Process for hydrometallurgical upgrading

A process for treating concentrates of sulphides of copper, zinc, nickel, cobalt, lead and iron and a particulate copper-containing matte for selectively concentrating said metal values into separate fractions which comprises the steps of:

• p1 a. slurrying said concentrates in an acidic solution containing about 10 to 70 g/1 sulphuric acid and about 20 to 80 g/1 copper as cupric ion and subjecting the slurry to an oxidation leach at an oxygen partial pressure in the range of about 50 to 200 psi and a temperature in the range of about 70.degree. C. to the melting point of sulphur for leaching cobalt and nickel values and for formation of lead sulphate;
• b. slurrying said particulate copper-containing matte in an aqueous solution of sulphuric acid containing about 2 to 10 g/1 iron as ferrous ion and subjecting the slurry to an oxidation leach at an oxygen partial pressure in the range of about 100 to 200 psi and a temperature in the range of about 100.degree. to 115.degree. C., said slurry having sufficient sulphuric acid to leach copper and any cobalt, nickel and zinc values, precipitate any lead as lead sulphate and provide a residual acid content of about 5 to 20 g/1, separating solids containing lead sulphate from the solution and feeding at least a portion of said solution containing copper sulphate to the oxidation leach of step (a);
• c. subjecting the reaction mixture from the oxidation leach of step (a) to precipitation leach under autogenous pressure in the absence of free oxygen and at a temperature in the range of about 140.degree. to 190.degree. C. for precipitation of soluble copper as insoluble simple copper sulphide and leach of iron as ferrous sulphate;
• d. subjecting the reaction mixture from the precipitation leach to differential flotation for separate recovery of a lead sulphate concentrate and a copper sulphide concentrate from the solution;
• e. raising the pH of the solution from the differential flotation to from about 1.5 to 2.0 by the addition of limestone whereby gypsum is precipitated and removing said gypsum from solution;
• f. precipitating iron in the solution as goethite, after removal of gypsum, by maintaining in the solution about 0.5 to 1.0 g/1 copper as cupric ion, adding sufficient lime to raise or to maintain the solution pH in the range of about 2.0 to 3.5, agitating the solution at a temperature in the range of about 60.degree. to 95.degree. C. in the presence of air and removing precipitated iron from the solution;
• and
• g. precipitating cobalt and nickel from the solution as sulphides, after removal of precipitated iron, at a temperature in the range of about 50.degree. C. to the solution boiling point at a pH in the range of about 1.8 to 4.5 by adding to the solution one of the group consisting of hydrogen sulphide gas, sodium sulphide and ammonium sulphide, and recovering a cobalt and nickel concentrate from residual solution.

A process for treating concentrates of sulphides of copper, zinc, nickel, cobalt, lead and iron and a particulate copper-containing matte for selectively concentrating said metal values into separate fractions which comprises the steps of:

• a. grinding said concentrates so that about 90 to 100% by weight of concentrates passes a 325 mesh screen;
• b. slurrying ground concentrates in an acidic solution containing about 10 to 70 g/1 sulphuric acid and about 20 to 80 g/1 copper as cupric iron and subjecting the slurry to an oxidation leach at an oxygen partial pressure in the range of about 100 to 200 psi and a temperature in the range of about 90.degree. to 115.degree. C. for leaching of cobalt and nickel values and for formation of lead sulphate;
• c. grinding said matte to a particle size to less than 10 mesh;
• d. slurrying ground copper-containing matte in an aqueous solution of sulphpuric acid containing about 2 to 5 g/1 iron as ferrous ion and subjecting the slurry to an oxidation leach at an oxygen partial pressure in the range of about 100 to 200 psi and a temperature in the range of about 100.degree. to 115.degree. C., said slurry having sufficient sulphuric acid to leach copper and any cobalt, nickel and zinc values, precipitate any lead as lead sulphate and provide a residual acid content of about 5 to 20 g/1, separating solids containing lead sulphate from the solution and feeding at least a portion of said solution containing copper sulphate to the oxidation leach of step (b);
• e. subjecting the reaction mixture from the oxidation leach of step (b) to a precipitation leach under autogenous pressure in the absence of free oxygen and at a temperature in the range of about 150.degree. to 180.degree. C. for precipitation of soluble copper as insoluble simple copper sulphide and leaching of iron as ferrous sulphate;
• f. subjecting the reaction mixture from the precipitation leach to differential flotation for separate recovery of a lead sulphate concentrate and a copper sulphide concentrate from the solution;
• g. raising the pH of the solution from the differential flotation to from about 1.5 to 2.0 by the addition of limestone whereby gypsum is precipitated and removing said gypsum from solution;
• h. precipitating iron in the solution as goethite, after removal of gypsum, by maintaining in the solution about 0.5 to 1.0 g/1 copper as cupric ion, adding sufficient lime to raise or to maintain the solution pH in the range of about 2.6 to 2.9, agitating the solution at a temperature of about 75.degree. C. in the presence of air and removing precipitated iron from the solution;
• i. precipitating copper and zinc from the solution as sulphides, after removal of precipitated iron, at ambient temperature and ambient pressure by adding hydrogen sulphide gas to the solution and recovering precipitated copper and zinc from the solution;
• and
• j. precipitating cobalt and nickel from the solution as cobalt and nickel sulphides, after recovering precipitated copper and zinc, at a temperature in the range of about 60.degree. to 70.degree. C. at a pH in the range of about 2.5 to 3.0 by adding to the solution one of the group consisting of hydrogen sulphide gas, sodium sulphide and ammonium sulphide, and recovering a cobalt and nickel concentrate from residual solution.