Sorption of Nutrients and Antibiotics on Biochar and Its Environmental Implications

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Title:
Sorption of Nutrients and Antibiotics on Biochar and Its Environmental Implications
Physical Description:
1 online resource (176 p.)
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english
Creator:
Yao, Ying
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University of Florida
Place of Publication:
Gainesville, Fla.
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Thesis/Dissertation Information

Degree:
Doctorate ( Ph.D.)
Degree Grantor:
University of Florida
Degree Disciplines:
Agricultural and Biological Engineering
Committee Chair:
Gao, Bin
Committee Members:
Li, Yuncong
Welt, Bruce Ari
Martinez, Christopher J
Harris, Willie G, Jr

Subjects

Subjects / Keywords:
antibiotics -- biochar -- clay -- dye -- mg-enrichment -- montmorillonite -- nutrients -- phosphate
Agricultural and Biological Engineering -- Dissertations, Academic -- UF
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Agricultural and Biological Engineering thesis, Ph.D.
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theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

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Abstract:
Biochar converted from agricultural residues or other carbon-rich wastes may provide new methods and materials for environmental management, particularly with respect to carbon sequestration and contaminant remediation. Combination of biofuel generation with biochar production would provide further environmental and economic benefits. In this study, two biochars were produced from anaerobically digested and undigested sugar beet tailings through slow-pyrolysis at 600 oC in a N2 environment. The digested sugar beet tailing biochar (DSTC) and raw sugar beet tailing biochar (STC)yields were around 45.5% and 36.3% of initial dry weight, respectively.  Compared to STC, DSTC had similar pH and surface functional groups, but higher surface area, and its surface was less negatively charged. SEM-EDS and XRD analyses showed that colloidal and nano-sized periclase (MgO) was presented on the surface of DSTC. Laboratory adsorption experiments were conducted to assess the phosphate removal ability of the two biochars, an activated carbon (AC), and three Fe-modified biochar/AC adsorbents. The DSTC showed the highest phosphate removal ability with are removal rate around 73%. Our results suggest that anaerobically digested sugar beet tailings can be used as feedstock materials to produce high quality biochars, which could be used as adsorbents to reclaim phosphate from water.
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In the series University of Florida Digital Collections.
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Includes vita.
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Description based on online resource; title from PDF title page.
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This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility:
by Ying Yao.
Thesis:
Thesis (Ph.D.)--University of Florida, 2013.
Local:
Adviser: Gao, Bin.
Electronic Access:
RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2014-05-31

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lcc - LD1780 2013
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UFE0045409:00001


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1 SORPTION OF PHOSPHATE AND OTHER CONTAMI N ANTS ON BIOCHAR AND ITS ENVIRONMENTAL IMPLICATIONS By YING YAO A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMEN TS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2013

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2 2013 Ying Yao

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3 To my family

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4 ACKNOWLEDGMENTS I would like to express my deep appreciation and gratitude to my advisor, Dr. Bin Gao for the patient guidance and mentorship he provided to me, all the way from when I was first considering applying to the Ph D program in the Agricultural and Biological heft is matched only by his genuinely good nature and down to earth humility, and I am truly fortunate to have had the opportunity to work with him. I would also like to thank my co chair Dr. Bruce Welt and committee members Dr. Willie G. Harris, Christop her J. Martinez and Yuncong Li for the friendly guidance, thought provoking suggestions, and the general collegiality that each of them offered to me over the years. I truly appreciate that Prof. Liuyan Yang at Nanjing University encouraged and guided me towards my academic life. I extend my gratitude to my colleagues Mandu Inyang, Dr. Yuan Tian, Ming Zhang, Lei Wu in the Environmental Nanotechnology Research Group for their valuable advice and help in my research. I also thank my friend s Dr. Congrong Yu, Dr. Hao Chen, Dr. Yanmei Zhou, Yining Sun, and Lin Liu for their kindly priceless help and support. I would like to acknowledge Paul Lane, Orlando Lanni, and Billy Duckworth for their lab support. able sacrifices made by my family Special thanks go to my parents and grandparents for their tremendous love and support in my whole life. Without them, I could not pursue this final degree.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 9 LIST OF FIGURES ................................ ................................ ................................ ........ 10 LIST OF ABBREVIATIONS ................................ ................................ ........................... 13 ABSTRACT ................................ ................................ ................................ ................... 14 CHAPTER 1 INTRODUCTORY REVIEWS ................................ ................................ ................. 17 Background and Problem Statement ................................ ................................ ...... 17 Why Use Biochar to Remove Nutrients ................................ ............................ 18 Why Use Biochar to Remove Antibiotics and Its Impact on Reclaimed Water Irrigation ................................ ................................ ................................ ........ 21 Why Use Biochar to Remove Cationic Dye (Methylene Blue) .......................... 23 Research Objectives ................................ ................................ ............................... 2 4 Objective 1: Determine the Effect of Biochar Amendment on Leaching of Nitrate, Ammonium, and Phosphate in Sandy Soils ................................ ...... 24 Objective 2: Develop a Low Cost Biochar Made from Anaerobically Digested Sugar Beet Tailings to Effectively Remove Phosphate from Wastewater ................................ ................................ ................................ ... 24 Objective 3: Determine the Mechanisms and Characteristics of Phosphate Adsorption onto the Digested Sugar Beet Tailing Biochar (DSTC) ............... 25 Objective 4: Determine Whether Engineered Mg Biochar Nanocomposites Could Be Prepared by Direct Pyrolysis of Mg Accumulated Tomato Ti ssues. ................................ ................................ ................................ ......... 25 Objective 5 : Determine Whether Engineered Biochars from Mg Enriched Tomato Tissues Can Be Used to Reclaim Aqueous P and Then Be Applied To Soils as a P Fertilizer ................................ ................................ .. 25 Objective 6 : Develop a Biochar Technology to Reduce the Contamination Risk of Reclaimed Water Irrigation ................................ ................................ 25 Objective 7: Develop Low Cost, Clay Modified Biochars for the Removal of Cationic Dyes from Wastewater ................................ ................................ .... 26 Organization of the Dissertation ................................ ................................ .............. 26 2 EFFECT OF BIOCHAR AMENDMENT ON SORPTION AND LEACHING OF NITRATE, AM MONIUM, AND PHOSPHATE IN A SANDY SOIL ........................... 29 Introduction ................................ ................................ ................................ ............. 29

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6 Materials and Methods ................................ ................................ ............................ 30 Materials ................................ ................................ ................................ ........... 30 Characterization of Sorbents ................................ ................................ ............ 31 Sorption of Nitrate, Ammonium, and Phosphate ................................ .............. 32 Leaching of Nutrients from Soil Columns ................................ ......................... 33 Results and Discussion ................................ ................................ ........................... 33 Biochar Properties ................................ ................................ ............................ 33 Adsorption of Nitrate, Ammonium and Phosphate by Biochars ........................ 34 Transport in Soil Columns ................................ ................................ ................ 35 Implications ................................ ................................ ................................ ............. 36 3 REMOVAL OF PHOSPHATE FROM AQUEOUS SOLUTION BY BIOCHAR DERIVED FROM ANAEROBICALLY DIGESTED SUGAR BEET TAILINGS: I. BIOCHAR CHARACTERIZATION AN D PRELIMINARY ASSESSMENT ............... 42 Introduction ................................ ................................ ................................ ............. 42 Materials and Methods ................................ ................................ ............................ 44 Biochar Production ................................ ................................ ........................... 44 Biochar Properties ................................ ................................ ............................ 45 Other Adsorbents ................................ ................................ ............................. 47 Phosphate Adsorption ................................ ................................ ...................... 48 Results and Discussion ................................ ................................ ........................... 48 Biochar and Bioenergy Production Rates ................................ ......................... 48 Elemental Composition ................................ ................................ .................... 49 Zeta Potential and pH ................................ ................................ ....................... 50 Surface Area ................................ ................................ ................................ .... 51 SEM EDS ................................ ................................ ................................ ......... 51 XRD ................................ ................................ ................................ .................. 52 Surface Functional Groups ................................ ................................ ............... 52 Phosphate Removal ................................ ................................ ......................... 53 Implications ................................ ................................ ................................ ............. 54 4 REMOVAL OF PHOSPHATE FROM AQUEOUS SOLUTIO N BY BIOCHAR DERIVED FROM ANAEROBICALLY DIGESTED SUGAR BEET TAILINGS: II. ADSORPTION MECHANISMS AND CHARACTERISTICS ................................ .... 59 Introductio n ................................ ................................ ................................ ............. 59 Materials and Methods ................................ ................................ ............................ 61 Materials ................................ ................................ ................................ ........... 61 Adsorption Kinetics ................................ ................................ ........................... 62 Adsorption Isotherm ................................ ................................ ......................... 62 Effect of pH and Coexisting Anions ................................ ................................ .. 63 Post adsorption Biochar Characterization ................................ ........................ 63 Results and Discussion ................................ ................................ ........................... 64 Main Adsorption Mechanism ................................ ................................ ............ 64 Other Potential Adsorption Mechanisms ................................ .......................... 65 Adsorption Kinetics ................................ ................................ ........................... 66

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7 Adsorption Isotherms ................................ ................................ ....................... 68 Effect of pH and Coexisting Anion s ................................ ................................ .. 69 Implications ................................ ................................ ................................ ............. 69 5 ENGINEERED CARBON (BIOCHAR) PREPARED BY DIRECT PYROLYSIS OF MG ACCUMULATED TOMATO TISSUES: CHARACTERIZATION AND PHOSPHATE REMOVAL POTENTIAL ................................ ................................ .. 75 Introduction ................................ ................................ ................................ ............. 75 Materials and Methods ................................ ................................ ............................ 78 Biochar production ................................ ................................ ........................... 78 Characterization ................................ ................................ ............................... 79 P sorption ................................ ................................ ................................ ......... 79 Statistical Methods ................................ ................................ ........................... 80 Results and Discussion ................................ ................................ ........................... 80 Mg and Ca in Feedstock and Biochar ................................ .............................. 80 Effect of Mg Enrichment of P Removal by Biochar ................................ ........... 81 Characterization of Mg Enriched Biochar (MgEC). ................................ ........... 82 Implications ................................ ................................ ................................ ............. 84 6 AN ENGINEERED BIOCHAR RECLAIMS PHOSPHATE FROM AQUEOUS SOLUTIONS: MECHANISMS AND POTENTIAL A PPLICATION AS A SLOW RELEASE FERTILIZER ................................ ................................ .......................... 92 Introduction ................................ ................................ ................................ ............. 92 Materials and Methods ................................ ................................ ............................ 95 Materials ................................ ................................ ................................ ........... 95 P Adsorption ................................ ................................ ................................ ..... 95 Post Sorption Characterization ................................ ................................ ......... 96 P Release ................................ ................................ ................................ ......... 97 Seeds Germination and Early Stage Seedling Growth Bioassay ..................... 97 Statistics ................................ ................................ ................................ ........... 98 Results and Discussion ................................ ................................ ........................... 98 Adsorption Kinetics and Isotherms ................................ ................................ ... 98 Adsorption/Desorption Mechanisms ................................ ............................... 101 P Desorption from P L aden Biochar as A Slow Release Fertilizer. ................ 103 Seeds Germination and Early Stage Seedling Growth Bioassay ................... 105 Implications ................................ ................................ ................................ ........... 105 7 ADSORPTION OF SULFAMETHOXAZOLE ON BIOCHAR AND ITS IMPACT ON RECLAIMED WATER IRRIGATION ................................ ............................... 113 Introduction ................................ ................................ ................................ ........... 113 Materials and Methods ................................ ................................ .......................... 116 Materials ................................ ................................ ................................ ......... 116 Characterization of Sorbents ................................ ................................ .......... 117 Sorption of SMX ................................ ................................ ............................. 118

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8 Transport of SMX in Reclaimed Water through Soil Columns ........................ 119 TCLP Extraction ................................ ................................ ............................. 120 Growth Inhibition ................................ ................................ ............................ 121 Results and Discussion ................................ ................................ ......................... 122 Bio char Properties ................................ ................................ .......................... 122 Sorption of SMX ................................ ................................ ............................. 123 Transport in Soil Columns ................................ ................................ .............. 123 TCLP Extraction ................................ ................................ ............................. 125 Growth Inhibition ................................ ................................ ............................ 125 Implications ................................ ................................ ................................ ........... 127 8 REM OVAL OF METHYLENE BLUE FROM AQUEOUS SOLUTION BY CLAY MODIFIED BIOCHAR ................................ ................................ ........................... 131 Introduction ................................ ................................ ................................ ........... 131 Materials and Methods ................................ ................................ .......................... 133 Biochar Production ................................ ................................ ......................... 133 Characterizations ................................ ................................ ........................... 134 Methylene Blue Sorption ................................ ................................ ................ 135 Adsorption Kinetics and Isotherm ................................ ................................ ... 135 Regeneration Experiments ................................ ................................ ............. 135 Results and Discussion ................................ ................................ ......................... 136 Surface Area and Elemental Analysis ................................ ............................ 136 Thermogravimetric Analysis (TGA) Of Clay Modified and Untreated Biochars ................................ ................................ ................................ ...... 137 Methylene Blue Removal Ability of Clay Modified Biochars ........................... 138 Adsorption Kinetics ................................ ................................ ......................... 139 SEM EDX and XRD ................................ ................................ ....................... 141 Regeneration of Exhausted BG MMT Sorbent ................................ ............... 142 Implications ................................ ................................ ................................ ........... 143 9 CONCLUSIONS ................................ ................................ ................................ ... 151 LIST OF REFERENCES ................................ ................................ ............................. 155 BIOGRAPHICAL SKETCH ................................ ................................ .......................... 176

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9 LIST OF TABLES Table page 2 1 Basic properties of the sandy soil used in this study ................................ ......... 38 2 2 Properties and elemental composition of biochars used in this study. ................ 39 3 1 Elemental analysis of raw and digested sugar beet tailings, and their associated biochars, STC and DSTC, respectively (mass %) a .......................... 55 4 1 Best fit parameter values for models of kinetic and isotherm data ..................... 71 5 1 Elemental analysis of feedstocks and biochars p roduced in this study (m ass %) ................................ ................................ ................................ ...................... 85 5 2 Correlation between biochar phosphat e removal rate (P) and different metal content (C), where P= a C+ b. ................................ ................................ ........... 86 6 1 Best fit parameter values from model simulations of P adsorption kinetics, isotherms and desorption kinetics. ................................ ................................ ... 106 7 1 Properties and elemental composition of biochar used in this study. ............... 128 8 1 Elemental analysis of biochars produced in this stud y (mass %)a. BG MMT, BB MMT, HC MMT, BG KLN, BB KLN, HC KLN, BG, BB, HC are biochars produced from clay modified and untreated feedstocks, respectively. ............. 144 8 2 Best fit kinetics and isotherms models parameters for MB adsorption to BG MMT biochar. ................................ ................................ ................................ .... 145

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10 LIST OF FIGURES Figure page 2 1 Removal of nitrate (A), ammonium (B), and phosphate (C) from aqueous solution by different types of biochars. ................................ ............................... 40 2 2 Cumulative amounts of nitrate (A), ammonium (B), and phosphate (C) in the leachates from biochar amended and unamended soil columns. ....................... 41 3 1 SEM images (left) and corresponding EDS spectra (right) of the two biochar samples: A) STC, 500X; B) DSTC, 500X; and C) DSTC, 7000X. The EDS spectra were obtained at the same location a s shown in the SEM images. ....... 56 3 2 XRD spectra of the two biochars. Crystallites were detected with peaks labeled as Q for quartz (SiO2), C for calcite (CaCO3), and P for periclase (MgO). ................................ ................................ ................................ ................ 57 3 3 FTIR spectra of the two biochar samples. ................................ .......................... 58 3 4 Comparison of phosphate removal by different adsorbents. .............................. 58 4 1 SEM image (A) and corresponding EDS spectra (B) of the post adsorption DSTC at 7000X. The EDS spectra were recorded at the same location as showing in the SEM image. ................................ ................................ ................ 71 4 2 XRD (A) and FTIR (B) spectra of the original and post adsorption DSTC. Crystallites were detected with peaks labeled in the XRD spectra as Q for quartz (SiO 2 ), C for calcite (CaCO 3 ), and P for periclase (MgO). ....................... 72 4 3 Adsorption kinetic data and modeling for phosphate onto DSTC (A) full, and (B) pre equilibrium adsorption versus square root of time. ................................ 73 4 4 Ad sorption isotherm for phosphate on DSTC. ................................ .................... 73 4 5 Effect of (A) pH and (B) coexisting anions on phosphate adsorption onto DSTC. ................................ ................................ ................................ ................. 74 5 1 Comparison of phosphate adsorption ability of five biochars produced in this study. CaEC, Ca enriched biochar; MgEC, Mg enriched biochar; LCC, laboratory control biochar; FCC, farm control biochar. ................................ ....... 87 5 2 Correlation between phosphate removal rate and Mg/ Ca (a) and other metal contents (Cu, Fe, Al, Zn, K) (b f) of a total of 25 biochars. Red and black colors represent Mg and Ca, respectively. ................................ ......................... 88 5 3 XRD spectrum of MgEC. ................................ ................................ .................... 89

