Ultra-thin DyFeO3/g-C3N4 p-n heterojunctions for highly efficient photo-Fenton removal of oxytetracycline and antibacterial activity

The design and synthesis of visible light-responsive heterogeneous catalysts for the effective removal of contaminants are critical areas of research in the environmental catalysis. In this study, DyFeO3/g-C3N4 p-n heterojunctions (DFCs) were successfully synthesized. TEM, HRTEM, SEM, FTIR and XPS results clarified the successful formation of DFCs and their ultra-thin and porous structure. DRS and XPS VB spectra revealed that the DFCs were type Ⅱ heterojunctions with strong visible light absorption. TPC, EIS, PL and PL decay spectra confirmed the increase of the separation efficiency and the inhibition of the recombination of the photogenerated charge carriers in DFCs. DFC-2 (containing 2 wt% of DyFeO3) exhibited the best photo-Fenton degradation performance. The highest degradation efficiency was 99.1%, 100%, and 99.6% on DFC-2 for oxytetracycline, methylene blue, and rhodamine B, respectively. The photo-Fenton antibacterial efficiency was over 99% after 15 min of visible light irradiation. Moreover, the antibacterial effect was 4 times and 2.7 times that of photocatalytic or Fenton antibacterial processes. The internal electric field generated at the interface between DyFeO3 and g-C3N4 ameliorated the spatial separation and transfer features of charge carriers. In addition, the accelerated transfer of the electrons facilitated the reduction of Fe3+ to regenerate Fe2+, which further enhanced the photo-Fenton degradation and antibacterial activity. In a radical scavenger experiment, ESR and HPLC-MS were employed to identify the major active species and intermediates in the photo-Fenton degradation of oxytetracycline. The degradation pathways and mechanism were reasonably inferred. This study proposes promising DFCs with p-n heterostructures for the effective photo-Fenton removal of oxytetracycline and antibacterial activity.