Electrokinetic remediation study for cadmium contaminated soil
Cadmium is a non-essential heavy metal pollutant of the environment resulting from various agricultural, mining and industrial activities and also from the exhaust gases of automobiles (Foy et al., 1978). Due to its high toxicity and greater solubility in water and its wide distributions in aquatic ecosystem, it has been considered as extremely significant pollutant (Lockwood, 1976). Great efforts have been made on the studies for removal of contaminants from soil in recent past. There were few remedial technologies like soil flushing, phytoremediation, bioremediation etc. but all these technologies are not satisfactory in low permeable soils where electrokinetics has proved its own ability in such soils (Stichnothe et al., 1996). Electrokinetic (EK) phenomena are the result of the coupling between hydraulic and electrical potential gradients in fine grained soils (Acar and Alshawabkeh, 1993). The phenomenon occurs due to the presence of the diffuse double layer around the fine-grained soil particles and fluids (Mitchell, 1993). The main mechanisms of contaminants movement in the electrical field involved in electrokinetic technology are electromigration of ionic species and elctroosmosis. Soils with very low permeability, high cation exchange capacity and expansive nature due to presence of clay minerals of illite or montmorillonite groups are extremely difficult to remediate if they are contaminated by heavy metals. Electrokinetics has emerged as a viable option for field remediation of such a contaminated soil. A laboratory study has been carried out in the present work in which a soil from field has been spiked by cadmium under laboratory controlled conditions. Then, the cadmium has been removed under various situations to study the efficiencies of removal process and thus its possible application in field conditions.