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11 5 4 SEM image and EDS spectrum of MgEC morphological structures, the insert is at a higher resolution. ................................ ................................ ..................... 90 5 5 XPS scan of magnesium (a) and phosphorus (b) on MgEC surfaces. ................ 90 5 6 TGA curves of MgEC and LCC1. ................................ ................................ ........ 91 6 1 Adsorption kinetic (a) and isotherm (b) data and modeling for phosphate on the engineered biochar. Symbols are experimental data and lines are model results. ................................ ................................ ................................ .............. 107 6 2 Kinetics pre equilibrium adsorption versus square root of time. ....................... 107 6 3 XRD spectrum of P laden biochar. ................................ ................................ ... 108 6 4 SEM image and EDX spectrum of P laden bioc har morphological structures. 108 6 5 XPS spectra of the Mg 1s (a) and P 2p3/2 (b) region for P laden biochar. ....... 109 6 6 Illustrati on scheme of adsorption and desorption mechanisms of P on the engineered biochar surface (S). ................................ ................................ ....... 110 6 7 (a) Desorption kinetics, symbols are experimental data and the line is model results. (b) S uccessive and repeatable release of phosphate by P laden biochar ................................ ................................ ................................ .............. 111 6 8 TGA curve of P laden bi ochar. ................................ ................................ ......... 111 6 9 Comparison of grass seedlings between P laden biochar and control groups. 112 7 1 The solid water distribution coef ficients (K d ) of SMX adsorption on different types of biochar. ................................ ................................ ............................... 129 7 2 Concentration of SMX in simulated reclaimed water leachates transported through biochar amended and unamended soil columns ................................ 129 7 3 Concentration of SMX in TCLP extracts of biochar amended and unamended soils irrigated with simulated reclaimed water with SMX. ................................ 130 7 4 Concentration of SMX in TCLP extracts of biochar amended and unamended soils irrigated with simulated reclaimed water with SMX. ................................ 130 8 1 TGA curves comparison of clay modified an d untreated biochars under air (a c) or nitrogen (d) atmosphere. ................................ ................................ ...... 146 8 2 Comparison of methylene blue (MB) adsorption ability of nine biochars produced in this study. ................................ ................................ ...................... 147

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12 8 3 Adsorption kinetics data and modeling (a), and intraparticle diffusion plot for methylene blue (MB) on BG MMT biochar. Symbols are experimental data and lines are model results. ................................ ................................ .............. 148 8 4 Adsorption isotherm data and modeling for methylene blue (MB) on BG MMT biochar. Symbols are experimental data and lines are model results. .............. 148 8 5 SEM ima ge (a c) and EDX spectrum (d) of BG MMT biochar. ......................... 149 8 6 XRD spectrum of BG MMT biochar. ................................ ................................ 150 8 7 Regeneration and cycle performanc e of BG MMT sorbent. ............................. 150

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13 LIST OF ABBREVIATIONS AC A ctivated carbon BB300/ 450/ 600 Bamboo biochar made at temperature 300/ 450/ 600 o C BG300/ 450/ 600 Bagasse biochar made at temperature 300/ 450/ 600 o C BP300/ 450/ 600 Peanut hull biochar made at temperature 300/ 450/ 600 o C CaEC/ CaET Ca biochar composites/ corresponding raw material DSTC Digested sugar beet tailing biochar FCC1/ FCT1 Biochar from Senibel farm control tomato tissues / corresponding raw material FCC2/ F CT2 Biochar from Rocky Tops farm control tomato tissues / corresponding raw material HTPH Peanut hull hydrochar HW300/ 450/ 600 Hickory wood biochar made at temperature 300/ 450/ 600 o C KLN Kaolinite LCC/ LCT Laboratory control biochar/ corresponding raw material MB Methylene blue MgEC/ MgET Mg biochar composites/ corresponding raw material MMT Montmorillonite P Phosphate PH300/ 450/ 600 Brazilian pepperwood biochar made at temperature 300/ 450/ 600 o C SMX Sul famethoxazole STC Raw sugar beet tailing biocha r

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14 Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy SORPTION OF PHOSPHATE AND OTHER CONTAMI N ANTS ON BIOCHAR AND ITS ENV IRONMENTAL IMPLICATIONS By Ying Yao May 2013 Chair: Bin Gao Major: Agricultural and Biological Engineering Biochar converted from agricultural residues or other carbon rich wastes may provide new solutions for environmental management, particularly wit h respect to carbon sequestration and contaminant remediation. This Ph.D. dissertation systematically investigated the application of various biochars to remov e various contaminants including nutrients, antibiotics, and cationic dye from aqueous solutions and its implications. T hirteen biochars were first tested in laboratory sorption experiments to determine their sorption ability to nutrients and most of them showed little/no ability to sorb nitrate or phosphate. However, nine biochars could remove ammo nium from aqueous solution. Column leaching experiment showed that the BP600 biochar effectively reduced the total amount of nitrate, ammonium, and phosphate (P) in the leachates by 34.0%, 34.7%, and 20.6%, respectively, relative to the soil alone. The PH6 00 biochar also reduced the leaching of nitrate and ammonium by 34% and 14%, respectively, but caused additional P release from the soil columns. Therefore, the nutrient sorption characteristics of a biochar should be studied prior to its use in a particul ar soil amendment project.

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15 To enhance biocha an engineered biochar (i.e., DSTC) was produced from anaerobically digested sugar beet tailings Its P removal ability (73%) was the highest compared to as is biochar (i.e., STC ) an a ctivated carbon (AC), and three Fe modified biochar/AC adsorbents. Batch adsorption kinetic and equilibrium isotherm experiments, mathematical models study, and post adsorption characterizations using SEM EDS, XRD, and FTIR suggested that the enhanced P so rption ability of the DSTC is due to the presence of colloidal and nano sized MgO ( per iclase) particles on its surface. A nother engineered biochar (i.e., MgEC) was prepared from magnesium (Mg) enriched tomato tissues and showe d better sorp tion ability to P in aqueous solutions compared to the other four tomato tissue biochars. Mathematical modeling and post sorption characterization results indicated that the sorption was mainly controlled by tw o mechanisms: precipitation of P through chemical reaction wit h Mg particles and surface deposition of P on Mg crystals on biochar surfaces. Most of the P retained in MgEC was bioavailable and significantly stimulated grass seed germination and growth. To test the sorption ability of biochars to antibiotics, eight bi ochar s derived from agricultural/forestry residuals were used to sorb SMX from aqueous solutions Two biochars have dramatically decreased SMX leaching with only 2~14% of the SMX transported through biochar amended soils. However, biochar with high accumul ations of SMX was found to inhibit the growth of the bacteria. Thus, biochar with very high pharmaceutical sorption abilities may find use as a low cost alternative sorbent for treating wastewater plant effluent, but should be used with caution.

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16 Finally, clay modified biochars were developed in laboratory, combining advantages of both biochar and clay to remove cationic contaminants from water The results showed that BG MMT could effectively adsorb MB, a cationic dye, with removal rate around 84.3 %. Eigh t commonly used mathematical models were used to fit the kinetics and isotherm data to inves tigate the sorption mechanisms and the findings showed ion exchange was the governing sorption mechanism of MB on the biochars. The clay modified biochars thus coul d be regenerated and reuse d after dye adsorption for multiple times The results of this dissertation indicate that biochar, as alternative sorbent, could effectively remove nutrients ( P ), antibiotics (SMX) and cationic dye (MB) from aqueous solutions. New preparation method s, such as a naerobically digestion,

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17 CHAPTER 1 INTRODUC TORY REVIEWS Background and Problem Statement Biochar is a pyrogenic black carbon that has attracted increased attention in both political and academic arenas [1] A number of studies have suggested that terrestrial land application of biochar could effectively sequester carbon in soils and thus mitigate global warming [1, 2] When biochar i s applied to soils, it may also present other potential advantages including enhanced soil fertility and crop productivity [3] increased soil nutrients and water holding capacity [4] and reduced emissions of other greenhouse gases from soils [5] In addition to its carbon seq uestration and soil amelioration applications, studies cost adsorbent, storing chemical compounds including some of the most common environmental pollutants. It has been demonstrated that biochars made from a variety of sources had strong sorption ability to different types of pesticides and other organic contaminants [6 9] The sorption ability of biochar has been shown to exceed that of the natural soil o rganic matter by a factor of 10 100 in some cases [10] In addition to strong organic compounds sorption ability, biochars have also been shown to remove metal contaminants from water and showed strong affinity for a number of heavy metal ions [11 13] This dissertation project was designed to determine the characteristics and mechanis ms that control the ability of biochar as a low cost adsorbent to remove nutrients ( mainly phosphate) antibiotics and cationic dye s from aqueous solutions.

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18 Why Use Biochar t o Remove Nutrients The release of nutrients, such as phosphate, ammonia, and nit rate, from both point and non point sources into runoff may impose a great threat on environmental health [14, 15] The high level growth limiting nutrient can promote excessive production of photosynthetic aquatic microorganisms in natural water bodies and ultimately becomes a major factor in the eutrophi cation of many freshwater and marine ecosystems [16] It is therefore very important to develop effective technologies to remove phosphate, ammonia and nitrate from aqueous solutions prior to their discharge in to runoff and natural water bodies [17] Typically raw domestic wastewater has a total phosphorus concentration of approximately 10 mg P/L, the principal forms of phosphate being orthophosphate (5 mg P/L), pyrophosphate (1 mg P/L), and tripolyphosphate (3 mg P/L), together with smaller phosphate from wastewaters prior to discharge into natural waters is required [18] Many nutrient removal technologies including biological, chemical, and physical treatment methods have been developed for water treatment applications, particularly for the removal of phosphate and n itrate from municipal and industrial effluents [16, 19] Both biological and chemical treatments have been well documented and proven to be effective to remove nut rients from wastewater. Addition of chemicals, such as calcium, aluminum, and iron salts into wastewater is considered a simple phosphate removal technique, which separates the phosphate from aqueous system through precipitation [ 20 23] However, the chemical precipitation methods require strict control of operating conditions and may potentially introduce new contaminants into the water such as chloride and sulfate ions [15, 20, 24] Biological treatment of phosphate and nitrate in

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19 waste effluents may have certain advantages over the chemical precipitation method because it does not require chemical additions and enhanced bi ological treatment has been reported effectively remove most of the nutrients in waste water [ 25, 26] This technology, however, is very sensitive to the operation conditions and its removal efficiency may be, at t imes, much less [27] Both the chemical and biological treatment methods are also subjected to the costs and risks asso ciated with nutrient rich sludge handling and disposal [28] .Various physical methods have also been developed to remove phosphate, nitrate, and ammonia from aqueous solution such as electrodialysis, reverse osmosis, and ion exchange [ 20, 29 32] However, most of these physical methods have proven to be either too expensive or inefficient. Simple physi cal adsorption might be comparatively more useful and cost effective for nutrients removal [ 33, 34] Several studies investigated activated carbons as nutrient adsorbents, but showed that the adsorption capacity wa s very low [ 14, 18, 35] For example, Namasivayam et al. [18] reported that activated carbon made from coir pith with ZnCl 2 activation had a phosphate adsorption capacity of only 5,100 mg/kg. Lower cost materials, such as slag, fly ash, dolomite, red mud, and oxide tailings have also been explored by several studies as alternative adsorbents of phosphate from waste water [ 36 40] Biochar is a low cost adsorbent that is receiving increased attention recently because it has many potential environmental applications and benefits. While most of the current biochar studies are focused on biochar land application as an easy and cost effective way to sequestrate carbon and increase fertility, a number of recent investigations suggest that biochar converted from agricultural residues have a strong

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20 ability to bind chemical contaminants in water including heavy metals and organic contaminants [8, 11, 12, 41, 42] Only few studies, however, have investigated the ability of biochar to remove nutrients fro m water [43] .Ideally, if biochar can be used as a sorbent to reclaim nutrients such as phosphate and nitrate from w ater, there would be no need to regenerate the exhausted biochar because it can be directly applied to agricultural fields as a slow release fertilizer to improve soil fertility and build (sequester) soil carbon. But little research has been conducted to e xplore the nutrient removal potential of biochar [44] Although almost all biomass can be converted i nto biochar through thermal pyrolysis, a life cycle assessment of pyrolysis biochar systems suggested that it is more environmentally and financially viable to make biochar from waste biomass [45] In this sense, agricultural residues (e.g. sugarcane bagasse, poultry litter, and manure) and other green waste have been proposed as good feedstock materials to make biochar [9 46, 47] However, the applications and functions of those biochars are highly depending on their physicochemical properties (e.g. elemental composition, surface charge, and surface area) [46] Because biochar can be made of various waste biomass sources under different processing conditions, it is therefore very important to characterize their physicochemical properties before use. In a recent study, Inyang et al. [48] explored the production of biochar from the residue materials of anaerobic digestion of sugarcane bagasse. Comparison of the physicochemical properties of the bi ochar from anaerobically digested bagasse to that from raw bagasse suggested that the former has more desirable characteristics for soil amelioration, contaminant remediation, or water treatment. Using anaerobically digested residue materials (or the remai ns of biofuel

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21 production) as feedstock to produce biochar could not only reduce the waste management cost, but also make bioenergy production more sustainable and eco friendly. It is therefore very important to test the generality of this innovative approa ch by examining the feasibility of using other anaerobically digested materials for biochar production. It is anticipated that biochars converted from digested feedstock materials would have good ability to remove nutrients from water. Although it is stil l a relatively unexplored concept, the use of biochar to remove nutrients from aqueous solutions presents an innovative and promising technology. Not only may biochar represent a low cost waste water treatment technology for nutrient removal, but the nutri ent laden biochar may also be used as a slow release fertilizer to enhance soil fertility that will also sequester carbon. Why Use Biochar to Remove Antibiotics and Its Impact o n Reclaimed Water Irrigation Water stress and scarcity resulting from rapid po pulation growth, global climate changes, and pollution is among the greatest environmental problems faced by many countries. [49] In the past dec ade, freshwater consumption in agricultures rising rapidly due to demand not only from water thirsty vegetables and meat, but also from biofuel crops. [50] Reclai med water therefore has been used in agricultural and landscape irrigations to satisfy the demand and to ease the water crisis. Globally, about 20 million ha of land were irrigated with reclaimed water and this has become undoubtedly a key strategy to figh t water shortage. [51, 52] On one hand, reclaimed water often contains some nutrient elements, so its application to agricultural field may bring additional benefit to soil and crop systems. [53] On the other hand, however, reclaimed water irrigation may also pose serious

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22 environmental risks by introducing various pollutants, such as organic compounds and heavy metals, to irrigated soils and groundwater und erneath. [54] Pharmaceutical residues, which are recognized as emerging contaminants, are frequently detected in the discharge of treated effluent from wastewater treatment facilities (WWTF). [55] Occurrences of pharmaceuticals in treated wastewater, surface water, and groundwater have been reported worldwide. [55 58] In a field study of pharmaceuticals in soil irrigated with treated urban wastewater, Furlong et al. [59] found that reclaimed water irrigation may result in leaching of pharmaceuticals through the vadose zone to contaminate groundwater. Adverse effect of reclaimed water irrigation in agriculture caused by pharmaceuticals has also been demonstrated in several other studies. [54, 56, 60, 61] Sulfamethoxazole (SMX) is one the most frequently detected pharmaceuticals in reclaimed water. [56, 59] As a sulfonamide bacteriostatic antib iotic, it is extensively used for treatment and prevention of both human and animal diseases. [62] SMX is characterized as low reactive and shows high mobilit y in soils. [63] Consequently, if it is released into the aquatic systems through discharges from WWTF, SMX not only has toxic effect to aquatic organisms, but also may induce drug resistance to disease causing bacter ia. [64, 65] Occurrences of SMX in groundwater have been reported in many places, so it is important to inhibit SMX leaching through the vadose zone during reclaimed water irrigation. As suggested by Munoz et al. [56] there is a critical need to develop new method or technology for reclaimed water irrigation in agriculture to reduce the contamination risk of pharmaceuticals, particularly with respect to SMX in reclaimed water.

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23 Recent development of biochar technology may provide such an opportunity to reduce the risk of pharmaceutical contamination of groundwater from reclaimed water irrigation. When biochar is used in agriculture as a soil amendment, it can effectively increase soil fertility and create a c arbon sink to mitigate global warming. [3, 66, 67] In cost adsorbent to control pollutant migration in soils. [48, 68] It has been demonstrated that biochars converted from agricultural residues had strong sorption ability to different types of contaminants. [8, 69, 70] Previous studies have showed th at biochar have strong affinities to soil organic matters and other organic pollutants such as phenanthrene (PHE), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). [8, 10] Although phar maceuticals are emerging organic contaminants, very little research, if any, has been conducted to investigate the ability of biochar to remove pharmaceuticals from water. If it has good sorption ability to pharmaceuticals, such as SMX, then biochar, as a soil amendment, could prevent pharmaceuticals leaching from soil into groundwater as well as improve soil fertility and sequester carbon. This would increase the safety and feasibility of using reclaimed water for agricultural irrigation. Why Use Biochar t o Remove Cationic Dye (Methylene Blue) Industrial dyes are produced more than 7 10 5 tons annually with over 100,000 commerci al types. A considerable fraction of the industrial dyes have been discharged directly in aqueous effluent [71] T his poses a seriou s hazard to aquatic living organisms as well as diminishing the transparency of the water because many dyes are toxic and even carcinogenic [71, 72] Adsorption techniques have been widely applied to treat the dye polluted wastewater The removal of cationic dyes such as methylene blue (MB)

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24 by clays and their inte raction have been extensively studied in the literature [38, 73] As one of the most popular dyes, MB has long been used as a model compound to study the interactions between organi c dyes and adsorbents. It has bee n reported that MB can be attracted toward and are thus suitable in this dissertation project to determine the sorption characteristics and properties of the clay modified biochars [74] Research Objectives The main objectives of this Ph.D. dissertation were as follows: Objective 1: Determine the Effect of Biochar Amendment on Leaching o f Nitrate, Ammonium, and Phosphate in Sandy Soils The specific objectives were to: 1) access the over all aqueous nitrate, ammonium, and phosphate sorption ability of the biochars by conducting laboratory batch sorption experiments, and 2) examine the leaching dynamics of the three nutrients in a sandy soil amended with two selected biochars by running lab oratory column experiments. Obje ctive 2: Develop a Low Cost Biochar Made f rom Anaerobically Digested Sugar Beet Tailings to Effectively Remove Phosphate from Wastewater The specific objectives were to: 1) determine whether the anaerobically digested sugar beet tailings can be efficiently used as feedstock for biochar and bioenergy production, 2) compare the physicochemical properties of biochar obtained from digested feedstock to those of biochar obtained from pyrolysis of sugar beet tailings directly, and 3) assess the phosphate removal ability of the biochars produced.

