Research On Electric Repair Of Heavy Metal Cd Contaminated Soil

As an in-situ remediation technology,electrokinetic remediation of heavy metal contaminated soil can remove heavy metal which adsorbed on soil particle surface under electric field when a DC voltage gradient is applied at both ends of the cell.In this paper,the heavy metal Cd contaminated soil was used as the electrokinetic remediation experiment.The electrokinetic remediation technology was used to repair of simulation Cd contaminated soil and the actual Cd contaminated soil.The effects of different extraction agents on the extraction rate of simulated Cd contaminated red soil,the effects of different cathodic electrolyte and its concentration,different voltage gradient and different electric repair time on the electrokinetic remediation of Cd contaminated red soil were studied.We found the best electrokinetic remediation parameters for Cd contaminated soil during the simulation experiment,and then repaired the actual Cd contaminated soil by the suitable electrokinetic remediation parameters in order to verify the electric repair parameters.The results are as follows.(1)Citric acid can be used as extractant to extract the heavy metal Cd from simulation Cd contaminated soil effectively.When citric acid was O.lmol/L,the extraction amount of Cd in the simulated Cd contaminated red soil was up to 746.15mg/kg,then the better extraction effect was achieved;(2)In the electric repair process,simulation of Cd contaminated soils in the catholyte selection directly affects the variation of cathode electrolysis chamber pH.Finally,the removal effect of heavy metal Cd in soils can be affected,experiments show that when using 0.1mol/L Fe(NO3)3 as cathode electrolyte,the repair is ideal;(3)When the voltage gradient is 1.5V/cm,the removal rate of Cd in red soil reached more than 90%.This can be attribute to the desorption of Cd which located in the surface of soil particles by the action of H+ which produced by the diffusion and electromigration.(4)A better repaired effection can be achieved when the electric repair time was 10 days.What's more,the energy consumption was very low.(5)Electrokinetic remediation of actual Cd contaminated soil based on the electrokinetic parameters are performed.Test results shows that the removal rate of Cd in soil reached more than 55%,showing good repair results.The electric repair parameters are suitable for the remediation of Cd contaminated soil.But with the Cd polluted soil removal rate still have a certain repair space when compared with red soil.There are many complex factors affecting the electrokinetic effect in the actual Cd contaminated soil,such as the soil used in the test have a strong acidic buffering capacity and high pH.Due to higher pH,Cd adsorbed on the surface of soil particles is not effective desorption and effective electromigration under the electric field.