Electrodialytic remediation of soils polluted with Cu,Cr, Hg,Pb and Zn

Electrodialytic remediation of heavy metal polluted soil is a method which combines the technique of electrodialysis with the electromigration of ions in the polluted soil. Results from laboratory-scale remediation experiments of soil samples from three real contaminated sites with different heavy metals are presented. In the three cases it was possible to mobilize and reduce the amount of the pollutants in the soil. The pollutants were (1) copper and chromium, (2) mercury and (3) copper, lead and zinc. For a loamy sand polluted with copper and chromium it was possible to decontaminate the soil to an extent lower than the recommended critical values for metal concentration in soil. Parameters that were identified as important for the efficiency of the electrodialytic remediation method were pH in the soil, lime content and speciation of the heavy metal. ©1997 SCI     

重金属污染土壤修复技术应用

重金属土壤污染是国内亟待解决的环境问题。本文在对贵冶周边区域土壤监测分析与重金属污染土壤修复技术评述的基础上,切实地、有针对性地提出该项目区污染土壤修复与综合治理的技术方案。     

不同电极电动修复铜镉复合污染土壤的研究

针对铜镉污染土壤问题,研究了不同电极材料对电动修复土壤效果的影响。采用不锈钢、石墨板、钛板、钛网四种不同电极对土壤进行修复。结果显示,石墨板电极对2种重金属的总去除率较好,Cu为40.34%,Cd为95.21%,且Cd的去除率明显高于Cu。另外,不同电极材料对修复过程中电流和处理后重金属形态分布的影响不大,其中石墨板电极电流稳定时的值为42mA,高于其他三种电极。     

复合污染土壤的生物修复研究进展

石油及重金属等原材料的广泛开采与使用,使石油、重金属污染及其复合污染日益加重,对环境和人类的危害也越来越大。生物法在污染物治理方面由于其成本效益良好以及环境友好性的特点被认为是最值得关注的方法。简要介绍了重金属和石油的污染类型、复合污染现状、降解石油和修复处理重金属污染的作用机理,重点说明添加微生物及添加营养物质在重金属-石油复合污染土壤修复中的重要性,并预测了未来在处理土壤污染方向的主流发展趋势。     

土壤重金属污染及治理技术

分析了土壤中重金属污染状况,总结了土壤重金属污染主要修复技术,包括物理化学修复、化学修复、生物修复和农业修复四种技术,并对四种修复技术进行了比较,使人们了解不同修复技术的特点及适用条件.对今后重金属主要研究方向进行了展望.     

Electrokinetic remediation of lead‐, zinc‐ and cadmium‐contaminated soil

Electrokinetic remediation of lead‐, zinc‐ and cadmium‐contaminated sand and clayey soils has been investigated under laboratory‐scale conditions. Soil extracts of heavy metals (by 1 M HCl solution) were analysed by optical emission spectrometry. The efficiency of electrochemical remediation was partially dependent on the pH of the soil media. With pH increase, the migration of heavy metal ions toward the cathode was limited. When acetic acid was added to the sandy soil, almost complete remediation was achieved. A clay layer inserted in the cathode area did enhance the remediation rate. The most effective clean‐up was achieved for zinc and cadmium, with less effective clean‐up being achieved for lead. The effectiveness of the electrokinetic remediation of heavy metal‐contaminated clayey soil was low. The appropriate acidity was not achieved using acetic acid because of the high buffering capacity of clay, and metal ion migration was impeded by its sorption onto some clay components. The conclusion was made that clays could be used as immobilizing media for heavy metal ions by electrokinetic remediation of various soils. © 2001 Society of Chemical Industry     

Layered double hydroxides:Scale production and application in soil remediation as super-stable mineralizer

Soil contamination by heavy metals has presented severe risks to human health through food chain.As one of the most promising remediation technologies,in-situ immobilization strategy has been widely adopted in practice.However,considering the large quantities of contaminated soil,it is still a huge challenge to design low-cost amendments with strong and long-term immobilization ability.Layered double hydroxides(LDHs) have drawn tremendous attention in fundamental research and practical applicati...     

