Iron-doped g-C3N4 catalysts fabricated by forming Fe–N moieties with outstanding photo-Fenton activity toward tetracycline degradation

Abstract

Heterogeneous photo-Fenton catalytic reactions have shown excellent prospects in the field of wastewater treatment as they can exert a synergistic role between photocatalysis and the Fenton reaction. Herein, porous Fe-doped g-C₃N₄ catalysts were fabricated by a convenient one-step pyrolysis of dicyandiamide, NH₄Cl, and FeCl₃·6H₂O mixtures, and applied in degrading tetracycline hydrochloride (TC) under photo-Fenton reaction conditions. The as-prepared catalysts were thoroughly characterized by multiple techniques, and the results revealed that the Fe element entered the g-C₃N₄ framework by forming Fe–N moieties. In addition, the porous structure of Fe-doped g-C₃N₄ could be obtained by using NH₄Cl as the gaseous template, which endowed it with higher photo-Fenton activity compared to the bulk counterpart. The experimental parameters, such as Fe doping amount, H₂O₂ concentration, solution pH value, and catalyst dosage were compared and optimized. The active-species trapping and electron-spin resonance (ESR) tests evidenced that the hydroxyl radicals (˙OH), superoxide radicals (˙O₂⁻), and holes (h⁺) all participated in the photo-Fenton reaction. Additionally, the plausible degradation pathways of TC were reasonably proposed in view of the high-performance liquid chromatography mass spectrometry (HPLC-MS) analytical results. Mechanism studies manifested that porous Fe-doped g-C₃N₄ not only possessed the more effective charge separation and transfer, but also the photoinduced electrons could accelerate the cycling of Fe³⁺/Fe²⁺ to promote the generation of ˙OH. This work presents a facile strategy to construct the promising heterogeneous photo-Fenton catalysts for environment remediation.