Effect of Nonionic Surfactants on Dissolution of Polycyclic Aromatic Hydrocarbons from Coal Tar

The remediation in the subsurface of low solubility compounds such as polycyclic aromatic hydrocarbons (PAHs) might be limited by their dissolution kinetics. Other studies have already proven that the addition of surfactants will enhance the solubility and dissolution rates of pure single-hydrophobic compounds in water. The purpose of this study is to investigate whether the addition of two nonionic surfactants (Tween 20 and Tween 21) to a complex mixture (coal tar) would similarly enhance the dissolution rates of five PAHs contained within the coal tar. The five PAHs analyzed were naphthalene, phenanthrene, fluoranthene, pyrene, and benzo(a)pyrene. Through a series of partitioning experiments, it was discovered that the partitioning coefficients increased with increasing PAH ring structure. Dissolution experiments showed that the solubilities and dissolution rates of the PAHs also increased in the presence of the two surfactants. Finally, it was found that Tween 21, being the more hydrophobic surfactant, caused a greater enhancement in PAH dissolution rates than did Tween 20.