Copper-nickel sulfide ores from Jinchuan mine in China contain pentlandite, chalcopyrite and pyrrhotite as major sulfide minerals with serpentine and olivine as gangue minerals. Since it is difficult to yield high grade copper and nickel concentrate with low content of magnesium oxide by present bulk flotation, researches for suitable processes to extract copper and nickel from the ores are required. In this study, bacterial leaching of copper-nickel sulfide ores was investigated by using Thiobacillus ferrooxidans isolated from acid mine water.
As copper-nickel sulfide ores have an acid buffering capacity, the optimum initial pH of the leach solution was about 1.0. At the initial stage of the leaching, pyrrhotite was dissolved rapidly by acid.
The extraction of nickel over 90 percent could be achieved, but the extraction of copper was about 30 percent for 34 days of the bacterial leaching. The dissolution of copper was improved by neither using an adapted strain on copper-nickel sulfide ores, nor a Cu-tolerant strain of T. ferrooxidans