Peroxymonosulfate activation by iron-nickel nanoalloys anchored on nitrogen-doped biochar for efficient sulfadiazine degradation

Biochar-based transition metals have been intensively studied as promising catalysts for peroxymonosulfate (PMS) activation towards the degradation of recalcitrant organic contaminants, but their catalytic activities and stabilities remain to be improved. Herein, Fe-Ni nanoalloys anchored on nitrogen-doped biochar (FeNi-NBC) was developed for PMS activation towards sulfadiazine (SDZ) degradation. The results show that SDZ (10 mg/L) is completely degraded by the PMS/FeNi-NBC system within 60 min under optimum conditions, and the SDZ degradation rate constant (0.266 min-1) outperforms most reported catalysts. Besides, the prepared FeNi-NBC has a high stability with a SDZ removal efficiency of around 86% after twenty cycles. Electron paramagnetic resonance measurements and quenching tests fully demonstrate the nonradical PMS activation by FeNi-NBC. Combined with the results of electrochemical tests and DFT calculations, the formation of activated surface-PMS complexes is found to be the dominant pathway for PMS activation by FeNi-NBC. DFT calculations further reveal that the adsorption of PMS on the FeNi-N-C sites to form the surface-PMS complex is thermally spontaneous, and the FeNi-N-C sites in FeNi-NBC are dominant active sites for PMS activation.