Adsorption of saturated fatty acids (C-10, C-12, C-14, C-16 and C-18) was carried out on montmorillonite. The adsorption of fatty acids on a clay mineral (montmorillonite) was investigated at 25 +/- 0.5 degrees C using different weights of the clay (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8 g). The experiments proved that fatty acids are physisorbed on the montmorillonite surface. Monolayer coverage was determined to be 46.20, 44.68, 43.17, 41.45, 40.13 mg/g, respectively. The free energy of adsorption was determined to be -6.5938, -6.6693, -6.7448, -6.8204, -6.8959 kcal mol(-1) for the adsorbates, respectively. The equilibrium parameter indicated that montmorillonite is a good adsorbent for capric, lauric, myristic, palmitic and stearic acids examined. (c) 2005 Elsevier Inc. All rights reserved.