In this study adsorption efficiencies of various zeolites were tested for removal of ammonium ions from aqueous solutions. In the experiments performed with different initial ammonium concentrations, highest removal was obtained for Zeolite 13X so forthcoming studies were carried out with this zeolite type. The effects of initial NH4+ ion concentration, zeolite amount, pH and agitation time on adsorption efficiency were investigated with batch experiments. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were applied to experimental data and calculated correlation coefficients were determined as 0.54, 0.93 and 0.89 for the models, respectively. Main energy of adsorption (E), calculated as 0.542 kJ/mol, demonstrated physical characteristics of adsorption process. Optimal conditions determined for aqueous solutions were used also for hen slaughterhouse wastewaters. In kinetic calculations it was obtained that pseudo-second order reaction kinetic model was well-fitted for both synthetic solution and wastewater. (C) 2011 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.