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 sulphatizing roasting followed by aqueous leaching to recover the metallic values. Selective sulphation of nickel is found possible at 300°C, whereby 50% 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 one hour. Leaching is best carried out with 2% H2SO4 for a period of an hour. A flowsheet has been suggested for treatment of the ore by a stagewise roasting and differential leaching. (Shri A.K. Saha, Junior Scientific Assistant, Shri R.N. Misra, Scientist (now Chief Chemist, Kalinga Iron Works, IDCOL) and Shri P.P. Bhatnagar, Scientist and Head of Extractive Metallurgy Division, National Metallurgical Laboratory, Jamshedpur