A new approach to electrokinetic remediation of soils polluted by heavy metals

When the electrokinetic method is used to remove metals from soils, metals may precipitate as hydroxides in the region of the soil where pH is raised, which limits the remediation efficiency. The pH rise is caused by the generation of hydroxide ions as a result of electrolysis of water during the remediation. This paper proposes a new technique in which a conductive solution is inserted between the cathode and the soil to be treated. By this approach, the pH in the soil can be kept low so that no metal precipitation will occur. Thus metal ions may migrate out of the soil and precipitate in the inserted solution. Laboratory experiments have been carried out to remove copper and zinc from sand by the proposed technique. The experimental results show that metal removal efficiencies depend on the duration of the treatment and the content of electrolytes in the solution. Metal removal efficiencies of > 96% can be reached for both copper and zinc.