Combined Effects of Surfactant-Assisted Soil Washing and the Electro-Fenton Process on Fluorene Removal

Abstract

Soil washing has been widely used together with other remediation techniques to increase the overall removal efficiency of hydrophobic pollutants. In this study, the combined effects of soil washing followed by the electro-Fenton process were investigated. A loamy soil contaminated with fluorene (368.8 mg/kg) was used in a washing process including the non-ionic surfactant polyoxyethylene 20 cetyl ether (Brij 58). A total of 222.6 mg/kg fluorene was removed with 1% Brij 58 solution and a soilto-solution ratio of 1/5, which were determined to be the optimum treatment conditions. Both the first-order, two-compartment model and pseudo-second-order model described fluorene solubilization very well, implying that fluorene solubilization proceeded in two stages and that the fluorene concentration gradient in the washing solution influenced the process. Evaluation of Brij 58 adsorption together with fluorene removal revealed that adsorption and the release of organic constituents (Brij 58 and dissolved soil organic constituents) and fluorene from the soil seemed to occur simultaneously. The treatment of the Brij washing solution with the electro-Fenton process presented a fluorene removal efficiency of approximately 92.8% with 2% H2O2 and a reaction time of 60 min, a current density of 15 mA/cm(2) and an electrical conductivity of 2 mS/cm. The corresponding total destruction of the washing solution was approximately 67.6%. The results showed that with proper optimization of operational parameters, a strategy for the removal of target contaminants can be accomplished, enabling the reuse of the washing solution.