Surface Complexation of Hg(2+) on Goethite: Mechanism from EXAFS Spectroscopy and Density Functional Calculations.
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.
Collins
CR
Department of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, United Kingdom
Sherman
DM
Ragnarsdottir
KV