Desalination 317 (2013) 11–16

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Desalination
journal homepage: www.elsevier.com/locate/desal

Preliminary studies of lithium recovery technology from seawater by electrodialysis

using ionic liquid membrane
Tsuyoshi Hoshino ⁎
Breeding Functional Materials Development Group, Fusion Research and Development Directorate, Japan Atomic Energy Agency, 2-166 Obuchi, Omotedate, Rokkasho-mura, Kamikita-gun,
Aomori, 039-3212, Japan

H I G H L I G H T S

► We have proposed a new method for Li recovery from seawater by electrodialysis using an ionic liquid PP13-TFSI.
► Only Li ions can significantly permeate this membrane and thus pass from the anode side to the cathode side.
► The Li concentration reached to 22.2% after 2 V, 2 h.
► It should be suitable for use in seawater desalination plants and for the recycling of used Li-ion batteries.

a r t i c l e i n f o a b s t r a c t

Article history: Lithium (Li) procurement is becoming a matter of importance worldwide. I propose a new method for recov-
Received 5 November 2012 ering Li from seawater by electrodialysis, wherein Li selectively permeates from the anode side to the cathode
Received in revised form 2 February 2013 side through an organic membrane impregnated with an ionic liquid (PP13-TFSI). Measurements of the ion
Accepted 17 February 2013
concentration at the cathode side as a function of dialysis duration showed that the Li concentration in-
Available online 19 March 2013
creased to 5.94% after 2 h with an applied electric voltage of 2 V. Moreover, the other ions in the seawater
Keywords:
did not permeate the membrane. With both ends of the impregnated membrane covered with a Nafion
Lithium resource 324 overcoat to prevent outflow of the ionic liquid, the Li concentration increased to 22.2%. This new recovery
Lithium recovery method shows good energy efficiency and is easily scalable and thus is suitable for use in seawater desalina-
Seawater tion plants.
Lithium-ion batteries © 2013 Elsevier B.V. All rights reserved.
Electrodialysis
Ionic liquid

1. Introduction expected to be developed for lithium production. Lithium reserves in

these South American counties of Chile, Bolivia, and Argentina account
Lithium (Li), one of the 31 rare metal elements among the 112 for more than half of the world's lithium reserves and have outstanding
known elements, is fast becoming a valuable commodity. As a means lithium resources (brine water). Although lithium extraction from chlo-
of addressing global warming, the world is increasingly turning to the ride brine water is easy, the quantity of natural resources is limited. On
use of Li-ion batteries in electric vehicles and as storage batteries in the other hand, the quantity of natural resources in sulfate brine water
the home; therefore, there is a growing need for Li. Furthermore, as a is large, but the processing technology has not yet been established.
fuel for fusion reactors, tritium is produced by the reaction of lithium Recycling of used Li-ion batteries is another method for ensuring the
with neutrons in a tritium-breeding material [1]. supply of lithium resources. However, no lithium recycling technology
In South America, lithium is recovered from salt lakes and is currently has been established yet, and therefore, this process is not cost effective.
being produced at the Atacama Salt Lake (SQM Co. Ltd. and Chemetall As a result, urban mines have not been used effectively. Furthermore, it
Co. Ltd.) in Chile and Hombre Muerto Salt Lake (FMC Co. Ltd.) in is estimated that there are virtually inexhaustible lithium resources in
Argentina. The production in these two lakes accounts for approximate- seawater, totaling approximately 230 billion tons, although lithium
ly 70% of the world's lithium production [2,3]. Moreover, there are more concentration is low.
than 100 salt lakes in the Puna plateau, which is surrounded by the Li procurement is a national policy issue worldwide. Currently, Japan
Andes, located at altitudes greater than and above 3500 m. Areas such relies solely on Li imports from overseas. Li is primarily recovered from
as the Uyuni Salt Lake, Rincon Salt Lake, and Olaroz Salt Lake are salt lakes in South America but is also present in seawater. Thus, an effi-
cient means for its stable recovery from seawater is highly desirable.
⁎ Tel.: +81 175 71 6703; fax: +81 175 71 6502. Lithium resource recovery from seawater using lithium adsorbents
E-mail address: hoshino.tsuyoshi@jaea.go.jp. has been studied [4–6]. However, the efficiency of lithium absorption

