Effect of adsorbents coated with titanium dioxide on the photocatalytic degradation of propoxur

Photocatalytic oxidation of pesticides in aqueous media irradiated by UV light is a rapidly growing field of research. Therefore, the treatment technology for degradation of propoxur (an insecticide) using titanium dioxide coated on the supports such as activated carbon, zeolite, brick, quartz and glass beads, was performed in this research. Results show that GAC/TiO2 is the best complexing agent for oxidizing propoxur because of its adsorption properities. The others follow the sequence: plain TiO2 > glass beads > zeolite > brick > quartz. The degradation rate of propoxur with plain TiO2 is higher than that with TiO2/GAC complexing agent. But the mineralization rate of propoxur with plain TiO2 is lower than that with TiO2/GAC complexing agent. However, it can be concluded that using GAC as the support can improve the photocatalytic efficiency.     

Photocatalytic degradation of p-nitrophenol on nanometer size titanium dioxide surface modified with 5-sulfosalicylic acid

The surface of nanometer size TiO(2) was simply and fast modified by chemical adsorption in saturated solution of 5-sulfosalicylic acid. After surface modification, a stable, yellow surface complex was formed quickly, the wavelength response range of TiO(2) was expanded, it has obvious absorption in the region from 320 to 450 nm; the adsorption efficiency of p-nitrophenol (PNP) by TiO(2) was enhanced from 42% to 84%. The photocatalytic activity was tested on the degradation of PNP. The influences of catalyst and its dosage, pH value, and PNP concentration on the degradation were investigated. On optimal photodegradation conditions, including initial pH 4.0, PNP 5 mg l(-1), catalyst 100 mg, irradiation time 120 min with 160 W high-pressure mercury lamp, the degradation efficiency of PNP was increased from 40% to 88% after surface modification. Surface modification led not only to an increase in the light utilization, but also improved the surface coverage of PNP in comparison with the pure TiO(2). Both of these factors are crucial for the photocatalytic activity of heterogeneous photocatalysis, especially for photodegradation of benzenoid pollutants.     

Reducing degradation of azo dye by zero-valent iron in aqueous solution

The reducing degradation kinetics of five azo dyes, Acid orange II, Acid orange IV, Acid orange GG, Acid red 3B and Orange I, by zero-valent iron powder in aqueous solution were studied. It showed that the degradation is a two-step reaction, with the first step being reversible. Solution acidity and iron surface area are the factors greatly influencing the degradation rates, and with increasing of acidity and iron surface area, the degradation rates increase.     

Fe/沸石对偶氮染料活性黑5的催化降解

为了对水中偶氮染料活性黑5的去除进行研究,通过沉淀法在沸石上负载Fe2O3制备出一种具有较高催化活性的催化剂,采用X-射线衍射仪（XRD）和扫描电镜（SEM）对其结构和形貌进行了表征,并利用Fe/沸石进行非均相Fenton反应处理模拟染料废水的研究,考察不同操作条件对活性黑5降解效果的影响。实验结果表明,活性黑5的脱色率随催化剂投加量的升高而升高,但是随着染料初始浓度的升高而降低。H2O2浓度和pH的升高均使得活性黑5的脱色率先升高而后降低。在最佳pH为3,最佳H2O2浓度为200 mg·L-1的条件下,活性黑5的脱色率达到最大,为95.7%。通过对催化剂Fe/沸石稳定性研究,发现经5次连续循环使用后,活性黑5脱色率仍然可保持在94%以上,说明该催化剂具有良好的循环使用性能。     

Light-induced degradation of perfluorocarboxylic acids in the presence of titanium dioxide

