Kinetics of Sphalerite Leaching by MnO₂-KI Oxidation System in Sulfuric Acid

Abstract

Efficient extraction of zinc from polymetallic concentrates is crucial for the metallurgical industry. Traditional leaching techniques often rely on strong oxidizing agents, which can be wasteful and environmentally harmful. While cyclic oxidation systems like the Fe3+/Fe2+ pair are known, they often fail to achieve high leaching rates, especially when the raw material contains multiple sulfide minerals. In this study, we developed a novel oxidation system using manganese dioxide (MnO2) as the primary oxidizing agent and potassium iodide (KI) as a supporting material to create an I2/I− oxidation cycle in a sulfuric acid medium, at an atmospheric pressure between 40 °C and 80 °C. Leaching experiments were conducted under varying temperatures and KI doses. The results demonstrated that for the MnO2-KI system, a zinc leaching degree of 89.78% was achieved after 3 h of leaching at 80 °C, and kinetic studies indicated that the leaching process is diffusion-controlled (through the thin film), with an activation energy of 27.65 kJ mol−1. Moreover, this system offers an improved method for separating iodine from the leachate upon completion, enhancing the overall process efficiency. It also opens opportunities to test other primary oxidizing agents in combination with iodide salts. These findings suggest that the MnO2-KI oxidation system offers a promising approach for improving zinc recovery from sphalerite concentrates.

Keywords

• I₂/I⁻ cycle
• polymetallic materials
• zinc extraction
• sulfide oxidation
• sphalerite