Reduction of Ag-I, Au-III, Cu-II, and Hg-II by Fe-II/Fe-III hydroxysulfate green rust

Green rusts are mixed Fe-II/Fe-III. hydroxides that are found in many suboxic environments where they are believed to play a central role in the biogeochemical cycling of iron. X-ray absorption tine structure analysis of hydroxysulfate green rust suspensions spiked with aqueous solutions of AgCH3COO, AuCln(OH)(4-n), CuCl2, or HgCl2 showed that Ag-I, Au-III, Cu-II, and Hg-II were readily reduced to Ag-0, Au-0, Cu-0, and Hg-0. Imaging of the resulting solids from the Ag-I-, Au-III-, and Cu-II-amended green rust suspensions by transmission electron microscopy indicated the formation of submicron-sized particles of Ag-0, Au-0, and Cu-0. The facile reduction of Ag-I, Au-III, Cu-II, and Hg-II to Ag-0, Au-0, Cu-0, and Hg-0, respectively, by green rust suggests that the presence of green rusts in suboxic soils and sediments can have a significant impact on the biogeochemistry of silver, gold, copper, and mercury, particularly with respect to their mobility. (C) 2003 Elsevier Ltd. All rights reserved.