Liquid-liquid equilibrium study for the system (water plus phosphoric acid plus propylene carbonate) at different temperatures

Phase equilibria of the system (water + phosphoric acid + propylene carbonate) were investigated and experimental data for liquid-liquid equilibrium (LLE) were obtained at T = (298.2, 308.2 and 318.2) K and atmospheric pressure. Type-1 was demonstrated for the LLE ternary mixture. Phase relocation was observed in high phosphoric acid concentration at every temperature and critical densities were calculated. The UNIQUAC and NRTL thermodynamic models were applied to correlate the experimental tie-line results. The Othmer-Tobias and Hand equations confirmed that the experimental tie-line points were reliable. Distribution coefficients and separation factors were determined over the biphasic area. The effect of temperature on the solubility curves and distribution coefficients was found to be observable at the temperatures studied. The average rmsd (root mean square deviation) values between the experimental and calculated mass fractions were 0.89% and 2.73% for the UNIQUAC and NRTL models, respectively. The models produced values close to those of the experimental tie-lines. (C) 2016 Elsevier Ltd.