土壤清洗技术研究进展

针对普遍存在的土壤污染问题,综述了土壤清洗的机理、技术及研究现状,并分析了其中存在的问题,指出可生物降解的绿色清洗剂以及组合技术将是今后土壤清洗技术发展的重要方向。     

Remediation of phenanthrene contaminated soils by nonionic surfactants enhanced soil washing coupled with ozone oxidation

In the present work, soil washing followed by ozone oxidation for remediation of phenanthrene (PHE) contaminated soils was investigated. The PHE removal efficiencies of TX-100 and Brij-35 at 3000 mg/L were 80.2% and 73.8%, respectively. In the ozone oxidation process, the oxygen supply rate was more rapid and the ozone concentration in the water rose quickly after 2 h. The degradation efficiencies for PHE, Brij-35, and TX-100 at 20 mg/L ozone concentration were 99%, 99%, and 45%, respectively. Our investigation suggests that coupling ozone oxidation with surfactant-enhanced soil washing is an effective method for removing hydrophobic compounds from soils.     

除草剂在土壤中的微生物降解及污染土壤的生物修复

除草剂施入土壤中后，一般通过物理、化学与生物学过程而消失。微生物降解是除草剂在土壤中消失的最重要因素。评述了除草剂在土壤中的微生物降解及主要类型除草剂的降解特点，提出了长残留除草剂污染土壤的生物修复技术。     

Separation of polyaromatic hydrocarbons from contaminated soils using microwave heating

The microwave treatment of soils contaminated with heavy- and light-hydrocarbons was investigated. The soils were characterised to determine the total organic liquid content and PAH contents, and the dielectric properties of the soils were measured across a range of temperatures. The heavy- and light-contaminated soils behaved very differently in a microwave environment, with bulk soil temperatures limited to 100 °C for the light-contaminated soil. Microwave treatment is shown to remove PAHs from both the heavy- and light-contaminated soils, and it is demonstrated that 95%+ PAH removal can be achieved under moderate processing conditions. Complete remediation of the soils is possible at high microwave powers or long residence times. It is shown that PAH removal can take place at bulk temperatures well below the boiling point of those compounds and a number of explanations are proposed for this behaviour. The mechanisms of PAH removal are investigated for both the heavy- and light-contaminated soils and thermal desorption, selective heating and entrainment mechanisms can all be exploited.This is the first step in the development of a continuous microwave treatment process for the removal of PAHs from contaminated soil on an industrial scale.     

Exploration of contaminated soils and sediments

The scale and shape of areas and volumes of contamination at and below the Earth's surface are summarized. It is argued that in terms of their anomalous chemical composition, spatial distribution and relation with the host matrix, analogies can be drawn between bodies of contamination and deposits of metalliferous minerals. It is recommended that bodies of contamination are explored in much the same ways as mineral deposits. Additional attention must be given to their greater chemical complexity and degree of mobility. Characterization of clays and other sorbents is particularly important in contaminated soils and sediments. The scavenging property of clays means that they act as natural immobilizers of contaminants and can be employed as contaminant containment barriers. Clays are, however, vulnerable to alteration and degradation of their sorption capacity, which can lead to the release of absorbed contaminants.     

Statistical analysis of washing efficiency for solid particle soil

In a previous study, statistical method using two distributions was applied to analyze detergency of oily soil. The method uses statistical distributions of detergent power and adhesive force of soil. In this paper, this method was applied to an analysis of detergency of solid particles. Soiled cotton cloth was prepared with red iron oxide dispersion liquid in Terg-O-Tometer. Four-time consecutive washings tests were conducted with dodecyl sulfuric acid sodium salt (SDS) and alcohol ethoxylate (AE) aqueous solutions in Terg-O-Tometer. Change of removal efficiencies due to repetitive washing was utilized to seek the two distributions. Predicted removal efficiencies calculated from computer simulation corresponded to experimental values. Different adhered states of soil, prepared by varying soiling conditions, were expressed as Removal Resistance. As soiling mechanical power increased, Removal Resistance shifted toward higher adhesive force of soil and an amount of soil had also increased. Iron oxide concentration only had an affect on an amount of soil. The results showed that the method using two statistical distributions can be applied to the detergency of solid particle.     

