Abstract
? 2022 Elsevier B.V.The present study is based on the adsorption of Ni2+ in aqueous solution on the spinel MgCo2O4 synthesized by nitrate route, followed by calcination at 500 °C. The powder was characterized by X-ray diffraction (XRD), FTIR spectroscopy, SEM/EDX analysis and specific surface area. It crystallizes in a cubic symmetry (Space Group: Fd-3m) and the SEM image shows hexagonal-shaped grains with visible porosity. The effects of the initial Ni2+ concentration, catalyst dose, temperature and pH were investigated. The optimization was found for 0.5 g/ L, 25 mg/ L, pH ～ 6 and 50 °C respectively with a maximum efficiency of 99%. The experimental data were analysed by different isotherms. The Langmuir model indicates a better representation with a high adsorption capacity of 140 mg/g and a correlation coefficient (R2) of 0.99, thus showing that MgCo2O4 is an efficient adsorbent for the Ni2+ recovery. The kinetic data are well fitted by the pseudo second-order model. The positive zeta potential leads to a high adsorption capacity. The thermodynamic parameters revealed that the Ni2+ adsorption on the spinel is endothermic (ΔH° = 27.236 kJ/ mol) and spontaneous (ΔG° = ?2.045 kJ/ mol). The spinel is regenerated with diluted HCl solution without noticeable loss of adsorption quality after continuous cycles (adsorption / desorption).
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Elsevier