Facile synthesis of an effective g-C3N4-based catalyst for advanced oxidation processes and degradation of organic compounds

Abstract

Advanced oxidation processes (AOPs) aided by catalysts can efficiently degrade organic pollutants and decontaminate wastewater. In this work, a highly active catalyst composed of FeMn-functionalized graphitic carbon nitride (FeMn–C₃N₄) for AOPs is synthesized via a green synthetic route, involving a small amount of water and no organic solvents. The synthesis also produces only minimal wastewater as a biproduct. The material contains uniformly dispersed Fe and Mn atoms in the framework of g-C₃N₄. It shows a unique and high catalytic activity for three AOPs, namely a Fenton-like reaction, persulfate activation and visible-light photocatalysis, while also being reusable several times afterwards. Its catalytic activity is 2.6- to 8.0-fold higher than that of g-C₃N₄ in all three reactions. The optimal reaction conditions for the catalyst are determined, and the mechanisms by which it drives the reactions are proposed. Notably, the Fe and Mn species present in it contribute substantially to its enhanced catalytic activity. Moreover, compared with g-C₃N₄, FeMn–C₃N₄ has a narrower band gap and helps generate more ˙OH, SO₄˙⁻ and ¹O₂ species during the reaction. First-principles density functional theory (DFT) calculations reveal that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of FeMn–C₃N₄ are more delocalized than those of g-C₃N₄. As a result, the former shows enhanced photo-induced charge carrier separation. This highly active catalyst obtained with a facile synthetic route for these three aforementioned AOPs can have great potential for water treatment and environmental remediation applications.