XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3407
at 1100 °C before Li is extracted by sulfuric acid baking at
250 °C and water leaching at 90 °C (Salakjani et al., 2020,
2021 Yelatontsev and Mukhachev, 2021). For this reason,
a transformative methodology for the direct extraction of
Li from α-spodumene bypassing conventional, complex,
energy-intensive methods with high greenhouse gas emis-
sion is a timely requirement. Consequently, the authors
developed a patent-pending process for the direct Li extrac-
tion from α-spodumene using sequential NaOH-roasting
and leaching (Han et al., 2022 Rezaee et al., 2023, Rezaee
and Subasinghe, 2024). The reactions involved in the roast-
ing process of this study are summarized in Rxns. 1−4. The
Rxn. 1 represents the equilibrium products of the roasting
process calculated using FactSage 8.2 (Han et al., 2022).
The corresponding stoichiometric reactions were derived
based on Rxn. 1. Therefore, in this paper, we elucidate pro-
cess optimization of the NaOH-roasting and water-leach-
ing, emphasizing maximizing Li recovery during roasting
and water leaching.
1.9 g O
0.1 g SiO 3 g NaOH^sh
0.46250 g Li NaSiO
0.81372 g Na SiO
2.2112 g Na SiO
0.83172 g NaAlO
0.67562 g H O
2 6
2
3 4
2 3
4 4
2
2
"
a–LiAlSi
++
+
+
+
+
^s
^sh
^gh
^sh
^sh
^sh
^s
h
h (Rxn 1)
3 –LiAlSi O 14NaOH^sh
Li NaSiO 5Na SiO
3NaAlO 7H O
2 6
3 4 2 3
2 2
"a
++
^sh+
^sh+
^s ^gh
^sh
h
(Rxn 2)
SiO sh 2NaOH^sh
Na SiO sh H O^gh
2
2 3 2
"+
+
^
^(Rxn 3)
Na2 SiO 2NaOH^sh
Na SiO H O^gh
3
4 4 2
"^sh+
^sh+ (Rxn 4)
In this regard, roasting parameters (i.e., NaOH-to-α-
spodumene ratio, temperature, and duration) were initially
optimized with the aim of maximizing the α-spodumene
conversion into water-soluble phases for Li recovery.
Following this, water leaching parameters (e.g., stirring rate,
solid-to-liquid ratio, temperature, and duration) were opti-
mized at optimum roasting conditions. Finally, advanced
characterization techniques such as Inductively Coupled
Plasma Mass Spectrometry (ICP-MS) and X-ray diffraction
(XRD) were used to study roasting and leaching processes.
MATERIALS AND METHODS
Raw Materials
Raw spodumene sample from the North Carolina Tin-
Spodumene belt was provided by Piedmont Lithium Inc.
The sample was initially subjected to size reduction, flo-
tation, and magnetic separation to obtain α-spodumene
concentrate as detailed by the authors on microwave-
assisted calcination of spodumene (Rezaee et al., 2022).
Representative samples of this α-spodumene concentrate
was used as the main raw material for the laboratory analy-
sis described in this study. Analytical grade (Sigma Aldrich)
NaOH powder was used as the roasting reagent in the
experiments based on the results obtained by the authors
on salt-roasting and leaching of α-spodumene (Han et al.,
2022). In addition, ultrapure deionized water of resistivity
greater than 18 MΩ cm was used for all the water leaching
experiments. Furthermore, trace metal-grade HF, HCl and
HNO3 were used in sample digestion and dilution for ICP
analysis. All the experiments were carried out at least three
times to ensure repeatability and calculate 95% confidence
intervals.
Methodology
Roasting
Spodumene was thoroughly mixed with NaOH in 25 mL
zirconium crucibles using an agate pestle in different ratios
by weight as shown in Table 1. Sample mixtures were imme-
diately roasted at 325 °C under normal airflow in a Thermo
Scientific Thermolyne F30420C-80 Muffle Furnace for
2 h. The experiments were repeated at different tempera-
tures (Table 1) at optimized NaOH-to-α-spodumene ratio.
Finally, the experiment was repeated for different time peri-
ods at optimum ratio and temperature. Optimum condi-
tions for each roasting parameter were determined based on
Li recovery of water leaching step.
