Upgrading copper sulphide residues containing nickel and arsenic

Abstract

A process is disclosed for separating and recovering nickel and copper values from a nickel-copper matte which may contain iron and arsenic. Finely divided nickel-copper matte is leached in aqueous sulphuric acid solution under oxidizing conditions at atmospheric pressure and at a minimum temperature of about 80.degree. C. to selectively leach nickel from the matte to produce a nickel sulphate solution having a final pH in the range of about 4.0 to 6.5, preferably about 6.5, and to produce a copper-rich sulphide residue. The copper-rich sulphide residue is separated from the nickel sulphate solution and leached in a closed reaction vessel at a minimum temperature of about 120.degree. C. under a non-oxidizing atmosphere in a sulphuric acid solution containing an effective amount of copper and sulphuric acid to provide a terminal concentration of at least about 2 g/L Cu.sup.2+ and at least about 20 g/L sulphuric acid to produce a nickel sulphate solution containing any iron and arsenic and to produce a low nickel copper sulphide product essentially free of iron and arsenic.

Dependencies are inferred from the claim text.