Abstract

The photocatalytic technology based on Metal-Organic Frameworks (MOFs) has shown promising applications in the field of antibiotic pollution control. However, it still faces challenges in efficiently removing high-concentration antibiotic wastewater. A typical Fe-containing MOF, MIL-53(Fe), was successfully synthesized and demonstrated efficient photocatalytic activity under visible light irradiation for high-concentrations of tetracycline hydrochloride (TCH). However, the bare MIL-53(Fe) exhibited unsatisfactory photocatalytic performance. To overcome the low degradation efficiency resulting from the rapid recombination of light-induced electron-hole pairs, H2O2 was introduced as an external electron acceptor to establish a synergistic Fenton-like system to couple with the photocatalysis process. The results showed that in the MIL-53(Fe)/H2O2/Vis system, 99% of 1 g/L TCH was degraded within 80 min, while the degradation efficiency of the MIL-53(Fe)/Vis process was only 4.89% under identical conditions. The degradation mechanism of the coupling system was performed by radical scavenging experiments and Electron Spin Resonance characterization. The results indicated that ·OH was the dominant radical in the coupled reaction, and ·O2- and h+ also played a role in this system. The significant improvement in TCH degradation efficiency during the coupling process was attributed to the following three factors: (1) In the coupling reaction process, photo-generated electrons can stimulate H2O2 to form ·OH radicals, inhibiting the recombination of photo-generated electrons and holes, improving the efficiency of the photocatalytic reaction. (2) FeIII in MIL-53(Fe) can be excited by photo-generated electrons and converted to FeII, which then stimulates H2O2 to form ·OH radicals. (3) FeIII in MIL-53(Fe) can convert with FeII, stimulate H2O2 to form ·OH radicals, and participate in the degradation reaction. In addition, the reusability and stability of the MIL-53(Fe) photocatalyst in the coupled system, as well as the impact of operational parameters, were systematically studied. This work demonstrates a feasible strategy for environmental remediation by enhancing the efficiency of MIL-53(Fe) in photocatalytic Fenton-like systems, thereby providing a viable approach for the treatment of high-concentration antibiotic wastewater.

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