Photocatalytic Degradation of Escherichia coli Bacteria by Graphitic Carbon Nitride: A Comparative Study under Visible Light and Dark Conditions in Aqueous Solutions

Microbial disinfection of water involves the inactivation or removal of pathogenic microorganisms. Conventional methods for microbial water disinfection include chemical oxidation using various oxidants such as chlorine, chlorine dioxide, chloramine, and ozone, as well as ultraviolet radiation. Among these, advanced oxidation and photocatalytic disinfection using semiconductor nanomaterials have emerged as a novel approach for eliminating pathogenic bacteria from aqueous solutions. This study aims to investigate the photocatalytic removal of Escherichia coli (E.coli) bacteria using a graphitic carbon nitride photocatalyst synthesized from melamine as a precursor. The synthesis of the photocatalyst was confirmed through X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, Fourier-transform infrared spectroscopy (FTIR), photoluminescence (PL) spectroscopy, diffuse reflectance spectroscopy (DRS), and field emission scanning electron microscopy (FE-SEM). To evaluate the antibacterial performance of the synthesized photocatalysts, the disk diffusion assay and the determination of bacterial viability on solid media after the photocatalytic process were employed. The results demonstrated that the synthesized photocatalysts exhibited excellent removal efficiency against E.coli under visible light irradiation. Among them, graphitic carbon nitride synthesized at a temperature of 550°C and a nitrogen gas flow rate of 20 mL/min (CN-20) achieved complete removal of E.coli with an initial concentration of 10^7 CFU/mL within 4.5 hours under visible light irradiation.