Thermodynamic models for determination of solid-liquid equilibrium of the 4-methoxybenzoic acid in different solvents with solubility parameters and interaction energy aided analyses

Abstract In this work, solubility data of 4-methoxybenzoic acid in eight pure organic solvents were measured by using a static gravimetric method at temperatures ranging from 273.15 K to 318.15 K under atmospheric pressure. The results showed that the solubility of 4-methoxybenzoic acid increased with the increasing of temperature in the investigated temperature range. The modified Apelblat equation, the λh equation, the NRTL model and the Wilson model were used to correlate the experimental solubility data of 4-methoxybenzoic acid in selected solvents and the calculated data showed that the Apelblat equation can give better correlation results. Meanwhile, Hansen solubility parameters analysis and density functional theory calculation of interaction energy were also used to investigate the mechanism of the solubility behavior of 4-methoxybenzoic acid in different solvents. Finally, the dissolution thermodynamic properties of 4-methoxybenzoic acid in different solvents, including Gibbs energy, entropy and enthalpy, were calculated based on the NRTL model and the experimental solubility data.