Research On Remediating Heavy Metals Pb Contaminated Soil By Electrokinetic

Electrokinetic remediation is a new method of soil remediation in nearly decade. Mainly, this method applies a direct current in soil and it form voltage gradient between electrodes. Contaminants in soil would migrate by electromigration, electrophoresis and electroosmosis in electric, to achieve the aim that remediates contaminated soil. There’re some factors that influence the effect of electrokinetic remediation, such as electrode material, pH in soil, physicochemical property of soil, electric current, remediation time. This paper mainly researches electrokinetic remediation of Pb contaminated soil. First, To find the best type and concentration of cathodic control fluid, we do a desorption experiment. Then we do some experiment to find the best electrode material, voltage gradient and remediation time for the following step. At last with the best situation above, we make a remediation experiment to actual lead contaminated soil, through experiment and data analysis, the following main conclusions:1. For the lead contaminated soil, EDTA (Ethylene Diamine Tetraacetic Acid) has the best desorption ability in some kinds of common cathode control liquids(EDTA, acetic acid and citric acid). EDTA can enhance the transferability of heavy metal in soil, and it’s helpful for improving the effect of electrokinetic remediation.2. Different electrode materials have different result for the remediation. The result of experiment shows that compare with the other electrode materials, graphite electrode has the highest removal efficiency of Pb, where the removal rate is 60.14%. Besides, according to the situation of the speciation characteristics of heavy metals after experiments, the stability of heavy metal is graphite electrode> stainless steel electrode> titanium plate electrode, so it will choose graphite electrode to do the following jobs.3. Voltage is a motive force of electrokinetic remediation, electric current directly influence migration of heavy metal in soil and it will affect the result of electrokinetic remediation. The paper studies three different kinds of voltage gradient effects on electrokinetic remediation, the result shows that the removal rate of K1, K2 and K3 are 48.49%,61.36% and 66.10%, respectively. It means as voltage increasing, the current in soil will also increase, and it will enhance the effect of electromigration, electrophoresis and electroosmosis. Thus, the ion of heavy metal can be more quickly removed from soil, and accordingly the result of removal efficiency of heavy metal will be better. From the above, it will choose 1.5V/cm as voltage gradient to do the following jobs.4. It take times for heavy metal to migrate in soil, different remediation times can cause different result for the remediation experiment. The paper studies four different remediation time to find the best result. the result shows that it’s too short remediation time to do the experiment that all of four experiments appear enrichment phenomenon. And the removal rate of M1, M2, M3 and M4 are 67.97%,71.47%,72.62% and 74.68%, respectively. It can conclude that after four days from the experiment beginning, the removal efficiency of heavy metal decreases obviously. so considering the energy consumption and the removal efficiency, it will choose 4 days as remediation time to do the following jobs.5. Through the electrokinetic remediation experiments to real Pb contaminated soil, the results show that, the total Pb removal rate is 66.75%. But the total removal rate is lower than the simulated soil, it requires further study and discussion.