Formaldehyde degradation by UV/TiO2/O3process using continuous flow mode

The degradation of formaldehyde gas was studied using UV/TiO2/O3 process under the condition of continuous flow mode. The effects of humidity, initial formaldehyde concentration, residence time and ozone adding amount on degradation of formaldehyde gas were investigated. The experimental results indicated that the combination of ozonation with photocatalytic oxidation on the degradation of formaldehyde showed a synergetic action, e.g,, it could considerably increase decomposing of formaldehyde. The degradation efficiency of formaldehyde was between 73.6% and 79.4% while the initial concentration in the range of 1.84--24 mg/m^3 by O3/TiO2flJV process. The optimal humidity was about 50% in UV/TiO2/O3 processs and degradation of formaldehyde increases from 39.0% to 94.1% when the ozone content increased from 0 to 141 mg/m^3. Furthermore, the kinetics of formaldehyde degradation reaction could be described by Langmuir-Hinshelwood model. The rate constant k of 46.72 mg/（m^3.min） and Langmuir adsorption coefficient K of 0.0268 m^3/mg were obtained.     

Chlorobenzene degradation by electro-heterogeneous catalysis in aqueous solution: intermediates and reaction mechanism

This study was performed to investigate the variables that influence chlorobenzene (CB) degradation in aqueous solution by electro-heterogeneous catalysis.The effects of current density,pH,and electrolyte concentration on CB degradation were determined.The degradation effciency of CB was almost 100% with an initial CB concentration of 50 mg/L,current density 15 mA/cm2,initial pH 10,electrolyte concentration 0.1 mol/L,and temperature 25°C after 90 min of reaction.Under the same conditions,the degradation eff...     

Reaction site and mechanism in the UV or visible light induced TiO2 photodegradation of Orange G

For TiO2 heterogeneous reaction, the reaction site and the detailed mechanism are interesting and controversy topics. In this paper, effects of surface fluorination of TiO2 on the photocatalytic degradation of an azo dye, Orange G（OG） under UV or visible light irradiation were investigated, and the possible reaction site and mechanism were elucidated. The adsorption of OG on TiO2 was nearly inhibited by fluoride but its UV light induced photodegradation rate was greatly increased by a factor of about 2.7, which was due to the more generated free hydroxyl radicals. It supported the views that fluoride could desorb the oxidant species from surface and that the reaction sites could move to the bulk solution. In TiO2/Vis system, the observed inhibition effects of fluorination could be interpreted by the competitive adsorption, which provided additional evidences that the visible light sensitized photodegradation of dye pollutants on the catalyst surface.     

Efficient dechlorination of chlorinated solvent pollutants under UV irradiation by using the synthesized TiO2 nano-sheets in aqueous phase

Titanium dioxide(TiO2), which is the widely used photo-catalyst, has been synthesized by simple hydrothermal solution containing tetrabutyl titanate and hydrofluoric acid. The synthesized product has been applied to photo-degradation in aqueous phase of chlorinated solvents, namely tetrachloroethene(PCE), trichloroethene(TCE) and 1,1,1-trichloroethane(TCA). The photo-degradation results revealed that the degradation of these harmful chemicals was better in UV/synthesized TiO2 system compared to UV/commercial P25 system and UV only system. The photo-catalytic efficiency of the synthesized TiO2 was 1.4, 1.8 and 3.0 folds higher compared to the commercial P25 for TCA, TCE and PCE degradation, respectively. Moreover, using nitrobenzene(NB) as a probe of hydroxyl radical(.OH), the degradation rate was better over UV/synthesized TiO2, suggesting the high concentration of.OH generated in UV/synthesized TiO2system. In addition,.OH concentration was confirmed by the strong peak displayed in EPR analysis over UV/synthesized TiO2system. The characterization result using XRD and TEM showed that the synthesized TiO2 was in anatase form and consisted of well-defined sheet-shaped structures having a rectangular outline with a thickness of 4 nm, side length of 50 nm and width of 33 nm and a surface 90.3 m2/g. XPS analysis revealed that ≡Ti-F bond was formed on the surface of the synthesized TiO2. The above results on both photocatalytic activity and the surface analysis demonstrated the good applicability of the synthesized TiO2 nano-sheets for the remediation of chlorinated solvent contaminated groundwater.     

