Photocatalytic degradation of sulfonamide and fluoroquinolone antibiotics by Fe-N-co-doped biochar/carbon quantum dots p-n heterojunction materials

The misuse of sulfonamide and fluoroquinolone antibiotics leads to pollution of the water environment, necessitating the development of cost-effective and efficient degradation methods. This article presents a one-step hydrothermal method (200℃, 8 h) for the preparation of Fe-N-co-doped biochar/carbon quantum dots (Fe/N/BC/CQDs) as a photocatalytic material. The Fe/N/BC/CQDs was employed for the activation of H₂O and O₂, facilitating the degradation of sulfonamide and fluoroquinolone antibiotics, with superoxide radicals, photo-generated holes, hydroxyl radicals, and singlet oxygen dominated the photodegradation process. Under 1 h dark and 8 h natural light conditions, the degradation efficiency of norfloxacin, sulfathiazole, sulfamethoxazole, sulfamonomethoxine, sulfadoxin, sulfamethazine (10 mg/L) by Fe/N/BC/CQDs ranged from 74.21 % to 89.23 %. The potential degradation pathways of sulfonamide and fluoroquinolone antibiotics were proposed based on ultrahigh-performance liquid chromatography tandem high-resolution mass spectrometry analysis of the intermediates. The Fe-N-doped biochar’s hierarchical pore structure enhances synergistic adsorption-catalysis effects, while the incorporated carbon quantum dots (CQDs) broaden solar spectrum utilization, effectively overcoming the high-intensity light dependency common to conventional photocatalysts. Efficient charge separation was achieved through the formation of a p-n heterojunction between Fe-N-co-doped biochar and CQDs. Additionally, the applicability of Fe/N/BC/CQDs in real water systems was confirmed, providing valuable insights for the construction of p-n heterojunction structures to degrade organic pollutants in water.