活性碳纤维耦合喹啉铁的pH-tolerant性能研究

pH值适应范围窄一直是制约芬顿反应发展的技术瓶颈,因此,开发pH-tolerant类芬顿催化剂成为环境催化领域的研究热点和难点。采用活性碳纤维(ACFs)耦合喹啉铁(QuFe)制得一种新型pH-tolerant类芬顿催化纤维(QuFe@ACFs),该催化纤维在中性条件下可以活化双氧水有效降解活性艳红M-3BE。采用自由基捕获剂邻苯二胺,结合电子顺磁共振波谱、紫外-可见光谱等对催化纤维的重复稳定性进行了重点考察。结果显示,QuFe@ACFs在pH值为3~9范围内均具有良好的催化性能和重复使用性,表现出了优异的pH-tolerant性能。QuFe@ACFs制备方法简单,巧妙解决了制约传统芬顿反应发展的技术瓶颈,为制备新一代高活性pH-tolerant芬顿催化剂提供了新思路。     

钛网表面Fe3O4/FeS2膜层制备及其类芬顿降解苯酚研究

为了拓宽类芬顿催化剂的pH适用范围、改善其有机污染物降解性能并解决其分离回收难的问题,本文采用易于大规模制备的电沉积法在钛网表面沉积了Fe3O4/FeS2固定化膜层.通过XRD、SEM及XPS等表征手段研究了所合成催化剂的相组成、形貌及表面元素价态.结果 显示,所合成的材料主要由Fe3 O4与FeS2物相组成,且膜层表面呈现由纳米片间相互交联形成的多孔网状结构.类芬顿降解苯酚性能表明,在0.20 mol/L硫源含量下所得膜层于pH 6.0、H2 O2含量6 mmol/L、苯酚初始质量浓度35 mg/L、反应温度30℃的条件下降解60 min,可将98％的苯酚去除.因而,Fe3O4/FeS2固定化膜层催化剂表现出优异的类芬顿催化活性.分析发现:材料较大的比表面积可增强传质,同时提供更多的活性位点参与苯酚降解;而催化剂表面键合的S22-可促进≡Fe3+/≡Fe2+以及Fe3 +/Fe2的氧化还原循环,同时,以硫酸根形式存在的硫物种可为类芬顿反应提供合适的酸性微环境,从而提高羟基自由基的产生速率及产生量,最终显著改善该催化剂在近中性条件下的催化活性.     

Fe(III)/rGO/Bi2MoO6复合光催化剂制备及光催化芬顿协同降解苯酚

光催化-芬顿技术耦合可高效降解有机污染物。本研究采用溶剂热法制备了Fe(III)掺杂rGO/Bi₂MoO₆复合催化剂(Fe(III)/rGO/Bi₂MoO₆), 通过外加H₂O₂构建了光催化-芬顿协同体系, 可见光照射3 h后对苯酚的降解率(82%)远高于单独光催化(18%)或芬顿反应(48%), 进一步优化条件对苯酚可实现完全降解。这主要是通过Fe得失电子实现价态的转变, 并以此作为桥梁实现光催化-芬顿的协同作用。同时石墨烯的优异导电性能不仅克服了光催化中光生电子空穴难以分离的问题, 而且促进了Fe³⁺/Fe²⁺的循环反应, 促使芬顿反应产生更多的羟基自由基(?OH), 进一步提高了苯酚的降解效率。实验考察了Fe(III)含量、催化剂投加量、H₂O₂含量以及pH等因素对协同降解效果的影响。淬灭实验证明?OH是协同降解体系中最主要的活性物种, ?O₂^-和h⁺对降解活性也会产生一定的影响, 结合实验结果提出了Fe(III)/rGO/Bi₂MoO₆光催化-芬顿协同降解苯酚的机理。     

