抗坏血酸与柠檬酸对尾矿Pb污染土壤电动修复的强化效果

Electrokinetic Remediation of Pb-Contaminated Tailing Soil with Enhancing Reagents Ascorbic Acid and Citric Acid

为研究抗坏血酸与柠檬酸作为增强试剂对高酸性缓冲能力的尾矿Pb污染土壤[w(Pb)为(5491.9±24)mg/kg]电动修复的强化效果,利用0.1 mol/L柠檬酸作为阴极电解液并控制阴极p H在2~3之间,系统分析土壤饱和液中c(抗坏血酸)(0~0.4mol/L)、修复电压梯度(1~3 V/cm)对电动修复Pb污染土壤的影响,并对土壤中Pb的存在形态进行分析.结果表明:当电动修复过程中施加电压梯度为1 V/cm、c(抗坏血酸)(0~0.4 mol/L)作为饱和液时,随着c(抗坏血酸)的增加,土壤中Pb的迁移能力随之增加,Pb的去除率得到提高.当c(抗坏血酸)达到0.4 mol/L时,土壤中Pb的去除率为36.86%;保持c(抗坏血酸)为0.4mol/L,当施加电压梯度由1 V/cm增至2 V/cm时,土壤中Pb的去除率得到增加(最高可达87.09%),通过Pb的形态变化可知,w(弱酸提取态Pb)由初始的2.99%(1 V/cm)最大可降至0.34%(2 V/cm),w(可还原态Pb)由初始的83.86%(1 V/cm)最大降至2.94%(2 V/cm).研究显示,当c(抗坏血酸)为0.4 mol/L、柠檬酸(作为阴极电解液)控制阴极电解室p H在2~3之间、施加电压梯度为2 V/cm时,土壤中Pb的迁移能力显著提高并达到较好的修复效果.

We systematically studied the effects of different concentrations( 0-0. 4 mol/L) of ascorbic acid and voltage( 1-3 V/cm) on the electrokinetic remediation of Pb-contaminated tailing soil( [Pb]=( 5491. 9 ± 24) mg/kg) based on the enhancing reagents ascorbic acid and citric acid. The tailing soil had the property of high acid buffer capacity,and the pH of the catholyte was controlled at 2-3 in the presence of citric acid( 0. 1 mol/L). The results indicated that with the increase of ascorbic acid concentration( 0-0. 4 mol/L),the migration ability of Pb in soil increased,and the removal rate of Pb increased in the process of electric voltage gradient of 1 V/cm. The removal rate of Pb was 36. 86% when the concentration of ascorbic acid in the soil increased to 0. 4 mol/L. When the applied voltage gradient increased from 1 V/cm to 2 V/cm,the removal rate of Pb in soil increased to 87. 09%. The morphological changes of Pb showed w( acid extractable Pb) decreased from the initial 2. 99% to 0. 34%,and w( reducible Pb) increased from the initial value of 83. 86% to 2. 94%. When ascorbic acid( as saturated liquid) concentration was 0. 4 mol/L,citric acid( as cathode electrolyte) controlled the cathode chamber pH at 2-3 and the applied voltage gradient was 2 V/cm,the migration ability of Pb in soil significantly improved. Eventually,the removal efficiency of Pb in soil was more significant.