Significant enhancement on the performance of Fe₂O₃ by B doping for photocatalytic Fenton degradation of antibiotics

Antibiotics including tetracycline (TC), enrofloxacin (ENR), and norfloxacin (NOR) were efficiently degraded via photocatalytic Fenton reactions employing boron-doped ferric oxide (B-Fe₂O₃) as the catalyst. A series of boron-doped Fe₂O₃ catalysts (x-B/Fe₂O₃) was synthesized by pyrolyzing an iron-based metal–organic framework precursor (Fe-ZIF). Boron atoms were in situ incorporated using boric acid as the boron source during the pyrolysis process, enabling homogeneous doping of boron into the Fe₂O₃ lattice. Boron doping effectively narrows the band gap of Fe₂O₃ and shifts its conduction band edge negatively, resulting in an expanded light-response range and enhanced reduction potential. This modulation in the energy band structure increases visible-light absorption and favours the activation of H₂O₂, thereby promoting the generation of more reactive oxygen species in the Fenton process. The optimal degradation rate of tetracycline (TC, 100 mg·L⁻¹) reached 78 % within 15 min by using 0.6 g·L^-1B-Fe₂O₃ and 11 mmol·L⁻¹ H₂O₂ in a broad pH range from 4 to 10. Trapping experiments revealed that the addition of a hole scavenger accelerated TC degradation, while the use of scavengers for excited electrons, hydroxyl radicals (·OH), and superoxide anion radicals (O₂^·–) inhibited TC removal to varying extents. The generation of hydroxyl (·OH) and superoxide anion radicals (O₂^·–) was confirmed by electron spin resonance (ESR) experiments using DMPO as a spin-trapping agent. ·OH radicals were detected in aqueous suspension, while O₂^·– radicals were identified in ethanol suspension. This demonstrates the efficiency of the prepared photocatalyst in promoting Fenton-assisted degradation of antibiotics, while also providing mechanistic insights into the active species involved.