Magnetic porous carbon microspheres synthesized by simultaneous activation and magnetization for removing methylene blue

Magnetic porous carbon microspheres (MPCMs) based on Fe₃O₄-encapsulating carbon composites for removing methylene blue (MB) in aqueous solutions were synthesized by simultaneous activation and magnetization. A series of MPCMs were prepared by combining hydrothermal and annealing treatment with α-Fe₂O₃ nanoparticles as iron source, glucose as carbon source and ZnCl₂ as porogen. The phase structure, specific surface area, porosity, thermostability, magnetic property, as well as morphology of as-prepared MPCMs were verified by X-ray diffraction, Brunauer–Emmeltt–Teller surface area analysis, thermogravimetric analysis, vibrating sample magnetometry, field emission scanning electron microscopy and high resolution transmission electron microscopy. The results indicate that the maximum specific surface area of MPCMs is up to 480.32 m²/g when the mass ratio of ZnCl₂/glucose is 0.25, which is designated as MPCMs-0.25. The saturation magnetism of MPCMs-0.25 is 30.16 emu/g. Adsorption properties of MPCMs were detected by using MPCMs-0.25 as adsorbent to remove MB from aqueous solution. The outcomes suggest that the adsorption reaches equilibrium within 35 min and physical adsorption is involved in the whole adsorption processes. The results of adsorption isotherm reveal that the adsorption process might include monolayer and porous adsorption, meanwhile, various adsorption sites exist on the surfaces of MPCMs-0.25. The reusability and stability of MPCMs-0.25 were also confirmed by five adsorption–desorption cycle experiments.