Selective Extraction of Lithium Ion from Aqueous Solution with Sodium

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Selective extraction of lithium ion from aqueous solution with sodium phosphomolybdate as co-extraction agent Zhiyong Zhou, Haotian Liu, Jiahui Fan, Xueting Liu, Yafei Hu, Yulei Hu, Yong Wang, and Zhongqi Ren ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.9b00898 • Publication Date (Web): 15 Apr 2019 Downloaded from http://pubs.acs.org on April 19, 2019

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ACS Sustainable Chemistry & Engineering

Selective extraction of lithium ion from aqueous solution with sodium phosphomolybdate as co-extraction agent Zhiyong Zhou, Haotian Liu, Jiahui Fan, Xueting Liu, Yafei Hu, Yulei Hu, Yong Wang, and Zhongqi Ren* College of Chemical Engineering, Beijing University of Chemical Technology, NO. 15, N. 3rd Ring Rd East, Beijing 100029, China *Corresponding author: +86-10-64434925, [email protected] (Zhongqi Ren) ABSTRACT: Sodium phosphomolybdate with a spatial stereo symmetry structure and stability in acid and alkali was used as a new co-extraction agent for separating Li+. In addition, methyl isobutyl ketone and tributyl phosphate were used as diluent and extractant, respectively. The influence of operation conditions on separation performance of lithium ion was investigated. The single stage extraction efficiency of Li+ was 58.74% with the volume fraction of tributyl phosphate, O/A phase ratio and molar ratio of sodium phosphomolybdate to lithium as 40%, 3.6 and 1, respectively. Then the cross-flow and saturated extraction experiments were conducted. When the O/A phase ratio was 3, the washing efficiency of Mg2+ reached up to 99.59%. When 0.26 mol/L HCl solution was used as stripping agent and O/A phase ratio was 3, the stripping efficiency of Li+ reached to 98.3%. The difference in extraction efficiency was within 6.5% through ten recycling of the organic phase, indicating that the coextraction agent was very stable. The extraction mechanism was investigated and the binding ability of P=O in tributyl phosphate molecule followed the sequence Li+ >> Na+ > K+ > Mg2+.

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KEYWORDS: Solvent extraction, Heteropolyacids, Co-extraction agent, Lithium ion, Extraction efficiency, Separation factor INTRODUCTION Lithium is an essential element in modern energy production and storage equipment.1 With the gradual exhaustion of fossil fuels and growing serious environmental problems, clean energy has become a research hotspot in many countries. Various types of clean energies like wind energy, thermal energy, solar energy, and new batteries have been developed. Lithium-ion battery with the advantages of long-life cycle, environmentally friendly, and high storage capacity has been deeply studied all over the world. It is widely used in automotive industry and electronic equipment, resulting in higher demand of lithium resources than supply.2 It is estimated that the global demand of lithium carbonate will reach up to 400,000 tons per year in 2020. Therefore, it is urgent to improve the supply of lithium carbonate by developing new lithium resources. Lithium has two existing ways in nature: one is in the form of compound stored in ore, and the second is in the form of ion in aqueous solution like salt lake, brine and seawater.3-5 In addition, the content of lithium in aqueous solution is about 70% of the total resource reserve. Due to higher energy consumption, lower recovery rate and higher cost for lithium ore mining, the development of lithium resources from aqueous solution has attracted extensive attention.6 Lithium resource is quite abundant in salt lake brine in northwest China, mainly in Tibet and Qinghai province.7 However, the Mg/Li molar ratio in salt lake in Qinghai province in China is much higher than that in other countries. Since Mg and Li have


