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Lithium extraction from Chinese salt-lake brines:

opportunities, challenges, and future outlook
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Cite this: DOI: 10.1039/c7ew00020k

Jian Feng Song,ab Long D. Nghiem,c Xue-Mei Lia and Tao He *a

Chinese salt-lake brine is mainly of the magnesium sulfate subtype with a high Mg/Li ratio. Mining lithium
Received 18th January 2017, from Chinese salt-lake brine has been a decades-long technical challenge. The pros and cons of various
Accepted 19th April 2017
technologies are briefly discussed. Chemical extraction has been the most important technology for the
DOI: 10.1039/c7ew00020k
recovery of lithium from Chinese salt-lake brine with a high Mg/Li ratio. Several other innovative technolo-
gies, including lithium ion sieves, membrane separation, and electro–electrodialysis, have also emerged as
rsc.li/es-water potential options.

Water impact
Energy storage using Li-based rechargeable batteries is essential for the uptake of renewable energy. This mini-review highlights the challenge of extracting
lithium from Chinese salt-lake brine. The paper also reviews current and emerging technologies that can be used to extract lithium from a high Mg/Li ratio
brine which is typical of most Chinese salt lakes.

Introduction nologies for lithium production from salt-lake brines start to

emerge.3 Lithium concentration in salt-lake brines varies
Lithium, the lightest metallic element, is one of the most im- from site to site; however, in most cases, it is much higher
portant commodities because of its wide applications in nu- than that in seawater, as demonstrated in Table 1 which
clear fusion, chemical and metallurgical industries,1 and par- summarises lithium concentrations in several Chinese salt
ticularly in rechargeable lithium ion batteries.2 The rapid lakes.
expansion of the electric vehicles3 and grid energy storage4
markets places a strong demand for lithium from the battery
industry. The demand for lithium has dramatically increased Chinese salt-lake brine
in recent years.5,6 The price of lithium carbonate tripled from
In China, lithium-rich salt lakes are located mostly in the
2015 up to 129 000 RMB/t in December 2016.7
Qinghai Tibet Plateau. This region is known for its significant
Lithium can be obtained from seawater, Li-containing
lithium resources. Lithium deposits in the Qinghai provinces
ores, and lithium-rich salt-lake brines. Despite the large lith-
were estimated to be about 244.7 million tonnes.11 The
ium reserves in the ocean of about 231.4 trillion tonnes, lith-
enriched source of lithium in those brines is related to geo-
ium recovery from seawater is not yet economically viable be-
thermal activity from volcanic systems12 and anatectic
cause of the low concentration in seawater of around 0.178
magmatism.13 The volcanic hot water from the area between
mg L−1.8 There are other major lithium sources: namely Li-
the middle and southern Kunlun faults was an important
containing ores (e.g. spodumene, petalite and lepidolite) and
source of potassium, boron, and lithium in the Qarhan salt
salt-lake brines. The latter account for over 80% of total re-
lake. Based on the location of the brine in the salt lake, natu-
coverable lithium deposits.9 There is a clear trend for the
ral brine can be classified into surface, intergranular, and
lithium industry to shift from ores to salt-lake brines10 as the
over-saturated brine.13 The last two types can be used for
lithium-rich ore reserve is diminished and cost-effective tech-
mineral extraction and further classified into original brine,
brine after precipitation of sodium salt, brine after crystalliza-
a
Laboratory for Membrane Materials and Separation Technology, Shanghai tion of potassium salt, and concentrated brine (Fig. 1). As an
Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201203, example, for the East Taijinar salt lake, the concentration of
China. E-mail: het@sari.ac.cn
b
lithium increased sequentially to reach 4–5 g L−1 in the con-
University of Chinese Academy of Sciences, Beijing, 100049, China
c
Strategic Water Infrastructure Laboratory, School of Civil, Mining and
centrated brine (Fig. 1).
Environmental Engineering, University of Wollongong, Wollongong, NSW 2522, Based on the Kurnakov-Valyashko classification, salt lakes
Australia can be divided into the chloride type, sulfate type (with

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Table 1 Lithium ion concentration in the Chinese salt lakes

