Boron and Nitrogen Codoped Biochar for Efficient Activation of Peroxydisulfate in Oxytetracycline Degradation: Performance Study, Degradation Pathways, and Mechanism

A high-performance B/N codoped biochar (NB3GC) was synthesized using byproduct molasses via a combined hydrothermal treatment and pyrolysis process. A systematic investigation was carried out on the efficiency and underlying mechanism of NB3GC-activated peroxydisulfate (PDS) in degrading oxytetracycline hydrochloride (OTC). The results suggest that B/N codoping improved the pore structure and catalytic activity of the biochar material. The NB3GC catalyst exhibited exceptional performance in PDS activation for OTC removal. With NB3GC (0.4 g/L) and PDS (0.4 mM), the NB3GC/PDS system achieved a 99.1% OTC removal efficiency within 10 min, with a total organic carbon mineralization rate of 31.5%. The system maintained robust catalytic capability over the pH range (2–10) and in common interfering ions such as Cl– and HCO3–. Mechanistic studies identified O2•– as the primary reactive species, with •OH and SO4•– playing synergistic roles. Density functional theory calculations combined with liquid chromatography–mass spectrometry (LC–MS) analysis revealed that OTC underwent stepwise degradation via decarboxylation, ring-opening, and hydroxylation, ultimately forming low-molecular-weight products. This study offers a useable strategy for the valorization of waste molasses and an efficient nonmetal-based catalytic scheme , for environmental remediation.