Photodegradation overview

Some of the topics addressed here have been reviewed by other authors. Studies of photoinduced processes (direct or indirect) of chlorophenols carried out before 1998 have been covered comprehensively [8] this work will only cursorily be treated here. A detailed overview of the photochemical behavior of phenylurea herbicides was in press at the time of writing this article [9]. The related subject of the photodegradation of pharmaceuticals in the aquatic environment has been reviewed very recently [10]. 

In recent years, titania in general gained a lot of interest in the field of photocatalysis. Here, the titania is not only support but also catalyst. Various review articles with hundreds of references have been published in the last 10 years [56-59]. Mills and Lee [60] reported about a Web-based overview of current commercial applications. One big field of application is the treatment of (waste) water and air by photodegradation of inorganic compounds (like ammonia and nitrates) and organic substances (like chlorinated aliphatic and aromatic compounds) as well as volatile organic compounds (VOCs) in the air. Even 2,4,6,-trinitrotoluene (TNT) can be completely destroyed under aerobic conditions by the use of AEROXIDE TiOj P 25... 

Abstract A brief overview on the main photoprocesses applied to the treatment of water and wastewater is presented. The photodegradation methods that have been applied to the oxidation of organic pollutants are described. A review on advanced oxidation processes (AOP s) and photooxidation mechanisms in homogeneous and heterogeneous solution is presented and some practical applications discussed. Combinations of biological and chemical treatments are considered to be a good approach to improve the removal efihciencies and reduce costs. 

This review presents an overview of the mechanistic aspects of polymer photodegradation, with a primary emphasis on a special class of photodegradable polymer that has metal-metal bonds along the polymer backbones. Throughout the review, the major emphasis is on degradation pathways and the parameters that control the rates of degradation. 

Not only are the stresses directly caused by the operational temperatures important, but the module temperature as part of the microclimate is also a major parameter for the other microclimatic properties. The most important property is the surface humidity, but also the photodegradation by UV irradiation might be accelerated by the sample temperature. Numerous models have been proposed for the simulation of the module temperature and are discussed in a comprehensive overview [2]. One of the models was derived from the energy balance for a solar thermal collector by David Faiman [3] ... 

In the previous sections on crazing primarily mechanical and molecular parameters have been discussed while the chemical environment was not considered as a variable. At this point an overview over the physico-chemical response of a crazable material to an active chemical environment will be given. (The chemical response to an active physical environment such as photodegradation or ozonolysis has been treated or referenced in 8 III). 

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