Synthesis of amide imidazole-based functionalized ionic liquid for separation of Th/Pu

Abstract The plutonium in the highly radioactive waste liquid has a long half-life and this persistent radioactivity poses a great challenge to the long-term geological disposal of nuclear waste, making it necessary to separate it from other elements. Herein, three amide functionalized imidazolium ionic liquids (DXZ-1, DXZ-2 and MIMDIDOA) were synthesized for separation of Pu(IV) (Th(IV) used as a surrogate for plutonium) from a high-concentration nitric acid solution. The findings revealed that under the condition of 8 mol/L nitric acid, the kerosene solution with 0.1 mol/L MIMDIDOA has the highest extraction efficiency for Th(IV), with SF Th/U of 5.85, while the extraction of lanthanides (lanthanum and europium) can be ignored. The extraction mechanism was elucidated through Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The extraction process is an anion exchange process between chloride ions and thorium complex anions in solution assisted by N-containing functional groups in ionic liquids. The adsorption recovery rate of Th 4+ / 242 Pu 4+ by the extraction-elution resin impregnated using MIMDIDOA can reach 81 % under experimental conditions.