Comparison of chemical and biological leaching methods with the effect of chloride on the recovery of nickel, cobalt and copper from a pentlandite-pyrrhotite concentrate

In this study, a finely ground nickel sulphide concentrate, consisting mainly of pyrrhotite, pentlandite and chalcopyrite, was leached in shake flask and batch reactor experiments. The objective was to determine the optimal method to recover nickel and cobalt, both hosted in pentlandite, and copper hosted in pentlandite and chalcopyrite respectively. The selected leaching methods tested were sulphuric acid leaching, ferric sulphate leaching and bioleaching. In addition, the effect of chloride ions on the leaching efficiency was evaluated with different concentrations. The results of the chemical leaching experiments showed increase in nickel, cobalt and copper recovery with chloride addition as a result of increased leaching rate for pentlandite and chalcopyrite. The highest yields in the 8-hour reactor experiment (70 % Ni, 66 % Co and Cu 87 %) were obtained in ferric sulphate leaching with chloride concentration of 20 g/L at the temperature of 90 °C. The mineralogical analysis showed that pyrrhotite was dissolved almost completely in all the experiments. Pentlandite and chalcopyrite leaching was clearly improved by the addition of Cl− at similar temperatures.