Synthesis of magnetic Fe₃O₄/activated carbon nanocomposites with high surface area as recoverable adsorbents

The magnetic Fe₃O₄/activated carbon nanocomposites with high surface area were synthetized as recoverable adsorbents by chemical binding of Fe₃O₄ nanoparticles on activated carbon (AC) powders. The component AC and Fe₃O₄ in this nanocomposite possesses amorphous non-graphitic structure and cubic crystal structure, respectively. All composite samples presented superparamagnetic properties. The saturation magnetization of Fe₃O₄/AC nanocomposites was significantly lower than that of bare Fe₃O₄ particles, indicating that Fe₃O₄ particles were truly attached on AC surface. The microstructure image indicated that the Fe₃O₄ particles were uniformly dispersed on AC surface and thus maintained high specific surface area. The adsorption capacity of methyl orange (MO) at 30 °C slightly decreased from 384 mg/g on AC powders to 324 mg/g on Fe₃O₄/AC nanocomposites, which was reduced by 15% after magnetic fabrication. It was found that MO adsorption on Fe₃O₄/AC nanocomposites followed the pseudo-second order kinetic model and the isotherms could be described by the Langmuir model. The easy recovery of magnetic adsorbents from aqueous solution demonstrated their application potential to remove toxic pollutants in water and wastewater treatment.