黄土中铜铅金属的电动迁移及强化去除机理研究

Electrokinetic remediation of copper and lead contaminated Loess and enhancement mechanisms of combined methods

以人工配制的铜铅污染黄土为研究对象,使用性价比更高、二次污染风险更低的电动修复技术,研究污染黄土中铜铅金属离子迁移规律,分析电极材料、阳离子交换膜及酸预处理等单一强化方法对电动力学修复过程中电流、电渗流、pH、电导率、去除效率、离子赋存形态等的影响规律,揭示强化方法的电动修复机理,并在此基础上明确三者联用电动修复强化机理。结果表明:电动土工合成材料(EKG)电极比石墨电极具有更高的电流,同时能够快速释放较多的氢离子和氢氧根离子,在阳极附近提供了酸性环境促进了更多重金属离子的解吸和迁移,从而提高了修复效率,但阴极附近的沉淀导致去除效率较低;阳离子交换膜能够较好地调控阴极附近土壤的pH值,有益于金属离子的解吸,然而阳离子交换膜引起的浓度差极化作用,以及阳离子交换膜表面沉淀现象使电流和电渗流显著降低,限制了去除效率的提高;酸预处理能够降低污染黄土试样pH值,使黄土中黏土矿物、水合氧化物及有机质表面原始的负电荷减小甚至变为正电荷,有助于重金属提前解吸,显著提高电导率,从而提高电流和电渗流,与阳离子交换膜强化效果接近,是一种较为经济的强化手段;EKG电极、阳离子交换膜及酸预处理三者联用能够充分发挥各自的强化机制及优势,可提高电流且降低黄土pH值,避免重金属在阴极附近形成沉淀,促进重金属离子的解吸和迁移,强化电动修复去除效率。研究成果进一步证明了电动修复技术应用于去除黄土中铜铅金属污染的可行性及强化方法联用的有效性。

This study focuses on the use of electrokinetic remediation technology to investigate the migration of copper and lead metal ions in artificially prepared copper and lead contaminated loess.The technology chosen has a higher cost performance and lower risk of secondary pollution.The study also examines the impact of single-component remediation methods such as electrode materials,cation exchange membrane and acid pretreatment on various factors such as current,electroosmotic flow,pH,electrical conductivity,removal efficiency and ion occurrence during the process of electrokinetic remediation.The findings revealled the electrokinetic remediation mechanism of the strengthening methods and further clarified the strengthening mechanism of the combination of the three remediation methods.According to the results,the electrokinetic geosynthetics(EKG)electrodes have a higher current than graphite electrodes,while being able to rapidly release more hydrogen ions and hydroxide ions.An acidic environment is provided near the anode to promote the desorption and migration of more heavy metal ions,thereby improving the remediation efficiency,whereas precipitation near the cathode results in lower removal efficiency for this part.The use of cation exchange membrane can improve soil pH regulation near the cathode and aid in the desorption of metal ions.The polarization resulting from concentration differences across the cation exchange membrane and precipitation on its surface can substantially decrease the current and electroosmotic flow,thereby limiting the increase in removal efficiency.The pH value of polluted loess sample can be reduced through acid pretreatment.This leads to a decrease in the original negative charge on the surface of clay minerals,hydrated oxides,and organic matter in the loess,and can even make it positive.Such a change is beneficial for the early desorption of heavy metals,and greatly improves the electrical conductivity,therefore enhance the current and electroosmotic flow,which is comparable to the reinforcing effect of using a cation exchange membrane,so it is a cost-effective approach to strengthening.The combined use of EKG electrodes,cation exchange membranes and acid pretreatment can effectively enhance their individual mechanisms and advantages.This combination can increase current flow,lower the pH value of loess,prevent heavy metal precipitation near the cathode,promote the desorption and migration of heavy metal ions and ultimately enhance the electrokinetic remediation removal efficiency.This study further illustrates the effectiveness of electrokinetic removal of heavy metal in copper and lead contaminated loess and the feasibility of the proposed remediation methods.