**4.5 Liquid-liquid extraction using ionic liquid method to extract lithium from brine**

Unlike traditional liquid-liquid extraction, ionic liquid extraction is considered not only as a solvent but also as a co-extraction reagent. Gao et al. reported the extraction of lithium from salt lake brine using tri-isobutyl phosphate in ionic liquid and kerosene [82]. Three ionic liquids (ILs) have been reported, that is, 1-ethyl-3-methyl-imidazolium-bis[(trifluoromethyl)-sulfonyl]-imide, 1-butyl-3-methylimidazolium-bis[(trifluoromethyl)-sulfonyl]-imide and 1-butyl-3-methylimidazolium-hexafluorophosphate with triisobutyl phosphate (TIBP) and kerosene for ion recovery lithium from salt lake brine. The results show that the best selective lithium extraction was obtained using IL 1-ethyl-3-methylimidazole bis[(trifluoromethyl)-sulfonyl] imide. Under optimal extraction conditions, the one-stage efficiency of lithium ion extraction was 83.71% and the one-stage distillation efficiency was 85.61% at 1.0 mol L<sup>−</sup><sup>1</sup> HCl in 1.0 mol L<sup>−</sup><sup>1</sup> NaCl as a stripping

*Thermodynamics and Energy Engineering*

[88]

[88]

[89]

[93]

[66]

[91]

[92]

**194**

**Resources** Salt Lake brine

Brine Salt Lake brine Salt Lake brine

Brine Salt Lake brine Dead Sea brine

Brine Salt Lake brine

**Table 1.** *Recovery of lithium from brines by various processes.*

Ionic liquid liquidliquid extraction

Ionic liquid liquidliquid extraction

Ionic liquid liquidliquid extraction

Ionic liquid liquidliquid extraction

Bis(trifluoromethylsulfonyl) imide in TBP

Electro-electrodialysis

Membrane electrolysis

Solvent impregnated

membrane

Desalination Desalination

Nanofiltration membrane

Nanofiltration (NF90 membrane XLE membrane)

Bipolar membranes

Solvent-polymeric membranes (2-ethylhexyl)-diphenyl phosphate

Bipolar membranes


1-Alkyl-3-methylimidazolium-based ionic liquids (ILs), in which the alkyl chain lengths were 4-butyl (C4), 5-pentyl (C5), 6-hexyl (C6), 7-heptyl (C7), 8-octyl (C8) or 9-nonyl (C9)

1-Octyl-3-methyl-imidazolium hexafluorophosphate and tributyl phosphate (TBP)

**Process**

**Reagents**

**Mechanism**

**Reference**

[86]

[87]

agent at (O/A) = 2 [82]. Also, lithium extraction from brine is performed using imidazolium-containing ionic liquids with varying alkyl chain lengths in a series of ionic liquids based on 1-alkyl-3-methylimidazolium (ILs), in which the alkyl chain lengths are 4-butyl (C4), 5-pentyl (C5), 6-hexyl (C6), 7-heptyl (C7), 8-octyl (C8) or 9-nonyl (C9), in the presence of tri-isobutyl phosphate (TIBP) and kerosene systems presented by Gao et al. [83]. Studies have shown that the shorter the alkyl chain length of imidazolibased ILs, the higher the lithium recovery efficiency. Optimal lithium extraction can be achieved using ionic liquids based on n-butyl (C4) based on 1-alkyl-3-methylimidazoline (ILs). With a single contact of extraction and distillation, the efficiency of lithium extraction under optimal conditions was 74.14 and 86.37%, respectively. And the optimal condition was ionic liquids based on N-butyl-3-methylimidazole: TIBP: kerosene = 1:8:1 (vol/vol), pH = 5.0, O/A = 2.0 at the extraction stage using 1 mol L<sup>−</sup><sup>1</sup> HCl at O/A = 3 at the distillation stage [83]. Separation of lithium and magnesium from Salt lake brine by liquidliquid extraction using ILs containing tributyl phosphate, reported Chenglong et al. [84, 85]. Tributyl phosphate (TBP), ILs and 1-octyl-3-methylimidazolium hexafluorophosphate, respectively, were used as the extraction medium and extractant for lithium extraction from Salt lake brine. The most suitable conditions for the extraction of this system were the ratio of TBP/ILs at 9/1(vol), O/A at 2:1. The pH of the brines of salt lakes is maintained constant. The obtained data show that the efficiency of single-stage extraction of lithium and magnesium was 80.64 and 5.30%, respectively. The total extraction efficiency of 99.42% was achieved by three-stage countercurrent extraction. With a one-stage method of removing lithium and magnesium, the efficiency was at A/O phase ratio of 298.78 and 99.15%, respectively, at 80°C. Provisional result showed that ILs has the potential to replace volatile organic solvents in liquid-liquid recovery of lithium cations [84]. At room temperature, ionic liquid solvent extraction of lithium cations using TBP was reported by Chenglong et al. The authors used TBP against the widely used ILs bis(trifluoromethylsulfonyl) imide and quantitative reduction of lithium [85].

