LAUSR

To purify crude ZnCl2, which can be recovered by selective chlorination of electric arc furnace dust, vacuum distillation utilizing evaporation separation of volatile ZnCl2 was investigated. Experimental results indicated that vacuum distillation at 700 K or 800 K could effectively separate ZnCl2 and FeCl2. The ZnCl2-rich deposit in the low-temperature zone was contaminated with PbCl2 after a long distillation period owing to the overlapping ZnCl2 and PbCl2 deposition zones. On the contrary, purified ZnCl2 containing less PbCl2 was recovered after a shorter distillation period. Furthermore, minor impurities CuCl, CdCl2, and MnCl2 in the ZnCl2 melt remained in a crucible or were deposited in the high-temperature zone through vacuum distillation. CdCl2 and MnCl2 separated in a similar manner to that of PbCl2 and FeCl2, respectively. Despite its relatively high vapor pressure, CuCl partly remained in the crucible. Its behavior was considered based on polymerization of CuCl in molten salt consisting of ZnCl4-tetrahedral network structures. Combining vacuum distillation with other ZnCl2 purification processes will enable subsequent electrolysis of a molten ZnCl2-based salt to produce highly pure Zn metal.