Study on Leaching of Cobalt White Alloy by Acidithiobacillus ferrooxidans
氧化亚铁硫杆菌浸出钴白合金

Acidithiobacillus ferrooxidans (A.f) was used for leaching of the hard cobalt white alloy. The experiments determined the optimum pH value and temperature in the presence of A.f to be 2.0 and 30℃, respectively. Three modes of treatment of the bacteria, which are directly inoculated with 107 cells/mL in 9K culture medium, dispersed to 107 cells/mL in iron-free 9K culture medium and beforehand adapted by the alloy and collected by centrifugation, were used. The result showed that for the first mode, it took 6 d to finish the leaching of cobalt and 8 d for copper with decrease in number of the bacteria in leaching. For the second one, it needed 3 and 7 d to dissolve cobalt and copper out, respectively, and accompanied decrease in the bacteria. And for the third one, the modified A.f could be increased to 108 cells/mL, and the leaching of two metals was for 2 d and 5 d, respectively. In the leaching process, pH value increased first and then decreased. The electric potential increased with the leaching of copper. With the bacteria which were beforehand adapted by the leaching of cobalt white alloy, its leaching residue contained a little ammonium jarosite and the leaching rates of cobalt and copper were 99.50% and 99.0%. The leaching mechanism of copper in cobalt white alloy by A.f was the indirect effect.