Emulsification of calix[4]arenes bearing four chains and transportation of cesium ion through liquid surfactant membrane

Resorcinol-type calix[4]arenes bearing four alkyl side chains ([4]Ar-R(n)) have been applied as a liquid surfactant-membrane in the concentration process of Cs+. [4]Ar-R(n) formed a highly stable water-in-oil (w/o) emulsion for a mixture of toluene and HCl solution, and the w/o emulsion became a w/o/w emulsion by stirring it in a Cs+ solution. The Cs+ in the outer aqueous solution was transported through the liquid surfactant-membrane of w/o/w emulsion into the inner HCl solution. [4]Ar-R(6) was the most effective emulsifier capable carrying Cs+ in the [4]Ar-R(n) bearing alkyl chains of various lengths. The final amount of the transported Cs+ was 9 times as much as the molar of [4]Ar-R(6) in 100 min at the initially 10 times molar Cs+ in the outer solution (turnover number: 9). Moreover, the Cs+ was transported selectively from a mixture of alkali metal ions (Cs+, Na+, and K+) by using 2x10(-4) mol of [4]Ar-R(6).