Separation and Puri cation Technology 361 (2025) 131315

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Separation and Purification Technology

journal homepage: www.elsevier.com/locate/seppur

Direct lithium extraction (DLE) methods and their potential in Li-ion

battery recycling
Usman Saleem a,b, Andre Wilhelms c , Jonas Sottmann d, Hanna K. Knuutila a ,
Sulalit Bandyopadhyay a,b,*
a
Department of Chemical Engineering, Norwegian University of Science and Technology, Trondheim 7941, Norway
b
Particle Engineering Centre, Department of Chemical Engineering, Norwegian University of Science and Technology, Trondheim 7941, Norway
c
Chair of Geochemistry and Economic Geology, Institute of Applied Geosciences, Karlsruhe Institute of Technology, Karlsruhe, Germany
d
Norsk Hydro ASA, Hydro’s Batteries Unit, Oslo, Norway

A R T I C L E I N F O A B S T R A C T

Keywords: Lithium (Li) supply from secondary sources (e.g. batteries) will play a critical role in easing the demand from
direct lithium extraction (DLE) primary production (brines and minerals). To meet ambitious Li recycling targets from electric vehicle (EV) Li-
Lithium ion batteries (LIBs) imposed by the European Union, it is imperative to develop innovative recycling processes at
Electric vehicles
an accelerated pace. Direct Lithium Extraction (DLE) methods have been developed to produce Li from brines.
Li-ion batteries
Recycling
Herein we assess the application of various DLE technologies to extract Li from recycling streams of EV LIBs.
Hydrometallurgy Technical aspects and suitable initial solute concentration ranges of several DLE methods namely solvent
Froth flotation extraction, ion-exchange resins, sorbents, membranes, and electrochemical ion pumping have been mapped.
After this, an optimum pre-treatment route of the EV LIB recycling process has been chosen by estimation of Li
recoveries and losses through different combinations of dry and wet crushing followed by froth flotation for
anode and cathode separation. Pyrolyzing the whole cells/modules followed by dry crushing and flotation was
found to be the most ideal process which can minimize Li losses during pre-treatment. Furthermore, the esti­
mation of concentrations, compositions, and volumes of streams for the downstream hydrometallurgical process
is done to identify Li-containing streams where DLE can be used, and suitable technologies have been high­
lighted. The incorporation of DLE has the potential to minimize Li losses in the recycling process. However,
various DLE methods may be required to recover Li in different steps, with nanofiltration and reverse osmosis,
selective ion-exchange resins, and solvent extraction being the most promising options.

1. Introduction production came from Australia (minerals), Chile 25 % (brines),

Argentina 13 % (brines), and China 6 % (brine and minerals) in 2021
Lithium-ion batteries (LIBs) are critical for decarbonizing the [4]. The uneven distribution of Li reserves deems it necessary to secure
mobility sector, serving as efficient green energy storage devices. This supply from secondary sources with spent EV LIBs as the major source.
has led to their rapid adoption in electric vehicles (EVs). The EV market The current global recycling rate of LIBs is estimated to be < 5 % [1,5].
is anticipated to expand to approximately 130 million vehicles world­ According to a recent European Commission report the EOL recycling
wide by 2030, coinciding with around 11 million tons of LIBs expected input rate (supply into production from EOL products only) of Li in 2023
to reach the end-of-life (EOL) [1]. This surge in demand for LIBs is was 0 % [6]. This is mainly attributed to low volumes of spent materials
projected to increase the demand for lithium (Li) from 0.5 to up to 3.2 and inefficient recycling processes. To mitigate this European Union
million tons from 2022 to 2040 [1,2], respectively, making supply from (EU) has enacted a new directive imposing Li recycling targets of 50 %
secondary sources (recycled materials) critical. Li reserves in the form of and 80 % in 2027 and 2031 from batteries, respectively, and a minimum
brines and minerals (spodumene, lepidolite, petalite, and amblygonite of 6 % recycled Li in new batteries by 2031 [7]. The ambitious recycling
[3]) are concentrated in a few countries namely Chile, Australia, China, targets call for accelerated development and up-scaling of recycling
and Argentina holding major reserves [2]. Around 52 % of primary Li processes. Thus, we investigate the application of Direct Lithium

* Corresponding author.
E-mail address: sulalit.bandyopadhyay@ntnu.no (S. Bandyopadhyay).

https://doi.org/10.1016/j.seppur.2024.131315
Received 30 September 2024; Received in revised form 13 December 2024; Accepted 25 December 2024
Available online 26 December 2024
1383-5866/© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
U. Saleem et al. Separation and Puri cation Technology 361 (2025) 131315

