Measurement and Correlation of Liquid–Liquid Equilibrium Data for Extracting Acetic Acid from Water Using a Mixed Solvent Containing <i>n</i> -Hexane + Isopropyl Acetate + Methyl Ethyl Ketone

The mixed-solvent extraction–distillation method is widely employed for industrial acetic acid (HAc) recovery, and the water content in the extract critically determines the energy required for downstream distillation. Consequently, obtaining reliable liquid–liquid equilibrium (LLE) data for a mixed-solvent/HAc/water system is essential to optimize process energy consumption. This study focused on determining comprehensive LLE data, assessing predictive modeling, and analyzing process performance. Experiments were carried out at 298.15 K and 101.33 kPa for two ternary systems, n-hexane (HEX) + isopropyl acetate (IPAC) + H2O and methyl ethyl ketone (MEK) + IPAC + H2O, and for a HEX + MEK + HAc + IPAC + H2O quinary system over the temperature range of 298.15–318.15 K. Both NRTL and UNIQUAC thermodynamic models yielded RMSDs below 0.015 for all systems. Detailed analysis of the solvent composition, feed concentration, and phase ratio effects showed significant impacts on the water content in the organic phase and extraction efficiency. Further Aspen simulations validated the accuracy of NRTL model parameters with all deviations in the predicted water content and extraction efficiency limited to 0.0073 and 8.84%, respectively. These results provide accurate LLE data and actionable guidelines for optimizing HAc recovery processes in the industry.