Mechanism of microbial dissolution and oxidation of antimony in stibnite under ambient conditions.

In this study, we demonstrate that a bacterial isolate Paraccocus versutus XT0.6 from the Xikuangshan antimony mine, the world largest antimony deposit, is capable of stibnite dissolution, oxidation of Sb(III), and formation of secondary Sb(V) bearing mineral. The isolate could oxidize dissolved Sb(III) aerobically and anaerobically. It was able to dissolve Sb(III) in solid minerals, which was subsequently oxidized to Sb(V) completely. Part of Sb(V) was scavenged by the formation of secondary Sb(V)-bearing mineral mopungite [NaSb(OH)6] in the biotic experiments. In contrast, Sb(III) released from mineral/rocks was only partially oxidized to Sb(V) and no secondary Sb-bearing mineral was formed in abiotic controls. These results demonstrated that microbial processes involved in the mobilization, oxidation, and transformation of antimony in minerals/rocks under ambient environmental conditions and offer new insights in biogeochemistry of Sb at mining areas.