Abstract: Copper is processed via solutions of copper salts, both cupric and cuprous, in acidified aqueous solutions containing organic nitriles. Methods of producting solutions of cuprous salts include reduction of cupric salts and oxidation of copper and copper sulphides. Solutions of cuprous salts are thermally or electrochemically disproportionated to produce copper and solutions of cupric salts.

Abstract: Cuprous sulphate solutions, suitable for thermal or electrochemical disproportionation to yield copper, are obtained by dissolving copper sulphites, such as Chevreul's salt or cuprous ammonium sulphite, in acetonitrile-water or 2 hydroxycyanoethane-water mixtures, preferably in the presence of cupric sulphate. This discovery is capable of a number of applications, one of which is the recovery of copper from chalcopyrite by the following five steps. An oxidizing roast of chalcopyrite such as to produce either cupric sulphate and/or copper oxide, leaching of cupric sulphate from the calcine, precipitation of Chevreul's salt and/or other copper sulphites with a soluble salt of sulphurous acid, including bisulphites, dissolution of the copper sulphite as cuprous sulphate, using cupric sulphate in an acetonitrile-water solution as oxidant; precipitation of pure copper by thermal disproportionation of the cuprous sulphate solution. Acetonitrile and acidic cupric sulphate solution may be recycled.

Abstract: Methods of reducing aqueous solutions of cupric sulfate to cuprous solutions by using organic nitrile compositions are disclosed. The particular nitrile used is acetonitrile and the reductant is sulphur dioxide. The method has application commercially to leaching ores containing oxidised copper to obtain cuprous ion solutions. Such solutions can be treated by electrochemical or thermal disproportionation methods to obtain very pure copper.

Abstract: Method of preparing cuprous sulfate and bisulfate solutions from materials containing copper and impurities by a leaching process are disclosed. The leaching composition contains sulfuric acid, cupric ions, water and an organic nitrile. The leaching composition may be used with copper sulfide ores in particulate form. The cuprous solutions resulting from the leaching can be treated by disproportionation methods to recover pure copper.

Abstract: Copper is processed via solutions of copper salts, both cupric and cuprous, in acidified aqueous solutions containing organic nitriles. Methods of producting solutions of cuprous salts include reduction of cupric salts and oxidation of copper and copper sulphides. Solutions of cuprous salts are thermally or electrochemically disproportionated to produce copper and solutions of cupric salts.