Temperature dependent solubility of vanillic acid in aqueous methanol mixtures: Measurements and thermodynamic modeling

The solid-liquid equilibrium data of vanillic acid (VA) in pure ethanol and in various (methanol + water) mixed solvents were measured over the temperature range from (293.15 to 318.15) K at atmosphere pressure using a thermostatted reactor and UV/vis spectrophotometer analysis. The effects of the composition of binary systems and temperature on the solubility were discussed. The obtained solubility data were correlated with the Van't Hoff model, the modified Apelblat equation and the λh equation. In general, the regressed results with the three models were all within the acceptable limit for the solubility of vanillic acid in the (methanol + water) mixed solvents. Furthermore, thermodynamic properties of dissolution of the vanillic acid in the selected systems were estimated. Consequently, the experimental data and model parameters would be useful for optimizing the process of purification of vanillic acid in industry.