Facile and cost-effective synthesis of CNT@MCo2O4 (M = Ni, Mn, Cu, Zn) core-shell hybrid nanostructures for organic dye removal

This study presents four hybrid materials of CNT@MCo2O4 (M = Ni, Mn, Cu, Zn) which were prepared via a simple chemical bath deposition method at room temperature followed by a post-annealing treatment. The resulting materials were characterized by different techniques including SEM, EDS, XRD, FTIR, and BET surface area measurement and were first used as adsorbents for removal of methyl orange (MO). Experimental data suggested that the CNT@MCo2O4 samples especially CNTs@NiCo2O4 showed excellent adsorption properties (1188.3 mg g(-1)). The kinetic adsorption of different materials could be accurately described by the pseudo-second-order model and the overall rate process was apparently influenced by external mass transfer and intraparticle diffusion. Furthermore, Langmuir and Freundlich isotherms are employed and both of them fitted the experimental data with good correlation coefficients. Moreover, the thermodynamic parameters indicated that the adsorption process was spontaneous and physical adsorption mechanisms including electrostatic interaction might play a dominant role in the adsorption mechanism between MO and adsorbents. The results of this work are of great significance for environmental applications of CNT@MCo2O4 as promising adsorbents for organic pollutants from wastewater.