Solubilization of mixtures of polycyclic aromatic hydrocarbons in single and binary surfactant systems.

LADY CATALINA CABANA SAAVEDRA; MARIANA ADELA FERNÁNDEZ

Carlos Paz

Conferencia; 13th Latin American Conference on Physical Organic Chemistry; 2015

Comité Organizador de la Conferencia

Polycyclic aromatic hydrocarbons (PAHs) are a global environment concern due to their mutagenic and carcinogenic effects on both human and ecosystem. Micellar surfactant solutions have been studied and assessed as efficient agents for PAHs aqueous solubility, and thus increasing PAHs bioavailability for their biodegradation. Most investigations have focused on solubilization of individual compounds in single, binary or ternary surfactant systems. However, PAHs exist in mixtures of many compounds. Reports on co-solubilization of multiple solutes in micellar solutions have shown that the extent of solubilization of mixed solutes differs from their behaviors exhibited in single component systems. We studied the effect of the nonionic surfactants Tween 80 and Tween 20 and the anionic one sodium laurate (SL) in individual solutions or in their binary mixed systems, on the solubilization of mixtures of the pollutants naphthalene/phenanthrene and phenanthrene/anthracene. In a previous study we demonstrated that the mixtures formed by LS/Tween 80 present synergistic effect on the solubilization of naphthalene in water and that was one the reasons to continue working with these amphiphilic systems. The effect of the individual surfactants on the solubilization of the PAH from their mixtures was studied. A methodology based in derivative UV-visible spectrophotometry was developed for the quantification of the pollutants in the solutions. In all experiments we found that the solubilization of the contaminants from the mixed systems was lower than that obtained when they were alone in the solution. When mixtures of surfactants are used as medium to promote solubilization, the negative effect is more important (Figura 1), indicating that probably the contaminants compite for the same solubilization site as was previously described. We also analized the remanent solid after the solubilization experiments determining melting point and infrared spectroscopy, and our results indicate that in some cases there are adsorption of the surfactants on the solid pollutants that remain in excess. That fact produces a diminution of the real concentration of the surfactants in solution with the concomitant reduction of the amount of PAH solubilized. We will discuss these results taking into account the importance to consider the effect of coexisted contaminants on evaluating solubilization power of surfactant systems.