Separation of Zn and Fe in ZnFe2O4 by Reaction With MgCl2

Earth’s commercial and affordable zinc reserves are expected to be depleted in less than 50 years. Since electric arc furnace (EAF) dust contains a certain amount of Zn, recovery of Zn from EAF dust has become an important issue to assure a sustainable resource supply in the future. The key technical challenge is that Zn mainly occurs in EAF dust as ZnFe 2 O 4 , a very stable crystal which is difficult to reduce or leach. MgCl 2 is believed to be effective in breaking the structure of ZnFe 2 O 4 . This work investigates the fundamentals of the reaction between MgCl 2 and ZnFe 2 O 4 . Experiments show that Zn in ZnFe 2 O 4 is chlorinated to ZnCl 2 quickly with priority over Fe, implying the efficacy of MgCl 2 in separating Zn and Fe in ZnFe 2 O 4 by selective chlorination. Effects of MgCl 2 /ZnFe 2 O 4 molar ratio and temperature on the reaction are clarified. Overuse of MgCl 2 slows down the reaction and is detrimental to the selective chlorination of Zn. Temperature can effectively increase the reaction rate as well as the priority of chlorinating Zn. Utilization of MgCl 2 could be high, because evaporation of MgCl 2 is not as fast as the reaction with ZnFe 2 O 4 . According to these results, a new technology to recover Zn from EAF dust by using MgCl 2 is proposed.