Investigations on the Physicochemical and Radiolytic Degradation Properties of Tri-n-butylphosphate–Ionic Liquid in the Presence of Nitric Acid

Tri-n-butylphosphate (TBP) in an ionic liquid (IL) has been proposed as a suitable alternative for the solvent extraction of actinides from nitric acid solutions. This paper reports the detailed investigations on the physicochemical and hydrodynamic properties of the solvent system containing TBP in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTf2]) IL. The properties such as density, viscosity, phase separation time (PST), etc., were measured for irradiated and unirradiated solvent phases composed of TBP, [C4mim][NTf2] and 1.1 mol·L–1 TBP in [C4mim][NTf2]. The results are compared with the values obtained in acid-equilibrated IL phases. ATR–FTIR spectroscopy and dynamic light scattering measurement of the IL phase were employed to characterize the interactions among the IL, TBP and nitric acid medium, and the aggregate size of the adduct formed in the IL phase.