Chromium is recovered from superalloy scrap by sulfidation to provide a molten matte that is cooled and fragmented. The fragments are leached in an aqueous solution at 85 deg-105 deg c with chlorine while maintaining the redox potential at 250-550 mv. Chromium is retained in the insoluble residue, and all other metals are dissolved as chlorides. Thus, a superalloy matte containing ni 58.1, Cr 8, CO 3.1, Fe 5.2, Mo 0.38, and s 22.5 pct, was ground to - 48 mesh and slurried with an aqueous solution containing ni 80 and cu 10 g/l. Chlorine gas was bubbled through the slurry for 3 h at 80 deg-95 deg c and a redox potential of 550 mv to selectively dissolve the non-cr sulfides. Extractions of metal values into the leach solution were: ni 88, cr 13.4, Co 72.7, Fe 74.1, and mo 57 pct. Chromium is recovered from the residue by an oxidizing roast and smelting with aluminum.
U.S. Patent No. 4,377,410, March 22, 1983; Chem. Abstr. 94:87,877D