Scorodite (FeAsO4�2H2O) is a common As-rich mineral found in mining environments. Due to its low solubility, it is believed to be stable under oxidizing conditions, but its stability in the presence of known iron- and arsenic-reducing bacteria is poorly understood, especially ender environmentally relevant conditions.  We investigated the reduction of synthetic scorodite in the presence of Shewanella sp. CN32, an iron and arsenic reducer, and Shewanella sp. ANA-3, a well known arsenic reducer in a chemically defined medium containing various phosphate concentrations (15�M to 400 �M). The initial rates of reaction are 9.8 fmol/(cell*day) for ANA-3 and 6.3 fmol/(cell*day) for CN32 indicating that ANA-3 is a more efficient arsenate reducer than CN32. The concentration of dissolved Fe(II) is significantly lower than the concentration of dissolved As(III), and these concentrations are inversely related to the phosphate concentration. The solid phase post-reduction by-products were also characterized by XRD, SEM, HRTEM and XAFS. Results so far indicate solid amorphous scorodite containing islands rich in iron or arsenic.

Solubility  of scorodite in the presence of Shewanella sp. CN32 and  Shewanella sp. ANA-3 in a chemically defined growth medium containing various phosphate concentrations

243rd National Meeting (2012)

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