Selective adsorption of antibiotics on manganese oxide-loaded biochar and mechanism based on quantitative structure–property relationship model

In this study, MnCl2-impregnated biomass was oxygen-limited pyrolyzed to produce manganese oxide-loaded biochar (MBC), its adsorption behaviors and influencing factors on tetracycline (TTC), norfloxacin (NOR), and sulfamethoxazole (SMX) were systematically investigated. Three antibiotics exhibited enhanced adsorption behavior on MBC, with maximum adsorption capacity as accurately described by Sips isotherm: TTC (534 mg/g) > NOR (67 mg/g) > SMX (28 mg/g). Hydrogen bonding, n/π-π interactions, electrostatic interaction, surface coordination, and hydrophobic interaction are the major mechanisms for the improved adsorption. Manganese oxide particles on MBC promoted surface coordination and hydrogen bonding. Antibiotic molecules with more hydroxyl oxygen-containing functional groups are more susceptible to migrate to biochar surfaces and to be adhered. Moreover, the quantitative structure-property relationship (QSPR) model was constructed and revealed that hydrogen bonding and π-π interactions were crucial for tetracycline antibiotics selective adsorption. Hence, MBC was a prospective adsorbent with promising applications for antibiotic removal in sewage processing.