Fe3O4/g-C3N4/rGO nanocomposites were synthesized as visible light-powered, eco-friendly photocatalysts for treating dye-polluted wastewater. Methylene blue (MB) served as the model contaminant. The composite aimed to improve charge separation and light harvesting by integrating g-C3N4 with conductive rGO and catalytically active Fe3O4. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDX) were employed to analyze the microstructure, morphology, and elemental composition, as well as to assess compositional uniformity. Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) analysis confirmed the mesoporous nature of the Fe3O4/g-C3N4/rGO composite, with a specific surface area of 25.55 m2/g, a pore volume of 0.0236 cc/g, and an average pore diameter of 3.37 nm. UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) revealed that the nanocomposites possess enhanced absorption in the visible-light region, characterized by a distinct absorption edge around 475 nm. Photocatalytic tests under visible light irradiation demonstrated a remarkable degradation efficiency of 99.53% for MB dye at pH 11, significantly outperforming the individual components. Liquid Chromatography-Mass Spectrometry (LC-MS) confirmed the presence of intermediate products, supporting a stepwise degradation mechanism of MB through demethylation and oxidative reactions.
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