Micellization of Binary Mixture of Amino Sulfonate Amphoteric Surfactant and Octylphenol Polyoxyethylene Ether (10) in Aqueous Solution: Different Electrolyte Effect

The micellization behaviors of binary mixtures constituted by an amphoteric surfactant, sodium 3-(N-dodecyl ethylenediamino)-2-hydropropyl sulfonate, and a nonionic surfactant octylphenol polyoxyethylene ether (10), OP-10, in aqueous solutions containing seven inorganic salts were investigated. The values of mixed critical micelle concentration (cmc M) were determined by both the tensiometry and the UV–vis spectroscopy method using pyrene as a probe. The dependence of cmc M on inorganic salt was established. According to different theoretical models, the components in mixed micelle, interaction parameters between two surfactants, etc. were obtained. Upon adding inorganic salt, the component in real mixed micelle is inferior to the ideal case, indicating nonideal mixing. Different inorganic salts result in the variation of component in mixed micelle. For all mixed surfactant systems, a negative interaction parameter between surfactants shows synergistic effect. Thermodynamic parameters show that the process of micellization is spontaneous, and the addition of inorganic salt promotes the process of micellization. The contribution of micellization may result from three effects: salting-out effect, electrostatic shielding effect, and steric effect. And thermodynamic stability was also discussed. These results will help with understanding the micellization behavior between surfactants and to design surfactant formulations applied in many fields, especially relative to aqueous salt solutions.