The role of catalyst in chalcopyrite passivation during leaching

This work presents an investigation on the chalcopyrite leaching under different conditions, and studies the surficial characteristics of chalcopyrite using Scanning Electron Microscope to determine the composition of the passivation layer on the surface of chalcopyrite. The study of chalcopyrite dissolution was carried out in H₂SO₄ solution systems at pH of 1.2, with a chalcopyrite concentrate 5% in the redox potential of 460 mV at 90°C. The tests were meant to study the leaching of chalcopyrite in ferric sulfate solution to extract copper by adding pyrite, silver and silver coated pyrite. Using these approaches, the achieved recoveries were different. The results showed that in presence of pyrite, an elemental sulfur layer formed around chalcopyrite particles which hindered the complete dissolution of copper in chalcopyrite. No commercial process has been so far developed using silver as a catalyst to recover copper from chalcopyrite due to precipitation of argentojarosite which forms during the leaching process and limits the availability of silver ion as a catalyst. But, silver and pyrite assemblage to form silver coated pyrite caused an increase in dissolution. However, in presence of the pyrite coated silver, the leaching rate was very fast, and complete copper extraction was achieved within 10 hours.