亚微米级Cu0/Fe3O4复合物多相催化过一硫酸盐降解有机污染物

过一硫酸盐催化活化技术因其可产生强氧化性活性氧化物种,可快速氧化降解并矿化有机污染物的优异性能而备受关注.本文成功制备了亚微米级Cu0/Fe3O4复合物,发现其能多相催化过一硫酸盐产生单线态氧降解有机污染物.首先,以CuCl2·2H2O,FeCl2·4H2O和FeCl3·6H2O为铜源和铁源,水合肼为还原剂,采用水热法在180oC反应24 h制备了亚微米级磁性Cu0/Fe3O4复合物.表征结果显示,所制材料为Cu0和Fe3O4的复合物,颗粒大小约为220 nm;单一相Cu0和Fe3O4晶体粒径分别为33.8和106.2 nm,而Cu0/Fe3O4复合物中Cu0和Fe3O4晶体粒径分别减为20.8和31.9 nm.这表明Cu0和Fe3O4复合降低了Cu0和Fe3O4晶体粒径,有利于Cu0和Fe3O4的分散.BET测试结果表明,Cu0/Fe3O4复合物比表面积为4.6 m2/g,与Cu0颗粒的(4.2 m2/g)相当,但远小于Fe3O4的(15.6 m2/g).制备的Cu0/Fe3O4复合物可有效催化过一硫酸盐产生单线态氧降解罗丹明B、亚甲基蓝、金橙II、苯酚和对氯酚.当Cu0/Fe3O4复合物的用量为0.1 g/L,过一硫酸盐浓度为0.5 mmol/L和初始pH为7时,Cu0/Fe3O4复合物可在30 min内完全降解20μmol/L的罗丹明B、亚甲基蓝、金橙II以及0.1 mmol/L的苯酚和对氯酚.对比试验显示,在相同条件下,Cu0和Fe3O4颗粒分别可以降解28%和20%的罗丹明B.这表明Cu0/Fe3O4复合物中的Cu0和Fe3O4晶体在催化过一硫酸盐降解污染物的反应中具有协同作用,这主要来源于Cu0/Fe3O4复合物中Cu0和Fe3O4的晶体粒径变小和更好的分散.采用分光光度法测定了降解反应液中铜和铁离子的溶出量.当Cu0/Fe3O4复合物的用量为0.1 g/L,过一硫酸盐浓度为0.5 mmol/L和初始pH为7时,反应60 min后,降解液中铜和铁离子的浓度分别为0.22和0.1 mg/L,仅占复合物中总铜和总铁量的1.1%和0.2%,表明Cu0/Fe3O4复合物具有较强的化学稳定性.所制Cu0/Fe3O4复合物具有超顺磁性,借助磁场实现快速分离回收,可循环利用五次,表明其优越的催化稳定性.通过加入乙醇和叠氮化钠,考察了Cu0/Fe3O4复合物催化活化过一硫酸盐体系中的活性氧化物种.发现100 mmol/L乙醇的加入对污染物的降解无明显影响,而加入同等量的叠氮化钠可完全抑制污染物的降解,表明Cu0/Fe3O4复合物催化活化过一硫酸盐产生的主要活性氧物种为单线态氧.采用电子顺磁共振谱进一步证实了单线态氧的生成.基于以上研究,Cu0/Fe3O4复合物催化活化过一硫酸盐的机理为Cu0/Fe3O4作为一个电子媒介加速过一硫酸盐和污染物之间的电子转移,从而导致污染物被快速降解.该反应机理不同于常见的金属催化过一硫酸盐产生硫酸根和羟自由基的反应机理.我们推测,电导性优良的Cu0在此催化反应中起着关键性作用.本催化方法可作为一种绿色的氧化技术用于环境污染物的氧化降解处理.     

Improving the catalytic activity of magnetic Fe3O4/ZnO-CdO/reduced graphene oxide for ultrasonic degradation of the organic pollutants and the green oxidation of olefins

Magnetic Fe₃O₄/ZnO-CdO/reduced graphene oxide (MFZC/RGO) has been synthesized by simple hydrothermal method. The structure and morphology were investigated by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), Diffuse reflectance spectroscopy (DRS), Vibrating sample magnetometer (VSM), Raman and Fourier-transform infrared spectroscopy (FTIR). MFZC/RGO was applied as catalyst in degradation of methylene blue (MB), rhodamin B (RhB) and methylorange (MO) under ultrasonic irradiation. Based on the results, excellent degradation efficiencies of MB, RhB and MO (>99%) were achieved within 10, 20 and 20 min, respectively under oxygen flow. Moreover the catalytic property of MFZC/RGO was investigated in oxidation of styrene, α-methyl styrene, cyclohexene and cyclooctene under oxygen flow. In addition, MFZC/RGO can be easily collected and separated by an external magnet. The catalyst displayed negligible loss in activity and selectivity within several successive runs due to super paramagnetism.     

