Kinetics of the uptake of cadmium, lead, copper, nickel and zinc ions from single ion solutions and from their mixture by zeolitic rock has been studied. Removal of ions obeyed the kinetic equation for adsorption. Corresponding adsorption constants and distribution coefficients were determined for each metal ion uptake from single ion solution or mixture. An attempt was made to explain zeolite selectivity to different metal ions and the influence of water hardness on the uptake in terms of metal ionic radii and enthalpy of hydration. It was found that lead ions were strongly immobilized by the zeolite investigated, both from single ion and mixed solutions, as well as from soft and hard water.

Influence of zeolite-clinoptilolite transformation in a homoionic (Na) form on zeolite ability to immobilize Pb2+, Cd2+, Cu2+, Zn2+ and Ni2+ from single ion and multi-component solutions has been studied. Zeolite in Na form exhibits significantly increased ability to remove Cd2+, Cu2+, and Zn2+ from their single ion and multi-component solutions when the water hardness due to Ca2+ presence is not high. Zeolite pretreatment with NaCl leads to increased rate of heavy metal ions' immobilization, as well as to increased distribution coefficients that are indicative for more complete exchange process. Heavy metal ions are more strongly bound to zeolite pretreated with NaCl, compared to natural zeolite. Heavy metal ions immobilization is due to ion exchange adsorption, both in the case of natural and converted in Na form zeolite. Zeolite pretreatment with NaCl practically does not change zeolite selectivity sequence for the ions investigated.

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