Indexed on: 24 Jan '15Published on: 24 Jan '15Published in: Environmental Science and Pollution Research
Uptake of radioactive metal species from soils and solutions by clay particles could be a treatment option due to simplicity of operation and economic cost. In this concern, adsorption behavior of Cs(+) or Co(2+) onto bentonite as a function of contact time, pH, initial metal concentration, ionic strength, and temperature was studied by batch adsorption technique. Adsorption isotherm data were interpreted by Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. Bentonite exhibited maximum adsorption capacity of 83.3 mg g(-1) for Cs(+) and 15.9 mg g(-1) for Co(2+). Presence of humic acid (HA) as a representative model of organic matter did not significantly affect the adsorption capacity of bentonite for Cs(+), whereas it increased the adsorption capacity of bentonite for Co(2+). Thermodynamic parameters, standard enthalpy (ΔH°), standard entropy (ΔS°), and standard free energy (ΔG°) were determined through batch adsorption experiments performed at four different temperatures of 288, 298, 318, and 338 K. Co(2+) adsorption onto bentonite showed an endothermic reaction (ΔH° = 13.6 kJ mol(-1)) whereas Cs(+) adsorption displayed an exothermic nature (ΔH° = -4.65 kJ mol(-1)). Negative values of ΔG° and positive values of ΔS° indicated the feasibility and spontaneous nature of adsorption processes and more disordered form after adsorption.