- 225 - Exchange Ion Characteristics of Ammonium by Zeolite-HS Naela Abdullaha Geology department, Faculty of science and technology, National University of Malaysia , 4600 Bangi, Selangor , Malaysia e-mail: myemail@this.address Azimah Hussin Geology department, Faculty of science and technology, National University of Malaysia , 4600 Bangi, Selangor , Malaysia e-mail: abc@tech.edu.com ABSTRACT The purpose of this study was to investigate the adsorption characteristics of ammonium (NH 4 + ) ion from aqueous solution by the synthesis of zeolite; a Hydrothermally Synthetic (HS) from Bidor treated kaolinite by NaOH solution .The lab-scale batch experiments and preliminary experiments were employed. Experiments were carried out using batch method as a function of the solution pH, shaking time and the intital concentration. The data analysis was supported by the linear Langmuir, Freundlich and kinetics (pseudo-first and second– order) equilibrium and Isotherms. Those factors affected the uptake and the removal rate of ammonium ion from the solution due to the increase of the adsorption capacity (mg g -1 ) and the decrease of the removal degree (%) with the increase of those factors. The result showed the grates value of uptake; 7.9 (mg l -1 ). The Freundlich model reflected the best results of adsorption capacity compared with Langmuir and kinetics models. Based on the results of separation factors RL from linear plot Langmuir isotherm and constant Freundlich(n), it can be concluded that the synthesis zeolite–HS product is suitable for the removal of NH 4 + ions in wastewater treatments and to save the environmental quality. KEYWORDS: zeolite-HS, synthesis, isotherm, ammonium. I NTRODUCTI ON Today, the nitrogen (N) pollution in hydrosphere has increasingly attracted the attention for eutrophication of lakes and rivers all over the world. One of nitrogen pollutions contained is Ammonium as inorganic ion form in municipal sewage, industrial wastewater and agricultural wastes. Also the ammonia and ammonium ions are the more commonly encountered N compounds in wastewater. The increasing concentration of ammonium will cause a sharp decrease of dissolved oxygen and obvious toxicity on aquatic organisms (Guo et al. 2007) . Hence, removing ammonium from wastewater is of very importance to control nitrogen pollution to save ground water and environmental quality in intensive agricultural production. Zeolite in both forms; natural and synthesis, is used more as an adsorbent material. Several studies have also reported the use of natural zeolite as a sorbent for heavy metals, N compounds, and cations (He et al. 2002),and (Chlopecka& Adriano 1997) ,because it has a great capacity of exchanging cations. The huge natural zeolite reserves occur in the world most frequently in different parts