Liquid-Liquid Extraction and Supported Liquid Membrane Transport of Neptunium(IV) Across a Flat-Sheet Supported Liquid Membrane Containing a TREN-DGA Derivative

Liquid-liquid extraction and liquid membrane transport behavior of tetravalent actinide ions viz. Th(IV), Np(IV), and Pu(IV) were investigated for the first time using a diglycolamide (DGA) based dendrimer with a tris(2-aminoethyl)amine (TREN) scaffold as the organic extractant. The generation of 1 dendrimer with six DGA pendent moieties (termed as TREN-G1-DenDGA) extracted Np(IV) more effectively than the other two ions, the trend being Np(IV) > Pu(IV) > Th(IV). The extraction studies of Np(IV) from 3 M HNO3 indicated a 1:1 (metal:ligand) species and the extraction efficiency increased with increasing nitric acid concentration (1-6 M). The transport efficiency of Np(IV) increased with the nitric acid concentration (1-6 M) as well as with the ligand concentration. A very low concentration of 5.75 x 10(-4) M ligand, when used as the carrier, resulted in the transport of ca. 25% metal ion transport in 5 h, which increased to >85% with 4.4 x 10(-3) M ligand. The transport efficiency of the metal ion across the SLM followed the trend Np(IV) > Th(IV) > Pu(IV). The membrane stability was not satisfactory as seen over a period of 5 days suggesting long-term use may require regular replenishment of the carrier solvent. The effective diffusion coefficient (D-eff) of Np(IV)-TREN-G1-DenDGA were determined by the lag-time method and was found to be 5.1 x 10(-8) cm(2)/s.