Solubilization of mixed polycyclic aromatic hydrocarbon systems using an anionic surfactant

Using an anionic surfactant, solubilization experiments were conducted with a suite of four very hydrophobic polycyclic aromatic hydrocarbons (PAHs)—fluorene, phenanthrene, fluoranthene and pyrene—in all possible combinations to explore interactions in the microenvironment of the micellar core. Fluorene and phenanthrene demonstrated mutually competitive solubilization effects; however, fluoranthene and pyrene were less consistent in their demonstration of competitive effects. As a preliminary observation, it was postulated that hydrocarbons with similar hydrophobicities (i.e., log Kow values) and melting points could compete for a similar locus in the micelle. In addition, with increasing number of solubilizates in a system, the total mass and volume of the solubilized product increased, with fluorene and phenanthrene demonstrating relatively greater contributions than fluoranthene and pyrene. Furthermore, the outer limits of the solubilization pattern approached a plateau of about 0.17 for Xm (0.20 for MSR) indicating a limiting maximum value, which conceptually could lend to an understanding of solubilization responses for multi-solubilizate systems as encounter in real remedial scenarios.