Tetracycline degradation by persulfate activated with magnetic γ-Fe2O3/CeO2 catalyst: Performance, activation mechanism and degradation pathway

Tetracycline is a typical antibiotic that is eco-toxic and easily causes bacterial resistance, and thus it is necessary to eliminate tetracycline from the water environment. In this work, γ-Fe2O3/CeO2 was prepared and used to activate persulfate for tetracycline degradation. The catalyst was characterized by XRD, VSM and XPS, and results showed that it had excellent crystallinity and magnetism. The low valence metals (Fe (II) and Ce (III)) in γ-Fe2O3/CeO2 benefited persulfate activation. Tetracycline removal efficiency reached 84% with the γ-Fe2O3/CeO2/persulfate system; and the value was 70% in the surface water matrix. In addition, γ-Fe2O3/CeO2 kept high activity from pH 3 to 9. It had high stability and reusability and was easily recycled from solution due to its good magnetism. Mechanism analyses showed that SO4− and OH on catalyst surface catalyst were the major active species, O2− and 1O2 were also produced due to the excess oxygen vacancies of catalyst. Moreover, the degradation products of tetracycline were determined, and the degradation pathway was proposed. Hydroxylation, demethylation, decarbonylation, dehydroxylation, C-N bond cleavage and ring-opening were the main pathway. The cost of wastewater treatment with the γ-Fe2O3/CeO2/persulfate system was estimated to be 0.106 $/m3. This study provided an efficient and stable catalyst for tetracycline degradation.