Calculation of Component Activities for Se-Based Binary Systems by NRTL Equation

Abstract

The interaction energy parameters of the Nonrandom two-liquid (NRTL) equation for the Bi–Se, Pb–Se, Sb–Se, and Tl–Se binary systems were determined. The difference in the goodness of fit between the systems was discussed for each system. The activities of components at corresponding temperatures for the four binary systems were calculated and discussed using the NRTL equation. The mixing enthalpies and Gibbs free energies of these systems were obtained. The calculations for the four binary systems are in agreement with the experimental data from the literature. It shows that the NRTL equation is reasonable and accurate based on the concept of local composition and two-fluid theory, especially for binary systems containing liquid–liquid equilibria. The results we obtained using the NRTL equation can be very useful in performing vacuum experiments for crude selenium.