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

Abstract

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) [C_nmim][NTf₂] (where n = 4, 6, or 8). Uranium extraction (D_U) 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: D_Pu(IV) ≥ D_Np(IV) > D_U(VI) using D2EHiBA as extractant suggesting that RTILs can modify the extraction behavior of extractants.

Keywords:

• uranium
• plutonium
• ionic liquid
• amide
• extraction

ACKNOWLEDGEMENTS

The authors thank Dr. A. Goswami, Head, Radiochemistry Division, for his keen interest in this work.