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25 Objective 3: Determine the Mechanisms and Characteristics of Phosphate Adsorption onto the Digested Sugar Beet Tailing Biochar ( DSTC ) The specific objectives were to: 1) identify the mechan isms governing the adsorption of phosphate onto the DSTC; 2) measure the kinetics and equilibrium isotherms of phosphate adsorption onto DSTC; and 3) determine the effect of initial solution pH and coexisting anions on the adsorption of phosphate onto the DSTC. Objective 4: Determine Whether Engineered Mg Biochar Nanocomposites Could Be Prepared b y Direct Pyrolysis o f Mg Accumulated Tomato Tissues. The specific objectives were to : Objective 5 : Determine Whether Engineered Biochars fr om Mg Enriched Tomato Tissues Can Be Used t o Reclaim Aqueous P and Then Be Applied To Soils as a P Fertilizer The specific objectives were to : 1) measure the sorption characteristics of P to the engineered biochar, 2) characterize the post sorption biocha r to identify the governing P sorption/desorption mechanisms, 3) measure the release characteristics of P from the post sorption biochar and 4) determine the biological effects of the post sorption biochar on seed germination and seedling growth Objecti ve 6 : Develop a Biochar Technology to Reduce the Contamination Risk of Reclaimed Water Irrigation The specific objectives were to: 1) test the ability of different types of biochar to sorb aqueous SMX, 2) determine the leaching and retention of SMX in sim ulated reclaimed water through soils amended with selected biochar; and 3) evaluate the effect of SMX laden biochar on the growth of E. coli

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26 Objective 7: Develop Low Cost, Clay Modified Biochars for the Removal of Cationic Dyes from Wastewater The specifi c objectives were to: 1) develop a novel ap proach to prepare clay modified biochars 2) characterize the physicochemical properties of the clay modified biochar s, 3) assess the MB removal ability of the clay modified biochar s, and 4) determine the sorption mechanisms. Organization of the Dissertation This Ph.D. dissertation has nine chapters, including the present introductory chapter (Chapter 1). Chapter 2 discusses the effect of biochar amendment on leaching of nitrate, ammonium, and phosphate in sandy s oils. Biochars were produced from a range of commonly used feedstock materials. Laboratory batch sorption experiments were conducted to access the overall aqueous nitrate, ammonium, and phosphate sorption ability of the biochars. L aboratory column experime nts were used to examine the leaching dynamics of the three nutrients in a sandy soil amended with two selected biochars. Chapter 3 investigates phosphate removal ability of biochar made from anaerobical ly digested sugar beet tailings. Physicochemical prop erties of the biochar produced were characterized and a simple adsorption experiment was conducted as a preliminary assessment of the phosphate removal ability of the biochars. As a follow up study of Chapter 3, Chapter 4 applies laboratory adsorption expe riments and mathematical models to determine the mechanisms and characteristics of phosphate adsorption onto the digested su gar beet tailing biochar Chapter 5 explores whether engineered Mg biochar nanocomposites could be prepared by direct pyrolysis of M g accumulated tomato tissues and its phosphate removal ability. An innovative approach was used to produce engineered biochars directly from tissues of tomato, a commonly

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27 used model plant, enriched with Mg/Ca through bioaccumulation. Greenhouse experiments were conducted using a sand zeolite culture system to produce tomato tissues (leaves) containing high concentration of Mg/Ca for production of the engineered biochars. Physicochemical properties of the biochars produced were characterized in details. A pr eliminary adsorption experiment was conducted to assess the P removal ability of the biochars and together with the published results to Chapter 6 describes the poten tial of engineered Mg biochar nanocomposites to reclaim aqueous P and then be applied to soils as a P fertilizer. A series of laboratory experiments were conducted to determine the mechanisms and characteristics of P adsorption on the engineered biochar T he bioavailability, desorption characteristics, and seed germination ability of the adsorbed P within the spent (i.e. P laden) biochar were also evaluated. Chapter 7 from reclaimed water in order to red uce the contamination risk of reclaimed water irrigation and protect the groundwater A series of laboratory experiments were conducted to study the adsorption of SMX, a common pharmaceutical contaminant in reclaimed water, on biochar and its impact on rec laimed water irrigation. Chapter 8 describes the effect of clay modifi ed biochar on the removal of cationic contaminants (MB) from wastewater, using a low cost method combining biochar and clay together. Six new clay modifi ed engineered biochar were produc ed in laboratory through slow pyrolysis of clay (montmorillonite and kaolinite) pretreated biomass (bamboo, bagasse, hickory chips). Physicochemical properties of the clay modified biochar were characterized and MB adsorption experiment was conducted. Chap ter 9 summarizes

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28 the results of all the previous chapters and makes recommendations on future work. References are included at the end of this document.

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29 CHAPTER 2 EFFECT OF BIOCHAR AMENDMENT ON SORPTION AND LEACHING OF NITRATE, AMMONIUM, AND PHOSPHATE IN A SANDY SOIL 1 Introduction Excessive application of fertilizer has caused the release of nutrient elements, such as nitrogen and phosphorus, from agricultural fields to aquatic systems. Leaching of nutrients from soils may deplete soil fertility, accelera fertilizer costs for the farmers, reduce crop yields, and most importantly impose a threat to environmental health [14, 15, 75] High nutrient levels in surface and/or groundwater can promote eutrophication, excessive production of photosynthetic aquatic microorganisms in freshwater and marine ecosystems [16] It is therefore very important to develop effective technologies to hold nutrients in soils. An option to reduce nutrient leaching could be the application of biochar to soils. Biochar, sometimes called agrichar, is a charcoal derived from the thermal dec omposition of a wide range of carbon rich biomass materials, such as grasses, hard and soft woods, and agricultural and forestry residues. The approach of land application of biochar in agriculture is receiving increased attention as a way to create a carb on sink to mitigate global warming, increase soil water holding capacity, and reduce emissions of NO x and CH 4 as well as to control the mobility of a variety of environmental pollutants, such as heavy metals, pesticides and other organic contaminants [1, 66, 76, 77] In addition, it is suggested that application of biochar can 1 Reprint with permission from Yao, Y.; Gao, B.; Zhang, M.; Inyang, M.; Zimmerman, A. R., Effect of biochar amendment on sorption and leaching of nitrate, ammonium, and phosphate in a sandy soil. Chemosphere 2012, 89, (11), 1467 1471.

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30 increase soil fertility and crop productivity by reducing the leaching of nutrients or even supplying nutrients to plants [3, 4, 78] Only a few studies, however, have investigated the ability of biochars to retain nutrients, particularly for a range of different biochars. For example, Lehmann et al. [78] reported that amendment of biochar produced from secondary forest residuals significantly reduced the leaching of fertilizer N and increased plant growth and nutrition. Ding et al. [79] showed that bamboo biochar sorbed ammonium ions by cation exchange and retarded the vertical movement of ammonium into deeper soil layers within the 70 day observation time. Laird et al [75] reported the additi on of biochar produced from hardwood to typical Midwestern agricultural soil significantly reduced total N and P leaching by 11% and 69%, respectively. The overarching objective of this work was to determine the effect of biochar amendment on leaching of n itrate, ammonium, and phosphate in sandy soils. Biochars were produced from a range of commonly used feedstock materials. Laboratory batch sorption experiments were conducted to access the overall aqueous nitrate, ammonium, and phosphate sorption ability o f the biochars. In addition, laboratory column experiments were used to examine the leaching dynamics of the three nutrients in a sandy soil amended with two selected biochars. Materials and Methods Materials Biochar samples were produced from commonly u sed biomass feedstock materials: sugarcane bagasse (BG), peanut hull (PH), Brazilian pepperwood (BP), and through slow pyrolysis using a furnace (Olympic 1823HE) in a N 2 envi ronment at

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31 henceforth referred to as BG300, BG450, BG600, PH300, PH450, PH600, BP300, BP450, BP600, BB300, BB450, and BB600. Another biochar (hydrochar) was produced through the h ydrothermal carbonization of PH submerged in deionized (DI) water in an autoclave at 300 o C for 5 hours and is referred to as HTPH. All biochar samples were then crushed and sieved yielding a uniform 0.5 1 mm size fraction. After rinsing with DI water seve ral times to remove impurities, such as ash, the biochar samples were oven production procedures were reported previously [80] Sandy soil was collected from an agricultural field at the University of Florida in an oven. Basic properties of the soil are listed in Table 2 1. Nitrate, ammonium, and phosphate solutions were prepared by dissolving ammonium nitrate (NH 4 NO 3 ) or potassium phosphate dibasic anhydrous (K 2 HPO 4 ) in deionized (DI) water. All the chemicals used in the study were A.C.S certifi ed and obtained from Fisher Scientific. Characterization of Sorbents A range of physicochemical properties of the biochar samples produced were determined. The pH of the biochars was measured using a biochars to deionized (DI) water mass ratio of 1:20 foll owed by shaking and an equilibration time of 5 minutes before measurement with a pH meter (Fisher Scientific Accumet Basic AB15). Elemental C, N, and H abundances were determined, in duplicate, using a CHN Elemental Analyzer (Carlo Erba NA 1500) via high t emperature catalyzed combustion followed by infrared detection of the resulting CO 2 H 2 and NO 2 gases, respectively.

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32 Major inorganic elements were determined by acid digestion of the samples followed by inductively coupled plasma atomic emission spectrosco pic (ICP AES) analysis. The surface area of the biochars was determined on Quantachrome Autosorb1 at 77 K using the Brunauer Emmett Teller (BET) method in the 0.01 to 0.3 relative pressure range of the N 2 adsorption isotherm. Sorption of Nitrate, Ammonium, and Phosphate Batch sorption experiments were conducted in 68 mL digestion vessels sample was added into the vessels and mixed with 50 mL 34.4 mg/L nitrate and 10.0 mg/L ammonium solution or 30.8 mg/L phosphate solution. Vessels without either biochar or nutrient elements were included as experimental controls. The mixtures were nylon membr ane filters (GE cellulose nylon membrane). In addition to pH, concentrations of nitrate in the supernatants were determined using an ion chromatograph (Dionex Inc. ICS90). Concentrations of ammonium and phosphate in the supernatants were measured using the phenate method [81] and the ascorbic acid method (ESS Method 310.1; [82] ), respectively using a dual beam UV/VIS spectrophotometer (Thermo Scientific, EVO 60). Nutrient elements concentrations on the solid phase were calculated based on the initial and final aqueous concentrations. All the experimental treatments we re carried out in duplicate and the average values are reported. The variance between any duplicate measurements in this study was smaller than 5%.

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33 Leaching of Nutrients from Soil Columns Two biochar samples, PH600 and BP600, were selected to study th eir effect on nutrients retention and transport in a sandy soil. Soil columns were made of acrylic cylinders measuring 16.5 cm in height and 4.0 cm in diameter, and the bottom of the columns were covered with a stainless steel mesh with 60 m pore size to prevent soil loss. The sandy soil with (2% by weight) or without biochars was wet packed into the column (200 g total) following procedures reported previously [83] These columns were flushed with 10 pore volumes of DI water before use to precondit ion the column. A nutrient solution containing 34.4 mg/L nitrate, 10.0 mg/L ammonium and 30.8 mg/L phosphate was then applied to these laboratory soil columns to study biochar effect on nutrients retention and transport. About one pore volume of DI water w as poured into the soil columns on the first day. On days 2 and 3, same amount of nutrient solution was applied to the soil columns. After that, the columns were flushed with one pore volume DI water each day for another four days. All the leachate samples were collected from the outlet at the bottom of the columns and immediately filtered through concentrations in leachate samples were measured using the same method described above. Results and Discussion Biochar Properties The biochar production rate ranged 21. 7 51.5% on a mass basis (Table 2 2). In general, more biochar was yielded at the lower pyrolysis temperatures due to lower losses of volatile components [84, 85] T he pH of the biochars ranged from 5.2 to 9.1 (Table 2 2). Most of the biochars were alkaline, which is common for thermally

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34 produced biochars [86] While two biochars had considerable N 2 surface area (BP600 and BB600, 234.7 and 470.4 m 2 /g, respectively), the surface areas of most biochars were relativ ely very small ranging from 0.70 to 81.1 m 2 /g (Table 2 2). Positive correlation between N 2 measured surface area and pyrolytic temperature was found for all tested biochars, which is consistent with the results of several previous biochar studies [87 89] Elemental composition analysis indicated all the biochar samples to be carbon rich with carbon compositions ranging 56.4 86.4% carbon ( Table 2 2), which is typ ical of pyrolyzed biomass [67, 90] The oxygen and hydrogen contents of all the samples ranged 10.0 36.7% and 1.4 5.6%, respectively. As reported in the literature, some of these oxygen and hydrogen contents are likely in organic functional groups on biochar surface [90, 91] The biochar samples contained relatively small amount of nitrogen (0.1 1.6%) and relatively low levels of phosphorous (0.03 0.5%) and metal element s ( Table 2 2). Adsorption of Nitrate, Ammonium and Phosphate by Biochars The four biochars made at a higher temperature (600 o C), BG600, BB600 PH600, and BP600 could remove nitrate from aqueous solution with removal rates of 3.7%, 2.5%, 0.2%, and 0.12%, re spectively ( Figure 2 1a). The rest of the biochars (nine) showed no nitrate removal ability, and even released nitrate into the solution. Thus, increase in pyrolysis temperature may improve the sorption ability of biochars to aqueous nitrate Mizuta et al. [92] reported that bamboo biochar made at 900 had relatively higher nitrate adsorption capacity even compared to a commercial activated carbon, which is consistent with the findings of this study.

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35 Nine of the thirteen tested biochars showed some ammonium sorption ability, with removal rate ranged 1 .8 15.7% ( Figure 2 1b) The BP biochars had the best overall ammonium sorption performance with removal rates of 3.8%, 15.7% and 11.9% for BP300, BP450 and BP600, respectively. There was no apparent pyrolysis temperature trend in the ammonium sorption dat a. Only five biochars had any ability to remove phosphate from aqueous solution, with the rest of the biochars releasing phosphate into the solution ( Figure 2 1c). The BG450 biochar had the highest removal rate of 3.1%. The HTPH, BG300, PH600, and the thre e bamboo biochars released relatively large amount of phosphate into the solution (> 2%). The hydrothermally produced biochar, HTPH, showed no nutrient sorption ability and released the greatest amount of nitrate and phosphate. It is well accepted that biochar can be used as a soil amendment to improve soil fertility and crop productivity. Some previous studies attributed this function to the ability of biochar to retain nutrients in soils [93 96] The sorption experimental results in this work, however, showed that the ability of biochar to adsorb nutrient elements is not universal, but depends on both the nutrient and the biochar type. In fact, most of the biochars tested in this work showed little/no sorption ability to phosphate or nitrate, but performed slightly better in removing ammonium from aqueous solutions. Perhaps it not surprising that biochars are more effective at removing cationic species from solution given that most biochars have been reported to have a net negative surface charge [93, 94] Transport in Soil Columns Two biochars ( PH600 and BP600 ) with relatively good sorption ability for nutrients were selected for the soil column leaching study. When appl ied to the sandy

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36 soil, the two biochars reduced the leaching of both nitrate and ammonium ions from the column ( Figure 2 2a & 2b). Compared to the columns without biochar, after 6 days, the PH600 and BP600 amended soil columns released about 34.3% and 34.0 % less of total nitrate and 14.4% and 34.7% less ammonium, respectively. These results are in line with findings of the batch sorption experiment that both biochars could remove nitrate and ammonium from aqueous solutions ( Figure 2 1). ffect on the leaching of phosphate from the soils columns was different ( Figure 2 2c). BP600 reduced the total amount of phosphate in the leachates by about 20.6%, whereas PH600 increased the amount of phosphate leached from the soil columns by about 39.1% These results are also consistent with the results of the batch sorption experiment ( Figure 2 1). Although multiple mechanisms could be responsible to the enhanced or reduced retention of nutrients in the biochar amended soil [97] several recent studies have suggested that, when applied to soils, biochar may not only affect soil ion exchange capacity but als o provide refugia for soil microbes to influence the binding of nutritive cations and anions [98, 99] Further investigations are still needed to unveil the governing mechanisms of nutrient retention and leaching i n biochar amended soils. Implication s Biochar land application is commonly assumed to be an effective way to sequester carbon and improve soil fertility by reducing nutrient leaching. The finding from this work, however, suggests that the effect of biocha r on the retention and release of nutrient ions (i.e., nitrate, ammonium, and phosphate) varies with nutrient and biochar type. Of the thirteen biochars tested in this study, most of them showed little to no nitrate or phosphate sorption ability. However, nine biochars removed aqueous

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37 ammonium. When two selected biochars with relatively good sorption ability were used in soil columns, they could effective reduce the leaching of nitrate and ammonium. Only one biochar, however, could reduce the leaching of ph osphate from the soil columns. The results obtained from the leaching column study were consistent with finding from the sorption experiments, suggesting the effect of biochar on nutrients in soils could be determined through laboratory batch sorption stud ies. It is also recommended that sorption ability of biochars to nutrients should be determined before their applications to soils as amendment.

