Adsorption of ions at the interface oil|aqueous electrolyte and at interfaces with adsorbed alcohol

• The desorption of many electrolytes at the water|oil interface follows Schmutzer’s model.
• The penetration of alcohol groups into the surface layer of water shifts the Gibbs surface.
• The desorption of ions at the water|alcohol interface is decreased compared to water|alkane.
• The electrolyte in the water phase decreases the chemical potential of adsorbed alcohol.
• The exchange of air with oil magnifies the attractive forces acting upon large ions.

We investigate the applicability of the Schmutzer’s model for three types of interfaces: aqueous electrolyte|alkane, aqueous electrolyte|long chained alcohol phase, and aqueous electrolyte|alkane with adsorbed alcohol. The model predicts a strong decrease of the electrolyte desorption at water|alcohol interface in comparison with water|alkane, in quantitative agreement with the tensiometric data. The effect is related to the penetration of the alcohol –OH group into the surface layer of the aqueous solution. The same model predicts a decrease with the electrolyte concentration of the chemical potential of the alcohol molecules adsorbed at the water|oil interface, which results in an increase of the adsorption activity of oil-soluble alcohols, again in quantitative agreement with the experiment. The analysis of the deviations of Schmutzer’s model predictions from the experimental data for large polarizable anions allows making qualitative conclusions for the magnitude of the ion-specific hydrophobic and dispersion forces at water|gas and water|oil interfaces.

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