原料粒度对粉煤灰成型吸附剂结构和性能的影响(英文)

In this paper, different particle sizes of coal fly ash FA-R (D50=15.75μm), FA-A (D50=3.61μm) and FA-B (D50=1.73μm) were treated with NaOH solution to prepare the forming adsorbents FFA-R, FFA-A and FFA-B. The structure and adsorption properties of the forming adsorbents for methylene blue (MB) from aqueous solu-tion were examined. The results showed that the specific surface areas and adsorption capacities of the forming adsorbent for MB increased with decreasing particle size of raw coal fly ashes. The adsorption kinetic data of MB on FFA-R, FFA-A and FFA-B fitted the second-order kinetic model very wel with the rate constants (k2) of 3.15 × 10?2, 3.84 × 10?2 and 6.27 × 10?2 g·mg?1·min?1, respectively. The adsorption process was not only con-trol ed by intra-particle diffusion. The isotherms of MB on FFA-R, FFA-A and FFA-B can be described by the Lang-muir isotherm and the Freundlich isotherm, and the adsorption processes were spontaneous and exothermic. ? 2014 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. Al rights reserved.     

粉煤灰在酸性废水处理中的应用

粉煤灰是燃煤电厂排放的固体废弃物。近年来,人们开始致力于粉煤灰在环境保护方面的开发利用,其处理废水已经成为研究的热点之一。本文综述了近年来国内粉煤灰处理工业酸性废水的研究进展,并介绍了粉煤灰处理酸性废水的机理、存在的问题及其应用前景。     

Influence of the type of ash on the fire resistance characteristics of ash-enriched mortars

The possibility of using different types of fly ash as a major component of pastes used for the manufacture of thermal insulating elements was studied. Fly ashes from the combustion of pulverized coal in a power plant and from the combustion of biomass were tested. The insulating capacity and compressive strength of the cured pastes were measured. The effect of some binders and additives were also studied. A good linear correlation between the insulating capacity of the mortars and the energy absorbed by them in the Differential Scanning Calorimetry test was observed. This relationship allows us to draw conclusions about the insulating capacity of different ashes, and makes it easier to choose those ashes that present better behavior. Consequently, there is no need to prepare such a large number of test pieces and the work involved in the experiment is simplified. Results show that some of the products prepared in this experiment, containing a high proportion of ash, have promising thermal and mechanical properties, and show a potential use as new fireproof products.     

分选与磨细粉煤灰对水泥胶砂性能的影响

研究了分选与磨细粉煤灰的颗粒分布与形貌的差异及对水泥胶砂性能的影响。研究结果表明:当勃氏比表面积相近,磨细粉煤灰的中位粒径大于分选细粉煤灰,其圆珠状颗粒较少,表面较为粗糙。在相同水胶比的条件下,掺分选粗粉煤灰的水泥胶砂流动度及强度均低;分选粗粉煤灰磨细后,不仅减少了颗粒的粘连,增加了比表面积,而且提高了粉煤灰的反应活性和水泥胶砂流动度及强度,虽其水泥胶砂流动度仍小于掺分选细粉煤灰的水泥,3d水泥胶砂强度也略低,但其28d水泥胶砂强度略高于掺分选细粉煤灰的水泥;在相同水泥胶砂流动度的条件下,掺磨细粉煤灰配制的水泥胶砂3d强度低于掺分选细粉煤灰的水泥,但随着水化龄期的增长,其差距逐步缩小,至60d时可超过后者。     

Characterization of sintered coal fly ashes

Çan, Çatala?z?, Seyitömer and Af?in-Elbistan thermal power plant fly ashes were used to investigate the sintering behavior of fly ashes. For this purpose, coal fly ash samples were sintered to form ceramic materials without the addition of any inorganic additives or organic binders. In sample preparation, 1.5 g of fly ash was mixed in a mortar with water. Fly ash samples were uniaxially pressed at 40 MPa to achieve a reasonable strength. The powder compacts were sintered in air. X-ray diffraction analysis revealed that quartz (SiO₂), mullite (Al₆Si₂O₁₃), anorthite (CaAl₂Si₂O₈), gehlenite (Ca₂Al₂SiO₇) and wollastonite (CaSiO₃) phases occurred in the sintered samples. Scanning electron microscopy investigations were conducted on the sintered coal fly ash samples to investigate the microstructural evolution of the samples. Different crystalline structures were observed in the sintered samples. The sintered samples were obtained having high density, low water adsorption and porosity values. Higher Al₂O₃ + SiO₂ contents caused to better properties in the sintered materials.     

