Partitioning of cesium from a simulated high level liquid waste by extraction chromatography utilizing a macroporous silica-based supramolecular calix[4]arene-crown impregnated polymeric composite

1,3-[(2,4-Diethyl-heptylethoxy)oxy]-2,4-crown-6-calix[4]arene (Calix[4]arene-R14) is a supramolecular compound exhibiting Cs ion recognition in high level liquid waste (HLLW). To separate effectively Cs(I) from HLLW, a novel silica-based Calix[4]arene-R14 polymeric material (Calix[4]arene-R14/SiO2-P) was prepared. It was done through impregnating a mixture of Calix[4]arene-R14 and tri-n-butyl phosphate (TBP), a molecular modifier, into the pores of macroporous SiO2-P particles utilizing a vacuum sucking technique. The sorption of some typical fission product (FP) elements Na(I), K(I), Cs(I), Rb(I), Sr(II), and La(III) towards Calix[4]arene-R14/SiO2-P was investigated by examining the influence of contact time and the HNO3 concentration. It was found that with an increase in the HNO3 concentration from 1.0 M to 4.0, the sorption of Cs(I) towards Calix[4]arene-R14/SiO2-P increased quickly and then decreased with further increase of HNO3 concentration to 5.0 M. At the optimum HNO3 concentration of 4.0 M HNO3, the Calix[4]arene-R14/SiO2-P adsorbent exhibited excellent sorption ability and selectivity for Cs(I) over all of the tested elements, which showed very weak or almost no sorption except Rb(I). The chromatographic separation of Cs(I) from a simulated HLLW containing similar to 5 mM of the FP elements and 4.0 M HNO3 was performed by Calix[4]arene-R14/SiO2-P packed column at 298 K. Na(I), K(I), Sr(II), and La(III) were found to elute facilely and flowed into the effluent along with 4.0 M HNO3. Cs(I) and Rb(I), adsorbed strongly onto Calix[4]arene-R14/SiO2-P, were desorbed sufficiently by water. The leakage behavior of Calix[4]arene-R14 and TBP from Calix[4]arene-R14/SiO2-P was also investigated.