TiO2光催化氧化水中有机污染物进展

TiO2-水体系在紫外光照射下,在TiO2表面产生氧化能力很强的OH.自由基和超氧离子O2-,利用这一特性处理水中有机污染物得到很多环境工作者的密切关注.作者对TiO2光催化的影响因素、光电催化和太阳能利用等方面的研究与应用进展作了综合评述.     

半导体二氧化钛光催化氧化的研究进展

介绍了二氧化钛光催化氧化的基本原理,分析了光催化氧化的影响因素。阐述了光催化剂的固定方法及降解有机污染物的现状及发展方向,并提出了光催化氧化技术未来的发展趋势。     

金属离子掺杂对TiO2光催化性能的影响研究

锐钛矿型的TiO2具有光催化性能,在其制备过程中掺入杂质离子是改善其光催化性能的重要方法.采用不同的掺杂将会不同程度的改善其光催化活性.阐述了碱金属离子、过渡金属离子、贵金属离子、稀土离子等金属离子掺杂纳米TiO2光催化性能的影响.     

纳米TiO2光催化氧化机理及研究进展

本文探讨了TiO2光催化氧化机理及影响催化反应的因素，综述了在降解有机染料、净化空气和杀菌方面的研究进展。     

Hydrodynamics,mass transfer,and photocatalytic phenol selective oxidation reaction kinetics in a fixed TiO2 microreactor

Photocatalytic phenol dissociation was studied in a microreactor, with a TiO₂ layer immobilized on the reactor inner walls. Experiments were conducted for various residence times, initial concentrations, pH values, and UV light irradiation intensities. The intermediates and products (catechol, hydroquinone, and resorcinol) were quantitatively investigated to determine the predominant reaction pathways for the investigated anatase catalyst. A three‐dimensional mathematical model was used to simulate the heterogeneous photocatalysis reaction conditions with Langmuir–Hinshelwood mechanism, considering the adsorption/desorption thermodynamic equilibria, and for kinetic parameter estimation via regression analysis. The effectiveness factor, Thiele modulus, and the correction function were calculated to determine the pore diffusion effects. The value of pH had the dramatic effect of lowering the reaction rate due to the competitive adsorption of hydroxide ions and protons on the catalyst surface. A phenol conversion of 79.5% was achieved at the residence time of 7.22 min, but without total mineralization. © 2014 American Institute of Chemical Engineers AIChE J, 61: 572–581, 2015     

强化TiO2膜光催化性能的研究进展

概述了TiO2膜光催化机理,在光催化技术理论的基础上,根据TiO2膜的最新研究发展,重点介绍了目前TiO2膜光催化效率提高和光催化剂改良的新技术,对影响TiO2膜光催化性的因素进行了总结归纳。     

强化TiO_2膜光催化性能的研究进展

概述了TiO2膜光催化机理,在光催化技术理论的基础上,根据TiO2膜的最新研究发展,重点介绍了目前TiO2膜光催化效率提高和光催化剂改良的新技术,对影响TiO2膜光催化性的因素进行了总结归纳。     

TiO_2光催化氧化处理废水的研究概况

TiO2光催化氧化法降解废水是目前废水处理方面的热点,为彻底解决废水处理问题提供了新的手段。综述了TiO2光催化氧化降解废水的反应机理、影响因素及提高光催化效率的途径。同时,指出了光催化降解废水技术需要进一步解决的问题。     

Dynamic processes on vanadium phosphorous oxides for selective alkane oxidation

The use of complementary physicochemical tools (XRD, Raman spectroscopy, XPS, ³¹P NMR, and electron microscopy techniques), sometimes used in in situ conditions has allowed to evidence the dynamic processes occurring during the oxidation of light alkanes on the vanadium phosphorus oxide (VPO) system. The transformations of the VPO system in the course of the oxidation of n-butane to maleic anhydride and of the oxidation of propane to acrylic acid are contrasted in connection with the evolution of the catalytic performances.     

Effect of surface hydroxyl groups of pure TiO2 and modified TiO2 on the photocatalytic oxidation of aqueous cyanide