Adsorptive removal of thiophene and benzothiophene over zeolites from Mae Moh coal fly ash

Zeolites have been hydrothermally synthesized using Thai coal fly ash from Mae Moh Power Plant as silica and alumina sources. The synthesis conditions, i.e., SiO₂/Al₂O₃ ratio, amount of water, amount of base, and aging temperature, were varied to prepare different topologies of zeolitic products. The zeolites attained were sodalite (SOD), gismondine (GIS), and cancrinite (CAN). The zeolites have been applied to adsorption of thiophene and benzothiophene in n-hexane solution. It was found that GIS with higher specific surface area and average pore volume had superior performance to other synthesized materials. Adsorption capacity of our developed zeolites was compared to those of commercial zeolites, i.e. NaY, HUSY, beta, and ZSM-5 obtained via the conventional synthesis methods. The results suggested a potential of zeolites derived from Mae Moh coal fly ash for removal of refractory sulfur compounds, such as benzothiophene.     

β-SiAlON Hollow Spheres Prepared from Coal Fly Ash Microspheres

β-SiAlON hollow spheres were prepared by carbothermal reduction method, using coal fly ash (＜15 μm, 43-77 μm, and ＞100 μm) and active carbon in some proportion (20% less than theoretical addition, theoretical addition and 10% excess theoretical addition) as starting materials, putting into alumina crucible in high temperature nitriding furnace after well mixed, and holding at 1 300 ℃, 1 350 ℃, 1 400 ℃, 1 450 ℃, and 1 500 ℃ for 6 h. Effects of temperature, particle size of the microsphere, and addition of active carbon on the phase composition and microstructure of the nitridized products were studied by means of XRD and SEM. The results show that the nitridation reaction starts at 1 300 ℃; excess active carbon is necessary to form β-SiAlON hollow spheres, and particle size is the important parameter to form the hollow spheres nitridized products β-SiAlON; at 1 500 ℃, when the active carbon is 10% in excess, the β-SiAlON hollow spheres, which were prepared using coal fly ash with particle size＞100 μm, are featured with rough surface, high hollowness and low density.     

粉煤灰处理含砷工业废水的研究

研究了以粉煤灰为吸附剂处理含砷工业废水.实验结果表明,在不调节含砷工业废水pH的条件下,粉煤灰投加质量浓度为0.05 g/mL,吸附时间为60 min,温度为25 ℃,砷的去除率达87.0%,处理后的水符合GB 8978-1996污水综合排放标准.该工艺简单,以废治废,成本低廉,具有良好的应用前景.     

粉煤灰的改性及吸附作用的研究

采用单因子试验的方法,选择合适的改性剂,研究了粒径大小、吸附等温线、溶液pH值等因素对改性粉煤灰吸附性能的影响,并对改性粉煤灰吸附机理进行了研究。研究结果表明,改性灰的吸附效果优于粉煤灰,极大的提高了对难降解染料废水的去除能力,在pH值大于11,投加量为20g/L时,CODCr去除率可达95%以上。     

粉煤灰-膨润土复合吸附剂处理含Cr(Ⅵ)废水

以粉煤灰和膨润土为原料,制备了粉煤灰-膨润土复合吸附剂,研究了该复合吸附剂对水中Cr(Ⅵ)的吸附性能,结果表明:在温度为25℃,pH值为4,Cr(Ⅵ)初始质量浓度为22 mg/L,复合吸附剂用量为8 g/L,吸附时间为1 h,Cr(Ⅵ)的去除率可达到91%以上。     

改性粉煤灰陶粒的制备及其吸附SO2性能研究

以改性粉煤灰为主要原料,掺杂膨润土、石灰石及水泥,经造粒、烘干、焙烧等工艺制得陶粒。利用扫描电镜(SEM)、比表面和孔径分布测定仪等方法对其表征。考察了陶粒对SO2的吸附性能。结果表明:质量比为改性粉煤灰∶膨润土∶石灰石∶水泥=10∶1∶1∶0.4,在500℃下烧制10 min得到3～4 mm的陶粒,陶粒比表面积为32.8 m2·g-1,陶粒表面粗糙,内部多孔。该陶粒对SO2最大吸附容量为30.939.5 mg·g-1。     

煤矸石对粉煤灰陶粒滤料性能的影响

以粉煤灰、黏土为主料,添加不同比例的造孔剂煤矸石制备粉煤灰陶粒滤料,研究了煤矸石用量对粉煤灰陶粒滤料性能的影响,结果表明,随着煤矸石比例的提高,粉煤灰陶粒滤料的烧失量、吸水率及比表面积逐渐增大,而堆积密度、强度和耐酸碱性逐渐减小。     

