碱性矿物水镁石催化臭氧化—机理与应用

文章系统综述了碱性矿物水镁石及其煅烧产物在臭氧化净水中的应用及其机理。以活性艳红染料、硝基苯、苯胺、苯酚为例,分别研究了水镁石煅烧前后对不同类型的有机污染物的催化臭氧化降解效果。文章在前文实验的基础上,提出了水镁石煅烧前后的不同催化机理,进一步发展了臭氧化催化理论,为碱性矿物水镁石及其煅烧产物的利用提供了理论上的指导。     

Catalytic ozonation of azo dye active brilliant red X-3B in water with natural mineral brucite

Natural mineral brucite was used directly in catalytic ozonation of dye wastewater of active brilliant red X-3B. Compared with single ozonation, degradation of X-3B increased from 47% to 89%, and removal rate of COD increased from 9% to 32.5% in catalytic ozonation for 15 min. The catalytic ozonation of X-3B followed a direct oxidization mechanism by ozone molecule, and this was actually a homogeneous catalysis of OH⁻ due to dissolution of Mg(OH)₂ from natural brucite. As a natural mineral catalyst, brucite has supplied an economical and feasible choice for catalytic ozonation of X-3B in industrial wastewater.     

科研与开发MnO_x/颗粒活性炭催化臭氧氧化技术降解硝基苯效能研究

通过半动态实验,对MnOx/GAC(颗粒活性炭)催化臭氧氧化技术氧化硝基苯的降解效能与动力学规律进行了初步研究。结果表明MnOx/GAC催化臭氧氧化过程对硝基苯具有较高的催化活性,在相同的反应条件下,MnOx/GAC催化臭氧氧化技术对硝基苯的降解效率是单独臭氧氧化的2.4倍。催化剂对硝基苯有一定的吸附作用。MnOx/GAC催化剂的存在提高了臭氧的利用率。MnOx/GAC催化臭氧氧化过程存在着催化剂最佳投量,硝基苯初始浓度与反应速率常数有良好的线性相关性,水质本底对MnOx/GAC催化臭氧氧化效率也有影响。     

Assistance of Magnesium Cations on Degradation of Refractory Organic Pollutant by Ozone: Nitrobenzene as Model Compound

Selecting nitrobenzene as a model compound, the assistance of magnesium cations on ozon ation of refractory organic pollutant was investigated in pure water background. It is interesting to find that the presence of magnesium cations with a level of tens of millimoles per liter can obviously increase the degradation and mineralization efficiency of nitrobenzene compared with the case of ozonation alone. At lower pH condition, the magnesium cations still effectively assisted the ozonation of nitrobenzene. Ozone decomposition was accelerated by the presence of magnesium cations. It was confirmed that the presence of magnesium cations promoted the generation of hydroxyl radicals. It was speculated that the formation of hydroxyl group by the deprotonation of the hexaqueous magnesium cations complex Mg[H₂O]₆ ²⁺ promoted the hydroxyl radical formation. However, the promotion was found to be unremarkable and should not be the sole reason for the assistance of magnesium cations on ozonation. The complexation reaction between the hexaqueous magnesium cations complex and carboxylic group may be part of the reason for the magnesium cation- assisted ozonation of organic pollutants. This finding will provide fundamental support for the applications of ozone to treat the concentrated water from membrane filtration which contains both high concentration of magnesium cations and organic pollutants.     

Ozonation of Trace Nitrobenzene in Water in the Presence of a TiO2/Silica-Gel Catalyst

Heterogeneous catalytic ozonation was investigated for the degradation of nitrobenzene in the presence of TiO₂ supported on Silica-gel as a solid catalyst. The conditions in preparing the catalyst are experimentally optimized. The catalytic activity of the supported TiO₂ is strongly influenced by the calcination temperature. The TiO₂/Silica-gel calcined at 500 °C showed the highest activity for the degradation of nitrobenzene. An approximate increase of 21% in removal efficiency was achieved for catalytic ozonation compared with the case of ozonation alone. Nitrobenzene degradation was significantly influenced by the presence of carbonate and t-butanol, which confirmed that TiO₂/Silica-gel catalyzed ozonation followed a radical-type mechanism. Kinetic study demonstrated that catalytic ozonation is pseudo–first-order with no respect to the initial nitrobenzene concentration. The effect of catalyst dosage and pH on the oxidation efficiency of nitrobenzene was also investigated. Catalyst dosage exerted a positive influence on nitrobenzene removal, and nitrobenzene degraded more completely under neutral or basic conditions. Finally, the catalyst stability was tested through repeated experiments.     

