In-situ construction of mesoporous CuCo₂O₄ decorated CNTs networks as a long-lasting peroxymonosulfate activator for rapid removal of aqueous micropollutants

The sluggish redox cycle occurring during the oxidation processes and the biological toxicity caused by the leaching of dissociated cobalt ions dramatically hinder the practical application of cobalt-based catalysts. Herein, we synthesized the hydroxylated multi-walled CNTs coated with mesoporous CuCo2O4 (M-CuCo2O4@CNTs) to enhance peroxymonosulfate (PMS) activation. The introduction of CNTs enabled M-CuCo2O4@CNTs with a much better thermal stability. M-CuCo2O4@CNTs with dual electron-rich active sites (=Co and Cu)= exhibited a longlasting reactivity for the rapid degradation of micropollutants under mild conditions. In the process of PMS activation, the Cu+/Cu2+ redox couple as an electron donor participated in the conversion of Co3+ to Co2+ through rapid charge transfer. More importantly, this functional material with a highly interconnected conductive network and a strong surface adsorption effect significantly limited the leaching of cobalt ions. Meanwhile, the acute toxicity (LC50 and EC50) and the chronic toxicity (ChV) of the intermediates of RAN were significantly reduced compared with RAN after the treatment of the M-CuCo2O4@CNTs/PMS reaction system. DFT calculations were coupled with experiments to prove that PMS molecules were more favorable to be activated at Co= sites compared with =Cu sites. Finally, this study offered a new perspective for the activation mechanism of PMS-induced heterogeneous oxidation and an attractive alternative for micropollutants elimination in water treatment.