Co3O4@ZIF-67 core–shell heterogeneous catalyst for degradation of dye contaminants

Advanced oxidation processes based on sulfate radicals (SR-AOPs) are gaining more and more attention for their efficient treatment of refractory organic contaminants, and the rational design of catalyst is the key for the effectiveness of the method. In this paper, a Co3O4@ZIF-67 core–shell heterogeneous catalyst for activation of peroxymonosulfate (PMS) to degrade methylene blue (MB), a refractory dye, was prepared successfully. Under conditions of 20 mg/L catalyst, PMS 100 mg/L and and 25 °C temperature, nearly 100 % degradation of MB (10 mg/L) occured within 5 min, indicating that the core–shell catalyst possessed excellent catalytic performance. Furthermore, this core–shell structure provided stability for the nanoparticles (NPs) as less leaching of Co ions was observed. To identify the reactive species involved, quenching tests and electron paramagnetic resonance (EPR) were carried out. The results found that radical species including •OH, SO4∙- and non-radical (1O2) contributed to the degradation of MB and 1O2 was the leading one. Some important parameters, such as PMS and Co3O4@ZIF-67 doses, were explored and evaluated. Moreover, cycling study was conducted and Co3O4@ZIF-67 showed good recyclability. This work puts forward an idea of developing high-performance catalysts with structure more stable.