Nitrogen-doped biochar as peroxymonosulfate activator to degrade 2,4-dichlorophenol: Preparation, properties and structure-activity relationship

Nitrogen-doped biochar (NCMs) has shown great potential as metal-free catalysts for persulfates. To understand the evolution law of properties of NCMs with preparation conditions, eleven NCMs were prepared and charac-terized by EA, BET, Raman, XPS, and conductivity. Surface area and conductivity can be improved by higher pyrolysis temperature and longer retention time. Distribution of nitrogen species of NCMs was greatly influenced by pyrolysis temperature. Subsequently, these NCMs were applied to activate peroxymonosulfate to degrade 2,4-dichlorophenol. A linear correlation of the initial apparent degradation rate constant (kobs) of 2,4-dichlorophenol with conductivity and ratio of graphitic N was newly established, revealing that conductivity and graphitic N of NCMs would be the key property deciding degradation efficiency of 2,4-dichlorophenol. Positive effect of con-ductivity can be ascribed to the mediated electron-transfer mechanism. Electron-transfer mechanism is also proved by quenching experiments and solvent deuterium isotope effect experiment. Graphitic N would be the main active site for PMS activation. Understanding the evolvement rule of properties of NCMs with preparation conditions combined with the correlations between reactivity and properties of NCMs is meaningful for prepa-ration of nitrogen-doped biochar as well as the development of carbonaceous materials with high performance in persulfates-based advanced oxidation processes.