The degradation of an azo dye in aqueous solutions by high-intensity electron-beam irradiation

Abstract

A study of the degradation of Acid Red 265 (azo dye) in aqueous solutions by high-intensity electron- irradiation was carried out in a flow system. For the oxygen-saturated solutions (oxygen bubbled during irradiation), the change of absorption spectra, the degree of decoloration at 542 nm, the reduction in optical density at 230 nm, the change of pH, and the amount of dissolved oxygen were measured as functions of dose under various conditions (dye concentration, dose rate, solution flow rate, and oxygen flow rate). The decoloration scheme in the flow system by electron beam irradiation was similar to that in the batch system by gamma radiation. Oxygen was not necessary for the destruction of the chromophore but was absolutely essential for the destruction of substituted aromatic rings in the dye molecule. For the purpose of the destruction of the skeleton of the Acid Red 265 molecules, it was necessary to keep the concentration of dissolved oxygen above at about 30 ppm (in mass) in the case of the 60 ppm dye solution.