粉煤灰物化性质对单质汞吸附性能的影响

在固定床实验台上考察了三种不同来源粉煤灰对单质汞的吸附性能,采用X射线荧光光谱仪、X射线光电子能谱仪、激光粒度分析仪、扫描电子显微镜等对不同粉煤灰的物化性质进行了表征,并探讨了物化性质对汞吸附性能的影响。结果表明,粉煤灰对汞的吸附包括物理吸附和化学吸附;粉煤灰中未燃尽碳是影响粉煤灰汞吸附性能的重要因素之一,其中,表面C元素与Ti、Si等元素(M)相互作用形成的"C-M"化学键促进了单质汞的氧化,同时粉煤灰中含有的无机化合物Fe₂O₃等也对单质汞的氧化有促进作用;增大比表面积和减小孔径,及适中的颗粒粒径均有利于提高粉煤灰单质汞吸附性能。     

Diffusion of nonionic azo dyes in nylon-6

Diffusion of 2,4-dinitroaniline and three nonionic azo dyes in Nylon-6 film was studied by analysis of the concentration-distance curves (profiles) of penetrants in the polymer. Actual diffusivities D_(c) of penetrants in polymer, diffusion coefficients as a function of the concentration C_f of penetrant in polymer, were calculated from the profile. It was found that D_(c) is almost constant or decreases gradually with decreasing C_f in the range of high-medium C_f but decreases appreciably with decreasing C_f at low C_f. The change in D_(c) with C_f was explained in terms of the dual-mode sorption-diffusion model. The penetrants diffuse in the polymer as two distinct species, i.e., a dissolved species and an adsorbed species. The former is the penetrant taken up by the polymer by a partition mechanism (dissolved species) and the latter is that taken up by Langmuir sorption (adsorbed species). The actual diffusivity D_P(c) of the dissolved species decreases with decreasing C_f. While the actual diffusivity D_L(c) of the adsorbed species normally increases gradually with decreasing C_f. D_P(c) is usually larger than D_L(c). © 1993 John Wiley & Sons, Inc.     

油页岩飞灰对重金属离子的吸附动力学及热力学

采用批式振荡吸附法研究了燃油页岩电厂循环流化床锅炉飞灰对重金属离子Pb²+、Cu²+、Zn²+、Cd²+的吸附动力学及吸附热力学特性,并提出了吸附机理。结果表明,油页岩飞灰对Pb²+、Cu²+、Zn²+、Cd²+的吸附平衡数据符合Langmuir和Freundlich吸附等温方程,但Freundlich方程能够更好地描述吸附等温线。在油页岩飞灰对重金属离子吸附的初始阶段,拉格朗日准一级动力学方程、准二级动力学方程、Elovich方程、粒子内扩散模型均能很好地反映吸附模式,而整个吸附过程则遵循二级反应动力学方程,其吸附过程是液膜扩散和粒子内扩散共同作用的结果。油页岩飞灰对Pb²+、Cu²+、Zn²+、Cd²+的吸附是吸热反应。     

镍铁类水滑石对偶氮阴离子染料的吸附脱色作用

采用镍铁类水滑石作为吸附剂,对偶氮阴离子染料酸性大红G、活性艳红X-3B和直接耐酸大红4BS废水进行脱色处理,研究了时间、镍与铁的物质的量之比、初始pH和无机电解质添加剂等因素对脱色率的影响,并结合红外光谱和X射线衍射分析结果讨论了其吸附脱色机理.结果表明,三种染料在镍铁类水滑石上的吸附均为层间的阴离子交换吸附和外表面的吸附.通过阴离子交换进入层间后,不同于直接耐酸大红4BS阴离子,酸性大红G和活性艳红X-3B两种阴离子与水滑石层间水分子之间产生氢键作用;在化学键合过程中,染料分子被镍铁类水滑石表面Fe3+氧化,同时偶氮键断裂导致脱色.     

Photochromic properties of thienylpyrrole azo dyes in solution

The photochromic behaviour of thienylpyrrole azo dyes in THF solutions was studied for the first time. The photochromic properties are strongly dependent on the substitution pattern on the dyes. Nitro-substituted thienylpyrrole azo dyes are particularly interesting since they exhibit very fast colouration/decolouration processes. The activation energies of these compounds are among the lowest values reported for heterocyclic azo dyes. These compounds show aggregation phenomena in freshly prepared solutions of THF, which lead to variable photochromic behaviours. Only after 1-5 h the solutions reach equilibrium and then reproducible photochromic behaviour can be observed.     

Delocalized cationic azo dyes containing a thiazole moiety

Several new delocalized cationic azo dyes incorporating a bathochromic thiazole moiety have been prepared in moderate to good yields. The synthesis involved the Knoevenagel condensation of an intermediate azo compound, bearing a terminal formyl group, with methylenic bases generated in situ from benzoazolium and quinolinium salts. All dyes display strong absorption around 700 nm and have shown negative solvatochromic behaviour.     

