垃圾焚烧飞灰颗粒的微观形态特征及能谱研究

利用SEM/EDX，观察了垃圾焚烧飞灰颗粒的微观形态特征，探讨了其主要组成元素及其质量分数。实验结果表明，飞灰颗粒形态多样化，其中以不规则形状聚合体居多，球形体、絮状集合体相对较少，少数颗粒为棒状集合体。球形飞灰颗粒很少有重金属分布，不规则形状聚合体或絮状集合体的表面易分布重金属。从飞灰颗粒表面、内部组成元素的质量分数来看，Si、Ca、Al为主要元素。飞灰颗粒表面、内部有重金属Pb、Cu等分布，局部测定点其质量分数可高达16.2%和14.5%。     

垃圾焚烧中氯化物对重金属Pb迁移转化特性的影响

采用管式炉和模拟垃圾对垃圾中氯化物对重金属Pb迁移转化特性的影响进行了研究,使用ICP-AES(美国EPA消解方法)、SEM、EDS和XRD等对重金属浓度、灰渣表面形貌、成分和灰渣X射线衍射物相等进行了分析。结果表明,氯化物含量的增加使得Pb生成更多易挥发性物质,从而向飞灰迁移分布,但有机氯PVC的影响比无机氯NaCl的大。无机氯NaCl和有机氯PVC对焚烧中Pb迁移转化作用机理不同,NaCl易与Pb反应生成PbCl2,而PVC与Pb反应除了生成PbCl2外,还生成了Pb(ClO4)2、PbCl2O4和PbO2。同时焚烧温度和停留时间也是焚烧中Pb迁移分布的两个主要影响因素。     

Direct Conversion of Pretreated Straw Cellulose into Citric Acid by Co-cultures of Yarrowia lipolytica SWJ-1b and Immobilized Trichoderma reesei Mycelium

The immobilized cellulase-producing mycelium of Trichoderma reesei was found to produce 2.9 U/ml of cellulase activity within 144 h while 2.1 U/ml of cellulase activity was produced within 120 h by the free mycelium of the same strain. When the immobilized mycelium of T. reesei was co-cultivated with the free cells of Yarrowia lipolytica SWJ-1b in flask, Y. lipolytica SWJ-1b could yield 10.7 g/l of citric acid and 3.9 g/l of isocitric acid from 40.0 g/l pretreated straw within 240 h. Under the similar conditions, Y. lipolytica SWJ-1b could yield 32.8 g/l of citric acid and 4.7 g/l of isocitric acid from 40.0 g/l pretreated straw supplemented with 20.0 g/l glucose within 288 h. When the co-cultures were grown in 10-l fermentor, Y. lipolytica SWJ-1b could yield 83.4 g/l of citric acid and 8.7 g/l of isocitric acid from 100.0 g/l of pretreated straw supplemented with 50.0 g/l glucose within 312 h.     

Comparison of Yarrowia lipolytica and Pichia pastoris Cellular Response to Different Agents of Oxidative Stress

Yeast cells exposed to adverse conditions employ a number of defense mechanisms in order to respond effectively to the stress effects of reactive oxygen species. In this work, the cellular response of Yarrowia lipolytica and Pichia pastoris to the exposure to the ROS-inducing agents’ paraquat, hydrogen peroxide, and increased air pressure was analyzed. Yeast cells at exponential phase were exposed for 3 h to 1 mM paraquat, to 50 mM H₂O₂, or to increased air pressure of 3 or 5 bar. For both strains, the cellular viability loss and lipid peroxidation was lower for the cells exposed to increased air pressure than for those exposed to chemical oxidants. The glutathione induction occurred only in Y. lipolytica strain and reached the highest level as a response to PQ exposure. In general, antioxidant enzymes were more expressed in Y. lipolytica than in P. pastoris. The enzyme superoxide dismutase was induced in both strains under all the oxidant conditions but was dependent on the cellular growth phase, being undetectable in non-growing cells, whereas glutathione reductase was more induced in those conditions. Hydrogen peroxide was the most efficient inducer of catalase. Both yeast cultures underwent no cellular growth inhibition with increased air pressure, indicating that these yeast species were able to adapt to the oxidative stressful environment.     