The UV-photon-induced degradation of heptafluorobutanoic acid was investigated in acidic aqueous solutions in the presence of titanium dioxide. Heptafluorobutanoic acid could be degraded with this photocatalyst in a light-induced reaction generating carbon dioxide and fluoride anions. Carbon dioxide evolution in a significant amount occurred only in the presence of molecular oxygen and the photocatalyst. The light-induced degradation of trifluoroacetic acid, pentafluoropropanoic acid, nonafluorobutanoic acid, pentadecafluorooctanoic acid, nonafluorobutanesulfonic acid, and heptadecafluorooctanesulfonic acid in the presence of titanium dioxide was also studied. The perfluorocarboxylic acids under investigation are degraded to generate CO(2) and fluoride anions while both perfluorinated sulfonic acids are persistent under the experimental conditions employed in this study. For all compounds photonic efficiencies of the mineralization reaction were estimated to be smaller than 1x10(-5). To increase the photocatalytic activity mixed systems containing homogeneous phosphotungstic acid and heterogeneous titanium dioxide catalysts were also investigated. In the mixtures of these two photocatalysts, the formation rate of CO(2) increased with illumination time.     

Application of titanium dioxide immobilized on a cellulosic material for the photocatalytic degradation of Acid Black 24 dye in a continuous flow cascade reactor

Environmental Science and Pollution Research - The aim of this work is the study of the photocatalytic degradation of Acid Black 24 dye (AB24), in a continuous flow cascade reactor, using titanium...     

Photoelectrocatalytic degradation of 4-chlorophenol and oxalic acid on titanium dioxide electrodes

Photocatalytically active thin TiO(2) films were produced by spin-coating or dip-coating an alkoxy precursor onto a transparent conducting electrode substrate and by thermal oxidation of titanium metal. The thin films were used to study the photoelectrocatalytic or photoelectrochemical degradation of oxalic acid and 4-chlorophenol (4-CP) under near UV (monochromatic, 365 nm) light irradiation. Degradation was monitored by a variety of methods. In the course of oxalic acid degradation, CO(2) formation accounted for up to 100% of the total organic carbon degradation for medium starting concentrations; for the degradation of 4-CP, less CO(2) was detected due to the higher number of oxidation steps, i.e. intermediates. Incident-photon-to-current conversion efficiency, educt degradation and product formation as well as Faradaic efficiencies were calculated for the degradation experiments. Quantum yields and Faradaic efficiencies were found to be strongly dependent on concentration, with maximum values (quantum yield) around 1 for the highest concentrations of oxalic acid.     

铁屑还原及微波铁屑诱导氧化降解偶氮染料历程的研究

研究了铁屑内电解还原及微波诱导氧化降解偶氮染料的反应历程,采用胶束毛细管电泳法对跟踪了2种不同降解方法下的中间产物变化.实验结果表明,染料的偶氮键(-N=N-)易被铁屑内电解还原,反应过程中有中间产物苯胺生成.微波诱导铁屑氧化偶氮染料的反应过程中未检测到其他芳环类化合物生成,在微波辐照2 min时脱色率已达90%以上,TOC去除率也高达78%,矿化较为彻底;在微波辐照铁屑诱导氧化降解污染物的同时,也使铁屑自身得以活化再生,提高了铁屑的内电解能力.     

天然沸石负载TiO2光催化降解敌敌畏和对硫磷

以钛酸丁酯为原料,以天然沸石作载体负载TiO2制备光催化剂;并采用高压汞灯为光源,用负载型TiO2光催化降解敌敌畏和对硫磷.结果表明,浓度为1.2×10-4mol/L的农药光照2 h左右可完全被光催化氧化为PO3-4.同时,还研究了合成光催化剂的处理温度、溶液的初始pH值、过氧化氢浓度等对负载TiO2光催化降解的影响.     

Photocatalytic degradation of an azo dye using N-doped NaTaO3 synthesized by one-step hydrothermal process

N-doped NaTaO₃ compounds (NaTaO_3−xN_x) with nano-cubic morphology were successfully synthesized by one-step hydrothermal method and Methyl Orange (MO) was used as a model dye to evaluate their photocatalytic efficiency under visible-light irradiation. The as-prepared NaTaO_3−xN_x samples were characterized by various techniques, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectra and GC-MS. The results indicate that NaTaO_3−xN_x displays a pure perovskite structure when the synthesis temperature is higher than 180 °C. Moreover, as observed by SEM images, the particles of resultant NaTaO_3−xN_x show cubic morphology with the edge length of 200-500 nm, which can be easily removed by filtration after photocatalytic reaction. Doping of N increases the photocatalytic activity of NaTaO₃, and NaTaO_2.953N_0.047 shows the highest visible-light photocatalytic activity for the degradation of MO. Based on the experiment results, a possible mechanism of the photocatalysis over NaTaO_3−xN_x and the photodegradation pathway of MO were proposed.     

