3168 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
In nature, lithium is primarily found in salt brines
located near volcanic centres, with significant deposits
also occurring in spodumene-bearing pegmatites. Smaller
quantities are also found in sedimentary deposits and geo-
thermal brines. Due to the expected increase in demand
for lithium, the development of efficient recycling and
beneficiation routes is crucial. The key methods currently
available for recycling of LIBs include pyrometallurgy and
hydrometallurgy or a hybrid of both (Tabelin et al. 2021).
Pyrometallurgical recycling has the advantage to be appli-
cable to many waste streams and existing plants can be
used, e.g., for copper and nickel recycling. Due to its igno-
ble character, lithium is concentrated in the slag beside the
noble main components with high melting temperatures,
such as cobalt and nickel.
LIBs commonly contain between 2 %to 15 %lithium
depending on the LIB technology. Consequently, LIBs are
generally more enriched in lithium compared to natural
resources (Maarten Quix et al. 2017). Thus, the processing
of lithium-bearing slags becomes more attractive and offers
a novel way to recover high grade lithium from the waste
stream. The main objective during lithium processing is to
enrich lithium into artificial minerals during slagging by
adjusting cooling rates to form large crystals that are more
amenable to processing. The most prominent engineered
artificial mineral (EnAM) is lithium aluminate (LiAlO2),
which contains the highest lithium molar content. It
is typically embedded into the gangue phase gehlenite
(Ca2Al(AlSiO7)) which is a sorosilicate (Elwert et al. 2012).
Both the natural Li-bearing spodumene, as well as the
slag with Li-bearing EnAMs, need to undergo upgrading
processes until they can be further transferred into Li2CO3
for industrial applications. First, the material undergoes
comminution, which is then followed by magnetic separa-
tion, density separation and flotation to produce concen-
trates containing 4–8% Li2O (Tabelin et al. 2021). In order
to improve the separation stage of flotation, more efficient
reagent regimes, especially for the flotation of spodumene,
need to be developed.
Anionic collectors, like the benchmark collectors
sodium oleate (Filippov et al. 2019) and oleic acid (OA)
(Tadesse et al. 2019 Yu et al. 2015), are generally used for
spodumene flotation because they offer higher selectivity
than cationic collectors. It was found that sodium oleate
not only works as a collector for spodumene but also for
LiAlO2 (Qiu et al. 2021). Recently, research was done on
both sources with new and mixed collector systems of cat-
ionic and anionic collectors for spodumene (Tian et al.
2017, Acker et al. 2023). In this study oleic acid was chosen
as a collector for the flotation of lithium bearing EnAMs,
in order to establish a benchmark case for this type of slag.
Although, the flotation is strongly determined by the
differences in particle wettability, other particle properties,
such as shape, size or liberation, also play a crucial role.
Recoveries of particles that are either too fine or too coarse
are generally low, due to slow flotation kinetics of fines and
less stable particlebubble aggregates for coarse particles,
respectively (Schubert 1996 Dai et al. 2000 Gontijo et al.
2007). Investigations with respect to the particle shape are
more complex, as the influence may depend on the particle
system itself, especially on the size class studied, and also
on the flotation apparatus used, i.e., if the flotation was
carried out in a mechanical cell, flotation column or micro
flotation etc. (Koh et al. 2009 Xie et al. 2017 Sygusch
2023 Hassas et al. 2016). With all these properties add-
ing to the complexity of the separation, a multidimensional
evaluation is needed in order to understand the interplay
of particle descriptors, which can then be used to improve
the beneficiation of the Li-bearing EnAMs. Wilhelm et al.
(2023) demonstrated that bivariate Tromp functions can
be computed from scanning electron microscopy-based
image data of the input and the output streams. With this
method, the influence of the particle shape (aspect ratio)
and size (areaequivalent diameter) on the separation behav-
iour of LiAlO2 via flotation is investigated.
METHODS AND MATERIALS
Materials
The slag which was provided by RWTH Aachen University
(IME Process Metallurgy and Metal Recycling, RWTH
Aachen, Germany) is a mock slag close to the composi-
tion of real LIBs slags Li2O-CaO-SiO2-Al2O3-MgO-
MnOx (Rachmawatil et al. 2024, Wittkowski et al. 2021).
The particular initiating composition was Li2O 8.5 mol%,
Al2O3 45 mol%, SiO2 19 mol%, CaO 17 mol%, MnO 10
mol% and the applied cooling rate was 25°C/h with a batch
size of 120 kg.
For the sample preparation 80 kg of slag were crushed
in a jaw crusher in 30 cm blocks at UVR-FIA GmbH,
Freiberg, Germany. The material was crushed three times
to a particle size smaller than 10 mm. Afterwards the mate-
rial was given into a sieve ball mill and milled to a particle
size smaller than 100 µm. The result is a red brown powder,
as seen on Figure 1.
Solutions of 0.01 g/ml of oleic acid as collector (Sigma-
Aldrich, St. Louis, MO, USA) and methyl isobutyl car-
binol, MIBC, as frother (Sigma-Aldrich, St. Louis, MO,
USA) were prepared in ethanol (Technical grade, Carl Roth
GmbH +Co. KG, Karlsruhe, Germany).