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similar physical and chemical properties, separation of Li+ from salt lake brine in China is very difficult.8 The separation of Li+ from aqueous solution has been studied by various methods, such as adsorption,9 electrodialysis,10,11 membrane separation,12-14 precipitation,15,16 solvent extraction,17 and etc. Thereinto, solvent extraction is considered to be a promising separation method for lithium ions, due to its low energy consumption and easy industrialization. The traditional liquid-liquid extraction system for lithium ion consists of extractant, co-extraction agent and diluent. Tributyl phosphate (TBP) is usually used as extractant due to its high efficient and low cost.18,19 Since TBP has very high density and viscosity, the dilution of TBP is commonly needed. Various diluents have been used for TBP, such as sulfonated kerosene, methyl isobutyl ketone (MIBK), dichloromethane, N, N-bis(2-ethylhexyl)acetamide (N523) and so on.20,21 There are two kinds of co-extraction agent, salt compound18-21 and ionic liquid.22,23 Ionic liquid used as co-extraction agent has many advantages, such as easy dissolution in extractant and high Li/Mg separation factor. However, the synthesis process of ionic liquid is complex and the cost is high, which is not conducive to industry application. FeCl3 is the most typical co-extraction agent for extraction of Li+.18,19 According to the literature,23 both the extraction efficiency of Li+ and separation factor with TBP-MIBK-FeCl3 extraction system increase with the presence of boron compounds (B(OH)4-) in real salt lake brine. Furthermore, it is found that the special complex anion with spatial three-dimensional symmetrical structure used as coextraction agent has high extraction efficiency and selectivity of lithium ions. Various kinds of complex anions with tetrahedral or octahedral structure, such as FeCl4-,18



ClO4-,24,25 NTf2-,22 PF6- and BF4-, have been used as co-extraction agent. The classical extraction system is TBP+kerosene+FeCl3, in which TBP, kerosene and FeCl3 are used as extractant, diluent and co-extraction agent, respectively. However, the presence of the third phase is bad for continues operation. In order to solve this problem, polar solvent MIBK was selected to replace kerosene, which is beneficial to eliminate the formation of the third phase.26 However, the formation reaction of FeCl4from FeCl3 and Cl- is a reversible reaction. In order to avoid the decomposition of FeCl4in the organic phase, large amount of Cl- is needed in washing, stripping and regeneration agents. Meanwhile, since the coordination effect between TBP and cations follows the sequence Na+ < Li+ < H+,19 NaOH was used to regenerate HFeCl4·nTBP in the organic phase, which might easily form precipitation of Fe(OH)3, resulting in poor reuse performance.27 ClO4- may be a good choice for replacing FeCl4- to solve the above problem. Yang et al.24 investigated the separation performance of Li+ with NaClO4 and TBP as co-extraction agent and extractant, respectively. The extraction efficiency of Li+ reached up to 64.51%. However, since the acidity of HClO4 is stronger than HCl, Li+ could not be stripped effectively to the aqueous phase by HCl. Therefore, no lithium product could be obtained and the whole recovery process could not be repeated. In addition, the complex anions of NTf2-,28 PF6- and BF4- used as co-extraction agents also showed good extraction performance with TBP as the extractant. However, fluoridecontaining ions are easily decomposed in aqueous solution to form hydrofluoric acid, which brings badly problem to extraction equipment and extremely threat to human body.


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To solve these problems and satisfy the characteristic of spatially symmetrical structure,29-33 heteropoly acid anions were selected as suitable co-extraction agent in the extraction process. There are three main types of heteropoly acid structures, namely Keggin, Silverton, and Dawson. The Keggin structure consists of a regular tetrahedron and a regular octahedron structure, which has simple composition and is easy to dissolve in TBP or aqueous solution. Sodium phosphomolybdate (Na3PMo12O40), as a typical heteropoly acid which has stable and spatially symmetrical structure,34 was selected as co-extraction agent in this work. Effects of diluent type, O/A phase ratio, dosage of co-extraction agent and volume fraction of TBP on extraction performance were investigated. Besides, the saturated and multi-stage cross-flow extraction, washing and stripping experiments were conducted too. Moreover, the extraction mechanism of TBP-MIBK-Na3PMo12O40 was studied. EXPERIMENTAL SECTION Materials. All chemical reagents used in this work were of analytical grade. LiCl (purity > 99%) was supplied by Beijing HWRK Chem Co., Ltd (Beijing, China). MgCl2 ·6H2O (purity > 98%), NaCl (purity > 99%), KCl (purity > 99%), HCl (36–38 wt%) and NaOH (purity > 96%) were supplied by Beijing Chemical Works (Beijing, China). Na3PMo12O40 (purity > 99%) was supplied by Aladdin (Shanghai, China). TBP (purity > 99%) and MIBK (purity > 99%) were supplied by Sino-pharm Chemical Reagent Co., Ltd (Beijing, China). Methods. The extraction experiments were carried out in 50-mL conical flasks at