电-生物耦合技术对偶氮染料的去除研究

酸性大红GR是一种较难生物降解的偶氮染料,采用一种电场和生物耦合的新型技术处理酸性大红GR模拟废水,并与单纯电化学法和好氧生物法进行试验对照。结果表明：反应6 h后,电化学法、好氧生物法、电-生物耦合技术对酸性大红GR的去除率分别达到15.7%、25.8%和71.2%,电-生物耦合技术能明显提高酸性大红GR的去除效果,起到强化生物处理的作用。在15 mA微电流条件下电-生物技术能克服50 mg/L酸性大红GR对好氧生物处理的抑制作用,为高浓度难降解染料废水的生物强化处理提供了可能。     

Photodegradation of an azo dye of the textile industry

An advanced oxidation treatment, UV/H2O2, was applied to an azo dye, Hispamin Black CA, widely used in the Peruvian textile industry. Rates of color removal and degradation of the dye have been evaluated. A strongly absorbing solution was completely decolorized after 35 min of treatment, and after 60 min an 82% reduction of the total organic carbon (TOC) was obtained. It has been found that the degradation rate increased until an optimum value, beyond which the reagent exerted an inhibitory effect. The degradation rate was also function of pH.     

改性TiO2对X-3B的光催化性能及其降解动力学研究

以活性艳红X-3B为模型化合物,比较了改性前后TiO2光催化活性的变化.试验结果表明,通过改性大大提高了TiO2的光催化活性,Fe3+和Ag+的掺杂量均有一个最佳值,在试验的掺杂范围内Fe3+和Ag+的最佳掺杂量分别是0.1%和0.05%.对其宏观降解反应动力学的研究表明,X-3B在TiO2、Fe3++TiO2和Ag++TiO2 3种催化剂上的光催化降解动力学均能很好地符合Langmiur-Hinshelwood动力学模型.其表观反应速率常数的大小顺序依次是Ag++TiO2＞Fe3++TiO2＞TiO2;吸附平衡常数则是Fe3++TiO2和Ag++TiO2两者基本相等,两者均比纯TiO2大2～3倍.     

掺硫改性TiO2对活性艳红X-3B的光催化降解性能研究

以硫脲为硫的源物质,以钛酸四丁酯为TiO2的前驱体,采用溶胶-凝胶法制备了掺硫改性TiO2光催化剂。以活性艳红X-3B为目标污染物,研究了该催化剂的光催化降解性能,对硫掺杂量、催化剂焙烧温度、溶液pH值以及催化剂添加量等影响因素进行了研究,并采用XRD分析手法对光催化剂进行表征。结果表明,经掺硫改性后的TiO2的催化活性有了很大提高,且硫的掺杂有一个最佳值,即Ti∶S的摩尔比为1∶1。经掺硫改性的TiO2在可见光区具备一定的催化活性, 180 min内对活性艳红X-3B的去除率可达35.1%,且在紫外光区的催化活性优于纯TiO2。     

Photocatalytic degradation of amoxicillin from aqueous solutions by titanium dioxide nanoparticles loaded on graphene oxide

Environmental Science and Pollution Research - The photocatalytic degradation of amoxicillin (AMX) by titanium dioxide nanoparticles loaded on graphene oxide (GO/TiO2) was evaluated under UV light....     

