Photocatalytic Simultaneous Removal of Nitrite and Ammonia via a Zinc Ferrite/Activated Carbon Hybrid Catalyst under UV–Visible Irradiation

Nitrite and ammonia often coexist in waters. Thus, it is very significant to develop a photocatalytic process for the simultaneous removal of nitrite and ammonia. Herein, zinc ferrite/activated carbon (ZnFe2O4/AC) was synthesized and characterized by X-ray diffraction spectroscopy, transmission electron microscopy, Raman spectroscopy, and ultraviolet–visible diffuse reflectance spectroscopy. The valence band level of ZnFe2O4 was measured by X-ray photoelectron spectroscopy–valence band spectroscopy, and first-principles calculation was performed to confirm the band structure of ZnFe2O4. The as-synthesized ZnFe2O4/AC species functioned as a photocatalyst to simultaneously remove nitrite and ammonia under anaerobic conditions upon UV–visible light irradiation at the first stage. The results indicated that an average removal ratio of 92.7% with ±0.2% error for nitrite degradation for three runs was achieved in 50.0 mg/L nitrite + 100.0 mg/L ammonia solution with pH 9.5 under anaerobic conditions for 3 h at t...