GEOC 151 |
| Chris Konek, Hind Al-Abadleh, Amanda Mifflin, and Franz Geiger. Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 |
| Hexavalent chromium in ground water has received much attention in the past decades. While much research has focused on the interaction of hexavalent chromium with geosorbents, little is known about how organic adlayers, originating for instance from biosurfactants, can impact chromium binding under environmentally representative chromium concentration conditions. Using the nonlinear optical laser spectroscopy surface second harmonic generation (SHG), we have studied chromate adsorption and desorption at silica/water interfaces in the presence of acid-terminated carbon-11 silanes. The chromate surface coverage is measured directly at the interface, in real time, at room temperature and at chromate concentrations ranging from 1x10-6 to 2x10-4 M. Results show that, in sharp contrast to the silica/water interface, chromium adsorption to carboxylic acid terminated silanes on silica is only partially reversible. Experiments using acid-terminated SAMs diluted in methyl-terminated SAMs are in progress and show less and fully reversible chromate binding. Our results are consistent with interfacial pKa measurements. |
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Interfacial Phenomena: Linking Atomistic and Macroscopic Properties
8:05 AM-11:30 AM, Wednesday, March 31, 2004 Marriott -- Marquis NW, Oral
Division of Geochemistry |