Extraction Equilibrium of Typical Alkali Metals with a Macrocyclic Calixbiscrown Derivative in Two-Phase System HNO₃/o‑Nitroanisole and HNO₃/HCCl₃

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.