溶胶负载法制备的Au/AC催化分解低浓度臭氧

采用溶胶负载法制备了高分散的活性炭载纳米Au(Au/AC),研究了其在室温下对低浓度臭氧的催化分解性能,并用N<,2>吸附-脱附、扫描电镜、X射线光电子能谱等手段对反应前后的催化剂进行了表征.结果表明,与普通的传导加热方式相比,微波加热方式所制备的活性炭载Au颗粒的分布更均匀、尺寸更小,具有更高的催化臭氧分解性能.Au前驱体溶液pH值对Au/AC催化剂的臭氧分解性能有显著影响,以pH=8最佳.降低空速而延长臭氧与催化剂的接触时间可以提高催化剂对臭氧的分解性能.空速120000 h-1条件下.催化剂处理约1 g臭氧后,臭氧去除率降低至78.6%:而60 000 h-1条件下处理1.25 g臭氧后,臭氧的去除率仍保持在93.3%.Au/AC催化剂在分解臭氧后,表面部分C被氧化而含氧量增加,但比表面积和孔容等变化不大,主要通过负载Au颗粒本身催化分解臭氧.     

室温催化分解空气中臭氧污染物

臭氧污染是我国目前面临的突出环境问题,臭氧及其室内反应形成的二次污染物危害着人体健康。室温催化分解是避免空气臭氧污染的有效方法,本文首先总结了碳、沸石、贵金属与过渡金属氧化物等材料的臭氧催化分解性能;然后聚焦锰氧化物,比较分析了不同锰氧化物的臭氧催化活性,阐述了锰氧化物催化分解臭氧机理的研究进展。水蒸气导致的失活是当前臭氧催化剂研发面临的主要挑战,对臭氧催化分解与失活机理的深入认识是指导高效抗湿臭氧催化材料研发的关键。     

TiO2晶型对Au/TiO2上光催化分解臭氧的影响

以不同晶型TiO2为载体,采用沉积-沉淀法制备了Au/TiO2光催化剂,并用紫外-可见漫反射光谱、X射线光电子能谱(XPS)和表面光电压谱(SPS)等手段进行了催化剂表征,详细考察了Ti O2晶型对Au/TiO2光催化分解臭氧活性的影响.结果表明,光催化分解臭氧的活性顺序为Au/P25>Au/Anatase>Au/Rutile,这与不同的单一Ti O2对光催化臭氧分解的活性顺序是一致的.但在TiO2上沉积金后,其对光催化臭氧的分解活性有了显著的提高.由催化剂的Au4fXPS分析发现,不同晶型Ti O2上的电荷向金簇迁移的能力有明显差异,加之载体本身对光催化臭氧分解活性不同,两者协同作用导致负载金催化剂光催化分解臭氧活性的不同.SPS信号强度与催化剂光催化活性有很好的对应关系,SPS信号越强,光生电子和空穴分离效率越高,光催化活性越好.     

负载型过渡金属氧化物催化剂催化分解臭氧性能研究

通过浸渍法制备了γ-Al_2O_3负载镍、锰、钴等不同金属氧化物催化剂,在25℃、200000 mL/(gcat·h)的空速条件下,研究了其臭氧催化分解性能。结果表明,10%NiO/γ-Al_2O_3催化剂催化活性最佳,20 h内臭氧转化率高于96%。借助XRD、XPS、TEM、SEM-EDS、H2-TPR等表征手段,揭示出在NiO/γ-Al_2O_3催化剂表面形成的镍铝尖晶石结构可能是其优良臭氧分解性能的内在原因。此外,揭示出在不同过渡金属氧化物负载型催化剂上臭氧分解机理不同,相关研究为镍、锰等过渡金属氧化物催化剂催化分解臭氧的反应机理提供了新思路,并为开发高效的臭氧分解催化剂提供了指导。     

在空气中杀菌灯产生臭氧及其催化分解的研究

用流动型反应装置,对8W杀菌灯(主波长λ=253.7nm)辐照空气时产生的臭氧进行了研究.发现在一定条件下当空气与杀菌灯接触大约7s时,就有超出0.33μg/L的臭氧产生.随着空气流速的减小,产生的臭氧的量随之变大.采用臭氧分解催化剂对臭氧的消除进行了研究,当体积空速小于1.1×10⁵h^-1时,臭氧可以降解到安全范围.     

