2D–2D ZnO/N doped g-C3N4 composite photocatalyst for antibiotics degradation under visible light

ZnO and g-C3N4 provide excellent photocatalytic properties for degradation of antibiotics in pharmaceutical wastewater. In this work, 2D-2D ZnO/N doped g-C3N4 (NCN) composite photocatalysts were prepared for degradation of tetracycline (TC), ciprofloxacin (CIP) and ofloxacin (OFLX). The addition of ZnO resulted in higher separation efficiency and lower recombination rate of photogenerated charge under visible light. The composite photocatalyst showed better degradation performance compared to ZnO or NCN alone. The TC degradation reached 81.3% in 15 minutes by applying the prepared 20% ZnO/NCN composite photocatalyst, showing great competitiveness among literature reported g-C3N4 based photocatalysts. After 30 minutes, the degradation rate of TC, CIP and OFLX reached 82.4%, 64.4% and 78.2%, respectively. The TC degradation constant of the composite photocatalyst was 2.7 times and 6.4 times higher than NCN and CN, respectively. Radical trapping experiments indicated that ·O2- was the dominant active substance. The transference of excited electrons from the conduction band (CB) of NCN to ZnO enhanced the separation of photogenerated electron-hole pairs and simultaneously suppressed their recombination. This study provides a possibility for the design of high-performance photocatalysts for antibiotics degradation in wastewater.