g-C3N4/chitosan catalyst modulated hydroperoxyl radical generation for high-performance self-Fenton mineralization of refractory organic contaminants

The generation of hydroperoxyl radical ( OOH) radicals is an important issue and has significant value in the highly selective removal of pollutants in complex water environment. However, the metal active center catalysts frequently encounter the limited surface site type and energy level mismatch, making it difficult to maintain a stable supply of OOH. Therefore, a novel photocatalytic self-Fenton system based on metal-free g-C 3 N 4 /chitosan (g-C 3 N 4 /CS) catalyst was developed to achieve excellent efficiency in the removal of tetracycline, bisphenol A and 2,4-dichlorophenol across a broad pH range (3.14–9.04), superior the conventional Fenton system which only works at pH 3–5. Chitosan modification enhanced the charge separation and transfer efficiency of the S-scheme charge transfer pathway, optimized the formation of OOH, O 2 − , h + , enhancing the selective generation and stable supply of OOH radical with a high ratio of 33 %, led to the efficiency removal of pollutants. Further mechanistic analysis demonstrated the unique dominance of the desired OOH radicals. g-C 3 N 4 /CS catalyst exhibited excellent stability and reusability by the cycling experiments, suggesting durable OOH supplying. This work offers novel insights into g-C 3 N 4 based metal-free catalyst with special radical features through chitosan modification, demonstrating the potential for industrial applications of OOH dominated g-C 3 N 4 /CS self-Fenton system in wastewater treatment.