A strategy for characterizing the surface layer at the liquid-vapor interface of binary liquid mixtures containing non-ionic surfactants: An approach from Gibbs adsorption isotherm

Abstract

Abstract In this work, an alternative physicochemical procedure is presented to characterize the liquid-vapor interface of binary liquid mixtures containing non-ionic surfactants, using the Gibbs adsorption isotherm, the solute activity, and the surface partial molar areas. This model allowed to calculate the moles of solute and solvent present in equilibrium for both bulk and surface phase. The excess surface concentration, relative surface concentration, and molar fraction of both components was also calculated. The results reflected that the excess surface concentration of the solute was not proportional to the adsorption of the solute with the increase in its concentration in the bulky phase. This gives evidence that the dilute solutions were able to saturate the surface layer at an early stage and after it, for the entire concentration range where it remains approximately constant, which showed the existence of a compact molecular arrangement.