Ammonium ion removal from aqueous solution by Petra clay minerals has been established. To study the efficiency of the Petra clay as sorbent, the effect of relevant parameters, such as temperature, contact time, pH and initial ammonium (NH4+) concentration were examined. Kinetics experiments were also done at different parameters. The pseudo first-order. pseudo second-order kinetic models and intra-particle diffusion model were used to describe the kinetic data. The pseudo second-order kinetic model provided excellent data fitting (R-2 > 0.99), and the rate constant for sorption was predicted. Activation energy of sorption has also evaluated as 22.60 kJ/mol based on the pseudo second-order rate constants, the findings of this investigation suggest that physical sorption plays a role in controlling the sorption rate. Ammonium uptake rate was controlled by particle diffusion at different variables. (c) 2009 Elsevier B.V. All rights reserved.