Iron-nitrogen modified biochar as a persulfate activator for metronidazole degradation

This study synthesized porous nitrogen-rich magnetic biochar (Fe-N-BC) using banyan branch as precursors to through co-pyrolysis with potassium ferrate and urea. The as-prepared composite was employed as an efficient activate peroxymonosulfate (PMS) activator for metronidazole (MNZ) degradation. Results demonstrated that iron-nitrogen co-modification significantly enhanced the catalytic performance of the composite. During pyrolysis, thermal decomposition of urea generated gaseous products that disrupted the carbon framework, creating additional porous structures while simultaneously facilitating the reductive formation of α-Fe0. A systematic investigation of operational parameters was conducted, included catalyst dosage, PMS concentration, reaction temperature, initial solution pH, and inorganic anions. Under optimal conditions (Fe-N-BC=0.1 g·L−1, PMS=0.1 g·L−1, MNZ=10 mg·L−1, T=25 °C), the Fe-N-BC/PMS system achieved 96.5% MNZ removal within 40 min (kobs= 0.1541 min−1). Radical quenching experiments confirmed the generation of reactive species, including radicals (SO4·− and ·OH) and non-radical singlet oxygen (1O2). And SO4·−played a more dominant role than ·OH in MNZ degradation. Synergistic interactions between radical and non-radical pathways enabled efficient MNZ degradation and mineralization.