COADSORPTION OF ANIONIC AND NONIONIC SURFACTANT MIXTURES AT THE ALUMINA WATER INTERFACE

The adsorption of monodispersed, isomerically pure anionic surfactant, p-octylbenzenesulfonate, and nonionic surfactant, dodecyloxyheptaethoxyethyl alcohol, and their mixtures on alumina was investigated to determine interactions between such surfactants. In a single surfactant system, only the anionic sulfonate was found to adsorb to any appreciable extent. In the mixed surfactant system, the sulfonate was found to induce significant coadsorption of the nonionic surfactant. This was attributed to hydrophobic interaction between the sulfonate and the alcohol at the mineral/solution interface. Adsorption of the sulfonate was also enhanced due to both hydrophobic interaction and the reduction of electrostatic repulsion between sulfonate head groups which are shielded from each other by the nonionic surfactant molecules.