ABSTRACT

In this study, electrokinetic remediation (EKR) was performed to reduce the risk of heavy metal contaminants viz., Cd, Cu, Ni, Pb and Zn associated with different fractions of lake sediments. Firstly, batch experiments were performed to estimate the optimal concentration of enhancing agents such as EDTA, nitric acid and acetic acid for effective dissolution of heavy metals from sediments and to minimize the dissolution of earth metals (Fe and Al) to maintain good soil health. In addition to that, the effect of pH on dissolution of these heavy metals with optimized concentration was studied separately. The results from batch experiments showed that EDTA with the concentration of 0.01 M enhanced the heavy metal dissolution as 38–88% in the pH range 2–12. Nitric acid and acetic acid with the concentration of 0.05 M enhanced the heavy metal dissolution as 18–85% and 15–80%, respectively in the pH range 2–6. For enhancing agents like nitric acid and acetic acid, the increase of pH (above 6) led to the formation of metal hydroxides and carbonates, which reduced the efficiency of heavy metal dissolution. Secondly, EKR experiments were conducted in a reactor with optimal concentration of EDTA (0.01 M), nitric acid and acetic acid (0.05 M) as electrolyte and sediment saturation solution for 7–21 days of treatment time. After 21 days of EKR with 0.01 M of EDTA as enhancing agent, the average removal of heavy metals achieved about 46.4–78.8 % and associated risk with metals viz., Cd, Pb, Zn and Cu reduced from high to low risk and Ni reduced from high to medium risk, according to risk assessment category. Alternatively, the EKR treatment using nitric acid and acetic acid showed the average removal of heavy metals of about 17.2–43.60% and 24.9–57.2 %, respectively, and all heavy metals pose medium risk, except for Cd, which showed low risk to the environment.

摘要

在这项研究中，进行了电动修复（EKR）以减少重金属污染物即与湖泊沉积物的不同部分相关的Cd，Cu，Ni，Pb和Zn的风险。首先，进行分批实验以评估增强剂（如EDTA，硝酸和乙酸）的最佳浓度，以有效地从沉积物中溶解重金属，并最大程度地降低土壤金属（Fe和Al）的溶解，以保持良好的土壤健康。除此之外，还分别研究了pH对优化浓度的这些重金属溶解的影响。批处理实验的结果表明，浓度为0.01 M的EDTA在2-12的pH范围内使重金属的溶解度提高38-88％。硝酸和乙酸的浓度为0。05 M在2-6的pH范围内分别提高了18-85％和15-80％的重金属溶解度。对于硝酸和乙酸等增强剂，pH值的升高（高于6）导致形成金属氢氧化物和碳酸盐，从而降低了重金属溶解的效率。其次，在反应器中以EDTA（0.01 M），硝酸和乙酸（0.05 M）作为电解质和沉积物饱和溶液的最佳浓度进行EKR实验，处理时间为7-21天。在用0.01 M EDTA作为增强剂的EKR 21天后，重金属的平均去除率达到46.4-78.8％，与金属相关的风险即Cd，Pb，Zn和Cu从高风险降低到低风险，Ni减少根据风险评估类别，从高到中风险。或者，