Highly effective catalytic degradation of bisphenol A through activation of peroxymonosulfate by an Fe-Nx structure anchored on novel lignin-based graphitic biochar: Electron transfer mechanism

A lignin-based Fe/N co-doped carbonaceous catalyst was synthesized via freeze-drying followed by pyrolysis to activate peroxymonosulfate (PMS) for efficient degradation of bisphenol A (BPA). The Fe/N co-doped biochar exhibited a high specific surface area (364.84 m(2)/g), hierarchical porous structures, and abundant oxygen-containing functional groups (hydroxyl and carboxyl groups), which enhancing the dispersion of Fe3O4 nanoparticle and exposure of catalytic site. The Fe-8-N-10-C/PMS system achieved 100 % BPA degradation within 20 min with a corresponding first-order reaction rate constant (k(obs)) of 0.4056 min(-1), which outperformed most reported catalysts in efficiency. Quenching and EPR analyses revealed that both free radicals ((OH)-O-center dot, SO4 center dot-, and O-2(center dot-)) and non-radical (O-1(2)) were rate-limiting steps, while graphitic N and Fe-N-x structures facilitated direct electron transfer from BPA to PMS in electrochemical tests. XPS results confirmed that pyrrolic N, rather than pyridinic N, played a crucial role in forming the Fe-N-x structure. Moreover, the catalyst showed excellent stability, regeneration capability, and adaptability under diverse conditions, highlighting the potential of the Fe-N-C/PMS system for practical wastewater treatment applications.