Thermal Behavior of Natural and Cation-Exchanged Clinoptilolite From Sardinia (Italy)

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Abstract:

The thermal behavior of two clinoptilolites from an epiclastic and a pyroclastic deposit of central-northern Sardinia and of their exchanged forms (Li, Na, K, Cs, Mg, Ca, Sr and ammonium) were investigated by differential thermal analysis and thermogravimetry up to 1000ºC. Their thermal stability was studied by evaluating the residual crystallinity (expressed as rehydration capacity) after 2 h thermal treatments at 450, 600 and 900ºC. The water loss at 1000ºC was linearly related to the radius (r) and the charge (z) of the exchangeable cations by the equation r2/z or r3/z, which are proportional to the inverse of the charge density over the surface or to the charge density over the volume of the cations.

The cation composition plays a crucial role in determining the thermal behavior of clinoptilolite. The presence of cations such as Cs or K, which have low surface or volume charge densities, was found to increase the thermal resistance. In particular, the crystallinity of Cs- and K-exchanged forms of both clinoptilolites was not affected by thermal treatment at 450ºC and was only slightly reduced by thermal treatment at 600ºC.

Predicting the thermal behavior of natural and cation-exchanged forms of these clinoptilolites can provide useful information for possible applications in catalysis, in the case of high thermal stability, or for thermal transformation into ceramics or lightweight aggregates.

Keywords: CLINOPTILOLITE; IONIC POTENTIAL; ITALY.; REHYDRATION CAPACITY; SARDINIA; THERMAL STABILITY

Document Type: Research Article

DOI: http://dx.doi.org/10.1346/CCMN.2003.0510605

Publication date: December 1, 2003

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  • The JOURNAL publishes articles of interest to the international community of clay scientists, including but not limited to areas in mineralogy, crystallography, geology, geochemistry, sedimentology, soil science, agronomy, physical chemistry, colloid chemistry, ceramics, petroleum engineering, foundry engineering, and soil mechanics. Clays and Clay Minerals exists to disseminate to its worldwide readership the most recent developments in all of these aspects of clay materials. Manuscripts are welcome from all countries.

    Clays and Clay Minerals is the official publication of The Clay Minerals Society.

    The Editor-in-Chief is Professor Joseph W. Stucki jstucki@illinois.edu

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