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38 Table 2 1. Basic properties of the sandy soil used in this study. Texture Sand (%) Silt (%) Clay (%) Density (g/cm 3 ) Organic Matter (%) Sandy 94.0 3.0 3.0 2.4 1.0

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39 Table 2 2. Properties and elemental composition of biochars used in this study. Production rate (%,mass based) BET surface area ( m 2 /g ) pH Elemental composition (%, mass based) C H O a N P K Ca Mg Zn Cu Fe Al BG300 33.4 5.2 7.2 69.5 4.2 24.5 0.9 0.05 0.27 0.46 0.14 0.01 0.00 0.02 0.10 BG450 28.0 15.3 7.9 78.6 3.5 15.5 0.9 0.07 0.25 0.83 0.18 0.01 0.00 0.06 0.11 BG600 26.5 4.2 7.9 76.5 2.9 18.3 0.8 0.08 0.15 0.91 0.21 0.01 0.00 0.05 0.11 PH30 0 38.4 0.8 7.8 73.9 3.9 19.1 1.6 0.09 0.86 0.32 0.13 0.00 0.00 0.00 0.06 PH450 21.7 21.8 8.2 81.5 2.9 13.0 1.0 0.09 0.94 0.33 0.13 0.00 0.00 0.00 0.06 PH600 30.8 27.1 8.0 86.4 1.4 10.0 0.9 0.10 0.71 0.34 0.12 0.00 0.00 0.00 0.06 HTPH300 44.9 5.6 6.8 56. 4 5.6 36.7 0.9 0.08 0.00 0.20 0.02 0.00 0.00 0.07 0.07 BP300 51.5 81.1 6.6 59.3 5.2 34.1 0.3 0.03 0.10 0.73 0.12 0.01 0.00 0.04 0.03 BP450 32.0 0.7 7.3 75.6 3.6 17.2 0.3 0.07 0.25 1.32 0.23 0.00 0.00 0.05 0.03 BP600 28.9 234.7 9.1 77.0 2.2 17.7 0.1 0.09 0.12 1.81 0.29 0.00 0.00 0.08 0.03 BB300 73.2 1.3 6.7 66.2 4.7 27.7 0.4 0.24 0.30 0.22 0.14 0.01 0.00 0.00 0.08 BB450 26.3 18.2 5.2 76.9 3.6 18.1 0.2 0.36 0.35 0.29 0.19 0.01 0.00 0.00 0.04 BB600 24.0 470.4 7.9 80.9 2.4 14.9 0.2 0.50 0.52 0.34 0.23 0.0 1 0.00 0.00 0.04 a: Determined by weight difference assuming that the total weight of the samples was made up of the tested elements only. b: < 0.01%.

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40 (A) (B) (C) Figure 2 1. Removal of nitrate (A), ammonium (B), and phosphate (C) from aqueous solut ion by different types of biochars. b c a

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41 (A) (B) (C) Figure 2 2. Cumulative amounts of nitrate (A), ammonium (B), and phosphate (C) in the leachates from biochar amended and unamended soil columns. a b c

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42 CHAPTER 3 REMOVAL OF PHOSPHATE FROM AQUEOUS SOLUTION B Y BIOCHAR DERIVED FROM ANAEROBICALLY DIGESTED SUGAR BEET TAILINGS: I. BIOCHAR CHARACTERIZATION AND PRELIMINARY ASSESSMENT 1 Introduction Biochar is a pyrogenic black carbon that has attracted increased attention in both political and academic arenas [1] A number of studies have suggested that terrestrial land application of biochar could effective ly sequester carbon in soils and thus mitigate global warming [1, 2] When biochar is applied to soils, it may also present other potential advantages including enhanced soil fertility and crop productivity [3] increased soil nutrients and water holding capacity [4] and reduced emissions of NO x and CH 4 two other greenhouse gases from s oils [5] In addition to its carbon sequestration and soil amelioration applications, studies cost ads orbent, storing chemical compounds including some of the most common environmental pollutants. It has been demonstrated that biochars made from a variety of sources had strong sorption ability to different types of pesticides and other organic contaminants [6 9] The sorption ability of biochar has been shown to exceed that of the natural soil organic matter by a factor of 10 100 in some cases [10] In addition to strong organic compounds sorption ability, biochars have also been shown to remove metal contaminants from water and showed strong affinity for a number of heav y metal ions [11 13] Only few studies, however, have investigated the ability of biochar to remove nutrients from water, particularly with respect to phosphate [43] Ideally, if biochar can 1 Reprinted with permission from Yao, Y.; Gao, B.; Inyang, M.; Zimmerman, A. R.; Cao, X.; Pullammanappallil, P.; Yang, L., Biochar derived from anaerobically digested sugar beet tailings : Characterization and phosphate removal potential. Bioresource Technology 2011, 102, (10), 6273 6278

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43 be used as a sorbent to reclaim nutrients such as phosphate from water, there would be no need to regenerate the exhausted biochar bec ause it can be directly applied to agricultural fields as a slow release fertilizer to improve soil fertility and build (sequester) soil carbon. Although almost all biomass can be converted into biochar through thermal pyrolysis, a life cycle assessment of pyrolysis biochar systems suggested that it is more environmentally and financially viable to make biochar from waste biomass [45] In this sense, agricultural residues (e.g. sugarcane bagasse, poultry litter, and manure) and other green waste have been proposed as good feedstock materials to make biochar [9, 46, 47] However, the applications and functions of those bioc hars are highly depending on their physicochemical properties (e.g. elemental composition, surface charge, and surface area) [46] Because biochar can be made of va rious waste biomass sources under different processing conditions, it is therefore very important to characterize their physicochemical properties before use. In a recent study, Inyang et al. [48] explored the production of biochar from the residue materials of anaerobic digestion of sugarcane bagasse. Comparison of the physicochemical properties of the biochar from anaerobically digested bagasse to that from raw bagasse suggested that the former has more desirable characteristics for soil amelioration, contaminant remediation, or water treatment. Using anaerobically digested residue materials (or the remains of biofuel production) as feedstock to pr oduce biochar could not only reduce the waste management cost, but also make bioenergy production more sustainable and eco friendly. It is therefore very important to test the generality of this innovative approach by examining the feasibility of using ano ther anaerobically digested material for biochar production.

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44 Sugar beet tailings are the waste byproducts from the production of beet sugar, which have been mainly managed by landfill disposal or direct land applications. Because beet sugar accounts for a lmost 40% of all refined sugar consumed in the U.S., significant amount of sugar beet tailings are generated by the sugar industry as solid waste every day. It has been demonstrated that sugar beet tailings can be anaerobically digested to generate bioener gy (biogas) [100] Although this practice may also reduce the volume of the sugar beet tailing waste, disposal of residue materials from the anaerobic digestion still poses significant economic a nd environmental problems. In this chapter, biochars were made from both undigested and anaerobically digested sugar beet tailings at 600 o C through slow pyrolysis. Physicochemical properties of the biochar produced were characterized and a simple adsorpt ion experiment was conducted as a preliminary assessment of the phosphate removal ability of the biochars. Our objectives were to: 1) determine whether the anaerobically digested sugar beet tailings can be efficiently used as feedstock for biochar and bioe nergy production, 2) compare the physicochemical properties of biochar obtained from digested feedstock to those of biochar obtained from pyrolysis of sugar beet tailings directly, and 3) assess the phosphate removal ability of the biochars produced. Mate rials and Methods Biochar Production Raw sugar beet tailings and anaerobically digested sugar beet tailing residues were obta ined from American Crystal Sugar Company (East Grand Forks, MN). These scale slow pyrolyzer was used to convert the samples into biochars. For each experiment, about 500 g of the dried samples were fed into a stainless cylinder reactor (50 cm diameter, 30 cm height)

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45 designed to fit inside of a furnace (Olympic 1823HE). The cylinder reactor was first purged with nitrogen gas (10 psi) and an oxygen sensor attached to the reactor ensured that the o xygen content in the reactor was less than 0.5% before it was inserted into the furnace. The reactor was purged again with N 2 along with the furnace and sealed for pyrolysis. Stainless steel tubing and fittings were installed on the furnace and the reactor to collect the oil and the non condensable gases evolved during the slow pyrolysis. The controller of the furnace was programmed to drive the internal biomass chamber temperature to 600 o C at a rate of 10 o C/min and held at the peak temperature for 2 h be fore cooling to room temperature. Biochar produced from the pyrolysis was gently crushed and sieved into two size fractions: <0.5 mm and 0.5 1mm. Only the latter was used in the experiments to minimize the presence of residual ash particles. In addition, t he biochar samples were then washed with deionized (DI) water for several Biochar Properties Elemental C, N, and H abundances were determined using a CHN Elemental Analyzer (Carlo Erba NA 15 00) via high temperature catalyzed combustion followed by infrared detection of the resulting CO 2 H 2 and NO 2 gases, respectively. Major inorganic elements were determined using the AOAC method of acid digesting the samples for multi elemental analysis by inductively coupled plasma emission spectroscopy (ICP AES). A range of physicochemical properties of the digested sugar beet tailing biochar (DSTC) and the undigested sugar beet tailing biochar (STC) were determined. The pH of the biochar was measured by adding biochar to deionized water in a mass ratio of 1:20. The solution was then hand shaken and allowed to stand for 5 minutes before

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46 measuring the pH with a pH meter (Fisher Scientific Accumet Basic AB15). The surface area of the biochar was determined u sing N 2 sorption isotherms run on NOVA 1200 and the Brunauer Emmett Teller (BET) method to determine mesopore enclosed surfaces and using CO 2 sorption isotherms run on a Quantachrome Autosorb measured at 273 K an interpreted using grand canonical Monte Car lo simulations of the non local density functional theory for micropore enclosed (<1.5 nm) surfaces. The surface charge of the samples was determined by measuring the zeta [101] About 1g of each sample was added to 100ml of DI water and the solution was shaken at 250 rpm for 30 minutes using a mechanical shaker. The shaken solution was then placed in a sonic bath to break the particles into colloids and the solution filtered using a 0.45 m filter paper. The electric mobility of each supernatant solution was determined using a Brookhaven Zeta Plus (Brookhaven Ins truments, Holtsville, NY) and Scanning electron microscope (SEM) imaging analysis was conducted using a JEOL JSM 6400 Scanning Microscope. Varying magnifications were use d to compare the structure and surface characteristics of the two biochar samples. Surface element analysis was also conducted simultaneously with the SEM at the same surface locations using energy dispersive X ray spectroscopy (EDS, Oxford Instruments Lin k ISIS). The EDS can provide rapid qualitative, or with adequate standards, semi quantitative analysis of elemental composition with a sampling depth of 1 2 microns [102]

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47 X ray diffraction (XRD) analysis was carried out to identify any crystallographic structure in the two biochar samples using a computer controlled X ray diffractometer (Philips Electronic Instruments) equipped with a stepping motor and gra phite crystal monochromator. Crystalline compounds in the samples were identified by comparing diffraction data against a database compiled by the Joint Committee on Powder Diffraction and Standards. Fourier Transform Infrared (FTIR) analysis of the biocha rs was carried out to characterize the surface organic functional groups present on these samples. To obtain the observable FTIR spectra, STC and DSTC were ground and mixed with KBr to 0.1 wt% and then pressed into pellets. The spectra of the samples were measured using a Bruker Vector 22 FTIR spectrometer (OPUS 2.0 software). Other Adsorbents Granulated activated carbon (AC, from coconut shell) was obtained from Fisher Scientific and was gently crushed, sieved, and washed using the same procedures as the biochar samples. In addition, each of the three biochars were modified by impregnating ferric hydroxide onto the AC (i.e., FeAC), STC (i.e., FeSTC), and DSTC (i.e., FeDSTC) samples according to the procedure employed by Thirunavukkarasu et al. [103] and Chen et al. [104] Briefly, 6 grams of AC, STC, and DSTC were added to 30 mL of 2M Fe(NO 3 ) 3 9H 2 O solution separately, and pH was then adjust ed to 4 5 with NaOH to create an iron precipitate. The mixture was then heated at 105 0 C overnight and the grains were separated, sieved, and washed thoroughly with DI water. The FeAC, FeSTC, and FeDSTC samples were then oven dried for further use.

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48 Phosph ate Adsorption Phosphate solutions were prepared by dissolving Potassium Phosphate Dibasic Anhydrous (K 2 HPO 4 certified A.C.S, Fisher Scientific) in DI water. The experiments were carried out in 68 mL digestion vessels (Environmental Express) at room tempe solutions of 61.5 mg/L (i.e., 20 mg/L P) and 0.1 g of each adsorbent (DSTC, FeDSTC, STC, FeSTC, AC, or FeAC) were added into the vessels. The pH of the solution was then adjusted t o 7, which is not only the typical pH of secondary wastewater, but also among the optimal pH values for phosphate adsorption as reported by previous studies [35, 105] After being shaken at 200 rpm in a mechanical shaker for 24 h, the vials were filters (GE cellulose nylon membrane). The phosphate concentrations of the liquid phase samples were then determined by the ascorbic acid meth od (ESS Method 310.1; [82] ) with aid of a s pectrophotometer (Thermo Scientific EVO 60). The phosphate removal rates were calculated based on the initial and final aqueous concentrations. All the experimental treatments were performed in duplicate and the average values are reported. Additional anal yses were conducted whenever two measurements showed a difference larger than 5%. Results and Discussion Biochar and Bioenergy Production Rates On a weight basis, about nine percent more biochar was produced from digested sugar beet tailing residue feedst ock than from the undigested sugar beet tailings. The biochar production rates of the digested and undigested materials were 45.5% and 36.3% of initial dry weight, respectively. Although studies have shown that increased

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49 biochar production through slow pyr olysis is often accompanied by decreased yield in bio oil [106] the bio oil production rates were similar for the digested and undigested suga r beet tailings with values of 12.5% and 10.9%, respectively. By summing to 100%, it follows that the amount of the non condensable gases extracted from the digested sugar beet tailings (43.6%) must have been lower than that from the undigested sugar beet tailings (51.2%). These results suggest that residue materials from anaerobic digestion of sugar beet tailings are comparable with undigested sugar beet tailings, and thus can be used as feedstock for both biochar and further bioenergy production. Element al Composition Elemental analysis of the feedstock materials showed that the residue of the anaerobically digested sugar beet tailings were carbon rich and had carbon content around 34% ( Table 3 1). This carbon content was only slightly lower than that of the undigested feedstock ( Table 3 1), confirming that the residue of anaerobically digested sugar beet tailings can be used as feedstock for biochar production. Compared to the undigested sugar beet tailings, the digested feedstock contained more hydrogen and nitrogen, but less oxygen element. It is notable that, after the anaerobic digestion, most of the inorganic elements in the residue materials increased except potassium. For instance, the magnesium content of the digested sugar beet tailings increased from about one half percent to above one percent. The calcium content also increased dramatically from above one percent to about ten percents. These results are consistent with findings of published studies that anaerobic digestion may concentrate exchang eable cations, such as calcium and magnesium, into the residue materials [107, 108]

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50 After being converted into biochar through slow pyrolysis, the carbon content of DSTC (31.81%) was slightly lower than th at of the feedstock, but the carbon content of STC increased dramatically to more than 50% ( Table 3 1). This indicates that the two biochars could be very different because of the effects of anaerobic digestion on the feedstock materials. The hydrogen, oxy gen, and nitrogen contents of the two biochars were similar to each other ( Table 3 1). But some of the nutrient elements including phosphorous, calcium, and magnesium were much higher in the DSTC than in the STC ( Table 3 1). High levels of calcium and phos phorous were also found in studies of some other biochars [46] However, the DSTC had a surprisingly high level of magnesium of about 10%, which is more than 6 time s of the STC. These results suggest that the digested sugar beet tailing biochar may, when applied to soils, provide a more concentrated source of nutrients to crops. Zeta Potential and pH The surface of charcoals (biochar, activated carbon) is often neg atively charged, which makes them unlikely to sorb negatively charged ions such as phosphate [109, 110] The measured ze ta potentials of the STC ( 54.23 mV) and DSTC ( 18.11 mV) were both negative, confirming that the two biochars are negatively charged at circum neutral conditions. The STC had a much lower zeta potential than the DSTC, however, suggesting that it might be more difficult for STC than for DSTC to adsorb phosphate. Measurements of the pH of the two biochars were alkaline (9.45 and 9.95 for STC and DSTC, respectively), which are similar to the reported values of other biochars produced at high temperatures [46, 48] The high pH of the two biochar samples suggests their potential to be used as amendments to reduce soil acidity [1]

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51 Surface Area Two methods were used to determine the surface area of the biochars. The liquid N 2 adsorption BET method (77 K) is more commonly used. However, this method may be inaccur ate for materials that include micropores (< 1.5 nm pore diameter) as N 2 may be kinetically limited in their diffusion into smaller pores at the low temperatures at which the measurement must be carried out [111 113] The CO 2 adsorption method (273 K) has, therefore, been promoted to be a better way to determine the true surface area of biochar samples [8, 114] The CO 2 su rface area measurements showed that the surface area of DSTC (449 m 2 /g) was much higher than that of STC (351 m 2 /g). While the DSTC had significant N 2 surface area (336 m 2 /g, indicating the presence of mesopores), the N 2 surface area of the STC was very sm all (2.6 m 2 /g), indicating that its surface was dominated by the micropores only. The surface area of DSTC is comparable to that of many commercial activated carbon (AC) adsorbents [115] Because surface area is one the digested sugar beet tailing biochar (i.e., DSTC) may be useful for wate r treatment or environmental remediation. SEM EDS The SEM imaging of the STC (500 X) showed that the undigested sugar beet tailing biochar had smooth surfaces ( Figure 3 1a). This is consistent with the findings from the N 2 surface area measurement, which suggested that micropores dominated the STC surface. The EDS spectrum of the STC surface ( Figure 3 1a) identified the same elements detected in the elemental analysis ( Table 3 1). The SEM imaging of the DSTC (500 X), however, showed knaggy surfaces ( Figur e 3 1b), perhaps reflecting the

