Synergistic photo-Fenton catalysis by Fe3Se4 for tetracycline removal: Insights into degradation pathways and reaction mechanisms

This study investigates the efficacy of magnetic Fe 3 Se 4 as a catalyst in the photo-Fenton oxidation process for degrading tetracycline hydrochloride (TCH), a widely used antibiotic posing significant environmental risks due to its persistence in aquatic systems. Fe 3 Se 4 was synthesized via a one-pot hot-melt method and characterized using X-ray diffraction, Raman spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The catalyst demonstrated exceptional performance under visible light irradiation, achieving a 92.5% removal rate of TCH (30 mg L −1 ) within 90 min under optimal conditions (pH = 3.2, H 2 O 2 = 10 mM, catalyst dosage = 0.2 g L −1 , 25 °C). The degradation kinetics followed pseudo-first-order behavior, with a mineralization rate of 34.1%. Mechanistic studies revealed that hydroxyl radicals (•OH) and superoxide radicals (•O 2 − ) played pivotal roles in the degradation process, facilitated by the synergistic interplay between Fe and Se species. Density functional theory (DFT) calculations indicated that the (310) crystal plane of Fe 3 Se 4 exhibited strong adsorption energy for H 2 O 2 , promoting O-O bond cleavage and •OH generation. High performance liquid chromatography–mass spectrometry analysis identified intermediate products and proposed three degradation pathways, and ECOSAR modeling indicated reduced ecotoxicity of most intermediates. Additionally, Fe 3 Se 4 exhibited broad applicability, effectively degrading other organic pollutants such as methylene blue and rhodamine B. These findings highlight Fe 3 Se 4 as a promising, environmentally benign catalyst for advanced oxidation processes, offering a sustainable solution for antibiotic-contaminated wastewater treatment.