Boosted photocatalytic antibiotic degradation performance of Cd0.5Zn0.5S/carbon dots/Bi2WO6 S-scheme heterojunction with carbon dots as the electron bridge

Abstract

Building high-performance and robust S-scheme heterojunction photocatalysts for sustainable pollutant abatement has been a prospective tactics to restore environment. Herein, Cd0.5Zn0.5S/carbon dots/Bi2WO6 (CZS/CDs/BWO) S-scheme heterojunctions have been designed and fabricated as an efficient and durable visible-light-responsive photocatalyst for tetracycline oxidation with 0.7-fold, 6.4-fold and 0.5-fold enhancement compared with neat CZS, BWO and CZS/BWO. The superb photo-activity is primarily derived from the synergy between carbon dots and S-scheme heterojunction, which not only effectively diminishes the interface resistance but also achieves the fostered disintegration and preservation of the photo-carriers with great redox ability. The impact of water conditions on the photo-activity is explored in view of the complexity of the authentic aquatic environment. The findings of the scavenging tests and ESR analysis evidence that h+, O2−, and OH may mainly drive the antibiotic decomposition, mineralization and detoxification reaction. The photoreaction mechanism and TC degradation pathway over CZS/CDs/BWO are unraveled according to LC–MS analysis. The intermediate toxicity assessment indicates that most of the degradation byproducts’ acute and developmental toxicities are abated to a markedly lower level than that of TC. Moreover, CZS/CDs/BWO also could effectively degrade other popular pharmaceutical antibiotics (e.g., levofloxacin, norfloxacin, oxytetracycline, and enrofloxacin), demonstrating its universal photocatalytic potency for the treatment of pharmaceutical antibiotics. This work illustrates the potential practicability on carbon dots modulated S-scheme heterojunction photocatalysts for efficient water remediation.