pH值对氮掺杂TiO2物化性质和光催化活性的影响

以TiCl4为前驱体,水合肼和氨水的混合溶液为氮源,采用共沉淀法制备了可见光响应型氮掺杂二氧化钛(N-TiO2)光催化剂,重点研究了制备过程中pH值对催化剂的微结构和光催化活性等物化性质的影响.采用XRD、BET、UV-vis和XPS等表征方法对光催化剂性质进行了表征.催化剂主要以锐钛矿相存在,具有介孔结构和较高的比表面积(～90m2/g).随着pH值增大,锐钛矿相(101)面衍射峰逐步增强,晶粒尺寸逐渐增大,比表面积逐渐减小.XPS结果表明催化剂掺杂的氮主要以系列氮氧化物形式存在.氮掺杂小幅降低了禁带宽度,感光范围拓展到可见光区.光催化降解实验表明,pH=3.5时,催化剂的可见光降解效率最高,为39.65%.随着pH值增大,催化剂可见光催化活性逐渐降低;而在紫外光照射下,pH=9.5时,催化活性最低;pH=5.5时,催化活性最高.     

Fe(Ⅲ)/rGO/Bi_2MoO_6复合光催化剂制备及光催化芬顿协同降解苯酚

光催化–芬顿技术耦合可高效降解有机污染物。本研究采用溶剂热法制备了Fe(Ⅲ)掺杂rGO/Bi_2Mo O_6复合催化剂(Fe(Ⅲ)/rGO/Bi_2Mo O_6),通过外加H_2O_2构建了光催化–芬顿协同体系,可见光照射3 h后对苯酚的降解率(82%)远高于单独光催化(18%)或芬顿反应(48%),进一步优化条件对苯酚可实现完全降解。这主要是通过Fe得失电子实现价态的转变,并以此作为桥梁实现光催化–芬顿的协同作用。同时石墨烯的优异导电性能不仅克服了光催化中光生电子空穴难以分离的问题,而且促进了Fe~(3+)/Fe~(2+)的循环反应,促使芬顿反应产生更多的羟基自由基(·OH),进一步提高了苯酚的降解效率。实验考察了Fe(Ⅲ)含量、催化剂投加量、H_2O_2含量以及p H等因素对协同降解效果的影响。淬灭实验证明·OH是协同降解体系中最主要的活性物种,·O_2~–和h~+对降解活性也会产生一定的影响,结合实验结果提出了Fe(Ⅲ)/rGO/Bi_2Mo O_6光催化–芬顿协同降解苯酚的机理。     

多孔炭:一种在电芬顿与类芬顿反应中受青睐的材料

类芬顿反应,因其能够克服传统芬顿反应工作pH范围较窄,易产生大量铁泥的局限而受到了大量关注。尽管炭材料在无驱动力时,同过氧化氢的反应活性不佳,多孔炭材料在类芬顿反应中依然得到了广泛应用。在各种研究中,这些多孔炭材料扮演了多种不同角色,诸如吸附剂、金属材料载体、以及过氧化氢选择性电合成的催化剂。本综述中,讨论了近年里多孔材料在上述情况的研究进展。由于成熟的合成工艺,很高的化学及热稳定性以及多样的功能,多孔炭材料已成为一种应用广泛的材料。在类芬顿过程中,更是有助于电子与物质的转移,防止金属泄露,并较大地提升了反应效率。     

4A分子筛固载PEG络合铂催化苯乙烯硅氢加成反应

研究了4A分子筛固载聚乙二醇络合铂催化剂的制备及其催化苯乙烯与甲基二氯硅烷硅氢加成反应的反应规律,常压下该催化剂对连续式多相硅氢加成反应有着很高的催化活性和稳定性,在反应温度为90℃、投料速率为6.7mL.h-1、催化剂铂含量为5.87×10-3mmol.g-1的条件下甲基二氯硅烷单程转化率可达94.8%,β-加成产物选择性100%。并且考察了温度、催化剂铂含量和投料速率等参数对硅氢加成反应的影响。     

