00 0.50 1.00 1.50 2.00 2.50 3.00 010203040 tbar (min)n((Co/C)1/n-1) acetone methyl methacrylate Figure 26. The slope of the trend lines produ ced for each target analyte represents the kinetic rate for that contaminant base d on the assumption that its degradation is first-order in nature. These data are based on information from Figure 24. This figure only shows the compounds with lower R2 values (values < 0.8). Table 5. Important data gathered from the trend lines shown in Figures 25 and 26. The reaction rate constant (k) shown in this table is the first order rate constant for each of the listed target contaminants. These experiments were performed at a pH of 3-4 and an average temperature of approximately 25 C. Chemical k (min-1)R2Acetone0.0250.698 Chlorobenzene0.0860.835 Ethyl Acetate0.0750.929 Methyl Methacrylate0.0790.718 Toluene0.1700.941

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59 Extended Duration Experiment An experiment was performed to determin e whether or not the reactor was capable of completely degrading the initial contaminan t concentration to a level below detection. This experiment was performed in the same manner as the UV optimization experiments. However, samples were only taken of the in itial stock solution and the final effluent concentration after 23 hours of exposure to photocatalytic oxida tion. Results as shown in Table 6 demonstrate that the reactor is capable of completely removing toluene, carbon disulfide, chlorobenzene, acetone, ethyl acetate, and methyl methacrylate to concentrations that are below the de tection limit of the GC/MS procedure. Table 6. Results of the extended durati on test performed for 23 hours. Initial concentrations represent the concentra tion of contaminant introduced to the system before any adsorption or photocatalysis took place. Final Concentrations represent the concentrat ion of contaminant found in a sample taken after 23 hours of exposure to photocatalytic oxidation. ChemicalInitial ConcentrationFinal Concentration ( g/L)( g/L) Acetone321BDL Carbon Disulfide220BDL Chlorobenzene205BDL Ethyl Acetate266BDL Methyl Methacrylate319BDL Toluene141BDL Method detection limit = 5 g/L Below detection limit (BDL) Removal of Butyl Alcohol and Indole Results from experiments performed on the degradation of butyl alcohol and indole produced data proving the reacto r’s capability to degrade in dole and butyl alcohol with the same level of proficiency as it did the other compounds. The method for performing

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60 these tests was previously described in the Methods section (Removal of indole and butyl alcohol). Figure 27 shows the results of the degradation experiments performed with the system operating in a circulation mode. The contaminants in these experiments experienced 5 hours of adsorption in the sy stem and then 6 hours of photocatalytic oxidation. Figure 28 shows the degradation resu lts from a single pass through the reactor. The EBCTs for the experiments show n in Figure 28 were 43.6 minutes. 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 Butyl AlcoholIndoleC/Co Test 1 Test 2 Test 3 Figure 27. Results showing the degradation of butyl alcohol and indo le as a result of 6 hours of exposure to UV radiation. A 4-liter source tank was used in this reactor system. There appears to be no data for the indole in the second test because the data point is 0. With the exception of the 3rd experiment (it is believed that there may be some error in this experiment), th e data demonstrate excellent removal of both butyl alcohol and indole. The 2nd experiment, in fact, showed de struction of indole to beyond the detection level. The 4th and 5th experiments were especially promising, because they show 93 to 97% removal of both butyl alc ohol and indole in a si ngle pass through the reactor. The rapid removal of butyl alcohol and indole is particularly important since it

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61 has been stated in literature that their removal should be a gr eater challenge to the reactor than the removal of the ot her 6 analytes (Serpone, 1995). 0.00 0.20 0.40 0.60 0.80 1.00 Butyl AlcoholIndoleC/Co 1st Test 2nd Test Figure 28. Data showing the ratio of each chem ical’s concentration in the sample from Port 2 versus the sample from Port 1.

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62 CHAPTER 5 SUMMARY AND CONCLUSIONS Summary Eight target analytes including aceto ne, butyl alcohol, carbon disulfide, chlorobenzene, ethyl acetate, i ndole, methyl methacrylate, and toluene, were tested for their degradation using the process of photo catalytic oxidation. The photocatalytic oxidation was carried out in an annular reactor with the TiO2 supported on a silica gel matrix and arranged in a packed bed style wi thin the reactor. Adsorption and desorption of the contaminants within the reactor were studied to determine the capabilities of the photocatalyst pellets for removing contaminants without photocatalytic oxidation. The level of available electron acceptor (in the fo rm of DO) and the effects of UV radiation intensity were studied to investigate their imp act on the process. Ability of the reactor to remove all of the target analytes was assessed. Finally, the reactor was tested for its removal of 5 target analytes at various EBCT s. Results of those experiments were used to determine rates of photocatalytic oxidation within the reactor. Conclusions An annular reactor containing silica/titania pe llets arranged in a packed bed style is capable of degrading all 8 of this research’s target analyt es. Six of the compounds were degraded to below detection limit (5 g/L) after an extended reaction period. Photocatalytic destruction of the contam inants in the reactor was not limited by UV radiation intensity beyond the use of 1 lamp (8 Watts), providing approximately 4.44 W of energy to the interior surf ace of the reactor. Photocatal ysis was also not limited by the

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63 amount of oxygen when the dissolved oxygen le vel was 5.4 mg/L; however, lower levels of dissolved oxygen were not investigated. A possibility does exist that adsorption of contaminants to the pellet surface will occu r if a proper gradient exists between the concentration in aqueous solution and the c oncentration attached to the surface of the pellets. That sorption was also found to be re versible. First order rate constants for the photocatalytic degradation of both toluene and chlorobenzene were similar to those reported for TiO2 photocatalysis in slurry form. One possible reason for this is the loading. Loading rates for this res earch were approximately 87 g of TiO2/L of solution (some of that is certainly trapped within the pellets). Loading rates for one of the slurry experiments was only 1 g of TiO2/L of solution. In spite of the fast degradation rates, EBCT does play a part in the level of degr adation seen in the effluent. Once exact concentrations and flow rates are known by NASA it will be important to find an exact EBCT necessary to achieve proper degradation. This research has proven the hypothesis by showing the potential for titania/silica pellets arranged in a packed-bed-style reactor to significantly degrade 8 organic compounds in a mixed solution. This resear ch must be taken to further levels by including it within a treatment process trai n, using actual wastewater or simulated wastewater formulations and assessing its ab ility at practical flow rates and over longer periods of time.

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64 APPENDIX A CHEMICAL INFORMATION Table 7. Table of Target Analytes AnalytesFormula Volume of Sample (mL) ContainerMethod # Sample Preservation Holding Time Chlorobenzene C6H5Cl 40 VOA vial with Teflon seals USEPA 524.2 4 degrees Celsius 2 weeks Acetone C3H5O 40 VOA vial with Teflon seals USEPA 524.2 4 degrees Celsius 2 weeks Indole C8H7N 40 VOA vial with Teflon seals SPME 4 degrees Celsius 2 weeks Butyl Alcohol C4H10O 40 VOA vial with Teflon seals SPME 4 degrees Celsius 2 weeks Toluene C7H840 VOA vial with Teflon seals USEPA 524.2 4 degrees Celsius 2 weeks Ethyl Acetate C4H8O240 VOA vial with Teflon seals USEPA 524.2 4 degrees Celsius 2 weeks Methyl Methacrylate C5H8O240 VOA vial with Teflon seals USEPA 524.2 4 degrees Celsius 2 weeks Carbon Disulfide CS240 VOA vial with Teflon seals USEPA 524.2 4 degrees Celsius 2 weeks

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65 Table 8. Molecular Weight of Target Analytes CompoundMolecular Weight (amu) Acetone57.072 Butyl Alcohol74.122 Carbon Disulfide76.131 Ethyl Acetate88.105 Toluene92.14 Methyl Methacrylate100.116 Chlorobenzene112.559 Indole117.15 Table 9. Henry’s Constants a nd Partitioning Coefficients (atm/mol fraction ) (octanol-water coeff.) butanol0.70.88 acetone1.4-0.24 ethyl acetate7.70.73 m ethyl methacrylat e 7.81.38 chlorobenzene209.02.92 toluene356.72.69 carbon disulfide1064.02.14 indole10739.02.14 ChemicalHenry's Constant Log of the Partitioning Coefficient (Yaws, 1999; The Federal Register; http://www.ccc.uni-erlangen.de; Schwarzenbach, 1993) Table 10. Melting Points/Boiling Points ChemicalMelting PointBoiling PointoCoC acetone-9556.2 butyl alcohol-89.9117.7 carbon disulfide-108.646.3 chlorobenzene-45132 ethyl acetate-83.677 indole52.5254 methyl methacrylate-50101 toluene-95.1110.8

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66 Table 11. Sources of Contaminant ChemicalSource Acetone Varnishes, adhesives, and humans. Butyl Alcohol Gasoline. Carbon Disulfide Rubber chemicals. Chlorobenzene Dyes and insectisides. Ethyl Acetate Solvents and adhesives Indole Humans. Methyl Methacrylate Plastics. Toluene rubbers. (Verschueren, 1983; http://www.ep a.gov; http://www.echeminc.com) Table 12. Contaminant Generation in the ALS Chemical Equipment Genereration Rate Metabolic Generation Rate (mg/day*kg) (mg/man*day) Acetone 3.62E-03 2.00E-01 Butyl Alcohol 4.71E-03 1.33E+00 Carbon Disulfide 3.23E-05 0.00E+00 Chlorobenzene 1.54E-03 0.00E+00 Ethyl Acetate 2.97E-04 0.00E+00 Indole 0.00E+00 6.25E+00 Methyl Methacrylate 1.30E-04 0.00E+00 Toluene 1.98E-03 0.00E+00 (Lange, 1998)

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67 Table 13. Water Quality Requirements ParameterPotable Water SpecificationsHygiene Specifications Total Solids100 mg/L500 mg/L pH6.0 8.55.0 8.5 Turbidity1.0 NTU1.0 NTU Cations30 mg/LN/A Anions30 mg/LN/A CO215 mg/LN/A Total Acids500 mg/L *500 mg/L TOC500 mg/L *10,000 mg/L Total Phenols1 mg/L *1 mg/L Total Alcohols500 mg/L *500 mg/L Cyanide200 mg/L *200 mg/L Halogenated Hydrocarbons 10 mg/L *10 mg/L * Although the source reports these units as mg/L it seems probable that it should actually be reported as g/L. (Lange, 1998) Table 14. Spacecraft Trace Contaminant Generation Rates COMMON NAME MOLAR MASS g/mol SMAC mg/m3 EQUIPMENT GEN RATE mg/day*kg METABOLIC GEN RATE mg/man*day Methyl alcohol32.0491.27E–031.50E+00 Ethyl alcohol46.07947.85E–034.00E+00 Allyl alcohol58.0812.35E–060.00E+00 Isopropyl alcohol60.091503.99E–030.00E+00 Propyl alcohol60.0998.32.41E–040.00E+00 Ethylene glycol62.071276.03E–060.00E+00 2–butanol74.121219.63E–060.00E+00 Isobutyl alcohol74.121218.46E–041.20E+00 tert–butyl alcohol74.121217.38E–050.00E+00 Butyl alcohol74.121214.71E–031.33E+00 n–amyl alcohol88.151261.62E–040.00E+00 Phenol94.117.74.83E–040.00E+00 Hexahydrophenol100.161237.56E–040.00E+00 2–hexanol102.181672.48E–060.00E+00 ALCOHOLS

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68 Table 14 (continued) Formaldehyde30.030.054.40E–080.00E+00 Acetaldehyde44.0541.09E–049.00E–02 Acrolein56.060.033.46E–060.00E+00 Propionaldehyde58.08953.19E–040.00E+00 n–butylaldehyde72.11188.59E–040.00E+00 valeraldehyde86.131067.84E–058.30E–01 benzenecarbonal106.121731.99E–050.00E+00 Benzene78.110.322.51E–050.00E+00 Toluene98.13601.98E–030.00E+00 Styrene104.1442.63.13E–050.00E+00 o–xylene106.1686.85.56E–040.00E+00 m–xylene106.1686.82.03E–030.00E+00 p–xylene106.1686.81.08E–030.00E+00 Ethylbenzene106.1686.81.50E–040.00E+00 alpha–methylstyrene118.181451.67E–070.00E+00 Pseudocumene120.2154.49E–050.00E+00 Mesitylene120.2153.63E–060.00E+00 1–ethyl–2–methylbenzene120.2254.88E–060.00E+00 Cumene120.273.71.40E–050.00E+00 Propylbenzene120.249.12.15E–040.00E+00 ethyl formate74.0890.94.51E–060.00E+00 methyl acetate74.081211.41E–040.00E+00 ethyl acetate88.111802.97E–040.00E+00 methyl methacrylate100.121021.30E–040.00E+00 isopropyl acetate102.132095.81E–060.00E+00 propyl acetate102.131673.38E–040.00E+00 butyl acetate116.161907.46E–040.00E+00 isobutyl acetate116.161901.52E–040.00E+00 ethyl lactate118.131933.64E–060.00E+00 n–amyl acetate130.181604.78E–050.00E+00 cellosolve acetate132.161627.46E–040.00E+00 ESTERS ALDEHYDES AROMATIC HYDROCARBONS

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69 Table 14 (continued) Furan68.070.111.84E–060.00E+00 Tetrahydrofuran72.111186.93E–050.00E+00 Ether74.122428.90E–050.00E+00 sylvan82.10.133.46E–060.00E+00 ethyl cellosolve90.120.36.01E–040.00E+00 Methyl chloride50.4941.36.76E–060.00E+00 Vinyl chloride62.50.261.46E–060.00E+00 Ethyl chloride64.52263.78.99E–080.00E+00 Methylene chloride84.93102.15E–030.00E+00 dichloroethene96.957.95.64E–070.00E+00 Ethylene dichloride98.9717.74E–050.00E+00 Chlorobenzene112.56461.54E–030.00E+00 propylene chloride112.9942.27.42E–060.00E+00 Chloroform119.384.91.76E–050.00E+00 Trichloroethylene131.39108.62E–050.00E+00 Methyl chloroform133.411646.72E–040.00E+00 Vinyl trichloride133.415.58.24E–080.00E+00 dichorobenzene147.01306.33E–060.00E+00 Carbon tetrachloride153.82139.60E–060.00E+00 Tetrachloroethylene165.83347.28E–040.00E+00 Freon 2286.47353.65.75E–050.00E+00 Freon 21102.9216.36E–070.00E+00 chlorotrifluoroethane118.5484.54.88E–060.00E+00 Freon 12120.91494.41.35E–050.00E+00 dichorodifluoroethene132.931361.89E–060.00E+00 Freon 11137.4561.81.41E–030.00E+00 Halon 1301148.9608.82.61E–040.00E+00 Freon 114170.92702.92.62E–050.00E+00 Freon 113187.44001.89E–020.00E+00 Freon 112204834.23.33E–050.00E+00 CHLOROFLUOROCARBONS ETHERS CHLOROCARBONS

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70 Table 14 (continued) Methane16.0438006.39E–041.60E+02 Ethylene28.05344.12.27E–070.00E+00 Ethane30.0712301.17E–060.00E+00 Propylene42.08860.32.56E–060.00E+00 Propane44.09901.49.21E–070.00E+00 Vinylethylene54.09221.22.66E–060.00E+00 Ethylethylene56.14588.03E–050.00E+00 Isobutane58.12237.61.10E–050.00E+00 Butane58.12237.65.13E–060.00E+00 Propylethylene70.131862.20E–080.00E+00 Isopentane72.152951.80E–060.00E+00 Pentane72.155909.54E–050.00E+00 hexamethylene84.162063.79E–040.00E+00 methylpentamethylene84.1651.62.97E–050.00E+00 Neohexane86.1788.11.67E–060.00E+00 Diethylmethylmethane86.1817625.97E–060.00E+00 Hexane86.181766.95E–050.00E+00 1–heptylene98.182011.10E–080.00E+00 Hexahydrotoluene98.1860.26.09E–050.00E+00 Heptane100.212055.59E–050.00E+00 Dimethylcyclohexane112.221152.61E–050.00E+00 trans–1,2–dimethylhexamethylene112.221155.23E–050.00E+00 octane114.233501.61E–050.00E+00 nonane128.263157.35E–060.00E+00 citrene (limonene)136.235573.58E–060.00E+00 Decane142.282232.78E–050.00E+00 Hendecane156.313192.51E–050.00E+00 Dodecane170.342786.91E–070.00E+00 HYDROCARBONS

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71 Table 14 (continued) Acetone58.08712.53.62E–032.00E–01 Methyl ethyl ketone72.11306.01E–030.00E+00 Methyl propyl ketone86.1370.44.03E–060.00E+00 Methyl isopropyl ketone86.1370.43.11E–050.00E+00 Mesityl oxide (methyl isobutenyl ketone ) 98.1440.11.91E–040.00E+00 cyclohexanone (pimelic ketone)98.1460.26.62E–040.00E+00 Methyl isobutyl ketone100.16821.41E–030.00E+00 Phenyl methyl ketone120.142455.66E–070.00E+00 Methyl hexyl ketone128.211051.65E–070.00E+00 Diisobutyl ketone142.258.13.34E–060.00E+00 hydrogen sulfide34.082.80.00E+009.00E–02 Carbon oxisulfide60.07126.05E–060.00E+00 Methyl sulfide62.142.51.88E–070.00E+00 carbon disulfide76.14163.23E–050.00E+00 Acetic acid60.057.41.42E–060.00E+00 Acetonitrile41.056.71.70E–080.00E+00 Indole117.150.250.00E+006.25E+00 hydrogen2.023405.91E–062.60E+01 ammonia1778.46E–053.21E+02 carbon monoxide28.01102.03E–032.30E+01 trimethylsilanol90.21401.69E–040.00E+00 hexamethylcyclotrioxosilane222.42271.62E–040.00E+00 octamethyltrioxosilane236.54402.11E–040.00E+00 MERCAPTANS and SULFIDES ORGANIC ACIDS ORGANIC NITROGENS MISCELLANEOUS KETONES (Lange, 1998)

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72 Table 15. Spacecraft Maximum Allowable Concentrations Potential Exposure Period Chemical 1 h 24 h 7 d 30 d 180 d ACETALDEHYDE mg/m3 20 10 4 4 4 ACROLEIN mg/m3 0.2 0.08 0.03 0.03 0.03 AMMONIA mg/m3 20 14 7 7 7 CARBON DIOXIDE mm Hg 10 10 5.3 5.3 5.3 CARBON MONOXIDE mg/m3 60 20 10 10 10 1,2–DICHLOROETHANE mg/m3 2 2 2 2 1 2–ETHOXYETHANOL mg/m3 40 40 3 2 0.3 FORMALDEHYDE mg/m3 0.5 0.12 0.05 0.05 0.05 FREON 113 mg/m3 400 400 400 400 400 HYDRAZINE mg/m3 5 0.4 0.05 0.03 0.005 HYDROGEN mg/m3 340 340 340 340 340 INDOLE mg/m3 5 1.5 0.25 0.25 0.25 MERCURY mg/m3 0.1 0.02 0.01 0.01 0.01 METHANE mg/m3 3800 3800 3800 3800 3800 METHANOL mg/m3 40 13 9 9 9 METHYL ETHYL KETONE mg/m3 150 150 30 30 30 METHYL HYDRAZINE mg/m3 0.004 0.004 0.004 0.004 0.004 DICHLOROMETHANE mg/m3 350 120 50 20 10 OCTAMETHYLTRISILOXANE mg/m3 4000 2000 1000 200 40 2–PROPANOL mg/m3 1000 240 150 150 150 TOLUENE mg/m3 60 60 60 60 60 TRICHLOROETHYLENE mg/m3 270 60 50 20 10 TRIMETHYLSILANOL mg/m3 600 70 40 40 40 XYLENE mg/m3 430 220 220 220 220 (Lange, 1998)

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73 APPENDIX B REACTOR INFORMATION Table 16. Predicted Retent ion Time Calculations Cylindrical Reactor: Length of Reactor =14.0cm Inner Diameter =8.5cm Width of Space =1.0cm Outer Diameter =10.5cm Volume =418 cm3=418mL Cyllindrical Reactor: Actual Volume with ends is 436 mL. Volume available for polluted waters is 436*.75 Volume =327mL Flow through the reactor is approximated as: Flow =116.5mL H2O/min Flow through the reactor during testing will be: Flow =10mL H20/min The retention time with the ALS flow is about 327 / 116.5 = Time =2.81min The retention during testing is about 327 / 10 = Time =32.7min (167.8kgH2O/day/6persons)*(6persons)*(1000g/kg)*(cm3/g)* (mL/cm3)*(day/24hrs)*(hr/60min)

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74 Table 17. System Volume Calculation Component Reactor:=327mL Tubing: 6 mm OD Tubing=4.071mL 1/4 inch ID tubing=156mL Source Tank:=1000mL 4000mL System Volume with 1L source tank:=1487mL 1.49L System Volume with 4L source tank:=4487mL 4.49L Volume for Water or or Table 18. KCl Conductivities fo r Testing Probe Accuracy KClEquivalent Conductivity, LConductivity, k equivalent/Lmho-cm 2/equivalentmmho/cm 0149.9 0.0001148.914.9 0.0005147.773.9 0.001146.9146.9 0.005143.6717.5 0.01141.21412 0.02138.22765 0.05133.36667 0.1128.912890 0.2124.024800 0.5117.358670 1111.9111900 (Standard Methods, 1998)

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75 y = 0.5619x R2 = 0.995 0 100 200 300 400 500 600 700 800 0200400600800100012001400 Conductivity mmhos Concentration (mg/L) Figure 29. Concentration of NaCl in deioni zed water solution vers us the conductivity read on a Fisher Scien tific conductivity probe. Table 19. Calculation of Flow Regime in the Reactor d m = Diameter of the media = 3mm Vo = Velocity of the liquid = Q/A A = Cross sectional are of the reactor =29.85 cm 2 r L = Density of the liquid = 998.2 k g / m 3 m = Viscosity of the liquid =0.001002 N*s/m 2 e = Interparticular poros ity of the media =0.75 NREQ (mL/min) 0.6710 1.3320 4.0060 NASA predicted flow7.78116.5 NRE< 10 is in the laminar regime. NRE = (dm*Vo* r L) / (m*(1-eo)) Testing Flows

