Role of manganese dioxide in the recovery of oxide–sulphide zinc ore

Highlights: • Addition of MnO₂ can realize effective recovery of oxide–sulphide zinc ore. • The thermodynamic mechanism is investigated by exploiting the Equilib module of FactSage. • MnO₂ will directly oxidize ZnS to ZnMn₂O₄, with S₈ and S₁₃ forming. - Abstract: In this article, the role of MnO₂ in the recovery of oxide–sulphide zinc ore discussed. Through adopting various modern analysis techniques (such as X-ray diffraction pattern, X-ray photoelectron spectroscopy, scanning electron microscope, energy dispersive X-ray analysis, and fourier transform infrared spectroscopy), the function and mechanism of MnO₂ during the phase transformation process is found out. Thermodynamic mechanisms involved in the phase transformation process with or without addition of manganese dioxide investigated by exploiting the Equilib module of FactSage. What's more, XRD patterns, XPS spectra and SEM-EDAX analyses of zinc calcines verify well the calculations of FactSage. Results reveal that the addition of MnO₂ will produce an aggregation of ZnMn₂O₄, a valuable energy material, while roasting on its own, results in generating undesirable Zn₂SiO₄, the oxidation degree being relatively low. Moreover, XRD pattern of zinc calcine and FT-IR spectrum of yellow product collected in the calcination process prove that the sulphur-fixing value of the additive MnO₂, which can promote transforming to the elemental sulphur. The volatile S can be collected through a simple guiding device. In this process, the emission of SO₂ effectively avoids, thus MnO₂ deems as a potential additive in the recovery of oxide–sulphide zinc ore.