Extraction (DLE), used in primary Li production, to extract Li from environmental impact of conventional evaporative processes of Li pro­
recycling streams of LIBs to ease the burden on primary Li supply. duction from brines and compared them with DLE processes. They
Several studies have been published on Li extraction from primary suggested monitoring the environmental impact of both evaporative
resources using DLE, Table 1. Stringfellow et al. [8] discussed various processes and DLE-based technology, even though the latter consumes
DLE technologies in detail and presented their potential to recover Li less fresh water and other resources. Meng et al. discussed the conven­
from geothermal brines. They also urged for commercial scale testing for tional practices for Li recovery from brines, ores, and LIBs [3]. Recently,
further development of processes. Vera et al. [9] evaluated the Farahbakhsh et al., [10] in their review, recommended employing DLE
for Li production from evaporation brines, brine pumping, and hard rock
ores. They also discussed the possibility of DLE application to recover Li
Table 1 from batteries, but the potential of different technologies available to
Overview of recent studies on DLE extract Li from the recycling stream of LIBs was not critically evaluated.
Focus area Brief summary Ref. Moreover, several DLE technologies have already been applied for Li
DLE Discussed the potential of different DLE [8] recovery from recycling streams but there is a need to critically assess
methods and materials to recover Li from and evaluate the available materials with respect to recycling streams
geothermal brines with possible which differ from brines in many aspects such as pH, composition,
improvements.
concentration, among others. Li brines are rich in magnesium, sodium,
DLE Evaluated the environmental impact of [9]
evaporative processes of Li production from calcium, and potassium with high salinity while the recycling streams
brines and compared them with DLE are dominated by nickel (Ni), manganese (Mn), cobalt (Co), iron (Fe),
processes. copper (Cu), aluminum (Al) etc. as the competing ions. By focusing
Production from Industrial Li production processes from ores, [3] solely on the recovery of Li from recycling streams of EV LIBs, this re­
different sources brines, and spent LIBs were reviewed. The
view can provide concise recommendations on materials and processes
production from LIBs was mainly focused on
commercial recycling processes. as well as identify materials that can potentially recover Li from such
DLE from brines Reviewed DLE technologies and [10] streams but have not been investigated as of now.
recommended employing DLE for Li In this study, the application of DLE to recover Li from EV LIBs
production from different sources. Briefly
recycling streams has been investigated. First, the DLE concept has been
discussed the possibility of DLE application to
recover Li from batteries. introduced followed by an extensive literature review of different pro­
DLE from geothermal Reviewed different DLE technologies with a [11] cesses and materials which have been critically evaluated on their lim­
brines focus on sorbents. itations to recover Li from the later devised EV LIBs recycling process.
Primary production Compared the impact of Li production from [12] Furthermore, different pre-treatment routes of a recycling process for
open pit mining, evaporation in ponds, and
spent EV LIBs have been explored with a focus on dry & wet crushing
DLE on water and society.
Extraction from salt Reviewed different technologies and advances [13] and froth flotation for graphite separation from black mass. The most
lake brines in Li production from salt lake brines. optimal pre-treatment route has been chosen by calculating Li recoveries
Production from Reviewed the established and emerging [14] and losses through their combinations. This is followed by the estima­
seawater, brines and technologies and identified the bottlenecks.
tion of concentration, composition, and volumes of streams throughout
lakes
Production from Briefly discussed Li production from ores. The [15]
the downstream hydrometallurgical recycling process. Finally, the
seawater and brines extraction from seawater and brines using optimal DLE materials and processes have been proposed to recover Li
different technologies was critically evaluated. from different streams of the devised recycling process. This study will
DLE from geothermal Reviewed different DLE technologies to find [16] give impetus for researchers and industries trying to optimize Li recy­
brines suitable candidates for extraction from
cling yields by recovery and valorization of Li from different waste/feed
geothermal brines in Indonesia.
DLE from salt lake Critically reviewed adsorbents for DLE from [17] streams and provide a basis for further investigation of the application
brines salt lake brines with a focus on structure, and development of DLE methods in LIB recycling.
extraction mechanisms, performance,
limitations, and challenges.
2. Direct lithium extraction (DLE)
DLE Reviewed the Li extraction from oilfield brines [18]
using metal oxide sorbents.
Extraction from salt Identified solvent extraction as an [19] Li recovery from brines is conventionally conducted by stepwise
lakes environmentally friendly technology and concentration and impurity removal by precipitation in solar evapora­
reviewed different extraction systems for Li tion ponds, the final product being a concentrated lithium chloride
extraction from salt lakes.
(LiCl) solution. Such a process is resource-intensive in water and reagent
Extraction from salt Different technologies to extract Li from high [20]
lake brines Mg2+ brines were reviewed. consumption (acids, bases, precipitating reagents, etc.), with a produc­
Extraction from brines Membrane-based technologies for Li [21] tion time of up to 2 years [8,9]. To mitigate the low concentration in
extraction from brines were reviewed. ponds DLE technologies (Fig. 1a) have been gaining interest in recent
Extraction from brines Application of nanofiltration membranes for Li [22] years. DLE processes employ different materials/mechanisms to selec­
extraction is critically reviewed and
commercial applications are also briefly
tively isolate Li from other ions present in the brine. Such processes can
discussed. rely on several mechanisms including solvent extraction, adsorption, ion
Extraction from brines Reviewed different electrochemical lithium [23] exchange, membrane or electrochemical processes, Fig. 1b-g [8,9]. The
ion pumping systems for Li recovery from preference of most commercial materials to bind di- and trivalent metal
primary sources.
ions over monovalent Li ions complicates this separation, highlighting
DLE Extraction from brines with a focus on [24]
sorbents and electrochemical methods. the need for specific chemistry and properties of materials. Herein we
DLE from battery • Critical review and evaluation of DLE This discuss the most promising processes and materials with a focus on
recycling streams technologies with a focus on the chemistry work selectivity, cycling performance, and limitations. Several reviews have
of LIB recycling streams been reported on DLE from brines [3,8–10], Table 1, but as the
• Estimation of concentration and
composition of Li containing streams in the
composition and concentration of LIB recycling streams are different
EV LIB recycling process compared to brines, an evaluation of their adaptability for specifically Li
• Recommendations to investigate different extraction from LIB recycling streams is needed.
DLE technologies and materials to extract Li
from such streams

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U. Saleem et al. Separation and Puri cation Technology 361 (2025) 131315

Fig. 1. Schematic of a) Direct lithium extraction (DLE) b) solvent extraction c) adsorption d) ion exchange e) nanofiltration f) reverse osmosis g) electrochemical ion
pumping process.

2.1. Solvent extraction removal of multivalent cations such as Ca2+ and Mg2+. Some of the
β-diketones investigated are benzoyl-1,1,1-trifluotoacetone (HBTA),
Solvent extraction is a mass transfer unit operation based on the thenoyltrifluoroacetone (TTA), 4,4,4 Trifluoro-1-phenyl-1,3-
distribution of solute between two phases which are immiscible with butanedione (TPB), dibenzoylmethane (HDBM), with neutral extrac­
each other (liquid–liquid extraction). The phase containing a species of tants such as tributyl phosphate (TBP), trioctyl phosphine oxide (TOPO),
interest with competing ions (usually aqueous) is mixed with the other in diluents such as kerosene, etc. [8,25–29]. Pranolo et al. [26] reported
phase (usually organic) which selectively extracts the species of interest. a commercial extractant system of 0.4 M LIX 54 (β-diketone
The extracted ions are stripped using an acid e.g., hydrochloric acid. derivative) + 0.2 M Cyanex 923 (trialkyl phosphine oxide) in ShellSol
Solvent extraction has been extensively studied for extracting Li from D70 achieving a Li+/Na+ separation factor of 1100–1500 at pH 11.
seawater and brines and we review the rigorously investigated solvents Furthermore, iron (III) chloride and TBP in kerosene has been reported
with possible industrial applications. to selectively extract Li from brines and LIB recycling streams at the
Synergistic solvent extraction of Li from brines with expense of high Cl- concentration > 6 mol/L [30–33]. Ji et al. [32] added
β-diketones + neutral extractants has been reported to selectively N, N − bis(2-ethylhexyl)-3-oxobutamide in TBP and FeCl3 extraction
extract Li+ over Na+ in alkaline pH 8–12 with the prerequisite of system for which they reported a separation factor of Li+ and Mg2+ of

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U. Saleem et al. Separation and Puri cation Technology 361 (2025) 131315

450. Wesselborg et al. [30] succeeded in extracting Li over Ni and Co minimize the need for post Li up-concentration processes as a high
using 80 % TBP + 20 % kerosene with Fe3+/Li+ ratio of 1.3 achieving concentration of Li can be achieved during elution by controlling the
separation factor of Li+ over Ni and Co of 2825 and 854, respectively, in amount of concentrated acid.
acidic pH. This confirmed the selectivity of solvent towards Li+ in the
presence of multivalent cations. However, the use of concentrated 2.2.2. Inorganic sorbents
acid ~ 6 mol/L HCl during stripping to prevent Fe loss from the organic Sorption based DLE encompasses materials that can either exhibit
phase is a major challenge to overcome for FeCl3/TBP solvent system adsorption or ion exchange properties for Li extraction. In adsorption
[30,34]. Recently, crown ethers have been gaining interest in extracting processes, solute is intercalated onto the surface of an adsorbent from an
Li, but they are still limited to lab-scale studies due to complex synthesis aqueous solution which is eluted with fresh water e.g., aluminum-based
processes and low extraction efficiencies [8,25,35–38]. Some other sorbents[10,11], Fig. 1c. While in ion exchange, an insoluble solid ma­
solvent systems and ionic liquids have also been reported to extract Li terial exchanges cation or anion with the species of interest in aqueous
from different streams, but these are still in the early stages of devel­ solution e.g. manganese and titanium based sorbents [10,11], Fig. 1d.
opment [32,39–43]. Table S1 in supplementary information (SI) sum­ Inorganic crystalline solids, e.g. various aluminum hydroxides (AlOH),
marizes the different solvent extraction publications to extract Li, aluminum oxides (AlOx), lithium manganese oxides (LMO), lithium ti­
including information about feed stream composition, separation effi­ tanium oxides (LTO), lithium iron phosphate (LFP) are proven to be
ciency and selectivity. selective Li sorbents, among others [8,11].

