Investigation of similar element selenium and tellurium volatilization behavior in the vacuum distillation separation process

Abstract

Despite being an eco-friendly and efficient method for purifying crude selenium (Se) and tellurium (Te), due to their similar physical and chemical properties and the lack of the evaporation parameters of selenium during distillation cannot determine the best distillation conditions, so vacuum distillation struggles to achieve complete separation of Se and Te. This study focused on the volatilization behavior of Se and Te during vacuum distillation, using a 97%Se–3%Te alloy produced in the Se extraction industrial. The volatilization behavior of the Se–Te alloy was investigated through differential gravimetrical distillation temperatures of 523 K–723 K and system pressures of 5 Pa–1000 Pa. The results indicated that the evaporation rates of Se and Te in Se–Te alloy and the temperature exhibit an exponentially relationship, which followed the model ω = e^(a+bT). Additionally, the relationship between system pressure and evaporation rate followed a logistic model $\omega =A_2+\frac{A_1-A_2}{1+{\left(\frac{p}{P_0}\right)}^b}$.Notably, the Te content in the volatile compounds was inversely correlated with the system pressure, thereby decreasing significantly with increasing system pressure. The mass transfer coefficient of Se in the Se–Te alloy was also determined, exhibiting a significant increase with increasing temperature and decreasing pressure. Furthermore, through comparative X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis of the residual and volatiles phases. The phase of selenium and tellurium in the raw materials, residues, and volatiles remains unchanged, existing in the form of elemental selenium and tellurium, which meets the requirements of the volatilization experiments. Through experimental and data analysis, this study investigated the evaporation rates of selenium and tellurium in a selenium-tellurium alloy system and developed a fundamental model relating to pressure and temperature to obtain evaporation parameters, providing valuable insights into the volatilization behavior of Se and Te under vacuum conditions, thereby offering theoretical guidance for the vacuum distillation separation of these elements.