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.