Electrical energy determination for an azo dye decolorization and mineralization by UV/H2O2 advanced oxidation process

Abstract

Abstract This study examined the photolytic degradation of C.I. Acid Orange 7 azo dye, in aqueous solution by combined UV and hydrogen peroxide. A continuous circulated photoreactor equipped with a low-pressure mercury lamp was used. Different initial dosages of hydrogen peroxide and initial concentrations of dye were used for the synthetic wastewaters preparation. The rate of color removal and aromatic ring destruction were monitored spectrophotometrically at the visible maximum absorption wavelength and UV region. The decrease in total organic carbon (TOC) in dye solutions was measured to monitor the dye mineralization process. Decolorization and mineralization reactions after decolorization period follow apparent first order kinetics. The pseudo-first order rate constants values for each case were calculated from the experimental kinetic curves. It was found that mineralization of C.I. Acid Orange 7 undergoes about five times slower kinetics than decolorization reaction. By applying only 3.75 W l −1 of the UV dosage in the reaction mixture of 17.5 mg l −1 dye and 525 mg l −1 H 2 O 2 , nearly 90% total organic carbon can be removed in 100 min. Process electrical energy consumption for different synthetic wastewaters was determined.