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

More documents

Recommendations

Info

18greater affinity for Pb than Cu. Cd <strong>adsorption</strong> is strongly influenced by the presence ofcompeting cations such as divalent Ca and Zn (Benjamin and Leckie, 1981a; Bradl(2004). Kanungo et al. (2004) found in a study on Co, Ni, Cu, and Zn sorption to HMOthat Ni experienced the greatest degree of displacement. Crawford et al. (1993) observedZn and Ni in equal concentrations adsorb independently of each other on ferrihydrite; it'slikely that the site density was not limited in this study. However, Zn was observed tohave higher affinity than Ni on goethite (Tiller et al. 1984; Crawford et al. 1993; Gupta,1998; Dube et al. 2001; Trivedi et al. 2001b; Jeon et al. 2003). Nevertheless, competitionbetween trace <strong>metal</strong>s may be difficult to demonstrate when site density is not limiting(Swallow et al. 1980; Benjamin and Leckie, 1981a; Palmqvist et al. 1999).For soil samples, Gomes et al. (2001) found Cr, Pb, and Cu were the moststrongly sorbed heavy <strong>metal</strong> cations, whereas Cd, Ni, and Zn were the least competitive.They also found that for <strong>metal</strong>s of the same valence, sequences did not exactly follow theorder of electronegativity. Stefanova (2001) observed a high selectivity of Cu and Pbover Zn and Cd ions by Keramzite sand. Khaodhiar et al. (2000) found Cu(II) <strong>adsorption</strong>increased slightly in the presence of arsenate but was not affected by chromate. Arsenate<strong>adsorption</strong> was not affected by either copper or chromate, while chromate <strong>adsorption</strong>increased in the presence of Cu(II) and decreased in the presence of arsenate. Theauthors modeled the single-sorbate behavior successfully with the triple layer model, butcould not predict <strong>adsorption</strong> for multi-sorbate systems with surface complexationconstants from single-sorbate systems. The local structure of the sorbed species isneeded to constrain surface complexation modeling.
19Overall, macroscopic <strong>adsorption</strong> studies are just a starting point for investigating<strong>metal</strong> partitioning at the solid/liquid interfaces. Efforts to further describe and predicttheir behavior are restricted by poor understanding of the <strong>adsorption</strong> mechanism. Recentadvances in addressing speciation using in situ spectroscopic techniques such as XAShave made it possible to overcome this drawback (Brown, 1990; Brown and Sturchio,2002; Hayes and Katz, 1996). Spectroscopic studies are introduced in the next section.2.3 Adsorption on Oxides — Spectroscopic StudiesXAS and its derivatives XANES (X-ray absorption near edge structure) and EXAFS(extended X-ray absorption fine structure) spectroscopy are powerful tools forascertaining the speciation of trace <strong>metal</strong>s in natural soils and sediments (O'Day et al.1998). Many researchers have used EXAFS to study the speciation of <strong>metal</strong> ions innatural sediments. O'Day et al. (1998) found that as sphalerite (ZnS) weathers, Zn isscavenged primarily as zinc hydroxide and/or zinc-iron oxyhydroxide phases, dependingon the total amount of iron in the system. Similarly, Pb sorbed to iron oxyhydroxides atlow pH (7)depending on the lead and iron concentrations in the system. Cd released from sphaleriteweathering is preferentially partitioned into the aqueous phase. Scheinost et al. (2002)studied Zn speciation in soils near a former sphalerite smelter. They found that in thetopsoil, Zn exists as franklinite (ZnFe2O4) (60%), sphalerite (30%), and aqueous or outersphereZn2+; in the subsoil, aqueous or outer-sphere Zn 2+ prevailed (55%) and theremaining 45% was incorporated by hydroxyl-Al interlayers of phyllosilicates. The
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: 17mole Cu g-1 goethite (-1-7% of th
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 146 and 147:
CHAPTER 9SURFACE COMPLEXATION MODEL
Page 148 and 149:
Figure 9.1 Potentiometric titration
Page 150 and 151:
128Table 9.1 Surface Reactions and
Page 152 and 153:
Page 154 and 155:
132Table 9.2 Model Parameters for N
Page 156 and 157:
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 168 and 169:
Page 170 and 171:
Figure 10.2 Zn adsorption</
Page 172 and 173:
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 ...

Create successful ePaper yourself

Delete template?

Save as template?