In order to find an effective and reliable method for separating mixed ion-exchange resins, the flotation method was tested with the aid of a surfactant. Cationic surfactants selectively bound acidic resins in the presence of basic resins, while anionic surfactants were preferentially bound on basic resins rather than acidic resins. Only the surfactant-adsorbed resins floated in aqueous solution, so that easy separation and recovery of mixed resins could be achieved. Surfactant adsorption was examined by elemental analysis and surfactant titration, and the recovered resins were identified by SEM. Finally, the flotation method was applied to the sensing of surfactants in aqueous solution. (C) 2002 Elsevier Science B.V. All rights reserved.