Removal of Cd^2+ from Aqueous Solution by Nickel Oxide/CNT Nanocomposites

The present work investigates the efficiency of the nickel oxide/carbon nanotube (NiO/CNT) nanocomposite for the removal of Cd^2+ metal ions from an aqueous. The NiO/CNT nanocomposite was synthesized by the direct co-precipitation method in an aqueous media in presence of CNTs. The resulting materials were characterized by FTIR, XRD, SEM, N2 adsorption–desorption analysis. In order to optimize the adsorption of Cd^2+ ions on NiO/CNT nanocomposite, the effects of the different parameters—namely pH, contact time, initial concentration of Cd^2+, and adsorbent dosage—were also studied. Experimental data revealed that the Cd^2+ ions adsorption of the NiO/CNT nanocomposite was through Langmuir and Temkin isotherm models rather than the Freundlich model. The kinetic data of adsorption of Cd^2+ ions on the adsorbent was best described by a pseudo-second-order equation, indicating their chemical adsorption. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were calculated. The obtained values showed that the adsorption was spontaneous and exothermic in nature. The reusability test showed that the Cd^2+ could be easily removed from the surface site of NiO/CNT nanocomposite by a 0.1 M nitric acid solution as the adsorption capacity was maintained after 5 cycles of the adsorption/desorption process. This suggests that NiO/CNT nanocomposite can be reused through many cycles of water treatment and regeneration.