Effective and fast adsorptive removal of toxic cationic dye (MB) from aqueous medium using amino-functionalized magnetic multiwall carbon nanotubes

Abstract

Amino functionalized multi-walled carbon nanotubes (NH2-MWCNTs) were prepared via chemical modification of the surface of multiwall carbon nanotubes. The magnetic nanoparticles (Fe3O4) were embedded with NH2-MWCNTs and the developed magnetic carbon nanotube (NH2-MWCNTs@Fe3O4) were characterized via several analytical techniques including FT-IR, Raman, XRD, TEM, SAED, SEM, BET and VSM. The fabricated NH2-MWCNTs@Fe3O4 was used for the removal of toxic methylene blue dye (MB) from aqueous medium. The results of VSM indicated that the fabricated NH2-MWCNTs@Fe3O4 had magnetic nature and the saturated magnetization was 37.91 emu/g. The effect of initial solution pH, temperature and contact time on MB adsorption was also investigated. The results of adsorption kinetics exhibited that the adsorption followed the linear pseudo-second-kinetic model well. Langmuir and Freundlich isotherm models were applied to understand the adsorption behaviors. The maximum adsorption capacity from the Langmuir isotherm equation reached 178.5 mg g−1 indicated that it was a good adsorbent for MB removal. The thermodynamics parameters such as Gibbs free energy (ΔG0), enthalpy (ΔH0) and entropy (ΔS0), supported the spontaneous and exothermic nature of adsorption. It was noted that after six repetitive cycles, the adsorption capacity of NH2-MWCNTs@Fe3O4 was 80% of the original value. Hence, it can be concluded that NH2-MWCNTs@Fe3O4 had substantial reusability which made it an economical adsorbent for MB removal from aqueous medium.