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52 presence of mesopores indicated by the N 2 surface area measurement. The EDS spectrum of the STC surface ( Figure 3 1b) also showed many elements detected in the elemental analysis ( Table 3 1). Although the element analysis su ggested that the DSTC had similar amount calcium and magnesium (i.e., about 10%), the EDS spectrum of the DSTC indicated a magnesium content greater than that of calcium, suggesting more magnesium may present on the biochar surfaces. This was further confi rmed by the SEM EDS analysis at a high resolution (7000 X). The SEM image of the DSTC taken at the high resolution showed evidence of mineral crystals on the biochar surface ( Figure 3 1c). These crystals were mainly magnesium minerals as evidenced in the E DS spectrum at the same location ( Figure 3 1c), which showed an extremely high peak of magnesium. The magnesium crystals are colloidal or nano sized and could contribute to the high surface area of the digested sugar beet tailing biochar. XRD The XRD spec tra of the DSTC and STC showed several peaks ( Figure 3 2), indicating the presence of mineral crystals. In the DSTC spectrum, the two strong peaks at 43.2 o (d = 2.09 ) and 62.2 o (d = 1.49 ) were identified as periclase (MgO), suggesting that the colloida l and nano sized magnesium crystals on the DSTC surface (as shown in the SEM EDS analysis) were MgO. Quartz (SiO 2 ) and calcite (CaCO 3 ) were found in both the DSTC and STC, which is also consistent with the elemental analyses and EDS spectra of the two bioc hars. Surface Functional Groups The infrared spectra of the DSTC and STC were very similar ( Figure 3 3) with both biochars showing three significant bands at: 1) wave number near 1427, which could be attributed to O H bending or C O stretching vibration o f phenol [109] 2) wave

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53 number near 1049, which could be attributed to C O stretching vibrations of polysaccharides [116] and 3) wave near 874, which is characteristic of C H bending glucosidic linkage [109] All of the observed functional groups have been reported as chemical groups c haracterizing many other carbon based adsorbents including biochars and activated carbons [117 120] Phosphate Removal Both AC and STC showed very low phosphate re moval and AC even released a small amount of phosphate back into the solution ( Figure 3 4). This is consistent with the literature [109, 110] and the fact that STC has very high negative zeta potential. Although the zeta potential measurements showed that the surface of DSTC was also negatively charged, the DSTC demonstrated the highest phosphate removal with a rate about 7 3%, which was much higher than the phosphate removal rates of all the other adsorbents tested. The ferric hydroxide impregnation did increase the phosphate removal for the AC and STC, with FeAC and FeSTC removal of about 10% and 8% of phosphate, respective ly. The Fe surface modification, however, reduced the phosphate removal rate of DSTC dramatically from around 73% to 22%. This preliminary assessment suggests that anaerobically digested sugar beet tailing biochar could be used as low cost adsorbent to eff ectively remove phosphate from aqueous solution without any modification. The enhanced removal of phosphate by the DSTC was probably because of the large amount of colloidal and nano sized periclase (MgO) on its surface, which has a strong ability to bind phosphate in aqueous solution [121, 122] Precipitation of ferric hydroxide onto the SDTC might cover the colloidal and nano sized periclase, thus reducing the phosphate sorption ability of the biochar. Detailed d iscussion about the

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54 adsorption mechanisms and characteristics of phosphate onto the SDTC can be found in the part II of this study [123] Implications Based on the characterization of DSTC biochar physicochemical properties and the preliminary phosphate sorption assessment, it is evident that (1) residue from the anaerobic digestion of sugar beet tailings can be u sed as a feed stock for biochar production, (2) some of the physicochemical properties (e.g., pH and surface functional groups) of the two biochars are similar, but only the anaerobically digested sugar beet tailing biochar has colloidal and nano sized per iclase (MgO) on its surface, and (3) anaerobic digestion enhances the phosphate adsorption ability of biochar produced from digested sugar beet tailings relative to undigested ones.

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55 Table 3 1 Elemental analysis of raw and dig ested sugar beet tailings, and their associated biochars, STC and DSTC, respectively (mass %) a Sample C H O b N P S Ca Mg K Fe Al Zn Na Cu Digested Tailing 33.94 4.53 46.89 0.34 0.28 9.68 1.20 0.79 c Raw Tailing 36.06 3.43 55.82 1.23 0.16 0.09 1.80 0.53 0.88 DSTC 30.81 1.38 39.87 2.74 2.18 1.97 0.75 0.24 0.03 STC 50.78 2.08 36.70 1.83 0.35 1.04 0.59 0.64 a: Expressed on a total dry weight basis. b: Determined by weight difference assumed that the total weight of the samples was made up of the tested elements only. c: Below 0.01%.

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56 (A) STC 500X (B) DSTC 500X (C) DSTC 7000X Figure 3 1 SEM images (left) and corresponding EDS spectra (right) of the two biochar samples: A) STC, 500X; B) DSTC, 500X; and C) DSTC, 7000X. The EDS spectra were obtained at the same location as shown in the SEM images.

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57 Figure 3 2 XRD spectra of the two biochars. Crystallites were detected with pea ks labeled as Q for quartz (SiO2), C for calcite (CaCO3), and P for periclase (MgO).

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58 Figure 3 3 FTIR spectra of the two biochar samples. Figure 3 4 Comparison of phosphate removal by differe nt adsorbents.

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59 CHAPTER 4 REMOVAL OF PHOSPHATE FROM AQUEOUS SOLUTION BY BIOCHAR DERIVED FROM ANAEROBICALLY DIGESTED SUGAR BEET TAILINGS: II. ADSORPTION MECHANISMS AND CHARACTERISTICS 1 Introduction The release of phosphate from both point and non point sourc es into runoff may impose a great threat on environmental health [14, 15] As a growth limiting nutrient, high level phosphate can promote excessive production of photosynthetic aquatic microorganisms in natural water bodies and ultimately becomes a major factor in the eutrophication of many freshwater and marine ecosystems [16] It is therefore very important to develop effective technologies to remove phosphate from aqueous solutions prior to their discharge into runoff and natural water bodies [17] Many phosphate removal technologies including biological, chemical, and physical treatment methods have been developed for various applications, particularly for the removal of phosphate from municipal a nd industrial effluents [16] Both biological and chemical treatments have been well documented and proven to be effective to remove phosphate from wastewater. Addition of chemicals, such as calcium, aluminum, and iron salts into wastewater is considered a simple phosphate removal technique, which separates the phosphate from aqueous system through precipitation [20 23] However, the chemical precipitation methods require strict control of operating conditions and may potentially introduce new contaminants into the water such as chloride and sulfate ions [15, 20, 24] Biological t reatment of phosphate in waste effluents may have certain advantages over the chemical precipitation method because 1 Reprinted with permission from Yao, Y.; Gao, B.; Inyang, M.; Zimmerman, A. R.; Cao, X. D.; Pullammanappallil, P.; Yang, L. Y., Removal of phosphate from aqueous solution by biochar derived from anaerobically digested sugar beet tailings. J Hazard Mater 2011, 190, (1 3), 501 507

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60 it does not require chemical additions and enhanced biological treatment has been reported to remove up to 97% of the total phosphorus in wa ste water [25] This technology, however, is very sensitive to the operation condi tions and its phosphate removal efficiency may be, at times, much less [27] Both the chemical and biological treatment methods are also subjected to the costs and risks associated with phosphate rich sludge handling and disposal [28] Various physical metho ds have also been developed to remove phosphate from aqueous solution such as electrodialysis, reverse osmosis, and ion exchange [20, 29, 30] However, most of these physical methods have proven to be either too ex pensive or inefficient. Simple physical adsorption might be comparatively more useful and cost effective for phosphate removal. Several studies investigated activated carbons as phosphate adsorbents, but showed that the adsorption capacity was very low [14, 18, 35] For example, Namasivayam et al. [18] reported that activated carbon made from coir pith with ZnCl 2 activation h ad a phosphate adsorption capacity of only 5,100 mg/kg. Lower cost materials, such as slag, fly ash, dolomite, red mud, and oxide tailings have also been explored by several studies as alternative adsorbents of phosphate from waste water [36 40] Biochar is a low cost adsorbent that is receiving increased attention recently because it has many potential environmental applications and benefits. While most of the c urrent biochar studies are focused on biochar land application as an easy and cost effective way to sequestrate carbon and increase fertility, a number of recent investigations suggest that biochar converted from agricultural residues have a strong ability to bind chemical contaminants in water including heavy metals and organic

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61 contaminants [8, 11, 12, 41, 42] The use of biochar to remove phosphate from aqueous solutions, however, is still a relatively unexplored, though promising concept. Not only may biochar represent a low cost waste water treatment technology for phosphate removal, but the phosphate laden biochar may be used as a slow release fertilizer to enhance soil fertility that will also sequester carbon. But little research has been conducted to explore the phosphate removal potential of biochar [44] In the Chapter 3 of this dissertation, we characterize the physicochemical properties of two biochars and compared their phosphate removal abilities with activated carbon and their Fe impregnated forms [44] Our results showed that biochar derived from the residues of anaerobically digested sugar beet tailings had much better phosphate removal ability tha n all the other tested adsorbents. As a follow up, laboratory adsorption experiments and mathematical models were used in this study to determine the mechanisms and characteristics of phosphate adsorption onto the digested sugar beet tailing biochar (DSTC) The specific objectives were to: a) identify the mechanisms governing the adsorption of phosphate onto the DSTC; b) measure the kinetics and equilibrium isotherms of phosphate adsorption onto DSTC; and c) determine the effect of initial solution pH and c oexisting anions on the adsorption of phosphate onto the DSTC. Materials and Methods Materials The biochar sample (DSTC) used in this study was obtained by pyrolyzing residues of anaerobically digested sugar beet tailings at 600 o C inside a furnace (Olympi c 1823HE) in a N 2 environment. The DSTC was then crushed and sieved to give a 0.5 1 mm size fraction. After washing with deionized (DI) water to remove impurities,

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62 Detailed information about bio char production its physiochemical properties can be found in part I of this study [44] Phosphate so lutions were prepared by dissolving Potassium Phosphate Dibasic Anhydrous (K 2 HPO 4 ) in DI water. All the chemicals used in the study are A.C.S certified and from Fisher Scientific. Adsorption Kinetics Adsorption kinetics of phosphate onto DSTC were examine d by mixing 0.1 g of the biochar with 50 ml phosphate solutions of 61.5 mg/L (20 mg/L P) in 68 mL digestion adjusted to close to 7 prior to the measurements of the adsorption kinetics. The vessels were then shaken at 200 rpm in a mechanical shaker. At appropriate time intervals, the pore size nylon membrane filters (GE cellulose nylon membrane). T he phosphate concentrations in the liquid phase samples were determined by the ascorbic acid method (ESS Method 310.1; [82] ) and a spectrophotometer (Thermo Scientific EVO 60). Phosphate concentrations on the solid phase were calculated based on the initial and final aqueous concentrations. All the experimental treatments were performed in duplicate and the average values are reported. Additional analyses were conducted whenever two measurements showed a difference larger than 5%. Adsorption Isotherm Adsorption isotherm of phosphate onto DSTC was determined similarly by mixing 0.1 g DSTC with 50 ml phosphate solutions of different concentrations ranging from 15 to 640 mg/L in the digestion vessels. After pH adjustment to about 7, the vessels were

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63 shaken in the mechanical shaker for 24 h at room tem perature, this time periods having been previously determined by kinetic experiments as sufficient for adsorption equilibrium to be established. The samples were then withdrawn and filtered to determine adsorbed phosphate concentrations by the same method. Following the experiments, the post adsorption DSTC were collected, rinsed with deionized water, Effect of pH and Coexisting Anions The effect of initial solution pH on phosphate removal was stud ied over a range of 2 to11 (i.e., 2.0, 4.0, 6.2, 7.1, 8.1, and 10.4). In addition, the effect of the common coexisting anions, chloride, nitrate, and bicarbonate, was also investigated by adding 0.01M of NaCl, NaNO 3 or NaHCO 3 to the 61.5 mg/L phosphate so lutions into separate digestion vessels. The adsorbent to initial solution phosphate concentration were the same as the kinetics experiment. The vessels were shaken in the mechanical shaker for 24 h at room temperature. The same procedures were then used t o determine aqueous and adsorbed phosphate concentrations. Post adsorption Biochar Characterization To investigate the crystallographic structures on the post adsorption DSTC, X ray diffraction (XRD) patterns were acquired with a computer controlled X ra y diffractometer (Philips APD 3720) equipped with a stepping motor and graphite crystal monochromator. Fourier Transform Infrared (FTIR) spectra were collected using a Bruker Vector 22 FTIR spectrometer (OPUS 2.0 software) to identify the surface functiona l groups of post adsorption DSTC samples. The P loaded DSTC was ground and mixed with KBr to approximately 0.1 wt% and pressed into a pellet using a mechanical device. Scanning electron microscopy (SEM, JEOL JSM 6400) coupled with

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64 dispersive X ray spectros copy (EDS, Oxford Instruments Link ISIS) was used to the surface of the post adsorption DSTC and to determine its surfacial elemental composition. These characteristics of the phosphate loaded DSTC were compared with those of the original biochar [44] to determine the adsorption mechanisms. Results and Discussion Main Adsorption Mechanism The Chapter 3 o f this study [44] showed that DSTC had a relatively high surface area measured with N 2 (336 m 2 /g) and CO 2 (449 m 2 /g), which is generally desirable for phosphate adsorption. In addition, characterization results from elemental, SEM EDS, and XRD analyses revealed that the DSTC surface was covered with colloidal or nano sized MgO (periclase) particles, which could serve as the main adsorption sites for phosphate removal [44] SEM EDS analysis of the post a dsorption DSTC samples confirmed the hypothesis that the MgO particles on the DSTC surface may dominate the phosphate adsorption. At a high resolution of 7000X, when the SEM was focused on the MgO crystals on the P loaded DSTC surface, the corresponding ED S spectrum showed an elevated peak of phosphorus ( Figure 4 1). Although phosphorus was also detected in the original DSTC ( Chapter 3 ), its EDS signal of phosphorus was much lower [44] For the P loaded DSTC, the phosphorus signal was even higher than those of the magnesium and oxygen, which showed the second and third highest EDS peaks ( Figure 4 1). Metal oxides have showed strong ability to adsorb negative charged compounds, such as phosphate and arsenate [124] When in contact with water, the metal oxide surface becomes hydroxylated and thus introduces either a positive or negative surface

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65 charge, depending on the solution pH. The charge development of MgO on the biochar surface can be described in a simplified manner as [125] : (2 1) where S MgO denotes the MgO surface. The point of zero charge (PZC) of MgO is very high (PZC MgO =12 [126] ), thus its surface is expected to be positively charged in most natural aqueous conditions. In aqueous solution, phosphate exists in four species with pKa values of 2.12 (pKa 1 ), 7.21(pKa 2 ), and 12.67 (pKa 3 ). When solution pH is lower than PZC MgO the hydroxylated MgO surface can electrostati cally attract negatively charged phosphate species to form mono and polynuclear complexes [125, 127] : mononuclear (0.12
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66 4 2a), suggesting that the precipitation might not be an important mechanism for phosphate rem oval. This could be explained by two reasons: 1) some of the calcium in the biochar was in form of calcite ( Figure 4 2a), which has a very low solubility; and 2) a portion of the calcium might be incorporated inside of the biochar and could not be released into the solution [46] Because there was abundance of surface functional groups on the DSTC surface [44] phosphate could also be removed by the biochar through interacting with the functional groups. However, again, the similarity between the FTIR spectra of the original and P loaded DSTC provides no evidence of adsorption of phosphate onto the surface functional groups in the P loaded biochar ( Figure 4 2b). Adsorption Kinetics The adsorption of phosphate onto the DSTC increased smoothly over time and reached e quilibrium after 24 h ( Figure 4 3a). The slow kinetics further suggests that precipitation might not play an import role in the removal of phosphate by the biochar. Mathematical models were used to simulate the experimental kinetics. In addition to the com monly used pseudo first order and pseudo second order models, the Ritchie N_th order model and Elevich model were also tested [128] and are represented by the following equations: first order (4 3a) second order (4 3b) N_th order (4 3c) Elevich (4 3d)

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67 wh ere q t and q e are the amount of phosphate adsorbed at time t and at equilibrium, respectively (mg kg 1 ), and k 1 k 2 and k n are the first order, second order, and N_th order apparent adsorption rate constants (h 1 ), respectively. Also, is the initial adso rption rate (mg kg 1 ) and is the desorption constant (kg mg 1 ). The first order, second order, and N_th order models describe the kinetics of the solid solution system based on mononuclear, binuclear, and N nuclear adsorption, respectively, with respect to the sorbent capacity [128] while the Elevich model is an empirical equation considering the contribution of desorption. All the models closely reproduced the kinetic data ( Figure 4 3a), with all correlation coefficients ( R 2 ) exceeding 0.98 ( Table 4 1). However, the first order, second order, and N_th order (N=1.14) models fitted the data slightly better than the Elevich model and N_th order model had the highest R 2 (0.9970). This result is consistent with the proposed predominant mechansim that phosphate removal by the biochar wa s mainly through adsorption onto the colloidal and nano sized MgO crystals on DSTC surface. Both mononuclear and polynuclear adsorption of phosphate would be favored in the kinetics experiment, perhaps explaining why fittings from the N_th order model were slightly better than that of either the first or second order model. Previous studies on the kinetic behaviors of microporous sorbents showed that intraparticle surface diffusion may be important to the adsorption process [129, 130] In this study, the adsorption of phosphate onto DSTC also showed diffusion limitation. The pre equilibrium (i.e. before 24 h) phosphate adsorption showed a strong linear dependency ( R 2 =0.9959) on the square root of time ( Figure 4 3b). This result suggests

