Evaluation of two calix-crown-6 ligands for the recovery of radio cesium from nuclear waste solutions: Solvent extraction and liquid membrane studies

Recovery of radio-cesium from high level radioactive waste is one of the major challenges in the back end of fuel cycle. Calix-crown ligands have been found to be highly selective for the recovery of Cs(I) from acidic feed solutions. The present work deals with the evaluation of the bis-(octyloxy)calix[4]arene-mono-crown-6 (BOCMC) as a selective extractant for radiocesium from nuclear waste solution. BOCMC was evaluated for Cs uptake using several diluents such as NPOE (2-nitro phenyl octyl ether), 1-octanol, hexone, nitrobenzene, PTMS (phenyl trifluoromethyl sulfone) and chloroform. Feed acidity variation studies revealed more favorable extraction at 2–3 M HNO3 and inefficient stripping due to H+ ion extraction was countered by the addition of Alamine-336 to the organic phase. Batch co-current extraction studies revealed quantitative extraction of Cs in four successive contacts which was not affected significantly even when the solvent system was exposed to 100 MRad gamma ray dose. Results obtained was compared with the previously studied commercially available extractant, calix[4]-bis-2,3-naptho-crown-6 (CNC).Supported liquid membrane studies were also carried out using BOCMC using 2.0×10−3 M of the extractant in a mixture of 80% NPOE and 20% n-dodecane containing 0.4% Alamine-336. Diffusion coefficient values calculated from Wilke–Chang equation were compared with those obtained by Danesi's method and time lag method. The stability of membrane, studied over a period of 20 days was found to be reasonably good.

► Comparative evaluation of two calix-crowns was done for Cs(I) extraction.
► SLM studies were carried out for possible application for Cs recovery from HLW.
► An interesting opposing trend of extraction and transport behavior was seen with the calix-crowns.
► Recycling and reusability options were evaluated