Magnetic Fe₂O₃/biochar composite prepared in a molten salt medium for antibiotic removal in water

Abstract

The large-scale use of antibiotics is causing serious water pollution problems, and it is of great significance to develop new technologies to remove antibiotics from water. As an environmentally friendly and economical adsorption material, carbon derived from biomass is a low-cost and feasible material for removing antibiotics in sewage, but the current removal efficiencies are not high enough for large-scale practical application. In this study, poplar wood chips are used as raw material, and a magnetic biochar is prepared by co-pyrolysis of poplar wood chips and FeCl₃/CaCl₂ mixed molten salt. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N₂-isothermal adsorption and desorption, X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) techniques showed the successful synthesis of Fe₂O₃/bioC composite. In-situ formed Fe₂O₃ makes the biochar possess the characteristic of superparamagnetic, which is conducive to the recycling of biochar. Due to the etching effect of the molten salts, rough surface was formed on Fe₂O₃/bioC, resulting in a maximum norfloxacin (NOR) adsorption ability up to 38.77 mg g⁻¹ at pH 6.0. The NOR adsorption behavior on Fe₂O₃/bioC followed the pseudo second order kinetic model and the equilibrium data was best fitted the Langmuir model. In addition, the adsorption process of NOR on Fe₂O₃/bioC was thermodynamically spontaneous. The results show that this low-cost and reusable magnetic biochar has the potential for rapid and efficient removal of antibiotic from aqueous solution.

Highlight

•	A magnetic Fe2O3 modified porous biochar composite was prepared in a molten-salt medium.
•	Molten salt made a higher proportion of micropores in Fe2O3/biochar during the carbonization.
•	Fe2O3/biochars composite exhibited higher removal efficiency for NOR than original biochars.

Funding

national natural science foundation of china(21908242)