Studies on the Extraction of Actinides Using a Solvent Containing D2EHiBA in Room Temperature Ionic Liquids: Unusual Extraction of the Tetravalent Ions

The extraction behavior of U(VI), Pu(IV), and Np(IV) from nitric acid medium has been studied using branched chain di(2-ethylhexyl)isobutyramide (D2EHiBA) dissolved in different room temperature ionic liquids (RTILs) [Cnmim][NTf2] (where n = 4, 6, or 8). Uranium extraction (DU) increased gradually with aqueous phase acidity for the three RTILs used in this study suggesting solvation mechanism. There was a reversal in the extraction behavior of Pu(IV) and Np(IV) from nitric acid medium using D2EHiBA dissolved in RTILs as solvents as compared to the behavior reported in the molecular diluent, n-dodecane, which shows negligible extraction of these metal ions. The extraction of Pu(IV) increased with aqueous phase acidity in different RTILs in the order: [C8mim][NTf2] > [C6mim][NTf2] > [C4mim][NTf2]. The distribution ratio values of these metal ions followed the order: DPu(IV) ≥ DNp(IV) > DU(VI) using D2EHiBA as extractant suggesting that RTILs can modify the extraction behavior of extractants.