臭氧氧化-光催化降解水中的五氯酚

利用臭氧氧化-光催化技术降解水中的有机污染物五氯酚(PCP)。对比了紫外光照射、臭氧氧化、光催化、臭氧氧化-光催化4种方法降解PCP的情况。考察了臭氧氧化-光催化体系中臭氧流量、臭氧产量、PCP初始质量浓度、pH和CO23-等因素对PCP降解率的影响。实验结果表明,臭氧氧化-光催化法比单独使用紫外光照射、臭氧氧化、光催化法更能有效的去除PCP;增加臭氧流量和臭氧产量有利于提高PCP的降解率;降低PCP的初始浓度,PCP的降解率显著提高;pH对PCP的降解效果影响不明显;CO23-的存在显著降低了PCP的降解率。在臭氧氧化-光催化体系中,除臭氧直接氧化降解PCP外,臭氧与TiO2协同作用产生的.OH对PCP的降解也起到了重要作用。     

Tb掺杂对纳米TiO_2光催化活性的影响

以溶胶-凝胶法制备了纳米TiO2和掺杂Tb的TiO2(Tb-TiO2),用X射线衍射、示差扫描量热、热重分析、红外光谱和荧光光谱等技术对纳米TiO2和Tb-TiO2的结构进行了表征;考察了以纳米TiO2及Tb-TiO2为催化剂光催化氧化环己烷合成环己酮和环己醇的情况。表征结果表明,掺杂Tb后明显抑制了TiO2中锐钛矿相向金红石相的转变,提高了TiO2催化剂的热稳定性,晶格发生了膨胀现象,晶格膨胀可有效降低光生载流子的复合几率,减小晶粒尺寸,提高光催化活性;光催化氧化环己烷的实验结果表明,与TiO2催化剂相比,Tb-TiO2催化剂的环己烷转化率和环己酮、环己醇的选择性大幅度提高,表明Tb-TiO2催化剂的光催化活性和光催化效率提高。     

Photocatalytic degradation of methyl tert‐butyl ether (MTBE) in contaminated water by ZnO nanoparticles

BACKGROUND: Over the past several decades methyl tert‐butyl ether (MTBE) as additive to gasoline, intended to either boost ratings of fuel or to reduce air pollution, has been accepted worldwide. Since MTBE has high water solubility, the occurrence of fuel spills or leaks from underground storage tanks or transferring pipeline has led to the contamination of natural waters. In this study the degradation of aqueous MTBE at relatively high concentrations was investigated by a UV‐visible/ZnO/H₂O₂ photocatalytic process. The effects of important operational parameters such as pH, amount of H₂O₂, catalyst loading and irradiation time were also investigated. Concentration of MTBE and intermediates such as tert‐butyl formate and tert‐butyl alcohol were measured. RESULTS: Time required for complete degradation increased from 20 to 150 min when the initial concentration was increased from 10 to 500 mg L^?1. The first‐order rate constants for degradation of MTBE were estimated to be 0.183–0.022 min^?1 as the concentration increased from 10 to 500 mg L^?1. Study of the overall mineralization monitored by total organic carbon analysis showed that at an initial concentration of 100 mg L^?1 MTBE complete mineralization was obtained after 100 min under UV‐visible/ZnO/H₂O₂ photocatalysis. CONCLUSION: The data presented in this paper clearly indicated that UV‐visible/ZnO/O₂ as an advanced oxidation process provides an efficient treatment alternative for the remediation of MTBE‐contaminated waters. Copyright © 2008 Society of Chemical Industry     

Response surface methodology applied for Orange II photocatalytic degradation in TiO2 aqueous suspensions

BACKGROUND: Heterogeneous photocatalysis is influenced by a number of parameters involving synergistic effects; hence, an experimental strategy design that considers interactions between the main variables is needed. The response surface methodology was applied for the investigation of photodegradation of 20 mg L^?1 Orange II in aqueous solutions and for optimization of color removal efficiency. Preliminary studies were performed to identify the parameters to be selected for optimization. RESULTS: The input variables considered for experimental design were: solution initial pH, oxidizing agent (H₂O₂) initial concentration and UV‐A irradiation time. The multivariate experimental design allowed the development of a quadratic response surface model to be used for the prediction of color removal efficiency over the full range of the experimental region. Under the optimum conditions established in the region of experimentation (pH = 6.9, [H₂O₂]₀ = 183 mg L^?1 and t = 32 min), a 100% color removal efficiency was obtained in experiments. CONCLUSIONS: It was found that the variables considered have important effects on color removal efficiency. The results demonstrate that the use of experimental design strategy is indispensable for successful investigation and adequate modeling of the process because the interdependence of the reaction parameters cannot be neglected. Copyright © 2008 Society of Chemical Industry     

