Abstract
Bacterial leaching tests of pyrite with Thiobacillus ferrooxidans were performed, and leaching solutions and pyrite surfaces were analyzed during the tests.The leaching of pyrite mainly proceeded according to the indirect bacterial leaching mechanism. The main reactions in this mechanism, i. e. the enzymatic oxidation of ferrous iron and sulfur by T ferrooxidans and the chemical oxidation of pyrite by ferric iron, accelerated when the number of the bacteria increased logarithmi-cally. With the rapid increase in the concentrations of ferric iron and sulfate in the leaching solutions, insoluble sulfate compounds were precipitated on pyrite. The redox-potential (Eh) was dependent on the mole ratio [Fe3+]/[Fe2+] int he leachings olutions. The redox-potentiailn creasedi n the activep hase of bacteria nd decreased in the latter inactive phase. It indicates that Eh can be a measure of the activity of T. ferrooxidans in the leaching process as reported by others. In the latter inactive phase, the insolubel sulfate compound formed on pyrite was shown to be jarosite by FTIR and XPS.
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