Recovery of platinum metals from sulphidic raw materials

摘要

Platinum metals (specifically platinum, palladium, osmium, iridium, rhodium and ruthenium) contained in sulphidic raw materials comprising iron and copper and/or nickel and/or cobalt, are recovered by at least partly converting the iron sulphide to oxide by roasting to a sulphur content at least sufficient to combine with said non-iron metals as sulphides, solubilizing said metals by sulphatizing and/or chloridizing roasting, leaching the product with water, acids, e.g. dilute sulphuric acid, salt solutions or ammonia, separating the solution and treating the residue, preferably in aqueous suspension and in the presence of a chloride, e.g. sodium chloride (whereby a complex salt, e.g. Na2Pt Cl6 is formed), with chlorine, separating the platinum metals from the residue after leaching if necessary, and recovering them from solution, e.g. by precipitation with a nonprecious metal such as copper or iron, or with formic or sulphurous acid. In modifications, (1) the leaching is carried out with ammonia and the chloridizing and/or sulphatizing roasting is omitted, (2) the leaching is carried out with water, acids or salt solutions and the chlorine treatment is effected simultaneously, (3) the leaching is carried out with ammonia and air, the ironcontaining residue is not roasted until after the leaching and is then treated with chlorine. In all cases where ammonia is used for leaching is should be expelled, e.g. by heating with lime before introducing chlorine. Roasting is preferably carried out by fluidized technique, e.g. at above 600 DEG C.; the temperature may then be reduced and chloridizing agents such as sodium chloride added. In the example a rotary kiln was used for the first roasting at 600 DEG C., and a hearth roaster for the chloridizing roasting at 400 DEG C. with 20 per cent of sodium chloride; leaching with 1 per cent sulphuric acid was employed and the leached product treated with a solution containing 20 per cent of sodium chloride into which chlorine was led. Specification 739,827 is referred to.ALSO:Platinum metals are recovered from solution by precipitation with a non-precious metal such as copper or iron or with formic or sulphurous acid.