Mixed Micelle Formation and Co-adsorption of Anionic/Non-ionic Surfactant Mixtures on Rutile

Abstract

Mixed micelle formation between the anionic surfactant p-dodecyl benzene sulphonate and the non-ionic surfactants Brij-58, Brij-78 and Brij-99, having the same number of oxyethylene units but a varying number of hydrophobic groups, has been studied using surface tension and NMR spectroscopic measurements. Both hydrophobic–hydrophobic and hydrophilic–hydrophilic interactions play an important role in mixed micelle formation leading to greater non-ideality. The effect of mixed micelle interactions on the adsorption of these surfactants from their mixtures on rutile have been investigated using adsorption and zeta potential measurements. Adsorption above the CMC level is dictated by the relatively higher tendency of mixed micellization over mixed aggregation at the solid/liquid interface.