重金属污染土壤修复研究进展

世界范围内的土壤中广泛存在重金属污染,正确认识土壤中重金属的存在形式有利于采取适当的方式进行土壤修复。现有技术中,根据修复原理可分为物理、化学、生物、电气和热修复五种,具体方法为覆盖、封装、填埋、土壤冲洗、电动萃取、稳定化/固化、玻璃化、植物修复及微生物修复。这些技术具有相应的优缺点和适用性,覆盖、封装和填埋适用于污染严重面积小的区域;土壤冲洗工程量大,需要对螯合剂进行处理;电动萃取适用于浅层、低浓度污染场地,处理时间长;稳定化/固化应用广泛但不能从土壤中根除重金属;植物修复需提高效率。合适的修复技术对于重金属污染土壤再利用至关重要,需结合污染的类型和程度、修复目标、场地特征、成本效益、修复时间。     

Diagnostic analysis of electrodialysis in mine tailing materials

Removal of heavy metals from mine tailings and soil contaminated by copper mining activities was studied under batch electrodialytic conditions. Two types of mine tailings were treated: (i) freshly produced tailings coming directly from the flotation process, and (ii) tailings deposited in a tailings pond, for approximately 20 years. The main contaminant was copper—found in concentration around 800-1800 ppm. The fractionation of copper and other characteristics of the tailings differ for the two tailings, indicating natural oxidation reactions in the old deposited ones. Electrodialytical removal results of a soil sampled close to an abandoned cupric pyrite mine—mainly polluted with lead (around 3800 ppm) are also presented. The results show that the heavy metals could be mobilized in all three contaminated solid materials using the electrodialytic process.The effect of adding different types of extracting solutions, such as distilled water, or H₂SO₄ at pH 0, H₂SO₄ + HNO₃ at pH 1.9 and 4.2 or NH₄Cl, in the electrodialytic cell, was investigated. From all the experiments, H₂O presented the best performance for the electro-removal of Cu from the old deposited mine tailings, achieving 63%. However, water removed only 15% of Pb from the soil, and no Cu from the fresh tailings. The soil fractionation of the metals before and after the experiments was evaluated by sequential chemical extractions, in order to work further on the optimization of the remediation conditions.     

陕北煤矿区农田土壤重金属污染现状及修复研究

为了研究煤炭开采过程对周边农田土壤的重金属污染影响,对神木大柳塔煤矿区周边农田土壤和玉米幼苗进行采样,测定分析35个典型采样点和空白对照的重金属含量。结果表明：煤矿区农田土壤中Cu、Zn、Pb、Cr、Cd、Hg、As等重金属平均含量均高于对照区,说明煤矿开采过程对农田带来了重金属污染。Zn、Cu、Pb、Cr、Hg等重金属元素在土壤中的含量与玉米中的含量显示出正相关性,表明土壤中的重金属含量直接影响着植物对重金属的吸收,并有针对性地提出了土壤重金属污染的防治和修复措施,以期为矿区污染治理提供科学依据。     

Leaching of Pb Contaminated Soil using Ozone/UV Treatment of EDTA Extractants

Abstract

One of the main problems of EDTA based soil‐washing technologies for remediation of heavy metals contaminated soils is the separation of EDTA‐heavy metals complexes from the waste extractant. In our study an advanced oxidation process using ozone and UV was used for the decomposition of EDTA‐Pb complexes in soil extractants obtained during leaching of Pb contaminated soil. Released Pb was removed by absorption. Twenty consecutive soil treatments with 2.5 mmol kg^?1 EDTA removed 58.4% of Pb and greatly reduced the Pb mobility and oral‐availability. The waste extractant was colorless, with slightly basic pH and with low Pb and EDTA concentrations.     

