Experimental investigation and calculation for Te-X (X=Cu, Pb and Fe) systems in vacuum distillation based on Gibbs-Duhem equation

Experiments on the relationship between temperature and vapor phase composition (T-y curve) of the Cu-Te and Pb-Te binary systems at 5 Pa were carried out, with distillation temperatures in the range of 900-1370 K and 724-920 K, respectively. The experimental results indicate that copper and lead can be satisfactorily removed from crude tellurium. The recovery rate of tellurium is relatively low due to the formation of a high melting point compound in the liquid phase. The activities of Cu and Pb of the Cu-Te and Pb-Te systems were obtained by function fitting and G-D equation, which are used to predict vapor phase composition. The results show good agreement with the experimental data. The activities and T-y curve of the Fe-Te binary system were calculated using the same method and believed to be reliable. A possible high-purity tellurium production cycle combined with vacuum distillation was also discussed.