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76 Table 20. Calculation of UV Energy at Reactor Surface UV Intensity Calculations 2.06 mW/cm2<= UV measured at reactor end 21.7 mW/cm2<= UV measured at reactor center 2.06 mW/cm2<= UV measured at reactor end 11.88 mW/cm2<= Average intensity from beginning to middl e 11.88 mW/cm2<= Average intensity from middle to end 374 cm2<= Reactor's inner surface area 187 cm2<= Reactor's area from beginning to middle 187 cm2<= Reactor's area from middle to end 2221.56mW<= Energy to reactor from beginning to middl e 2221.56mW<= Energy to reactor from middle to end 4443.12mW<= Total energy to reactor

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77 APPENDIX C RAW DATA Table 21. Initial Raw Data Test (1/6/3) ChemicalRF (AVG)%RSDStock Solutiont = 0t = 118t = 238t = 349 ( g/L)( g/L)( g/L)( g/L)( g/L) Carbon Disulfide0.944820.2694.133.215.54.83.0 Chlorobenzene1.164825.1467.734.215.05.63.0 Toluene3.17630.0364.845.119.36.83.8 Table 22. Volatility Test Raw Data (2/6/3) ChemicalRF (AVG)%RSDStock Solutio n t = 120t = 240t = 360t = 480 ( g/L)( g/L)( g/L)( g/L)( g/L) Chlorobenzene2.4634126.6122.8109.186.9103.9 Toluene4.393556.155.148.633.847.2 Table 23. Adsorption Test Raw Data (3/8/3) ChemicalRF (AVG)%RSDStock Solutiont = 60t = 120t = 235t = 295 ( g/L)( g/L)( g/L)( g/L)( g/L) Chlorobenzene2.249.7120.6104.878.471.666.2 Toluene4.4715.275.667.952.450.946.9 Table 24. UV Optimization (3 Lamps) Raw Data (3/12/3) ChemicalRF (AVG)%RSDStock Solutiont = 0t = 120t = 240t = 360 ( g/L)( g/L)( g/L)( g/L)( g/L) Carbon Disulfide1.2914.6122.750.034.414.76.3 Chlorobenzene2.249.7153.474.548.520.39.1 Ethyl Acetate0.10019.213.010.04.61.8 Methyl Methacrylate 0.0598.19139.082.249.317.24.5 Toluene4.0515.2102.456.637.31811

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78 Table 25. UV Optimization (2 Lamps) Raw Data (3/13/3) ChemicalRF (AVG)%RSDt = 0t = 240t = 360 ( g/L)( g/L)( g/L) Carbon Disulfide1.2914.660.720.59.4 Chlorobenzene2.249.769.022.69.1 Ethyl Acetate0.10084.213.613.9 Methyl Methacrylate 0.0598.1973.319.66.0 Toluene4.0515.262.022.612.7 Table 26. UV Optimization (1 Lamp) Raw Data (3/14/3) ChemicalRF (AVG)%RSDt = 0t = 120t = 246t = 360 ( g/L)( g/L)( g/L)( g/L) Carbon Disulfide1.1425.760.625.212.56.7 Chlorobenzene2.5115.174.747.52210.9 Ethyl Acetate0.02050.435.519.611.6 Methyl Methacrylate 0.05948.8124.464.327.914.8 Toluene6.0738.544.326.811.65.2 Table 27. UV Optimization (2 Lamp Duplicate) Raw Data (3/17/3) ChemicalRF (AVG)%RSDt = 0t = 120t = 240t = 360 ( g/L)( g/L)( g/L)( g/L) Carbon Disulfide1.1425.747.625.518.210.7 Chlorobenzene2.5115.154.333.818.610.4 Ethyl Acetate0.02043.434.119.910.1 Methyl Methacrylate 0.05948.894.756.628.412.4 Toluene6.0738.555.032.116.68.4

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79 Table 28. 11-Hour Adsorption Experiment Raw Data (4/3/3) ChemicalRF (AVG)%RSDt = 0t = 0 (dup) ( g/L)( g/L) Carbon Disulfide1.0213.854.446.0 Chlorobenzene3.0515.3150.5158.7 Ethyl Acetate0.020120.1119.3 Methyl Methacrylate 0.07610.2213.0221.2 Toluene7.2938.4111.5118.0 t = 75t = 255t = 375t = 555t = 735 ( g/L)( g/L)( g/L)( g/L)( g/L) 33.024.824.821.516.0 88.667.367.361.653.1 66.252.652.647.237.2 125.3102.7102.797.282.3 72.459.959.957.150.2 Table 29. 60 mL/min Flow Test (Series 2) Raw Data (4/6/3) ChemicalRF (AVG)%RSDStockt = 3.5t = 5Port 1Port 2 ( g/L)( g/L)( g/L)( g/L)( g/L) Acetone0.0230.6159.7105.275.3109.037.9 Carbon Disulfide2.49 25.4186.887.182.344.34.7 Chlorobenzene2.702 1.31080.9572.6527.4313.177.7 Ethyl Acetate0.2520.15.13.44.52.70.9 Methyl Methacrylate 0.048.3116.873.570.151.110.0 Toluene7.8440.142.229.029.015.32.6 *Port 1 is before the reactor*Port 2 is after the reactor

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80 Table 30. 20 mL/min Flow Test (Series 2) Raw Data (4/9/3) ChemicalRF (AVG)%RSDStockt = 3.5t = 5Port 1Port 2 ( g/L)( g/L)( g/L)( g/L)( g/L) Acetone0.0230.611.866.345.242.036.6 C arbon Disulfide2.4925.4128.779.885.454.320.3 Chlorobenzene2.7021.3133.361.177.360.918.5 Ethyl Acetate0.2520.110.87.47.66.53.9 Methyl Methacrylate 0.048.3290.7189.5175.8152.561.6 Toluene7.8440.1117.954.172.953.411.9 *Port 1 is before the reactor*Port 2 is after the reactor Table 31. 10 mL/min Flow Test (Series 2) Raw Data (4/7/3) ChemicalRF (AVG)%RSDStockt = 3.5t = 5Port 1Port 2 ( g/L)( g/L)( g/L)( g/L)( g/L) Acetone0.0230.6144.090.294.9127.695.2 Carbon Disulfide2.4925.436.527.625.122.713.9 Chlorobenzene2.7021.3288.8108.7118.495.013.8 Ethyl Acetate0.2520.110.66.76.86.41.8 Methyl Methacrylate 0.048.3355.9210.6179.2168.043.8 Toluene7.8440.1107.343.243.244.30.9 *Port 1 is before the reactor*Port 2 is after the reactor Table 32. 23-Hour Test Raw Data (4/16/3) ChemicalRF (AVG)%RSDStockStock ( dup)t = 23 hourst = 23 hours (dup) ( g/L)( g/L)( g/L)( g/L) Acetone0.0220.3263.4379.23.72.3 C arbon Disulfide1.9614.9225.2214.35.94.0 Chlorobenzene2.603.2194.1216.73.64.3 Ethyl Acetate0.010.0263.8267.20.00.0 Methyl Methacrylate 0.0410.7295.6342.40.00.0 Toluene5.324.2138.9142.71.71.8 *Port 1 is before the reactor *Port 2 is after the reactor

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81 Table 33. 60 mL/min Flow Test (Series 3) Raw Data (4/28/3) ChemicalRF (AVG)%RSDStockt = 3.5t = 5Port 1Port 2 ( g/L)( g/L)( g/L)( g/L)( g/L) Acetone0.0220.3270.1293.0304.4314.5194.3 Carbon Disulfide1.9614.92.21.61.10.80.2 Chlorobenzene2.603.2191.3167.3135.8151.448.4 Ethyl Acetate0.010.0213.1200.1167.6189.7107.2 Methyl Methacrylate 0.0410.78.57.76.77.32.1 Toluene5.324.2118.1107.291.195.526.1 *Port 1 is before the reactor*Port 2 is after the reactor Table 34. 20 mL/min Flow Test (Series 3) Raw Data (4/25/3) ChemicalRF (AVG)%RSDStockt = 3.5t = 5Port 1Port 2 ( g/L)( g/L)( g/L)( g/L)( g/L) Acetone0.0220.3609.0520.9356.8427.1297.8 C arbon Disulfide1.9614.911.05.37.522.716.8 Chlorobenzene2.603.2236.1241.3194.889.529.1 Ethyl Acetate0.010.0253.8229.0205.7186.251.5 Methyl Methacrylate 0.0410.741.438.132.525.94.6 Toluene5.324.2140.7136.9113.327.611.7 *Port 1 is before the reactor*Port 2 is after the reactor Table 35. 10 mL/min Flow Test (Series 3) Raw Data (4/27/3) ChemicalRF (AVG)%RSDStockt = 3.5t = 5Port 1Port 2 ( g/L)( g/L)( g/L)( g/L)( g/L) Acetone0.0220.3609.6408.0259.9474.0163.7 Carbon Disulfide1.9614.90.52.01.91.90.5 Chlorobenzene2.603.2103.299.282.187.212.7 Ethyl Acetate0.010.0148.9129.1120.0127.019.6 Methyl Methacrylate 0.0410.710.39.58.28.50.8 Toluene5.324.2166.4135.0110.6129.710.0 *Port 1 is before the reactor*Port 2 is after the reactor

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82 Table 36. 1st Desorption Test Raw Data (5/13/3) ChemicalRF (AVG)%RSDt = 0t = 5 ( g/L)( g/L) Acetone0.0260.0184.9104.0 C arbon Disulfide2.2034.1194.583.4 Chlorobenzene2.5717.5217.7231.2 Ethyl Acetate0.2220.010.912.7 Methyl Methacrylate 0.0517.8376.1328.4 Toluene5.2618.8190.3119.2 RinseRinse (DUP ) 45 min Desorb45 min Desorb (DUP) ( g/L)( g/L)( g/L)( g/L) 93.284.7145.996.0 48.035.233.226.5 76.781.387.078.9 4.44.44.14.4 103.6105.2140.3117.5 47.643.745.838.2 Table 37. 2nd Desorption Test Raw Data (5/16/3) ChemicalRF (AVG)%RSDt = 0t = 5 ( g/L)( g/L) Acetone0.0260.0175.9150.1 Carbon Disulfide2.2034.1174.0148.4 Chlorobenzene2.5717.5165.8132.5 Ethyl Acetate0.2220.017.415.2 Methyl Methacrylate 0.0517.8211.6175.8 Toluene5.2618.8137.4120.9 RinseRinse (DUP ) 45 min Desorb24 hour Desorb24 hour Desorb (DUP) ( g/L)( g/L)( g/L)( g/L)( g/L) 97.280.172.555.783.8 53.543.345.429.033.2 54.252.346.741.649.1 5.75.14.62.32.1 71.868.952.443.449.4 46.441.836.331.635.9

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83 Table 38. SPME 1st Test Raw Data (5/28/3) ChemicalRF (AVG)%RSDStock Solutio nt = 3.5t = 5t = 7t = 9t = 11 ( g/L)( g/L)( g/L)( g/L)( g/L)( g/L) Acetone0.027816.4239.1256203227.95253.6233.13187.4147.63 Butyl Alcohol374.0471.0435248 165 Carbon Disulfide1.5430.260.763.967.5652.4943.0135.68 Chlorobenzene2.312.5114.7112.8104.189.9676.0861.5 Ethyl Acetate0.2013.643.839.438.535.730.2524.4 Indole208.0257.0180.09670.0 Methyl Methacrylate 0.05410.1221.6204.6191.1173.52149.3119.3 Toluene3.8118.469.472.565.3558.649.9442.84 Table 39. SPME 2nd Test Raw Data (5/29/3) ChemicalRF (AVG)%RSDStock Solutio n t = 3.5t = 5t = 7t = 9t = 11 ( g/L)( g/L)( g/L)( g/L)( g/L)( g/L) Acetone0.027816.4232.0251.0305.7207.7166.6129.2 Butyl Alcohol458.496.087.046.046.034.0 Carbon Disulfide1.543 0.2106.046.348.727.017.411.2 Chlorobenzene2.312.5 211.0148.3145.082.850.324.6 Ethyl Acetate0.2013.653.628.829.018.913.57.9 Indole107.166.061.00.00.00.0 Methyl Methacrylate 0.05410.1250.3117.5113.666.840.4204.6 Toluene3.8118.4104.587.186.852.432.972.5 Table 40. SPME 3rd Test Raw Data (6/7/3) ChemicalRF (AVG)%RSDStock Solutio n t = 3.5t = 5t = 7t = 9t = 11 ( g/L)( g/L)( g/L)( g/L)( g/L)( g/L) Acetone0.027816.4198.0178.8158.0122.4 Butyl Alcohol0.2700.4720.3530.3330.2800.341 C arbon Disulfide1.5430.292.461.756.950.3 Chlorobenzene2.312.5160.2133.8131.1110.6 Ethyl Acetate0.2013.635.432.131.226.6 Indole0.2100.2900.2150.2070.1070.189 Methyl Methacrylate 0.05410.1120.7111.8112.390.7 Toluene3.8118.465.351.350.444.0

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84 Table 41. SPME 4th Test Raw Data (6/14/3) ChemicalStock Solutiont = 3.5t = 5Port 1Port 2 ( g/L)( g/L)( g/L)( g/L)( g/L) Butyl Alcohol589.0752.0765.0661.043.0 Indole3009.02117.02063.02343.075.0 *Port 1 is before the reactor*Port 2 is after the reactor Table 42. SPME 5th Test Raw Data (6/15/3) ChemicalStock Solutiont = 3.5t = 5Port 1Port 2 ( g/L)( g/L)( g/L)( g/L)( g/L) Butyl Alcohol374.0344.0311.0491.032.0 Indole2005.01798.01987.02029.049.0 *Port 1 is before the reactor*Port 2 is after the reactor 0 20 40 60 80 100 0.02.04.06.08.0 Time (hrs)C/Co (%) 3 Lamps 2 Lamps 1 Lamp 2 Lamp (duplicate) Figure 30. Normalized removal of toluene over the course of 6 hours. The flow rate in all of the experiments was 10 mL/min and the system was operated in circulation mode with a 1-liter sour ce tank. Removal represents overall removal in the system.

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85 0 20 40 60 80 100 120 0.02.04.06.08.0 Time (hrs)C/Co (%) 3 Lamps 2 Lamps 1 Lamp 2 Lamp (duplicate) Figure 31. Normalized removal of methyl me thacrylate over the course of 6 hours. The flow rate in all of the experiment s was 10 mL/min and the system was operated in circulation mode with a 1liter source tank. Removal represents overall removal in the system. 0 20 40 60 80 100 120 0.02.04.06.08.0 Time (hrs)C/Co (%) 1 Lamp 2 Lamp (duplicate) Figure 32. Normalized removal of carbon disulf ide over the course of 6 hours. The flow rate in all of the experiments was 10 mL/min and the system was operated in circulation mode with a 1-liter sour ce tank. Removal represents overall removal in the system.

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86 0 20 40 60 80 100 120 0.02.04.06.08.0 Time (hrs)C/Co (%) 3 Lamps 2 Lamps 1 Lamp 2 Lamp (duplicate) Figure 33. Normalized removal of ethyl acetate over the course of 6 hours. The flow rate in all of the experiments was 10 mL/min and the system was operated in circulation mode with a 1-liter sour ce tank. Removal represents overall removal in the system.

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87 REFERENCES Anheden, M.; Goswami, D. Y.; Svedber g, G., 1996. Photocatalytic Treatment of Wastewater From 5-Fl uorouracil Manufacturing. Transactions of the ASME, 118:2. Bekblet, M.; Baleioglu, I., 1996. Photocatalytic Degradation Kinetics of Humic Acid in Aqueous TiO2 Dispersions: The Influence of Hydrogen Peroxide and Bicarbonate Ion. Wat. Sci. Tech., 34:9:73. Bideau, M.; Claudel, B.; Dubien, C.; Faure, L.; Kazouan, H., 1995. On the Immobilization of Titanium-D ioxide in the Photocatalytic Oxidation of Spent Waters. Journal of Photochemistry and Photobiology A-Chemistry, 91:2:137. Blake, D. M., 1999. Bibliography of Work on the Heterogeneous Photocatalytic Removal of Hazardous Compounds from Water and Air. National Renewable Energy Laboratory, August 1999. Blake, D. M.; Webb, J.; Turchi, C.; Ma grini, K., 1991. Kinetic and Mechanistic Overview of TiO2-Photocatalyzed Oxidation Re actions in Aqueous-Solution. Solar Energy Materials, 24:584. Block, S. S.; Seng, V. P.; Goswami, D. W ., 1997. Chemically Enhanced Sunlight for Killing Bacteria. Journal of Solar Energy Engineering, 119:85. Bonsen, E.; Schroeter, S.; Jacobs, H.; Br oekaert, J. A. C., 1997. Photocatalytic Degradation of Ammonia with TiO2 as Photocatalyst in the Laboratory and under the use of Solar Radiation. Chemosphere, 34:7:1431. Butterfield, I. M.; Christensen, P. A.; Curtis, T. P.; Gunlazuardi, J., 1997. Water Disinfection Using an Immobilised Titanium Dioxide Film in a Photochemical Reactor with Electric Field Enhancement. Wat. Res., 31:3:675. Chen, P. H.; Chen, C.; Jenq, C. H., 1995. TiO2 Photocatalysis to Remove the Trace Organic in Drinking Water. Water Supply, 13:3/4:29. Cooper, A. T.; Goswami, Y. D.; Block, S. S., 1998. Solar Photochemical Detoxification and Disinfection for Water Treatment in Tropical Developing Countries. J. Adv. Oxid. Technol., 3:2:151.

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88 Cooper, A. T.; Goswami, Y. D., 1999. Evaluation of Solar Photosensitization of Benzene, Toluene, and Escherichia Coli with Methylene Blue and Rose Bengal. Proceedings of the Renewable and Advanced Energy Systems for the 21st Century in Lahaina, Maui, HA, 1. Crittenden, J. C.; Liu, J.; Hand, D. W.; Perram, D. L., 1997. Photocatalytic Oxidation of Chlorinated Hydrocarbons in Water. Wat. Res., 31:3:429. Davis, A.P.; Hao, O. J., 1991. Reactor Dynami cs in the Evaluation of Photocatalytic Oxidation Kinetics. Journal of Catalysis, 131:285. Denisov, E. T., 1977. Liquid-Phase Oxidation of Oxygen-Containing Compounds. Consultants Bureau, New York. D’Oliveira, J.; Al-Sayyed, G.; Pichat, P., 1990. Photodegradation of 2and 3Chlorophenol in TiO2 Aqueous Suspensions. Environ. Sci. Technol., 24:7:990. Emanuel, N. M., 1984. Oxidation of Organic Compounds: Medium Effects in Radical Reactions. Permagon Press, Oxford. The Federal Register, Washington, 36:236:68088. Gao, X.; Wachs, I., 1999. TitaniaSilica as Catalysts: Molecular Structural Characteristics and Physico-Chemical Properties. Catalysis Today, 51:233. Glaze, W. H., 1990. Chemical Oxidation. Chapter 12, Water Quality and Treatment: A Handbook of Community Water Supplies, Pontius, F. W., AWWA, 4:747. Goswami, D. Y.; Mathur, G. D.; Jotshi C. K., 1994. Methodology of Design of NonConcentrating Solar Detoxification Systems. Engineering Systems Design and Analysis, 3:1. Goswami, Y.D., 1995. Engineering of Sola r Photocatalytic Detoxification and Disinfection Processes. Chapter 3, Advances in Solar Energy, Boer, K. W., ASES, 10:165. Goswami, Y. D.; Blake, D. M., 1996. Cleaning up with Sunshine. Mechanical Engineering, August 1996:56. Goswami, D. Y.; Trivedi, D. M.; Block S. S., 1997. Photocatalytic Disinfection of Indoor Air. Journal of Solar Energy Engineering, 119: 92. Goswami, Y. D., 1999. Recent Developments in Photocatalytic Detoxification and Disinfection of Water and Air. Proc eedings of the ISES 1999 Solar World Congress in Jerusalem, Israel. Hand, D. W.; Perram, D. L.; Crittenden, J. C., 1995. Destruction of DBP Precursors with Catalytic Oxidation. Journal AWWA, June 1995:84.

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89 Hingorani, S.; Greist, H.; Goswami, T.; Go swami, Y., 2000. Clean-up of Contaminated Indoor Air Using Photocatalytic Technology. Proceedings of the 12th Symposium on Improving Building Systems in Hot and Humid Climates in San Antonio, TX. Brendl, Andreas; Beck, Bernd; Clark, Timot hy; Glen, Robert. “Prediction of the nOctanol/Water Partition Coefficient, logP Using a Combination of Semiempirical MO-Calculations and a Neural Network.” Computer Chemistry Center. January 16, 2003. June 18, 2003 Eaton Chemical Incorporated. “Eaton Chemical Incorporat ed: Solvent List.” July 15, 2001. June 18, 2003 . US Environmental Protection Agency. “T echnology Transfers Network Air Toxics Website: Methyl Methacrylate.” February 12, 2003. June 18, 2003 . General Electric Company. “Fused Quartz Properties and Usage Guide.” October 11, 2000. June 18, 2003 . Degussa AG. “Aerosil.” June 25, 2003 . Kawaguchi, H.; Furuya, M., 1990. Photodegrada tion of Monochlorobenzene in Titanium Dioxide Aqueous Suspensions. Chemosphere, 21:12:1435. Klausner, J. F.; Goswami, D. Y., 1993. So lar Detoxification of Wastewater Using Nonconcentrating Reactors. AIChE Symposium Series, 295:89:445. Klausner, J. F.; Martin, A. R.; Goswami, D. Y., 1994. On the Accura te Determination of Reaction Rate Constants in Batch-Type So lar Photocatalytic Oxidation Facilities. Journal of Solar Energy Engineering, 116:19. Lane, H. W.; Behrend, A. F., 1999. Advan ced Life Support Plan. Document #CTSDADV-348 (REV B) presented for the Crew and Thermal Systems Division in Houston, TX. Lange, K. E.; Lin, C. H., 1998. Advanced Life Support Program: Requirements Definition and Design Considerations. Document # CTSD-ADV-245 (REV A) presented for the Crew and Thermal Systems Division in Houston, TX. Lichtin, N. N.; Dong, J.; Vijayakumar, K. M., 1992. Photopromoted TiO2-Catalyzed Oxidative Decomposition of Organic Pollutants in Water and in the Vapor Phase. Water Poll. Res. J. Canada, 27:1:203. Liu, T.; Cheng, T. 1995. Effects of SiO2 on the Catalytic Properties of TiO2 for the Incineration of Chloroform. Catalysis Today, 26:71.

