Direct formation of the γ-CaSO4 phase in dehydration process of gypsum:: In situ FTIR study

被引：92

作者：

Prasad, PSR ^{[1
]}

Chaitanya, VK

Prasad, KS

Rao, DN

机构：

[1] Natl Geophys Res Inst, Hyderabad 500007, Andhra Pradesh, India

[2] Univ Hyderabad, Sch Phys, Hyderabad 500046, Andhra Pradesh, India

来源：

AMERICAN MINERALOGIST | 2005年 / 90卷 / 04期

关键词：

D O I：

10.2138/am.2005.1742

中图分类号：

P3 [地球物理学]; P59 [地球化学];

学科分类号：

0708 ; 070902 ;

摘要：

The dehydration mechanism of natural single crystals of gypsum was investigated in the temperature range 300-430 K by in situ infrared (FTIR) spectroscopy. The thermal evolution of the second-order modes of H2O and SO4 groups in gypsum, in the wavenumber range 4850-5450 cm(-1) and 2050-2300 cm(-1) respectively, were used to probe the dehydration and rehydration sequence. A total disappearance of the combination modes of H2O and the replacement of four SO4-2 bands (2245, 2200, 2133, and 2117 cm(-1)) observed at room temperature by three bands (2236, 2163, and 2131 cm(-1)) observed at 390 K indicates the direct formation of gamma-CaSO4 upon heating. Upon cooling water re-enters into the gamma-CaSO4 structure at around 363 K to form bassanite. This observation, that the dehydration of gypsum directly yields gamma-CaSO4 (anhydrite) without the intermediate formation of hemi-hydrate (bassanite), is further corroborated by the dehydration behavior of bassanite. The second-order SO, modes of bassanite observed around 2218, 2136, and 2096 cm(-1) were replaced with the bands of gamma-CaSO4 at about 378 K upon heating.

引用

页码：672 / 678

页数：7

共 30 条

[1] THE OCCURRENCE OF BASSANITE IN SOME AUSTRALIAN ARID-ZONE SOILS [J].

AKPOKODJE, EG .

CHEMICAL GEOLOGY, 1984, 47 (3-4) :361-364

[2] Study of gypsum dehydration by controlled transformation rate thermal analysis (CRTA) [J].

Badens, E ;

Llewellyn, P ;

Fulconis, JM ;

Jourdan, C ;

Veesler, S ;

Boistelle, R ;

Rouquerol, F .

JOURNAL OF SOLID STATE CHEMISTRY, 1998, 139 (01) :37-44

[3] INFRARED ABSORPTION SPECTRA OF ALPHA AND BETA-CALCIUM SULPHATE HEMIHYDRATES [J].

BARTRAM, DA .

NATURE, 1969, 223 (5205) :494-&

[4] INVESTIGATION OF CALCIUM SULPHATE-WATER SYSTEM BY INFRARED SPECTROSCOPY [J].

BENSTED, J ;

PRAKASH, S .

NATURE, 1968, 219 (5149) :60-&

[5] RAMAN SPECTRUM OF GYPSUM [J].

BERENBLUT, BJ ;

DAWSON, P ;

WILKINSON, GR .

SPECTROCHIMICA ACTA PART A-MOLECULAR SPECTROSCOPY, 1971, A 27 (09) :1849-+

[6] Application of thermo-Raman spectroscopy to study dehydration of CaSO4•2H2O and CaSO4•0.5H2O [J].

Chang, H ;

Huang, PJ ;

Hou, SC .

MATERIALS CHEMISTRY AND PHYSICS, 1999, 58 (01) :12-19

[7]

CHANG LLY, 1996, ROCK FORMING MINER B, V5, P40

[8] Micro-Raman studies of gypsum in the temperature range between 9 K and 373 K [J].

Chio, CH ;

Sharma, SK ;

Muenow, DW .

AMERICAN MINERALOGIST, 2004, 89 (2-3) :390-395

[9] RAMAN-SPECTRA OF GYPSUM UNDER PRESSURE [J].

COUTY, R ;

VELDE, B ;

BESSON, JM .

PHYSICS AND CHEMISTRY OF MINERALS, 1983, 10 (02) :89-93

[10]

Follner S, 2002, CRYST RES TECHNOL, V37, P207, DOI 10.1002/1521-4079(200210)37:10<1075::AID-CRAT1075>3.0.CO

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