Determination and Correlation of Liquid–Liquid Equilibrium Data for the n -Hexane + Pyridine System Separated by Different Alcoholamine Extractants

This study investigates the separation of n-hexane and pyridine using three alcoholamine solvents, monoethanolamine (MEA), isopropanolamine (MIPA), and 2-(2-aminoethoxy)ethanol (DGA), as extractants. Liquid–liquid equilibrium (LLE) data for ternary systems {n-hexane + pyridine + MEA/MIPA/DGA} were experimentally determined at 298.15 K and 101.3 kPa. Based on the equilibrium data, ternary phase diagrams were constructed and the distribution coefficients (D) and selectivity factors (S) were calculated for each system. The experimental data were correlated using the nonrandom two-liquid (NRTL) activity coefficient model, and the regressed binary interaction parameters were validated through Gibbs energy topology analysis. The results confirm that all systems satisfy thermodynamic consistency, verifying the reliability of the fitted model parameters. Finally, the obtained results can provide a basis for the simulation and optimization of its separation process.