Enhanced photocatalytic degradation of paraben preservative over designed g-C3N4/BiVO4 S-scheme system and toxicity assessment

Paraben preservatives have been listed as emerging pollutants due to their ubiquity in various environmental matrices, especially the water bodies. How to efficiently and practically eliminate these paraben pollutants is therefore of great importance. Herein, a designed S-scheme heterojunction photocatalyst, consisting of graphitic carbon nitride (g-C₃N₄) and monoclinic bismuth vanadate (BiVO₄), was fabricated by a facile hydrothermal synthesis and employed to treat benzyl-paraben (BzP). TEM and XPS analysis testified the intimate interaction between g-C₃N₄ and BiVO₄, and the consequently smoothed interfacial charge transfer rendered the feasible recombination of the photoexcited electrons (from BiVO₄) and holes (from g-C₃N₄). The as-established S-scheme system enabled the left g-C₃N₄ electrons and BiVO₄ holes to maintain the high redox abilities and accelerated the charge separation concurrently. In particular, the g-C₃N₄/BiVO₄ composite generated much higher photocurrent response as compared with pure g-C₃N₄ and BiVO₄, highlighting the improved separation of photoinduced charges. Therefore, under visible light and natural solar light irradiation, the g-C₃N₄/BiVO₄ composite showed the significantly enhanced photocatalytic degradation of BzP, which was further optimized with 5 wt% g-C₃N₄ in the composite. According to the Mott-Schottky plots and identified active species, the mechanism of the g-C₃N₄/BiVO₄ S-scheme heterojunction system was illustrated. In addition, during the photocatalytic degradation process, the acute toxicity of the reaction solutions on zebrafish embryos was notably reduced. In conclusion, the demonstrated strategy to enhance the photocatalytic performance by designing S-scheme heterostructure may provide more insights into the development of high-efficiency photocatalyst towards the solar energy utilization and environmental treatment. Furthermore, photocatalytic degradation had been proved to be an efficient method for eliminating the ecological risk of paraben pollutants, warranting more attention in future work.