SPHALERITE OXIDATION BY THIOBACILLUS-FERROOXIDANS AND THIOBACILLUS THIOOXIDANS

Sphalerite (ZnS) oxidation was monitored in Thiobacillus ferrooxidnns and Thiobacillus thiooxidans cultures and in abiotic controls by X-ray diffraction (XRD) analysis of solid phases and by chemical analysis of solution composition. X-ray diffraction data revealed no solid-phase reaction products in unsupplemented sphalerite media, whereas minor amounts of S-0 accumulated in FeSO4-amended sphalerite media with or without T. ferrooxidans inoculum. Jarosite ((K,Na,H3O,NH4)Fe-3(SO4)(2)(OH)(6)) also precipitated in the amended T. ferrooxidans cultures. When sphalerite media inoculated with T. thiooxidans were amended with S-0, acid production was enhanced, decreasing the pH to 1.1, but Zn dissolution was not accelerated. By comparison with T. thiooxidans, T. ferroxidans was more efficient in the oxidation of sphalerite.