Chlorination of ZnFe2O4 by Molten MgCl2: Effect of Adding CaCl2

Natural Zn reserves might be exhausted in the following decades. Electric arc furnace (EAF) dust is an essential secondary Zn resource. The recovery of Zn from EAF dust is a critical factor in the sustainable development of the Zn industry and steelmaking industry. Efficient destruction of the ZnFe2O4 crystal structure and separation of Zn and Fe are the key issues to recycle EAF dust. Molten metal chlorides are believed to be effective in breaking the structure of ZnFe2O4. This work clarifies the distinct reaction behavior between ZnFe2O4 and MgCl2 or CaCl2. Experiments show that although MgCl2 is a more powerful chlorinating agent, the capability of separating Zn and Fe is not as good as that of CaCl2. Fast and selective chlorination of Zn from ZnFe2O4 happens by reacting ZnFe2O4 and MgCl2- CaCl2 mixture. CaCl2 facilitates the formation of stable Fe-bearing phases, such as MgFe2O4 and Ca2Fe2O5, thereby inhibiting the chlorination of Fe. Moreover, it becomes more effective in promoting the selectivity of chlorinating Zn by increasing temperature after adding CaCl2 in MgCl2. When ZnFe2O4 is subjected to chlorination using a MgCl2- CaCl2 mixture ( MgCl2-CaCl2-ZnFe2O4 molar ratio = 1.5: 1.5:1) at 950 degrees C for 120 min, the process results in a chlorination percentage of over 90% for Zn, with Fe chlorination percentage lower than 5%. These results demonstrate the prospect of efficient separation of Zn from ZnFe2O4 by reaction with molten MgCl2- CaCl2 mixture.