Green synthesis of β-cyclodextrin conjugated Fe3O4/NiO nanocomposites and its synergistic effect of adsorption and photocatalytic degradation for Congo red removal

The Fe3O4/NiO magnetic nanomaterials were prepared by microwave-assisted and hydrothermal synthesis in β-cyclodextrin (β-CD) solution, which can be employed as absorbents and photocatalysts for the degradation of Congo red (CR). The XRD, EDX and TEM characterizations were used to determine the structure, composition and morphology of the as-prepared samples. The interaction between Fe3O4/NiO nanoparticles and β-CD molecules was investigated by TGA and FT-IR spectra. The results indicate that β-CD molecules can encapsulate the as-prepared nanoparticles and control the nucleation and growth of Fe3O4/NiO nanocrystals to certain extent. The pyrolysis of β-CD molecules and calcination treatment produced porous structure that provides more adsorption sites for CR molecules. The effect of reaction factors including calcination temperature and pH values was studied to determine the optimum condition. In addition, the thermodynamic and kinetic parameters of CR absorbed on Fe3O4/NiO nanoparticles were measured to understand the adsorption mechanism. The high removal efficiency for CR in aqueous solution was achieved within 60 min of adsorption and 40 min of UV-light irradiation, which can be attributed to the synergistic effect of the adsorption–photodegradation process. The prepared Fe3O4/NiO nanocrystals exhibit high adsorption capacity, magnetic separability, good photocatalytic activity and renewability, making it a potential material for wastewater treatment.