Iodide-assisted leaching of chalcopyrite in acidic ferric sulfate media

Abstract

Chalcopyrite leaching in acidic ferric sulfate media at ambient temperature exhibits slow kinetics due to the formation of passivation layers on chalcopyrite surfaces. In this study, we investigated the use of potassium iodide to assist chalcopyrite leaching and proposed mechanisms by which iodide enhanced the leaching efficiency. The effect of ferric concentration, temperature and iodide concentration on chalcopyrite leaching was studied by factorial experimental design and statistical analysis of data using the analysis of variance (ANOVA) method. The addition of 0.5 g/L of potassium iodide to the leaching media containing Fe(III) resulted in the production of I2 and led to an increase of copper extraction by 47% at 50 °C. Controlled potential experiments highlighted an optimal potential window for leaching at 700–800 mV, thus suggesting that tri-iodide might play a significant role in leaching enhancement. Mineral liberation analysis (MLA) highlighted that elemental sulfur was the surface product generated from the oxidation of chalcopyrite. The rate parameters in the presence of KI were significantly higher, especially at lower temperature, and consistent with those observed for the H2SO4-I2 leaching media. The addition of potassium iodide into the leaching media led to a decrease of activation energy from 81.4 to 33.8 kJ/mol.