25 ± 2 °C. 10 mL organic phase (40% TBP and 60% MIBK, v/v) and 10 mL aqueous solution (0.05 mol/L LiCl, 4.0 mol/L MgCl2, 0.02 mol/L KCl and 0.08 mol/L NaCl) were mixed. The conical flask was shaken for about 10 min to obtain extraction equilibrium. Then the mixed solution was separated by centrifugal force for about 3 min and the aqueous phase was removed and diluted for analyzing. In the extraction experiment, the extraction efficiency (E), distribution coefficient (D) and lithium-magnesium separation factor (𝛽Li Mg) are calculated as follows. E (%) = 𝐷=

𝐶0 ― 𝐶e 𝐶0

𝐶0 ― 𝐶e 𝐶e

(1)

ⅹ100%

ⅹ𝑅(A/O)

𝐷Li

(2) (3)

𝛽Li Mg = 𝐷Mg

where R represents the phase ratio. A and O represent the aqueous and organic phases. C0 and Ce represent the initial and equilibrium concentrations in aqueous solution, mol/L. The washing/stripping efficiencies (E’) can be obtained as follow.

𝐸′(%) =

𝐶f 𝐶o

× 𝑅(A O) × 100

(4)

where Cf represents the concentration of the aqueous phase after washing/stripping process, Co represents the concentration of the organic phase before washing/stripping process. The organic phase was prepared by three steps. Firstly, a certain amount of phosphomolybdic acid was added to a 50-mL conical flask containing 40% TBP and 60% MIBK (v/v). Then a certain amount of 0.3 mol/L NaOH solution was added to this


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conical flask according to the concentration of acid. The acid-base neutralization rapid reaction was conducted and no solid residue could be found. Then the organic phase consists of Na3PMo12O40, TBP and MIBK was used to extract the aqueous solution (0.05 mol/L LiCl, 4.0 mol/L MgCl2, 0.02 mol/L KCl and 0.08 mol/L NaCl). After that, the organic phase was washed and stripped to obtain H3PMo12O40. Finally, 0.3 mol/L NaOH solution was used to neutralize the H+ and Na3PMo12O40 was obtained again for next extraction cycle. Analysis. The concentrations of cations in the sample were determined by atomic absorption spectrometer (AA530, Shimadzu, Japan). The lithium ion concentration in the organic phase was obtained based on the conservation of mass. Since the concentrations of the other cations like Mg2+ in aqueous solution are very high, the calculation based on the conservation of mass will lead to high deviation. Therefore, the concentrations of the other cations in the organic phase after extraction were determined by measuring the stripping solutions by AA530 atomic absorption spectrometer. Characterization. In order to clearly realize both the combination of metal ions and extractant and the binding capacity during the extraction process, 5 mol/L lithium chloride solution, 5 mol/L potassium chloride solution and 5 mol/L magnesium chloride solution were prepared, respectively. TBP, MIBK and Na3PMo12O40 were used as extractant, diluent and co-extraction agent, respectively. The sodium ions in coextraction agent will exchange with different metal ions existed in different solutions during the extraction process, which influences the electron cloud distribution of P=O



group in TBP molecule. By analyzing the change of the electron cloud dense cloth, the exchange capacity of sodium ions with lithium ions, magnesium ions and potassium ions could be obtained. Then the binding energy of each metal ion with TBP could be obtained too. The 31P nuclear magnetic resonance (NMR) spectrometer (Bruker AV400, Germany) was used for analyses of the organic phase. RESULTS AND DISCUSSION Effect of diluent species on extraction performance of Li+. Based on our previous studies,21-23,26,27 TBP is the optimal selection as extractant used in selective extraction of Li+ from aqueous solution. In addition, diluent is also a very important factor for extraction process. Both the density and viscosity of TBP are very high. Besides, the formed big organic complexes after extraction always show not very good solubility in TBP itself, which causes the formation of the third phase sometimes. Therefore, a suitable diluent should be selected to dilute the organic phase to decrease the density and viscosity of TBP and increase the solubility of the formed big organic complexes after extraction. Various common organic solvents like octane, n-octanol, kerosene, dimethyl phthalate and MIBK are used for investigating effect of diluent species on extraction performance of lithium ions. As shown in Figure 1, the extraction efficiencies with n-octanol and MIBK as diluents are higher than those with the other three solvents as diluents. Moreover, the third phase was not found with n-octanol and MIBK as diluents. Since the hydrogen bond could be formed between n-octanol and TBP, which decreases the molar fraction of free TBP molecules, MIBK was selected as the optimal diluent. Besides, MIBK is a colorless and transparent solvent with a


