Experimental adsorption isotherm of two basic dyes: Basic Blue 3 and Basic Red 24 from aqueous solution onto modified nylon 6,6 were analyzed by using a double layer adsorption model with two energy levels. Such model is based on statistical physics treatment. The parameters involved in the analytical expression of this model such as the fraction or the number of adsorbed dye molecule(s) per site, n, the receptor sites density, NM, and the energetic parameters, c1 and c2, were determined by fitting the experimental adsorption isotherms at four temperatures between 293 and 353 K with different degrees of grafting between 20 and 80%. The evolution of these parameters versus temperature and the grafting percent allows us to interpret and better understand this adsorption process at molecular level. Two different behaviors of the two dye molecules were highlighted according to their localized and non localized charges. The configurational entropy at various temperatures has also been studied. This parameter allowed to deduce some results related to the evolution of the disorder at the adsorption surface. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012