Chlorination of ZnFe₂O₄ in Molten MgCl₂–KCl

Abstract

Recovery of zinc from electric arc furnace dust (EAF dust) has been an important issue for the steelmaking industry, yet a sustainable technology is absent. As a fundamental study to develop a new process of recovering metals from EAF dust by using molten salt, this work clarifies the reaction behavior of solid ZnFe₂O₄ in molten MgCl₂–KCl at temperatures from 773 K to 973 K. MgCl₂ is the chlorinating agent and KCl is an additive to make a low melting point molten salt. The experimental results indicate the efficacy of converting ZnFe₂O₄ to ZnCl₂ and FeCl_x (x = 2 or 3) by MgCl₂. Zn is chlorinated prior to Fe in ZnFe₂O₄ under all conditions, implying the possibility of separating Zn from Fe. Improving the mass transfer in the melt accelerates the reaction. Lower temperatures and larger O₂ partial pressure favor the selective chlorination of Zn, yet the reaction is more stagnant. This work has thus demonstrated the feasibility of treating EAF dust by using MgCl₂-based molten salt.