GEOC 162 |
| Satish C. B. Myneni, Department of Geosciences, Princeton University, 151 Guyton Hall, Princeton, NJ 08544, Glenn A. Waychunas, Earth Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 70-0120, Berkeley, CA 94720, Samuel J. Traina, Sierra Nevada Research Institute, University of California, Merced, P.O. Box 2039, Merced, CA 95344, and Gordon E. Brown Jr., Department of Geological and Environmental Sciences, Stanford Synchrotron Radiation Laboratory, SLAC, 2575 Sand Hill Road, Menlo Park, CA 94025. |
| Several elements exist as oxoanions (e.g. AsO43-, CrO42-) in aqueous systems, and information on their coordination chemistry is critical for predicting their reactivity in environmental, biological and industrial systems. However, the binding environments of oxoanions and the chemical variables that influence them have been highly debated. Using sulfate and iron oxides as model oxoanion and substrates, respectively, we show that the structural environment of sulfate on iron oxide surfaces correlates with sulfate protonation state and sample water content. Sulfate forms dominantly hydrated and H-bonded complexes above pH 3.0 in water-rich systems. Their concentration decreases and sulfate binds directly to surface Fe atoms below this pH, where the fraction of protonated sulfate is large in aqueous solutions. We hypothesize that the tendency of oxoanions to form complexes and polymers in aqueous systems varies as the solution pH approaches the proton association constants of oxoanions. Details of these results will be presented. |
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Interfacial Phenomena: Linking Atomistic and Macroscopic Properties
1:20 PM-5:40 PM, Wednesday, March 31, 2004 Marriott -- Marquis NW, Oral
Division of Geochemistry |