This paper concerns the removal of ammonium ions (NH4+) from aqueous solution using a hydrogel composite chitosan grafted poly (acrylic acid)/rectorite prepared from in situ copolyrnerization. The effects of rectorite content, contact time, pH, NH4+ Concentration and temperature on the adsorption capacity were discussed. Langmuir, Freundlich, Tempkin and Redlich-Peterson isotherms were used to describe the experimental data. The results indicate that the adsorption equilibrium can be achieved within 3-5 min and, the hydrogel composite has a higher adsorption capacity for NH4+ in a wide pH levels ranged from 4.0 to 9.0. No significant changes in the adsorption capacity are found over the temperature range studied. The adsorption mechanism of NH4+ onto hydrogel composite was proposed, and the reusable ability of this hydrogel adsorbent was evaluated. (C) 2009 Elsevier B.V. All rights reserved.