Modulating the electronic structure of Co center via MgO@C co-doping for PMS activation to remove levofloxacin

Developing a Co-based heterogeneous activator with efficient electron migration is vital for peroxymonosulfate (PMS) activation. Herein we fabricate the Co3O4-MgO@C composite via pyrolysing mixture of ZIF-67 and precursors of MgO and C. The density functional theory calculation and experiment results unveil that the incorporation of MgO@C, which has reversed electronegativity compared to Co, into Co3O4 promoted the overlapping of Co 3d and O 2p orbitals for a faster electron transport ability in the activator. The uplifting d-band center and increasing electron density of Co active sites significantly enhance intrinsic reactivity for PMS activation. TEM and Mott-Schottky plot ((M-S) plot) confirm the formation of p-n heterojunction. Levofloxacin (LEV) removal rate constant (kapp) is 1.04 min  1. It is 2.4-fold and 38.4-fold times those of Co3O4 (0.44 min  1) and MgO@C (0.037 min  1). It exceeds many state-of-art Co-based PMS catalysts. Quenching experiments and electron paramagnetic resonance (EPR) demonstrated SO4 & BULL; and 1O2 were the dominant reactive oxygen species. A high degradation rate is maintained from pH 3 to 10 with outstanding reusability and universality towards antibiotics. The effects of ambient ions and humic acid on LEV removal were studied. Reaction temperature experiments revealed the activation energy of Co3O4-MgO@C was 37.3 kJ/mol. This work provides a novel codoping strategy to modulate electronic configuration for active centers in Co-based heterogeneous activators.