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Synthesis of a Novel Macroporous Silica-Calix[4]arene-Crown Supramolecular Recognition Material and its Adsorption for Cesium and some Typical Metals in Highly Active Liquid Waste

Abstract A novel macroporous silica-based 25,27-bis(iso-propyloxy)calix[4]arene-26,28-crown-6 (BiPCalix[4]C6) supramolecular recognition material, BiPCalix[4]C6/SiO2-P, was synthesized. It was prepared by impregnation and the immobilization of the BiPCalix[4]C6 molecule into the pores of the macroporous SiO2-P particles. The adsorption of Cs(I) and some typical elements Na(I), K(I), Rb(I), Sr(II), Ba(II), Ru(III), Mo(VI), La(III), and Y(III) onto the BiPCalix[4]C6/SiO2-P material was investigated. The effects of the HNO3 concentration, contact time, and temperature on the adsorption of the tested metals were studied. It was found that at the optimum concentration of 3.0 M HNO3, BiPCalix[4]C6/SiO2-P exhibited excellent adsorption ability and high selectivity for Cs(I) over all the tested elements, which showed weak or almost no adsorption except Rb(I). A pseudo-second-order model was found to be able to describe the adsorption kinetics of Cs(I). The chemical complexation of Cs(I) with BiPCalix[4]C6/SiO2-P was considered to be the rate-controlling step. Meanwhile, the thermodynamic parameters of the Cs(I) adsorption, ΔH˚, ΔG˚, and ΔS˚ were determined. The adsorption of Cs(I) onto BiPCalix[4]C6/SiO2-P was exothermic. It was demonstrated that in 3.0 M HNO3, the novel macroporous BiPCalix[4]C6/SiO2-P material shows promise for the partitioning of Cs(I) from highly active liquid waste.