Hybrid photocatalytic membranes embedding decatungstate for heterogeneous photooxygenation

The incorporation of decatungstate in polymeric membranes provides new heterogeneous photocatalysts for the oxidation of organic substrates under oxygen atmosphere at 25 °C. Photocatalytic membranes have been prepared yielding polymeric films with a high thermal, chemical and mechanical stability (PVDF, PDMS, Hyflon). Surface spectroscopy techniques including transmittance and reflectance UV-Vis and FT-IR have been used to assess the photocatalyst integrity within the polymeric support. Catalyst screening has been performed under both homogeneous and heterogeneous photooxygenation conditions. The photocatalyst activity has been evaluated in terms of the substrate conversion, turnover numbers, and recycling experiments. A membrane induced selectivity behavior has been evidenced by comparison with homogeneous oxidations.     

光催化降解废气过程中紫外辐射照度模拟和优化

为在光催化设计中合理布置紫外灯,减少光在传输过程中的损失,概括总结径向辐射模型、多点源叠加近似辐射模型和离散坐标辐射模型等3种经典的紫外辐射物理模型;基于离散坐标辐射模型模拟某公司生产的光催化氧化废气处理装置的紫外辐射照度;通过调整灯管布置距离改变光强分布,并拟合光催化单元和光催化网表面的平均紫外辐射照度随灯管布置距离变化曲线.结果表明,距离参数在55～65 mm时,该光催化反应装置的光能利用率较好;紫外灯的合理布置可有效提高光能利用率.     

Efficient photodegradation of phenol assisted by persulfate under visible light irradiation via a nitrogen-doped titanium-carbon composite

To realize the utilization of visible light and improve the photocatalytic efficiency of organic pollutant degradation in wastewater, a nitrogen-doped titanium-carbon composite (N-TiO₂/AC) prepared by sol-gel methods was applied in the photodegradation of phenol assisted by persulfate under visible light irradiation (named N-TiO₂/AC/PS/VIS). The results show that a synergistic effect exists between visible-light photocatalysis and persulfate activation. Compared with TiO₂/PS/VIS, the phenol degradation rate was found to be observably improved by 65% in the N-TiO₂/AC/PS/VIS system. This significant increase in degradation rate was mainly attributed to the following two factors: 1) The N and C doping can change the crystal structure of TiO₂, which extends the TiO₂ absorption wavelength range to the visible light region. 2) As an electron acceptor, PS can not only prevent electrons and holes from recombining with each other but can also generate strong oxidizing radicals such as ∙SO₄^– and ∙OH to accelerate the reaction dynamics. The process of phenol degradation was found to be consistent with the Langmuir pseudo-first-order kinetic model with an apparent rate constant k of 1.73 min^–1. The N-TiO₂/AC/PS/VIS process was proven to be a facile method for pollutant degradation with high pH adaptability, excellent visible-light utilization and good application prospects.     

光催化降解甲醛的波长效应研究

分别以紫外杀菌灯和黑光灯为光源，研究了TiO2薄膜催化剂上甲醛的光催化氧化反应．实验结果表明，紫外杀菌灯照射下，甲醛的光催化降解率明显低于以黑光灯为光源时甲醛的光催化降解率．采用傅立叶红外光谱(FT-IR)和热分析(TG-DTA)对反应后的TiO2光催化剂进行分析和表征，对两种不同光源照射下甲醛光催化降解率的差异进行了初步探讨．     

稀土掺杂二氧化态光催化的研究进展

论述了半导体光催化反应机理，单一半导体光催化剂的光催化活性普遍不高，通过掺杂可以提高光催化活性，甚至在提高活性的同时扩展光谱响应范围，提高光的利用率。纳米TiO2是一种宽禁带半导体光催化剂，可用于有机污染物及无机污染物等方面的降解。     

三相流化床中光催化降解反应特性的研究

在设计并建立的流态化光催化反应器中,采用负载型光催化剂对甲基橙水溶液进行了光催化降解实验研究。优化了三相流化状态下光催化反应器的操作条件, 其结果为:气体流量200-250Lh-1,液体流量30 Lh-1,催化剂用量为1.5gkg-1处理液;考察了该反应器中催化剂的使用寿命,为光催化降解技术的工业应用研究提供了参考。