Methylene blue removal by carbon nanotube-based aerogels

•Carbon nanotube-based aerogels with high surface areas and porosities were fabricated.•Performance of these aerogels as adsorbent for methylene blue removal was promising.•Macroscopic dimensions of the adsorbent facilitated its separation from the solution. In this study, carbon nanotube-based porous structures were utilized as novel adsorbents for removal of methylene blue (MB) from aqueous solutions. The adsorbents were fabricated from CNT-contained resorcinol/formaldehyde gels which were subsequently freeze-dried and thermally treated under an inert atmosphere. The densities of the as-prepared SWCNT and MWCNT aerogels were 0.140g/cm3 and 0.149g/cm3 and the specific surface areas were 197m2/g and 537m2/g, respectively. The investigation on the adsorption behavior of these aerogels revealed that the MB adsorption kinetics followed a pseudo-second order model, and the equilibrium data were best described by Freundlich isotherm model. Moreover, the calculated thermodynamic parameters indicated that the process was spontaneous and endothermic. Our experimental results suggest that the advantage of using these porous adsorbents is not only their effective performances due to their compositional and structural properties, but also their facile separation from the solutions due to their macroscopic dimensions.