Effect of partial vapor pressure on the co-adsorption of surfactants and hexane at the water/hexane vapor interface

•The adsorption of surfactants at the water/air interface is enhanced due to the presence of alkane vapor in the air phase.•The alkane vapor effect can be described in terms of a co-adsorption of alkane molecules.•The alkane vapor effect depends on the partial vapor pressure.•A thermodynamic model developed for surfactant mixtures described the co-adsorption process.•The alkane vapor co-adsorption effect depends on the surface activity and type of the surfactant.

The adsorption of surfactants from aqueous solution at the water/air interface is changed when the air phase contains hexane vapor. This co-adsorption of surfactant and hexane depends on the hexane vapor pressure. A thermodynamic model developed for the adsorption of surfactant mixtures can be adapted to the present situation. The surfactants studied were SDS, C12TAB and C12DMPO, and the dependence of their adsorption characteristics on the partial hexane vapor pressure was determined. The co-adsorption of hexane from the vapor phase increases the surface activity of the adsorbing surfactants.

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