Mechanistic insights into KOH-regulated biochar derived from waste Myriophyllum aquaticum biomass for 1O2-mediated degradation of 2,4,6-trichlorophenol

Porous biochar has emerged as a promising heterogeneous catalyst for the activation of persulfate (specifically peroxymonosulfate, PMS) to degrade organic contaminants, owing to its highly-developed pore structure and abundant surface functionalities. However, its catalytic efficiency is critically influenced by intrinsic structural defects and surface chemistry, yet the underlying structure–activity relationships remain elusive. Notably, the specific mechanisms governing electron transfer within non-radical pathways during PMS activation require further clarification. In this study, a series of porous biochars were synthesized from waste Myriophyllum aquaticum via KOH activation followed by pyrolysis at varying temperatures. The results demonstrate that the synergistic effect of high-temperature pyrolysis and alkali activation significantly augments structural defects and the density of oxygen-containing functional groups, thereby accelerating electron transfer and PMS activation. Among these catalysts, the PMaB-800-1/PMS system achieved complete removal of 2,4,6-trichlorophenol (2,4,6-TCP) within 15 min, exhibiting a high apparent rate constant ( k obs ) of 0.35 min −1 and an ultra-high PMS utilization efficiency of 0.53. Radical quenching experiments, electron paramagnetic resonance (EPR), and electrochemical analyses confirmed that 2,4,6-TCP degradation was predominantly driven by a non-radical oxidation pathway involving 1 O 2 , O 2 •- , and direct electron transfer. Insights from XPS, Raman spectroscopy, and density functional theory (DFT) calculations further revealed that C=O/O–C=O groups and pyridinic N served as the primary active sites for PMS activation and the selective generation of reactive oxygen species. This study not only provides a sustainable route for the upcycling of spent aquatic plants, but also offers a robust strategy for constructing efficient remediation systems for organic pollutants.