Physicochemical soil-contaminant interactions during electrokinetic extraction

The feasibility of using electrokinetics to extract contaminants from soils has been established by bench-scale laboratory experiments and small-scale field tests. However, the physics and chemistry associated with the innovative remediation technology are not yet fully understood. Many physicochemical reactions occur simultaneously during the process. These reactions may enhance or reduce the cleanup efficiency of the process. They are particularly important in fine-grained soils because the large specific surface area of the soil provides numerous active sites for these reactions. In this paper, several prominent physicochemical soil-contaminant interactions during electrokinetic extraction and their influences on the cleanup efficiency of the technology are discussed. These interactions include: (1) change of zeta potential at the soil particle/pore fluid interface; (2) resistance of the soil-fluid-contaminant system to pH change; and (3) sorption/desorption of reactive contaminants onto or from the soil particle surface and precipitation/dissolution of metallic contaminants in the pore fluid. The effects on these interactions of injecting an enhancement fluid into the contaminated soil are also discussed. In addition, a brief review on the state-of-development of the technology is presented.