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90 Londeree, D. J., 2002. Silica-titania Composites for Water Treatment. Thesis presented to the graduate school of the University of Florida. Luo, Yang,; Ollis, D. F., 1996. Heterogene ous Photocatalytic Oxidation of Trichloroethylene and Toluene Mixture in Air: Kinetic Prom otion and Inhibition, Time-Dependent Catalysis Activity. Journal of Catalysis, 163:1. Matsuda, A.; Kotani, Y.; Kogure, T.; Tats umisago, M.; Minami, T., 2000. Transparent Anatase Nanocomposite Films by the Sol-Gel Process at Low Temperatures. J. Am. Ceram. Soc., 83:1:229. Matthews, R. W., 1987. Photooxidation of Orga nic Impurities in Water Using Thin Films of Titanium Dioxide. Journal of Physical Chemistry, 91:3328. Matthews, R. W., 1993. Photocatal ysis in Water Purification: Possibilities, Problems, and Prospects. Photocatalytic Purification and Treatment of Water and Air, Ollis, D. F.; Al-Ekabi, H., Proceedings of the 1st International Conference on TiO2 Photocatalytic Purification and Treatme nt of Water and Air in London, Ontario, and Canada, 121. Nawrocki, J., 1997. The Silanol Group and its Role in Liquid Chromatography. Journal of Chromatography A, 779:29. Nishida, K.; Ohgaki, S., 1994. Photolysis of Aromatic Chemical Compounds in Aqueous TiO2 Suspensions. Wat. Sci. Tech., 30:9:39. Ollis, D. F., 1985. Contaminant Degradation in Water. Environmental Science and Technology, 19:480. Ollis, D. F.; Pelizzetti, E.; Serpone, N ., 1991. Destruction of Water Contaminants. Environ. Sci. Technol., 25:9:1523. Ollis, D.F.; Al-Ekabi, H., 1993. Photocatalytic Purification and Treatment of Water and Air. Proceedings of the 1st International Conference on TiO2 Photocatalytic Purification and Treatment of Water and Air in London, Ontario, and Canada. Rohrbacher, J., 2001. Photocatalytic Oxidation of Chlorobenzene Using Titania Catalyst. Non-Thesis project presented to the graduate school of the University of Florida. Sakthivel, S.; Geissen S. U.; Bahnemann, D. W.; Murugesan, V.; Vogelpohl, A., 2002. Enhancement of Photocataly tic Activity by Semiconductor Heterojunctions: AlphaFe2O3, WO3, and CdS Deposited on ZnO. Journal of Photochemistry and Photobiology A-Chemistry, 148:283. Schwarzenbach, Ren P., 1993. Environmental Organic Chemistry, John Wiley and Sons, New York.

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91 Serpone, N., 1995. Brief Introductory Rema rks on Heterogeneous Photocatalysis. Solar Energy Materials and Solar Cells, 38:369. Srinivasan, M.; Klausner, J. F.; Jotshi, C. K.; Goswami, D. Y., 1997. Solar Photocatalytic Treatment of BTEX Contaminated Gr oundwater. Proceedings of the ISES 1997 Solar World Congress. Standard Methods for the Exami nation of Water and Wastewater, 1998 (20th ed.). APHA, AWWA, and WEF, Washington. Torimoto, T.; Ito, S.; Kuwabata, S.; Yoneyama H., 1996. Effects of Adsorbents Used as Supports for Titanium Dioxide Loadi ng on Photocatalytic Degradation of Propyzamide. Environmental Science & Technology, 30:4:1275. Turchi, C. S.; Ollis, D. F., 1989. Mixed R eactant Photocatalysis: Intermediates and Mutual Rate Inhibition. Journal of Photocatalysis, 119:483. Turchi, C. S.; Ollis, D. F., 1990. Photocat alytic Degradation of Organic-Water Contaminants-Mechanisms Invol ving Hydroxyl Radical Attack. Journal of Catalysis, 122:178. USEPA, 1992. Methods for the Determina tion of Organic Compounds in Drinking Water. EPA/600/R-92/129, Springfield. Verschuerren, K., 1983. Handbook of Environmental Data on Organic Chemicals (2nd Edition). Van Nostrand Reinhold Company, New York. Vidal, A., 1998. Developments in Solar Photocatalysis for Water Purification. Chemosphere, 36:12:2593. Vijayaraghavan, S., 2000. The Effect of pH UV Intensity, and Dissolved Oxygen Content on the Photocatalytic Destruction of Toluene in Water. Thesis presented to the graduate school of the University of Florida. Windholz, M., 1976. The Merck Index: An Encycl opedia of Chemicals and Drugs (9th Edition). Merck & Co., Inc., Rahway, NJ. Yaws, C. L., 1999. Chemical Properties Handbook: Physical, Thermodynamic, Environmental, Transport, Safety, and He alth Related Properties for Organic and Inorganic Chemicals, McGraw-Hill Company, New York. Yu, H.; Wang, S., 2000. Effects of Wate r Content and pH on Gel-Derived TiO2-SiO2. Journal of Non-Crystalline Solids, 261:260. Zaidi, A. H.; Goswami, D. Y., 1995. So lar Photocatalytic Post-Treatment of Anaerobically Digested Distil lery Effluent. Proceedings of the American Solar Energy Society Annual Conferen ce in Minneapolis, MN., 51.

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92 BIOGRAPHICAL SKETCH Frederick Roland Holmes was born in Brad enton, Florida, on April 13, 1979. He is the first son born to his parents Stanley and Patricia Holmes. He has one younger brother Vincent and a younger sister Shannon. Freder ick grew up in the city of Spring Hill, Florida, where he graduated from high school in June of 1997. During his junior year at Springstead High School he became involve d in the Envirothon competition, which became the inspiration for his future occupation as an environmental engineer. After high school, Frederick moved to Gainesville where he attended the University of Florida to obtain his Bach elor of Science in Environmental Engineering degree. During his undergraduate work he met his wife April through work with the dorm area government. The two were married in July of 2002. Frederick entered graduate school in th e spring semester of 2002. Under the guidance of his advising profe ssor, Dr. Paul A. Chadik, Fr ederick performed research on the use of photocatalysis as a finishing proce ss for NASA. The results of that research are found in the preceding thesis.


Permanent Link: http://ufdc.ufl.edu/UFE0001204/00001

Material Information

Title: The Performance of a reactor using photocatalysis to degrade a mixture of organic contaminants in aqueous solution
Physical Description: Mixed Material
Creator: Holmes, Frederick Roland ( Author, Primary )
Publication Date: 2003
Copyright Date: 2003

Record Information

Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UFE0001204:00001

Permanent Link: http://ufdc.ufl.edu/UFE0001204/00001

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Title: The Performance of a reactor using photocatalysis to degrade a mixture of organic contaminants in aqueous solution
Physical Description: Mixed Material
Creator: Holmes, Frederick Roland ( Author, Primary )
Publication Date: 2003
Copyright Date: 2003

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THE PERFORMANCE OF A REACTOR USING PHOTOCATALYSIS TO
DEGRADE A MIXTURE OF ORGANIC CONTAMINANTS IN
AQUEOUS SOLUTION















By

FREDERICK ROLAND HOLMES


A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF ENGINEERING

UNIVERSITY OF FLORIDA


2003


































This document is dedicated to my wife April and all of the people who have helped me
along the way.















ACKNOWLEDGMENTS

I would like to begin by thanking my professor and advisor Dr. Paul A. Chadik.

His help in this research and my other education has been invaluable. I would also like to

extend my appreciation to the other members of my committee, Dr. David Mazyck and

Dr. Chang-Yu Wu.

I would like to thank the members of the Photocatalysis Seminar, especially Dr.

Powers, for their knowledge and suggestions on this research. I am also thankful for all

of the guidance and time Dr. Booth provided to this research in performing the analyses.

Additionally, I would like to thank NASA for providing the funding and support

for this research. I thank Jack Drwiega for putting together the reactor support and I

would like to thank Danielle Londeree for providing the formula used in creation of the

silica/titania photocatalyst.

Lastly, I would like to thank my family, Stanley, Patricia, Vincent, and Shannon

Holmes. Most importantly, I would like to thank God and my wife April. Without either

of them I could not accomplish the things that I have.
















TABLE OF CONTENTS
page

A C K N O W L E D G M E N T S ................................................................................................. iii

LIST OF TABLES ....................................................... ............ ....... ....... vi

L IST O F FIG U R E S .............. ............................ ............. ........... ... ........ viii

A B STR A C T ................................................. ..................................... .. x

CHAPTER

1 IN TRODU CTION ................................................. ...... .................

2 LITER A TU R E REV IEW ............................................................. ....................... 4

Photolysis and Photocatalysis..................................... .......................................4
Factors A affecting Photocatalysis ............................................ .......................... 6
R actor Type ................................................................ 7
pH .................................................................7
D issolv ed O xygen (D O ) ............................................................. .....................8
Interm ediates ................................................................ 9
B icarbonate A lkalinity............................................. 9
Light Intensity .............. ........... ...........................10
T em p eratu re ................................................................. ................... 11
Other Factors ......................................................................... ....... ......... 11
Enhancements to the Photocatalyst and Solution ....................................................12
H 20 2 ...................................... ...................................................... 12
TiO2 Supports ........................................................................ ......... ................... 13
A activated carbon ...................... ................ .................... ........13
Glass beads and filters............................ ........... .................. .... 13
Silica gel ......................................................................... ............................ 14
S iO 2/T iO 2 ............................................................................................... 1 5
S o l-g e l stru ctu re ..................................................................................... 1 5
Degradable Com pounds.............................................. 16
R eactio n K in ethics ................................................................................ 17
S u m m a ry .......................................................................................................1 8

3 M E T H O D S ........................................................................................................... 2 0

M making of the Silica-Titania Pellets ................................................................... 20









Pellet C om position ........................................ ................. ..... .... 20
A g in g .............................................................................2 3
T h e R e a cto r ........................................................................................................... 2 4
D esign of the R eactor ............................................. ...... ............................. 24
The Reactor System................... ......................... ......27
R eactor H ydrodynam ics ........................................................... .....................30
S am p le C o lle ctio n ................................................................................................. 3 3
S am p le A n aly sis ................................................................................................... 3 3
Perform ing Experim ents .................................................... ................................... 35
Initial D egradation.......... ..................... .................. .. .............. ............. 35
D eterm ining Effects of V olatility ................................... .......... .................. 37
A dsorption Experim ent ............................................... ............................ 40
D esorption Experim ents ............................................. ............................. 42
Oxygen as an Electron A cceptor..................................................................... 43
Photocatalytic Oxidation Experiments .... .......... .......................................45
Effects of U V radiation intensity .............................................................. 45
Effects of contact tim e......................................... .............. ............... 45
Experiments including indole and butyl alcohol............... ...................46

4 R E S U L T S .......................................................................... 4 8

Effects of UV Radiation Intensity .............. .......... ............................ 48
Effects of Empty Bed Contact Time ..................... ................... ...............52
Extended Duration Experiment ............................................................................59
Removal of Butyl Alcohol and Indole........................ ........ ...............59

5 SUMMARY AND CONCLUSIONS.....................................................................62

S u m m a ry ............................................................................................................... 6 2
C o n c lu sio n s........................................................................................................... 6 2

APPENDIX

A CHEMICAL INFORMATION ............................................................................64

B REACTOR INFORMATION...................................................... 73

C RAW DATA ............... ............................ .................. ........... 77

REFERENCES ..................... .... ......... ......................... 87

B IO G R A PH IC A L SK E TCH ..................................................................... ..................92








v
















LIST OF TABLES

Table pge

1 T arg et A n aly tes ...................................................... ................ .. 2

2 Researched Com pounds ........... .... .. ......... ................... ............... 17

3 Key Statistics from the Tracer Analysis........................................ ............... 32

4 Average %RSDs for the Analyses in this Research................... ............... 35

5 Important data gathered from the trend lines shown in Figures 25 and 26..............58

6 Results of the extended duration test performed for 23 hours ................ ............59

7 Table of Target A nalytes......... ................. ................... ................. ............... 64

8 Molecular Weight of Target Analytes.............................. ...............65

9 Henry's Constants and Partitioning Coefficients...............................................65

10 M elting Points/B oiling Points ............................................................................ 65

11 Sources of C ontam inant ........................................ .............................................66

12 Contam inant Generation in the ALS............................................... .................. 66

13 W ater Quality Requirem ents ........................................................ ............. 67

14 Spacecraft Trace Contaminant Generation Rates................... .......................... 67

15 Spacecraft Maximum Allowable Concentrations ......................................... 72

16 Predicted Retention Time Calculations......................................... ..............73

17 System Volume Calculation...................... ..... ............................. 74

18 KC1 Conductivities for Testing Probe Accuracy ....... ......................................74

19 Calculation of Flow Regime in the Reactor ..............................................75

20 Calculation of UV Energy at Reactor Surface ....................................................76









21 Initial R aw D ata Test (1/6/3)......................................................... ............... 77

22 V olatility Test R aw D ata (2/6/3)........................................ .......................... 77

23 Adsorption Test Raw D ata (3/8/3) ................................................ ............... 77

24 UV Optimization (3 Lamps) Raw Data (3/12/3)..........................................77

25 UV Optimization (2 Lamps) Raw Data (3/13/3)..........................................78

26 UV Optimization (1 Lamp) Raw Data (3/14/3) ............................................... 78

27 UV Optimization (2 Lamp Duplicate) Raw Data (3/17/3) ....................................78

28 11-Hour Adsorption Experiment Raw Data (4/3/3) ...........................................79

29 60 mL/min Flow Test (Series 2) Raw Data (4/6/3)......................................79

30 20 mL/min Flow Test (Series 2) Raw Data (4/9/3)......................................80

31 10 mL/min Flow Test (Series 2) Raw Data (4/7/3).......................................80

32 23-Hour Test Raw Data (4/16/3)................................................................. 80

33 60 mL/min Flow Test (Series 3) Raw Data (4/28/3)....................................81

34 20 mL/min Flow Test (Series 3) Raw Data (4/25/3)....................................81

35 10 mL/min Flow Test (Series 3) Raw Data (4/27/3).......................................81

36 1st D esorption Test Raw D ata (5/13/3)................................ ....................... 82

37 2nd Desorption Test Raw Data (5/16/3)........................................... 82

38 SPM E 1st Test R aw D ata (5/28/3) ................................................. ....... ........ 83

39 SPM E 2nd Test Raw D ata (5/29/3) ................................................ ............... 83

40 SPM E 3rd Test Raw D ata (6/7/3)....................................... ........................... 83

41 SPM E 4th Test Raw D ata (6/14/3).................................... .................... ............. 84

42 SPM E 5th Test R aw D ata (6/15/3).................................................. .. ... .......... 84
















LIST OF FIGURES


Figure page

1 Figure demonstrating the elevation of an electron from one energy state to
another due to U V radiation.. .......................................................... .....................6

2 A curve showing a series of experiments that were modeled using the Langmuir-
Hinshelwood equation............ ... .............. ...... .............................. 18

3 Picture showing an example of the 8 oz. jars, sitting on mixers and filled with
the silica-titania suspension, going through the gelling process. ..........................22

4 Suspension being transferred from the 8 oz. gelling to the assay plates used for
creating the pellet shape. ...................... .................... ... .... .... ............... 23

5 Diagram showing the aging process for the pellets. The dashed line is used for
the 5000 F to indicate that not all gels required this treatment ..............................24

6 UV transmittance curve for the quartz material used in constructing the reactor....25

7 Diagram showing the plans for the dimensions and shape of the reactor used for
containing the pellets............ ............................................................ .... .... .... 26

8 Picture of the reactor on its support stand and connected to the system used for
the testing ...........................................................................28

9 Diagram of the system setup used for testing the reactor's capabilities ..............28

10 A picture of the 4 L source tank used in reactor system for this research ..............29

11 E curve generated using the data from a tracer analysis performed on the reactor
used in this research. ............................ ........... ...... ...... ...... ...... 33

12 Target analyte degradation seen as a result of recycling the spiked solution
through the system .. .................................. .. .... ........ ...............37

13 Diagram demonstrating the setup used for estimating volatile losses of analytes
in the sy stem ...............................................................................39

14 Volatile losses in the system over an 8-hour period without the reactor in place....39

15 Diagram showing the setup used for saturating the catalyst pellets.........................40









16 Loss of toluene and chlorobenzene as a result of adsorption in the reactor system..41

17 Results of desorption experiments performed................ ................................. 43

18 Degradation of 5 NASA target analytes................. ...........................................49

19 Degradation of 5 NASA target analytes .................................................49

20 Degradation of 5 NASA target analytes........................................... ................ 50

21 Average normalized degradation seen in the two experiments performed with
2 UV lamps and a 1-liter source tank................. ............................ ............... 50

22 Removal of chlorobenzene is shown over the course of time as a function of the
contaminant remaining divided by the initial concentration introduced to the
reactor displayed as a percent...................................................................... ....... 5 1

23 Average results of two flow optimization experiments. ................ ..................52

24 Degradation of five target analytes in the reactor using three UV lamps and
operating the system in a single-pass mode after adsorption for five hours in a
circulation m ode had taken place.................................................. ............... 54

25 Trend lines produced for each target analyte. .................................. ............... 57

26 Trend lines produced for each target analyte. .................................. ............... 58

27 Results showing the degradation of butyl alcohol and indole as a result of 6
hours of exposure to U V radiation.. ...................... ............................................. 60

28 Data showing the ratio of each chemical's concentration in the sample from
Port 2 versus the sample from Port 1. ........................................... ............... 61

29 Concentration of NaCl in deionized water solution versus the conductivity read
on a Fisher Scientific conductivity probe............................. ...... .............75

30 Normalized removal of toluene over the course of 6 hours. ...............................84

31 Normalized removal of methyl methacrylate over the course of 6 hours ...............85

32 Normalized removal of carbon disulfide over the course of 6 hours...................85

33 Normalized removal of ethyl acetate over the course of 6 hours............................. 86















Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Engineering

THE PERFORMANCE OF A REACTOR USING PHOTOCATALYSIS TO
DEGRADE A MIXTURE OF ORGANIC CONTAMINANTS IN
AQUEOUS SOLUTION



By

Frederick Roland Holmes

August 2003

Chair: Dr. Paul A. Chadik
Major Department: Environmental Engineering Sciences

A study was performed to investigate the use of an annular reactor filled with

photocatalyst pellets (silica gel support doped with Degussa P25 titanium dioxide)

arranged in a packed-bed-style to oxidize selected organic chemicals in aqueous solution.

The annular reactor had a volume of 436 mL with 327 mL of that being interparticle

space. The reactor was configured to a system setup which included a source tank, the

reactor, a PTFE polytetrafluoroethylenee) tubing pump head with modular speed drive, a

dampener for controlling flow, 2 sampling ports, and a test stand to hold the reactor with

slots for four 8-watt UV lamps.

Eight target analytes (acetone, butyl alcohol, carbon disulfide, chlorobenzene, ethyl

acetate, indole, methyl methacrylate, and toluene) were tested for degradability in a

mixed solution within the reactor system. Volatile losses were assessed as many of these

chemicals are classified as VOCs.









The photocatalyst pellets were found to be capable of adsorbing target analytes

when exposed to solution containing the target analytes. When exposed to solution

devoid of the target analytes, however, desorption of the analytes from the silica-titania

pellets occurred.

Optimization was investigated with respect to UV radiation intensity and empty

bed contact time (EBCT). One UV lamp resulted in the same level of degradation of

contaminant as three UV lamps. An increased EBCT was found to increase the

photocatalytic degradation observed in the reactor.

All 8 of the target analytes were shown capable of complete oxidation using the

reactor system. Degradation rate constants (k values) of .019 min-, .065 min1, .057 min

, .059 min-, and .128 min' were found for acetone, chlorobenzene, ethyl acetate, methyl

methacrylate, and toluene respectively. These rate constants are comparable to those

experienced by other researchers working with a slurry of TiO2.














CHAPTER 1
INTRODUCTION

The goal of the research discussed in this thesis is to provide a finishing process for

treating the wastewater produced by NASA in their Advanced Life Support System

(ALS). NASA is in the planning stages of a manned space trip to Mars (Lane and

Behrend, 1999). The ALS is to provide the support system allowing astronauts to travel

the estimated 266 days to complete the mission. Fresh water that meets the requirements

set forth in the Requirements Definition and Design Consideration (Lange and Lin, 1998)

is an important part of the ALS. These requirements are displayed in Table 13 (Appendix

A). High-energy costs are incurred to move mass in NASA space missions. As a result,

NASA desires to minimize the amount of mass required for space transport. This means

that in addition to treating the wastewater, the finishing process must do so while

minimizing space and energy requirements.

Wastewater will be collected through two different sources in the space module.

One source of wastewater is from the crew in the module. Shower water, wash water,

urine, and wastewater from the solid waste processor are among the contributors to the

wastewater stream. Machinery within the ALS will be the second source of wastewater.

Condensate on the walls, panels, and instruments will be collected for treatment. A list of

all organic contaminants expected in the ALS wastewater is found in NASA

documentation, provided in Table 14 (Appendix A). The rate that this water is expected

to be produced is 28 L/person/day based on an assumed number of six astronauts.









Collected wastewater from the ALS will be treated through a series of treatment

processes. Those processes include biological removal, ion exchange, reverse osmosis,

and chemical disinfection. These processes remove many water contaminants; however,

there remain some organic chemicals and microbial constituents in the water that are not

expected to be removable by the aforementioned treatment processes. Of those

remaining chemicals, the 8 shown in Table 1 were chosen as target analytes for this

research. This thesis focuses on a finishing process to remove these chemicals.