固体添加剂对垃圾掺烧污泥焚烧飞灰高温过程中重金属挥发特性的影响

在研究垃圾与污泥掺烧后焚烧飞灰中重金属浸出特征的基础上,重点研究了飞灰在1 000 ℃条件下高温处置过程中重金属(Cu、Zn 、Pb、Cd)随不同停留时间的挥发特性及添加剂(CaO、Al₂O₃、SiO₂、高岭土、粉煤灰)对重金属转化与挥发特性的影响。研究结果表明,飞灰中重金属Zn、Pb、Mn含量较高,Ni的含量较低,而毒性较大的Cd达到29.4 mg/kg。浸出液中七种金属都满足危险废物鉴别标准(GB5085.3-1996),并且重金属的浸出浓度受浸取时间及浸取液pH值影响较大。在同样的高温处置条件下,焚烧飞灰中不同重金属的挥发特性有较大的差别。其中,Pb表现出易挥发的特性,其挥发率超过80%,而Cu挥发性较小,其挥发率小于30%。综合来看,飞灰中重金属的挥发性大小依次为Pb>Cd>Zn>Cu。飞灰中添加Al₂O₃和高岭土可以抑制Cd的挥发,添加Al₂O₃后Pb的挥发率有所减少,添加SiO₂、CaO、高岭土、粉煤灰均使Zn的挥发率降低,而对Cu的挥发率没有抑制作用,这与飞灰中高Cl含量及各痕量元素化合物对固体添加剂活性位选择性的竞争吸附有关。     

城市生活垃圾焚烧飞灰重金属的浸出特性

对用流化床焚烧炉混烧垃圾和煤的布袋飞灰进行了重金属的TCLP(Toxicity Characteristic Leaching Procedure)浸出特性实验，探讨了液固比、初始pH值及浸出时间对飞灰中重金属Pb、Cr、Cd、Ni、Cu、Zn的浸出影响。结果表明，重金属的浸出量都随着液固比的增加而增加，其中Cr、Cu一般呈上升趋势，Cd、Ni、Zn在液固比大于20时曲线变化较平缓，Pb的浸出规律比较特殊，有一个明显的波峰和波谷。重金属在浸取液的pH≤2.90时的浸出浓度远远大于pH≥4.03时的浸出浓度。Pb、Cr、Zn随着浸出时间的增加，浸出浓度下降，而Cd、Ni上升，Cu是先上升后下降。在液固比、初始pH值及浸出时间这三个影响因素中，pH值对重金属的浸出影响较大，重金属在酸性环境下较易浸出。     

Leaching Studies of Inorganic and Organic Compounds from Fly Ash

Fly ash is produced in massive quantities by fossil fuel based power plants and waste incinerators, and contains high levels of potentially toxic chemicals. Various leaching tests exist to determine the available fractions, but the outcome is strongly dependent on the experimental conditions, and these have not yet been harmonised at the international level. In order to test existing protocols for heavy metals, several intercomparisons were organised within the framework of an EU-INCO project "ANALEACH", in which seven institutes from five countries participated. Two existing reference materials were made available for the project and test batches of two new fly ash reference materials were produced. Availability tests, leaching tests and pH-stat tests were studied and critical steps in the procedures were identified. Fly ashes can also contain large amounts of inorganic sulphur and nitrogen compounds, and the determination and leaching behaviour of these compounds were also studied. In one intercomparison for metals, inorganic S and N-compounds were also included. A five-step leaching test was optimised for fly ash in order to link metal fractions to different types of binding. Column leaching experiments were carried out to investigate leaching from fly ash into soil, mimicking the effects of (acid) rain on fly ash deposited on topsoil after atmospheric transport. The major fraction of the leached metal ions was retained by the soil. Also large numbers of organic compounds (including many toxic ones) were identified in fly ash extracts, especially in city waste incinerator ash. Leaching procedures based on ultrasonic extraction were developed for organic compounds and an intercomparison exercise was organised. In a field study at the river Nitra(Slovakia) numerous organic pollutants were found at elevated levels downstream from a major fly ash dump site.     

