Spatial confinement-regulated peroxymonosulfate activation by bimetallic-doped hollow carbon spheres for rapid...

Non-radical advanced oxidation processes (AOPs) have gained significant attention as a highly promising approach for eliminating persistent pollutants from water. These methods demonstrate superior effectiveness in mitigating the interference of coexisting anions compared to traditional radical-based methods. In this study, a singlet oxygen (¹O₂)-dominated process is developed for the degradation of metronidazole (MNZ), employing bimetallic-doped hollow carbon spheres (CoCu-HCS) as catalysts and peroxymonosulfate (PMS) as the oxidant. The experimental results highlight that ¹O₂ serves as the dominant reactive species, with the bimetallic-doped hollow carbon spheres facilitating electron transfer processes and enhancing surface interactions through spatial confinement, while simultaneously regenerating Co(II) and Cu(I). This significantly enhances the generation of ¹O₂ and the degradation of MNZ. The CoCu-HCS-4/PMS system achieves a remarkable 100% degradation rate of MNZ within just 5 min and a 70% mineralization rate within 30 min. These results represent degradation efficiencies 1.4 times and 10 times higher than those achieved by the Co-HCS-4/PMS and Cu-HCS-4/PMS systems, respectively. Furthermore, CoCu-HCS-4 demonstrates exceptional PMS utilization efficiency, robust cycling performance, and strong resistance to certain inorganic anions. This study not only provides innovative strategies for the development of advanced hollow catalysts but also offers valuable insights into the exploration of non-radical AOP pathways. Environmental Implication In this work, new effective catalysts of bimetallic-doped hollow carbon spheres (CoCu-HCS) have been synthesized and tested for the first time to activate peroxymonosulfate (PMS) for the removal of metronidazole (MNZ). CoCu-HCS displayed excellent catalyst activity on PMS for the removal of MNZ with good reusability and stability over five cycles. ^.OH, SO₄^•- and ¹O₂ were the dominant ROS responsible for MNZ removal. The spatial confinement promotes electron transfer and surface interactions, reduces the mass transfer distance, and enhances concentration diffusion, thereby improving the efficient utilization of PMS and ROS in wastewater treatment.