Preparation Of The Novel Macroporous Silica-based Calix[4]Biscrown Materials And Their Adsorption For Cesium

Cs(I) and Sr(II) are called heat generators. The isotopes of Cs(I) and Sr(II), Cs-137with a half-life of30yr and Sr-90with a half-life of28.5yr contained in highly active liquid waste (HLW), are harmful for vitrified HLW in final geological disposal. To significantly decrease the adverse impact, the separation of Cs(I) and Sr(II) from HLW to a great extend is required. However, the effective partitioning and recovery of them have always been one of the most challenging works.Calix[4]BisCrowns is the derivatives of the third generation supramolecular recognition agents, containing calixarene host unit and crown which has similar size to Cs(I). Considering the low content of cesium in HLW, it is valuable for the chromatographic separation of Cs(I) by Calix[4]BisCrowns containing materials.In the present work, the six derivatives of Calix[4]BisCrowns such as1,3-Calix[4]arene-bis(crown-6)(Calix[4]BC6)、1,3-Calix[4]arene-bis(o-benzo-crown-6)(Calix[4]BBenC6)、1,3-Calix[4]arene-bis(naph-crown-6)(Calix[4]BNaphC6)、1,3-tBu-Calix[4]arene-bis(crown-6)(tBu-Calix[4]BC6),1,3-tBu-Calix[4]arene-bis(o-benzo-crown-6)(tBu-Calix[4]BBenC6)and1,3-tBu-Calix[4]arene-bis(naph-crown-6)(tBu-Calix[4]BNaphC6), were synthesized. While the synthesis of tBu-Calix[4]BBenC6and tBu-Calix[4]BNaphC6have not been reported yet. The structure and composition of theses compouds were characterized by elemental analysis, ESI-MS,’H-NMR, FT-IR, TG-DSC, XRD, and SEM, respectively.Six novel macroporous silica-based Calix[4]BisCrown materials, Calix[4]BC6/SiO2-P, Calix[4]BBenC6/SiO2-P. Calix[4]BNaphC6/SiO2-P、tBu-Calix[4]BC6/SiO2-P、tBu-Calix[4]BBenC6/SiO2-P and tBu-Calix[4]BNaphC6/SiO2-P, were prepared by impregnation and immobilization. The synthesis of the materials can be improved by increasing the proportion of SiO2-P. The composition and structure of the novel macroporous silica-based materials were characterized by SEM, FT-IR, TG-DSC, XRD, and BET, respectively. The composite mechanism between Calix[4]BisCrowns and SiO2-P through intermolecular interaction was discussed. The adsorption of Cs(I) and some typical co-existent metals onto the six new macroporous silica-based supramolecular recognition materials were investigated. The impact of contact time and the HNO3concentration on the Cs(I) adsorption was examined. It was showed that in3.0M HNO3, the materials Calix[4]BC6/SiO2-P、 Calix[4]BBenC6/SiO2-P and Calix[4]BNaphC6/SiO2-P had excellent adsorption ability Cs(I), while as tert-butyl group was introduced into the calixarene units, the optimum acidity for the Cs(I) adsorption onto the latter materials was6.0M HNO3or7.0M HNO3. As a result, Calix[4]BBenC6/SiO2-P showed excellent adsorption ability and high selectivety for Cs(I) over all of the tested metals. It was hopeful to separate Cs(I) from the geniune HLW in3.0M HNO3. While tBu-Calix[4]BC6/SiO2-P had excellent selectivety for Cs(I). It might be promising to application in the separation of Cs(I) from HLW of high HNO3concentration. In addition, the structure of the Calix[4]BisCrown materials were characterized by FT-IR and XRD before and after the adsorption of Cs(I). The complexation of Calix[4]BisCrown with Cs(I) was confirmed.The extraction mechanism of Cs(I) with Calix[4]BC6was studied. The results showed that in HNO3solution, Cs(I) was effectively extracted with Calix[4]BC6and formed to the stable complex. The composition of the extracted species of Calix[4]BC6and Cs(I) was determined to be1:1type or1:2type. A1:1type of the complex composition of Cs(I) with tBu-Calix[4]BBenC6was also comformed by the analysis of ESI-MS.