Research on the Crystallization Thermodynamics of Diammonium Hydrogen Phosphate in H2O-Ethylene Glycol Binary System

Diammonium Hydrogen Phosphate (DAP) serves as a highly efficient compound fertilizer and industrial raw material. However, commercial industrial—grade DAP commonly contains numerous impurities and has drawbacks in terms of particle size distribution and shape. As a result, there is a need to research the crystallization of DAP in H2O–ethylene glycol (EG) binary systems to seek possible remedies. This article presents the outcomes of an all—inclusive research into how the proportions of the H2O–EG binary system impact the thermodynamics of DAP. Five established models such as the Apelblat model, Van’t Hoff model, Redlich–Kister model, Polynomial model, and Jouyban-Acree–Van’t Hoff model are adopted in this research. They are used to correlate the experimental data and determine the thermodynamic parameters involved in the crystallization process of DAP. Moreover, the Mersmann and Barata models are used for calculating the solid–liquid surface tension (γ) as well as the crystal surface entropy factor (f) of DAP in the relevant systems. The results show that the dissolution of DAP represents an endothermic and non-spontaneous event, mainly propelled by alterations in enthalpy. Among the models considered, the Polynomial model seems to afford a more in-depth comprehension of DAP’s solubility behavior. The outcomes of this research furnish essential data for optimizing and enhancing the production process of DAP. This, in turn, can lead to improvements in both the quality and efficiency of DAP production.