MINERAL PRODUCTS OF PYRRHOTITE OXIDATION BY THIOBACILLUS-FERROOXIDANS

The biological leaching of pyrrhotite (Fe1-xS) by Thiobacillus ferroox idans was studied to characterize the oxidation process and to identif y 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 potentia l. Elemental S was one of the first products of pyrrhotite degradation detected by X-ray diffraction. Pyrrhotite oxidation also yielded K-ja rosite [KFe3(SO4)2(OH)6], goethite (alpha-FeOOH), and schwert-mannite [Fe8O8(OH)6SO4] as solid-phase products. Pyrrhotite was mostly deplete d after 14 days, whereas impurities in the form of pyrite (cubic FeS2) and marcasite (orthorhombic FeS2) accumulated in the leach residue.