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

More documents

Recommendations

Info

CHAPTER 9SURFACE COMPLEXATION MODELING OF HEAVY METAL ADSORPTIONAND COMPETITION ON GOETHITEThis chapter focuses on constraining surface complexation modeling with XAS results todevelop one unique set of SCM parameters for the description of both <strong>adsorption</strong> edgeand isotherm data. Data represent those covering a broad range of conditions, includingpH, ionic strength, <strong>metal</strong> concentration, and the presence of a competing ion. Ni(II) andZn(II) are two common <strong>metal</strong> contaminants that may coexist due to release fromhistorically poor waste management practices including industries such as electroplating.Ni and Zn <strong>adsorption</strong> and competition at the goethite/water interface are investigated inthis chapter.First, the <strong>adsorption</strong> mechanism needs to be defined. Based on the last chapter Niforms mononuclear bidentate edge-sharing complexes on HFO with loadings up to8.1x10-3 mole Ni g -1 and similar surface species may form on goethite. Zn(II) was foundto form bidentate surface complexes on both 2-line ferrihydrite (Waychunas et al. 2002,2003; Trivedi et al. 2004) and goethite (Schlegel et al. 1997; Trivedi et al. 2001a).Schlegel et al. (1997) reported that Zn(II) formed inner-sphere mononuclear edge- andcorner-sharing complexes upon <strong>adsorption</strong> to goethite at 10% proton site coverage (total[Zn] = 2x10 -4 M). Trivedi et al. (2001a) also observed inner-sphere surface complexesup to a loading of 2x10 -5 mol Zn g-1 . For these reasons, bidentate surface complexes areassumed in this study, where SOH represents a surface hydroxyl group and the surfacereaction for either Ni or Zn (Me) on goethite is the following:124
125This reaction is also consistent with the reported proton release for Zn <strong>adsorption</strong> ongoethite (Forbes et al. 1976; Kooner, 1993; Trainor et al. 2000). Although the systemswere open to the atmosphere, there was no evidence of structural contributions fromcarbonate in XAS analyses (Chapter 8; Trivedi et al. 2001a). Carbonate species have notbeen reported to affect <strong>adsorption</strong> of Zn, Ni, Cd, and Pb under atmospheric conditions(Balistrieri and Murray, 1982; Lützenkirchen and Behra, 1994; Green-Pedersen et al.1997; Villalobos et al. 2001; Strathmann and Myneni, 2005).9.1 Potentiometric Titration DataTitration results (Figure 9.1) reveal that the point of zero charge (PZC) for goethite is atpH 8.8 ± 0.97 (pHpzc). This value is consistent with reported ones, which range from 7.5to 9.5 (Lumsdon and Evans, 1994; Robertson and Leckie, 1998; Peacock and Sherman,2004). The variation in the reactivity of goethite is caused by the synthetic conditionssuch as total base added, rate of addition, the presence of sorbing ions, and aging time(Schwertmann et al. 1985; Villalobos et al. 2003). Each crystal plane has a distinct sitedensity (Hiemstra et al. 1989); the pHpzc may also be a function of the particle shape,size, and surface area. Sverjensky (2005) reported that pHpzc may be lower withoutsufficient purging to remove carbon dioxide compared to otherwise obtained values.Previous studies (Evans et al. 1979; Zeltner and Anderson, 1988) have shown that whenthe goethite suspension was purged for 2 months, the PZC increased from 8.1 to 9.1; intheir interpretation, changes in PZC were due to CO2 <strong>adsorption</strong> and desorption.However, aging also affects crystallinity, which would impact the PZC as well.
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 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
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 94 and 95:
72goethite and silica results in on
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)
Page 144 and 145: Table 8.4 EXAFS Results of HFO and
Page 148 and 149: Figure 9.1 Potentiometric titration
Page 150 and 151: 128Table 9.1 Surface Reactions and
Page 154 and 155: 132Table 9.2 Model Parameters for N
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
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
Page 210 and 211:
18876. Elzinga E. J. and Sparks D.
Page 212 and 213:
190102. Gupta V. K. (1998) Equilibr
Page 214 and 215:
192126. Joshi A. and Chaudhuri M. (
Page 216 and 217:
194150. Liu C. and Huang P. M. (200
Page 218 and 219:
196175. Muller B. and Sigg L. (1992
Page 220 and 221:
200. Perry R. H. and Green D. W. (1
Page 222 and 223:
200226. Scheinost A. C., Kretzschma
Page 224 and 225:
202252. Swallow C. K., Hume D. N. a
Page 226 and 227:
204278. Villalobos M., Trotz M. A.
Page 228:
304. Zhong Z. Y., Prozorov T., Feln
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?