Study of lithium ion exchange by two synthetic zeolites: Kinetics and equilibrium
| Autor: | R. Navarrete-Casas, Antonio Navarrete-Guijosa, C. Valenzuela-Calahorro, A. Garcia-Rodriguez, J.D. López-González |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Aqueous solution
Ion exchange Inorganic chemistry chemistry.chemical_element Cations Monovalent Lithium Molecular sieve Surfaces Coatings and Films Electronic Optical and Magnetic Materials Ion Exchange Biomaterials Kinetics chemistry.chemical_compound Colloid and Surface Chemistry Adsorption chemistry Delayed-Action Preparations Zeolites Sodalite Physical chemistry Qualitative inorganic analysis Zeolite |
| Zdroj: | Journal of Colloid and Interface Science. 306:345-353 |
| ISSN: | 0021-9797 |
| DOI: | 10.1016/j.jcis.2006.10.002 |
| Popis: | We examined the exchange of univalent cations (Na+ and H+) retained on two commercially available synthetic zeolites with Li+ ions present in aqueous solutions in contact with the solids with a view to preparing effective controlled-release pharmaceutical forms. The studied zeolites were manufactured by Merck and featured channel diameters of 0.5 (Zeolite 5A, Ref. 1.05705.250, designated Z-05 in this work) and 1.0 nm (Zeolite 13X, Ref. 1.05703.250, designated Z-10 here). The XRD technique revealed that Z-05 possesses an LTA structure derived from that of sodalite and Z-10 a faujasite-type structure. Their exchange capacities were found to be 2.72 and 3.54 meq/g. The Z-Na + Li(+) / Z-Li + Na(+) and Z-H + Li(+) / Z-Li + H(+) ion-exchange processes were found to be reversible and their kinetic laws to obey the equation (-dC/dt) = k(a) x C(n) x (1-theta) - (k(d) x theta), with n = 1 for Z-10 and n = 2 for Z-05. Based on the equilibrium results, the overall processes involve one (with Z-05) or two single ion-exchange processes (with Z-10). In both cases, the equations that govern equilibrium are direct results of the kinetic laws. Thus, the first process-the one with only Z-05-involves the retention of Li+ cations at anionic sites on the outer surface of the solid and their access to the larger pores; the second process-which occurs with Z-10 only-involves the retention of lithium(I) cations within the zeolite channels. In both systems, the exchange with Li+ (from the aqueous solution) is easier than that with H+; this is consistent with our kinetic, equilibrium, and thermodynamic results. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect