Advanced photocatalytic degradation of highly chlorinated organic wastewater using anthraquinone-modified carbon nitride: Driven by superoxide and dichloride radicals

The development of sustainable and efficient wastewater treatment technologies is vital for tackling the challenges posed by high salinity and antibiotic-contaminated industrial wastewater. In this study, a highly active, metal-free photocatalyst (AQ@CN) was successfully synthesized via a simple and environmentally friendly method. Under conditions of high chloride ion (Cl - ) concentration, AQ@CN exhibited a for significantly enhanced degradation rate constant for sulfadiazine (SDZ), achieving a rate five times higher than that of g-C 3 N 4 . Mechanistic investigations identified superoxide radicals ( • O 2 – ), dichloride radicals ( • Cl 2 - ), and photogenerated holes (h + ) as the primary reactive species. Photoelectrochemical experiments and density functional theory (DFT) calculations revealed that the incorporation of anthraquinones (AQs) optimized local electron density, facilitating the separation of photogenerated carriers and enhancing the electron transfer rate. Furthermore, the degradation pathway of SDZ was proposed, and the toxicity of the degradation products was substantially reduced. This study offers an effective strategy to enhance the performance of metal-free photocatalysts, providing a robust theoretical and technical foundation for pollutant degradation in complex high-salinity industrial wastewater.