Ameliorating the sensitivities,thermal and combustion properties of RDX by in situ self-assembly TA-Pb/Cu shells to RDX surface

In order to ameliorate the sensitivities, thermal and combustion properties of cyclotrimethylenetrinitramine (RDX), tannic acid (TA) is used to react with lead and copper via in situ self-assembly to coat RDX for preparing RDX@TA-Pb/Cu microcapsules. The structures of RDX@TA-Pb/Cu microcapsules are characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Fourier-transform infrared spectra (FT-IR). The surface topography of RDX@TA-Pb/Cu microcapsules are characterized by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The mechanical sensitivities and explosion points of RDX@TA-Pb/Cu microcapsules are measured to study the influence of TA-Pb/Cu shells on mechanical and thermal safeties of RDX. The non-isothermal properties of RDX@TA-Pb/Cu microcapsules are characterized by differential scanning calorimetry (DSC). The catalytic effects of TA-Pb/Cu shells on RDX are characterized by accelerating rate calorimeter (ARC). The residues of RDX@TA-Pb/Cu microcapsules after combustion in air are collected and characterized by SEM and XRD to further study the catalytic effect of TA-Pb/Cu shells. The study results show that a 150 nm TA-Pb/Cu shells are uniformly coated on RDX surfaces. The chemical structure of RDX maintains constant during in situ self-assembly coating process. The mechanical and thermal safeties of RDX are enhanced after coating with TA-Pb/Cu shells. The decomposition and combustion property of RDX can be catalyzed by TA-Pb/Cu, and the catalytic effects of in situ self-assembly coating are better than that of physical mixing. The RDX@TA-Pb/Cu microcapsules can be used in RDX based composite modified double base (CMDB) propellants.     

粉煤灰漂珠负载Bi2WO6复合材料的制备及光催化性能研究

以工业固体废弃物粉煤灰漂珠(fly ash cenospheres, FACs)为载体, 采用水热法制备了新颖的漂珠负载Bi₂WO₆复合材料(Bi₂WO₆/FACs), 通过X射线衍射(XRD), 扫描电子显微镜(SEM), X-射线光电子能谱(XPS), 和紫外-可见漫反射光谱(DRS)技术对其进行了表征。XRD数据显示了正交相Bi₂WO₆的特征衍射峰。DRS结果证实了引入FACs后Bi₂WO₆对可见光的吸收增强。在可见光的照射下, 以亚甲基蓝溶液的光催化降解评价了Bi₂WO₆/FACs复合材料的光催化性能。结果表明：Bi₂WO₆/FACs的光催化性能优于纯Bi₂WO₆的, 其一级反应速率常数(k)为后者的2.4倍。尤其是由于漂珠质轻中空的特性, Bi₂WO₆/FACS复合光催化剂可长时间漂浮于水面, 既能充分吸收光能, 又有利于催化剂的回收和重复利用。     

Sequestration of radioactive nickel in fly ash by incorporating nanogoethite

Sequestration of radioactive nickel (⁶³Ni²⁺) in fly ash coming from hospital wastes incineration plant by incorporating nano-goethite as a function of pH, particle size and the ratio of solid and liquid was investigated under the batch leaching experiments. The synthetic nanogoethite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and specific surface area (SSA). The admired needle nanogoethite was obtained in terms of XRD, TEM and SSA analysis. Approximate 5% of ⁶³Ni²⁺ was desorbed from the nanogoethite/fly ash composite under the circum natural pH conditions. The ratio of solid to liquid has little effect on desorption of ⁶³Ni²⁺ from nanogoethite/fly ash composite. These results indicate that the radioactive nickel in fly ash can be sequestrated by incorporating nanogoethite. The results may play significantly a role in immobilization in situ of trace radionuclides in the natural environment.     

Fly ASH Reactivity. Formation of hydrate phases

In this study the process of hydration of fly ash, produced by a municipal solid waste (MSW) incinerator, is examined in water and in a solution enriched with Ca(OH)₂. The examined fly ash samples are characterized by a high content of alkaline chlorides and anhydrite and by remarkable amounts of heavy metals. Investigations using differential thermal analysis/thermogravimetry (DTA/TG) and X-ray diffractometry (XRD)show particular kinetics of the formation of the ettringite phase. The development of such a hydrated phase is much more intense in the presence of an excess of Ca(OH)₂so as to consume the ‘free’ sulphate in the case of the more reactive fly ash. Experimental results from thermal analysis and X-ray diffractometry show the presence of different hydrated phases during the interaction between fly ash and aqueous solution. The analytical determinations, related to the aqueous solution, point out an interesting decrease in concentration of metals Pb, Zn and Cr(VI), relating to the middle period of the interaction. This revised version was published online in July 2006 with corrections to the Cover Date.     

