Highly Dispersed Co/CoO Nanoparticles Anchored on N-Doped Biochar Enhanced Peroxymonosulfate Activation for Efficient Norfloxacin Degradation

In the current study, N-doped apple tree branch-based biochar-supported Co/CoO catalyst (Co/CoO@NBCs) was prepared using an impregnation-pyrolysis synergistic strategy, which addressed the issues of easy aggregation, poor stability, and low specific surface area of the Co/CoO catalyst. The characterization results show that Co/CoO@NBCs has a large specific surface area (1871.02 m2/g), a developed pore structure (0.99 cm3/g), and Co exists in the form of Co atoms and CoO. Under conditions of 0.25 mM peroxymonosulfate (PMS), 10 mg of catalyst, and room temperature, the degradation rate of norfloxacin (NOR, 30 mg/L) reached equilibrium within 70 min, with a removal rate of 99.06%. Besides the strong alkali condition (pH = 11) and the presence of HCO3–, the removal rate of NOR by Co/CoO@NBCs in other pH ranges and in anionic environments can still exceed 73%. Furthermore, analysis of the degradation mechanism shows that the active sites of Co0 and Co2+ can activate PMS to produce reactive oxygen species, with O2–• and 1O2 serving as the main active substances involved in NOR degradation. Additionally, tests with real water systems and cycling experiments further demonstrate that Co/CoO@NBCs have practical application potential. This work offers new insights into designing heterogeneous catalysts with multiple active sites for wastewater treatment.