Thermodynamic parameters and sorption of U(VI) on ACSD

Abstract

This paper discusses the sorption properties for U(VI) by alginate coated CaSO 4 ·2H 2 O sepiolite and calcined diatomite earth (Kieselguhr) (ACSD). The removal of U(VI) from aqueous solution by sorption onto ACSF in a single component system with various contact times, pH, temperatures, and initial concentrations of U(VI) was investigated. The sorption patterns of uranium on the composite adsorbent followed the Langmuir, Freundlich and Dubinin-Radushkhevic (D-R) isotherms. The Freundlich, Langmuir, and D-R models have been applied and the data correlated well with Freundlich model and that the sorption was physical in nature (sorption energy, E a = 17.05 kJ/mol). The thermodynamic parameters such as variation of enthalpy ?H, variation of entropy ?S and variation of Gibbs free energy ?G were calculated from the slope and intercept of lnK 0 vs. 1/T plots. Thermodynamic parameters (?H ads = 31.83 kJ/mol, ?S ads = 167 J/mol·K, ?G o ads (293.15 K) = -17.94 kJ/mol) showed the endothermic heat of sorption and the feasibility of the process. The thermodynamics of U(VI) ion/ACSD system indicates the spontaneous and endothermic nature of the process. It was noted that an increase in temperature resulted in a higher uranium loading per unit weight of the adsorbent. © 2008 Springer Science+Business Media, LLC.