Hydrometallurgical treatment of nickel and copper bearing intermediates

According to the process described, non-ferrous metal values, particularly nickel, copper and/or cobalt, are extracted from metallurgical intermediates, such as matte and speiss, by reacting the material under oxidizing conditions at a pH of about 4.5 to 6.5 with an ammonia free aqueous solution containing ammonium sulphate, sodium sulphate and/or nickel sulphate. The reaction-products of this operation are then mixed with sulphuric acid under ambient conditions to decrease the pH to about 3-4.5 and to dissolve the non-ferrous metals in the solution which is then separated from the undissolved residue. The process is particularly useful in treating intermediates containing precious metals in that the precious metals are substantially completely recovered in concentrated form in the undissolved residue.