2.2. Ion exchange resins and inorganic sorbents (ion exchange and 2.2.2.1. Al-based. Aluminum hydroxides are generally used as Li se­
adsorption) lective sorbents with lithium aluminum layered double hydroxides (Li-
Al-LDH) as the most promising material [10,55]. Li-Al-LDH can be
The following section discusses ion exchange resins and inorganic represented by the general formula LiX.2Al(OH)3⋅nH2O, Fig. 2a,
sorbents in detail. The relevant literature is also summarized in Table S2. where X is an anion e.g. Cl- and n represent the number of H2O [56].
They have octahedral voids between a two-dimensional aluminum hy­
2.2.1. Ion exchange resins droxide layer where Li is intercalated, also responsible for their selec­
Ion exchange resins generally consist of specific functional groups tivity, with anion e.g., Cl- adsorbed simultaneously for charge neutrality
stabilized in a polymer matrix and were investigated for Li recovery [56]. Although their adsorption capacity is lower (typically < 10 mg/g)
from seawater as early as 1970 [8,44]. The cationic resins have compared to Mn, Ti, and Fe type sorbents they have achieved technology
exchangeable cations replaced with Li ions during loading. However, it readiness level (TRL) of 9 mainly due to their excellent cycling perfor­
has been reported that most commercial organic ion-exchange resins mance and reagent friendly process as they can be eluted and regener­
lose their selectivity towards Li+ in the presence of competing cations ated with only water [10,56–58]. The sorbent tends to dissolve below
(Na+, K+, Mg2+, Ca2+, among others) due to the higher affinity of resins pH 6 and can be eluted with fresh water thus negating the dissolution
towards them [8,44,45]. Arroyo et al. [45] investigated Li extraction which is prominent in case of elution with acids [57]. The dissolution
from a LiCl solution and real brine sample using three commercial ion loss of LDH in low pH rules them out for capturing Li from acidic waste
exchangers namely Lewatit K2629 (sulfonic, H+ form), TP 207 streams. Al-based sorbents have been reported to efficiently reduce
(chelating, iminodiacetic acid, Na+ form) and TP 208 (Na+ form) which Mg2+/Li+ ratio of 284–301.58 in the Qarhan Salt Lake brine to 0.4–0.43
were eluted with 4 M HCl. They reported > 95 % retention from solu­ with an adsorption capacity of 6–7.26 mg/g [58,59]. However, Li-Al-
tions containing only Li+ for all the resins but it decreased considerably LDH sorbents need high salinity, optimum temperature (typically
in the real brine samples [45]. In another report, 30 commercial ion 45–95 ◦ C), and a minimum Li concentration of 100 mg/L for effective
exchange resins were tested to extract Li from LiCl solution with only adsorption [55]. Another Al-based Li adsorption process is the precipi­
sulfonate, iminodiacetate, and aminomethylphosphonate resins suc­ tation of aluminum hydroxide (Al(OH)3) on which Li is adsorbed [56].
cessfully extracting Li but the selectivity was poor when tested in a This is achieved by adding an aluminum salt such as aluminum chloride
synthetic brine feed solution [44]. Therefore, ion exchange resins must to the brine and adjusting the pH with an alkali which results in the
be altered to improve their selectivity. This is possible by imprinting precipitation of aluminum hydroxide containing an appreciable amount
them with Li selective sorbents also called ion imprinted polymers (IIP). of adsorbed Li. However, such sorbents need acids during the elution
The selectivity in IIPs mainly arises from the generation of specific Li process [60,61].
containing sites during the imprinting process from which Li is eluted
with a dilute acid before application in brines [8,46]. A Li imprinted 2.2.2.2. Lmos. In addition to being used as cathode material in LIBs,
polymer using crown ether have been reported to achieve Li+ selectivity LMOs are gaining interest as sorbents to capture Li due to their selec­
of 50.88 and 42.38 over Na+ and K+, respectively [47]. In another report tivity and sorption capacity. They act as ion sieves which is related to the
week acid cation exchange resins with carboxyl, carbonyl, phosphorus memory effect, prohibiting entry of other ions in hydrated or dehydrated
oxygen double bonds and sulfur oxygen double bonds have been forms, with Li+/H+ occupying the tetrahedral sites of spinel-type LMOs
demonstrated to efficiently isolate Li achieving high concentration of Li while Mn occupies octahedral [62,63]. While the Li sorption mechanism
(up to 29 g/L) after elution by controlling the amount of acid [48,49]. is still debatable, it is proposed to be an ion exchange between Li+ and
Furthermore, ion sieve type resins maintained more than 80 % selec­ H+ or a redox reaction (under acidic conditions) where Mn III is reduced
tivity for Li in high Mg2+/Li+ brines for 500 cycles [50]. However, the to soluble Mn II leaving sites for Li intercalation or a combination of both
preparation of IIP is usually complex and complicated [51]. An alternate (composite) [10,56,63]. The loss of sorbent material occurs during
simple way to improve the selectivity is to impregnate the resins with Li elution with acids due to the reduction of Mn to Mn II species which can
selective extractants. During this process the extractant is adsorbed onto be dissolved into the eluate. The theoretical sorption capacities of three
the porous structure of the resin materials which is called solvent LMO sorbents namely LiMn2O4, Li1.33Mn1.67O4 and Li1.6Mn1.6O4 are
impregnated resin (SIR) [51,52]. A β-diketone and trioctylphosphine 39.9, 59.5, and 72.8 mg/g, respectively, Fig. 2b-c [56,62]. The theo­
oxide impregnated resin has been reported to efficiently isolate Li+ over retical sorption capacity increases with increasing Li/Mn ratio and de­
Na+ and K+ which was eluted with 1 M HCl [53,54]. The SIRs suffer pends on the crystal structure of spinels. Granulation of sorbent is done
from poor cycling as the extractant tends to be lost from the porous for continuous operation on a commercial scale which usually results in
support over extended use needing further stabilization [51]. Summa­ a decrease of uptake. Chitosan granulated Li1.33Mn1.67O4 exhibited Li
rizing, ion exchange resin can be a promising technology if the resin uptake of 8.98 – 11.4 mg/g from seawater containing 25–––30 mg/L of
properties are modified to improve Li selectivity. They can also

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Fig. 2. Structure of different metal-based sorbents a) LiAl − LDH, b-c) LMO, d-e) LTO, f) LFP, where gray, green, yellow, blue, orange, violet, red and white spheres
represent the Li, Al, Ti, Mn, Fe, P, O and H atoms, respectively,
reproduced with permission from [17].