Conc. g L−1 Deposita/million

Salt lake Li Mg tonne Ref.
West Taijinar 0.25–6.70 12.80–92.43 2.68 14–16
East Taijinar 0.14 22.20 2.47 14, 16
Qarhan 0.21–0.35 66.5–115.0 7.17 17
Zabuye 0.42–1.61 0.01 1.84–7.90 18
Dangxiongcuo 0.30–1.60 <1.0 0.86–0.95 19
Yiliping 0.13–2.2 17.36 1.78–99.1 11, 20
Da Qaidam 0.1–1.30 9.0–117.0 2.00 11
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Jiezecaka 0.56 0.40 2.30 21

Longmucuo 1.21 89.5 2.17 21
a
Ref. 10, 11 and 22.

magnesium sulfate and sodium sulfate subtypes), and car- Lithium recovery from brine of high
bonate type.23 Carbonate-rich lakes are located in the south- Mg/Li ratio
ern and south western part of the plateau, and magnesium/
sulfate-rich lakes are in the Qaidam Basin, in the northern Most salt-lake brines in China are of the magnesium sul-
part of the plateau.13 fate subtype and the ratio of Mg/Li can be as high as 500
The most important lithium-bearing deposit in the zone (Table 1).16,18 The chemical precipitation approach that has
of carbonate-type lakes is Zabuye Lake. Because of very low been successfully applied to low calcium and magnesium
magnesium concentrations (Zabuye and Jezecaka Lake in brines (such as those from Zabuye and Jezecaka Lake)
Table 1), production of lithium from these lakes can be read- would consume a large quantity of chemicals and generate
ily achieved. Lithium carbonate can be precipitated directly a huge amount of solid waste.25 In addition, lithium loss
from the brine by evaporation. This is similar to the process due to co-precipitation and adsorption to calcium/magne-
currently used to extract lithium from the Silver Peak Lake in sium precipitate is also significant.
the US and Atacama Lake in Chile.24 The Mg/Li ratios in The technologies to extract lithium from brine with a high
brine from Silver Peak Lake and Atacama Lake are only 2 and Mg/Li ratio include calcination, adsorption, extraction and
0.1–1, respectively. membrane separation25,30 (Table 2). These technologies have
been explored for potential large-scale production. However,
most of these technologies are still at a pilot stage or in
small-scale production. A project for 10 000 t per year Li2CO3
was implemented using calcination technology at East
Taijinar salt lake,31 but has not yet reached the target opera-
tion due to the high energy cost and emission of acid mist
which corrodes the equipment and causes severe air pollu-
tion. Adsorption using lithium ion selective sieve was claimed
to reach commercialisation (capacity of 10 000 t per year) in
2007. However, until now, the project has not yet achieved
full-scale operation due to several undisclosed technical is-
sues. Nanofiltration and electrodialysis membranes have also
been investigated for lithium recovery from salt-lake brine
over the last decade. The separation of magnesium and lith-
ium by either nanofiltration or electrodialysis is technically
challenging given their very similar hydrated radius.29 As a
traditional technology, chemical extraction has seen a recent
resurgence in both research and industry. In the following
Fig. 1 The sequential evaporation pond for the enrichment of lithium
section, technologies with a strong potential will be further
from brine at East Taijinar salt lake. The intergranular brine was discussed.
pumped from an underground basin to a trench (A); brine was further
distributed via a reservoir (B); evaporation by solar power to precipitate
sodium chloride (C); the brine after production of potassium chloride,
Lithium ion sieve
at this stage the lithium concentration was about 2 g L−1 (D); further
evaporation of the brine enriched the lithium concentration up to 4–5
The lithium ion sieve is a specific absorbent with a high se-
g L−1 (E); finally, the concentrated brine was used for the lithium lectivity for lithium ions. Li–Mn–O ternary oxides have been
recovery. Lithium concentration was measured in our lab. used to prepare ion sieves for lithium recovery from salt-lake

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Table 2 State-of-the-art of the technologies of recovery lithium from salt brine in China

Technology Status and pros and cons

Calcination • The brine is sprayed dry to get a solid mixture of MgCl2·2H2O and LiCl. After carbonation to MgO and LiCl in a rotary kiln at
800–100 °C, the LiCl is dissolved because the solubility of MgO is low; LiCl is then precipitated to Li2CO3.
• 10 000 t per year pilot in East Taijinar; but stopped.
• Mature technology but high energy cost;
• Air pollution due to emission of acid mist.26
Adsorption • Lithium ion sieve: lithium ion selective sieves can selectively absorb Li+ from brine; then Li+ are desorbed by dilute
HCl solution to obtain a lithium-rich solution.
• 10 000 t per year in Qarhan installed in 2007; not yet in full-scale operation.
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• Low cost and easy to realize larger scale;

