Sequestration of Np(IV) and Pu(IV) with Hexa-n-octyl nitrilotriacetamide (HONTA) in an Ionic Liquid: Unusual Species vis-a-vis a Molecular Diluent

The extraction of Np(IV) and Pu(IV) was studied using a tripodal amide ligand (N,N,N ',N ',N '',N ''-hexa-n-octyl nitrilotriacetamide termed as HONTA) in an ionic liquid (C(4)mimNTf2) as well as in a molecular diluent mixture (95% n-dodecane +5% iso-decanol) from an aqueous feed containing diluted nitric acid. The extraction efficiency of Pu(IV) was higher than that of Np(IV), while the RTIL-based solvent system extracted the metal ions better than the molecular diluent-based solvent system. The extracted species were ascertained by slope analysis as M(NO3)(5)L(LH) and M(NO3)(4)L-2 for the ionic liquid- and the molecular diluent-based solvent systems, respectively. The stripping of the metal ions from the organic extracts was achieved efficiently when a buffered complexing medium of 0.05 M EDTA and 1 M guanidine carbonate was used. Cyclic voltammetry was done for the Np(IV) extract in the ionic liquid-based solvent system in view of the wide electrochemical window experienced.