Study of the solid solution of MoO3 in Fe2V4O13

Differential thermal and phase X-ray analyses have shown that MoO₃ and Fe₂V₄O₁₃ form a solid substitution solution, in which Mo⁶⁺ ions are incorporate into the crystal lattice of Fe₂V₄O₁₃ in place of V⁵⁺ ions. The solubility limit of MoO₃ in Fe₂V₄O₁₃ at ambient temperature is 18 mole % of MoO₃. The phase equilibria in the system Fe₂V₄O₁₃-FeVMoO₇, were also studied. Results are presented in the form of a phase diagram.

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Zusammenfassung Durch DTA und Röntgenphasenanalyse wurde gezeigt, daß MoO₃ und Fe₂V₄O₁₃ Substitutionsmischkristalle bilden, in denen Mo⁶⁺-Ionen anstelle von V⁵⁺-Ionen in das Kristallgitter von Fe₂V₄O₁₃ eingebaut sind. Die Löslichkeitsgrenze von MoO₃ in Fe₂V₄O₁₃ beträgt bei Umgebungstemperatur 18 Mol-% MoO₃. Ebenfalls wurden die Phasengleichgewichte im System Fe₂V₄O₁₃-FeVMoO₇ untersucht. Die Ergebnisse sind in Form eines Phasendiagramms dargestellt.

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- , ₃ Fe₂V₄O₁₃ , o⁶⁺ V^5– Fe₂V₄O₁₃. ₃ Fe₂V₄O₁₃ 18 %. Fe₂V₄O₁₃-FeVMoO₇ .

     

Constructing magnetic Fe3O4‐Au@CeO2 hybrid nanofibers for selective catalytic degradation of organic dyes

Au nanoparticles (Au NPs) play a vital role in heterogeneous catalytic reactions. However, pristine Au NPs usually suffer from poor selectivity and difficult recyclability. In this work, Fe₃O₄‐Au@CeO₂ hybrid nanofibers were prepared via a simple one‐pot redox reaction between HAuCl₄ and Ce (NO₃)₃ in the presence of Fe₃O₄ nanofibers. CeO₂ shell was uniformly coated on the surface of Fe₃O₄ nanofibers to form a unique core‐shell structure, while Au NPs were encapsulated inside the CeO₂ shell. The as‐prepared Fe₃O₄‐Au@CeO₂ hybrid nanofibers have been proved to be positively surface charged due to the formation of CeO₂ shell, enabling them to be good candidates for predominant selective catalytic activity towards the degradation of negatively charged organic dyes. In addition, the Fe₃O₄‐Au@CeO₂ hybrid nanofibers showed magnetic properties, offering them excellent recyclable usability. This work presents a facile and effective solution to prepare magnetic noble metal/metal oxide hybrid nanomaterials with unique chemical structure and surface characteristic for promising applications in heterogeneous catalysis.     

Compared catalytic properties of OMS-2-based nanocomposites for the degradation of organic pollutants

In this study,Mn catalysts have been designed based on manganese oxide octahedral molecular sieve(OMS-2) supports to optimize the catalytic activity in the degradation of organic pollutants.Herein,two different synthetic strategies:Pre-incorporation vs.wet-impregnation have been employed to synthesize[PW]-OMS-2 and [PW]/OMS-2.For [PW]-OMS-2,energy dispersive X-ray spectroscopy(EDX) confirmed that dispersed granular phosphotungstic acid attached and located at the surface of OMS-2,meanwhile some W atoms have been doped into frameworks of OMS-2.However,for [PW]/OMS-2,the W atoms cannot enter the OMS-2 frameworks.A correlation has been established between the different synthetic strategies and catalytic activities.The [PW]-OMS-2 is the most highly effective and stable over than[PW]/OMS-2 and OMS-2 itself for the organic pollutants removal.This may be caused not only by the synergetic effect of [PW] and OMS-2,but also by doping W into frameworks of OMS-2.Therefore,this work provides a new environmentally-friendly and heterogeneous PMS activator and it may be put into practice to degrade organic pollutants.     

Size-dependent peroxidase-like catalytic activity of Fe3O4 nanoparticles

Peroxidase-like catalytic properties of Fe3O4 nanoparficles （NPs） with three different sizes, synthesized by chemical coprecipitation and sol-gel methods, were investigated by UV-vis spectrum analysis. By comparing Fe3O4 NPs with average diameters of 11, 20, and 150 nm, we found that the catalytic activity increases with the reduced nanoparticle size. The electrochemical method to characterize the catalytic activity of Fe3O4 NPs using the response currents of the reaction product and substrate was also developed.     

