DOUBLY CROWNED CALIX[4]ARENES IN THE 1,3-ALTERNATE CONFORMATION AS CESIUM-SELECTIVE CARRIERS IN SUPPORTED LIQUID MEMBRANES

Calix[4]biscrowns 9-15 in the 1,3-alternate conformation are prepared by a one-step procedure in similar to 50-80% yields, which are suffici ently high enough to allow their use as selective cesium carriers in s upported liquid membranes (SLMs). The application of the Danesi diffus ional model allows the transport isotherms of trace level Cs-137 throu gh SLMs (containing calix[4]biscrowns) to be determined as a function of the ionic concentration of the aqueous feed solutions. Compound 13 appeared to be much more efficient than mixtures of crown ethers and a cidic exchangers, especially in very acidic media. Decontamination fac tors greater than 20 are obtained in the treatment of synthetic acidic radioactive wastes. Permeability coefficient measurements are conduct ed for repetitive transport experiments in order to qualify the SMLs' stability with time. Very good results (over 50 days of stability) and high decontamination yields are observed with 1,3-calix[4]biscrowns 1 3 and 14, The 1,3-calix[4]biscrowns are shown to be a new family of se lective carriers for cesium removal from radioactive liquid wastes.