Preparation and characteristics of carbon-supported platinum catalyst and its application in the removal of phenolic pollutants in aqueous solution by microwave-assisted catalytic oxidation

Granular activated carbon-supported platinum (Pt/GAC) catalysts were prepared by microwave irradiation and characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). Pt particles dispersing onto the surface of GAC could be penetrated by microwave and acted as "reaction centre" in the degradations of p-nitrophenol (PNP) and pentachlorophenol (PCP) in aqueous solution by microwave-assisted catalytic oxidation. The reaction was carried out through a packed bed reactor under ambient pressure and continuous flow mode. Under the conditions of microwave power 400 W, influent flow 6.4 mL min(-1) and air flow 120 mL min(-1), phenolic solutions with high concentration (initial concentrations of PNP and PCP solutions were 1469 and 1,454 mg L(-1), respectively) were treated effectively by Pt/GAC, 86% PNP and 90% PCP were degraded and total organic carbon (TOC) removal reached 85% and 71%, respectively. Compared with GAC, loaded Pt apparently accelerated oxidative reaction so that Pt/GAC had a better degrading and mineralizing efficiencies for PNP. Hydraulic retention time was only 16 min in experiment, which was shortened greatly compared with catalytic wet air oxidation. Pyrolysis and oxidation of phenolic pollutants occurred simultaneously on the surface of Pt/GAC by microwave irradiation.     

Catalytic activity of CuOn-La2O3/gamma-Al2O3 for microwave assisted ClO2 catalytic oxidation of phenol wastewater

In order to develop a catalyst with high activity and stability for microwave assisted ClO2 catalytic oxidation, we prepared CuOn-La2O3/gamma-Al2O3 by impregnation-deposition method, and determined its properties using BET, XRF, XPS and chemical analysis techniques. The test results show that, better thermal ability of gamma-Al2O3 and high loading of Cu in the catalyst can be achieved by adding La2O3. The microwave assisted ClO2 catalytic oxidation process with CuOn-La2O3/gamma-Al2O3 used as catalyst was also investigated, and the results show that the catalyst has an excellent catalytic activity in treating synthetic wastewater containing 100 mg/L phenol, and 91.66% of phenol and 50.35% of total organic carbon (TOC) can be removed under the optimum process conditions. Compared with no catalyst process, CuOn-La2O3/gamma-Al2O3 can effectively degrade contaminants in short reaction time and with low oxidant dosage, extensive pH range. The comparison of phenol removal efficiency in the different process indicates that microwave irradiation and catalyst work together to oxidize phenol effectively. It can therefore be concluded from results and discussion that CuOn-La2O3/gamma-Al2O3 is a suitable catalyst in microwave assisted ClO2 catalytic oxidation process.     

Catalytic ozonation of p-chlorobenzoic acid by activated carbon and nickel supported activated carbon prepared from petroleum coke

The aim of this research was to investigate catalytic activity of petroleum coke, activated carbon (AC) prepared from this material, Ni supported catalyst on activated carbon (Ni/AC) in the ozonation of aqueous phase p-chlorobenzoic acid (p-CBA). Activated carbon and Ni/AC catalyst were characterized by XRD and SEM. The presence of petroleum coke did not improve the degradation of p-CBA compared to ozonation alone, but it was advantageous for p-CBA mineralization (total organic carbon, TOC, reduction), indicating the generation of highly oxidant species (*OH) in the medium. The presence of either activated carbon or Ni/AC considerably improves TOC removal during p-CBA ozonation. Ni/AC catalyst shows the better catalytic activity and stability based on five repeated tests during p-CBA ozonation. During the ozonation (50 mg/h ozone flow rate) of a 10 mg/L p-CBA (pH 4.31), it can be more mineralized in the presence of Ni/AC catalyst (5.0 g/L), TOC removal rate is over 60% in 60 min, 43% using activated carbon as catalyst, only 30% with ozonation alone.     