Enhanced catalytic activity of composites of NiFe2O4 and nano cellulose derived from waste biomass for the mitigation of organic pollutants

This study reports facile in situ synthesis of magnetically retrievable nanocomposites of nanocellulose (derived from waste biomass) and NiFe₂O₄ nanoparticles using hydrothermal method. The synthesized nanocomposites were characterized using various techniques such as FT-IR, powder XRD, HR-TEM, BET and VSM. The characterization of nanocomposites clearly revealed that NiFe₂O₄ nanoparticles were well dispersed on the surface of cellulose nanofibres. The catalytic performance of the synthesized nanocomposites was assessed for both the photocatalytic oxidation and reduction of organic pollutants. The prepared nanocomposites displayed excellent catalytic performance in comparison to pristine NiFe₂O₄ nanoparticles due to stabilization and increased dispersability of NiFe₂O₄ nanoparticles on the cellulose matrix. The present work promotes the use of bio based renewable sources to fabricate environment friendly materials to be used in the field of catalysis for the abatement of organic pollutants.     

Improved photocatalytic activity of WO3 through clustered Fe2O3 for organic degradation in the presence of H2O2

Photocatalytic degradation of organic substrates over WO(3) in an aerated aqueous suspension is very slow due to the difficulty of O(2) reduction by the conduction band electron on WO(3). In this work, we report on H(2)O(2) as an electron scavenger significantly accelerating the photodegradation of phenol and azo-dye X3B in water under UV or visible light. More importantly, an iron-containing WO(3) (FeW) synthesized through thermal decomposition of a ferrotungstenic acid displayed a much higher activity than pure WO(3) (HW) prepared in parallel. As the sintering temperature increased, both FeW and HW showed an exponential increase in activity. The maximum rate constant of phenol degradation obtained with FeW at 400 °C was about 2 times larger than that with HW at 600 °C. Sample characterization with electron paramagnetic resonance (EPR) spectroscopy and other techniques revealed that ferric species (0.3 wt % Fe(2)O(3)) were mainly present as clusters on the oxide surface at 120 °C and then they diffused toward the lattice sites of WO(3) at high temperature, which was detrimental to the photocatalytic reaction. 5,5-Dimethyl-1-pyrroline N-oxide spin-trapping EPR showed that the production of hydroxyl radicals was greatly enhanced upon the addition of H(2)O(2), the trend of which among different catalysts was the same as that of the rate of phenol degradation. The catalysts after excitation at 350 nm displayed a blue emission centered at 469 nm, the intensity of which varied with the catalyst activity nearly as expected. A possible mechanism for the improved photoactivity of WO(3) is proposed involving the electron transfer from WO(3) to Fe(2)O(3) and the reaction of the reduced oxide with H(2)O(2) to generate hydroxyl radicals.     

The enhanced catalytic activity and stability of Fe3O4-S@C Fenton-like catalyst for phenol degradation

Research on Chemical Intermediates - Carbon-coated Fe3O4-S (Fe3O4-S@C) Fenton-like catalyst on carbon cloth is successfully prepared by electrodeposition and subsequent ethanol solvothermal...     

Metal-free activation of H2O2 by g-C3N4 under visible light irradiation for the degradation of organic pollutants

Semiconducting carbon nitride materials were successfully prepared via a thermal poly-condensation of dicyandiamide as a precursor at >500 °C. The resulting materials were investigated as metal-free catalysts for the activation of H(2)O(2) with visible light under mild conditions, using the decomposition of Rhodamine B (RhB) in aqueous solution as a model reaction. Results revealed that carbon nitride catalysts can activate H(2)O(2) to generate reactive oxy-radicals under visible light irradiation without employment of any metal additives, leading to the mineralization of the dye. Factors affecting the degradation of organic compounds are pH values and the concentration of H(2)O(2). Recycling of the catalyst indicated no obvious deactivation during the entire catalytic reaction, indicating good (photo)chemical stability of metal-free polymeric carbon nitride photocatalysts for environmental purification. This study demonstrated a promising approach for the activation of green oxidant, hydrogen peroxide, by the newly-developed polymer photocatalysts for environmental remediation and oxidation catalysis.     

