EK/Fe~0-PRB联合修复实际砷污染土壤的协同机制

以我国某矿区砷污染土壤为研究对象,采用EK/Fe~0-PRB联合修复工艺去除土壤中的砷,考察了土壤含水率及增强试剂对砷去除的影响,分析了修复前后土壤中砷的迁移分布及砷价态分布变化,并借助X射线光电子能谱(XPS)对修复前后PRB填料Fe~0进行了表征分析,探讨了EK/PRB修复砷污染的协同机制。结果表明,在EK/PRB联合修复过程中,EK去除作用所占比例为22%～43%,而PRB的去除作用所占比例为52%～71%,以PRB的去除作用为主;未添加增强试剂时,阳极液砷收集含量明显高于阴极液砷收集含量,电动去除机制主要为电迁移作用,添加增强试剂后,阴极液砷收集含量所占比例明显升高;EK/PRB修复后,As(Ⅴ)和As(Ⅲ)在土壤、电极液、PRB中的含量比例基本没有变化,As(Ⅴ)含量比例略微升高,即处理之后土壤中的五价砷并不会经氧化还原作用而转变成毒性较高的三价砷;反应后Fe~0表面存在As(Ⅲ)和As(Ⅴ),未发现As(0)的存在,因此砷在PRB中仅通过铁表面氧化物的吸附作用而去除。     

土壤环境中砷污染修复技术综述

土壤砷污染是我国亟待解决的环境问题之一。论述了土壤砷污染修复中涉及的物理修复、化学修复及微生物修复研究现状,并对修复技术的发展趋势进行了展望。     

砷污染土壤修复中钝化剂的筛选及其工艺条件优化研究

以广西南丹县砒霜厂周边土壤为研究对象,开展了4种钝化剂修复砷污染土壤的研究。在单因素实验结果基础上,选取钝化时间、土壤粒径和FeSO_4/As用量比进行3因素3水平的中心组合设计实验和响应面分析。结果表明,硫酸铁在去除有效态砷方面效果显著。硫酸铁去除有效态砷的最佳工艺条件是:钝化时间22 d,粒径40目,用量FeSO_4/As为5.6/1。在此条件下,有效态砷的去除率可达到85.45%。     

砷污染土壤修复中钝化剂的筛选及其工艺条件优化研究

以广西南丹县砒霜厂周边土壤为研究对象,开展了4种钝化剂修复砷污染土壤的研究。在单因素实验结果基础上,选取钝化时间、土壤粒径和FeSO_4/As用量比进行3因素3水平的中心组合设计实验和响应面分析。结果表明,硫酸铁在去除有效态砷方面效果显著。硫酸铁去除有效态砷的最佳工艺条件是:钝化时间22 d,粒径40目,用量FeSO_4/As为5.6/1。在此条件下,有效态砷的去除率可达到85.45%。     

电动修复重金属污染土壤的研究进展

电动修复是当前重金属污染土壤原位修复研究领域的热点,首先详细阐述了电动修复技术的特点和修复效果的影响,如电场、电压、pH、离子强度等,并对电动修复与其它典型技术(如:淋洗、PRB、植物、微生物等)联合修复技术的特点和适应场地作了详细介绍;在此基础上,对电动修复重金属污染土壤技术的关键问题和发展方向作了展望,以期为电动修复的发展提供参考。     

电动力联合可渗透反应墙修复铀污染土壤试验研究

以铀浓度为80 mg/kg的铀污染土壤作为研究对象,分别采用电动(EK)和电动-可渗透反应墙(EK-PRB)联合修复技术对铀污染土壤进行了修复对比试验,并重点考察了电流强度、pH、铀残余量和去除率等因素的变化,以及分别对两种方法修复效果的影响。结果表明,在初始pH为4.35,电压梯度1 V/cm的条件下,铀离子随着电渗流往阴极迁移效果明显。经过168 h的修复后,EK-PRB修复技术对铀的去除率最大,要比EK修复技术提高46.5%。研究表明,EK-PRB联合修复技术比单独EK修复技术有明显的优势,在修复铀污染土壤方面具有良好的发展应用前景。     

