Bacterial leaching of nickel-bearing pyrrhotite

The bioleaching of high-magnesium Jinchuan nickel-bearing pyrrhotite using Acidithiobacilus ferrooxidans was investigated. The experimental results show that the bioleaching time can be reduced from 16 days to 10 days by sulphuric acid pretreatment of the nickel-bearing pyrrhotite and by using ore-adapted A. ferrooxidans. At pH 2.0, 30 °C, pulp density 5% (wt./vol.), cell transfer quantity 10% and rotary shaker at 180 min− 1, the leaching of Ni was 88%, Co 78%, Cu 45% and Mg ∼ 50%. The leaching of Cu was poor due to chalcopyrite, which exhibited slower leaching rate by bacteria. Mg was dissolved from magnesium-containing gangue minerals by acid and its dissolution was related to the acid concentration of leaching liquor. Mineralogical examination indicated that the relative order of leaching for the sulphide minerals by A. ferrooxidans was nickel-bearing pyrrhotite > pentlandite > chalcopyrite and the relative order of dissolution for the gangue minerals by acid pretreatment was chlorite > antigonite > olivine > tremolite and talc.