Reaction paths and efficiency of photocatalysis on TiO_2 and of H_2O_2 photolysis in the degradation of 2-chlorophenol

摘要

The kinetics of 2-chlorophenol (2-CP) degradation and mineralization in the aqueous phase was investigated under irradiation at 254 nm, employing either photocatalysis in the presence of titanium dioxide, or hydrogen peroxide photolysis, to compare the efficiency of these photoinduced advanced oxidation techniques. Photocatalysis under 315-400 nm wavelength irradiation was also investigated. The concentration versus time profiles of the degradation intermediates catechol, chloro- and hydroxy-hydroquinone allowed the identification of the reaction paths prevailing under the different experimental conditions. Efficient C—Cl bond cleavage occurred as a consequence of direct light absorption by 2-CP, while hydroxyl radicals, photogenerated at the water-photocatalyst interface or during H_2O_2 photolysis, were the main oxidation agents, able to attack both 2-CP and its degradation intermediates. Highest degradation and mineralization efficiencies were achieved under H_2O_2 photolysis at 254 nm.