Cosolubilization of 4,4′-dibromodiphenyl ether, naphthalene and pyrene mixtures in various surfactant micelles

• Cosolubilization effects of PAHs were observed in all surfactant systems.
• BDE-15 probably had great affinity for hydrophilic chains of surfactants.
• Synergism occurred for BDE-15/pyrene in all surfactant systems.
• Inhibition occurred for BDE-15/naphthalene in Brij58, Brij78, and CTAB systems.
• Tween80 has great potential in removal of PBDEs and PAHs mixtures.

The present study aims to investigate the cosolubilization of a range of mixtures of polybrominated diphenyl ether (PBDE) (specifically, 4,4′-dibromodiphenyl ether) and two polycyclic aromatic hydrocarbons (PAHs) (specifically, naphthalene and pyrene) in nonionic, cationic, and anionic surfactant systems. Cosolubilization effects were quantified in terms of molar solubilization ratio, micelle-water partition coefficient, and synergistic/suppressive ratio. 1H nuclear magnetic resonance (NMR) spectroscopy was used to investigate the solubilization sites of naphthalene, pyrene, and 4,4′-dibromodiphenyl ether in surfactant micelles. During cosolubilization, synergism was observed for naphthalene/pyrene in Tween80, Brij58, CTAB, and SDBS micellar solutions due to palisade layer solubilization of naphthalene and pyrene that resulted in reduction of interfacial tension, enabling the core volume to increase. In contrast, inhibition occurred in Brij78 surfactant system due to weak interactions between PAHs and the hydrophilic chain, and competitive solubilization of PAHs for the same solubilization site. 4,4′-Dibromodiphenyl ether probably had great affinity for hydrophilic chains of surfactants due to non-covalent halogen bonding that occurred between bromines and electron donors on the hydrophilic chains, resulting in synergism for 4,4′-dibromodiphenyl ether/pyrene in all surfactant systems and resulting in inhibition for 4,4′-dibromodiphenyl ether/naphthalene in Brij58, Brij78, and CTAB surfactant systems. The results of this study provide valuable information that may improve the effective utilization of surfactants in removal of PBDEs and PAHs from contaminated soils and non-aqueous phase liquids (NAPLs) treated with surfactant enhanced remediation (SER) technology.