Alkaline lignin-derived N-doped biochars as peroxymonosulfate activators for acetaminophen degradation: Performance and catalytic bridging mediated Electron-Transfer mechanism

Abstract

Carbon-catalyzed persulfate activation processes are promising techniques for oxidizing aqueous organic pollutants, while high-performance and low-cost carbocatalysts are urgently needed. To address this issue, nitrogen-doped biochar catalyst from alkaline lignin was developed to activate peroxymonosulfate (PMS) for acetaminophen (APAP) degradation. The optimized N-doped biochar achieved a complete removal of 50 ppm APAP within 15 min under the conditions of 0.1 g/L catalyst and 0.5 mM oxidant across a wide pH range of 4–10. Notably, the optimized N-doped biochar exhibits remarkable stability, retaining 75% APAP removal after four cycles. Moreover, a comprehensive investigation, including quenching tests, electron paramagnetic resonance measurements, and electrochemical analyses, elucidated the electron-transfer mechanism involved in the nonradical N-doped biochar/PMS system. Surprisingly, the results indicated that the primary species responsible for APAP oxidation was an activated state of N-doped biochar with electron deficiency generated from the interactions between the catalyst and PMS. This work not only provides cost-effective and high-performance biochar catalyst for selectively removing APAP from actual water body, but also sheds new light on the electron-transfer mechanism involved in nonradical carbon/PMS systems.