Enhanced catalytic degradation of sulfamethazine by magnetic N-doped biochar: Performance evaluation and mechanism insight

Persulfate-based advanced oxidation processes catalyzed by heterogeneous Fe-carbon composites represent a promising and competitive technology for the degradation of antibiotics. Herein, an environmentally friendly carbon material derived from tobacco stalk biomass was developed using potassium ferrate as both activator and Fe source, with urea serving as the N precursor. Magnetic N-doped biochar (H-Fe-N@BC) with abundant microporous-mesoporous structures and a high graphitization degree was obtained, and loaded Fe 3 N made the biochar with magnetism and simultaneously improved the ability of potassium persulfate (PS) activation in antibiotic-sulfamethazine (SMT) degradation. SMT (the initial pH≈7) could be degraded to 90.8 % within 15 min in the H-Fe-N@BC/PS system. In addition, H-Fe-N@BC maintained excellent catalytic activation performance under acidic and weakly basic conditions, and Cl - promoted the SMT degradation, while CO 3 2- and HPO 4 2- exerted inhibitory effects. The degradation mechanism by H-Fe-N@BC mainly consists of O 2 · − -dominated radical pathway as well as 1 O 2 and electron transfer-dominated non-radical pathway. Variation in composition of biochar and density functional theory calculation revealed that C O, graphite N, and Fe 3 N sites were crucial for activating PS to degrade SMT. These findings are of great significance by converting tobacco straw waste into high value-added biochar products with multiple active sites and applying them in the remediation of antibiotic-contaminated environment.