TI+/NA+ COMPETITIVE-BINDING AT THE SURFACE OF DODECYL-SULFATE BRIJ 35 MIXED MICELLES

Competition between Tl+ and Na+ ions to bind with the surfaces of mixed micelles composed of dodecylsulfate and Brij 35 surfactants has been studied by a fluorescence-quenching technique. The quenching data are interpreted in terms of the pseudophase ion-exchange formalism. It is found that the competitive binding is well described by a unique K( Tl+ Na+) = 2.6 ± 0.2 selectivity coefficient irrespective of the micelle's composition within the range considered (mole fraction of the ionic component in the micelle between 1 and 0.5). The results further reinforce previous conclusions obtained in a cationic/nonionic micellar system [E. Abuin and E. Lissi, J. Colloid Interface Sci.143, 97 (1991)] by showing that selective binding of counterions to mixed micelles is almost totally related to the nature of the exchanging counterions and depends very little on the composition of the micelles. © 1992.