| Heavy metal pollution of soil is a concern at home and abroad.Because of the very serious harm done by heavy metals to soil ecological structure,animals,plants and human health,it is very important to choose suitable technology to remove heavy metals from soil.According to the heavy metal soil pollution remediation problem,the arsenic contaminated site of a chemical plant in Hunan site is chosen as the research object.In this paper,the characteristics of arsenic pollution in contaminated sites are analyzed.Then,the technical parameters of electrokinetic remediation are discussed by small scale and pilot scale experiments.This can provide technical support for the remediation of this contaminated soil.In the contaminated site,the area with high content of arsenic in the surface soil of 0?50 cm includes the production area of the arsenic agent,Xiangjiang transport terminal and the storehouse of the arsenic agent,of which the total pollution area is about 30,000 m.Arsenic in the site is not easy to migrate to the depths of the soil,and most of the arsenic pollutants are concentrated in the shallow soil of 0?3 m.The volume of soil containing arsenic of more than 20 mg·kg-1 can reach 386262 m3,accounting for 26.29%of the total volume of soil,with an average As concentration of 58.8 mg·kg-1;the volume of soil containing arsenic of more than 80mg/kg can reach 56277 m3,accounting for 3.83%of the total volume of soil,with an average As concentration of 191.2 mg·kg-1.In this paper,three parameters,such as the type of activator,the amount of activator and the voltage,are discussed from the aspects of current,pH and the residual content of arsenic in the soil.The experiments show that comparing with the other two activators of EDTA and citric acid,the#1 activator can make the electric current and pH in the electric experiment relatively larger,and the residual content of arsenic in soil lowest.The content of arsenic in the cathode decreases from 227.49 mg·kg-1 to 170.53 mg·kg-1.#1 activator is added in seven different gradients,0.0%,0.1%,0.2%,0.3%,0.4%,0.5%,0.6%,respectively.The residual content of arsenic in the soil is the lowest when the activator content is 0.3%,and the concentration of arsenic in the cathode reduces from 227.49 mg·kg-1 to 171.53 mg·kg-1.The voltages used in the experiments are 12 V,24 V,36 V and 45 V.The greater the voltage,the longer the time,the current and pH also increase more significantly.Considering the removal rate,energy consumption and time,the optimum condition of the small scale experiment is keeping the experiment for 8 consecutive days under the voltage of 36 V.Under this condition,the average removal rate of arsenic is 20.55%,and the arsenic content in the cathode reduces to 150.61 mg·kg-1,which means that the maximum removal rate is 33.3%,and the energy consumption is about 320.47 kW·h·kg-1.The pilot test results show that the concentration of arsenic in the cathode decreases from 318.5 mg·kg-1 to 215.59 mg·kg-1,and the maximum removal rate is up to 32.6%,after experimenting for 96 hrs.In general,the electrokinetic experiment has a certain effect on the removal of arsenic.But whether it can be used in the actual site restoration project,also depends on some other conditions,such as the cost,site characteristics,time limit conditions and so on. |
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