Study on Electrokinetic Soil Remediation Method

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Electrokinetic remediation is an emerging technology that can be used to remove contaminants from heterogeneous fine-grained soils in situ. Contarninants in the subsurface are removed by the application of a low level direct current electric field across the contaminated soil. The primary contaminant transport and removal mechanisms are electrosmotic advection and ionic migration. However, there are many complex physicochemical reactions occurring simultaneously during the process that may enhance or retard the cleanup process. Nevertheless, the feasibility of the process has been demonstrated by results obtained from many bench scale and large scale laboratory and pilot scale field experiments performed on various soils.In the present study, major factors affection the removal process are examined. Also, enhancement techniques and hybrid process are considered and the results are described. In the study of elecrokinetic processing of kaolinite under the condition of constant applied v … More oltage, cadmium accumulation near the cathode without reducing the diffusion of hydroxide ion into the soil. In keeping the catholyte pH at neutrality, cadmium migrates toward the cathode without any accumulation of cadmium near the cathode and is successfully removed at the cathode reservoir. It was also found that the progress of electrokinetic processing of cadmium could be grasped to a certain extent by monitoring the local voltage and the current density. The effectiveness of introducing a complexing agent to enhance the removal of cadmium from kaolinite in the region of neutral pH by ionic migration is also examined. The complexing agent selected was ethylenediamineteraacetic acid(EDTA). The investigation was carried out in a laboratory-scale column containing kaolinite contaminated with cadmium. As the results of the study, cadmium migrates toward the anode without accumulation of cadmium and successfully removed at the anode reservoir. Also, in the study of the contaminant removal from Low permeability soils by coupled electric-hydraulic gradient using theoretical model, the following results are obtained: The coupled clcctric-hydraulic gradient can be effectively utilized to remove cadmium from soil with relatively high hydraulic conductivity compared with clayey/silty soils, but can not be effectively utilized in remove cadmium from clayey/silty soils. Meanwhile, in the removal of TCE from clayey/silty soils, the coupled electric-hydraulic gradient can be effectively utilized. Macmillan number and coefficient of clectroosmotic permeability affect the cleanup efficiency of cadmium Meanwhile, in the removal of TCE, the effect of Macmullin number is negligible, but the effect of coefficient of electrosmotic permeability is significant. Less