Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

This paper concerns the solubility of maleic acid, using inorganic salts and organic solvents. Several types of organic solvents were investigated such as methyl isobutyl ketone (MIBK), n-butanol, toluene, ethyl acetate and ethyl methyl ketone. Results showed that the solubility of maleic acid increased as follows: n-butanol greater than ethyl methyl ketone (EMK) greater than methyl isobutyl ketone (MIBK) greater than ethyl acetate (EA) greater thantoluene. The effect of inorganic salts on the solubility of maleic acid was also investigated and was found accordingly: LiCl greater than NaCl greater than KCl greater than CaCl2greater than MgCl2greater than BaCl2 greater than ZnCl2. In order to investigate thermodynamics parameters, temperatures ranging from 303.15 to 333.15 K were explored. As temperature increased, the efficiency of solubility of maleic acid increased. Correlations, based on the GibbseHelmholtz equation and the Van't Hoff equation, were used to calculate Gibbs energy, enthalpy and entropy and to explain the thermodynamic properties for the solution process. The positive value of enthalpy and the negative value of Gibbs free energy were endothermic and nonspontaneous, respectively for the dissolution process of maleic acid. In order to predict the experimental data, thermodynamic models, such as the BuchowskieKsiazaczak lh model, the modified Apelblat model and NRTL, were investigated. NRTL proved to be the most suitable for predicting the solubility behavior of maleic acid with temperature exhibiting low values of RAD and RMSD.