Li in ~ 24––72 hrs at pH ~ 12 reaching extraction efficiencies of > 90 % composite already explained for LMOs previously [10]. In general,
[64,65]. The adsorption uptakes observed are significantly less than the research shows LTOs have at least the same efficiency as LMOs regarding
theoretical capacity of the sorbent. This can be attributed to the low the sorption of Li ions from aqueous solution however kinetics are
initial concentration of Li with sorption uptake increasing to 54.65 mg/g comparatively slower [8]. Even though LTOs have already been tested at
with an initial Li concentration of 360 mg/L within 72 hrs [66]. The a lab scale more research is needed to commercialize them.
dissolution of active material from chitosan granulated sorbent was
reduced to 9.2 % after three cycles during acid treatment [66] and the 2.2.2.4. Lfps. LFP is one of the most commercialized cathode materials
selectivity factor of Li+ over Na+, K+ and Ca2+ reached ~ 70, 51, and 87, for EV LIBs alongside NMC cathodes [75]. They have also been
respectively [64]. In addition to chitosan, other types of materials are employed to capture Li from brines as a sorbent. Olivine LFP sorbents,
also used for granulation/foaming [67–69]. However, the major chal­ Fig. 2f, can capture Li by a redox reaction involving oxidation producing
lenge with LMOs remains the dissolution as Mn II and slow kinetics heterosite iron phosphate which then reversibly captures Li ions when
prohibiting its commercial application. reduced [11,44,76]. The process uses oxidation and reducing agents,
which can increase the cost, but they benefit from better kinetics and
2.2.2.3. Ltos. LTO sorbents are gaining interest due to their improved selectivity over other inorganic sorbents. High sorption capacities
stability over LMO and eco-friendliness [20]. Similar to LMOs their of ~ 46 mg/g is reported with the extraction of Na+, K+ and Mg2+ less
selectivity arises from the memory effect in the structure which allows than 4 mg/g, Li+/Na+ selectivity factor of 2541 and fast equilibrium
the de-/insertion of Li ions while rejecting others due to varying ionic time of 1.5–3 hrs [44,76]. However, iron dissolution becomes signifi­
radius or dehydration energy (steric hindrance) [10,56,63]. LTO sor­ cant, up to 20 %, during sorption in acidic conditions at pH 4 [44].
bents can have a spinel or layered structure depending on the type of Xiaong et al. [77] reported exceptional selectivity of Li+ over Na+, K+
precursors i.e., Li4Ti5O12 and Li2TiO3, respectively, (Fig. 2d-e) with the and Mg2+ of 8704, 2460 and 6864, respectively, with an uptake of
former having better cycling performance and the latter has improved 9.13 mg/g in 20 mins, reaching 90 % extraction. The low uptake of Li
selectivity for Li+ over Mg2+ reaching 4783 with 36.3 mg/g capacity could be attributed to the low initial concentration which was 0.1 g/L
[56,63,70,71]. В-Li2TiO3 has been reported to possess a high theoretical [77] and a high Na+ concentration of 82.34 g/L. The Li concentration is
capacity of 142.9 mg/g of which 76.7 mg/g was achieved experimen­ much lower compared to others [44]. LFPs have also been applied in
tally from a LiOH solution containing 2 g/L Li+ [72]. Spinel Li4Ti5O12 electrochemical cells to selectively capture Li. However, more research
nanotubes showed even higher practical adsorption uptake of 160.6 mg/ is needed to explore suitable reagents and continuous operation to
g in 24hrs from a LiCl solution with 2000 mg/L Li+. The high uptake was commercialize them.
attributed to the significantly higher surface area of nanotubes e.g.,
115.4 m2/g [73]. The uptake decrease/vary considerably in the pres­
2.3. Membranes
ence of competing ions when sorbent is granulated (reduced sorption
sites on the surface) with low initial Li concentration and the process of
Membranes are barriers that allow the transport of certain species
production of sorbent. For example, the separation factor of Li+ over
from one fluid to another across them. They benefit from their modular
Na+, K+ and Ca2+ of ~ 297, 521 and 273, respectively, was achieved
design, ease of integration, and environmentally friendly process due to
with an uptake of 12.84 mg/g at 328.15 K in 12hrs employing Li2TiO3
less use of reagents during operation. However, membrane technologies
granulated using polyvinyl chloride with 25 mg/L initial Li [74]. The Li
having TRL above 7 are mostly used for DLE pre- or post-treatment. The
sorption mechanism is attributed to ion exchange, redox reaction, and
dominant membrane technologies are nano, micro, and ultrafiltration

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U. Saleem et al. Separation and Puri cation Technology 361 (2025) 131315

[10]. Nanofiltration (NF) membranes allow monovalent ions to pass which travel across respective ion-selective membranes, under an elec­
while prohibiting the flow of multivalent. This can be used to separate tric field. Recently, selective electrodialysis has shown improved sepa­
Li+ over divalent ions such as Mg2+ and Ca2+ but the separation of ration of Li+/Mg2+ due to the incorporation of a monovalent selective
monovalent ions such as Na+ and K+ needs further processing ion exchange membrane [86,88–90]. In summary, a combination of
[8,78–81]. The mass transfer through NF membranes is governed by several membrane technologies might be necessary for complete DLE
Donnan exclusion, steric hindrance, and dielectric exclusion [10,80,82]. applications, with membrane fouling and energy consumption being the
The dilution of bines might become necessary in case of high salinity to major challenges to overcome [78,91,92]. The membrane processes for
reduce osmotic pressure [11,78,82]. Reverse osmosis (and pervapora­ DLE applications are summarized in Table S3 including membrane
tion) is not considered a DLE method, but it is highly effective in up- types, feed stream composition, selectivity, performance, and cycles.
concentrating a Li+ solution or rejecting water. Even though reverse
osmosis is an energy-intensive process, it offers higher water recovery
2.4. Electrochemical lithium-ion pumping (ELIP)
efficiency, more flexibility, reduced time consumption, and a smaller
footprint than other methods e.g., evaporation in ponds [8,83]. Mem­
ELIPs comprise an external electric field, Li selective electrode
brane technologies that can be regarded as viable DLE options, such as
(sorbents such as LMO and LFP), and often an ion-exchange membrane.
supported liquid membranes (SLM), ion imprinted membranes, ion-
During the extraction process, a certain external voltage is applied, and
selective membranes, etc., are in an early stage of development [10].
Li and counter anion in the feed are captured by the respective positive
SLM is a promising technology employing a membrane suspended in a
and negative electrodes, Fig. 1g. These ions are released when voltage is
hydrophobic Li selective organic solvent, which separates the aqueous
reversed in the recovery solution, thus generating the electrode material
feed and strip solutions, achieving Li+/Na+ separation factor of ~ 400
for the next cycle [23,93]. ELIPs can generally be divided into five
[25,84]. However, several challenges, such as solvent degradation,
electrochemical systems, namely: (1) water split (Fig. 3a) where an
leakage, and stability, need further exploration. Ion imprinted mem­
active electrode captures/releases Li+ with a water split reaction on the
branes incorporate adsorbing units such as crown ethers (e.g., 12C4)
counter electrode, (2) salt capturing (Fig. 3b) which captures/releases
along with functional monomer and crosslinking agents during the
Li+ and anion (e.g. Cl-) on respective electrodes without water splitting
polymerization process for better selectivity performance
reaction, (3) rocking chair (Fig. 3c) which involves reciprocating mo­
[36,38,85–87]. Electrodialysis processes separate cations and anions
tion of Li+ between electrodes divided by an anion exchange membrane,

Fig. 3. Principles of different ELIPs battery system a) water split, b) salt capturing, c) rocking chair, d) capacitive deionization system, e and f), ion exchange.
reprinted with permission from [23].

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U. Saleem et al. Separation and Puri cation Technology 361 (2025) 131315