钢渣用作砷污染地下水修复PRB介质的研究

在分析钢渣的资源利用特性与污染风险的基础上,模拟研究钢渣作为可渗透反应墙(PRB)介质对砷污染地下水的去除性能,分析初始砷浓度、原水流速等对除砷性能的影响,并对钢渣用作砷污染地下水原位修复的PRB材料的可行性进行探索。结果表明,钢渣的主要元素为Ca、Fe、Si、Mg、Al,主要矿物质为Ca2SiO4和Ca3Mg(SiO4)2,利用钢渣碱度高,机械强度大,呈多孔结构,可作为良好的过滤性能和吸附材料;钢渣浸出液的pH、重金属与氟含量均低于我国危险废物浸出毒性鉴别标准,环境污染风险很小;在流量相同的情况下,钢渣PRB对砷的去除率在初始砷质量浓度0.1 mg/L时达到最大,流量为0.5 mL/min时,初始砷质量浓度对去除效果影响不明显,去除率均在96%以上;在初始砷质量浓度相同的情况下,钢渣PRB对砷的去除率随流量的增大而降低;整体上钢渣PRB对砷的去除率随处理水样量增加呈下降趋势,但处理水样量为3 L时,去除率最低仍可达90%以上。钢渣作为PRB材料处理高砷地下水成本低、稳定可靠、去除效率高,是一种具有广阔开发应用前景的PRB材料。     

砷污染土壤修复技术综述

综述了砷污染土壤不同修复技术的研究进展。可用的方法可分为化学、物理和生物学方法。化学方法中,常用的是土壤洗涤或固定剂;物理技术主要是从产量的角度进行讨论;植物提取技术是目前中国最广泛用于砷污染土壤的技术,是生物修复的重点。多种技术的综合利用对于提高修复效率也是很普遍的。此外,总结了评价土壤修复效率的方法,提出了进一步的研究方向。     

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。     

A new method for remedial treatment of contaminated clayey soils by electrokinetics coupled with permeable reactive barriers

This paper presents the results of preliminary investigations into the potential application of a remediation system that couples the electrokinetic (EK) remediation with the permeable reactive barrier (PRB) concept. Atomizing slag was adopted as a PRB reactive material for freshing groundwater contaminated with either inorganic or organic substances. Laboratory experiments were performed with variable conditions including (i) type of pollutant, (ii) processing time, and (iii) the application of PRB system during the EK processing. From the results of the preliminary investigations, the coupled technology of EK with PRB system could effectively remediate contaminated groundwater in situ without extracting pollutants from subsurface through the effectiveness of the reactions between the reactive materials and contaminants.     

王水分解-电感耦合等离子体质谱法测定土壤中砷镉

本文采用电感耦合等离子体质谱法(ICP-MS)测定土壤样品中As、Cd,对样品预处理方法,条件等进行了改进和优化,同时给出了方法的检出限、线性范围、精密度、准确度、加标回收率等方法参数。经国家标准土壤样品验证,方法的精密度符合分析要求,结果令人满意。研究表明,该方法适用于土壤样品中As、Cd的分析测定。     

Synergistic effects of conductive carbon nanofillers based on the ultrahigh-molecular-weight polyethylene with uniform and segregated structures

