Adsorption at the liquid-vapor surface of a binary liquid mixture

Area of Science:

• Physical Chemistry
• Surface Science
• Thermodynamics

Background:

• The component with lower surface tension preferentially adsorbs at the liquid-vapor interface in binary liquid mixtures.
• Adsorption in critical binary mixtures near the critical temperature (T(c)) is well-understood, governed by a universal function of the bulk correlation length.
• Quantitative studies of off-critical mixtures are less common due to the complexity of accounting for bulk and surface crossover phenomena.

Purpose of the Study:

• To quantitatively examine liquid-vapor adsorption in off-critical binary mixtures.
• To compare experimental adsorption measurements with existing crossover theory.
• To validate the Kiselev and co-workers' crossover theory for aniline+cyclohexane mixtures.

Main Methods:

• Extensive liquid-vapor ellipsometric adsorption measurements were performed.
• Measurements were conducted on the aniline+cyclohexane mixture at various critical and non-critical compositions.
• Experimental data were compared with the crossover theory developed by Kiselev and co-workers.

Main Results:

• Experimental adsorption data for aniline+cyclohexane were systematically compared with theoretical predictions.
• The study provides a quantitative assessment of adsorption behavior across different mixture compositions.
• The findings offer insights into the crossover from fluctuation-dominated to mean-field dominated regimes.

Conclusions:

• The crossover theory of Kiselev and co-workers provides a framework for understanding adsorption in off-critical mixtures.
• Experimental ellipsometry measurements validate the theoretical model for the aniline+cyclohexane system.
• This work advances the understanding of surface adsorption phenomena in binary liquid mixtures.