OXIDATION OF GALENA BY THIOBACILLUS-FERROOXIDANS AND THIOBACILLUS THIOOXIDANS

The objective of this work was to determine solution- and solid-phase alterations associated with galena (PbS) oxidation by Thiobacillus ferrooxidans and Thiobacillus thiooxidans. In T. ferrooxidans experiments with 2.5-5% (w/v) galena, the pH remained almost constant at pH 2, whereas the pH increased in uninoculated controls. In T. thiooxidans cultures, the pH initially increased from 2 to 4. This initial increase was comparable to the pH change in an abiotic control, but the oxidation reaction in T. thiooxidans cultures subsequently became acid producing. Anglesite (PbSO4) was detected by X-ray diffraction as a solid-phase product of galena decomposition in both abiotic and inoculated experiments. When ferrous sulfate was added as a supplementary energy source for T. ferrooxidans, jarosite (MFe(3)(SO4)(2)(OH)(6)) was detected as a new solid phase. Elemental S was not detected in the residues.