Removal of radioactive elements from aqueous solutions by adsorption onto polyacrylamide-expanded perlite: Equilibrium, kinetic, and thermodynamic study
In this research, a novel composite, poly(aaylamide-expanded perlite) [P(AAm-EP)], was synthesized and its adsorptive features were investigated for UO22+ and Th4+ ions. The composite's adsorptive features were evaluated for UO22+ and Th4+ ions in light of the dependency of the ion concentration, pH, temperature, time, and reusability. The composite could bind UO22+ and Th4+ ions with strong chemical affinity. The correlation coefficients indicate that the Langmuir model fits better for the UO22+ and Th4+ onto P(AAm-EP) composite with adsorption capacities as 0.66 and 0.74 mol kg, respectively. Adsorption equilibrium of UO22+ and Th4+ ions was achieved in about 34 and 32 min, respectively. The kinetic data conformed better to the pseudo-second order equation. The adsorption of UO22+ and Th4+ ions increased with increasing pH and reached a plateau value at around pH 3.0. Thermodynamic parameters,o,H and AS values showed that the sorption process was spontaneous (Delta G<O), endothermic (Delta H>0), and had increased entropy (Delta S> 0). It was also found that the adsorption kinetics followed the pseudo-second-order model and that the rate-controlling step was chemical adsorption. The reusability of the composites was confirmed for 5 sequential reuses. (C) 2012 Elsevier B.V. All rights reserved.