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

J Colloid Interface Sci. 2014 Aug 15:428:257-66. doi: 10.1016/j.jcis.2014.04.063. Epub 2014 May 9.

Abstract

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.

Keywords: Adsorption of alcohols; Brine; Gibbs dividing surface; Hofmeister series; Hydrophobic gap; Interfacial tension; Ion hydration; Ion-free layer; Surface ion distribution; Water|oil interface.