The leaching of pentlandite by Acidithiobacillus ferrooxidans with a biological–chemical process

The Fe3+ leaching solution which was produced by Acidithiobacillus ferrooxidas was used to leach pentlandite. The effects of several kinetic parameters including temperature, Fe3+ concentration and Cl− on Ni recovery were investigated in a container independently. The results showed that the leaching rate of Ni was favored by the rise of temperature, the increase of Fe3+ concentration and the partial replacement of SO42− by Cl−, all of which could prove the indirect mechanism for sulfides leaching. Then a bioleaching process comprising biooxidation and chemical leaching is proposed. In the biooxidation process, A. ferrooxidans was used to produce Fe3+ at 30 °C, which was then fed to the chemical process to oxidize pentlandite at 50 °C. This biological–chemical leaching process features the continuous production of Fe3+ in the bioreactor and the high temperature leaching of pentlandite in the chemical reactor. By using this process, Ni leaching rate of 83.8% was obtained at 5 days. According to the results, the present heap leaching process could be improved by the results obtained by this biological–chemical leaching process.