GB1371086A - Acid leaching process for treating high grade nickel-copper mattes - Google Patents

Abstract

1371086 Recovering copper and nickel values SHERRITT GORDON MINES Ltd 17 Dec 1971 [22 Jan 1971] 58878/71 Heading C1A A process for recovering and separating copper and nickel values contained in nickel-copper matte having a nickel - copper weight ratio up to 2À5 and containing sulphur in amount less than 1 mole per mole of total acid reactive metals contained in the matte comprises: (a) leaching finely divided particles of said matte in a first stage leach under an oxygen overpressure of at least 10 p.s.i.g. and at a temperature above 100‹ C. in aqueous sulphuric acid, which may contain dissolved nickel and copper values, having a pH in the range of 2À5 to 5À0; (b) continuing said first stage leach to effect preferential extraction of a major portion of the nickel values contained in said matte while leaving a minor portion of said nickel values unextracted to provide a first stage leach solution containing a relatively high concentration of dissolved nickel and a low concentration of dissolved copper and a first stage leach residue; (c) separating said first stage leach solution from said first stage leach residue; (d) leaching said first stage leach residue in a second stage leach at a temperature above 100‹ C. and under an oxygen overpressure of at least 15 p.s.i.g. with aqueous sulphuric acid, which may contain dissolved nickel and copper values, containing sufficient sulphur values to combine as sulphates with substantially all copper and nickel values contained therein to provide a second stage leach residue and a second stage leach solution containing a relatively high concentration of dissolved copper values and a relatively low concentration of dissolved nickel values; (e) recovering dissolved copper values from said second stage leach solution in a copperwinning step whilst simultaneously generating sulphuric acid to produce a spent solution containing sulphuric acid, dissolved nickel values and residual dissolved copper values; and (f) recycling sufficient of said spent solution from said copper-winning step to said first stage leach to maintain the pH of the first stage leach solution within said range of 2À5 to 5À0 and to adjust the total sulphur content of the slurry in said first stage leach such that there is about 1 mole of sulphur in said slurry for each mole of nickel and copper. If the matte also contains precious metals such as Pt and Pd, the second stage leach residue may be passed to a third leaching stage under more severe oxidizing conditions with sulphuric acid, to provide a third stage leach residue containing the precious metals in relatively high concentrations, the third stage leach solution being recycled to the second stage.