Reductive leaching of indium-bearing zinc ferrite in sulfuric acid using sulfur dioxide as a reductant

Abstract

Indium extraction from synthetic indium-bearing zinc ferrite (IBZF) was investigated using sulfur dioxide as a reductant in sulfuric acid medium, and the recovery of indium and the full use of sulfur dioxide were achieved. The leaching kinetics of indium from synthetic IBZF were studied, and the influence of leaching temperature, particle size, initial sulfuric acid concentration and sulfur dioxide partial pressure were investigated. The results showed that the leaching efficiencies increased as the leaching temperature increased from 65 to 85 °C, the initial sulfuric acid concentration increased from 5 to 65 g/L, the sulfur dioxide partial pressure increased from 0.10 to 0.30 MPa, and the particle size decreased from 150–270 μm to 48–58 μm. The unreacted shrinking core model was applied well to the kinetics of indium leaching, which showed that the rate was controlled by a chemical reaction with a calculated activation energy of 57.22 kJ/mol. The order of indium leaching with respect to particle size, initial sulfuric acid concentration and sulfur dioxide partial pressure was −0.2343, 0.02625 and 0.35618, respectively. Meanwhile, sulfur dioxide could reduce the dependency of IBZF dissolution on the initial sulfuric acid concentration.