Enhanced PMS activation by MOF-derived Co3O4/sepiolite composite for norfloxacin degradation: Performance, mechanism and degradation pathway

In this study, cobalt metal-organic framework (Co-MOF) derived Co3O4/sepiolite hybrid catalyst was prepared by a facile wet chemical method followed by the calcination crystallization process. In Co3O4/sepiolite composite, Co3O4 nanoparticles with smaller grain size were well dispersed on sepiolite surface. The larger reaction rate constant was obtained in Co3O4/sepiolite/PMS system for norfloxacin (NFX) degradation (0.2588 min−1), which was almost 3.44 times that in Co3O4/PMS. The greatly enhanced NFX degradation performance was mainly ascribed to the combination of Co-MOF precursor and sepiolite support resulting in higher adsorption capacity, more exposed reaction active sites and overspreading surface hydroxyl groups. The electron paramagnetic resonance (EPR) and quenching experimental results indicated that the radical and non-radical pathway were responsible for the NFX degradation, and the SO4•- and 1O2 were the major contributors. Moreover, the continuous redox cycle of Co(III)/Co(II) and the surface -OH on catalyst played the important roles in the continuous production of the reaction active species thereby achieving the efficient degradation for NFX. In addition, the enhanced catalytic mechanisms and NFX degradation pathways were proposed. Overall, our study provides new insights for designing and developing efficient and environmentally friendly catalysts for practical wastewater treatment via activating PMS.