A new mesoporous adsorbent iPCalixC5X containing 1,3-alternate calix[4]­crown-5 derivative iPCalixC5 was prepared by vacuum suction. It was immobilized into the pores and channels of XAD-7, a polar carrier containing polyalkyl ester, by introduction and self-assembly. The uptake of Rb, Cs, K, and a total of 20 coexisting metals onto iPCalixC5X was investigated in the range of 0.4–6.0 M HNO3. The separation factor (SF) of Rb with Cs was 186.5 in 1.0 M HNO3 and 95.83 in 3.0 M HNO3. The Rb adsorption capacity was 0.5239 mM/g under the conditions of 298 K, 3.0 M HNO3, and a contact time of 120 min. The removal efficiency was greater than 99.6% for Rb and less than 0.22% for Cs. The Rb adsorption data fitted well with the Langmuir model, reflecting the monolayer adsorption mechanism. The thermodynamic parameters ΔH°, ΔG°, ΔS°, and some fundamental chemical engineering data of Rb adsorption were obtained. Efficient Rb removal from Cs-containing effluents by iPCalixC5X is promising.

A neutral extractant, tetra(tert-butyl)-calix­[4]­bis­[(4,4′-dimethyl-1,2-phenelyene)-crown-6] (TTCalixB6), was prepared. The extraction equilibrium of Cs­(I), Na­(I), K­(I), and Rb­(I) and some coexisting metals Sr­(II), Ba­(II), Fe­(III), and Ru­(III) with TTCalixB6 was investigated in the range of 0.42–6.0 M HNO3. The effects of two types of organic diluents o-nitroanisole, an electron donor, and chloroform, an electron acceptor, on the extraction of TTCalixB6 were examined. It showed a high extraction ability for Cs­(I) in HNO3/o-nitroanisole over others in HNO3/chloroform. The association of TTCalixB6 with HNO3 and chloroform through hydrogen bonding was the reason why Cs­(I) extraction decreased in HNO3/chloroform. The composition of Cs­(I)-extracted species was a 1:1 type of the complex, CsNO3·TTCalixB6, determined by electrospray ionization mass spectrometry. More than 98% of Cs­(I) alone with less than 5% of Rb­(I) were extracted with TTCalixB6/o-nitroanisole based on a separation framework. The thermodynamic parameters ΔH°, ΔG o, and ΔS° and some fundamental chemical engineering data of TTCalixB6 extraction were obtained. TTCalixB6/o-nitroanisole is promising to apply in Cs­(I) removal from a high-level liquid waste.