电动力学辅助植物修复重金属污染土壤的特征机制与机遇

土壤重金属污染具有污染过程复杂、危害突出和修复困难等特点,修复刻不容缓。电动力学辅助植物修复（EKAPR）致力于弥补电动力学和植物修复各自劣势,协同发挥二者优势,解决电动力学无法彻底清除土壤重金属和植物修复缓慢、作用范围有限等突出问题。本文通过分层总结,归纳了电动力学辅助植物修复重金属的研究现状、影响类型与作用特征、相互作用关系及强化修复机制等。综述表明,EKAPR体系电动力学和植物相互作用,存在有利或不利于重金属清除的影响,在克服自身的局限方面两者也存在很多协同效应;EKAPR过程主要受电场类型、电场布置与强度、pH演变、添加剂等的控制。电动力学通过改善重金属的空间及形态分布,促进养分吸收及刺激根际分泌等作用机制,可有效提高重金属植物吸收富集及污染土壤修复效果。EKAPR被认为是新颖、绿色、可持续的原位重金属污染场地修复技术,在实现污染场地修复方面具有较大发展前景。分析表明,现有研究工作开展较少,若干技术问题和应用挑战仍然存在。加大关键变量影响特征分析及调控、电动力学辅助下植物营养与重金属分布变化机制、累积特征及强化机制研究是克服难点及推动EKAPR技术应用的关键。     

Effect of different treatments on electrokinetic remediation of Zn,Pb and Cd from a contaminated calcareous soil

Electrokinetic remediation is a promising method to decontamination of the heavy metals from soils.In this paper,the remediation of a contaminated calcareous soil with Zn,Cd and Pb sampled from around Zanjan province of Iran,was investigated using electrokinetic method.In this paper,the soil contain a high concentration of Zn (1400 mg·kg-1),Cd (15 mg·kg-1) and Pb (250 mg·kg-1).Electrokinetic decon-tamination consists of two series of experiments as follows:(1) the effect of five treatments including the use of distilled water,acetic acid and EDTA electrolyte solutions,and approaching anodes systems,and the circulation flow of electrolyte at two different voltage gradient (i.e.1.33 and 2.66 V·cm-1),and(2) the effect of moisture content (saturated,FC and 0.7FC,FC indicated soil moisture at "Field Capacity") with a voltage gradient of 1.33 V·cm-1.After applying electric current for 5 days,the results of experiments indicated that the removal efficiency of heavy metals can be increased by raising the volt-age gradient.In this matter,the highest remediation can be observed among different treatments in EDTA(Ethylene diamine tetra acetic acid) treatment (40.11％,43.10％ and 24.7％ for Zn,Cd and Pb,respectively).Moreover,the heavy metals removal at the saturated moisture was at the highest level so that 32.62％cadmium,31.33％ zinc and 18.82％ lead being removed after 120 h of electric current application.By decreasing moisture to 0.7FC,the removal percentage for the three heavy metals obtained 20.97％,18.44％ and 12.25％,respectively.Furthermore,Cd had the highest removal,and Zn and Pb were next among the three heavy metals in question.     

生物质炭在重金属污染土壤修复中的应用研究现状

为充分发挥生物质炭多孔性、表面活性、选择性吸附和高碱性等性能在有效控制重金属生物迁移中的作用,以期为重金属污染土壤修复技术提供参考。介绍了我国重金属污染土壤的概况,综述了生物质炭在重金属污染土壤修复中的应用,重点介绍了植物修复、化学淋洗、土壤性能改良、固化/稳定化、热解吸修复和电动力学修复等技术的应用情况,简要概述了原料种类、热解温度和表面官能团对生物质炭性质及生物质炭对土壤环境的影响,并展望了生物质炭在重金属污染土壤修复中的发展前景。     

重金属污染土壤化学萃取修复技术研究进展

重金属污染土壤的修复已成为土壤及环境科学领域的热点问题。化学萃取法是少数能彻底去除土壤中重金属的技术之一,具有高效、快速的特点。萃取剂是化学萃取技术的关键。常用化学萃取剂有螯合剂、酸、表面活性剂等。其中螯合剂的研究及应用最广泛。为了加速我国重金属污染土壤的修复工作,结合近年来的研究进展对萃取剂进行综合描述,并且分析化学萃取法的发展前景。     

