Synthesis of Monodisperse Magnetic Fe3O4 Microspheres and Their Photocatalytic Degradation of Xylenol Orange

To further enhance the safety and energy efficiency of the Fe3O4 preparation experiment, we proposed a strategy for synthesizing monodisperse Fe3O4 microspheres through a one-step solvothermal process. In this environmentally friendly synthesis method, stable FeCl3∙6H2O was utilized as the sole raw material, while ethylene glycol, characterized by its high boiling point and favorable safety profile, served as the solvent. Additionally, inexpensive and readily available urea was selected to function either as a mineralizer or surfactant. Through this one-step solvothermal reaction, the target product of Fe3O4 could be obtained without subsequent calcination under reducing or inert atmospheres, thereby enhancing experimental safety and promoting energy conservation. By controlling the amount of urea added, it became feasible to produce monodisperse magnetic Fe3O4 microspheres characterized by complete crystallinity and high yield. Utilizing the as-synthesized Fe3O4 as a catalyst, we investigated its photocatalytic activity against xylenol orange organic dyes along with its regeneration characteristics. When 40 mmol of urea was incorporated into the reaction mixture, the resulting Fe3O4 sample exhibited optimal photocatalytic performance; a 20 mg/L xylenol orange solution became colorless and transparent after just 1.5 h of UV light irradiation. Furthermore, during five consecutive regeneration cycles, its catalytic activity could be restored to its initial level. Importantly, Fe3O4 demonstrated excellent magnetic sensitivity properties that facilitated rapid targeted separation under an external magnetic field, providing convenience for recovery and collection purposes.