Removal of nickel ions from aqueous solutions using natural zeolite; kinetic, equilibrium and thermodynamic studies

The aim of the present study is to investigate the removal of nickel ions from aqueous solutions using natural zeolite. Batch experimental studies were conducted to evaluate by changing relevant parameters such as initial pH of solution, dosage of adsorbent, contact time, initial nickel ion concentration and temperature. The experimental isotherm data are analyzed using Langmuir and Freundlich equations. The Langmuir model fits the equilibrium data better than the Freundlich model. According to the Langmuir equation, the maximum uptake for nickel ions is 18.09 (mg/g). Pseudo-first-order and pseudo-second-order models are used to represent the kinetics of the process. The results indicate that the pseudo-second-order model is the one that best describes the kinetics of the adsorption of metal ions. The calculated thermodynamic parameters (ΔG°, ΔH°, and ΔS°) show that the adsorption process is feasible, spontaneous and endothermic at 20-50°C. Based on the experimental results, it can be concluded that natural zeolite has the potential of application as an efficient adsorbent for the removal of heavy metals from aqueous solutions.