Leszczynska Danuta, Ahmad Hafiz
Civil and Environmental Engineering Department, Florida State University,2525 Pottsdamer Street, Tallahassee, FL 32310, USA.
Int J Environ Res Public Health. 2006 Jun;3(2):196-201. doi: 10.3390/ijerph2006030023.
The electrokinetic technique is an emerging technology presently tested in situ to remove dissolved heavy metals from contaminated groundwater. There is a growing interest for using this system to cleanse clayey soil contaminated by toxic metallic ions. Currently, there are very few available non-destructive treatment methods that could be successfully applied in situ on low permeable type of soil matrix. The main objective of presented study was to validate and possibly enhance the overall efficiency of decontamination by the electrokinetic technique of the low permeable soil polluted by the arsenic in combination with chromium and copper ions. The chosen mixture of ions was imitating leak of pesticide well known as chromate copper arsenate (CCA). The chosen technique is showing a big promise to be used in the future as a portable, easy to install and run on sites with spills or leaks hard to reach otherwise; such as in the dense populated and urbanized areas. Laboratory electrokinetic experiments were designed to understand and possibly manipulate main mechanisms involved during forced migration of ions. All tests were conducted on artificially contaminated kaolinite (low permeable clay soil). Electrokinetic migration was inducted by the low voltage dc current applied through soil column. Series of experiments were designed to assess the efficiency of arsenic-chromium-copper remediation by applying (1) only dc current; and (2) by altering the soil environment. Obtained results showed that arsenic could be successfully removed from the soil in one day (25 hours) span. It was significant time reduction, very important during emergency response. Mass recovered at the end of each test depended on initial condition of soil and type of flushing solution. The best results were obtained, when soil was flushed with either NaOH or NaOCl (total removal efficiency 74.4% and 78.1%, respectively). Direct analysis of remained arsenic in soil after these tests confirmed substantial drop of the initial mass of arsenic in soil profile from 51.54 mg to 10.62 mg (NaOH) and 5.68 mg (NaOCl) after 25 hours of treatment.
电动技术是一种正在现场测试的新兴技术，用于从受污染的地下水中去除溶解的重金属。人们越来越有兴趣使用该系统来净化被有毒金属离子污染的粘性土壤。目前，很少有可用的非破坏性处理方法能够成功地在低渗透性土壤基质上进行现场应用。本研究的主要目的是验证并可能提高电动技术对受砷与铬和铜离子污染的低渗透性土壤的去污整体效率。所选择的离子混合物模拟了一种名为铬酸铜砷酸盐（CCA）的农药泄漏。所选择的技术显示出在未来有很大的应用前景，可作为一种便携式、易于安装且能在难以到达的泄漏或溢出现场运行的技术；例如在人口密集和城市化地区。实验室电动实验旨在了解并可能操纵离子强制迁移过程中涉及的主要机制。所有测试均在人工污染的高岭土（低渗透性粘土）上进行。通过施加低电压直流电流穿过土壤柱来引发电动迁移。设计了一系列实验来评估通过（1）仅施加直流电流；以及（2）改变土壤环境来修复砷 - 铬 - 铜的效率。获得的结果表明，砷可以在一天（25小时）内成功从土壤中去除。这是显著的时间缩短，在应急响应中非常重要。每次测试结束时回收的质量取决于土壤的初始条件和冲洗溶液的类型。当用NaOH或NaOCl冲洗土壤时获得了最佳结果（总去除效率分别为74.4%和78.1%）。这些测试后对土壤中残留砷的直接分析证实，经过25小时处理后，土壤剖面中砷的初始质量从51.54毫克大幅下降至10.62毫克（NaOH处理）和5.68毫克（NaOCl处理）。