Synergistic photocatalytic degradation of pyridine using precious metal supported TiO2 with KBrO3

A series of precious metals catalysts （M/TiO/, M = Ru, Rh, Pd, Ag, Ir, Pt or Au） were prepared by a light deposition method and the synergistic photocatalytic degradations of pyridine （20 mg/L） under UV irradiation （365 nm） using M/TiO2 with electron capture agent KBrO3 have been investigated. The results show that KBrO3 has a greatly synergistic role on M/TiO2 and the photocatalytic activity of M/TiO2 is closely related to its work function. Ag could greatly enhance the activity of TiO2 due to the binding characteristics of pyridine on Ag. Under the conditions of 0.5 wt.% Ag loading, Ag/TiO2 concentration of 0.1 g/L, KlrO3 concentration of 10 mmol/L and reaction liquid pH value at 9, the pyridine can be degraded by 64% within 3 hr, doubled than TiO2 photocatalytic system. The degradation kinetics of pyridine follows first-order kinetics and k = 5.53 × 10-3 min^-1.     

Degradation of nitrobenzene in wastewater by γ-ray irradiation

The degradation of nitrobenzene(NB) by γ-ray irradiation was studied. The influences of dose rate and initial NB concentration were investigated in details. At a dose rate of 55 Gy/min, the degradation kinetics was pseudo-first-order at NB concentrations from 0.2 mmol/L to 4.0 mmol/L. At an initial NB concentration of 0.8 mmol/L, the degradation of NB at various dose rates also followed pseudo-first-order kinetics. Dissolved oxygen was found to have a positive effect on NB degradation. The degradation products were identified as nitrophenol,nitrosobenzene, and hydroquinone, and so on. Based on the product analysis, possible degradation pathways of nitrobenzene were proposed.     

Effect of electron beam irradiation on the degradation of monochlorophenols in aqueous solution

Electron beam was successfully used for the degradation of 2-chlorophenol (2-CP) and 4-chlorophenol (4-CP) in aqueous solutions in this research. The effect of radiation dose on substrate degradation and dechlorination of solutions with concentration of 50mg/L was investigated. The effect of initial concentration, pH and presence of oxygen was also investigated. The concentration of 2-CP and 4-CP remaining in solution after irradiation were measured by HPLC. The results showed that increased radiation dose led to increased degradation of the chlorophenols and increased CI^- yield. Deaeration was also found to significantly increase the rate of degradation of chlorphenols in water while degradation and dechlodnation under alkaline condition was lower than at low to neutral pH.     

Preparations of TiO2 film coated on foam nickel substrate by sol-gel processes and its photocatalytic activity for degradation of acetaldehyde

Anatase TiO2 films were successfully prepared on foam nickel substrates by sol-gel technique using tetrabutyl titanate as precursor. The characteristics of the TiO2 films were investigated by XPS, XRD, FE-SEM, TEM and UV-Vis absorption spectra. The photocatalytic activities of TiO2 films were investigated by photocatalytic degradation reactions of gaseous acetaldehyde, an indoor pollutant, under ultraviolet light irradiation. It was found that Ni^2＋ doping into TiO2 films due to the foam nickel substrates resulted in the extension of absorption edges of TiO2 films from UV region to visible light region. The pre-heating for foam nickel substrates resulted in the formation of NiO layer, which prevented effectively the injection of photogenerated electrons from TiO2 films to metal nickel. The TiO2 films displayed high photocatalytic activity for the degradation of acetaldehyde, and were enhanced by calcining the substrates and coating TiO2 films repeatedly. The high activity was mainly attributed to the improvement of the characteristics of substrate surface and the increase of active sites on photocatalyst.     

