UV-H2O2 oxidation of monoazo dyes in aqueous media: a kinetic study

During the past few years attention has been drawn on chemical techniques t hat could be used to discolour textile wastewaters. We have studied the pho tooxidation of several aqueous monoazodyes solutions in the presence of hyd rogen peroxide. Irradiation was carried out with a low-pressure mercury lam p. We observed that the reaction is pseudo-first-order with respect to the dye concentration. The effects of hydrogen peroxide and dye dosages, temper ature, pH, and chemical structure of the organic matter were also investiga ted. Results suggest that molecules, hydrazone form of which predominates, are the most sensitive to degrees OH oxidation. If a labile hydrogen atom i s present in the chromophore, it is the primary target of the attack. (C) 1 998 Elsevier Science Ltd. All rights reserved.