Unravelling the effect of non-metal doping on polymeric carbon nitride for enhanced degradation of broad-spectrum antibiotics under visible light

Abstract

Advanced oxidation processes, such as heterogeneous photocatalysis, offer a green pathway for eliminating refractory organic pollutants. Despite notable advancements in photocatalyst design, poor light-harvesting efficiency and fast electron-hole recombination remain significant bottlenecks for real-world deployment. To circumvent these shortcomings, herein, non-metal (B, S, P, and F) doped graphitic carbon nitride (GCN) was prepared via solid-state polycondensation of melamine with appropriate precursors of the respective dopants, showcasing its superiority over conventional photocatalysts in degrading two representative broad-spectrum antibiotics, namely ofloxacin (OFC) and sulfamethoxazole (SMZ). The successful incorporation of non-metal dopants (B, S, P, and F) into the GCN framework was confirmed by a series of microscopic, spectroscopic, optical, and electrochemical characterizations. The maximum degradation of antibiotics (98.9% for OFC and 96.6% for SMZ) was achieved using F-doped g-C3N4 (F-GCN) within 90 min of visible light illumination, primarily facilitated by holes and superoxide radicals. Although F-doping did not significantly enhance the photon absorption capacity of the GCN sample, the marked improvement in photocatalytic performance was clearly attributed to more efficient charge separation and migration. These findings coherently suggest that incorporating non-metal dopants can effectively enhance charge separation, making it a promising strategy for improving photocatalyst efficiency. To further validate the practical applicability of the F-GCN photocatalyst for water and wastewater treatment, its performance in removing a pharmaceutical cocktail from diverse aqueous matrices was evaluated. Comprehensive toxicity assessments of the photocatalytic degradation byproducts, using bacterial colony counting and seed germination tests, confirmed the ecological safety of the treated antibiotic solution. Moreover, F-GCN exhibited remarkable reusability and photostability, underscoring its strong potential for large-scale photocatalytic wastewater treatment.