Photocatalytic degradation of oxytetracycline under visible light by nanohybrids of CoFe alloy nanoparticles and nitrogen-/sulfur-codoped mesoporous carbon

Abstract Efficient photodegradation of antibiotics in water systems is significant for environmental restoration and water purification. In this work, a series of catalysts for oxytetracycline (OTC) degradation under visible light was proposed. The hybrids (denoted by CoFe@NSC) of CoFe alloy and N/S-codoped mesoporous carbon were obtained by annealing CoFe Prussian blue analogue (CoFe PBA) nanocubes under different temperatures using thioacetamide as the N and S resource. The CoFe@NSC photocatalysts show substantially boosted photocatalytic activity for OTC degradation compared with that of the CoFe PBA catalyst. Among the three CoFe@NSC hybrids obtained by pyrolyzing at 800 °C, 900 °C, and 1000 °C, the CoFe@NSC-1000 hybrid at 1000 °C exhibits the highest photocatalytic activity toward OTC degradation under visible light irradiation for its highly conjugated nanostructure, large specific surface area (733.0 m2 g−1), enhanced visible light absorption capacity, and improved separation/migration rate for photogenerated charge carriers. Approximately 90% of OTC was degraded by CoFe@NSC-1000 catalyst after visible light irradiation for 150 min. Electron spin resonance (ESR) and trapping tests indicate that the photoinduced superoxide and hydroxyl radicals are the main active species for photodegradation. The possible photocatalytic mechanism was proposed based on the active species, trapping experiments and ESR analysis. The biotoxicity of photocatalytic degradation products and residual antibiotic were also explored using E. coli as the reference organism. This work offers new insight into the development of novel catalysts for photodegradation of antibiotics.