Bioleaching of Cobalt White Alloy in the presence of Acidithiobacillus ferrooxidans

Acidithiobacillus ferrooxidans (A. ferrooxidans) was used to leach the hard cobalt white alloy in this study. The optimum pH and temperature in the presence of A. ferrooxidans was 2.0 and 30 degrees C respectively. Three methods of treating the bacteria, which are directly inoculated with 10(7) cell.ml(-1) in 9K culture medium, collected bacteria by centrifugation and dispersed to 10(7) cell.ml(-1) in the iron-free 9K culture medium, and beforehand adapted by the alloy and collected by centrifugation, were employed. The result showed that for the first mode, it took 6ds to finish the leaching of cobalt and 8d for copper with decrease in the number of the bacteria in leaching. For the second one, it needs 3d and 7d to dissolve cobalt and copper, and also accompanied decrease in the bacteria. And for the third one, the modified A. ferrooxidans could increase to 10(8) cell.ml(-1), and the leaching of two metals was, respectively, for 2d and 5d with the extracting rate of them being 99.50% and 99.0%.