(189d) Prediction of Aqueous Solubility and Vapor Pressure of Polycyclic Aromatic Compounds

Polycyclic aromatic hydrocarbons (PAHs) are compounds resulting from incomplete combustion and many fuel processing operations. They exist commonly as a subsurface environmental contaminant at sites of former manufactured gas plants or petroleum processing or handling sites. Aqueous solubility and vapor pressure are fundamental properties, which are the key to predicting the fate and transport of compounds or mixtures in the environment. Measurement of these properties involves some considerable experimental effort. In this study, the above two properties of 9 PAHs are predicted using the COSMO-RS method in conjunction with readily available measurable properties. Aqueous solubilities of solid PAHs are estimated by use of properties measurable by differential scanning calorimetry (DSC) with COSMO-RS predictions. Results suggest that this method can be used to predict the aqueous solubility of PAHs with less than 4 aromatic rings. The vapor pressure values are calculated by 2 methods. Method 1 uses the same properties measured by differential scanning calorimetry (DSC) with COSMO-RS predictions while method 2 combines enthalpies of fusion, melting point and boiling point data with COSMO-RS predictions. Results demonstrate that method 2 is preferable, even though the predictions also become poorer when PAHs have more than 4 aromatic rings.

Working from the results for PAH predictions, the aqueous solubilities and vapor pressures of chlorinated and brominated PAHs have been calculated utilizing the above methods.