Electro-Fenton reaction was limited by the generation of H₂O₂ and the circulation of Fe(Ⅱ)/Fe(Ⅲ). Herein, an efficient electro-Fenton-like process was constructed based on Fe₃O₄–CaO₂ cathode promoted by peroxymonosulfate (PMS). Levofloxacin (LEV) could be efficiently degraded (92.1%) and mineralized with the TOC removal of 74.5% in this self-circulating process. More importantly, the Fe₃O₄–CaO₂ exhibited good stability in the recycles due that CaO₂ was covered by Fe₃O₄, which inhibited the rapid release of H₂O₂. Mechanism analysis indicated that CaO₂ could not only replace H₂O₂ to accelerate the oxidation of Fe(Ⅱ) to Fe(Ⅲ), but also could form complexes with Fe(Ⅲ) and PMS to transfer electrons from ligands to metals, thereby enhancing the reduction of Fe(Ⅲ) to Fe(Ⅱ). As a result, the electrical consumption was significantly reduced, which was only 5.0% of the Fe₃O₄ in electro-Fenton reaction. Meanwhile, the hydrolyzed product of Ca(OH)₂ reacted with Fe(Ⅲ) in the presence of H₂O₂ and converted into CaO₂. Thus, the self-circulation of CaO₂/Ca(OH)₂ and Fe(Ⅲ)/Fe(Ⅱ) was realized, which accelerated the generation of active species, such as, ·OH, O₂·^- and ¹O₂. This work first proposed a self-circulating electro-Fenton-like system and demonstrated the potential application of Fe₃O₄–CaO₂ in the treatment of wastewater.

Electro-Fenton反应受到H ₂ O ₂的生成和Fe(Ⅱ)/Fe(Ⅲ)循环的限制。在此，基于由过氧单硫酸盐 (PMS) 促进的Fe ₃ O ₄ –CaO ₂阴极构建了一种高效的类芬顿过程。在这个自循环过程中，左氧氟沙星 (LEV) 可以有效降解 (92.1%) 并矿化，TOC 去除率为 74.5%。更重要的是，Fe ₃ O ₄ –CaO ₂在循环中表现出良好的稳定性，因为 CaO ₂被 Fe ₃ O ₄覆盖，抑制了 H ₂ O _{2的快速释放}. 机理分析表明，CaO ₂不仅可以代替H ₂ O ₂加速Fe(Ⅱ)氧化为Fe(Ⅲ)，还可以与Fe(Ⅲ)和PMS形成络合物，将电子从配体转移到金属，从而促进Fe(Ⅲ)向Fe(Ⅱ)的还原。结果，电耗显着降低，仅为电-Fenton反应中Fe ₃ O _4的5.0%。同时，Ca(OH) _{2的水解产物在H 2} O ₂存在下与Fe(Ⅲ)反应并转化为CaO ₂。因此，CaO ₂ /Ca(OH) _{2的自循环}实现了Fe(Ⅲ)/Fe(Ⅱ)，加速了·OH、O ₂ · ^-和¹ O ₂等活性物质的生成。这项工作首先提出了一种自循环类电芬顿系统，并展示了Fe ₃ O ₄ –CaO ₂在废水处理中的潜在应用。