Fe2O3/ZnO/ZnFe2O4 composites for the efficient photocatalytic degradation of organic dyes under visible light

In this study, novel ternary Fe₂O₃/ZnO/ZnFe₂O₄ (ZFO) composites were successfully prepared through a simple hydrothermal reaction with subsequent thermal treatment. The as-prepared products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analysis, Barrett-Joyner-Halenda (BJH) measurement, and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The photocatalytic degradation of rhodamine B (Rh B) under visible light irradiation indicated that the ZFO composites calcined at 500 °C has the best photocatalytic activity (the photocatalytic degradation efficiency can reach up to 95.7% within 60 min) and can maintain a stable photocatalytic degradation efficiency for at least three cycles. In addition, the photocatalytic activity of ZFO composites toward dye decomposition follows the order cationic Rh B > anionic methyl orange. Finally, using different scavengers, superoxide and hydroxyl radicals were identified as the primary active species during the degradation reaction of Rh B.     

原位相分离合成V_2O_5/Fe_2V_4O_(13)纳米复合材料及其储钠性能

钠具有资源丰富、成本低廉等优势,因此钠离子电池被认为是未来替代锂离子电池的最佳候选者之一。然而,寻找合适的电极材料是当前制备高性能钠离子电池面临的难题之一。在众多候选材料中,钒酸盐材料通过引入阳离子增加钒的配位数,使得材料结构的稳定性得到提高,从而改善了钠离子电池的电化学性能。本文研究了一种原位相分离法合成V_2O_5/Fe_2V_4O_(13)纳米复合材料。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)等对电极材料形貌、组成和结构进行了表征。实验结果显示,V_2O_5/Fe_2V_4O_(13)纳米复合材料相对于V2O5纳米线材料,结构更加稳定,在0.1 A·g~(-1)电流密度下,初始放电容量由295.4 m Ah·g~(-1)提升到342 m Ah·g~(-1),循环100圈容量保持率由26.6%提高到65.8%,获得了更加优异的倍率性能(在1.0 A·g~(-1)电流密度下,容量由44 m Ah·g~(-1)提高到160 m Ah·g~(-1))。因此,V_2O_5/Fe_2V_4O_(13)纳米复合材料的研究为开拓新型高性能钠离子电池负极材料拓宽了思路。     

Intermetallic PdBi aerogels with improved catalytic performance for the degradation of organic pollutants in water

It is always highly pursued to develop efficient and durable catalysts for catalytic applications. Herein, intermetallic PdBi aerogels with tunable activity were prepared successfully via a surfactant-free spontaneous gelation process. The prepared PdBi aerogels have a three-dimensional high porous structure and plentiful active sites pervaded on the ultrathin interlinked nanowires network. These unique structures, as well as the synergistic effect between Pd and Bi, can accelerate mass and electron transfer, and improve the atom utilization ratio of Pd atoms to promote the catalytic efficiency. As a proof-of-concept application, the optimized Pd₂Bi₁ aerogels exhibit 4.2 and 6.2 times higher catalytic activity for the reduction of 4-nitrophenol (4-NP) and methylene blue (MB) than those of commercial Pd/C, respectively. With the introduction of non-noble metal of Bi, the cost of the resulted PdBi aerogels can be dropped significantly while the catalytic capability of PdBi aerogel will be improved sharply. This strategy will bring good hints to rationally design fine catalysts for various applications.     

CoFe2O4/CdS纳米复合物的制备、表征及其声催化降解有机染料污染物

在低温(200℃)下采用一步水热分解CoFe2O4纳米粒子表面的镉二硫代氨基甲酸酯配合物制备了磁性CoFe2O4/CdS纳米复合物,运用X射线衍射、红外光谱、扫描电镜、X射线能量散射谱、紫外-可见光谱、透射电镜(TEM)、N2吸附-脱附、X射线光电子能谱和振动样品磁强计对所制样品进行了表征.TEM结果表明,CoFe2O4/CdS纳米复合物由几乎均一的约20nm球形纳米粒子组成.光吸收谱显示该样品的带隙为2.24 eV,很适合用于声/光催化降解有机污染物.在紫外光照射下评价了CoFe2O4/CdS纳米复合物的声催化H2O2辅助降解甲基蓝、罗丹明B和甲基橙反应活性.结果表明,该纳米复合物对这3种染料均表现出很好的声催化活性(5-9 min内完全降解).另外,比较实验结果表明,CoFe2O4/CdS纳米复合物是一个比纯CdS更高效的声催化剂.因此,纳米复合是一种非常好的提高CdS声催化活性的手段.该CoFe2O4/CdS纳米复合物表现出的磁性使其很容易从反应混合物中分离出来而重复使用.     

