Removal of potassium chloride as a complex salt in the hydrometallurgical production of copper

In a hydrometallurgical process for the production of metallic copper comprising an oxidation stage in which materials containing copper sulfide ore or concentrates are oxidized with a solution containing ferric chloride and cupric chloride to effect substantial solubilization of the copper content of the materials in the form of cuprous chloride, a reduction stage in which any remaining cupric chloride in the solution from the oxidation stage can be reduced to cuprous chloride, an electrolysis stage in which metallic copper is recovered from the cuprous chloride solution, and cupric chloride is regenerated by electrolysis of the cuprous chloride solution from the reduction stage, and a regeneration-purge stage in which the ferric chloride and cupric chloride are regenerated by oxidation with concurrent purge of excess iron;

• the improved process for increasing the purity of the metallic copper recovered from the system in the electrolysis stage by removal of impurities, which comprise:
• (a) effecting a separation following the first oxidation stage to remove insoluble materials and form a reduced leach solution containing cuprous chloride, cupric chloride, potassium chloride and iron chloride;
• (b) adding sufficient potassium chloride to the solution to provide at least 2 moles of KCl per mole of CuCl that is to be removed from the system, and provide a solution containing about 4.0 to 6.0 molal potassium chloride;
• (c) cooling the resultant saturated solution to allow precipitation of a solid complex salt of potassium chloride and cuprous chloride;
• (d) removing the crystallized salt complex from the resulting reduced leach feed solution;
• and
• (e) passing the reduced feed solution to the electrolysis stage, and recovering copper of increased purity.