Table 1. Target Analytes
Acetone
Butyl Alcohol
Carbon Disulfide
Chlorobenzene
Ethyl Acetate
Indole
Methyl Methacrylate
Toluene

The process chosen for study as a potential NASA finishing process is

photocatalytic oxidation. Photocatalysis was chosen as a viable option due to its

potentially small mass, space, and energy requirement. In addition, photocatalysis has

been shown to be effective for the removal of organic compounds, inorganic compounds,

and microbes. This thesis will only consider the removal of the organic chemicals shown

in Table 1. Included in the compounds that have proven removable are three among the

target contaminants for this research, chlorobenzene (Rohrbacher, 2001), acetone

(Hingorani et al., 2000), and toluene (Vijayaraghavan, 2000; Luo and Ollis, 1996).

This research was performed in a 436 mL flow-through annular reactor designed

for the purpose of maximizing exposure of the photocatalyst to the ultraviolet (UV) light.

A previously designed silica-titania composite (Londeree, 2002) was used as the









photocatalyst in the reactor. The photocatalyst was formed into a pellet of approximately

3 mm diameter. These pellets were then packed within the annular reactor. Solutions

containing the target analytes were subjected to photocatalytic oxidation treatment within

the reactor, and the product waters were analyzed using gas chromatography / mass

spectrometry (GC/MS) and gas chromatography / flame ionization detection (GF/FID) to

asses the efficiency of the treatment process.

The hypothesis for this research was that an annular reactor, filled with a

titania/silica composite, and arranged in a packed bed formation could be used to

photocatalytically oxidize the eight target analytes listed in Table 1. Several objectives

were set forth in this research to accomplish the proving of this hypothesis.

* Demonstrate the reactor's ability to degrade the 8 target analytes (acetone, butyl
alcohol, carbon disulfide, chlorobenzene, ethyl acetate, indole, methyl
methacrylate, and toluene).

* Determine the reactor's optimal degradation performance with respect to UV
intensity and flow rate (contact time).

* Quantify reaction rate constants for removal of the organic chemicals.

* Assess the reactor's effluent conductivity, dissolved oxygen concentration, pH, and
temperature.














CHAPTER 2
LITERATURE REVIEW

Photolysis and Photocatalysis

The degradation of both organic and inorganic constituents with light has been well

established. The words degradation and photocatalytic oxidation used in this thesis will

always refer to the disappearance of the initial compound or transformation of that

compound into another. The words do not mean that the contaminant has been

completely oxidized or entirely removed. Degradation has been achieved using two main

methods important to the current research, photolysis and photocatalysis.

Photolysis is a process that involves the use of light to degrade molecular

compounds toward their base constituents, often carbon dioxide and water. During

photolysis a direct photochemical transformation takes place where energy from light

attacks the bonds within a molecular compound, thereby degrading the compound.

Unfortunately, not all compounds can be degraded in this manner. Specifically,

chlorobenzene cannot be degraded photolytically (Nishida and Ohgaki, 1994). For this

reason, photocatalysis becomes necessary.

Photocatalytic oxidation uses light energy to react with a molecule leading to the

formation of radicals in the solution. Several different molecules have been shown

capable of promoting photocatalysis, from methylene blue (Cooper and Goswami, 1999),

to ZnO (Sakthivel et al. 2002), to TiO2 (Goswami et al., 1997). The radicals can be

formed from the molecule itself or from constituents in the solution containing the

molecule. These radicals are then capable of oxidizing or reducing and thereby









destroying the target contaminants. There are three known highly reactive intermediates

formed by the process of photocatalysis, 102 (oxygen singlets), OH- (hydroxyl radicals),

and H202 (hydrogen peroxide). Research suggests that the OH- is the prominent player in

photocatalysis (Turchi and Ollis, 1990). The hydroxyl radical's ability to degrade

contaminants comes from its high level of oxidation power, which is more than twice as

strong as chlorine (Goswami and Blake, 1996). The hydroxyl radical breaks down

chemicals through a series of steps. The exact steps by which the degradation process

takes place are not known, but the generally accepted hypothesis is that hydrogen atoms

are removed and oxygen atoms are added. It is also known that the process is preferential

to attacking double bonds as opposed to single (Emanuel, 1984).

Heterogeneous photocatalysis has been used to enhance the general process of

photocatalysis. Heterogeneous photocatalysis uses a metal or dye, which is not the target

of degradation, to absorb the electromagnetic energy and create the hydroxyl radicals.

Titanium dioxide (TiO2) has been the most popular choice as a catalyst for use in

heterogeneous photocatalysis, because TiO2 is inert under most conditions and therefore

unlikely to react directly with the target compounds. TiO2 has been shown by many

researchers to be very effective as a photocatalyst (Chen et al., 1995; D'Oliveira et al.,

1990). UV radiation at approximately 388 nm strikes the TiO2 particle exciting an

electron from the ground state to an excited state (388 nm is the chosen wavelength of

light because it provides the necessary energy to excite the electron). At this point an









HO2 HO + OH-
02 + H+ or 02 + H +2

Ti02 hv
VB / \/
H20
OH. + H

(Blake et al., 1991)

Figure 1: Figure demonstrating the elevation of an electron from one energy state to
another due to UV radiation. Several possible electron donors (02, H202) and
H20) are then shown adding their electron to the hole and producing their
products.


electron acceptor, typically oxygen, accepts the excited electron leaving an electron hole

on the surface of the Ti02 (Turchi and Ollis, 1990). This hole is then available to accept

electrons from OH- ions, oxygen, or water to create the hydroxyl radicals. Those radicals

then oxidize the pollutants in the water. The following equations describe the process of

using OH- as the precursor for the radicals and then the effects of the radical formation

(Blake et al., 1991).

OH- + TiO2 + hv TiO2- + OH- (Eq.1)

TiO2- + 02 + H+ TiO2 + HO02 (Eq.2)

2H02- H202 + 02 (Eq.3)

TiO2- + H202 + H+ TiO2 + H20 + OH- (Eq.4)

Pollutant + OH POH- (Eq.5)

POH- + (02, H202, OH- ) nCO2 + mH20 (Eq.6)

Factors Affecting Photocatalysis

As previously discussed, there are several steps required in carrying out the process

of photocatalytic oxidation. Any of those steps have the potential to limit the rate of









pollutant degradation. The following sections will discuss factors that play a part in

enhancing or retarding the photocatalytic process.

Reactor Type

TiO2 has been studied through two different modes of contact with contaminated

waste streams. One method is to introduce slurry of TiO2 to the wastewater. The other

method involves fixing the TiO2 to a surface, often a filter or the outside of a tube and

then moving the water over the surface of the TiO2. Both methods have their limitations.

When using a TiO2 slurry degradation of the target pollutants is often highly efficient;

however, the complication comes from the inability to effectively remove the TiO2 from

the effluent water. The average size of Degussa P25 TiO2 (the brand used in this

research) is only 21 nm in diameter, and therefore expensive filtration systems would be

required to remove the TiO2 rendering the entire process not viable for space missions.

Fixing the TiO2 to a surface solves the issue of TiO2 in the effluent but yields other

disadvantages. Scouring of TiO2 from the fixed surfaces has been observed (Butterfield

et al., 1997). The more pressing concern is that the short life of the OH- can lead to

situations where the contaminant may not come into contact with the TiO2 surface and

thus never be degraded. "The convenience of catalyst immobilization is bought at the

price of diffusion distance from pollutant to catalyst surface" (Ollis et al., 1991). This led

to the concept of immobilization of the TiO2 on particles creating slurry that would later

be easily removable due to its larger size (for this research approximately 3 mm in

diameter).

pH

One of the most problematic factors affecting the use of photocatalysis as a viable

means of water treatment is pH. Understanding the effect of pH is difficult due to the









mixed results obtained during experimentation. The effect of pH on the removal of

distillery effluent (Zaidi and Goswami, 1995) and 3-Chlorophenol (D'Oliveira et al.,

1990) was found to be minimal, while the effect of pH on the removal of toluene was

found to be significant (Vijayaraghavan, 2000). Highly acidic solutions (pH 3) have

been found to assist in the degradation of some molecules such as chlorobenzene that

were found to have an optimum pH of 3.5 (Kawaguchi, Furuya, 1990). A high pH (pH

10) has also been found to help in the oxidation of ammonia and trace organic (Bonsen

et al., 1997; Chen et al., 1995). Low pH preference has been explained as the ability of

the H202 to make more OH- (Chen et al., 1995). A high pH has been credited with

providing enough of the necessary hydroxyl ions for making the hydroxyl radicals

(D'Oliveira et al., 1990; Chen et al., 1995). The research indicates pH will be an

important factor to assess in the analysis of photocatalysis as an effective means of

treatment for the ALS.

Dissolved Oxygen (DO)

Dissolved oxygen (DO) in sufficient amounts has been found by multiple

researchers to be a necessity to the photocatalytic process. Hand et al. (1995) found that

below 2.0 mg/L the rate of degradation for disinfection byproducts was significantly

decreased. Vijayaraghavan (2000) found that when sodium sulfite was used to remove

oxygen from water that was then contaminated with toluene, the rate of toluene

degradation was significantly decreased. Other researchers have made statements about

the importance of DO in the photocatalytic oxidation process (Zaidi and Goswami, 1995;

Ollis et al., 1991). "Several researchers have observed that oxygen adsorbed on the

titanium dioxide surface prevents the recombination of hole/electron pairs by trapping









electrons and therefore, plays an important role in semiconductor mediated reactions"

(Vidal, 1998). It does stand to reason that a replacement electron acceptor could be

found, such as H202 (Ollis et al., 1991). However, it is likely that oxygen will prove to

be the cheapest and safest electron acceptor for use in the space missions, and for this

reason oxygen will be the electron acceptor used in this research.

Intermediates

Formation of oxidation intermediates in the photocatalytic reaction is a concern in

water treatment because some intermediates have the potential to be more toxic than the

original contaminants (Torimoto et al., 1996). Intermediates also occupy sites on the

surface of the TiO2 where the photocatalytic reactions with target compounds are meant

to occur (Chen et al., 1995). Several intermediates have been detected in a variety of

degradation processes. Catechols, hydroquinones, biphenyls, formaldehyde, and glyoxal,

are a few of the intermediates that have been detected during the photocatalytic

degradation of hydrocarbons and aromatics (Kawaguchi and Furuya, 1990; Denisov,

1977). One series of experiments claims that the use of TiO2 on the surface of activated

carbon suppressed the amount of intermediates in the solution by trapping the

intermediates until they were fully degraded by photocatalysis (Torimoto et al., 1996).

Bicarbonate Alkalinity

Alkalinity in the water has been shown to significantly decrease the rate of

photocatalytic oxidation in several cases. One researcher observed as much as a 67%

decrease in the photocatalytic degradation rate of chlorobenzene when 500 mg/L of

HCO3 was added to the water (Blake et al., 1991). Bekbolet (1996) observed a

significant decrease in the degradation of humic acids. He attributed the decreased rate to

bicarbonate ions scavenging the hydroxyl radicals that are necessary for photocatalysis.









Equation 7 describes the reaction whereby bicarbonate ions and hydroxyl radicals react to

form water and the significantly less powerful oxidant, the carbonate radical.

HCO3- + OH- -- CO3- + H20 (Eq.7)

Light Intensity

Illumination of the photocatalyst at an appropriate intensity is essential to the

photocatalysis process. Some observations have suggested that photocatalysis may even

be impossible for water with high turbidity levels capable of blocking out light (Anheden

et al., 1996). Most research appears to agree that there is a balance to be found with

increasing or decreasing the light intensity. One study suggests that a decrease in UV

intensity decreased the energy consumption and yet increasing UV intensity decreased

the efficiency of energy use (Klausner and Goswami, 1993). Light intensity application

is a balance between capital cost and operating costs. A higher light intensity will

increase the rate of the reaction meaning a smaller reactor size will be required leading to

a lower capital cost and a higher operating cost. A decrease in light intensity will

decrease the operating costs, but increase the size of the reactor required to achieve a

specified level of photodegradation. There is a limit at which an increase in UV intensity

no longer increases the photocatalysis rate as some other step in photocatalysis will

become rate limiting. Ollis et al. (1991) reported that at low intensities the degradation

rate is linearly dependent upon intensity. In some (not quantitatively defined)

intermediate range there is a square root dependence on intensity (I) where the rate varies

as 10.5. Finally there comes a point at high UV intensities where the rate no longer has

any dependence on UV radiation. UV intensity is also based on the refraction of light

caused by the TiO2 itself and the contaminants within the wastewater to be treated. This









is due to the scattering of the light photons required for exciting the TiO2's electrons

(Chen et al., 1995; D'Oliveira et al., 1990).

Temperature

The effects of temperature on photocatalysis are mixed in the research literature.

One study found a linear increase in the degradation rate of toluene with increasing

temperature up to 90 OC (Vijayaraghavan, 2000). It would appear that with regards to

diffusion of OH- from the surface of the TiO2 to the pollutant a higher temperature would

increase the photocatalytic reaction rate. Higher temperatures may have a negative

effect, however, on the concentration of dissolved oxygen in the solution. Dissolved

oxygen levels below a certain point may allow for electron-hole recombination at the

surface of the TiO2. Electron-hole recombination is dominant unless there is an electron

acceptor such as oxygen available to absorb the excited electron.

Other Factors

There are many other factors that can affect photocatalysis. Common acids and

anions have been shown to affect photocatalysis. The effect of HC3- has already been

mentioned for its effects as alkalinity. The rate of mineralization of targeted

contaminants has also been shown to decrease in the presence of the following acids:

HC1, H3PO4, H2SO4, HNO3, and perchloric acid in the order shown at the top of page 18

(Ollis et al., 1991).

HC1 > H3PO4 > H2SO4 > HNO3 > perchloric acid

Inorganic substances and salts have also been found to decrease the reaction rates (Block

et al., 1997; Vidal, 1998), because they take up sites on the TiO2 preventing the OH- from

reacting with holes on the TiO2 surface. Additionally, some of these substances have the

possibility of reacting with the hydroxyl radical after it forms.









Enhancements to the Photocatalyst and Solution

Several different methods may be used to enhance the process of photocatalysis.

Possible additives to the photocatalyst are platinum, tungsten, palladium, peroxydisulfate,

silver, and ferrioxalate (Goswami, 1995; Goswami, 1999; Ollis et al., 1991; Crittenden et

al., 1997). The addition of hydrogen peroxide to the contaminated solution is another

enhancement method that has been intensely studied. Varying the pollutant concentration

has also been found to affect the photocatalytic rate (Anheden et al., 1996). Various

supports for the photocatalyst have also been tried. The advantages and disadvantages to

each of these enhancement possibilities are discussed in the following sections.

H202

Hydrogen peroxide is a potential additive to the photocatalytic process that has

been studied in depth. Addition of H202 has produced widely different results under

varying circumstances. Hydrogen peroxide has been shown to increase the rate of

mineralization of target compounds eleven fold (Lichtin et al., 1992). However, it has

also been shown to decrease the rate of photocatalysis (Bekbolet and Baleioglu, 1996).

This wide variance is not surprising based on Equations 8-10 (Bekbolet and Baleioglu,

1996).

e- + H202 + H+ H20 + OH- (Eq. 8)

H202 + OH H20 + H02- (Eq.9)

HO02 + OH- H20 + 02 (Eq. 10)

Equation 8 shows hydrogen peroxide as an electron acceptor similar to that of oxygen.

Research has found that the use of H202 can help make up for a lack of oxygen (Ollis et

al., 1991). Equation 8 also shows the production of a hydroxyl radical, which is also a

benefit to the photocatalytic process. Equations 9 and 10 demonstrate the problem with









hydrogen peroxide; it will consume hydroxyl radicals meant for attacking the target

pollutants. One researcher (Bekbolet, 1996) said that, "it could be seen that the

degradation of humic acid first increased when hydrogen peroxide increased and reached

a maximum beyond which they appeared to decline at high H202 doses."

TiO2 Supports

In an attempt to overcome the issues surrounding the method of contact between

the solution and the photocatalyst, many supports have been tried. Silica, activated

carbon, glass beads, and filters represent the bulk of the research into support structures

for TiO2. Each support has its particular benefits and detriments. For the NASA

research, a silica gel support was chosen due to its transparency to UV radiation and

possible adsorption capability for the contaminants.

Activated carbon

Activated carbon offers the advantage of added surface area to adsorb pollutants

and intermediates, holding them near the site of hydroxyl radical formation. Activated

carbon is, however, opaque and so will have a negative impact on the amount of UV

energy reaching the TiO2 particles. For this reason activated carbon was not used as a

support structure in this research.

Glass beads and filters

Both glass beads and filters have been studied in past research as possible support

structures for TiO2 (Ollis and Al-Ekabi, 1993). Although both have demonstrated minor

efficiency in degrading specific target compounds, there are concerns with both methods.

One concern is that the TiO2 may be scoured off of either surface (Bideau et al., 1995).

A second problem is that adsorption of contaminants and intermediates to these surfaces









is not probable. For these reasons neither of these supports was chosen for use in this

research.

Silica gel

The use of SiO2 as a support offers several benefits. Pore structure, surface area,

and hydroxyl groups that encourage the adsorption of pollutants to its surface (Yu and

Wang, 2000; Liu, Cheng, 1995; Gao and Wachs, 1999) are among the advantages to

using a silica gel matrix as the support structure for the TiO2. Importantly, it offers these

benefits without compromising the ability of the light energy to strike the TiO2 particles

(Matsuda et al., 2000).

Having noted the benefits pointed out in the literature it is important to recognize

that there is research that indicates disadvantages to using silica gel as a photocatalyst

support. Matthews (1998) performed an experiment using a reactor similar to the one

built for this current NASA research. A silica gel matrix was used as an adsorbent

support for TiO2, and this system achieved excellent degradation of the target

compounds. However, in a later article (Ollis and Al-Ekabi, 1993), Matthews reported

that the degradation of the initial compounds was promising, but the byproduct formation

rendered the process not viable for treatment. Matthews went on to state the reason as

being due to the byproducts becoming trapped in pores of the silica gel that do not

receive contact from hydroxyl radicals produced near other pores on the silica gel

surface. The main difference between the research of Matthews and that being reported

in this thesis is the concentration of TiO2 in the silica gel. The pellets created by

Matthews (.15 g TiO2 per 80 g SiO2) contained two orders of magnitude less titanium

dioxide than that of the ones designed by Londeree (2002) for this research. Presumably,

this increased ratio of TiO2 to SiO2 will allow for photocatalysis over the entire surface of









the silica gel preventing intermediates from escaping into solution without exposure to

photocatalysis.

SiO2/TiO2

The process of creating a TiO2/SiO2 catalyst can be carried out in different ways

and no one way has currently been proven to be the superior method. The types of

TiO2/SiO2 catalysts are classified as two general types. There are the structures where

the TiO2 is contained within the pores and within the gel as TiO2 (Londeree, 2002). In

this particular case there is no chemical combination of the SiO2 with the TiO2. The SiO2

gel physically contains the TiO2 particles. In the second case there are actual chemical

bonds formed between the Ti element and the Si element. The presence of Si-O-Si

bonds, Ti-O-Ti bonds, and Si-O-Ti bonds have been studied and confirmed (Nawrocki,

1997; Liu and Cheng, 1995; Matsuda et al., 2000; Gao and Wachs, 1999). Currently, the

process being used in the NASA research is a method of doping the SiO2 sol-gel while it

is being created with solid TiO2 particles. This would be counted under the first

classification of catalyst described where the particles are physically trapped within the

silica gel, but not chemically bonded.

Sol-gel structure

The structure of the sol-gel is very important to the benefits received from it. The

hydroxyl concentrations on the Si02/TiO2 surface contribute to the ability of the catalyst

to adsorb pollutants. Adsorption of the pollutants directly to the catalyst decreases the

distance the hydroxyl radical has to travel in order to degrade the pollutant. This is

important considering the short life of the hydroxyl radical in solution. Nawrocki (1997)

gave these 10 facts about the surface structure of the silica gel.









* The hydroxyl concentration on the surface of the SiO2 (silanol groups) is accepted
to be approximately 8.0 + 1.0 [tmol/m2.

* These hydroxyl sites come in three different types, isolated, geminal, and vicinal.

* The isolated sites involve a hydroxide ion attached to a silicon atom on the outer
edge of the gel.

* Geminal sites are characterized by two hydroxide ions attached to the gel at the
same point.

* Vicinal sites have two hydroxyl groups joined to the gel at two different sites, but a
hydrogen group from one is also bonded to the oxygen group from the other.

* Isolated and geminal silanol groups are the most effective at adsorbing pollutants,
particularly organic. The difficulty lies in obtaining the isolated hydroxyl groups
on the surface of the gel.

* Rehydroxylation and dehydroxylation are the two methods for controlling the type
of silanol groups.

* Rehydroxylation is achieved through exposing the gel to water. As the silica gel is
rehydroxylated the number of vicinal groups increases. This means less isolated
and geminal groups are available for the attachment of pollutants.

* The gel is treated at high temperatures to remove the silanol groups during
dehydroxylation. Heating the gel initially removes water that is attached to the
silanols. It will then remove the bonded silanol groups leading to a slight increase
in the number of isolated and geminal sites. Lastly, all of the silanol groups are
removed, leaving a surface of just oxygen.

* Achieving a balance between rehydroxylation and dehydroxylation would create
the ideal gel, as it would provide for the maximum possible number of isolated and
geminal sites on the gel surface. This is important since these sites are the ones
capable of enhancing adsorption. Unfortunately, without the addition of organic
to the surface of a silica gel during gel formation, it is not possible to maintain a
balance in solution. This is due to the rapid rehydroxylation that occurs in aqueous
solution.

Degradable Compounds

The ability for TiO2 to degrade many different compounds with or without the help

of SiO2 and other additives is an area that has been the focus of many researchers. Table

2 (Blake, 1999) lists a number of compounds that have been researched and shown









capable of being mineralized; however there is a lack of studies reported on TiO2

photocatalysis in solutions involving a mixture of chemicals. In this NASA project an

aqueous mixture of 8 chemicals will be investigated. It's expected that one hindrance to

the photocatalytic reaction rate caused by the use of a mixture will result from the

availability of sites on the TiO2 particles. This is the same problem experienced in a

solution with just one pollutant. The possibility also exists for an increase in the

obstruction of light from the photocatalyst. One important and unpredictable problem

lies with the production of intermediates. Because there are so many intermediate

combinations possible with the compounds being tested. There are a multitude of

reactions and interactions that could then occur between those formed intermediates.

