Stable metal-organic framework fixing within zeolite beads for effectively static and continuous flow degradation of tetracycline by peroxymonosulfate activation

Heterogeneous peroxymonosulfate (PMS) based advanced oxidation process has been proven as a promising method for tetracycline removal from water. Among the heterogeneous catalysts, Co based metal-organic framework (ZIF-67) is a good candidate to activate PMS in the aforementioned advanced oxidation system. However, their high metal ion leaching and fine powder form limit their practical application. Herein, zeolite bead-supported ZIF-67 was prepared through the Co ion-exchange and organic ligand reaction, which is simple, cost-efficient and recyclable. The obtained zeolite@ZIF-67 composites were employed for PMS activation to degrade tetracycline in the water. The uniform ZIF-67 loading could provide abundant catalytic sites and the results demonstrated that 93.7% of tetracycline (50 mg/L) could be removed in 60 min with high recycling stability. Intriguingly, due to the strong metal-support interaction, the Co ion leaching from the composite beads during the degradation reaction was much lower compared to pure ZIF-67 particles. In addition, zeolite@ZIF-67 composites with the microsphere form could be easily packed into the bed column to effectively remove tetracycline in a continuous flow process. The degradable mechanism and degradation pathway were comprehensively investigated by quenching experiments, electron paramagnetic resonance spectra, X-ray photoelectron spectroscopy and liquid chromatography-mass spectroscopy. Overall, our work provides a novel PMS heterogeneous catalyst based on macroscopic supported MOF composites for efficient tetracycline removal.

Automated summary

In this study, zeolite bead-supported ZIF-67 composites were prepared and utilized for the activation of PMS to remove tetracycline from water. The obtained composites exhibited high catalytic activity, recycling stability, and effective removal of tetracycline in a continuous flow process.