GEOC 42 |
| Arsenic contaminated soils and groundwater threatens human health in many parts of the world. The mobility of arsenic is largely governed by reactions at the surfaces of soil minerals. These reactions need to be understood at a molecular scale in order to accurately predict arsenic mobility and bioavailability. The adsorption of arsenate at the surface of goethite has been characterized at molecular level using combined infrared and potentiometric titrations, EXAFS, and adsorption measurements over a broad range of pH values and surface coverages. The changes observed in the OH stretching region of the infrared spectra of arsenate-goethite surface complexes are practically identical to changes observed for phosphate adsorption onto goethite. By analogy to our results for the phosphate-goethite system and by comparison with the spectra of model compounds, we conclude that arsenate forms predominately doubly-protonated monodentate complexes below approximately pH 4. Above this pH deprotonation into monoprotonated state is observed. |
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General Poster Session
7:00 PM-9:00 PM, Sunday, 10 September 2006 Moscone Center -- Hall D, Poster
Division of Geochemistry |