The behaviour of surfactants in concentrated acids 6. Micellization and interfacial behaviour of n-hexadecyltrimethylammonium bromide in mixtures of methane sulphonic acid and concentrated sulphuric acid |
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| Institution: | 1. Centre de Biochimie Structurale, INSERM, CNRS, Université de Montpellier, France;2. Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan;3. Institut Laue Langevin, Institut de Biologie Structurale, CNRS, CNRS, UGA, Grenoble, France;4. Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan;5. Research Reactor Institute, Kyoto University, Kumatori, Sennan-gun, Osaka 590-0494, Japan.;1. Centro de Estudios Parasitológicos y de Vectores (CONICET, UNLP), Bvd. 120 s/n entre 60 y 64, 1900 La Plata, Buenos Aires, Argentina;2. Dirección Regional Patagonia Norte, Administración de Parques Nacionales (APN - CONICET), 8400 S.C. de Bariloche, Argentina;3. Centro de Estudios Aplicados a la Conservación (CENAC), Parque Nacional Nahuel Huapi (APN), 8400 S.C. de Bariloche, Argentina;4. Grupo de Estudio de Mamíferos Terrestres (GEMTE), Instituto Patagónico para el Estudio de los Ecosistemas Continentales (IPEEC-CONICET), Bvd. Brown 2915, 9120 Puerto Madryn, Chubut, Argentina;5. Universidad Nacional de la Patagonia San Juan Bosco, Sede Puerto Madryn, Chubut, Argentina;6. Centro de Investigaciones y Transferencia del Noroeste de la Provincia de, Buenos Aires – CITNOBA (CONICET-UNNOBA- UNSAdA), Ruta Provincial 32 Km 3.5, 2700 Pergamino, Argentina;1. State Key Laboratory of Chemical Resource Engineering, Beijing 100029, PR China;2. College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, PR China;3. Faculty of Science, Beijing University of Chemical Technology, Beijing 100029, PR China |
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| Abstract: | The surface and interfacial activity of cationic surfactants depends on the polarity of the bulk phase. If concentrated sulphuric acid is mixed with water, physical properties such as density, and surface and interfacial tension go through a maximum as the molar composition is changed. Also the properties of surfactants, i.e. surface activity and CMC, do not vary linearly in such aqueous mixtures. However, if concentrated sulphuric acid is mixed with methane sulphonic acid we find a linear relationship.The adsorption isotherms of n-hexadecyltrimethylammonium bromide at the surface (interface) of mixtures of H2SO4 and CH3SO3H/air (n-hexane) and the CMC were determined for various compositions of the acid phase and approximated by the Von Szyskowski equation. The change in the energy of micelle formation, — ΔMG, and the energy of adsorption, — ΔAG°, were calculated as a function of solvent composition. The surface concentration as a function of bulk concentration, the maximum surface coverage and the percentage surface concentration were also calculated.We found a linear dependence of the CMC, and of the lowering of σ and γ at the CMC, on the mole fraction of the acid phase. Also the constant A of the Von Szyskowski equation decreases and the logarithm of B increases linearly with the mole fraction of methane sulphonic acid. Therefore it is possible to calculate all the data needed for the characterization of systems of different acid composition. A special pattern was found for acid mixtures with XCH3SO3H < 0.1. This can be explained by the transformation of micelle structure and the possibility that micelles can solubilize hydrocarbons in this region. |
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