Granular activated carbon promoted ozonation of a food-processing secondary effluent

This paper reports on the application of a simultaneous combination of ozone and a granular activated carbon (O(3)/GAC) as a tertiary treatment of a wastewater generated from the activity of various food-processing industries. Prior to the O(3)/GAC treatment, the wastewater was subjected to conventional primary and secondary treatments in a full-scale wastewater treatment plant (WWTP). The effluent from the WWTP presented high organic load (COD>500 mg/l and TOC>150 mg/l), which could be much reduced by the O(3)/GAC treatment. Results from the O(3)/GAC experiments were compared with those obtained in single ozonation, single adsorption onto GAC and sequential O(3)-GAC adsorption experiments. While single processes and the sequential one showed limited capacity to remove organic matter for the food-processing effluent (COD removal <40%), the simultaneous O(3)/GAC process led to decreases of COD up to 82% at the conditions here applied. The combined process also improved the ozone consumption, which decreased from about 19 g O(3)/g TOC (single ozonation process) to 8.2-10.7 g O(3)/g TOC (O(3)/GAC process). The reusability of the GAC throughout a series of consecutive O(3)/GAC experiments was studied with no apparent loss of activity for a neutral GAC (PZC = 6.7) but for a basic GAC (PZC = 9.1).     

Wet peroxide oxidation and catalytic wet oxidation of stripped sour water produced during oil shale refining

Catalytic wet oxidation (CWO) and wet peroxide oxidation (WPO) of stripped sour water (SSW) from an oil shale refinery was investigated. Greater than 70% total organic carbon (TOC) removal from SSW was achieved using Cu(NO(3))(2) catalysed WO under the following conditions using a glass lined reaction vessel: 200 degrees C, pO(2)=0.5MPa, 3h, [Cu(NO(3))(2)]=67mmol/L. Significant TOC removal ( approximately 31%) also occurred in the system without added oxygen. It is proposed that this is predominantly due to copper catalysed oxidative decarboxylation of organics in SSW based on observed changes in copper oxidation state. Greater than 80% TOC removal was achieved using WPO under the following conditions: 150 degrees C, t=1.5h, [H(2)O(2)]=64g/L. Significantly more TOC could be removed from SSW by adding H(2)O(2) in small doses as opposed to adding the same total amount in one single dose. It was concluded that WPO was a far more effective process for removing odorous compounds from SSW.     

Microwave induced catalytic degradation of crystal violet in nano-nickel dioxide suspensions

Nickel oxide catalyst was obtained by precipitation–oxidation method with the assistance of microwave irradiation. The samples were characterized by X-ray diffraction, Raman spectrophotometer, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, surface area and porosity analyzer. On the basis of the results, the as-prepared product was nano-NiO₂ with OH group and active oxygen. The catalytic activity of the as-prepared product might be attributed to its microwave absorbing property and the role of active oxygen, OH group under microwave irradiation. The microwave induced catalytic degradation process (MICD) with as-prepared product was further applied to degrade triphenylmethane dye crystal violet (CV). 97% of a 100 mg L^?1 sample of CV was rapidly degraded in 5 min with the corresponding 81% TOC removal. The main intermediates were separated and identified by LC–ESI-MS and GC–MS techniques. The LC–ESI-MS analytical results demonstrated that a series of N-de-methylation products were obtained in a stepwise manner, namely mono-, di-, tri-, tetra-, penta-, and hexa-de-methylated CV species. Nine organic acids with benzene ring and four low molecular acids were yielded with the assistance of GC–MS. The proposed degradation pathways were discussed in this study. The degradation processes might include N-de-methylation, destruction of conjugated structure and opening-benzene ring. MICD, as a potential technique with wide application perspective, can be used to purify triphenylmethane dye wastewater with nanosized nickel dioxide.     

