Preparation method of beta-diketone functionalized vegetable fat extraction agent and application of beta-diketone functionalized vegetable fat extraction agent in lithium extraction

Abstract

The invention discloses a preparation method of a beta-diketone functionalized vegetable fat extraction agent and application of the beta-diketone functionalized vegetable fat extraction agent in lithium extraction. The method comprises the following steps: hydrolyzing vegetable fat (such as sunflower seed oil, rapeseed oil and the like) to obtain unsaturated fatty acid, esterifying with ethylene glycol to generate fatty acid with hydroxyl, and finally modifying with diketene to obtain the beta-diketone functionalized extracting agent. The extraction agent solves the problems that a traditional beta-diketone extraction agent is serious in emulsification and long in phase separation time and has excellent lithium extraction performance, the extraction capacity reaches 1.44 g / L, and the lithium / sodium separation factor can reach 286.5. In addition, the extraction agent is low in solution loss, the efficiency is still kept above 80% after the extraction agent is recycled for 10 times, and the extraction agent is suitable for efficiently recovering lithium ions from lithium-containing wastewater. The method is simple in process and low in cost, and has large-scale application potential.

Description

Technical Field

[0001] The present invention belongs to the field of metal separation and liquid-liquid extraction, and particularly relates to a β -A method for synthesizing an extractant from diketone-functionalized plant oils and fats, and the use of the extractant for lithium extraction. Background Art

[0002] In recent years, with the promotion and popularization of new energy vehicles, the consumption and demand for lithium resources have been increasing rapidly. China's reliance on lithium imports has remained above 60%, which has hindered the stable supply of lithium resources. Furthermore, a large number of lithium batteries are facing retirement (lithium grades in lithium batteries range from 5-7%, while lithium content in lepidolite and spodumene is less than 4%). The China Battery Industry Association predicts that by 2030, China's retired power battery volume will reach 6.028 million tons. Recycling lithium from spent lithium batteries can significantly reduce dependence on lithium imports and promote resource recycling. The currently widely used pyrometallurgical-hydrometallurgical process for lithium recovery generates a large amount of high-sodium lithium-containing wastewater during the sodium carbonate precipitation step, which is difficult to recover (low-concentration lithium-containing wastewater: sodium / lithium ratio approximately 10-30, pH = 9-12, lithium concentration 2-5 g / L). This wastewater carries a significant portion of lithium ions (5% of the total lithium content), resulting in a decrease in lithium recovery efficiency. The 2024 edition of the lithium battery recycling industry regulations released by the Ministry of Industry and Information Technology also set new requirements for lithium recovery rates and wastewater reuse rates. The lithium recovery rate during the smelting process is increased from no less than 85% to no less than 90%, and the recycling rate of process wastewater is required to reach above 90%. Therefore, how to effectively separate and recover lithium ions from the high-sodium solution after lithium precipitation is of great practical significance for the recycling of lithium resources.

[0003] The methods reported for extracting lithium from low-concentration lithium-containing aqueous solutions mainly include electrochemical lithium extraction, adsorption, membrane separation, and liquid-liquid extraction. The electrochemical lithium extraction method, which relies on electrical energy to drive both the insertion and removal of lithium, has high energy consumption, and impurity ions from different solutions co-precipitate with lithium, making it difficult to promote large-scale application. The adsorption method has good selectivity when separating lithium ions, but the adsorption capacity of the adsorbent is relatively low (the adsorption capacity in industrial applications is generally less than 10 mg / g). This means that a large amount of adsorbent is required when treating large-scale lithium-containing solutions, which not only increases the cost of the adsorbent but also requires larger equipment and space, resulting in increased infrastructure and operating costs. The membrane cost of the membrane separation method is relatively high, and it is easily contaminated by impurities and microorganisms in the solution during use, resulting in a decrease in membrane performance and the need for frequent replacement of the membrane material. In addition, the membrane material has a low membrane flux. Whether from a cost or technical perspective, the membrane material is not suitable for large-scale lithium extraction processes. Compared with the above methods, liquid-liquid extraction has a relatively high lithium extraction capacity, a simple phase separation process, and a strong recycling regeneration ability, making it more suitable for lithium extraction processes in lithium-containing aqueous solutions.

