Leaching of chalcopyrite (CuFeS2) with an imidazolium-based ionic liquid in the presence of chloride

The effects of independent variables such as, temperature, concentration of ionic liquid (1-butyl-3-methyl-imidazolium hydrogen sulphate, [bmim][HSO4]), chloride and sulphuric acid on copper extraction from chalcopyrite (CuFeS2) ore were studied by surface optimization methodology. The Central Composite Face approach and a quadratic model were applied to the experimental design. The optimal copper extraction conditions given by the above methodology were 20% (v/v) of [bmim][HSO4] in water, 100 g L−1 chloride, and 90 °C. The concentration of chloride and the temperature together exert a synergistic effect in enhancing chalcopyrite dissolution. Experimental data were fitted by multiple regression analysis to a quadratic equation and analyzed statistically. A model was developed for predicting copper extraction from CuFeS2 ore with variables such as Cl−, [bmim][HSO4], H2SO4 concentrations and temperature in the range studied. The activation energy was calculated to be 60.4 kJ/mol (temperature range 30-90 °C), indicative of chemical control of the reaction and [bmim][HSO4] acts as an acid in the reaction.