城市污水污泥与固体垃圾混烧过程中重金属迁移特性的研究

通过城市污水污泥与固体垃圾合成样品在小型管式焚烧炉内的混烧实验,采集灰渣样品进行XRF化学成分分析和浸出毒性鉴别测试,结合污水污泥焚烧过程中热力学平衡计算,定量表征了污水污泥中Cu、Pb、Zn、 Mn、Ni在焚烧过程中向底灰、飞灰和烟气迁移的特性及对灰渣的毒性影响。研究结果表明,污水污泥混烧显著提高了飞灰和底灰中重金属含量,其中Zn和Pb增加量最大,而Ni、Mn、Cu依次减少;随着有机氯的加入,飞灰中重金属含量呈现递增趋势,其中Zn表现最明显。毒性测试结果显示,污水污泥的混烧也导致了垃圾焚烧飞灰中Zn和Pb的浸出浓度超过中国对危险废物浸出的控制标准值。同时,重金属迁移的热力学平衡模型预测结果与实验结果差距较大。这表明热力学平衡计算方法还需进一步考虑影响重金属氯化物形成的其他因素,如在焚烧过程中反应动力学、焚烧室内氧气含量变化、与其他元素间的化学反应等。     

Evaluation of a mixed chelator as heavy metal stabilizer for municipal solid‐waste incineration fly ash: Behaviors and mechanisms

This paper compares the stabilization performances of three dithiocarbamate and three phosphate chemical stabilizing agents, selects the best agents from each group, combines them as a mixed heavy metal stabilizer for municipal solid‐waste incineration (MSWI) fly ash, and investigates the effectiveness of the mixed chelator in stabilizing heavy metals in MSWI fly ash from southwest China. The mechanism of stabilization is also analyzed. Results indicate that piperazine dithiocarbamate can stabilize Cd, Cu, and Ni effectively, while sodium dihydrogen phosphate can stabilize Pb better. With the addition of the mixed chelator (2% sodium dihydrogen phosphate and 1% piperazine dithiocarbamate), all the targeted heavy metal concentrations in the leachate were below the standards for pollution control on municipal solid waste landfill sites in China. The stabilizing agents combined with the heavy metals in fly ash could not generate insoluble crystals; however, the heavy metals could combine with the agents' effective groups, generating flocs in the pores or on the surfaces of the fly ash and offering significant densification. The mixed chelator could transfer heavy metals from unstable fractions to stable fractions, so the leaching of heavy metals from the fly ash was greatly decreased.     

The use of X-ray fluorescence (XRF) analysis in predicting the alkaline hydrothermal conversion of fly ash precipitates into zeolites

