The cation exchange capacity (CEC) of porous zeolites allows to adsorb in the framework cavities the cations as pollutant heavy metal ions. We investigate the CEC behaviour of different zeolites in different experimental conditions; in solution where the ion's mobility is spontaneous and free and in the electrokinetic system where the ion's mobility is driven by the electric field. The aim of this study is to investigate if the CEC is an useful property to create a special interface region of zeolites, that if placed in the electrokinetic cell, just before the cathode, could allow to capture and concentrate the heavy metallic ions, during their migrating process. The zeolite 13X investigated in the electrokinetic proofs, retains a good high ions adsorption, even if quite smaller than the relevant free solution condition and well acts as confined trap for the heavy metal ions. In fact no trace of metallic deposition are present on the electrode's surface. (c) 2006 Elsevier B.V. All rights reserved.