This study presents the influence of molecular interaction and molecular ordering on the physicochemical properties and the excess values of the binary mixtures containing several alkanediols and a symmetric cyclic ketone (cyclopentanone) at 298.15 K and 101.3 kPa. Thus, experimental values of the permittivity, density, and refractive index were determined for the alkanediol−cyclopentanone systems over the entire range of mole fraction. A series of straight-chain primary alkanediols, each having two primary hydroxyl groups, were 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, and 1,5pentandiol. Meanwhile, the other alkanediols (1,2-propanediol and 1,3-butanediol) possesses both primary and secondary hydroxyl groups. The measured data were coherently analyzed by the conventional methods, leading to different excess values. The calculated excess quantities indicate the existence of hydrogen-bonding network in the studied systems. The excess values of relative permittivity, molar volume, and Kirkwood correlation factors were found to be negative for all of the binary mixtures, suggesting the formation of multimer structures, the reduction of the effective dipole moments, and the opposite alignment of dipoles in the mixtures. In order to support the experimental data, theoretical calculations were performed using density functional theory (DFT). The optimization of the structures were performed by the B3LYP/6-311G (d,p) DFT level.

Ternary liquid−liquid equilibrium (LLE) data were measured for the {water + phosphoric acid + aromatic esters (benzyl acetate, benzyl benzoate, dimethyl phthalate, and diethyl phthalate)} systems at T = 298.2 K and P = 101.3 kPa. Moreover, to investigate the effect of temperature on LLE behavior, the LLE measurement was performed for a ternary system of (water + phosphoric acid + benzyl acetate) at three different temperatures (298.2, 308.2, and 318.2) K and the above pressure as well. Among the studied ternary systems, only the phase diagram for the system containing benzyl acetate clearly displays type-1 LLE behavior. The quality of the tie-line data was checked through the Othmer−Tobias correlation equation. The experimental data were correlated using the UNIQUAC model. For all of the systems studied, the separation factors are larger than unity, which means that the chosen aromatic esters might have the potential to extract phosphoric acid from water. As the solubility of the acid in benzyl benzoate is poor and it might be hydrolyzed in water after having been rested for a while, it is not a suitable solvent in the recovery of the acid from water.

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.