Heavy metal adsorption on iron oxide and iron oxide-coated silica ...

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132Table 9.2 Model Parameters for Ni and Zn Adsorption Isotherms for Goethite atDifferent pH ValuespH Log Kt, Log Kll NsH (mol/g)Parameters for Ni <strong>adsorption</strong>4 -1.93 3.73 2.5x10-64.5 -2.62 2.18 2.5x10-65 -3.34 0.39 2.5x10-65.5 -4.42 -0.42 5.0x10-66 -5.34 -1.15 2.0x10-56.5 -6.63 -2.45 3.5x10-57 -6.89 -3.04 6.0x10-5Parameters for Zn <strong>adsorption</strong>4 -2.10 4.18 5.0x10-74.5 -2.66 3.29 1.0x10-65 -3.56 2.34 3.1x10-65.5 -3.92 2.14 3.1x10-66 -4.36 0.86 7.3x10 -66.5 -4.60 0.41 7.3x10 -67 -5.00 -0.29 7.3x10-6
133isotherm data (Figure 9.2). The results suggest that although polynuclear surfacecomplexes and/or precipitation can account for isotherms with slopes not equal to one(Lützenkirchen and Behra, 1994; Katz and Hayes, 1996), multisite <strong>adsorption</strong> isapplicable when supported by spectroscopic data. More than one type of surface site hasbeen experimentally observed on ferric oxyhydroxide (Bottero et al. 1993) and supportedin crystallographic analysis (van Riemsdijk and Hiemstra, 1999). As Robertson andLeckie (1997) note, even when slopes equal one, this does not guarantee that only onetype of site is present; it is more likely that several site types exist.Even if site density is a function of pH, it appears that at least in this study, thehigh affinity site density falls within an order of magnitude of each other. Therefore, interms of applying the TLM, a single set of parameters describing both <strong>adsorption</strong> edgeand isotherm data would be more practical. Adsorption edges (Figure 9.3) are consistentwith isotherm data, the % Ni sorbed increased significantly from pH 5 to 6.5 at low Niconcentrations (Figure 9.3); however, at the highest [Ni]0 (Fig. 3a) the typical sigmoidcurve is not observed potentially due to site saturation. All seven sets of TLM parametersderived from isotherms were used to predict edge data (Figure 9.3). Overall, only the pH6.5 set of parameters was found to predict all edge data reasonably well (represented bythe solid line in each edge plot in Figure 9.3). These parameters were further tested onthe isotherms, and results (Figure 9.4) indicate that this one set of parameters successfullymodeled <strong>adsorption</strong>. Therefore, a single set of TLM parameters was found to describe Ni<strong>adsorption</strong> on goethite over a broad range of conditions, covering almost seven orders ofmagnitude in concentration (10 -10 to 10-3 M), ionic strength from 10 -3 to 10-2, and anenvironmentally relevant pH range from 5 to 6.5.
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Copyright Warning & RestrictionsThe
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ABSTRACTHEAVY METAL ADSORPTION ON I
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HEAVY METAL ADSORPTION ON IRON OXID
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APPROVAL PAGEHEAVY METAL ADSORPTION
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Fan, M.; Boonfueng, T.; Xu, Y.; Axe
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ACKNOWLEDGMENTI would like to expre
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TABLE OF CONTENTS(Continued)Chapter
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TABLE OF CONTENTS(Continued)Chapter
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LIST OF TABLES(Continued)TablePageB
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LIST OF FIGURES(Continued)FigurePag
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LIST OF FIGURES(Continued)FigurePag
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CHAPTER 1INTRODUCTIONHeavy<
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3and Sigg, 1992; Gunneriusson et al
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CHAPTER 2OXIDES AND THEIR EFFECT ON
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7et al. 1996; Green-Pedersen et al.
