The International Information Center for Geotechnical Engineers

Electrokinetic Remediation - INTRODUCTION




Soil remediation can be conducted in two ways: in-situ and ex-situ. Electrokinetic remediation can be performed as an in-situ remediation where the soil is not excavated for the purpose of decontamination (De Battisti and Ferro., 2007). This method involves the application of direct current of low density to the contaminated site. An electric field is created by inserting electrodes in the contaminated site and passing low density DC making the contaminant particles mobile in the soil media. The contaminants get transported towards the electrodes and they are pumped out. 


This technique is usually used for removing organic and inorganic pollutants including heavy metals, radionuclides and hydrocarbons from soils with low permeability. A low current is used in the order of mA/cm2 per cross sectional area since it would be safer for the personnel working there and also to avoid the adverse effects of heating. The ground water in the boreholes generally suffices as a conductive medium for the passage of current but in a situation where the groundwater proves to be insufficient, external processing fluid is used as conductive medium (Acar and Alshawabkeh., 1993).


Figure 1 shows how the electrodes with their casings are inserted in the soil which is contaminated. There should be a minimum of two electrodes to carry out the process and they are the anode and the cathode. The anode is positively charged and it attracts the negatively charged contaminants and the cathode is negatively charged and it attracts the positively charged contaminants when the current is passed (Sharma and Reddy. 2004). The contaminated water from the electrode casings are removed by pumps. The removal sometimes is improved by using surfactants or weak acids at the reservoirs. The electrode arrangement depends on the extent of contamination. In areas of extensive contamination of soils the electrodes may even be arranged in a grid with alternating cathode and anode layers.  


Electrokinetic remediation may also be referred to as electrokinetics, electromigration, electrorestoration, electroremediation and electroosmosis. 



Figure 1: Principle of Electrokinetic Remediation (Cameselle et al., 2013).


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