Polymer Inclusion Membranes Containing N,N,N′,N′-Tetra(2-ethylhexyl) Diglycolamide: Uptake Isotherm and Actinide Ion Transport Studies

Polymer inclusion membranes (PIMs) containing N,N,N′,N′-tetra(2-ethylhexyl) diglycolamide (T2EHDGA), a branched diglycolamide extractant as the carrier, cellulose triacetate (CTA) as the polymer matrix, and 2-nitrophenyloctyl ether (NPOE) as the plasticizer were evaluated for the recovery of actinide ions such as Am3+, Pu4+, UO22+, and Th4+ from acidic feed solutions. The optimized PIM composition used in this study was 69% T2EHDGA, 17% NPOE, and 14% CTA. Sorption isotherm experiments were carried out using macro concentrations of Eu carrier (100 mg/L) spiked with 152Eu tracer, and modeling of the data was performed. The sorption kinetics data fitted to the pseudo-second-order model and the Langmuir isotherm suggested a monolayer chemisorption mechanism. Transport studies were carried out in a two-compartment cell in which the feed solution was 1 M HNO3 spiked with the respective radiotracer while the receiver compartment contained 1 M α-hydroxy-iso-butyric acid (AHIBA) solution. Slow transport rate and lack of mass balance in the receiver indicated a significant fraction of the radioactivity was held up in the PIM. Membrane stability studies showed marginal decrease in the transport rate after five consecutive runs. Diffusion coefficient values were calculated by a lag-time method and showed the trend Pu4+ > Am3+ > UO22+ > Th4+.