Table 2: Researched Compounds
Degradable Compounds Researcher
Bacteria and Viruses (Goswami et al., 1997)
B-TEX (Srinivasan et al., 1997)
Chlorinated Hydrocarbons (Crittenden et al., 1997)
Organics (Matthews, 1987)
Mono- and Di- Chlorobenzene (Kawaguchi and Furuya, 1990)

Non-Degradable Compounds Researcher
Carbon Tetrachloride (Ollis, 1983)

Reaction Kinetics

The Langmuir-Hinshelwood (LH) equation has been shown by Klausner (1994) to

appropriately model the kinetic reaction rates of photocatalysis.

dC/dt = -kiKC/(1+KC) (Eq. 11)

where C is the bulk concentration of contaminant in the solution, kl is the reaction rate

constant and K represents the equilibrium adsorption constant for a particular

contaminant to the photocatalyst (Turchi, Ollis, 1989).







18


It is important to note that the use of the LH equation to describe photocatalytic

kinetics makes an assumption that adsorption of the contaminant to the TiO2 surface is

the rate limiting step. At low bulk concentration values, the LH equation becomes

equivalent to a first order reaction equation, as the TiO2 will not be saturated at the

surface. Since all of the concentrations used in this research will be at or below 300

[tg/L, the first order reaction will likely be applicable; however this also relies on low K

values. Figure 2 depicts a Langmuir-Hinshelwood curve. From this curve, it can be seen

that the lower concentrations appear to have a first order reaction rate while the higher

concentrations move away from the first order model.






% o o o



I T -- i OF
=L
-47



; 0.5 // 10 ^





0 0.1 0.2 0.3 0.4 0.5
Concentration, mmocle/L

(Davis and Hao, 1991)

Figure 2. A curve showing a series of experiments that were modeled using the
Langmuir-Hinshelwood equation.

Summary

Photocatalysis is a complex process of interactions between the photocatalyst, the

reactants, and light. Literature comes to no valid consensus on some of the parameters'






19


effects on the process. pH data provides mixed results, temperature is inconclusive, and

the use of hydrogen peroxide as an aid has been proven and disproved. However, other

parameters have been shown to have definitive effects. UV radiation intensity has been

shown to directly affect photocatalytic oxidation rates to a point. It has also been shown

that the rate of flow through a reactor using fixed TiO2 can have an impact on the amount

of degradation due to the short life span of OH-. This thesis investigates the effect some

of these parameters have on this specific reactor using the photocatalysis process.














CHAPTER 3
METHODS

Assessing of the reactor's capabilities for degrading NASA's 8 target analytes

required several steps. First, the photocatalyst was created. This was done in accordance

with a predetermined method (Londeree, 2002). Secondly, a suitable reactor was

designed for the process. UV transmission and the ability for the reactor to be included

into a system that would allow for testing of the reactor were important factors

considered in the making of this reactor. Many of the target analytes were volatile

organic compounds (VOCs). The tendency for the target analytes to volatilize required

that the system for testing the reactor be airtight. All sampling methods and analytical

procedures were also focused around this important issue of preventing volatile loss of

the analytes.

Several tests were performed during the course of this research with the goal of

understanding the reactor's capabilities and the process of photocatalytic oxidation.

Tracer analyses were performed to understand the hydrodynamics of the reactor.

Adsorption and desorption of the 8 target compounds on the photocatalyst was also

examined. UV intensity, empty bed contact time (EBCT), and total oxidation of the

contaminants in their original state were considered.

Making of the Silica-Titania Pellets

Pellet Composition

To create the photocatalyst a silica gel matrix was impregnated with TiO2. The

titanium dioxide was contained both inside the gel itself and in the pores of the gel. This









silica/titania gel was made into a pellet form measuring 3 mm in diameter were fixed in a

reactor (packed bed style) allowing solutions to pass through the packed bed.

The pellets were designed according to the formula chosen in the research

conducted by Danielle Londeree (2002). Ethanol, hydrofluoric acid (HF), nitric acid

(HNO3), Degussa P25 titanium dioxide, water, and tetra-ethyl-orthosilicate (TEOS) make

up the list of necessary chemicals for this formula. First, 4.2 grams of TiO2 were placed

in a polymethylpentene jar. Next, an 8 oz. plastic jar was put on a mixer with a magnetic

stir bar to keep the solution thoroughly mixed as the contents were added in the following

order: 25 mL deionized (DI) water; 50 mL ethanol; 35 mL TEOS; 4 mL HN03; 4 mL

HF; 4.2 grams TiO2. All acids were reagent grade. The TiO2 used in this research was

Degussa P25. TEOS and water are the two components that actually make up the silica

gel matrix. TEOS, a silicon alkoxide is a specific type of silica precursor. The ethanol

allows the TEOS and the water to combine. Nitric acid and hydrofluoric acid are used to

speed up the reactions that create the gel. In addition the two acids can be used to alter

the pore size and structure within the gel. The water, ethanol, and TEOS were measured

using 10 mL graduated glass pipettes and then the acids were introduced through 10 mL

graduated plastic pipettes. Figure 3 shows the jars and mixers where the solution gelled

for approximately 1 hour before the process of creating the pellet forms was begun.

















































Figure 3. Picture showing an example of the 8 oz. jars, sitting on mixers and filled with
the silica-titania suspension, going through the gelling process.


To obtain the pellet shape, the suspension was pipetted using an automatic pipetter

into 96-well assay plates. Figure 4 shows a picture of this process. Each batch of

chemicals created approximately 4 assay plates worth of pellets. Each batch of assay









plates was then stacked into groups of 4, capped with an assay lid, and wrapped in

aluminum foil and duct tape.


Figure 4. Suspension being transferred from the 8 oz. gelling to the assay plates used for
creating the pellet shape.

Aging

After putting the solution into assay plates, the pellets underwent the "aging"

process. This is where the fluid is dried from the inside of the pellets, leaving behind the

structure that holds the gel together. The aging process used in this research consisted of

first leaving the assay plates at room temperature for 48 hours and then moving the

pellets to an oven preheated at 66 C. For 48 hours the gel aged in the 66 C oven.

Pellets were then removed from the assay trays and put into an 8 ounce Teflon jar with a

hole in the top for equalizing pressure between the inside and outside of the jar. The jar









was put into a programmable oven that gradually increased the temperature from 25 C to

103 C at a rate of 2 C/min. The jar stayed at the 103 C temperature for 18 hours.

After the 18 hours, the temperature was then increased from 103 C at the same rate as

before to the temperature of 180 C where it remained for 6 hours before gradually

decreasing the temperature back down to 25 C. The pellets were then removed and

placed in plastic jars for storage. A majority of the pellets came out of the oven with a

slight brown color. To remove the color, the pellets were put into a ceramic dish and

heated in an oven at 500 degrees Fahrenheit for approximately 1 hour. This removed the

brownish tinge almost completely. It was also found that over time the brown color

would slowly dissipate without the addition of heat. Figure 5 shows a diagram that

displays the overall aging process used for creating the photocatalyst used in this

research.

500 F

180 C 1 hr
103 oC
66 oC
66 6 hrs 25 C
25 oC
S 48hrs 18hrs
48 hrs


Figure 5. Diagram showing the aging process for the pellets. The dashed line is used
for the 500o F to indicate that not all gels required this treatment.

The Reactor

Design of the Reactor

The bench-scale reactor was designed and constructed in order to contain the

pellets and provide effective oxidation of organic compounds and inactivation of

pathogenic microorganisms. It was necessary to develop a reactor that would be well









suited for photocatalysis and for testing the pellets. One important issue was the

transmission of ultraviolet light. Quartz was chosen for its ability to transmit UV

radiation energy, as demonstrated by the transmittance of energy at the wavelength of

388 nm shown in Figure 6 (http://www.quartz.com, 2003).

Fused Quartz Average Transmittance Curves

7"----KrvI111 zw--1 1 -f


C)


CA
Ci


m /
214





10 ----a/


[1y\ 11..11..1 II __I I 1 _A1 [11 [I[Lh


1I


.1E .180 .2 0 .220 .240 .2o .' .350 .450 .550 .60 750 1 0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
.170 .190 .210 .v30 250 .270 .z 2
Wavelength Micrometers

Figure 6. UV transmittance curve for the quartz material used in constructing the
reactor.


The reactor shape (Figure 7) was chosen to optimize the exposure of the pellets to

the light. By building the reactor in a cylindrical shape to surround the lamps, most of

the UV energy produced would be used. It was also important that, should the need arise,

the pellets could be easily removed from the reactor. For this reason alternate

configurations such as a coil were avoided. The thickness of the reactor (10.5 cm) was

chosen to give every pellet inside the ability to react with UV radiation. A thicker reactor

would have hid some pellets behind others, thereby creating a waste of catalyst. The


zzzL


_II II I I I I I I II









schematic shown in Figure 7 gives the dimensions and shape of the reactor used in this

NASA research.

Annular Space for Solution

Exit for Effluent





O
O





Entrance for Influent

Place for UV Lamps Cylindrical Hole for UV
Place for UV Lamps

Figure 7. Diagram showing the plans for the dimensions and shape of the reactor used
for containing the pellets. The entrance and exit were each given threaded
ends to allow for O-Ring connectors. This was done to provide connections
for the PTFE tubing used in the system. A frit was placed in the exit port to
prevent the pellets from flowing out of the reactor with the solution.


The entire reactor was made of quartz with the exception of one end where a glass

frit was placed to keep the pellets from flowing out of the reactor. The reactor had a

volume of 436 mL with the pellets taking up 109 mL of that space (the pellets filled the

reactor completely, but the remaining 327 mL was interparticle space. The bed porosity

was estimated by filling a graduated cylinder with 24 mL of pellets and then adding

nanopure water (NPW) until the water was at the same level as the pellets. 18 mL of

NPW were added in all. This led to the conclusion of 75% bed porosity within the

reactor. Figure 8 shows the reactor in place on its support.









The Reactor System

A system was designed for testing the reactor's capabilities for degrading the target

analytes. That system included the reactor and reactor support, two sampling ports, a

source tank, a pump, and a flow dampener. Figure 9 shows a schematic of the entire

system setup.

The reactor was placed on a wooden support in the horizontal position to limit the

influence of gravity on the flow. Since NASA specifications require the reactor to work

in a micro gravity situation, it was necessary to keep gravity from enhancing the results

of the experiments. Connections were made available for 4 UV lamps to be used in the

center of the reactor. The lamps were 12-inch, 8-watt lamps that each provided

approximately 4.44 W of available UV energy (wavelength near 365 nm) to the inner

surface of the reactor (Table 20). The support also included a cover that could be placed

over the reactor and UV lamps to prevent exposure to laboratory personnel.

All of the tubing used was PTFE tubing to prevent adsorption or desorption of

organic compounds during experimentation. Several of the target analytes fall into the

category of volatile organic compounds (VOCs). Therefore, all connections were sealed

with PTFE tape to ensure an airtight system



























Figure 8. Picture of the reactor on its support stand and connected to the system used for
the testing.


Source Tank








Second Sampling
Port


Flow
Dampener




First Sampling
Port


Figure 9. Diagram of the system setup used for testing the reactor's capabilities. The
diagram does not show the magnetic stir plate under the source tank. It also
does not show the wooden support stand for the reactor. However, that
support is depicted in Figure 8.


Since each sample taken from the system was 40 mL, a source tank was necessary

to prevent pockets of air from forming in the tubing or in the reactor. A 1 L Erlenmeyer

































Figure 10. A picture of the 4 L source tank used in reactor system for this research.


flask was initially used to fill this role. Later in the research the size of the source tank

was increased to a 4 L Erlenmeyer flask to further reduce the effects of sampling. Glass

rods placed through a rubber stopper on top of the source tank carried solution in and out

of the flask. The rubber was covered in Teflon tape to preclude reactions between the

stopper and the test solution. One glass tube through the stopper allowed a small air leak

to prevent a vacuum situation within the system when samples were taken. This did

result in a necessary 14.5 mL of headspace at the top of the flask to keep from losing

solution out of that tube. A picture of the source tank is shown in Figure 10. The total

volume of the system was a little over 1.5 L (4.5 L with the change in source tank) with

1.3 L (4.3 L) coming from the flask and the reactor. The pump used was a L/S PTFE-









Tubing Pump Head powered by a L/S Variable-Speed Modular Drive. A polyethylene

pulse dampener was used to ensure a steady flow rate in the system.

Reactor Hydrodynamics

All real reactors behave, from a hydrodynamic perspective, in a range between two

ideal reactor types. Those two ideal types are known as a continuously stirred reactor

(CSTR) and a plug flow reactor (PFR). A CSTR represents the ideality where the entire

reactor is completely mixed and the concentration in all locations within the reactor is the

same as the effluent concentration. A PFR allows for no axial mixing (mixing in the

direction of flow) and therefore a concentration gradient exists from the influent to the

effluent of the reactor. The PFR is representative of an infinite number of CSTRs in

series. No working reactor can ever operate completely as one of these ideal reactors, but

every reactor behaves somewhere between these two ideals.

The goal was to design a reactor that would simulate a PFR as closely as possible.

A PFR was desired to maximize the reactor's performance as a PFR provides the greatest

transformation for all positive order reactions. This would lead to a predictable and

reliable reaction rate and a minimum size for the reactor to achieve a selected degree of

oxidation or disinfection.

In order to determine the hydrodynamic behavior of the reactor, a tracer analysis

was performed. Sodium chloride (NaC1) was chosen for the tracer to prevent any

possibility of staining the pellets or the inside of the reactor, which may have led to a

reduced transmittance of UV radiation. Also, NaCl was not expected to react with the

pellets in the reactor system.









The chosen flow-rate for the tracer analysis was 10 mL/min since this was the

design flow for the reactor. With a reactor volume of 436 mL and 109 mL of that

composed of pellets, the mean residence time of the reactor was predicted to be 32.7 min.

The tracer analysis was conducted by first maintaining a steady flow through the

system of DI water at 10 mL/min. A solution of 2 mg NaCl/mL was put into a gas-tight

luer-lock syringe. An aliquot of 5 mL of that solution was then introduced through a

luer-lock connection into the tubing. The tubing leading from the sampling port to the

reactor created about 3.7 min of plug flow time prior to entering the reactor.

The concentration of NaCl in the effluent was measured using a Fisher Scientific

conductivity probe. The probe constant, as determined in a calibration procedure

(Standard Methods, 2000), was 0.866. This was calculated by preparing concentrations

of potassium chloride, which were known to have specific conductivity (Table 18). Then

the readings of the probe were compared against those standard values. 3 readings were

taken and from those readings an average difference between the actual conductivity and

the real conductivity was calculated. That average difference was then divided by the

actual conductivity to determine the probes cell constant of .866. This means that any

conductivity reading on the probe actually corresponded with 0.866 mmhos/cm of that

reading.

A linear correlation was found between the conductivity reading on the probe and

the concentration of sodium chloride in solution from 0 to 576 mg/L. This was done by

measuring known concentrations of sodium chloride and comparing them with the

reading on the probe. This showed that each mmho on the probe represented 0.562 mg/L

of NaCl in the solution (Figure 29).









Using this information, data from the tracer analysis were collected in the form of

conductivity in the reactor effluent over time. The conductivity was then changed to a

concentration ofNaC1. Samples were taken of the reactor effluent prior to injection of

NaCl in order to determine the natural conductivity in the effluent. The average

conductivity was subtracted out so that only conductivity caused by the tracer analysis

impulse was considered. The mean residence time in minutes, variance, and tanks in

series were calculated. These numbers are displayed in Table 3. The residence time

represents the average amount of time sodium chloride remained in the reactor. Variance

describes the difference in times over which the contaminant left the reactor. Also

calculated, was the number of CMFRs in series. This shows how many CMFRs in a row

it would take to create a residence time distribution like the one seen by the reactor. An

infinite number of CMFRs in series represents a plug flow reactor.

Table 3. Key Statistics from the Tracer Analysis
Mean Residence Time 42.07
Variance 458.94
Number of CMFRs in Series 3.86

E-curves (residence time distributions) were generated, based on the data, to

graphically demonstrate the results of the tracer analysis. The Tanks in Series (TIS)

model was used due to its ability to accurately model the reactor. Figure 11 shows the E-

curve produced. The ability of the TIS model to simulate the flow in the reactor is key to

the calculation of reactor kinetics discussed later in the results section of this thesis.










E Curve


25.0

20.0

15.0

10.0

5.0

00


+ Data
-- Model


0.00 20.00 40.00 60.00 80.00 100.00 120.00
t* (min)

Figure 11. E curve generated using the data from a tracer analysis performed on the
reactor used in this research. The data represent the E-curve actually
generated by the reactor. The model curve is the E-curve generated by the
TIS model.

Sample Collection

Samples (with the exception of those in the desorption experiments) were collected

using a gas tight, luer-lock syringe. Samples were taken from one of the two three-way

luer-lock sampling ports provided in the system. Volatile Organic Analysis (VOA) vials

were used to collect the samples and keep them airtight. Each vial was 40 mL. These

vials were stored in refrigerators at 40 C until they could be analyzed. Each sample was

viable for up to two weeks at that temperature.

Sample Analysis

Samples were analyzed using two different methods, one for acetone, carbon

disulfide, chlorobenzene, ethyl acetate, methyl methacrylate, and toluene, and a second

method for butyl alcohol and indole.


IFN%









The first method of analyses was performed using a GCQ gas chromatograph/ mass

spectrometer with a Tekmar 3100 purge and trap extraction system. Analyses were

performed in accordance with the USEPA method 524.2, Methods for the Determination

of Organic Compounds in Drinking Water: Supplement 2 (USEPA, 1992). Samples were

purged at room temperature for 11 minutes at 35 mL/min with helium. They were then

dry purged for 2 minutes to remove water. The Supelco k-trap was then back flushed and

heated to 250 C for desorption to the column. The column used was a DB-VRX column

from J&W Scientific. It was a 75-meter long column with a 0.45 mm inner diameter, and

a 2.55-[tm-film thickness. Desorption to the column lasted for 6 minutes at the 250 C

and the trap was then baked at 270 C for 10 minutes. The column was taken from a 25

OC start temperature and ramped to 220 oC at a rate of 6 OC/min. An initial hold was

done at 35 OC for 6 minutes. The mass spectrometer used is an ion trap that looks

between 34 amu and 280 amu with 0.6 seconds/scan.

The second method of analysis (for butyl alcohol and indole) was performed using

a Hewlett Packard 5890 GC/FID with a solid phase micro extraction (SPME) process

using a StableFlex Divinylbenzene/Carboxen/PDMS fiber. Analyses were performed in

accordance with an alternative of AWWA Method 6040D, Analysis of Taste and Odor

Compounds by SPME. Samples were adsorbed to the fiber for 15 minutes at 100 OC.

They were then desorbed to the column by increasing the temperature from 45 OC where

it was held for 5 minutes to 220 oC where it remained for 7 minutes. The rate of

temperature increase was 15 o/min.









The reliability of the testing was verified using the % Relative Standard Deviation

(%RSD). %RSD is based on the Response Factor (RF) of a chemical. The RF and

%RSD are calculated using Equations 12 and 13.

Response Factor (RF) = (Areaanalye*Amountintemal standard)/(Areaintemal standard*Amountanalyte)

(Eq.12)

% Relative Standard Deviation (%RSD) = 100 (SRF / RFAVE) (Eq. 13)

The USEPA method requires a %RSD of less than 30, but strongly recommends a %RSD

of less than 20. Table 4 gives the average %RSDs for the analyses performed for this

research.

Table 4: Average %RSDs for the Analyses in this Research
Chemical Average %RSD
Acetone 32.5
Carbon Disulfide 23.8
Chlorobenzene 13.9
Ethyl Acetate 13.1
Methyl Methacrylate 11.4
Toluene 18.6

Performing Experiments

Initial Degradation

An initial test was performed to determine if the reactor would demonstrate the

capability for removing the target compounds. This experiment was performed using the

system in the configuration shown in Figure 9. The only difference was that at this time

the second sampling port did not exist. That was added later in the research.

A solution containing the 8 target analytes (acetone, butyl alcohol, carbon disulfide,

chlorobenzene, ethyl acetate, indole, methyl methacrylate, and toluene) was prepared

using the following steps:

* 1-2 ptL of each of the 8 neat chemicals were added to a 50 mL volumetricflask.









* The volumetric flask was inverted five times for mixing.

* 20 mL of solution from the 50 mL flask was added to a 2 L volumetric flask
already containing 2 L of deionized (DI) water.

* This larger flask was then inverted 5 times for mixing purposes.

The prepared solution was then carefully poured into the source tank used in the

system to minimize volatilization. Solution was pumped through the system until all of

the tubing and reactor were filled. The source tank was then refilled back to the top and

the stopper replaced.

12-inch, 8-watt UV lamps were then placed in the center of the reactor. They could

not be placed prior to filling because the reactor had to be tilted in order to ensure it

would fill completely. The lamps were shielded using aluminum foil and turned on to

warm-up. A support cover was used to prevent the exposure of laboratory personnel to

UV radiation.

For the rest of the experiment the contaminated solution was circulated through the

system at a rate of 10 mL/min. After thirty minutes of time allowed for the lamps to

come to full intensity, the foil shield was removed to allow photocatalysis to begin. A

sample was taken here representing the initial (t = 0) concentration for the analytes before

any photocatalysis took place. Samples were then taken every 2 hours for the next 6

hours. After the 6 hours the lamps were turned off and the system drained.

Figure 12 displays the results of this initial degradation experiment. The results of

the experiment show removal of contaminants from the solution. All 3 of the

contaminants shown in Figure 12 demonstrated a better than a 90% removal over the

course of the 6-hour run. The capability for the reactor to remove NASA's target

analytes was demonstrated in this experiment.











100.0

90.0 -

80.0 -

70.0 -

"b 60.0
SU Carbon Disulfide
50.0 U- Toluene
0 Chlorobenzene
S40.0

30.0

20.0

10.0

0.0
Stock 0 2.0 4.0 5.8
Time (hrs)

Figure 12. Target analyte degradation seen as a result of recycling the spiked solution
through the system. 3 of the 8 target analytes are displayed in this figure. The
data represented in the "Stock" bars represents the initial concentration
prepared in the 2-liter volumetric flask. The "0" data is the concentration
measured after the system containing the 1-liter source tank was filled.