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medium boiling point and usually used for extracting industrial inorganic salt and organic solvents. MIBK with high polarity can effectively dissolve the formed big organic complexes, which is conducive to the elimination of the third phase. Effect of extraction conditions on extraction performance of Li+ Effect of dosage of co-extraction agent. Since the co-extraction agent plays an important role in the extraction process, the dosage of co-extraction agent will definitely affect the extraction performance of lithium ions. Thus, effects of dosage of coextraction agent on extraction performance were investigated and the results are shown in Figures 2 and 3. Since Na3PMo12O40 was used as co-extraction agent, the Na/Li molar ratio represents the adding dosage of co-extraction agent. The extraction efficiency of Li+ increases first and then remains unchanged with the increase of Na/Li molar ratio. Besides, the extraction efficiency of Mg2+ remains nearly unchanged first and then increases with the increase of Na/Li molar ratio. Therefore, the separation factor of lithium to magnesium shows a first increase and then decrease tendency with increasing Na/Li molar ratio. Thus, the optimal Na/Li molar ratio was selected as 3.6. Effect of TBP volume concentration. Figure 4 shows that the extraction efficiency of Li+ shows a first increase and then decrease tendency with increasing TBP volume concentration. Meanwhile, the extraction efficiency of Mg2+ remains nearly unchanged with increasing TBP volume concentration. Therefore, the lithium-magnesium separation factor also shows a first increase and then decrease tendency with increasing the volume concentration of TBP (Figure 5). Therefore, the optimal TBP volume concentration was selected as 40%.



Effect of R(O/A). As shown in Figure 6, the increase of R(O/A) gradually increases the extraction efficiency of Li+ and decreases the extraction efficiency of Mg2+. However, the increase of R(O/A) first increases and then decreases the separation factor of lithium to magnesium, as shown in Figure 7. When R(O/A) is higher than 1, the organic loading of Li+ tends to be saturated and extraction efficiency of Li+ remains nearly unchanged. However, other metal ions coexisted in the aqueous solution could be extracted by the residual free TBP molecules. Thus, 1 was selected as the suitable R(O/A). Cross-flow extraction. Cross-flow extraction refers to a continuous extraction process, in which the extraction raffinate obtained from the last extraction stage is continuously extracted by a fresh extractant. Effect of cross-flow extraction times on extraction efficiency of Li+ was investigated. The single stage extraction efficiency of Li+ decreases with increasing extraction times (Figure 8). 99.09% of lithium ions were extracted after six-stage cross-flow extractions processes. Therefore, the extraction system consisting of TBP, MIBK and Na3PMo12O40 shows good extraction performance of Li+. Extraction saturation. To determine the saturation extraction capacity, effect of extraction times on extraction efficiency of Li+ was investigated. The total extraction efficiency of Li+ is up to 327.24% after ten extraction times (Figure 9). Since the optimal Na/Li molar ratio was selected as 3.6, 3.6 times of Li+ could be exchanged with Na+ theoretically. The results confirm that the sodium ions in the co-extraction agent could be exchanged into the aqueous phase by lithium ions. In other words, the


