GEOC 67 |
| Glenn Waychunas1, Thomas P. Trainor2, Peter Eng3, Matthew Newville3, Jeffrey G. Catalano4, and Gordon E. Brown Jr.5. (1) Earth Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, (2) Department of Chemistry and Biochemistry, University of Alaska, Fairbanks, Fairbanks, AK 99775-6160, (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 Geological and Environmental Sciences, Stanford University, Bldg. 320, Room 118, Stanford, CA 94305-2115, (5) Department of Geological & Environmental Sciences and Stanford Synchrotron Radiation Laboratory, Stanford University, Building 320 Room 118, Stanford, CA 94305 |
| Arsenate sorbed on single crystal hematite surfaces under aqueous solution has been studied via surface diffraction (CTR-crystal truncation rod) and via grazing incidence EXAFS. On the C(0001) surface arsenate binds as a bidentate or tridentate inner sphere complex with a well-defined angular relationship to the surface plane. This topology is consistent with the features of this surface refined from independent CTR analysis. On the R (1-102) surface the arsenate is also inner sphere but attaches in quite different motifs at several positions, and with some shorter Fe-As distances. Very notable is that we can refine the position of sorbed arsenate from CTR data, so that GIXAFS and CTR measurements are highly complementary. This enables independent evaluation of surface response to sorbate binding. Our work indicates that habit, topology and aggregation geometry of hematite can have a considerable effect on the sorption geometry, and probably also on surface reaction kinetics. |
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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 |