3290 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Phosphoric acid leaching has also generated interest
due to its mild acidity and low corrosivity compared to
HCl and H2SO4.
The use of organic acids (oxalic, ascorbic, Maleic etc.)
in the leaching of pretreated LIB materials has attracted
some interest due to the milder conditions required with
respect to materials of construction. The organic acids
without a reducing co-reagent have also been reported
to perform better than inorganic acid without reducing
reagent (Larouche et al., 2020). As reported by Larouche et
al. (2020), the use of organic acids is still deemed an expen-
sive option relative to the commercially available inorganic
acids previously discussed.
Ammonia Leaching
Leaching with basic ammoniacal solutions is known to be
less efficient than acid leach reagents, it requires higher con-
centrations, longer leaching times, and liquid/solid ratios,
this approach has generated interest due to the observed
selectivity toward Li, Ni, Co, and Cu in addition to ammo-
nia/ammonium being a more environmentally friendly
reagent.
The ammoniacal solution comprises ammonia as the
leaching agent, an ammonium compound as the buffering
agent, and a sulfite or thiosulfate compound as the reducing
agent. Selective leaching is driven by the formation of sta-
ble coordination complexes between ammonia and metal-
lic ions, particularly Li+,Ni2+,Co2+, and Cu2+, whereas Fe,
Mn, and Al typically remain precipitated as hydroxides.
Although leaching with ammonia alone is thermodynami-
cally favorable, the reaction has poor kinetics, and thus
minimal leaching is observed for Li, Ni, and Co even at
high concentrations (Or et al., 2019).
Deep Eutectic Solvent (DES) Leaching
Deep eutectic solvents (DESs) are a new class of green sol-
vents, first introduced in 2003 by Abbott (Padwal et al.,
2022) and exhibit several similar characteristics to ionic
liquids (ILs) such as, low cost, environmentally benign in
nature, low volatility, biodegradable, and easy to synthe-
size. The strong ability of donating and accepting electrons
or protons makes them ideal chemicals for the degradation
process of a range of components such as sugars, polysac-
charides, salts, drugs, proteins, and amino acids.
DESs can be used in chemical reactions such as electro-
deposition, separation of metal, medical industry, biodiesel
production, catalytic activity, cross-coupling synthesis and
carbon capture etc. Suffice to say the use of DES liquids is
an evolving field for the recycling of LIBs cathode materials.
The selection DES liquids is boundless as described by
Padwal et al., 2022 where the characteristics require of the
DES can be synthesized in a lab for specific applications
such as recovery of nickel, cobalt and lithium.
Bio Leaching
Biohydrometallurgy relates to the use of microorganisms
(i.e., bacteria and fungi) that secrete various organic acids
for metal leaching. The main advantages of this method
include the ecofriendly composition and lower material
cost from substituting the use of chemically synthesized
acids. This process does require long incubation/leaching
times to achieve good leaching efficiency (1‐2 weeks) (Or et
al., 2020), high liquid/solid ratios, and lengthy preparation
steps to culture (grow) the microorganism. The mentioned
challenges have all been experienced in by operators when
applied to bio metallurgy of gold and copper. Important
parameters that must be monitored and optimized in the
bioreactor, to maximize organic acid production include
the type and concentration of carbohydrates (energy source
for microbes) in the culture medium, pH, temperature,
degree of aeration, presence of toxic trace elements, and the
microbial population density.
The use of bacteria in leaching processes has been
practiced for near 40 years in both refractory sulphide ore
processing (BIOX Process 2021,Metso). Some of the bac-
teria that are used consist of a combination of sulfur‐oxi-
dizing (Acidithiobacillus thiooxidans) and Fe2+oxidizing
Acidithiobacillus ferriphilum) bacteria with a food source of
elemental sulfur and pyrite respectively. Acidithiobacillus.
ferriphilum can produce H2SO4 from the bio oxidation
of elemental sulfur, while Acidithiobacillus. Thiooxidans
catalyze the release of Fe2+ from pyrite, which can be used
to reduce Mn4+ and Co3+ (from Fe2+ /Fe3+ redox) and is
essential to achieve high leaching efficiencies.
The leaching process then follows the previously
described inorganic acid leaching of EOL LIBs.
DIRECT RECYCLING PROCESSES
Direct Recycling is a comprehensive and environmentally
friendly process that focuses on the recovery and re-use of
active materials essential to the functioning of electronic
devices. These materials comprise the cathode and anode,
which are the positive and negative electrodes, respectively.
Another critical component is the separator, a perme-
able membrane placed between the cathode and anode to
prevent a short circuit while still allowing the flow of ions.
