Process for recovery of non-ferrous metals from oxide ores and concentrates

Nickel, cobalt and copper are recovered from oxide ores and oxide ore concentrates, especially those ores and concentrates containing substantial amounts of iron oxides, by selectively reducing the non-ferrous metal oxides to their elemental state in the absence of water vapor at temperatures ranging from 350 DEG C to 600 DEG C using carbon monoxide as the sole reductant. The reduced ore is then cooled and subjected to an oxidizing leach using an aqueous ammonia-ammonium sulfate solution as the leaching medium. Leaching is controlled in such a fashion that the non-ferrous metals are oxidized and stabilized in solution as their ammine complexes prior to the occurrence of any substantial oxidation of ferrous iron to the ferric state. Non-ferrous metal values are then separately recovered from the leach solution by techniques such as solvent extraction and precipitation. The process allows recovery of more than 90% of the nickel and more than 85% of the cobalt from laterite ores.