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
- Stanford Univ., CA (United States)
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.
- DOE Contract Number:
- FG03-93ER14347
- OSTI ID:
- 576306
- Journal Information:
- Geochimica et Cosmochimica Acta, Vol. 61, Issue 13; Other Information: PBD: Jul 1997
- Country of Publication:
- United States
- Language:
- English
Similar Records
XAFS study of Pb(II) chemisorption at the {alpha}-Al{sub 2}O{sub 3}-water interface
XAFS spectroscopy study of Cu(II) sorption on amorphous SiO{sub 2} and {gamma}-Al{sub 2}O{sub 3}: Effect of substrate and time on sorption complexes