Tuning Defective N-Doped Mesoporous Carbon Properties to Modulate Nonradical-to-Radical Oxidation Pathways for Peracetic Acid Activation and Naproxen Degradation

Radical oxidation characterized by rapid reaction efficiency and a direct electron transfer (DET) pathway indicative of high selectivity in advanced oxidation processes (AOPs) has received continuous attention in recent years. This study discovered that regulating N-doped mesoporous carbon materials' properties can tune the radical oxidation and DET pathway. Particularly, we synthesized a series of N-doped mesoporous carbon materials containing N vacancies (NMC-NV) and persistent free radicals (PFRs) by adjusting the dosage of the modifier ascorbic acid to activate peracetic acid (PAA) for naproxen (NAP) removal. The experimental results indicate that the PFRs in NMC-NV are the intrinsic catalytic centers that stimulate PAA to produce free radicals via transferring electrons to PAA. Additionally, graphitic N strengthens the adsorption of PAA on NMC-NVx and the electron transfer process between them to generate the complex (PAA*) responsible for the DET process. In addition, it is found that the nonradical oxidation pathway could resist the interference of inorganic anions, while the free radical oxidation pathway is suitable for treating chlorine-containing wastewater. This study provides insights into the mechanisms regulating radical and nonradical oxidation in PAA-based AOPs and sheds light on rational carbonaceous catalyst design for wastewater purification technology.