无机材料固化镉铅镍污染土的环境效应及失稳机制

固化污染土的环境效应是废土二次应用过程中需研究的工程问题。以镉、铅、镍污染土为研究对象,通过固化率指标初筛适宜固化材料配比,模拟干湿循环、长期浸水、高温、冻融循环环境,以浸出毒性指标评价水泥、水泥+粉煤灰、石灰固化后土体的环境效应,并结合微观形态及重金属形态分析,评价失稳机制。结果表明:无机材料可将土中重金属的固化率提高至90%以上,8%的石灰适用于镉污染土的固化,32%+8%的水泥+粉煤灰适用于铅及镍污染土的固化。水环境(干湿、浸水)条件下固化污染土均不存在环境风险,其浸出毒性均低于《危险废物鉴别标准浸出毒性鉴别》(GB 5085.3-2007)中的限值;但无机材料固化污染土对温度(高温、冻融)敏感,特别是水泥、水泥+粉煤灰固化污染土,在温度超过70℃时的浸出毒性超过标准中限值,在冻融循环5~7次时接近标准限值。高温会促使重金属赋存形态从稳定态向非稳定态转化,冻融循环会破坏重金属-固化产物体系的结构。无机材料固化重金属污染土的应用需要考虑环境温度的影响。

酸碱盐胁迫环境下水泥固化重金属污染土的长期性能:现状与展望

土壤和地下水常受到工业、农业、海水和生活污水的影响,存在不同种类的腐蚀性离子。采用水泥基材料固化/稳定化修复重金属污染场地时,这些腐蚀性离子会降低水泥基固化土的性能和重金属的固化效果,长期条件下面临二次污染问题。目前采用水泥基材料的土壤固化研究多集中于新型复合固化剂的研发,对环境胁迫下固化体的耐久性问题需要更多关注。针对环境胁迫下因水泥基固化土劣化引起的工程特性和淋滤特性问题,总结国内外研究现状,系统阐述土—水泥—重金属—胁迫环境之间的相互作用机理,明晰基于酸/碱、盐环境胁迫下水泥基固化土性能演化规律及机制,为重金属污染土壤固化修复效果及耐久性提升的研究提供参考。

冻融循环条件下水泥固化铅污染土强度模型研究

以冻融循环条件下水泥固化铅污染土为研究对象,通过室内试验研究冻融条件下水泥固化铅污染土的抗压强度特性。试验结果表明:水泥固化铅污染土的强度随水泥掺量增大而增大,随冻融循环次数的增加先略微增加,达到峰值后,随冻融循环次数的增加而快速减小,最后趋于稳定。随着冻融循环次数的增加,不同铅离子浓度的固化铅污染土的强度损失量不同,并表现出在相同水泥掺量下,铅离子浓度为0.5%的固化污染土抗压强度损失量最小。通过回归分析,建立了水泥固化铅污染土强度随冻融循环次数变化的预测模型,为实际工程提供理论参考。

冻融循环对固化铅污染土强度与孔隙特征影响的试验研究

水泥基固化剂封闭是近年来重金属污染修复治理的主要技术手段之一。冻融循环作用是影响水泥固化重金属污染土力学特性的重要外营力。本文以人工制备的铅污染土为研究对象,结合冻融实验和室内土工试验,研究冻融循环作用对铅污染土无侧限抗压强度的影响。结果表明:随着水泥掺量的增大,水泥固化铅污染土的无侧限抗压强度增大,破坏应变减小;随着铅离子掺量的增大(污染程度升高),水泥固化铅污染土的无侧限抗压强度q u降低,应力-应变曲线变化趋势更加相似;水泥固化铅污染土的无侧限抗压强度q u随冻融频次的增大而降低;相同冻融频次条件下,随着水泥掺量的增加,水泥固化铅污染土的无侧限抗压强度q u损失率降低。基于SEM图像对固化铅污染土进行微观结构定量分析,表明随着冻融次数的增加,试样中细颗粒(<1μm)和细孔隙(<2μm)所占比例均提高。冻融作用对土体结构的破坏可能是导致土样无侧限抗压强度q u降低的主要原因。

