Fe Immobilized\nwithin Accordion-Like Tubular Carbon\nNitride As a Catalyst for the Fenton-Like Degradation of Ranitidine:\nSynergetic Roles of <sup>•</sup>OH and <sup>1</sup>O<sub>2</sub>

Advanced oxidation processes (AOPs) based on H<sub>2</sub>O<sub>2</sub> are considered effective strategies to remove emerging\norganic\npollutants from water bodies. In this work, Fenton-like Fe-based catalysts\nwere fabricated through a simple hydrothermal calcination method.\nFe was immobilized within carbon nitride with a structure of accordion-like\nhollow nanotubes enriched with open chinks (<i>at</i>CN).\nThe Fe-<i>at</i>CN catalysts were employed for Fenton-like\nreactions to degrade ranitidine (RAN). Due to the unique structure\nof the <i>at</i>CN substrate and the Fe–N interactions\nestablished between highly dispersed Fe sites and the <i>at</i>CN matrix, the 3.4Fe-<i>at</i>CN/H<sub>2</sub>O<sub>2</sub> system was able to completely eliminate RAN within 30 min at an\ninitial pH of 3 (<i>k</i> = 0.143 min<sup>–1</sup>). It also remained highly active after four cycles of regeneration.\nMoreover, the 3.4Fe-<i>at</i>CN/H<sub>2</sub>O<sub>2</sub> system showed good adaptability in a pH range of 3–6, with\ncoexisting inorganic anions, and in diverse water bodies. Good oxidative\nactivities on various pollutants were also demonstrated, including\nsulfamethoxazole, tetracycline, 4-chlorophenol, and methyl orange.\nAfterward, mechanism exploration suggested that the dominant reactive\noxygen species driving the degradation of RAN in the 3.4Fe-<i>at</i>CN/H<sub>2</sub>O<sub>2</sub> system were not only the\ngenerally reported <sup>•</sup>OH but also the unexpected nonradical\nof <sup>1</sup>O<sub>2</sub>. The activation mechanism of 3.4Fe-<i>at</i>CN to H<sub>2</sub>O<sub>2</sub>, intermediates, and degradation\npathways of RAN were then unveiled for providing further guidance\nto the development of Fenton-like technology.