Fe-doped g-C₃N₄ with duel active sites for ultrafast degradation of organic pollutants via visible-light-driven photo-Fenton reaction: Insight into the performance, kinetics, and mechanism

The photo-Fenton process provides a sustainable and cost-effective strategy for removing refractory organic contaminants in wastewater. Herein, a high-efficient Fe-doped g-C₃N₄ photocatalyst (Fe@CN₁₀) with a unique 3D porous mesh structure was prepared by one-pot thermal polymerization for ultrafast degradation of azo dyes, antibiotics, and phenolic acids in heterogeneous photo-Fenton systems under visible light irradiation. Fe@CN₁₀ exhibited a synergy between adsorption-degradation processes due to the co-existence of Fe₃C and Fe₃N active sites. Specifically, Fe₃C acted as an adsorption site for pollutant and H₂O₂ molecules, while Fe₃N acted as a photocatalytic active site for the high-efficient degradation of MO. Resultingly, Fe@CN₁₀ showed a photocatalytic degradation rate of MO up to 140.32 mg/L min⁻¹. The dominant ROS contributed to the removal of MO in the photo-Fenton pathway was hydroxyl radical (•OH). Surprisingly, as the key reactive species, singlet oxygen (¹O₂) generated from superoxide radical (•O₂⁻) also efficiently attacked MO in a photo-self-Fenton pathway. Additionally, sponge/Fe@CN₁₀ was prepared and filled in the continuous flow reactors for nearly 100% degradation of MO over 150 h when treating artificial organic wastewater. This work provided a facile route to prepare highly-active Fe-doped photocatalysts and develop a green photocatalytic system for wastewater treatment in the future.