Bioleaching of pyrrhotite by Sulfobacillus thermosulfidooxidans

Abstract

The bioleaching of pyrrhotite was investigated using Sulfobacillus thermosulfidooxidans. The effects of pH, pulp concentration, inoculation amount, external addition of ferrous and ferric ions were examined. The pH is found to exert a profound effect on the leaching process for controlling the bacterial activity and precipitation of ferric ions mainly as jarosite. The results show that low pulp content increases the leaching rate of iron. The inoculation amount from 1×10⁷ cell/mL to 1×10⁸ cell/mL has positive effects on the leaching rate. The results also imply that addition of ferrous sulfate (1 g/L) is required for the bacteria to efficiently drive the extraction of iron, however, the leaching efficiency has no obvious enhancement when 2 g/L ferrous sulfate was added. Comparatively, addition of ferric sulfate (2 g/L) significantly inhibits the bioleaching process. At the end of bioleaching, jarosite and sulfur are observed on the surface of pyrrhotite residues by using XRD and SEM. With the passivation film formed by jarosite and sulfur, the continuous iron extraction is effectively blocked.

Keywords

pyrrhotite / bioleaching / Sulfobacillus thermosulfidooxidans / jarosite

References

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