The modeling study on simultaneous adsorption of three binary systems (nitrobenzene-aniline (NI-AN), nitrobenzene-phenol (NI-PH) and phenol-aniline (PH-AN)) onto granular activated carbon (GAC) in aqueous solution were performed at 30 degrees C by conducting batch experiments. The single solute equilibrium adsorption data of nitrobenzene (NI), aniline (AN) and phenol (PH) were fitted with Langmuir, Freundlich and Redlich-Peterson model. The Redlich-Peterson and Freundlich model gave better fitting as compared to Langmuir model for individual adsorption. The binary adsorption data were examined and compared by using ideal adsorbed solution theory (IAST) and real adsorbed solution theory (RAST) models. IAST model didn't provide an acceptable prediction of binary data except for low liquid concentration levels, as it undervalued AN and PH adsorption capacity and overvalued NI adsorption capacity. This is due to the non-ideality of binary mixtures at high concentration levels in the solution. The RAST model gave an excellent prediction of binary adsorption experimental data, thus it can be used as a reliable model for the design of industrial adsorption equipment. (C) 2013 Elsevier B.V. All rights reserved.