Selective removal of cesium from model nuclear waste solutions using a solid membrane composed of an unsymmetrical calix[4]arenebiscrown-6 bonded to an immobilized polysiloxane backbone

The extraction of the two long lived isotopes of cesium (Cs-135 and Cs-137) is an important issue because of the specific mobility of (135)cesium from nuclear disposals. The selective removal of the latter from high active wa ste allows its destruction by transmutation or disposal in specific matrixe s. Calis[4]biscrown-6 blocked in a 1,3-alternate cone conformation, extract s Inert cesium than sodium, with a high efficiency and selectivity from sim ulated acidic and high sodium content liquid wastes. In order to reduce the possible loss of the calixarene into the aqueous phases in supported liqui d membranes (SLM) and answer, in a further stage, to a practical clean fixe d-site carrier membrane separation process, an unsymmetrical calix[4]areneb iscrown-6 containing two different a own leaps were synthesized for this sp ecific purpose and grafted by a sol-gel process onto a polysiloxane backbon e. Solid-liquid extraction was carried out with crushed powders and the res ults were compared to liquid-liquid extraction using a soluble analogous of the complexing sits. The decrease of performances, efficiency and selectiv ity, can be explained in terms of steric hindrance, cavity deformation and micro-environment polarity due to the grafting of the carrier Removal of ce sium from acidic and high sodium content liquid waste by facilitated diffus ion process was performed with membranes containing bonded. Again, the sele ctivity was strongly reduced compared to solid-liquid extraction. A mechani sm of transport for cesium was proposed in which the step of stripping in t he receiving phase is the limiting factor. (C) 2001 Elsevier Science B,V. A ll rights reserved.