Photocatalytic degradation of an organophosphorus pesticide phosalone in aqueous suspensions of titanium dioxide

The present work deals with photocatalytic degradation of an organophosphorus pesticide, phosalone, in water in the presence of TiO2 particles under UV light illumination (1000 W). The influence of the basic photocatalytic parameters such as pH of the solution, amount of TiO2, irradiation time, stirring rate, and distance from UV source, on the photodegradation efficiency of phosalone was investigated. The degradation rate of phosalone was not high when the photolysis was carried out in the absence of TiO2 and it was negligible in the absence of UV light. The half-life (DT50) of a 20 ppm aqueous solution of phosalone was 15 min in optimized conditions. The plot of lnC (phosalone) vs. time was linear, suggesting first order reaction (K=0.0532 min(-1)). The half-life time of photomineralization in the concentration range of 7.5-20 ppm was 13.02 min. The efficiency of the method was also determined by measuring the reduction of Chemical Oxygen Demand (COD). During the mineralization under optimized conditions, COD decreased by more than 45% at irradiation time of 15 min. The photodegradation of phosalone was enhanced by addition of proper amount of hydrogen peroxide (150 ppm).     

纳米TiO2改性可见光催化降解有机物研究进展

光催化降解水中有机污染物是一项颇有发展前途的废水处理技术.目前主要的研究工作由紫外光逐步向可见光催化方向发展,使这项技术向实用性又迈进了一步.系统介绍了纳米TiO2的光催化降解有机污染物的原理,光催化处理水的现状,并从离子掺杂、表面光敏化和分子筛负载几个方面综述了可见光化的研究现状和发展方向.     

纳米TiO2改性可见光催化降解有机物研究进展

光催化降解水中有机污染物是一项颇有发展前途的废水处理技术.目前主要的研究工作由紫外光逐步向可见光催化方向发展,使这项技术向实用性又迈进了一步.系统介绍了纳米TiO2的光催化降解有机污染物的原理,光催化处理水的现状,并从离子掺杂、表面光敏化和分子筛负载几个方面综述了可见光化的研究现状和发展方向.     

Comparison of azo dye degradation efficiency using UV/single semiconductor and UV/coupled semiconductor systems

This study examined degradation of azo dyes using photocatalytic oxidation (UV/semiconductor). The model substrates employed in this work were Procion Red MX-5B and Amaranth, while the photocatalysts were TiO2, ZnO, and SnO2. UV-Vis spectrum analysis demonstrated that the band gap energies of TiO2, ZnO, and SnO2 were 3.17, 2.92, and 4.13 eV, respectively. The band gap energy of SnO2 is insufficient to initiate photocatalytic reaction after UV irradiation (365 nm). The reaction rate constants fit a first-order reaction model and the reaction rate constant of Procion Red MX-5B for TiO2+SnO2 (0.31 h-1) is larger than that of TiO2 (0.24 h-1) and SnO2 at pH 10. The difference between the conduction bands of SnO2 and TiO2 enables the former to act as a sink for the photogenerated electrons. Most of the reaction rate constants had higher values at pH 10 than pH 7, and thus the OH attack could be assumed to represent the main reaction in this investigation. The quantities of sulfate and chloride ions released are below stoichiometry during the degradation. Owing to the sulfonate groups of Amaranth exceeding Procion Red MX-5B, Amaranth had larger electrostatic attraction than Procion Red MX-5B with the surface of ZnO, and also had higher adsorption percentage than Procion Red MX-5B on the surface of ZnO. The trend of adsorption is consistent with the reaction rate constant at pH 7, namely Amaranth>Procion Red MX-5B. The sulfate dissociation rate constant of Amaranth in UV/ZnO at pH 7 (0.49 h-1) approaches the overall rate constant (0.53 h-1); therefore, the first step involved in Amaranth can be suggested to the cleavage of the bonds of the C-S in Amaranth, causing sulfate ion formation.     

Exploration of the key functional strains from an azo dye degradation microbial community by DGGE and high-throughput sequencing technology

Environmental Science and Pollution Research - This study investigated a previously developed thermophilic microbial community with the ability to effectively degrade azo dyes. To identify the key...