Solid–Liquid Phase Equilibria of the KH₂PO₄–KCl–H₃PO₄–H₂O and KH₂PO₄–KCl–C₂H₅OH–H₂O Systems at T = (298.15 and 313.15) K

Abstract

Solid−liquid phase equilibrium and physical properties of KH 2 PO 4 in the mixture solution at 298.15 and 313.15 K were determined by an isothermal solution saturation method and moist residues. According to the experimental data, the solubility curves and physical parameter (μ, ρ) curves of KH 2 PO 4 −KCl−H 3 PO 4 −H 2 O systems were plotted. In a mixture solution of KCl and H 3 PO 4 , the solubility of KH 2 PO 4 increased with the increasing concentration of H 3 PO 4 and decreased with the increaing solubility of KCl because of the same ion effect. For the system of KH 2 PO 4 − KCl−C 2 H 5 OH−H 2 O 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 was 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 and KH 2 PO 4 . In addition, the crystallization region of KH 2 PO 4 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 KH 2 PO 4 −KCl−C 2 H 5 OH−H 2 O 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 KH 2 PO 4 by the solvent extraction method.

Thermodynamic Modeling the Solid–Liquid Phase Equilibrium of a Water–Methanol–Potassium Dihydrogen Phosphate Ternary System with a Mixed-Solvent Electrolyte (MSE) Model

“…Zhou et al chose ethanol as an antisolvent and determined the solubility of MKP in the H 2 O–C 2 H 5 OH solvent at 293.2–323.2 K and constant pressure by the static equilibrium method. Cao et al used ethanol as an antisolvent to measure the phase equilibrium and physical property data of the KCl–KH 2 PO 4 –C 2 H 5 OH–H 2 O system at 298.15 K by the isothermal solution saturation method and moist residues. Yang et al proposed the method of introducing ethylene glycol to reduce the solubility of MKP.…”

Phase Behavior of N-Methylpyrrolidone + MCl (M = Na, K, Rb, Cs) + H2O Systems at 288.2, 298.2, and 308.2 K

“…Therefore, researchers have done a lot of research on the phase equilibrium of inorganic salts in organic solvent–water systems. For example, the solubilities of NaCl/KCl/LiCl/LiBr + CH 3 OH/C 2 H 5 OH/CH 3 COCH 3 + H 2 O , in the temperature range of 293.15–333.15 K were determined. The solubilities of MCl (M = Na, K, Rb, Cs) in ethylene glycol/glycerin + H 2 O at different temperatures were discussed based on the structure and properties of the organic solvent. − For the inorganic salt–alcohol–water ternary system, the structure of alcohols has a great influence on the properties of the solution.…”