title: Surface Complexation of Hg(2+) on Goethite: Mechanism from EXAFS Spectroscopy and Density Functional Calculations.
abstract: EXAFS spectra of Hg(2+) sorbed on goethite at pH 4.60 has revealed the existence of an inner-sphere complex with an immediate coordination shell of 2 O atoms at 2.04 Å and a further shell of 1 Fe atom at 3.28 Å. Using density functional calculations, we determined the optimized geometries of small clusters representing surface complexes. These results shows that adsorption of Hg(2+) occurs via two oxygen atoms bound to edge-sharing Fe sites on the (110) surface. This is the same surface site we find for Cd (1, 2) and Sr (3). The short Hg-O bond length shows that the oxygens bridging Hg and Fe atoms are deprotonated. Copyright 1999 Academic Press.
authors.affiliation: Department of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, United Kingdom
authors.initials: CR
authors.lastname: Collins
authors.initials: DM
authors.lastname: Sherman
authors.initials: KV
authors.lastname: Ragnarsdottir