Liquid-Liquid Equilibria in Aqueous Mixtures of Phosphoric Acid with Two Primary Aryl Alcohols at T = (298.2, 308.2, and 318.2) K: Measurements and Correlation

This comparative study reports the measured liquid-liquid equilibrium (LLE) data and phase diagrams for the two ternary systems of {water + phosphoric acid + aryl alcohols (2-phenylethanol and 3-phenylpropanol)} at temperatures of (298.2, 308.2, and 318.2) K and atmospheric pressure (p = 0.1 MPa). Solubility data and mutual solubilities between the aryl alcohols and water were determined using turbidity measurements (cloud point titration method). Tie-line data were measured through acid-base titration and refractive index measurements. The results were validated through the Karl-Fischer titration method and mass balance calculations. The studied systems displayed Treybal's type-1 phase behavior, having one liquid pair that is partially miscible. The Othmer-Tobias correlation equation was applied to check the reliability of the tie lines. The experimental LLE data were correlated using the NRTL and UNIQUAC thermodynamic models, and the model binary interaction parameters between each pair of components were calculated. The results show the ability of these correlation models in representing the LLE data with acceptable average root-mean-square deviation (rmsd) values. As a result, the effect of temperature on the immiscibility region for the studied systems is small. For the studied systems, the separation factors are larger than unity, which means that the aryl alcohols have potential for separation of phosphoric acid from water.