Development of bimetallic g-C3N4 nanocatalysts for efficient organic dye catalytic ozonation and antibacterial activities

Abstract

The catalytic ozonation performance of g-C₃N₄@Cu@Ag and g-C₃N₄@Cu@Ni nanocatalysts was systematically evaluated for the degradation of methylene blue (MB) and methyl orange (MO). The catalysts were successfully synthesized through a simple one-step thermal calcination of melamine with the corresponding metal nitrates. Their morphology, crystallinity, and composition were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), Raman spectroscopy, and Energy-dispersive X-ray (EDS), which confirmed the formation of porous nanosheets with uniform metal dispersion and well-integrated CuO, AgO, and NiO phases. The g-C₃N₄@Cu@Ag catalyst exhibited outstanding performance with 95 % MO removal (k = 0.045 min⁻¹) under alkaline conditions, achieving 80.23 % mineralization efficiency after four reuse cycles, with minimal loss due to intermediate adsorption and partial metal leaching. In addition to dye degradation, g-C₃N₄@Cu@Ag demonstrated broad antimicrobial activity. It produced inhibition zones of 1.40 cm (Enterococcus), 1.25 cm (Bacillus cereus), 1.00 cm (K. pneumoniae and Pseudomonas), and significant antifungal action with 5.0 cm against Aspergillus niger and 4.2 cm against Candida albicans. In contrast, pristine g-C₃N₄ and g-C₃N₄@Cu@Ni showed negligible inhibition. These results highlight the intrinsic Cu–Ag–g-C₃N₄ synergy in enhancing ozone activation and hydroxyl radical generation, while conferring dual functionality, efficient catalytic ozonation and potent antimicrobial effects, making g-C₃N₄@Cu@Ag a promising multifunctional material for sustainable wastewater treatment.