The objective of this study is to remove the nitrate from aqueous solution by using the original and activated red mud in batch adsorption technique. The effects of pH, adsorbent dosage and contact time on the adsorption were investigated. The nitrate adsorption capacity of activated red mud was found to be higher than that of the original form and decreased above pH 7. Adsorption process was expressed by using Langmuir and Freundlich isotherms. Langmuir isotherm curves was found to be significant compared to Freundlich isotherm. Adsorption capacity of the original and activated red mud was found to be 1.859 and 5.858 mmol nitrate/g red mud, respectively. It was found that sufficient time for adsorption equilibrium of nitrate ions is 60 min. The mechanism for nitrate removal was explained by considering of chemical nature of red mud and interaction between metal oxides surface and nitrate ions. © 2006 Elsevier B.V. All rights reserved.