[0004] at present β -The lithium extraction by diketones benefits from the enol tautomerism of its diketone structure. The protons in the enol form can exchange protons with lithium ions in an alkaline environment to form a stable lipophilic organic complex, thereby achieving the extraction and separation of lithium ions. However, the current extractants have serious emulsification and long phase separation time (the phase separation time in industrial applications is generally higher than 30 min), which is not conducive to the large-scale expansion of the extraction process. Modifying the diketone extractant into a structure with stronger lipophilicity is expected to improve the serious emulsification problem of the extractant. We noticed that the relative polarity of plant oils is weak and their compatibility with organic solvents is good. Therefore, we proposed a method to use plant oils with β -Preparation method and application technology of diketone functionalized lipophilic extractant to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a β - A method for preparing an extractant from diketone-functionalized plant oils and its application in lithium extraction is intended to address the technical issues mentioned in the background art regarding the severe emulsification and long phase separation time of the extractants currently used in the market.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: A sort of β - A method for preparing an extractant from diketone functionalized vegetable oils, characterized by comprising the following steps: (1) Preparation of fatty acids: The vegetable oil and strong base solution are added into a round bottom flask in sequence, stirred magnetically, and hydrolyzed by heating. After the hydrolysis is completed, the unsaturated fatty acid is obtained by acidification using an acid solution.

[0007] Preferably, in the fatty acid preparation step, the vegetable oil is sunflower seed oil.

[0008] Preferably, in the fatty acid preparation step, the strong base solution is a sodium hydroxide solution, and the molar ratio of the vegetable oil to the sodium hydroxide is 1: (0.5-1.5).

[0009] Preferably, in the fatty acid preparation step, the hydrolysis temperature is 60-70°C, and the reaction time is 5-60 min.

[0010] Preferably, in the fatty acid preparation step, in the acidification step, the acid solution is a sulfuric acid solution with a concentration of 2 mol / L.

[0011] Preferably, the fatty acid obtained after the hydrolysis of the vegetable oil is oleic acid, linoleic acid, linolenic acid, α unsaturated fatty acids such as linolenic acid, arachidonic acid, etc.

[0012] (2) Synthesis of unsaturated fatty acid with hydroxyl group: The diol and the fatty acid prepared in step (1) are dissolved in solvent 1, and then added into a round bottom flask in sequence, and a concentrated acid is added for catalysis, and an esterification reaction is performed by stirring and heating to obtain the unsaturated fatty acid with hydroxyl group.

[0013] Preferably, in the extractant synthesis step, the unsaturated fatty acid is oleic acid.

[0014] Preferably, in the unsaturated fatty acid with hydroxyl group preparation step, the diol is ethylene glycol, and the molar ratio of the fatty acid to the ethylene glycol is 1: (0.5-1.5).

[0015] Preferably, in the unsaturated fatty acid with hydroxyl group preparation step, the solvent 1 is chloroform.

[0016] Preferably, in the unsaturated fatty acid with hydroxyl group preparation step, the catalyst concentrated acid is concentrated sulfuric acid, and the molar ratio of the fatty acid to the concentrated sulfuric acid is 1: (0.05-0.2).

[0017] Preferably, in the unsaturated fatty acid with hydroxyl group preparation step, the esterification temperature is 50-60°C, and the heating time is 3-6 h.

[0018] (3) β- Preparation of plant oil extractant functionalized with diketone: The unsaturated fatty acid with hydroxyl group and the acid binding agent are sequentially added into a round bottom flask, the raw materials are fully dissolved by adding solvent 2, and then the mixture is uniformly stirred by magnetic stirring; the flask is sealed by a rubber plug and purged with nitrogen to remove air; after the nitrogen is completely replaced, diacetylene ketone is added, the magnetic stirring is started, and the reaction is completely dissolved by using solvent 2, and then the reaction is started by heating; after the reaction is completed, the solvent in the solution is removed, and the product is purified by using a chromatographic column to obtain β - a plant oil extractant functionalized by diketone.

[0019] The esterified fatty acid modification is obtained by grafting diacetylene ketone in chloroform, and after the reaction is completed, the solvent is removed and purified to obtain an extractant prepared from a plant oil functionalized by β-diketone.

[0020] Preferably, in the extractant synthesis step, the acid binding agent is triethylamine.

[0021] Preferably, in the extractant synthesis step, the solvent 2 is chloroform.

[0022] Preferably, in the extractant synthesis step, the amount-of-substance ratio of the unsaturated fatty acid with hydroxyl group to the acid binding agent is 1: (0.5-2.0).

[0023] Preferably, in the extractant synthesis step, the amount-of-substance ratio of the unsaturated fatty acid with hydroxyl group to diacetylene ketone is 1: (0.1-2.0).

