Removal of tetrachloroethylene from homogeneous and heterogeneous porous media: Combined effects of surfactant solubilization and oxidant degradation

Abstract

High efficiency and cost-effective remediation technologies are needed to remove tetrachloroethylene (PCE) from the source zones in soil and groundwater systems. This work evaluated the ability of a biodegradable surfactant (Tween 80) coupled with an effective oxidant (Fe2+ (activation agent)–citrate (chelating agent) activated persulfate (PS, oxidant)) to remove PCE from porous media. Batch experiments were used to optimize the oxidant by testing the effects of PS, citrate, and Fe2+ concentrations on the PCE degradation. The optimal molar ratio of PS/citrate/Fe2+/PCE was 15:15:5:1 for PCE degradation in presence of the surfactant. Four sandbox experiments were performed to compare the effectiveness of the surfactant and the combination of the surfactant with the optimized oxidant in the removal of PCE from homogeneous and heterogeneous porous media. PCE saturation distributions in the sandboxes were quantified using a light transmission system. In addition, the PCE, PS, and Cl− concentrations in the effluents were also monitored during the experiments. While the Tween 80 solution removed about 52% and 67% of PCE from the homogeneous and heterogeneous porous media; the combination solution was more effective with removal rates of 80% and 84%, respectively. The enhanced PCE removal was due to the combined effects of the surfactant solubilization and PS oxidation: (1) Tween 80-enhanced solubilization resulted in an enlarged effective contact and reaction between PCE and PS; and (2) PS degraded the PCE from the soluble phase and thus facilitated its dissolution from the source zone, resulting in more efficient use of Tween 80. Findings from this work indicate that the combination of surfactant and oxidant can provide an effective way for the remediation of PCE in soils and groundwater.