Reduction of AgI, AuIII, CuII, and HgII by FeII/FeIII hydroxysulfate green rust

Green rusts are mixed FeII/FeIII 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 AgCH3COO, AuCln(OH)4−n, CuCl2, or HgCl2 showed that AgI, AuIII, CuII, and HgII were readily reduced to Ag0, Au0, Cu0, and Hg0. Imaging of the resulting solids from the AgI-, AuIII-, and CuII-amended green rust suspensions by transmission electron microscopy indicated the formation of submicron-sized particles of Ag0, Au0, and Cu0. The facile reduction of AgI, AuIII, CuII, and HgII to Ag0, Au0, Cu0, and Hg0, 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.