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

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72goethite and silica results in only the two distinct spectra (Figure 6.5). In attempt tounderstand the oxide-silica interfacial interactions, other samples coated by precipitation(pH 12) or with differing temperature (i.e., 35, 90, and 110 °C) were evaluated; becauseof the lower iron concentrations, however, only one goethite band was discernible in thedifference spectra. Interactions between silica and the oxide coatings potentially involveelectrostatic, van der Waals, and/or chemical bonds. Goethite was coated at pH 12 (as inprecipitation method), where both goethite and silica are negatively charged, suggestingelectrostatic repulsion. Furthermore, fluid shear from the abrasion study is approximatelyone to two orders of magnitude greater than van der Waals forces. Therefore, theseresults along with FTIR suggest the iron oxide-silica interaction may involve chemicalforces.Optically, red-brown goethite coatings were observed to be non-uniform andmostly located in concave rough areas (even before abrasion) (Figure 6.6), indicating thatrougher areas of silica may result in higher loadings of coating material. ESEM images(Figure 6.7) reveal needle-shaped goethite crystals located mostly in rough areas as well.The precipitation method produced smaller crystals of goethite (< 150 nm) than the<strong>adsorption</strong> method (100-1000 nm) (Figure 6.7), and is somewhat consistent with theextraction analysis in that ferrihydrite was present suggesting the presence of silica mayinhibit crystal growth. Elemental mapping from EDX analysis (Figure 6.8) shows Feconcentrating in rough areas, and the relative distribution of Fe and Si demonstrates anon-uniform coating on the silica surface, which is in agreement with others (Edwardsand Benjamin, 1989; Scheidegger et al. 1993).
Figure 6.6 Optical micrograph of uncoated and coated US silica (1 cm in photographrepresents 0.2 mm of real size).73
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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
Page 43 and 44: 21hematite (up to 9.9 limo' Pb ril-
Page 45 and 46: 23concentration in their system was
Page 47 and 48: 25Surface complexation modeling (SC
Page 49 and 50: 27Overall, surface complexation mod
Page 51 and 52: 29Spectroscopic techniques, especia
Page 53 and 54: 31• Understand the effect of comp
Page 55 and 56: 33existing in almost all soils and
Page 57 and 58: CHAPTER 4EXPERIMENTAL METHODSIn thi
Page 59 and 60: 37included coating temperature (T),
Page 61 and 62: 39generated at 45 kV and 40 mA, sca
Page 63 and 64: 41PZC include electrophoretic mobil
Page 65 and 66: 43Lin-edge, from 8,133 to 8,884 eV
Page 67 and 68: CHAPTER 5CHARACTERIZATION OF IRON O
Page 69 and 70: 47measured by potentiometric titrat
Page 71 and 72: Table 5.2 XRD Data of Alfa Aesar (A
Page 73 and 74: 51Table 5.3 XRF Results for Alfa Ae
Page 75 and 76: Figure 5.4 Particle size distributi
Page 77: 55Figure 5.5 ESEM micrograph for Al
Page 80 and 81: 585.2.5 Surface Charge Distribution
Page 82 and 83: Figure 5.10 Potentiometric titratio
Page 84 and 85: CHAPTER 6SYNTHESIS AND CHARACTERIZA
Page 86 and 87: Figure 6.1 Comparison between Fecon
Page 88 and 89: Figure 6.2 XRD patterns for goethit
Page 90 and 91: 68iron oxide coatings at 60 °C, go
Page 92 and 93: 70substrate diameter of 0.2 mm, an
Page 96 and 97: Figure 6.7 ESEM micrograph (9000x)
Page 98 and 99: 76Furthermore, because discrete goe
Page 100 and 101: 78Table 6.2 Surface Area and Porosi
Page 102 and 103: 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)
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Table 8.4 EXAFS Results of HFO and
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CHAPTER 9SURFACE COMPLEXATION MODEL
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Figure 9.1 Potentiometric titration
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128Table 9.1 Surface Reactions and
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Figure 9.2 Ni adsorption</s
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132Table 9.2 Model Parameters for N
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Figure 9.3 Ni adsorption</s
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1369.3 Zn Adsorption on GoethiteReg
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Figure 9.6 Zn adsorption</s
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140data over a broad range of condi
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142Figure 9.8 Ni adsorption
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144oxide-coated silica. Ni and Zn s
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Figure 10.1 Ni adsorption</
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Figure 10.2 Zn adsorption</
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Figure 10.4 Ni adsorption</
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152one for GACS (2.77x10 -6 mole si
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Figure 10.6 Zn adsorption</
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CHAPTER 11CONCLUSIONS AND FUTURE WO
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158surfaces are needed for successf
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Figure A.2 Ni speciation in 1x10 -5
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Figure A.4 Pb speciation in 5x10 -8
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Figure A.6 Zn speciation in 1x10 -5
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166Table B.2 Potentiometric Titrati
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168Table BA Potentiometric Titratio
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170Table C.3 Zn Adsorption Edges on
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APPENDIX DADSORPTION STUDIES ON SIL
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174Table D.5 Zn Adsorption Isotherm
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176Table E.3 Pb CBC Study on 0.3 g
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APPENDIX GINTRAPARTICLE DIFFUSION M
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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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