Nitrogen-rich porous polymeric carbon nitride with enhanced photocatalytic activity for synergistic removal of organic and heavy metal pollutants

The development of highly efficient photocatalysts is crucial to realize water remediation via photocatalysis technology. In this work, nitrogen-rich porous polymeric carbon nitride (DCCN-S) was prepared through calcining the intermediate obtained by solvothermal treatment of dicyandiamide (DCD) and cyanuric acid (CA). DCCN-S shows superior photocatalytic performance for the degradation of various high concentration organic pollutants including antibiotics and dyes. The removal rate of levofloxacin (LEV, 50 mg L-1) reaches 93.5% within 60 min, surpassing most of the reported photocatalysts. Moreover, DCCN-S exhibits excellent photocatalytic activity towards synergistic removal of LEV and Cr(vi). The outstanding photocatalytic performance of DCCN-S can be ascribed to the rich amino defects and the porous structure, which significantly promote the absorption of visible light as well as the separation and transfer of photogenerated charges. The possible degradation routes of LEV were proposed from liquid chromatography-mass spectrometry analysis, and the ecotoxicity of the degradation intermediates was evaluated by the ECOSAR predictive model. The photocatalytic mechanism for the synergistic removal of mixed pollutants was proposed based on the free radical quenching experiments, contrast experiments and electron spin resonance spin-trapping tests. This work provides a new idea for the design and synthesis of high-efficiency CN-based photocatalytic materials for wastewater treatment.