Facile preparation of AlCo-LDH/sepiolite composites as peroxymonosulfate catalysts for efficient degradation of norfloxacin: Performance, reaction mechanism and degradation pathway

Abstract

In this study, AlCo-LDH/sepiolite composite catalysts were successfully prepared by a simple water bath method. In the AlCo-LDH/sepiolite composite catalyst, the nanosheet structure of LDH was uniformly immobilized on the surface of sepiolite fibers. The AlCo-LDH/sepiolite composite catalyst was proposed to activate peroxymonosulfate (PMS) to remove norfloxacin (NOR). The reaction rate constant for the degradation of NOR was investigated to be 0.3405 min−1 in the AlCo-LDH/sepiolite/PMS system, which was 2.22 times higher than that of the AlCo-LDH/PMS system. The combination of AlCo-LDH with sepiolite carriers increased the specific surface area of the catalysts, exposing more active sites and widening the distribution of surface hydroxyl groups, which resulted in a significant enhancement of the combination of AlCo-LDH with sepiolite/PMS significantly improved the degradation performance of NOR. Quenching experiments revealed that SO4•- and 1O2 played the main roles in the degradation of NOR, with both radical and non-radical pathways contributing, and the Co(III)/Co(II) redox cycle was found to be crucial for the activation of PMS to degrade NOR efficiently. In addition, the reaction mechanism and degradation pathway of NOR degradation in this system were elucidated. In conclusion, the AlCo-LDH/sepiolite composites provide a new reference for the development of environmentally friendly catalysts, and have good application prospects in activating PMS for wastewater treatment.