Microbial Reduction of Antimony(V)-Bearing Ferrihydrite by Geobacter sulfurreducens.

The reduction of Sb(V)-bearing ferrihydrite by Geobacter sulfurreducens was studied to determine the fate of the metalloid in Fe-rich systems undergoing redox transformations. Sb(V) added at a range of concentrations adsorbed readily to ferrihydrite, and the loadings had a pronounced impact on the rate and extent of Fe(III) reduction and the products formed. Magnetite dominated at low (0.5 and 1 mol%) Sb(V) concentrations, with crystallite sizes decreasing at higher Sb loadings: 37-, 25-, and 17-nm particles for no-Sb, 0.5% Sb, and 1% Sb samples, respectively. In contrast, goethite was the dominant end product for samples with higher antimony loadings (2 and 5 mol%), with increased goethite grain size in the 5% Sb sample. Inductively coupled mass spectrometry (ICP-MS) analysis confirmed that Sb was not released to solution during the bioreduction process, and X-ray photoelectron spectroscopy (XPS) analyses showed that no Sb(III) was formed throughout the experiments, confirming that the Fe(III)-reducing bacterium Geobacter sulfurreducens cannot reduce Sb(V) enzymatically or via biogenic Fe(II). These findings suggest that Fe (bio)minerals have a potential role in limiting antimony pollution in the environment, even when undergoing redox transformations.