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The oxidation of some chlorophenols: 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, tetrachlorocatechol (3,4,5,6-tetrachloro-2-hydroxy phenol) and 4-chloroguaiacol (4-chloro-2-methoxy phenol) has been studied via single photodecomposition produced by polychromatic UV irradiation, oxidation by hydroxyl radicals generated by Fenton's reagent (hydrogen peroxide plus ferrous ions), and degradation by hydroxyl radicals produced by combinations of UV irradiation plus hydrogen peroxide, and UV irradiation plus hydrogen peroxide and ferrous ions (photo-Fenton system). These organics have been selected as models of chlorophenolic derivative pollutants present in wastewaters and groundwaters. The degradation levels obtained in each process are reported. The quantum yields in the single photodecomposition reaction and the rate constants between the chlorophenols and the hydroxyl radicals in the reaction with Fenton's reagent are determined. Finally, the additional contributions to the photodecomposition promoted by the radical reaction in the combined UV/H 2 O 2 and photo-Fenton systems are also evaluated.

The kinetics of the decomposition of 2,4,6-trichlorophenol by ozonation, by Fenton's reagent reaction, and by a polychromatic UV radiation is investigated from experiments performed in a batch reactor. In each oxidation system, the degree of removal of the organic compound from water is evaluated and the influence of the operating variables is established. The ozonation process is conducted at pH = 2 and in the presence of radical scavengers:  In these conditions the kinetic constants and reaction orders for the direct reaction between ozone and that organic compound are deduced by using a model based in the film theory. The oxidation by Fenton's reagent (Fe2+ ion and H2O2), a generating system of hydroxyl radicals, leads to the evaluation of pseudo-first-order rate constants for the global reaction and to the determination of the kinetic constant for the direct radical reaction. Finally, the quantum yields in the photodecomposition process are determined from the rate equation, with the radiation flow rates absorbed previously calculated by means of a radiation source emission model.

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