A predictive model (ETLM) for arsenate adsorption and surface speciation on oxides consistent with spectroscopic and theoretical molecular evidence |
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| Authors: | Keisuke Fukushi Dimitri A Sverjensky |
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| Institution: | Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD 21218, USA |
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| Abstract: | The nature of adsorbed arsenate species for a wide range of minerals and environmental conditions is fundamental to prediction of the migration and long-term fate of arsenate in natural environments. Spectroscopic experiments and theoretical calculations have demonstrated the potential importance of a variety of arsenate surface species on several iron and aluminum oxides. However, integration of the results of these studies with surface complexation models and extrapolation over wide ranges of conditions and for many oxides remains a challenge. In the present study, in situ X-ray and infrared spectroscopic and theoretical molecular evidence of arsenate (and the analogous phosphate) surface speciation are integrated with an extended triple layer model (ETLM) of surface complexation, which takes into account the electrostatic work associated with the ions and the water dipoles involved in inner-sphere surface complexation by the ligand exchange mechanism.Three reactions forming inner-sphere arsenate surface species |
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