High-Efficient Elimination of Spiramycin by Fe3O4/ZSM-5/Sch via Heterogeneous Photo-Fenton Oxidation at Neutral pH

Abstract

Spiramycin (SPM), a widely employed antibiotic in both clinical therapy and the livestock industry, poses significant challenges in terms of safe and efficacious management. A heterogeneous photo-Fenton system, devised using Schwertmannite (Sch), can effectively degrade contaminants. However, it is accompanied by a relatively low conversion efficiency of ≡Fe3+/≡Fe2+ and a significant iron loss. In this study, a catalyst featuring Fe3O4 and ZSM-5 molecular sieve-modified Sch (Fe3O4/ZSM-5/Sch) was devised to enhance the catalytic activity and stability. The findings revealed that Fe3O4/ZSM-5/Sch exhibited exceptional catalytic activity, with the reaction first-order kinetic exceeding that of pure Sch. The active species including ·OH, h+, e−, ·O2− and SO4·− were identified in the UV/Fe3O4/ZSM-5/Sch-H2O2 system. The enhanced catalytic activity of Fe3O4/ZSM-5/Sch could be ascribed to the effective conversion of ≡Fe3+/≡Fe2+. The photogenerated electrons within Fe3O4 were transported to Sch via ZSM-5, which effectually reduced ≡Fe3+/≡Fe2. Moreover, Fe3O4/ZSM-5/Sch demonstrated outstanding stability; even after six cycles, the degradation efficiency of SPM remained above 86.50%, and the leaching quantity of Fe remained below 0.24 mg/L. This research not only develops an excellent catalyst for the safe treatment of SPM but also proffers innovative perspectives for the future design of efficient iron-based catalysts.