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68 that intraparticle surface diffusion may play an important role in controlling the adsorption of phosphate onto the biochar, likely due to its abundance of mesopores. Adsorption Isotherms With the maximum observed phosphate adsorption of greater than 100,000 mg/kg ( Figure 4 4), the DSTC showed phosphate sorption ability to superior to most of the reported values of other carbonaceous adsorbents [15, 18, 35] Three isotherm equations were tested to simulate the phosphate adsorption onto the biochar [128] : Langmuir (4 4a) Freundlich (4 4b) Langmuir Freundlich (4 4c) where K and K f represents the Langmuir bonding term related to interaction energies (L mg 1 ) and the Freundlich affinity coefficient (mg ( 1 n) L n kg 1 ), respectively, Q denotes the Langmuir maximum capacity (mg kg 1 ), C e is the equilibrium solution concentration (mg L 1 ) of the sorbate, and n is the Freundlich linearity constant. The Langmuir model assumes monolayer adsorption onto a homogen eous surface with no interactions between the adsorbed molecules. The Freundlich and Langmuir Freundlich models, however, are empirical equations, which are often used to describe chemisorptions onto heterogeneous surface. All the models reproduced the is otherm data fairly well ( Figure 4 4), with correlation coefficients ( R 2 ) exceeding 0.95 ( Table 4 1). However, fittings of the Freundlich and Langmuir Freundlich matched the experimental data better than those of the Langmuir model, suggesting the adsorptio n of phosphate onto the DSTC was controlled by heterogeneous processes. This result is consistent with the proposed

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69 predominant adsorption mechanism of phosphate removal by the biochar through both mononuclear and polynuclear adsorption onto the colloidal and nano sized MgO particles on DSTC surface. Effect of pH and Coexisting Anions The adsorption of phosphate onto the DSTC depended on initial solution pH ( Figure 4 5a). The phosphate adsorption was lowest when pH equaled 2.0. When pH was increased from 2 .0 to 4.1, the adsorption of phosphate by the biochar increased. Further increases in pH from 4.1 to 6.2, 7.1, 8.1, and 10.4, however, decreased the adsorption of phosphate onto the DSTC ( Figure 4 5a), suggesting the existence of an optimum pH for the maxi mum phosphate adsorption. Similar results were found in studies of the pH effect on phosphate removal from aqueous solution by other carbon based adsorbents [35] Although molecular concentrations of the coexisting anions were about 15.5 times of the phosphate, chloride and nitrate had little effect on the adsorption of phosphate (4.3 and 11.7 percent decrease, respecti vely) onto the biochar ( Figure 4 5b), suggesting low competitions between phosphate and these two ions for the MgO sites on the DSTC surface. The existence of high concentrations of bicarbonate in the solution, however, reduced the phosphate adsorption for about 41.4% ( Figure 4 5b). Two factors could be responsible for the reduction: 1) the competition for the adsorption site between bicarbonate and phosphate; and 2) the increase of solution pH due to the addition of bicarbonate. Implications Biochar conv erted from anaerobically digested sugar beet tailings (DSTC) demonstrated superior ability to remove phosphate from water under a range of pH and

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70 competitive ion conditions. Batch sorption experiments and post sorption characterizations suggested that phos phate removal was mainly controlled by adsorption onto colloidal and nano sized MgO particles on the DSTC surface. Because both the original and anaerobically digested sugar beet tailings are waste materials, the cost to make DSTC should be very low. Howev er, the use of pre digested sugar beet tailings has the benefit of additional energy generation and more efficient production (with less CO 2 release during production). Thus, DSTC should be considered a promising alternative water treatment or environmenta l remediation technology for phosphate removal. In addition, when used as an adsorbent to reclaim phosphate from water, the exhausted biochar can be directly applied to agricultural fields as a fertilizer to improve soil fertility because the P loaded bioc har contains abundance of valuable nutrients. Potential additional environmental benefits from this approach include fuel or energy produced during both the anaerobic digestion and pyrolysis and carbon Beca use arsenate and molybdate are phosphate analogues [124] it is expected that the digested sugar beet tailing biochar would also be an eff ective adsorbent for them.

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71 Table 4 1. Best fit parameter values for models of kinetic and isotherm data Model Parameter 1 Parameter 2 Parameter 3 R 2 First order k 1 = 0.1554 (h 1 ) q e = 23474.94 (mg kg 1 ) -0.9968 Second order k 2 = 5.211x10 6 (kg mg 1 h 1 ) q e = 28771.04 (mg kg 1 ) -0.9949 N_th order k N = 0.000701 (kg N mg N h 1 ) q e = 23927.64 (mg kg 1 ) N = 1.1359 0.9970 Elevich = 0.000139 (mg kg 1 ) = 5967.70 (mg kg 1 ) -0.9855 Langmuir K = 0.02551 (L mg 1 ) Q = 133084.7 (mg kg 1 ) -0.9526 Freund lich K f = 11642.39 (mg (1 n) L n kg 1 ) n = 0.4527 -0.9781 Langmuir Freundlich K = 0.01562 (L n mg n ) Q = 705873.6 (mg kg 1 ) n = 0.4954 0.9785 (A) (B) Figure 4 1. SEM ima ge (A) and corresponding EDS spectra (B) of the post adsorption DSTC at 7000X. The EDS spectra were recorded at the same location as showing in the SEM image.

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72 (A) (B) Figure 4 2. XRD (A) and FTIR (B) spectra of the original and post adsorption DSTC. Crystallites were detected with peaks labeled in the XRD spectra as Q for quartz (SiO 2 ), C for calcite (CaCO 3 ), and P for periclase (MgO).

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73 (A) (B) Figure 4 3. Adsorption kinetic data and modeling f or phosphate onto DSTC (A) full, and (B) pre equilibrium adsorption versus square root of time. Figure 4 4. Adsorption isotherm for phosphate on DSTC.

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74 (A) (B) Figure 4 5. Effect of (A) pH and (B) coexisting a nions on phosphate adsorption onto DSTC.

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75 CHAPTER 5 ENGINEERED CARBON (BIOCHAR) PREPARED BY DIRECT PYROLYSIS OF MG ACCUMULATED TOMATO TISSUES: CHARACTERIZATION AND PHOSPHATE REMOVAL POTENTIAL 1 Introduction 1 Reprinted with permission from Yao, Y.; Gao, B.; Chen, J.; Zhang, M.; Inyang M.; Li, Y.; Alva, A.; Yang, L ., Engineered carbon (biochar) prepared by direct pyrolysis of mg accumulated tomato tissues: Characterization and phosphate removal potential. Bioresource Technol 2013, doi: 10.1016/j.biortech.2013.03.057

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76

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77

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78 Materials and Methods Biochar production

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79 Characterization P sorption

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80 Statistical Methods Results and Discussion Mg and Ca in Feedstock and Biochar

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81 Effect of Mg Enrichment of P Removal by Biochar

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82 Characterization of Mg Enriched Biochar (Mg EC ).

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83

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84 Implications

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85 Table 5 1. Elemental analysis of feedstocks and biochars produced in this st udy (mass %)a. Feedstocks: Ca enriched tomato tissues (CaET), Mg enriched tomato tissues (MgET), laboratory control of tomato tissues (LCT), farm control from Senibel (FCT1), and farm control from Rocky Tops (LCT2). CaEC, MgEC, LCC, FCC1, and FCC2 are bioc hars produced form these feedstocks, respectively.

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86 Table 5 2. Correlation between biochar phosphate removal rate (P) and different metal content (C), where P= a C+ b.

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87 Figure 5 1. Comparison of phosphate adsorption abili ty of five biochars produced in this study. CaEC, Ca enriched biochar; MgEC, Mg enriched biochar; LCC, laboratory control biochar; FCC, farm control biochar.

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88 Figure 5 2. Correlation between phosphate removal rate and M g/ Ca (a) and other metal contents (Cu, Fe, Al, Zn, K) (b f) of a total of 25 biochars. Red and black colors represent Mg and Ca, respectively.

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89 Figure 5 3. XRD spectrum of MgEC.

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90 Figure 5 4. SEM image and EDS spectrum of MgEC morphological struc tures, the insert is at a higher resolution. Figure 5 5. XPS scan of magnesium (a) and phosphorus (b) on MgEC surfaces.

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91 Figure 5 6. TGA curves of MgEC and LCC1.

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92 CHAPTER 6 AN ENGINEERED BIOCHAR RECLAIMS PHOSPHATE FROM AQUEOUS SOLUTIONS: MECHANISMS AND POTENTIAL APPLICATION AS A SLOW RELEASE FERTILIZER Introduction

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93

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94 The overarching objective of this study was to determine whether engineered bioc hars can be used to reclaim aqueous P and then be applied to soils as a P fertilizer. A series of laboratory experiments were conducted to determine the mechanisms and characteristics of P adsorption on an engineered biochar prepared from Mg enriched tomat o tissues. The bioavailability, desorption characteristics, and seed germination ability of the adsorbed P within the spent (i.e. P laden) biochar were also evaluated The specific objectives were as follows: 1) measure the sorption characteristics of P to the

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95 engineered biochar, 2) characterize the post sorption biochar to identify the governing P sorption/desorption mechanisms, 3) measure the release characteristics of P from the post sorption biochar and 4) determine the biological effects of the post s orption biochar on seed germination and seedling growth Materials and Methods Materials P Adsorption

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96 Post S orption Characterization

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97 P R elease Seeds Germination and Early Stage Seedling Growth Bioassay eeds germination

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98 Statistics Results and Discussion Adsorption Kinetics and Isotherms first order (6 1a) second order (6 1b) N_th order (6 2c) Elovich (6 3d)

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99

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100 Langmuir (6 2a) Freundlich (6 2b) Langmuir Freundlich (6 2c) Redlich Peterson (6 2d) Temkin (6 2e),

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101 Adsorption /Desorption Mechanisms

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102

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103 P Desorption f rom P Laden Biochar a s A Slow Release Fertilizer.

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104

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1 05 Seeds Germination and Early Stage Seedling Growth Bioassay I mplications

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106 Table 6 1. Best fit parameter values from model simulations of P adsorptio n kinetics, isotherms and desorption kinetics. Parameter 1 Parameter 2 Parameter 3 R 2 Adsorption kinetics First order k 1 = 0.337 (h 1 ) q e = 11.950 (mg g 1 ) 0.989 Second order k 2 = 0.032 (g mg 1 h 1 ) q e = 13.260 (mg g 1 ) 0.999 n_th order k n = 0. 406 (g n 1 mg 1 n h 1 ) q e = 12.820 (mg g 1 ) n = 1.744 1.000 Elovich = 2.390 (g mg 1 ) = 2.538 (mg g 1 h 1 ) 0.975 Adsorption isotherms Langmuir K = 0.090 (L mg 1 ) Q = 116.600 (mg g 1 ) 0.972 Freundlich K f = 21.690 (mg (1 n) L n g 1 ) n = 0.342 0.85 0 Langmuir Freundlich K lf = 0.023 (L n mg n ) Q = 103.800 (mg g 1 ) n = 1.749 0.991 Redlich Peterson K r = 0.015 (L n mg n ) a = 7.082 (L g 1 ) n= 1.298 0.994 Temkin b =129.700 (J g mg 1 ) A = 2.008 (L mg 1 ) 0.912 Desorption kinetics Second order k ds = 0.126 (L mg 1 h 1 ) Ce = 11.740 (mg L 1 ) 0.916

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107 Figure 6 1. Adsorption kinetic (a) and isotherm (b) data and modeling for phosphate on the engineered biochar. Symbols are experimental data and lines are model results. Figure 6 2. Kinetics p re equilibrium adsorption versus square root of time.

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108 Figure 6 3. XRD spectrum of P laden biochar. Figure 6 4. SEM image and EDX spectrum of P laden biochar morphological structures.

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109 Figure 6 5. XPS spectra of the Mg 1s (a) and P 2p3/2 (b) region for P laden biochar.

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110 Figure 6 6. Illustration scheme of adsorption and desorption mechanisms of P on the engineered biochar surface (S).

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111 Figure 6 7. (a) Desorption kinetics, symbols are experimental data and the line is model re sults. (b) Successive and repeatable release of phosphate by P laden biochar as each time fresh solution was introduced to the system to mimic conditions under plant growth. Figure 6 8. TGA curve of P laden biochar.

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112 Figure 6 9. Comparison of g rass seedlings between P laden biochar and control groups.

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113 CHAPTER 7 ADSORPTION OF SULFAMETHOXAZOLE ON BIOCHAR AND ITS IMPACT ON RECLAIMED WATER IRRIGATION 1 Introduction Water stress and scarcity resulting from rapid population growth, global climate cha nge, and pollution is among the greatest environmental problems today [49] In the past decade, freshwater consumption by agriculture had been risi ng due not only to water thirsty vegetables and meat, but also to the increase in biofuel crops [50] Reclaimed water has been used for both agricultural and lan dscape irrigation to satisfy this demand. Globally, about 20 million ha of land is now irrigated with reclaimed water and this has become a key strategy in fighting water shortages [190, 191] However, the benefits and hazards associated wi th the application of reclaimed water must be considered. On one hand, reclaimed water typically contains some nutrient elements, such as nitrogen, so its application to agricultural fields may bring additional benefit to soil and crop systems and reduce t he need for fertilizer application [53] On the other hand, reclaimed water irrigation may also pose environmental risks by introducing various pollutants, including orga nic pollutants and heavy metals, to irrigated soils and the underlying groundwater [192] Another major concern with irrigation and direct injection of reclaimed water is that active/infective human enteric vir uses and bacteria might be delivered with the reclaimed water to the subsurface environment [193 195] Pharmaceutical residues, which are recognized emerging contaminants, are frequently detected in the discharge of treated effluent from 1 Reprinted with permission from Yao, Y.; Gao, B.; Chen, H.; Jiang, L.; Inyang, M.; Zimmerman, A. R.; Cao, X.; Yang, L.; Xue, Y.; Li, H., Adsorption of sulfamethoxazole on biochar and its impact on reclaimed water irrigation. Journal of Hazardous Materials 2012, 209, 408 413.

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114 wastewater treatment plants (WWTP) [55] Various technologies including physical (e.g., filtration), chemical (e.g., chlorination), and biological (e.g., activated sludge) methods have been developed and applied in WWTP [196] However, most of the wastewater treatment methods, except member filtration technologies (e.g., Nanofilitration and Reverse Osmosis), cannot completely remove pharmaceuticals in the effluent [196] Occurrences of pharmaceuticals in treated wastewater, surface water, and groundwater have been reported worldwide [55, 57, 58, 197] In a field study of pharmaceuticals in soil irrigated with treated urban wastewater, Furlong et al [59] found that reclaimed water irrigation resulted in leachi ng of pharmaceuticals, such as erythromycin, carbamazepine, and fluoxetine, through the vadose zone to contaminate groundwater. Soil and groundwater contaminations by reclaimed water irrigation in agriculture caused by pharmaceuticals, such as antibiotics and hormones, have also been demonstrated in several other studies [60, 192, 197] Sulfamethoxazole (SMX) is one of the most frequently detected pharmaceuticals in reclaimed water and other environmental samples [59, 197] As a sulfonamide bacteriostatic antibiotic, SMX is extensively used for treatment and prevention of both human and animal diseases [198] It has been ubiquitously found in the high ng/L range in discharges from WWTP and in the low ng/L range in rivers an d groundwater [199] SMX is characterized as relatively unreactive to soil surfaces and shows high mobility in soils [200] If released into aquatic systems through discharges from WWTP, SMX may have toxic effects on aquatic organisms and also may induce drug resistance in pathogens [201, 202] Occurrences of SMX in groundwater have been reported in the U.S. and other countries [60, 197, 203] so it is important to limit SMX leaching through

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115 the vadose zone during reclaimed water irrigation. As suggested by Munoz et al. [197] there is a critical need to develop new methods or technologies for reclaimed water irrigation in agriculture to reduce the contam ination risk of pharmaceuticals, particularly with respect to SMX. Recent development in biochar technology may provide such an opportunity to reduce the risk of pharmaceutical contamination of groundwater from reclaimed water irrigation. Biochar, sometime s called agrichar, is a charcoal derived from the thermal decomposition of carbon rich biomass. When biochar is used in agriculture as a soil amendment, it can effectively increase soil fertility and create a carbon sink to mitigate global warming [67, 77, 204] In addition, a number of investigations have also revealed cost adsorbent to control pollutant migration in soils [205, 206] Biochar converted from agricultural residues has demonstrated strong sorption ability for a variety of contaminants through various mechanisms [8, 207, 208] Previous studies have showed that biochar has strong affinities for soil organic matters and organic pollutants such as phenanthrene (PHE), phenols, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) [8, 10] Although pharmaceuticals are emerging org anic contaminants, very little research, if any, has been conducted to investigate the ability of biochar to remove pharmaceuticals from water. If shown to have sufficient sorption ability for pharmaceuticals such as SMX, biochar amendment could limit phar maceuticals leaching from soil into groundwater or surface water in addition to improving soil fertility and carbon sequestration. This would increase the safety and feasibility of using reclaimed water for agricultural and landscape irrigation.

