Enhanced photocatalytic degradation of ciprofloxacin using novel C-dot@Nitrogen deficient g-C3N4: Synergistic effect of nitrogen defects and C-dots

Removal of typical antibiotics from secondary effluent is critical to reducing the risk of wastewater recycling. In this study, a visible-light-driven green photocatalyst C-dot@Nitrogen Deficient g-C3N4 was firstly synthesized and applied to degrade ciprofloxacin (CIP) in water. Compared with the pure g-C3N4, the removal efficiency of CIP was increased by more than 3.5 times under visible light irradiation. The promotion mainly resulted from the enhancement of the absorption capacity of the material to visible light and the reduction of the electron-hole pair recombination rate, which were attributed to the introduction of nitrogen defects and C-dots. The ROS scavenging experiments showed that superoxide radicals and hydroxyl radicals were the main active species to decompose CIP. Cycled experiments demonstrated that C-dot@ND-g-C3N4 could maintain more than 50% CIP removal rate after 5 cycles of recycling. The influences of typical environmental factors on the degradation of CIP showed that the removal rate of CIP under neutral or weak alkaline conditions was significantly higher than that under acidic conditions. The degradation rate of CIP was highest when the HPO42− concentration was 0.6 mmol/L. NO3− could improve the degradation of CIP in water slightly, while NH4+ had little effect on the degradation of CIP. Our work opens a new channel for the exploration and application of a new and green photocatalyst to reduce the risk of wastewater recycling.