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Influence of Rehydration and Activation on Cation Exchange Capacity and Swelling Index of Foundry Sodium Bentonite from Different Deposits.

Published online by Cambridge University Press:  27 April 2020

Farai Chrispen Banganayi  and
Didier Kasongo Nyembwe
Farai Chrispen Banganayi*
Affiliation:
Metal Casting Technology Station, University of Johannesburg, 37 Nind street Doornfontein Johannesburg, South Africa (e-mail: fcbanganayi@ uj.ac.za).
Didier Kasongo Nyembwe
Affiliation:
Department of Metallurgy, University of Johannesburg, 37 Nind street Doornfontein, Johannesburg, South Africa.Doornfontein, Johannesburg, South (e-mail: [email protected])
*
*(Email: [email protected])
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Abstract

Bentonite is the most widely used foundry binder. Most of the iron castings are made in greensand systems which make use of bentonite as a binder. The bentonite used in greensand moulding is usually activated with sodium carbonate to achieve desirable properties. Activation of bentonite is known to improve mould related properties like giving a high wet tensile strength and improving the durability. The practice of activation is more common with calcium bentonite. A number of bentonite deposits tend to remain unbeneficiated due to their low cation exchange capacity (CEC) which are regarded as low quality commercial grade. The primary characteristic that shows the increased activation is the swelling index of the bentonite. This study investigated the influence of rehydration and activation in improving the quality of low commercial grade sodium bentonite. The bentonite samples were activated with sodium carbonate. Rehydration and activation was seen to improve the CEC and swelling index. The increase in CEC and swelling index was however not consistent with the gains in sodium.

Keywords

activation analysischemical substitution
Type
Articles
Information
MRS Advances , Volume 5 , Issue 26: African Materials Research Society 2019 , 2020 , pp. 1397 - 1404
Copyright
Copyright © Materials Research Society 2020

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