0011-9164/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.desal.2013.02.014
12 T. Hoshino / Desalination 317 (2013) 11–16

must be improved to enable cost-effective production. Furthermore, seawater by electrodialysis using an organic membrane impregnated
Li-ion selective membranes using crown ethers have been developed with an ionic liquid.
[7–11]. These membranes are unsuitable for the continuous Li recovery
from seawater because the chemical reaction rate depends on absorp- 2. Experimental
tion and desorption of Li. Therefore, the lithium recovery technology
from seawater was not established yet, and the preliminary studies of 2.1. Principle
the innovative recovery system were carried out.
Hoshino developed a novel Li-isotope separation technique that Fig. 1 shows our proposed method for Li recovery from seawater.
uses organic membranes impregnated with an ionic liquid [12,13]. The method involves the use of an ionic-liquid-impregnated organic
This technique could also be used to recover Li from seawater. Building membrane (IL-i-OM) through which only the Li ions in seawater
on this previous work, I report a new method for Li recovery from and not the other ions, including Na, Mg, Ca and K, permeate from

Ionic-Liquid
Impregnated Organic
Solution Membrane
included Li Seawater

Li+ Li+
Cathode Anode

Na +
major
element

Solution (HCl) Seawater

Fig. 1. Proposed Li recovery method using an ionic-liquid-impregnated organic membrane.

 T. Hoshino / Desalination 317 (2013) 11–16 13

IL-i-OM
Ionic liquid Nafion 324
Gore-TexTM

H2O
(a) IL-i-OM (b) High-durability IL-i-OM
Fig. 2. Ionic-liquid impregnated organic membrane (IL-i-OM).

the anode side to the cathode side during electrodialysis. Thus, the Li 2.3. Experimental conditions
ions become concentrated on the cathode side and can be recovered.
PP13-TFSI (N-methyl-N-propylpiperidium bis (trifluoromethane- Fig. 3 shows the experimental electrodialysis conditions. An electrical
sulfonyl) imide) was selected as the ionic liquid for impregnating the potential was applied between the cathode (working electrode: WE) and
organic membrane because the TFSI functional group exhibits high Li anode (counter electrode: CE) using a potentiostat. The concentration of
conductivity. For the organic membrane, I selected Gore-Tex™ with a 0.1 M HCl recovered from the Li solution through the cathode was
thickness of 1 mm because it can be efficiently impregnated by the measured by inductively coupled plasma atomic emission spectrometry
ionic liquid. For accurate measurement of the Li recovery characteristics, (ICP-AES, Optima7000DV of PerkinElmer Co., Ltd) and inductively
seawater was added to the anode side, and a solution without Li was coupled plasma mass spectrometry (ICP-MS, ELAN DRC-e of PerkinElmer
added to the cathode side. Co., Ltd), and the recovery ratio of Li for three types of membranes was
investigated. The Li recovery ratio was calculated as the ratio of the con-
centration of HCl recovered from the Li solution to the concentration of Li
2.2. Membrane in seawater. The applied dialysis voltage was 2 V, and the duration of
dialysis was 2 h. The electrode was Pt 80 mesh and electrode area was
Two types of Li-permeable membranes were prepared: a PP13- 9 cm2.
TFSI-impregnated organic membrane [LI-i-OM, Fig. 2 (a)] and a high-
durability LI-i-OM [Fig. 2 (b)]. Both sides of the LI-i-OM were covered 3. Results and discussion
with a Nafion 324 overcoat to prevent the loss of the impregnated ionic
liquid. The improvement of the durability of LI-i-OM is one of the main 3.1. Li concentration
issues for maintaining good performance during stable long-term elec-
trodialysis. In addition, I prepared SELEMION™ CMV as the reference Fig. 4(a) shows the plots of the Li ion concentration on the cathode
membrane. This membrane is permeable to all cations (Li, Na, Mg, Ca side as a function of dialysis time for each membrane type. Li permeation
and K) present in seawater, enabling Li and the other ions to permeate from the anode side to the cathode side is greater for the high-durability
the membrane and become concentrated on the cathode side. LI-i-OM and the reference membrane than for the LI-i-OM. However, Na