堇青石蜂窝陶瓷负载锰氧化物催化分解臭氧性能

为了提高臭氧分解催化剂的实际应用能力,通过采用过渡金属锰氧化物为原料与铝胶混合涂覆到堇青石蜂窝陶瓷载体表面,制备了不同锰氧化物负载的整体式催化剂。 然后在常温常压下考察了整体式催化剂分解臭氧的性能。 通过X射线衍射(XRD)、扫描电子显微镜(SEM)、拉曼(Raman)光谱、X射线光电子能谱仪(XPS)、BET比表面积法和程序升温还原技术(H₂-TPR)对催化剂进行了表征。 研究结果表明,不同锰氧化物催化剂的活性按以下顺序排列:氧化锰八面体分子筛(OMS-2)＞MnO₂＞Mn₂O₃＞Mn₃O₄＞MnO。 相比其它锰氧化物,OMS-2负载的整体式催化剂对臭氧的反应活性最高,这可能归因于OMS-2具有较大的比表面积和较好的还原性能,从而有利于表面氧空位的生成和参与臭氧分解反应。 研究结果为提高堇青石蜂窝陶瓷负载型整体式催化剂应用于臭氧分解的性能提供了理论依据。     

非均相催化臭氧氧化反应机制

臭氧催化氧化作为高级氧化技术是目前水处理领域研究的热点,其中非均相臭氧催化氧化技术因其氧化能力强、降低臭氧投加量特别是能显著提高有机物矿化率等优点而备受关注。非均相催化臭氧氧化领域不断研究新的催化剂,但是其反应过程及机制更加复杂。催化臭氧氧化的性能很大程度上取决于催化剂及其表面性质。污染物在催化剂表面形成络合物,或者臭氧在催化剂表面分解产生不同的含氧物种如表面氧原子、过氧化物和羟基自由基等。本文评述了非均相臭氧催化氧化反应中存在的多种机理,主要是自由基理论、氧空位理论、表面原子氧理论、表面络合物理论和臭氧直接氧化理论。催化剂表面的羟基基团是主要的催化活性中心,本文探讨了表面羟基基团催化反应机制,得出催化剂表面性质决定其表面活性位点的特性及含量,对诱导臭氧分解产生含氧活性物种起了关键作用;概述了催化剂改性后的结构形态、比表面积及其性能和作用机制;并讨论了非均相臭氧催化氧化反应催化剂未来的发展趋势,为催化臭氧氧化污水处理技术提供了理论参考。     

臭氧氧化优尼素红B-B染料废水及脱色动力学研究

研究了在鼓泡反应器中,臭氧氧化优尼素红B-B模拟染料废水在10~70℃范围内的脱色反应动力学.发现并解释了不同温度下出现的反应速率交叉现象,利用紫外可见分光光度法定量分析染料特征颜色(浓度)变化情况.结果表明,在不同温度下,表观脱色反应动力学都符合一级动力学规律,相关系数都达到了0.95以上.40℃下,反应速率常数为0.011 83 s~(-1),臭氧氧化脱色过程符合y=exp(0.521-0.014x+5.02×10~(-6)x~2)方程.随着温度的升高,臭氧在高温下氧化染料的反应速率小于臭氧的分解速率,低温时臭氧氧化的速率高于臭氧的分解速率,导致高温下氧化速率变慢.在40~50℃时,臭氧氧化优尼素红B-B染料废水脱色率最高,利用紫外可见分光光度法对氧化后废水进行分析,结果表明脱色率达到了99.5%.     

臭氧化物生成机理研究综述

以Criegee三步反应机理为核心对烯烃臭氧化反应中的臭氧化物生成机理进行了综述。论述了初级臭氧化物的生成与分解和臭氧化物生成过程的选择性和立体化学。讨论了烯烃结构和反应各步骤的选择性和立体化学的关系。     

问答栏

问:氧是怎样结成臭氧的?它和温度有没有关系?为什么?答:氧结合成臭氧,是利用电场或触媒,使分子的氧(O_2)分解为活泼性原子的氧(O),原子氧比较活泼,在离开电场或触媒时又互相结合成臭氧(O_3),温度加高或时间较久,这种臭氧是不安定的,它容易再分解为一分子氧(O_2)及一原子氧(O),原子氧又合成分子,故制臭氧的电场中温度不宜超过10O℃,(常     

大气臭氧化学研究进展

臭氧是大气化学中的核心物种。在平流层中,臭氧层可以吸收对生物有害的紫外辐射,对地球生命起保护伞作用。在对流层大气中,适量臭氧对清洁大气是有益的。但是,由于对流层中臭氧前体物排放量的增加,特别是在大城市,产生的高浓度臭氧会对大气环境造成严重污染,对人类、动植物和生态环境具有极大危害。臭氧的研究一般结合外场观测、实验室烟雾箱模拟和计算机数值模拟进行。深入开展大气臭氧化学研究,不仅有助于全面深入理解大气氧化过程以及全面掌握区域乃至全球大气自净能力,而且能为对流层污染控制提供科学依据和方案。本文总结了近年来有关臭氧化学的研究进展,论述了臭氧问题与人类当前面临的一些主要环境问题间的相互关系;重点综述了近年来有关南极臭氧空洞、中纬度地区臭氧低值和北极地区臭氧的损耗机理及其发展趋势;综述了臭氧与大气光化学和气溶胶间的耦合关系,并结合我国实际情况,提出了大气臭氧化学尚待深入开展研究的一些重要科学问题。     

