Amine functionalized multi-walled carbon nanotubes: Single and binary systems for high capacity dye removal

- Simplified novel production method for amino dendrimer CNTs.
- Exceptional high adsorption capacities for dyestuffs removal-over 500 mg/g.
- Exceptionally fast contact time to reach equilibrium.
- Equilibrium data fitted Langmuir model; rate data fitted pseudo-second order model.

The aim of this study was to develop a feasible and cost effective method to produce amine functionalized multi-walled carbon nanotubes (CNT-NH2) and investigate the ability of this CNT-NH2 material to adsorb anionic dyes in single and binary (mixture of dyes) systems. For this purpose, pristine CNTs were functionalized by primary and secondary functional groups namely (-NH2) and (-NH), respectively. Acid Blue 45 (AB45) and Acid Black 1 (AB1) were used as anionic dye models for adsorption. FTIR, SEM, BET, Raman Spectra, and Zeta potential measurements have been employed for characterizing the synthetic nanocomposite and these techniques indicated that the amino functionalized CNTs have been favorably synthesized. The effects of different operational parameters including pH, initial dye concentration, adsorbent dosage, and salt on dye removal were evaluated. The dye adsorption isotherm and kinetics were also studied. The results of this study indicated that the stronger interactions between CNT-NH2 and AB1 suggest a higher adsorption of AB45 compared to AB1 in both single and binary dye systems. Moreover, the maximum adsorption capacities of the studied functionalized nanotube in single dye solutions, for AB45 and AB1 were 714 and 666 mg g−1, respectively. These capacities are exceptionally high for the removal of acid dyes. It was found that AB45 and AB1 adsorption on the CNT-NH2 followed the Langmuir isotherm model and pseudo-second order kinetics model in both single and binary systems. According to the results of this study the CNT-NH2 were an effective adsorbent to remove anionic dyes from single and binary systems.