(4) membrane capacitive deionization system (Fig. 3d) incorporates Table 2

Li intercalation in selective electrode with a cation exchange membrane Overview of different DLEs (the limitations and improvements needed for ma­
while anion passes through anion exchange membrane and captured, terials is summarized in the respective subsections)
and finally (5) ion exchange (Fig. 3e-f) involving replacement of Li+ in Process Pros Cons
the solution with ions from counter electrodes of similar electric charge Solvent extraction • Effective to separate Li • Not recommended when
e.g. Zn2+ [23,93]. The Li selective electrodes are made from conven­ (β-diketones + and Na divalent ions exist in
tional cathode materials such as LMO and LFP, sometimes doped to Neutral extractants) • Can be recycled solution
improve performance [94–99]. Jang et al. utilized an LMO electrode for • Can be used to up- • High capital and
concentrate Li, working operational cost
the first time to capture Li from the industrial LIB leachate of pH 2.1,
pH 8-12, extraction • Complex operation
achieving a separation factor of Li/Ni of approximately 90 [100]. time <30 mins
Although ELIP has already been demonstrated at a pilot scale, achieving Ion exchange resins • Cleanliness of process • Long(er) time spans for
product purity of 88 % [101] they are still at a very early stage of • More environmental reaching equilibrium
development often requiring a high amount of electrolyte (TRL 3–4) friendly (less energy • Poor selectivity of Li over
consumption compared di-trivalent cations
[9,10]. Future research should be focused on standardized protocols and to membranes) • High energy cost for
operating conditions. Some of the relevant literature reports exploring • Can up-concentrate Li recovering material
ELIPs have been summarized in Table S4. using acids during • Need chemical treatment
elution for recovery
• Good cyclic
2.5. Technological mapping of DLEs
performance
Inorganic sorbents • High separation • Long(er) time spans for
The literature presented about the DLE methods in the aforemen­ (LMO, LTO, LFP) efficiency reaching equilibrium
tioned sections is condensed in a high-level overview in Table 2. The • High selectivity and • Depended on good
recovery preparation. Influences
shortlisted DLE methods with the most efficient materials/technologies
• High product quality the degree of crystallinity
have also been presented. In addition, several companies/industries • Cleanliness of process and regeneration ability
offering DLE technology/materials are summarized in Table S5. • Can be used in streams • Loss of active material
Furthermore, an attempt has been made to combine all the gathered with low(er) Li (more the smaller the
information to visualize and compare the strengths and weaknesses of concentration sorbent)
• More environmental • Need chemical treatment
the different DLE methods on nine parameters, shown in Fig. 4 (superior
friendly (less energy for recovery
performance away from the center). These parameters have been chosen consumption compared • Often low or unknown
by extensively reviewing the literature presented in previous sections to membranes) durability/recyclability
and SI Table S1--4 and the mapping has been done accordingly. How­ • Different forms, mainly
ever, it must be mentioned that, besides having significant objective powder at beginning
Membranes • High separation • Very low selectivity
indicators of the categories, summarizing and generalizing one DLE (Nanofiltration, efficiency between monovalent
method is hard by itself due to them being also dependent on other reverse osmosis) • High selectivity for cations
parameters (e.g. feed solution, different planned recycling steps and divalent cations • Membrane fouling
others). Therefore, there is a certain portion of subjective views included • Modular design -> • Often chemical reagent
promising for large- needed for desorption
in the categorization by the authors. The parameters include the cost of
scale applications • High investment and
material, Li extraction/sorption efficiency, kinetics, recyclability or cy­ • Preprocessing step used operating costs
clic stability, ease of integration into an existing process, technical for the feed stream • Leakage of inorganic
maturity, Li+/Na+ selectivity, energy consumption, and environmental • Relatively eco-friendly particles possible for
impact (CO2 footprint, water consumption, land use, waste generation, operation (low some
footprint) • Efficiency and selectivity
etc.). In the following, the strengths, and drawbacks of all DLE methods can go down after few
are explained concisely. cycles
Solvents (Fig. 4a): They show fast kinetics and a high selectivity Electrochemical(Ion • Low to no amount of • Electrochemical processes
between monovalent ions, which is very important to separate Li+ and pumping) chemicals/chemical need to operate under a
waste (strong acids) current flow, high energy
Na+. This, combined with their well-established technical maturity,
• High Li removal consumption
makes them efficient as many commercial solvents are available. How­ capacities • Very often information
ever, the cost of material and lower rates of recyclability, compared to • High efficiency like removal, recovery,
ion exchange resins and sorbents, could make them not so ideal from an • Flexible operation uptake, duration,
economic and environmental point of view, Table S1. modes = better control selectivity, energy
of Li production rates consumption and/or
Ion-exchange resins (Fig. 4b): Ion-exchange resins, together with purity of the final solution
inorganic sorbents, have the highest form of technical maturity and not (completely) given in
there are already resins available for commercial use on the market. most studies
Selectivity between monovalent ions is a little worse than for solvents,
but, depending on the material and Li concentration in the solution, they
multivalent ions, and poor recyclability (dissolution of active material
are reported to work well. However, the selectivity in the presence of di-
occurs during elution). They can be used to extract Li from low-
trivalent ions is poor. Kinetics are generally slower, leading to lower
concentration feed solutions, Table S2.
efficiency. However, recyclability is higher as well as the cost of material
Membranes (Fig. 4d): NF and reverse osmosis are mapped here
and energy consumption is lower, which makes them more environ­
(cannot be considered as DLE methods). They are easy to integrate into a
mentally and economically friendly, Table S2.
process because very often they are already delivered as finished mod­
Inorganic sorbents (Fig. 4c): Aluminum based sorbents with physical
ules or module packs. Also, they show fast kinetics and even though the
adsorption as the mechanism are not mapped here due to the need of
costs of material and energy consumption are relatively high, they are
high salinity for their application. Since LIBs recycling streams generally
often considered environmentally friendly as during operation no
have low salinity compared to brines, explained earlier, that’s why they
chemicals are needed. The main challenge is their cyclability (fouling,
have been omitted here. Other inorganic sorbents show somewhat
clogging) and their low selectivity between monovalent ions (NF),
similar characteristics to ion-exchangers resins, just mainly a tradeoff
which makes them inefficient for such feeds. Although, they could be
between cost of material, better Li selectivity in the presence of

7
U. Saleem et al. Separation and Puri cation Technology 361 (2025) 131315

Fig. 4. Technological mapping of different DLE methods a) solvent extraction b) ion exchange resins c) inorganic sorbents d) membranes and c) ELIPs.

used efficiently for up-concentrating Li or rejecting water, Table S3. Since several DLE methods can be used to extract Li from a certain
Electrochemical ion pumping (Fig. 4e): These methods are very se­ stream it is vital to identify the most optimal choice regarding the ease of
lective between monovalent ions. Most systems are relatively robust and process operation. The recommendations based on the initial Li con­
operate stably over several cycles, which makes them efficient for bat­ centration in the feed solution are presented in Fig. 5 and are based on
tery recycling processes in that regard. Also, the cost of the material is the reported literature, Table S1-4. Fig. 5 shows the most suitable ranges
low due to the longevity of the material and little to no use of chemicals for different DLE methods for efficient operation. These recommenda­
during the ELIP process, but water consumption can be high [9]. tions fall under the category of Principle 4 which is Maximize Mass,
Furthermore, they can be energy intensive as one study reported ~ 300 Energy, space, and Time Efficiency from The Twelve Principles of
folds more energy demand to only pump the solutions through cells Circular Hydrometallurgy, and are adapted to our process by keeping
compared to reactions [9], which makes them worse from an economic the fundamentals same as suggested by Kentish et al., and Binnemans
point of view. The TRL levels of ELIPs being a relatively new method is et al., [102,103]. It should be mentioned here that all these processes
low and therefore ease of integration is low or unknown, Table S4. can be and have been used outside their recommended range of initial

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U. Saleem et al. Separation and Puri cation Technology 361 (2025) 131315

oxide (NMC), and others), anode (graphite, and others), electrolyte

(lithium hexafluorophosphate (LiPF6) in carbonate-based solvents,
etc.,), separator (polypropylene, and others), and current collectors (Al
or Cu metal). The cathode and anode further contain conductive addi­
tives (carbon black, and others) and binders (polyvinylidene fluoride
(PVDF) etc.,). The battery cells are packed in modules which are further
assembled to form a battery pack. After reaching the end of life a battery
pack needs to be discharged, dismantled, crushed, and sorted to get a
powder called black mass (BM). The process adopted to produce BM
influences downstream hydrometallurgical processing to recover metal
values and is explained here [106–108].

