Ecofriendly synthesis and characterization of oxygen-enriched g-C3N4 from diverse precursors for efficient organic dye decontamination

Industrial wastewater from sectors such as textiles, printing, and pharmaceuticals contain harmful pollutants, including nonbiodegradable dyes, which pose significant challenges for environmental safety. Neutral red, a cationic dye commonly found in wastewater, obstructs photosynthesis in aquatic ecosystems and carries potential toxicity. Traditional methods of dye removal often prove ineffective due to the chemical stability of these compounds. In this study, oxygen-doped graphitic carbon nitride (O-doped g-C₃N₄) was synthesized as an innovative photocatalyst for the degradation of neutral red dye under visible light. The material was synthesized through a sustainable process involving the calcination of urea, dicyandiamide, and oxalic acid, and its characteristics were evaluated using various techniques, including XRD, FT-IR, UV-Vis spectroscopy, and SEM. Photocatalytic degradation of neutral red was analysed using a custom photoreactor under visible light. The results demonstrated that O-doped g-C₃N₄ exhibited enhanced photocatalytic efficiency compared to pure g-C₃N₄, reducing the recombination of electron-hole pairs and effectively degrading the dye. Adsorption kinetics followed a pseudo-2nd-order model, while adsorption isotherms suggested that the Langmuir model best described the adsorption process, indicating monolayer adsorption. The maximum adsorption capacity of O-doped g-C₃N₄ for neutral red was 9.643 mg g^-1, surpassing pure g-C₃N₄. The photocatalytic performance of OCN-UD was assessed under visible light, revealing a significant degradation efficiency of 86% for neutral red after 60 min, compared to 51% for pure g-C₃N₄. Kinetic studies indicated that the adsorption of neutral red onto OCN-UD primarily followed a pseudo-2nd-order model, demonstrating chemical adsorption processes. The synergistic effects of adsorption and photocatalysis were evident, as the initial adsorption phase concentrated dye molecules near active sites, facilitating efficient photocatalytic degradation through reactive oxygen species generation. This study highlights the potential of O-doped g-C₃N₄ as an efficient, eco-friendly solution for the treatment of dye-laden wastewater.