TiO2光催化降解苯和甲苯的动力学研究

利用溶胶-凝胶法制备了粒径约为13nm、晶型为锐钛矿相和金红石相混晶的TiO2光催化剂,并利用此催化剂对挥发性有机污染物苯和甲苯进行了光催化降解研究,对不同的催化剂用量、光源、污染物的初始浓度以及氧气对光催化反应速率的影响进行了研究。结果表明,光催化降解甲苯和苯的反应均符合假一级动力学方程,光强与光催化降解甲苯的反应的速率常数之间呈指数关系,光波长对光催化降解苯的影响也很显著;随着甲苯和苯初始浓度的增加,光催化反应速率常数降低;氧气加快了光催化降解甲苯和苯的速率;对于光催化降解初始浓度为37.6μmol/L的甲苯而言,催化剂的最佳使用量为0.30g,对于光催化降解初始浓度为9.0μmol/L的苯来说,催化剂的最佳用量为0.10g。     

TiO2/BixTiyOz气相光催化降解苯的动力学模型及反应机理

在密闭不锈钢反应器内考察了TiO2/BixTjyOz催化剂气相光催化降解苯的性能.结果表明,TiO2负载于Bi12TiO20,Bi2Ti2O7和Bi4Ti3O12上制成的催化剂,光催化活性得到很人的提高,TiO2最佳负载量为2.0%;其中,TiO2/Bi12TiO20的光催化活性最高,苯最高转化率是纯TiO2的2倍,催化剂使用寿命也延长了1倍.在本文实验条件下,TiO2/Bi12TiO20上苯气相光催化降解符合Lang-muir-Hinshelwood动力学模型,光催化反应速率常数k和Langmuir吸附常数K分别为0.006 4mg/(L·min)和9.670 2L/mg.采用红外光谱对失活的催化剂进行表征,结果表明催化剂表面出现了羰基与羟基等的振动峰,同时检测到主要的中间产物是2,6-二叔丁基-4-甲基苯酚,它吸附在催化剂表面活性化上而导致催化剂失活.最后推测了苯在催化剂表面气相光催化降解的反应机理.     

苯在TiO2上的气相光催化氧化反应历程

 以超细TiO2为催化剂,在内循环光反应装置中考察了苯的气相光催化氧化反应．苯的初始质量浓度为50mg／m3时,在0．1g催化剂和0．013m2的光照面积下,460min后苯几乎全部分解完毕;光照面积增大1倍时,反应时间缩短为240min．常温下苯在TiO2表面不易吸附,但反应中间产物有较强的吸附性,能吸附在催化剂表面从而引起催化剂失活．经红外检测可知,反应的中间产物是个六元环醇,据此推测了苯的气相光催化可能的反应历程．通过实验结果并参考有关文献的结论,证明苯的气相光催化氧化在不同的反应条件下遵循不同的反应历程．     

Ce0.5-xZr0.5-xBa2xO2负载TiO2光催化降解气相苯

在密闭不锈钢反应器内研究了Ce0.5-xZr0.5-xBa2xO2负载锐钛型TiO2光催化降解气相苯的性能.确定了该系列光催化剂的最佳Ba含量,并应用X射线衍射、紫外-可见漫反射光谱以及X射线光电子能谱对催化剂进行了表征.结果表明,TiO2在载体表面均匀分散.在210~400 nm范围内,TiO2/Ce0.5-xZr0.5-xBa2xO2比TiO2吸收更多的紫外光.TiO2/Ce0.5-xZr0.5-x-Ba2xO2包含Ti和O两种元素,TiO2/Ce0.5-xZr0.5-xBa2xO2的Ti 2p结合能向低能端偏移.Ce0.5-xZr0.5-xBa2xO2表面负载TiO2能有效提高催化剂的光催化活性.Ce0.5-xZr0.5-xBa2xO2的作用是转移电子和使催化剂在紫外区的吸收增强.     

稀土掺杂TiO2光催化的研究进展

利用稀土掺杂对TiO2进行改性以实现可见光响应和提高量子效率是提高光催化剂活性的重要方法之一.总结了国内外利用稀土掺杂TiO2催化剂的制备方法及利用稀土掺杂对TiO2进行改性以提高其光催化效率的研究结果,分析了稀土元素种类、掺杂量等因素对光催化活性的影响.     