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9identify components, distribution,
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11oxides. Because extraction method
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13Table 2.2 Some Coating Work and C
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15increasing the sorbate concentrat
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17mole Cu g-1 goethite (-1-7% of th
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19Overall, macroscopic adso
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21hematite (up to 9.9 limo' Pb ril-
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23concentration in their system was
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25Surface complexation modeling (SC
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27Overall, surface complexation mod
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29Spectroscopic techniques, especia
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31• Understand the effect of comp
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33existing in almost all soils and
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CHAPTER 4EXPERIMENTAL METHODSIn thi
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37included coating temperature (T),
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39generated at 45 kV and 40 mA, sca
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41PZC include electrophoretic mobil
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43Lin-edge, from 8,133 to 8,884 eV
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CHAPTER 5CHARACTERIZATION OF IRON O
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47measured by potentiometric titrat
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Table 5.2 XRD Data of Alfa Aesar (A
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51Table 5.3 XRF Results for Alfa Ae
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Figure 5.4 Particle size distributi
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55Figure 5.5 ESEM micrograph for Al
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585.2.5 Surface Charge Distribution
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Figure 5.10 Potentiometric titratio
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CHAPTER 6SYNTHESIS AND CHARACTERIZA
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Figure 6.1 Comparison between Fecon
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Figure 6.2 XRD patterns for goethit
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68iron oxide coatings at 60 °C, go
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70substrate diameter of 0.2 mm, an
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72goethite and silica results in on
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Figure 6.7 ESEM micrograph (9000x)
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76Furthermore, because discrete goe
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78Table 6.2 Surface Area and Porosi
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Figure 6.10 Surface charge distribu
Page 104 and 105: Figure 6.11 Ni adsorption</
Page 106 and 107: 84that for pure silica, and the goe
Page 108 and 109: Table 7.1 Sample Preparation Condit
Page 110 and 111: Figure 7.2 EXAFS spectra of Pb/HFO
Page 112 and 113: Figure 7.3 Fourier transform and fi
Page 114 and 115: Figure 7.4 Fourier transform and fi
Page 116 and 117: Table 7.3 EXAFS Results of Pb/HFO S
Page 118 and 119: 967.2 Fe XAS of Iron Oxides and Pb/
Page 120 and 121: Figure 7.7 EXAFS spectra of iron ox
Page 122 and 123: 100and Venturelli, 1999). Overall t
Page 124 and 125: 102(hematite, goethite, akaganeite,
Page 126 and 127: 104adsorption proc
Page 128 and 129: 106of pH, ionic strength, Pb loadin
Page 130 and 131: Figure 8.1 Ni adsorption</s
Page 132 and 133: 110high metal load
Page 134 and 135: Figure 8.3 x(k)•k3 spectra and Fo
Page 136 and 137: Figure 8.4 (k)•k3 spectra of Ni-H
Page 138 and 139: Figure 8.5 Fourier transforms (magn
Page 140 and 141: 118be fit using either Fe or Ni ato
Page 142 and 143: 1208.3 EXAFS Analysis of FeThe x(k)
Page 144 and 145: Table 8.4 EXAFS Results of HFO and
Page 146 and 147: CHAPTER 9SURFACE COMPLEXATION MODEL
Page 148 and 149: Figure 9.1 Potentiometric titration
Page 150 and 151: 128Table 9.1 Surface Reactions and
Page 158 and 159: 1369.3 Zn Adsorption on GoethiteReg
Page 160 and 161: Figure 9.6 Zn adsorption</s
Page 162 and 163: 140data over a broad range of condi
Page 164 and 165: 142Figure 9.8 Ni adsorption
Page 166 and 167: 144oxide-coated silica. Ni and Zn s
Page 170 and 171: Figure 10.2 Zn adsorption</
Page 174 and 175: 152one for GACS (2.77x10 -6 mole si
Page 176 and 177: Figure 10.6 Zn adsorption</
Page 178 and 179: CHAPTER 11CONCLUSIONS AND FUTURE WO
Page 180 and 181: 158surfaces are needed for successf
Page 182 and 183: Figure A.2 Ni speciation in 1x10 -5
Page 184 and 185: Figure A.4 Pb speciation in 5x10 -8
Page 186 and 187: Figure A.6 Zn speciation in 1x10 -5
Page 188 and 189: 166Table B.2 Potentiometric Titrati
Page 190 and 191: 168Table BA Potentiometric Titratio
Page 192 and 193: 170Table C.3 Zn Adsorption Edges on
Page 194 and 195: APPENDIX DADSORPTION STUDIES ON SIL
Page 196 and 197: 174Table D.5 Zn Adsorption Isotherm
Page 198 and 199: 176Table E.3 Pb CBC Study on 0.3 g
Page 200 and 201: APPENDIX GINTRAPARTICLE DIFFUSION M
Page 202 and 203: 180DofA = flier ^ 2fA = Exp(-fD * f
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REFERENCES1. Adamson A. W. (1982) P
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18426. Blake R. L., Hessevick R. E.
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18650. Combes J. M., Manceau A. and
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18876. Elzinga E. J. and Sparks D.
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190102. Gupta V. K. (1998) Equilibr
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192126. Joshi A. and Chaudhuri M. (
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194150. Liu C. and Huang P. M. (200
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196175. Muller B. and Sigg L. (1992
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200. Perry R. H. and Green D. W. (1
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200226. Scheinost A. C., Kretzschma
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202252. Swallow C. K., Hume D. N. a
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204278. Villalobos M., Trotz M. A.
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304. Zhong Z. Y., Prozorov T., Feln
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