Efficient chlorination reaction of Pt/RuO2/g-C3N4 under visible light irradiation for simultaneous removal of ammonia and bacteria from mariculture wastewater

The removal of ammonia nitrogen (NH₄⁺-N) and bacteria from aquaculture wastewater holds paramount ecological and production significance. In this study, Pt/RuO₂/g-C₃N₄ photocatalysts were prepared by depositing Pt and RuO₂ particles onto g-C₃N₄. The physicochemical properties of photocatalysts were explored by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV–vis diffuse reflectance spectrometer (UV–vis DRS). The photocatalysts were then applied to the removal of both NH4+-N and bacteria from simulated mariculture wastewater. The results clarified that the removals of both NH₄⁺-N and bacteria were in the sequence of g-C₃N₄ < RuO₂/g-C₃N₄ < Pt/g-C₃N₄ < Pt/RuO₂/g-C₃N₄. This magnificent photocatalytic ability of Pt/RuO₂/g-C₃N₄ can be interpreted by the transfer of holes from g-C₃N₄ to RuO₂ to facilitate the in situ generation of HClO from Cl⁻ in wastewater, while Pt extracts photogenerated electrons for H₂ formation to enhance the reaction. The removal of NH₄⁺-N and disinfection effect were more pronounced in simulated seawater than in pure water. The removal efficiency of NH₄⁺-N increases with an increase in pH of wastewater, while the bactericidal effect was more significant under a lower pH in a pH range of 6–9. In actual seawater aquaculture wastewater, Pt/RuO₂/g-C₃N₄ still exhibits effective removal efficiency of NH₄⁺-N and bactericidal performance under sunlight. This study provides an alternative avenue for removement of NH₄⁺-N and bacteria from saline waters under sunlight.