Desulfurization Mechanism of Lead–Zinc-Bearing Hematite–Limonite Ore Through Oxidation Roasting Process

The impurity sulfur in lead–zinc-bearing hematite–limonite ore mainly exists in the form of galena, sphalerite, pyrite, and natural sulfur, and deep reduction roasting–low intensity magnetic separation does not effectively remove sulfur in a low valence state, which affects the quality of iron ore concentrate. Thereby, the desulfurization mechanism of the oxidative roasting process was investigated via XRD, TG, microscopy, thermodynamics, electron probe micro-analysis–energy-dispersive spectroscopy (EPMA-EDS) analyses. It is noted that hematite–limonite ore contains the valuable components of Fe₂O₃ (59.72 wt.%), SiO₂ (15.43 wt.%), which are 46.32% of total of Fe, with a numerous number of impurities such as S (3.34 wt.%), Pb (1.50% wt.%), Zn (1.25% wt.%), etc. Microscopic identification revealed a complex relationship between hematite, pyrite, galena, sphalerite, and silica inclusions. Therefore, optimal roasting conditions were 60 min and 1050°C, respectively, where the total desulfurization rate was 92.33%, with the desulfurization rate of low valent sulfur reaching 98.64%. Meanwhile, thermodynamic and XRD analyses showed that pyrite was oxidized to ferrous oxide, magnetite, and hematite, etc., sphalerite was oxidized to zinc oxide, while galena was oxidized to lead oxide, and the difficulty of removing products such as PbO·PbSO₄, and PbSO₄ is noted