It is still debatable whether the photocatalytic oxidation of cyanide proceeds via hydroxyl radicals or by photogenerated holes. We synthesized pure TiO₂ catalysts via sol-gel process. In order to elucidate the oxidation pathway of cyanide, we used hydroxyl radical scavengers and controlled the concentration of surface hydroxyl group on the catalysts adopting fluoride-exchange. The degree of fluoride-exchange of TiO₂ catalysts was independent of the pH of suspension. We also adopted a polyoxometalate, tungstophosphoric acid (TPA, H₃PW₁₂O₄₀) which is well known for high charge transfer ability and hydrolytic stability. TPA-modified TiO₂ catalysts were prepared with sol-gel technique to overcome the high solubility of TPA in water. As another attempt for the insoluble TPA, proton of TPA supported on TiO₂ catalysts was replaced by cesium ion to form Cs-TPA/TiO₂ catalysts. Both attempts were successful in immobilizing TPA on TiO₂ catalysts. Commercially available TiO₂ catalysts such as P25 from Degussa AG were also used as catalysts. XRD analysis revealed that pure TiO₂ and TPA-modified TiO₂ catalysts prepared by sol-gel process were composed of well-developed anatase crystalline structure. In the presence of hydroxyl radical scavengers, the photoactivity of TPA-modified TiO₂ catalysts was retarded much less than that of pure TiO₂ catalysts. The concentration of surface hydroxyl group was effectively suppressed by the fluoride-exchange causing the decrease of the activity of the catalysts. In the case of fluoride-exchanged catalysts, the drop in activity was obvious for the pure TiO₂ catalysts in the presence of iodide as a hydroxyl radical scavenger suggesting that indirect oxidation via hydroxyl radicals was the preferential reaction pathway. For the TPA-modified TiO₂ catalysts, meanwhile, the diminution was such a small extent suggesting that direct oxidation by photogenerated holes was the main reaction pathway. The activity arising from TPA in the catalysts was due to the Keggin structured anion (PW₁₂O ₄₀ ^3- ) which acted as an electron relay with the aid of dissolved oxygen in the reaction system. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

TiO2光催化氧化处理敌敌畏生产废水研究

采用TiO2光催化氧化法处理敌敌畏生产废水,试验结果表明,光催化5 h后,对废水中污染物的去除率不高,废水的COD去除率为24.1%,无机磷生成率为36.7%,TOC的去除率为18.0%,但是BOD5与COD的比值则由0.18提高到0.68,废水可生化性得到大大改善,为后续生化处理创造了有利条件.     

Synergic effect of cation doping and phase composition on the photocatalytic performance of TiO2 under visible light

The synergic effect of cation doping and phase composition for the further improvement of the photocatalytic activity of TiO₂ under visible light is reported for the first time. Fe^3 + and Sn^4 + co-doped TiO₂ with optimized phase composition were synthesized through a simple soft-chemical solution method. The visible-light-driven photocatalytic activity of Fe^3 + and Sn^4 + co-doped TiO₂ was 5 times of that of Evonik P25 TiO₂ using degradation of methylene blue as model reaction. The synthesized photocatalysts were characterized by powder X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, ¹¹⁹Sn Mössbauer spectroscopy, and X-ray absorption fine structure spectroscopy. It is indicated that Sn^4 + doping can facilitate the phase transition from anatase to rutile. The different ratios of anatase and rutile can be achieved by tuning the amount of Sn^4 + doped into the lattice. Furthermore, the doping of Sn^4 + into TiO₂ lattice can stabilize the phase composition when Fe^3 + is co-doped. In the Fe^3 + and Sn^4 + co-doped TiO₂, Sn^4 + is mainly used to tune and stabilize the phase composition of TiO₂ and Fe^3 + acts as a doping cation to narrow the band gap of TiO₂. Both band gap and phase composition of TiO₂ can be tuned effectively by the simultaneous introduction of Fe^3 + and Sn^4 +. The synergic effect of optimized phase composition (anatase/rutile = 25/75) and narrowed band gap should be the two main reasons for the promoted photocatalytic activity of TiO₂ under visible light.     

二氧化钛的沉积-沉淀水热制备及其光催化性能

以硫酸钛为原料,采用沉积-沉淀水热法制得了TiO2粉体光催化剂。以光催化降解活性艳红X-3B作为模型反应,考察了所制得的TiO2粉体的光催化性能。发现140℃沉积-沉淀水热反应20 h、600℃焙烧制得的TiO2粉体光催化活性明显高于Degussa P25 TiO2,并且该TiO2粉体光催化剂沉降性好,易分离。     

Ce掺杂TiO_2纳米粒子的制备及其光催化活性研究

以钛酸四丁酯为原料,采用溶胶-凝胶法制备了纯的和掺杂铈的TiO2纳米粒子,并利用XRD和UV-VIS对其进行表征,且在紫外光下,以甲基橙的光催化降解为模型反应,考察了TiO2纳米粒子的光催化活性和不同Ce掺杂量对光催化活性的影响。结果表明,Ce的掺杂抑制了锐钛矿晶粒的生长,并使TiO2纳米粒子的光谱响应范围拓展到可见光区,掺杂Ce的摩尔分数为0.05%时,TiO2纳米粒子具有最佳的光催化活性。     

Kinetics of the photocatalytic total oxidation of different alkanes and alkenes on TiO2 powder

Although photocatalyzed total oxidation reaction of hydrocarbon species has been discussed in the literature, most of these studies were performed to obtain an appropriate reaction mechanism. Studies on the kinetics of this type of reaction are rare. Using titanium dioxide as the photo catalyst, the kinetics of the total oxidation of methane, ethane, ethene, as well as propene, have been investigated using a continuous‐stirred tank reactor. In the experiments, the hydrocarbon concentrations, the oxygen concentration, and the irradiation intensity were varied. The results obtained are evaluated on the basis of a kinetic model to derive rate equations which can be used for reactor design.     

