Liquid–Liquid Equilibrium Study for the Ternary System of Water + Acetic Acid + 2-Octanol

Abstract

Excellent extraction ability and easy regeneration of the extractant are highly important for the recovery of acetic acid from water by solvent extraction. In this paper, the extraction capability of octanol isomers and some conventional extractants was investigated. It was found that the extraction capability of 2-octanol was significantly better than that of the traditional extractant isopropyl acetate. The liquid–liquid equilibrium data for the ternary system of water + acetic acid + 2-octanol were measured at different temperatures (293.2, 303.2, and 313.2 K) under 101 kPa. The results showed that the distribution coefficient and selectivity decreased with an increase in acetic acid concentration and the temperature had little impact on the distribution coefficient, suggesting that the extraction could be conducted over a large temperature range. The reliability of the equilibrium data was also verified using the Othmer–Tobias and Hand equations, and the correlation coefficients were all close to 1.0, suggesting that the experimental data was reliable. Furthermore, the NRTL (nonrandom two-liquid) and UNIQUAC (universal quasichemical) models were employed to correlate the experimental data, and the binary interaction parameters of the ternary system were obtained. The results indicated that, for the UNIQUAC model, the root-mean-square deviations between the experimental and simulated data at different temperatures were from 0.63% to 0.94% and those for the NRTL model were all within 0.6%, which indicate that the NRTL model is more suitable for the ternary system of water + acetic acid + 2-octanol.