3.1. Discharging and dismantling

The first step in the recycling process is discharging the spent EV

battery packs either by connecting it to a load, chemical discharge e.g.,
in a NaCl solution, or by cryogenic freezing [106]. Residual charge in the
Fig. 5. Suitable initial Li concentration range of different DLEs.
batteries is a potential safety hazard which deems it necessary to
discharge them efficiently [106]. The next step is the dismantling of
solute concentrations. Generally, solvent extraction is preferred when
battery packs to recover casings, plastics, and cables. This could be done
the solute concentration is high in the feed stream, and this can also be
up to module or cell level depending on the process flowsheet.
verified by some of the studies that reported the use of this process for Li
Dismantling is typically done manually because of the different shapes
extraction [26–28,30,104]. This technology is not recommended when
and sizes of battery packs from different manufacturers containing cy­
the solute concentration is low because of high aqueous/organic phase
lindrical, prismatic, and pouch cells among others [106].
ratios leading to loss of the organic phase due to entrainment [102,103].
Ion exchange resins and inorganic sorbents are used when the solute
3.2. Crushing and sorting
concentration is low. We have recommended a higher operational range
for ion-exchange resins [44,45,48,49] compared to sorbents (~500 mg/
The next step is crushing and sorting of batteries. Crushing can be
L [44,57,58,60,61,64–66,74]) as the former can be easily packed in the
done in an inert atmosphere known as dry crushing or in a brine solution
columns. This can also be true for inorganic sorbents when granulated
called wet crushing, Fig. 6 [109].
with an organic backbone, considerably increasing the volume of sor­
bent increasing equipment sizes and decreasing uptake. Furthermore,
3.2.1. Dry crushing
inorganic sorbents are susceptible to leakage during elution with acids
In dry crushing battery cells or modules are broken up into individual
which makes them less favorable to use at higher solute concentrations.
fractions. The electrodes are freed from the current collector foils. The
In such feed solutions the desirable case would be to get a higher con­
electrolyte solvents are removed in a drying step which may use vacuum
centration of Li after elution using concentrated acids which can be
and heat. The electrolyte Li salts remain with the solid fractions. The dry
obtained using ion-exchange resins and solvent extraction processes
fragments are easy to handle during the recycling process. An overview
thus minimizing the use of post up-concentration processes
of a typical industrial pretreatment process based on dry crushing to
[26–28,30,48,104]. The membrane technology recommended here is
produce BM is shown in Fig. 7. After discharging, dismantling, crushing,
reverse osmosis and nanofiltration (only to separate monovalent and
and drying a first air classification is carried out in a zig-zag-sifler which
divalent ions). They are recommended to be used when the solute
separates the particles based on their density concentrating Al 74.3 %,
concentration is very low to up-concentrate and pretreatment of feed
steel 13.8 %, copper 5 %, among others, in the light fraction while
streams in terms of separating multivalent ions [78,81–83]. Electro­
electrode particles are recovered in heavy products. This is followed by
chemical ion pumping is an emerging technology, and distinct condi­
the sieving of particles after a second crushing step and 97 % BM
tions need to be evaluated in future research. However, based on
(cathode active material (CAM) and graphite) are collected with particle
existing literature, a favorable solute concentration range is recom­
sizes below 500 µm. Finally, a second air classification is carried out to
mended [94,96–99]. This range can also be broad but in those cases, it
concentrate 97.8 % of the separator in the light fraction while Cu and Al
would need to outcompete more mature technologies such as solvent
are recovered in the heavy product. The BM obtained is further pro­
extraction. To summarize, a suitable choice of DLE method can offer fast
cessed by hydro or pyrometallurgical methods or their combination
kinetics, high extraction capacities, less process complications,
[106]. The Li loss in such a process occurs during the loss of electrode
improved economy (capital and operational), and efficient plant
material in different fractions which can amount to 10–14 % [110] and
operation.
Li deposited and penetrated in the separator.
The insights gained after mapping technological aspects and suitable
Zhang et al. [110] further optimized the dry crushing of LIB cells by
initial concentration of Li for different DLE methods allow us to inves­
pyrolysis treatment of electrode scraps at 500 ◦ C followed by crushing
tigate their potential to recover Li from recycling streams. To do that it is
and reported shorter crushing times with effective liberation of elec­
essential to know the composition and concentration of such streams. In
trode particles from the current collector foils. They reported a signifi­
the following section, we identify the Li flow through the pre-treatment
cant decrease in crushing loss of ~ 10 % for Ni, Mn, Co, and Li for
process of recycling EV LIBs and the downstream hydrometallurgical
pyrolytic electrode scrap compared to raw electrode sheets. This
process from which Li is finally recovered.
decrease in crushing loss is attributed to the removal of binder which is
burned off at an optimum temperature of ~ 500 ◦ C aiding in the liber­
3. Recycling routes to recover Li from EV LIBs
ation of electrode particles from the collector foils.
EV LIBs are discarded when they reach around 80 % of the state of
3.2.2. Wet crushing
health [105]. These LIBs may find other applications e.g., stationary
In this type of crushing whole battery pack, module, or individual
energy storage in power plants, and eventually need to be recycled. A
cells are crushed in an aqueous or brine solution which can dissipate
typical LIB cell consists of the cathode (lithium nickel manganese cobalt
heat due to salt acting as a conducting medium. Since the whole feed

9
U. Saleem et al. Separation and Puri cation Technology 361 (2025) 131315

Fig. 6. Pre-treatment routes of recycling EV LIBs.

Fig. 7. An example of industrial pre-treatment process of BM production from EV LIBs, reprinted with permission from [106].

material is submerged potential fire hazards can be avoided due to a

reduced supply of oxygen. Furthermore, the dissolution of LiPF6 can
form aqueous HF which can be converted into insoluble products such as
calcium fluoride if the crushing is done in a calcium hydroxide solution
[111]. However, this process generates an aqueous stream containing Li
which then needs to be treated [109]. Li from the electrolyte can
dissolve according to reaction (1) [106]. Furthermore, some dead Li
deposited and penetrated in the separator (~18 µg/mg of separator
[112]), and anode (~16 % [113,114]) can also be dissolved and needs to
be recovered. If a basis of 2 m3 brine/m3 [111] feed of LIBs is considered
and wet crush a 25 kg [107] module of dimensions 79 mm * 302 mm *
665 mm [107] comprised of cylindrical cells with the composition
shown in Fig. 8 the water required is calculated to be 31.73 L. The
calculated concentration of Li in crushing water can amount to 3.5 g/L
(Appendix S1 in SI): where 0.36 g/L Li+ arises from the dissolution of
electrolyte i.e., 1 M LiPF6 (density 1.27 g/mL in ethylene carbonate),
2.64 g/L Li+ from anode considering 16 % Li (basis [113,114]) is
deposited and penetrated, and 0.50 g/L Li+ from separator ((basis 18 µg/
mg [112]) which otherwise will be lost in dry crushing (Fig. 7)
amounting to 3 % (calculated) of the total Li in the module.
On the other hand, wet crushing makes the separation of materials
difficult as they stick together, extensive cleaning of equipment is
required and more impurities concentrate in the BM due to the scouring
effect of water [109]. Zhang et al [109] compared dry and wet crushing
Fig. 8. Composition of a typical NMC 111 module, reprinted with permission
and concluded that for selective crushing characteristics dry crushing from [106].
should be preferred.
LiPF6 + H2 O = LiF + 2HF + POF3 (1)

