Sulfadiazine degradation via peroxydisulfate activation: insights into B/S co-doped biochar and the role of singlet oxygen

Abstract

Developing sustainable, metal-free catalysts for persulfate (PDS) activation is crucial for antibiotic removal in water environments. In this work, boron–sulfur–nitrogen co-doped biochar (BS4C) was synthesized via one-step pyrolysis of walnut shell, boric acid, and thiourea. The introduction of B, N, and S atoms synergistically modulated the electronic structure of carbon, creating abundant electron-deficient sites for PDS activation. As a result, BS4C exhibited excellent catalytic performance toward sulfadiazine (SDZ) degradation, achieving 83.8% removal within 60 min, and maintained strong resistance under the coexistence of various anions and natural organic matter. Radical quenching and EPR analyses confirmed that the process followed a ¹O₂-dominated non-radical oxidation pathway. These findings highlight the potential of biomass-derived, heteroatom-doped carbon materials as sustainable, metal-free catalysts for antibiotic degradation and water purification.