Use of natural and modified magadiite as adsorbents to remove th(IV), u(VI), and eu(III) from aqueous media - thermodynamic and equilibrium study
Guerra, Denis L. (Universidade Federal de Mato Grosso. UFMT. Centro de Recursos Minerais)
Ferrreira, Josane. (Universidade Federal de Mato Grosso. UFMT. Centro de Recursos Minerais)
Pereira, Mário J. (Universidade Federal de Mato Grosso. UFMT. Centro de Recursos Minerais)
Viana, Rúbia R. (Universidade Federal de Mato Grosso. UFMT. Centro de Recursos Minerais)
Airoldi, Claudio (State University of Campinas. Chemistry Institute)

Date:	2010
Abstract:	The contamination of aquatic environments by toxic metals such as radionuclides is of great concern because of the tendency of those metals to accumulate in the vital organs of humans and animals, causing severe health problems. The objective of this study was to investigate the use of natural and modified magadiite clay as an adsorbent to remove Th(IV), U(VI), and Eu(III) from aqueous solutions. Magadiite from the Amazon region, Brazil, was modified chemically with 5-mercapto-1-methyltetrazole (MTTZ) using a multi-step or heterogeneous synthesis pathway. The natural and modified materials were characterized using Si and C nuclear magnetic resonance, scanning electron microscopy, nitrogen gas adsorption, and elemental analysis. The physical-chemical properties of the chemically modified magadiite sample were modified, e. g. the specific surface area changed from 35. 0 to 678. 9 m2 g-1. The ability of the magadiite to remove Th(IV), U(VI), and Eu(III) from aqueous solution was then tested by a series of adsorption isotherms adjusted to a Sips equation. The effects of properties such as pH, contact time, and metal concentration on the adsorption capacity were studied. The adsorption maxima were determined to be 7. 5610, 9. 8610, and 12. 9610 mmol g-1 for Th(IV), U(VI), and Eu(III), respectively. From calorimetric determinations, the quantitative thermal effects for all these cations/basic center interactions gave exothermic enthalpy, negative Gibbs free energy, and positive entropy, confirming the energetically favorable conditions of such interactions at the solid/liquid interface for all systems.
Rights:	Tots els drets reservats.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Calorimetry ; Chemical Synthesis ; Interfaces ; Magadiite ; Surface Properties ; Thermodynamic Properties
Published in:	Clays and Clay Minerals, Vol. 58, Núm. 3 (2010) , p. 327-339, ISSN 1552-8367

DOI: 10.1346/CCMN.2010.0580304

13 p, 1.1 MB  UAB restricted access

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