Measurement and modeling of phase equilibria for Sb-Sn and Bi-Sb-Sn alloys in vacuum distillation

- Vapor-liquid equilibria (VLE) of Sb-Sn and Bi-Sb-Sn systems under vacuum condition were measured.
- The experimental data of VLE in vacuum distillation were correlated using Wilson equation for the Sb-Sn and Bi-Sb-Sn system.
- Good results of component activity are obtained for the Bi-Sb-Sn alloy using binary interaction parameters.

Vapor-liquid equilibria (VLE) and purification of tin from crude Sn containing Bi and Sb has been studied in vacuum distillation. The Sb-Sn and Bi-Sb-Sn systems were investigated in the temperature range from 1000 to 1500 K and at pressure of 5 Pa. Consequently, the content of Sn for the Bi-Sb-Sn system in the liquid phase reached more than 0.99 mol fraction as the temperature higher than 1500 K. It is shown that Bi and Sb can be satisfactorily removed from crude Sn. The VLE data of Sb-Sn and Bi-Sb-Sn alloys were calculated by using Wilson equation and compared with experimental values under vacuum condition. The capability of the equation to predicting the activities of components in whole composition range was also tested. It provides an efficient way to guide the process of vacuum distillation. The experiment results revealed that vacuum distillation is a promising method for the separation and purification of crude metals.