Higher acidity promoted photodegradation of fluoroquinolone antibiotics under visible light by strong interaction with a niobium oxide based zeolitic octahedral metal oxide

Abstract

Zeolitic octahedral metal oxide based on niobate (ZOMO-NbOx) with high acidity was synthesized as an effective catalyst for fluoroquinolone antibiotics degradation under visible light. Higher acidity promoted the adsorption of ciprofloxacin (CIP), a represented fluoroquinolone antibiotic, on ZOMO-NbOx. The adsorption of CIP on ZOMO-NbOx enabled the material to expand the light-absorbing region from UV to visible range through the ligand to metal charge transfer. ZOMO-NbOx showed high catalytic activity with the total over frequency (TOF) value (22.27 μmolCIP min−1 gcat−1), which was 53 times higher than of the commercial Nb2O5 (0.42 μmolCIP min−1 gcat−1). The stable heterogeneous ZOMO-NbOx was reused 5 times without loss of activity. ZOMO-NbOx showed good resistance to inorganic ions and humic acids (HAs), and CIP was able to be degraded by the catalyst from various natural freshwater bodies. The intermediate products were determined, and the degradation pathways were proposed.