Magnetic NiFe2O4 decorated-exfoliated graphite for adsorptive removal of anionic dyes and cationic dyes from aqueous solution

This study focused on the fabrication, characterization of magnetic NiFe2O4-decorated exfoliated graphite (MEG) as well as its potential application as a low-cost, flexible and efficient adsorbent to remove different kinds of cationic and anionic dyes from aqueous solution. The exfoliated graphite was first fabricated using highly efficient microwave-assisted exfoliation technique and the ferrite magnetic component (NiFe2O4) was then introduced to the graphitic structure by sol-gel process. The materials were characterized using relevant analytical techniques such as scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N-2 adsorption measurement and vibrating sample magnetometry. The adsorption behavior of widely used ionic dyes including methylene blue (MB), crystal violet (CV), methyl orange (MO) and congo red (CR) was investigated under effects of exfoliation degree, NiFe2O4 loading on EG structure, preparation temperature and adsorption conditions (i.e. pH and dye concentration). The adsorption mechanism was discussed taking into account the electrostatic force, hydrogen bonding, pi-pi interaction between delocalized pi electrons of the basal planes and free electrons of aromatic rings and multiple bonds in dye molecules.