CuO-Co3O4@CeO2 as a heterogeneous catalyst for efficient degradation of 2,4-dichlorophenoxyacetic acid by peroxymonosulfate

CuO-Co3O4@CeO2 nanoparticles used as a heterogeneous catalyst were prepared via a sol-gel method and characterized by various techniques. For comparison, a series of oxides was investigated for activating peroxymonosulfate (PMS) during the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D). The results indicated that CuO-Co3O4@CeO2 exhibited the highest catalytic performance among the catalysts. Complete degradation of 2,4-D (20 mg/L) was realized within 45 min at 1 mM PMS, CuO-Co3O4@CeO2 loading of 0.07 g/L, and pH of 6. Recycling experiments confirmed that CuO-Co3O4@CeO2 was very stable, and the 2,4-D degradation efficiencies ranged from 100% to 97.5%, decreasing by only 2.5% after the fifth run. The outstanding catalysis of CuO-Co3O4@CeO2 resulted from the synergy of cerium, cobalt, and copper. Electron paramagnetic resonance and radical scavenger experiments confirmed the production of SO4 center dot- and (OH)-O-center dot radicals in the CuO-Co3O4@CeO2/PMS system, which were responsible for efficient decomposition of 2,4-D. Furthermore, the combination of CuO-Co3O4@CeO2 andPMS was applied to treat natural water containing 2,4-D, and a high 2,4-D removal rate was also achieved. Based on these results, it was deduced that CuO-Co3O4@CeO2 can be utilized as a catalyst to activate PMS and destroy organic contaminants in aqueous solution.