Fractionation of pure solvent components from degraded PUREX solvent using room temperature ionic liquids

With the view point of recovery of pure solvent components from degraded PUREX (Plutonium URanium Extraction) solvent, comprising of mixture of 30% TBP-HDBP-n-dodecane, three homologues of room temperature ionic liquids (CnmimCl, n = 4, 6, 8) have been investigated in batch equilibration mode (liquid-liquid extraction). While lower homologues of RTIL (C4 and C6) could effectively separate out HDBP from pure TBP-HDBP-n-dodecane mixture, the higher homologue C8mimCl could quantitatively remove TBP and HDBP together leaving behind pure n-dodecane as organic phase. Efficacy of RTIL solutions have also been studied as a function of RTIL concentration, composition of various components in organic mixture, kinetics of extraction, etc. These ionic liquids were found to retain their efficacy even after five cycles of operation after their regeneration. Studies from actual degraded solvent showed that C8mimCl could remove HDBP quantitatively and TBP (∼45% of the initial concentration) whereas C6mimCl and C4mimCl showed very little extraction even for HDBP. The mechanism of extraction was found to be formation of micelles and ion-pair formation.