Efficient removal of tetracycline in water by a Fe3O4-mediated persulfate activation and biodegradation coupled system: Performance, validation, and mechanism

The cost-effective removal of antibiotic contaminants from the aqueous environment has become a hot research topic now. In this study, we proposed a novel coupled system, i.e., nano-Fe3O4 (nFe3O4) mediated persulfate (PDS) activation and biodegradation process, for efficient removal of tetracycline (TCH). The feasibility of the coupled system (nFe3O4 + PDS + microbe) was proved by comparing it with a single AOP (nFe3O4 + PDS) in batch and column experiments. The highest removal efficiencies of TCH (20 mg/L) and TOC reached 99.5 % and 43.2 % by the coupled system within 60 days. SEM spectra exhibited that nFe3O4 and microorganisms were well loaded on the non-woven fabric. Meanwhile, XPS results proved that more Fe(II) was on the surface of nFe3O4 in the coupled system than that in the single AOP. The presence of abundant Fe(II) in the coupled system suggested the potential electron transfer from Fe(III) with the assistance of microbes. High-throughput sequencing results indicated Proteobacteria played an important role in the coupled system. The degradation intermediates of TCH were analyzed by ultraperformance liquid chromatography-mass spectrometer (UPLC-MS), and reasonable degradation pathways were proposed. The coupling of nFe3O4 + PDS and biological treatment improved the TCH removal efficiency and reduced the burden of subsequent water treatment, which provided a feasible idea for the treatment of antibiotic-containing wastewater.