Abstract: The surface tension and adsorption of liquid mixtures have been widely studied, but there is still a lack of universal thermodynamic prediction models. Recently, we proposed a predictive model, called the “surface aggregation adsorption(SAA)” model, which has two parameters with definite physical meaning, i.e., the adsorption equilibrium constant(K)and the average surface aggregation number(n). The SAA model can predict the surface tension and composition of multicomponent liquid mixtures using the model parameters of corresponding binary systems. However, its applicability needs to be examined, especially for the systems with four or more components. In the current work, the surface tensions of ternary, quaternary, and quinary mixtures composed of iso-propanol(iPrOH), water, n-decane(DA), ethanol(EtOH), and n-butanol(nBuOH)were determined under different bulk compositions. A good agreement between the model prediction and experimental results was observed, confirming the rationality and universality of the SAA model. Based on the SAA model, the surface adsorption behavior of liquid mixtures was investigated. For a given liquid mixture, adding another liquid will weaken the relative adsorption tendency of the component with the highest n value in the original system, while enhance that of the component with the lowest n value. This work has deepened our understanding of the surface adsorption behavior of liquid mixtures.

Key words: liquid mixture, surface tension, surface adsorption, surface aggregation, thermodynamic model