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Title:
The reaction between spodumene and tachyhydrite
Authors:
El-Naggar, M. M. A.; Medina, L. F.; Espinola, A.
Affiliation:
AA(Department of Chemical Engineering, Faculty of Engineering, King Abdulaziz University), AB(Institute of Chemistry, The Federal University of Rio de Janeiro), AC(Institute of Chemistry, The Federal University of Rio de Janeiro)
Publication:
Metallurgical Transactions B, Volume 19, Issue 4, pp.663-668
Publication Date:
08/1988
Origin:
SPRINGER
Abstract Copyright:
(c) 1988: The Metallurgical Society and ASM INTERNATIONAL
DOI:
10.1007/BF02659159
Bibliographic Code:
1988MTB....19..663E

Abstract

The reaction between spodumene (Li2O • A12O2 • 4SiO2) and tachyhydrite (CaCl2 2MgCl2 • 12H2O) at temperatures above 1270 K, when the spodumene has transformed from the unreactive α-form to the β-form, was studied varying the reaction temperature and the relative proportions of the two minerals in the reaction mixtures. Mass balances as well as X-ray diffraction to identify the reaction products indicate that the reactions that occur are 1. a decomposition of the tachyhydrite, losing at first some of its water of crystallization, followed by MgCl2 hydrolyzing to MgO; 2. a transformation of the α-spodumene into β-spodumene; and 3. a reaction between the β-spodumene, MgO produced from tachyhydrite, and CaCl2 of the tachyhydrite according to the equation: Li2O • A12O3 • 4SiO2 + CaCl2 + 8MgO = 2LiCl + CaO • MgO • SiO2 + 3SiO2 • 2MgO + A12O3 • MgO. X-ray diffraction confirmed the presence of all the phases in the products except the phase containing alumina. Considerations of the quaternary phase diagram Al203-SiO2-MgO-CaO show that the phases indicated as reaction products are the ones expected under equilibrium conditions at the reaction temperature. Calculated standard free energy change (△G°) of the suggested reaction is ‑211926 Joules at 1423 K, indicating that under standard conditions the reaction is possible.
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