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

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14Ephraim et al. 1991; Bar-Tal et al. 1988; Lion et al. 1982; Baccini et al. 1982; Buerge-Weirich et al. 2002), sorbate/sorbent ratio (Gadde and Laitinen, 1974; Hayes and Leckie,1986; Weesner and Bleam, 1998; Webster et al. 1998), and competing <strong>metal</strong> ions(Benjamin and Leckie, 1981b; Voegelin et al. 2001; Christi and Kretzschmar, 1999;Christophi, 1998; Christophi and Axe, 2000; Gadde and Laitinen, 1974; Palmqvist, et al.1999; Swallow et al. 1980; Trivedi et al. 2001b; Vulava et al. 2000). Other factorsinvolve redox, temperature, supersaturated solutions of <strong>metal</strong> ions, and microbial effects.Generally, <strong>metal</strong> cation <strong>adsorption</strong> increases with increasing pH as the surface chargebecomes more negative. Ionic strength affects <strong>metal</strong> <strong>adsorption</strong> by influencing adsorbateactivity as well as the surface charge and double-layer capacitance and thickness.However, the effect of ionic strength is often relatively minor compared to pH.Complexing ligands may decrease or increase adsorbate uptake. Adsorption competitionoccurs when multiple species are present and compete for a limited number of surfacesites.Macroscopic studies include <strong>adsorption</strong> edges and isotherms. The formeraddresses pH and ionic strength dependence of <strong>adsorption</strong>, while the latter describes<strong>metal</strong> concentration dependence. In the following, both <strong>adsorption</strong> edges and isothermsas well as <strong>metal</strong> competition studies are introduced.2.2.1 Adsorption EdgeA plot of cation <strong>adsorption</strong> to iron oxides vs. pH is usually sigmoidal with percent <strong>metal</strong>sorbed increasing from 0 to 100% over a narrow pH range (Cornell and Schwertmann,1996; Hayes and Leckie, 1986). Sorbate/solid ratio influences the position of edge jump.Adding more solid causes the edge jump to shift to a lower pH; on the other hand,
15increasing the sorbate concentration will cause either no shift at very low coverage or ashift to higher pH values becoming less steep with increasing coverage (Hayes and Katz,1996). Temperature has also been observed to affect cation uptake; <strong>adsorption</strong> edges ofZn, Cu, Pb, and Cd on goethite (Johnson, 1990; Rodda et al. 1993) and Ni, Gd, and Y onalumina (Kosmulski, 1997) shifted to lower pH values as temperature rose from 10-70and 15-35 °C, respectively. The relative affinity of a <strong>metal</strong> is reflected by the position ofthe edge jump. Dzombak and Morel (1990) reported the following trend for <strong>metal</strong>affinity to HFO Ca < Ni < Zn < Cd < Pb < Cr and Cornell and Schwertmann (1996)discussed a trend of Mn < Ni < Co < Cd < Zn < Pb< Cu.The effect of ionic strength on the <strong>adsorption</strong> edge although suggestive, is notconcrete. Nonspecific <strong>adsorption</strong> of cations (such as alkali cations) is dependent on ionicstrength, where specific <strong>adsorption</strong> is typically absent ionic strength effects (Cornell andSchwertmann, 1996). Hayes and Leckie (1987) observed little ionic strength (IS = 102-100) effect on Pb and Cd <strong>adsorption</strong> on goethite, the results were best modeled as aninner-sphere surface reaction. In modeling, the absence or presence of an ionic strengtheffect on <strong>metal</strong> <strong>adsorption</strong> is usually interpreted as inner-sphere or outer-sphere<strong>adsorption</strong>, respectively. Additionally, cation <strong>adsorption</strong> is often accompanied by protonrelease. The number in the past has been attributed to mononuclear or binuclearcomplexes and typically restricted to one or two (Cornell and Schwertmann, 1996).Intermediate values (Forbes et al. 1976; Hayes and Leckie, 1986; Müner and Sigg, 1992;Kooner, 1993; Gunneriusson et al. 1994; Trainor et al. 2000) may be caused byhydrolysis of the cation and/or occurrence of two types of sites or surface species(Cornell and Schwertmann, 1996). Benjamin and Leckie (1981a) observed 3.2 protons
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 and 30: 7et al. 1996; Green-Pedersen et al.
Page 31 and 32: 9identify components, distribution,
Page 33 and 34: 11oxides. Because extraction method
Page 35: 13Table 2.2 Some Coating Work and C
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
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
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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
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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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132Table 9.2 Model Parameters for N
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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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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
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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.
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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.
Page 228:
304. Zhong Z. Y., Prozorov T., Feln
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