Measurement and Thermodynamic Analysis of Liquid–Liquid Equilibrium for Ternary Systems of Water, Methacrylic Acid, and n-Alkyl Acetates

Amid growing interest in biomass-derived fuels, the environmental impact of methacrylic acid (MAA) industrial synthesis─particularly its wastewater generation─has necessitated efficient aqueous phase separation strategies for process optimization and ecological sustainability. This study systematically characterized the liquid–liquid equilibrium (LLE) of water-MAA-ester solvent ternary systems under standard conditions. Thermodynamic correlations using nonrandom two-liquid (NRTL) and UNiversal QUAsi Chemical (UNIQUAC) models (both yielding 1% root-mean-square deviation (RMSD%)) demonstrated exceptional predictive accuracy for MAA recovery, with butyl acetate exhibiting optimal separation performance. Rigorous statistical validation of LLE data and independent verification of binary interaction parameters ensured the reliability of model predictions.