XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3315
additional production from China and Brazil. Chile was
the major producer of lithium from brine deposits, fol-
lowed by Argentina and China (Jaskula 2023). At present,
there is no reported commercial lithium production from
clay deposits.
Spodumene (LiAlSi2O6) – a pyroxene aluminosilicate
– is the most common lithium bearing mineral exploited
for lithium extraction due to its high lithium content (8%
Li2O) and abundance in hard-rock pegmatite deposits.
Other lithium bearing minerals are also found in these
deposits, including lepidolite (KLiAl2Si3O10(OH,F)3),
petalite (LiAlSi4O10), and amblygonite ((Li,Na)
AlPO4(F,OH)), however lithium production from these
minerals is less common (Swain 2017, Tadesse et al. 2019,
Jaskula 2023). The predominant gangue minerals in peg-
matite deposits are also silicates (quartz, feldspars, micas,
and amphiboles) which have similar physiochemical prop-
erties to spodumene. Rejection of iron-bearing minerals
is critical for many developing spodumene projects, as
spodumene concentrates typically target 6.0% Li2O and
1.0% Fe2O3 for downstream lithium extraction and pro-
duction of battery-grade lithium carbonate and hydroxide
(McCracken et al. 2021).
Spodumene beneficiation can be achieved with dense
media separation (DMS) and froth flotation. DMS is a
gravity separation method best suited to coarser particles
larger than 0.5 mm. It exploits the differences in specific
gravity (s.g.) of spodumene (s.g. 3.10–3.20) and the lighter
silicate minerals like quartz and feldspars (s.g. 2.60–2.65).
While concentrate production with high lithium recovery
(60%) is possible using DMS, it is uncommon and limited
by spodumene grain size and deposit mineralogy (Tadesse
et al. 2019, Patriot Battery Metals 2023). Spodumene flota-
tion can be performed in addition to DMS but can also be
used as the sole beneficiation process (Sayona Mining 2023).
Industrial spodumene flotation is performed with fatty acid
collectors – usually tall oil fatty acids (TOFA) – and is best
suited to processing particles under 300 µm using conven-
tional flotation equipment. While several upstream gangue
rejection stages are needed for selective spodumene recovery
(magnetic separation, desliming, and mica pre-flotation)
a major challenge remains the poor selectivity and strong
collecting power of fatty acid collectors (Bulatovic 2007,
Tadesse et al. 2019). Commercial TOFA collectors contain
primarily oleic and linoleic acid, both nearly insoluble long-
chain C18 unsaturated fatty acids. The primary impurities
in TOFAs are pine rosin acids (e.g., abietic, palustric, and
neoabietic acid) that have the same chemical formula of
C20H30O2 but different terpenic rings structures (Bulatovic
2007, Filippov et al. 2018).
Small scale spodumene flotation studies typically use
readily soluble sodium oleate (the sodium salt of oleic acid).
These studies found that spodumene flotation is driven
by anionic chemisorption of the molecular fatty acid-
anion complex at cationic aluminum (Al3+) surface sites.
Collector adsorption was found to peak at pH 8–8.5, where
the concentration of the acid-anion complex is at a maxi-
mum (Pugh &Stenius 1985, Moon &Fuerstenau 2003,
Yu et al. 2015). This coincides directly with the pH used
in industrial spodumene flotation using TOFAs where it
is reported that a well-executed conditioning stage at high-
pulp density is needed to address poor collector solubility
and achieve proper collector adsorption. This has led some
researchers to speculate that the adsorbed collector species is
changing during conditioning, but further work is required
to validate this (Arbiter et al. 1961, Redeker 1979, Sayona
Mining 2023). In addition to the challenge of overcom-
ing poor solubility, selective rejection of gangue minerals
with similar surface sites (Al3+ and Fe3+) like Fe-Al silicates,
and to some extent feldspars, is difficult because adsorption
onto Al3+ and Fe3+ sites occurs under similar conditions
(Cook &Gibson 2023). Additionally, a study by Zhu et
al. (2020) found that Fe can be present in the spodumene
crystal and lead to an increase in collector adsorption.
At present, the most effective way to reject iron bearing
impurities is through upstream magnetic separation with
medium and high intensity wet magnetic separation, how-
ever, this can result in significant lithium losses through
association and entrainment, or if iron content in the spod-
umene crystal is high. An alternative approach to rejecting
iron-bearing silicates is through improving collector design
and understanding how rosin acids impurities in TOFAs
can impact flotation performance.
TOFAs are produced from pine trees, as a byproduct
of the Kraft paper making process. Different types of rosin
acids are removed during the TOFA production process
the remaining impurities are the rosin acids that are diffi-
cult to remove and/or other unsaponifiables (Logan 1979).
A study conducted by Gibson et al. (2017) suggested that
targeting the total rosin acid content to below 1.0% in
commercial TOFA spodumene collectors may improve iron
rejection to the flotation concentrate, however the mecha-
nism or specific rosin type was not investigated. A 2018
study by Filippov et al. investigating the impact of TOFA
rosin content on scheelite flotation concluded that the large
terpenic ring structures of rosin acids adsorb unselectively
on cationic Ca2+ surface sites. At higher rosin acid concen-
trations (up to 30%), the authors reported higher recovery
with poor selectivity, while TOFAs with lower rosin acid
concentration (~2.5%) provided improved selectivity but
additional production from China and Brazil. Chile was
the major producer of lithium from brine deposits, fol-
lowed by Argentina and China (Jaskula 2023). At present,
there is no reported commercial lithium production from
clay deposits.
