Electrokinetic movement of hexachlorobenzene in clayed soils enhanced by Tween 80 and beta-cyclodextrin

This study describes the comparative behavior of hexachlorobenzene (HCB) contaminated clayed soils in an electrokinetic (EK) system enhanced by Tween 80 and beta-cyclodextrin (beta-CD). The pH of the soils was controlled by Na2CO3/NaHCO3 buffer. Negligible HCB movement was observed when NaOH or Na2CO3/NaHCO3 buffer was used as anodic flushing solution. While Tween 80 or beta-CD was introduced to Na2CO3/NaHCO3 buffer, obvious HCB movement was achieved. Although beta-CD led to a less desorption of HCB from kaolin than Tween 80, the removal of HCB with beta-CD was much higher than that with Tween 80 in the EK system. Tween 80 could be sorped by kaolin more than beta-CD, which was responsible for the result. The mechanism of the movement of HCB was proposed as the enhanced desorption of HCB from soil, the dissolving of HCB in the soil pore fluid and the movement of HCB with the electroosmotic flow. Obvious movement of HCB was also observed in the EK treatment of real HCB-contaminated clayed soil enhanced by beta-CD. It is an alternative approach to use facilitating agents such as beta-CD to enhance the EK movement of HCB in the contaminated clayed soils.