Extraction of Diethylene Glycol Butyl Ether from Aqueous Solutions Using Acetate Esters: Liquid–Liquid Equilibrium and Thermodynamic Modeling of Ternary Systems

To separate diethylene glycol butyl ether (DGBE) from water, liquid–liquid equilibrium data of water-DGBE-ethyl acetate/n-propyl acetate/n-butyl acetate ternary systems were measured. Distribution coefficient (D) and separation factor (S) were calculated to evaluate extraction capacity, proving that ethyl acetate performs best. Experimental data were correlated with NRTL and UNIQUAC models to obtain binary interaction parameters, among which UNIQUAC matches measurements better. Thermodynamic consistency checks were performed using the GMcal_TieLinesLL program; the results satisfied the Gibbs phase equilibrium stability criteria, demonstrating the reliability of the model parameters. σ-Profile analysis reveals that ester solvents rely on ester hydrogen-bond sites and van der Waals forces for extraction, accounting for their superior separation effect microscopically. This work provides theoretical guidance and experimental data for acetate extractant selection and relevant industrial processes.