## **4.6 Membrane process of extraction of lithium from brine**

The extraction of lithium from brine by membrane method is a relatively modern and novel technology reported by various authors, which are discussed below. Through electroelectrodialysis with bipolar membranes, the production of lithium hydroxide from brines has been reported by Jiang et al. [86]. In a laboratory-scale process, a sequentially configured electro-electrodialysis with a bipolar membrane was installed with a permutation of the conventional electrodialysis stack. Standard electrodialysis stacks were reconfigured using five cation exchange membranes and four anion exchange membranes. With conventional electrodialysis and Na2CO3, through preconcentrating and precipitating brine, respectively, 98% pure Li2CO3 powder can be recovered. The authors investigated the influence of current density and raw material concentration on the production of lithium hydroxide (LiOH). Cost-effective was electro-electrodialysis with bipolar membranes at a current density of 30 mA/cm<sup>2</sup> and a feed concentration of 0.18 MPa. Jiang et al. argued that the process is environmentally friendly and cost-effective [86]. The extraction of lithium from salt lake brine by membrane electrolysis was reported by Liu et al. [87]. Different technological parameters are optimized: the distance between the anode and the cathode, the initial concentration of lithium in the analyte, the electrolyte temperature, the electrolysis time and the surface density of the active substrate. The electrode demonstrates a remarkable Li<sup>+</sup> 38.9 mg g<sup>−</sup><sup>1</sup> exchange capacity and an analyte pH value below 8.00 at optimal conditions [87]. Extraction of lithium from Dead sea brine by membrane separation using an ion-exchange hybrid

**197**

Li+

*Lithium Recovery from Brines Including Seawater, Salt Lake Brine, Underground Water…*

tively permeated by solvent-polymer membranes. Better selectivity of Li+

as pressure, supply water temperature, pH and Mg2+ to Li+

, 10 times dilution). An 85% separation between Mg2+/Li+

final. Lithium can easily be separated by dialysis from the solution [90].

process reported by Jagur-Grodzinski and Schori [88]. Lithium cations can be selec-

by Mg2+ and Ca2+ gave membranes with (2-ethylhexyl)-diphenyl phosphate. No significant changes in membrane permeability and selectivity were observed during the 6 months of operation. Preliminary concentration of lithium and subsequent selective separation of lithium by membrane and ion exchange fusion were described by Jagur-Grodzinski and Schori. The expediency of lithium separation by combination of ion exchange process and membrane is substantiated [88]. The processes of concentration and separation of lithium from brine by reverse osmosis, nanofiltration was used. Sun et al. reported the isolation of lithium and magnesium from brine using a desalination nanofiltration membrane [89]. Magnesium lithium rejection rate was estimated by optimizing various operational parameters such

tions from salt lake brine using RO and NF processes have also been investigated. Studies show that the separation of magnesium and lithium was strongly dependent

salt lake brine has been reported using NF and a low-pressure RO membrane by Somrani et al. [90]. Lithium selective membrane NF90 compared with XLE with

is more efficient than the XLE on the low pressure RO membrane due to its higher permeability to clean water and 0.1 m NaCl solution. A lower critical pressure (Pc = 0) and higher selectivity were obtained at a low operating transmembrane pressure (<15 bar) between monovalent cations (40%). Nf90 membrane showed 100% magnesium rejection in the initial step separation from dilute brine (15% for

