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

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16released from Zn sorption to HFO; the authors explained their results as formation ofmultinuclear species. Although these approaches are usually successful in modeling, thesurface species may not be unique or physically meaningful.2.2.2 Adsorption IsothermIsotherms exhibit several types of shapes depending on <strong>metal</strong> concentration and/orsurface coverage (Hayes and Katz, 1996). At low concentration and low surfacecoverage, isotherms are often linear, the slope of which is referred to as distributioncoefficient (K,1). Kd has been used extensively to describe the partitioning of ions at thesolid/liquid interface and is often found to be a function of pH, solution composition, andsolid/liquid ratio (Jackson and Inch, 1989; Kooner, 1993; Lee et al. 1996; Larsen andPostma, 1997). Therefore, one condition may not be applicable to another. When anisotherm is conducted over a wider concentration range, it often becomes highlynonlinear and may level off at relatively high <strong>metal</strong> concentration. This type of isothermcan be described by the Langmuir model using two parameters, K for the equilibriumconstant and C t for site density. The Langmuir isotherm has been applied in a variety of<strong>adsorption</strong> studies (Pierce and Moore, 1980; Kanungo, 1994; Lee et al. 1996; Gupta,1998; Small et al. 2001; Christophi and Axe, 2000; Trivedi et al. 2001b; Dong et al.2001; Vaishya and Gupta, 2002, 2004; Delolme et al. 2004; Juang and Chung, 2004).The Freundlich isotherm has been used often for <strong>metal</strong> <strong>adsorption</strong> on oxides or soilsamples (Barrow et al. 1989; Gupta, 1998; Sen et al. 2002; Vaishya and Gupta, 2002,2004), and suggests the existence of more than one type of site.Isotherms may be more complicated than discussed above. Robertson and Leckie(1998) observed three regions in the isotherm for Cu <strong>adsorption</strong> to goethite: below —10-5
17mole Cu g-1 goethite (-1-7% of the total sites), between —10 -5 and —10 -4.3 Cu g-1goethite (-3-30% of the total sites), and above —10 -4.3 mole Cu g -1 goethite. Similartrends for isotherms were found in other studies on Cd/HFO (Dzombak and Morel, 1986;Spadini et al. 2003), Cr/HFO (Charlet and Manceau, 1992), Zn/HFO (Kinniburgh andJackson, 1982), and Co/Al2O3 (Katz and Hayes, 1995a). Homogeneous precipitationmay occur if the <strong>metal</strong> ion is supersaturated resulting in an abrupt increase in theisotherm slope (Hayes and Katz, 1996). Gradual increases in the slope at high <strong>metal</strong>concentrations were modeled as surface polymers or surface precipitation (Katz andHayes, 1995b; Dzombak and Morel, 1986; Charlet and Manceau, 1992) and have beensupported by XAS for Cr/HFO system (Charlet and Manceau, 1992). Similar features inCd/goethite isotherm (Robertson and Leckie, 1998) were successfully modeled using thetriple layer model assuming several surface species. Based on wet chemical,spectroscopic, and crystallographic considerations, Spadini et al. (2003) proposed a lowaffinitysite for modeling isotherms at high surface coverage.Although many studies have been conducted with single sorbate systems, <strong>metal</strong>ions may co-exist in the environment resulting in competition, which is discussed in thefollowing section.2.2.3 Competition StudiesMany researchers have investigated competition, for example, Gadde and Laitinen (1974)concluded that Pb sorbed more strongly than other ions, Zn, Cd, and Ti, on HFO andHMO. Adsorption of trace <strong>metal</strong>s (Cu, Pb, Zn, Ni, and Cd) tends to be suppressed byhigh levels of weakly adsorbing alkaline earth ions (Balistrieri and Murray, 1982; Cowanet al. 1991; Trivedi et al. 2001b). Christophi and Axe (2000) observed that goethite has a
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 and 36: 13Table 2.2 Some Coating Work and C
Page 37: 15increasing the sorbate concentrat
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
Page 88 and 89:
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
Page 192 and 193:
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
Page 206 and 207:
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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