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Title: Surface complexation of Pb(II) at oxide-water interfaces: I. XAFS and bond-valence determination of mononuclear and polynuclear Pb(II) sorption products on aluminum oxides

Abstract

Pb(II) sorption on Al{sub 2}-O{sub 3} powders was studied as functions of sorption density (from 0.5 to 5.2 {mu}moles/m{sup 2}) and [Pb]{sub eq} (0.03-1.4 mM) in 0.1 M NaNO{sub 3} electrolyte solution using XAFS spectroscopy. At pH 6 and 7, Pb(II) ions were found to be fully hydrolyzed and adsorbed preferentially as mononuclear bidentate complexes to edges of AlO{sub 6} octahedra. At higher sorption densities ({Gamma} {ge}3.4 {mu}moles - m{sup -2}), XAFS results suggest the presence of dimeric Pb(II) surface complexes. A bond-valence model was used in conjunction with these results to constrain the compositions and reaction stoichiometries of adsorption complexes. We conclude that Pb(II) adsorption on alumina is attributable to complexation by [Al{sub Al}{sup Al}(>)O{sup -{1/2}}] and [Al-OH{sup -{1/2}}] surface functional groups. Several plausible Pb(II) adsorption reactions are proposed, based on these results, which provide a basis for chemically realistic descriptions of surface complexation of Pb(II) on aluminum oxides. 46 refs., 7 figs., 4 tabs.

Authors:
;  [1];  [2]
  1. Stanford Univ., CA (United States)
  2. Stanford Univ., CA (United States)|[Stanford Synchrotron Radiation Lab., CA (United States)
Publication Date:
OSTI Identifier:
576306
DOE Contract Number:  
FG03-93ER14347
Resource Type:
Journal Article
Resource Relation:
Journal Name: Geochimica et Cosmochimica Acta; Journal Volume: 61; Journal Issue: 13; Other Information: PBD: Jul 1997
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 36 MATERIALS SCIENCE; 58 GEOSCIENCES; ADSORPTION; LEAD; SORPTIVE PROPERTIES; CONTAMINATION; SOILS; GROUND WATER; ECOLOGICAL CONCENTRATION; ENVIRONMENTAL TRANSPORT; GEOCHEMISTRY; ALUMINIUM OXIDES

Citation Formats

Bargar, J.R., Parks, G.A., and Brown, G.E. Jr. Surface complexation of Pb(II) at oxide-water interfaces: I. XAFS and bond-valence determination of mononuclear and polynuclear Pb(II) sorption products on aluminum oxides. United States: N. p., 1997. Web. doi:10.1016/S0016-7037(97)00124-5.
Bargar, J.R., Parks, G.A., & Brown, G.E. Jr. Surface complexation of Pb(II) at oxide-water interfaces: I. XAFS and bond-valence determination of mononuclear and polynuclear Pb(II) sorption products on aluminum oxides. United States. doi:10.1016/S0016-7037(97)00124-5.
Bargar, J.R., Parks, G.A., and Brown, G.E. Jr. Tue . "Surface complexation of Pb(II) at oxide-water interfaces: I. XAFS and bond-valence determination of mononuclear and polynuclear Pb(II) sorption products on aluminum oxides". United States. doi:10.1016/S0016-7037(97)00124-5.
@article{osti_576306,
title = {Surface complexation of Pb(II) at oxide-water interfaces: I. XAFS and bond-valence determination of mononuclear and polynuclear Pb(II) sorption products on aluminum oxides},
author = {Bargar, J.R. and Parks, G.A. and Brown, G.E. Jr.},
abstractNote = {Pb(II) sorption on Al{sub 2}-O{sub 3} powders was studied as functions of sorption density (from 0.5 to 5.2 {mu}moles/m{sup 2}) and [Pb]{sub eq} (0.03-1.4 mM) in 0.1 M NaNO{sub 3} electrolyte solution using XAFS spectroscopy. At pH 6 and 7, Pb(II) ions were found to be fully hydrolyzed and adsorbed preferentially as mononuclear bidentate complexes to edges of AlO{sub 6} octahedra. At higher sorption densities ({Gamma} {ge}3.4 {mu}moles - m{sup -2}), XAFS results suggest the presence of dimeric Pb(II) surface complexes. A bond-valence model was used in conjunction with these results to constrain the compositions and reaction stoichiometries of adsorption complexes. We conclude that Pb(II) adsorption on alumina is attributable to complexation by [Al{sub Al}{sup Al}(>)O{sup -{1/2}}] and [Al-OH{sup -{1/2}}] surface functional groups. Several plausible Pb(II) adsorption reactions are proposed, based on these results, which provide a basis for chemically realistic descriptions of surface complexation of Pb(II) on aluminum oxides. 46 refs., 7 figs., 4 tabs.},
doi = {10.1016/S0016-7037(97)00124-5},
journal = {Geochimica et Cosmochimica Acta},
number = 13,
volume = 61,
place = {United States},
year = {Tue Jul 01 00:00:00 EDT 1997},
month = {Tue Jul 01 00:00:00 EDT 1997}
}