Residual aqueous ozone determination by gas diffusion reverse flow injection analysis

A novel system based on reverse flow injection analysis with a gaseous diffusion step (GD-r-FIA) has been developed for the analysis of ozone. It includes an automatic microburet injection system. The ozone diffuses through a microporous membrane of polyvinylidene difluoride (PVDF) from the donor stream to the acceptor stream containing nitrite ions. The nitrite concentration in the acceptor solution decreases due to the ozone reduction reaction. In this way, a simple indirect measurement of the ozone concentration can be performed using the Griess–Ilosvay reaction for the nitrite ion. This correlates with the decrease in absorbance of the azoic dye formed with the ozone concentration in the donor stream. The system has been optimised by investigating the effect of the nitrite concentration in the acceptor stream on the diffusion flow. The optimum nitrite concentration was set at 0.250 ppm with a flow rate of 1.5 ml/min. The efficiency of the ozone diffusion through the membrane was only 4.4%. This affects the average sensitivity, which is low (0.0092±0.0012 AU/ppm), although the detection limit is similar to that obtained with other reported methods (0.03 ppm). The main advantage of the system reported here is that it has a linear range that is an order of magnitude broader than those observed for other GD-FIA systems. This is especially useful for continuous monitoring systems, since the residual ozone concentration is normally between 0.05 and 5.0 ppm. Additionally, using the reverse flow injection analysis (FIA) technique minimises chemical consumption and residue generation. Finally, the stability of the ozone solution and the repeatability and reproducibility of the method have been studied.     

Development of a new automatic ozone concentration control system

An automatic ozone control recorder was developed in order to perform more reproducible ozone tests and to facilitate ease of operation. It is based on the principle of the iodometric method, and is in good agreement with the counter current method and the coulometric method. This development has been found to simplify the operational procedure and to improve the reproducibility of ozone tests.     

Characteristics of Dielectric Barrier Discharge Ozone Synthesis for Different Pulse Modes

This paper features the pulse polarity effect on ozone generation efficiency by adjusting the applied voltage and the flow rate in a coaxial dielectric barrier discharge reactor. Results show that utilization of unipolar pulse has better performance when compared with the bipolar mode, but on the other hand, utilization of the positive pulse has slightly higher efficiency than that of negative mode. Meanwhile, changing the gas flow rate shows a minor effect on ozone generation. Utilization of bipolar pulse would decrease the breakdown voltage and ozone generation efficiency when compared with unipolar pulse while it would lead to higher ozone concentrations at fixed applied voltage. The maximum ozone yield reaches 186.9 g/kWh at 6 kV positive pulse with ozone concentration of 11.9 g/Nm³.     

Personal and atmospheric concentrations of ozone in southeastern hyogo prefecture, Japan

Twenty-one data sets composed of readings collected by atmospheric ozone monitors worn by individuals on their clothing and installed outside their home or office were collected using Ogawa passive ozone samplers in southeastern Hyogo prefecture, Japan from September 12 to 13, 2011. The concentrations of personal and outdoor ozone ranged from not detectable to 23.2?ppb and from 4.7 to 38.3?ppb, respectively. The mean concentration of personal exposure to ozone was 3.7?ppb and was significantly lower than that of outdoor ozone (18.5?ppb). This suggests that the concentrations of outdoor ozone affect personal ozone exposure. However, in this study, we found no correlation between the concentrations of personal ozone and the total time spent outdoors or the time of day the individual was outside. In contrast, the mean concentrations of outdoor ozone were similar to those of ozone measured at the 12 nearest Ambient Monitoring Stations (AMSs). However, when the AMS was situated near a main road, the regional ozone levels were underestimated.     

A study on the effects of ozone treatment on the properties of raw and degummed mulberry silk fabrics

Ozone is a powerful oxidizing agent and is widely used in various applications, which includes bleaching of cotton. Its application on the processing of silk is non-existent. Research studies on degumming and bleaching of silk reveal that almost no work involving ozone has been carried out. Therefore a study was carried out to understand the effects of process parameters namely wet pickup, pH and time in the ozone treatment of raw and degummed mulberry and tassar silk fabrics on their properties. This paper reports on the effects of ozone treatment on the mulberry silk fabrics. The study was extended with a view to compare the ozone treatment with soap degumming and hydrogen peroxide treatment carried out on raw and degummed mulberry silk fabrics, respectively. The treatment results in increase in yellowness index and amino group content and decrease in breaking strength and elongation, weight and flexural rigidity. The results obtained are substantiated with tyrosine content, scanning electron micrographs and infrared spectroscopy of the treated materials. The effect of pH on the treatment is maximum up to pH 4 and then decreases. The treatment is more severe when the wet pickup used is 50% compared to that of 10 and 100%. With respect to treatment time, though the severity increases with time, it is maximum during the first 10 min of the treatment. Soap degumming of raw silk fabric results in lower yellowness index and flexural rigidity and lesser loss in breaking strength and elongation compared to that of ozone treated material. There is not much of difference between ozone and hydrogen peroxide treatments of degummed silk fabric except for the lower yellowness index obtained in the latter case.     

