2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 14
Presentation Time: 8:00 AM-12:00 PM


DESISTO, Stephanie L.1, ELZINGA, Evert J.2 and REEDER, Richard J.2, (1)Geology Department, State Univ of New York at Cortland, P.O. Box 2000, Cortland, NY 13045, (2)Center for Environmental Molecular Science, Stony Brook University, Stony Brook, NY 11794-2100, DeSist29@cortland.edu

The sorption behavior of chromate (CrO42-) was studied on an aluminum oxide model solid in order to better understand the environmental conditions that may lead to its removal from natural waters. This work is part of a broader study to assess the molecular-scale mechanisms of the sorption of oxyanion complexes on common minerals.  The hexavalent form of chromium is the focus of this study because it is toxic and a likely carcinogen. We use gamma alumina (γ-Al2O3) as a model sorbent to represent potential behavior of aluminum components in minerals.  

Chromate adsorption was characterized by a combination of electrophoretic measurements and batch experiments performed under varying conditions of pH and CrO42- concentrations. The electrophoretic mobility experiments were conducted over the pH range 3-10, and showed that CrO42- adds negative charge to the surface of alumina, but does not change its point of zero charge (pH 9.2). Results from batch uptake experiments performed over the same pH range provide additional insight into the uptake behavior of CrO42- on alumina, and allow us, in combination with the electrophoretic mobility results, to propose that CrO42- interacts with the Al2O3 surface primarily via electrostatic interactions, possibly involving hydrogen bonding. This implies that alumina minerals may not be an effective sink for CrO42- removal from aqueous solutions.