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extraction mechanism is the cation exchange. Washing experiment. In order to obtain pure lithium product, the foreign ions extracted during the extraction process should be removed from the organic phase. Thus, the purpose of washing process is to purify the organic phase by removing foreign ions, especially Mg2+. Meanwhile, Li+ should not be washed during washing process. Since the coordination ability of TBP to cations was H+ > Li+ >> Na+ ≈ Mg2+,21-23,26,27 HCl, LiCl and NaCl could be considered as washing agents. Firstly, pure NaCl solution was used as washing agent. The concentration of NaCl solution was selected as 0.12, 0.24, 0.36, 0.48, 0.60 and 0.72 mol/L. As shown in Figure 10, the increase of NaCl solution concentration increases all the washing efficiencies of Mg2+, K+ and Li+. However, large amount of Li+ was also washed down from the organic phase in the washing processes, which is not conducive to yield of product. Therefore, pure NaCl solution was not suitable for washing the organic phase obtained after extraction process. O/A phase ratio always has great effect on washing performance. Figure 11 shows that the increase of R(O/A) sharply decreases the washing efficiency of Li+. However, the washing efficiencies of both magnesium and potassium ions remain nearly unchanged. Higher R(O/A) favors for reducing lithium ion loss. In order to ensure that the extracted Li+ could be remained in the organic phase as much as possible, appropriate amount of LiCl should be added in the washing agent. Influence of LiCl concentration on washing efficiencies was studied. Figure 12 shows that increasing LiCl concentration sharply decreases washing efficiency of Li+.



However, increasing LiCl concentration slightly increases washing efficiencies of Mg2+ and K+. Finally, 0.2 mol/L LiCl + 1.8 mol/L NaCl was chosen as the optimal washing solution. Stripping experiment. After washing process, only lithium and sodium ions existed in the organic phase. According to the binding ability of TBP to cations,21-23,26,27 HCl was regarded as suitable stripping agent in the stripping process. Increasing HCl concentration from 0.18 to 0.24 mol/L increases stripping efficiency of Li+ (Figure 13). The stripping efficiency of Li+ remains basically constant with further increase of HCl concentration. The maximum stripping efficiency is approximately 98.30%. Thus, the optimal HCl concentration was 0.24 mol/L. Figure 14 shows that increasing R(O/A) first slightly increases and then decreases the stripping efficiency of Li+. When R(O/A) is less than 3, since the concentration of HCl is enough for stripping all the lithium ions in the organic phase, the stripping efficiency of Li+ is nearly not influenced by R(O/A). However, when R(O/A) is higher than 3, not enough H+ could be used for stripping Li+ in the organic phase, resulting in decreasing the stripping efficiency of Li+. Therefore, the optimal R(O/A) was 3. Reusability of the extraction system. Since the coordination effect between TBP and H+ is larger than that between TBP and Li+,21-23,26,27 the organic phase after stripping with HCl solution (H+ as the cation) can’t be used for the next extraction cycle. Thus, the organic phase after stripping needs to be neutralized. 0.26 mol/L NaOH solution was used to neutralize the organic phase (H3PMo12O40·nTBP) in regeneration process. The regeneration reaction shows as follow:


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H3PMo12O40·nTBP+3NaOH= Na3PMo12O40·nTBP +3H2O

(5)

The complete extraction process consists of extraction, washing, stripping and regeneration processes. Ten complete extraction cycles were carried out to study the stability and reusability of the extraction system. The extraction efficiency of Li+ changes within 6.5% with the increase of regeneration times (Figure 15), indicating that the extraction system showed relatively high stability and reusability. Extraction mechanism. In our previous studies, it was found that the P=O group in TBP molecule had the selective binding ability for metal ions in aqueous solution.26,27 The extraction of metal ions was realized by cation exchange. Therefore, the combination of P=O group and different metal ions will influence the

31P

NMR

spectrum of the organic phase. To obtain the binding abilities of P=O group for different metal ions, LiCl, MgCl2 and KCl solutions were extracted respectively by the organic phase (40% TBP, 60% MIBK and Na3PMo12O40 as co-extraction agent). Then the 31P NMR spectra of the organic phase were recorded. Figure 16 shows the position shift before and after extraction. This is because the combination of metal ions with O atom causes the movement of electron cloud distribution of P=O group, which affects the electron cloud dense cloth of P atom. The larger the position of P shifts, the stronger the binding ability of P=O group and metal ion. Therefore, the coordination ability of P=O in TBP molecule is Li+ >> Na+ > K+ > Mg2+. CONCLUSIONS Na3PMo12O40 as a new type of co-extraction agent was used for extracting lithium ions from aqueous solution with TBP as extractant. Effect of diluent species on



