Effect of room temperature ionic liquid on the extraction behavior of Plutonium (IV) using a novel reagent, bis-(2-ethylhexyl) carbamoyl methoxy phenoxy-bis-(2-ethylhexyl) acetamide [Benzodioxodiamide, BenzoDODA]

• Significant increase in extractability of Pu(IV) by BenzoDODA in RTIL.
• Much higher extraction even from HCl medium.
• Mechanism of extraction varies from cation-exchange to anion-exchange.
• Selectivity of Pu(IV) was dependent on the nature and concentration of acid.

A novel Plutonium (Pu) (IV) selective ligand, bis-(2-ethylhexyl) carbamoyl methoxy phenoxy-bis-(2-ethylhexyl) acetamide (BenzoDODA) was studied for its Pu(IV) extraction behavior in presence of 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide {[Cnmim][Tf2N]}ionic liquids. BenzoDODA was observed to behave differently in RTIL compared to n-dodecane toward Pu(IV) extraction. The presence of C4mimTf2N tends to bring about significant enhancement in the extraction of Pu in both the acidic media (HCl and HNO3) as compared to that of using n-dodecane as diluent. The investigation of the extraction mechanism revealed that while using in RTIL (as diluent), the cation-exchange prevails up to 3 M acidity, in contrast to anion exchange mechanism ruling above 3 M acidic strength. However, in n-dodecane (as diluent) the metal extraction takes place via formation of anion-assisted neutral complex formation only at all acidities. Studies on the nature of species formed by Pu(IV) and BenzoDODA in both HNO3 and HCl medium showed formation of a di-solvate species for RTIL in contrast to mono-solvate formed in n-dodecane. Selectivity of BenzoDODA-RTIL system appears to be lost at lower acidities due to significant extent of extraction of other matrix elements along with target metal ion. However at higher nitric acid concentration (7 M) BenzoDODA was found to be selectively extracting Pu(IV).