Task-specific ionic liquids for An and Ln extraction: unusual speciation and extraction mechanisms

Extraction mechanisms of uranium by TBP (tributylphosphate) diluted in an ionic liquid BumimTf2N (1-butyl-3-methyl-imidazolium bis(tri-fluoro-methyl-sulfonyl)imide) and by Task-Specific Ionic Liquids (TSILs) bearing a phosphoryl group were investigated. Great differences between these mechanisms and the one in the industrial solvent, dodecane, have been put in evidence. While in dodecane, the neutral species, UO2(NO3)2(TBP)2, is the major extracted complex, in BumimTf2N and TSILs, at least two species are extracted with more or less similar proportions. Moreover, no uranyl species with two nitrates could be observed in these ionic liquids. Finally, the mechanisms vary from TBP in BumimTf2N to TSILs. These results led to a so-to-say new kind of actinide chemistry. (authors)