Doubly Crowned Calix[4]arenes in the 1,3-Alternate Conformation as Cesium-Selective Carriers in Supported Liquid Membranes
摘要:
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 sufficiently high enough to allow their use as selective cesium carriers in supported liquid membranes (SLMs). The application of the Danesi diffusional model allows the transport isotherms of trace level Cs-137 through 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 acidic exchangers, especially in very acidic media. Decontamination factors greater than 20 are obtained in the treatment of synthetic acidic radioactive wastes. Permeability coefficient measurements are conducted 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 13 and 14, The 1,3-calix[4]biscrowns are shown to be a new family of selective carriers for cesium removal from radioactive liquid wastes.
Cation binding properties of a novel 1,3-alternate calix[4]biscrown. Formation of 1:1 and 1:2 complexes and unique cation tunneling across a calix[4]arene cavity
A novel 1,3-alternate calix[4]biscrown was synthesized by the reaction of calix[4]arene and tetraethyleneglycol ditosylate in the presence of K-2 CO3. It formed a 1:2 complex as well as a 1:1 complex with alkali metal and ammonium cations and the cation tunneling phenomenon across the calix[4]arene cavity was detectable with H-1 NMR spectroscopy even at room temperature.