ION EXCHANGE IN POROUS CRYSTALS. PART I. SELF- AND EXCHANGE-DIFFUSION OF IONS IN CHABAZITES

Journal Article · Mon Dec 31 23:00:00 EST 1962 · Phys. Chem. Solids

DOI:https://doi.org/10.1016/0022-3697(63)90041-6· OSTI ID:4719448

Barrer, R M; Bartholomew, R F; Rees, L V.C.

Self-diffusion and exchange diffusion kinetics were studied for a number of ions in hydrated chabazites, and the corresponding diffusion coefficients were determined. Values of the self-diffusion coefficients follow the Arrhenius equation STAD/sup */ = D/sub o/ exp (E/RT)!. The energy barriers, E, associated with each unit self-diffusion process are about 7 kcal for all the ions Na/sup +/ , K/sup +/, Rb/sup +/, and Cs/sup +/; for Ca/su p 2+/ and Sr/sup 2+/ the barriers are approximately twice this magnitude, but for Ba/sup 2+/ they are 8.7/sub 5/ kcal. The results are considered in terms of the structure of the crystals and of the possibility that the periodic variation in the intracrystalline electrostatic field determines E. Entropies of activation, and also comparison with other rate processes in chabazite (self-diffusion of water, electrical conductivity, and dielectric relaxation) suggest that ions and water molecules may participate together in each unit diffusion process. In mixed (Ca,Sr)- chabazites the self-diffusion coefficients D/sup */ of Ca/sup 2+/ and of Sr/sup 2+/ each decrease strongly with the exchangeable cation fraction of Ca/sup 2+/ and of Sr/sup 2+/, respectively. Values obtained for exchange diffusion coefficients of Ca-Sr, Ca-Ba, and Sr- Ba pairs are integral values over a range of cation fractions. (auth)

• Research Organization: Imperial Coll. of Science and Tech., London
• NSA Number: NSA-17-020029
• OSTI ID: 4719448
• Journal Information: Phys. Chem. Solids, Journal Name: Phys. Chem. Solids Vol. Vol: 24
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ALUMINUM SILICATES
ARRHENIUS EQUATION
BARIUM
CALCIUM
CALCIUM SILICATES
CESIUM
CHABASITE
CHEMISTRY
CRYSTALS
DIELECTRICS
DIFFUSION
ELECTRIC CONDUCTIVITY
ELECTRIC FIELDS
ELECTROSTATICS
EQUATIONS
ION EXCHANGE
LATTICES
MINERALS
POROSITY
POTASSIUM
QUANTITATIVE ANALYSIS
REACTION KINETICS
RUBIDIUM
SODIUM
STRONTIUM
THERMODYNAMICS
WATER