Co ₃ O ₄ /g‐C ₃ N ₄ Composites Modified With Bi ₂ O ₃ and MgO for Peroxymonosulfate Activation and Organic Dye Degradation

A series of Co, Co–Bi, and Co–Mg/g‐C ₃ N ₄ (graphitic carbon nitride) composites with 5 wt% metal content were synthesized via a one‐pot thermal polycondensation method using pristine and HNO ₃ ‐protonated melamine as precursors for g‐C ₃ N ₄ . The obtained catalysts were characterized by inductively coupled plasma‐optical emission spectrometry, X‐ray diffraction, transmission electron microscopy, Selected Area Electron Diffraction (SAED), Fourier transform infrared spectroscopy, and Brunauer‐Emmett‐Teller method (BET) techniques. Their catalytic performance was evaluated for peroxymonosulfate (PMS) activation and the degradation of Acid Orange 7 (AO7) and methylene blue (MB) in aqueous solutions under ambient conditions. The Co‐g‐C ₃ N ₄ composite exhibited significantly higher catalytic activity than bare Co ₃ O ₄ and pristine g‐C ₃ N ₄ , which can be attributed to the synergistic interaction between the two components. It was found that the synthesis of g‐C ₃ N ₄ via pyrolysis of HNO ₃ ‐protonated melamine enhances the PMS‐activation capability of the resulting composite catalysts. A further enhancement in catalytic performance was achieved by modifying Co‐g‐C ₃ N ₄ with MgO and Bi ₂ O ₃ . The superior performance of Co–Mg‐g‐C ₃ N ₄ (pm) is attributed to the increased basicity of the catalyst surface. Quenching experiments using ethanol (EtOH) and tert‐butyl alcohol (TBA) as radical scavengers confirmed the generation of sulfate radicals in the investigated systems. In addition, the effects of catalyst dosage, PMS/dye molar ratio, and initial solution pH on the degradation rates of AO7 and MB were also examined.