Influencing Factors and Mechanisms of Zinc Recovery from Electric Arc Furnace Dust via Microwave-Assisted Carbothermic Reduction

Electric arc furnace dust (EAFD) is a zinc-containing solid waste generated during steelmaking, and advanced recycling strategies are needed to facilitate the recovery of valuable zinc. This study investigated the microwave-assisted carbothermic reduction in EAFD using coke as a reductant, with a focus on temperature (900-1100 degrees C), holding time (0-60 min), and the C/Zn molar ratio (3-5). The results demonstrated that the zinc removal rate exhibited positive correlations with both temperature and time. Under optimized conditions (1100 degrees C, 60 min), a zinc removal rate of 95.45% was achieved, accompanied by a complete decomposition of the ZnO phases. Furthermore, increasing the C/Zn molar ratio enhanced the zinc recovery efficiency and product purity. Isothermal kinetic analyses indicated that the reaction proceeds in two stages: during the initial stage (0-30 min), the process was governed by three-dimensional diffusion control with an activation energy of 146.50 kJ/mol, while the final stage (30-60 min) transitioned to chemical reaction control with an activation energy of 267.32 kJ/mol. Comparative assessments indicated that microwave processing significantly reduced the activation energy compared to conventional heating methods. These findings suggest that microwave-assisted reduction is capable of attaining a high-grade recovery of Zn from EAFD, thus opening up new avenues for the resource-oriented utilization of EAFD.