A kinetic comparative study of azo dye decolorization by catalytic wet peroxide oxidation using Fe–Y zeolite/H₂O₂ and photooxidation using UV/H₂O₂

A comparative study between the catalytic wet peroxide oxidation (CWPO: Fe(III)–Y zeolite/H₂O₂) and photooxidation (PO: UV/H₂O₂) of three different azo dyes—namely, reactive yellow, reactive red, and methyl orange—was conducted. Compared to CWPO, PO demonstrated higher initial reaction rates and final conversions. The contributions of H₂O₂, UV, UV/H₂O₂, Fe–Y zeolite, and Fe–Y zeolite/H₂O₂ to the decolorization of reactive yellow were investigated and the results showed that treatment with UV/H₂O₂ was the most effective process for the color removal. The effect of [H₂O₂]₀, UV irradiation power, [Fe–Y zeolite], and the reusability of the catalyst were also studied. The catalyst was found to be reusable, but with loss in its catalytic activity. An optimum [H₂O₂]₀ existed in both the PO and CWPO processes. However, this was higher in the latter process. The extent of decolorization increased as the UV irradiation power and [Fe–Y zeolite] increased, but there was a limit in the second case. In addition, the decolorization kinetics of the reactive yellow in both processes were investigated. It was concluded that PO followed an apparent first order kinetic model while CWPO followed the Chu kinetic model. Furthermore, a pseudo-second order rate law, which could be used in continuous flow reactor design equations, was proposed and verified to describe the CWPO rate of reaction.