Iron Leaching Behavior During Oxygen Pressure Leaching of Zinc Sulfide Concentrate

The behavior of iron during the two-stage countercurrent pressure leaching of zinc sulfide concentrate was systematically investigated to elucidate its regulation mechanisms. In the first stage, controlled conditions (120 °C, 0.2 MPa O₂, 60 g/L H₂SO₄) suppressed Fe³⁺ hydrolysis and jarosite formation, facilitating the efficient Fe²⁺ transfer into the leachate. In the second stage, high oxygen pressure (0.8 MPa) promoted the oxidation of Fe²⁺ to Fe³⁺, enhancing mineral dissolution, while the residual acid (~50 g/L) inhibited Fe³⁺ precipitation. As a result, over 98% of Zn and 81% of Fe were extracted, with Fe primarily present as Fe²⁺ in the first-stage solution, while a small fraction remained as pyrite in the residue. Lead and sulfur were concentrated as lead sulfate and elemental sulfur, respectively. These findings provide a practical approach for optimizing Fe control, contributing to the optimization and sustainability of zinc pressure leaching processes.