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Redox properties of MX-80 and Montigel bentonite-water systems

Published online by Cambridge University Press:  11 February 2011

Cecilia Lazo ,
Ola Karnland ,
Eva-Lena Tullborg  and
Ignasi Puigdomenech
Cecilia Lazo
Affiliation:
Dept. Inorg. Chem., Royal Institute of Technology, Stockholm, Sweden.
Ola Karnland
Affiliation:
Clay Technology AB, IDEON Research Center, Lund, Sweden.
Eva-Lena Tullborg
Affiliation:
Terralogica AB, Gråbo, Sweden.
Ignasi Puigdomenech
Affiliation:
Swedish Nuclear Fuel and Waste Management Co. (SKB), Stockholm, Sweden.
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Abstract

The uptake of dissolved oxygen (O2) has been studied in bentonite suspensions in 0.1 M NaCl media at (25±2)°C. MX-80 and Montigel bentonites were used in concentrations varying from 18 to 73 g/L. The experiments were performed in a magnetically stirred closed glass vessel, in an N2-glove box. Redox potentials where measured with Pt-wires, and dissolved O2 was measured both with a membrane electrode and with an optode. The experiments with MX-80 show that dissolved O2 disappears in ∼5 days under these conditions. Redox potentials decreased from ∼ +500 to ∼ +125 mVSHE (versus Standard Hydrogen Electrode). The data for the Montigel bentonite show similar time scales for O2 uptake but lower redox potentials at the end of the experiments ∼ −175 mVSHE. Pyrite oxidation is perhaps not the main process for O2 uptake, as MX-80 contains 0.3% FeS2 while Montigel bentonite only has a negligible amount.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 757: Symposium II – Scientific Basis for Nuclear Waste Management XXVI , 2002 , II8.1
Copyright
Copyright © Materials Research Society 2003

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References

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