The structural environments of cations adsorbed onto clays: A sup 133 CsMAS NMR spectroscopic study

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:7039093

Weiss, Jr, C A

Chapter One investigates the local structural environment of adsorbed cations on the mineral hectorite using {sup 133}Ca Variable-Temperature Magic-Angle-Spinning Nuclear Magnetic Resonance (VT-MAS NMR) spectroscopy. The results show that Cs on hectorite occurs in several distinctly different chemical environments, and that motional averaging of Ca between some of these sites occurs above {approximately}{minus}40{degree}C if water is present in the interlayer. Above {approximately}{minus}10{degree}C, spectra for slurries of hectorite in CsCl solutions yield two peaks, one due to Cs in solution, and the other due to Cs motionally-averaged on the clay. Below {approximately}{minus}60{degree}C, motional averaging of the adsorbed Cs slows sufficiently to allow resolution of two peaks representing different Cs-environments on the clay. The Stern-Gouy model is employed to explain these peaks and assign one to Cs in the Stern layer (relatively tightly bound to the basal oxygens), and the other to Cs in the Gouy diffuse layer. Between {approximately}{minus}60 and {approximately}{minus}10{degree}C peaks for these two sites and a motionally-averaged peak are present. Cs-exchanged hectorite dehydrated at 500{degree}C yields peaks for two different sites on the clay, interpreted to be highly coordinated site (probably 12), and a less coordinated site (possibly 9), both in the interlayer. Chapter II discusses {sup 133}Cs MAS NMR results for a number of other Cs-exchanged clays and the relationship of chemical and structural parameters to the {sup 133}Cs chemical shift. Increased rotational distortions of the basal oxygen sheet, total layer charge and tetrahedral Al{sup 3+} for Si{sup 4+} substitution correlate with increased deshielding of the {sup 133}Cs chemical shifts for both hydrated slurry and anhydrous samples. Correlations for the slurries are poorer because of the distances between the clay silicate and the CO in solution.

• Research Organization: Illinois Univ., Urbana, IL (United States)
• OSTI ID: 7039093
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102* -- Chemical & Spectral Procedures
400201 -- Chemical & Physicochemical Properties
ADSORPTION
ALKALI METAL ISOTOPES
CATIONS
CESIUM 133
CESIUM ISOTOPES
CHARGED PARTICLES
CHEMICAL SHIFT
CLAYS
DATA
EXPERIMENTAL DATA
INFORMATION
INTERMEDIATE MASS NUCLEI
IONS
ISOTOPES
MAGNETIC RESONANCE
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
RESONANCE
SORPTION
STABLE ISOTOPES