Typically, the adsorption of surfactants at water/oil interfaces is described by models developed for the most frequently studied water/air interface.
However, the presence of an oil phase leads to interaction between the hydrophobic chains of the surfactant molecules with the oil molecules [1].
On the basis of experimental data for the homologous series of alkyltrimethylammonium bromides (CnTAB) the equilibrium surface tension isotherms at the aqueous solution/alkane interface are discussed. It is shown that the adsorption characteristics are described by different thermodynamic approaches. A model which assumes the co-adsorption of alkane molecules in addition to the CnTAB molecules at the interface can describe the experimental data in the best way [2].
Fig. 1 Dependencies of partial and total surface coverages on the surfactant concentration in aqueous solution. Red lines, octane; blue line, C10TAB; black line, C12TAB; green lines, total surface coverages. Solid and dashed lines refer to the octane – C10TAB and octane – C12TAB, respectively.
1. V.B. Fainerman, N. Mucic, V. Pradines, E.V. Aksenenko and R. Miller, Adsorption of alkyltrimethylammonium bromides at water/alkane interfaces – competitive adsorption of alkanes and surfactants, Langmuir, 29 (2013) 13783–13789
2. V.B. Fainerman, E.V. Aksenenko, N. Mucic, A. Javadi and R. Miller, Thermodynamics of adsorption of ionic surfactants at water/alkane interfaces, submitted to Soft Matter
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