In nature, lithium is primarily found in salt brines
located near volcanic centres, with significant deposits
also occurring in spodumene-bearing pegmatites. Smaller
quantities are also found in sedimentary deposits and geo-
thermal brines. Due to the expected increase in demand
for lithium, the development of efficient recycling and
beneficiation routes is crucial. The key methods currently
available for recycling of LIBs include pyrometallurgy and
hydrometallurgy or a hybrid of both (Tabelin et al. 2021).
Pyrometallurgical recycling has the advantage to be appli-
cable to many waste streams and existing plants can be
used, e.g., for copper and nickel recycling. Due to its igno-
ble character, lithium is concentrated in the slag beside the
noble main components with high melting temperatures,
such as cobalt and nickel.
LIBs commonly contain between 2 %to 15 %lithium
depending on the LIB technology. Consequently, LIBs are
generally more enriched in lithium compared to natural
resources (Maarten Quix et al. 2017). Thus, the processing
of lithium-bearing slags becomes more attractive and offers
a novel way to recover high grade lithium from the waste
stream. The main objective during lithium processing is to
enrich lithium into artificial minerals during slagging by
adjusting cooling rates to form large crystals that are more
amenable to processing. The most prominent engineered
artificial mineral (EnAM) is lithium aluminate (LiAlO2),
which contains the highest lithium molar content. It
is typically embedded into the gangue phase gehlenite
(Ca2Al(AlSiO7)) which is a sorosilicate (Elwert et al. 2012).
Both the natural Li-bearing spodumene, as well as the
slag with Li-bearing EnAMs, need to undergo upgrading
processes until they can be further transferred into Li2CO3
for industrial applications. First, the material undergoes
comminution, which is then followed by magnetic separa-
tion, density separation and flotation to produce concen-
trates containing 4–8% Li2O (Tabelin et al. 2021). In order
to improve the separation stage of flotation, more efficient
reagent regimes, especially for the flotation of spodumene,
need to be developed.
Anionic collectors, like the benchmark collectors
sodium oleate (Filippov et al. 2019) and oleic acid (OA)
(Tadesse et al. 2019 Yu et al. 2015), are generally used for
spodumene flotation because they offer higher selectivity
than cationic collectors. It was found that sodium oleate
not only works as a collector for spodumene but also for
LiAlO2 (Qiu et al. 2021). Recently, research was done on
both sources with new and mixed collector systems of cat-
ionic and anionic collectors for spodumene (Tian et al.
2017, Acker et al. 2023). In this study oleic acid was chosen
as a collector for the flotation of lithium bearing EnAMs,
in order to establish a benchmark case for this type of slag.
Although, the flotation is strongly determined by the
differences in particle wettability, other particle properties,
such as shape, size or liberation, also play a crucial role.
Recoveries of particles that are either too fine or too coarse
are generally low, due to slow flotation kinetics of fines and
less stable particlebubble aggregates for coarse particles,
respectively (Schubert 1996 Dai et al. 2000 Gontijo et al.
2007). Investigations with respect to the particle shape are
more complex, as the influence may depend on the particle
system itself, especially on the size class studied, and also
on the flotation apparatus used, i.e., if the flotation was
carried out in a mechanical cell, flotation column or micro
flotation etc. (Koh et al. 2009 Xie et al. 2017 Sygusch
2023 Hassas et al. 2016). With all these properties add-
ing to the complexity of the separation, a multidimensional
evaluation is needed in order to understand the interplay
of particle descriptors, which can then be used to improve
the beneficiation of the Li-bearing EnAMs. Wilhelm et al.
(2023) demonstrated that bivariate Tromp functions can
be computed from scanning electron microscopy-based
image data of the input and the output streams. With this
method, the influence of the particle shape (aspect ratio)
and size (areaequivalent diameter) on the separation behav-
iour of LiAlO2 via flotation is investigated.
METHODS AND MATERIALS
Materials
The slag which was provided by RWTH Aachen University
(IME Process Metallurgy and Metal Recycling, RWTH
Aachen, Germany) is a mock slag close to the composi-
tion of real LIBs slags Li2O-CaO-SiO2-Al2O3-MgO-
MnOx (Rachmawatil et al. 2024, Wittkowski et al. 2021).
The particular initiating composition was Li2O 8.5 mol%,
Al2O3 45 mol%, SiO2 19 mol%, CaO 17 mol%, MnO 10
mol% and the applied cooling rate was 25°C/h with a batch
size of 120 kg.
For the sample preparation 80 kg of slag were crushed
in a jaw crusher in 30 cm blocks at UVR-FIA GmbH,
Freiberg, Germany. The material was crushed three times
to a particle size smaller than 10 mm. Afterwards the mate-
rial was given into a sieve ball mill and milled to a particle
size smaller than 100 µm. The result is a red brown powder,
as seen on Figure 1.
Solutions of 0.01 g/ml of oleic acid as collector (Sigma-
Aldrich, St. Louis, MO, USA) and methyl isobutyl car-
binol, MIBC, as frother (Sigma-Aldrich, St. Louis, MO,
USA) were prepared in ethanol (Technical grade, Carl Roth
GmbH +Co. KG, Karlsruhe, Germany).