Solubilization of polycyclic aromatic hydrocarbons by gemini–conventional mixed surfactant systems

Abstract

The effects of mixed gemini–conventional surfactants on the aqueous solubility of polycyclic aromatic hydrocarbons (PAHs—naphthalene, anthracene, pyrene) were investigated. The critical micelle concentration (cmc) of the cationic gemini pentanediyl-1,5-bis(dimethylcetylammonium bromide) (G5) and its 1:1 mixtures with conventional surfactants cetyltrimethylammonium bromide (CTAB), sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and polyoxyethylene (20) cetyl ether (Brij 58) were evaluated using the surface tension measurements. The maximum surface excess concentration at the air/water interface (Γmax), minimum area per head group (Amin), interaction parameters (βm, βσ) as well as other thermodynamic and micellar parameters were evaluated. Above cmc, for each of the single or binary system, the solubility of PAH in water is greatly enhanced in a linear fashion; the enhancement being more in the mixed surfactants. For the binary surfactant systems synergism in G5–CTAB, G5–Brij 58 and antagonism in G5–AOT are observed. The gemini–conventional mixed surfactant systems can solubilize PAHs synergistically due to the increase in molar solubilization ratio (MSR) and partition coefficient (Km) of the solute in the micellar phase.Results from this study could be exploited for the use of surfactant mixtures for environmental remediation as the mixed surfactants are anticipated to improve the performance of surfactant-enhanced remediation of soils and sediments contaminated by hydrophobic organic compounds by decreasing the applied surfactant level for the needed solubility of the PAHs in aqueous solutions.