Endogenous Fe-N co-doped biochar for persulfate activation: Synergistic enhancement of persulfate adsorption by...

To prepare high-performance biochar for persulfate-based wastewater treatment, a series of endogenous Fe-N co-doped magnetic biochars were prepared from Chlorella biomass, where endogenous N originated from Chlorella itself, while endogenous Fe originated from Fe accumulated by the algae during the simulated wastewater treatment process. Among them, Fe5-NCB exhibited the highest sulfamethazine (SMZ) removal efficiency, achieving 99.2% removal within 30 min via peroxydisulfate (PDS) activation. Fe5-NCB maintained stable performance under conditions including broad pH range, coexistence of anions, and in actual wastewater samples, along with high TOC removal (84.1%) and good reusability. Mechanistic analyses revealed that SMZ degradation occurred mainly via an electron transfer pathway. In situ Raman and electrochemical analyses supported the formation of the surface complex Fe5-NCB-PDS*, which promoted the oxidation potential. Further structural characterization and DFT calculations indicated that the improved performance primarily resulted from enhanced adsorption. This enhancement was synergistically driven by the well-developed porous structure of Fe5-NCB and the strong PDS ligand coordination via Fe-induced p-d orbital coupling. In addition, this coupling may also favor interfacial electron transfer. The developmental toxicity of most degradation intermediates was predicted to be lower.