The adsorption of Disperse Orange 25 (3-[N-ethyl-4-(4-nitrophenylazo) phenylaminol propionitrile) onto activated carbon was investigated in a batch system with respect to contact time, carbon dosage, pH and temperature from aqueous solutions. The Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were also determined. The Langmuir isotherm model agrees with the experimental data well. Maximum adsorption capacity (q(max)) of Disperse Orange 25 onto adsorbent was 118.93 mg g(-1) at 20 degrees C. The first-order, pseudo-second-order kinetic models and the intraparticle diffusion model were used to describe the kinetic data and the rate constants were evaluated as well. The experimental data fitted very well to pseudo-second-order kinetic model. The results show that activated carbon prepared from Euphorbia rigida by sulfuric acid chemical activation could be employed as low-cost material to compare with commercial activated carbon for the removal of disperse dyes from effluents. (C) 2008 Elsevier B.V. All rights reserved.