Solid–Liquid Equilibria in the Quaternary System K+//H2PO42–, SO42–,Cl––H2O at 298.2 K and 323.2 K

Abstract

The solubility data of the quaternary system K+//H2PO42–, SO42–, Cl––H2O is basically required for the design and optimization of the crystallization process of KH2PO4 which is produced by the solvent extraction method using the wet-process H3PO4 and KCl as the raw materials. In this study, the solubility data of the quaternary system K+//H2PO42–, SO42–, Cl––H2O at 298.2 K and 323.2 K were investigated by the isothermal solution saturation method. The solubilities of salts and equilibrium solid phases were determined. The phase and water content diagrams were constructed based on the experimental results. The appearance of the phase diagram at 323.2 K is similar to that at 298.2 K, while the crystallization area of each salt varies slightly with the changing of temperature. The phase diagrams both contain one quaternary invariant point, three univariant curves, and three crystallization regions corresponding to KH2PO4, K2SO4, and KCl. The crystallization region of K2SO4 is the largest, while that of KCl i...