• Dissolution of adsorbent;
• Reduced adsorbing capacity due to blockage of the ion channels.26
Extraction Organic extractants are able to selectively extract Li+ from brine; theoretical basis is known; however, suitable extracting
equipment with small footprint, low cost, high efficiency is required.17
Mixer-settler27
• 1000 t per year in Da Qaidam;
• Low cost and easy to realize larger scale;
• Large volume, footprint, long equilibrium time, auto control difficult;
Centrifuge28
• Pilot in East Taijina; 1000 t per year
• High efficiency, short equipment time;
• High CAPEX; very difficult to realize large scale.
Membrane • Electrodialysis: Monovalent and divalent cations diffuse at different speeds in electric field across the ion
exchange membrane; separation occurs for Li+ and Mg2+.
• Project of 10 000 t per year in East Taijinar; not yet full-scale operation;
• Nanofiltration (NF) membrane separates monovalent ions and divalent ions; thus is able to separate Mg2+ from Li+;
the brine has to be diluted to reduce osmotic pressure;
• Failed in pilot stage; NF process can separate the monovalent and divalent salts, and the same for Li+ and Mg2+;
• Easy to control and low energy consumption;
• Emerging technology; no commercial membrane system available; potential membrane fouling/scaling.29

brines because the Li–Mn–O framework can maintain a cubic prove the performance, the granulation and regeneration of
spinel structure during the Li+ insertion and extraction pro- lithium sieve still need further study.
cess. These oxides contain a series of chemicals, such as the
spinel manganese oxides,32–35 and nanostructure MnO2.36 In- Chemical extraction
spired by the lithium ion sieve, titanium lithium ionic and
lithium iron phosphate (LiFePO4) sieves have also been Liquid–liquid extraction has been widely studied for recover-
investigated.37–40 These absorbents have been tested for re- ing lithium from brine with a high ratio of Mg/Li.
covery of lithium from brine from Qarhan saline lake.41 Chal- β-diketones and n-butanol were reported as extractants to ex-
lenges for ionic sieves include: (1) dissolution of metal ion tract lithium from brine in the 1970s.42,43 In addition to
from the adsorbent together with lithium ions during the these studies, neutral organophosphorus extractants44,45 have
acid treatment; (2) splitting of sieve particles into smaller also been investigated. One typical extraction system is
ones; (3) collecting the particles, and the washing and reg- tributyl phosphate (TBP)/kerosene-FeCl3. In this system,
enerating processes are still expensive; (4) reduced adsorbing FeCl3 solution plays the role of a co-extracting agent, which is
capacity due to blockage of the ion channels. Hence, to im- crucial for extracting lithium. In the mechanism of extraction
by TBP,46–48 the co-extraction performances of methyl iso-
butyl ketone (MIBK),49 N,N-bisIJ2-ethylhexyl) acetamide
(N523),50 and ionic liquid51 were investigated. As to other
extractants, N503,52 N523,53 di-(2-ethylhexyl) phosphoric acid
(D2EHPA) were studied as single extractants. Of those
extractants, TBP is probably the most suitable for brine with
a high Mg/Li ratio and a pilot-scale extraction process based
on this extractant has been studied.
Equipment selection has been a major challenge in
implementing chemical extraction for lithium recovery. A
Fig. 2 The purity of lithium chloride obtained in a continuous
mix-settler was selected as the extraction equipment by Qing-
extraction experiment using a Karr column and brine from West
Taijinarlake. TBP was used as the extractant. The purity as indicated in
hai Institute of Salt Lakes of Chinese Academy of Sciences in
the graph corresponds to different adjustments of the process the 1990s. Some plants have also used a mix-settler for pilot-
parameters. scale production. A typical example is the mix-settler

