Experimental measurements and modified Fu model for surface tension of imidazolium ionic liquids with alcohol and water

Investigation of interfacial characteristics of ionic liquids (ILs) and their ternary blends with conventional solvents is critical for chemical applications; yet, comprehensive datasets remain scarce. Here, the surface tension (ST) of ternary mixtures comprising ILs ([C 12 mim][Cl] or [C 18 mim][Cl]), short-chain alcohols (methanol and ethanol), and water was systematically characterized across the full compositional range using the pendant drop method. The synthesized ILs were structurally confirmed via Fourier-transform infrared (FTIR) alongside nuclear magnetic resonance (NMR) spectroscopy. Results revealed that alcohol addition markedly decreases ST, with ethanol exerting a more pronounced effect than methanol, while elongation of the IL cationic alkyl chain further reduces ST via increased hydrophobic orientation of the alkyl tails at the air–liquid interface. To address experimental challenges in ternary characterization, the Fu model was modified (MFu) and optimized using a genetic algorithm (GA). Literature data for [EMIM][DEP] and [MMIM][DMP] in combination with water and 1-propanol or 2-propanol were also incorporated for model validation and compared with the Jouyban–Acree equation. The MFu model exhibited high predictive accuracy for both the present experimental data and literature datasets, with AARD% values typically below 5% for the modified ST (σ*) correlations and below 1.5% for ternary mixtures’ ST predictions, with coefficients of determination R² > 0.99 for the literature systems. The model accurately captured both negative and positive deviations from ideality and enabled reliable prediction of ST even for ternary systems containing solid ILs. This integrated experimental–modeling framework establishes a robust predictive tool for IL–alcohol–water systems, supporting the development of IL-based solvents for sustainable chemical engineering.