静电纺丝纳米纤维催化剂在环境治理中的应用进展

静电纺丝纳米纤维催化剂具有较高的催化活性且易回收再利用,已广泛地应用于环境治污,具有一定的应用前景。简述静电纺丝纳米纤维催化剂的制备方法,分析了纤维膜孔径大小、纤维立体结构等纤维形貌结构对纳米纤维催化剂催化性能的影响,详细论述了纳米纤维催化剂在光催化降解、电催化降解以及类Fenton反应催化降解等环境治污领域的应用研究进展。     

过渡金属氧化物非均相催化过硫酸氢盐(PMS)活化及氧化降解水中污染物的研究进展

近年来,水体中富集的难降解污染物导致了诸多环境问题,传统水处理工艺并不能对其进行有效处理。高级氧化技术是目前处理难降解污染物的最有效方法。过渡金属氧化物非均相催化过硫酸氢盐(PMS)活化生成硫酸根自由基(SO_4~-·)处理水体中难降解污染物是近些年新兴的高级氧化技术,与以生成羟基自由基(·OH)为基础的传统高级氧化技术相比,该技术具有对pH适应范围更宽、中性条件下氧化性更强、自由基半衰期更长的优势,同时也克服了均相催化体系中金属离子的二次污染、难以重复利用的问题,受到环境领域学者的广泛关注,为去除水体中抗生素、激素等难降解污染物提供了新的思路和方法。然而,由于活性点位的减少,相较于均相催化,非均相催化的催化效率更低,同时也存在催化稳定性差、难以回收等不足。针对上述问题,近几年除了探寻对PMS的活化具有催化活性的新型过渡金属氧化物外,研究者主要从催化材料的负载、改性以及复合三方面进行尝试,并取得了丰富的研究成果,在发挥非均相催化经济、环保优势的同时,大幅提高了催化剂的催化效率及可回收性,为其步入实际应用做出了巨大的贡献。在众多过渡金属元素中,钴、铁、锰的氧化物已被证明对PMS的活化具有催化活性并得到了广泛的研究。其中,由于钴离子对PMS表现出最强的活化能力,因此对钴系氧化物研究得最早。随后,铁及锰的氧化物因环境友好、廉价易得的优势逐渐成为钴氧化物的替代品。近五年的研究工作将纳米碳、介孔材料以及金属-有机框架等引入催化剂的制备合成中,对过渡金属氧化物进行负载和改性,加强了催化材料的电子传递速度和化学稳定性,为解决催化剂的催化效率低与催化稳定性差等问题提供了有效方法。此外,以两种过渡金属元素为催化核心的二元复合材料,在降低催化剂制作成本的同时,还可以实现催化剂效能和稳定性的双重提高。文章介绍了钴系氧化物、锰系氧化物、铁系氧化物等三种能够催化PMS活化的一元非均相催化剂的研究进展,并阐述了二元复合催化剂的研究现状,总结了现阶段研究的不足并对未来的发展方向做出了展望,以期为制备经济高效的过渡金属氧化物催化剂提供参考。     

生物质基碳材料的制备及其在电芬顿降解体系中的应用

偶氮类染料因其色度高、毒性大的特点,借助传统处理方法很难对其进行有效降解。高级氧化技术中的阴极电芬顿法利用H_2O_2和Fe~(2+)生成氧化能力较强的羟基自由基(·OH),从而实现水体中偶氮染料的高效降解。该研究选取生活中常见且蛋白质含量较高的韭苔为前驱体,以KHCO_3为活化剂,高温热解制备生物质基碳电极材料(CS-R),并成功应用于电芬顿法降解甲基红(MR)体系。经过对所制备得到的系列样品进行优化筛选,CS-3表现出良好的氧还原性能,其作为阴极电催化剂对MR染料的降解效率在60min时达到了99%。研究结果表明,高的比表面积、氮含量、石墨化程度和超亲水性对于生物质基碳材料的电芬顿降解性能至关重要,这为电芬顿体系阴极材料的选择、制备提供了技术指导。     

