A novel production method of antimony trioxide from stibnite concentrate and the dielectric properties of antimony sulfide with different desulfurizer

Dielectric properties of stibnite concentrate, pure antimony sulfide, three different desulfurizers and their mixtures were assessed using resonant cavity perturbation technique. Dielectric properties of ZnO and CaO are largely independent of temperature, while CuO and Sb₂S₃ have strong dependency with temperature. For the mixtures, the Sb₂S₃ + CuO exhibit strong responsiveness to microwave from 25 °C to 400 °C. The CuO could be efficiently heated and reacted with Sb₂S₃ in microwave field, in agreement with thermodynamic result. Based on the dielectric properties and thermochemical characteristics during the desulfurization process, the phase evolution and reaction mechanism were systematically investigated. Results show that the majority of antimony elements in the concentrate were volatilized in the form of Sb₂O₃ and the rest were left in the form of Sb. Effects of roasting temperature, desulfurizer dosage, and holding duration on microwave roasting were assessed and roasted sample were subjected to XRD, EDX and SEM analysis. Optimum roasting conditions were identified to be 700 °C, 1.4 times the stoichiometric requirement of CuO additive and holding duration of 1.5 h. Microwave roasting of stibnite concentrate with CuO additive promises to be a better alternative technology for traditional pyrometallurgical antimony roasting.