Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

Solid-liquid phase equilibrium and physical properties of KH2PO4 in the mixture solution at 298.15 K and 313.15 K were determined by isothermal solution saturation method and moist residues. According to the experimental data, the solubility curves and physical parameters (, ) curves of KH2PO4 - KCl - H3PO4 - H2O systems were plotted. In mixture solution of KCl and H3PO4, the solubility of KH2PO4 increased with the concentration of H3PO4 increasing and decreased with the solubility of KCl increasing because of the same ion effect. For the system of KH2PO4 -KCl - C2H5OH H2O at 298.15K, corresponding phase diagrams and diagrams of physical properties were plotted on the basis of the experimental data, and the initial mass fraction of ethanol were 10%, 30% and 50% in the salt-free binary solvent water + ethanol. In the phase diagrams, there are one invariant point, two univariant curves, and two crystallization regions corresponding to KCl, KH2PO4. In addition, the crystallization region of KH2PO4 is larger than that of KCl, and the two crystallization regions become smaller as the mass fraction of water + ethanol mixture solvent increased. The physical properties of the system KH2PO4 -KCl - C2H5OH - H2O changed regularly with the concentration change of the liquid phase. The equilibrium solids were verified by X-ray diffraction. The measured data and physical property diagrams for the investigated systems can provide the fundamental basis for the industrial production of KH2PO4 by the solvent extraction method.