Dual-mode sorption of nonionic azo dyes by Nylon 6

Sorption isotherms of 2,4-dinitroaniline and three 4-amino-azobenzene derivatives (nonionic dyes with adequate solubility in water) on Nylon 6 (film and fiber) from water were determined at various temperatures. The observed isotherms were curved, not linear. They were very well described in terms of the dual-mode sorption model, Nernst-type partitioning, plus Langmuir sorption. The contribution of the Langmuir sorption to the total dye sorption decreased with increasing temperature. The saturation value for the Langmuir sorption increased with the crystallinity of Nylon 6 film, suggesting that the Langmuir sorption is associated with the crystalline phase.     

褐煤SHELL气化飞灰黏附影响因素的研究

通过激光粒度仪、X射线荧光光谱仪、扫描电子显微镜等现代化分析测试技术对褐煤样、飞灰样以及换热废锅中的积灰样进行了粒度分布、化学组成、晶体矿物组成、微观形貌、微区化学组成等特征的分析,研究影响飞灰黏附特性的因素。并通过引入富集系数,描述各个元素在煤灰、正常飞灰、废锅积灰中的迁移富集情况。结果表明,在废锅积灰中有含铁矿物的生成,同时Na、K、Fe、S、P元素在废锅积灰中发生富集,在飞灰与积灰颗粒边缘处有大量的Fe、Na元素的富集。     

Preparation and characterization of activated carbon from bagasse fly ash

Activated carbons from bagasse fly ash (BFA) were prepared by one step chemical activation using ZnCl₂ as activating agent, or combination method of chemical with CO₂ physical activation (physicochemical activation). The development of porosity was studied in correlation with the method of activation, activation temperature, and also the chemical weight ratio. A typical sample by the combination method at 600 °C and weight ratio of ZnCl₂:BFA = 2 exhibited micropore volume of 0.528 cc/g, mesopore volume of 0.106 cc/g and surface area of 1200 m²/g. For determining the adsorption capacity of the carbon samples in solutions, phenol and methylene blue equilibrium adsorption experiments were conducted. The properties and adsorption capacity of the synthesized activated carbons has been compared to commercial activated carbon (Norit^® SX Plus).     

Keggin和Dawson结构多金属氧酸盐光催化脱色偶氮染料

The investigation photocatalytic degradation of three azo dyes solution(Acid Mordant Navy Blue RRN,Acid Mordant Black PV,Acid Mordant Brown RH) under UV light irradiation using the polyoxometalates as catalyst was reported in this article.The research results showed that the photocatalytic activity of Keggin catalyst is higher than that of Dawson,and the catalyst α-H4SiW12O40 had the best efficiency to the photocatalytic decoloration of RRN.In 350 mg·L-1(30 mL) RRN solution,the optimum reaction condition wa...     

粉煤灰合成Na-X沸石去除废水中镍离子的研究

粉煤灰通过碱熔融 水热法合成了Na-X型沸石,研究了Na-X型沸石的用量、吸附时间、溶液pH值、初始镍离子浓度和温度对废水中镍离子去除效果的影响。结果表明,Na-X型粉煤灰沸石对镍离子的去除性能与化学原料合成的13X相当,明显优于粉煤灰。在20℃,pH值为6,沸石用量10g/L,吸附15min时,对初始浓度为20mg/L~150mg/L的镍离子去除率均可达90%以上。镍离子的吸附过程符合Langmiur吸附等温方程式,其单层吸附量为11.2×10^-3。粉煤灰沸石重复使用5次,对废水中镍离子的去除率仍高达95%,再生性能良好。     

Enhancement of the photochromic switching speed of bithiophene azo dyes

A series of heteroaryl substituted bithiophene azo dyes in solution were irradiated with visible light to promote the azo E-Z isomerization and then the kinetics of the thermal Z-E back reaction was studied. The speed of this process is strongly influenced by the nature of the aromatic ring linked to the NN function. While thiazole bithiophene azo dyes exhibit high switching speeds between the two isomers, but limited interconversion, for benzothiazole and substituted thiadiazole bithiophene azo dyes the switching between the two photoisomers can be performed in 3 s with a significant conversion of the trans-isomer to the thermal unstable cis-isomer (19-21%) and therefore a notable variation of the visible spectrum is observed.     

基于QSAR对偶氮染料光响应性及降解路径研究

采用密度泛函理论方法计算偶氮染料类化合物的量子化学参数,研究该类化合物结构与光响应活性的定量构效关系(QSAR),应用多元回归方法建立的方程具有显著统计学意义,并结合紫外光谱结果进行降解过程预测.结果表明:光催化体系中会最先造成偶氮染料的N=N键与萘环的断开,然后再生成其他副产物,副产物再经过电子转移、开环等一系列反应...     

