'Critical' effect of hydrogen peroxide in photochemical oxidative decolorization of dyes: Acid Organge 8, Acid Blue 74 and Methyl Organge

摘要

Advanced oxidation processes (AOPs) have proved very effective in treatment of the various hazardous organic pollutants in water. The photochemical decolorization of three dyes, namely Acid Organge 8 (AO8), Acid Blue 74 (AB74) and Methyl Orange (MO) was studied in the UV/hydrogen peroxide process by using a continuous photo-chemical reactor with a 15 W low pressure mercury lamp. Decolorization was complete in relatively short time and follows apparent first order kinetics with respect of dye concentration. The rate of disappearance of a given dye was monitored spectrophotometrically at the visible maximum absorption wavelength. It was found that the rate of decolorization rises by increasing the initial dosage of H_2O_2 up to a "critical" value at which it is maximum and beyond which it is inhibited. A simple reactions pathway, describing adequately the process, has been studied. Based on this reaction schema, we have established a mathematical relation between the apparent rate constant of the dye removal and applied H_2O_2 dosage presented by the ratio of its initial mass concentration to that of the dye. The rate constant values obtained by model for the three dye solutions are in good agreement with the experimental data. The model parameters have been determined.