Sorption of Copper(II) and Nickel(II) Ions from Aqueous Solutions Using Calcium Oxide Activated Date (Phoenix dactylifera) Stone Carbon: Equilibrium, Kinetic, and Thermodynamic Studies

In this study, calcium oxide activated Phoenix dactylifera (commonly known as Date palm) stone carbon (ADS) was prepared, characterized, and used as a unconventional adsorbent for the removal of Cu(II) and Ni(II) ions from aqueous solutions in a batch process. The obtained activated carbon was characterized for pore size distribution and total surface area using BET isotherm, surface morphology using scanning electron microscopy, and surface functional groups using Fourier transform infrared spectroscopy, and the amorphous nature of the ADS was confirmed by X-ray diffraction studies. The kinetic data obtained at different temperatures were analyzed by applying pseudofirst-order, pseudosecond-order, and Weber-Morris diffusion models, as well as the Elovich equation. The applicability of Langmuir, Freundlich, and Dubinin–Radushkevich (D-R) adsorption isotherms was evaluated to better understand the adsorption process. The results of this study revealed that ADS has a honeycomb like surface morphology with large mesoporous surface area (645.5 m2·g–1) for adsorption and removal of copper and nickel was followed the pseudosecond-order kinetics and Langmuir model of isotherms. Thermodynamic studies revealed that the heat of adsorption of Cu(II) and Ni(II) ions was −4.99 kJ·mol–1 and −10.78 kJ·mol–1, respectively, which suggested that the adsorption was exothermic in nature.