改性生物炭对土壤重金属污染修复研究进展

土壤中金属污染导致食用林产品、农产品中重金属高富集,严重威胁人类健康。生物炭作为简单易得,来源广泛的吸附材料,可用于土壤重金属污染物修复。本文主要综述了生物炭的制备、改性剂的选择与功能、改性方法及改性生物炭的特性。介绍了改性生物炭的表征手段如傅里叶变换红外光谱、扫描电子显微镜、X射线光电子能谱和比表面积和孔径分析仪在生物炭改性过程中的作用及分析方法。客观分析了改性生物炭的制备方式及对土壤重金属污染修复的机制及效果,并讨论生物炭及改性生物炭对重金属常见的吸附机理以及表面吸附、静电作用、离子交换和共沉淀的特征和条件。大量的研究结果表明,生物炭对降低土壤中重金属的有效态含量具有显著效果,且经过酸碱、氧化还原、吸附剂复合等方式改性后吸附性能更加高效和稳定。生物炭改性是为了提高生物炭的安全性、高效性、重复使用性和环境友好性,同时加强生物炭的重金属修复性能。因此,功能型生物炭的研制及拓展改性生物炭的应用是生物炭改性的进一步深入研究方向。     

淋溶条件下生物炭对矿区土壤中重金属迁移的影响

以玉米秸秆为原料在450℃下制备生物炭,将生物炭按5%的炭土比例施入矿区重金属污染土壤中。通过室内土柱淋溶试验,分析加入生物炭对土壤淋出液pH、重金属纵向迁移行为及重金属累积释放量的影响。结果表明：加入生物炭处理后土壤淋出液的pH显著高于对照处理,说明生物炭可以在一定程度上缓解土壤的酸性。与对照相比,添加生物炭降低了重金属向下层土壤迁移的风险,淋溶后土柱中Pb、Cu、Zn和Mn的纵向迁移量分别降低了65.93%、50.95%、49.29%和30.95%,生物炭对土壤中重金属纵向迁移抑制的顺序为Pb>Cu>Zn>Mn,生物炭对Pb的钝化效果最好。随着淋溶液体积的增加,Pb、Cu、Zn和Mn这4种重金属的淋溶累积释放量总体上呈现出前期快速溶出和后期缓慢溶出两个明显的阶段。4种重金属的累积释放量大小为Pb>Mn>Zn>Cu,添加生物炭后明显降低了重金属的累积释放量。对土壤中金属释放过程进行数学方程拟合后发现,应用Elovich方程能较好地描述重金属释放过程,说明这4种重金属元素在土壤中的淋溶和释放过程的机制不是单一反应过程,而是属于活化能变化较大的复杂反应过程。加入生物炭后各重金属的b值均低于对照组,重金属迁移速率随着生物炭的添加而降低,说明生物炭能提高土壤对重金属离子的吸附力,降低因土壤淋溶作用而引起的重金属迁移,可以实现对重金属复合污染矿区土壤的修复。     

Electro-partitioning with composite ion-exchange material: an innovative in-situ heavy metal decontamination process

Selective in-situ removal of heavy metals from a contaminated soil/sludge combines the benefits of: (a) being a low risk operation since the soil/sludge is not excavated and transported, (b) being economically prudent since only the target contaminant is removed, and (c) providing the possibility of reuse/recycle of the heavy metals since they are selectively removed. However, the main problem faced in such a process is inserting a material into the soil/sludge which can selectively remove heavy metals from the background of other ions which are much higher in concentration than the target heavy metals but are innocuous from a regulatory point-of-view. The affinity of chelating ion-exchange resins toward heavy metal cations is well established but their morphology (spherical beads of diameter <5 mm) is unsuitable for use in an in-situ process. This communication explores the use of a novel material termed composite ion-exchange material (CIM) which allows microspheres of chelating resins to be entrapped in a Teflon^® network, thus producing a thin sheet (≈0.5 mm) which can be easily introduced into or withdrawn from a soil/sludge sample. The CIM is used in a physico-chemical process where application of DC potential gradient forces the heavy metal cations to move toward the cathode and consequently contact the CIM sheet wrapped around the cathode. The strong affinity of chelating exchangers inside the CIM forces selective uptake of the heavy metals from the contaminated solid phase. After passage of current for a determined amount of time, the CIM is withdrawn from the soil/sludge and chemically regenerated, thus allowing the heavy metals to be concentrated in an acid solution. This communication presents preliminary results of experiments performed to explore the use of this process and also discusses modifications required to achieve higher suitability.     

