Recovery of Cu and Fe from a Sphalerite Concentrate by the MnO2–KI Leaching Oxidation System

This study examined the leaching behavior of copper and iron from a sphalerite concentrate in sulfuric acid utilizing an ensemble MnO2–KI oxidizing system. The temperature was shown to significantly influence the leaching kinetics, with the efficiency notably improving between 40 °C and 80 °C. The introduction of KI affected the balance between sulfur passivation and oxidant availability, facilitating increased leaching efficiencies. At 3 wt% KI, maximum recoveries of 82.1% Cu and 85.3% Fe were achieved, which indicates a notable decrease in surface passivation. Kinetic study analysis revealed low activation energies of 28.90 kJ mol−1 for copper and 18.94 kJ mol−1 for iron, indicating that both processes proceed readily at moderate temperature regimes. Despite being diffusion-controlled, the mechanisms of dissolution are different: iron leaching is more complicated, involving pyrite oxidation, sulfur layer formation, transformation to marcasite, and ultimately iron (III) release, whereas copper leaching involves direct interaction of chalcopyrite with the oxidants, similar to the behavior of sphalerite.