Abstract.1 Adsorption of zinc ions in water on natural and treated clay has been studied. Natural clay before and after activation was characterized using TGА/DTА techniques and chemical analysis.The effects of various parameters, such as an initial concentration, temperature, pH, contact time and adsorbent concentration, has been examined. It was shown that treated clay is a good adsorbent compared to natural clay for removing Zn 2+ ions and can be used instead of expensive adsorbents. The thermodynamic parameters have been calculated which have shown that the adsorption of Zn 2+ on natural and activated clay is endothermic.