Thermodynamic modeling of natural zeolite stability
Zeolites occur in a variety of geologic environments and are used in numerous agricultural, commercial, and environmental applications. It is desirable to understand their stability both to predict future stability and to evaluate the geochemical conditions resulting in their formation. The use of estimated thermodynamic data for measured zeolite compositions allows thermodynamic modeling of stability relationships among zeolites in different geologic environments (diagenetic, saline and alkaline lakes, acid rock hydrothermal, basic rock, deep sea sediments). This modeling shows that the relative cation abundances in both the aqueous and solid phases, the aqueous silica activity, and temperature are important factors in determining the stable zeolite species. Siliceous zeolites (e.g., clinoptilolite, mordenite, erionite) present in saline and alkaline lakes or diagenetic deposits formed at elevated silica activities. Aluminous zeolites (e.g., natrolite, mesolite/scolecite, thomsonite) formed in basic rocks in association with reduced silica activities. Likewise, phillipsite formation is favored by reduced aqueous silica activities. The presence of erionite, chabazite, and phillipsite are indicative of environments with elevated potassium concentrations. Elevated temperature, calcic water conditions, and reduced silica activity help to enhance the laumontite and wairakite stability fields. Analcime stability increases with increased temperature and aqueous Na concentration, and/or with decreased silica activity.
- Research Organization:
- Los Alamos National Lab., NM (United States)
- Sponsoring Organization:
- USDOE Assistant Secretary for Management and Administration, Washington, DC (United States); USDOE Office of Financial Management and Controller, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 619676
- Report Number(s):
- LA-UR--97-2160; CONF-9706169--; ON: DE97008886
- Country of Publication:
- United States
- Language:
- English
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