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Surface Charge and Electrophoretic Properties of Colloids Obtained From Homoionic and Natural Bentonite

Published online by Cambridge University Press:  10 February 2011

T. Missana ,
M.J. Turrero  and
A. Adell
T. Missana
Affiliation:
CIEMAT -Departamento de Impacto Ambiental de la Energía Avenida Complutense 22, 28040 MADRID (SPAIN)
M.J. Turrero
Affiliation:
CIEMAT -Departamento de Impacto Ambiental de la Energía Avenida Complutense 22, 28040 MADRID (SPAIN)
A. Adell
Affiliation:
CIEMAT -Departamento de Impacto Ambiental de la Energía Avenida Complutense 22, 28040 MADRID (SPAIN)
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Abstract

Suspensions of colloids obtained from a Spanish bentonite were studied by potentiometric acid-base titrations and electrophoresis in order to analyse their surface chemical properties, which are responsible of their stability behaviour and that are very important to consider in radionuclides sorption modelling.

“Fast” titrations and “batch - back” titrations techniques were used to determine the contribution of the pH - dependent charge and the difference in the results obtained are discussed. Experimental data obtained by acid/base titrations were interpreted according the EDL theory. The model prediction agreed satisfactorily with the experimental data in the alkaline pH range. Protonation / deprotonation reactions of surface functional groups (SOH) appeared to be the main surface charge - determining mechanism in the alkaline pH range whereas ion - exchange type reactions, had to be taken into account over the acidic pH range. Surface potentials were calculated for different salt concentrations, from experimental data and taking into account both layer and edge sites charge contributions.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 608: Symposium QQ – Scientific Basis for Nuclear Waste Management XXIII , 1999 , 255
Copyright
Copyright © Materials Research Society 2000

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References

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