Effect of Oleic Acid on the Dynamic Interfacial Tensions of Surfactant Solutions

Abstract

The dynamic interfacial tensions (IFTs) of three different types of surfactant solutions, cationic surfactant hexadecyl trimethylammonium (CTAB), anionic surfactant sodium dodecyl benzenesulfonate (SDBS), and non-ionic surfactant Triton X-100 (TX-100), against model oil containing oleic acid (OA) have been investigated by a spinning drop interfacial tensiometer. The influences of the OA concentration and addition of alkali have been studied. The experimental results show that OA added to the oil phase has a significant effect on interfacial behaviors of surfactant solutions. An obvious synergistic effect on reducing IFT can be observed for low-concentration cationic surfactant CTAB solution because the tight mixed adsorption films will be formed through electrostatic attraction between CTAB and OA molecules. However, the synergistic effect will disappear at a high surfactant concentration by the formation of mixed micelles. For the anionic surfactant SDBS system, the mixed adsorption of SDBS and OA molecu...