Recovery of elemental sulphur and copper values from chalcopyrite concentrates by direct leaching in ferric chloride solution

The influence of different variables on the recovery of copper and sulphur from chalcopyrite concentrates by direct leaching in ferric chloride solution has been studied. It is found that the finer the grind of the concentrate and the higher the strength of ferric chloride in the solution, the higher is the recovery of copper and sulphur. The amount of ferric chloride for maximum recovery is found to be 3-5% more than the stoichiometric equivalent to form respective chlorides of the sulphides present in the concentrate other than the pyrite. With increase in concentration of free HCl in the leach upto 100g/l, the recovery of copper and sulphur increased but with further increase no perceptible influence on recovery is observed. A recovery of more than 99% copper and 92% chalcopyrite sulphur is obtained on leaching a low grade concentrate for 2 hr in a solution containing 520 g/l FeCl3 and 100g/l HCl with a ratio of FeCl3: CuFeS2=2.78:1 at a temperature of 105 ± 1°C. (Sarvashri G.Basu and P.K. Sinha, Senior Scientific Assistants; Shri S.C. Aush and Dr. N. Dhananjayan, Scientists; and Prof. V.A. Altekar, Director, National Metallurgical Laboratory, Jamshedpur)