The use and application of synthetic zeolites for ion exchange, adsorption and catalysis has shown enormous potential in industry. In this study, X-ray fluorescence (XRF) analysis was used to determine Si and Al in fly ash (FA) precipitates. The Si and Al contents of the fly ash precipitates were used as indices for the alkaline hydrothermal conversion of the fly ash compounds into zeolites. Precipitates were collected by using a co-disposal reaction wherein fly ash is reacted with acid mine drainage (AMD). These co-disposal precipitates were then analysed by XRF spectrometry for quantitative determination of SiO₂ and Al₂O₃. The [SiO₂]/[Al₂O₃] ratio obtained in the precipitates range from 1.4 to 2.5. The [SiO₂]/[Al₂O₃] ratio was used to predict whether the fly ash precipitates could successfully be converted to faujasite zeolitic material by the synthetic method of [J. Haz. Mat. B 77 (2000) 123]. If the [SiO₂]/[Al₂O₃] ratio is higher than 1.5 in the fly ash precipitates, it favours the formation of faujasite. The zeolite synthesis included an alkaline hydrothermal conversion of the co-disposal precipitates, followed by aging for 8 h and crystallization at 100 °C. Different factors were investigated during the synthesis of zeolite to ascertain their influence on the end product. The factors included the amount of water in the starting material, composition of fly ash related starting material and the FA:NaOH ratio used for fusing the starting material. The mineralogical and physical analysis of the zeolitic material produced was performed by X-ray diffraction (XRD) and nitrogen Brunauer-Emmett-Teller (N₂ BET) surface analysis. Scanning electron microscopy (SEM) was used to determine the morphology of the zeolites, while inductively coupled mass spectrometry (ICP-MS), Fourier transformed infrared spectrometry (FT-IR) and Cation exchange capacity (CEC) [Report to Water Research Commission, RSA (2003) 15] techniques were used for chemical characterisation. The heavy and trace metal concentrations of the zeolite products were compared to that of the post-synthesis filtrate and of the precipitate materials used as Si and Al feed stock for zeolite formation, in order to determine the trends (increase or decrease) and ultimate fate of any toxic metals incorporated in the co-disposed precipitated residues.     

Copper(I) stabilized on N,N′-methylene bis-acrylamide crosslinked polyvinylpyrrolidone: An efficient reusable catalyst for click synthesis of 1,2,3-triazoles in water

N,N′-methylene bis-acrylamide crosslinked N-vinyl-2-pyrrolidone (NVPMBA) polymer was prepared via suspension polymerization technique and used as a polymeric support for the reduction of Cu(II) to Cu(I). It was observed that NVPMBA matrix facilitated the stabilization of Cu(I) particles. Furthermore, the copper supported polymer catalyst (CuNVPMBA) was characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy (SEM), energy dispersive X-ray analysis, transmission electron microscope (TEM), X-ray photoelectron spectra (XPS), inductively coupled plasma optical emission spectroscopy, and derivative thermogravimetry analysis. SEM showed that both the polymer and CuNVPMBA exhibit a spherical morphology. TEM revealed that copper nanoparticles formed on the polymer surface have an average particle size of 5.14 nm. XPS analysis confirmed the presence of Cu(I) and Cu(II) in the ratio 1:2. The copper content in CuNVPMBA was found to be 1.25 wt%. CuNVPMBA was found to be very effective in promoting the click reaction between terminal alkynes and azides in aqueous media in the absence of ascorbate or external base under mild conditions to form 1,2,3-triazoles in excellent yield with a copper loading as low as 0.2 mol%. The catalyst could be reused and recycled several times without significant loss of catalytic activity.     

Effect of sintering temperature and thermoelectric power studies of the system MgFe2−xCrxO4

Mixed metal oxides showing the spinel structure exhibit interesting structural and electrical properties. Substances with specific compositions in the system MgFe_2?xCr_xO₄ were synthesized by the simple co-precipitation method and have been investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM) to study the effect of temperature on the size of particles and grains. The infrared spectrum shows, two strong bands around 600 and 500 cm^?1. An elemental composition of one of the samples, MgFeCrO₄ was found by energy dispersive X-ray spectroscopy (EDS). The thermoelectric power measurements carried out from room temperature to 500 °C, show both n-type and p-type behavior.     

Effect of Atmospheres on Transformation of Heavy Metals during Thermal Treatment of MSWI Fly Ash: By Thermodynamic Equilibrium Calculation

The vaporization behaviors of eight heavy metals (Pb, Zn, Cu, Cd, Cr, Co, Mn, and Ni) in municipal solid wastes incineration (MSWI) fly ash during thermal treatment under air atmosphere (21% O₂/79% N₂), an inert atmosphere (100% N₂), and a reducing atmosphere (50% CO/50% N₂) were evaluated based on a thermodynamic equilibrium calculation by FactSage 8.1. The results show that the reducing atmosphere promotes the melting of MSWI fly ash, resulting in a more liquid phase than in air or an inert atmosphere. Except for Cd, the formation of liquids can dissolve heavy metals and reduce their vaporization ratio. In the air and inert atmospheres, Pb, Zn, Cu, Co, Mn, and Ni vaporize mainly in the form of metallic chlorides, while Cd volatilizes in the form of metallic Cd (g) and CdO (g). In the reducing atmosphere, Co, Mn, and Ni still vaporize as chlorides. Zn and Cd mainly vaporize in the form of Zn (g) and Cd (g), respectively. In terms of Pb, in addition to its chlorides, the volatiles of Pb contain some Pb (g) and PbS (g). Cr has a low vaporization ratio, accounting for 2.4% of the air atmosphere. Cr, on the other hand, readily reacts with Ca to form water-soluble CrCaO₄, potentially increasing Cr leaching. Except for Cd, the results of this study suggest that the reducing atmosphere is used for the thermal treatment of MSWI fly ash because it promotes the melting of fly ash and thus prevents heavy metal vaporization.     

