Preparation of magnetic nanoparticles as photo‒Fenton catalysts by a hydrothermal‒assisted thermal treatment method

Abstract

The magnetic CoFe2O4 nanoparticles, prepared by hydrothermal method combining with the heat treatment at 600oC, were used to act as a photo‒Fenton catalyst in the methylene blue (MB) degradation reaction. The composition, structure, and surface morphology of the prepared materials were studied by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDX) spectroscopy. The optical properties of CoFe2O4 before and after calcination, analyzed by UV-Vis diffuse reflectance (DRS) spectroscopy, demonstrated that after heating at 600oC, the structure and crystallinity of CoFe2O4 were increased. The calcination process also caused the CoFe2O4 sintering to grow to a larger size, thereby reducing the surface area of the CoFe2O4 after calcination compared to the original ones. This value was determined through nitrogen the adsorption‒desorption isotherms curve. The magnetism of CoFe2O4 before and after calcination was studied by vibrating sample magnetometer (VSM). After sintering at 600oC, the saturation magnetization (Ms) and residual magnetism (Mr) of CoFe2O4 were higher than those of the original. The Fenton photocatalytic performance was evaluated by MB degradation reaction under UVA radiation in the presence of oxalic acid as an active free radical generating agent. In the methylene blue degradation reaction at room temperature, the prepared CoFe2O4 catalyst showed the maximum degradation efficiency of 97% for MB and the reaction yields were almost unchanged after three consecutive reactions. This method promised in making ferrite materials for water treatment based on some advantages such as simple process, low cost, and environmentally friendly solvent usage.