Simulation prediction and experimental study of phase equilibria of Bi-Sb and Bi-Sb-Cd alloys in vacuum distillation

In this study, experimental determination and model prediction of the vacuum distillation vapor-liquid equi-librium (VLE) values of Bi-Sb binary alloy and Bi-Sb-Cd ternary alloy at different temperatures were undertaken under a vacuum of 1-5Pa. The experimental result shows that Bi and Sb were separated effectively from Bi-Sb binary alloy and Cd in Bi-Sb-Cd ternary alloy preferentially volatilized and entered the vapor phase completely. Combined with the above two-step experiments, the segmented distillation can purify crude antimony. The molecular interaction volume model (MIVM) was used to predict both the activity of each alloy element of Bi-Sb, Bi-Cd and Sb-Cd and VLE values. The average relative deviation of activity was <+/- 5.19% compared with the adopted experimental values, and the VLE values were consistent with the trend of the experimental values. The MIVM was further used to predict the activity and VLE values of Bi-Sb-Cd ternary alloy, and the result corre-sponds with the experimental values. This combination of experiment and model prediction not only verified the reliability of the MIVM in predicting the activity and VLE values of antimony-based alloys, but also optimized their process parameters of vacuum distillation, providing theoretical guidance for vacuum distillation purifi-cation of crude antimony and further industrial experiments.