水热法制备氧化铬及其常温低浓度一氧化氮催化性能

以十六烷基三甲基溴化铵(CTAB)为模板剂, 氨水为沉淀剂, 通过水热法并焙烧处理合成氧化铬催化剂。采用X射线衍射分析(XRD)、傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)和透射电镜(TEM)等技术对催化剂的物化性质进行了表征, 并考察常温不同NO初始浓度下氧化铬催化剂的NO氧化性能。结果表明: 在空速为60000 mL/(g·h)和NO浓度为1×10^-6的条件下, 100℃水热温度制备的Cr-100催化剂表现出最优的性能, 常温下NO消除率高达90%以上并保持120 h, 其优异的常温催化性能与催化剂表面较高的Cr⁶⁺/Cr³⁺摩尔比有关。研究结果表明: 催化剂的失活主要是由于硝酸根在催化剂表面的累积而导致催化剂活性中心被覆盖, 低浓度下能减缓硝酸根的积累。     

微波辅助酸化蒙脱土催化合成乳酸正丁酯的研究

采用微波辐照法对钠基蒙脱土进行了酸化改性,制备出了酸化蒙脱土(H-MMT)固体酸催化剂,并利用X射线衍射、低温物理吸附等技术对催化剂性质进行了表征,结果表明,经微波辐照酸改性的催化剂层状结构没有被破坏,层间距略有下降,结晶度降低;比表面积和孔径都增大,形成了较好的介孔结构;表面酸量增加.这些特性使得催化剂表现出良好的催化活性.而后,以H-MMT为催化剂,系统研究了乳酸正丁酯的微波辅助合成方法,考查了催化剂用量、微波功率以及微波辐照时间对酯化率的影响.结果表明,微波功率200W、辐照15min、催化剂用量6.0%(占乳酸和正丁醇总质量)为最优的酯化条件,在此条件下,酯化率可达72.4%.最后,探讨了微波辅助H-MMT催化合成乳酸正丁酯的机制,发现H-MMT与微波具有协同作用.微波辅助H-MMT催化合成乳酸正丁酯是一种高效、节能、环境友好的方法,具有市场推广前景.     

直流电弧等离子体制备纳米SiC及其催化特性

利用工业块体硅为硅源, CH₄为碳源, 在含有H₂和Ar混合气氛中, 采用直流电弧等离子体法制备SiC纳米粒子。CH₄含量影响SiC纳米粒子的化学组成和形貌。结果显示: 产物中含有3C-SiC和6H-SiC两种物相, 而在CH₄压力为0.005 MPa条件下制备的SiC纳米粒子还含有Si/SiC核壳结构。利用制备的SiC纳米颗粒作为催化剂, 在恒光强下光电催化还原脱除2,4-二氯酚中的Cl原子。结果显示在-1.02 V偏压下光电催化180 min后, 对2,4-二氯酚的去除效率达92.5%, SiC纳米粒子的吸附效率为19.6%。因此, SiC纳米颗粒可取代贵金属, 作为低成本光电催化候选材料用于污水处理。     

Catalytic ozonation of dimethyl phthalate over cerium supported on activated carbon

Cerium supported on activated carbon (Ce/AC), which was prepared by dipping method, was employed to degrade dimethyl phthalate (DMP) in water. The mineral matter present in the activated carbon positively contributes to its activity to enhance DMP ozonation process. A higher dipping Ce(NO₃)₃ concentration and calcination process increase its microporous volume and surface area, and decreases its exterior surface area. The catalytic activity reaches optimal when 0.2% (w/w) cerium is deposited on activated carbon. Ce/AC catalyst was characterized by XRD, SEM and BET. The presence of either activated carbon or Ce/AC catalyst considerably improves their degradation and mineralization in the ozonation of DMP. During the ozonation (50 mg/h ozone flow rate) of a 30 mg/L DMP (initial pH 5.0) with the presence of Ce/AC catalyst, TOC removal rate reaches 68% at 60 min oxidation time, 48% using activated carbon as catalyst, only 22% with ozonation alone. The presence of tert-butanol (a well known OH radical scavenger) strongly inhibits DMP degradation by activated carbon or Ce/AC catalytic ozonation. TOC removal rate follows the second-order kinetics model well. In the ozonation of DMP with 50 mg/h ozone flow rate, its mineralization rate constant with the presence of Ce/AC catalyst is 2.5 times higher than that of activated carbon, 7.5 times higher than that of O₃ alone. Ce/AC catalyst shows the better catalytic activity and stability based on 780 min sequential reaction in the ozonation of DMP. Ce/AC was a promising catalyst for ozonizing organic pollutants in the aqueous solution.     

