土壤污染修复技术分析及其应用案例

概括了目前常用的土壤污染修复技术原理及其国内外相关工程应用的情况,分析不同修复技术存在的优缺点,以期为土壤修复技术的推广和应用提供一定参考。     

Electrokinetic Demixing of Two-Phase Aqueous Polymer Systems. I. Separation Rates of Polyethylene Glycol-Dextran Mixtures

Abstract

The separation of biomolecules and cells using aqueous two-phase systems provides a mild, nontoxic extraction medium, in contrast with conventional organic-aqueous phase extraction. However, due to their similar physical properties, immiscible aqueous phases do not separate rapidly. Because a net surface potential occurs on phase droplets due to the unequal partitioning of certain dissolved ions, a study was undertaken in which the resulting motion in an electric field (electro-phoresis) was explored as a possible method for rapid demixing of aqueous two-phase systems in a vertical electrophoresis column. The effects of electric field strength, buffer concentration, and field polarity on the demixing rate of mixtures of polyethylene glycol and dextran in phosphate buffer were measured. It was found that an optimum field strength of around 29.2 V/cm exists at which demixing is most rapid and occurs at about twice the rate in zero field at 25 ± 2°C using normal polarity (anode at the top of the column). With reverse polarity (anode at the bottom; electric field opposing gravitational settling) at a field strength of 14.6 V/cm the rate was 3 times as fast as in zero field. Strong convection was observed at high field strengths. Increasing the phosphate concentration increased the demixing rate.     

模拟Cd污染土壤的电动修复

文章研究电压、修复时间,添加新型绿色络合剂-PASP和缓冲液对电动修复实验效果的影响。结果表明,升高电压和加长修复时间都能提高Cd的迁移率。随络合剂浓度由2g,L升高到4g/L,阳极附近的迁移率由68．8％提高到78．5％,实验中在阴极加入醋酸后,阴极附近Cd的迁移率升高了12．3％,说明添加络合剂和醋酸可以提高修复效果。     

Electrokinetic Remediation. II. Amphoteric Metals and Enhancement with a Weak Acid

Abstract

A One-Dimensional Modl Is Developed For The Electrokinetic Treatment Of Aquifers Contaminated With An Ionic Salt. Electrokinetic Removal Of Amphoteric Metals Such As Zinc And Lead Is Simulated. The Use Of A Weak Acid (Acetic Acid) To Neutralize A Portion Of The Oh^? Generated Electrolytically In The Cathode Compartment Is Explored In Connection With The Electrokinetic Removal Of Nonamphoteric Metals Such As Copper And Cadmium.     

Modeling the Electrokinetic Decontamination of Concrete

Abstract

The decontamination of concrete is a major concern in many Department of Energy (DOE) facilities. Numerous techniques (abrasive methods, manual methods, ultrasonics, concrete surface layer removal, chemical extraction methods, etc.) have been used to remove radioactive contamination from the surface of concrete. Recently, processes that are based on electrokinetic phenomena have been developed to decontaminate concrete. Electrokinetic decontamination has been shown to remove from 70 to over 90% of the surface radioactivity. To evaluate and improve the electrokinetic processes, a model has been developed to simulate the transport of ionic radionuclei constituents through the pores of concrete and into the anolyte and catholyte. The model takes into account the adsorption and desorption kinetics of the radionuclei from the pore walls, and ion transport by electro-osmosis, electromigration, and diffusion. A numerical technique, orthogonal collocation, is used to simultaneously solve the governing convective diffusion equations for a porous concrete slab and the current density equation.

This paper presents the theoretical framework of the model and the results from the computation of the dynamics of ion transport during electrokinetic treatment of concrete. The simulation results are in good agreement with experimental data.

     

电极材料对电动修复重金属镉污染土壤效果的影响

电动修复法作为土壤重金属污染的有效修复方法,成为研究热点。目前影响土壤电动修复效率的因素很多,包括土壤类型、污染物性质、电压和电流大小、电极材料和结构等,但很少有文献报道电极材料对电动修复土壤重金属污染的效率影响。本作品采用不同电极材料(石墨、不锈钢和钛板)对尾矿附近重金属镉污染的土壤进行电动修复,研究了修复效率及土壤pH随时间的变化情况。当电场强度为1 V/cm,采用石墨电极电动修复土壤48 h总镉的去除效率为73%,不锈钢电极和钛电极的修复效率分别为44%和40%。石墨电极修复效率的提高归因于相比于不锈钢电极和钛电极,石墨电极提供更多的电子传递所需的活性界面。     

Fundamentals and Modeling of Electrokinetic Transport in Nanochannels

When the channel size approaches the thickness of the charged layer (typically, ∼10–100 nm), the resulting molecular and non-equilibrium effects are markedly different from those observed in larger channels and have a significant effect on the transport behavior of solutes and solvents. As a result, the problem of modeling fluidic behavior at the nanoscale has attracted increasing interest in recent years. This review introduces the fundamental theories and principles associated with electrokinetic transport and molecular dynamics modeling, and discusses various applications of nanofluidic devices in the physics, mechanics, and chemistry fields.     

The computer-derivation of thermodynamic equations Part I. First and Second Derivatives for Simple Systems

An algorithm is described for the systematic derivation of expressions for first and second thermodynamic derivatives involving the use of Jacobians. The algorithm is implemented by means of a list-processing language in conjunction with a commercially available symbolic mathematical system for use with a microcomputer. The algorithm is intended to replace tables and procedures currently used “by hand”. Attention is limited in this paper to simple systems with two degrees of freedom, but the algorithm is to be extended ultimately to chemical systems subject to equilibrium constraints. Examples are given to illustrate the procedure.     

