Binary adsorption of nickel and zinc from aqueous solutions onto the Serbian natural clinoptilolite

Abstract

Sorption of the Zn²⁺ and Ni²⁺ ions by the Na⁺-enriched natural clinoptilolite (Na-CLI) from aqueous solutions containing both Zn²⁺ and Ni²⁺ ions at a range of concentrations has been studied at 298, 308, and 318 K. It was found that the sorption of a particular ion by Na-CLI increases with the increase in the initial concentration of the solution of that ion. At a given initial concentration, the sorption degree increases with temperature. Also, the sorption of a particular ion is greater when the initial solution contains a second ion than it is when the particular ion is present alone. The sorption kinetics is in accord with the pseudo-second-order reaction rate model. The values of the k₂ rate constant do not show a regular change with the initial Zn²⁺/Ni²⁺ concentrations probably because the presence of the second ion has a significant effect on the reaction rate. Thermodynamic study has shown that the sorption is exothermic, occurring spontaneously in the 298–318 K range and with a positive entropy change.

Keywords:

• Adsorption
• Clinoptilolite
• Binary
• Heavy metal
• Kinetics
• Zeolite

Acknowledgements

This work was supported by the Serbian Ministry of Science (project no 172018). The authors also thank the Nemetali Company from Vranjska Banja (Serbia) for kindly providing the zeolite samples.