Thermodynamic models for determination of solid-liquid equilibrium of the 4-methylbenzoic acid in pure and binary organic solvents

Data on corresponding solid-liquid equilibrium of 4-methylbenzoic acid in different solvents are essential for a preliminary study of industrial applications. In this paper, the solid-liquid equilibrium of 4-methylbenzoic acid in methanol, ethanol, isopropanol, 1-butanol, acetone and acetonitrile pure solvents and (acetone + acetonitrile) mixture solvents were explored in the temperatures (from 278.15 to 323.15 K) under atmosphere pressure. For the temperature range investigated, the solubility of 4-methylbenzoic acid in the solvents increased with increasing temperature. The modified Apelblat model, the Buchowski-Ksiazaczak λh model, and the ideal model were adopted to describe and predict the change tendency of solubility. Computational results showed that the modified Apelblat model had more advantages than the other two models. The solubility data were fitted using a modified Apelblat equation, a variant of the combined nearly ideal binary solvent/Redich-Kister (CNIBS/R-K) model, Jouyban-Acree model and Ma model in (acetone + acetonitrile) binary solvent mixture. In addition, the calculated thermodynamic parameters indicated that in each studied solvents the dissolution of 4-methylbenzoic acid is endothermic and entropy-driven process.