Catalytic ozonation for the degradation of nitrobenzene in aqueous solution by ceramic honeycomb-supported manganese

Catalytic ozonation of nitrobenzene in aqueous solution has been carried out in a semi-continuous laboratory reactor where ceramic honeycomb and Mn–ceramic honeycomb have been used as the catalysts. The presences of the two catalysts significantly improve the degradation efficiency of nitrobenzene, the utilization efficiency of ozone and the production of oxidative intermediate species compared to the results from non-catalytic ozonation, and the improvement of them is even more pronounced in the presence of Mn–ceramic honeycomb. Adsorptions of nitrobenzene on the two catalytic surfaces have no remarkable influence on the degradation efficiency. Addition of tert-butanol causes the obvious decrease of degradation efficiency, suggesting that degradation of nitrobenzene follows the mechanism of hydroxyl radical (OH) oxidation. Some of the main operating variables like amount of catalyst and reaction temperature exert a positive influence on the degradation efficiency of nitrobenzene. Initial pH also presents a positive effect in the ozonation alone system while the optimum working initial pH is found to be around 8.83 and 10.67 to the processes of ozonation/ceramic honeycomb and ozonation/Mn–ceramic honeycomb, respectively. The surface characteristics measurement of the two catalysts indicates that the loading of Mn increases the specific surface area, the pH at the point of zero charge (pH_PZC) and the density of surface hydroxyl groups, and results in the appearance of new crystalline phase of MnO₂. The results of mechanism research confirm that the loading of Mn promotes the initiation of OH.     

水处理中的多相催化臭氧化技术

随着水质污染的日益严重,以产生大量自由基为主体的高级氧化技术越来越受到人们的关注。作为高级氧化技术的一种新形式,多相催化臭氧化将臭氧的氧化能力和催化剂的吸附性、催化作用更好地结合起来,对有机物的矿化程度更高。该文综述了该技术在水处理中的应用及其反应机理。     

Mineralization of aniline and 4-chlorophenol in acidic solution by ozonation catalyzed with Fe2+ and UVA light

Solutions with 1.07 mmol dm⁻³ aniline or with 1.38 mmol dm⁻³ 4-chlorophenol at pH ca. 3 have been treated with ozone and ozonation catalyzed with Fe²⁺ and/or UVA. The initial mineralization rate increases as more oxidizing hydroxyl radical is produced in the medium by the catalyzed ozonations. Direct ozone treatment leads to stable oxidation products, which are quickly destroyed under UVA illumination. In the presence of Fe²⁺ as catalyst, the degradation process is inhibited by the formation of Fe³⁺ complexes with short organic diacids, being photodecomposed by UVA light. Each initial pollutant is destroyed at similar rate in all processes. p-Benzoquinone and nitrobenzene are identified as intermediates of aniline oxidation. The former product is only detected when high amounts of hydroxyl radical are produced by the action of Fe²⁺. Ammonium ion released during p-benzoquinone formation is also generated in larger extension under the same conditions. Nitrate ion reaches maximum production under UVA irradiation, indicating that generation of nitrobenzene from selective attack of O₃ on the amino group of aniline is photocatalyzed. Reaction of 4-chlorophenol with ozone leads to 4-chloro-1,3-dihydroxybenzene and 4-chloro-1,2-dihydroxybenzene. The last product is produced in larger extension when high amounts of hydroxyl radical can selectively attack the initial pollutant. Chloride ion is completely lost during the further degradation of both dihydroxylated derivatives. Oxidation of all aromatic intermediates detected during aniline and 4-chlorophenol degradation gives maleic acid, which is further mineralized via oxalic acid. A general reaction pathway for the degradation of each pollutant is proposed.     

纳米TiO_2催化臭氧化降解水中草酸

本实验以钛酸四丁酯为前驱物,乙醇和正己烷作为晶形导向剂,通过水热法合成不同晶形的TiO2催化剂。催化剂的结构特性采用X射线衍射(XRD)来表征。催化剂的催化活性通过对水中草酸晶形催化臭氧化降解来进行评估;通过研究叔丁醇对催化剂臭氧化反应的影响,证明反应遵循羟基自由基(HO·)反应机理。     

催化臭氧化技术在废水处理中的应用

阐述了均相催化臭氧化和非均相催化臭氧化技术在废水处理中的应用研究进展,并提出了技术发展趋势与存在的问题。非均相催化臭氧化技术是现代催化技术与环境化学处理技术的组合,其中催化剂具有活化臭氧、提高臭氧氧化降解能力的作用。该技术具有降解能力强、效率高、不产生二次污染等优点,将在环保领域发挥越来越大的作用。     

Heterogeneous Catalytic Ozonation of Refinery Wastewater over Alumina-Supported Mn and Cu Oxides Catalyst

