Cupric Chloride Leaching of Chalcopyrite

Abstract

In a strong chloride solution the predominant cuprous, cupric, ferrous, and ferric chloride complexes are CuCl3 −2, CuCl+, CuCl2, FeCl2, and FeCl2 + respectively. The probable dissolution reaction for chalcopyrite in cupric chloride solution is CuFeS2 + 3CuCl+ + 11Cl−2 = 4CuCl3 −2 + FeCl2 + 2S The standard free energy change for this reaction at 25°C and unit activities is +43.84 kJ, indicating that the reaction is not thermodynamically feasible. The reaction becomes thermodynamically feasible at high chloride concentration when the ratio of cuprous to cupric copper in solution is less than about 1.9. When the cuprous to cupric ratio becomes larger than a critical value (dependent upon the operating conditions) the dissolution ceases because it is no longer thermodynamically feasible. Over the range 0.79–1.46 M Cu+2 and 2.82–6.21 M Cl− at 90°C, neither cupric nor chloride ion concentration influences the rate of chalcopyrite dissolution, which is directly proportional to mineral surface area. The activation energy for the reaction is 134.7 kJ/mole, and the rate controlling process is probably a step in the anodic reaction.