Oxygen species properties generated by carbon nanotube modified BiFeO3 and degradation of ammonia using visible light

This study prepared carbon nanotube-modified BiFeO₃ (CNT‑BiFeO₃) composite photocatalysts for visible‑light‑driven degradation of ammonia nitrogen. The introduction of CNTs promotes the separation of photogenerated carriers and constructs a type‑II heterojunction with an internal built‑in electric field, which effectively suppresses electron‑hole recombination and improves photocatalytic activity. The optimized CNT‑BiFeO₃ catalyst achieves an ammonia degradation efficiency of 87.43% under visible light. With the assistance of 0.2 mmol/L H₂O₂, the degradation efficiency reaches 99.8% within 180 min, and ammonia is selectively converted into N₂ without generating nitrite or nitrate. Kinetic analysis indicates that the degradation process follows pseudo‑first‑order kinetics. The composite shows excellent reusability and stability during cycling tests. This work provides a high‑efficiency photocatalytic strategy for ammonia nitrogen removal from wastewater.