Influence of Alginate Encapsulation on Point of Zero Charge (pHpzc) and Thermodynamic Properties of the Natural and Fe(III) - Modified Zeolite

In this paper influence of alginate encapsulation on point of zero charge (pH pzc ) and thermodynamic properties of the natural and Fe(III)- modified zeolite were investigated. The pH pzc was determined by using 0.1000 g of the samples and 50 cm 3 of the solution containing KNO 3 in concentrations of 0.0001–0.01 mol/dm 3 for initial pH (pH i ) in range between 2 and 12. The obtained pH pzc were 6.2 for natural (NZA) and 6.5 for modified zeolite encapsulated with alginate (FeA). Influence of the temperature on the adsorption of lead was investigated for different initial lead ions concentrations (180–3200 mgPb 2+ /dm 3 ) and temperatures of 30, 40 and 60 o C. For both adsorbents, adsorption of lead ions increased with increasing its initial concentration as well as with increasing of the temperature. Also, the best fits of the experimental data were obtained by Freundlich isotherm. The temperature had positive influence adsorption and removal of lead ions increased with increasing its initial concentration as well as with increasing of the temperature. The thermodynamic parameters (the standard free energy of adsorption, standard enthalpy and standard entropy ) were also determined. The results showed that lead ions removal from aqueous solutions is much favourable for FeA then NZA.