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

Abstract

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 fine structure analysis of hydroxysulfate green rust suspensions spiked with aqueous solutions of AgCH 3COO, AuCl n (OH) 4− n , CuCl 2, or HgCl 2 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.