Analysis of Predictive Thermodynamic Models for Estimation of Polycyclic Aromatic Solid Solubility in Hot Pressurized Water

The ability of two thermodynamic approaches to predict the solubility of solid compounds in hot pressurized water is studied and compared. The Regular Solution Theory, based on the solubility parameter concept, and UNIFAC- based models were applied to calculate the solute activity coefficient and then, solubility predictions were compared with experimental data reported in the literature. The analysis was carried out considering polycyclic aromatic hydrocarbons as model substances, i.e. substances which contain only the aromatic AC and ACH groups, and for which reliable pure physical properties such as melting point, fusion enthalpy and molar volume are available in the literature. The solubility values predicted with the UNIFAC-based models were considerably better than those obtained with the solubility parameter approach. Particularly, the modified Dortmund UNIFAC model presented an appropriate functionality of solubility with temperature, and the extension of this model to other type of aromatic compounds also provided a satisfactory prediction of solubility data.