Evaluation of a novel tripodal diglycolamide for actinide extraction: Solvent extraction and SLM transport studies

A novel tripodal diglycolamide (T-DGA) extractant in a diluent mixture (10:1 n-dodecane–iso-decanol) was evaluated for the extraction of actinide ions such as UO22+, Np(IV), Pu(IV), and Am(III) and fission product element ions such as Cs+ and Sr2+ from acidic feed solutions. Conditions for quantitative extraction and stripping were found out for the actinide ions other than UO22+ which is poorly extracted. Solvent extraction studies were carried out at varying concentrations of the extractant and nitric acid using Am(III) and were compared with the results obtained with TODGA (N,N,N′,N′-tetraoctyldiglycolamide), a representative diglycolamide extractant proposed for actinide partitioning. The extracted species was found out to be Am(NO3)3·2T-DGA(o) at higher T-DGA concentrations, while mixed 1:1 and 1:2 species were observed at lower T-DGA concentrations. The prevalence of 1:2 species in the present case as compared to the 1:1 species reported in a similar system was attributed to the low dielectric constant diluent medium used in the present study. Supported liquid membrane studies were also carried out using the T-DGA under varying feed acidities, carrier extractant concentration and compared with TODGA under identical conditions. The transport rates are dependent on the strippant used in the receiver phase and a 0.01 M EDTA solution (pH 3.0) was found to yield quantitative transport of Am(III) using T-DGA as compared to dilute nitric acid, which was efficiently used for the TODGA system in an earlier study. The transport efficiency of the carrier solvent system was Am(III) > Pu(IV) ≫ Np(IV) > UO22+. The diffusion parameters were calculated for the T-DGA system and compared with the experimentally determined parameters.