Extraction of actinide ions using three CMPO-functionalized pillar[5]arenes in a room temperature ionic liquid

Extraction of actinide ions from nitric acid feeds was investigated using solutions of three CMPO (carbamoyl methyl phosphine oxide) functionalized pillar[5]arenes with varying spacer lengths in a room temperature ionic liquid, [C8mim][NTf2]. The extraction of Am3+ was found to decrease with increasing nitric acid concentration suggesting a mechanism analogous to a cation-exchange mechanism. The nature of the extracted species was determined by the conventional slope analysis method to be ML type which was subsequently confirmed by luminescence spectroscopy. Studies carried out to determine the thermodynamic parameters suggested highly exothermic reactions with negative entropy values. The reusability and recycling studies involved stripping and radiolytic stability of the solvent systems which suggested reasonably encouraging results. While a DTPA solution in guanidine carbonate was found to back extract the extracted metal ion from the ionic liquid phase, the radiolytic stability of the CMPO-pillararenes were reasonably good.