Visible light-powered eco-friendly Fe₃O₄/g-C₃N₄ nanocomposites for rapid malachite green degradation

Malachite Green (MG), a widely used textile dye, is a toxic and non-biodegradable product commonly found in industrial wastewater. In this work, Fe₃O₄/g-C₃N₄ nanocomposites showed as an eco-friendly photocatalyst, effectively degrading the persistent pollutant to support sustainable wastewater treatment. Fe₃O₄ nanoparticles (NPs) were synthesized using a green route with Camellia sinensis (green tea) leaf extract method and integrated with g-C₃N₄, to form a hetero-structured photocatalyst. X-ray diffraction (XRD) analysis confirmed the successful formation of Fe₃O₄ and the preserved structural integrity of g-C₃N₄ structure. UV–visible diffuse reflectance spectroscopy (UV–vis DRS) revealed that Fe₃O₄ and g-C₃N₄ nanocomposites exhibit enhanced visible-light absorption. Photoluminescence (PL) spectra indicated suppressed recombination of photogenerated charge carriers, implying improved charge separation. Field emission scanning electron microscopy (FESEM) revealed a crumpled, sheet-like morphology. Brunauer–Emmett–Teller (BET) and Barrett-Joyner-Halenda (BJH) analysis confirmed the mesoporous nature of the nanocomposites. Photocatalytic tests under visible light irradiation demonstrated a remarkable degradation efficiency of 99.20% for MG 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 MG dye through demethylation and oxidative reactions.