Preparation of Antimony Metal by Carbothermal Reduction of Antimony Oxide Powder in a Microwave Field: Mechanism and Process

Antimony is often used as a hardener for alloys. There are few studies on the preparation of antimony from Sb₂O₃ by microwave carbothermal reduction. In this study, Sb₂O₃ was used as the raw material, and the resonant cavity perturbation method was used to select anthracite as the reducing agent according to the microwave absorption of the material mixture. The single-factor experiment of reduction temperature, reduction time, and reducing agent ratio was carried out in a microwave tube furnace. The process parameters were optimized by response surface methodology (RSM). Under the optimized conditions, the reduction temperature was 758 °C, the reduction time was 56 min, the reducing agent addition ratio was 0.123, and the molten salt addition ratio was 0.1. An antimony ingot with a yield of 92.19% and a purity of 99.45% was obtained. The products and residue of the antimony ingot were analyzed by X-ray diffraction analysis (XRD), X-ray fluorescence (XRF), thermogravimetric (TG) analysis, scanning electron microscopy (SEM), and the mechanism of carbothermal reduction of antimony oxide powder in a microwave field was studied. The results showed that the microwave carbothermal reduction process of Sb₂O₃ under a microwave field had three stages: 25~655 °C, 655~850 °C, and >850 °C. Different stages changed with temperature. This green and energy-saving microwave heating technology can provide a feasible method for the efficient preparation of antimony.

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