To discuss the synergistic effects of mixed conductive filler on nanocomposites, different structural carbon nanofiller/ultrahigh-molecular-weight polyethylene (UHMWPE) hybrid nanocomposites with uniform and segregated structure were prepared by using ethanol-assisted dispersion, hydrazine reduction, and hot-pressing methods. Scanning electron microscopy and polarized optical microscopy images of the nanocomposites fracture showed that the complete conductive channels could be formed in segregated nanocomposites prepared by powder mixing method. By contrast, the discontinuous electric path could be observed in the homogeneous nanocomposites prepared by the solution method. The test of conductivity performance demonstrated that the percolation threshold of carbon black (CB)/UHMWPE and multiwalled carbon nanotubes (MWCNTs)-CB/UHMWPE nanocomposites with segregated structure were 0.42 and 0.18 vol %, which were lower than those of the nanocomposites with uniform structure (4.91 and 2.62%). The electrical conductivity of MWCNTs-CB/UHMWPE nanocomposites with segregated structure reached to 3.0 × 10⁻² S m⁻¹ with the filler content of 1.5 vol %. In addition, the results of differential scanning calorimetry indicated that the crystallinity of UHMWPE decreased slightly with the addition of mixed filler. All of the study showed that the conductivity of MWCNTs-CB/UHMWPE nanocomposites with segregated structure has better electrical conductivity than the uniform. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47317.     

磷系阻燃剂FR/APP协效阻燃PP

采用氧指数测定仪、热重分析仪和锥形量热仪研究了磷系阻燃剂1,3,5-三(5,5-二甲基-1,3-二氧杂环己内磷酸基)苯(FR)和聚磷酸铵(APP)复配体系对聚丙烯(PP)材料阻燃性能的影响.结果表明,FR/APP提高了PP的极限氧指数(LOI)、热稳定性和残炭率,降低了热释放速率.当w(FR)为15%和w(APP)为10%复配阻燃PP时,复合材料的LOI为29.6%.阻燃级别达到UL 94 V-0级.     

Synergistic effects of organically modified montmorillonite in combination with metal oxides on the fire safety enhancement of intumescent flame-retarded epoxy resins

Synergistic effects of organically modified montmorillonite (OMMT) in combination with different metal oxides (Bi₂O₃, Sb₂O₃, and MoO₃) on the fire safety enhancement of the intumescent flame-retarded epoxy resins (EPs) were systematically evaluated. The results from X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses show that the OMMT and metal oxides acquire a uniform distribution in the EP matrix, and OMMT platelets exhibit a fully exfoliated state. The flammability and thermogravimetry (TG) tests show that the intumescent flame retardant (IFR)-OMMT-metal oxide ternary system can endow EPs with the higher synergistic efficiencies on the enhancement of flame retardancy, smoke suppression properties, and charring ability compared to those of IFR or IFR-OMMT system, and the synergistic efficiency is the following order: IFR/OMMT/Sb₂O₃ > IFR/OMMT/MoO₃ > IFR/OMMT/Bi₂O₃. In particular, the sample, filled with 1.5 wt% OMMT, 1.5 wt% Sb₂O₃, and 27 wt% IFR, passes the UL94 V-0 rating and acquires the highest limiting oxygen index value of 28.5% among the samples. The IFR-OMMT-metal oxide ternary system exerts a better synergistic effect on the generation of crosslinking and aromatic structures that supply the excellent charring effect and barrier effect for the EPs, and the synergistic efficiency of IFR-OMMT-metal oxide ternary system is varied with the types of metal oxides.     

微波密闭消解-ICP-MS测定土壤中铬的研究

建立了微波消解-电感耦合等离子体质谱(ICP-MS)法检测分析土壤中铬元素含量的方法。采用HNO3+HCl+HF混合体系为消极试剂,以铟(In)内标进行补偿校正,同时通过国家土壤标准物质(GBW07439)验证了方法的准确性。结果表明,检出限<0.01 ng/g,工作曲线线性关系较好(r>0.9998),RSD<2.5%,标准物质中Cr元素回收率为93.0%~105.3%。该法操作便捷,测量准确,适于土壤中多种微量元素的检测。     

Switching effects of electrode polarity and introduction direction of reagents in electrokinetic-Fenton process with anionic surfactant for remediating iron-rich soil contaminated with phenanthrene