WE Seawater CE

Li+ Li+ Li+

Na+ Na+ Na+

Cl- Cl- Cl-

0.1 M HC
0.1 M HC (Li recovery)
(Li recovery) loop Seawater loop
100ml 100ml
Ionic-liquid-impregnated organic membrane
Anion permeable film (SELEMIONTM AMV)

Fig. 3. Experimental conditions of electrodialysis.

14 T. Hoshino / Desalination 317 (2013) 11–16

50
Reference membrane
High-dur abilit y LI-i-OM
40 LI-i-OM

Li (ppb)
30
Li
20

10

0
0 30 60 90 120
Time (min)
a) Li ion
100
Reference membrane Reference membrane
High-durability LI-i-OM High-durability LI-i-OM
LI-i-OM 80 LI-i-OM
160

Na Mg
Na (ppm)

Mg (ppm)
60

80 40

20

0 0
0 30 60 90 120 0 30 60 90 120
Time (min) Time (min)

100 100
Reference membrane Reference membrane
High-durability LI-i-OM High-durability LI-i-OM
80 LI-i-OM 80 LI-i-OM

Ca K
Ca (ppm)

K (ppm)

60 60

40 40

20 20

0 0
0 30 60 90 120 0 30 60 90 120
Time (min) Time (min)

b) Na, Mg, Ca and K ions

Fig. 4. Plots of the Li, Na, Mg, Ca and K ion concentrations on the cathode side as a function of dialysis time. (a) Li ion (b) Na, Mg, Ca and K ions.

permeation is greater for the reference membrane than for the LI-i-OM 3.2. Recovery ratio of ions in seawater
and the high-durability LI-i-OM.
These results suggest that both the LI-i-OM and the high-durability The ion recovery ratio is calculated from the following formula:
LI-i-OM are candidate Li-permeable membranes and that the ionic
liquid is effective for the selective recovery of Li by electrodialysis. Recovery ratioð% Þ
I recovered Li from seawater by electrodialysis using three types of ¼ cathode−side ion concentration=anode−side ion concentration
membranes. Fig. 4 (b) shows the plots of the Na, Mg, Ca and K ion con-  100:
centrations on the cathode side as a function of the dialysis time for each
ð1Þ
membrane type. Both the LI-i-OM and the high-durability LI-i-OM
essentially prevent Na, Mg, Ca and K ions from permeating from the
anode side to the cathode side. In contrast, as expected, the reference The calculated Li recovery ratios for the LI-i-OM and the high-
membrane allows the four ions to permeate from the anode side to durability LI-i-OM are shown in Fig. 5(a) and (b), respectively. The Li re-
the cathode side. It is assumed that the movement speed of the Na, covery ratio is higher for the high-durability LI-i-OM (22.2%) than for the
Mg, Ca, and K ions is slower in the LI-i-OM and in the high-durability LI-i-OM (approximately 5.94%). However, the recovery ratios of Na, Mg,
LI-i-OM than in the reference membrane. The residual ratio of ionic Ca, and K are higher for the high-durability LI-i-OM than for the
liquid in the membrane without the overcoat was 10%. On the other LI-i-OM (Table 1). Therefore, the next steps to further improve the ratio
hand, the residual ratio of ionic liquid in the high-durability LI-i-OM are to optimize the electrodialysis cell conditions, particularly for the
with a Nafion 324 overcoat was about 95%. It was observed that the du- high-durability LI-i-OM, and to investigate the major factors that affect
rability of the LI-i-OM was improved by the Nafion 324 overcoat. permeation speed. Finally, the concentration of Li will be increased
 T. Hoshino / Desalination 317 (2013) 11–16 15

