Preparation of CoFe2O4/α-Fe2O3 magnetic composite as a fenton photocatalyst for methylene blue degradation under visible radiation

Abstract

CoFe2O4 (CFO) material was prepared by solvothermal method and then used to synthesize the magnetic CFO/α-Fe2O3 composite. CFO/α-Fe2O3 material was fabricated using the sol-gel technique and sintering at 500oC. The chemical structure, surface morphology and properties of materials were analyzed by X-ray diffraction, Fourier-transform infrared spectroscopy, thermal analysis, energy dispersive X-ray spectroscopy, field emission scanning electron microscopy and vibrating sample magnetometer. The prepared CFO/α-Fe2O3 material possessed a spherical form with an average size of 98 ± 23 nm. The formation and binding of α‒Fe2O3 on the CFO surface caused decreasing the saturation magnetization value of CFO/α-Fe2O3 and increasing the coercivity value compared to the CFO matrix phase. CFO/α-Fe2O3 was then used as a Fenton photocatalyst in the decomposition reaction of methylene blue (MB) under visible radiation with the presence of the electron donor oxalic acid. The resulted apparent rate constant value was 0.696 h-1. The photocatalytic Fenton process followed the pseudo-first-order kinetic equation with the result of after 180 minutes of reaction, the MB content was decomposed by 90%. The binding of α-Fe2O3 changed the material structure's phase composition and caused a redistribution of metal cations on the surface of CFO/α-Fe2O3. The increase of Fe on the surface of CFO/α-Fe2O3 promoted the formation of surface ferrioxalate complexes via the reaction between the Fe3+ ion on the surface and oxalic acid. Then, under visible radiation, these ferrioxalate complexes could be stimulated and produced free radicals such as C2O4•-, •OH, and O2•- which could effectively decompose the MB molecule in solution. In addition, the CFO/α-Fe2O3 catalyst showed high stability and good performance after five consecutive reuses. The results would be promising for the practical application of this material in treating toxic organic dyes in water.