Removal of 209Po from aquatic environment and its equilibrium and thermodynamic parameters

In this study, removal of Po-209 from aqueous media using a natural zeolite as an adsorbent material was investigated. The adsorption experiments were performed by batch technique. The influence of specific process parameters such as initial concentration, pH of solution, contact time and temperature was studied to predict the optimum conditions for effective removing of Po-210. Initial and equilibrium activity concentration of Po-209 in solutions was counted by a ZnS(Ag) alpha scintillation counter. Adsorption yield of Po-209 onto the zeolite was determined as 90 +/- 2% at pH: <3 and 25 degrees C for 40 min of contact time. The applications of the isotherm models such as Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms were studied to evaluate adsorption characteristics of Po-209 onto natural zeolite. Results indicated that the Dubinin-Radushkevich and Freundlich models gave a better fit to the experimental data than Langmuir isotherm models. The thermodynamic parameters such as Gibbs free energy COG-1, enthalpy (Delta H degrees) and entropy (Delta S degrees) of adsorption process were calculated. The change in entropy (Delta S degrees) and enthalpy (Delta H degrees) were estimated to be -0.0003 J nmol(-1) K-1 and 0.1008 kJ nmol(-1), respectively.