Treatment of Low-level BTEX-contaminated Soils by Anionic Surfactant Washing

Abstract

Soil contamination generated by petroleum hydrocarbons, including benzene, toluene, ethylbenzene and xylene isomers (BTEX), has raised concern around the world. Soil flushing is the process of treating polluted soils with water, surfactants, or solvents, and it is usually feasible for the remediation of petroleumhydrocarbon contaminated soils. Surfactant-enhanced flushing was developed from the conventional pump-and-treat method. A mixture of water and surfactants is often applied to polluted soils and groundwater to improve the solubility of the pollutants during soil flushing. The objective of this study was to investigate the effects of applying anionic surfactants flushing on the treatment of low and high level BTEXcontaminated soils. A surfactant, sodium dodecylsulfate (SDS, anionic type), was used as a washing agent in the column experiments. Column studies were conducted to evaluate the efficiency of BTEX removal from unsaturated porous media using different concentrations of SDS for soil flushing. The soil column [4.2 cm (ID) × 12 cm (L)] was packed with low-level BTEX-contaminated soils (100 and 1,000 mg/kg) and DI water was pumped into the column with a flow rate of 11±1 mL/min. Results from the column study show that BTEX removal efficiencies varied from 63 to 95% when 0.5-2% (v/v) of SDS was pumped through the system. Higher BTEX removal efficiency was obtained when the higher surfactant concentration was applied. The results from this study provide insights into the surfactant washing technology, and will be useful in designing a scaled-up system for field applications.