Iodide-assisted leaching of chalcopyrite concentrate in acidic chloride solution: Effect of different parameters on the copper extraction rate

Abstract

Chalcopyrite leaching has slow kinetics in sulfate media compared to other copper minerals. Studies have shown that these slow kinetics are caused by a passivation layer generated during the mineral ‘s dissolution and/or by its semiconductor properties. In the continuous search for regents to improve kinetics, the use of iodide in sulfate media has led to a significant improvement in the leaching rate of copper from chalcopyrite. However, no detailed information on the effect of the chloride concentration in this system has been informed so far. In this present work, the leaching of a chalcopyrite concentrate using iodide in chloride solution was evaluated, varying parameters such as temperature, particle size, the initial potential of the solution, chloride, iodide, and cupric ion concentrations. The results indicated a copper extraction of 75.8 % in 30 days in the presence of 50 g/L chloride, a 43.1 % more than in the absence of chloride (32.7 % extraction) obtained under the same conditions (100 mg/L I – , 0.5 g/L Cu 2+ , 9 g/L Fe 3+ , 1 g/L Fe 2+ , pH = 1.5, 35 degrees C and an initial potential solution of 700 mV vs SHE). Additionally, the most statistically significant factors on copper extraction in order of influence were temperature, iodide concentration, and chloride concentration. QEMSCAN-PMA analysis of the leached solids showed a significant amount of elemental sulfur and possible intermediate copper species of chalcocite and covellite, which are not observed for the leaching of chalcopyrite concentrate in the presence of iodide in sulfate media. The measurements of the chalcopyrite potential and the solution potential indicate that they are similar for high concentrations of Fe 2+ and for iodide concentrations higher than 200 mg/L in the presence of Fe 3+ . The chalcopyrite potential obtained for the central condition of this study indicates that the predominant iodine species was triiodide, which suggests that this was the main oxidant in this system.