Silver nanoparticles deposited multiwalled carbon nanotubes for removal of Cu(II) and Cd(II) from water: Surface, kinetic, equilibrium, and thermal adsorption properties

A novel composite based on functionalized multiwalled carbon nanotubes (FMWCNTs) reduced with N,N-dimethylformamide and cross-linked with silver nitrate, i.e., Ag-MWCNTs, was fabricated for effective removal of Cu(II) and Cd(II) ions. The performance of Ag-MWCNTs was characterized by Fourier transform infrared, Raman spectroscopy, thermal gravimetric analysis, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The adsorption characteristics were explored using well-established and effective parameters including pH, contact time, adsorbent dosage, initial metal ion concentration, and temperature. Optimum adsorption of Cu(II) and Cd(II) was observed at pH 6.0 and 7.0, respectively. Kinetic studies revealed that the adsorption data fitted well to the pseudo-second-order kinetic model and Langmuir model gave a better fit than the other models. Thermodynamic properties, i.e., Delta G degrees, Delta H degrees, and Delta S degrees, showed that adsorption of Cu(II) and Cd(II) onto Ag-MWCNTs was endothermic, spontaneous and feasible in the temperature range of 293-313 K. (C) 2013 Elsevier B.V. All rights reserved.