Equilibrium and thermodynamic study of cobalt adsorption on activated carbon derived from date seeds

Preparation of activated carbon from date seeds and the possibility of using it as an adsorbent were evaluated. Pyrolysis of date seeds under nitrogen flow and activation with carbon dioxide was performed at three different temperatures (700, 800, and 900°C). SEM micrographs of activated carbon produced at 900°C indicate a rough structure on the surface with more mesopores than that produced at lower temperatures. In addition, EDS analysis showed that it has higher oxygen surface groups. However, the yield was 16.5% compared with 18.9% and 20.9% at 800, 700°C, respectively. Batch adsorption of cobalt on S900 showed type III adsorption isotherm at three studied temperatures (25, 35, and 45°C). This type of isotherm was explained using Freundlich's and BET models that showed very good agreement with the experimental data. The Gibbs free energy change was calculated as -4.154, -4.374, and -4.595 kJ/mol at 25, 35, and 45°C, respectively. The adsorption of cobalt was found to be endothermic process (ΔH° = 2.415 kJ/mol) and entropy-driven rather than enthalpy-driven with ΔS° = 0.022 kJ/mol.K.