Magnetic biochar-based manganese oxide composite for enhanced fluoroquinolone antibiotic removal from water

Magnetic biochar-based manganese oxide composite (MMB) and raw biochar (BC) were synthesized via pyrolysis at a temperature of 500 °C under anoxic conditions of potato stems and leaves, characterized, and successfully used for the removal of norfloxacin (NOR), ciprofloxacin (CIP), and enrofloxacin (ENR) as representative compounds of fluoroquinolone antibiotics (FQs). Characterization results suggested that Fe₃O₄ and MnO_x are the dominant crystals in MMB. MMB possessed large surface area and pore volume than BC. Batch adsorption experiments showed that the maximum adsorption abilities of MMB for norfloxacin (NOR), ciprofloxacin (CIP), and enrofloxacin (ENR) were 6.94, 8.37, and 7.19 mg g^-1. In comparison to BC, the adsorption abilities of MMB increased 1.2, 1.5, and 1.6 times for NOR, CIP, and ENR, respectively. The pseudo-second-order kinetic model and the Langmuir model correlated satisfactorily to the experimental data. Thermodynamic studies revealed that the adsorption processes were spontaneous and endothermic. The adsorption capacity of MMB decreased with increasing solution pH (between 3.0 and 10.0) and increasing ionic strength (0.001-0.1). The MMB with high FQ removal efficiency, easy separation, and desirable regeneration ability may have promising environmental applications for the removal of fluoroquinolone antibiotics from water environment.