Remediation Of Chromium Residue Contaminated Soil By Electrokinetic Remediation Technology

Since the production of chromate,it has resulted in serious pollution in China. Up to the end of 2012,Our country has disposed of most of the chromium slag,but the long-term existence of chromium slag has resulted in serious soil pollution.The contents of total chromium and chromium（Ⅵ） in soil have reached 30000 mg/kg and 5000mg/kg, respectively.which pose great threat to human health.At present, electrokinetic remediation have been developed to restore polluted soil,it is an efficient method, which it has a wide range of adaptability and high repair efficiency and has aroused scientific community’s widely attention. In addition,Cr（Ⅲ） is mainly matter in the chromium contaminated soil, and the removal efficiency of total chromium is lower by the conventional electrokinetic remediation method.Therefore,based on the existing research,in order to improve the efficiency of electrokinetic remediation of chromium contaminated soil,this paper puts forward two kinds of enhanced electrokinetic remediation: the combination of electrokinetic technology and oxidation（EK-oxidation）, the combination of electrokinetic technology and permeable reactive barrier（EK-PRB）. In the former, the concentration of dissolved hexavalent chromium increased for trivalent chromium is oxidized by the oxidizing agent, resulting in higher efficiency of electrokinetic remediation. For the latter, the advantages of EK and PRB were combined by changing PRB media to improve the efficiency of electrokinetic remediation. After a series of experiments, the results are as follows:（1） Kaolin was polluted by Cr（Ⅲ）, which concentration is 500mg/kg. The removal rate and efficiency of total chromium of electrokinetic experimental with potassium permanganate is significant higher than that of without potassium permanganate after 4 days and applying 1V/cm DC voltage, the higher concentration of potassium permanganate added, the higher removal rate was observed. When the concentration of potassium permanganate is 20 g/L, the removal efficiency of total chromium is up to 82.05%, which was higher than that of without potassium permanganate（18.45%）.（2） For the actual soil which the concentration of total chromium is up to 30000 mg/kg, the repair effect of combining electrokinetic technology and oxidation is three times than electrokinetic remediation technology alone. Nearly 50000 mg chromium was removed when 4kg soil is treated by electrokinetic remediation and oxidation for 4 days and applying 1V/cm DC voltage.（3） Actual soil which concentration of total chromium up to 30000 mg/kg is disposed by the combination of electrokinetic technology and permeable reactive barrier applying 1V/cm DC voltage. After 9 days, the efficiency of PRB media followed the order : Fe₃O₄+ Fe₃O₄> Fe₃O₄+hydroxy alumina > Fe₃O₄+ activated carbon. The effect of reduction was greater than that of adsorption, and the effect of chemical adsorption was greater than that of physical adsorption in PRB.Through the above experiments, we found that both EK-oxidation and EK-PRB have higher removal efficiency of total chromium compared with the traditional electrokinetic technology. And this paper provides technical support for the enhanced electrokineti c remediati on of chromi um contami nated soil.