Studies on ammoniacal pressure leaching of bulk Ni-Cu-Mo sulphide concentrate

The bulk Ni-Cu-Mo concentrate containing 1.56% Ni, 0.94% Cu and 0.28% Mo obtained at the Jaduguda plant of Uranium Corporation of India has been tested for the recovery of metallic values by pressure leaching. The variable factors studied for ammoniacal pressure leaching include: (1) oxygen pressures, (2) temperatures of leaching, (3) concentrating of sulphate ions, (4) ammonia concentrations, (5) solid/liquid ratio, and (6) kinetics of leaching. The maximum recovery of 93-92% Ni and 95.00% Cu was obtained on leaching with 20% NH4OH solution and 35 g/l (NH4)2 SO4 at 100°C at 25 kg/cm2 oxygen pressure, duration of leaching being two hours and maintaining solid/liquid ratio 1:6. The maximum recovery of molybdenum (69.64% was obtained in two hours leaching at 150°C even without the addition of extra sulphate anions. (Shri D.S. Tandon, Scientist, Shri A.K. Saha, Senior Scientific Assistant, Shri M.S. Mahanty, Senior Scientific Assistant, and Shri P.P. Bhatnagar, Scientist and former Head of Extractive Metallurgy Division, National Metallurgical Laboratory)