Evaluation of polymer inclusion membranes containing calix[4]-bis-2,3-naptho-crown-6 for Cs recovery from acidic feeds: Transport behavior, morphology and modeling studies

Transport of cesium across polymer inclusion membrane (PIM) containing calix[4]-bis-2,3-naptho-crown-6 (CNC) was investigated using acidic feed conditions. The PIMs were prepared using cellulose triacetate (CTA) as the polymer, 2-nitrophenyloctyl ether (NPOE) as the plasticizer and CNC as the carrier extractant. The studies included effects of nature of plasticizer, plasticizer concentration, CNC concentration, CTA fraction, feed acidity, and cesium concentration. Optimized membrane composition was found to be 33% CTA, 5% CNC and 62% NPOE which could result in ca. 85% Cs transport in 24 h. While significant Cs transport was seen with NPOE and TBP as the plasticizer, nearly no transport was noticed with TEHP (tris-2-ethylhexyl phosphate) and di-n-octyl phthalate (DOP). The transport behavior of Cs(I) was correlated with membrane morphology using Transmission Infrared Mapping Microspectroscopy (TIMM) plots and AFM profiles. Selectivity studies were also carried out which were found to be quite encouraging. A mathematical model was developed to simulate the transport process of Cs(I) ion from feed side to the strip side.