Extraction of Uranium(VI) and Thorium(IV) from Nitric Acid Solution by N,N,N′,N′ – Tetraoctylglutaricamide

Abstract

Synthesis and characterization of N,N,N′,N′-tetraoctylglutaricamide (TOGA) was carried out and used for extraction of U(VI) and Th(IV) from nitric acid solutions. The processes of extraction were determined by the slope analysis and by analyzing a function that allows the simultaneous treatment of all the experimental points obtained in different conditions. The different factors affecting the extraction distribution ratio(D) of U(VI) and Th(IV) (extraction concentration, concentrations of nitric acid, salting-out agent NaNO3 concentration, equilibration time, temperature, and types of diluents) were investigated. The results obtained indicated that the extraction species of U(VI) and Th(IV) are mainly extracted as UO2(NO3)2·1.0TOGA and Th(NO3)4·1.5TOGA. The apparent equilibrium constant of U(VI) and Th(IV) extraction determined are 3.35 ± 0.03 L3/mol3 and 1.87 ± 0.01 L5/mol5 at 298 ± 1 K. Thermodynamic parameters such as the free energy(ΔG), enthalpy(ΔH), and entropy(ΔS) changes associated with the extraction processes could be evaluated. Back-extraction of U(VI) and Th(IV) from organic phases was also studied.