extraction performance of Li+ was studied and the results indicated that MIBK was the optimal diluent for the extraction system. Effects of extraction, washing and stripping conditions on extraction performances were investigated. The extraction efficiency of lithium and lithium-magnesium separation factor were 58.74% and 207.95, respectively. In order to ensure that the magnesium ions could be eluted as much as possible and no lithium ions would loss during the washing process, 0.2 mol/L LiCl and 1.8 mol/L NaCl was selected as the optimal washing solution. In addition, 98.30% of lithium ions could be stripped to the aqueous phase with 0.26 mol/L HCl solution as stripping agent with O/A phase ratio of 3. In addition, the extraction efficiency of Li+ was 99.09% and 327.24% after six-stage cross-flow and ten-stage consecutively saturated extraction experiments, which indicated that each sodium ion could exchange with lithium ion during extraction process. The co-extraction agent Na3PMo12O40 was not decomposed under acid and alkali conditions during recycling the organic phase by ten times and the change percentage of extraction efficiency was within 6.5%, indicating that this extraction system was relatively stable. These results showed that this extraction system was suitable for extracting lithium ions from aqueous solution with high Mg/Li ratio. Finally, 31P NMR spectra was recorded to investigate the extraction mechanism and the results showed that the coordination ability of P=O in TBP molecule was Li+ >> Na+ > K+ > Mg2+. AUTHOR INFORMATION Corresponding Author *(Z.R.) Tel.: +86-10-64433872. E-mail: [email protected].


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ORCID Zhiyong Zhou: 0000-0001-6436-1399 Zhongqi Ren: 0000-0002-2571-5702 Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (21576010, 21606009, U1607107 and U1862113) and Beijing Natural Science Foundation (2172043). The authors gratefully acknowledge these grants. REFERENCES (1) Choubey, P. K.; Kim, M.; Srivastava, R. R.; Lee, J.; Lee, J. Y. Advance review on the exploitation of the prominent energy-storage element: Lithium. Part I: From mineral and brine resources. Miner. Eng. 2016, 89, 119–137. (2) Grosjean, C.; Miranda, P. H.; Perrin, M.; Poggi, P. Assessment of world lithium resources and consequences of their geographic distribution on the expected development of the electric vehicle industry. Renew. Sust. Energ. Rev. 2012, 16, 17351744. (3) Swain, B. Recovery and recycling of lithium: A review. Sep. Purif. Technol. 2017, 172, 388–403. (4) Kesler, S. E.; Gruber, P. W.; Medina, P. A.; Keoleian, G. A.; Everson, M. P.; Wallington, T. J. Global lithium resources: Relative importance of pegmatite, brine and other deposits. Ore Geol. Rev. 2012, 48, 55-69.



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(21) Zhou, Z. Y.; Qin, W.; Liu, Y.; Fei, W. Y. Extraction equilibria of lithium with tributyl phosphate in kerosene and FeCl3. J. Chem. Eng. Data 2012, 57, 82–86. (22) Zhou, Z. Y.; Qin, W.; Liang, S. K.; Tan, Y. Z.; Fei, W. Y. Recovery of lithium using tributyl phosphate in methyl isobutyl ketone and FeCl3. Ind. Eng. Chem. Res. 2012, 51, 12926-12932. (23) Xiang, W.; Liang, S. K.; Zhou, Z. Y.; Qin, W.; Fei, W. Y. Extraction of lithium from salt-lake brine containing borate anion and high concentration of magnesium. Hydrometallurgy 2016, 166, 9–15. (24) Yang, L. X.; Wu, S. X.; Liu, X. L. Lithium and magnesium separation from salt lake brine by tributyl phosphate under action of co-extraction reagent ClO4-. Chem. J. Chinese U. 2013, 34, 55-60. (25) He, J.; Yang, L. X.; Wang, Y.; Fu, M. New extraction system for lithium from brine with high magnesium content. Acta Geol. Sin.-Engl. 2014, 88, 333-334. (26) Zhou, Z. Y.; Qin, W.; Fei, W. Y. Extraction equilibria of lithium with tributyl phosphate in three diluents. J. Chem. Eng. Data 2011, 56, 3518–3522. (27) Xiang, W.; Liang, S. K.; Zhou, Z. Y.; Qin, W.; Fei, W. Y. Lithium recovery from salt lake brine by counter-current extraction using tributyl phosphate/FeCl3 in methyl isobutyl ketone. Hydrometallurgy 2017, 171, 27–32. (28) Gras, M.; Papaiconomou, N.; Chainet, E.; Tedjar, F.; Billard, I. Separation of cerium(III) from lanthanum(III), neodymium(III) and praseodymium(III) by oxidation and liquid-liquid extraction using ionic liquids. Sep. Purif. Technol. 2017, 178, 169– 177.


