One-step synthesis of hierarchical porous Fe-supported biochar for rapid and efficient removal of antibiotics from water

The widespread use of antibiotics has led to their accumulation in water, posing serious environmental risks. Biochar has emerged as a promising adsorbent for antibiotic removal, but its performance is often limited by low capacity and slow kinetics, especially for high-molecular-weight antibiotics. In this study, a hierarchical porous Fe-supported biochar (HPFeBC) was synthesized via one-step pyrolysis of pine sawdust using Fe(NO 3 ) 3 as both activator and template. The obtained HPFeBC exhibited a well-interconnected pore structure with a high surface area (417.23 m 2 /g) and enhanced mesoporosity, significantly improving mass transfer and accessibility of adsorption sites. HPFeBC demonstrated exceptional adsorption performance for both low-molecular-weight antibiotic tetracycline (TC) and high-molecular-weight antibiotic tylosin (TYL), with maximum capacities of 361.23 mg/g and 173.61 mg/g, respectively. Notably, HPFeBC achieved rapid adsorption equilibrium within 5 mins for TC and 30 mins for TYL, far surpassing commercial adsorbents. The adsorption process followed the pseudo-second-order kinetics and the Freundlich isotherm model, and thermodynamic analysis confirmed the spontaneous and endothermic nature of adsorption. The adsorption mechanism involved pore filling, π-π interactions, hydrogen bonding, surface complexation, and limited redox reaction. HPFeBC also exhibited excellent stability over a wide pH range, strong anti-interference ability, and good reusability. Overall, the synthesis HPFeBC can act as an effective candidate for rapid and efficient removal of antibiotics from water.