基于温度效应下二灰固化石油污染滨海盐渍土力学特性优化固化需求

温度是影响石油污染土性能的重要因素。依托滨海地区特有气候环境特点,借助抗压强度指标及应力-应变分布,从抗温敏性角度,优化石油污染滨海盐渍土对二灰的固化需求。研究结果表明:(1)在-20~40℃温度变化范围内,石油污染土抗压强度波动幅度高达1倍,采用二灰进行固化处理后,抗压强度波动缩小至10%~20%。二灰固化作用可将热敏性物质(石油、水、盐)吸附、包裹于胶体内外,增强对环境温度变化的抵抗性。(2)石油污染土及固化石油污染土的无侧限抗压强度均随温度变化呈先减小后增大趋势,10℃为强度转折点,也即最低点,实际工程中应加以重视。(3)温度作用下,固化石油污染土呈应变软化型破坏,且随温度及污染水平的增大,塑性变形阶段延长,轴向应变增大,出现四周型层状破坏。(4)土体自身的污染程度影响固化效果,高污染条件下抗压强度波动幅度约为40%,实际工程中应依据土体自身的污染程度调整固化配比。低污染土的固化配比选取只需略高于未污染土,过高固化配比并不利于增强稳定性,同比率石灰掺量的改变较粉煤灰的更有助于增强稳定性。污染水平≤6%的石油污染盐渍土,可选固化配比为石灰10%+粉煤灰20%。

三种不同固化剂对Cr(Ⅵ)污染土壤固化试验研究

通过无侧限抗压强度和浸出毒性试验,研究硅酸盐水泥固化剂、二灰固化剂和高效复合固化剂等3种固化剂对铬污染土壤固化效果。试验结果表明:硅酸盐水泥固化剂、二灰固化剂和高效复合固化剂的最佳掺量分别为6%、30%和10%;掺加3种固化剂的固化稳定土,早期强度良好,后期强度无倒缩,符合相关标准对道路基层或底基层的强度要求。且Cr(Ⅵ)的浸出浓度<5 mg/L,符合相关标准中对Cr(Ⅵ)浸出浓度的限值要求。

氯盐侵蚀作用对水泥固化铅污染土化学稳定性的影响

含侵蚀性盐离子(SO_4^(2-)、Cl-等)的地下水环境可能会改变水泥固化污染土中重金属离子的溶出特性.通过毒性浸出试验模拟研究了遭受NaCl溶液侵蚀的水泥固化铅污染土的化学稳定性.试验结果表明,遭受NaCl溶液侵蚀后,随着NaCl浓度的增加,浸出液pH值略有减小,浸出液中Pb^(2+)质量浓度亦有所降低.短期浸泡,浸出液pH值最低,Pb^(2+)质量浓度最大;随后,pH值随浸泡时间增加而增大,Pb^(2+)质量浓度随浸泡时间增加而减小.当Pb^(2+)含量≤5 000 mg/kg时,浸出液中Pb^(2+)质量浓度均小于5 mg/L,满足环境要求;而Pb^(2+)含量为10 000 mg/kg的固化土体,滤出的Pb^(2+)质量浓度均超过5 mg/L,不能满足环境要求.

冻融作用下水泥固化煤化工废水污染土的强度特性及微观结构

为了解水泥固化煤化工废水污染土的强度特性及微观结构,以凹凸棒土为外掺剂,通过室内试验的方法研究了冻融循环作用下固化土的无侧限抗压强度、质量损失率及T2谱分布曲线。结果表明:养护28 d后,随外掺剂掺量增加,固化土的强度逐渐降低;随冻融循环次数增加,固化土的强度先增长后降低;掺加外掺剂固化土相比无外掺剂固化土,其强度明显降低;掺加外掺剂、无外掺剂和无苯酚无外掺剂三类固化污染土的累计质量损失率随循环次数的增加而增大,且呈相似的变化规律;在冻融循环3次时,固化土的孔隙减小且孔径变小,冻融循环5次和10次时,固化土的孔隙增加且孔径变大。由此可见,凹凸棒土虽使固化土强度降低,但因特殊的性质,对污染物的固化稳定化效果增强;固化土的强度变化与其内部孔隙和孔径有关。

碱渣固化锌污染土的工程性质试验研究

采用无侧限抗压试验、淋滤试验等方法,对碱渣固化锌污染土的工程性质、淋滤特性进行了研究。通过试验研究得到以下结论:无侧限抗压强度随着锌离子浓度的增加呈下降趋势;无侧限抗压强度随着碱渣掺量的增加先增大后减小,在碱渣掺量为30%时得到最大值。

垃圾渗滤液膜浓缩液资源化利用试验研究

膜浓缩液是一种富集污染物、重金属的高盐有机废水,其处理难度大、处理成本高。固化与稳定化处理技术用于处理膜浓缩液具有低成本、易操作、无二次污染的优势。以成都某生活垃圾填埋场膜浓缩液为处理对象,探究了粉煤灰-矿渣-钢渣基胶凝材料中不同n(SiO_(2)/Al_(2)O_(3))值对抗压强度的影响,得出3组分别以粉煤灰、矿渣、钢渣为主要成分的固化配比方案。且当发泡剂掺量为9%,样品具有良好的孔隙率,在中低频段表现出较好的吸声性能;且对重金属离子及污染物有优异的固定能力;微观分析表明,3组多孔吸声材料形成了致密良好的网络状结构,能有效固化膜浓缩液。