Synergistic catalysis of cluster and atomic copper induced by copper-silica interface in transfer-hydrogenation

To data, using strong metal-support interaction (SMSI) effect to improve the catalytic performance of metal catalysts is an important strategy for heterogeneous catalysis, and this effect is basically achieved by using reducible metal oxides. However, the formation of SMSI between metal and inert-support has been so little coverage and remains challenge. In this work, the SMSI effect can be effectively extended to the inert support-metal catalysis system to fabricate a Cu⁰/Cu-doped SiO₂ catalyst with high dispersion and loading (38.5 wt.%) through the interfacial effect of inert silica. In the catalyst, subnanometric composite of Cu cluster and atomic copper (in the configuration of Cu-O-Si) can be consciously formed on the silica interface, and verified by extended X-ray absorption fine structure (EXAFS), in situ X-ray photoelectron spectroscopy (XPS), and high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) characterization. The promoting activity in transfer-hydrogenation by the SMSI effect of Cu-silica interface and the synergistic active roles of cluster and atomic Cu have also been revealed from surface interface structure, catalytic activity, and density functional theory (DFT) theoretical calculation at an atomic level. The subnanometric composite of cluster and atomic copper species can be derived from a facile synthesis strategy of metal-inert support SMSI effect and the realistic active site of Cu-based catalyst can also been identified accurately, thus it will help to expand the application of subnanometric materials in industrial catalysis.

     

The catalytic oxidation of aromatic hydrocarbons over supported metal oxide

The catalytic activity of metals (Cu, Mn, Fe, V, Mo, Co, Ni, Zn)/gamma-Al2O3 was investigated to bring about the complete oxidation of benzene, toluene and xylene (BTX). Among them, Cu/gamma-Al2O3 was found to be the most promising catalyst based on activity. X-ray diffraction (XRD), Brunauer Emmett Teller method (BET), electron probe X-ray micro analysis (EPMA) and temperature programmed reduction (TPR) by H2 were used to characterize a series of supported copper catalysts. Increasing the calcination temperature resulted in decreasing the specific surface areas of catalysts and, subsequently, the catalytic activity. Copper loadings on gamma-Al2O3 had a great effect on catalytic activity, and 5 wt.% Cu/gamma-Al2O3 catalyst was observed to be the most active, which might be contributed to the well-dispersed copper surface phase. Using TiO2 (anatase), TiO2 (rutile), SiO2 (I) and SiO2 (II) as support instead of gamma-Al2O3, the activity sequence of 5 wt.% Cu with respect to the support was gamma-Al2O3 > TiO2 (rutile) > TiO2 (anatase)>SiO2 (I) > SiO2 (II), and this appeared to be correlated with the distribution of copper on support rather than with the specific surface area of the catalyst. The smaller particle size of copper, due to its high dispersion on support, had a positive effect on catalytic activity. The activity of 5 wt.% Cu/gamma-Al2O3 with respect to the VOC molecule was observed to follow this sequence: toluene > xylene > benzene. Increasing the reactant concentration exerted an inhibiting effect on the catalytic activity.     

Preparation of activated carbon@ZnO composite and its application as a novel catalyst in catalytic ozonation process for metronidazole degradation

The present study aimed to investigate the efficiency of granular activated carbon modified with ZnO nanoparticles (GAC@ZnO composite) as a catalyst for metronidazole degradation using catalytic ozonation process. The catalytical properties of GAC@ZnO composite were measured by using FESEM, FT-IR, XRD, EDX, and BET advanced techniques. Also, the effects of pH factor (3, 5, 7, 9, and 11), initial concentration of contaminant (10–30 mg/L), reaction time (5–90 min), catalyst dosage (0.2–2.5 g/L), on the catalytic ozonation process, were studied. In addition, the effects of the interfering factors on the work of ozone degradation agent and hydroxyl radicals are tested. The results of characterisation study showed a successful formation of GAC@ZnO composite with favorable catalytic properties. In addition, the GAC surface properties were enhanced by the modification with ZnO nanoparticles, where more efficient reaction sites for metronidazole degradation were created onto GAC. The degradation performance of the GAC@ZnO composite was high in which 83% of metronidazole removal was achieved in optimum conditions (pH = 11, catalyst dosage = 2 g/L, and reaction time = 30 min). In addition, the degradation rate was noticeably found to be higher in case of using catalytic ozonation process than using ozonation process alone. The kinetic degradation reactions of metronidazole followed the pseudo-first-order equation. According to the results of this model’s parameters, the degradation process is occurred on or near GAC@ZnO composite surface depending on the concentration of the pollutant. From the results obtained, it can be concluded that the GAC@ZnO composite in the catalytic ozonation treatment process was efficacious catalyst as it has excellent performance toward eradication of metronidazole wastewater.     

