GEOC 68 |
| Zhan Zhang1, Paul Fenter1, Michael J. Bedzyk2, Neil C. Sturchio3, Michael L. Machesky4, and David J. Wesolowski5. (1) Environmental Research Division, Argonne National Laboratory, 9700 Cass Ave., ER-203, C-137, Argonne, IL 60439, (2) Materials Science and Engineering Department, Northwestern University, 2220 N. Campus Dr, Evanston, IL 60208, (3) Department of Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, IL 60607, (4) Illinois State Water Survey, 2204 Griffith Drive, Champaign, IL 61820-7495, (5) Chemical Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6110 |
| Atomic level structures at rutile TiO2 (110)-water and rutile-Rb+ solution interfaces were investigated with X-ray reflectivity. Measurements were made of surface crystal truncation rods (CTR) to obtain the surface specific structural information. These results demonstrate that the rutile-water interface is terminated by rows of bridging oxygen (BO) and terminal oxygen (TO) sites. There is an additional 'hydration' layer adsorbed above the BO and TO sites. No evidence of layering of water was observed further from the interface. At the rutile-Rb+ solution interface there is a significant increase of electron density near the interface, indicating that Rb+ displace some water molecules in the hydration layer. In both cases, the surface atom relaxations are small compared to the same surface in vacuum. The observation that Rb+ occupies the same tetradentate site as divalent and trivalent ions at the rutile (110) surface suggests that the alkali ions compete for the surface adsorption sites with the more strongly adsorbing multivalent ions. This implies that alkali ions are not an 'indifferent' background electrolyte as is often assumed. |
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Interfacial Phenomena: Linking Atomistic and Macroscopic Properties
8:00 AM-11:40 AM, Tuesday, March 30, 2004 Marriott -- Marquis NW, Oral
Division of Geochemistry |