碳化对水泥固化铅污染土的电阻率特性影响规律

为确保重金属污染场地再开发利用的稳定性和安全性，采用室内加速碳化试验研究碳化对水泥固化铅污染土电阻率特性的影响规律。人工配制不同铅含量的污染土，采用水泥固化后进行室内加速碳化试验，分析碳化作用对固化土电阻率和pH值的影响规律，并讨论固化土的电阻率与无侧限抗压强度的相关关系。试验结果表明，碳化作用下水泥固化铅污染土的电阻率随着碳化时间和水泥掺入量的增加而增大，随着铅含量、孔隙率和饱和度的增加而减小。提出一个能够有效反映碳化时间、水泥掺入量和铅含量等因素对固化土电阻率影响的表征参数，采用该参数替代 Archie 电阻率模型中的土体孔隙率即可将Archie电阻率模型扩展应用到水泥固化重金属污染土领域。固化土的pH值随着铅含量增加而有所降低；碳化后固化土的pH值从11～12降低到8～9。固化土的电阻率与强度具较好的对应关系，电阻率法可作为一种有效的水泥固化铅污染土性能评价方法。

f矿坑恢复中的生态系统恢复运作方法——以大孤山矿坑为例

在我国前期经济发展与资源积累过程中,矿产资源作为最重要的资源之一为中国持续不断的供给发展所需的血液,但随着国家内工业类型的逐步转变与矿产资源的逐渐消耗殆尽,有大量的各类矿坑在完成历史使命之后被暂时弃置,弃置的矿坑由于其各种问题破坏了周边的生态环境,并且难以被利用,成为了大地的伤疤,急需一些确切有效的方案对其进行生态修复。

Fixation of Multiple Metals in Contaminated Soil by Different Passivators

The effects of 4 passivators, zeolite, lime, red mud and peanut shell biochar, on the fixation of Cd, Pb, Cu and Zn in acidic multi-metal contaminated soils were studied by passivator culture experiment in order to screen out the passivator with better fixation effects. The results showed that the soil pH values of zeolite, lime, red mud and peanut shell biochar increased significantly by 0.511.02, 0.821.29, 0.720.89 and 0.300.35 respectively. The effects of 4 passivators on the fixation of Cd and Zn in soil are lime>red mud>zeolite>peanut shell biochar. The order of effects on the fixation of Pb is red mud>lime>zeolite>peanut shell biochar. The order of the fixation effects of Cu is red mud>lime>peanut shell carbon>zeolite. The contents of Cd, Pb, Cu and Zn in the extractable state of CaCl2 decreased with the increase in the dosage of 4 passivators. Lime and red mud showed good fixation effects on Cd, Pb, Cu and Zn. The contents of Cd, Pb, Cu and Zn in the extractable state of CaCl2 at the low dosage(2.5 g/kg) of lime and red mud decreased by 41%, 84%, 76% and 83% respectively. Soil pH value was negatively correlated with CaCl2-Cd, Pb, Cu and Zn(P<0.01). Lime and red mud had significant fixation effects on Cd, Pb, Cu and Zn in acidic multi-metal contaminated soils at low application dosages.

Effect of sulfate erosion on strength and leaching characteristic of stabilized heavy metal contaminated red clay

Solidification/stabilization(S/S)technology has been widely used for remediation of the heavy metal contaminated soils.The heavy metal ions will be leached from the stabilized contaminated soil under sulfate erosion conditions,which gives rise tosecondary contamination to the areas around the mine sites.The commonly used Portland cement,fly ash and quicklime were takenas binder raw materials with various mix proportions.And then,the sulphuric acid and nitric acid method was used to investigate theleaching characteristic of stabilized heavy metal contaminated soils.The effects of binder types and binder contents,sulfateconcentrations(1.5,3.0and6.0g/L)and erosion time(0,7,14and28d)on leached concentrations of heavy metal ions fromcontaminated soils were studied.Moreover,a parameter named immobilization percentage(IP)was introduced to evaluate theinfluence of erosion time and sulfate concentration on immobilization effectiveness for heavy metal ions.The results showed that,theleached heavy metal concentrations increased with sulfate concentration and erosion time.Comparatively speaking,the compositebinders that had calcium oxide in it exhibited the worst solidification effectiveness and the lowest immobilization percentage,withthe largest leached heavy metal concentration.

