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Selective Cation Exchange in Substituted Tobermorites
Author(s) -
Komarneni Sridhar,
Tsuji Masamichi
Publication year - 1989
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1989.tb06301.x
Subject(s) - tobermorite , selectivity , chemistry , ion exchange , magic angle spinning , inorganic chemistry , steric effects , crystallography , ionic radius , ion , nuclear magnetic resonance spectroscopy , stereochemistry , materials science , organic chemistry , cement , metallurgy , catalysis
Selective cation exchange in tobermorites with three levels of Al 3+ and Na + substitution for Si 4+ has been investigated. The cation exchange selectivity for a tobermorite with 2 mol% Al 3+ and 0 mol% Na + substitution increased as follows: Mg 2+ > Ba 2+ > Sr 2+ . Cation exchange in the above tobermorite is postulated to take place mainly from edge and planar surface sites and apparently from interlayer Ca 2+ sites. Tobermorites with 10 and 15 mol% Al 3+ (and Na + ) substitution have additional Na + exchange sites in the interlayers and show the following selectivity: Ba 2+ > Sr 2+ > Mg 2+ . The cation exchange selectivity in the substituted tobermorites can be explained by the hydrated radii of cations and the steric limitations of the ion exchange cavity in tobermorite; the latter was determined by 27 Al and 29 Si magic angle spinning nuclear magnetic resonance spectroscopy. These basic selective cation exchange studies of substituted tobermorites are of relevance in nuclear waste treatment and disposal.