The efficient separation of thorium from rare earth using oxamic acid in hydrochloric acid medium

Abstract

Thorium (Th) is a promising element that can be converted to fissile uranium for nuclear energy. A large amount of slag containing Th need to be effectively treated and stacked in rare earth (RE) industry. It is of importance to develop some novel processes for separating Th from REs using solvent extraction. The amide group was considered to have good selectivity for Th separation from REs. In order to solve the problem of RE entrainment during Th separation together with primary amine (N1923, (CnH2n+1)2CHNH2 n = 9–11) does not extract Th in hydrochloric acid system, three oxamic acid type extractants have been designed and synthesized in this paper. Among the extractants, the separation performance of 2-(dibenzylamino)-2-oxoacetic acid (DBOA) was indicated to be the best. As for the effective separation, the electron affinity of Th was larger, it was more preferred to coordinate with the extractant. The hydrogen ions released by the extractant could inhibit the extraction of REs rather than Th. Accordingly, Th could be separated from REs. Saponification process of oxamic acid extractant could be omitted in this separation process. By extracting Th using a lower concentration of oxamic acid selectively, not only the loss of RE could be reduced, but also a higher purity of Th could be obtained. Using a simplified fractional extraction experiment, the purity of RE in aqueous phase was increased to be 99.92% or higher, and the purity of obtained Th after stripping from loaded organic phase was increased to be 99.5%.