A study was undertaken to determine the influence of temperature and surfactant concentration on the adsorption of cetyl pyridinium bromide on two ZSM-5 zeolites, and on natural clinoptilolite. The effect of temperature on adsorption and thermodynamic properties was investigated by making measurements at (297, 303, 307, 313) K. The results show that the calculated curves from the general isotherm equation can represent the experimental data very well up to T = 313 K. Based on the calculation of the thermodynamics of adsorption, it is evident that the principle contribution to the DeltaG(hm)degrees of negative value is the large positive value of DeltaS(hm)degrees (36 to 52 J (.) mol(-1)), whereas DeltaH(hm)degrees, is positive and in the range of 1 to 7 kJ (.) mol(-1). Therefore, similar to the micellisation in bulk solution, the second step of surfactant adsorption is an entropy-driven process. (C) 2003 Elsevier Ltd. All rights reserved.