[0024] Preferably, in the extractant synthesis step, the amount ratio of the unsaturated fatty acid with hydroxyl group to solvent 1 is 1 g: (5-15 mL).

[0025] Preferably, in the extractant synthesis step, the stirring speed is 300-500 rpm.

[0026] Preferably, in the extractant synthesis step, the reaction temperature is 35-45°C, and the reaction time is 12-24 h.

[0027] Preferably, in the extractant synthesis step, the volume ratio of the chromatographic solvent petroleum ether to ethyl acetate is 1: (0.5-1).

[0028] Preferably, in the extractant synthesis step, the β The structure of the plant oil extractant functionalized by diketone is as follows: wherein, is a straight-chain or branched-chain unsaturated alkane with C10-C24, the value of is between 10 and 24.

[0029] The above examples are a plant oil extractant functionalized by β-diketone provided by the present application. β-The method for preparing the extractant of the diketone functionalized vegetable oil and fat is as follows: unsaturated fatty acids are obtained by hydrolyzing the vegetable oil and fat with a strong alkali solution, the unsaturated fatty acids with hydroxyl groups are obtained by esterifying the fatty acids with diols, the unsaturated fatty acids with hydroxyl groups are reacted with diacetylene ketone in an anaerobic manner, and the diketone with good coordination ability with lithium ions is modified to the vegetable oil and fat β - the diketone structure is modified to the vegetable oil and fat to obtain β - the diketone functionalized vegetable oil and fat extractant.

[0030] The application example of the present application also provides a lithium extraction method using the extractant of the diketone functionalized vegetable oil and fat. β- The application example of the present application also provides a lithium extraction method using the extractant of the diketone functionalized vegetable oil and fat.

[0031] Preferably, in the preparation step of the extractant organic phase, the concentration of the diketone functionalized vegetable oil and fat is 0.1-1.1 mol / L. β - the concentration of the diketone functionalized vegetable oil and fat is 0.1-1.1 mol / L.

[0032] Preferably, in the extraction step, the pH of the lithium-containing pre-extraction solution is 1-14, and the concentration of lithium ions is 0.01-10 g / L.

[0033] Preferably, in the extraction step, the extraction temperature is 5-75℃.

[0034] Preferably, in the extraction step, the volume ratio of the pre-extraction solution to the extractant organic phase is 1:10-10:1.

[0035] Preferably, in the stripping step, the stripping temperature is 35-55℃.

[0036] Preferably, in the stripping step, the concentration of the stripping agent hydrochloric acid or sulfuric acid solution is 0.1-10 mol / L.

[0037] Preferably, in the stripping step, the volume ratio of the organic phase to the stripping agent is 1:10-10:1.

[0038] Compared with the existing lithium ion purification technology in the lithium-containing solution, the present application has the following advantages: (1) The present application can modify the diketone with good coordination ability with lithium ions to the vegetable oil and fat through a simple reaction. β - the diketone is modified to the vegetable oil and fat to synthesize the lithium extractant, the raw material cost is low, the reaction conditions are mild, and the present application has the potential for large-scale production.

[0039] (2) The present application uses the extractant organic phase prepared from the diketone functionalized vegetable oil and fat. β- The extractant organic phase prepared from the diketone functionalized vegetable oil and fat can separate and purify lithium ions, and can recycle the extractant organic phase, which has stable recycling effect, low solution loss, reduces cost, and is green and environmentally friendly.

[0040] (3) The modified vegetable oil is used as the extractant and the phosphorus oxygen compound is used as the co-extractant, so that the standing and layering time after extraction is shortened, the problems of traditional extraction methods are solved, and the lithium ion extraction capacity is high. β - The dione extractant is emulsified seriously, the phase separation time is long, the lithium ion extraction capacity is high, the separation effect of impurity ions is good, and the method has good industrial application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 The extraction efficiency diagram of the extraction system prepared by different extractants of the application; Figure 2 The extraction efficiency diagram of the extraction system of the application under different pH values for lithium ions; Figure 3 The lithium extraction efficiency and lithium / sodium separation factor of the extraction system of the application after ten cycles β Li / Na Figure; Figure 4 The lithium extraction efficiency and lithium / sodium separation factor of the extraction system of the application under different environmental temperatures β Li / Na Figure; Figure 5 The lithium extraction efficiency and lithium / sodium separation factor of the extraction system of the application under the influence of different extraction organic phase and pre-extraction solution ratio (O / A) during extraction β Li / Na Figure; Figure 6 The lithium ion purification effect diagram of the extraction system of the application under different acid concentration stripping agents during stripping. DETAILED DESCRIPTION

