Abstract
Spodumene concentrate from the Pilbara region in Western Australia was characterized by X-ray diffraction (XRD), Scanning Electron Microscope Energy Dispersive Spectroscopy (SEM-EDS) and Mineral Liberation Analysis (MLA) to identify and quantify major minerals in the concentrate. Particle diameters ranged from 10 to 200 microns and the degree of liberation of major minerals was found to be more than 90%. The thermal behavior of spodumene and the concentration of its polymorphs were studied by heat treatments in the range of 900 to 1050 °C. All three polymorphs of the mineral (α, γ and β) were identified. Full transformation of the α-phase was achieved at 975 °C and 1000 °C after 240 and 60 min treatments, respectively. SEM images of thermally treated concentrate revealed fracturing of spodumene grains, producing minor cracks initially which became more prominent with increasing temperature. Material disintegration, melting and agglomeration with gangue minerals were also observed at higher temperatures. The metastable γ-phase achieved a peak concentration of 23% after 120 min at 975 °C. We suggest 1050 °C to be the threshold temperature for the process where even a short residence time causes appreciable transformation, however, 1000 °C may be the ideal temperature for processing the concentrate due to the degree of material disintegration and α-phase transformation observed. The application of a first-order kinetic model yields kinetic parameters which fit the experimental data well. The resultant apparent activation energies of 655 and 731 kJ mol−1 obtained for α- and γ-decay, respectively, confirm the strong temperature dependence for the spodumene polymorph transformations.
Highlights
Lithium is undergoing important investigations in order to meet its worldwide stable supply as this element is considered a critical metal by many countries
The lithium concentration was determined as 2.14 wt.%; the calculated lithium oxide and spodumene concentrations were 4.61 wt.% and 57.39 wt.% respectively. This is in close agreement with the 60.21 wt.% spodumenes indicated by the Mineral Liberation Analysis (MLA) result (Table 2) and 3 wt.% Li content in spodumene from the Pilbara region reported in the literature [17]
The physicochemical characteristics of spodumene concentrate from the Pilbara region were studied
Summary
Lithium is undergoing important investigations in order to meet its worldwide stable supply as this element is considered a critical metal by many countries. It is produced from salar brines or ores. The production from salar brines involves three major steps; evaporation, purification and precipitation. The recovery of the metal by this approach faces many challenges, including the delay in production due to solar evaporation and the presence of many impurities which demand the implementation of refining stages. The main interest of lithium production from salar brine comes from the low cost of the operations. The recent increase in the price of lithium has resulted in huge investments into lithium production from ores
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