KINETICS AND MECHANISM OF PHOTODEGRADATION OF CHLOROPHENOLS

The photodegradation of mono-, di-, tri- and pentachlorophenols in aqu eous solution is surveyed from several viewpoints, namely kinetic and mechanistic, the nature of the reactive intermediates and final produc ts, and the potential of photochemical means of treating water contami nated by chlorophenols. In direct photolysis, the roles of heterolytic and homolytic processes are considered, and the appearance of carbene , in addition to ionic and radical, intermediates noted. Sensitized ph otolysis deals with the roles of singlet oxygen and of a variety of me tal complexes. The induced degradation of chlorophenols refers to the oxidation of chlorophenols by free radicals generated from photo- and radiolytic systems, particularly illuminated semiconductors such as ti tanium dioxide. The article finishes with an overview of the reactions of various types of reactive intermediates with chlorophenols.