[0042] In order to make the technical scheme of the application clearer and more concise, the application will be described more clearly and completely in combination with the embodiments. Obviously, the following embodiments are only examples of the application. Without creativity, the remaining embodiments obtained by workers in the art based on the embodiments of the application all belong to the scope of protection of the application. Example 1:

[0043] (1) 10 g of sunflower seed oil is hydrolyzed using an appropriate amount of NaOH solution, and oleic acid, α - linolenic acid, arachidonic acid, etc., 0.2 M oleic acid, α- Linolenic acid, arachidonic acid and glycol esterification to form hydroxyl esters, respectively, three kinds of hydroxyl unsaturated fatty acids and 0.2 M triethylamine were dissolved in chloroform, and were transferred to a 250 mL round-bottom flask, and were uniformly stirred by magnetic stirring; rubber plug sealing, nitrogen was introduced to remove air; after complete replacement with nitrogen, 0.2 M divinyl ketone was added, magnetic stirring was started, and heating was carried out at 35°C for 12 h; after the reaction was completed, the solvent was removed under reduced pressure, and the product was purified by chromatography column method to obtain β- Diketone functionalized vegetable oil extractant.

[0044] (2) The three kinds of β- Diketone-based extractant 0.15 M was dissolved in 1 L sulfonated kerosene and ethyl acetate mixed solvent to obtain three kinds of 0.15 mol / L extraction organic phase.

[0045] (3) Extraction: the pre-extraction solution was the solution after lithium precipitation by sodium carbonate, the Li + concentration was 0.20 g / L, and the pH was 11.10; at an ambient temperature of 35°C, the pre-extraction solution was mixed with the four kinds of 0.15 mol / L extraction organic phase prepared in step (1) at a volume ratio of 1:1 for 10 min, and then static separation was carried out to obtain the loaded organic phase and the raffinate solution, and the lithium ion concentration in the raffinate solution was detected.

[0046] (4) Stripping: 3 mol / L sulfuric acid solution was used as stripping agent for the loaded organic phase obtained in step (3), the ambient temperature was controlled at 35°C, the volume ratio of stripping agent to loaded organic phase was 1:10, the stripping time was 10 min, and then static separation was carried out to obtain the purified lithium sulfate solution and the unloaded extraction organic phase, and the extraction organic phase was returned to step (3). The purified lithium sulfate solution was detected. The influence diagram of different extractants on extraction efficiency was drawn (Figure Figure 1 ), and it can be seen from the figure that the extractants prepared by functionalizing oleic acid and α- linolenic acid are better than arachidonic acid. Implementation:2:

[0047] (1) β- Synthesis of diketone functionalized vegetable oil extractant: the synthesis steps were consistent with step (1) of example 1, except that only oleic acid was used as the fatty acid.

[0048] (2) Preparation of extraction organic phase: this step was consistent with step (2) of example 1.

[0049] (3) Extraction: the pre-extraction solution was the solution after lithium precipitation by sodium carbonate, and there were five different solutions, the pH was 5, 7, 9, 11 and 13, respectively, the Li+ The concentration is 0.2 g / L; at an ambient temperature of 35°C, the pre-extraction solution and the 0.15 mol / L extraction organic phase prepared in step (1) are mixed in a volume ratio of 1:1 and extracted for 10 min. After that, the liquid is allowed to stand and separate to obtain the loaded organic phase and the raffinate solution, and the lithium ion concentration in the raffinate solution is detected.

[0050] (4) Stripping: This step is consistent with step (4) of Example 1. Detect the concentration of lithium sulfate in the solution and draw a graph of extraction efficiency at different pH values ​​( Figure 2 ). As can be seen from the figure, the extraction efficiency of the extraction system gradually increases with the increase of the pH of the pre-extraction solution. The results show that the extraction efficiency of lithium ions is higher in an alkaline environment. Implementation:3:

[0051] (1) β- Synthesis of diketone functionalized plant oil extractant: The synthesis steps are consistent with step (1) of Example 2.

[0052] (2) Preparation of the extracted organic phase: This step is consistent with step (2) of Example 2.

[0053] (3) Extraction: The pre-extraction solution is the solution after lithium extraction by sodium carbonate precipitation. + The concentration is 0.2 g / L, Na + The concentration is 3 g / L and the pH is 10.98. At an ambient temperature of 35°C, the pre-extraction solution and the 0.15 mol / L extraction organic phase prepared in step (1) are mixed in a volume ratio of 1:1 and extracted for 10 min. The mixture is then allowed to stand and separated to obtain the loaded organic phase and the raffinate solution, and the lithium ion concentration in the raffinate solution is detected.

