3406
Process Optimization for the Direct Extraction of Lithium from
α-Spodumene via NaOH-Roasting and Water Leaching
H.C.S. Subasinghe, Mohammad Rezaee
John and Wille Leone Family Department of Energy and Mineral Engineering, Center for Critical Minerals, EMS
Energy Institute, College of Earth and Mineral Sciences, Pennsylvania State University, University Park, PA, USA
ABSTRACT: To address the economic and environmental challenges associated with the current commercial
process for extracting lithium from spodumene, the authors have developed a patent-pending method for
direct lithium extraction from α-spodumene. This innovative approach involves NaOH-roasting followed by
sequential water and acid leaching. This paper presents the outcomes of optimizing this extraction process,
primarily focusing on maximizing lithium recovery in the water-leaching step, thereby eliminating the need
for acid leaching. The process was first optimized for roasting parameters, including temperature, time, and
the NaOH-to-α-spodumene ratio to maximize the transformation of Li to water-soluble phases. Subsequently,
the parameters for water leaching, including stirring rate, solid-to-liquid ratio, temperature, and duration, were
optimized. A patent-pending two-stage sequential roasting and water leaching was carried out to avoid the need
for acid leaching and a Li extraction of 99% in water leaching was obtained. A comprehensive investigation into
the reaction kinetics for both roasting and water-leaching steps was carried out under the established optimum
conditions.
Keywords: lithium, spodumene, direct-extraction, process optimization, reaction kinetics
INTRODUCTION
Lithium (Li), a lightweight metal (i.e., specific gravity of
0.534) with high specific capacity (~3.8 Ah g–1) and elec-
trochemical potential (~3 V) has assumed a pivotal role
at the core of modern energy solutions in the global shift
towards sustainable energy generation (Greim et al., 2020
Tabelin et al., 2021). It powers electric vehicles, stores
renewable energy, and finds applications across diverse
industries (Meshram et al., 2014 Azevedo et al., 2018).
As the demand for this critical element escalates with the
growth of renewable energy and electric vehicles, secur-
ing a stable supply chain has become a pressing concern.
Although Li will not be a limiting constraint in the near
future, higher consumption and environmental sustainabil-
ity have necessitated innovative processing approaches.
Spodumene (LiAlSi2O6) takes the forefront of
Li-bearing minerals mainly due to grade and geographi-
cal abundance (Grosjean et al., 2012 Speirs et al., 2014
Alhadad et al., 2022 Ding et al., 2023). It is a pyroxene
group sheet silicate with three polymorphs α, β and γ, where
α is the low-temperature naturally occurring form with a
monoclinic structure (Peltosaari et al., 2015). In this intact
structure, Li occupies cavities between Si-centered tetrahe-
dra and Al-centered octahedra (Quezada and Toledo, 2019).
Due to the nature of Li occurrence in between polyhedra
of α-spodumene, it is traditionally converted to tetragonal
β-spodumene using a high-temperature calcination process
Process Optimization for the Direct Extraction of Lithium from
α-Spodumene via NaOH-Roasting and Water Leaching
H.C.S. Subasinghe, Mohammad Rezaee
John and Wille Leone Family Department of Energy and Mineral Engineering, Center for Critical Minerals, EMS
Energy Institute, College of Earth and Mineral Sciences, Pennsylvania State University, University Park, PA, USA
ABSTRACT: To address the economic and environmental challenges associated with the current commercial
process for extracting lithium from spodumene, the authors have developed a patent-pending method for
direct lithium extraction from α-spodumene. This innovative approach involves NaOH-roasting followed by
sequential water and acid leaching. This paper presents the outcomes of optimizing this extraction process,
primarily focusing on maximizing lithium recovery in the water-leaching step, thereby eliminating the need
for acid leaching. The process was first optimized for roasting parameters, including temperature, time, and
the NaOH-to-α-spodumene ratio to maximize the transformation of Li to water-soluble phases. Subsequently,
the parameters for water leaching, including stirring rate, solid-to-liquid ratio, temperature, and duration, were
optimized. A patent-pending two-stage sequential roasting and water leaching was carried out to avoid the need
for acid leaching and a Li extraction of 99% in water leaching was obtained. A comprehensive investigation into
the reaction kinetics for both roasting and water-leaching steps was carried out under the established optimum
conditions.
Keywords: lithium, spodumene, direct-extraction, process optimization, reaction kinetics
INTRODUCTION
Lithium (Li), a lightweight metal (i.e., specific gravity of
0.534) with high specific capacity (~3.8 Ah g–1) and elec-
trochemical potential (~3 V) has assumed a pivotal role
at the core of modern energy solutions in the global shift
towards sustainable energy generation (Greim et al., 2020
Tabelin et al., 2021). It powers electric vehicles, stores
renewable energy, and finds applications across diverse
industries (Meshram et al., 2014 Azevedo et al., 2018).
As the demand for this critical element escalates with the
growth of renewable energy and electric vehicles, secur-
ing a stable supply chain has become a pressing concern.
Although Li will not be a limiting constraint in the near
future, higher consumption and environmental sustainabil-
ity have necessitated innovative processing approaches.
Spodumene (LiAlSi2O6) takes the forefront of
Li-bearing minerals mainly due to grade and geographi-
cal abundance (Grosjean et al., 2012 Speirs et al., 2014
Alhadad et al., 2022 Ding et al., 2023). It is a pyroxene
group sheet silicate with three polymorphs α, β and γ, where
α is the low-temperature naturally occurring form with a
monoclinic structure (Peltosaari et al., 2015). In this intact
structure, Li occupies cavities between Si-centered tetrahe-
dra and Al-centered octahedra (Quezada and Toledo, 2019).
Due to the nature of Li occurrence in between polyhedra
of α-spodumene, it is traditionally converted to tetragonal
β-spodumene using a high-temperature calcination process