Multi-walled carbon nanotubes decorated with Cu(II) triazole Schiff base complex for adsorptive removal of synthetic dyes

This research focuses to prepare a new adsorbent with high adsorption capacity and great selectivity. The synthesized adsorbent was utilized for elimination of dyes from aqueous solution. In order to achieve that hydroxyl functionalized Cu(II) Schiff base named N,N-bis(4 hydroxysalicylidene)-4-FI-1,2,4-triazole-3,5-diaminediaminedicopper(II) has been synthesized and supported on modified MWCNT via covalent bonds. The obtained MWCNT anchored copper complex ([Cu-2-L]@MWCNT) has been characterized by different tools including elemental analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmittance electron microscopy (TEM), thermal analysis, UV-Vis spectra and X-ray diffraction which confirmed the loading of bimetallic complex on CNTs. The efficiency of ([Cu-2-L]@MWCNT) for the adsorptive removal of Sunset yellow (SY), Direct red 81 (DR-81), and acid blue 92 (AB-92) from aqueous solutions, has been studied under alternative experimental conditions. The experimental data were analysed by the Langmuir and Freundlich isotherm models. The Langmuir adsorption isotherm was perfectly fitted for equilibrium adsorption data. The experimental kinetic of the data were analysed applying pseudo-first-order, pseudo-second-order and Weber Morris intra-particle kinetic models. The adsorption process follows the second-order kinetics. The adsorption process was confirmed, by thermodynamic studies, to be endothermic and spontaneous. It was found that adsorption capacities followed the order: DR-81 > AB-92 > SY with the values of: 75.70, 58.29 and 26.63 mg/g. Moreover, it has been found that the high adsorptivity observed for direct red dye which has highest molecular weight and contain two azo groups. (C) 2019 Elsevier B.V. All rights reserved.