A study of interactions between soil fractions and PAH compounds in thermal desorption of contaminated soils

The interactions between three polynuclear aromatic hydrocarbons (PAHs), namely fluorene, naphthalene and anthracene, and three fractions of a soil, namely fulvic acid (FA), humic acid (HA) and humin/inorganic fractions, were studied experimentally. Prepared PAH + soil fraction binary mixtures, with PAH concentrations ranging over 0.8–7 mass%, were tested using a differential scanning calorimeter (DSC) over a temperature range of 20?390°C. The DSC thermograms for the PAH + HA mixtures showed distinctly different characteristics compared to mixtures with the other two soil fractions, where the endothermic peak for the vaporization of the PAH was absent. With the aid of vapour-liquid flash calculations, the lack of the boiling point peak is interpreted to be due to the liquid-phase miscibility of the PAHs and the HA fraction. Implications of the DSC results on the design and performance of the thermal desorption process are discussed.     

Remediation of soil contaminated with lubricating oil by extraction using subcritical water

The remediation of lubricating oil contaminated soil was investigated by extraction using subcritical water. The effects of temperature and time on extraction efficiency were studied by performing eight individual extractions and varying the subcritical water temperature (200, 225, 250, and 275 °C) and extraction time (90, 120, 180, and 240 min) in a dynamic mode. Also, a comparison was carried out of the feasibility of two operational modes, namely, dynamic and static-dynamic mode. Of the 25,088 mg/kg of lubricating oil as the total petroleum hydrocarbon (TPH) concentration in untreated soil, the residual concentration was found to be ∼500 and 235 mg/kg for after 120 min extraction in a lab-scale apparatus and 150 min extraction in a 30-fold scale-up experiment, respectively, at 275 °C in static-dynamic mode. The result of this study showed the significant effect of the static-dynamic mode on extraction efficiency. The time and volume of water needed for the static-dynamic mode were much lower than those needed for the dynamic mode. These results are of practical interest in developing the subcritical water extraction technology for extraction of lubricating oil and, in a broad sense, petroleum hydrocarbons contaminated soil.     

Evaluation of basidiomycetous fungi for pretreatment of contaminated soil

BACKGROUND: For most dioxin‐contaminated sawmill soils, combustion is recommended. However, the process may be inefficient if the soil has a high organic matter content. The use of saprotrophic basidiomycetous fungi is an alternative for pretreatment of this kind of soil. A total of 147 fungi were evaluated for their ability to grow in sawmill soil. From this screening, the best soil colonizing fungi were selected to study their enzyme activities and degradation of soil organic matter. Pine (Pinus sylvestris) bark was used as a co‐substrate to propagate the fungi into the soil. The activities of manganese peroxidase (MnP), laccase, endo‐1,4‐β‐glucanase, endo‐1,4‐β‐xylanase, and endo‐1,4‐β‐mannanase were analysed from the inocula and fungal treated soil. RESULTS: The screening revealed that 56 out of 147 fungi were able to grow in non‐sterile soil, and most of them were litter‐decomposing fungi (LDF). In pine bark cultures, the highest enzyme activities were observed with Phanerochaete velutina, which produced 5 U g^?1 of MnP. The activity of endo‐1,4‐β‐glucanase was generally higher than that of other hydrolytic enzymes. The highest carbon loss from soil with a high organic matter content was achieved by P. velutina (3.4%) and Stropharia rugosoannulata (2.4%). CONCLUSIONS: Many LDF, and in addition the white‐rot fungus P. velutina, are potential degraders of soil organic matter since they showed good growth and respiratory activity. Pine bark was a suitable lignocellulosic co‐substrate and a good promoter of MnP activity. Copyright © 2009 Society of Chemical Industry     

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.     

Electrokinetic remediation of soils contaminated with heavy metals

This paper describes the results obtained from an electrokinetic treatment of a real soil polluted by lead acetate. Powdered soil samples were pressed with a consolidometer till 100 kPa to obtain cylindrical specimens with the same characteristics as a subsoil. Tests were carried out in a Perspex electrochemical cell where soil specimens were introduced with a hollow punch. A low intensity direct current was applied in order to remove contaminants, due to electrophoresis and electroosmosis phenomena. The water flow, conductivity, apparent electroosmotic coefficient, as well as other characteristic parameters, were measured throughout the test. The water content and degree of pore saturation were estimated at the beginning and end of the test. The soil slab was divided into four slices and the Pb concentration profile determined. The main factor governing the extraction of contaminant was found to be the pH in the acidic range. Indeed, under these conditions high removal efficiencies could be reached. These results could lead to the design of a new electrochemical treatment cell equipped with a cationic membrane to expand the region of favourable pH within the soil.     

