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

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-MWCNT5@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 (Delta G(0)), enthalpy (Delta H-0) and entropy (Delta S-0), 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. (C) 2019 Published by Elsevier B.V.