Solubility Determination and Model Evaluation of Triethylamine Hydrochloride in Three Binary Mixed Solvents

In this study, the saturated solubility of triethylamine hydrochloride (TEA·HCl) was determined using the static method in binary mixed solvents ((1-Butanol, dimethyl sulfoxide (DMSO), 1-Octanol) + dimethyl carbonate (DMC)) at temperatures ranging from 298.15 to 333.15 K and ambient pressure (p = 0.1 MPa). Quantum chemistry calculations were performed to analyze the dissolution process among different solvents. Results showed that the obtained solubility data correlated well with five equations. Evaluation of solubility data was carried out by mean Average Relative Deviation (ARD) and Root-Mean-Square Deviation (RMSD). The findings indicated that the modified Apelblat model demonstrated the strongest correlation among the five models. The ARD and 10⁴ RMSD were 1.39% and 2.61, respectively. Subsequently, the Gibbs energy, enthalpy, and entropy of TEA·HCl dissolved in each mixed solvent can be determined by applying van’t Hoff equations, revealing an endothermic and entropy-driven dissolution process. The experimental results indicated that the solubility of TEA·HCl in the selected binary solvents increased with the increasing temperature and decreased with the increasing molar fraction of DMC. The solubility sequence in various systems was explained in terms of the solvation free energy. The solubility values, model parameters, and thermodynamic properties of TEA·HCl in different mixed solvents can be obtained through experimentation, providing foundational support for its preparation, crystallization process, and further theoretical research.