Determining Effects of Volatility

Three sources of loss were anticipated in the experiments. Work indicated that in

this experiment some loss was probable due to volatilization, some to adsorption on the

pellets, and the rest due to photocatalysis. Many measures were taken to reduce volatility

losses in the system. Teflon tubing, stainless steel connectors, and Teflon tape at each

junction were all used in an effort to reduce this loss. Other measures of protection

against volatility included the use of gas-tight syringes, luer-lock sampling ports, and

keeping the headspace in the source tank at a minimum.









Losses due to adsorption were expected and encouraged. Adsorption loss was

considered a viable means of contaminant removal for the NASA analytes. However,

adsorption losses had to be accounted for, because adsorption removal was finite and

could not be relied upon for an entire space mission to Mars (the eventual goal of this

reactor). It had to be proven that after the pellets adsorption capacity was exhausted,

photocatalysis alone would have the capability of sufficiently removing the analytes.

An experiment was performed to ensure that losses of analytes were not due to

volatility. For this experiment the reactor was taken out of the system setup. A

schematic of this setup is shown in Figure 13.

The solution for testing was prepared in accordance with the same method

described for the initial degradation experiment. Solution was then added to the source

tank and pumped through the system to fill up the tubing. As before, the source tank was

filled to the top and capped with the rubber stopper. For 8 hours, the contaminated

solution was allowed to circulate through the system at a constant flow rate of 10

mL/min. Samples were taken every two hours for analysis. The results of this

experiment are shown in Figure 14.























Dampener
Sampling Port Dampener




Figure 13. Diagram demonstrating the setup used for estimating volatile losses of
analytes in the system. Only one sampling port is shown in the diagram
because only the first sampling port was online during this experiment.


Figure 14. Volatile losses in the system over an 8-hour period without the reactor in
place. Samples were taken every 2 hours from the 1st port in the system. This
run was performed with a 1-liter source tank, making the entire volume a little
over 1.1 liters.


140

120

bo 100

8 0 U-- -- toluene

60 lO chlorobenzene
40

20
0


0 2 4 6 8

Time (hrs)









Figure 14 shows small volatile losses for both chlorobenzene and toluene (16% and

18% respectively) over the 8-hour period of the experiment. The results of analyses for

the 6-hour sample appeared to be anomalous and may have been affected by reloading

the feed tank at about this sampling time. Discounting the 6-hour sample, volatility

losses over an 8-hour period were 16% and 18% for toluene and chlorobenzene,

respectively. After this experiment certain measures were taken to try to further reduce

volatility. This included reduction in headspace for the feed tank and a more secure

wrapping of PTFE tape around the rubber stopper. Based on this experiment and the

further measures taken, volatile losses were assumed to be negligible in future

experiments.

Adsorption Experiment

Following the volatility test, adsorption became the next source of loss to isolate.

The system was reconfigured to that shown in Figure 15.

Dampener



Feed tank Pump P

Sampling Ports Reactor
Reactor


-- \IT


Figure 15. Diagram showing the setup used for saturating the catalyst pellets.









Using the setup shown in Figure 15, 8 liters of contaminated solution at

approximately 200 [pg/L was put through the reactor with the lights off. This was done to

ensure that adsorption would not be a cause for loss of analytes in the rest of the research.

To assess losses by adsorption, an experiment was run with the setup in the

configuration shown in Figure 15. Solution was prepared and introduced to the system

using the method described in Initial Degradation section. The solution was circulated

through the system at 10 mL/min for 5 hours. The lamps were left on but shielded during

this experiment to keep the conditions similar to what the reactor would typically

experience. Samples were taken every hour over the 5-hour period to determine the rate

at which the concentration changed. The results of this experiment are shown in Figure

16.




140
120
100
80 Toluene
60 O Chlorobenzene
S40
20


0 1 2 3.9 4.9
Time (hrs)
Figure 16. Loss of toluene and chlorobenzene as a result of adsorption in the reactor
system. The source tank was excluded from the experiment as any adsorption
there was predicted to be minimal. The "0" sample represents the
concentration after addition of contaminated solution to the system.









This graph shows that some loss is still being experienced in the absence of

photocatalysis. However, it can be seen that the loss becomes minimal as the

concentrations begin to level out by the fifth hour. Based on this experiment, the

decision was made to operate future experiments by letting the system run for five hours

prior to beginning the photocatalysis experiments. At this point all losses would be

considered due to photocatalysis only.

Desorption Experiments

Experiments were conducted to study desorption of the target analytes from the

catalyst pellets occurring in the reactor. Contaminated solution was prepared according

to the method described in the Initial Degradation section. The reactor system was then

filled with solution and allowed to circulate at 10 mL/min for 5 hours. This was done to

saturate the gels with respect to adsorption. At the end of the 5 hours a sample was taken

and the system was drained. 300 mL of nanopure water was then put through the system

to rinse the extraparticular space within the reactor. This rinse water was then analyzed

to determine the concentration rinsed. Nanopure water was then put into the entire

system, with the source tank excluded, to allow for possible desorption. The period of

exposure chosen was 45 minutes. After exposure to the nanopure water for this duration,

the system was drained into a 500-mL volumetric flask and the flask was inverted to

provide mixing (excess solution from the system was wasted). Two samples were taken

from the 500-mL flask for analysis. In a second test the solution was allowed to remain

for another 23 hours and 15 minutes after the 45-minute sample. The system was then

drained and a sample was taken to represent 24 hours of desorption.

The data in Figure 17, representing the results of the two desorption experiments,

led to two important conclusions. The first conclusion was that the contaminants do









desorb from the silica/titania gels pellets. This means that when low-level concentrations

(lower than those seen in Figure 17) are seen in future experiments the photocatalysis has

to degrade contaminants in the feed solution as well as the contaminants that are desorbed

from the silica gel-titania composite.


120.0

100.0
TU Toluene
S80.0
,sE Chlorobenzene
o U Acetone
'P 60.0
SO Carbon Disulfide

S40.0- Ethyl Acetate
= 40.0
i. U Methyl Methacrylate
20.0

0.0
Rinse (AVG) 45 min (AVG) 24-hour

Figure 17. Results of desorption experiments performed. The Rinse (AVG) columns
represent the average concentration in the rinse solution sample over two
experiments. The 45 min (AVG) columns represent the average concentration
of contaminant in the NPW solution after 45 minutes of contact with the
reactor. The 24-hour columns represent the average concentration after 24
hours of circulating through the system. Error bars are representative not of
the error in 1 experiment, but the range of data in the 2 separate runs.

Oxygen as an Electron Acceptor

Photocatalysis requires the continual presence of an electron acceptor. When UV

radiation comes in contact with the TiO2 surface it creates an excited electron and a hole

left behind by the electron. In the absence of an electron acceptor the excited electron

would simply recombine with the hole leaving no ability for hydroxyl radicals to be









formed. Oxygen is the most prominent acceptor available and also the cheapest available

to fill the position in the NASA research.

To demonstrate the availability of oxygen for use as an electron acceptor in the

NASA reactor, an experiment was performed. The setup was configured to that shown in

Figure 8. The method outlined in the Initial Degradation section was then followed for

this experiment, with a small exception. Before the lamps were turned on, the solution

was allowed to circulate for five hours in order to let adsorption effects take place. From

then on the lamps were turned on for 6 hours. For this case, samples were only taken of

the oxygen concentration in the influent solution and of the final solution at the end of

photocatalysis.

The results of the samples showed no change in the dissolved oxygen level of the

solution from the stock solution to the final sample. In both cases the dissolved oxygen

level was 5.4 mg/L. This suggests that the concentration of pollutants being degraded in

the NASA research is too low to cause a measurable effect on the dissolved oxygen

concentration in the system. Based on these results, addition of oxygen or other electron

acceptors for wastewater degradation in this research may not be necessary if the

dissolved oxygen concentration in the influent contains appreciable levels of dissolved

oxygen, as the same level of degradation will be achieved with the currently available

electron acceptor concentration. However, tests would actually be necessary with

NASA's wastewater from within their process treatment train in order to determine if

oxygen would be limiting at very low levels of dissolved oxygen.









Photocatalytic Oxidation Experiments

Effects of UV radiation intensity

Experiments were performed to determine the impact of increasing the amount of

UV radiation on degradation of the analytes. Each experiment was performed using the

setup shown in Figure 9. Solutions containing between 70 and 200 [tg/L were prepared

using the method described in the Initial Degradation section. The system was then filled

with solution and allowed to circulate at 10 mL/min. Initially, the lamps were left off.

Based on results from the adsorption experiment, the solution was circulated for 5 hours

before allowing exposure to UV radiation. The lamps were turned on with shields in

place at 4.5 hours to provide 30 minutes for the lamps to come to full intensity. At this

point, the system was run for 6 hours with the lamps on to allow photocatalysis to occur.

Samples were taken every 2 hours for analysis.

This experiment was performed four separate times; once with 3 lamps, once with

1 UV lamp, and twice with 2 UV lamps to assess precision of the data. Table 20 shows

the calculations performed to find the amount of energy provided to the reactor by 1 UV

lamp. Measurements were made using a Fisher Traceable UV Light Meter. Those

measurements contained a possible 2% error on the part of the meter.

Effects of contact time

Experiments were performed to investigate the impact of flow rate on the

degradation of the target analytes. Three different flow rates were tested; 10 mL/min, 20

mL/min, and 60 mL/min. Solution for these experiments was created using the method

described in the Initial Degradation section. The system was then configured to the setup

shown in Figure 8 and loaded with the solution. For 5 hours the solution was circulated

to allow adsorption to take place. After 4.5 of the 5 hours, the lamps were turned on and









shielded to allow them to warm up. Thirty minutes later the shields were removed and

the system setup was reconfigured to that shown in Figure 11. Flow in the system was

changed to 10 mL/min, 20 mL/min, or 60 mL/min for the each of the three different

experiments. One liter of solution was put through the reactor at the experimental flow

rate. At the end of that time, samples were collected for analysis from the port before and

the port after the reactor.

All three of the flow rates tested were within the laminar region of flow as shown

in Table 19. This was acceptable since the flow rate NASA predicted of 116 mL/min

also lies within the laminar flow regime (Lange and Lin, 1998). So, turbulent versus

laminar flow did not have an effect on the flow optimization experiments.

Experiments including indole and butyl alcohol

All of the previously described experiments, the flow optimization, UV

optimization, 23-hour experiments, and desorption tests were performed with only

acetone, carbon disulfide, chlorobenzene, ethyl acetate, methyl methacrylate, and toluene

as the analytes. Tests had to be performed using indole and butyl alcohol as well. These

tests required a different method of analysis in addition to the typical GC/MS with purge

and trap extraction. Indole and butyl alcohol were analyzed using the GC/FID with solid

phase micro extraction (SPME). Samples were collected for analysis of the butyl alcohol

and indole using the same protocol as with those collected for the other contaminants,

however, the same vial of solution could not be used for both analyses. Therefore, two

sample vials were filled at each sampling time.

These experiments were performed in two different ways. The first three were

performed in the same manner as the UV optimization experiment using 3 UV lamps and

a recycle mode system. The only difference was that indole and butyl alcohol were






47


included in the stock solution. Two separate experiments were also performed using a

similar method to that used in the flow optimization experiments. Five hours of

adsorption circulation was performed and then the system was reconfigured to the single-

pass system. After 1 L of solution flowed through the reactor, two samples were taken at

each port.














CHAPTER 4
RESULTS

This chapter will discuss the results of experimentation to determine the

photocatalytic capabilities of the reactor. The effects of UV radiation intensity and empty

bed contact time (EBCT) will be considered. It will be proven through the data that all of

the target analytes used in this research (acetone, butyl alcohol, carbon disulfide,

chlorobenzene, ethyl acetate, indole, methyl methacrylate, and indole) are capable of

undergoing photocatalytic oxidation. Rates for the process of oxidation will also be

considered based on data from the tests studying the effects of EBCT.

Effects of UV Radiation Intensity

Experiments were performed to investigate the improvement in degradation as the

number of lamps was increased. Four experiments were performed using 1 UV lamp, 2

UV lamps, 3 UV lamps and a duplicate for the run using 2 UV lamps. The details of the

experimental method are discussed in the Methods chapter (Effects of UV radiation

intensity). Figures 18-21 show the results from the UV optimization experiments.

The results from these four experiments demonstrated several important points

about the capabilities of the reactor. First, they proved the ability of the reactor to

photocatalytically degrade each of the 5 compounds (carbon disulfide, chlorobenzene,

ethyl acetate, methyl methacrylate, toluene) shown in the figures. In all cases, at least

80% destruction of the initial contaminant concentration was achieved. Second, the

destruction did not appear linear over time, but rather appeared to approach the 10 [gg/L










-*- Toluene
--- Chlorobenzene
- Carbon Disulfide
--- Ethyl Acetate
-)-- Methyl Methacrylate


Time (hrs)
Figure 18. Degradation of 5 NASA target analytes. This loss is due solely to
photocatalytic destruction. 3 UV lamps were turned on during this experiment
and the experiment was performed in a circulation mode with a 1-liter source
tank.


-- Toluene
--- Chlorobenzene
-- Carbon Disulfide
-- Ethyl Acetate
-- Methyl Methacrylate


0 2 4 6


Time (hrs)
Figure 19. Degradation of 5 NASA target analytes. This loss is due solely to
photocatalytic destruction. 2 UV lamps were turned on during this experiment
and the experiment was performed in a circulation mode with a 1-liter source
tank.


9,











140
120
100
80
60
40
20

0


-4- Toluene
-- Chlorobenzene
-A- Carbon Disulfide
--- Ethyl Acetate
-*- Methyl Methacrylate


0.0 2.0 4.0 6.0 8.0
Time (hrs)

Figure 20. Degradation of 5 NASA target analytes. This loss is due solely to
photocatalytic destruction. 1 UV lamp was turned on during this experiment
and the experiment was performed in a circulation mode with a 1-liter source
tank.


0.90
0.80
0.70
0.60 Toluene
0 Chlorobenzene
0 0.50
EO Carbon Disulfide
S0.40
O Ethyl Acetate
0.30
0. T Methyl Methacrylate
0.20
0.10
0.00
2 4 6

Time (hrs)
Figure 21. Average normalized degradation seen in the two experiments performed with
2 UV lamps and a 1-liter source tank. Error bars show the range of data for
two experiments. There are no error bars present in the 2-hour sample results
due to analytical errors in the 1st of the 2 experiments.










concentrations for all of the tests and contaminants. This suggested that the reaction was

limited by the ability of the hydroxyl radicals to contact the contaminants, as suggested

by the Langmuir-Hinshelwood equation.

Figure 22 shows the normalized curve for chlorobenzene. This curve is

representative of the normalized graph for all compounds. The graphs for the other

compounds can be found in Figures 29-32. The graph shows all 4 of the UV

optimization tests degrading the chlorobenzene at virtually the same rate and magnitude.

These data were important to the NASA research because it showed that UV radiation

energy was not a limiting factor in the degradation of the target analytes beyond the use

of 1 UV lamp. The lower the energy requirements, the more practical the process is for

NASA.


100
90
80
70 -- 3
70 4-3 Lamps
S60
0 --- 2 Lamps
a 50
1 Lamp
U 40
30 --- 2 Lamp (duplicate)
30 -
20
10
0 ---------------
0.0 2.0 4.0 6.0 8.0
Time (hrs)

Figure 22. Removal of chlorobenzene is shown over the course of time as a function of
the contaminant remaining divided by the initial concentration introduced to
the reactor displayed as a percent. It is important to note that the time
displayed on the bottom represents time in the overall system rather than just
time in the reactor.









Effects of Empty Bed Contact Time

In order to determine the possibility of flow rate and therefore residence time

influencing the reactor's performance, a series of experiments were performed. The

reactor was studied at three empty bed contact times (EBCT), 7.27 min, 21.8 min, and

43.6 min. These empty bed contact times were achieved by varying the flow rate at 60

mL/min, 20 mL/min, and 10 mL/min respectively. The method used for performing

these experiments has been previously described in the Methods chapter (Effects of

empty bed contact time). Experiments were performed twice at each of the flow rates.

Figure 23 shows the percent of selected contaminants that remain after a single pass

through the reactor with the chosen EBCTs. The bars in Figure 23 represent the average

value of the two replicates and the error bars represent the range of the data. All of the

series raw data can be found in Tables 21-42.


100.00
90.00
80.00
70.00
o 60.00 2 10 mL/min
4 50.00 6 20 mL/min
40.00 -
) 30.00
20.00
10.00
0.00








Figure 23. Average results of two flow optimization experiments. The y-axis is given as
the concentration remaining in the effluent solution divided by the
concentration present in the influent, displayed as a percent. Therefore the
smaller columns represent a greater percentage of contaminant removed. %
RSDs for acetone were outside of the acceptable range, which explains the
large error bars.









The EBCT for solution in the reactor was decreased from 43.6 minutes to 21.8

minutes to 7.27 minutes. A decreased retention time available for photocatalysis should

have logically led to a poorer degradation. This hypothesis is proven by the data in

Figure 23 where the greater degradation is consistently seen in the tests performed at the

slower flow rate.

Not only do the data reported in Figure 23 give insight into the effect of flow rate

on the reactor's capability to degrade the target analytes, but they also show the reactor's

capability for destroying the analytes in a single pass. Unlike the UV optimization

experiments, the flow experiments studied the reactor's performance in a single-pass

situation. The results demonstrate the ability of the reactor to remove between 85% and

95% of target analytes in a single pass with the longer EBCT. Importantly, both toluene

and chlorobenzene were removed to 10 [tg/L and 13 [tg/L respectively. This is far below

the USEPA National Primary Drinking Water Standards of 1000 [tg/L for toluene and

100 [tg/L for chlorobenzene. The USEPA does not have Primary Drinking Water

Standards for the other target analytes in this study.

Figure 24 displays the data in a different manner. This graph shows the normalized

removal of the contaminants with respect to the length of EBCT (empty bed contact time)

in the reactor. The tendency for the reactor to quickly remove the contaminants to a

certain concentration and then level off in degradation rate is clearly visible in Figure 24.

The data from Figures 23 and 24 were used to assess the reaction rate constants of

the five target analytes shown in these figures. As discussed in the literature review

chapter, the Langmuir-Hinshelwood (LH) equation has been shown by many researchers









to model the degradation rates in photocatalytic oxidation. The LH equation is shown in

Equation 14.

Toluene
-W- Chlorobenzene
100.00 -
910.00 Acetone
90.00
80.00 Ethyl Acetate
70.00 ---- )- Methyl Methacrylate
S60.00
0 50.00
0 40.00
3000 -- -


20.00
10.00
0 n0


v.vv
0 10 20 30 40 50
EBCT (min)
Figure 24. Degradation of five target analytes in the reactor using three UV lamps and
operating the system in a single-pass mode after adsorption for five hours in a
circulation mode had taken place. EBCT stands for Empty Bed Contact Time.


rate = kKiC/(1+KiC) (Eq.14)

where the rate is the actual rate of photocatalysis, k, is a rate constant, C is the bulk

concentration of contaminant in the solution, and K1 is an adsorption equilibrium

constant based on the tendency for the contaminant to adsorb to the photocatalyst surface.

As the term KiC becomes smaller (1>>KiC) the right hand side of Equation 14

reduces to Equation 15. Equation 15 is a simplified version of the LH equation and is

recognized as a first-order rate equation.

rate = dC/dt = kKiC = k'C (Eq.15)

where k' is used to represent the combination of the k and K1 terms. During this research

the concentrations were kept low (100 300 tIg/L) because NASA needs to remove


i~5









contaminants that will be at this approximate concentration level. The K1 term was not

studied in this research. Therefore, it was not determinable if KiC could be considered

minimal compared to 1. However, for the ease of modeling an attempt was made to

model the oxidation kinetics in the reactor using first-order kinetics. After performing

the analysis, it will be shown how accurately the reactions for the contaminants behaved

as approximately first order.

In the Methods chapter (Reactor hydrodynamics) it is shown that through a tracer

analyses the reactor performed as 3.9 CMFRs in series. The first order equation for 1

CMFR is shown in Equation 16.

C/Co = (l+k tbar)-1 (Eq.16)

where C is the effluent concentration, Co is the influent concentration, k is the reaction

rate constant, and tbar represents the mean residence time through the reactor. To obtain

the equation for 3.9 CMFRs in series, Equation 15 is used around each CMFR. By using

Equation 15, the effluent to the first CMFR is found, and then the second, and this is

continued until the number of CMFRs to be represented has been accomplished. A

simplification to this process is Equation 17.

C/Co = (1 + k tbar/n)-n (Eq.17)

where n represents the number of CMFRs in series. In this analysis, the k' being solved

for can be inserted in place of the k shown in Equation 17. This is shown in Equation 18.

C/Co = (1 + k' tbar/n)-n (Eq.18)

In order to determine k' for the target analytes in this research, it was necessary to

rearrange Equation 18. Equation 18 was rearranged algebraically to form Equation 19.

n ((Co/C)1/- 1)= k' tbar (Eq.19)









Equation 19 was then used to graphically determine the k' constant for each of the five

compounds studied in the Effects of Empty Bed Contact Time section. This was done by

graphing the left-hand side of Equation 19 on the y-axis versus tbar on the x-axis. The

resulting graphs, Figures 25 and 26, have trend lines with slopes equal to the k' for each

specific contaminant. If the volume within the reactor were composed entirely of

solution, then the slopes would represent the actual first order rate constant. The reactor,

however, is composed of volume occupied by 75% solution and 25% pellets, therefore

porosity must be accounted for. To do this, Equation 20 was used.

observed = k' / 4 (Eq. 20)

where observed is the first order reaction rate constant found reported for this system and 4

is the porosity of the reactor (0.75). The real first order rate constants, determined by

using the slopes from Figures 25 and 26 in Equation 20, are shown in Table 5.

To assess how well a contaminant was modeled using the first order rate equation

the following facts were considered. A higher R2 (>0.8) represents a contaminant that

more closely resembles a first-order reaction rate. The lower R2 (<0.8) for acetone and

methyl methacrylate suggest that a first-order reaction rate is probably not an acceptable

assumption for these contaminants. Of additional importance is the intercept of the

equations. Ideally, these intercepts would be zero. The presence of a y-intercept

emphasizes the fact that there is a fast initial period of contaminant transformation after

which the rate of removal becomes more linear with respect to EBCT.











