Electrokinetic-Fenton process for remediation of HOCs-contaminated soil

Abstract

Electrokinetic (EK)-Fenton process was recently developed to achieve a rapid remediation of soil contaminated with hydrophobic organic compounds (HOCs). Fenton reaction is the catalytic oxidation of hydrogen peroxide with iron and has been frequently used to oxidize contaminants in wastewater. Application of electroosmotic flow (EOF) enables hydrogen peroxide to be uniformly and rapidly transported into a soil system with low permeability. However, characteristics of the hybrid process associated with electrochemical condition in subsurface, electric field intensity, soil property, oxidizer supplement rate, etc. were not well understood. The objective of the present study is to test the feasibility of the EK-Fenton process by enhancing the removal efficiency of HOCs. Several process variables were investigated to get the optimized operating condition for a field application. Phenanthrene, one of polycyclic aromatic hydrocarbons (PAHs) contained in diesel fuel, was selected as a representative pollutant, because EK-Fenton process is appropriate to remove pollutants with low volatility. Model soils used in this EK experiments were Indonesia kaolin, Kyungnam-Sangcheong (KS) kaolin, Jumunjin sand, and field soil from a gas station near our institute. Kaolin as well as sand has a relatively low cation-exchange capacity so that several parameters such as electrical potential gradient, ionic transport, and soil pH under direct current field can be evaluated precisely. Also gas station soil was used for feasibility test of EK-Fenton process for a field application. During the EK operation Indonesia kaolin (40.6 mg Fe/kg soil) showed uniform distribution of hydrogen peroxide over the soil while KS kaolin (1,039 mg Fe/kg soil) showed the concentration decline towards cathode. It was because the high iron content of KS kaolin decomposed hydrogen peroxide prior to arrival at cathode. From modeling results, decomposition rate constants of hydrogen peroxide for Indonesia and...