Ingenious construction of a magnetic-recyclable photo-Fenton catalyst ZnFe2O4@MIL-88A(Fe) and its adsorption-degradation activity toward levofloxacin

Monotonic pore size and particles inseparability of metal-organic frameworks (MOFs) caused serious effects on its light absorption ability and charge separation, restricting its application for antibiotic such as levofloxacin (LEV) degradation in water. In this study, a magnetically detachable nano-photocatalyst (ZnFe₂O₄@MIL-88A(Fe)) was synthesized using a simple two-step hydrothermal technique. The morphology and microstructure analyses showed that n-type ZnFe₂O₄ catalyst particles were efficiently assembled onto the surface of MIL-88A(Fe) crystal. Photocatalytic activity studies indicated that the ZnFe₂O₄@MIL-88A(Fe) plus H₂O₂ exhibiting a significantly boosted photo-Fenton activity toward LEV at visible light irradiation, compared to the pure ZnFe₂O₄ and MIL-88A(Fe), the degradation efficiency accordingly reached up to nearly 82% and 25% within 60 min. This excellent photocatalytic performance was ascribed to the synergistic effects of the heterogeneous structure of ZnFe₂O₄ and MIL-88A(Fe), whereby the efficient separation of charge carriers in the catalytic system is mutually reinforced with the efficient reduction of Fe³⁺ and Fe²⁺. Meanwhile, the degradation mechanism and intermediates of LEV during the photo-Fenton reaction process were also studied in depth through free radical burst, electron paramagnetic resonance, and mass spectrometry analyses, etc. Additionally, the ZnFe₂O₄@MIL-88A(Fe) composite catalyst displayed significant stability and ease of separation, indicating potential for the photo-oxidative degradation of organic pollutants.