A thermodynamic and kinetic study of efficient selenium removal from highly acidic TeCl4 solution using tellurium powder

Abstract

High-purity tellurium is in high demand for applications in high-tech fields such as semiconductors and solar cells. To produce high-purity tellurium, one of the challenges is to effectively reduce selenium content of telluride (IV) solution. This study reports the thermodynamic and kinetic analysis for selenium removal by tellurium powder substitution in a TeCl₄ solution. The thermodynamic analysis revealed that the separation window of tellurium and selenium significantly varies with pH. Solutions of weak acidity or basicity are unfavorable for the separation of these two elements. In highly acidic systems, tellurium coexists with selenite ions in the form of Te⁴⁺ ions, and the redox equilibrium potential values for E(Te⁴⁺/Te) and E(H₂SeO₃/Se) significantly differ, indicating the thermodynamic feasibility of selenium removal through tellurium powder replacement. Under optimal reaction condition, the selenium removal efficiency in highly acidic tellurium tetrachloride could reach ∼99.9 % with a residual selenium concentration of 0.1 mg/L. Kinetic studies indicated that selenium removal by tellurium powder substitution is primarily controlled by a chemical reaction with an apparent activation energy of 84.6 kJ/mol. This study provides a simple but efficient method for of selenium impurity removal toward high-purity tellurium.