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.