Microbial Oxidation of Fe(2+) and Pyrite Exposed to Flux of Micromolar H(2)O(2) in Acidic Media

At an initial pH of 2, while abiotic oxidation of aqueous Fe(2+) was enhanced by a flux of H(2)O(2) at micromolar concentrations, bio-oxidation of aqueous Fe(2+) could be impeded due to oxidative stress/damage in Acidithiobacillus ferrooxidans caused by Fenton reaction-derived hydroxyl radical, particularly when the molar ratio of Fe(2+) to H(2)O(2) was low. When pyrite cubes were intermittently exposed to fluxes of micromolar H(2)O(2), the reduced Fe(2+)-Fe(3+) conversion rate in the solution (due to reduced microbial activity) weakened the Fe(3+)-catalyzed oxidation of cubic pyrite and added to relative importance of H(2)O(2)-driven oxidation in the corrosion of mineral surfaces for the treatments with high H(2)O(2) doses. This had effects on reducing the build-up of a passivating coating layer on the mineral surfaces. Cell attachment to the mineral surfaces was only observed at the later stage of the experiment after the solutions became less favorable for the growth of planktonic bacteria.