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

Abstract

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.

Physico-Chemical Characteristics of Spodumene Concentrate and Its Thermal Transformations

“…At 975 °C, almost all the α-phase had decayed and subsequent β-phase formation was solely dependent on the available γ-phase. Dessemond et al [ 24 ] investigated the effect of this phase concomitant with the β-phase and its effect on lithium extraction. They indicated that its presence adversely affects the lithium extraction if its content is above 10%, however, below it, its effect is minimal, and a typical industrial lithium recovery of 95% is attainable.…”

Characteristics of Thermal Parameters and Some Physical Properties of Mineral Eutectic Type: Petalite–Alkali Feldspars

“…Materials 2021, 14, x FOR PEER REVIEW 11 of 13 β-spodumene is 17% larger than that of the γ variety and as much as 26% larger than that of the α variety [43]. The graphs of linear shrinkage changes of sinter are shown in Figure 9.…”

Silicate Mineral Eutectics with Special Reference to Lithium

“…One of these is spodumene. With spodumene, it conducts the firing so that the following reaction occurs [ 17 ]: Li 2 O-Al 2 O 3 -4SiO 2 + 4SiO 2 → Li 2 O-Al 2 O 3 -8SiO 2 spodumene silica β-spodumene (solid solution) …”