Synthesis and mechanistic investigation of scrap metal-derived Fe3O4/g-C3N5 heterojunction photocatalyst for efficient H2O2-assisted degradation of cationic dye under visible light

Plausible mechanistic pathway of photo-Fenton catalysis by g-C 3 N 5 @Fe 3 O 4 heterojunction system. • g-C 3 N 5 @Fe 3 O 4 composites were synthesized from scrap metal containers. • The FeGCN 1:2 composite showed superior photocatalytic activity under visible light. • g-C 3 N 5 @Fe 3 O 4 boosts light absorption, improves charge separation, and raises ROS yield. • PXRD, FTIR, TGA, BET, XPS, SEM, TEM, EDS verified a stable heterojunction with more active sites. • Activity is achieved via electron-driven catalysis and H 2 O 2 -assisted photo-Fenton process. Herein, a novel g-C 3 N 5 /Fe 3 O 4 composite was successfully fabricated and characterized, employing discarded metal oil containers as an economical and eco-friendly iron source for synthesizing Fe 3 O 4 nanoparticles. The integration of g-C 3 N 5 , which features a narrower band gap and superior surface adsorption capability compared to the conventional g-C 3 N 4 , notably improved the composites’ visible light absorption and dye adsorption properties. Among all the synthesized samples, the FeGCN 1:2 composite, with the highest Fe 3 O 4 loading, demonstrated exceptional photocatalytic efficiency, achieving 98% methylene blue degradation in the presence of visible light within a short duration, having a rate constant of pseudo-first-order kinetics of 0.02303 min −1 . Methylene blue, which is a cationic dye, has been used here as a model water pollutant for photocatalytic performance evaluation of the engineered material. The remarkable photocatalytic enhancement was mainly attributed to the synergistic interplay between g-C 3 N 5 and Fe 3 O 4 , which promoted effective charge carrier separation and facilitated the formation of reactive oxidative species. Furthermore, utilizing waste-derived Fe 3 O 4 not only minimized production costs but also promoted environmental sustainability by valorizing waste materials. Consequently, this study offers a green, cost-effective, and efficient strategy for the development of advanced photocatalysts for dye degradation and other environmental purification applications.