Cu–Co–O-Codoped Graphite Carbon Nitride as an Efficient Peroxymonosulfate Activator for Sulfamethoxazole Degradation: Characterization, Performance, and Mechanism

This study presents the development of a novel Cu–Co–O-codoped graphitic carbon nitride (g-C3N4) catalyst for efficient peroxymonosulfate (PMS) activation to degrade sulfamethoxazole (SMX) in aqueous environments. The synthesized Cu–Co–O-g-C3N4 catalyst demonstrated exceptional catalytic performance, achieving 90% SMX removal within 10 min—significantly outperforming pristine g-C3N4 (14%) and O-doped g-C3N4 (22%)—with a reaction rate constant of 0.63 min−1. The superior activity was attributed to the synergistic effects of Cu-Co bimetallic doping and oxygen incorporation, which enhanced the active sites, stabilized metal ions, and minimized leaching. Mechanistic studies revealed a dual-pathway degradation process: (1) a radical pathway dominated by sulfate radicals (SO4•−) and (2) a non-radical pathway driven by singlet oxygen (1O2), with the latter identified as the dominant species through quenching experiments. The catalyst exhibited broad pH adaptability and optimal performance at neutral to alkaline conditions. Characterization techniques (XRD, FTIR, XPS) confirmed successful doping and revealed that oxygen incorporation modified the electronic structure of g-C3N4, improving charge carrier separation. This work provides a sustainable strategy for antibiotic removal, addressing key challenges in advanced oxidation processes (AOPs), and highlights the potential of multi-heteroatom-doped carbon nitride catalysts for water purification.