Study On Leaching Of Cobalt White Alloy By Acidithiobacillus Ferrooxidans

Because of the small cost, low pollution and high resource utilization, more and more attention has been paid to microbial metallurgy.Cobalt white alloy is the important form of cobalt and copper imports of china. Leaching cobalt white alloy by bacteria has practical significance. The main contents and results in this paper are as follows:The influence of pH and temperature about Leaching by bacteria was researched. Acidithiobacillus ferrooxidans(A. ferrooxidans) were dispersed to107cell.mL-1in the9K culture medium. The experiments were made at five initial pH, which were1.0、1.5、2.0、2.5、3.0and five temperatures such as24、27、30、33、36℃. The optimum pH and temperature in the presence of A. ferrooxidans were determined to be2.0and30℃.A. ferrooxidans was used for leaching of the hard cobalt white alloy. Three modes of treating the bacteria, which are directly inoculated with107cell.mL-1in9K culture medium, dispersed to107cell.mL-1in the iron-free9K culture medium and beforehand adapted by the alloy and collected by centrifugation, were employed. The result showed that for the first mode, it took6d to finish the leaching of cobalt and8d for copper with decrease in the number of the bacteria in leaching. For the second one, it needs3d and7d to dissolve cobalt and copper out, respectively and also accompanied decrease in the bacteria. And for the third one, the modified A. ferrooxidans could increase to108cell.mL-1, and the leaching of the two metals was, respectively, for2d and5d. In the process of leaching pH increases first and then decreases. The electric potential increases with leaching of copper. With the bacteria which beforehand adapted by the alloy leaching cobalt white alloy, leaching residue was a little ammonium jarosite and the extracting rate of cobalt and copper being99.50%and99.0%.The bacteria leaching of copper in cobalt white alloy is not direct. First, A. ferrooxidans could promote Fe2+to Fe3+in the presence of oxygen and always keep oxidation potentials of solution, and Fe3+would act the copper in alloy and oxidize it to Cu2+. The process might not need the direct contact between bacteria and alloy.