Activation of calcium sulfite by bismuth cobalt-copper perovskite-manganese dioxide composite for efficient degradation of metronidazole

Abstract

The highly efficient BiCo0.5Cu0.5O3-MnO2 catalyst was prepared using the hydrothermal method and utilized for the first time to activate sulfite for degrading metronidazole (MNZ) in this study. Physicochemical analysis of the BiCo0.5Cu0.5O3-MnO2 catalyst was performed using XRD, FTIR, BET, SEM, TEM, and XPS, confirming the successful synthesis of catalyst. BiCo0.5Cu0.5O3-MnO2 demonstrated a larger specific surface area, a more uniform pore structure, and prevented perovskite agglomeration. The catalyst effectively activated CaSO3, resulting in the degradation of 99.94 % of MNZ within 30 min, showing excellent catalytic performance. Quenching experiments and EPR tests indicated that SO•-4, SO•-5 and 1O2 were the main reactive species, with the oxygen vacancy on the catalyst surface playing a crucial role in accelerating the formation of reactive species and electron transfer. Moreover, the valence transformation of Co, Cu, and Mn was identified as the main contributor to the activation of CaSO3, demonstrating significant synergistic effects. Liquid chromatography-mass spectrometry detected eleven intermediates, revealing that the BiCo0.5Cu0.5O3-MnO2/CaSO3 system could convert MNZ into low-toxicity products through three potential degradation pathways. Density functional theory (DFT) calculations showed that higher Fukui indices of MNZ sites were more susceptible to free radical attack. The BiCo0.5Cu0.5O3-MnO2/CaSO3 system also exhibited excellent degradability to different natural water bodies and other pollutants. Furthermore, the catalyst displayed strong stability and outstanding catalytic performance after 5 cycles. This study presents a versatile strategy for developing highly efficient green catalysts, which could be utilized in organic wastewater treatment.