Size fraction characterization of highly-calcareous fly ash

The chemical and mineralogical composition of lignite fly ash (FA) varies as a function of the prevalent conditions in both the processes of power production and lignite mining. The differentiation of the qualitative and quantitative composition of the highly-calcareous lignite fly ash, as a function of its particle size distribution, is verified in this paper. According to the results of the conducted research, a fine-grained fraction of considerable amount presents properties that obstruct the sustainable exploitation of calcareous lignite fly ash in cement industry applications. On the other hand, the same grain fraction (because of its hydraulic properties) can be utilized in other sort of applications, based on different criteria, i.e. in road constructions. The coarse-grained fraction (which reflects a low proportion to the total fly ash output) presents the same undesired characteristics as well. Rather, the intermediate grain fraction (75-150 μm) presents the highly desirable properties when fly ash is utilized as a pozzolanic additive. In addition, the mechanism of the formation of the intermediate grain fraction strongly prevents the factors that cause the variation of fly ash-quality. It is therefore the optimum part of the whole amount of lignite FA, to be utilized as additive in cement manufacturing. The outcomes of this paper will hopefully contribute towards the crucial goal of the expansion of the utilization of calcareous lignite fly ash by proposing a more effective way of using this material, basically by taking advantage of its fundamental chemical and mineralogical properties.     

改性粉煤灰除去废水中的磷

利用水泥对电厂粉煤灰进行改性,并将改性粉煤灰应用于去除废水中的磷,探讨了吸附平衡时间、吸附剂用量、颗粒的大小、pH值以及初始浓度等对吸附效率的影响。在最佳条件下,磷的去除率可以达到98％以上。     

Application of B MAS-NMR to the characterization of boron in coal fly ash generated from Nantun coal

Boron and its compounds are environmentally hazardous substance and are well-known condensed products that appear in coal fly ash during combustion of coal in coal-fired electric power stations. In a previous study, we suggested that boron in coal fly ash obtained from Nantun coal in China, identified as Ash-N, may exist on the surface of relatively large coal fly ash particles or as very fine particles generated by homogeneous nucleation. Although the characterization of boron in coal fly ash is important for its effective stabilization or removal, its detection is quite difficult because of its low concentration in coal fly ash and its light atomic weight. In the present work, solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR) technique has been applied to reveal the local chemical structures of boron in Ash-N. In the ¹¹B MAS-NMR spectrum of Ash-N, two peaks which are attributed to a three-oxygen coordinated boron unit (BO₃) and a four-oxygen coordinated boron unit (BO₄) were observed with high resolution. We have estimated quadrupole parameters of the BO₃ unit in Ash-N using computer simulation, and we have fingerprinted these moieties with the parameters of borates. The result of the present analysis shows that calcium- or magnesium-bearing orthoborate or pyroborate are the most likely forms of boron in Ash-N.     

Influence of trace metal distribution on its leachability from coal fly ash

The risks associated with the reuse of coal fly ash in natural environmental settings in terms of their mobility and ecotoxicological significance is largely determined by: (1) the physicochemical conditions the fly ash is placed under; (2) the total leachable metal content in fly ash and; (3) the distribution or mineralogical fractionation of metals. In this study, we report the mobility of As, Cr, Pb, Fe, Cu and Zn from a single Class F fly ash (CFFA). The influence of pH on metal release was compared to the total leachable metal content, as determined by single and sequential chemical extractions. The results show that the CFFA sample is environmentally safe under natural pH conditions, with metal leaching less than the mandated RCRA limits. The elements Fe, Pb and Cr were moderately soluble at acidic pH and sparingly soluble beyond neutral pH. Arsenic release from CFFA was higher under aggressive pH conditions (pH < 4 and pH > 9) and consistent with its oxyanionic behavior. Partial dissolution of the acid soluble (exchangeable) fraction at acidic pH; desorption of oxyanions at alkaline pH; adsorption and or co-precipitation of metals with iron (hydr) oxides at neutral pH appeared to be the probable mechanisms controlling metal release. While simple EDTA extractions provided good indications of the total leachable amounts, a direct correlation with pH leaching data was impossible as the mineralogical distribution of the metals in the fly ash appeared to play a significant role in their leachability. In the case of Class F fly ash, metal association with Fe-oxide appeared to play a more dominant role in metal release.     

The influence of the binder on the properties of sintered glass-ceramics produced from industrial wastes

Sintered glass-ceramics were produced from coal fly ashes, red mud from aluminum production and silica fume. The capabilities of Tunçbilek fly ash and a mixture of Orhaneli fly ash, red mud and silica fume to be vitrified and devitrified by sintering process were investigated by means of scanning electron microscopy and X-ray diffraction analysis. To determine the effect of binder in the sintering technique, glass powders were pressed without or with the addition of polyvinyl alcohol. Owing to microstructural observations, density and hardness measurements, it can be said that physical properties and the hardness of the produced samples strongly depended on the crystallization degree of the samples. Toxicity characteristic leaching procedure test results showed that glass-ceramic samples produced by using sintering technique could be considered as non-hazardous materials. Chemical durability of the sintered glass-ceramic samples was also good. Microstructural investigations, hardness and physical properties of the samples indicated that the addition of polyvinyl alcohol improved the properties of sintered glass-ceramics obtained from Orhaneli fly ash, red mud and silica fume.