Fe Immobilized within Accordion-Like Tubular Carbon Nitride As a Catalyst for the Fenton-Like Degradation of Ranitidine: Synergetic Roles of ^•OH and ¹O₂

Advanced oxidation processes (AOPs) based on H2O2 are considered effective strategies to remove emerging organic pollutants from water bodies. In this work, Fenton-like Fe-based catalysts were fabricated through a simple hydrothermal calcination method. Fe was immobilized within carbon nitride with a structure of accordion-like hollow nanotubes enriched with open chinks (atCN). The Fe-atCN catalysts were employed for Fenton-like reactions to degrade ranitidine (RAN). Due to the unique structure of the atCN substrate and the Fe–N interactions established between highly dispersed Fe sites and the atCN matrix, the 3.4Fe-atCN/H2O2 system was able to completely eliminate RAN within 30 min at an initial pH of 3 (k = 0.143 min–1). It also remained highly active after four cycles of regeneration. Moreover, the 3.4Fe-atCN/H2O2 system showed good adaptability in a pH range of 3–6, with coexisting inorganic anions, and in diverse water bodies. Good oxidative activities on various pollutants were also demonstrated, including sulfamethoxazole, tetracycline, 4-chlorophenol, and methyl orange. Afterward, mechanism exploration suggested that the dominant reactive oxygen species driving the degradation of RAN in the 3.4Fe-atCN/H2O2 system were not only the generally reported •OH but also the unexpected nonradical of 1O2. The activation mechanism of 3.4Fe-atCN to H2O2, intermediates, and degradation pathways of RAN were then unveiled for providing further guidance to the development of Fenton-like technology.