Search results for "PHOTOCATALYSIS"
showing 10 items of 606 documents
Some working principles of heterogeneous photocatalysis by semiconductors
1993
The present paper outlines some of the principles which are the working base for the photocatalytic processes: we refer to those photocatalytic processes performed using irradiated semiconductors. The steps related to the photoproduction of electron-hole pairs and their separation are discussed. It is also shown how the step of pair separation induces the formation of various chemical species, some of which are useful for the oxidation reactions. It is also shown that in order to reach a detailed description of photocatalytic processes it is necessary to have the knowledge of both the electronic and the physicochemical features of the semiconductors. The paper finally reports a case study r…
Multi-doped Brookite-Prevalent TiO2 Photocatalyst with Enhanced Activity in the Visible Light
2018
© 2018 Springer Science+Business Media, LLC, part of Springer Nature Abstract: Enabling solar and/or visible light-driven photocatalysis is a crucial step to access innovative applications in environmental science and sustainable energy. Titanium dioxide is the most used photocatalyst because of its low cost and toxicity, however it is also limitedly active under visible light irradiation due to its wide band gap. Among its polymorphs, brookite holds promising optoelectronic properties for visible light photocatalysis, which have to the best of our knowledge been limitedly exploited. Here, a C,S,N-doped brookite-based TiO2has been prepared via a rapid one-pot sol–gel synthesis. Besides subs…
Effect of linker distribution in the photocatalytic activity of multivariate mesoporous crystals
2021
The use of Metal-Organic Frameworks as crystalline matrices for the synthesis of multiple component or multivariate solids by the combination of different linkers into a single material has emerged as a versatile route to tailor the properties of single-component phases or even access new functions. This approach is particularly relevant for Zr6-MOFs due to the synthetic flexibility of this inorganic node. However, the majority of materials are isolated as polycrystalline solids, which are not ideal to decipher the spatial arrangement of parent and exchanged linkers for the formation of homogeneous structures or heterogeneous domains across the solid. Here we use high-throughput methodologi…
Photocatalytic oxidation of gaseous toluene on polycrystalline TiO2: FT-IR investigation of surface reactivity of different types of catalysts
2000
Commercial TiO 2 Merck and TiO 2 Degussa P25 powders were employed as the catalysts for the photo-oxidation of toluene. By using TiO 2 Merck benzaldehyde was found in gas phase as the main product of the toluene partial oxidation. After an initial transient period, this catalyst exhibited a high stability in the presence of water vapour in the gaseous mixture, whereas the photoproduction of benzaldehyde sharply decreases after removal of H 2 O from the feed IR spectra of the used catalyst revealed that in the absence of water vapour benzaldehyde is molecularly held on the catalyst surface. This feature was confirmed by co-adsorbing benzaldehyde and water on the fresh catalyst. By contrast, …
VOC's abatement: Photocatalytic oxidation of toluene in vapour phase on anatase TiO2 catalyst
1997
Publisher Summary The photocatalytic oxidation of toluene in the presence of water was performed in the gas–solid regime at room temperature by using TiO2. It has been found that the presence of water was beneficial to achieve the almost complete photo-oxidation of toluene to CO2 and H2O, in fact, only very small amounts of benzaldehyde vapor that is the main product of toluene partial oxidation, were detected. Volatile organic compounds, VOC's, are an important class of air pollutants usually found in the atmosphere of all urban and industrial areas. Toluene is one of these compounds, and because of its noxious nature several strategies have been identified to reduce its presence in indoor…
Photocatalytic degradation of toluene in aqueous suspensions of polycrystalline TiO2 in the presence of the surfactant tetradecyldimethylamino-oxide
2000
The heterogeneous photocatalytic method has been used for carrying out the toluene oxidation in synthetic aqueous solutions containing also a zwitterionic surfactant, i.e. tetradecyldimethylamino-oxide (C 14 DMAO). A batch photoreactor with immersed lamp and two kinds of polycrystalline TiO 2 catalysts were used. The results indicate a substantial increase of the toluene degradation rate in the presence of the surfactant; the complete photo- oxidation of toluene was achieved in a few hours of irradiation at the used experimental conditions; at higher irradiation times also C 14 DMAO was completely degraded. The main intermediates of toluene degradation were p-cresol (4-methyiphenol) and ben…
Photocatalytic oxidation mechanism of benzonitrile in aqueous suspensions of titanium dioxide
2007
Abstract The photocatalytic oxidation of benzonitrile was carried out in aqueous suspensions (pH 11) of commercial polycrystalline TiO 2 (Merck and Degussa P25) irradiated by ultraviolet light. The rate of decomposition was dependent on the concentration of benzonitrile and followed a pseudo-first order kinetics. The complete mineralization of a 0.70 mM benzonitrile solution was achieved in ca. 8 h by using TiO 2 Degussa P25, whereas the substrate was only partially mineralized even after 14 h of irradiation in the presence of TiO 2 Merck. The final oxidation products were carbonate and nitrate. The appearance and the evolution of organic and inorganic intermediate species were also investi…
Solid State Fluorination on the Minute Scale: Synthesis of WO 3− x F x with Photocatalytic Activity
2020
Combination of ozonation and photocatalysis for purification of aqueous effluents containing formic acid as probe pollutant and bromide ion
2014
The treatment by advanced oxidation processes (AOPs) of waters contaminated by organic pollutants and containing also innocuous bromide ions may generate bromate ions as a co-product. In the present work heterogeneous photocatalysis and ozonation have individually been applied and in combination (integrated process) to degrade the organic compounds in water containing also bromide anions. The results show that: i) the sole photocatalysis does not produce bromate ions and in the case of its presence, it is able to reduce bromate to innocuous bromide ions; ii) the integration of photocatalysis and ozonation synergistically enhances the oxidation capabilities; and iii) in the integrated proces…