Investigation on the rapid degradation of congo red catalyzed by activated carbon powder under microwave irradiation

Azo dyestuff-congo red in aqueous solution can be degraded rapidly under microwave irradiation in the presence of activated carbon powder. The results showed that the degradation ratio could reach 87.79% for 25 mL total volume with 50mg/L congo red and 2.0 g/L activated carbon powder under 1.5 min microwave irradiation. Furthermore, within the same irradiation time, congo red could be degraded fully by increasing addition amount (e.g. 3.6g/L) of activated carbon powder and the degradation ratio was up to 96.49%. Otherwise, with the same addition amount, congo red also could be degraded completely by prolonging irradiation time (e.g. 2.5 min) and the degradation ratio was up to 97.88%. In addition, the influences of microwave irradiation time, initial concentration of congo red, addition amount and used times of activated carbon powder as well as solution acidity on the degradation were discussed in details adopting UV-vis spectra, FT-IR spectra, ion chromatography, high phase liquid chromatography (HPLC) and TOC analysis technologies. Here, the method using activated carbon powder as catalyst under microwave irradiation shows many advantages including high degradation ratios, short reaction time, low costs, no intermediates and no secondary pollution. Therefore, it may be fit for dealing with various azo dyestuff wastewaters on a large scale.     

Efficient strategy to Cu/Si catalyst into vertically aligned carbon nanotubes with bamboo shape by CVD technique

Bamboo-shaped vertically aligned carbon nanotubes (bs-VACNTs) were fabricated on Cu/Si catalyst by chemical vapour deposition (CVD) technique under the atmospheric pressure. The catalytic material (Cu/Si) played a vital role in attaining bs-VACNTs, which is synthesized by drop cast method in a cost-effective manner. Using this catalytic support, we have achieved the tip growth bs-VACNTs at low temperature with well graphitization. The as-grown carbon material was then characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) analyzer, high-resolution transmission electron microscope (HRTEM) and Raman spectroscopy. XRD technique confirms the formation of hexagonal graphitic carbon planes of carbon nanotubes (CNTs). The surface morphology of the material was characterized by SEM, which clearly infer vertically aligned CNTs. The nature, diameter and crystallinity were noticed by HRTEM and Raman spectroscopy, respectively. Further, we have also studied the electrochemical properties of the bs-VACNTs and it seems to be proved as highly electroconductive when compared to multi-walled carbon nanotubes (MWCNTs).     

水热法制备Cu掺杂可见光催化剂BiVO4及其光催化性能研究

以Bi(NO3)3.5H2O、NH4VO3、Cu(NO3)2.3H2O为原料,采用水热法合成了Cu-BiVO4光催化剂,并利用X射线衍射(XRD)、扫描电镜(SEM)、X射线光电子能谱(XPS)、紫外漫反射(UV-Vis)等测试手段对催化剂进行了表征.结果表明,提高前驱液pH值,可得到单斜晶系白钨矿型Cu-BiVO4光催化剂,BiVO4的晶型结构并未随着Cu掺入量的增加而改变.光催化剂中的Cu元素以CuO和Cu2O的形式存在.Cu的引入使可见光吸收带发生红移,吸收强度明显提高.可见光催化降解亚甲基蓝溶液的结果表明,Cu掺杂有利于提高BiVO4的活性.其中pH值为5.0、Cu掺入量为1.0wt%的BiVO4具有最好的光催化效果,可见光照射60 min后,对初始浓度为10 mg/L的亚甲基蓝溶液的最高降解率由纯BiVO4的57.4%提高到97.8%.并对Cu掺入后光催化活性提高的机理进行了分析.     