Studies of fly ash using thermal analysis techniques

Improved thermoanalytical methods have been developed that are capable of quantitative identification of various components of fly ash from a laboratory-scale fluidized bed combustion system. The thermogravimetric procedure developed can determine quantities of H₂O, Ca(OH)₂, CaCO₃, CaSO₄ and carbonaceous matter in fly ash with accuracy comparable to more time-consuming ASTM methods. This procedure is a modification of the Mikhail-Turcotte methods that can accurately analyze bed ash, with higher accuracy regarding the greater amount of carbonaceous matter in fly ash. In addition, in conjunction with FTIR and SEM/EDS analyses, the reduction mechanism of CaSO₄ as CaSO₄+4H₂ CaS + 4H₂O has been confirmed in this study. This mechanism is important in analyzing and evaluating sulfur capture in fluidized-bed combustion systems.     

Coal fly ash decomposes diethyl phthalate

Decomposition of diethyl phthalate (DEP) exposed to a coal fly ash has been investigated in water by measuring UV-VIS spectra and GC-MS. Alkaline constituents eluted from the fly ash in the liquid phase gradually hydrolyzed DEP to produce monoethyl phthalate and/or phthalic acid. These products were adsorbed on the fly ash and decarboxylated into ethyl benzoate and benzoic acid, respectively, followed by decomposition into benzenes and/or the other compounds of lower molecular weight. The fly ash acts as not only an adsorbent but also a decomposer.     

Chemical characterization of density separated submicrometer coal fly ash

A new geometrical particle size separation method in the range of submicrometer has been developed for coal fly ash. Coal fly ash particles prefractionated less than 5m in geometrical diameter were fractionated with a coupling of supersonical dispersion in methyl alcohol and filtration through antistatic Nucleopore filter into >1.0, 1.0–0.8, 0.8–0.6m.Submicrometer (1.0–0.6m) and micrometer coal fly ash (25–20m) were separated into six density fractions and their compositions measured by SEM-EDX were compared. For the both size fractions, for the low density fractions (<2.8 g/cm³) consisted mainly of aluminosilicates and the fractions of 2.8–3.2 g/cm³ consisted of oxides of aluminum, silicon and calcium, and in the fraction above 3.2 g/cm³ iron was rich. In submicrometer fly ash, phosphor and sulfur concentrated to the particles rich in calcium. In the heaviest fraction, the particles containing over 30 wt% titanium as oxide observed among the particles rich in iron. These fractions were revealed not as a single component, but as mixtures of several components.     

Concurrent dyes adsorption and photo-degradation on fly ash based substrates

Most of the dyes are organic compounds, with different degree of polarization and different groups with various steric effects, making their complete biodegradation slow or even impossible. Adsorption on fly ash and fly ash based substrates represents a possible alternative for simultaneous removal of dyes and heavy metals form wastewaters resulted in the textile industry. Adsorption (under visible light) and adsorption and photodegradation (under UV irradiation) studies were done on Methylene blue solutions and on their mixtures with heavy metals (copper and cadmium), in systems using fly ash as single substrate, or mixed with a wide band gap semiconductor (TiO₂). The titanium oxides and hematite content in fly ash proved to be responsible for photodegradation processes even in the absence of the TiO₂ powder, confirming that modified fly ash is a viable candidate in developing up scalable processes for advanced wastewater treatment. The kinetic and thermodynamic studies allow to calculate the parameters and to describe the complex mechanisms, involving competitive adsorption.     

Crown-containing butadienyl dyes

Crown-containing butadienyl dyes containing various heterocyclic moieties and azacrown ether fragments were synthesized for the first time. The spatial structures and the absorption and fluorescence spectra of crown-containing butadienyl dyes and their complexes with metal cations were examined. The effects of the nature of the heterocyclic and crown ether fragments on fluorescence and generation of dyes and their complexes with metal cations were revealed based on the spectral data. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 530–541, March, 1999.     

Fast physics-chemical characterization of fly ash

This paper analyzes the effect of fly ash chemical character on early Portland cement hydration and the possible adverse effects generated by the addition of gypsum. Behaviour was analyzed for pure Portland cements with varying mineralogical compositions and two types of fly ash, likewise differing in chemical composition, which were previously characterized under sulphate attack as: silicic-ferric-aluminic or aluminic-silicic ash in chemical character, irrespective if they are in nature, siliceous or siliceous and aluminous materials according to the ASTM C 618-94a. The experimental results showed that water demand for paste with a normal consistency increased with the replacement ratio in fly ash with a more aluminic than silicic chemical character, whereas it declined when silicic-ferric-aluminic ash was used. On the other hand, the differences between the total heat of hydration released at the first valley and the second peak also clearly differentiated the two types of ash. While the relative differences increased in the more aluminic than silicic ash, they declined in the more silicic than aluminic. In another vein, the findings indicate that within a comparable Blaine fineness range, the reactive alumina (Al₂O₃^r−) content in pozzolanic additions has a greater effect on mortar strength than the reactive silica (SiO₂^r−) content, at least in early ages up to 28 days. Finally, the adverse effect generated in the presence of excess gypsum is due primarily to the chemical interaction between the gypsum and the C₃A in the Portland cement and the reactive alumina (Al₂O₃^r−) in the fly ash.