Photocatalytic technologies

Photocatalysis is a fundamental feature of life processes on our planet [1] (it provides photosynthesis in plants and bacteria) and of the chemistry of its atmosphere [2]. Work is under way to develop photocatalytic technologies for abatement of environmental problems [3,4]. Photocatalysis is anticipated to become in the coming years important also for selective organic synthesis [4]. In a more distant future thermal catalytic processes induced by heating with solcir radiation, together with photocatalytic processes may become important for environmentally friendly technologies of solar energy utilization [5-9]. 

Economic feasibility studies suggest that even at the present state of the art photocatalytic technology indeed can be competitive with the traditional carbon adsorption or incineration technologies in treatment of contaminated soil vapor extraction vents and small scale VOC-containing vents [28]. Rapid progress in basic and applied research in photocatalysis suggests... 

There are a number of examples of applications of environmental photocatalysis that are already at or near the stage of implementation or commercialization. Some selected applications of photocatalytic technology are listed in Table 2.1. 

Savinov, Evgueni N. is a Head of the Laboratory of photocatalysis on the semiconductors at the Boreskov Institute of Catalysis since 1987. Since 1996 he is a Head of the Chemical Physical Department at the Novosibirsk State University. His area of interest is the photocatalytic and photochemical processes in liquid and gas phase. This includes preparation and characterisation of photocatalysts study the mechanism of photocatalytic reactions design of photocatalytic reactors application of photocatalytic technology to the industry. 

Photocatalytic technology inherently requires some quantity of light, and highly hydrophilic technology is no exception. When it is to be used indoors, the quantity of light provided by indoor lighting may not be sufficient. Our research and development efforts have focused on this point, and we will discuss this later. 

Another interesting application of the photocatalytic technology is the removal (more than 99%) of mercury from hazardous wastes of a chlor-alkali plant. The process begins by acid attack of the solid wastes and treatment of the acid solution under UV irradiation in the presence of Ti02 and citric acid. The selective precipitation of reduced mercury took place, while the other metal compounds remained in the solution. It was claimed that the final effluents reached a quality close to that of the standards imposed by international environmental agencies (Bussi et al., 2002). 

Photocatalysis and its related technological issues have been strongly influenced by recent publications. The present Volume 36-Photocatalytic Technologies of the Elsevier s Advances in Chemical Engineering Series aims at offering a comprehensive overview of the state-of-the-art photocatalytic technology. In order to accomplish this, several prominent researchers were invited to contribute a chapter for the Volume 36. 

While no known commercial applications of the photocatalytic technology are in use for chemical agent destruc-... 

In general, the effective use of photocatalytic technology depends heavily on the specific way in which the Ti02 powder is used. One of the simplest approaches, often used in model studies on water treatment, is to mix the powder with the water and expose the suspension to UV light or sunlight. Although the separation of the catalyst powder from the water is not an insurmountable problem, an alternate approach is to immobilize the powder on a substrate [25]. 

The semiconductor catalyst is generally used as powder suspended in a hquid medium. The inconvenience of this approach at large scale is the catalyst-recovering step from the solution at the end of operation. The sohd-liquid separation is an extremely important issue for the development of the photocatalytic technology indeed, the best possible recovery of particles must be ensured, in order to prevent their wash out and consequent decrease of their amount in the reactor system. 

To encourage the sound development of both photocatalytic technologies and their market. Photocatalysis Industry Association of Japan (PIAJ) runs campaigns for market awareness and sales expansion of photocatalyst products and, in technical terms, works on drafting standards for testing performance and normalization of photocatalytic products. 

Murata Y (2000) A new photocatalytic technology for the atmospheric removal. J Soc Inorg Mater 7 323-330 (in Japanese)... 

Slurry reactors are the most common and conventional reactors in photocatalytic technology [136]. In a slurry system, the catalysts are suspended in the liquid phase with the help of mechanical or gas-promoted agitation. 

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