不飽和汚染土壌への動電学的手法の適用に関する研究 ‐六価クロム汚染土壌への適用‐

Abstract

Electrokinetic soil remediation can be used as remediation tool to extract dissolved ions and organic compounds from soils. To initiate electrokinetic transport, a DC electric potential field is applied to soils. The magnitude of the transport velocity due to electromigration and electroosmosis is directly related to the electric potential gradient. Most researches have been focused at the remediation of saturated soils. However, many contaminant sources lie within unsaturated soils as a result of leaking chemical storage tanks and landfills. Electrokinetic induced transport of soil water and ions within the water may provide a remediation alternative to unsaturated soils. Hexavalent chromium is more mobile and easily soluble. Hexavalent chromium has high solubility in water and exists as chromate, monochromate or dichromate anions depending on the pH of the solutions. This hexavalent chromium is the chemical form requiring remediation. In this study, hexavalent chromium ion transport in unsaturated soils is predicted with a simple numerical method in which electrical flow is coupled with hydraulic flow, and the treatment for unsaturated soils are investigated. The results obtained in this study are summarized as follows: Hexavalent chromium ion migrates toward the anode well in unsaturated soils, however, the movement in unsaturated soils is lower compared with saturated soils. And then, remediation is applied successfully to unsaturated soils by coupled electric-hydraulic gradient.