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。     

Acid Enhanced Electrokinetic Remediation of a Contaminated Soil using Constant Current Density: Strong vs. Weak Acid

The most typical enhancement for electrokinetic remediation (EKR) involves the neutralization of the alkaline front generated at the cathode by the addition of an acid to the catholyte. Although the use of strong and weak acids can be found in the literature, there is still a clear lack of reliable comparisons between them. This paper presents a comparison of the results obtained for a real lead contaminated soil treated by EKR enhanced with nitric or with acetic acid. The divergences that are usually observed in those experimental results obtained when using constant voltage drop are avoided here by the use of EKR with constant current intensity and the disposition in series of the soil lab columns. Important differences are observed in the behavior of the system when the acid was changed. The time needed to achieve the same metal recovery is more than 3 times longer for the nitric acid. A standard sequential extraction procedure was used to fractionate the lead concentration in the soil according to its mobility in a before- and after-treatment way. Regardless of these important differences observed in the remediation time, the fractionation results after the experiments were almost the same for the two acid enhanced EKRs.     

Electrokinetic dewatering and thickening. I. Introduction and historical review of electrokinetic applications

An introduction to electrokinetics and a historical review of electrokinetic devices is presented.     

零价铁反应墙联合电动法修复铅锌矿区重金属复合污染农田土壤的试验研究

采用ZVI-EKR联用技术对Pb、Cu、Zn、As污染的农田土壤进行修复。与简单EKR技术对比,ZVI-EKR联用技术可以增加电流密度,零价铁比表面积大,铁粉在土壤和水的混合物中发生氧化还原反应和水解反应,生成氧化铁、四氧化三铁以及氢氧化铁胶体,能够吸附迁移到附近的重金属离子,提高电动修复的效率。     

城市污泥重金属电动修复技术与应用研究进展

重金属污染是目前城市污水处理厂污泥农用的主要障碍之一。电动修复作为一门新兴的污染环境介质绿色修复技术,具有投资少、去除效率高和处理时间短等优点。特别是对于水力渗透性差的污泥,电动修复技术具有良好的应用前景。论文介绍了城市污泥重金属电动去除技术原理,并综述了近几年国内外在修复效果及其影响因素等方面的研究现状。同时,对该技术应用过程中存在的问题和未来研究方向进行了讨论和展望。     

Electrokinetic dewatering and thickening. III. Electrokinetic cells and their application to a range of materials

The choice of electrokinetic cell for use with materials of differing flow characteristics is reviewed with special reference to products previously evaluated in the author's laboratory. Areas in which electrokinetic methods are at present applied are summarized.     

An Acidic Injection Well Technique for Enhancement of the Removal of Copper from Contaminated Soil by Electrokinetic Remediation Process

An experimental study constituting eight different tests was performed to investigate the effect of relevant factors on the remedial efficiency of electro-kinetic process applied to clean-up Cu contaminant from three types of Iraqi soil. An efficiency enhancement scheme was employed involving pH control, acid-injection wells, and optimized potential gradient as part of the investigative program. With pH controlled within the range 2.5-3, four acid-injection wells, and a potential gradient of 0.8 V/cm; overall clean-up efficiencies of 85%, 58%, and 34% were achieved for sandy, sandy loam, and silty loam soils, respectively.     

腐植酸强化电动修复铅锌矿区复合重金属污染农田土的实验研究

电动修复实验中,通过加入络合剂腐殖酸,提高对水口山铅锌矿区农田土壤中铅、锌、镉、铜的去除效率。实验结果表明,当修复电压达到17.6 V·cm~(-1)的时候,修复时间为7天的时候,铅、镉、铜、锌的去除效率分别达到65.04%、94.92%、89.88%、91.05%。电动修复后,土壤中可交换态和碳酸盐结合态的Cd含量大大降低,减少了Cd的环境毒性影响。     

Groundwater Cleanup by in-situ Sparging. I. Mathematical Modeling

Abstract

The technique of in-situ sparging may provide a cheaper and more rapid method for removal of volatile organic compounds (VOCs) from groundwater than conventional pump and treat operations. A local equilibrium model is developed to describe in-situ sparging by means of a horizontal lateral slotted pipe at the bottom of a trench filled with crushed rock and normal to the direction of flow of the groundwater. The effects of air flow rate, groundwater flow rate, aquifer thickness, number of theoretical transfer units (related to axial dispersion), Henry's constant of the VOC, and initial VOC concentration are explored. Also, a method is developed for using vadose zone soil gas pressure measurements in the vicinity of a single sparging well to estimate the radius of influence of the well.     

Experiments in extensive mixing in laminar flow. I. Simple illustrations

Simple quantitative mixing experiments in well-defined deformations clearly demonstrate the validity of previously derived equations relating deformation and mixing. A simple mixture of black and white polyethylene is studied by direct measure of striation thickness. The well-known linear relationship in simple shear is demonstrated. By using a simple method for uniform reorientation, the second power relationship in shear once interrupted, the third power relationship in shear twice interrupted and the fourth power relationship in shear interrupted three times are demonstrated. In uniaxial elongational mixing of a silicone fluid, exponential dependence of mixing on strain is demonstrated.     

Properties of Some Simple Glass/Ceramic Systems

The density, transformation-range behavior, and electrical conductivity of three glass-crystal systems of increasing complexity were measured. The systems studied included glass/alumina composites, spherulitic lithium disilicate crystallized from glass of the same composition, and a commercial glass-ceramic in which the crystallization of lithium metasilicate resulted in changes in the composition of the residual glass.