The effect of magnetized water on TiO2 based varistors

The effect of magnetized water on TiO₂ based varistors was investigated. The results of the electrical behavior reveal that the water magnetized at 0.2 T yielded lower varistor voltage and the water magnetized at 0.3 T yielded higher varistor voltage compared to non-magnetized deionized water. The XRD and EDAX results show that the main polycrystalline phase is rutile TiO₂ surrounded by the second phase composed of Ce, Si, and Ti. The SEM micrographs suggest more preferable microstructure may be obtained by using the 0.2 T magnetized water. The role of the magnetized water was examined by the perturbation of the gas-to-liquid interface that changes inter-particle forces, and consequently leads to higher electrostatic stabilization of the slurries.     

铈硅包覆金红石型钛白粉及光催化性研究

采用溶胶-凝胶法,制备了铈硅包覆金红石型钛白粉,通过正交实验考察了浆液浓度、分散剂用量和两种包膜剂含量对铈硅包覆金红石型钛白粉性能的影响。采用Nano-ZS型粒度仪、扫描电镜（SEM）、透射电镜（TEM）和能谱（EDS）等测试手段,对金红石型钛白粉的Zeta电位、表面形貌和元素进行了表征。结果表明：在水浴温度为80 ℃左右、转速为600 r/min、浆液质量浓度为400 g/L、分散剂质量分数为0.1%、二氧化铈质量分数为3%、二氧化硅质量分数为4%的条件下,金红石型钛白粉表面包覆了两层均匀而致密的二氧化硅和二氧化铈膜;罗丹明B光催化降解实验证实,铈硅包覆明显改善了金红石型钛白粉的光催化屏蔽性。     

TiO_2光催化还原去除饮用水中硝酸盐的实验研究

在间歇式反应器中,以TiO2为催化剂,进行了光催化还原去除饮用水中硝酸盐的实验,考察了空穴清除剂种类、甲酸用量、催化剂用量和硝酸盐浓度对去除硝酸盐效率的影响。结果表明,在TiO2作用下,硝酸盐能被有效地还原去除,去除率可达35.16%;与甲醇、甲酸钠和EDTA相比,甲酸作空穴清除剂时硝酸盐去除效果最佳;甲酸和硝酸盐的浓度对光催化反应的影响显著,催化剂最佳用量为100 mg。探讨了反应机理,认为光催化还原硝酸盐是一分步反应。     

Coupling copper and hydrogenated TiO2 to bare TiO2 structures for improved photocatalytic performance

Coupling of metals and hydrogenated TiO₂ (HT) to bare TiO₂ may improve synergistically the photocatalytic activity of TiO₂ for pollutant decomposition. Herein, we address this issue by investigating the photocatalytic performances of Cu‐loaded HT (CuHT)/bare TiO₂ (CuHTT) heterojunction nanocomposites for the degradation of harmful n‐butanol under simulated solar light illumination. CuHTT with a CuHT‐to‐TiO₂ composition ratio of 0.1 showed a photocatalytic efficiency exceeding those of four reference photocatalysts, exhibiting the advantages of improved visible light absorption efficiency, charge carrier separation, and adsorption capacity. Increasing the CuHT‐to‐TiO₂ ratio from 0.01 to 0.1 improved the photocatalytic efficiency of CuHTT, whereas a further increase to 0.9 resulted in a decreased photocatalytic efficiency. Moreover, the photocatalytic efficiency improved as relative humidity increased from 20% to 70%, decreasing upon its further increase to 95%. The efficiencies of n‐butanol to CO₂ conversion over CuHTT were lower than the corresponding decomposition efficiencies. Incompletely oxidized CO and three organic vapors (butanal, propanal, and 1‐propanol) were determined as major intermediates. A possible mechanism for CuHTT‐catalyzed photodegradation under simulated solar illumination was proposed.     

Photocatalysed selective oxidation of cyclohexane to benzene on MoOx/TiO2

Heterogeneous oxidative dehydrogenation of cyclohexane to benzene was found to occur under photocatalytic conditions on MoO_x/TiO₂. Initial cyclohexane conversion of 15% and maximum selectivity to benzene of 65% were achieved at 308 K on 8 wt.% MoO_x/TiO₂ under irradiation with a continuous flow reactor. The main by-product was carbon dioxide. Catalyst deactivation was observed. Titania exhibited high activity of total oxidation to carbon dioxide but was not selective for conversion to benzene. Polymolybdate species seem to be responsible for changing the selectivity of titania, favouring the formation of benzene. Nevertheless, when supported on α- or γ-alumina they promote only the formation of carbon dioxide.