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(29) Makoto, M.; Noritaka, M.; Koichi, K.; Atsushi, K.; Yasuo, K.; Kanji, S.; Toshio, O.; Yukio, Y. Catalysis by heteropoly compounds. III. The structure and properties of 12-heteropolyacids of molybdenum and tungsten (H3PMo12−xWxO40) and their salts pertinent to heterogeneous catalysis. B. Chem. Sco. Jpn. 1982, 55, 400-406. (30) Hu, J.; Diao, H. L.; Luo, W. J.; Song, Y. F. Dawson-type polyoxomolybdate anions (P2Mo18O626-) captured by ionic liquid on graphene oxide as high-capacity anode material for lithium-ion batteries. Chem.-Eur. J. 2017, 23, 8729 – 8735. (31) Fu, S. P.; Chu, J. F.; Chen, X.; Li, W. H.; Song, Y. F. Well-dispersed H3PW12O40/H4SiW12O40 nanoparticles on mesoporous polymer for highly efficient acid-catalyzed reactions. Ind. Eng. Chem. Res. 2015, 54, 11534−11542. (32) Song, Y. F.; Tsunashima, R. Recent advances on polyoxometalate-based molecular and composite materialsw. Chem. Soc. Rev. 2012, 41, 7384–7402. (33) Yao, Z. X.; Miras, H. N.; Song, Y. F. Efficient concurrent removal of sulfur and nitrogen contents from complex oil mixtures by using polyoxometalate-based composite materials. Inorg. Chem. Front. 2016, 3, 1007–1013. (34) Haushalter, R. C.; Strohmaier, K. G.; Lai, F. W. Structure of a three-dimensional microporous molybdenum phosphate with large cavities. Science 1989, 246, 12891291.



Figure Captions Figure 1. Effect of diluent species on extraction efficiency of Li+. Figure 2. Effect of Na/Li molar ratio on extraction efficiencies of Li+ and Mg2+. Figure 3. Effect of Na/Li molar ratio on separation factor of Li/Mg. Figure 4. Effect of volume concentration of TBP on extraction efficiencies of Li+ and Mg2+. Figure 5. Effect of volume concentration of TBP on separation factor of Li/Mg. Figure 6. Effect of O/A phase ratio on extraction efficiencies of Li+ and Mg2+. Figure 7. Effect of O/A phase ratio on separation factor of Li/Mg. Figure 8. Effect of cross-flow extraction times on extraction efficiency of Li+. Figure 9. Effect of extraction times of the same organic phase on extraction efficiency of Li+. Figure 10. Effect of concentration of NaCl solution on washing efficiencies of metal ions. Figure 11. Effect of O/A phase ratio on washing efficiencies of metal ions. Figure 12. Effect of concentration of LiCl on washing efficiencies of metal ions. Figure 13. Effect of concentration of HCl on stripping efficiency of Li+. Figure 14. Effect of O/A phase ratio on stripping efficiency of Li+. Figure 15. Effect of regeneration times of the organic phase on extraction efficiency of Li+. Figure 16.

31P

NMR spectra (400 MHz, in CD3Cl) of the organic phase before

extraction, the organic phase after extraction of LiCl, KCl and MgCl2 solutions.


