Abstract: A process for recovering nickel and cobalt values from nickel- and cobalt-containing laterite ores as an enriched mixed nickel and cobalt sulphide intermediate and for producing nickel and cobalt metal from the nickel and cobalt sulphide intermediate. The laterite ore is leached as a slurry in a pressure acid leach containing an excess of aqueous sulphuric acid at high pressure and temperature, excess free acid in the leach slurry is partially neutralized to a range of 5 to 10 g/L residual free H2SO4 and washed to yield a nickel- and cobalt-containing product liquor, the product liquor is subjected to a reductant to reduce any Cr(VI) in solution to Cr(III), the reduced product liquor is neutralized to precipitate ferric iron and silicon at a pH of about 3.5 to 4.0, and the neutralized and reduced product liquor is contacted with hydrogen sulphide gas to precipitate nickel and cobalt sulphides.

Abstract: A process is provided for selectively precipitating and removing manganese relative to magnesium from an acidic solution, preferably barren of one or more of cobalt, nickel, copper and zinc, but containing appreciable amounts of manganese, magnesium, and aluminum. The process comprises a) adding a first alkaline reagent, for example lime and/or limestone, to neutralize the acidic solutions and to precipitate a majority of the aluminum as aluminum-containing solids, without precipitating a substantial amount of the magnesium; b) removing the precipitated aluminum-containing solids to create an aluminum-depleted solution; c) adding a second alkaline reagent, for example lime, to the aluminum-depleted solution and aerating for a sufficient retention time to preferentially precipitate a majority of the manganese as manganese-containing solids; and d) removing the precipitated manganese-containing solids.

Abstract: An improved process for separating cobalt values from nickel values in an aqueous nickel and cobalt sulphate-containing solution in which the solution is contacted with a water-immiscible organic solution containing an organophosphorous acid in a cobalt extraction circuit. The process is particularly useful for aqueous solutions containing high total metals content and elevated cobalt concentrations, while avoiding the formation and precipitation of ammonium sulphate containing double salts during the solvent extraction of the cobalt. The improvement includes contacting a portion or all of the water-immiscible organic solution required for cobalt extraction with a nickel-containing ammoniacal solution to produce a nickel-loaded organic phase and a partially nickel-depleted raffinate.

Abstract: There is disclosed a process for separating and recovering nickel and copper values from a nickel-copper matte which may contain iron and arsenic. Finely divided nickel-copper matte undergoes one or more steps of sulphuric acid leaching at atmospheric pressure to produce a nickel sulphate solution and an iron and/or arsenic containing copper-rich sulphide residue. The copper-rich sulphide residue is repulped in sulphuric acid solution to selectively redissolve most of the iron and arsenic and the iron and arsenic containing solution is separated from the copper-rich residue. The iron and arsenic are largely precipitated from the leach solution in a pressure hydrolysis step and the iron and arsenic containing precipitate is separated and discarded. The iron and arsenic-depleted solution is recombined with the copper-rich sulphide residue from the acid repulp step and the resulting slurry is treated in a non-oxidizing pressure leach in which nickel arsenic and iron are extracted.