Radiolysis of pentachlorophenol (PCP) in aqueous solution by gamma radiation

Steady-state radiolysis experiments were performed to investigate the γ-irradiation treatment of pentachlorophenol (PCP) in aqueous solution. The e?ect of initial concentration on the PCP degradation was also investigated. The experimental results showed that γirradiation was able to degrade PCP in aqueous solution successfully, and the radiolytical degradation process of PCP could be described by the first-order kinetic model. When the initial concentration of PCP was 25 and 50 mg/L and the radiation dose ...     

Heterogeneous Fenton-like degradation of 4-chlorophenol using iron/ordered mesoporous carbon catalyst

Ordered mesoporous carbon supported iron catalysts(Fe/OMC) were prepared by the incipient wetness impregnation method and investigated in Fenton-like degradation of 4-chlorophenol(4CP) in this work. XRD and TEM characterization showed that the iron oxides were well dispersed on the OMC support and grew bigger with the increasing calcination temperature. The catalyst prepared with a lower calcination temperature showed higher decomposition efficiency towards 4CP and H2O2, but more metals were leached. The effect of different operational parameters such as initial pH, H2O2 dosage, and reaction temperature on the catalytic activity was evaluated. The results showed that 96.1% of 4CP and 47.4% of TOC was removed after 270 min at 30°C, initial pH of 3 and 6.6 mmol/L H2O2. 88% of 4CP removal efficiency was retained after three successive runs, indicating Fe/OMC a stable catalyst for Fenton reaction. 4CP was degraded predominately by the attack of hydroxyl radical formed on the catalyst surface and in the bulk solution due to iron leaching. Based on the degradation intermediates detected by high performance liquid chromatography, possible oxidation pathways were proposed during the 4CP degradation.     

RGO/TiO2光催化降解2,4-二氯苯氧乙酸研究

通过Hummers法及紫外光/热还原工艺制得还原氧化石墨烯(RGO),采用溶胶-凝胶-煅烧法,以RGO和钛酸酊脂为前驱体制备出RGO/TiO2光催化复合材料,并利用XRD、FT-IR等对其进行了表征.对RGO/TiO2光催化降解性能的研究发现,复合光催化剂RGO/TiO2对2,4-二氯苯氧乙酸(2,4-D)的光催化降解活性显著优于纯TiO2,并且发现负载量和pH值对光催化降解性能有较大的影响:RGO/TiO2投加量为1.2g·L~(-1)、RGO负载量2%、pH为3、初始浓度为50 mg·L~(-1)反应12 h,2,4-D去除率达到98.75%;2,4-D降解率随着RGO/TiO2投加量的增大先增大后减小;RGO/TiO2对2,4-D的降解为脱氯还原和催化氧化过程,产生氯酚、苯酚等中间产物.     

光催化体系中噻虫胺降解动力学及机制

利用光催化技术探讨了烟碱类杀虫剂噻虫胺在水体环境中降解的可行性,不同催化剂浓度、反应温度、底物浓度、溶液初始p H值和不同阴阳离子等因素对其光催化降解动力学的影响,及其初步的光催化降解机制.结果表明噻虫胺的光催化降解符合L-H动力模型,其降解假一级动力学速率常数为0.050 6 min-1.当催化剂用量(TiO_2)为3.0 g·L~(-1)时,噻虫胺的光催化降解速率最大;高温和较低的底物浓度有利于噻虫胺的光催化降解;溶液的初始p H值为5时噻虫胺的降解速率最大,强酸和强碱均不利于其光催化降解.而无机阴、阳离子对噻虫胺降解均有明显的抑制作用.最后,通过GC/MS对噻虫胺光催化降解中间产物进行了初步鉴定,研究发现在活性氧物种的作用下噻虫胺降解途径主要有母体化合物的羟基化,硝基胍基团中N—N的断裂,以及连接硝基胍和噻唑环的C—N键的裂解等.     

TiO2降解迪美唑的动力学及活性物质分析

兽类抗生素迪美唑是一种新兴的污染物质,对环境和人类健康具有潜在危害.以紫外光为光源,以TiO2为催化剂,对其进行光催化降解,考察了溶液pH值、TiO2投加量、溶液的初始浓度等影响因素对迪美唑降解效果的影响.结果表明,在TiO2投加量为1 g·L-1,迪美唑初始浓度为40 mg·L-1,溶液pH为11的最优条件下反应90 min后,迪美唑的去除率为90%,反应速率为0.025 7 min-1.反应符合伪一级动力学模型.光催化降解迪美唑有两个途径:一是·OH氧化过程,二是e-还原过程.     