生物炭对矿区土壤重金属有效性及形态的影响

为探索生物炭作为改良剂修复矿区重金属污染土壤的可行性,以玉米秸秆为原料在450℃制备生物炭,采用扫描电镜、能谱分析以及傅里叶变换红外光谱等分析与测试手段对其进行表征。采用室内连续培养的方法,研究在不同培养时间条件下,添加不同施用量（0、1%、3%和5%）的生物炭后,对矿区土壤pH,阳离子交换量（CEC）,土壤重金属Cu、Zn、Pb和Mn有效性以及重金属不同形态变化的影响。结果表明：生物炭能够提高土壤的pH和CEC,且都随着添加量的增加而增加。56d土壤培养后,与对照相比,1%、3%和5%添加水平下pH分别增加了1.14个、1.42个和1.67个单位,土壤CEC分别增加了2.02cmol/kg、3.60cmol/kg和5.39cmol/kg。添加不同含量生物炭后,土壤中有效态重金属均呈现不同程度的降低,而且生物炭添加量越大,降幅也越大。在5%添加水平下,生物炭分别使Cu、Zn、Pb和Mn有效态下降了49.2%、46.2%、72.5%和26.3%。重金属有效态含量与土壤pH、CEC均呈显著负相关关系。添加生物炭后,土壤中重金属的形态发生了变化,由易迁移的弱酸提取态向更加稳定的残渣态转化,且生物炭添加量越大,钝化效果越显著。综上所述,玉米秸秆生物炭的添加提高了矿区重金属复合污染土壤的pH和CEC,促进了重金属复合污染土壤中Cu、Zn、Pb和Mn的弱酸提取态向化学性质稳定的残渣态转化,降低了土壤重金属的有效性,实现了对重金属复合污染土壤的修复。     

Electrokinetic remediation of metals and organics from historically contaminated soil

The electrokinetic remediation of an historically contaminated soil is described. The soil was contaminated with a range of metals including lead, zinc, manganese, copper and arsenic, polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene and xylene (BTEX). A small‐scale experiment (973.2 g dry weight soil), utilising a planar electrode configuration, investigated the potential for moving metals and organics. After 23 days treatment at a current density of 3.72 A /m⁻², 44% of calcium and 29% of manganese were removed from the soil at the cathode. Of the other contaminating metals, zinc and lead moved towards the cathode, but with no significant removal from the soil. Movement of PAHs was also observed, with a 94% reduction in concentration in the third of the soil closest to the anode after 23 days. A larger scale experiment (46.7 kg dry weight soil) utilised a hexagonal array of tubular anodes surrounding a central tubular cathode. Treatment for 112 days led to acidification of the soil to pH 2.59 closest to the anode in a direct line between the anode and cathode. Soil not directly in line between the electrodes was not acidified significantly. Movement of metal ions was observed, in line with the electrodes, with concentrations of lead and arsenic increasing to 162% and 171% of starting concentrations closest to the anode, respectively, and those of zinc, copper and manganese decreasing to 42%, 68% and 57%, respectively. At positions not directly in line with the electrodes, no significant metal movements were observed. Overall, there was no significant removal of contaminating metals from the soil. PAHs and BTEX compounds were moved by electroosmosis towards the cathode, with soil concentrations of PAHs reduced from 720 mgkg⁻¹ to 4.7 mgkg⁻¹ after 22 days. PAHS (28 mg) and benzene (9660 mg) were recovered in granular activated carbon (GAC) columns. © 2000 Society of Chemical Industry