Decolorization of KN-R catalyzed by Fe-containing Y and ZSM-5 zeolites

Decolorization of an anthraquinone dye, Reactive Brilliant Blue KN-R by hydrogen peroxide was examined using Fe-containing Y and ZSM-5 zeolites as heterogeneous catalysts. Catalysts were prepared by ion-exchange and coprecipitation methods, and calcined at different temperatures. The surface morphologies, crystalline phases, and chemical-state of the catalysts were characterized by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Influences of reaction conditions, such as dye concentration, catalyst dosage and solution pH, were evaluated and the relations between catalytic capacity and surface microstructures were discussed. The results showed that Fe-containing Y and ZSM-5 zeolites generally exhibited similar or better catalytic efficiency compared with homogeneous Fenton reagent, with Fe-containing ZSM-5 being more efficient. Synthesis method and calcination temperature affected catalytic efficiency and the stability of catalysts. Fe-containing ZSM-5, which was prepared by coprecipitation and calcined at 450 degrees C, displayed the greatest decolorization capacity. Under the conditions of initial pH 2.5, 30.0 mmol/L H(2)O(2) and 4.0 g/L catalyst, 250 mg/L KN-R could be decolorized over 90% within 20 min.     

Design of a neutral electro-Fenton system with Fe@Fe(2)O(3)/ACF composite cathode for wastewater treatment

The narrow pH range limits the wide application of Fenton reaction in the wastewater treatment. It is of great importance to widen working pH range of Fenton reaction from strong acidic condition to neutral, even basic ones. In this study, for the first time nanostructured Fe@Fe(2)O(3) was loaded on active carbon fiber (ACF) as an oxygen diffusion cathode to be used in a heterogeneous electro-Fenton (E-Fenton) oxidation system. This novel Fe@Fe(2)O(3)/ACF composite cathode was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), and element mapping. On the degradation of dye pollutant rhodamine B in water, this heterogeneous E-Fenton system with the Fe@Fe(2)O(3)/ACF cathode showed much higher activity than other E-Fenton systems with commercial zero valent iron powders (Fe(0)) and ferrous ions (Fe(2+)) under neutral pH. On the basis of experimental results, we proposed a possible pathway of rhodamine B degradation in this heterogeneous Fe@Fe(2)O(3)/ACF E-Fenton process. This heterogeneous E-Fenton system is very promising to remove organic pollutants in water at neutral pH.     

Porous Carbon‐Hosted Atomically Dispersed Iron–Nitrogen Moiety as Enhanced Electrocatalysts for Oxygen Reduction Reaction in a Wide Range of pH

As one of the alternatives to replace precious metal catalysts, transition‐metal–nitrogen–carbon (M–N–C) electrocatalysts have attracted great research interest due to their low cost and good catalytic activities. Despite nanostructured M–N–C catalysts can achieve good electrochemical performances, they are vulnerable to aggregation and insufficient catalytic sites upon continuous catalytic reaction. In this work, metal–organic frameworks derived porous single‐atom electrocatalysts (SAEs) were successfully prepared by simple pyrolysis procedure without any further posttreatment. Combining the X‐ray absorption near‐edge spectroscopy and electrochemical measurements, the SAEs have been identified with superior oxygen reduction reaction (ORR) activity and stability compared with Pt/C catalysts in alkaline condition. More impressively, the SAEs also show excellent ORR electrocatalytic performance in both acid and neutral media. This study of nonprecious catalysts provides new insights on nanoengineering catalytically active sites and porous structures for nonprecious metal ORR catalysis in a wide range of pH.     

Copper-iron bimetal modified PAN fiber complexes as novel heterogeneous Fenton catalysts for degradation of organic dye under visible light irradiation

A series of Cu-Fe bimetal amidoximated polyacrylonitrile (PAN) fiber complexes with different molar ratios of Cu(2+) to Fe(3+) ions was prepared using a simple exhaustion method, and characterized using FTIR, DRS and XPS, respectively. Then they were tested as the heterogeneous Fenton catalysts for Rhodamine B degradation with H(2)O(2) in the dark and under visible light irradiation. The results indicated that Cu-Fe bimetal amidoximated PAN fiber complexes could more effectively catalyze the dye degradation in water than Fe amidoximated PAN fiber complex, especially in the dark. And introduction of Cu(2+) ions significantly increased their catalytic performance. 0.56 was the optimum molar ratio of Cu(2+) to Fe(3+) ions to achieve the best catalytic activity and stability. This was mainly due to the synergetic effect in the bimetal complexes. Visible light irradiation improved the catalytic activity of the complexes, especially with a low molar ratio of Cu(2+) to Fe(3+) ions.     

