XAFS Studies of Pb(II)-Chloro and Hg(II)-Chloro Ternary Complexes on Goethite

J.R. Bargar; P. Persson; G.E. Brown Jr.

doi:doi:10.1051/jp4:1997249

Numéro		J. Phys. IV France Volume 7, Numéro C2, Avril 1997 Proceedings of the 9th International Conference on X-Ray Absorption Fine Structure


Page(s)		C2-825 - C2-826
DOI		https://doi.org/10.1051/jp4:1997249

Proceedings of the 9th International Conference on X-Ray Absorption Fine Structure

J. Phys. IV France 7 (1997) C2-825-C2-826
DOI: 10.1051/jp4:1997249

XAFS Studies of Pb(II)-Chloro and Hg(II)-Chloro Ternary Complexes on Goethite

J.R. Bargar^{1, 2}, P. Persson³ and G.E. Brown Jr.¹

¹ Department of Geological and Environmental Sciences, Stanford University Stanford CA 94305-2115, U.S.A.
² US Geological Survey, 345 Middlefield Road, MS 465, Menlo Park CA 94025, U.S.A.
³ Department of Inorganic Chemistry, Umeå University, 90187 Umeå, Sweden

Abstract
EXAFS spectroscopy was used to study Pb(II) and Hg(II) adsorption complexes on goethite (α-FeOOH) in the presence of Cl^-. At pH 7, the dominant Pb(II) species are bonded to edges of FeO₆ octahedra and are similar to complexes that occur in the absence of Cl^-. At pH≤6, Pb(II)-chloro ternary complexes pedominate and are bonded to corners of FeO₆ octahedra. At pH 6.5, linear Hg(OH)Cl ternary complexes predominate that are bonded to goethite through surface oxygens in a bent Hg-O-Fe geometry. In the absence of Cl^-, the Hg(II) surface complexes retain this basic geometry, but an OH group replaces the chloride ion in the first coordination shell.