A Thermodynamic Model on Liquid–Liquid Interfacial Adsorption

In recent work [Qi et al., Langmuir 2023, 39, 507–518], we proposed a thermodynamic surface adsorption model, called the “surface aggregation adsorption” (SAA) model, which can predict the surface tensions and compositions of multicomponent single-phase liquid mixtures (homogeneous solutions). In the current work, based on the concept of the SAA model, a thermodynamic model for liquid–liquid interfacial adsorption, called the “interfacial aggregation adsorption” (IAA) model, was developed, which can predict the interfacial compositions of multicomponent (oil, water, and cosolvents) two-phase systems using only the SAA model parameters of binary solutions of one cosolvent with other components. Its rationality was examined, taking the ternary two-phase system of benzene (oil), water, and ethanol (cosolvent) as an example. The IAA model predicts that ethanol preferentially accumulates in the interfacial layer and its interfacial content changes with bulk compositions. This work provides a possible predictive model for adsorption at liquid–liquid interfaces, which helps to understand the interfacial adsorption behavior.