Condensation behavior and impurity removal during one-step vacuum distillation for direct preparation of high-purity Zn ingots

High-purity zinc is a critical raw material for advanced applications such as biomedical implants, batteries, and semiconductor devices. However, conventional techniques for producing high-purity Zn exhibit several limitations, including distillate-collection difficulties, introduction of impurities during remelting, and complex multistep processing. This study developed an innovative vacuum distillation apparatus for the direct preparation of high-purity Zn ingots in one step. Thermodynamic calculations were performed to evaluate the volatility and condensation temperature ranges of Zn and representative impurity elements, providing guidance for the design of separation and collection conditions. Numerical simulations were conducted to elucidate Zn vapor transport, condensation behavior, and phase transformation pathways in different crucibles under controlled temperature and pressure fields. Results showed that Zn vapor preferentially condenses into the liquid phase in crucibles maintained above the triple point of Zn and subsequently solidifies into Zn ingots, whereas gas–solid transformation dominates in crucibles maintained below the triple point, producing fine crystalline deposits. Furthermore, the purity of Zn ingots first increased and then decreased with increasing distillation temperature, while it improved with increasing temperature difference between the two separation crucibles. Under optimal conditions (distillation temperature of 823 K and a temperature difference of 70 K between the two separation crucibles), a high-purity Zn ingot (purity >99.9999% (6N grade)) was obtained with an ingot collection ratio above 80%. This work provides useful insights into condensation behavior and impurity removal during one-step vacuum distillation.