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

Abstract

The solubility measurement of potassium dihydrogen phosphate (MKP) in a water−methanol system is of great significance for the salting-out crystallization of MKP. The solubility of MKP in the H 2 O−CH 3 OH solution was determined by the static equilibrium method in the range of 283.15−343.15 K, and the molar fraction of CH 3 OH varied from 0.0588 to 0.6923. The mixedsolvent electrolyte model (MSE) was used to regress the experimental results, and new parameters were obtained. Based on it, the thermodynamic model of the H 2 O−CH 3 OH−MKP system was established, which is in good agreement with the experimental results, with a relative average absolute deviation of 6.46%. Then, the change in the ion concentration and the activity coefficients in the system were predicted by the thermodynamic model. Finally, the Pixact Crystallization Monitoring (PCM) system and a scanning electron microscope (SEM) were used to observe the crystallization process and the morphology of MKP in the H 2 O− CH 3 OH system, respectively.