IR spectroelectrochemical studies of Fe2V4O13, FeVO4 and InVO4 thin films obtained via sol-gel synthesis

In this paper we generalize the IR spectroscopic properties of M³⁺VO₄ (M=Fe, In) orthovanadate and Fe₂V₄O₁₃ films. The films were prepared using the sol-gel synthesis route from M³⁺ nitrates and vanadium oxoisopropoxide. The vibrational bands in the IR absorbance spectra of the films are classified in terms of terminal V-O stretching (1050–880 cm^–1), bridging V-O^...Fe and V^...O^...Fe stretching (880–550 cm^–1), mixed V-O-V deformations and Fe-O stretching (<550 cm^–1) modes. Ex situ IR spectra of films were measured after consecutive charging/discharging to various intercalation coefficients x and correlated to the current peaks in the cyclic voltammetry curves measured in 1 M LiClO₄/propylene carbonate electrolyte. We classified the ex situ IR spectra of charged/discharged films according to their vibrational band changes. The results reveal that, for small values of the intercalation coefficient, crystalline FeVO₄, InVO₄ and Fe₂V₄O₁₃ films exhibit a simultaneous decrease in the intensity of all IR bands while the band frequencies remain unaffected. For the higher intercalation levels, IR mode frequencies are shifted, signaling the presence of reduced vanadium. Further charging leads to an amorphization of the film structure, which was established from the similarity of the IR spectra of charged films with those of amorphous films prepared at lower annealing temperatures. The results confirm that ex situ IR spectroelectrochemical measurement is an effective way to assess the structural changes in films with different levels of intercalation. Electronic Publication     

Fe3O4的X射线微结构特征与催化活性间的关系

湿法工艺制备的不同晶型Fe2O3, 经水煤气还原后Fe3O4的X射线衍射微结构特征, 用分析微应变和晶粒尺寸的Voigt函数单峰分析法进行了测定。Fe3O4微应变大小同催化活性间存在一种对应关系。γ-Fe2O3还原的Fe3O4比α型还原的有更大的晶格畸变, 在325℃, 500空速条件下, CO转化率达97%以上, 比后者高出30%多。这种畸变结构在工业催化反应条件下能长期稳定, 但经600℃高温处理后, 畸变减小,活性下降。湿法工艺可以获得具有不同活性的Fe3O4前身, γ-Fe2O3与Fe3O4晶体结构上的类似, 使它在还原过程中, 能把这种高活性的结构状态保留下来。     

Study of phase equilibria established up to the solidus line in the system Fe2V4O13−WO3

The phase equilibria established up to the solidus line in the system Fe₂V₄O₁₃−WO₃, one of the intersections of the three-component system Fe₂O₃−V₂O₅−WO₃, have been studied. The system appears not to be a real two-component system.

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Zusammenfassung Es wurde eine Untersuchung des Phasengleichgewichtes durchgeführt, welches bezüglich der Solidus-Linie im System Fe₂V₄O₁₃−WO₃, einer der Zwischenbereiche im Dreikomponentensystem Fe₂O₃−V₂O₅−WO₃, nachgewiesen wurde. Dieses System scheint kein echtes Zweikomponentensystem zu sein.

     

Optimization of the catalytic activity of manganese dioxide (MnO2) nanoparticles for degradation of environmental pollutants

Research on Chemical Intermediates - A routine release of slow-degrading agrochemicals in the environment has resulted in their gradual accumulation posing a major threat both to the terrestrial...     

Review on augmentation in photocatalytic activity of CoFe2O4 via heterojunction formation for photocatalysis of organic pollutants in water

In previous years, cobalt ferrite has gained huge consideration in the field of semiconductor photocatalysis for waste water treatment. Cobalt ferrite and its derivatives own tunable magnetic properties which results in higher absorption capability in comparison with other photocatalyst semiconductors. In the current review, a brief overview of CoFe₂O₄ as a semiconductor photocatalyst is presented and ferromagnetic behaviour of CoFe₂O₄ is also discussed. Few drawbacks such as agglomeration, photocorrosion and recombination rate of electrons-holes are also discussed. For the enhancement of photocatalytic action of cobalt ferrite, the role of cobalt ferrite with type I, type II, direct Z-scheme, solid state Z-scheme heterojunctions, Schottky and p-n heterojunctions based on different heterostructures were also discussed. In conclusive outlook formation of cobalt ferrite based heterojunctions is best approach for the enhancement of photocatalytic performance. This is because heterojunction formation enhanced the rate of charge separation and thus reduced the electron–hole recombination. Herein, this review highlights the CoFe₂O₄ based heterojunctions for the photodegradation of noxious organic pollutants in water. Furthermore, the future expectations and challenges in exploiting CoFe₂O₄ nanocomposites for water treatment, also discussed in precise conclusion of this review.