The oxidation kinetics of zinc sulphide with Thiobacillus ferrooxidans

• Published in: Hydrometallurgy Vol. 48; no. 2; pp. 171 - 186
• Main Authors: Boon, M., Snijder, M., Hansford, G.S., Heijnen, J.J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.04.1998; Elsevier
• Subjects: Applied sciences; Bacteria; Exact sciences and technology; Fermenters; Hydrogen peroxide; Hydrometallurgy; Iron; Metals. Metallurgy; Oxidation; pH effects; Production of metals; Production of non ferrous metals. Process materials; Reaction kinetics; Slurries; Zinc sulfide; Bacteria; Oxidation; Experimental study; Reaction rate; Thiobacillus ferrooxidans; Chemical reaction kinetics; Hydrometallurgy; Sulfide ore
• ISSN: 0304-386X; 1879-1158
• DOI: 10.1016/S0304-386X(97)00081-9

The kinetics and rate limiting sub-processes in the bacterial oxidation of zinc sulphide with Thiobacillus ferrooxidans were examined. The oxidation rate of synthetic ZnS in the presence and absence of bacteria at equal ferrous and ferric iron concentration and pH, was measured in parallel batch experiments. Bacteria oxidize Fe 2+ produced in the chemical oxidation of ZnS with Fe 3+. In the fermenter without bacteria hydrogen peroxide was added to regenerate ferric iron and maintain the Fe 2+ concentration equal to that in the fermenter with bacteria. No significant differences in the oxidation rates of zinc sulphide were found between the slurry with and without bacteria at equal Fe 2+ and Fe 3+ concentrations. Consequently, an indirect mechanism (i.e. chemical oxidation of ZnS with Fe 3+ to Zn 2+, S 0 and Fe 2+, and bacterial oxidation of S 0 to SO 4 2− and Fe 2+ to Fe 3+) determines the oxidation rate of ZnS in the bacterial oxidation process. From the experiments it was shown that T. ferrooxidans prefers S 0 as a substrate and the regeneration of Fe 3+ can even become terminated. From the experimental data several suggestions for improved process design and experimental research are given.