Sorption of Co(II) on Metal Oxide Surfaces.
We have characterized the adsorption of Co(II) on the (0001) and (1102) surfaces of alpha-Al(2)O(3) single crystals under ambient conditions using polarization-dependent grazing-incidence X-ray absorption fine structure spectroscopy, in combination with bond valence modeling. Co(II) ions were found to be adsorbed on both surfaces in an inner-sphere fashion. Adions were found to adsorb dominantly in a tridentate fashion (i.e., bonded to three surface oxygens) on the (0001) surface and dominantly in a tetradentate fashion on the (1102) surface. Based on EXAFS results and bond valence analysis, plausible surface complexation reactions for Co(II) sorption on these two surfaces can be written as represent surface water molecules, hydroxyl groups, and oxygens bonded to one, two, and three Al cations, respectively. Copyright 1999 Academic Press.
Towle
SN
Department of Geological and Environmental Sciences, Stanford University, Stanford, California, 94305-2115
Bargar
JR
Brown
GE
Parks
GA