| Soil contamination by heavy metals is not a rare occurrence. Heavy metal contamination is found in more than 65% of Superfund sites in the United States, and in rice paddies in Taiwan and Japan. Moreover, heavy metal poisoning was responsible for more than 100 deaths in Japan in the last few decades. However, none of the existing soil remediation techniques is capable of remediating heavy metal contamination in soils successfully, especially in fine-grained soils.; The potential of electrokinetic extraction technique in remediation of heavy metal contaminated fine-grained soils has been demonstrated through successful bench-scale laboratory and pilot-scale field studies. However, many factors such as soil acid/base buffer capacity and zeta potential that may affect the efficiency of this technique have not been fully investigated.; In this experimental study on electrokinetic extraction technique, the effects of the properties of fine-grained soils, and interactions between the soil particle surface and the contaminant were investigated. The effects of ethylenediaminetetraacetate (EDTA) on enhancement of electrokinetic extraction technique under various operating conditions were also evaluated. Efforts to control soil pH and electroosmotic flow direction, and to experimentally explain some phenomena observed by many researchers were also made.; It was established in this research that electrokinetic process alone was not effective in mobilizing heavy metal contaminants that were sorbed on Milwhite kaolinite due to the relatively high acid/base buffer capacity property of this material and the reversal of electroosmotic flow direction. Very encouraging results were obtained by using EDTA enhancement under certain conditions. However, mobilized contaminants were accumulated in the vicinity of the anode and no significant removal of contaminants from the system was achieved except in one electrokinetic extraction test. Electrokinetic extraction technique was also demonstrated to be cost effective based on laboratory test results. While some phenomena were successfully explained in this study, there are still many others that remain to be investigated. Nevertheless, the study provided a better understanding for this technology and demonstrated its potential application on remediation of heavy metal contaminated soils. |