In the near future, to meet the needs of the world community in lithium, the ocean is considered the most important and promising resource for lithium [66]. It is reported that the total amount of lithium reserves in the oceans is approximately 2.6 × 1011 t [91]. Lithium extraction from hydromineral sources is carried out on a semi-industrial and industrial scale in the USA from salt lakes [66, 92, 94, 95], in Japan from thermal waters [96, 97], in Israel from the Dead sea [66, 73]. The extraction of lithium metal from geothermal and brine has also been studied in Russia, Germany, Bulgaria and Korea [98]. Typically, lithium is extracted from seawater by these two processes: (1) co-precipitation and extraction process and (2) ion

Various methods have emerged with the development of technology, such as liquid-liquid extraction, a membrane process is used to extract lithium from seawater **Table 2**. The process of lithium extraction from both brine and synthetic brine has been considered and generalized through various processes such as liquid–liquid extraction, ion exchange and sorption, co-deposition and membrane processes.

Like other methods, it has not received wide application the extraction process of lithium recovery and extraction by co-precipitation. For lithium recovery, an important problem is the presence of higher concentrations of alkali and alkali metals in seawater. The alkali metal group has a very similar parameter, which creates problems for lithium recovery. The problems associated with lithium recovery from

**5.1 Co-precipitation method for extracting lithium from seawater**

transport

ratio. Lithium extrac-

was achieved in the

extraction, the NF90 membrane

ratio and pH [89]. Lithium recovery from

*DOI: http://dx.doi.org/10.5772/intechopen.90371*

on the operating pressure, Mg2+/Li+

low-pressure reverse osmosis membrane. For Li<sup>+</sup>

**5. Lithium extraction from seawater**

exchange and sorption process.

*Lithium Recovery from Brines Including Seawater, Salt Lake Brine, Underground Water… DOI: http://dx.doi.org/10.5772/intechopen.90371*

process reported by Jagur-Grodzinski and Schori [88]. Lithium cations can be selectively permeated by solvent-polymer membranes. Better selectivity of Li+ transport by Mg2+ and Ca2+ gave membranes with (2-ethylhexyl)-diphenyl phosphate. No significant changes in membrane permeability and selectivity were observed during the 6 months of operation. Preliminary concentration of lithium and subsequent selective separation of lithium by membrane and ion exchange fusion were described by Jagur-Grodzinski and Schori. The expediency of lithium separation by combination of ion exchange process and membrane is substantiated [88]. The processes of concentration and separation of lithium from brine by reverse osmosis, nanofiltration was used. Sun et al. reported the isolation of lithium and magnesium from brine using a desalination nanofiltration membrane [89]. Magnesium lithium rejection rate was estimated by optimizing various operational parameters such as pressure, supply water temperature, pH and Mg2+ to Li+ ratio. Lithium extractions from salt lake brine using RO and NF processes have also been investigated. Studies show that the separation of magnesium and lithium was strongly dependent on the operating pressure, Mg2+/Li+ ratio and pH [89]. Lithium recovery from salt lake brine has been reported using NF and a low-pressure RO membrane by Somrani et al. [90]. Lithium selective membrane NF90 compared with XLE with low-pressure reverse osmosis membrane. For Li<sup>+</sup> extraction, the NF90 membrane is more efficient than the XLE on the low pressure RO membrane due to its higher permeability to clean water and 0.1 m NaCl solution. A lower critical pressure (Pc = 0) and higher selectivity were obtained at a low operating transmembrane pressure (<15 bar) between monovalent cations (40%). Nf90 membrane showed 100% magnesium rejection in the initial step separation from dilute brine (15% for Li+ , 10 times dilution). An 85% separation between Mg2+/Li+ was achieved in the final. Lithium can easily be separated by dialysis from the solution [90].
