Copper, nickel, and cobalt are recovered from lead-smelter matte by leaching with h2so4 and mNO2 to form a solution containing dissolved metal sulfates and a residue containing sulfur and pbso4. Thus, lead-smelter matte containing ni 23.2, Co 1.8, Cu 23.6, PB 30.6, Fe 1.2, As 4.8, and s 7.5 pct was heated at 75 deg-100 deg c with h2so4 and mNO2 for 2 h. After filtration, the leach solution contained as sulfates ni 98, CO 94, cu 94, pb 0, fe 96, as 94, and mn 99 pct (ed.: Evidently of original amounts). Iron and arsenic are removed by precipitation at ph 3.5-4.5. Copper is precipitated as sulfide with na2s. Cobalt and nickel are precipitated with h2s at ph 3-4.5 and filtered. The solution containing mnso4 is oxidized at ph 6.8, 70 Psi o2, and 25 deg c to precipitate mNO2, which is heated at 250 deg c for 3 h to form mNO2 and recycled to leaching.
U.S. Pat. 4,231,993; Nov. 4, 1980; Chem. Abstr. 93:29,793S