氮化硼纳米片负载纳米Cu2O及其催化还原对硝基苯酚

纳米级氧化亚铜具有高效的催化性能, 但较差的稳定性使其应用受限。本研究采用简单可控的抗坏血酸液相还原及气氛焙烧法, 制备了一种兼具高催化活性与催化稳定性的Cu₂O/BNNSs-OH负载型催化剂, 其中以聚乙烯吡咯烷酮(PVP)与水相变提供的“推-拉”作用剥离的氮化硼纳米片(BNNSs)为载体, 液相还原反应体系pH=11时, 抗坏血酸向Cu ²⁺滴定制备的Cu₂O纳米颗粒(2~7 nm)为活性组分。通过扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、原子力显微镜(AFM)、X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)、傅里叶变换红外光谱仪(FT-IR)及拉曼(Raman)光谱仪等对样品的形貌和结构进行表征, 结果表明: Cu₂O纳米粒子不但高度分散于载体表面, BNNSs对Cu₂O还有一定的稳定作用, 避免其被氧化成CuO。将Cu₂O/BNNSs-OH应用于对硝基苯酚催化还原反应中, 该催化剂表现出同贵金属类似的高催化活性, 5次重复利用后的转化率仍高达90%。     

基于SnO2/Fe3O4粒子电极的三维电极体系的电催化性能

通过水热法合成复合金属氧化物SnO_2/Fe_3O_4粒子电极,然后采用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、磁滞回线等技术分别对粒子电极的晶体组分、形貌、元素组成和分子结构以及粒子电极的磁性特征进行表征。采用循环伏安法分析了三维电极系统的电化学性能,并进行了电催化氧化降解罗丹明B(RhB)的实验。结果表明,SnO_2/Fe_3O_4粒子电极负载稳定、导电性强、便于回收再利用,有利于电催化氧化降解反应。三维电极降解罗丹明B的析氧电流高于其他电极体系,电催化活性效果明显,90min内罗丹明B的降解率为100%、TOC去除率为83%,反应中产生的·OH是降解有机物的主要活性基。粒子电极在重复利用5次的情况下,对罗丹明B的降解率仍保持93%以上、TOC去除率保持在77%以上,具有稳定的电催化性能。     

Synergistic Effect of Fe Single-Atom Catalyst for Highly Efficient Microwave-Stimulated Remediation of Chloramphenicol-Contaminated Soil

Chloramphenicol (CAP) has long been used extensively in agriculture and is severely toxic to the biological environment. Microwave catalysis appears a promising method for soil remediation due to its fast and effective heat transfer, but it is challenging to prepare catalysts with good electromagnetic wave absorption and robust catalytic activity. In this study, atomically dispersed Fe on three-dimensional N-doped carbon supports (3D Fe-NC) is firstly used for microwave remediation of soil. Thanks to the synergistic effect of microwave “hot spots” and reactive oxygen species (•OH, •O₂⁻), 3D Fe-NC can completely remove 99.9% of CAP in 5 min. The removal rate constant is nearly twice that of commercial activated carbon. Significantly, the germination rate of lettuce seeds in microwave-repaired soil contaminated by CAP reaches 70%. This work demonstrates the application of Fe single-atom catalyst in microwave remediation of contaminated soil, providing a novel insight for agricultural soil remediation.     

V2O5/CNFs/蜂窝状堇青石催化剂的结构控制及其烟气脱硝性能

采用化学气相沉积法,在涂层Al2O3的蜂窝状堇青石表面生长纳米碳纤维(CNFs),通过负载V2O5催化剂,制成低温蜂窝状脱硝催化剂.采用SEM、TEM、XRD和XPS等分析方法,对所制催化剂的物化性质及其脱硝性能进行了分析.研究结果表明,当CNFs在堇青石表面的生长厚度为0.74μm时,所制CNFs/堇青石载体的压缩强度达34.46 MPa;在150~250℃范围内,V2O5/CNFs/蜂窝状堇青石催化剂表现出较高的低温脱除NO活性,其中当CNFs的生长量为12.5%、V2O5担载量为1%时,在250℃下NO的转化率达95%左右.