Potential Use of Molecular Sieves for the Removal of Ni2+ Metal Ion: Kinetics, Isotherms and Thermodynamic Studies

Abstract

The potential of using molecular sieves as adsorbent for the removal of nickel from aqueous solution was investigated. The isotherms and kinetics of nickel adsorption using 3 A molecular sieves were evaluated. The results indicated that equilibrium was established in about 5 h. The effect of the pH was examined in the range of 2–6. The maximum removal of nickel obtained is at pH value of 5. The effect of dosage also evaluated to get optimum adsorption of nickel. The maximum adsorption capacity at 25 °C is 18.25 mg/g. The effect of temperature has been carried out at 15, 25, 30, and 40 °C. The data obtained from adsorption isotherms of nickel at different temperatures fit to linear form of Freundlich adsorption equation followed by Langmuir equations. Adsorption kinetic data were modelled using the pseudo-first and pseudo-second-order equation models. The results indicated that the pseudo-second-order model was best described adsorption kinetic data. The thermodynamic parameters such as enthalpy (ΔH°), free energy (ΔG°), and entropy (ΔS°) were calculated. They show that adsorption of nickel onto molecular sieves is an exothermic process. These results show that molecular sieves are a good adsorbent for the removal of nickel from aqueous solutions and could be used as a purifier for water and wastewater.