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 (NH 2 -MWCNTs) were prepared via chemical modification of the surface of multiwall carbon nanotubes. The magnetic nanoparticles (Fe 3 O 4) were embedded with NH 2 -MWCNTs and the developed magnetic carbon nanotube (NH 2 -MWCNTs@Fe 3 O 4) were characterized via several analytical techniques including FT-IR, Raman, XRD, TEM, SAED, SEM, BET and VSM. The fabricated NH 2 -MWCNTs@Fe 3 O 4 was used for the removal of toxic methylene blue dye (MB) from aqueous medium. The results of VSM indicated that the fabricated NH 2 -MWCNTs@Fe 3 O 4 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 (Δ G 0), enthalpy (Δ H 0) and entropy (Δ S 0), supported the spontaneous and exothermic nature of adsorption. It was noted that after six repetitive cycles, the adsorption capacity of NH 2 -MWCNTs@Fe 3 O 4 was 80% of the original value. Hence, it can be concluded that NH 2 -MWCNTs@Fe 3 O 4 had substantial reusability which made it an economical adsorbent for MB removal from aqueous medium. Highlights • Amino-functionalized magnetic multi-walled carbon nanotubes were prepared. • NH 2 -MWCNTs@Fe 3 O 4 was used as adsorbent for MB dye removal. • Adsorption kinetics and equilibrium isotherm models for MB dye were reviewed. • NH 2 -MWCNTs@Fe 3 O 4 was used for six cycles without significant loss in adsorptive performance. [ABSTRACT FROM AUTHOR]