Characteristics of leaf biochar and adsorption mechanism of ofloxacin in water

Biochars were prepared by pyrolysis at 300–700 °C. Structural features were characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) N₂ adsorption–desorption,, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Boehm titration. Using ofloxacin (OFX) as a model pollutant, batch adsorption experiments were performed, and kinetic/isotherm models were fitted to elucidate the adsorption mechanism. The 600 °C product (BC600) achieved the optimal balance among micropore volume, pore-size distribution, and residual oxygen-containing functionalities, thereby exhibiting the best adsorption performance. The isotherms were best described by the Langmuir model (R² > 0.97); at 308 K, the maximum adsorption capacity (Qm) of BC600 reached 80.9 mg·g⁻¹. Kinetic analysis indicated a multi-stage process—film diffusion–intraparticle diffusion–equilibrium; at low concentrations, physical diffusion dominated, whereas at higher concentrations hydrogen bonding, π–π interactions, and electron donor–acceptor (EDA) effects became significant. In simulated wastewater, BC600 achieved efficient co-removal of organics, nutrients, and OFX, demonstrating promising application potential. This study provides data support for the development of materials for removing ofloxacin from water. Density functional theory (DFT) calculations further demonstrate that surface sites containing hydroxyl/carboxyl groups enhance adsorption binding strength through improved interfacial electron coupling and hydrogen-bonded π–π synergistic effects.