Interfacial engineering of graphitic carbon nitride(g-C_3N_4)-based metal sulfide heterojunction photocatalysts for energy conversion: A review

As one of the most appealing and attractive technologies, photocatalysis is widely used as a promising method to circumvent the environmental and energy problems. Due to its chemical stability and unique physicochemical, graphitic carbon nitride (g-C3N4) has become research hotspots in the community. However, g-C3N4 photocatalyst still suffers from many problems, resulting in unsatisfactory photocatalytic activity such as low specific surface area, high charge recombination and insufficient visible light utilization. Since 2009, g-C3N4-based heterostructures have attracted the attention of scientists worldwide for their greatly enhanced photocatalytic performance. Overall, this review summarizes the recent advances of g-C3N4-based nanocomposites modified with transition metal sulfide (TMS), including (1) preparation of pristine g-C3N4,(2) modification strategies of g-C3N4,(3) design principles of TMS-modified g-C3N4 heterostructured photocatalysts, and (4) applications in energy conversion. What is more, the characteristics and transfer mechanisms of each classification of the metal sulfide heterojunction system will be critically reviewed, spanning from the following categories:(1) Type I heterojunction,(2) Type II heterojunction,(3) p-n heterojunction,(4) Schottky junction and (5) Z-scheme heterojunction. Apart from that, the application of g-C3N4-based heterostructured photocatalysts in H2 evolution, CO2 reduction, N2 fixation and pollutant degradation will also be systematically presented. Last but not least, this review will conclude with invigorating perspectives, limitations and prospects for further advancing g-C3N4-based heterostructured photocatalysts toward practical benefits for a sustainable future.

沸石材料在土壤修复工程中的应用研究进展

近年来,工业的快速发展导致土壤污染成为全球性的环境危机.土壤污染问题亟待解决,开发经济、长效的土壤修复材料是关键.沸石分子筛材料,由于其优异的离子交换性能和吸附性能,被广泛应用于土壤修复过程中,引起环境科学家、材料化学家、土壤学家、矿物学家的广泛关注.本文基于已被广泛用于土壤修复工程的典型沸石材料,并着眼于沸石材料的组成与结构,详细阐述了典型沸石材料的结构与性能之间的对应关系,综述了沸石材料分别用于不同土壤污染介质修复中的微观作用机理及研究进展.

Immobilization of Lead and Cadmium in Contaminated Soil Using Amendments: A Review

Since the inception of industrial revolution, metal refining plants using pyrometallurgical processes have generated the prodigious emissions of lead(Pb) and cadmium(Cd). As the core target of such pollutants, a large number of soils are nowadays contaminated over widespread areas, posing a great threat to public health worldwide. Unlike organic pollutants, Pb and Cd do not undergo chemical or microbial breakdown and stay likely in site for longer duration after their release. Immobilization is an in-situ remediation technique that uses cost-effective soil amendments to reduce Pb and Cd availability in the contaminated soils. The Pb and Cd contamination in the soil environment is reviewed with focus on source enrichment, speciation and associated health risks, and immobilization options using various soil amendments. Commonly applied and emerging cost-effective soil amendments for Pb and Cd immobilization include phosphate compounds, liming, animal manure, biosolids, metal oxides, and biochar. These immobilizing agents could reduce the transfer of metal pollutants or residues to food web(plant uptake and leaching to subsurface water) and their long-term sustainability in heavy metal fixation needs further assessment.

Experimental Studies on Combustion Characteristics of Mixed Municipal Solid Waste

In our country, municipal solid wastes (MSW) are always burnt in their original forms and only a few pretreatments are taken. Therefore it is vital to study the combustion characteristics of mixed waste. In this paper, thermogravimetric analysis and a lab scale fluidized bed facility were used as experimental means. The data in two different experimental systems were introduced and compared. It took MSW 3-3.5 min to burn out in FB, but in thermogravimetric analyzer, the time is 20-25 min. It can be concluded that, in general, the behavior of a mixture of waste in TGA can be expressed by simple combination of individual components of the waste mixtures. Only minor deviations from the rule were observed. Yet, in Fluidized Bed, it was found that, for some mixtures, there was interference among the components during fluidized bed combustion.

Immobilization of Escherichia coli for detection of phage T4 using surface plasmon resonance

Phage contamination is a very serious and unavoidable problem in modem fermentation industry. It is necessary to develop sensitive and rapid phage detection methods for the early detection of phage contamination. In the present work, a real-time, rapid, specific and quantitative phage T4 detection method based on surface plasmon resonance （SPR） technique has been in- troduced. Escherichia coli was immobilized onto the preformed MPA self-assembled monolayer （SAM） through the widely used EDC/NHS cross-linking reaction as the recognition element. The bacteria immobilization was verified efficiently through the electrochemical measurements and fluorescence microscopy observations. The specific adsorption was much stronger than the non-specific adsorption of phage T4 binding to the biosensor surface modified by E. coli, and the latter could be neglected. The detection sensitivity reached 1×10^7 PFU/mL within 10 min. Within the experimental phage concentrations, the linear cor- relation between the SPR response and the phage concentration was good. The results suggest that the SPR technique is a po- tentially powerful tool for the phage or other virus detections, as a label-free, real-time, and rapid method.