Extraction of $$ {\text{Np}}^{4+} $$ Np 4 + and $$ {\text{NpO}}_{2}^{2+} $$ NpO 2 2 + from Nitric Acid Medium Using TODGA in Room Temperature Ionic Liquids

Abstract

Extraction of Np4+ and $$ {\text{NpO}}_{2}^{2 + } $$ was carried out from nitric acid feeds using solutions of N,N,N′,N′-tetra-n-octyldiglycolamide (TODGA) in two imidazolium-based room temperature ionic liquids, viz., 1-butyl-3-methylimidazolium bis(trifluoromethanesulphonyl) imide ([C4mim][NTf2]) and 1-octyl-3-methylimidazolium bis(trifluoromethanesulphonyl) imide ([C8mim][NTf2]). The extraction equilibrium was attained within 2 h for both the metal ions in both the ionic liquids. While a cation exchange mechanism is proposed for the extraction of $$ {\text{NpO}}_{2}^{2 + } , $$ an ion-pair mechanism of extraction is proposed for the Np4+ ion. The nature of the extracted species was determined by carrying out experiments at varying concentrations of TODGA, and species of the type Np(L)2(NO3)4 and NpO2(L)2+ were found to be extracted in 3 mol·dm−3 HNO3. The identification of these extracted species was also supported from the variable nitrate and C4mim+ ion concentration experiments.