Comparative evaluation of actinide ion uptake by polymer inclusion membranes containing TODGA as the carrier extractant

摘要

Polymer inclusion membranes (PIM) containing TODGA [N,N,N',N'-tetra-n-octyl diglycolamide) were evaluated for the separation of actinide ions such as Am~(3+), Pu~(~(4+)), UO2~(2+) and Th~(~(4+)) from acidic feeds. The PIMs were prepared using cellulose triacetate (CTA) as the polymer matrix and 2-nitrophenyloctyl ether (NPOE) as the plasticizer along with the diglycolamide carrier extractants and were characterized by conventional techniques such as XRD, thermal analysis and AFM. The PIM composition was optimized by a series of studies which involved variation in the CTA, NPOE and carrier concentration which suggested 58% TODGA, 30% NPOE and 12% CTA to be optimum. The uptake studies were carried out using feed solutions containing varying concentrations of nitric acid and showed the trend: Am~(3+) ＞ Pu~(4+) ＞Th~(4+) ＞ UO2~(2+). Transport studies were carried out in a two-compartment cell where nitric acid concentration the feed was varied (1-3 M) while the receiver compartment contained alpha-hydroxy-iso-butyric acid (AHIBA). The actinide ion transport efficiencies with TODGA containing PIMs followed the same trend as seen in the uptake studies. The AFM patterns of the PIMs changed when loaded with Eu~(3+) carrier (used as a surrogate for Am~(3+)) while the regenerated membranes have displayed comparable morphologies. Diffusion coefficient values were experimentally obtained from the transport studies and were found to be 8.89 × 10~(-8) cm~2/s for Am~(3+) transport.