Influence of Inorganic Salts on Aqueous Solubilities of Polycyclic Aromatic Hydrocarbons

Influence of Inorganic Salts on Aqueous Solubilities of Polycyclic Aromatic Hydrocarbons

Setschenow constants of six alkali and alkaline earth metal-based electrolytes (i.e., NaCl, KCl, CaCl2, K2SO4, Na2SO4, NaClO4) for three polycyclic aromatic hydrocarbons (PAHs) (i.c., naphthalcne, pyrenc, and perylene) were investigated to evaluate the influence of a variety of inorganic salts on the aqueous solubility of PAHs. Inorganic salts showed a wide range of Ks values (L/mol), ranging from 0.1108 (NaClO4) to 0.6680 (Na2SO4) for naphthalene, 0.1071 (NaClO4) to 0.7355 (Na2SO4) for pyrene, and 0.1526 (NaClO4) to 0.8136 (Na2SO4) for perylenc. In general, the salting out effect of metal cations decreased in the order of Ca2+>>Na+>K+, The effect of SO42->Cl->ClO4- was observed for anions of inorganic salts. The Ks values decreased in the order of perylene>pyrene>naphthalene for K2SO4. However, the order of decreasing salting out effect for NaCl, KCl, CaCl2, and NaClo4 was perylene>naphthalene>pyrene. Hydration free energy of the 1:1 and 2:1 alkali and alkaline earth metal-based inorganic salts solution was observed to have a meaningful correlation with Setschenow constants. Thermodynamic interactions between PAII molecules and salt solution can be of importance in determining the magnitude of salting out effect for PAHs at a given salt solution.