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Acid character of nontronite: permanent and pH-dependent charge components of cation exchange capacity

Published online by Cambridge University Press:  09 July 2018

B. S. Kapoor*
Affiliation:
Institute of Soil Science, Agricultural University of Norway

Abstract

The cation exchange capacity (C.E.C.) of nontronite was determined by titrating the acid clay, prepared by the action of H-resin on nontronite, in water and some nonaqueous solvents. The base-titratable acidities of the acid nontronite, freshly prepared as well as aged, were found to be greater than the acidities extractable with 1 N NaCl; the difference was attributed to the non-exchangeable pH-dependent component of C.E.C. In the freshly prepared sample, H+ and Fe3+ ions were the only exchangeable cations. Ageing produced basic Fe ions which were exchangeable and whose amount increased at the cost of H and Fe3+ ions. Whatever the age, the total quantity of these exchangeable cations corresponding to the total isomorphous charge, remained constant. The amount of the pH-dependent acidity also remained unchanged. A likely mechanism to account for the observed pH-dependent component of the C.E.C, of nontronite is suggested.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1972

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