Adsorption is a major process responsible for accumulation of heavy metals which in turn leads to an increase in health hazards. Understanding absorption process of these heavy metals is crucial for the assessment of their fate and reclamation in polluted soils. In this study, the sorption mechanism of cadmium metal on lateritic soil was evaluated at two temperatures (298K and 323K) using the batch method. The lateritic soil samples used were collected from Ilaro, Ogun State. The Langmuir and Freundlich isotherms were used to describe the adsorption of the metal ion. Results of thermodynamic parameters revealed that the equilibrium constant (Keq) decreased with increase in temperature. The small but positive value for the free energy (∆G) indicated that the absorption of cadmium ion on the soil was spontaneous. The enthalpy of the reaction (∆H) was negative implying that the aborption of this metal ion is exothermic. The positive value (63.23Jmol -1 ) of the entropy of reaction, ∆S is an indication of disorder in the cadmium sorption process in the soil which leads to an increase in the degree of randomness at the surface of the soil which in turn results to an increase in the adsorption capacity of the ion in the soil. Keywords: Cadmium, Sorption, Freundlich, Langmuir, isotherms and thermodynamic
