Experimental Study On Enhanced Electrokinetic Remediation Of Lead-contaminated Soil

The western loess is rich in calcium carbonate,which has high adsorption performance to lead and strong buffer ability to acid.It is difficult to repair the lead-polluted loess.In this paper,the remediation experiments of lead contaminated silty soil and loess were carried out by means of electrokinetic remediation,and the effects of various factors on the removal of medium metals were discussed.The main work is as follows:(1)electrokinetic remediation experiment of lead-contaminated silty soil,mainly analyzed the influence of repair time,electrode type and sample density on the removal effect;(2)the electrokinetic remediation test of lead-contaminated loess mainly discusses the effects of cathode control electrolyte,conversion electrode method,pre-acid treatment of lead-contaminated soil,soil mixing during the test and other methods on the removal of lead from soil.After analyzing the test results,the following conclusions are drawn:(1)Electrokinetic remediation can effectively repair lead-contaminated silty soil.The repair time,electrode type and sample density controlled in this paper will affect the final removal effect.Repair time has the greatest influence on the repair effect.The sample density was 1.42g/cm3,the ruthenium-iridium plated grid electrode was used,and the cathode was 0.15mol/L citric acid solution was used to conduct the 4d-experiment.The daily removal rate of 1-4d was 14.25%,38.01%,77.61% and 95.27%.The effect of electrode type on the final removal rate is between 1% and 5%.Ruthenium-iridium plated titanium mesh has the highest removal rate,and the unit energy consumption is only 80-90% of that of the other two electrodes,so it is a suitable electrode type.The effect of different sample density on the final removal rate is about 3%-5%.The lower sample density achieves a higher removal rate,but the unit energy consumption will increase within 15%.(2)The removal efficiency of the calcium carbonate rich loess was only 7.46% after 7 days without the use of reinforcement.The conversion electrode method can reduce the overall removal rate and is not suitable for the electric restoration of loess.The use of citric acid in cathode control solution will cause the clogging of soil pores,which is not conducive to the removal of lead.The overall removal rate is not more than 25%,while the use of acetic acid can avoid this situation,and the removal rate is increased to 45.29%.Under the same conditions,the removal rate of stirred soil was increased by about 15% during the experiment.Comprehensive use of acidification in advance,mixing in the test process,acetic acid control of cathode chamber p H means,7d test,the removal rate reached 93.84%;The unit energy consumption of loess is about 4 times that of silty soil under the same restoration effect.