Visible light-assisted periodate activation by O-doped g-C3N4 for efficient Acid Orange 7 degradation via singlet oxygen-dominated nonradical pathway

Non-metallic photocatalysts represent a promising avenue for the green remediation of organic wastewater. In this study, O-doped g-C 3 N 4 (OCN) was synthesized using a one-step calcination strategy and synergistically coupled with periodate (PI) under visible light to develop a novel non-radical OCN/PI/Vis photo-Fenton-like system for the efficient degradation of Acid Orange 7 (AO7). Systematic characterization techniques, including transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) and photoluminescence (PL), along with density functional theory (DFT) calculations, were employed to elucidate the catalyst properties, oxidant adsorption, and reaction mechanisms. The OCN/PI/Vis system achieved a 93.9% removal of AO7 within 20 min and exhibited a reaction rate constant ( k = 1.48 × 10 −1 min −1 ) that was 4.4 times higher than that of the OCN/Vis system, significantly outperforming traditional oxidant-coupled systems (PMS/PDS/H 2 O 2 ). DFT calculations indicated that OCN exhibited an ultra-strong PI adsorption affinity ( E ads  = −2.541 eV), leading to the elongation of the PI I-O bond and facilitating its activation. Quenching and electron paramagnetic resonance (EPR) experiments confirmed that singlet oxygen ( 1 O 2 ) is the dominant reactive species. Notably, the system demonstrated excellent anti-interference performance. This work establishes a high-efficiency, metal-free photo-Fenton-like system for dye wastewater treatment and provides a theoretical and experimental foundation for the rational design of g-C 3 N 4 -based PI activators, thereby opening new avenues for PI-based advanced oxidation processes (AOPs) in environmental remediation.