铬渣污染场地土壤电动修复研究

Electrokinetic remediation to the chromiumcontaminated soils

以青岛某化工厂铬渣污染场地土壤为对象，研究了原位电动技术修复的铬去除率、迁移特征，以及电动修复前后土壤中铬形态的变化。结果表明，土壤总铬（Cr（T））质量比为7850mg／kg，大部分3价铬（Cr（Ⅲ））质量比为6464mg／kg。施加1 V／cm直流电压，电动修复4，6d后，6价铬（Cr（Ⅵ））以含氧阴离子的形式向阳极迁移，去除率在32％-44％，Cr（T）的去除率在5．1％～8．7％，去除效率较低，主要是因为土壤中大部分Cr（Ⅲ）以Cr（OH）3沉淀存在，在电场作用下较难发生迁移。污染土壤中的铬以有机物与硫化物结合态为主（占38．0％），同时存在大量的残渣态铬（占54．4％），可还原提取态铬所占比例最少（占1．5％）。电动运行后醋酸可提取态的铬比例有所降低，可还原提取态和有机物与硫化物结合态比例稍减小，对以残渣态存在的铬也几乎不产生影响。

The paper is engaged in a study on the electrokinetic re- mediation efficiency for the chromium-contaminated soil sites in Qing- dao due to the migration of chromiumalong with the change of chromi- um behavior in the contamination process. The results of our study show that the concentration of the total chromium [Cr（T） ] in the soil increased to 7 850 mg/kg, most of which is at presence in the form of trivalent chromium [ Cr（ Ⅲ ） ] with the concentration of 6 464 mg/kg. After a 4 - 6 days of remediation with 1 V/cm DC voltage, Cr（ Ⅵ ） in soil, which exists as an oxyanion, turns to migrate to the anode, the removal efficiency of which can be made as high as 32% -44%, though the removal efficiency of Cr（T） could only be made to reach 5.1% - 8.7%. It was mainly because that most of Cr（ Ⅲ ） in the soil is existing as Cr（OH）3, which is believed to be hard to migrate under the influence of the electric field. The problem can be thought to get somewhat improved as the result of adjusting the pH value by adding NaOH and acetic acid to the electrodes. For its special man- ner of distribution, the presence of chromium in the soil is mainly due to the organic matter（38.0% ） and residual（54.4% ）, and the con- tent of chromium left overby the iron and manganese oxides at least （ 1.5 % ）. After the reaction, the part of chromium which would be turned into weak acid, which can be basically reduced via extrac-tion, where at the cathode side it can be reduced from 1 693 mg/kg to 578 mg/kg. Chromium content bound to iron and manganese turns to get some-what decreased to make isequal to or less than other kinds of organic matters and residual. However, the residual chromium is hardly influenced by the electrokinetic remediation. Therefore, it can only be removed from the contaminated soil through electrokinetic re- mediation. The technology that is available for the removal from the soils at different permeability. And, therefore, whether the removal efficiency can be made high depends on the soil and the type of pollu- tion. The initial valence of chromium in the contaminated soil is like- ly to be affected more or less by the removal. However, on the most biological effective part, the chromium ingredients in the soil were weak, which can be extracted by using acid. Then, with the help of acid, it would be easy to remove the contaminant content of the chromium and in turn the environmental risk caused by the chromium will be able to get reduced and even ehminated to a great extent.