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

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8coatings were less resistant to acid. Kuan et al. (1998) reported that at a higher coatingpH (10.77-12.50), Al oxide coatings were more resistant to acidic and alkaline conditionsand tended to be crystalline. Lo et al. (1997) found that the Fe concentration had less ofan effect than pH on the degree of coating. Although the influence of substrate particlesize has not been investigated systematically, Coston et al. (1995) showed that oxideconcentration increased as particle size decreased in soils and sediments.2.1.2 Coating CharacterizationMany studies have been conducted to evaluate coating characteristics. Methods formineral identification are based on specific properties of the minerals (de Kimpe, 1993).These properties include crystallographic, optical (microscopic), physical (cleavage,color, density), and chemical properties. Numerous researchers (Edwards and Benjamin,1989; Zachara et al. 1995; Khaodhiar et al. 2000; Szecsody et al. 1994; Stahl and James,1991 a, b; Marchetti et al. 1997) have produced Fe oxide coatings ranging between 0.7and 50 mg Fe g-1 sand, while those of natural soils and sediments are in the range of0.074 to 44.2 mg Fe g -1 sand (Ryan and Gschwend, 1994; Coston et al. 1995; Wang et al.1993; Pieper et al. 1997). The oxide-silica interface has been investigated with x-rayphotoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR)(Scheidegger et al. 1993), where Fe-O-Si bonding was proposed. Liang et al. (2000)concluded that the quartz-ferrihydrite interface involves chemical interactions based ontheir observations that repulsive forces could not explain the results. Using Mössbauerspectroscopy, Marchetti et al. (1997) reported that the smaller the oxide particles thestronger the oxide-substrate interaction. X-ray diffraction (XRD), transmission electronmicroscopy (TEM), and scanning electron microscopy (SEM) have been used as well to
9identify components, distribution, and structure of surface oxide coatings (Coston et al.1995; Wang et al. 1993; Edwards and Benjamin, 1989; Kuan et al. 1998; Meng andLetterman, 1993b). Typically, oxides are non-uniform (Edwards and Benjamin, 1989)over the surface, as both the oxide and substrate have been observed (Anderson andBenjamin, 1990). Surface area combined with extractable Fe may be an effectivegeochemical 'indicator' of the potential variability of <strong>metal</strong> distribution in an aquifer(Fuller et al. 1996). The need to characterize the structure and behavior of sediments isclear.2.1.3 Measurement of CoatingIron concentration in coated silica is an important factor in evaluating the coating processand a number of researchers have used extraction (Kuan et al. 1998; Stahl and James,1991a, b; Fan, 1996; Wang, 1995; Szecsody et al. 1994). These techniques have beendeveloped by soil scientists, geologists, and oceanographers to enhance in clay mineralcharacterization (Ryan and Gschwend, 1991; Shuman, 1982; Furtado et al. 1990; Sequi etal. 1983; Borggaard, 1981; Geiger and Loeppert, 1986; Jackson et al. 1986; Kunze andDixon, 1986; Leoppert and Inskeep, 1996). For example, Ross and Wang (1993)summarized five extraction methods that may be used to approximate the amounts andforms of Fe in soils (Table 2.1): dithionite citrate, acid ammonium oxalate,hydroxylamine, tiron (4, 5-dihydroxy-1, 3-benzene-disulfonic acid), and pyrophosphate.Other extraction methods for Fe include citrate-ascorbate (Reyes and Torrent, 1997),ethylenediaminetetraacetic acid (EDTA) (Borggaard, 1981), HC1, and H2C2O4 (Chao andZhou, 1983) for amorphous iron oxides; and, ascorbic acid-oxalate (Shuman, 1982) andtitanium(III)-citrate-EDTA-HCO 3 (Ryan and Gschwend, 1991) for crystalline iron
Page 1 and 2: Copyright Warning & RestrictionsThe
Page 3 and 4: ABSTRACTHEAVY METAL ADSORPTION ON I
Page 5 and 6: HEAVY METAL ADSORPTION ON IRON OXID
Page 7 and 8: APPROVAL PAGEHEAVY METAL ADSORPTION
Page 9 and 10: Fan, M.; Boonfueng, T.; Xu, Y.; Axe
Page 11 and 12: ACKNOWLEDGMENTI would like to expre
Page 13 and 14: TABLE OF CONTENTS(Continued)Chapter
Page 15 and 16: TABLE OF CONTENTS(Continued)Chapter
Page 17 and 18: LIST OF TABLES(Continued)TablePageB
Page 19 and 20: LIST OF FIGURES(Continued)FigurePag
Page 21 and 22: LIST OF FIGURES(Continued)FigurePag
Page 23 and 24: CHAPTER 1INTRODUCTIONHeavy<
Page 25 and 26: 3and Sigg, 1992; Gunneriusson et al
Page 27 and 28: CHAPTER 2OXIDES AND THEIR EFFECT ON
Page 29: 7et al. 1996; Green-Pedersen et al.
Page 33 and 34: 11oxides. Because extraction method
Page 35 and 36: 13Table 2.2 Some Coating Work and C
Page 37 and 38: 15increasing the sorbate concentrat
Page 39 and 40: 17mole Cu g-1 goethite (-1-7% of th
Page 41 and 42: 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
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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
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Figure 6.11 Ni adsorption</
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84that for pure silica, and the goe
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Table 7.1 Sample Preparation Condit
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Figure 7.2 EXAFS spectra of Pb/HFO
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Figure 7.3 Fourier transform and fi
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Figure 7.4 Fourier transform and fi
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Table 7.3 EXAFS Results of Pb/HFO S
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967.2 Fe XAS of Iron Oxides and Pb/
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Figure 7.7 EXAFS spectra of iron ox
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100and Venturelli, 1999). Overall t
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102(hematite, goethite, akaganeite,
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104adsorption proc
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106of pH, ionic strength, Pb loadin
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Figure 8.1 Ni adsorption</s
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110high metal load
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Figure 8.3 x(k)•k3 spectra and Fo
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Figure 8.4 (k)•k3 spectra of Ni-H
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Figure 8.5 Fourier transforms (magn
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118be fit using either Fe or Ni ato
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1208.3 EXAFS Analysis of FeThe x(k)
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Table 8.4 EXAFS Results of HFO and
Page 146 and 147:
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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Page 154 and 155:
132Table 9.2 Model Parameters for N
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Page 158 and 159:
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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Page 170 and 171:
Figure 10.2 Zn 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
Page 194 and 195:
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
Page 204 and 205:
REFERENCES1. Adamson A. W. (1982) P
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18426. Blake R. L., Hessevick R. E.
Page 208 and 209:
18650. Combes J. M., Manceau A. and
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18876. Elzinga E. J. and Sparks D.
Page 212 and 213:
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.
Page 228:
304. Zhong Z. Y., Prozorov T., Feln
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