Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Neuhoff, P. S. Articles by Wang, J. Search for Related Content GeoRef GeoRef Citation

ISOTHERMAL MEASUREMENT OF HEATS OF HYDRATION IN ZEOLITES BY SIMULTANEOUS THERMOGRAVIMETRY AND DIFFERENTIAL SCANNING CALORIMETRY

Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL 32611-2120, USA

^* E-mail address of corresponding author: neuhoff{at}ufl.edu

A calorimetric method for determining isothermal partial and integral heats of hydration reactions (_R,T,P and _R,T,P, respectively) in zeolites and other mineral hydrates is presented. The method involves immersing a dehydrated sample in a humid gas stream under isothermal conditions within a thermal analysis device that records simultaneous differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA) signals. Monitoring changes in sample mass (corresponding to extent of reaction progress) coincident with a quantitative measurement of heat flow allows for direct detection of _R,T,P as a function of the extent of hydration, which can be integrated to determine _R,T,P. In addition, it eliminates uncertainties associated with imprecise knowledge of the starting and final states of a sample during hydration. Measurement under isothermal conditions removes uncertainties associated with heat capacity effects that complicate interpretations of DSC measurements of dehydration heats conducted under traditional scanning temperature conditions. Example experiments on the zeolites natrolite, analcime and chabazite are used to illustrate strategies for quantifying _R,T,P and _R,T,P and minimizing errors associated with baseline uncertainties. Results from this method agree well with previously published values determined by other calorimetric techniques and regression of phase equilibrium data. In the case of chabazite, the results allowed detailed measurements of the variation in _R,T,P for energetically different water types encountered progressively as the sample absorbed water. This technique complements and in many cases improves the quality of thermodynamic data obtained through phase equilibrium observations and other calorimetric techniques.

Key Words: Analcime • Calorimetry • Chabazite • Enthalpy • Hydration • Natrolite • Thermal Analysis • Thermodynamics • Zeolite

This article has been cited by other articles:

				J. Wang and P. S. Neuhoff Thermodynamics of dehydration in analcime: Absorption calorimetry and equilibrium observations American Mineralogist, August 1, 2008; 93(8-9): 1449 - 1459. [Abstract] [Full Text] [PDF]

				P. S. Neuhoff and J. Wang Heat capacity of hydration in zeolites American Mineralogist, August 1, 2007; 92(8-9): 1358 - 1367. [Abstract] [Full Text] [PDF]