Water 4-chlorophenol, decomposition

Baker MD, Mayfied Cl. 1980. Microbial and nonbiological decomposition of chlorophenols and phenol in soil. Water Air Soil Pollut 13 411-424. 

Scheme 4.2. Sonochemical decomposition of 4-chlorophenol in aerated water.

Sonolytic decomposition of chlorophenol in water was enhanced in the presence of Fe(II), assuming that the Fenton oxidations occur ... 

Huang H-H, Lu M-C, Chen J-N. Catalytic decomposition of hydrogen peroxide and 2-chlorophenol with iron oxides. Water Res 2001 35 2291-2299. 

In the late 1970s HPLC provided an ideal tool for the analysis of pollutants and other environmental contaminants. Techniques were developed for analyzing chlorophenols, pesticide residues, and metabolites in drinking water and soil (parts per trillion) and trace organics in river water and marine sediments, and for monitoring industrial waste water and polynuclear aromatics in air. Techniques were also developed for determining fungicides and their decomposition products and herbicide metabolites in plants and animals. 

Reaction Mechanisms. Our analysis of intermediates and reactions reported by other researchers leads to proposed reaction pathways describing the photocatalytic oxidation of 4-chlorophenol in TiOz aqueous suspensions. The photocatalytic oxidation reaction is brought about by OH radicals, which are formed mainly from water decomposition on the Ti02 surface upon UV light irradiation (9-13). The OH radicals can either directly react with the adsorbed organic species on the TiOa surface or diffuse to the solution and then react with the dissolved organic species in the solution phase. Both reactions lead to formation of hydroxylated products such as 4-chlorocatechol, hydroquinone, 4-chlororesorcinol, and hydroxyhydroquinone as the initial products (Figure 6). Eventually, the reaction will mineralize these interme-... 

Many problems may occur when natural organic matters are present in the water, since they can occupy the catalyst active sites causing much lower decomposition efficiency. A combination of adsorption and oxidative destruction techniques may become a useful method to overcome the above problem. Ilisz et al. [367] used a combination of r/02-based photocatalysis and adsorption processes to test the decomposition of 2-chlorophenol (2-CP). The group created three systems which are presented below ... 

The final examples refer to the detoxification of waste water or of oil residues. The cathodic hydrodehalogenation of 2,4-dichlorophenol was investigated in [13], including the comparison of paraffin oil and water as reaction media. The anodic and/or cathodic decomposition of 2-chlorophenol was studied with... 

Some studies reported enhancements in photoactivity in the presence of a small amount of rutile phase [122-124]. Even a mechanical mixture of anatase and rutile showed much higher photoactivity for naphthalene oxidation than either pnre anatase or rutile powders [123,124]. The P25 powder is produced from TiCl4 in a flow reactor [122]. Based on a detailed investigation by x-ray diffraction (XRD) and micro-Raman spectroscopy, the rutile (formed directly in the flame) was fonnd to be covered by anatase [122,124]. However, another study based on transmission electron microscopy (TEM) with selected-area electron diffraction reported the presence of separate particles of anatase and rutile in P25 [125,126]. Diffuse reflectance spectra of P25 could be reproduced by a mechanical mixture of anatase and rutile powders, and particles of pure rutile phase were isolated from P25 upon HF treatment. Photoactivity for the decomposition of 4-chlorophenol in water was compared on four commercial photocatalysts, applying criteria of (a) initial rate of pollutant disappearance, (b) amount of intermediate products formed, and (c) time necessary to achieve total mineralization [127]. Based on criterion (c), P25 was concluded to be the most efficient photocatalyst even though it contains 20% rutile and has a moderate BET surface area (ca. 50 m /g). It was also reported to have a higher photoactivity than catalyst All in the degradation of reactive black 5 (an azo-dye) [128]. 

To prevent the passivation, the successful strategy for BDD electrodes includes the oxidation at highly anodic potential in the region of water decomposition. Hydroxyl radicals produced by the high applied potential are believed to be responsible for the oxidation of the passivating layer. This concept was successfully applied also for selected dichloro- and trichlorophenols, " which are presumably more prone to inactivation of electrode surface than mono-substituted CPs. For them the detection at BDD electrodes is possible even without any electrochemical remediation of the electrode surface as demonstrated for phenol, 2-chlorophenol (2-CP), and 4-chlorophenol (4-CP). ... 

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