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。     

槐糖脂用于含油砂质土壤处理及石油资源回收

模拟了以生物型表面活性剂槐糖脂配制水溶液和微乳液对原油污染土壤进行处理并回收原油的实验,通过对比证明槐糖脂微乳液对含油土壤的原油脱除效果优于其水溶液,分析了槐糖脂、NaCl、丙三醇的添加量对原油脱除效果的影响,并筛选出3种微乳液配方。将原始原油、土壤与3种配方微乳液回收的原油、土壤进行理化性质对比发现：回收土壤的pH略高且大致呈中性,黏粒体积分数减少,zeta电位无明显变化,微乳液处理对土壤的理化性质影响较小;回收原油中饱和分含量升高,芳香分、胶质和沥青质含量降低,灰分含量增加,密度增大,黏度降低,表明回收原油具备一定的经济使用价值。将3种配方微乳液进行温度和循环利用实验以检验原油脱除效果的稳定性,结果表明：随着温度的升高,微乳液对含油土壤的原油脱除率先升高后趋于稳定,微乳液循环使用5次,对含油土壤的原油脱出率仍在60%以上,其中配方槐糖脂10%、丙三醇3.5%、NaCl 2.5%、柴油19.2%的微乳液处理含油土壤的稳定性最好。     

铬污染土壤的修复

目前,许多铬盐厂正在进行铬渣无害化处理,速度快的已基本完成.随着铬渣治理的深入进行,渣场底部及附近铬污染土壤的修复亦提上日程.铬污染土壤的修复有其特殊性.各种地质条件形成的土壤含铬量相差很大,而土地的用途有很多种,对总铬和 6价铬的容忍性各不相同,故尚未见到铬污染土壤治理标准.介绍了对铬污染土壤修复指标有参考价值的资料.同时对铬污染土壤的修复技术进行了评述,介绍了5种修复技术.     

Evaluation of phenanthrene removal from soil washing effluent by activated carbon adsorption using response surface methodology

Soil washing is a promising technology for the remediation of polycyclic aromatic hydrocarbons (PAH)-contaminated sites, but surfactant needs to be recovered to reduce remediation cost and avoid secondary pollution. In this study, activated carbon (AC), prepared from waste walnut shells, was applied to the adsorptive removal of phenanthrene (PHE) from synthetic soil washing effluent with Tween 80 as a model surfactant. Box-Behnken statistical experiment design (BBD) and response surface methodology (RSM) were used to investigate the influence of AC dosage, Tween 80 concentration and adsorption time, and their potential interaction effect on PHE removal. A response surface model was established based on the BBD experimental results. The goodness of fit of the model was confirmed by determination coefficient, coefficient of variation (CV) and residuals analysis. The RSM model indicates that AC dosage or adsorption time had positive effect on PHE removal while Tween 80 concentration had negative effect. The interaction effect between AC dosage and Tween 80 concentration was significant but the other two interaction effects were not. The 3D response surface plots were developed based on the RSM equation. The RSM model was validated by an additional experiment and the obtained result of PHE removal was very close to the model prediction, indicating the RSM model can effectively predict the PHE removal from soil washing effluent with activated carbon adsorption.     

A model system for cocomposting hydrocarbon contaminated soil by using water activity and porosity as response variables

Cocomposting of soil is the process of simultaneously stabilising organic materials and degrading toxic compounds foreign to the environment. The fraction of components in cocomposting modifies water activity (a_w), it is therefore important to define the composition of the bulk medium. Water activity and the porosity of the bulk medium were response variables applied to a system for the biodegradation of hydrocarbons in the soil. This work proposes a definition of a model system for cocomposting using hydrocarbon contaminated soil, sugarcane bagasse pith and water. The experimental mixtures were determined according to a simplex centroid design. The results were adjusted to a Scheffé multiple regression model and response surfaces were generated. In order to follow the biodegradation of hydrocarbons and a_w, an appropriate mixture (weight basis) was established at 25% sugarcane bagasse pith, 15% contaminated soil, and 60% water. This mixture was then tested in packed bed bioreactors of both 50 and 864 g, resulting in 40% biodegradation of total hydrocarbons after 150 h of composting.     

碱洗塔管道泄漏问题分析及处理

分析了VCM碱洗塔碱液循环管道故障情况,并结合生产实际介绍了对问题的具体分析过程以及采取的解决措施。     

Ultrasonic technologies for extracting oil products from oil-bearing sands and contaminated soils

The kinetics of the extraction of oil products (bitumen, oil, and fuel oil) from natural and model oil-bearing sands after ultrasonic treatment was studied. The effects of the process temperature, the nature and properties of the separated components, and the concentrations of the added reagents on the rate and extent of oil product extraction were also studied. The functional form of the dependences of the separation efficiency on the mean size of the solid particles and the working medium temperature was determined. The working solution of sodium silicate can be recycled in the separation, and its reuse can even accelerate the extraction of oil products at the first stage. Based on the obtained data, we created and tested a universal pilot apparatus for ultrasonic oil extraction from oil-bearing sands and the purification of soils contaminated with oil products.