Water Leaching
Roasted samples were ground using an agate pestle to dis-
mantle agglomerated particles during roasting. Leaching
experiments were carried out using three-neck round-
bottom flasks and overhead stirrers. Samples were initially
leached for 2 h using 200 mL of ultrapure DI water (i.e.,
1% Spodumene/Liquid ratio) and 400 rpm stirring rate at
room temperature for the investigation of optimum roast-
ing conditions. Subsequently, leaching parameters such as
stirring rate, solid-to-liquid ratio, temperature, and dura-
tion were optimized as shown in Table 1. Leachate samples
from the optimum leaching temperature were collected at 5
s, 10 s, 15 s, 30 s, 45 s, 60 s, 90 s, 2 min., 5 min., 15 min.,
at 1100 °C before Li is extracted by sulfuric acid baking at
250 °C and water leaching at 90 °C (Salakjani et al., 2020,
2021 Yelatontsev and Mukhachev, 2021). For this reason,
a transformative methodology for the direct extraction of
Li from α-spodumene bypassing conventional, complex,
energy-intensive methods with high greenhouse gas emis-
sion is a timely requirement. Consequently, the authors
developed a patent-pending process for the direct Li extrac-
tion from α-spodumene using sequential NaOH-roasting
and leaching (Han et al., 2022 Rezaee et al., 2023, Rezaee
and Subasinghe, 2024). The reactions involved in the roast-
ing process of this study are summarized in Rxns. 1−4. The
Rxn. 1 represents the equilibrium products of the roasting
process calculated using FactSage 8.2 (Han et al., 2022).
The corresponding stoichiometric reactions were derived
based on Rxn. 1. Therefore, in this paper, we elucidate pro-
cess optimization of the NaOH-roasting and water-leach-
ing, emphasizing maximizing Li recovery during roasting
and water leaching.
1.9 g O
0.1 g SiO 3 g NaOH^sh
0.46250 g Li NaSiO
0.81372 g Na SiO
2.2112 g Na SiO
0.83172 g NaAlO
0.67562 g H O
2 6
2
3 4
2 3
4 4
2
2
"
a–LiAlSi
++
+
+
+
+
^s
^sh
^gh
^sh
^sh
^sh
^s
h
h (Rxn 1)
3 –LiAlSi O 14NaOH^sh
Li NaSiO 5Na SiO
3NaAlO 7H O
2 6
3 4 2 3
2 2
"a
++
^sh+
^sh+
^s ^gh
^sh
h
(Rxn 2)
SiO sh 2NaOH^sh
Na SiO sh H O^gh
2
2 3 2
"+
+
^
^(Rxn 3)
Na2 SiO 2NaOH^sh
Na SiO H O^gh
3
4 4 2
"^sh+
^sh+ (Rxn 4)
In this regard, roasting parameters (i.e., NaOH-to-α-
spodumene ratio, temperature, and duration) were initially
optimized with the aim of maximizing the α-spodumene
conversion into water-soluble phases for Li recovery.
Following this, water leaching parameters (e.g., stirring rate,
solid-to-liquid ratio, temperature, and duration) were opti-
mized at optimum roasting conditions. Finally, advanced
characterization techniques such as Inductively Coupled
Plasma Mass Spectrometry (ICP-MS) and X-ray diffraction
(XRD) were used to study roasting and leaching processes.
MATERIALS AND METHODS
Raw Materials
Raw spodumene sample from the North Carolina Tin-
Spodumene belt was provided by Piedmont Lithium Inc.
The sample was initially subjected to size reduction, flo-
tation, and magnetic separation to obtain α-spodumene
concentrate as detailed by the authors on microwave-
assisted calcination of spodumene (Rezaee et al., 2022).
Representative samples of this α-spodumene concentrate
was used as the main raw material for the laboratory analy-
sis described in this study. Analytical grade (Sigma Aldrich)
NaOH powder was used as the roasting reagent in the
experiments based on the results obtained by the authors
on salt-roasting and leaching of α-spodumene (Han et al.,
2022). In addition, ultrapure deionized water of resistivity
greater than 18 MΩ cm was used for all the water leaching
experiments. Furthermore, trace metal-grade HF, HCl and
HNO3 were used in sample digestion and dilution for ICP
analysis. All the experiments were carried out at least three
times to ensure repeatability and calculate 95% confidence
intervals.
Methodology
Roasting
Spodumene was thoroughly mixed with NaOH in 25 mL
zirconium crucibles using an agate pestle in different ratios
by weight as shown in Table 1. Sample mixtures were imme-
diately roasted at 325 °C under normal airflow in a Thermo
Scientific Thermolyne F30420C-80 Muffle Furnace for
2 h. The experiments were repeated at different tempera-
tures (Table 1) at optimized NaOH-to-α-spodumene ratio.
Finally, the experiment was repeated for different time peri-
ods at optimum ratio and temperature. Optimum condi-
tions for each roasting parameter were determined based on
Li recovery of water leaching step.
Water Leaching
Roasted samples were ground using an agate pestle to dis-
mantle agglomerated particles during roasting. Leaching
experiments were carried out using three-neck round-
bottom flasks and overhead stirrers. Samples were initially
leached for 2 h using 200 mL of ultrapure DI water (i.e.,
1% Spodumene/Liquid ratio) and 400 rpm stirring rate at
room temperature for the investigation of optimum roast-
ing conditions. Subsequently, leaching parameters such as
stirring rate, solid-to-liquid ratio, temperature, and dura-
tion were optimized as shown in Table 1. Leachate samples
from the optimum leaching temperature were collected at 5
s, 10 s, 15 s, 30 s, 45 s, 60 s, 90 s, 2 min., 5 min., 15 min.,