Cobalt, nickel, and copper are selectively extracted from laterite ores or other oxide mixtures such as roasted sulfide concentrates and pulverized deep-sea nodules containing fe, by reduction of the dried material, preferably pelletized, with CO at 450 deg-600 deg c to reduce ni, CO, and cu oxides to metal and fe2o3 and feo, then cooling to about 200 deg c, leaching with an aqueous solution containing 25-150 g/l nh3 and 50-400 g/l (nh4)2so4 with oxygen injected sparsely at 5 deg-50 deg c to promote oxidation of nonferrous metals and stabilize their solution in the leach liquor as ammine complexes, with the least possible formation of fe3+. Nickel recovery >90 pct and CO >80 pct were obtained when the reducing gas was pure CO, but were decreased when h2 was used with the CO or the reduction temperature was <450 deg c.
U.S. Pat. 3,929,468; Dec. 30, 1975; Chem. Abstr. 84:138,915T