TiO2光催化降解PFOA的反应动力学及机制研究

全氟辛酸(PFOA)是一种新的持久性有机污染物,其处置技术是研究的热点.以UV254 nm紫外灯为光源,采用商品TiO2(P25)对PFOA进行光催化降解实验,并考察pH、TiO2用量、初始浓度、反应气氛对降解的影响.结果表明,反应符合准一级动力学方程,pH对反应有重要影响,氧气存在下能提高反应效率.在pH为3,TiO2用量为1.5 g·L-1,通入空气条件下反应7 h实现基本降解,速率常数为0.4206 h-1.投加俘获剂实验表明,空穴(h+)是主要的活性物质,其对反应速率贡献率为66.1%;羟基自由基(·OH)也参与PFOA的降解过程;投加NaF实验表明,PFOA在TiO2上吸附是反应发生的首要条件.UPLC-QTOF/MS分析表明,PFOA光催化降解逐级生成短链全氟羧酸(PFCAs).     

BiOCl/TiO2的氯化改性及其新式光生自由基催化反应

采用溶胶凝胶法制备了BiOCl/TiO₂复合催化剂,透射电镜（TEM）照片显示,两种半导体分布均匀、相互连接,形成的异质结可以为电子传导提供有效通道.经过氯化处理的复合材料具备更强的光催化能力,在紫外光条件下对苯的降解率达到90%,是原BiOCl/TiO₂的2倍、纯TiO₂的10倍.本文利用X射线光电子能谱、红外光谱和电子顺磁共振,对表面氯化的机理进行研究.结果表明,氯元素以Ti—Cl的方式吸附在催化剂表面,在光照条件下光生空穴夺取一个电子,使其生成氯自由基,进而配合超氧、羟基,构成一种新型的三自由基光催化体系,使催化降解能力大幅提升.最后,利用实验方法得到了光生氯自由基的直接证据,并构建了该体系的光催化反应机理.     

TiO2-石墨烯（Gn）复合材料光催化降解O3研究

通过改性Hummer法及溶胶凝胶法,制备出TiO2-石墨烯光催化复合材料.经吸附-光催化活性实验选出光催化活性最高的含C量为1.5%(质量分数)的TiO2-石墨烯复合材料,并在自行设计的模拟大型客机环境的气相光催化反应器中,进行O3光催化降解实验研究.结果表明,TiO2-石墨烯复合光催化材料在较短时间内对O3有较高的降解效率,且其光催化活性显著优于纯TiO2材料.初始O3浓度为(0.150～0.200)×10-6时,复合光催化剂受紫外光激发60 min的光催化降解率为66.12%,初始O3浓度为(0.950～1.000)×10-6时,其光催化降解率约为77%,较低浓度时((0.100～0.150)×10-6),O3去除率也能达到45.45%.此外,通过探讨光催化材料的重复使用性能,表明复合光催化剂重复使用4次以内,其对O3的光催化降解率保持基本稳定.     

Simulated-sunlight-activated photocatalysis of Methylene Blue using cerium-doped SiO2/TiO2 nanostructured fibers

Cerium-doped SiO₂/TiO₂ nanostructured fibers were fabricated by electrospinning technology. The prepared fibers were characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Using the fibers as catalysts, photocatalytic degradation of Methylene Blue (MB) aqueous solution was carried out under simulated sunlight. The 0.2% Ce doping proved to be the optimal concentration for the doping of TiO₂/SiO₂, compared to other Ce-doped molar concentrations. The 0.2% Ce-doped SiO₂/TiO₂ fibers exhibited higher photocatalytic activity than industrial Degussa P25 and the samples doped with only Ce or SiO₂. The reasons for improving the photocatalytic activity were also discussed. Several operational parameters were studied, which showed that the photocatalytic efficiency of MB was influenced by parameters such as the initial dye concentration, the initial pH, inorganic anions, and so on. In addition, the influences of an electron acceptor and a radical scavenger suggested that OH was the dominant photooxidant during the photocatalytic process. The reuse evaluation of the fibers indicated that their photocatalytic activity had good stability.     

