High rhodamine B and methyl orange removal performance of graphene oxide/carbon nanotube nanostructures

Novel three-dimensional (3D) graphene oxides (GOs) and carbon nanotubes (CNTs) nanostructures have been prepared via a facile freeze-drying method, aiming to obtain the uniform dispersed carbon-based nanostructures with high surface area. The subsequent N₂adsorption and desorption isotherms have confirmed the high BET surface area feature of the obtained products. Especially the GNT 1-5 sample, whose weight ratio of GOs: CNTs is 1:5, have showed a surface area of 257.6 m²/g. The organic dye removal experiments have demonstrated that the GNTs nanostructures display the ability to adsorb both cationic (Rhodamine B, RhB) and anionic (Methyl orange, MO) dyes in aqueous solution, and the maximum adsorption capacity can reach over 248.48 mg/g with RhB and 66.96 mg/g with MO. This study also reveals that the adsorption kinetics of both dyes follow the pseudo-second-order model, while the equilibrium during adsorption could be explained well by the Langmuir and Freundlich adsorption isotherm theory. Thus, the as-prepared 3D GNT nanostructures have shown great potential as a adsorbent to remove organic dyes in waste-water treatment.