Effective degradation of multiple antibiotics by 0D/3D/2D dual Z-heterojunction photocatalyst CdS QDs/Bi2WO6/g-C3N4 and study of degradation mechanism

With the production and application of antibiotics, the generated substandard antibiotic wastewater has brought unprecedented damage to the environment and finally the health of human beings. To alleviate this problem, photocatalytic degradation was proposed, and various catalysts have been developed with high efficiency and low cost. Herein, a novel 0D/3D/2D dual Z-heterojunction photocatalyst CdS QDs/Bi₂WO₆/g-C₃N₄ was constructed by in-situ growth method in order to efficiently degrade multiple antibiotic pollutants. The combination of multi-dimensional materials is more conducive to the close contact between materials and the effective transport of photogenerated carriers. Results reveal that the sample of 75 %CdS QDs/Bi₂WO₆/g-C₃N₄ (denoted as 0.75CSBC) showed the best degradation activity and stability for tetracycline (TC), and the degradation rate could reach 80.83 % within 12 min under visible light irradiation. Based on the detailed analysis of the results from free radical trapping experiment, Mott-Schottky test and liquid chromatography-mass spectrometry (LC-MS) test, the photocatalytic degradation mechanism and pathway were proposed. Besides, 0.75CSBC showed excellent degradation activity for levofloxacin (LVFX), oxytetracycline hydrochloride (OTC) and norfloxacin (NFLX), confirming its good universality. The multi-dimensional dual Z-heterojunction photocatalyst not only provides more active sites but also promotes the efficient migration of photogenerated charge, together with an excellent stability, indicating its wide practical application in the field of photocatalytic wastewater treatment. This work also provides an interesting method for the preparation of multi-dimensional heterogeneous catalysts.