A novel dual Z-scheme BiOBr/Bi-MOF/AgFeO2 heterojunction for activating peroxymonosulfate toward efficient photocatalytic removal of levofloxacin

In this work, a novel dual Z-scheme heterojunction BiOBr/Bi-MOF/AgFeO₂ (BBA) composite was prepared for constructing a photocatalytic activation system of PMS (BBA-PMS) toward degradation of levofloxacin (LFX). By characterizing and investigating using various techniques involving scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–visible diffuse reflectance spectrum (UV–vis-DRS), etc, it was confirmed that the BBA exhibits superior performance such as light absorption capability, surface and porous structure compared to any of the monomers and binary composites. Importantly, the BBA-PMS system exhibits superior degradation capability toward LFX, yielding a maximum degradation efficiency of LFX ∼ 95.9 % within 180 min under optimal conditions, which is 1.69 times, 3.38 times and 7.45 times higher than those of BiOBr, Bi-MOF and AgFeO₂. This can mainly be ascribed to its distinctive dual Z-scheme charges transfer scheme, which can effectively facilitate the transfer of photo-generated charges, extend the carrier lifetime, restrict the recombination of electron-hole pairs and provide more favorable reactive sites for activation of PMS. Furthermore, DFT calculation was performed to confirm the charge transfer and distribution in BBA. The radical trapping experiments and electron paramagnetic resonance (ESR) measurement reveal that the ·O₂^– and h⁺ are the predominant reactive oxygen species besides the ·SO₄^- in the BBA-PMS system. Additionally, several degradation pathways of LFX were presumably proposed based on the identified degraded intermediates using liquid chromatography-mass spectrometry (LC-MS) and the toxicity of the intermediates was assessed using ECOSAR software. This research offers a deep insight for the design of efficient dual Z-scheme heterojunction to ameliorate photocatalytic properties of BiOBr in environmental remediation.