Thermodynamic modeling of the solid-liquid equilibrium of two phenolic compounds in several solvents at temperatures ranging from 283.15 K to 323.15 K

Abstract

The solubility of two natural phenolic compounds (vanillic acid (VA) and vanillin (V)) in four individual solvents (ethanol, butan-2-ol, ethylene glycol, and ethyl acetate) was measured using the gravimetric method from 283.15 to 323.15 K at atmospheric pressure. The optimization of the complexes between VA–solvents and V–solvents using the B3LYP theoretic technique and the 6-31+G (d, p) basis set indicated that the absolute value of interaction energy was higher, suggesting that the interaction between solute and the solvent was stronger. In addition, two excellent activity coefficient models (NRTL and Wilson) were used to correlate and evaluate the equilibrium solubility results. The highest relative average deviation and root-mean-square deviation values for VA are 4.36% and 3.09 × 10-3, respectively, and 3.35% and 5.52 × 10-3 for V. Furthermore, the excess enthalpy of the solution was determined on the basis of thermodynamic relations and the Wilson model. The findings indicate that the dissolution process was endothermic. KEY WORDS: Solid-liquid equilibrium, Vanillin, Vanillic acid, NRTL and Wilson models, Thermodynamic parameters Bull. Chem. Soc. Ethiop. 2024, 38(3), 799-810.                                                         DOI: https://dx.doi.org/10.4314/bcse.v38i3.19