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116 The overar ching objective of this work was to develop a new technology to reduce the contamination risk of reclaimed water irrigation. It is our central hypothesis that biochar, when amended in soils irrigated with reclaimed water, can sorb pharmaceutical contaminan ts to protect the soils and groundwater. To test this hypothesis and achieve the overarching objective, a series of laboratory experiments were conducted to study the adsorption of SMX, a common pharmaceutical contaminant in reclaimed water, on biochar and its impact on reclaimed water irrigation. The specific objectives were to: (1) test the ability of different types of biochar to sorb aqueous SMX; (2) determine the leaching and retention of SMX in simulated reclaimed water through soils amended with sele cted biochar; and (3) evaluate the effect of SMX laden biochar on the growth of E. coli Materials and Methods Materials A total of 8 biochar samples were produced from four commonly used feedstock materials: bamboo (BB), Brazilian pepper wood (BP), sugarc ane bagasse (BG), and hickory wood (HW). The raw materials were converted into biochar through slow pyrolysis inside a furnace (Olympic 1823HE) in a N 2 environment at temperatures of BP450, BP600, BG450, BG600, HW450, and HW600. The biochar samples were then crushed and sieved yielding a uniform 0.5 1 mm size fraction. After w ashing with deionized (DI) water for several times to remove impurities, such as ash, the biochar information about biochar production procedures can be found in a previously published study [209]

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117 Sandy soil was collected from an agricultural station at the University of Florida in Gainesville, FL. The soil was sieved through a 1mm mesh an oven overnight and sealed in a container prior to use. Basic properties of the soil can be found in the Supporting Information (Table S1). Sulfamethoxazole (SMX, ACS 732 46 6) was purchased from Applichem (Germany). The phy sicochemical properties of SMX are summarized in the Supporting Information (Table S2). All the other chemicals were analytical reagents supplied by Fisher Scientific. Artificial reclaimed water was synthesized to simulate a typical Florida conserve II rec laimed water and its major element chemical composition can be found in the Supporting Information (Table S3) [53, 210] Characterization of Sorbents A range of physicochemical properties of the biochar samples were determined. The pH was measured using a biochar to deionized (DI) water mass ratio of 1:20 followed by shaking and an equilibration time of 5 minutes before measurement with a pH meter (Fisher Scientific Accumet Basic AB15). Elemental C, H, and N abundances were determined using a CHN Elemental Analyzer (Carlo Erba NA 1500) via high temperature catalyzed combustion followed by infrared detect ion of the resulting CO 2 H 2 and NO 2 gases, respectively [67] Major inorganic elements were determined using the APHA standard method of acid digesting the sam ples for multi elemental analysis by inductively coupled plasma emission spectroscopy (ICP AES) [211] The surface area of the biochar was determined on Micromeretics Autosorb1 and using the Brunauer Emmett Te ller (BET) method in the 0.01 to 0.3 relative pressure range of the N 2 sorption isotherm [212]

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118 Sorption of SMX Batch sorption experiments were conducted to comp are the sorption of SMX by the eight biochar samples in 68 mL digestion vessels (Environmental Express) at room weighted) was added into the vessels and mixed with 50 mL 10 m g/L SMX solution in DI water. To show the effectiveness of the sorbents, the concentration of SMX solution used in this work (mg/L) was much higher than that in real environmental samples (i.e., g/L or ng/L) [57] This approach has been successfully used in several studies to examine the sorption of SMX on various sorbents [57, 213, 214] The mixtures were shaken at 55 rpm in a mechanical shaker for 24 h, and the vials were then withdrawn. Vessels without either biochar or SMX were included as experimental controls. membrane filters (GE cellulos e nylon membrane) and the pH of the supernatant was measured. The concentration of SMX in the supernatant was measured with a dual beam UV/VIS spectrophotometer (Thermo Scientific, EVO 60) [215] The SMX detection wavelengths were set at 280 nm (BB450, BP450), 267 nm (BB600, BP600, BG600, HW450 and HW600), and 290 nm (BG450) to minimize the effect of background absorbance and the detection limit was about 0.1 mg/L. The pH of the standard solutions was adjusted to match that of each supernatant and the correlation coefficients (r 2 ) for all the spectrophotometric standard curves were higher than or equal to 0.999. Sorbed SMX concentr ation was calculated based on the difference between initial and final aqueous SMX concentration. Solid water distribution coefficients (K d ), defined as the ratio between adsorbed concentration on solid phase divided by the

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119 equilibrium concentration in sol ution, were used to compare the SMX sorption abilities of the various biochar types. All the experimental treatments were performed in duplicate and the average values are reported. Additional analyses were conducted whenever two measurements showed a dif ference larger than 5%. Transport of SMX in Reclaimed Water through Soil Columns Two biochar samples, BG450 and BB450, were selected to study their effect on SMX retention and transport in combination with soil. Simulated reclaimed water spiked with SMX wa s applied to laboratory soil columns to simulate reclaimed water irrigation. The soil columns were made of acrylic cylinders measuring 16.5 cm in height and 4.0 cm in internal diameter, and the bottom of the columns were covered with a stainless steel mesh with 60 m pore size to prevent soil loss. The sandy soil with or without biochar was wet packed into the column following the procedures reported by Tian et al. [216] Three types of soil columns, in duplicate, were used: (1) soil amended with 2% BB450 (by weight), (2) soil amended with 2% BG450 (by weight), and (3) soil with no biochar. The total amount of soil or biochar amended soil in the columns was a uniform 200 g. About one pore volume of artificial reclaimed wastewater (i.e., 51 mL) was first poured into the soil columns each day for two days to precondition the column. On days 3 a nd 4, same amount of reclaimed wastewater spiked with 2 mg/L SMX was applied to the soil columns. After that, the columns were flushed with one pore volume SMX free reclaimed water each day for another five days. The leaching process in each day took less than an hour, and all the leachate samples were collected from the outlet at the analyses.

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120 Reverse phase high performance liquid chromatography (HPLC, Waters 2695, Milford, MA) equipped with a Phenomenex Gemini C18 column (150 mm 4.6 mm I.D., samples. A Waters 2489 ultraviolet detector was used to detect SMX at a wavelength of 270 nm. The SMX 50 2 > 0.99. TCLP Extraction The toxicity characteristic leaching procedure (TCLP) was applied to the soil and soil biochar mixtures foll owing column experiments and entails extracting the adsorbed SMX following the USEPA Method 1311 [217] The TCLP has been used to determine the mobility and bioavailability of both organic and inorganic contaminants in soils [206] Soil wa s removed from the columns and air dried and homogenized after the transport experiments. Extraction fluid of the TCLP was prepared by adding 5.7 ml glacial acetic acid and 64.3 ml of 1N NaOH separately into 500 ml reagent water and then diluting to a volu me of 1L. The pH of the extraction fluid was 4.9. Solid phase samples were then mixed with the extraction fluid at a weight ratio of 1:20, respectively, in standard extraction vessels. The vessels were shaken for 18 h at room temperature and the liquid com ponent was separated from solid phases by filtering through 0.7 m pore size borosilicate glass fiber filters. The filtrates were analyzed for SMX concentration by HPLC as described previously. Three independent extraction experiments were conducted for ea ch soil sample and a one way ANOVA test with a significance level of 0.05 (p<0.05) was used to check for differences between treatments.

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121 Growth Inhibition To obtain SMX laden biochar for the growth inhibition experiments, 0.1 g of BB450 or BG450 was mixed with 50 mL SMX solution of three different concentrations (20, 30, and 50 mg/L) and the mixture was shaken for 24 hr. After filtration, SMX laden biochar samples were collected and oven dried at 80 o C. The SMX laden biochar was labeled as BB450S20, BB450S3 0, BB450S50, BG450S20, BG450S30, and BG450S50 based on the initial SMX concentration. E. coli agitation in a biochemical incubator. Biochar and SMX laden biochar samples were sterilized in an autoclave to kill native bacteria in the samples. Pre experiment comparing the growt h inhibition effects of SMX and sterilized SMX showed the autoclave treatment had no effect on the antibiotic properties of SMX because of its good thermal stability as reported in the literature [218, 219] 83 mg BG450S20 and BB450S20, 56 mg BG450S30 and BB450S30, and 33 mg BG450S50 and BB450S50 were then added to 5 mL fresh nutrient broth medium to test their effect on bacterial growth. The amount of the adsorbed SMX in each of BG treatments was around 0.15 mg, wh ich was much higher than that of BB treatments (0.10 mg each). SMX free biochar (33 mg) and blank controls without biochar were also included in the experiment. The pour plate method was used to enumerate E. coli following APHA standard procedures [211] Briefly, 0.5 ml of the diluted E. coli sample was placed on the center of a sterile petri dish (100 mm diameter) using a sterile pipette. Sterile, molten plate count agar (45 to 50C) including biochar and SMX laden biochar or blank controls was added and mixed with the sample by swirling the plate. The mixture was allowed to cool at room temperature until solidified and then were incubated

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122 (SenxinGRP 9160, Shanghai, China) at 35C for 48 hrs. Colonies in the me dium were counted to determine bacterial concentration following the standard procedures [211] The growth experiments were repeated six times for all tested samples and results were statistically analyzed wit h the t test and one way ANOVA with a significance level of 0.05 (p < 0.05). Results and Discussion Biochar Properties CHN analysis indicated that all the eight biochar samples prepared and used in this work were carbon rich and contained 75.6 83.6% carbo n ( Table 7 1), which is typical of pyrolyzed biomass [67, 208] The oxygen and hydrogen contents of all the samples ranged 11.5 18.1% and 2.2 3.6%, respectively, some of which are likely as surface functional group s, which are commonly found on biochar surfaces [208] The biochar samples contained relatively small amount of nitrogen (0.1 0.9%), but most of those values are still much higher than that of most of the natural soils in the US [220] Element analysis showed that all the biochar samples had relatively low levels of phosphorous and metal elements, except the two BP biochar had more than 2% of Calcium ( Table 7 1). Measurements of the pH indicated that all the biochar were alkaline (8.04 9.67) ( Table 7 1), suggesting that they could be used as amendments to reduce soil acidity. The BET surface area measurements showed that biochar produced at 450 o C had very low surface areas (0.7 1 3.6 m 2 /g), which is common for low temperature wood and grass biochar ( Table 7 1) [87] When the pyrolytic temperature increased to 600 o C, the surface area of the biochar increased dramatically to 243.7 401.0 m 2 /g. Strong positive

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123 correlation between N 2 measured surface area and pyrolytic temperature was also observed in several previous biochar studies [87, 88] Sorpt ion of SMX All the tested biochar showed certain ability to remove aqueous SMX. The solid water distribution coefficient (K d ) of the biochar ranged 2 104 L/kg with HW450 having the lowest sorption ability (Figure 6 1). The BG biochar had the highest K d val ues of 104 and 94 L/kg for BG450 and BG600, respectively. Other than for the biochar made from HW, biochar made at 450 o C showed better adsorption ability than the 600 o C biochar. This contrasts with the findings of Kasozi et al [8] showing an increase in biochar sorption of catechol with increasing combustion temperature but similar to the same study in th eir finding that grass biochar sorb catechol to a greater extent than hard wood biochar. Because biochar made at lower temperature may contain more surface functional groups than that prepared at a higher temperature [87, 221, 222] the higher sorption of SMX onto lower temperature biochar suggests that surface function groups on biochar may play a more important role in interactions between SMX and biochar than other factors such as surface area or hydrophobicity. Previous studies have indicated that, in soil, SMX has very small K d values (0.6 3.1 L/kg) and is highly mobile [200, 214] The K d values of seven out of eight biochar used in this work were an order of magnitude g reater than that of soils, suggesting that those biochar, when amended in soils, can reduce the mobility of SMX in the soil matrix. Transport in Soil Columns Two types of biochar, BG450 (K d = 104 L/kg) and BB450 (K d = 64 L/kg), which had relatively high sorp tion ability for SMX, were used in the column experiments. As expected, both biochar reduced the transport of SMX in reclaimed water through the

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124 soils ( Figure 7 2). When the SMX free artificial reclaimed water was added to the soil columns, there was no de tectable SMX in all the leachate, suggesting no background SMX in the soil or biochar soil mixtures ( Figure 7 2). Although the SMX spiked reclaimed water was added to the columns on day 3, SMX was not detected immediately as the solution simply replaced th e soil pore water. SMX was detected in all column leachates on day 4, but the breakthrough concentration of SMX in BG450 (5 g/L) and BB450 (54 g/L) amended columns were several orders lower than that of the unamended soil columns (329 g/L). The breakthr ough concentration of SMX in the unamended soil on day 5 was the highest (819 g/L), and was more than 40% of the input concentration (i.e., 2 mg/L). The average peak breakthrough concentrations of the SMX in the biochar amended soil columns were much lowe r (i.e., 139 and 25 g/L for BB450 and BG450 amended soil columns). The BG450 amended soil columns had the lowest SMX breakthrough concentration, which was consistent with the results obtained from the sorption experiments. When the SMX free reclaimed wate r was used to flush the columns on day 6, the SMX concentration of all leachates decreased ( Figure 7 2). Compared to the biochar amended columns, however, the unamended soil columns still showed much higher SMX breakthrough concentration. Mass balance calc ulation indicated that more than 60% of the SMX in the reclaimed water was transported through the unamended soil column by the end of the experiment, confirming that SMX has a high mobility in soils. The transport of SMX in the biochar amended soil column s, however, was much lower, with only about 15% and 2% of the SMX in the reclaimed water transported through the soil columns amended with BB450 and BG450, respectively. The leaching column experimental results suggest that biochar can be

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125 used as an amendm ent in agricultural soils irrigated with reclaimed water to adsorb SMX and to limit its mobility in the vadose zone, thus protecting groundwater quality. TCLP Extraction Although there was much more SMX retained by the biochar amended soils, the TCLP extr actable SMX levels in the biochar amended soils was significantly less than that of the unamended soils ( Figure 7 3) with the one way ANOVA analysis showing the differences among the tested samples was statistically significant (p = 0.028). The average SMX concentration in the TCLP extraction from the two biochar amended soils was only about 76% (BB450) and 14% (BG450) of that from the unamended soils. This result suggests that, in addition to reducing SMX mobility in soil, the bioavailability of SMX in soi ls will be reduced by biochar amendment, even if it is highly accumulated in the biochar. The effect of biochar on reducing the mobility and bioavailability of organic contaminants, such as pesticides, in soils was also observed in several recent studies [206, 223, 224] In a recent study, Cao et al. [206] found that biochar prepared from animal manure could reduce atrazine an d lead concentrations in the TCLP extractions by 53 77% and 70 89%, respectively. Growth Inhibition The growth response of E coli varied among the different samples, but all showed growth of bacterial colonies reaching colony forming units (cfu) on the or der of 10 5 to 10 8 cfu/ml ( Figure 7 4). The average number of bacteria in the blank control was 4.0 x 10 8 cfu/mL, which was almost identical to that of the BG450 treated growth media (4.0 x 10 8 cfu/mL) and was slightly higher than that in BB450 media (3.7 x 10 8 cfu/mL). The one way ANOVA analysis showed there were no significant differences in the bacterial growth number among these three treatments (p = 0.664), suggesting that the

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126 SMX free biochar does not have any antibiotic effect on E coli Previous stud ies showed that biochar amendment can often benefit soil microorganisms by providing them suitable habitats, and additional organic carbon and mineral nutrient sources [86, 225] The statistical analysis of the bacterial growth numbers among all the nine tested treatments (i.e., one control, two blank biochar, and six SMX laden biochar); however, showed statistically significant differences (p = 0.014). Those results indicated that some of the SMX laden biochar may inhibit the growth of the bacteria. Comparisons of treatments of three SMX laden BB biochar to th at of the controls showed that the SMX laden BB biochar had no inhibition effect on E. coli growth (p = 0.208). The average E coli number in the BB450S30 treated growth medium (4.010 8 cfu/mL) was even slightly higher than that in the control and SMX free BB450 media. The one way ANOVA analysis of the growth experimental data of the BG biochar, however, indicated that the three of the SMX laden BG biochar showed statistically significant inhibition of the growth of the bacteria (p < 0.001). The average E co li numbers in the BG450S20, BG450S30, and BG450S50 treated growth medium were 2.410 8 2.310 8 and 2.610 8 cfu/ml, respectively. This suggests that high levels of immobilized pharmaceuticals in biochar could cause adverse effect to the microbial populatio n which is important for soil and plant health. When selecting biochar as a soil amendment to reduce the environmental impacts of reclaimed water irrigation, biochar with the highest pharmaceutical sorption abilities may not be the best choice. As shown in this study, although BB450 showed lower sorption ability to SMX, it could be a better amendment than BG450 to soil irrigated with reclaimed water. Because the biochar (BB450) with higher amount of SMX showed slight antibiotic effect on the tested

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127 bacteria it could potentially affect the indigenous soil microbial community when applied to soils irrigated with reclaimed water. Further investigations are still needed to test the effect of pharmaceutical laden biochar to the soil ecosystems including the micr oecosystems. Implications Biochar land application has been suggested to be an effective way to sequester carbon as well as improving soil quality [204] Our results suggest that biochar soil amendment also has the potential to be used as a safeguard against the leaching of pharmaceuticals into surface or ground waters, which is of particular concern during application of reclaimed water to irrigate landscapes and agricultural fields. We found that mobility and bioavailability of SMX in biochar amended soils were lower than that of unamended soils. Biochar soil amelioration, therefore, should be promoted in areas where reclaimed water or wastewater is used for irrigation. Becau se high level accumulation of pharmaceuticals in biochar could cause adverse effect on the indigenous soil microbial community, comprehensive environmental risk assessments are recommended when selecting biochar to amend soils irrigated with reclaimed wate r.

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128 Table 7 1. Properties and elemental composition of biochar used in this study. BET surface area pH Elemental composition (%, mass based) C H O a N P K Ca Mg Zn Cu Fe Al BB450 10.2 8.70 76.89 3.55 18.10 0.23 0.36 0.35 0.29 0.19 0.01 b b 0.04 BB600 375.5 8.93 80.89 2.43 14.86 0.15 0.54 0.52 0.34 0.23 0.01 b b 0.04 BP450 0.7 9.36 75.63 3.59 17.22 0.28 0.08 0.29 2.59 0.26 0.01 b 0.01 0.04 BP600 234.7 9.67 76.99 2.18 17.65 0.10 0.09 0.26 2.42 0.25 0.01 b 0.01 0.04 BG450 13.6 8.95 78.60 3.52 15.45 0.92 0.07 0.25 0.83 0.18 0.01 b 0.06 0.11 BG600 388.3 7.70 77.91 2.42 17.76 0.41 0.08 0.15 0.91 0.21 0.01 b 0.05 0.11 HW450 12.9 8.04 83.62 3.24 11.45 0.17 0.02 0.33 0.92 0.18 0.01 b 0.01 0.06 HW600 401.0 9.36 81.81 2.17 14.02 0.73 0.02 0.24 0 .82 0.13 b b 0.01 0.06 a: Determined by weight difference assumed that the total weight of the samples was made up of the tested elements only. b: < 0.01%.

