Photocatalytic Degradation of Pollutant

Several articles have reviewed the ongoing work in the photocatalytic degradation of pollutants that involve oxidation or reduction processes (depending on the experimental conditions) [16,18,187,265-273], The addition of external oxidants such as ozone or hydrogen peroxide during the photocatalytic process can improve the degradation of the organic material when they are added in suitable doses [274-275],... 

Pichat, P. Photocatalytic degradation of pollutants in water and air basic concepts and applications. In Tarr MA, editor. Chemical degradation methods for wastes and pollutants - environmental and industrial applications. New York Marcel Dekker 2003 77-119. 

Radical reactions can also be initiated by irradiation using UV light. Prominent examples include photocatalytic degradation of pollutants with catalysts incorporating Ti02. Frequently, these reactions proceed at ambient or even lower temperatures, which makes their investigation by EPR spectroscopy rather facile. Nonetheless, EPR spectroscopy has been used only rarely to monitor photo-catalytic reactions as they occur (33,87). An example is presented below. 

So far quite few materials have been used in photocatalytic degradation of pollutants. Where such comparisons have been reported, the results almost invariably show that Ti02, followed by ZnO, are the two most active catalysts [67,68]. Because Ti02 fairly stable over a large range of pH and it is a cheap material, most of the investigations or degradations have been carried out with this material [14]. 

Patsoura, A., Kondarides, D.I., and Verykios, X.E. (2007) Photocatalytic degradation of organic pollutants with simultaneous production of hydrogen. Catalysis Today, 124 (3-4), 94-102. 

This section covers environmental applications of nanomaterials insofar as they are directly applied to the pollutant of interest. The photocatalytic degradation of organic pollutants and remediation of polluted soils and water are discussed here. The high surface areas and photocatalytic activities of semiconductor nanomaterials have attracted many researchers. Semiconductor nanomaterials are commercially available, stable, and relatively nontoxic and cheap. Prominent examples that are discussed are metal oxides such as Ti02 and ZnO and a variety of Fe-based nanomaterials. 

Photocatalytic degradation of environmental pollutants by solar energy is a very attractive technology for the remediation of contaminated water [253,323], In some variants of this process, solar UV radiation is absorbed by semiconductor catalyst particles suspended in water. TiOz photocatalytic particles are the most widely used for these applications. 

Nagaveni K, Silalingam G, Hegde MS, Madras G (2004) Photocatalytic degradation of organic compounds over combustion-synthesized nano TiO. Environ Sci Technol 38 1600-1604 Naiiagu JO (1996) History of global metal pollution. Science 272 223-224 Nel A, Xia T, Madler L, Li N (2006) Toxic potential of materials at the nanolevel. Science 311 622-627... 

There have been many studies on photocatalytic degradation of TCE or PCE in water because of many episodes of groundwater pollution by these substances. 

The photocatalytic degradation of chlorophenols on ZnO has also been demonstrated [127]. The photocatalytic degradation of other chlorinated aromatic compounds [127], phenol [128-134], fluorinated aromatic compounds [135], and other substituted phenols and aromatic compounds [Izumi 1981, 738 Matthews 1984, 2386 Abdullah 1990, 2099 [136-141] have been demonstrated. The degradation of halogenated aromatic pollutants such as polychlorinated biphenyls (PCBs) [142] and polybrominated dibenzofiirans [143] has also been attempted. 

Muneer, M. Das, S. Manilal, V. B. Haridas, A. Photocatalytic degradation of waste-water pollutants Titanium dioxide-mediated oxidation of methyl vinyl ketone, J. Photochem. Photobiol. 1992, A63, 107. 

Mestankova H, Mailhot G, Jirkovsky J, Krysab J, Bolte M. Mechanistic approach of the combined (iron-Ti02) photocatalytic systemfor the degradation of pollutants in aqueous solution an attempt of rationalisation. Appl Catal B Environ 2005 57 257-65. 

Bessekhouad, Y., D. Robert and J. Weber (2004). Bi2S3/Ti02 and CdS/Ti02 heterojunctions as an available configuration for photocatalytic degradation of organic pollutant. Journal of Photochemistry and Photobiology A-Chemistry, 163(3), 569-580. 

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