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U. Saleem et al. Separation and Puri cation Technology 361 (2025) 131315

particles from the collector foils, and the resulting BM could be suitable
3.3. Froth flotation for flotation. To verify this, the Li recovery and loss based on different
combinations of pre-treatment options of dry and wet crushing & sorting
The BM produced after crushing and sorting can be subjected to froth (C&S) followed by froth flotation has been calculated with reference to
flotation to separate graphite and CAM. This process separates particles Li content in an NMC 111 module (25 kg [107]) of the composition
by their surface wettability. Air is bubbled through a flotation cell which shown in Fig. 8. Four process routes have been considered and the re­
causes the hydrophobic graphite particles to attach and rise to the top as sults are displayed in Fig. 9 while the calculations are shown in Ap­
froth. Meanwhile, hydrophilic metal oxides from the cathode are pendix S2 in SI.
collected from the tailings at the bottom, Fig. 6 [113,115–118]. In a
study by Yu et al. [115], cathode and anode sheets from LCO-type bat­ • Process 1: Dry C&S followed by flotation
teries were crushed, sieved to 0.074 mm, and subjected to grinding • Process 2: Wet C&S followed by flotation
flotation. Electrode materials were grinded to improve the hydropho­ • Process 3: Pyrolysis of whole module followed by dry C&S and
bicity of particles by removing the coating of binder and other organics. flotation
They reported 97.19 % and 82.57 % of grade and recovery rates of • Process 4: Wet C&S followed by pyrolysis of the BM and flotation
49.32 % and 73.56 % of LCO and graphite, respectively. However, sig­
nificant electrode material loss occurred due to incomplete removal of The Li loss in dry C&S (Process 1) was calculated based on the
organic coatings. findings of Zhang et al. [110] who compared the metal loss during C&S
Salces et al. [113] proposed a thermal treatment before the flotation of pyrolyzed and unpyrolyzed electrode material and reported around
process to simultaneously recover Li and graphite. The thermal treat­ 2 % and 9 % loss of Li in fraction < 200 µm. Thus, by calculation the total
ment burns off the binder coating and improves the recovery and loss during C&S in process 1 amounts to 12 % of which 9 % is lost in
product grades in flotation. The LIB cells were pyrolyzed at 500 ◦ C for coarse fractions and 3 % lost in separator (deposited and penetrated Li)
1hr in N2 atmosphere followed by shredding and sieving and underwent calculated in the section on wet crushing. The flotation of such BM is
flotation at 8 wt% pulp density. The concentration of Li after 1st, 2nd, challenging because of the organics coating on the electrode materials
and 3rd cycle of water reuse was around 1100 mg/L, 2020 mg/L, and during C&S. The material separation efficiency in this step has been
2600 mg/L which corresponded to 45 %, 43 %, and 25 %, respectively, based on the findings of Yu et al. [115] who employed grinding flotation
recovery of Li. There was no appreciable increase in Li concentration to increase the hydrophobicity of particles by removing the organics
after 3rd cycle likely due to saturation of the solution with respect to Li. coating. To achieve higher grade and recovery rate of electrode material
The source of Li was related to the carbothermic reduction of metal they employed two flotation steps and reported 49.32 % and 73.56 %
oxide during pyrolysis, Li from the anode, and leftover Li from the recovery rate of graphite and cathode material, respectively. The re­
electrolyte. The main impurity incorporated in the solution was Al covery rate of cathode material could be higher because of two flotation
which reached a maximum concentration of 70 mg/L after 3rd cycle. steps. For the sake of simplicity and to reduce the number of streams we
The increased concentration of ions can negatively affect the flotation have considered only one flotation step in our calculations and the
process due to increased water viscosity, reduced froth stability, water separation efficiency between electrode materials has been kept at 50 %
drainage, and recovery by water entrainment. However, they suggested and pulp density of 40 g/L in flotation as reported by Yu et al [115]. The
that the graphite recovery (85 %) and grade (75 %) were reduced by results in process 1 indicate that from 88 % Li, after flotation around
only 1–2 % in the case of Li-rich water rendering it not significant. 14 % is dissolved in flotation water (calculated from own water leaching
Verdugo et al. [116] further investigated the effect of Li-ion on data reported by Saleem et al. [119] for unpyrolysed BM), 37 % is
flotation process. They performed a case study where froth flotation of recovered in tailings which can be further processed by hydrometal­
roasted BM (case 1) and water washing the BM before flotation (case 2) lurgical process and 37 % is lost in froth. The Li in froth can also be
were investigated. They studied pure NMC cathode, a semi-synthetic recovered by acid leaching or a second flotation step but this will in­
mixture mimicking a liberated LIB cell, and BM from spent LIBs. The crease the cost, and the poor flotation separation efficiency builds a
Li concentration in water for different feed materials was reported. Li stronger case against flotation of this type of BM. The maximum Li
concentration in the case of spent mixed BM was 2572.82 mg/L and recovered during process 1 could go up to 51 % (there could be addi­
when this BM was washed prior to flotation the concentration reduced to tional losses in the downstream processing) while around 49 % is lost
648.83 mg/L which also indicates that solution reaches saturation with which is attributed to C&S and loss in the froth. Thus, the combination of
regards to Li during the 1st washing. The separation efficiency in processing steps in process 1 can lead to significant losses if such a BM is
flotation experiments between electrode materials was higher in the subjected to flotation.
case of spent-mixed washed BM ~ 87 % with 648.83 mg/L of Li+ Process 2 incorporates wet C&S prior to flotation. A significant
compared to spent mixed unwashed which showed lower separation amount of Li can be recovered in crushing water which can amount to
efficiency of 66 % with Li+ 2572.82 mg/L in flotation water. However, 20.7 % compared to Li in an NMC111 module of the composition shown
the flotation kinetics are fast in experiments with high Li concentrations. in Fig. 8. The breakdown of Li contribution sources in crushing water is
They correlated the lower separation efficiencies with higher Li con­ explained in the section on wet crushing. The crushing loss of Li can
centration and froth stability arguing that oxide recovery in graphite amount to around 7 % calculated based on the findings of Zhang et al.
concentrate increases when water entrainment is the main mechanism [110]. Leftover Li in the BM before flotation amounts to around 72.3 %
of recovery [116]. which is then floated according to conditions explained in process 1,
[115]. Even though most of Li is recovered from electrolyte, separator,
3.4. Estimation of Li recovery and losses for different pre-treatment routes and anode in crushing water there could still be some leftover Li
of LIBs recycling dissolution in the flotation water. Considering the concentration of Li in
the flotation water of 0.25 g/L [119,120], around 13.9 % Li is recovered
The choice of routes to produce BM from spent EV LIBs influences the in flotation water while the remaining goes to hydrometallurgy and in
downstream processing. For example, a pyrolyzed BM can be subjected the froth. Although wet crushing in Process 2 reduces the overall Li loss
to froth flotation to separate CAM and graphite while a BM that is only such a BM will still not be suited for flotation because of organics
crushed without any thermal or chemical treatment to remove the coatings on the electrode particles thus higher losses in froth.
binder coating from electrode particles cannot. However, pyrolysis Process 3 includes the pyrolysis of the whole module prior to dry
treatment of LIB cells or modules followed by dry crushing could crushing followed by flotation. Pyrolysis in an inert atmosphere
minimize the crushing losses due to the complete liberation of electrode (~600 ◦ C) has been widely reported in the literature which not only

11
U. Saleem et al. Separation and Puri cation Technology 361 (2025) 131315

Fig. 9. Calculation of Li flow through different pre-treatment routes of a EV LIB recycling process.