Heterometallic M/Mn (M=Cu, Co, Zn) acetate complexes as precursors for binary oxides

A facile one-pot procedure, or so-called “direct synthesis,” was used to prepare the novel heterometallic complexes [M₂Mn(OAc)₆(bpy)₂], where M=Cu (1), Co (2), Zn (3), bpy=2,2′-bipyridyl, with high yields via oxidative dissolution of pure metals in a liquid phase. The complexes were characterized by an elemental analysis, single crystal X-ray diffraction method and FTIR. These complexes are proposed as precursors, whose thermal degradation may lead to the formation of solids possessing nano- to microsize levels of dispersity. The thermal behavior of the complexes obtained was studied by thermal analysis (TG/DTA/DTG) in both air and N₂ and also by TPD mass-spectrometry in vacuo. The FTIR, X-ray powder diffraction (PXRD) and thermoanalytical data were used for the identification of the solid products of thermal degradation. The morphology and microstructure of the solid residues were analyzed, using scanning electron microscopy with energy dispersive X-ray microanalysis (SEM/EDX) at mkm and sub-micro levels.     

粉煤灰漂珠负载Bi2WO6复合材料的制备及光催化性能研究

以工业固体废弃物粉煤灰漂珠(fly ash cenospheres,FACs)为载体,采用水热法制备了新颖的漂珠负载Bi2WO6复合材料(Bi2WO6/FACs),通过X射线衍射(XRD),扫描电子显微镜(SEM),X-射线光电子能谱(XPS),和紫外-可见漫反射光谱(DRS)技术对其进行了表征。XRD数据显示了正交相Bi2WO6的特征衍射峰。DRS结果证实了引入FACs后Bi2WO6对可见光的吸收增强。在可见光的照射下,以亚甲基蓝溶液的光催化降解评价了Bi2WO6/FACs复合材料的光催化性能。结果表明:Bi2WO6/FACs的光催化性能优于纯Bi2WO6的,其一级反应速率常数(k)为后者的2.4倍。尤其是由于漂珠质轻中空的特性,Bi2WO6/FACS复合光催化剂可长时间漂浮于水面,既能充分吸收光能,又有利于催化剂的回收和重复利用。     

Determination of trace elements in fly ash samples by FAAS after applying different digestion procedure

The fly ash samples obtained from Kangal Power Plant were prepared for FAAS analysis by a new approach. The trace elements of the fly ash samples were leached with appropriate solvents under suitable conditions. The leaching method is known as an effective technique for substances dissolving very hard and refractory materials. The leaching effects of solvents and their mixtures were investigated on fly ash samples that are used largely in analysis of soil and sediment samples.The fly ashes mainly consist of glassy aluminosilicates. The major components of the samples are SiO₂, Al₂O₃, CaO and Fe₂O₃. Therefore, decomposition of the silicate lattice of the fly ash is required for liberation of trace elements. The dissolution process can be completed by using a mineral acid such as concentrated HCl. This technique has an advantage that the fly ash can be dissolved without any oxidation at room temperature.Maximum element recoveries were obtained by the procedure of 37% HCl leaching after the samples were treated with 2.0 ml of concentrated HF. It was also observed that maximum mass loss occurred in this procedure. The effect of the four leaching reagents, which are HCl, HNO₃, HClO₄ and HNO₃ + HClO_4, were investigated on fly ash samples that were treated with concentrated HF. An optimum leaching method was determined based on the confidence of analytical results and element recovery rates.