Removal of UO₂²⁺ onto synthetic NaA zeolite. Characterization, equilibrium and kinetic studies

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2011-08, Vol.172 (1), p.296-305
• Main Authors: Nibou, D, Khemaissia, S, Amokrane, S, Barkat, M, Chegrouche, S, Mellah, A
• Format: Article
• Language: English
• Subjects: Adsorption; Applied sciences; aqueous solutions; Chemical engineering; crystallization; Crystallization, leaching, miscellaneous separations; effluents; Exact sciences and technology; ions; sorption isotherms; temperature; uranium; zeolites
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2011.05.113

The removal of UO₂ ²⁺ ions from aqueous solutions on zeolite NaA was investigated. The effects of initial uranium (VI) concentration, solution pH, solid/liquid ratio and temperature were studied in batch experiments. Zeolite NaA was synthesized according to a hydrothermal crystallization process. The Dubinin–Radushkevich, the Freundlich and the Langmuir models have been applied and the adsorption equilibrium has been found to follow the Langmuir model. Kinetic studies showed that the pseudo first-order sorption model was the most prevalent for the adsorption of UO₂ ²⁺ ions. The rate constant of the exchanged ions appears to be controlled by chemical sorption process. Rate limiting investigations suggested that the UO₂ ²⁺ ions diffusion was the determining step. The thermodynamic parameters were also determined and the negative values of adsorption entropies indicated that no significant change occurred in the framework of the NaA zeolite during the sorption of UO₂ ²⁺. The obtained optimal parameters were applied to real effluents containing UO₂ ²⁺ ions.