1 Destruction of Pharmaceuticals by Advanced Oxidation Processes in Ion Exchange Regeneration Brine Nicole Rivera, Kelly Landry, and Treavor H. Boyer College of Engineering, University of Florida Pharmaceuticals are a major contaminant in wastewater systems because of both increased usage and improper disposal. A promising method in removal of these pharmaceuticals in urine is the use of anion exchang e resins. In order to make this process more sustainable it would be advantageous to efficiently regenerate the resin, in a water salt methanol solution, and destroy the pharmaceuticals in the brine to produce a reusable regeneration solution, thus creatin g a closed loop system. Methanol is considered harmful to the environment; hence, the goal of this research is to find the minimum concentration of methanol needed to efficiently regenerate the resin and simultaneously decompose the pharmaceuticals in the regeneration brine. To do this, a series of batch experiments were conducted to compare the effect of methanol on the regeneration of the anion exchange resin and the destruction of the pharmaceutical through advanced oxidation process (AOP) using ultravio let irradiation (UV) and hydrogen peroxide (H 2 O 2 ). Percent destruction of the investigated pharmaceutical, ibuprofen, increases with increasing H 2 O 2 dosage and time. The regeneration of Dowex 22 resin increases and percent destruction of ibuprofen decrease s with increasing methanol to water ratio in regeneration solution. INTRODUCTION Pharmaceuticals are micro pollutants in wastewater systems due to increased usage and improper disposal. Conventional wastewater treatment methods are either inefficient or ineffective at removing these pharmaceuticals, thus allowing them to enter the environment via the was tewater effluent. Although some pharmaceuticals may not persist in the environment, they can still cause negative effects to living organisms due to their continuous i ntroduction to the environment. 1 A contributing source of pharmaceuticals in wastewater is due to urine, where ~70% of consumed pharmaceuticals are excreted; however urine only makes up 1% of the volumetric flow of wastewater. Thus, urine source separation has been proposed as an efficient method to isolate a concentrated waste stream to effi ciently remove these micro pollutants. A proposed method for removal of these pharmaceuticals in urine is sorption by anion e xchange resins. 2 This method was successful due to both the electrostatic interactions between the negatively charged carboxylic ac id functional group on the investigated pharmaceutical and anion exchange sites on the resin, and the non electrostatic interactions between the aromatic ring structure of the pharmaceutical and polystyrene resin matrix. 2 The resin was successfully regener ated using a 4.5% NaCl, water methanol regeneration solution, however methanol is considered harmful to the environment. In order to make this process more sustainable it would be advantageous to efficiently regenerate the resin and destroy the pharmaceuti cals in the brine to produce a reusable regeneration solution, thus creating a closed loop system.
2 MATERIALS AND METHODS Regeneration Solutions The experiments tested four different solutions, three regeneration solutions and a control. All four solutions were dosed with 0.2 mM of Ibuprofen. The first solution (Solution A) contained 5%NaCl (m/m ) in deionized water, and 0.2 mM of ibuprofen. The second solution ( Solution B) contained a 50/5 0 (v/v) water methanol solution and 0.2 mM of ibuprofen. The third solution (Solution C) contained 5% NaCl (m/m) in a 50/50 (v/v) water methanol solution and 0 .2 mM of ibuprofen. The control (Solution D) was comprised of solely deionized water (DI) and 0.2 mM of pharmaceutical. These solutions were chosen to look at the effect of both the sodium chloride and methanol in the destruction of ibuprofen in the advanced oxidation process. Advanced Oxidation Process The procedure for the advanced oxidation process (AOP) experiments was modeled after those used in Cooke (2012). A water bath, set to 25C, was used to keep tubing at room temperature. A low pressure, 8W 254nm U V lamp (Sankyo Denki) was used. 3 The light was allowed to w arm for 10 min wh ile the reactor was rinsed with deionized water three times and the tubing was assembled (See figure 1). The tested solution was dosed with a pre calculated hydrogen peroxide dose. For a low dose (10 mg/L) 14.9 2 O 2 for a medium dose (20 mg/L) 2 O 2 and for a high dose (40mg/L) 2 O 2 was added to 500mL of the tested solution. 100mL control of the 500m L regeneration solution was measured using a graduated cylinder to compare the concentration of ibupr ofen in the solution before and after running the AOP experiment The pump was started and the solution was allowed to flow through the reactor until all air bubbles wer e no longer visible. For a 5 min reaction time the solution was left in the reactor for 12 min and 27 s and for a 30 min reaction time the solution was left in the reactor for 1 h 1 4 min and 1 0 s. The H 2 O 2 residual and ibuprofen c oncentration of the 100mL control and tested sample were measured using the UV spectrophotometer. Figure 1: Experimental setup for AOP AOP Experiment The regeneration solutions were dosed with hydrogen peroxide in three batches high (40mg/L), medium (20mg/L), and low dose (10mg/L). Solutions A, B, C, and D were then put through the advanced oxidation process at a UV exposure time of 5 and 30 min. A control was taken for each solution before being exposed to UV to compare the concentration of ibuprofen in the solution before and after AOP so that the percent destruction could be calculated. The hydrogen peroxide residual was also measured before and after AOP. Batch Experiment To test the effect of methanol on both the regeneration of Dowex 2 2 resin and the destruction of i buprofen in the rege neration solution through AOP, batch experiment s were performed with two d ifferent regeneratio n solutions. The batch experiment included the full process from treatment and removal of pharmaceutical, to regeneration of the resin, and destruction of ibuprofen in the regeneration solution The first regeneration solution consisted of the same make up as Solution C used in the previous experiment. The second UV REACTOR Peristaltic Pump Water Bath Total Volume Including Tubing: 326 mL UV Reactor Volume: 163 mL
3 regeneration solution contained 5% NaCl (m/m) in a 99/1 (v/v) water methanol solution and 0.2 mM of ibuprofen. First, before beginning the experiments the Dowex 22 resin needed to be regenerated bef ore initial use. The resin was pre regenerated by mixing it in a sodium chloride solution for 1 h and then r insing the resin ten times in deionized water to remove excel Cl The experiments were performed in triplicate. 1mL of resin was added to 3 500 mL Erlenmeyer flasks o f 0.2mM ibuprofen DI solution. The resin was not added to a fourth flask that was used as a control The resin was allowed to mix for 24 h at 125 RPM. After 24h the mixing was stopped, the solution was filtered, and the resi n saved. The concentration of i buprofen was measured using UV spectro photo meter for each treated solution the control allowed the concentration of ibuprofen in the solution prior to treatment to be measured In triplicate, 500 mL of the regeneration solution being te sted was measured. The resin, 1 mL, was added to the regeneration solution and allowed to mix for an hour. The solution was filtered and the regeneration solution saved. Using a 500mL graduated cylinder, 450mL of regeneration solution was measured and the remaining 50mL of solution was saved to use as a control. The regenerati on solution was dosed with 13.4 of 30% H 2 O 2 (10 mg/L) and put through AOP with a UV exposure time of 30 min. After the reaction time was complete, the hydrogen peroxide residual and ibuprofen concentration were measured for the control and the tested regeneration solution using the UV spectro photo meter. This process was then repeated for the other regeneration solution being tested. Figure 2 : Experimental plan for batch experiments Treatment Regeneration AOP Resin removes IBP Resin 0.2 mM IBP DI Solution 0.2 mM IBP DI Solution 1% MeOH Regen. Soln. 50% MeOH Regen. Soln. [IBP] is Measured IBP is removed from Resin and into solution Regeneration Solution [IBP] is Measured UV 30 min. exposu re [IBP] is Measured AOP 10mg/L H 2 O 2
4 Sample Analysis Both Ibuprofen and H 2 O 2 were measured by UV spectroscopy. A standard calibration curve was determined by using the Hitachi U 2900, a spectrophotometer. For the H 2 O 2 the UV spectrophotometer was used to construct a calibration curve and measured the following solution for each standard; 2.5 mL of reagent A, 2.5 mL of reagent B, 4.9 mL deionized water of standard. Reagent A was made by adding 1g NaOH,33g KI, 0.1g (NH 4 ) 6 MO 7 O 24 4H 2 O 2, and DI in 500mL volumetric flask. Reagent B was made by adding 10g C 8 H 5 KO 4 and DI in a 500mL volumetric flask 3 To measure the i buprofen concentrations the UV spectrophotometer was also used to construct a calibration curve and the wavelength was adjusted in t he parameters to 222.5nm. RESULTS AOP Experiment Results of the AOP experiment are presented in Figures 3. Percent destruction of ibuprofen is highest in Solution D and lowest in Solution C. At the 30 min exposure time percent destruction is the gre atest but there is little variation in percent destruction with increasing hydrogen peroxide dosage at this time. Batch Experiment Results of the batch experiment are presented in F igure s 4 and 5. With a 1% methanol solution, Dowex 22 resin is regenera ted 35%, while at a 50% methanol solution Dowex 22 resin is regenerated 100%. Regeneration is expected to increase with increasing methanol percentage in the regeneration solution, a linear relationship is assumed. Percent destruction of ibuprofen (C o =0.2 mM) in 5%NaCl, water methanol regeneration solution with varying water methanol ratios decreases with increasing methanol percentage in regeneration solution. At a 30 min UV exposure time and H 2 O 2 dose of 10 mg/L, percent destruction decreases from 50% to 30% with increasing methanol to water ratio. DISCUSSION Looking at Figure 3 it can be concluded that percent destruction of ibuprofen increases with increasing hydrogen peroxide dosage and time, however, at 30 min UV exposure time the effect of increasing hydrogen peroxide dosage is decreased. In Figure 3 w e can see that there is little difference between the percent destruction of ibuprofen with a low hydrogen peroxide dose and the percent destruction of ibuprofen with a high hydrogen peroxide dose at the higher UV exposure time. It can also be concluded th at the percent destruction of ibuprofen is greatest in the ibuprofen DI solution and decreases with the addition of sodium chloride and methanol. Looking at Figure 4 it can be concluded that the regeneration of Dowex 22 resin increases with increasing methanol to water ratio. It is possible that this is a linear relationship but it is also possible that it is an exponential relationship. If this is the case, it is possible that one hundred percent regeneration is possible at a methanol ratio lower than fifty percent. Percent destruction of ibuprofen decreases with increasing water methanol ratio in the regeneration solution. This is due to methanol acting as another source of organic matter for the hydrogen peroxide radicals to break down thus, taking away from the destruction of ibuprofen.
5 Figure 3 : Percent destruction of ibuprofen (C 0 = 0.2 mM) in DI and 5% NaCl with varying H 2 O 2 doses (mg/L) at a five minute and 30 minute UV exposure time. The four different graphs re present the four tested regeneration solutions as their titles indicate. Figure 4 : Percent regeneration of Dowex 22 resin in 5% NaCl, water methanol solution with varying water methanol ratio. At a 1% methanol solution, Dowex 22 resin is regenerated 35%, while at a 50% methanol solution Dowex 22 resin is regenerated 100%. Regeneration is expected to increase with increasing methanol percentage in the regeneration solution,. 0% 20% 40% 60% 80% 100% 10 20 40 Percent Destruction Hydrogen Peroxide Dosage(mg/L) Percent Destruction of Ibuprofen in DI Solution 5 minute UV exposure time 30 minute UV exposure time 0% 20% 40% 60% 80% 100% 10 20 40 Percent Destruction Hydrogen Peroxide Dosage(mg/L) Percent Destruction of Ibuprofen in DI + NaCl Solution 5 minute UV exposure time 30 minute UV exposure time 0% 20% 40% 60% 80% 100% 10 20 40 Percent Destruction Hydrogen Peroxide Dose (mg/L) Percent Destruction of Ibuprofen in 50/50 Water Methanol Solution 5 minute UV exposure time 30 minute UV exposure time 0% 20% 40% 60% 80% 100% 10 20 40 Percent Destruction Hydrogen Peroxide Dosage(mg/L) Percent Destruction of Ibuprofen in 50/50 Water Methanol + NaCl Solution 5 minute UV exposure time 30 minute UV exposure time 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 Percent Regeneration( %) Percent Methanol in Regeneration Solution(%) Regeneration of Dowex22 Resin with Varying Methanol Solutions ?
6 Figure 5 : Percent destruction of Ibuprofen (C 0 = 0. 2 mM) in 5% NaCl, water methanol solution with varying water methanol ratios. At a 30 minute UV exposure time and H 2 O 2 dose of 10 mg/L Percent destruction decreases from 50% to 30% with increasing water methanol ratio. 0 10 20 30 40 50 60 0 10 20 30 40 50 Percent Destruction of IBP(%) Percent Methanol in Regeneration Solution (%) Percent Destruction of IBP in Varying Methanol Solutions
7 REFERENCES (1) Szab, R., Schrantz, K., Dombi, A., Mazellier, P., & Legube, B. (2010). Innovative phosphorus removal and recovery strategies (Master's thesis, University of Szeged). (2) Landry, K. A. & Boyer, T. H.,2013. Diclofenac removal in urine using strong base anion exchange polymer resins Water Research, 47, 6432 6444. (3) Cooke, J. (2012). Innovative phosphorus removal and recovery strategies (Honor's thesis, University of Florida).
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