Electrokinetic Remediation Of Co-contaminated Soils With Both Heavy Metals And Organochlorine

It is a common situation that soil is contaminated by a combination of heavy metals and organic compounds.Electrokinetic remediation effectively driving both heavy metals and organic matters in soil tends to be a promising treatment technology.On a basis of investigating pollution sites,Cd,Cr(?)and DDT were selected as the target pollutants.Batch experiments on electrokinetic-flushing and DDT desorption from real soil were conducted to select ideal facilitating agents.Two ways of controlling pH of anode and cathode were employed to find out the influence of pH on performances of the electrokinetic technology.Finally the selected purging solutions and the pH regulating ways were applied in the real soil.Based on the research findings,the main conclusions were as follows:1,For Cd-Cr polluted kaolin,the citric acid sodium citrate buffer was an ideal facilitating agent;rhamnolipid had excellent capacity of DDT desorption from the real contaminated soil;and the combination of the citric acid buffer and the rhamnolipid was selected as facilitating agents of compound contaminated soil.2,The reverse polarization control had no remarkable influence on depleting pollutants from soil.The addition of rhamnolipid promoted Cd migration,but did not favour the Cd removal from soil Furthermore,its addition had a certain inhibitory effect on Cr migration.3,pH control had no obvious promoting effect on DDT desorption.When the cathode pH was maintained below 4,the removal efficiency of Cd could reach 93.99%,and simultaneously the Cr was concentrated in the middle area near the anode.When the cathode pH was kept between 4 and 7,Cd was significantly migrated to the area close to the cathode,and Cr was gathered around the anode soil.The simultaneous control of cathode and anode pH values can render the Cd migration to the anode,and its removal efficiency reached 89.48%.4,Sequential application of different facilitating agents for the enhanced electroremediation of real contaminated soil showed that the main heavy metals in soil were Cd,Pb and the main organochlorine was DDT.At the given experimental conditions,the pollutants were hardly removed from soil,no matter what addition ways(sequential addition or simultaneous addition)were utilized.Cd near the anode can meet environmental quality standard for soils(class?).The exchangable Cd and Pb increased after electrokinetic remediation.After electrokinetic remediation the trend of DDT migration to the anode was observed,which was along the opposite direction of electroosmotic flow.In the process of electrokinetic remediation a certain amount of 4,4 '-DDT was transformed into 4,4'-DDE.