CeO2/ZIF-9 composites as a heterogeneous catalyst for peroxymonosulfate activation to degrade methylene blue

In the present work, a novel CeO 2 /ZIF-9 composites were prepared, characterized and used as a multiphase catalyst to activate peroxymonosulfate (PMS) to degrade methylene blue (MB). The effects of Ce/Co molar ratio, catalyst dose, PMS concentration, initial solution pH and reaction temperature were explored. The results showed that 20 mg/L MB was almost absolutely degraded, and the removal rate of COD reached 77.8% by 150 mg/L PMS activated with 50 mg/L 0.50-CeO 2 /ZIF-9 within 30 min at room temperature (20 °C) and initial pH 6.4. The active species such as SO 4 •− , 1 O 2 and • OH performed important roles in the catalytic process, as evidenced by quenching experiment and electron paramagnetic resonance (EPR) analysis. The synergistic catalytic mechanism of 0.50-CeO 2 /ZIF-9 in the heterogeneous activation of PMS was proposed, which mainly involves the enhanced redox cycle of Co 3+ /Co 2+ by Ce 3+ donated electrons. Recycling experiments suggested that the removal efficiency of MB can still reach 92.9% after four catalytic cycles, indicating good reusability of 0.50-CeO 2 /ZIF-9 catalyst. Therefore, because of its easy preparation, superior catalytic performance and reusability, the 0.50-CeO 2 /ZIF-9 composite catalyst has promising applications in water treatment.