Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/72985
Type: Artigo de periódico
Title: USE OF NATURAL AND MODIFIED MAGADIITE AS ADSORBENTS TO REMOVE Th(IV), U(VI), AND Eu(III) FROM AQUEOUS MEDIA - THERMODYNAMIC AND EQUILIBRIUM STUDY
Author: Guerra, DL
Ferrreira, JN
Pereira, MJ
Viana, RR
Airoldi, C
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-29 and C-13 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 m(2) 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 he 7.5 x 10(-3), 9.8 x 10(-3), and 12.9 x 10(-3) 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.
Subject: Calorimetry
Chemical Synthesis
Interfaces
Magadiite
Surface Properties
Thermodynamic Properties
Country: EUA
Editor: Clay Minerals Soc
Rights: embargo
Identifier DOI: 10.1346/CCMN.2010.0580304
Date Issue: 2010
Appears in Collections:Artigos e Materiais de Revistas Científicas - Unicamp

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