Preparation of 3D graphene-carbon nanotube-magnetic hybrid aerogels for dye adsorption

Novel hybrid aerogels, which can be magnetically extracted from water to avoid filtration, were prepared by adding ZnCl2, NiCl2·6H2O, FeCl2·4H2O and FeCl3·6H2O into a suspension of graphene oxide and oxidzed carbon nanotubes followed by co-precipatation under basic condition, crosslinking with polyvinyl alcohol in water and freeze-drying. The hybrid aerogels consist of magnetic Ni0.5Zn0.5Fe2O4 nanoparticles, graphene oxide, carbon nanotubes and polyvinyl alcohol, which have active sites that attract dye molecules and can be extracted from water by applying magnetic field. Under an optimal mass ratio of the components, the optimized hybrid aerogel has a high adsorption capacity (qe=71.03 mg g−1 for methylene blue) and a moderate magnetic strength of MS = 3.519 emu g−1. Its removal efficiencies for methylene blue, methyl orange, crystal violet and their mixture with an equal mass are 70.1%, 4.2%, 8.9% and 11.1%, respectively under the same dye concentration of 0.025 mg. mL−1. It can be reused for 3 regeneration cycles with a regeneration efficiency of over 82%. Also it is not toxic to the living organism, suggesting that it is promising as an adsorbent for treating industrial wastewater.