Extraction of Isobutanol from Aqueous Solution by Four Solvents: Liquid–Liquid Phase Equilibrium Measurements and Thermodynamic Modeling Studies

To solve the problem of treating isobutanol-containing wastewater in industrial production, four relatively green solvents (hexamethyldisiloxane, isopentyl acetate, ethyl acetate, and propylene carbonate) were selected as the extractants for the separation of water and isobutanol. Liquid–liquid equilibrium (LLE) data for water + isobutanol + hexamethyldisiloxane/isopentyl acetate/ethyl acetate/propylene carbonate were measured at 298.2 K and 101.3 kPa. The extraction performance of the four extractants was evaluated by the distribution coefficient ( D ) and separation factor ( S ). Meanwhile, the experimental LLE data were fitted using NRTL and UNIQUAC models to obtain the regression parameters. Mixed-surface analysis based on Gibbs energy topology verified the reliability of the binary interaction parameters. The root-mean-square deviation (RMSD) of the NRTL and UNIQUAC models was less than 0.0045 and 0.0059, respectively, which indicated that the NRTL and UNIQUAC models were suitable for the study of this system.