Photolysis, photochemical and homogeneous photocatalytic oxidation of Congo red dye by hydrogen peroxide

The kinetics of photolysis, photochemical and homogeneous photocatalytic oxidation of model solutions of azo dyes by hydrogen peroxide has been studied using the example of Congo red. The rate constants of the photolysis and photochemical oxidation reactions of Congo red based on quantum chemical calculations were consistent with the experimental rate constants of the reactions. It has been established that the highest oxidation state of the Congo red dye (99.9%) was observed under photochemical oxidation (catalyst iron (II) ions). A decrease in the intensities of absorption maxima in the spectra of a Congo red solution in the photochemical oxidation process with hydrogen peroxide and their complete disappearance after 4 hours in the presence of iron (II) ions shows that the dye is mineralized.