Supported catalysts for heterogeneous electro-Fenton processes: Recent trends and future directions

Extremely low pH requirement and additional sludge management for the homogeneous electro-Fenton (EF) process necessitated the development of heterogeneous electro-Fenton (HEF) reactions that utilize solid catalysts that can be recovered and reused. In the recent decades, supported catalysts have immensely attracted researchers owing to the outstanding physical, chemical, and electronic properties of the supports that benefit the EF process by enhancing the removal efficiency, reducing reaction time, and extending the operational pH range. This review enlightens the readers about various materials that have been used for supporting the catalysts, their importance, method of impregnation, and optimum conditions required to attain maximum pollutant removal. From the wide array of catalysts reviewed, porous supports with a high surface area such as activated carbon, biochar and fibres adsorbs the pollutants near their surface facilitating enhanced Fenton reactions and degradation of pollutants. Alginate-based catalysts can be prepared by a simple procedure and exhibit good degradation efficiency when used in batch and continuous EF reactors. Zeolite-based catalysts are structurally stable and display promising results for successive cycles. The flexible and conductive nature of fibre-based supports performs the dual role as a catalyst and cathode. The highly stable and conductive properties of graphene and carbon nanotubes promote electron transfer, much required for continuous EF reactions.     

Robust Catalysis on 2D Materials Encapsulating Metals: Concept,Application, and Perspective

Great endeavors are undertaken to search for low‐cost, rich‐reserve, and highly efficient alternatives to replace precious‐metal catalysts, in order to cut costs and improve the efficiency of catalysts in industry. However, one major problem in metal catalysts, especially nonprecious‐metal catalysts, is their poor stability in real catalytic processes. Recently, a novel and promising strategy to construct 2D materials encapsulating nonprecious‐metal catalysts has exhibited inimitable advantages toward catalysis, especially under harsh conditions (e.g., strong acidity or alkalinity, high temperature, and high overpotential). The concept, which originates from unique electron penetration through the 2D crystal layer from the encapsulated metals to promote a catalytic reaction on the outermost surface of the 2D crystal, has been widely applied in a variety of reactions under harsh conditions. It has been vividly described as “chainmail for catalyst.” Herein, recent progress concerning this chainmail catalyst is reviewed, particularly focusing on the structural design and control with the associated electronic properties of such heterostructure catalysts, and also on their extensive applications in fuel cells, water splitting, CO₂ conversion, solar cells, metal–air batteries, and heterogeneous catalysis. In addition, the current challenges that are faced in fundamental research and industrial application, and future opportunities for these fantastic catalytic materials are discussed.     

锰基催化剂低温选择催化还原处理NOx的研究现状与展望

锰基催化剂具有较高的催化活性,且成本低,在选择性催化还原(SCR)尾气中的NO_x领域具有广阔应用前景。介绍了锰基低温SCR催化剂处理NO_x的最新进展。锰基催化剂可分为两类:锰氧化物催化剂和锰基掺杂过渡金属氧化物催化剂。针对锰氧化物催化剂,主要分析了锰的氧化价态、结晶形态、比表面积以及形态学对催化效果的影响;对于锰基掺杂过渡金属氧化物催化剂,重点分析了掺杂物对催化剂的催化能力、催化温度范围、N_2的选择性和抗SO_2、H_2O毒化能力的影响。最后在总结全文的基础上,展望了锰基催化剂的应用前景。     

Synergistic effect of visible-light-driven FeOOH@Bi2MoO6 for removal of ciprofloxacin over a wide pH range: Efficient separation of photogenerated carriers and fast Fe(III)/Fe(II) cycling

