Integration of spectroscopic, theoretical molecular, and surface complexation model evidence of inorganic and organic anionic speciation at the oxide-electrolyte-water interface

GEOC 2

Dimitri A. Sverjensky, sver@jhu.edu, Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, MD 21218 and Keisuke Fukushi, fukushi@kenroku.kanazawa-u.ac.jp, Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa, Japan.
Linking experimental in situ X-ray and infrared spectroscopic evidence of surface speciation with theoretical molecular calculations and surface complexation models describing bulk adsorption data is a major challenge. The dipole extension of the triple-layer model (ETLM) is able to do this with a new treatment of inner-sphere anion adsorption. During the ligand exchange mechanism, the release of one or more water dipoles coordinated to a metal at the surface involves electrostatic work which has previously been neglected. Taking this effect into account enables the ETLM to closely fit anion adsorption, and surface protonation and proton coadsorption in the presence of anions using inner- and outer-sphere species consistent with spectroscopic and molecular evidence. Based on these results, the ETLM can then be used to make independent predictions of anion surface speciation as a function of pH, ionic strength and surface coverage. The predictions are in agreement with spectroscopic results.
 

Frontiers in Geochemistry: Commemorating the 25th Anniversary of the ACS-Geochemistry Division
9:00 AM-11:55 AM, Sunday, 10 September 2006 Moscone Center -- Room 262, Oral

Division of Geochemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006