Isotherm, kinetics, thermodynamics and mechanism of metal ions adsorption from electroplating wastewater using treated and functionalized carbon nanotubes

Abstract

The pollution of the environment emanating from the electroplating wastewater containing cadmium, copper, iron, nickel and lead is a universal critical issue that require efficient treatment methods. Herein, super carbon nanotubes (CNTs) were synthesized on iron-nickel/kaolin catalyst, treated (TR-CNTs) and functionalized (PN@TR-CNTs) as a suitable nanoadsorbent. The nanoadsorbents were characterized to confirm the properties by several physicochemical methods such as x-ray diffraction, Fourier transform infrared spectroscopy, high resolution scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive x-ray and Brunauer–Emmett–Teller. The characterizations indicate successful synthesis, purification and functionalization of the nanoadsorbents. The surface area of the CNTs, TR-CNTs and PN@TR-CNTs were evaluated as 583.31, 781.88 and 970.81 m2 g−1, respectively. The effect of pH, contact time, nanoadsorbent dosage and temperature on the adsorption of the selected metal ions was carried out and the best conditions were obtained at pH (5 and 6), contact time (60 min), nanoadsorbent dosage (0.4 g/L) and temperature (50 °C). Redlich-Peterson and pseudo second-order isotherm and kinetic models best fitted the experimental data. Similarly, the metal ions adsorption by TR-CNTs and PN@TR-CNTs were thermodynamically spontaneous. The adsorption mechanism was dominated by pore filling and electrostatic attraction, ahead of hydrogen bonding and surface complexation. With good reusability of 6 cycles, the nanoadsorbents can be utilized as a potential material for metal ions removal from electroplating wastewater.