Photodegradation mechanism and genetic toxicity of bezafibrate by Pd/g-C3N4 catalysts under simulated solar light irradiation: The role of active species

Fibrate pharmaceuticals are a group of ubiquitous emerging pollutants, which pose a potential threat to ecosystem and human health. Photocatalysis with inexhaustible solar energy is a sustainable option for fibrate pharmaceuticals photolysis removal from water. For high-efficiency use of solar light, the designed low-cost and high-activity solar-driven Pd/g-C3N4 photocatalysts took full advantages of the Pd plasmonic and electrons transformation for photocatalysis. The Pd/g-C3N4 photocatalysts with different Pd deposition were systematically designed and applied to investigate the degradation of bezafibrate (BZF), a representative fibrate pharmaceutical with two benzene rings and a fibrate chain in its structure. The as-prepared Pd/g-C3N4 catalysts presented promising photocatalytic activities in BZF degradation with respect to that of g-C3N4 under simulated solar (2.9 times) and visible light irradiation (2.4 times), as well as photocatalytic stability. The possible active species produced during the photocatalytic process of BZF were unveiled and verified by quenching electron spin resonance (ESR) analysis. Results revealed that hydroxyl radical (OH) contributed 79.39% of BZF degradation. Three main possible photocatalytic pathways of BZF were also proposed with the calculation of frontier election density (FED), including R-oxy substituent, OH-addition and oxidative dechlorination. The utilization of Pd/g-C3N4 catalysts was considered to be low toxicity and safe, and the genotoxicity of BZF solution could be decreased after photodegradation. This study presents a feasible approach for the enhancement removal of fibrate pharmaceuticals with the energy utilization from natural sunlight.