New approach to predict impurity concentration in high-purity antimony metal prepared by vacuum distillation

Abstract

Previous studies have shown that there is a significant difference in impurity concentration in the distillate, resulting in an unclear average impurity concentration in the distilled product. To address this issue, a variation model of impurity average concentration in the distillate was developed based on the mass conservation of the solute during the vacuum distillation process. Five continuous distillation experiments of crude antimony (Sb) metal were carried out to obtain the variation regularity of impurity average concentration in the distillate, and two verification experiments of vacuum distillation were conducted to verify the model. The research results showed that, the concentration of As impurity in residue decreases exponentially as the distillation proceeds, whereas the concentration of Bi impurity increases exponentially; there are the increasing and decreasing concentration gradients of As and Bi impurities in the distillate along with the decreasing condensing temperature, respectively; the average concentrations of As and Bi impurities in the distillate present the linearly decreasing and exponentially increasing tendency, respectively; the calculated values of As and Bi impurities average concentrations in the distillate are in good agreement with the values of two verification experiments, confirming the efficacy of the model.