Polymer inclusion membrane containing a diglycolamide-functionalized calix[4]arene for actinide ion uptake and transport

Abstract

Cellulose triacetate (CTA) -based polymer inclusion membranes (PIM) containing a diglycolamide-functionalized calix[4]arene (C4DGA) as the carrier extractant and 2-nitrophenyl octyl ether (NPOE) as the plasticizer were evaluated for the separation of actinides such as Am3+, Pu4+, UO22+, and Th4+ from dilute acidic feeds. The optimized PIM composition was found to be 6.5% C4DGA, 67.7% NPOE, and 25.8% CTA. The PIM of optimized composition was characterized physically by different techniques, viz., thermogravimetry, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and transmission infrared mapping microscopy (TIMM). The feeds in the batch uptake as well as transport studies involved solutions of the actinide tracer in the required oxidation state in 1M HNO3, while the receiver solutions used in the transport studies contained a 1M alpha-hydroxy-iso-butyric acid (AHIBA) solution at pH 3.0. The uptake efficiency followed the order: Am3+>Pu4+>Th4+≫UO22+, while the transport efficiency order was: Pu4+>Am3+>Th4+ with no detectable transport of the UO22+ ion. The effective diffusion coefficient (Deff) was determined from time-lag experiments, while the permeability coefficient (P) values were obtained from the transport studies and compared with those reported for TODGA (N,N,N′,N′-tetra-n-octyl diglycolamide) and T2EHDGA (N,N,N′,N′-tetra-2-ethylhexyl diglycolamide) containing PIMs. The reusability of the PIMs was assessed by successive uptake and stripping studies, while the stability of the PIMs was assessed by carrying out continuous transport studies over a period of time.