The novel extractants, bis-triamides: Synthesis and selective extraction of thorium(IV) from nitric acid media

Abstract Four novel soft-hard donor bis-triamide extractants were rationally designed, synthesized and characterized for the highly efficient extraction of Th(IV) from nitric acid medium in different diluents. The results indicate that L2 and L3 exhibit higher distribution ratio values for thorium than those of L1 and L4 in nitrobenzene. Further studies including the effects of acidity, the concentration of extractant, the determination of extraction capacity of Th(IV) and the temperature on the distribution ratios of Th(IV) were limited to L2 and L3 . The results reveal that Th(IV) is extracted into the organic phase as the extracted complex with a metal/extractant ratio of 1: 2. The maximum extraction capacity of Th(IV) with L2 and L3 is 995 mg/L and 1085 mg/L, respectively. The thermodynamic parameters (Δ H , Δ S and Δ G ) associated with the extraction process were determined, and the results show that the process is endothermic and spontaneous at room temperature. Moreover, L3 shows the highest selectivity for Th(IV) over U(VI), Am(III), Eu(III) and Sr(II) in 0.1–3.0 M HNO 3 solution. Stripping experiments indicate that the best stripping performance for Th(IV) is achieved by using 2.0 M Na 2 CO 3 as a stripping agent and its stripping percentages can reach 99% by the third stage.