25
Li Potentiostat
20 K
Ca
Recovery ratio Mg
15 Na
Voltage 2V

10 LiCl
1M
5
10ml
0
0 30 60 90 120 Li+
Time (min) HCl H2 O
a) IL-i-OM 0.1 M Cl-
30ml 30ml
25
Li
Cation Anion
20 K
Ca
exchange exchange
Recovery ratio

Mg membrane membrane
15 Na
Voltage 2V
100
10
Voltage 18V
5 80

Li separationratio (%)
0
0 30 60 90 120
Time (min) 60
b) High-durability IL-i-OM
Fig. 5. Recovery ratio achieved by electrodialysis. (a) IL-i-OM and (b) High-durability
40
IL-i-OM.

20

using the multi-staged electrodialysis system on the similar principle as

enriched uranium.
0
0 10 20 30 40 50 60 70
Time (min)
3.3. Separation of Li and Cl ions
Fig. 6. Separation test of Li and Cl ions by electrodialysis.
After Li recovery using this method, Li exists as LiCl on the cathode
side, and ultimately, the Li and Cl ions must be separated for further Li re-
fining. Fig. 6 shows a preliminary test separation of the Li and Cl ions exchange membrane that allows Li ions to permeate and an anion ex-
from the cathode solution by means of electrodialysis using a cation change membrane that allows Cl ions to permeate. The applied dialysis
voltage was 18 V, and the dialysis duration was 1 h. The Li separation
percentage from 0.1 M HCl achieved by electrodialysis using cation and
Table 1
anion exchange membranes was approximately 95%. This result shows
Recovery ratio achieved by electrodialysis.
that the separation of Li and Cl ions is easily achieved by electrodialysis.
(a) IL-i-OM
Na Mg Ca K Li
4. Conclusions
Concentration in seawater 10500 ppm 1350 ppm 400 ppm 380 ppm 170 ppb
(Oarai beach, Japan)
I have proposed a new method for Li recovery from seawater by elec-
trodialysis using an organic membrane impregnated with the ionic liquid
PP13-TFSI. Only Li ions can significantly permeate this membrane and
Na Mg Ca K Li
thus pass from the anode side to the cathode side. Because the other
Concentration in HCl 1.24 ppm 0.37 ppm 0.05 ppm 0.43 ppm 10.1 ppb
ions (Na, Mg, Ca and K) in seawater are much less capable of permeating
Recovery ratio 0.009% 0.03% 0.01% 0.27% 5.94% the membranes, Li becomes selectively concentrated on the cathode side.
In the measurements of the ion concentration on the cathode side as a
(b) High-durability IL-i-OM
function of the duration of the applied dialysis voltage, the Li concentra-
Na Mg Ca K Li
Concentration in seawater 10500 ppm 1350 ppm 400 ppm 380 ppm 170 ppb
tion increased with time, reaching 5.94% after 2 h. The other ions in sea-
(Oarai beach, Japan) water did not permeate the membrane. In measurements taken under
the same conditions (2 V, 2 h) but with both ends of the impregnated
membrane covered with a Nafion 324 overcoat to prevent outflow of
Na Mg Ca K Li the ionic liquid, the Li concentration increased to 22.2%.
Concentration in HCl 39.41 ppm 11.6 ppm 12.34 ppm 15.87 ppm 37.7 ppb This new recovery method shows good energy efficiency and is
easily scalable. It should be suitable for use in seawater desalination
Recovery ratio 0.38% 0.86% 3.09% 4.18% 22.2%
plants and for the recycling of used Li-ion batteries. The recovered
16 T. Hoshino / Desalination 317 (2013) 11–16

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