掺杂TiO2的光催化性能研究进展

本文综述了掺杂TiO2在可见光范围的响应及其光催化性能的研究状况,讨论了掺杂金属离子的种类、浓度、光催化剂的粒径以及其它因素对TiO2光催化活性的影响。列出了掺杂TiO2的制务方法,并对今后的研究作了展望。     

TiO2光催化氧化研究进展

探讨了TiO2光催化氧化技术的原理,其研究现状,以及可能提高TiO2光催化氧化效率的途径。采用参考文献18篇。     

气相色谱法同时测定醇酸类油漆中苯系物

用乙酸乙酯稀释油漆样品,在汽化温度下直接进样,采用PEG-20M毛细管柱,FID为检测器,用气相色谱法测定了醇酸类油漆中的苯、甲苯和二甲苯,内标法定量.测定结果的回收率为97.21%～100.66%,相对标准偏差不大于1.3%(n=4).     

TiO2－SnO2复合纳米膜的制备及其光催化降解甲苯的活性

 采用溶胶－凝胶法制备了nano－TiO2－SnO2复合溶胶，经一次镀膜就能在玻璃上得到没有缺陷、结构紧密均匀的nano－TiO2－SnO2复合膜．通过扫描电镜观察到复合膜颗粒为球形，比纯TiO2膜的颗粒小，平均粒径为15nm，且粒径分布非常均匀．以空气中的有机挥发物甲苯模拟污染物，测定了nano－TiO2－SnO2复合膜的光催化降解性能．结果表明，n（SnO2）／n（TiO2）＝0．05的nano－TiO2－SnO2复合膜催化剂具有最高的光催化活性，且比纯TiO2膜的活性高；甲苯初始浓度为920mg／m3时，反应5h甲苯完全降解．XRD分析表明，此复合物具有锐钛矿和金红石两种TiO2晶相，没有检测到SnO2的特征峰．     

Pt/TiO2光催化降解甲苯

选择甲苯作为研究对象,探讨了在不同光源照射、不同光催化剂的作用下,气相甲苯的降解情况,结果表明甲苯在紫外杀菌灯照射下有明显的光化学反应发生。在光催化剂作用、转折灯照射时,甲苯发生催化氧化反应;并对催化剂在降解甲苯反应中的失活原因做了初步探讨。     

纳米二氧化钛光催化降解喹啉动力学

利用溶胶-凝胶法制备纳米二氧化钛光催化剂,探讨了其光催化降解废水中典型含氮杂环化合物喹啉的动力学行为。实验条件下,TiO₂光催化降解喹啉的反应为准一级反应,可用Langmuir-Hinshelwood动力学模型描述,其表达式为r=0.296kc_t/(1+0.296c_t),其中,lnk =-0.411 1lnc₀+2.278。     

Effect of silver deposition on tio for photocatalytic oxidation of benzene in the gas phase

Summary Deposition of Ag on TiO₂ surface by photodeposition method improved the photooxidation rate of benzene in air by inhibiting the build-up of intermediate compounds on the catalyst surface. Although the reaction rate decreased with the increase in benzene concentration, the decrement of reaction rate became smaller by Ag deposition. The selectivities to CO₂ and CO were 95 and 5%, respectively, which were almost independent of Ag loading and benzene conversion.     

Photocatalytic decomposition of tetrachloroethylene in the gas phase with titanium dioxide as catalyst

The gas phase photocatalytic destruction of tetrachloroethylene (PCE) was investigated by using an in situ photocatalytic reactor with FT-IR analysis in batch mode. The main products of PCE degradation are CO₂ and COCl₂, with trichloroacetylchloride as an intermediate. It was found that the rate of PCE degradation and the appearance of products in the gas phase are highly dependent on their adsorption properties on the surface of the catalyst, besides other reaction conditions, such as the intensity of irradiation and the composition of the reaction mixture.     

活性炭负载纳米TiO_2光催化降解甲醛废水研究

甲醛对人和温血动物的毒性很强,如果人类长期饮用被甲醛污染的水源,会引发头昏、贫血以及各种神经系统疾病.为此,研究学者对甲醛废水的处理进行了很多的试验研究.目前处理甲醛废水的主要方法有:芬顿法、光催化氧化法、湿式氧化处理等高级氧化技术,二氧化氯法,蒸汽吹脱法,氧化吸附法,SBR工艺等.     

Influence of humidity and acidity of the titanium dioxide surface on the kinetics of photocatalytic oxidation of volatile organic compounds

The influence of the humidity and acidity of the TiO₂ surface on the kinetics of the photocatalytic processes of deep oxidation of volatile organic compounds was studied. At 20 °C the rates of acetone and benzene oxidation are maximum at the coverages of TiO₂ with water close to monolayer and are 3—5 times higher than that in the dry atmosphere. The activation energy of benzene oxidation (E _a = 6.3±0.4 and 43.0±3.2 kJ mol^–1 at relative humidities of 8 and 70%, respectively) at a humidity higher than 30% decreases according to the exponential law with an increase in the surface acidity when multilayer water films are formed on the surface. Under the real conditions of operation of photocatalytic air purifiers, a TiO₂ particle is covered by water nanofilms. As in aqueous solutions, photoprocesses on the TiO₂ surface depend substantially on the solvation of the participants of the reaction, the formation of the double electric layer, and the concentration of the electrolyte (due to the dissociation of the surface acid-base groups).     

