MINERAL PRODUCTS OF PYRRHOTITE OXIDATION BY THIOBACILLUS-FERROOXIDANS

The biological leaching of pyrrhotite (Fe1-xS) by Thiobacillus ferrooxidans was studied to characterize the oxidation process and to identify the mineral weathering products. The process was biphasic in that an initial phase of acid consumption and decrease in redox potential was followed by an acid-producing phase and an increase in redox potential. Elemental S was one of the first products of pyrrhotite degradation detected by X-ray diffraction. Pyrrhotite oxidation also yielded K-jarosite [KFe3(SO4)2(OH)6], goethite (alpha-FeOOH), and schwert-mannite [Fe8O8(OH)6SO4] as solid-phase products. Pyrrhotite was mostly depleted after 14 days, whereas impurities in the form of pyrite (cubic FeS2) and marcasite (orthorhombic FeS2) accumulated in the leach residue.