Effect of ionic liquid on the extraction of uranium with pillar[5]arene-based phosphine oxide from nitric acid solutions

Abstract

Abstract The extraction of U(VI) from aqueous nitric acid solutions with pillar[5]arene-based phosphine oxide (L) and [C8mim][NTf2] ionic liquid dissolved in 1,2-dichloroethane was explored. A great positive impact in this system was observed. The effect of IL concentration in the organic phase and HNO3 concentration in the aqueous phase is considered. The distribution ratios of U(VI) were significantly enhanced upon adding a small amount of ionic liquid as compared with organic diluent. The extraction system was also examined for its ability towards extraction of lanthanides and Th4+. The results revealed higher separation factors towards UO2 2+ over Th4+ in the presence of ionic liquid compared with organic diluent. Other factors such as C8mim+ and NTf2 − have also been considered. This extraction system has shorter equilibrium time as compared with in IL diluent. Stripping experiments showed almost quantitative back extraction of UO2 2+ within two stages. With high selectivity towards UO2 2+ and efficient back extraction, this new POP5A-ionic liquid-organic diluent system shows promise for future application of uranium recovery.