Electrokinetic processing for the removal of radionuclides in soils

Abstract

Electrokinetic soil remediation is one of the most promising soil decontamination processes because it has high removal efficiency and time effectiveness in low permeability soils, such as clay. Uranium and strontium were efficiently removed from kaolinite by electrokinetic remediation. In the case of cesium, the rate of removal may be significantly slower than those of the uranium and strontium. Acetic acid was effective as enhancement agent for buffering hydroxide ions produced by the cathode reaction, resulting in the prevention of the precipitation of uranium ions in the cathode region. This also decreased energy consumption because hydroxide precipitation increased the resistance and the electrical gradient across the soil cell. The use of citric acid was not efficient in removing uranium from kaolinite because the direction of electromigration was opposite to that of electroosmosis. Since most metal-citrate chelates are negatively charged, they were transported towards the anode by electromigration, whereas electroosmosis flowed toward the cathode, resulting in lowering removal efficiency. Uranium was not effectively removed from the weathered soil of black shale by electrokinetic remediation process. This may be due to the low proportion of the mobile ions because most of uranium exists in the residual fraction.