Heterogeneous activation of hydrogen peroxide using γ-Al2O3 supported bimetallic Fe, Mn for the degradation of reactive black 5

Abstract

A Fe–Mn/γ-Al₂O₃ catalyst was prepared via a wet impregnation method and used for the degradation of reactive black 5 (RB5) as an activator of hydrogen peroxide (H₂O₂). The prepared catalyst was characterized using XRD, FTIR and SEM-EDS. The results show that γ-Al₂O₃ can effectively restrain Fe and Mn. The catalytic activity of Fe–Mn/γ-Al₂O₃ was significantly higher than that of pure γ-Al₂O₃, Fe/γ-Al₂O₃ and Mn/γ-Al₂O₃. After four reuse cycles, Fe–Mn/γ-Al₂O₃ maintained a high catalytic activity and approximately 98% of the color removal was reached after 75 min reaction. The effects of important operational parameters, such as the initial pH of solution, H₂O₂ amount and catalyst addition on the decolorization efficiency, were investigated. The results displayed that the RB5 discoloration efficiency initially increased and then decreased with increasing H₂O₂ concentration and pH, as well as initially increasing and then maintaining stability with increasing catalyst addition. The best decolorization efficiency (98.02%) was obtained with the following parameters: pH = 3, H₂O₂ amount = 7 mmol L⁻¹ and catalyst addition = 2.5 g L⁻¹ for an initial RB5 concentration of 50 mg L⁻¹. Finally, the TOC removal was only 39.60% after 75 min of reaction, by prolonging the reaction time to 160 min, 62.23% of TOC removal can be achieved under the optimal operational parameters.