TY - JOUR
T1 - Phase transformation mechanism of spodumene during its calcination
AU - Abdullah, Arif A.
AU - Oskierski, Hans C.
AU - Altarawneh, Mohammednoor
AU - Senanayake, Gamini
AU - Lumpkin, Gregory
AU - Dlugogorski, Bogdan Z.
N1 - Funding Information:
The authors would like to thank Dr Bjorn Dybdahl, Talison Lithium Pty. Ltd, for providing spodumene concentrates and valuable insights into the operation of the processing plant at Greenbushes. We are grateful to Australian Institute of Nuclear Science and Engineering ( AINSE ) research grant ALNGRA16030 awarded to HCO, MA, GS and BZD, which enabled HT-XRD measurements at ANSTO. We like to thank Professor Gordon Thorogood and Dr Robert Aughterson for their assistance with the HT-XRD measurements. Synchrotron experiments were carried out on the powder diffraction beam line at the Australian Synchrotron during beam time award PD10844. We would like to thank Drs Helen Brand and Fang Xia for beam line set-up and assistance with synchrotron data collection, respectively. AAA thanks the Ministry of Higher Education and Scientific Research of the Iraqi Government for the award of a postgraduate scholarship.
Funding Information:
The authors would like to thank Dr Bjorn Dybdahl, Talison Lithium Pty. Ltd, for providing spodumene concentrates and valuable insights into the operation of the processing plant at Greenbushes. We are grateful to Australian Institute of Nuclear Science and Engineering (AINSE) research grant ALNGRA16030 awarded to HCO, MA, GS and BZD, which enabled HT-XRD measurements at ANSTO. We like to thank Professor Gordon Thorogood and Dr Robert Aughterson for their assistance with the HT-XRD measurements. Synchrotron experiments were carried out on the powder diffraction beam line at the Australian Synchrotron during beam time award PD10844. We would like to thank Drs Helen Brand and Fang Xia for beam line set-up and assistance with synchrotron data collection, respectively. AAA thanks the Ministry of Higher Education and Scientific Research of the Iraqi Government for the award of a postgraduate scholarship.
Publisher Copyright:
© 2019
PY - 2019/8/15
Y1 - 2019/8/15
N2 - This contribution provides a detailed in-situ account of transformation reactions during calcination of a typical high-grade α-spodumene (α-LiAlSi2O6) concentrate, a pre-treatment step required to refine spodumene into commercial lithium chemicals. We observe four reaction pathways during the transition of spodumene, employing in-situ high-temperature powder XRD measurements using both cathode-tube and synchrotron radiation. At a relatively slow heating rate of 8 °C min−1, we observe a close relationship between the development of γ-spodumene, with an onset temperature of 842 °C, and reduction of the amorphous background, in the collected XRD spectra. This demonstrates that, initially γ-spodumene recrystallises from amorphous spodumene. At the fast initial heating rate of 100 °C min−1, γ-spodumene first appears at a higher temperature of 1025 °C. This mineral subsequently transforms into β-spodumene at high temperatures along the reaction pathways denoted as pathway (1) amorphous spodumene → γ-spodumene → β-spodumene and (3) crystalline α-spodumene → γ-spodumene → β-spodumene. The stability of γ-spodumene strongly depends on the mechanical treatment of the sample, and the heating rate of the calcination process, suggesting high and low activation energies for pathways (3) and (1), respectively. In another experiment, we observe rising peaks of β-quartz, a minor gangue mineral in the spodumene concentrate, that reflect the substitution of Li+ and Al3+ for Si4+ above 875 °C. This phase ultimately transforms to β-spodumene at 975 °C. The same experiment demonstrates the spectrum of β-spodumene continuously increasing in magnitude, above 975 °C, with decreasing abundance of α-spodumene, indicating a direct conversion of α- to β-spodumene. Thus, the two other reaction corridors comprise: (2) crystalline α-spodumene → β-quartzss → β-spodumene; (4) crystalline α-spodumene → β-spodumene. Heating of a finely ground sample results in faster and more-complete conversion of α-spodumene compared to a coarser specimen. Our experiments establish the characteristic temperatures of phase transformations during spodumene calcination and reveal the influence of amorphous material and thermal history on reaction sequences. Approaches that integrate the optimisation of grinding and heating thus bear the potential to reduce the energy requirements of the calcination process, including the extraction of lithium from γ-spodumene formed at a lower temperature.
AB - This contribution provides a detailed in-situ account of transformation reactions during calcination of a typical high-grade α-spodumene (α-LiAlSi2O6) concentrate, a pre-treatment step required to refine spodumene into commercial lithium chemicals. We observe four reaction pathways during the transition of spodumene, employing in-situ high-temperature powder XRD measurements using both cathode-tube and synchrotron radiation. At a relatively slow heating rate of 8 °C min−1, we observe a close relationship between the development of γ-spodumene, with an onset temperature of 842 °C, and reduction of the amorphous background, in the collected XRD spectra. This demonstrates that, initially γ-spodumene recrystallises from amorphous spodumene. At the fast initial heating rate of 100 °C min−1, γ-spodumene first appears at a higher temperature of 1025 °C. This mineral subsequently transforms into β-spodumene at high temperatures along the reaction pathways denoted as pathway (1) amorphous spodumene → γ-spodumene → β-spodumene and (3) crystalline α-spodumene → γ-spodumene → β-spodumene. The stability of γ-spodumene strongly depends on the mechanical treatment of the sample, and the heating rate of the calcination process, suggesting high and low activation energies for pathways (3) and (1), respectively. In another experiment, we observe rising peaks of β-quartz, a minor gangue mineral in the spodumene concentrate, that reflect the substitution of Li+ and Al3+ for Si4+ above 875 °C. This phase ultimately transforms to β-spodumene at 975 °C. The same experiment demonstrates the spectrum of β-spodumene continuously increasing in magnitude, above 975 °C, with decreasing abundance of α-spodumene, indicating a direct conversion of α- to β-spodumene. Thus, the two other reaction corridors comprise: (2) crystalline α-spodumene → β-quartzss → β-spodumene; (4) crystalline α-spodumene → β-spodumene. Heating of a finely ground sample results in faster and more-complete conversion of α-spodumene compared to a coarser specimen. Our experiments establish the characteristic temperatures of phase transformations during spodumene calcination and reveal the influence of amorphous material and thermal history on reaction sequences. Approaches that integrate the optimisation of grinding and heating thus bear the potential to reduce the energy requirements of the calcination process, including the extraction of lithium from γ-spodumene formed at a lower temperature.
KW - Calcination of α-spodumene
KW - Decrepitation of α-spodumene
KW - Lithium extraction
KW - Lithium pegmatites
KW - Lithium refining
KW - Phase transitions of spodumene
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U2 - 10.1016/j.mineng.2019.105883
DO - 10.1016/j.mineng.2019.105883
M3 - Article
AN - SCOPUS:85069911054
SN - 0892-6875
VL - 140
JO - Minerals Engineering
JF - Minerals Engineering
M1 - 105883
ER -