Chlorination of ZnFe2O4 in Molten MgCl2–KCl

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 FeClx (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.