Decoration of multi-walled carbon nanotubes (MWCNTs) with different ferrite nanoparticles and its use as an adsorbent

A simple and inexpensive synthesis route to produce multi-walled carbon nanotubes (MWCNTs) decorated with CoFe2O4 and Co0.5Ni0.5Fe2O4 nanoparticles using a simplified hydrothermal precipitation is reported. Transmission electron microscopy and X-ray diffraction confirm the formation of 14.9 nm CoFe2O4 and 26 nm Co0.5Ni0.5Fe2O4 nanoparticles on MWCNTs surface. The prepared composite was used for methyl green adsorption. The effects of various parameters, such as temperature, initial dye concentration, and composite dosage, were investigated. Experimental results have shown that the amount of adsorbed dye increased with increasing initial dye concentration, composite dosage, and temperature. The adsorption kinetic data were analyzed using pseudo-first -order, pseudo-second-order, and intraparticle diffusion models. It was found that the pseudo-second-order kinetic model was the most appropriate model in describing the adsorption kinetics. The adsorption isotherms of methyl green onto MWCNTs decorated with CoFe2O4 and Co0.5Ni0.5Fe2O4 nanoparticles were determined at 298, 313, and 323 K. Equilibrium data were fitted to the Langmuir and the Freundlich isotherm models, then the isotherm constants were determined. The equilibrium data were best represented by the Langmuir isotherm model. Thermodynamic parameters such as changes in the free energy of adsorption, enthalpy, entropy, and activation energy were calculated.