Low Aqueous Solubility Measurement (down to 10-12 in molar fraction) of a 5 Arenes Polycondensed Hydrocarbons Using Dynamic Saturation Method

Polycyclic aromatic hydrocarbons, known as PAH, are generated principally during the incomplete combustion of fossil fuel. These anthropogenic compounds are found in the environment at different levels and concentration leading to an enhancement of the human contamination. Their physical chemical characterization is then a necessity in order to estimate their fate and transport in the ecological system.

The aqueous solubility is a key property in the knowledge of the mass transfer PAH between different compartments (water, air, soil). The determination of such data are difficult due to the low solubility of the PAH (high molecular weight compounds). Thus a dynamic saturation apparatus was realized based on the saturation of a heated fluid passing through a saturation cell. The transported solute is subsequently trapped in a specific extraction column. Back flashing method is then applied to dissolve the compound. The analysis that follows, allow the determination of solubility at the consign temperature.

The validation of our apparatus was achieved by measuring the aqueous solubility of the ethyl benzene and Carbaryl at 313.15 K. A standard deviation about 0.2 % was obtained, knowing that the literature value was done by means of a static method. Thereafter solubilities in pure and mineral water of 3 PAH were determined. They ranged from 1.42.10-10 to 9.21.10-12 in molar fraction. The data were fitted to a 3 parameters Heidman's equation in order to calculate the thermodynamic properties of dissolution.