valorizes electrode particles from current collector foils by decomposing additional losses in the downstream processing), and major losses occur
the binder (~450 ◦ C) but also phase transforms the cathode material in the froth. Those can be minimized by a second flotation step at a
into Li2CO3, Ni, and respective transition metal oxides [121,122]. The Li higher S/L or mild acid treatment to keep the cost at a minimum.
can then be recovered by water leaching the BM after crushing. The Finally, Process 4 starts with wet C&S of the module followed by
additional advantage of pyrolyzing the whole LIB module or cell is a pyrolysis of the BM (<200 µm fraction). The Li content in crushing water
supplementary source of CO2 which aids in the carbothermic reduction and crushing loss in this process is similar to Process 2 and has been
of metal oxides provided by the decomposition of the separator which calculated in the same way. However, the flotation separation efficiency
otherwise is removed in dry C&S prior to BM pyrolysis [122]. The C&S and Li in flotation water have been calculated in the same way as Process
loss in process 3 is calculated to be only 2 % from the data provided by 3 due to the pyrolysis of BM. In this process, the major loss occurs in C&S
Zhang et al. [110]. They further floated this BM and reported around at around 7 % followed by a loss in froth i.e., 2 %. The maximum cu­
85 % recovery of metal oxide in the tailings with the S/L ratio of 40 g/L. mulative recovery of Li in different steps can amount to 90.9 % while the
Additionally, the pyrolysis of LIBs transforms Li in the BM into water- losses are 9 %.
soluble phase specifically Li2CO3. The Li concentration in the flotation To summarize, Process 3 and 4 offer the maximum recovery of Li
water can amount to around 1.05 g/L (own water leaching data reported with Process 3 giving minimum crushing loss. Although Li loss in froth is
by Saleem et al. [119] for pyrolyzed BM) representing around 56 % slightly higher for Process 3 compared to 4 the number of aqueous
compared to Li in an NMC 111 module of composition shown in Fig. 8. streams is less in Process 3 and dry fractions are easier to handle in a
The Li content in froth and tailings is calculated based on the afore­ recycling process compared to wet. Thus, Process 3 was chosen for
mentioned separation data from Zhang et al. [110] and corresponds to further optimization and estimation of concentrations, composition, and
around 6.2 % and 35.3 %, respectively. Choosing a lower S/L ratio in volumes of all the streams in a hydrometallurgical BM recycling process.
flotation can allow for greater Li recovery in flotation water, although
this will result in an increased volume of this stream. The maximum
recovery of Li in this process can go up to 91.3 % (there might be

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U. Saleem et al. Separation and Puri cation Technology 361 (2025) 131315

3.5. Hydrometallurgical recycling process of LIBs compared to the latter only 55.1 %. Although the concentration of
metals in inorganic acid leaching is calculated at 100 g/L S/L ratio two
Process 3 from the previous section was selected for the estimation of levels of concentration are obtained due to two S/L ratios used in the
concentrations, compositions, and volume of streams with a basis of 1 kg water leaching step. After pH adjustment to remove impurities and
of BM to be recycled, shown in Fig. 10, calculations shown in Appendix precipitate NMC at pH 11 with 5 M NaOH a 50 % increase in volume has
S3 in SI. The BM composition was taken from Schwich et al. [121] who been considered with a 10 % loss of Li in these steps [125]. The leftover
pyrolyzed the whole battery cells followed by dry C&S. A similar type of stream (5) is rich in Na+ and SO2- 4 with Li concentration ranging from
pretreatment was applied to the BM by Verdugo et al. [116] who 0.33-2.74 g/L with a volume of 5.53–5.74 L. This stream can be pro­
investigated the simultaneous recovery of Li and graphite in flotation. In cessed separately or combined with Li rich stream after water leaching
addition, we thoroughly investigated optimum water leaching condi­ and flotation (stream 2) as shown under Li salt recovery in Fig. 10. Li-
tions on a similar type of BM in our previous work [119]. The water containing streams are shown in blue blocks in Fig. 10 with major im­
leaching step was added before flotation as suggested by Verdugo et al. purities of Na+ and SO4 2- in the stream after NMC precipitation and only
[116]. It has been calculated at two S/L ratios of 20 g/L (concentration Li after water leaching and flotation. In the following section, the
data taken from [123]) and 150 g/L (concentration data taken from application of DLE will be explored to recover Li from these streams.
[116]) while the flotation has been calculated at 150 g/L (conditions
and concentration taken from [116]). They are set up in a way that fresh 3.5.1. DLE to recover Li from recycling streams
water is added in the flotation step which is then used to wash a fresh There are two Li-containing streams after water leaching and NMC
batch of BM in the water leaching step. The froth is subjected to mild precipitation (stream 2 and 5, respectively), Fig. 10. These streams can
acid leaching to recover leftover metal oxide from the flotation step. The also be combined with Na+ and SO2- 4 ions as major impurities. We
tailings are leached by the combination of sulfuric acid and hydrogen recommend to up-concentrate (by rejecting water) Li after flotation and
peroxide using the conditions and efficiency data reported by [124]. water leaching (stream 2) using membranes (nanofiltration and reverse
After the removal of impurities (Fe, Al, Cu), nickel manganese cobalt osmosis). Although reverse osmosis is a mature technique it has not been
hydroxide has been co-precipitated with the leftover stream containing rigorously investigated for DLE purposes [23]. This will improve the
Li+ and Na+ [125]. The total Li loss has been kept at 10 % in impurity overall water efficiency and will offer a simpler process. In addition, the
removal and NMC precipitation combined, and 5 M NaOH has been used salinity in this stream is low compared to real brines (up to 500 g/L
in the calculation for the pH adjustment and a 50 % increase in the [9,82,83]) which should reduce membrane fouling and prolong life.
volume of the inorganic acid leachate has been assumed to reach pH 11 After NMC precipitation (stream 5), Na+ is the major impurity, and Li+
[125]. can be isolated using inorganic sorbents, ion exchange resins, or sol­
The Li concentration after water leaching and flotation combined vents. It should be noted that although the concentration of Li+ in this
(stream 2) reached 0.7 g/L and 3.05 g/L reaching leaching efficiencies of stream can be as low as 0.33 g/L, reverse osmosis and nanofiltration
94 % and 55.1 % with a total volume of 50 L and 6.67 L at S/L ratio of membranes are not recommended here for up-concentration. This is
20 g/L and 150 g/L in water leaching, respectively. A significant amount primarily due to the high salinity resulting from the presence of Na+ and
of Li (94 %) can be leached at a lower S/L ratio of 20 g/L but at the SO2-
4 . The choice of these processes/materials should depend on the
expense of around 7.5 times the water used at a higher S/L ratio. Py­ concentration recommendations in Fig. 5. It should be mentioned that
rolyzed BM gives pH ~ 11 in the water with a major impurity of Al ion exchange resins and solvents are more resistant to acids during
(~70–––320 mg/L [113,119]) which can be minimized if the pH of the elution compared to metal-based sorbents. This can minimize the use of
water is adjusted and kept at 10 (~5mg/L [119]). The concentration of post up-concentration process as a controlled amount of concentrated
Li after inorganic acid leaching of froth and tailings combined reached acids (e.g. 2–3 M HCl) can be used during elution to get equally
0.51–––4.32 g/L (stream 4) which is justifiable as around 94 % of Li is concentrated Li solutions [26–28,30,48,104]. Moreover, an attempt can
already removed during water leaching and flotation in the former be made to extract Li after inorganic acid leaching (stream 4) using FeCl3

Fig. 10. Estimation of composition, concentration, and volumes of streams with basis of 1 kg pyrolyzed BM and recommendations to employ suitable DLE technology
to recover Li from them.

13
U. Saleem et al. Separation and Puri cation Technology 361 (2025) 131315

and tributyl phosphate solvent system in kerosene which has been Norwegian Center for Environment-friendly Energy Research (FME), co-
demonstrated to reach high separation factors of Li over Ni and Co [30]. sponsored by the Research Council of Norway (project number 257653)
However, this may result in a loss of NMC metals during pH adjustments and 40 partners from research, industry and the public sector.
and will complicate the system. In addition, more research is needed to
extract Li over NMC metals as only limited literature is found with Appendix A. Supplementary data
complicated extraction systems. Combining the two Li-containing
streams (2 and 5) the concentration becomes favorable for ion- Supplementary data to this article can be found online at https://doi.
exchange resins and solvent extraction. org/10.1016/j.seppur.2024.131315.

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