Ecofriendly extraction of zinc from hazardous electric arc furnace dust via sulphating roasting: Non-isothermal and isothermal kinetics analyses

Electric arc furnace dust (EAFD) formed during steelmaking in electric arc furnace is a hazardous solid waste that is rich in zinc and iron. In our previous study, we realized the efficient extraction and separation of Zn and Fe from EAFD by co-roasting with FeSO₄·7H₂O followed by water leaching processes, which achieved a high extraction rate of Zn (98.79 %) and a low extraction rate of Fe (0.11 %). However, the high temperature would lead to high energy consumption. Therefore, non-isothermal kinetic and isothermal kinetic were exploited in this study to analyze the heating and holding process for further optimizing roasting conditions. The heating process was divided into four reaction stages with different reaction models. Moreover, the holding process was also divided into two reaction stages with the Anti-Jander 3D diffusion model and Z-L-T 3D diffusion model, respectively. The major reactions in the heating and holding process were defined by thermodynamic equilibrium calculations and in situ X-ray diffraction. The rate-determining step was deduced as the desulfurization of Fe₂(SO₄)₃ with a three-dimensional diffusion reaction model. Aiming to accelerate Fe₂(SO₄)₃ desulfurization, the insulation conditions of this process were optimized from 675 °C for 3 h to 600 °C for 3 h, significantly reducing energy consumption.