Silicate adsorption on the r-plane (1-102) hematite surface: A crystal truncation rod study

GEOC 26

Young-Shin Jun, ysjun@berkeley.edu1, Glenn A. Waychunas, gawaychunas@lbl.gov2, Peter Eng, eng@cars.uchicago.edu3, Thomas P. Trainor4, and Sanjit K. Ghose, ghose@cars.uchicago.edu3. (1) Earth and Planetary Science, University of California at Berkeley/Lawrence Berkeley National Laboratory, 307 McCone Hall, Berkeley, CA 94720-4767, (2) Earth Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 70-0120, Berkeley, CA 94720, (3) GSECARS, Consortium for Advanced Radiation Sources, University of Chicago, Building 434A, Advanced Photon Source, 9700 South Cass Avenue, Argonne, IL 60439, (4) Department of Chemistry and Biochemistry, University of Alaska Fairbanks, PO Box 756160, Fairbanks, AK 99775-6160
Although dissolved silicate is ubiquitous in the environment and is known to alter the reactivity of host minerals, our understanding about silicate adsorption onto iron oxide surfaces is very limited. In principle, knowledge of the silicate adsorption geometry on the hematite surface can provide a structural baseline for the interpretation of the effect of aqueous silicate and other anions on the chemical reactivity of host minerals. We report here, the three-dimensional geometry of silicate monomer adsorption on a r-plane hematite surface at circumneutral pH as determined from measurements of specular and nonspecular x-ray scattering at 90% RH and 298 K along ten crystal-truncation rods (CTR's). The scattering data provide both vertical and lateral information about the interfacial structure. Intensity changes due to silicate adsorption are evident in the (00Ls), (02Ls), (10Ls), and (11Ls) rods when compared to the clean surface scattering, and we focus on these for our analysis.
 

Physical Chemistry of Soil and Aquifer Systems: A Symposium in Honor of Garrison Sposito
1:30 PM-5:10 PM, Sunday, 10 September 2006 Moscone Center -- Room 256, Oral

Division of Geochemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006