Resorcinol-type calix[4]arenes bearing four alkyl side chains ([4]Ar-Rn) have been applied as a liquid surfactant-membrane in the concentration process of Cs+. [4]Ar-Rn 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-R6 was the most effective emulsifier capable carrying Cs+ in the [4]Ar-Rn bearing alkyl chains of various lengths. The final amount of the transported Cs+ was 9 times as much as the molar of [4]Ar-R6 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 2 × 10−4 mol of [4]Ar-R6.

Trimeric-type anionic surfactants (3C n taAm, where n is a hydrocarbon chain length of 8, 10, or 12) with three hydrocarbon chains and three carboxylate headgroups were synthesized from tris(2-aminoethyl)amine, and their properties were investigated by surface tension, electrical conductivity, dynamic and static light-scattering, fluorescence of pyrene, and emulsification power techniques. The critical micelle concentrations (CMC) of 3C n taAm were 0.00092-0.00834 mmol dm −3 , and the surface tensions at the CMC were 33.3-39.9 mN m −1 . The areas per molecule occupied by 3C 10 taAm and 3C 12 taAm were extremely small, showing they were highly compact at the air/water interface. In addition, adsorption or micellization behavior of 3C n taAm was estimated by parameters such as pC 20 (the efficiency of surface adsorption), CMC/C 20 (the ease of adsorption relative to the ease of micellization), and ∆G M o (Gibbs energy of micellization). Dynamic and static light-scattering measurements of 3C n taAm showed a hydrodynamic radius of 45-61 nm above the CMC and aggregation numbers of 10-82 at the CMC, respectively. The fluorescence intensity ratio of the first to the third band in the emission spectra of pyrene started to lower from far above the CMC for 3C 8 taAm and 3C 10 taAm, and below the CMC for 3C 12 taAm. This suggests that loose micelles or premicellar aggregates are formed in solutions. Mixtures of aqueous solutions of 3C n taAm and toluene formed oil-in-water-type emulsions, and the stabilizing abilities were in the order of 3C 8 taAm > 3C 10 taAm > 3C 12 taAm. The degree of emulsification of 3C 8 taAm remained at 69% after 24 h of standing. Thus, 3C n taAm exhibited unique properties superior to monomeric or dimeric surfactants that were significantly influenced by their hydrocarbon chain lengths.

No abstract

No abstract

No abstract