Patent ID: 7387767

Claim:
A process for producing an enriched mixed nickel and cobalt sulphide intermediate from a laterite ore slurry containing nickel, cobalt, copper, chromium, zinc, iron and silicon, comprising leaching the laterite ore slurry in a pressure acid leach containing an excess of aqueous sulphuric acid at high pressure and temperature for a time sufficient to extract nickel and cobalt, partially neutralizing excess free acid in the leached slurry with limestone to a range of 5 to 10 g/L residual free H 2 SO 4 , washing the partially neutralized leached slurry to separate leached nickel and cobalt in a product liquor from residual solids, subjecting the product liquor to a reductant to reduce Cr(VI) in solution to Cr(III), neutralizing the reduced product liquor for hydrolyzing and precipitating impurities including ferric iron and silicon at a pH at about 3.5 to 4.0, separating precipitated solids from the neutralized liquor by a liquid-solid separation, and contacting the neutralized liquor with hydrogen sulphide gas to precipitate nickel and cobalt sulphides.