Equilibrium Solubility Determination and Modeling of Thifensulfuron Methyl in Four Solvent Mixtures

This study used five pure solvents as raw materials and formed four sets of mixed solvents by mixing methanol, ethanol, n-propanol, and N,N-dimethyl formamide (DMF) in water. According to the principle of the isothermal static state, the reaction temperature was increased from 278.15 to 323.15 K at 5 K intervals. Under normal pressure (101.1 kPa) and at a constant the mole fraction of the solute, the equilibrium solubility of thifensulfuron methyl was obtained using high-performance liquid chromatography (HPLC). The influence of temperature on the solute cannot be ignored. Low to high amounts of thifensulfuron methyl are dissolved at low to high temperature. The difference was that the water content of the mixed solvent was repulsive to the dissolution of the solute. With the increase in the water content, the mole fraction of thifensulfuron methyl decreased. At any temperature, the same proportion of water was added to the four organic solvents. Compared with other solvents, the mixture of DMF and water had an absolute dissolution advantage. In addition, the Jouyban–Acree model, the van’t Hoff–Jouyban–Acree model, and the Apelblat–Jouyban–Acree model were used to calculate the solubility of thifensulfuron methyl. The obtained average relative deviations were lower than 1.51% for correlative studies. The acquisition of solubility helps to obtain solubility parameters, which is a measure of intermolecular forces. Solubility is required in the fields of recrystallization and fractional crystallization in the chemical industry and the synthesis and separation of compounds.