Abstract
Natural gonnardite (Na5Ca2(Al9SinO40).12 H20), belonging to the fibrous zeolites group, was cation-exchanged with Na and Ca to give a series of Na+∗∗∗Ca2+ exchanged forms. The NazO/(Na2O+CaO+K2O) ratios of the obtained products were in the range from 82.84% to 6.88% (Ca-form). Dehydration behaviour and thermal stability of these products as well as natural three gonnardite and one tetranatrolite were examined by high-temperature X-ray diffraction and thermal analysis (TG-DTA). The lattice parameters a and c were almost unchanged in the whole Na+∗∗∗Caz+ exchanged series. Ca-gonnardite, of which occurrence in nature was very seldom, showed two endotherms due to dehydration at 222°C and 350°C. This indicates that the Ca-gonnardite essentially dehydrates in two steps like scolecite. It transformed directly into amorphous phase at about 360°C by the destruction of the framework structure due to dehydfation. This destruction temperature was about 240°C and lower by 70°C than those of tetranatrolite and gonnardite. In the framework of the gonnardite type, the Ca-exchange makes the hydrated phase more stable, while it lowers the thermal stability. This is because in the Ca-form water molecules occupy vacant sites produced by 2 Na+∗∗∗Ca2+ exchange, and that the framework structure is, more easily susceptible to distortion and hence to thermal destruction on heating.
| Original language | English |
|---|---|
| Pages (from-to) | 405-409 |
| Number of pages | 5 |
| Journal | Nippon Kagaku Kaishi / Chemical Society of Japan - Chemistry and Industrial Chemistry Journal |
| Volume | 1989 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - 1989 |
| Externally published | Yes |
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Cite this
Dyhydration Behaviour and Thermal Stability of (Na, Ca)-Exehanged Gonnardite. / Yamazaki, Atsushi; Otsuka, Ryohei.
In: Nippon Kagaku Kaishi / Chemical Society of Japan - Chemistry and Industrial Chemistry Journal, Vol. 1989, No. 3, 1989, p. 405-409.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Dyhydration Behaviour and Thermal Stability of (Na, Ca)-Exehanged Gonnardite
AU - Yamazaki, Atsushi
AU - Otsuka, Ryohei
PY - 1989
Y1 - 1989
N2 - Natural gonnardite (Na5Ca2(Al9SinO40).12 H20), belonging to the fibrous zeolites group, was cation-exchanged with Na and Ca to give a series of Na+∗∗∗Ca2+ exchanged forms. The NazO/(Na2O+CaO+K2O) ratios of the obtained products were in the range from 82.84% to 6.88% (Ca-form). Dehydration behaviour and thermal stability of these products as well as natural three gonnardite and one tetranatrolite were examined by high-temperature X-ray diffraction and thermal analysis (TG-DTA). The lattice parameters a and c were almost unchanged in the whole Na+∗∗∗Caz+ exchanged series. Ca-gonnardite, of which occurrence in nature was very seldom, showed two endotherms due to dehydration at 222°C and 350°C. This indicates that the Ca-gonnardite essentially dehydrates in two steps like scolecite. It transformed directly into amorphous phase at about 360°C by the destruction of the framework structure due to dehydfation. This destruction temperature was about 240°C and lower by 70°C than those of tetranatrolite and gonnardite. In the framework of the gonnardite type, the Ca-exchange makes the hydrated phase more stable, while it lowers the thermal stability. This is because in the Ca-form water molecules occupy vacant sites produced by 2 Na+∗∗∗Ca2+ exchange, and that the framework structure is, more easily susceptible to distortion and hence to thermal destruction on heating.
AB - Natural gonnardite (Na5Ca2(Al9SinO40).12 H20), belonging to the fibrous zeolites group, was cation-exchanged with Na and Ca to give a series of Na+∗∗∗Ca2+ exchanged forms. The NazO/(Na2O+CaO+K2O) ratios of the obtained products were in the range from 82.84% to 6.88% (Ca-form). Dehydration behaviour and thermal stability of these products as well as natural three gonnardite and one tetranatrolite were examined by high-temperature X-ray diffraction and thermal analysis (TG-DTA). The lattice parameters a and c were almost unchanged in the whole Na+∗∗∗Caz+ exchanged series. Ca-gonnardite, of which occurrence in nature was very seldom, showed two endotherms due to dehydration at 222°C and 350°C. This indicates that the Ca-gonnardite essentially dehydrates in two steps like scolecite. It transformed directly into amorphous phase at about 360°C by the destruction of the framework structure due to dehydfation. This destruction temperature was about 240°C and lower by 70°C than those of tetranatrolite and gonnardite. In the framework of the gonnardite type, the Ca-exchange makes the hydrated phase more stable, while it lowers the thermal stability. This is because in the Ca-form water molecules occupy vacant sites produced by 2 Na+∗∗∗Ca2+ exchange, and that the framework structure is, more easily susceptible to distortion and hence to thermal destruction on heating.
UR - http://www.scopus.com/inward/record.url?scp=85008580437&partnerID=8YFLogxK
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U2 - 10.1246/nikkashi.1989.405
DO - 10.1246/nikkashi.1989.405
M3 - Article
AN - SCOPUS:85008580437
VL - 1989
SP - 405
EP - 409
JO - Nippon Kagaku Kaishi / Chemical Society of Japan - Chemistry and Industrial Chemistry Journal
JF - Nippon Kagaku Kaishi / Chemical Society of Japan - Chemistry and Industrial Chemistry Journal
SN - 0369-4577
IS - 3
ER -