Metals are recovered from ore concentrates by dry grinding, followed by a 2-stage leach process. The ground concentrate is leached with h2so4 at 90 deg-100 deg c to selectively remove ni and fe. The residue is then leached with h2so4 containing naocl or h2o2 to extract pt, pd, cu, and au. Thus, a flotation concentrate was smelted at 1,450 deg-1,600 deg c for 0.5 H, yielding a matte containing pt 12, pd 39.7, Au 1.3 Oz/ton, cu 8, ni 14, fe 47, and s 26 pct. The matte was ground to 95 pct -200 mesh and leached at 100 deg c for 3 h with h2so4 at an acid-to-matte weight ratio 2:1. The leach solution contained ni 17, fe 38, and cu 0.003 G/l. The residue contained cu 58, ni 0.9, Fe 0.8 pct, and all the pt, pd, and au. The residue was leached at 95 deg c for 4 h with a solution containing 320 g/l h2so4 and 50 g/l naocl. The leach solution contained cu 12, pd 0.051, and pt 0.023 G/l, for a copper recovery of 99 pct.
U.S. Pat. 4,337,226, June 29, 1982; Chem. Abstr. 96:127,019A