Enhancing photocatalytic activity of titanium dioxide through incorporation of MIL‐53(Fe) toward degradation of organic dye

Photocatalytic activity of titanium(IV) oxide (TiO₂) can be enhanced through modification of its surface‐active sites. Here, iron(III) carboxylate [MIL‐53[Fe]]‐incorporated TiO₂ (as MIL‐53(Fe)/TiO₂) was prepared using a hydrothermal method. This material was then calcined at 500°C to obtain a MIL‐53(Fe)‐derived γ‐Fe₂O₃/TiO₂ photocatalyst. A photocatalytic study of MIL‐53(Fe)/TiO₂ and MIL‐53(Fe)‐derived γ‐Fe₂O₃/TiO₂ toward cationic methylene blue (MB) and anionic methyl orange (MO) showed that MIL‐53(Fe)/TiO₂ (0.25 wt%) and MIL‐53(Fe)‐derived γ‐Fe₂O₃/TiO₂ (0.75 wt%) resulted the best degree of dye degradation. The MIL‐53(Fe)‐derived γ‐Fe₂O₃/TiO₂ (0.75 wt%) composite for instance is capable of degrading almost 100% of 20‐ppm MB and MO, respectively, within 6 hr. Photocatalytic degradation of MB and MO was well fitted to the Langmuir‐Hinshelwood pseudo‐first order kinetics model, which indicates physisorption as the key partway that facilitates dye decomposition on the surface of a photocatalyst under UV‐A irradiation. This study provides new insights into the exploration of MILs/TiO₂ materials for the environmental remediation and pollution control.     

Heterogeneous composite titanium dioxide photocatalysts on phosphate supports

A series of heterogeneous composite photocatalysts was prepared by the deposition of titanium dioxide on porous magnesium phosphate, calcium phosphate, titanium phosphate, zirconium phosphate, and aluminum phosphate supports. The activities of these photocatalysts were compared in the photodecomposition of Rhodamine C dye by the action of UV irradiation. The best functional characteristics were found for the photocatalysts on the magnesium phosphate support treated at 750°C. The use of the photocatalysts on phosphate supports was found to hold promise in photocatalytic water purification. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 1, pp. 36–41, January–February, 2009.     

Doped titanium dioxide nanocrystalline powders with high photocatalytic activity

Doped titanium dioxide nanopowders (M:TiO₂; M=Fe, Co, Nb, Sb) with anatase structure were successfully synthesized through an hydrothermal route preceded by a precipitation doping step. Structural and morphological characterizations were performed by powder XRD and TEM. Thermodynamic stability studies allowed to conclude that the anatase structure is highly stable for all doped TiO₂ prepared compounds. The photocatalytic efficiency of the synthesized nanopowders was tested and the results showed an appreciable enhancement in the photoactivity of the Sb:TiO₂ and Nb:TiO₂, whereas no photocatalytic activity was detected for the Fe:TiO₂ and Co:TiO₂ nanopowders. These results were correlated to the doping ions oxidation states, determined by Mössbauer spectroscopy and magnetization data.     

掺氮二氧化钛可见光照射降解微囊藻毒素-LR

采用溶胶凝胶法制备了N掺杂TiO2(N-TiO2)纳米粉体光催化剂,利用X射线光电子能谱(XPS)、X射线衍射(XRD)、紫外可见反射光谱及透射电镜(TEM)分析测定,对光催化剂N/TiO2进行了结构表征.发现N掺杂TiO2相对纯TiO2禁带宽度变窄,可见光区有明显吸收.在可见光照射下,利用纳米N/TiO2作为光催化剂降解微囊藻毒素(Microcystin-LR,MC-LR),通过高效液相色谱仪(HPLC)跟踪检测降解过程MC-LR浓度变化,液质联用仪(LC-MS)检测MC-LR降解中间产物变化.利用电子自旋共振法(ESR)及过氧化物酶催化氧化方法跟踪定性定量测定光催化过程中氧化物种的种类变化.采用总有机碳(TOC)测定仪测定了MC-LR光催化深度氧化矿化效果.结果表明,可见光(λ420nm)照射可有效激发光催化剂N-TiO2活化分子氧降解MC-LR,在反应条件下,光催化反应14h,MC-LR降解率达到100%,20h矿化率达到59%.其光催化反应体系中氧化物种主要为羟基自由基(·OH).质谱检测到13种降解产物,主要反应机理为光催化反应产生·OH进攻MC-LR结构四个易氧化部位,以及一些氨基酸之间的肽键的水解.