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Aqueous coordination and location of exchangeable Cu/sup 2 +/ cations in montmorillonite clay studied by electron spin resonance and electron spin-echo modulation

Journal Article · · J. Am. Chem. Soc.; (United States)
DOI:https://doi.org/10.1021/ja00217a008· OSTI ID:7200391
Electron spin resonance (ESR) and electron spin-echo modulation (ESEM) spectroscopies have been used to characterize the aqueous coordination and location of exchangeable Cu/sup 2 +/ cations in the interlayer regions of montmorillonite clay. Mg/sup 2 +/ montmorillonite, in which 5% of the exchangeable cations were replaced by Cu/sup 2 +/, was investigated. Under complete hydration, ESR indicates freely rotating Cu/sup 2 +/ ions in the interlayer region, and the corresponding ESEM indicates six directly bound water molecules. Under partial dehydration ESR shows Cu/sup 2 +/ in a second site with restricted rotation, and the corresponding ESEM indicates coordination to four water molecules. Following the collapse of the aqueous interlayer region on further dehydration, the Cu/sup 2 +/ enters a third site in a hexagonal cavity of the lattice structure, also with restricted rotation, in which it remains coordinated to only one water molecule. The natures and interconversions of these three sites are discussed.
Research Organization:
Univ. of Houston, TX (USA)
OSTI ID:
7200391
Journal Information:
J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 110:9; ISSN JACSA
Country of Publication:
United States
Language:
English