An economical method was proposed to develop an efficient alumina-supported manganese (Mn) and copper (Cu) oxides (Mn-Cu-O/Al₂O₃) catalyst with a high surface area, 184.06 cm² g^?1. The catalyst was utilized for degradation refinery wastewater by heterogeneous catalytic ozonation. The effects of various operating variables including pH, ozone and catalyst dosages, and temperature were systematically investigated in detail to obtain the optimized conditions for accelerated degradation of refinery wastewater. The optimum values were as follows: ozone dose 50.0 mg L^?1, catalyst dose 3.0 g L^?1, initial pH = 6.8, T = 17 °C. Refinery wastewater samples were analyzed by chemical oxygen demand (COD) and the results indicated that kinetics of COD followed a pseudo–first-order degradation. Moreover, hydroxyl radical mechanism rather than absorption was proposed, indicating that the surface hydroxyl groups were the active sites that played a significant role in catalytic ozonation.     

Interlayer-confined two-dimensional manganese oxide-carbon nanotube catalytic ozonation membrane for efficient water purification

Catalytic ozonation technology has attracted copious attention in water purification owing to its favorable oxidative degradation of pollutants and mitigation of membrane fouling capacity. However, its extensive industrial application has been restricted by the low ozone utilization and limited mass transfer of the short-lived radical species. Interlayer space-confined catalysis has been theoretically proven to be a viable strategy for achieving high catalytic efficiency. Here, a two-dimensional MnO₂-incorporated ceramic membrane with tunable interspacing, which was obtained via the intercalation of a carbon nanotube, was designed as a catalytic ozonation membrane reactor for degrading methylene blue. Benefiting from the abundant catalytic active sites on the surface of two-dimensional MnO₂ as well as the ultralow mass transfer resistance of fluids due to the nanolayer confinement, an excellent mineralization effect, i.e., 1.2 mg O_3(aq) mg^–1 TOC removal (a total organic carbon removal rate of 71.5%), was achieved within a hydraulic retention time of 0.045 s of pollutant degradation. Further, the effects of hydraulic retention time and interlayer spacing on methylene blue removal were investigated. Moreover, the mechanism of the catalytic ozonation employing catalytic ozonation membrane was proposed based on the contribution of the Mn(III/IV) redox pair to electron transfer to generate the reactive oxygen species. This innovative two-dimensional confinement catalytic ozonation membrane could act as a nanoreactor and separator to efficiently oxidize organic pollutants and enhance the control of membrane fouling during water purification.     

Catalytic Ozonation of Gasoline Compounds in Model and Natural Water in the Presence of Perfluorinated Alumina Bonded Phases

Gasoline compounds are one of the most widespread causes of soil and groundwater contamination. Their degradation in model and natural waters due to catalytic ozonation in the presence of perfluorooctylalumina (PFOA) is presented and discussed in this paper. The results obtained clearly indicate that the PFOA/O₃ system is effective mainly for ether (MTBE and ETBE) removal from both model and natural water. The catalytic activity of PFOA is not so significant in the case of BTEX ozonation. An investigation into by-product formation has shown that the concentration of both carboxylic acids (mainly oxalic acid) and carbonyl compounds (mainly acetone) increases after catalytic ozonation when compared with ozonation alone. A decrease of formic acid and formaldehyde takes place after the PFOA/O₃ system as opposed to the usage of ozonation alone.     

掺杂多孔碳材料催化硝基苯还原反应的研究进展

苯胺是重要的化工原料和合成中间体,通过硝基苯的催化还原反应可以方便地制备苯胺类化合物。多孔碳材料因其高比表面积、发达的孔隙结构和容易回收等特点在催化领域越来越受到重视,然而其应用受到自身活性位点缺乏和化学惰性的限制。杂原子掺杂可以增强碳材料的表面极性,调节电子结构,改善其催化性能,可作为硝基苯催化还原反应的有效催化剂。本文对近年来掺杂多孔碳材料在硝基苯催化还原反应中的研究进展进行了总结。本文概述了氮掺杂型多孔碳材料、共掺杂型多孔碳材料、负载贵金属的掺杂多孔碳材料和负载廉价金属的掺杂多孔碳材料这4种主要的掺杂多孔碳材料的制备方法,并详细介绍了不同掺杂多孔碳材料在催化硝基苯催化还原反应时的催化性能、可能的催化活性位点以及催化机理。最后,指出目前掺杂多孔碳材料催化硝基苯还原还需要解决反应选择性、催化剂催化活性和生产成本等问题,以生物质为前体,开发共掺杂型和二元双金属负载的掺杂多孔碳材料是未来的重要发展方向之一。     

Catalytic decomposition of ozone and para-Chlorobenzoic acid (pCBA) in the presence of nanosized ZnO