A platinum-like behavior electrocatalyst and solid polymer electrolyte technique used on high concentration of electrochemical ozone water generation

This study presents an advanced ozone production process using the solid polymer electrolyte (SPE) technique, similar to the fabrication of proton exchange membrane fuel cell (PEMFC) membrane electrode assembly (MEA). Tungsten carbide and platinum on carbon black are coated on anode and cathode sides of a polymer membrane (Du Pont), respectively, to produce high concentration of ozone water. The water electrolysis of ozone generation requires a higher voltage than that of hydrogen production. On one hand, tungsten carbide, which is a platinum-like behavior electrocatalyst, plays a key role in preventing the MEA from corroding or oxidizing under high voltage. On the other hand, the carbon paper is replaced by a titanium porous disc to bear higher voltage. Moreover, an outstanding electronic control system can produce 1.37 ppm ozone water at atmosphere by adjusting the voltage range (6–10 V) with a current set to the maximum of 3 A for a household demand of ozone water generation.     

铜和铝离子/UV催化臭氧降解偶氮二异丁腈废水研究

利用多相催化臭氧(O3)工艺处理偶氮二异丁腈(AIBN)废水,探讨不同催化O3体系(Cu2+、Al3+、Cu2++Al3+/UV催化O3)对AIBN废水中氰类污染物的降解特性,并对不同催化O3体系的动力学特性进行研究。结果表明,金属离子对催化O3工艺的处理效率具有明显影响,不同催化O3工艺对CN-去除作用都呈现起始去除速率较高而后减弱的特点,其中Cu2+和Al3+共同催化O3工艺的整体去除率较高,优于单独Cu2+和Al3+的催化性能。这可能是由于p H变化、金属离子与CN-配合作用、金属离子和O3作用的综合影响结果。动力学研究结果表明,不同催化O3体系降解AIBN废水中的CN-污染物的氧化反应符合准一级动力学反应,表观反应速率常数k在0.0245~0.00301 min-1之间。     

Excitonic Chemiluminescence in Si and CdSe Nanocrystals Induced by their Interaction with Ozone

The results of a systematic study of spectral and kinetic patterns of ozone‐adsorption‐induced luminescence (AL) in nanostructured Si and, for the first time, in colloidal CdSe/ZnS quantum dots (QDs) are reported and compared with photoluminescence (PL) of the same structures. The common excitonic nature of light emission under ozone chemisorption and photoexcitation is confirmed by excellent coincidence of AL and PL emission bands. This coincidence is maintained during correlated quenching of AL and PL emission caused by nonradiative defects generated under ozone adsorption. A possible mechanism for energy conversion is proposed in the framework of an exothermic oxidation reaction of core materials caused by ozone. The significant role of the quantum confinement effect differentiates the observed phenomenon from well‐known chemiluminescence in molecular systems. This research establishes a physicochemical basis for the development of a gas sensor with high selectivity to ozone. Also, our findings may be useful for testing core–shell colloidal QDs with ozone.     

Crystal-face-selective adsorption of Au nanoparticles onto polycrystalline diamond surfaces

Crystal-face-selective adsorption of Au nanoparticles (AuNPs) was achieved on polycrystalline boron-doped diamond (BDD) surface via the self-assembly method combined with a UV/ozone treatment. To the best of our knowledge, this is the first report of crystal-face-selective adsorption on an inorganic solid surface. Hydrogen-plasma-treated BDD samples and those followed by UV/ozone treatment for 2 min or longer showed almost no adsorption of AuNP after immersion in the AuNP solution prepared by the citrate reduction method. However, the samples treated by UV/ozone for 10 s showed AuNP adsorption on their (111) facets selectively after the immersion. Moreover, the sample treated with UV/ozone for 40-60 s showed AuNP adsorption on the whole surface. These results indicate that the AuNP adsorption behavior can be controlled by UV/ozone treatment time. This phenomenon was highly reproducible and was applied to a two-step adsorption method, where AuNPs from different batches were adsorbed on the (111) and (100) surface in this order. Our findings may be of great value for the fabrication of advanced nanoparticle-based functional materials via bottom-up approaches with simple macroscale procedures.