The kinetics and thermodynamics behind the sorption process of Cs (Caesium) on the soil are important to understand as these studies give information about the mobility of Cs in the environment. In the present study, sorption kinetics and the parameters influencing sorption (viz. time of contact, competing ions, temperature, solution pH and Cs concentration) were studied on the soil samples collected from Tarapur area. Site-specific distribution coefficient (Kd) of Cs was also estimated in soil samples collected from different locations across Tarapur, India using laboratory batch method. The effect of soil parameters (viz. pH, cation exchange capacity, organic matter and CaCO3) on Kd values of Cs was also investigated. The data of Cs adsorption on the soil is well fitted with the pseudo-second-order kinetic equation with the correlation coefficient (R2) value of 0.99. The rate constant (k2) of Cs adsorption (at 25 ºC) on collected soil samples was found to be 3.33×105 g µg-1 min-1. In the present study, Cs adsorption data were well fitted with Freundlich and Dubinin–Radushkevich (D–R) isotherm models. The change of enthalpy (ΔH), entropy (ΔS) and Gibbs free energy (ΔG) were estimated for the Cs adsorption on soil samples. Results showed that the adsorption process was exothermic (ΔH = -3.69 J mol−1) and favoured at a lower temperature. The calculated ΔG value (< 0) indicates that the Cs sorption on the soil is a spontaneous process. The Kd values were found to the range of 58 ± 2 to 275 ± 10 kg-1. The parametric study indicated CEC to have a stronger influence as compared to pH, OM and CaCO3 in the soil samples.
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