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Phase Transitions in the α–γ–β Spodumene Thermodynamic System and Impact of γ-Spodumene on the Efficiency of Lithium Extraction by Acid Leaching

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Département de Génie Chimique et Biotechnologique, Université de Sherbrooke, Sherbrooke, QC J1K 2R1, Canada
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Polytechnique Montréal, Université de Montréal, Montréal, QC H3T 1J4, Canada
*
Author to whom correspondence should be addressed.
Minerals 2020, 10(6), 519; https://doi.org/10.3390/min10060519
Received: 25 March 2020 / Revised: 29 May 2020 / Accepted: 2 June 2020 / Published: 5 June 2020
(This article belongs to the Section Mineral Processing and Metallurgy)
Heat-treatment of spodumene concentrate at 1323 K (1050 °C) for 30 min in a rotary kiln yielded a successful decrepitation. Particle size decreased from 2 cm to less than 425 µm for 80% of the initial mass. X-ray analysis of both fractions did not reveal the presence of α-spodumene or γ-spodumene. The coarse fraction was ground to less than 425 µm with minimal mechanical energy and mixed with the finer fraction to perform lithium extraction. The lithium extraction efficiency reached 98 wt% without the need for flotation. Some aspects of the thermodynamic behavior of the spodumene system were assessed. Results show that metastable γ-spodumene may hinder the formation of β-spodumene at lower heat treatment temperatures. Some heat-treated samples presented non-negligible γ-spodumene content and lithium extraction efficiency decreases as the γ content increases. Finally, the assumed irreversibility of the transformations was studied by analyzing heat-treated samples following long controlled-storage periods. The results show that concentrate composition is not static over the studied time. This suggests that the β formation is not as irreversible as claimed. It is recommended to avoid long periods between heat-treatment and extraction to avoid the slow conversion of β-spodumene to other allotropes, which are less susceptible to lithium extraction. View Full-Text
Keywords: spodumene heat treatment; phase transitions; thermodynamic phase diagram; acid leaching lithium extraction spodumene heat treatment; phase transitions; thermodynamic phase diagram; acid leaching lithium extraction
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Dessemond, C.; Soucy, G.; Harvey, J.-P.; Ouzilleau, P. Phase Transitions in the α–γ–β Spodumene Thermodynamic System and Impact of γ-Spodumene on the Efficiency of Lithium Extraction by Acid Leaching. Minerals 2020, 10, 519.

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