XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3411
exhibits distinct behavior, resulting in a substantial increase
in Li recoveries of 75 ± 4.78%, 73 ± 4.74%, and 74 ±
7.84% achieved at 325 °C, 400 °C, and 600 °C, respec-
tively (Figure 4). This observation underscores that the
reaction between NaOH and α-spodumene produces
leachable Li phases at temperatures surpassing the melt-
ing point of NaOH (Fertani-Gmati and Jemal, 2016 Li
et al., 2019 Han et al., 2022). Consequently, 325 °C was
identified as the optimal roasting temperature, as further
increases in temperature did not yield any significant differ-
ence in Li extraction, as confirmed by the 95% confidence
interval. The importance of roasting temperature in Li
extraction is clear, with a need for elevated temperatures to
destroy the structure of α-spodumene, thereby enhancing
the reaction rate (Song et al., 2019). Therefore, this indi-
cates that the energy requirements for breaking bonds and
initiating reactions at temperatures above the melting point
of NaOH can be sufficient to drive the reaction to a point
where further increases do not result in a substantial change
in Li extraction. However, the increase of Si recovery with
the increase of temperature can be related to the faster and
favorable reaction of silicates with alkali compounds at high
temperatures (Dover et al., 2008 Li et al., 2019).
Effect of Roasting Time
Roasting for shorter durations, such as 5 minutes, 30 min-
utes, and 60 minutes, proves inadequate for achieving
substantial Li extraction from α-spodumene, resulting in
Figure 4. Effect of roasting temperature on Li extraction from α-spodumene
Table 2. Phase transformations during the roasting process using different mass ratios of NaOH
Symbol Phase Peak Position (2θ)
A LiAl(SiO
4 )19.98, 47.13
B Na(AlSi
3 O
8 )31.32, 32.11, 35.52, 40.57, 43.11, 43.93, 58.74
C Li2Al2Si4O12(H2O)2 21.11, 23.36, 29.17, 31.32, 43.11
D Al(OH)3 18.53, 67.01
E NaAlSiO
4 29.72, 34.89, 54.75
F NaAlSi
2 O
6 .H
2 O 23.36, 29.72
G Na3Li2Al(SiO4)2 30.72
H NaCaAl(Si2O7) 37.39, 60.71
I NaAlSi
2 O
6 31.32, 54.75, 64.88
J Li
2 Ca
4 Si
4 O
13 35.52, 37.39
K NaAlO2 54.77
S α-spodumene (LiAlSi
2 O
6 )14.44, 21.05, 29.93, 30.53, 33.53, 46.95, 49.78, 52.51, 60.5563.60
exhibits distinct behavior, resulting in a substantial increase
in Li recoveries of 75 ± 4.78%, 73 ± 4.74%, and 74 ±
7.84% achieved at 325 °C, 400 °C, and 600 °C, respec-
tively (Figure 4). This observation underscores that the
reaction between NaOH and α-spodumene produces
leachable Li phases at temperatures surpassing the melt-
ing point of NaOH (Fertani-Gmati and Jemal, 2016 Li
et al., 2019 Han et al., 2022). Consequently, 325 °C was
identified as the optimal roasting temperature, as further
increases in temperature did not yield any significant differ-
ence in Li extraction, as confirmed by the 95% confidence
interval. The importance of roasting temperature in Li
extraction is clear, with a need for elevated temperatures to
destroy the structure of α-spodumene, thereby enhancing
the reaction rate (Song et al., 2019). Therefore, this indi-
cates that the energy requirements for breaking bonds and
initiating reactions at temperatures above the melting point
of NaOH can be sufficient to drive the reaction to a point
where further increases do not result in a substantial change
in Li extraction. However, the increase of Si recovery with
the increase of temperature can be related to the faster and
favorable reaction of silicates with alkali compounds at high
temperatures (Dover et al., 2008 Li et al., 2019).
Effect of Roasting Time
Roasting for shorter durations, such as 5 minutes, 30 min-
utes, and 60 minutes, proves inadequate for achieving
substantial Li extraction from α-spodumene, resulting in
Figure 4. Effect of roasting temperature on Li extraction from α-spodumene
Table 2. Phase transformations during the roasting process using different mass ratios of NaOH
Symbol Phase Peak Position (2θ)
A LiAl(SiO
4 )19.98, 47.13
B Na(AlSi
3 O
8 )31.32, 32.11, 35.52, 40.57, 43.11, 43.93, 58.74
C Li2Al2Si4O12(H2O)2 21.11, 23.36, 29.17, 31.32, 43.11
D Al(OH)3 18.53, 67.01
E NaAlSiO
4 29.72, 34.89, 54.75
F NaAlSi
2 O
6 .H
2 O 23.36, 29.72
G Na3Li2Al(SiO4)2 30.72
H NaCaAl(Si2O7) 37.39, 60.71
I NaAlSi
2 O
6 31.32, 54.75, 64.88
J Li
2 Ca
4 Si
4 O
13 35.52, 37.39
K NaAlO2 54.77
S α-spodumene (LiAlSi
2 O
6 )14.44, 21.05, 29.93, 30.53, 33.53, 46.95, 49.78, 52.51, 60.5563.60