Insights into Fenton-like oxidation of oxytetracycline mediated by Fe-doped porous g-C3N4 nanomaterials: synthesis, performance and mechanism

Abstract

Photo-Fenton catalytic oxidation is considered economical and eco-friendly technology for energy development and environmental protection. However, high-performance catalysts are vital in this process. Thus, in this study, an Fe-doped porous g-C₃N₄ (Fe/PCN) nanomaterial was prepared via a one-step self-assembly strategy, which showed a large specific surface area, relatively negative conduction potential and intense visible light utilization, exhibiting an enhanced catalytic performance. As expected, in the photo-Fenton catalytic system, 99.24% oxytetracycline (OTC) degraded over Fe/PCN within 60 min, and the photo-Fenton degradation rate constant was up to 0.076 min⁻¹. Furthermore, a thimbleful of hydrogen peroxide (H₂O₂) could meet the requirement in this photo-Fenton reaction system. The catalytic mechanism of Fe/PCN was discussed in depth, where Fe/PCN not only activated H₂O₂ to generate hydroxyl radicals (˙OH), but also photo-generated superoxide radicals (˙O₂⁻) due to its more negative conduction potential (−0.78 eV vs. NHE) than E⁰ (O₂/˙O₂⁻) (−0.33 eV vs. NHE). Besides, the stability experiment showed that the precipitation of iron salts was prevented, which is conductive for practical applications. The possible degradation pathway of OTC was proposed and proven to be green according to the toxicity estimation software tool (TEST). The low consumption of H₂O₂, high tolerance to pH changes and coexisting ions and green degradation pathway of the prepared Fe/PCN make it a potential candidate for OTC removal. This work proposes a simple method to modulate the morphology and structure of g-C₃N₄ to enhance the catalytic activity of Fenton-like reactions.