Hydrothermal synthesis of CuCoFe layered double hydroxide and its performance in the degradation of antibiotics: Influencing factors, degradation pathways, and reaction mechanism

In this study, the CuCoFe-LDH catalyst was synthesized by hydrothermal method and applied to degrade levofloxacin (LFX) by peroxymonosulfate (PMS) activation. The physicochemical properties of the synthesized samples were analyzed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The influence of various factors such as catalyst system, pH, catalyst content, PMS , pH, and coexisting ions on the degradation of LFX was systematically investigated. The results showed that after 10 min, 94.57 % of LFX was decomposed under the conditions of 200 mg/L of catalyst, 500 mg/L of PMS, 10 mg/L of LFX, and pH 7.0. Besides, the CuCoFe-LDH/PMS system can effectively remove LFX over a wide pH range from 3.5 to 9.0. Both radical superoxide (O 2 •- ) and non-radical singlet oxygen ( 1 O 2 ) were major reactive oxygen species in the CuCoFe-LDH/PMS system. Mass spectrometry identified 16 major degradation products of LFX, and 38.43 % of LFX was mineralized after 30 min of reaction. Besides, the CuCoFe-LDH/PMS system had the ability to effectively degrade different groups of antibiotics (e.g., fluoroquinolone, tetracycline , and sulfonamide). The mechanism of PMS activation by CuCoFe-LDH and the LFX degradation pathway were proposed. Finally, testing the reusability of CuCoFe-LDH in LFX degradation showed that a decrease of nearly 7 % occurred after five consecutive cycles, suggesting its stability for practical applications.