Leaching of chalcopyrite with Brønsted acidic ionic liquid

A Brønsted acidic ionic liquid 1-butyl-3-methyl-imidazolium hydrogen sulphate ([bmim]HSO4) and its aqueous solutions were used for the leaching of chalcopyrite concentrate at ambient pressure under air in the temperature range of 50 to 90 °C. Copper extraction increased from 52% to 88% as the ionic liquid concentration in solution increased from 10% (v/v) to 100%. Copper extraction was very low at temperatures below 70 °C, but increased significantly at temperatures from 70 to 90 °C, suggesting a high activation energy for the chemical reaction. Elemental sulfur formed a solid layer surrounding the surface of unreacted core during the leaching to affect the reagent diffusion and limit the leaching rate. Hydrogen ion, released by the ionic liquid, and dissolved oxygen were determined to be foremost responsible for the oxidative leaching of chalcopyrite. Compared with leaching of chalcopyrite in acidic aqueous sulphate solutions, the pure ionic liquid and its aqueous solutions exhibited easier leaching of chalcopyrite at higher temperatures which is attributed to increasing the oxygen solubility and transfer of dissolved oxygen to speed up the oxidation reaction.