Issue 6, 2004

Alkaline earth cation exchange with novel Na-3-mica: kinetics and thermodynamic selectivities

Abstract

The cation-exchange kinetics and thermodynamic equilibria for alkaline-earth metals by Na-3-mica [chemical composition of Na2.94(Mg5.55Ti0.07Fe0.04)oct(Al2.07Si5.83)tetO20F4·1.72H2O] with a high layer charge were investigated at room temperature. The Ba, Sr, Ca and Mg uptake kinetics were determined and first-order, modified Freundlich, parabolic diffusion and Elovich kinetic models were examined for the experimental data. The first-order model gave a relatively good fit throughout for these cations and indicated a kinetic selectivity order of Ca2+ < Mg2+ < Sr2+ < Ba2+. The cation exchange isotherms for Ba, Sr, Ca and Mg uptakes with the Na-3-mica were also determined. The Kielland plots evaluated from the cation exchange isotherms showed a thermodynamic selectivity order of Ba2+ ≫ Sr2+ ≫ Ca2+ > Mg2+. The above basic studies on the selective cation exchange of the highly charged ion exchanger are of relevance in the separation, immobilization and disposal of 90Sr from aqueous nuclear wastes.

Graphical abstract: Alkaline earth cation exchange with novel Na-3-mica: kinetics and thermodynamic selectivities

Article information

Article type
Paper
Submitted
04 Nov 2003
Accepted
08 Jan 2004
First published
17 Feb 2004

J. Mater. Chem., 2004,14, 1031-1035

Alkaline earth cation exchange with novel Na-3-mica: kinetics and thermodynamic selectivities

K. Shimizu, K. Hasegawa, Y. Nakamuro, T. Kodama and S. Komarneni, J. Mater. Chem., 2004, 14, 1031 DOI: 10.1039/B314013J

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