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Abstract

Acar, Gale, et al. [4] described the principles of electrokinetic remediation, direct electric current was applied to electrodes immersed in water, results in oxidation at the anode and reduction at the cathode. This is the original EKR, also termed unenhanced electrokinetic remediation. Electric fields are applied to soil to migrate the charged ions via electrodes placed into the ground, negative ions move to anode, and positive ions (such as heavy metal ion) are attracted to cathode. It has been confirmed that the initiates movement of contaminants by electromigration, electro osmosis, electrolysis and diffusion [5], and non-ionic species are transported along with the electroosmotic flow [6]. The key electron transfer reactions that occur at electrodes during the EKR process is the electrolysis of water: 12H 2 O+2e -→2OH -+H 2 (g) Equation 2Application of Combined TechnologyAccording to the experiments and pilot-scale studies conducted in the last 10 years, metals such as cadmium [7], chromium [8][9][10][11][12][13][14][15][16][17][18][19], copper [20][21][22][23][24][25][26][27][28], lead [29][30][31][32][33][34][35], manganese [36,37], mercury [38,39], nickel [40], uranium [41], and zinc [42], as well as dye [43,44], hydrocarbon[45-54], organochlorines [55-59], polychlorinated biphenyls [60,61], phenols [62,63], chlorophenols [64], are suitable for electrokinetic remediation and recovery. The author divides those technologies combined with EKR into physical technology, biotechnology and chemical technology, provides the application of these combination-technologies in soil remediation and evaluates these technologies. The most commonly used of these techniques are physical techniques, such as activated bamboo charcoal [65,66], electrode matrix-rotational operation mode [67], flushing [30,68-71], hexagonal two dimensional [72-74], ion exchange membranes [75], permeable reaction barrier (e.g. activated charcoal [28,76], Fe(0) [77,78]), pulsed variable electric field [26,79-81], sequential extraction analysis [82], ultrasonically [83], upward [84], washing [85] and several methods about electrode configuration [11,86, 87]. As for chemical technology, some enhancement methods such as acid enhanced [88], ammonia enhanced [21,66], iodide-enhanced [89] and enhanced solution (e.g. complexing agent [86], chelate agents [90-93], cosolvent [94], surfactants [51,52,[95][96][97]) are also more