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129 Figure 7 1. The solid water distribution coefficients (K d ) of SMX adsorption on different type s of biochar. Figure 7 2. Concentration of SMX in simulated reclaimed water leachates transported through biochar amended and unamended soil columns.

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130 Figure 7 3. Concentration of SMX in TCLP extracts of biochar amended and unamended soils irrigated w ith simulated reclaimed water with SMX. Figure 7 4. Concentration of SMX in TCLP extracts of biochar amended and unamended soils irrigated with simulated reclaimed water with SMX.

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131 CHAPTER 8 REMOVAL OF METHYLENE BLUE FROM AQUEOUS SOLUTION BY CLAY MODIF IED BIOCHAR Introduction

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132

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133 Materials and Methods Biochar Production

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134 Characterizations

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135 Methylene Blue Sorption Adsorption Kinetics and Isotherm Regeneration Experiments Adsorbent regeneration studies were carried out by using the MB saturated BG MMT biochar obtained from isotherm experiment afte r discarding the supernatant dye

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136 solution. The resulted sorbent was then washed three times with DI water for removing non adsorbed dye, and agitated with 50 ml of 0.50 mol l 1 KCl solution for 2 h. The regenerated biochar was separated and oven dried at 8 with same procedure described above. This sorption regeneration procedure was repeated for multiple times. Results and Discussion Surface Area and Elemental Analysis

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137 Thermogravimetric Analysis ( TGA ) O f Clay Modified and Untreated Biochars

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138 Methylene Blue Removal Ability of Clay Modified Biochars

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139 Adsorption Kinetics first order ( 8 1a) second order (8 1b) N_th order (8 2c) Elovich (8 3d)

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140

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141 Langmuir (8 2a) Freundlich (8 2b) Lan gmuir Freundlich (8 2c) Redlich Peterson (8 2d), where K, K f K lf and K r Q (mgg 1 ) denotes the maximum capacity; C e (mgL 1 ) is the sorbate concentration at equilibrium; and n and a are constants for Freundlich and Redlich Peterson models, respectively [128] See details in Yao et al. [238] All four tested isotherm models fit the experimental data fairly well and the parameters are also shown in Table 8 2. Freundlich and Redlich Peterson models had slightly better fitting performance t han the other two, with R 2 of 0.940 and 0.937, respectively. Hence, MB sorption should be onto a heterogeneous surface, and the process could be governed by multiple mechanisms, which is consistent with kinetics study results. SEM EDX and XRD showed layered surfaces ( Figure 8 5c), which is a common montmorillonite struct ural morphology reported in literatures [243, 244] The surface coverage with montmorillonite was confirmed by EDX analysis. The spectrum of

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142 EDX of the surface at the same spot with SEM imaging identified extremely high peak of silicon and aluminum, as well as sodium, calcium, magn esium, and iron, all of which are typical of the elemental composition of montmorillonite ( Figure 8 5d). The layered montmorillonite on the surface of the engineered biochar could contribute to the lower surface area of the material because it could cover the surface pores, which is consistent with the findings from the N 2 surface area measurement. XRD analysis of the BG MMT revealed the presence of mineral crystals. In the spectrum, the four strong peaks at 6.4 o (d = 13.840 ), 6.9 o (d = 12.803 ), 19.9 o (d = 4.449 ) and 35.1 o (d = 2.555 ) were identified as expansible phyllosilicate, i.e., m ontmorillonite ( Figure 8 6). The XRD result concurs to the SEM EDX analyses that the surface modification method in the work has successfully added montmorillonite o n the enhancement. Quartz (SiO 2 ), as a common mineral within biochars, were also found in BG MMT, which is consistent with the EDX results [80] Regeneration of Exhausted BG MMT Sorbent Regeneration study was carri ed out to evaluate the cyclic performance of BG MMT as an adsorbent by performing multiple cycle adsorption experiments. At first, the MB adsorption capacity of BG MMT was 11.26 mg g 1 Multiple cycle dye adsorption revealed that the regenerated biochar co ntinue to adsorb MB after each adsorption regeneration cycle, with a stable capacity of around 7.90 mg g 1 ( Figure 8 7), which account for 70.11% of initial capacity. Considering the MB sorption experiment results discussed above, BG and BG MMT removed 25. 60% and 84.33% MB, respectively ( Figure 8 2). In other words, BG biochar accounts for 30.35% dye sorption while MMT explains for the remaining 69.65%, which is a perfect match with the regeneration study

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143 results. Hence, biochar itself is capable of the upt ake of a small part of MB from solution. However, the process is nonreversible. The mechanism could be explained considering the electrostatic interaction between the surface of the biochar, which is usually negatively charged, with the positively charged MB [ 141, 245] Montmorillonite is the main factor for MB uptake (70.11%) which could be desorbed by KCl solution. When also taking into consideration the high CEC of montmorillonite (119 meq/100 g), the adsorption mechanism of montmorillonite could therefore be cation exchange [ 246 248] After multiple cycle adsorptions, the BG MMT material is still stable, which is consistent with TGA results. The sorbent could be regenerat ed easily by KCl solution and recovered most of its MB removal ability reveals that the BG MMT provides the potential to be recycled and reused after MB dye adsorption. Implications A new engineered biochar with clay modification has been successfully deve loped. Both biochar and clay are relatively cheap due to their accessibility and abundance compared to activated carbons [230] Besides its low cost the clay modified biochar has much higher sorption ability to cationic dye (MB) than the original char. Due to stability and cycle performance, the engineered biochar has the potential to be regenerated and reused for repeated dye sorption.

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144 Table 8 1. Elemental analysis of biochars produced in this study (mass %)a. BG MMT, BB MMT, HC MMT, BG KLN, BB KLN, HC KLN, BG, BB, HC are biochars produced from clay modifi ed and untreated feedstocks, respectively. Sample ID %, mass based C H N O K Na Mg Ca Cu Cr Fe Al As Cd Ag P Mn Pb Zn BB MMT 83.27 2.26 0.25 12.41 0.33 0.14 0.14 0.21 0.01 0.23 0.68 0.08 0.01 BG MMT 75.31 2.25 0.75 18.87 0.32 0.13 0.22 0.85 0.01 0.47 0.75 0.03 0.01 0.01 HC MMT 80.93 2.21 0.28 15.14 0.11 0.04 0.19 0.57 0.0 1 0.15 0.32 0.00 0.04 0.00 BB KLN 81.02 2.15 0.25 15.85 0.07 0.05 0.19 0.01 0.08 0.30 0.03 0.00 0.00 BG KLN 70.20 2.44 0.74 24.44 0.06 0.16 0.88 0.02 0.46 0.53 0.03 0.05 0.00 HC KLN 78.08 2.11 0.33 18.12 0.05 0.18 0.5 2 0.01 0.07 0.51 0.00 0.03 0.00 BB 80.89 2.43 0.15 14.86 0.52 0.23 0.34 0.00 0.00 0.04 0.54 0.01 BG 76.45 2.93 0.79 18.32 0.15 0.21 0.91 0.00 0.05 0.11 0.08 0.01 HC 81.81 2.17 0.73 14.02 0.24 0.13 0.82 0.00 0.01 0.06 0.02 0.00 below detection limit.

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145 Table 8 2. Best fit kinetics and isotherms models parameters for MB adsorption to BG MMT biochar. Parameter 1 Parameter 2 Parameter 3 R 2 Adsorption kinetics First order k 1 = 0.928 (h 1 ) q e = 6.888 (mg g 1 ) 0.769 Second order k 2 = 0.201 (g mg 1 h 1 ) q e = 7.265 (mg g 1 ) 0.852 n_th order k n = 3.215 (g n 1 mg 1 n h 1 ) q e = 9.298 (mg g 1 ) n = 5.000 0.931 Elovich = 0.872 (g mg 1 ) = 160.019 (mg g 1 h 1 ) 0.950 Adsorption isotherms Langmuir K = 0.373 (L mg 1 ) Q = 11.940 (mg g 1 ) 0.908 Freundlich K f = 5.640 (mg (1 n) L n g 1 ) n = 0.169 0.940 Langmuir Freundlich K lf = 0.494 (L n mg n ) Q = 15.000 (mg g 1 ) n = 0.449 0.928 Redlich Peterson K r = 3.211 ( L g 1 ) a = 20.000 ( L n mg n ) n= 0.852 0.937

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146 Figure 8 1. TGA curves comparison of clay modifi ed and untreated biochars under air (a c) or nitrogen (d) atmosphere.

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147 Figure 8 2. Comparison of methylene blu e (MB) adsorption ability of nine biochars produced in this study.

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148 Figure 8 3. Adsorption kinetics data and modeling (a), and intraparticle diffusion plot for methylene blue (MB) on BG MMT biochar. Symbols are experimental data and lines are model r esults. Figure 8 4. Adsorption isotherm data and modeling for methylene blue (MB) on BG MMT biochar. Symbols are experimental data and lines are model results.

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149 Figure 8 5. SEM image (a c) and EDX spectrum (d) of BG MMT biochar.

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150 Figure 8 6. X RD spectrum of BG MMT biochar. Figure 8 7. Regeneration and cycle performance of BG MMT sorbent.

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151 CHAPTER 9 CONCLUSION S Biochar converted from agricultural residues or other carbon rich wastes may provide new solutions for environmental management, particularly with respect to carbon sequestration and contaminant remediation. This Ph.D. dissertation systematically investigated the application of various biochars to remove various contaminants, including nutrients, antibiotics, and cationic dye from a queous solutions and its implications. In Chapter 2, I studied whether and how biochar can affect soil nutrients (nitrate, ammonium, and phosphate) leaching T he effect of biochar on the retention and release of nutrient ions (i.e., nitrate, ammonium, and phosphate) varies with nutrient and biochar type. Of the thirteen biochars tested in this study, most of them showed little to no nitrate or phosphate sorption ability. However, nine biochars removed aqueous ammonium. When two selected biochars (BP600, PH 600) with relatively good sorption ability were used in soil columns, they could effective reduce the leaching of nitrate and ammonium. Only one biochar, however, could reduce the leaching of phosphate from the soil columns. The results obtained from the l eaching column study were consistent with finding from the sorption experiments, suggesting the effect of biochar on nutrients in soils could be determined through laboratory batch sorption studies. It is also recommended that sorption ability of biochars to nutrients should be determined before their applications to soils as amendment. In Chapter 3, b ased on the characterization of DSTC biochar physicochemical properties and the preliminary phosphate sorption assessment,

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152 it is evident that (1) residue fro m the anaerobic digestion of sugar beet tailings can be used as a feed stock for biochar production, (2) some of the physicochemical properties (e.g., pH and surface functional groups) of the two biochars are similar, but only the anaerobically digested su gar beet tailing biochar has colloidal and nano sized periclase (MgO) on its surface, and (3) anaerobic digestion enhances the phosphate adsorption ability of biochar produced from digested sugar beet tailings relative to undigested ones. In Chapter 4, b io char converted from anaerobically digested sugar beet tailings (DSTC) demonstrated superior ability to remove phosphate from water under a range of pH and competitive ion conditions. Batch sorption experiments and post sorption characterizations suggested that phosphate removal was mainly controlled by adsorption onto colloidal and nano sized MgO particles on the DSTC surface. Because both the original and anaerobically digested sugar beet tailings are waste materials, the cost to make DSTC should be very l ow. However, the use of pre digested sugar beet tailings has the benefit of additional energy generation and more efficient production (with less CO 2 release during production). Thus, DSTC should be considered a promising alternative water treatment or env ironmental remediation technology for phosphate removal. In addition, when used as an adsorbent to reclaim phosphate from water, the exhausted biochar can be directly applied to agricultural fields as a fertilizer to improve soil fertility because the P lo aded biochar contains abundance of valuable nutrients. Potential additional environmental benefits from this approach

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153 include fuel or energy produced during both the anaerobic digestion and ure. In Chapter 5, an innovative method has been developed to produce engineered biochar directly (without pretreatment) from plant tissues enriched with Mg. The results from the initial P sorption evaluation and biochar characterization indicated that th is novel approach successfully created Mg biochar composites, containing both nanosized MgO and Mg(OH) 2 particles within the matrix, which can be used as a high efficiency adsorbent to remove P form aqueous solutions. In Chapter 6, engineered biochar conve rted form Mg enriched tomato tissues showed strong P removal ability. The spent biochar, which is P laden, behaved as a slow release fertilizer and could release P into aqueous solution in multiple times (mimics slow release P source for plant uptake) to s timulate grass used to develop new sustainable and eco friendly strategies to synthesize and apply the engineered biochar to reclaim P, reduce eutrophication, fertilize soils, imp rove soil quality, and sequester carbon. In Chapter 7, biochar soil amendment as a safeguard against the leaching of pharmaceuticals into surface or ground waters, which is of particular concern during application of reclaimed water to irrigate landscapes and agricultural fields, was investigated. I found that mobility and bioavailability of SMX in biochar amended soils were lower than that of unamended soils. Biochar soil amelioration, therefore, should be promoted in areas where reclaimed water or

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154 waste water is used for irrigation. Because high level accumulation of pharmaceuticals in biochar could cause adverse effect on the indigenous soil microbial community, comprehensive environmental risk assessments are recommended when selecting biochar to amend soils irrigated with reclaimed water. In Chapter 8, new engineered biochars with clay has been successfully developed using two low cost materials, which combined advantages of both biochar and clay. The clay modified biochar has much higher sorption ability to cationic dye (MB) than the original char. The regeneration experiment reveals that the clay modified biochar has the potential for recycle and reuse after dye adsorption and sorption mechanisms are cation exchange and electrostatic inte raction. My results suggest that the simple surface modification method with clay in this study could be used to prepare sorbent with enhanced capacity and high regeneration performance. The results of this dissertation indicate that biochar, as alternative sorbent, could effectively remove nutrients (phosphate), antibiotics (SMX) and cationic dye (MB) from aqueous solutions. New preparation method s, such as a naerobically digestion,

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155 LIST OF REFERENCES 1. Verheijen, F.; Jeffery, S.; Bastos, A. C.; Velde, M. v. d.; Diafas, I., Biochar application to soils a critic al scientific review of effects on soil properties, processes and functions EUR 24099 EN, Office for the Official Publications of the European Communities, Luxemburg, 149pp: 2009. 2. Lehmann, J.; Gaunt, J.; Rondon, M., Bio char sequestration in terrestria l ecosystems a review. Mitigation and Adaptation Strategies for Global Change 2006 (11), 403 427. 3. Major, J.; Rondon, M.; Molina, D.; Riha, S. J.; Lehmann, J., Maize yield and nutrition during 4 years after biochar application to a Colombian savanna o xisol. Plant and Soil 2010, 333 (1 2), 117 128. 4. Glaser, B.; Lehmann, J.; Zech, W., Ameliorating physical and chemical properties of highly weathered soils in the tropics with charcoal a review. Biology and Fertility of Soils 2002, 35 (4), 219 230. 5 Singh, B. P.; Hatton, B. J.; Singh, B.; Cowie, A. L.; Kathuria, A., Influence of Biochars on Nitrous Oxide Emission and Nitrogen Leaching from Two Contrasting Soils. Journal Of Environmental Quality 2010, 39 (4), 1224 1235. 6. Yang, Y. N.; Sheng, G. Y., Enhanced pesticide sorption by soils containing particulate matter from crop residue burns. Environmental Science & Technology 2003, 37 (16), 3635 3639. 7. Chen, B. L.; Chen, Z. M., Sorption of naphthalene and 1 naphthol by biochars of orange peels with different pyrolytic temperatures. Chemosphere 2009, 76 (1), 127 133. 8. Kasozi, G. N.; Zimmerman, A. R.; Nkedi Kizza, P.; Gao, B., Catechol and humic acid sorption onto a range of laboratory produced black carbons (biochars). Environmental Science & Techn ology 2010, 44 (16), 6189 6195. 9. Valix, M.; Cheung, W. H.; McKay, G., Preparation of activated carbon using low temperature carbonisation and physical activation of high ash raw bagasse for acid dye adsorption. Chemosphere 2004, 56 (5), 493 501. 10. Co rnelissen, G.; Gustafsson, O.; Bucheli, T. D.; Jonker, M. T. O.; Koelmans, A. A.; Van Noort, P. C. M., Extensive sorption of organic compounds to black carbon, coal, and kerogen in sediments and soils: Mechanisms and consequences for distribution, bioaccum ulation, and biodegradation. Environmental Science & Technology 2005, 39 (18), 6881 6895. 11. Cao, X. D.; Ma, L. N.; Gao, B.; Harris, W., Dairy Manure Derived Biochar Effectively Sorbs Lead and Atrazine. Environmental Science & Technology 2009, 43 (9), 3 285 3291.

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176 BIOGRAPHICAL SKETCH Ying Yao was born 1984 in Handan, China. She received the Bachelor of Science in Environmental Science from Southwest University in China in 2007 and the Mast er of Science in Environmental Science from the Nanjing University in 2010. She was awarded the National Oversea Scholarship of Chinese Government in 2009. S he enrolled as a PhD student in the Agricultural and Biological Engineering Department at Universi ty of Florida in 2009. Her doctoral research, under the direction of Dr. Bin Gao, focused on using biochar technology to improve environment sustainability, particularly with respect to using biochar as a low cost adsorbent to reclaim nutrients from wastew ater. As a reward to her high quality research, She has published nine peer review journal articles (five first author papers) in top ranking international journals. She was also a recipient of outstanding international student academic achievement award a t University of Florida. After graduation, she will pursue an academia career in China.