Effects of exchangeable cation composition on the thermal expansion/contraction of clinoptilolite

Journal Article · Mon Dec 31 04:00:00 EST 1984 · Clays and Clay Minerals

DOI:https://doi.org/10.1346/CCMN.1984.0320602· OSTI ID:60604

Bish, D L

To understand and predict the effects of a thermal pulse induced by a radioactive waste repository on clinoptilolite-bearing rocks, the lattice parameters of 6 natural and 3 cation-exchanged (Ca, K, Na) clinoptilolites were studied as a function of temperature. The samples were examined at room temperature, under vacuum, and at 50{sup 0}C increments to 300{sup 0}C using a high-temperature x-ray powder diffractometer. The unit cell of all samples decreased in volume between 20 and 300{sup 0}C; Na-saturated clinoptilolite underwent the greatest volume decrease (8.4%) and K-saturated clinoptilolite the smallest (1.6%), of the clinoptilolites studied. The volume decrease for the Ca-saturated clinoptilolite was 3.6%. The highest percentage decrease for each sample was along the b axis, generally 80 to 90% of the total volume decrease. The change in the a axis was the smallest and was usually <5%, although 26.5% of the contraction of the Na-exchanged clinoptilolite was along a. The bulk of the volume contraction of many samples occurred on evacuation at room temperature, demonstrating that the observed changes were due to water loss and not to temperature-induced structural changes. Low-angle scattering was significantly reduced upon evacuation for every sample, and the 110 reflection of clinoptilolite at 7.35{sup 0}2 {theta} became obvious, whereas it was not in the untreated samples. These data show that the effects of heating on the unit-cell volume of clinoptilolite depend strongly on the exchangeable cation content. Significant reductions in the unit-cell volumes of natural, mixed Na-K-Ca clinoptilolites could take place in rocks in a repository environment, particularly if the clinoptilolites occurred in unsaturated, dehydrated rock. The unit-cell volumes of clinoptilolites in partially saturated rocks at temperatures below 100{sup 0}C, however, should not decrease significantly.

• Research Organization: Los Alamos National Lab., New Mexico
• Sponsoring Organization: USDOE
• OSTI ID: 60604
• Journal Information: Clays and Clay Minerals, Journal Name: Clays and Clay Minerals Journal Issue: 6 Vol. 32; ISSN 0009-8604; ISSN CLCMAB
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
36 MATERIALS SCIENCE
CALCIUM COMPOUNDS
CHEMICAL COMPOSITION
CLINOPTILOLITE
CONTRACTION
DEHYDRATION
EXPERIMENTAL DATA
LATTICE PARAMETERS
POTASSIUM COMPOUNDS
SODIUM COMPOUNDS
TEMPERATURE DEPENDENCE
THERMAL EXPANSION
Yucca Mountain Project
ZEOLITES