Determination of Solubility and Thermodynamic Analysis of Solubility Behavior of 2,5-Furandicarboxylic Acid in Water and Ether Binary Solvent System

2,5-Furandicarboxylic acid (FDCA) is a promising biomass-derived monomer, and the study of FDCA dissolution behavior is of paramount importance to its purification. In this study, the solubility of FDCA in four different ethers (1,4-dioxane, tetrahydrofuran, 1,2-dimethoxyethane, and diethylene glycol dimethyl ether), as well as four binary solvent systems containing these above ethers with water, was measured by a gravimetric method. The solubility of FDCA could be improved in binary solvent systems as compared to corresponding pure solvents. More interestingly, the solubility of FDCA increased first and then gradually dropped back with the increasing mole fraction of water in binary solvent systems. The KAT-LSER model was used to explore the influence of solvent effect on solubility. The Hansen solubility parameter was utilized to probe the solute-solvent molecular interactions. Apelblat equation, van't Hoff equation, lambda h equation, Wilson model, and nonrandom two-liquid model were applied to analyze the experimental solubility data in pure ether solvents and binary solvent systems. Furthermore, the dissolution thermodynamic characteristics of FDCA in particular binary solvent systems were analyzed by the van't Hoff equation, which revealed that the dissolving process of FDCA is endothermic, entropy-driven, and spontaneous in the other three examined solvent systems, with the exception of the 1,4-dioxane/water mixture.