Comparative Study of Liquid–Liquid Equilibria for Aqueous Mixtures of Phosphoric Acid with Two Structurally Similar Carbonyl Compounds: Measurement and Correlation

Abstract

This comparative study demonstrates the experimental liquid–liquid equilibrium (LLE) data for the aqueous mixtures of phosphoric acid with the two structurally similar carbonyl compounds (i.e., dipropyl ketone and ethyl butyrate) at T = 298.2, 308.2, and 318.2 K and p = 101.3 kPa. Despite the close structural similarity between them, however, they belong to different chemical classifications. Thus, the extractive features of the selected carbonyl solvents were analyzed and compared. Both the studied systems were displayed as Treybal’s type-1 liquid–liquid phase diagrams. The biphasic region was found to be larger for the system containing a less polar solvent (ethyl butyrate), but the acid distribution coefficient and selectivity values were almost similar for both the carbonyl solvents. The measured tie-line data were satisfactorily fitted by the UNIQUAC activity coefficient model. Values of the model binary interaction parameters were optimized using the MATLAB fminsearch function that applies the Nelder–Mead algorithm. The reliability of the experimental tie-line data was determined through the Othmer–Tobias plot. The LLE data and selectivities specify that both the carbonyl solvents were found to be promising extractants for the separation of phosphoric acid from its dilute aqueous solutions.