Ce/TiO2/g-C3N4异质结的制备及光催化降解PFOA反应机制

采用溶胶凝胶-超声混合法制备了铈/二氧化钛/石墨相氮化碳（Ce/TiO₂/g-C₃N₄）异质结催化剂，通过透射电子显微镜（TEM）、X-射线粉末衍射仪（XRD）、傅里叶变换红外光谱仪（FTIR）和紫外-可见分光光度计（UV-Vis）等表征了复合材料的结构、晶相、活性基团和光吸收性能，并考察了可见光下该催化剂对模拟全氟辛酸（PFOA）废水的降解效果.结果表明，Ce/TiO₂/g-C₃N₄分散性好，粒径小于20 nm，金属Ce的掺入及TiO₂/g-C₃N₄异质结的生成，有效抑制了光生电子和空穴对的复合，使复合光催化剂禁带宽度减小，光吸收范围增大，光催化性能得到明显提升.在pH值为2，PFOA浓度为4 mg·L^-1，催化剂投加量为1 g·L^-1的条件下，可见光照射180 min后，可降解94.4%的PFOA，脱氟率为38.6%.降解过程符合准一级反应动力学，速率常数为0.522 h^-1.通过HPLC-MS分析降解产物，同时结合氟元素物料平衡的计算结果，认为降解机制主要是以阴离子形式存在的PFOA吸附至表面带有大量正电荷的催化剂表面后，在光生空穴和活性自由基的作用下，以自由基机理逐步脱去CF₂生成短链的PFCAs，同时生成氟离子.     

In_2TiO_5纳米带的静电纺丝法制备及光催化性能

以酞酸丁酯(Ti(OC_4H_9)_4)、硝酸铟(In(NO3)3)和聚乙烯吡咯烷酮(PVP-K30)为原料,采用静电纺丝技术制备了In_2TiO_5纳米带.利用X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外-可见漫反射光谱(UV-vis DRS)和氮气吸附-脱附等温线(BET)等技术对样品进行了表征.考察了In_2TiO_5纳米带在光催化降解罗丹明B(RhB)、甲基橙(MO)、亚甲基蓝(MB)和左氧氟沙星(LEV)过程中的应用性能,研究了不同离子型物质、溶液的pH和MB起始浓度对In_2TiO_5纳米带光催化活性的影响.结果表明:In_2TiO_5纳米带具有正交晶系结构,禁带宽度为3.47 eV,比表面积为20.71 m~2·g~(-1),可应用于4种不同离子型物质的光催化降解,发现光催化效果与被降解物质的表面带电性质有关.在紫外光照射下,90 min,对MB的降解率达98.1%,其降解过程服从一级动力学模型.     

Solar photocatalytic decomposition of two azo dyes on multi-walled carbon nanotubes (MWCNTs)/TiO2 composites

Multi-walled carbon nanotubes (MWCNTs)/TiO₂ composite photocatalysts with high photoactivity were prepared by sol-gel process and further characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), and UV-vis absorption spectra. Compared to pure TiO₂, the combination of MWCNTs with titania could cause a significant absorption shift toward the visible region. The photocatalytic performances of the MWCNTs/TiO₂ composite catalysts were evaluated for the decomposition of Reactive light yellow K-6G (K-6G) and Mordant black 7 (MB 7) azo dyes solution under solar light irradiation. The results showed that the addition of MWCNTs enhanced the adsorption and photocatalytic activity of TiO₂ for the degradation of azo dyes K-6G and MB 7. The effect of MWCNTs content, catalyst dosage, pH, and initial dye concentration were examined as operational parameters. The kinetics of photocatalytic degradation of two dyes was found to follow a pseudo-first-order rate law. The photocatalyst was used for seven cycles with photocatalytic degradation efficiency still higher than 98%. A plausible mechanism is also proposed and discussed on the basis of experimental results.