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 ZnFe 2 O 4 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 ZnFe 2 O 4 . This work clarifies the distinct reaction behavior between ZnFe 2 O 4 and MgCl 2 or CaCl 2 . Experiments show that although MgCl 2 is a more powerful chlorinating agent, the capability of separating Zn and Fe is not as good as that of CaCl 2 . Fast and selective chlorination of Zn from ZnFe 2 O 4 happens by reacting ZnFe 2 O 4 and MgCl 2 –CaCl 2 mixture. CaCl 2 facilitates the formation of stable Fe-bearing phases, such as MgFe 2 O 4 and Ca 2 Fe 2 O 5 , thereby inhibiting the chlorination of Fe. Moreover, it becomes more effective in promoting the selectivity of chlorinating Zn by increasing temperature after adding CaCl 2 in MgCl 2 . When ZnFe 2 O 4 is subjected to chlorination using a MgCl 2 –CaCl 2 mixture (MgCl 2 –CaCl 2 –ZnFe 2 O 4 molar ratio = 1.5:1.5:1) at 950 °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 ZnFe 2 O 4 by reaction with molten MgCl 2 –CaCl 2 mixture. Graphical Abstract