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Photochemistry is concerned with the interaction between light and matter. The present chapter outlines the basic concepts of photochemistry in order to provide a foundation for the various aspects of environmental photochemistry explored later in the book. Electronically excited states are produced by the absorption of radiation in the visible and ultraviolet regions of the spectrum. The excited...
Heterogeneous reactions are widespread in all the environmental compartments: soils, hydrosphere, troposphere and at medium altitudes in the stratosphere. In particular, heterogeneous photochemical processes are concerned with the effect of light on interacting molecules and solid surfaces. Sorption, ion exchange, dissolution, precipitation and redox processes bear a decisive role on these reactions,...
Key features of tropospheric photochemistry are highlighted including both homogeneous gas-phase and heterogeneous reactions that are important in clouds and haze aerosol. Fundamental aspects of photochemical kinetics are reviewed and then extended to the major chromophores present in the multi-phasic, tropospheric atmosphere. Tables of up-to-date absorption cross sections and quantum yields as a function...
An overview of the gas-phase reactions responsible for the photooxidation of air pollutants is provided. Starting with an introduction to the field of atmospheric chemistry we proceed to discuss the concept, and utility, of atmospheric lifetime. The processes responsible for the degradation of alkanes, alkenes, aromatics, NOx, SOx, CFCs and their replacements...
The halogenated phenols and anilines are the parent chromophores of a number of widely used pesticides, among them phenoxyacetic acid and phenylurea derivatives, and of other biocides. The direct photolysis of these substances in the environment has become a subject of increasing interest. In the first part of this review, investigations of the photochemistry of halogenated phenols and anilines carried...
This article updates the one on the same topic published in this series in 1999. The photochemistry of PAHs and PCBs in liquid water and on ice and other solids such as silica, soil and titanium dioxide continues to be actively studied. The photochemistry of PAHs in all phases continues to be dominated by oxidation by O2, with superoxide (O2·), excited singlet oxygen (1O2), and hydroxyl...
This review describes the reaction mechanisms of nitrate and nitrite ions, which play a role in the photochemical processes occurring in natural waters and in atmospheric aerosols. The UV excitation of nitrate ions leads to the formation of hydroxyl radicals, nitrogen dioxide, atomic oxygen and nitrite. Hydroxyl radicals induce the oxidation of organic substrates and account for the photodepollution...
In this chapter, photochemical processes in natural aquatic systems involving iron in one way or another are reviewed. Homogeneous and heterogeneous processes are examined with attention given to both simple model systems in which the species distribution is generally well understood and to complex systems more typical of natural or treatment environments. Insights into mechanistic aspects are provided...
This review will first give a brief description of coloured dissolved organic matter (CDOM) from the aquatic environment or extracted from soil. Data on chemical structure and spectroscopic properties are presented and the major photochemical processes involving CDOM as well as the main reactive species produced upon their irradiation are described. The fourth part of this chapter is an overview of...
In this chapter, an overview of Photochemical Advanced Oxidation Technologies (PAOTs) is given, together with recent relevant literature examples and references. Short-UV and VUV photolysis, UV/H2O2, UV/O3, UV/O3/H2O2, photo-Fenton and iron-based technologies, photo-ferrioxalate and UV/periodate, are exposed, together with a brief introduction of heterogeneous photocatalysis. Fundamental grounds with...
The use of semiconductor photocatalysis for treatment of water and air has been a topic of intense research activity over the past 20 years. This chapter provides a review of this highly effective technology. The fundamental processes involved in the technique are initially detailed with a discussion of some recent novel concepts in photocatalysis. A range of applications of water and air treatment...
There are two types of photo-effects on a TiO2 surface. One is the well-known photocatalytic reaction and another is the highly hydrophilic conversion under ultra-violet light irradiation. Using these functions, TiO2 has already been put to practical use in water purification, air purification, anti-bacteria, and so on. In addition, various materials coated with this type of TiO2 transparent...
Nuclear fuel processing has two main waste management requirements: (1) the disposal of waste organic solvent (secondary waste) generated by solvent extraction processes during the separation and purification of uranium and plutonium in nuclear fuel and materials processing; and (2) the management of the small fractions of U and Pu that are inseparable during reprocessing (primary waste). Environmental...
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