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equipment built to recover lithium from Da Qaidam salt lake ion phosphate rechargeable battery. Based on this reaction, a
in 2016. However, its large footprint, large liquid volume, se- battery technology that consists of a lithium capturing
vere corrosion by the extractant and long equilibrium time electrode, the FePO4 anode, and LiFePO4 cathode was stud-
are still among a few remaining technical issues to be solved. ied.58,59 A chloride-capturing electrode (Ag)60,61 and sodium
The extractant and extraction processes have been thiosulfate were found to have an optimum redox potential62
optimised;49,50 however, selection of suitable equipment is during the process of lithium recovery. Another ion sieve
still a technical and scientific challenge. obtained from spinel phases of lithium manganese oxides
To reduce the large liquid volume and long equilibrium (LiMO), such as LiMn2O4 and Li1.33Mn1.67O4, retains the
time, a centrifuge system was proposed in a key project from framework of the parent compounds and it is highly selective
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the Chinese Academy of Sciences in 2014. Since a large quan- for lithium in aqueous environments.34,63 Spinel LiMn2O4
tity of fluid (organic extractant and brine) is involved in ex- (LMO) has been reported as a lithium ion intercalation
traction, exceptionally large anticorrosive centrifuges were electrode and polypyrrole (PPy) reversible chloride
needed; furthermore, the low energy efficiency of the centri- electrode.64 A λ-MnO2 positive electrode and an Ag negative
fuge leads to high energy cost. As a partner in this project, the electrode65 were also investigated. To reduce the cost and in-
membrane team from Shanghai Advanced Research Institute crease long-term stability, a λ-MnO2/activated carbon hybrid
(SARI) selected different approaches: membrane chemical ex- supercapacitor system was studied to recovery lithium from
traction and reciprocal column (Karr column) extraction. solution.66 However, the redox reactions caused the dissolu-
The potential advantages of membrane extraction techniques tion of manganese ions and destablized the MnO2. Therefore,
are low capital and operating costs, low energy consumption, po- the development of new materials for lithium-ion-capturing
tentially small footprint (compared to a mix-settler). In a mem- electrodes remains an active subject for further study.
brane extraction process, a membrane barrier, which is perme-
able to cations (i.e. Li+, Mg2+, Na+) and impermeable to organic Summary and outlook
extraction, is located at the interface between the organic
extractant and brine; lithium ions are selectively extracted and Brine has been the most important target for lithium ion ex-
purified. However, a solvent-stable membrane barrier is required traction for lithium battery development. Particularly in
with long-term stability.54–56 A recent report on a solvent-stable China, salt-lake brine, mainly of the sulfate type, has been
hydrophilic nanoporous poly(ethylene-co-vinyl alcohol) mem- the core for lithium recovery. However, the high Mg/Li ratio
brane15 showed stable lithium extraction for 1037 hours. This commonly found in most Chinese salt lakes is still a chal-
stable performance indicates the potential of the present mem- lenge for large-scale lithium production. Potential technolo-
brane for large-scale applications. gies to overcome this challenge include lithium sieves, chem-
Reciprocal extraction columns have been widely used in ical extraction, nanofiltration, and electro–electrodialysis.
the petrochemical industry. The Karr reciprocating plate ex- Chemical extraction is the most promising approach in the
traction column with high load capacity is an effective solu- near future. We compared the pros and cons of current ex-
tion. This equipment is efficient in treating a large amount traction techniques and equipment including mix-settler,
of liquid, with a small footprint, easy automation, and toler- centrifuge, column and membrane contactors. Column ex-
ance to liquid with a high load of foulant. After thorough traction technology was promising. Novel extraction technolo-
analysis and balance of the treatment capacity, energy con- gies driven by electrochemical reactions were introduced; the
sumption as well as the risk of separation of organics from development of new materials for electrodes and long-term
brine, we have evaluated column technology for lithium ex- stability, and selectivity are the main challenges for these po-
traction. A high load Karr column was developed to extract tential technologies.
lithium from West Taijinar lake brine in our research; the
TBP system was selected and a new chemical exchange pro- Acknowledgements
cess was used to improve the purity of the lithium product. The authors thank National Natural Science Foundation of
The purity of lithium can be controlled and the highest value China (U1507117, 21676290), TMSR from Chinese Academy of
was 99.9% (Fig. 2). Sciences (XDA02020100), Key Research Fund (CAS2014
Y424541211) for financial support and a Vice Chancellor
International Visiting Award Fellowship to Tao He from the
Electro chemical process University of Wollongong is also gratefully acknowledged.

Electro–electrodialysis with a bipolar membrane (EEDBM) Notes and references

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