Effect of anionic and nonionic surfactants on sorption and micellar solubilization of monocyclic aromatic compounds

The effect of anionic and nonionic surfactants on the sorption and micellar solubilization of monocyclic aromatic compounds in soil-free and soil-water systems was investigated at 25 °C to examine the feasibility of in situ remediation. Benzene, chlorobenzene and styrene (BCS) were selected as the target compounds due to their suspected carcinogenic and mutagenic properties. Sodium dodecyl sulfate (SDS) and Triton X-100 were used to represent the anionic and nonionic surfactants, respectively. The addition of Triton X-100 had little effect on the micellar solubilization of BCS. However, the solubilization of aromatic compounds increased significantly with the increase of SDS concentration. A 20% to 43% enhancement of the solubilization in SDS-amended systems was demonstrated. The adsorption isotherms of BCS with Triton X-100 can conveniently be fitted by Langmuirian expression. However, multilayer adsorption of chlorobenzene and styrene was observed in SDS-amended systems. The values of maximum adsorption capacity ranged from 323 to 736 μg/g. Also, the effect of Triton X-100 on maximum adsorption capacity was greater than that of SDS. Moreover, a correlation between the maximum sorption capacity and partition coefficient was established. The results of this study demonstrate that surfactants can be effectively used as chemical amendments to minimize the volatilities of monocyclic aromatic compounds and enhance sorption and solubilization in soil environments contaminated by proper selection of surfactant type and concentration.