An achieved strategy for magnetic biochar for removal of tetracyclines and fluoroquinolones: Adsorption and mechanism studies

In this study, poplar wood biochar modified with Fe3O4 (MPBC) was prepared using poplar wood as carbon source applied to remove tetracyclines and fluoroquinolones. The adsorption behavior was investigated by batch experiments, and a series of characterization techniques were used to study the corresponding mechanism. Characterizations indicated that pore filling, electrostatic interactions, π-π interaction, surface complexation, and hydrogen bond contributed to the adsorption of antibiotics on MPBC. Most importantly, the thermodynamic experiment results showed that the adsorption capacity of MPBC for tetracyclines (70.28-89.58 mg⋅g-1) was significantly higher than fluoroquinolones (35.54-60.31 mg⋅g-1), which was further explained by hydrogen bond interactions calculated from Conductor-like screening model for real solvents (COSMO-RS). In addition, the adsorption between MPBC and antibiotics was favorable at lower ionic strengths and neutral conditions. Conclusively, this study could provide a promising approach to controlling the pollution of tetracyclines and fluoroquinolones.