Synergistic enhanced activation of peroxymonosulfate by heterojunction Co3O4–CuO@CN for removal of oxytetracycline: Performance, mechanism, and stability

Abstract

Metal-organic frameworks (MOFs) as precursors for catalysts has drawn growing attentions. In this study, heterojunction Co3O4–CuO doped carbon materials (noted as Co3O4–CuO@CN) were prepared by direct carbonization of CuCo-MOF in air. It was found that the Co3O4–CuO@CN-2 exhibited excellent catalytic activity with the highest Oxytetracycline (OTC) degradation rate of 0.0902 min−1 at 50 mg/L of Co3O4–CuO@CN-2 dosage, 2.0 mM of PMS and 20 mg/L of OTC, which was 4.25 and 4.96 times that of CuO@CN and Co3O4@CN, respectively. Furthermore, Co3O4–CuO@CN-2 was efficient over a wide pH range (pH 1.9–8.4), and possessed good stability and reusability without OTC degradation decrease after five consecutive uses at pH 7.0. In a comprehensive analysis, the rapid regeneration of Cu(II) and Co(II) is responsible for their excellent catalytic performance, and the p-p heterojunction structure formed between Co3O4 and CuO acts as an intermediary of electron transfer to accelerate PMS decomposition. Moreover, it was interesting to find that Cu rather than Co species played a vital role in the PMS activation. The quenching experiments and electron paramagnetic resonance demonstrated that .OH, SO4•−, and 1O2 were the reactive species responsible for oxidation of OTC and the non-radical pathway triggered by 1O2 was dominant.