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

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.