Fabrication of FeOOH@Bi₂MoO₆ composites was successfully carried out by the solvent thermal-impregnation method, and they were used as effective visible light-driven photo-Fenton catalysts. The catalyst can achieve effective degradation of CIP in the pH range of 3.5–10.5, which overcomes the problems of harsh pH application conditions and low H₂O₂ utilization in Fenton. Notably, FeOOH@Bi₂MoO₆ exhibited stronger photo-Fenton catalytic activity compared with pure FeOOH, pure Bi₂MoO₆ and their simple physical mixtures, indicating that the interfacial active sites of FeOOH and Bi₂MoO₆ are favorable for the rapid transfer of photogenerated electrons from Bi₂MoO₆ to FeOOH. Combined with the characterization analysis and performance experiments, the catalytic mechanism of the FeOOH@Bi₂MoO₆-H₂O₂ system is reasonably proposed. The photocatalytic-Fenton synergy facilitates the rapid separation of photogenerated carriers and the valence cycling of Fe(III)/Fe(II), which drives the reaction system to produce a large amount of OH, O₂^? and a small amount of h⁺ to participate in the degradation process of CIP. In this study, the preparation of composite catalysts and the coupled use of photocatalytic-Fenton provided a feasible idea to overcome the problems of narrow pH application and low H₂O₂ utilization in Fenton.     

Synthesis and characterization of supported polysugar-stabilized palladium nanoparticle catalysts for enhanced hydrodechlorination of trichloroethylene

Palladium (Pd) nanoparticle catalysts were successfully synthesized within an aqueous phase using sodium carboxymethyl cellulose (CMC) as a capping ligand which offers a green alternative to conventional nanoparticle synthesis techniques. The CMC-stabilized Pd nanoparticles were subsequently dispersed within support materials using the incipient wetness impregnation technique for utilization in heterogeneous catalyst systems. The unsupported and supported (both calcined and uncalcined) Pd nanoparticle catalysts were characterized using transmission electron microscopy, energy dispersive x-ray spectrometry, x-ray diffraction, and Brunauer-Emmett-Teller surface area measurement and their catalytic activity toward the hydrodechlorination of trichloroethylene (TCE) in aqueous media was examined using homogeneous and heterogeneous catalyst systems, respectively. The unsupported Pd nanoparticles showed considerable activity toward the degradation of TCE, as demonstrated by the reaction kinetics. Although the supported Pd nanoparticle catalysts had a lower catalytic activity than the unsupported particles that were homogeneously dispersed in the aqueous solutions, the supported catalysts retained sufficient activity toward the degradation of TCE. In addition, the use of the hydrophilic Al(2)O(3) support material induced a mass transfer resistance to TCE that affected the initial hydrodechlorination rate. This paper demonstrates that supported Pd catalysts can be applied to the heterogeneous catalytic hydrodechlorination of TCE.     

磁性纳米CeO2/Fe3O4非均相Fenton反应催化降解氧氟沙星

为了提高Fe₃O₄的催化活性, 制备了磁性CeO₂/Fe₃O₄复合纳米粒子, 构成非均相Fenton反应体系, 催化降解水环境中的氧氟沙星抗生素。研究了CeO₂含量、H₂O₂浓度、pH等因素对CeO₂/Fe₃O₄非均相催化活性的影响, 并通过溶出铁离子测定、动力学拟合等方式对反应机理进行探究。结果表明, CeO₂/Fe₃O₄较Fe₃O₄具有更强的催化活性, 氧氟沙星的降解率随CeO₂含量、H₂O₂浓度和溶液酸度的增加而提高, 当H₂O₂浓度为100 mmol/L 以及pH为3时, CeO₂/Fe₃O₄(摩尔比=0.780)-H₂O₂体系催化降解氧氟沙星的效果最佳。CeO₂/Fe₃O₄体系催化降解氧氟沙星反应遵循一级反应动力学方程, 反应机理主要为催化剂表面的催化反应, 同时CeO₂产生氧空位的电子转移对Fe₃O₄的催化反应起到协同强化的作用。