Spodumene (LiAlSi2O6) – a pyroxene aluminosilicate
– is the most common lithium bearing mineral exploited
for lithium extraction due to its high lithium content (8%
Li2O) and abundance in hard-rock pegmatite deposits.
Other lithium bearing minerals are also found in these
deposits, including lepidolite (KLiAl2Si3O10(OH,F)3),
petalite (LiAlSi4O10), and amblygonite ((Li,Na)
AlPO4(F,OH)), however lithium production from these
minerals is less common (Swain 2017, Tadesse et al. 2019,
Jaskula 2023). The predominant gangue minerals in peg-
matite deposits are also silicates (quartz, feldspars, micas,
and amphiboles) which have similar physiochemical prop-
erties to spodumene. Rejection of iron-bearing minerals
is critical for many developing spodumene projects, as
spodumene concentrates typically target 6.0% Li2O and
1.0% Fe2O3 for downstream lithium extraction and pro-
duction of battery-grade lithium carbonate and hydroxide
(McCracken et al. 2021).
Spodumene beneficiation can be achieved with dense
media separation (DMS) and froth flotation. DMS is a
gravity separation method best suited to coarser particles
larger than 0.5 mm. It exploits the differences in specific
gravity (s.g.) of spodumene (s.g. 3.10–3.20) and the lighter
silicate minerals like quartz and feldspars (s.g. 2.60–2.65).
While concentrate production with high lithium recovery
(60%) is possible using DMS, it is uncommon and limited
by spodumene grain size and deposit mineralogy (Tadesse
et al. 2019, Patriot Battery Metals 2023). Spodumene flota-
tion can be performed in addition to DMS but can also be
used as the sole beneficiation process (Sayona Mining 2023).
Industrial spodumene flotation is performed with fatty acid
collectors – usually tall oil fatty acids (TOFA) – and is best
suited to processing particles under 300 µm using conven-
tional flotation equipment. While several upstream gangue
rejection stages are needed for selective spodumene recovery
(magnetic separation, desliming, and mica pre-flotation)
a major challenge remains the poor selectivity and strong
collecting power of fatty acid collectors (Bulatovic 2007,
Tadesse et al. 2019). Commercial TOFA collectors contain
primarily oleic and linoleic acid, both nearly insoluble long-
chain C18 unsaturated fatty acids. The primary impurities
in TOFAs are pine rosin acids (e.g., abietic, palustric, and
neoabietic acid) that have the same chemical formula of
C20H30O2 but different terpenic rings structures (Bulatovic
2007, Filippov et al. 2018).
Small scale spodumene flotation studies typically use
readily soluble sodium oleate (the sodium salt of oleic acid).
These studies found that spodumene flotation is driven
by anionic chemisorption of the molecular fatty acid-
anion complex at cationic aluminum (Al3+) surface sites.
Collector adsorption was found to peak at pH 8–8.5, where
the concentration of the acid-anion complex is at a maxi-
mum (Pugh &Stenius 1985, Moon &Fuerstenau 2003,
Yu et al. 2015). This coincides directly with the pH used
in industrial spodumene flotation using TOFAs where it
is reported that a well-executed conditioning stage at high-
pulp density is needed to address poor collector solubility
and achieve proper collector adsorption. This has led some
researchers to speculate that the adsorbed collector species is
changing during conditioning, but further work is required
to validate this (Arbiter et al. 1961, Redeker 1979, Sayona
Mining 2023). In addition to the challenge of overcom-
ing poor solubility, selective rejection of gangue minerals
with similar surface sites (Al3+ and Fe3+) like Fe-Al silicates,
and to some extent feldspars, is difficult because adsorption
onto Al3+ and Fe3+ sites occurs under similar conditions
(Cook &Gibson 2023). Additionally, a study by Zhu et
al. (2020) found that Fe can be present in the spodumene
crystal and lead to an increase in collector adsorption.
At present, the most effective way to reject iron bearing
impurities is through upstream magnetic separation with
medium and high intensity wet magnetic separation, how-
ever, this can result in significant lithium losses through
association and entrainment, or if iron content in the spod-
umene crystal is high. An alternative approach to rejecting
iron-bearing silicates is through improving collector design
and understanding how rosin acids impurities in TOFAs
can impact flotation performance.
TOFAs are produced from pine trees, as a byproduct
of the Kraft paper making process. Different types of rosin
acids are removed during the TOFA production process
the remaining impurities are the rosin acids that are diffi-
cult to remove and/or other unsaponifiables (Logan 1979).
A study conducted by Gibson et al. (2017) suggested that
targeting the total rosin acid content to below 1.0% in
commercial TOFA spodumene collectors may improve iron
rejection to the flotation concentrate, however the mecha-
nism or specific rosin type was not investigated. A 2018
study by Filippov et al. investigating the impact of TOFA
rosin content on scheelite flotation concluded that the large
terpenic ring structures of rosin acids adsorb unselectively
on cationic Ca2+ surface sites. At higher rosin acid concen-
trations (up to 30%), the authors reported higher recovery
with poor selectivity, while TOFAs with lower rosin acid
concentration (~2.5%) provided improved selectivity but