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Ion Exchange Behavior of the Febex Bentonite: 2. Batch Experiments and Geochemical Modeling

Published online by Cambridge University Press:  21 March 2011

J. Delgado ,
P. Carretero ,
R. Juncosa ,
J. Samper ,
F.J. Huertas ,
C. Jiménez De Cisneros ,
E. Caballero ,
F. Huertas  and
J. Linares
J. Delgado
Affiliation:
E.T.S. de Ingenieros de Caminos, Canales y Puertos, Universidade da Coruथa, Campus de Elviथa s/n, 15192 A Coruथa, SpainEmail: delgado@iccp.udc.es
P. Carretero
Affiliation:
E.T.S. de Ingenieros de Caminos, Canales y Puertos, Universidade da Coruथa, Campus de Elviथa s/n, 15192 A Coruथa, Spain
R. Juncosa
Affiliation:
E.T.S. de Ingenieros de Caminos, Canales y Puertos, Universidade da Coruथa, Campus de Elviथa s/n, 15192 A Coruथa, Spain
J. Samper
Affiliation:
E.T.S. de Ingenieros de Caminos, Canales y Puertos, Universidade da Coruथa, Campus de Elviथa s/n, 15192 A Coruथa, Spain
F.J. Huertas
Affiliation:
Department of Earth Sciences and Environmental Chemistry, Estación Experimental de El Zaidín, CSIC, Profesor Albareda 1, 18008 Granada, Spain
C. Jiménez De Cisneros
Affiliation:
Department of Earth Sciences and Environmental Chemistry, Estación Experimental de El Zaidín, CSIC, Profesor Albareda 1, 18008 Granada, Spain
E. Caballero
Affiliation:
Department of Earth Sciences and Environmental Chemistry, Estación Experimental de El Zaidín, CSIC, Profesor Albareda 1, 18008 Granada, Spain
F. Huertas
Affiliation:
Department of Earth Sciences and Environmental Chemistry, Estación Experimental de El Zaidín, CSIC, Profesor Albareda 1, 18008 Granada, Spain
J. Linares
Affiliation:
Department of Earth Sciences and Environmental Chemistry, Estación Experimental de El Zaidín, CSIC, Profesor Albareda 1, 18008 Granada, Spain
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Abstract

Ion exchange experiments have been performed with the FEBEX bentonite. Five grams of dry powder of this clay were put inside dialysis bags, which were located inside PFA reactors filled with 125 ml of water of a given chemical composition (Moody, Grimsel, and bentonitic-granitic type waters). The reactors containing the clay powder/water mixture were heated to different temperatures (from room temperature up to 80°C) along a time span ranging from 1 day to 1 year. Water was renewed according to a prescribed schedule but not the clay, which remained in place for the whole extent of each test. After each water renewal, major cations, silica, total inorganic carbon, and pH were analyzed. At the end of each test, the exchange complex and CEC of the bentonite were measured. These experiments have been modeled with a conveniently modified version of the EQ3/6 software package where ion exchange reactions were formulated as half reactions and added to its database. In general, model results are in fairly good agreement with experimental data, especially in the case of dissolved cations. Computed values of exchanged concentrations also match the measurements, although in some cases they deviate from them. The fact that the numerical results reproduce the observed patterns of exchange tests indicates that the adopted geochemical conceptual model is appropriate. Some features of the geochemical evolution of these tests also take place at the “mock-up” and “in situ” FEBEX tests.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 663: Symposium – Scientific Basis for Nuclear Waste management XXIV , 2000 , 597
Copyright
Copyright © Materials Research Society 2001

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References

REFERENCES

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