A highly efficient solvent system containing TODGA in room temperature ionic liquids for actinide extraction

Extraction behavior of several actinide ions viz. Am3+, Pu4+ and UO22+ was investigated using N,N,N′,N′-tetra-n  -octyl diglycolamide (TODGA) as extractant in three different room temperature ionic liquids (RTIL), viz. C4mim+·NTf2- , C6mim+·NTf2- , and C8mim+·NTf2- as the diluents. The solvent systems containing TODGA in the RTILs were found to result in higher distribution ratios for all the actinides (trivalent, hexavalent, tetravalent) as compared to that containing n-dodecane as the diluent. Moreover, the distribution ratio values of the metal ions at lower acidities were found to decrease with increasing feed nitric acid concentration. Extraction was found to be independent of the anion of the aqueous phase. Mechanism of extraction of the actinides was found to be different compared to n-dodecane, molecular diluent. Cation-exchange was found to be the mechanism of extraction followed in RTILs. Effect of carbon chain length of alkyl groups of the RTILs conclusively proved the mechanism of extraction of the actinides by TODGA. Nature of extracted species was also found to differ from n-dodecane. Stripping studies were carried out using complexing agents such as EDTA, DTPA in guanidine carbonate or a buffer mixture.

► Extraction of actinide ions viz. Am3+, Pu4+ and UO22+.
► TODGA in room temperature ionic liquids.
► Ion-exchange mechanism of extraction.
► Significantly enhanced separation factors.