Adsorption isotherms, kinetics, thermodynamics and desorption studies for uranium and thorium ions from aqueous solution by novel microporous composite P(HEMA-EP)

Abstract

In this research, a novel composite, poly(2-hydroxyethylmethacrylate-expanded perlite) [P(HEMA-EP)], was synthesized and its adsorptive features were investigated. P(HEMA-EP)'s adsorptive features were evaluated for UO22+ and Th4+ ions in terms of the dependency upon the ion concentration, pH, temperature, and time. P(HEMA-EP) was able to bind UO22+ and Th4+ ions with strong chemical affinity. The adsorption results were fitted to the classical Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) sorption models. P(HEMA-EP) was also used to study the removal of UO22+ and Th4+ ions from aqueous solutions in a batch system. The adsorption capacity (X-L) of UO22+ and Th4+ ions was found to be 0.29 and 0.44 mol kg(-1), respectively. The kinetic data corresponds well to the pseudo-second-order equation. Changes in the enthalpy and entropy values demonstrated that the overall adsorption process was spontaneous (Delta G < 0), endothermic (Delta H > 0), and had increased entropy (Delta S > 0), as expected. The reusability of the composites was confirmed for five sequential reuses. (C) 2012 Elsevier B.V. All rights reserved.