Adsorption capacity of clinoptilolite for Zn2+ ions in acidic solution

Abstract

The adsorption capacity of clinoptilolite for Zn²⁺ ions in acidic solutions has been examined. Adsorption experiments were carried out at 25 °C in a thermostatic absorber by stirring 1 g of clinoptilolite in 100 ml of Zn(NO₃)₂ solution for 120 min. The initial concentration of Zn²⁺ ions was equal to 0.3 and 1.4 Zn²⁺g/dm³. In the acidic solution the intrusion of Zn²⁺ ions into the clinoptilolite structure was found to proceed by two types of chemical reaction: substitution and addition. During adsorption, ion exchange occurs between divalent ions and single-charged ions, because Zn²⁺ ions replace 68 % of Ca²⁺, ~13 % of Na⁺, and 0.5 % of K⁺ ions as the remaining part of these ions are combined by clinoptilolite according to the addition reaction. It has been proven that, independently of the solution pH value, the cation exchange reactions are irreversible. The X-ray diffraction and simultaneous thermal analysis results have confirmed that the crystal structure of clinoptilolite remains stable after the adsorption process.

DOI: http://dx.doi.org/10.5755/j01.ct.63.1.4517