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 (kobs) 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 1O2, O2•-, 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.