High-performance and stable Schwertmannite/Al₂O₃ composite for efficient tetracycline hydrochloride degradation via...

In this study, the composite material (Sch/Al₂O₃) of Schwertmannite (Sch) and γ-Al₂O₃ was prepared by the coprecipitation method, which was used to degrade tetracycline hydrochloride (TCH) in a Fenton-like system. The materials were characterised using a scanning electron microscope, Brunauer-Emmett-Teller, X-ray diffractometer, Fourier transform infrared spectrometer and X-ray photoelectron spectroscopy. The findings revealed that the introduction of γ-Al₂O₃ effectively inhibited the agglomeration of Sch, and the specific surface area of the composite catalyst reached 95.50 m²/g, with a richer pore structure, which substantially increased the number of catalytic active sites. Under the optimised reaction parameters of catalyst dosage (0.2 g/L), reaction temperature (25 °C), H₂O₂ addition (20 μL) and pH (3), the removal rate of TCH (20 mg/L) reached 98.3 % after 60 min of reaction. The cyclic experiment revealed that the removal rate of TCH remained above 93.5 % after the catalyst was reused six times. Free radical quenching experiments combined with electron paramagnetic resonance spectroscopy analysis established •OH as the dominant active species, whereas O₂^•- and ¹O₂ contributed cooperatively to the degradation process. According to the liquid chromatography-mass spectrometry detection of intermediates, four possible TCH degradation pathways in the Sch/Al₂O₃/H₂O₂ system were deduced. This work offers a viable strategy for designing efficient and stable Fenton-like catalysts.