Experimental Investigation of Thermodynamics, Kinetics, and Equilibrium of Nickel Ion Removal from Wastewater Using Zinc Oxide Nanoparticles as the Adsorbent

Abstract

In the present study commercial zinc oxide (ZnO) nanoparticles in the size of 30 nm were utilized as an adsorbent for the removal of Ni (II) ion from synthetic waste aqueous solution. Adsorption capacity of ZnO for removing Ni (II) ions from aqueous solutions was measured at different pH, adsorbent dose, contact time, temperature and metal ion concentration. Moreover, adsorption isotherms, kinetics and thermodynamics were studied to understand the nature and mechanism of adsorption. ZnO nanoparticles were characterized by X-Ray diffract analysis(XRD),Fourier Transform Infrared Spectroscopy(FT-IR), scanning electron microscopy (SEM),energy dispersive X-ray spectroscopy(EDS) and Brunauer-Emmett-Teller (BET). The maximum amount of Ni (II) removal were found to be (98.71%) from its aqueous solutions by ZnO nanoparticles which was achieved at the evaluated optimum conditions. The experimental kinetic data were examined using the pseudo-second-order rate model with a high regression coefficient. The adsorption isotherm was well described to the equilibrium data by Langmuir isotherm model (R2=0.990). In addition, the calculated thermodynamic parameters, the standard Gibbs free energy ΔGo, the change in standard enthalpy ∆Ho and the standard entropy change ∆So showed that the adsorption of Ni (II) onto ZnO nanoparticles was feasible, endothermic and spontaneous respectively. The experimental results suggest that ZnO nanoparticles can be used as a potential adsorbent for the efficient removal of heavy metals from aqueous solutions than any other adsorbent because an economical and low- consumption energy due to its ambient operation conditions.