The separation behavior of impurity in antimony during vacuum distillation

Abstract

The models for depicting the variation tendencies of contents of Cu, Fe, Ni, Pb and Bi impurities in melt and distillate were established. The results proved that the mass transfer process was determined by the hybrid steps of mass transfer processes in the liquid boundary layer and at the liquid-gas interface for Pb and Bi impurities, whereas the rate-determining step was the mass transfer process at the liquid-gas interface for Cu, Fe and Ni impurities. The experimental results of Cu, Fe, Ni and Pb impurities in melt were coincident with the calculated results, while the experimental result was lower than the calculated result for the Bi impurity; the experimental result of Bi impurity in distillate was consistent with the calculated result, whereas there existed discrepancy for the Pb impurity; the marked increases of keff of Pb and Bi impurities during distillation were responsible for the difference between the experimental and calculated results in distillate. Additionally, the removal efficiencies of Cu, Fe and Ni impurities were higher than those of Pb and Bi impurities, the reason arose from that the vapor pressures of the latter were much closer to that of antimony than those of the former.