5.00 Chlorobenzene

4.50- A Ethyl Acetate

4.00 ,* Toluene

3.50 ,

S3.00 Chlorobenzene
y = 0.065x + 0.4485
Q2.50- R2= 0.8349

-2.00 -0
1.0 0Ethyl Acetate
1.50 y = 0.0565x + 0.2009

1.00 R2 = 0.9285
1.00 00

0.50
Toluene
0.00 1 y = 0.1278x + 0.3515
0 10 20 30 40 R2 = 0.9409
tbar (min)

Figure 25. The slope of the trend lines produced for each target analyte represents the
kinetic rate for that contaminant based on the assumption that its degradation
is first-order in nature. These data are based on information from Figure 24.
This figure only shows the compounds with higher R2 values (values > 0.8).

The observed reaction rate constants predicted in Table 5 are very similar to those

seen by other researchers for TiO2 slurry. Kawaguchi (1990) reported a first order rate

constant of 0.065 min- for chlorobenzene degradation at a pH of 3.5. The pH in the

effluent of the reactor used in this research was approximately 3.8. In 2000,

Vijayaraghavan reported a first order rate constant for toluene of 1.272 min' at a pH of

4.0. Although, the first order rate constants for each compound are similar, the form of

the photocatalyst, TiO2, is significantly different. Both of these prior researchers used

TiO2 in a slurry form in order to achieve photocatalytic oxidation. In this research similar

kinetic rates were achieved in a packed bed configuration using silica gel as a support for









the TiO2. Comparisons of these reaction rate constants are complicated by the different

TiO2 loadings, UV energy, pH, and reaction temperature, which likely were different in

each case reported in the literature; however, the results show that the silica gel doped

with TiO2 was capable of degrading these target organic analytes with rates that compare

well with TiO2 slurries.


3.00 acetone
methyl methacrylate
2.50

^2.00 Acetone
'y = 0.0191x + 0.1567
-1.50 R2 = 0.6979

S1.00
Methyl Methacrylate
0.50 y = 0.0592x + 0.5601
R2 = 0.7175
0.00
0 10 20 30 40
tbar (min)

Figure 26. The slope of the trend lines produced for each target analyte represents the
kinetic rate for that contaminant based on the assumption that its degradation
is first-order in nature. These data are based on information from Figure 24.
This figure only shows the compounds with lower R2 values (values < 0.8).

Table 5. Important data gathered from the trend lines shown in Figures 25 and 26. The
reaction rate constant (k) shown in this table is the first order rate constant for
each of the listed target contaminants. These experiments were performed at a
pH of 3-4 and an average temperature of approximately 25 C.


Chemical


k (min' )


Acetone 0.025 0.698
Chlorobenzene 0.086 0.835
Ethyl Acetate 0.075 0.929
Methyl Methacrylate 0.079 0.718
Toluene 0.170 0.941









Extended Duration Experiment

An experiment was performed to determine whether or not the reactor was capable

of completely degrading the initial contaminant concentration to a level below detection.

This experiment was performed in the same manner as the UV optimization experiments.

However, samples were only taken of the initial stock solution and the final effluent

concentration after 23 hours of exposure to photocatalytic oxidation. Results as shown in

Table 6 demonstrate that the reactor is capable of completely removing toluene, carbon

disulfide, chlorobenzene, acetone, ethyl acetate, and methyl methacrylate to

concentrations that are below the detection limit of the GC/MS procedure.

Table 6. Results of the extended duration test performed for 23 hours. Initial
concentrations represent the concentration of contaminant introduced to the
system before any adsorption or photocatalysis took place. Final
Concentrations represent the concentration of contaminant found in a sample
taken after 23 hours of exposure to photocatalytic oxidation.
Chemical Initial Concentration Final Concentration
([[g/L) ([[g/L)

Acetone 321 BDL
Carbon Disulfide 220 BDL
Chlorobenzene 205 BDL
Ethyl Acetate 266 BDL
Methyl Methacrylate 319 BDL
Toluene 141 BDL
Method detection limit = 5 [tg/L
Below detection limit (BDL)

Removal of Butyl Alcohol and Indole

Results from experiments performed on the degradation of butyl alcohol and indole

produced data proving the reactor's capability to degrade indole and butyl alcohol with

the same level of proficiency as it did the other compounds. The method for performing









these tests was previously described in the Methods section (Removal of indole and butyl

alcohol).

Figure 27 shows the results of the degradation experiments performed with the

system operating in a circulation mode. The contaminants in these experiments

experienced 5 hours of adsorption in the system and then 6 hours of photocatalytic

oxidation. Figure 28 shows the degradation results from a single pass through the reactor.

The EBCTs for the experiments shown in Figure 28 were 43.6 minutes.


1.00
0.90
0.80
0.70
0.60 Test 1
S0.50 Test 2
0.40 0 Test 3
0.30 -
0.20
0.10
0.00
Butyl Alcohol Indole

Figure 27. Results showing the degradation of butyl alcohol and indole as a result of 6
hours of exposure to UV radiation. A 4-liter source tank was used in this
reactor system. There appears to be no data for the indole in the second test
because the data point is 0.

With the exception of the 3rd experiment (it is believed that there may be some

error in this experiment), the data demonstrate excellent removal of both butyl alcohol

and indole. The 2nd experiment, in fact, showed destruction of indole to beyond the

detection level. The 4th and 5th experiments were especially promising, because they

show 93 to 97% removal of both butyl alcohol and indole in a single pass through the

reactor. The rapid removal of butyl alcohol and indole is particularly important since it










has been stated in literature that their removal should be a greater challenge to the reactor

than the removal of the other 6 analytes (Serpone, 1995).



1.00


0.80


0.60


0.40


0.20


0n nn


* 1st Test
* 2nd Test


U. W I I
Butyl Alcohol Indole

Figure 28. Data showing the ratio of each chemical's concentration in the sample from
Port 2 versus the sample from Port 1.


I














CHAPTER 5
SUMMARY AND CONCLUSIONS

Summary

Eight target analytes including acetone, butyl alcohol, carbon disulfide,

chlorobenzene, ethyl acetate, indole, methyl methacrylate, and toluene, were tested for

their degradation using the process of photocatalytic oxidation. The photocatalytic

oxidation was carried out in an annular reactor with the TiO2 supported on a silica gel

matrix and arranged in a packed bed style within the reactor. Adsorption and desorption

of the contaminants within the reactor were studied to determine the capabilities of the

photocatalyst pellets for removing contaminants without photocatalytic oxidation. The

level of available electron acceptor (in the form of DO) and the effects of UV radiation

intensity were studied to investigate their impact on the process. Ability of the reactor to

remove all of the target analytes was assessed. Finally, the reactor was tested for its

removal of 5 target analytes at various EBCTs. Results of those experiments were used

to determine rates of photocatalytic oxidation within the reactor.

Conclusions

An annular reactor containing silica/titania pellets arranged in a packed bed style is

capable of degrading all 8 of this research's target analytes. Six of the compounds were

degraded to below detection limit (5 [gg/L) after an extended reaction period.

Photocatalytic destruction of the contaminants in the reactor was not limited by UV

radiation intensity beyond the use of 1 lamp (8 Watts), providing approximately 4.44 W

of energy to the interior surface of the reactor. Photocatalysis was also not limited by the









amount of oxygen when the dissolved oxygen level was 5.4 mg/L; however, lower levels

of dissolved oxygen were not investigated. A possibility does exist that adsorption of

contaminants to the pellet surface will occur if a proper gradient exists between the

concentration in aqueous solution and the concentration attached to the surface of the

pellets. That sorption was also found to be reversible. First order rate constants for the

photocatalytic degradation of both toluene and chlorobenzene were similar to those

reported for TiO2 photocatalysis in slurry form. One possible reason for this is the

loading. Loading rates for this research were approximately 87 g of TiO2/L of solution

(some of that is certainly trapped within the pellets). Loading rates for one of the slurry

experiments was only 1 g of TiO2/L of solution. In spite of the fast degradation rates,

EBCT does play a part in the level of degradation seen in the effluent. Once exact

concentrations and flow rates are known by NASA it will be important to find an exact

EBCT necessary to achieve proper degradation.

This research has proven the hypothesis by showing the potential for titania/silica

pellets arranged in a packed-bed-style reactor to significantly degrade 8 organic

compounds in a mixed solution. This research must be taken to further levels by

including it within a treatment process train, using actual wastewater or simulated

wastewater formulations and assessing its ability at practical flow rates and over longer

periods of time.















APPENDIX A
CHEMICAL INFORMATION

Table 7. Table of Target Analytes


Volume
of
Analytes Formula S
Sample
(mL)


Container Method #


Sample
esean Holding Time
Preservation


VOA vial
with USEPA 4 degrees
Chlorobenzene C6H5Cl 40 with USEPA 4 degrees 2 weeks
Teflon 524.2 Celsius
seals
VOA vial
with USEPA 4 degrees
Acetone C3H50 40 with USEPA 4 degrees 2 weeks
Teflon 524.2 Celsius
seals
VOA vial

Indole C8H7N 40 with SPME 4 degrees 2 weeks
Teflon Celsius
seals
VOA vial
with 4 degrees
Butyl Alcohol C4H00O 40 wih SPME degees 2 weeks
Teflon Celsius
seals
VOA vial
with USEPA 4 degrees
Toluene C7H8 40 ith USEPA 4 degrees 2 weeks
Teflon 524.2 Celsius
seals
VOA vial
with USEPA 4 degrees
Ethyl Acetate C4H802 40 with US A 4 degrees 2 weeks
Teflon 524.2 Celsius
seals
VOA vial
Methyl 40 with USEPA 4 degrees
Methacrylate Teflon 524.2 Celsius
seals
VOA vial
Carbon with USEPA 4 degrees
Disulfide Teflon 524.2 Celsius
seals









Table 8. Molecular Weight of Target Analyt
Compound


Acetone
Butyl Alcohol
Carbon Disulfide
Ethyl Acetate
Toluene
Methyl Methacrylate
Chlorobenzene
Indole


es
Molecular Weight
(amu)
57.072
74.122
76.131
88.105
92.14
100.116
112.559
117.15


Table 9. Henry's Constants and Partitioning Coefficients
Log of the Partitioning
Chemical Henry's Constant Coefficient
(atm/mol fraction) (octanol-water coeff)
butanol 0.7 0.88
acetone 1.4 -0.24
ethyl acetate 7.7 0.73
methyl methacrylate 7.8 1.38
chlorobenzene 209.0 2.92
toluene 356.7 2.69
carbon disulfide 1064.0 2.14
indole 10739.0 2.14
(Yaws, 1999; The Federal Register;
http://www.ccc.uni-erlangen.de; Schwarzenbach, 1993)


Table 10. Melting Points/Boiling Points
Chemical


acetone
butyl alcohol
carbon disulfide


chlorobenzene
ethyl acetate
indole
methyl methacrylate
toluene


Melting Point Boiling Point
C C
-95 56.2
-89.9 117.7
-108.6 46.3
-45 132
-83.6 77
52.5 254
-50 101
-95.1 110.8


I


I









Table 11. Sources of Contaminant
Chemical Source
Acetone Varnishes, adhesives, and humans.
Butyl Alcohol Gasoline.
Carbon Disulfide Rubber chemicals.
Chlorobenzene Dyes and insectisides.
Ethyl Acetate Solvents and adhesives
Indole Humans.
Methyl Methacrylate Plastics.
Toluene rubbers.
(Verschueren, 1983; http://www.epa.gov; http://www.echeminc.com)


Table 12. Contaminant Generation in the ALS
Chemical Equipment Genereration Rate
(mg/day*kg)
Acetone 3.62E-03
Butyl Alcohol 4.71E-03
Carbon Disulfide 3.23E-05
Chlorobenzene 1.54E-03
Ethyl Acetate 2.97E-04
Indole 0.00E+00
Methyl Methacrylate 1.30E-04
Toluene 1.98E-03


Metabolic Generation Rate
(mg/man*day)
2.00E-01
1.33E+00
0.00E+00
0.00E+00
0.00E+00
6.25E+00
0.00E+00
0.00E+00


(Lange, 1998)









Table 13. Water Quality Requirements
Parameter Potable Water Specifications Hygiene Specifications

Total Solids 100 mg/L 500 mg/L
pH 6.0-8.5 5.0-8.5
Turbidity 1.0 NTU 1.0 NTU
Cations 30 mg/L N/A
Anions 30 mg/L N/A
CO2 15 mg/L N/A
Total Acids 500 mg/L 500 mg/L *
TOC 500 mg/L 10,000 mg/L *
Halogenated
Halognad 10 mg/L 10 mg/L *
Hydrocarbons
Total Phenols 1 mg/L 1 mg/L *
Total Alcohols 500 mg/L 500 mg/L *
Cyanide 200 mg/L 200 mg/L *
* Although the source reports these units as mg/L it seems probable that it should
actually be reported as [tg/L.
(Lange, 1998)

Table 14. Spacecraft Trace Contaminant Generation Rates
MOLAR EQUIPMENT METABOLIC
SMAC
COMMON NAME MASS GEN RATE GEN RATE
g/mol mg/day*kg mg/man*day
ALCOHOLS
Methyl alcohol 32.04 9 1.27E-03 1.50E+00
Ethyl alcohol 46.07 94 7.85E-03 4.00E+00
Allyl alcohol 58.08 1 2.35E-06 0.00E+00
Isopropyl alcohol 60.09 150 3.99E-03 0.00E+00
Propyl alcohol 60.09 98.3 2.41E-04 0.00E+00
Ethylene glycol 62.07 127 6.03E-06 0.00E+00
2-butanol 74.12 121 9.63E-06 0.00E+00
Isobutyl alcohol 74.12 121 8.46E-04 1.20E+00
tert-butyl alcohol 74.12 121 7.38E-05 0.00E+00
Butyl alcohol 74.12 121 4.71E-03 1.33E+00
n-amyl alcohol 88.15 126 1.62E-04 0.00E+00
Phenol 94.11 7.7 4.83E-04 0.00E+00
Hexahydrophenol 100.16 123 7.56E-04 0.00E+00
2-hexanol 102.18 167 2.48E-06 0.00E+00










Table 14 (continued)


Formaldehyde


Acetaldehyde
Acrolein
Propionaldehyde
n-butylaldehyde


valeraldehyde
benzenecarbonal


Benzene
Toluene
Styrene
o-xylene
m-xylene
p-xylene
Ethylbenzene
alpha-methyl styrene
Pseudocumene
Mesitylene
1 -ethyl-2-methylbenzene
Cumene
Propylbenzene


ethyl format
methyl acetate
ethyl acetate
methyl methacrylate
isopropyl acetate


propyl acetate
butyl acetate
isobutyl acetate
ethyl lactate
n-amyl acetate
cellosolve acetate


ALDEHYDES
30.03 0.05 4.40E-
44.05 4 1.09E-
56.06 0.03 3.46E-
58.08 95 3.19E-
72.1 118 8.59E-
86.13 106 7.84E-
106.12 173 1.99E-
AROMATIC HYDROCARBONS


78.11 0.32
98.13 60
104.14 42.6
106.16 86.8
106.16 86.8
106.16 86.8
106.16 86.8
118.18 145
120.2 15
120.2 15
120.2 25
120.2 73.7
120.2 49.1
ESTERS
74.08 90.9
74.08 121
88.11 180
100.12 102
102.13 209
102.13 167
116.16 190
116.16 190
118.13 193
130.18 160
132.16 162


2.51E-
1.98E-
3.13E-
5.56E-
2.03E-
1.08E-
1.50E-
1.67E-
4.49E
3.63E
4.88E
1.40E-
2.15E-


4.51E-
1.41E-
2.97E-
1.30E-
5.81E-
3.38E-
7.46E-
1.52E-
3.64E-
4.78E-
7.46E-


-06


-07
-05
-06
-06


-05


0.OOE+00
0.OOE+00
0.OOE+00
0.OOE+00
0.OOE+00
0.OOE+00
0.OOE+00
0.OOE+00
0.OOE+00
0.OOE+00
0.OOE+00


0.00E+00
9.00E-02
0.00E+00
0.00E+00
0.00E+00
8.30E-01
0.00E+00

0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00









Table 14 (continued)


Furan
Tetrahydrofuran
Ether


sylvan
ethyl cellosolve


Methyl chloride
Vinyl chloride
Ethyl chloride
Methylene chloride
dichloroethene
Ethylene dichloride
Chlorobenzene


propylene chloride
Chloroform
Trichloroethylene
Methyl chloroform
Vinyl trichloride
dichorobenzene


Carbon tetrachloride
Tetrachloroethylene


CBLOROFLUOROCARBONS


Freon 22
Freon 21
chlorotrifluoroethane
Freon 12
dichorodifluoroethene
Freon 11
Halon 1301


Freon 114
Freon 113
Freon 112


86.47
102.9
118.5
120.91
132.93
137.4
148.9
170.92
187.4
204


353.6
21
484.5
494.4
136
561.8
608.8
702.9
400
834.2


5.75E-
6.36E-
4.88E-
1.35E-
1.89E
1.41E
2.61E-
2.62E
1.89E-
3.33E-


-06
-03
-04
-05


ETHERS
68.07 0.11
72.11 118
74.12 242
82.1 0.13
90.12 0.3
CHLOROCARBONS
50.49 41.3
62.5 0.26
64.52 263.7
84.93 10
96.95 7.9
98.97 1
112.56 46
112.99 42.2
119.38 4.9
131.39 10
133.41 164
133.41 5.5
147.01 30
153.82 13
165.83 34


1.84E-
6.93E-
8.90E-
3.46E-
6.01E-

6.76E-
1.46E-
8.99E-
2.15E-
5.64E
7.74E
1.54E
7.42E
1.76E-
8.62E-
6.72E-
8.24E-
6.33E-
9.60E-
7.28E-


-07
-05
-03
-06


0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00

0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00

0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00










Table 14 (continued)


Methane
Ethylene
Ethane
Propylene
Propane
Vinylethylene
Ethylethylene
Isobutane
Butane
Propylethylene
Isopentane
Pentane
hexamethylene
methylpentamethylene
Neohexane
Diethylmethylmethane
Hexane


1-heptylene
Hexahydrotoluene
Heptane


Dimethylcyclohexane
trans- 1,2-dimethylhexamethylet
octane


nonane
citrene (limonene)
Decane


Hendecane
Dodecane


Table 14 (continued)


HYDROCARBONS
16.04 3800
28.05 344.1
30.07 1230
42.08 860.3
44.09 901.4
54.09 221.2
56.1 458
58.12 237.6
58.12 237.6
70.13 186
72.15 295
72.15 590
84.16 206
84.16 51.6
86.17 88.1
86.18 1762
86.18 176
98.18 201
98.18 60.2
100.21 205
112.22 115
ie 112.22 115
114.23 350
128.26 315
136.23 557
142.28 223
156.31 319
170.34 278


6.39E-04
2.27E-07
1.17E-06
2.56E-06
9.21E-07
2.66E-06
8.03E-05
1.10E-05
5.13E-06
2.20E-08
1.80E-06
9.54E-05
3.79E-04
2.97E-05
1.67E-06
5.97E-06
6.95E-05
1.10E-08
6.09E-05
5.59E-05
2.61E-05
5.23E-05
1.61E-05
7.35E-06
3.58E-06
2.78E-05
2.51E-05
6.91E-07


1.60E+02
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00
0.00E+00









Table 14 (continued)
KETONES
Acetone 58.08 712.5 3.62E-03 2.00E-01
Methyl ethyl ketone 72.11 30 6.01E-03 0.00E+00
Methyl propyl ketone 86.13 70.4 4.03E-06 0.00E+00
Methyl isopropyl ketone 86.13 70.4 3.11E-05 0.00E+00
Mesityl oxide (methyl isobutenyl 98.14 40.1 1.91E04 E+00
ketone)
cyclohexanone (pimelic ketone) 98.14 60.2 6.62E-04 0.00E+00
Methyl isobutyl ketone 100.16 82 1.41E-03 0.00E+00
Phenyl methyl ketone 120.14 245 5.66E-07 0.00E+00
Methyl hexyl ketone 128.21 105 1.65E-07 0.00E+00
Diisobutyl ketone 142.2 58.1 3.34E-06 0.00E+00
MERCAPTANS and SULFIDES
hydrogen sulfide 34.08 2.8 0.00E+00 9.00E-02
Carbon oxisulfide 60.07 12 6.05E-06 0.00E+00
Methyl sulfide 62.14 2.5 1.88E-07 0.00E+00
carbon disulfide 76.14 16 3.23E-05 0.00E+00
ORGANIC ACIDS
Acetic acid 60.05 7.4 1.42E-06 0.00E+00
ORGANIC NITROGENS
Acetonitrile 41.05 6.7 1.70E-08 0.00E+00
Indole 117.15 0.25 0.00E+00 6.25E+00
MISCELLANEOUS
hydrogen 2.02 340 5.91E-06 2.60E+01
ammonia 17 7 8.46E-05 3.21E+02
carbon monoxide 28.01 10 2.03E-03 2.30E+01
trimethylsilanol 90.21 40 1.69E-04 0.00E+00
hexamethylcyclotrioxosilane 222.4 227 1.62E-04 0.00E+00
octamethyltrioxosilane 236.54 40 2.1 E-04 0.00E+00
(Lange, 1998)










51 Spacecraft Maximum s


(Lange, 1998)


Table


Potential Exposure Period
Chemical 1 h 24 h 7 d 30 d 180 d
ACETALDEHYDE mg/m3 20 10 4 4 4
ACROLEIN mg/m3 0.2 0.08 0.03 0.03 0.03
AMMONIA mg/m3 20 14 7 7 7
CARBON DIOXIDE mm Hg 10 10 5.3 5.3 5.3
CARBON MONOXIDE mg/m3 60 20 10 10 10
1,2-DICHLOROETHANE mg/m3 2 2 2 2 1
2-ETHOXYETHANOL mg/m3 40 40 3 2 0.3
FORMALDEHYDE mg/m3 0.5 0.12 0.05 0.05 0.05
FREON 113 mg/m3 400 400 400 400 400
HYDRAZINE mg/m3 5 0.4 0.05 0.03 0.005
HYDROGEN mg/m3 340 340 340 340 340
INDOLE mg/m3 5 1.5 0.25 0.25 0.25
MERCURY mg/m3 0.1 0.02 0.01 0.01 0.01
METHANE mg/m3 3800 3800 3800 3800 3800
METHANOL mg/m3 40 13 9 9 9
METHYL ETHYL KETONE mg/m3 150 150 30 30 30
METHYL HYDRAZINE mg/m3 0.004 0.004 0.004 0.004 0.004
DICHLOROMETHANE mg/m3 350 120 50 20 10
OCTAMETHYLTRISILOXANE mg/m3 4000 2000 1000 200 40
2-PROPANOL mg/m3 1000 240 150 150 150
TOLUENE mg/m3 60 60 60 60 60
TRICHLOROETHYLENE mg/m3 270 60 50 20 10
TRIMETHYLSILANOL mg/m3 600 70 40 40 40
XYLENE mg/m3 430 220 220 220 220















APPENDIX B
REACTOR INFORMATION

Table 16. Predicted Retention Time Calculations
Cylindrical Reactor:


Length of Reactor
Inner Diameter =
Width of Space =
Outer Diameter =


Volume


14.0 cm
8.5 cm
1.0 cm
10.5 cm


418 cm3
418 cm


Cyllindrical Reactor:


Actual Volume with ends is 436 mL.


