Removal of polycyclic aromatic hydrocarbons from surfactant solutions by selective sorption with organo-bentonite

Surfactant-enhanced soil washing is known to be an effective remediation approach for contaminated soils and groundwater. However, the recovery of surfactant solutions after soil washing is required for reducing the operation costs of the soil washing process. In this study, selective sorption with organo-bentonite was employed for the removal of polycyclic aromatic hydrocarbons (PAHs) from aqueous surfactant solution as a potential means of recovering surfactant solution after soil washing. The sorption of phenanthrene onto organo-bentonite from surfactant solution was well described by the pseudo-second-order kinetic model and the linear sorption isotherm model, respectively. PAHs can be effectively removed by organo-bentonite from surfactant solutions in a high proportion relative to the sorption loss of surfactant under all experimental conditions. The selectivity for PAH removal to surfactant sorption increased with increasing PAH hydrophobicity and surfactant hydrophilicity, but decreased with increasing surfactant concentration. However, increasing the organo-bentonite dose did not have obvious effect on the selectivity for surfactant recovery since it synchronously enhanced phenanthrene removal and surfactant sorption. The sorbent of organo-bentonite could be repeatedly used for recovering surfactant solution, which greatly reduced the sorption loss of surfactant and subsequently increased the selectivity for surfactant recovery considerably. The results suggest that selective sorption with organo-bentonite provides an alternative means of recovering surfactant solution after soil washing.