Studies on Leaching of Bulk Ni-Cu-Mo Sulphides

A Ni-Cu-Mo concentrate containing 1.56% Ni, 0.94% Cu and 0.28% Mo has been obtained as a by-product from a concentrate. The concentrate has been subjected to sulphatising roasting followed by aqueous leaching to recover the metallic values. Selective sulphation of nickel is found possible at 300°C, where by 50% recovery of nickel is separated by aqueous leaching. A maximum of 81% recovery of nickel was attained by roasting the ore at 450°C and leaching with 2% H2SO4. Sulphation of copper starts above 300°C, but a maximum of 92% copper recovery is possible by roasting at 400°C and leaching with 2% H2SO4. Sulphation of molybdenum starts at 300°C and 95% of molybdenum is recovered by roasting at 500°C and leaching with 2% H2SO4, the leaching being completely inhibited in the absence of acid. Roasting reactions are virtually complete in an hour. Leaching is best carried out with 2% sulphuric acid for a period of an hour. A flow sheet has been suggested for treatment of the ore by a stage wise roasting and differential leaching.