RECOVERY OF CONSTITUENTS FROM METAL ALLOY SCRAP

1,210,503. Recovery of metals from nickel alloy scrap. BRANDHURST CO. Ltd., and CHARTER CONSOLIDATED Ltd. 14 Nov., 1967 [14 Nov., 1966], No. 50975/66. Heading C1A. Metals are recovered from Ni base alloy scrap containing Ni, Co and Cr with optional additions of one or more of Mo, Fe, Al, Ti, Mn, Si, W, C, Cu and Nb by:- (a) Dissolving metal values therefrom with aqueous HCl with the optional incorporation of chlorine gas; (b) Adding MgO to the solution until it has a pH of 2-4, whereby Cr and any Fe are precipitated, and separating the precipitate from the liquid phase; (c) Effecting liquid/liquid extraction under acidic chloride conditions using an organic phase so that any acidic cobalt chloride complex formed in the aqueous phase passes into the organic phase; (Stages (b) and (c) can be used in the above order or stage (c) may precede stage (b).) (d) Adding MgO to the resulting aqueous phase to give a pH of 7À5-8 and precipitate nickel which is separated from the liquid phase, which latter is then heated to produce MgO and HCl; and (e) Recycling the MgO to at least one of stages (b) and (d) and the HCl to stage (a). When stage (c) precedes stage (b) the latter may combine with stage (d) and high pressure hydrogen used to selectively reduce Ni from the mixed Ni, Cr Œ Fe hydroxides. Any Mo values in the solution formed in stage (a) are removed, prior to the first of stages (b) or (c), by contact of the solution with activated carbon, preferably after contacting with Cl 2 gas to increase the valency state thereof and eluted from the column as Na or NH 4 molybdate which may be precipitated as Ca molybdate using a Ca salt. Alternatively the Mo may be removed by counter-current extraction with tri-butyl phosphate. Metals may be recovered from the various solutions or precipitates by suitable methods such as hydrogen reduction.