Evaluation of the Thermodynamic Parameters for the Adsorption of Cadmium Ion from Aqueous Solutions

Hamzeh Al-Omari*
Department of Chemistry, Mu’tah University, 61710, P.O. Box (7), Al-Karak, Jordan
E-mail: hamzehsmo@yahoo.com

Abstract
Adsorption behavior of Cd(II) onto Tripoli was studied at 0, 20, 30 and 40 °C at pH in the range of 5–6. Thermodynamic equilibrium constant values at infinite dilution, Ko, were obtained from the intercept of lnK against ionic strength (I) plots by extrapolation of the line obtained to zero ionic strength. The thermodynamic parameters ∆H^o and ∆S^o of adsorption were calculated from the intercept and the slope of the plot of lnK^o against 1/T, respectively. These values were used to calculate the values of the free energy (∆G^o) at different temperatures. The adsorption isotherm was found to fit Freundlich model. The adsorption capacity was found to increase with the decrease in temperature. Flam atomic absorption spectrophotometry was used to measure the equilibrium concentrations of cadmium ion.

Keywords: Thermodynamics, adsorption, cadmium, tripoli, Freundlich isotherm.