comparison of absorption properties of iranian natural zeolites in removal of eu3+ ions from aqueous solution

Extraction and recovery of lanthanide metals from nuclear and metal-containing industrial waste streams is important both environmentally and economically. otherwise, the consequence of the presence of such waste in the environment generates damaging effects on human societies and the earth’s environment. therefore, there is much interest concerning on the separation of these metal ions [1-2]. zeolites are valuable inorganic crystalline materials, which are porous having wide variety of industrial applications due to their unique properties including molecular sieving, ion-exchange and catalytic behavior. considerable attention has been paid on utilizing zeolitic nano-particles because their advantages over conventional micron sized materials. studies have been shown that the particle size and morphology of the zeolitic materials play an important role in their properties and efficiencies as catalysts, adsorbents for separation scopes [3-4]. there are numerous natural zeolite minerals in iran. in this communication we report the adsorption properties of clinoptilolite (a type of natural zeolites in sabzevar and semnan regions) and ferrocarpholite (a type of natural zeolites in tabriz region) in removal eu3+ ion from aqueous solution. the adsorption efficiencies of the sorbents were found to be ph dependent. the maximum adsorption of eu3+ion was obtained at ph 5 (25.05% for tabriz, 55.18% for semnan and 78.68% for sabzevar). the selectivity of adsorption varies as sabzevar>semnan>tabriz. however, the tabriz zeolite was shown to be an adsorbent with lower adsorption percentage towards eu3+ ion. in order to improve the adsorptive properties of zeolits, modification of the zeolite’s surface by bis(2-hydroxybenzaldehyde)-1,2-diaminoethane ligand has been done. it is noteworthy that with the modification of nano-crystalline zeoliteʼs surface, the uptake of metal ions significantly increase to 88.65%, 85.09% and 97.97% by adsorbents tabriz, semnan and sabzevar, so that in the optimum conditions ph=5, 60 min. by 0.05 g of the adsorbent, eu3+ ions can be quantitatively removed from 20 ml aqueous solutions containing 20 mgl-1 of metal ions in compared to the unmodified zeolites.