This study investigated effective operating method of enhanced electrokinetic-Fenton (EK-Fenton) process with anionic surfactant to remediate contaminated iron-rich clayey soil with phenanthrene, which had soil properties being frequently in contaminated sites. Introduction of 30 mM SDS as H₂O₂ stabilizer improved not only H₂O₂ stability but also degradation of phenanthrene compared to experiment without SDS. However, electrical potential drop in regions near cathode terminated electro-osmotic flow, and then phenanthrene in region near cathode kept initial concentration before switching of the electrodes polarities and introduction direction of reagents. After the polarity of the electrodes and introduction direction of reagents were switched, electro-osmotic flow was re-generated with re-distribution of electrical potential and electrical current. Furthermore, after switching electrode, decrease of iron concentration and pH in the soil specimen near cathode before switching electrode generated decrease of H₂O₂ decomposition rate. Therefore, H₂O₂ could be introduced in the cathode regions before switching the polarity of the electrodes and introduction direction of reagents. Furthermore, residual phenanthrene was degraded homogeneously after switching of the electrodes polarity and introduction direction of reagents, and then about 70% phenanthrene could be degraded.     

Synergistic effects of exfoliated LDH with some halogen‐free flame retardants in LDPE/EVA/HFMH/LDH nanocomposites

The synergistic effects of exfoliated layered double hydroxides (LDH) with some halogen‐free flame retardant (HFFR) additives, such as hyperfine magnesium hydroxide (HFMH), microencapsulated red phosphorus (MRP), and expandable graphite (EG), in the low‐density polyethylene/ethylene vinyl acetate copolymer/LDH (LDPE/EVA/LDH) nanocomposites have been studied by X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermal analysis (TGA and DTG), mechanical properties, limiting oxygen index (LOI), and UL‐94 tests. The XRD results show that EVA as an excellent compatilizer can promote the exfoliation of LDH and homogeneous dispersion of HFMH in the LDPE/EVA/HFMH/LDH nanocomposites prepared by melt‐intercalation method. The TEM images demonstrate that the exfoliated LDH layers can act as synergistic compatilizer and dispersant to make the HFMH particles dispersed homogeneously in the LDPE matrix. The results from the mechanical, LOI, and UL‐94 tests show that the exfoliated LDH layers can also act as the nano‐enhanced and flame retardant synergistic agents and thus increase the tensile strength, LOI values, and UL‐94 rating of the nanocomposites. The morphological structures of charred residues observed by SEM give the positive evidence that the compact charred layers formed from the LDPE/EVA/HFMH/LDH nanocomposites with the exfoliated LDH layers play an important role in the enhancement of flame retardant and mechanical properties. The TGA and DTG data show that the exfoliated LDH layers as excellent flame retardant synergist of MRP or EG can apparently increase the thermal degradation temperature and the charred residues after burning. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

渗流作用下垂直埋管换热器钻孔内外耦合传热计算与分析

为了研究渗流对地埋管换热器性能的影响,综合多孔介质中移动有限长线热源与钻孔内准三维传热模型建立了地埋管换热器钻孔内、外非稳态耦合传热的解析模型,并通过热响应试验数据验证了耦合模型的正确性。探讨了渗流作用下埋管出口水温及其周围土壤温度动态响应的变化规律,利用埋管换热能效系数和单位井深换热量两个指标的变化评估了渗流对埋管换热器传热性能的影响。结果表明:不同类型的土壤中埋管传热性差别较大, 若忽略渗流速度较大的砂砾层中渗流的影响将导致其中埋管的单位井深换热量设计偏差高达41%;渗流对埋管散热起到促进作用且散热达到稳定所需的时间随渗流速度增大而缩短;推荐采用埋管的进口质量流量流速大于0.4 kg·s^-1,但不宜过大;埋管进口温度对换热能效系数的影响可忽略。并对典型水文条件下各土壤中渗流对串联管群的换热能效系数的影响进行了对比,指出地下管群环路的换热能效系数由土壤物性、渗流速度及串联埋管的钻孔数量共同决定的。