Solubility-enhanced electrokinetic movement of hexachlorobenzene in sediments: A comparison of cosolvent and cyclodextrin

Though solubility-enhanced electrokinetics (EK) has been investigated in remediation of soils contaminated with hydrophobic organic chemicals (HOCs), few comparative studies were performed regarding the effect of varied solubilizing agents on both EK parameters and contaminant removal. In this study, performances of two solubilizing agents, ethanol and methyl-β-cyclodextrin (MCD), were compared in terms of either EK parameters or enhancement of hexachlorobenzene (HCB) movement in real contaminated sediments. Six bench-scale EK tests were conducted under a voltage gradient of 2 V cm−1 for 14 or 21 d. Results reveal that ethanol had a more negative effect on cumulative electroosmotic flow (EOF) than MCD. Furthermore, the distribution of ethanol in the sediment upon the completion of EK tests was lower than that of MCD. The movement of HCB in sediments was observed to increase with increasing concentrations of ethanol or MCD. Test with 50% ethanol exhibited the highest performance, followed by test with 50 g L−1 MCD. The different performance of HCB removal for tests with varied solubilizing agents was found to be a combined effect of the distribution of solubilizing agents in sediments, the dissolution of HCB by pore liquid and the quantity of cumulative EOF. Finally, an integrated consideration of both EK parameters and contaminant removal suggests that MCD can perform better than ethanol for a long-term field application.