Construction of Rice Husk-Derived Magnetic Biochar and Its Synergistic Roles in Adsorption and Visible-Light-Driven Photocatalytic Degradation of Levofloxacin: Performance Evaluation and Mechanistic Insights

Abstract

Rice husk-derived magnetic biochar (Fe3O4@BC) was fabricated via KOH activation and one-step hydrothermal Fe3O4 loading. The composite possessed a specific surface area of 73.99 m2/g, average pore diameter of 3.94 nm, and saturation magnetization of 6.66 emu/g enabling efficient magnetic separation. Adsorption experiments showed Fe3O4@BC exhibited a maximum LVX adsorption capacity of 57.83 mg/g, following pseudo-second-order kinetics and Freundlich isotherm models. Thermodynamic results confirmed spontaneous (ΔG < 0) and endothermic (ΔH = 19.443 kJ/mol) adsorption driven by electrostatic interactions, hydrogen bonding, and π-π interactions. In the Fe3O4@BC/PMS/visible light system, 95.34% of LVX was degraded, with •O2- identified as the dominant active species. Three degradation pathways involving hydroxylation, decarboxylation, and defluorination were proposed. After five consecutive cycles, the degradation efficiency remained 79.66% with stable structure. This work realizes agricultural waste valorization and provides a synergistic adsorption-photocatalysis strategy for efficient LVX removal, offering technical support for antibiotic-contaminated water remediation.