Reusable CuFe2O4-Fe2O3 catalyst synthesis and application for the heterogeneous photo-Fenton degradation of methylene blue in visible light

Mixed iron and copper oxides were synthesized by the modified Pechini method. Calcined (at different temperatures), characterized and used for the removal of methylene blue dye (MB) by solar photocatalysis. The materials exhibited magnetic behavior and low values of surface area (0.1 to 42.2 m(2).g(-1)). According to the diffuse reflectance spectra, the prohibited band intervals of the samples ranged from 1.92 to 2.4 eV. The results of the X-ray diffraction analysis showed that the hematite and copper ferrite phases were the main responsible for the high efficiency of the photochemical reaction, with apparent kinetic constant equal to k = 0.016 min(-1) and 100% removal of the dye in 180 min of reaction (starting from an initial solution with 50 mg.L-1 of the dye). MB removal from the aqueous solution occurred in the presence of H2O2 (with 300 mg.L-1), with 1.0 g.L-1 of catalyst, at neutral pH and under solar radiation. The stability of the catalyst was confirmed by its reuse in four consecutive cycles. A kinetic mechanism for photochemical reaction has been proposed, which explains the experimental results obtained.