Synthesis Of A Few Macroporous Silica-based Supermolecular Recognition Materials And Their Adsorption Properties For Cesium

It is known that the supramolecular recognition agents have high selectivity for Cs(Ⅰ), one of the main heat emitting nuclides. For effective partitioning of Cs(Ⅰ) from highly level liquid waste (HLLW), the derivatives of 25,27-bis(1-alkyloxy)calix[4]arene-26,28-crown-6(Calix[4]arene-Crown): 25,27-bis(1-butyloxy)calix[4]arene-26,28-crown-6(ButCalix[4]C6), 25,27-bis(1-hexyloxy)calix[4]arene-26,28-crown-6(HexCalix[4]C6), and 25,27-bis(1-hepxyloxy)calix[4]arene-26,28-crown-6(HepCalix[4]C6), were synthesized. The relevant intermediates and target products were characterized by elemental analysis, FT-IR, TG-DSC, ESI-MS and 1H NMR. The synthetic mechanism of Calix[4]arene-Crown was discussed.The synthesis of an intermediate product,5,11,17,23-tetra-butyl-25,26,27,28-tetrahydroxycalix[4]arene(TBTHC4), was examined. The results showed that as the molar ratio of p-tert-buthypheno, NaOH, and formaldehyde solution was 1:0.1:1.5, refluxing for 5h in diphenyl ether at 260℃, and recrystallizing with ethyl acetate, the yield of the TBTHC4 product was 66.38%.The novel supramolecular recognition materials, ButCalix[4]C6/SiO2-P, HexCalix[4]C6/SiO2-P and HepCalix[4]C6/SiO2-P, were synthesized. It was done through impregnation and immobilization of the relevant supramolecular recognition agent into the pores of the macroporous SiO2-P particles support. The composite mechanism and micro-structures of the novel supramolecular recognition materials were understood by characterization using FT-IR, TG-DSC, XRD and BET.The adsorption of Cs(Ⅰ) and more than 10 typical elements onto the ButCalix[4]C6/SiO2-P, HexCalix[4]C6/SiO2-P and HepCalix[4]C6/SiO2-P materials were investigated at 25℃. It was carried out by examining the effects of contact time and the HNO3 concentration in the range of 0.4-5.0 M. ButCalix[4]C6/SiO2-P, HexCalix[4]C6/SiO2-P and HepCalix[4]C6/SiO2-P showed excellent adsorption ability and high selectivity for Cs(Ⅰ) over all the tested metals except Rb(Ⅰ) and Pd(Ⅰ Ⅰ). The complexation of Cs(Ⅰ) with the supramolecular recognition materials as well as the association of the supramolecular recognition materials with HNO3 through hydrogen bonding were two competitive reactions. The optimum HNO3 concentration in the adsorption of Cs(Ⅰ) was 2.0 M HNO3 for ButCalix[4]C6/SiO2-P and HepCalix[4]C6/SiO2-P as well as 3.0 M HNO3 for HexCalix[4]C6/SiO2-P. The adsorption ability of three novel materials for Cs(Ⅰ) in 3.0 M HNO3 was as follows: HexCalix[4]C6/SiO2-P>HepCalix[4]C6/SiO2-P>ButCalix[4]C6/SiO2-P. It is known that the HNO3 concentration in genuine HLLW is around 3.0 M, it is therefore of great beneficial to application of HexCalix[4]C6/SiO2-P in the separation of Cs(Ⅰ) from HLLW.