The products of selenite hydrothermal treatment in lithium chloride solutions

Abstract

Selenite was boiled in LiCl solutions of different concentrations (1 M, 2 M, 3 M, 4 M and 5 M) at the respective boiling temperatures and atmospheric pressure. The products were subjected to X -ray diffraction analysis, qualitative infrared analysis, differential thermal analysis, thermogravimetric analysis and microscopic examination. The product obtained in the 1 M LiCl solution was the b-form of calcium sulphate hemihydrate (b-CaSO4·0.5H2O). In more concentrated LiCl solutons, 2 M and 3 M, the a-form of calcium sulphate hemihydrate (a-CaSO4·0.5H2O) was formed. The product obtained in the 4 M LiCl solution was also the a-form of calcium sulphate hemihydrate, only mixed with the g-form of calcium sulphate (g-CaSO4). Finally, in the 5 M LiCl solution the g-form of calcium sulphate or g-anhydrite was formed.

Keywords

• selenite
• hemihidrate
• hydrothermal treatment
• calcium sulphate