The electrolyte is another component that is recovered dur-
ing the Direct Recycling process. It serves as the medium
Phosphoric acid leaching has also generated interest
due to its mild acidity and low corrosivity compared to
HCl and H2SO4.
The use of organic acids (oxalic, ascorbic, Maleic etc.)
in the leaching of pretreated LIB materials has attracted
some interest due to the milder conditions required with
respect to materials of construction. The organic acids
without a reducing co-reagent have also been reported
to perform better than inorganic acid without reducing
reagent (Larouche et al., 2020). As reported by Larouche et
al. (2020), the use of organic acids is still deemed an expen-
sive option relative to the commercially available inorganic
acids previously discussed.
Ammonia Leaching
Leaching with basic ammoniacal solutions is known to be
less efficient than acid leach reagents, it requires higher con-
centrations, longer leaching times, and liquid/solid ratios,
this approach has generated interest due to the observed
selectivity toward Li, Ni, Co, and Cu in addition to ammo-
nia/ammonium being a more environmentally friendly
reagent.
The ammoniacal solution comprises ammonia as the
leaching agent, an ammonium compound as the buffering
agent, and a sulfite or thiosulfate compound as the reducing
agent. Selective leaching is driven by the formation of sta-
ble coordination complexes between ammonia and metal-
lic ions, particularly Li+,Ni2+,Co2+, and Cu2+, whereas Fe,
Mn, and Al typically remain precipitated as hydroxides.
Although leaching with ammonia alone is thermodynami-
cally favorable, the reaction has poor kinetics, and thus
minimal leaching is observed for Li, Ni, and Co even at
high concentrations (Or et al., 2019).
Deep Eutectic Solvent (DES) Leaching
Deep eutectic solvents (DESs) are a new class of green sol-
vents, first introduced in 2003 by Abbott (Padwal et al.,
2022) and exhibit several similar characteristics to ionic
liquids (ILs) such as, low cost, environmentally benign in
nature, low volatility, biodegradable, and easy to synthe-
size. The strong ability of donating and accepting electrons
or protons makes them ideal chemicals for the degradation
process of a range of components such as sugars, polysac-
charides, salts, drugs, proteins, and amino acids.
DESs can be used in chemical reactions such as electro-
deposition, separation of metal, medical industry, biodiesel
production, catalytic activity, cross-coupling synthesis and
carbon capture etc. Suffice to say the use of DES liquids is
an evolving field for the recycling of LIBs cathode materials.
The selection DES liquids is boundless as described by
Padwal et al., 2022 where the characteristics require of the
DES can be synthesized in a lab for specific applications
such as recovery of nickel, cobalt and lithium.
Bio Leaching
Biohydrometallurgy relates to the use of microorganisms
(i.e., bacteria and fungi) that secrete various organic acids
for metal leaching. The main advantages of this method
include the ecofriendly composition and lower material
cost from substituting the use of chemically synthesized
acids. This process does require long incubation/leaching
times to achieve good leaching efficiency (1‐2 weeks) (Or et
al., 2020), high liquid/solid ratios, and lengthy preparation
steps to culture (grow) the microorganism. The mentioned
challenges have all been experienced in by operators when
applied to bio metallurgy of gold and copper. Important
parameters that must be monitored and optimized in the
bioreactor, to maximize organic acid production include
the type and concentration of carbohydrates (energy source
for microbes) in the culture medium, pH, temperature,
degree of aeration, presence of toxic trace elements, and the
microbial population density.
The use of bacteria in leaching processes has been
practiced for near 40 years in both refractory sulphide ore
processing (BIOX Process 2021,Metso). Some of the bac-
teria that are used consist of a combination of sulfur‐oxi-
dizing (Acidithiobacillus thiooxidans) and Fe2+oxidizing
Acidithiobacillus ferriphilum) bacteria with a food source of
elemental sulfur and pyrite respectively. Acidithiobacillus.
ferriphilum can produce H2SO4 from the bio oxidation
of elemental sulfur, while Acidithiobacillus. Thiooxidans
catalyze the release of Fe2+ from pyrite, which can be used
to reduce Mn4+ and Co3+ (from Fe2+ /Fe3+ redox) and is
essential to achieve high leaching efficiencies.
The leaching process then follows the previously
described inorganic acid leaching of EOL LIBs.
DIRECT RECYCLING PROCESSES
Direct Recycling is a comprehensive and environmentally
friendly process that focuses on the recovery and re-use of
active materials essential to the functioning of electronic
devices. These materials comprise the cathode and anode,
which are the positive and negative electrodes, respectively.
Another critical component is the separator, a perme-
able membrane placed between the cathode and anode to
prevent a short circuit while still allowing the flow of ions.
The electrolyte is another component that is recovered dur-
ing the Direct Recycling process. It serves as the medium