Adsorption and photodegradation of methylene blue with Fe2O3-activated carbons under UV illumination in oxalate solution

• Fe2O3-activated carbons are used for adsorption–photodegradation of methylene blue.
• Dye desorption influences on heterogeneous photodegradation experiments.
• Simultaneous mineralization of MB and oxalic acid occurs under UV-irradiation.
• Fe2O3-activated carbons are used in the cycle run experiment in presence of oxalic acid.

Materials based on iron oxide (Fe2O3) and activated carbons (Fe-ACs) were prepared by pore volume impregnation of activated carbon in an iron nitrate solution followed by heat treatment at 250 °C. The Fe-AC materials were amorphous and microporous, and the specific surface areas (SBET) values were higher than 1000 m2/g. The effects of Fe content, porous properties, pH of the treatment solution, oxalic acid (OA) and MB concentrations were systematically investigated. The increase of the Fe content caused a significant decrease in the SBET values, lowering of the MB adsorption capacity and the photodegradation rate constant of the Fe-AC samples. The simultaneous processes of MB adsorption–photodegradation samples were complex owing to a strong influence of MB desorption during the photodegradation experiments under UV illumination. The MB decomposition was intensified by the enhanced simultaneous heterogeneous and homogeneous catalytic reactions. The almost complete simultaneous mineralization of MB and OA was confirmed by total organic carbon (TOC) analysis. The present system has advantages on the viewpoint of no hydrogen peroxide in operation, the low Fe leaching near neutral pH, no sludge formation, the possibility to recycle the iron promoter and cyclic usage.

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