Magnetic biochar prepared by a dry process for the removal of sulfonamides antibiotics from aqueous solution

Sulfonamides antibiotics are representatives of new pollutants which are difficult to be biodegraded. In this study, bagasse-derived magnetic material (Fe-BCs) prepared by a totally dry process were used for the removal of sulfamethoxazole (SMZ) and sulfamerazine (SMR) from aqueous solution. Various characterization techniques revealed abundant porous structures and various functional groups as well as the graphite-like heterogeneous structure of Fe-BCs. Langmuir isotherm model demonstrated that the maximum adsorption amounts of SMZ and SMR on Fe-BC-800 with surface area of 843.6 m2 g−1 were 414.2 and 386.3 mg/g at 20 °C, respectively. The interaction between sulfonamides antibiotics and magnetic biochar was analyzed by adsorption isotherm, adsorption kinetics and density functional theory (DFT), and the possible adsorption mechanism was proposed. DFT calculation confirmed that Fe-O played an important role in the adsorption process of SMZ and SMR on the Fe-BCs. The adsorption mechanism of SMZ and SMR on the Fe-BCs included electrostatic, Lewis acid-base, pore filling, π-π EDA, conventional hydrogen bond and negative charge assisted H-bond interactions. This study could provide valuable information for the removal of antibiotic pollutants from water by biomass-based functional materials.