| Electrokinetic remediation is an emerging technology in situ remediation of heavymetals in soil, this method is simple and easy to operate, low cost, and difficult to causesecondary pollution.Its principle is similar to the original battery, DC is applied at bothends of the contaminated soil,heavy metal ions in soil migrate out of the soil with theelectrophoresis, electro-migration and electro-osmosis. There was a lot of factors affectingrestorative effects of electrokinetic remediation, such as electrode material, pH, soilproperties, Current, repair time et al.In this paper,electrokinetic remediation of complexCu2+and Cd2+contaminated soil was studied.First, determine the best cathode controlsolution by orthogonal experiment,control solution of citric acid being added to the cathodechamber by constant Current peristaltic pump to control the OH-generated at the cathodeinto the soil, then carried out research respectively on electrode material,concentration ofcathodic control solution,voltage gradient and repair time. The results showed:1.By range analysis of orthogonal experiment, Kinds of cathode control liquid has greateffect on the parse rate of Cu2+and Cd2+. The results showed that the desorption rate ofcitric acid was the highest, good for removing heavy metals from soil.2. The results of the experiment with different electrodesshowed that the best repaireffect is graphite electrode, the stabilizing effect of Cu2+and Cd2+is similar with differentelectrode materials, the removal effects of Cd2+issignificantly better than Cu2+no matterwhat kinds of electrodes,it may be related to their interaction.3.Concentration on the factor of the cathode control solution, the results showed thatheavy metal removal rate of0.1M was similar to0.15M, and just a little difference betweenthem, taking the economic costs and removal efficiency into account,0.1M citric acid wasselected as cathode control solution.4.Through experimental studies on different voltage gradient, the results showedthat:For Cu2+,the total removal was improved as the voltage gradient increases, and theremoval increased the maximum when the voltage gradient from2V/cm to3V/cm, thentheimprovement of removal rate is not obvious after increasing the voltage; For Cd2+,thetotal removal rate also increases with the voltage gradient improve,the total removal ofCd2+was more than95%when the voltage gradient is2V/cm, then the removal was notsignificantly improved as the voltage increased. Considering the total removal and energy,3V/cm was selected to subsequent experiments.5.Under these optimal conditions, investigated the impacts of five different kinds ofrepair time,2d,3d,4d,5d and7d to the repair effects. The results showed that with theincrease of repair time, the total removal rate of Cu2+and Cd2+was respectively continuedto improve. When the repair time was2days, the enrichment phenomenon appeared in bothCu2+and Cd2+, and the enrichment phenomenon of Cu2+was more serious. But they bothdisappeared as the time went by. When the repair time was4days, the removal rate ofCu2+and Cd2+reached a high value, since then, with the increase of time, neither of theremoval rate improved a lot. Therefore, according to the total removal rate and energyconsumption of Cu2+and Cd2+,the best repair time is4days. |
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