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.

中文翻译：

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真空蒸馏从低挥发性氯化物中分离 ZnCl2

为了纯化可通过电弧炉粉尘选择性氯化回收的粗ZnCl2，研究了利用蒸发分离挥发性ZnCl2的真空蒸馏。实验结果表明，700 K 或800 K 真空蒸馏可有效分离ZnCl2 和FeCl2。由于 ZnCl2 和 PbCl2 沉积区重叠，低温区富 ZnCl2 沉积物经过长时间蒸馏后被 PbCl2 污染。相反，在较短的蒸馏期后回收含有较少 PbCl2 的纯化 ZnCl2。此外，ZnCl2 熔体中的少量杂质 CuCl、CdCl2 和 MnCl2 留在坩埚中或通过真空蒸馏沉积在高温区。CdCl2 和 MnCl2 的分离方式分别类似于 PbCl2 和 FeCl2。尽管其蒸气压相对较高，但 CuCl 部分仍留在坩埚中。其行为被认为是基于 CuCl 在由 ZnCl4-四面体网络结构组成的熔盐中聚合。将真空蒸馏与其他 ZnCl2 纯化工艺相结合，将能够随后电解熔融的 ZnCl2 基盐，以生产高纯度的 Zn 金属。