Investigation of cation environment and framework changes in silicotitanate exchange materials using solid-state 23Na, 29Si, and 133Cs MAS NMR

Brian Cherry, May Nyman, Todd M. Alam

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

Crystalline silicotitanate (CST), HNa3Ti4Si 2O14·4H2O and the Nb-substituted CST (Nb-CST), HNa2Ti3NbSi2O14· 4H2O, are highly selective Cs+ sorbents, which makes them attractive materials for the selective removal of radioactive species from nuclear waste solutions. The structural basis for the improved Cs+ selectivity in the niobium analogs was investigated through a series of solid-state magic angle spinning (MAS) NMR experiments. Changes in the local environment of the Na+ and Cs+ cations in both CST and Nb-CST materials as a function of weight percent cesium exchange were investigated using 23Na and 133Cs MAS NMR. Framework changes induced by Cs+ loading and hydration state were investigated with 29Si MAS NMR. Multiple Cs+ environments were observed in the CST and Nb-CST material. The relative population of these different Cs+ environments varies with the extent of Cs+ loading. Marked changes in the framework Si environment were noted with the initial incorporation of Cs+, however with increased Cs+ loading the impact to the Si environment becomes less pronounced. The Cs+ environment and Si framework structure were influenced by the Nb-substitution and were greatly affected by the amount of water present in the materials. The increased Cs+ selectivity of the Nb-CST materials arises from both the chemistry and geometry of the tunnels and pores.

Original languageEnglish (US)
Pages (from-to)2079-2093
Number of pages15
JournalJournal of Solid State Chemistry
Volume177
Issue number6
DOIs
StatePublished - Jun 1 2004
Externally publishedYes

Fingerprint

Magic angle spinning
metal spinning
Cations
Ion exchange
Positive ions
Nuclear magnetic resonance
solid state
cations
nuclear magnetic resonance
Crystalline materials
Niobium
Radioactive Waste
selectivity
Cesium
Sorbents
Radioactive wastes
sorbents
Hydration
radioactive wastes
Tunnels

Keywords

  • Cesium
  • Ion exchange
  • Selectivity
  • Silicotitanate
  • Solid-state NMR

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry
  • Materials Chemistry

Cite this

Investigation of cation environment and framework changes in silicotitanate exchange materials using solid-state 23Na, 29Si, and 133Cs MAS NMR. / Cherry, Brian; Nyman, May; Alam, Todd M.

In: Journal of Solid State Chemistry, Vol. 177, No. 6, 01.06.2004, p. 2079-2093.

Research output: Contribution to journalArticle

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AB - Crystalline silicotitanate (CST), HNa3Ti4Si 2O14·4H2O and the Nb-substituted CST (Nb-CST), HNa2Ti3NbSi2O14· 4H2O, are highly selective Cs+ sorbents, which makes them attractive materials for the selective removal of radioactive species from nuclear waste solutions. The structural basis for the improved Cs+ selectivity in the niobium analogs was investigated through a series of solid-state magic angle spinning (MAS) NMR experiments. Changes in the local environment of the Na+ and Cs+ cations in both CST and Nb-CST materials as a function of weight percent cesium exchange were investigated using 23Na and 133Cs MAS NMR. Framework changes induced by Cs+ loading and hydration state were investigated with 29Si MAS NMR. Multiple Cs+ environments were observed in the CST and Nb-CST material. The relative population of these different Cs+ environments varies with the extent of Cs+ loading. Marked changes in the framework Si environment were noted with the initial incorporation of Cs+, however with increased Cs+ loading the impact to the Si environment becomes less pronounced. The Cs+ environment and Si framework structure were influenced by the Nb-substitution and were greatly affected by the amount of water present in the materials. The increased Cs+ selectivity of the Nb-CST materials arises from both the chemistry and geometry of the tunnels and pores.

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