Efficient degradation of acetaminophen by activated peroxymonosulfate using Mn/C composites: Performance and mechanism

The synthesis of manganese oxide (MnOx) composites often leads to particle aggregation and the formation of larger metal nanoparticles, which greatly reduces the efficient use of manganese (Mn) as catalyst. Additionally, the structurally unstable Mn matrix composites increase the risk of metal precipitation during the reaction process. To address these issues, a series of Mn-carbon (Mn/C) co-doped composites (Mn@CA400, Mn@CA500, and Mn@CA600) were synthesized using potassium permanganate (KMnO4) and citric acid (CA) as precursors. The Mn@CA400 exhibited exceptional catalytic activity towards peroxymonosulfate (PMS) resulting in complete removal of 10 mg/L acetaminophen (ACT) within 10 min. Furthermore, Mn@CA400 demonstrated significant selectivity and resistance in complex matrices to interference for pollutant degradation. The results showed that Mn@CA400 exhibited higher catalytic activity and better stability compared with the reported Mn-based composites. Quenching experiments, electron paramagnetic resonance (EPR), solvent exchange experiments, and electrochemical analysis confirmed that singlet oxygen (1O2) and electron transfer pathways were responsible for ACT degradation. The mechanism analysis revealed that ACT could be degraded under three pathways. The current study not only presents an effective method to solve the problem of metal agglomeration and precipitation in the synthesis of MnOx composites but also establishes an efficient and selective oxidation system. In addition, it greatly improves the understanding of PMS activation and ACT degradation mechanisms.