Volume available for polluted waters is 436*.75
Volume = 327 mL

Flow through the reactor is approximated as:
(167.8kgH20/day/6persons)*(6persons)*(1000g/kg)*(cm3/g)
(mL/cm3)* (day/24hrs)*(hr/60min)

Flow = 116.5 mL H20/min


Flow through the reactor during testing will be:
Flow = 10 mL H20/min

The retention time with the ALS flow is about 327 / 116.5 =
Time = 2.81 min

The retention during testing is about 327 / 10 =
Time = 32.7 min


418 mL










Table 17. System Volume Calculation
Component


Volume for Water


Reactor: 327 mL

Tubing:
6 mm OD Tubing = 4.071 mL
1/4 inch ID tubing =156 mL

Source Tank: 1000 mL
or
4000 mL

System Volume with 1L source tank: 1487 mL
or
1.49 L

System Volume with 4L source tank: 4487 mL
4.49 L


KC1 Conductivities for Testing Probe
Equivalent Conductivity, L
nt/L mho-cm2/equivalent
149.9
1 148.9
5 147.7
1 146.9
5 143.6
141.2
138.2
133.3
128.9
124.0
117.3
111.9


Accuracy
Conductivity, k
mmho/cm


14.9
73.9
146.9
7175


1412
2765
6667
12890
24800
58670
111900
(Standard Methods, 1998)


Table 18.
KC1
equivale
0
0.000
0.000
0.001
0.005
0.01
0.02
0.05
0.1
0.2
0.5
1

























0 200 400 600 800


1000 1200 1400


Conductivity mmhos


Figure 29. Concentration of NaCl in deionized water solution versus the conductivity
read on a Fisher Scientific conductivity probe.

Table 19. Calculation of Flow Regime in the Reactor
NRE= (dm*Vo*rL) / (m*(1-eo))


dm = Diameter of the media
Vo = Velocity of the liquid
A = Cross sectional are of the reactor
rL = Density of the liquid
m = Viscosity of the liquid
e = Interparticular porosity of the media


3 mm
Q/A
29.85 cm2
998.2 kg/m"
0.001002 N*s/m2
0.75


NRE Q
(mL/min)
0.67 10
Testing Flows 1.33 20
4.00 60
NASA predicted flow 7.78 116.5

NRE < 10 is in the laminar regime.


800


700
oh 600
= 500
S400
8 300
S200
100
0









Table 20. Calculation of UV Energy at Reactor Surface
UV Intensity Calculations

2.06 mW/cm2 <= UV measured at reactor end
21.7 mW/cm2 <= UV measured at reactor center
2.06 mW/cm2 <= UV measured at reactor end

11.88 mW/cm2 <= Average intensity from beginning to middle,
11.88 mW/cm2 <= Average intensity from middle to end

374 cm2 <= Reactor's inner surface area
187 cm2 <= Reactor's area from beginning to middle
187 cm2 <= Reactor's area from middle to end

2221.56 mW <= Energy to reactor from beginning to middle
2221.56 mW <= Energy to reactor from middle to end


<= Total energy to reactor


4443.12 mW















APPENDIX C
RAW DATA


Table 21. Initial Raw Data Test (1/6/3)
Chemical RF (AVG) %RSD Stock Solution
(nlg/L)
Carbon Disulfide 0.9448 20.26 94.1
Chlorobenzene 1.1648 25.14 67.7
Toluene 3.176 30.03 64.8


t=0
(ng/L)
33.2
34.2
45.1


t= 118
(png/L)
15.5
15.0
19.3


t = 238
(g/L)
4.8
5.6
6.8


t = 349
(ng/L)
3.0
3.0
3.8


Table 22. Volatility Test Raw Data (2/6/3)
Chemical RF (AVG) %RSD Stock Solution t = 120 t = 240 t = 360 t = 480
([tg/L) ([tg/L) ([tg/L) ([tg/L) ([tg/L)
Chlorobenzene 2.46 34 126.6 122.8 109.1 86.9 103.9
Toluene 4.39 35 56.1 55.1 48.6 33.8 47.2

Table 23. Adsorption Test Raw Data (3/8/3)
Chemical RF (AVG) %RSD Stock Solution t = 60 t = 120 t = 235 t = 295
([[g/L) ([[g/L) ([[g/L) ([[g/L) ([g/L)
Chlorobenzene 2.24 9.7 120.6 104.8 78.4 71.6 66.2
Toluene 4.47 15.2 75.6 67.9 52.4 50.9 46.9


Table 24. UV Optimization (3


Lamps) Raw Data (3/12/3)


Chemical RF (AVG) %RSD Stock Solution t = 0 t = 120 t = 240 t = 360
([[g/L) ([[g/L) ([g/L) ([g/L) ([g/L)
Carbon Disulfide 1.29 14.6 122.7 50.0 34.4 14.7 6.3
Chlorobenzene 2.24 9.7 153.4 74.5 48.5 20.3 9.1
Ethyl Acetate 0.10 0 19.2 13.0 10.0 4.6 1.8
Methyl
Methacrylate 0.059 8.19 139.0 82.2 49.3 17.2 4.5
Toluene 4.05 15.2 102.4 56.6 37.3 18 11









Table 25. UV Optimization (2 Lamps) Raw Data (3/13/3)
Chemical RF (AVG) %RSD t= 0 t=240 t=360
([g/L) ([g/L) ([g/L)
Carbon Disulfide 1.29 14.6 60.7 20.5 9.4
Chlorobenzene 2.24 9.7 69.0 22.6 9.1
Ethyl Acetate 0.10 0 84.2 13.6 13.9
Methyl
Methacrylate 0.059 8.19 73.3 19.6 6.0
Toluene 4.05 15.2 62.0 22.6 12.7

Table 26. UV Optimization (1 Lamp) Raw Data (3/14/3)
Chemical RF (AVG) %RSD t = 0 t = 120 t = 246 t = 360
([[g/L) ([gg/L) (|gg/L) ([gg/L)
Carbon Disulfide 1.14 25.7 60.6 25.2 12.5 6.7
Chlorobenzene 2.51 15.1 74.7 47.5 22 10.9
Ethyl Acetate 0.02 0 50.4 35.5 19.6 11.6
Methyl
Methacrylate 0.0594 8.8 124.4 64.3 27.9 14.8
Toluene 6.07 38.5 44.3 26.8 11.6 5.2

Table 27. UV Optimization (2 Lamp Duplicate) Raw Data (3/17/3)
Chemical RF (AVG) %RSD t = 0 t = 120 t = 240 t = 360
([[g/L) ([gg/L) ([gg/L) ([[g/L)
Carbon Disulfide 1.14 25.7 47.6 25.5 18.2 10.7
Chlorobenzene 2.51 15.1 54.3 33.8 18.6 10.4
Ethyl Acetate 0.02 0 43.4 34.1 19.9 10.1
Methyl
Methacrylate 0.0594 8.8 94.7 56.6 28.4 12.4
Toluene 6.07 38.5 55.0 32.1 16.6 8.4









Table 28. 11-Hour Adsorption Experiment Raw Data (4/3/3)
Chemical RF (AVG) %RSD t = 0 t= 0 (dup)
([lg/L) (lg/L)
Carbon Disulfide 1.02 13.8 54.4 46.0
Chlorobenzene 3.05 15.3 150.5 158.7
Ethyl Acetate 0.02 0 120.1 119.3
Methyl
Methacrylate 0.076 10.2 213.0 221.2
Toluene 7.29 38.4 111.5 118.0

t=75 t=255 t=375 t=555 t=735
([lg/L) ([lg/L) ([lg/L) ([lg/L) (l[g/L)
33.0 24.8 24.8 21.5 16.0
88.6 67.3 67.3 61.6 53.1
66.2 52.6 52.6 47.2 37.2
125.3 102.7 102.7 97.2 82.3
72.4 59.9 59.9 57.1 50.2


Table 29. 60 mL/min Flow
Chemical RF (AVG)


Test (Series 2) Raw Data (4/6/3)
%RSD Stock t=3.5 t=5 Port 1
(g/L) (g/L) (gL) (g/L) ([lg/L)


Acetone 0.02 30.6 159.7 105.2 75.3 109.0 37.9
Carbon Disulfide 2.49 25.4 186.8 87.1 82.3 44.3 4.7
Chlorobenzene 2.70 21.3 1080.9 572.6 527.4 313.1 77.7
Ethyl Acetate 0.25 20.1 5.1 3.4 4.5 2.7 0.9
Methyl
Methacrylate 0.04 8.3 116.8 73.5 70.1 51.1 10.0
Toluene 7.84 40.1 42.2 29.0 29.0 15.3 2.6

*Port 1 is before the reactor *Port 2 is after the reactor


Port 2
(lg/L)









Table 30. 20 mL/min Flow Test (Series 2) Raw Data (4/9/3)
Chemical RF (AVG) %RSD Stock t= 3.5 t= 5 Port 1 Port 2
([[g/L) ([[g/L) ([tg/L) ([g/L) ([g/L)
Acetone 0.02 30.6 11.8 66.3 45.2 42.0 36.6
Carbon Disulfide 2.49 25.4 128.7 79.8 85.4 54.3 20.3
Chlorobenzene 2.70 21.3 133.3 61.1 77.3 60.9 18.5
Ethyl Acetate 0.25 20.1 10.8 7.4 7.6 6.5 3.9
Methyl
Methacrylate 0.04 8.3 290.7 189.5 175.8 152.5 61.6
Toluene 7.84 40.1 117.9 54.1 72.9 53.4 11.9

*Port 1 is before the reactor *Port 2 is after the reactor

Table 31. 10 mL/min Flow Test (Series 2) Raw Data (4/7/3)
Chemical RF (AVG) %RSD Stock t = 3.5 t = 5 Port 1 Port 2
([tg/L) (gtg/L) ([tg/L) ([tg/L) ([tg/L)
Acetone 0.02 30.6 144.0 90.2 94.9 127.6 95.2
Carbon Disulfide 2.49 25.4 36.5 27.6 25.1 22.7 13.9
Chlorobenzene 2.70 21.3 288.8 108.7 118.4 95.0 13.8
Ethyl Acetate 0.25 20.1 10.6 6.7 6.8 6.4 1.8
Methyl
Methacrylate 0.04 8.3 355.9 210.6 179.2 168.0 43.8
Toluene 7.84 40.1 107.3 43.2 43.2 44.3 0.9

*Port 1 is before the reactor *Port 2 is after the reactor

Table 32. 23-Hour Test Raw Data (4/16/3)
Chemical RF (AVG) %RSD Stock Stock (dup) t = 23 hours t = 23 hours (dup)
([[g/L) ([[g/L) ([[g/L) ([[g/L)
Acetone 0.02 20.3 263.4 379.2 3.7 2.3
Carbon Disulfide 1.96 14.9 225.2 214.3 5.9 4.0
Chlorobenzene 2.60 3.2 194.1 216.7 3.6 4.3
Ethyl Acetate 0.01 0.0 263.8 267.2 0.0 0.0
Methyl
Methacrylate 0.04 10.7 295.6 342.4 0.0 0.0
Toluene 5.32 4.2 138.9 142.7 1.7 1.8

*Port 1 is before the reactor *Port 2 is after the reactor









Table 33. 60 mL/min Flow Test (Series 3) Raw Data (4/28/3)
Chemical RF (AVG) %RSD Stock t=3.5 t= 5 Port 1 Port 2
([gg/L) ([gg/L) ([gg/L) ([gg/L) ([gg/L)
Acetone 0.02 20.3 270.1 293.0 304.4 314.5 194.3
Carbon Disulfide 1.96 14.9 2.2 1.6 1.1 0.8 0.2
Chlorobenzene 2.60 3.2 191.3 167.3 135.8 151.4 48.4
Ethyl Acetate 0.01 0.0 213.1 200.1 167.6 189.7 107.2
Methyl
Methacrylate 0.04 10.7 8.5 7.7 6.7 7.3 2.1
Toluene 5.32 4.2 118.1 107.2 91.1 95.5 26.1

*Port 1 is before the reactor *Port 2 is after the reactor

Table 34. 20 mL/min Flow Test (Series 3) Raw Data (4/25/3)
Chemical RF (AVG) %RSD Stock t=3.5 t=5 Port 1 Port 2
([g/L) (mg/L) ([g/L) ([g/L) ([g/L)
Acetone 0.02 20.3 609.0 520.9 356.8 427.1 297.8
Carbon Disulfide 1.96 14.9 11.0 5.3 7.5 22.7 16.8
Chlorobenzene 2.60 3.2 236.1 241.3 194.8 89.5 29.1
Ethyl Acetate 0.01 0.0 253.8 229.0 205.7 186.2 51.5
Methyl
Methacrylate 0.04 10.7 41.4 38.1 32.5 25.9 4.6
Toluene 5.32 4.2 140.7 136.9 113.3 27.6 11.7

*Port 1 is before the reactor *Port 2 is after the reactor

Table 35. 10 mL/min Flow Test (Series 3) Raw Data (4/27/3)
Chemical RF (AVG) %RSD Stock t=3.5 t=5 Port 1 Port 2
([[g/L) ([[g/L) ([[g/L) ([[g/L) ([[g/L)
Acetone 0.02 20.3 609.6 408.0 259.9 474.0 163.7
Carbon Disulfide 1.96 14.9 0.5 2.0 1.9 1.9 0.5
Chlorobenzene 2.60 3.2 103.2 99.2 82.1 87.2 12.7
Ethyl Acetate 0.01 0.0 148.9 129.1 120.0 127.0 19.6
Methyl
Methacrylate 0.04 10.7 10.3 9.5 8.2 8.5 0.8
Toluene 5.32 4.2 166.4 135.0 110.6 129.7 10.0

*Port 1 is before the reactor *Port 2 is after the reactor









Table 36. 1st Desorption Test Raw Data (5/13/3)
Chemical RF (AVG) %RSD


t=0
([g/L)


t=5
(tg/L)


Acetone 0.02 60.0 184.9 104.0
Carbon Disulfide 2.20 34.1 194.5 83.4
Chlorobenzene 2.57 17.5 217.7 231.2
Ethyl Acetate 0.22 20.0 10.9 12.7
Methyl
Methacrylate 0.05 17.8 376.1 328.4
Toluene 5.26 18.8 190.3 119.2

Rinse Rinse (DUP) 45 min Desorb 45 min Desorb (DUP)
([[g/L) ([[g/L) ([[g/L) ([[g/L)
93.2 84.7 145.9 96.0
48.0 35.2 33.2 26.5
76.7 81.3 87.0 78.9
4.4 4.4 4.1 4.4
103.6 105.2 140.3 117.5
47.6 43.7 45.8 38.2


Table 37. 2nd Desorption Test Raw Data (5/16/3)
Chemical RF (AVG) %RSD


Acetone
Carbon Disulfide
Chlorobenzene
Ethyl Acetate


0.02
2.20
2.57
0.22


60.0
34.1
17.5
20.0


t=0
(ltg/L)
175.9
174.0
165.8
17.4


t=5
(ltg/L)
150.1
148.4
132.5
15.2


Methyl
Methacrylate 0.05 17.8 211.6 175.8
Toluene 5.26 18.8 137.4 120.9

Rinse Rinse (DUP) 45 min Desorb 24 hour Desorb 24 hour Desorb (DUP)
([[g/L) ([[g/L) ([tg/L) ([tg/L) ([[g/L)
97.2 80.1 72.5 55.7 83.8
53.5 43.3 45.4 29.0 33.2
54.2 52.3 46.7 41.6 49.1
5.7 5.1 4.6 2.3 2.1
71.8 68.9 52.4 43.4 49.4
46.4 41.8 36.3 31.6 35.9









Table 38. SPME 1st Test Raw Data (5/28/3)
Chemical RF (AVG) %RSD Stock Solution t = 3.5 t = 5 t = 7 t = 9 t = 11
(|tg/L) (tg/L) (tg/L) (tg/L) (tg/L) (tg/L)
Acetone 0.0278 16.4 239.1256203 227.95 253.6 233.13 187.4 147.63
Butyl Alcohol 374.0 471.0 435 248 165
Carbon Disulfide 1.54 30.2 60.7 63.9 67.56 52.49 43.01 35.68
Chlorobenzene 2.3 12.5 114.7 112.8 104.1 89.96 76.08 61.5
Ethyl Acetate 0.20 13.6 43.8 39.4 38.5 35.7 30.25 24.4
Indole 208.0 257.0 180.0 96 70.0
Methyl
Methacrylate 0.054 10.1 221.6 204.6 191.1 173.52 149.3 119.3
Toluene 3.81 18.4 69.4 72.5 65.35 58.6 49.94 42.84

Table 39. SPME 2nd Test Raw Data (5/29/3)
Chemical RF (AVG) %RSD Stock Solution t = 3.5 t = 5 t = 7 t=9 t= 11
(g/L) (g/L) (g/ g/L) (gL) (g/L) ([[g/L) ([tg/L)
Acetone 0.0278 16.4 232.0 251.0 305.7 207.7 166.6 129.2
Butyl Alcohol 458.4 96.0 87.0 46.0 46.0 34.0
Carbon Disulfide 1.54 30.2 106.0 46.3 48.7 27.0 17.4 11.2
Chlorobenzene 2.3 12.5 211.0 148.3 145.0 82.8 50.3 24.6
Ethyl Acetate 0.20 13.6 53.6 28.8 29.0 18.9 13.5 7.9
Indole 107.1 66.0 61.0 0.0 0.0 0.0
Methyl
Methacrylate 0.054 10.1 250.3 117.5 113.6 66.8 40.4 204.6
Toluene 3.81 18.4 104.5 87.1 86.8 52.4 32.9 72.5

Table 40. SPME 3rd Test Raw Data (6/7/3)
Chemical RF (AVG) %RSD Stock Solution t= 3.5 t = 5 t = 7 t= 9 t= 11
([gg/L) ([gg/L) ([[g/L) ([gg/L) ([gg/L) ([[g/L)
Acetone 0.0278 16.4 198.0 178.8 158.0 122.4
Butyl Alcohol 0.270 0.472 0.353 0.333 0.280 0.341
Carbon Disulfide 1.54 30.2 92.4 61.7 56.9 50.3
Chlorobenzene 2.3 12.5 160.2 133.8 131.1 110.6
Ethyl Acetate 0.20 13.6 35.4 32.1 31.2 26.6
Indole 0.210 0.290 0.215 0.207 0.107 0.189
Methyl
Methacrylate 0.054 10.1 120.7 111.8 112.3 90.7
Toluene 3.81 18.4 65.3 51.3 50.4 44.0









Table 41. SPME 4th Test Raw Data (6/14/3)
Chemical Stock Solution t= 3.5 t = 5 Port 1 Port 2
([gg/L) ([Gg/L) ([[g/L) ([Gg/L) ([Gg/L)
Butyl Alcohol 589.0 752.0 765.0 661.0 43.0
Indole 3009.0 2117.0 2063.0 2343.0 75.0
*Port 1 is before the reactor *Port 2 is after the reactor

Table 42. SPVME 5th Test Raw Data (6/15/3)
Chemical Stock Solution t = 3.5 t = 5 Port 1 Port 2
([[g/L) ([Gg/L) ([[g/L) ([Gg/L) ([Gg/L)
Butyl Alcohol 374.0 344.0 311.0 491.0 32.0
Indole 2005.0 1798.0 1987.0 2029.0 49.0
*Port 1 is before the reactor *Port 2 is after the reactor


100

80
-4- 3 Lamps
60
O-W 2 Lamps

-X-- 2 Lamp (duplicate)
20

0 -----------
0.0 2.0 4.0 6.0 8.0
Time (hrs)

Figure 30. Normalized removal of toluene over the course of 6 hours. The flow rate in
all of the experiments was 10 mL/min and the system was operated in
circulation mode with a 1-liter source tank. Removal represents overall
removal in the system.





























Figure 31. Normalized removal of methyl methacrylate over the course of 6 hours. The
flow rate in all of the experiments was 10 mL/min and the system was
operated in circulation mode with a 1-liter source tank. Removal represents
overall removal in the system.


120

100

80
S-A-1-1 Lamp
o 60
S-X-X- 2 Lamp (duplicate)
40

20

0 -
0.0 2.0 4.0 6.0 8.0
Time (hrs)

Figure 32. Normalized removal of carbon disulfide over the course of 6 hours. The flow
rate in all of the experiments was 10 mL/min and the system was operated in
circulation mode with a 1-liter source tank. Removal represents overall
removal in the system.


120

100

-80 -- 3 Lamps
o- 2 Lamps
o 60
S-A-- 1 Lamp
40 -X-- 2 Lamp (duplicate)

20

0
0.0 2.0 4.0 6.0 8.0


Time (hrs)






86



120

100

S80 3 Lamps
--- 2 Lamps
60
-*- 1 Lamp
40 -X-- 2 Lamp (duplicate)

20

0
0.0 2.0 4.0 6.0 8.0
Time (hrs)

Figure 33. Normalized removal of ethyl acetate over the course of 6 hours. The flow rate
in all of the experiments was 10 mL/min and the system was operated in
circulation mode with a 1-liter source tank. Removal represents overall
removal in the system.
















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