This research forwards the evaluating of the efficiency of nanosized ZnO in the application of the catalytic ozonation, determines the reaction kinetics of ozone with the nanosized ZnO, and delineates the characteristics of the decomposition of para-Chlorobenzoic acid (pCBA) and ozone in catalytic ozonation using the nanosized ZnO particles. It was found that the nanosized ZnO enhanced the degradation of ozone and the catalytic ozonation on the surface of the nanosized ZnO significantly enhanced the degradation of pCBA. In catalytic reactions the degradation of pCBA followed two-stage kinetics, initial rapid removal phase (Phase I) and a slower decomposition phase (Phase II). The total degradation rate of pCBA was well matched with the initial removal of pCBA in Phase I. The R_ct values representing the ratio of hydroxyl radicals [OH] and ozone [O₃] were found to increase with an increased concentration of the nanosized ZnO indicating the enhanced transformation of ozone into OH.     

改性活性炭强化催化臭氧氧化降解草酸

对工业活性炭进行酸预处理、硝基化和氨基化表面改性,并在半连续反应器中研究其催化臭氧氧化降解草酸的活性. 结果表明,酸预处理的活性炭比表面积、等电点pH值(pHpzc)和碱性官能团含量提高了5%~10%,但催化降解草酸效率降低15.6%,氨基化活性炭的pHpzc和碱性官能团含量分别由2.6和234.8 mmol/g升至7.0和764.5 mmol/g,而硝基化活性炭的pHpzc和表面碱性官能团含量均降低. 在中性和酸性溶液中,两种改性活性炭降解草酸的活性均高于预处理活性炭. 在pH=7的溶液中,氨基化活性炭在45 min内催化降解草酸降解率为42.4%. 加入叔丁醇会抑制活性炭催化降解草酸,活性炭催化臭氧氧化草酸主要是羟基自由基起作用.     

Degradation and Transformation of Organic Compounds in Songhua River Water by Catalytic Ozonation in the Presence of TiO2/Zeolite

This paper presents experimental results of the catalytic ozonation of Songhua River water in the presence of nano-TiO₂ supported on Zeolite. The removal efficiency of TOC and UV₂₅₄, the variation of AOC and molecular weight distribution of organics was studied. Results showed that TOC and UV₂₅₄ removal efficiency by ozone was improved in the presence of TiO₂/Zeolite, and increased by 20% and 25%, respectively. The part of organic compounds less than 1000 Da increased in ozonation, but decreased in catalytic ozonation. The AOC of water increased in catalytic ozonation, and the increase of AOC was particularly obvious when ozone dose increased from 28.8 mg·L^?1 to 46.6 mg·L^?1. The degradation and transformation of organic compounds was analyzed by means of GC-MS. The total number of organic compounds was reduced from 50 in the untreated water to 36 and 20, respectively, in ozonation and catalytic ozonation. The removal efficiency of the total organic compounds peak area in ozonation and catalytic ozonation were 23.5% and 62.5%, respectively. Most of the hydrocarbons could be removed easily in ozonation and catalytic ozonation. The organic compounds having hydroxyl, carboxyl or carbonyl groups were hard to be removed in ozonation, but could be removed efficiently in the presence of TiO₂/Zeolite.     

BRUCITE MAGNESIA *

A discussion of the occurrence of brucite in limestone, the method of extracting it in the form of magnesia, and uses for which this particular type of magnesia is best suited is presented with emphasis on the possibilities of brucite magnesia in the ceramic industry.     

Adsorption of reaction species for hydrogenation of nitrobenzene on copper chromite at catalytic conditions

Adsorption of nitrobenzene, aniline and water on copper chromite has been investigated at the temperatures (483–558 K) and partial pressures (0–40 kPa) involved in the catalytic process (viz. hydrogenation of nitrobenzene), using the gas chromatographic pulse technique. The adsorption of reaction species was found to follow the Freundlich adsorption isotherm. The data on isosteric heats of adsorption (at different surface coverages) were obtained from the adsorption isotherms. The results indicated that nitrobenzene and water are physically adsorbed, whereas aniline is chemisorbed on the catalyst. The variation in the heat of adsorption with surface coverage for the adsorption of aniline indicated the presence of surface heterogeneity on the copper chromite.     

负载稀土氧化物的Y沸石材料催化臭氧化降解水中苯酚

催化臭氧化是降解水中有机污染物的有效途径。为了开发高效稳定的臭氧化催化剂,文章研究了负载稀土的Y型沸石材料。结果表明,负载稀土氧化物的Y沸石具有高的比表面积和表面羟基密度,从而显示了优越的催化臭氧化性能。该沸石材料在5～35℃的室温范围内都体现了较好的催化性能,并且显示了较好的重复使用性能,具有良好的实际应用前景。