Page 20 of 37

Page 21 of 37

60

50

40

E (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


30

20

10

0

Octane

N-octanol

kerosene

DMP

MIBK

Diluent

Figure 1. Effect of diluent species on extraction efficiency of Li+.



100

Li Mg 80

E (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 37

60

40

20

0 1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Molar ratio of Na+ to Li+

Figure 2. Effect of Na/Li molar ratio on extraction efficiencies of Li+ and Mg2+.


Page 23 of 37

200

160

120

βLi/Mg

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


80

40

0

1.8

2.4

3.0

3.6 +

4.2

4.8

+

Molar ratio of Na to Li

Figure 3. Effect of Na/Li molar ratio on separation factor of Li/Mg.



100

Li Mg

80

60

E (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 37

40

20

0

10

20

30

40

50

60

Volume concentration of TBP (%)

Figure 4. Effect of volume concentration of TBP on extraction efficiencies of Li+ and Mg2+.


Page 25 of 37

140 120 100 80

βLi/Mg

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


60 40 20 0

10

20

30

40

50

60

Volume concentration of TBP (%)

Figure 5. Effect of volume concentration of TBP on separation factor of Li/Mg.



100

Li Mg

80

E (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 37

60

40

20

0

0.5

1.0

1.5

2.0

2.5

3.0

R (O/A)

Figure 6. Effect of O/A phase ratio on extraction efficiencies of Li+ and Mg2+.


Page 27 of 37

240

200

160

βLi/Mg

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


120

80

40

0

0.5

1.0

1.5

2.0

2.5

3.0

R (O/A)

Figure 7. Effect of O/A phase ratio on separation factor of Li/Mg.



60

50

40

E (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 37

30

20

10

0

1

2

3

4

5

6

Extraction times

Figure 8. Effect of cross-flow extraction times on extraction efficiency of Li+.


Page 29 of 37

60

50

40

E (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


30

20

10

0

1

2

3

4

5

6

7

8

9

10

Extraction times

Figure 9. Effect of extraction times of the same organic phase on extraction efficiency of Li+.



100

80

60

E' (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 37

40

K Mg Li

20

0

0.12

0.24

0.36

0.48

0.60

0.72

Molar concentration of NaCl (mol/L)

Figure 10. Effect of concentration of NaCl solution on washing efficiencies of metal ions.


Page 31 of 37

100

80

Mg K Li

60

E' (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


40

20

0

2

4

6

8

10

12

R (O/A)

Figure 11. Effect of O/A phase ratio on washing efficiencies of metal ions.



100 80 60

Mg K Li

40 20

E' (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 37

0 -20 -40 -60 -80 -100 -120 0

0.05

0.10

0.15

0.20

0.25

Molar concentration of LiCl (mol/L)

Figure 12. Effect of concentration of LiCl on washing efficiencies of metal ions.


Page 33 of 37

100

80

60

E' (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


40

20

0

0.18

0.20

0.22

0.24

0.26

0.28

Molar concentration of HCl (mol/L)

Figure 13. Effect of concentration of HCl on stripping efficiency of Li+.



100

80

60

E' (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 37

40

20

0

2

4

6

8

10

R (O/A)

Figure 14. Effect of O/A phase ratio on stripping efficiency of Li+.


12

Page 35 of 37

60

50

40

E (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


30

20

10

0

1

2

3

4

5

6

7

8

9

10

Regeneration times

Figure 15. Effect of regeneration times of the organic phase on extraction efficiency of Li+.



-0.829

Page 36 of 37

+

The organic phase after extraction (Li ) + The organic phase before extraction (Na ) + The organic phase after extraction (K ) 2+ The organic phase after extraction (Mg )

-0.839

-0.845

-1.064

0.0

-0.5

-1.0

-1.5

-2.0

f1 (ppm)

Figure 16.

31P

NMR spectra (400 MHz, in CD3Cl) of the organic phase before

extraction, the organic phase after extraction of LiCl, KCl and MgCl2 solutions.


Page 37 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


For Table of Contents Use Only

Na3PMo12O40 with a spatial stereo symmetry structure and high stability in acid and alkali was first used as co-extraction reagent for selective extraction of Li+ from salt lake brine.


Selective Extraction of Lithium Ion from Aqueous Solution with Sodium

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