[0054] (4) Stripping: Use 3 mol / L sulfuric acid solution as stripping agent to strip the loaded organic phase obtained in step (3). The ambient temperature is controlled at 35°C. The volume ratio of stripping agent to loaded organic phase is 1:10. The stripping time is 10 min. After that, the liquid is allowed to stand and separate to obtain the purified lithium sulfate solution and the unloaded extracted organic phase. The concentrations of lithium sulfate and sodium sulfate in the solution are detected. The extracted organic phase is returned to step (3) for recycling. Repeat steps (3) and (4) ten times. Draw a cyclic extraction efficiency diagram ( Figure 3 ). As can be seen from the figure, the extraction efficiency of lithium ions remains above 80% after the extractant is recycled ten times, and the Li / Na separation effect does not decrease significantly. The results show that the extractant suffers little dissolution loss during use and has good recycling potential. Implementation:4:

[0055] (1) β-Synthesis of diketone functionalized vegetable oil extractant: the synthesis procedure is consistent with step (1) of Example 2.

[0056] (2) Preparation of the extraction organic phase: this step is consistent with step (2) of Example 2.

[0057] (3) Extraction: the pre-extraction solution is consistent with the solution used in step (3) of Example 3; the pre-extraction solution is mixed with the 0.15 mol / L extraction organic phase prepared in step (1) at a volume ratio of 1:1 at ambient temperatures of 15°C, 25°C and 35°C respectively for 10 min, and then allowed to stand to separate into a loaded organic phase and a raffinate solution, and the lithium ion concentration in the raffinate solution is detected.

[0058] (4) Stripping: 3 mol / L sulfuric acid solution is used as a stripping agent to strip the loaded organic phase obtained in step (3), the ambient temperature is controlled at 15°C, 25°C and 35°C respectively, the volume ratio of the stripping agent to the loaded organic phase is 1:10, the stripping time is 10 min, and then allowed to stand to separate into a purified lithium sulfate solution and a stripped extraction organic phase, and the lithium sulfate and sodium sulfate concentrations in the solution are detected. The extraction organic phase is returned to step (3) for recycling, and a temperature effect on extraction efficiency graph is drawn. Figure 4 ). As can be seen from the graph, the extraction efficiency of the extraction system for lithium ions gradually increases with increasing temperature. Example 5:

[0059] (1) β- Synthesis of diketone functionalized vegetable oil extractant: the synthesis procedure is consistent with step (1) of Example 2.

[0060] (2) Preparation of the extraction organic phase: this step is consistent with step (2) of Example 2.

[0061] (3) Extraction: the pre-extraction solution is the solution after lithium precipitation by sodium carbonate, the Li + concentration in the solution is 2.01 g / L, the Na + concentration is 34.31 g / L, and the pH is 11.98; the pre-extraction solution is mixed with the 0.15 mol / L extraction organic phase prepared in step (1) at volume ratios of 0.5:1, 1:1 and 2:1 respectively at an ambient temperature of 35°C for 10 min, and then allowed to stand to separate into a loaded organic phase and a raffinate solution, and the lithium ion concentration in the raffinate solution is detected.

[0062] (4) Stripping: this step is consistent with step (4) of Example 1. The lithium sulfate and sodium sulfate concentrations in the solution are detected, and an extraction efficiency graph at different O / A ratios is drawn. Figure 5). It can be seen from the figure that with the increase of organic phase, the extraction efficiency of lithium ion in the extraction system gradually increases, but after the O / A ratio is greater than 1:1, the extraction and separation efficiency of lithium ion increases slowly, and the Li / Na separation effect gradually becomes poor. Implementation:6:

[0063] (1) β- Synthesis of diketone functionalized vegetable oil extractant: the synthesis step is consistent with step (1) of example 2.

[0064] (2) Preparation of extraction organic phase: this step is consistent with step (2) of example 2.

[0065] (3) Extraction: the extraction step is consistent with step (3) of example 3.

[0066] (4) Stripping: 0.3 mol / L, 1.0 mol / L, 3 mol / L sulfuric acid solution was used as stripping agent for the stripping of the loaded organic phase obtained in step (3), the environmental temperature was controlled at 35℃, the volume ratio of stripping agent to loaded organic phase was 1:10, the stripping time was 10 min, then the purified lithium sulfate solution and the unloaded extraction organic phase were obtained by standing and separating, and the extraction organic phase was returned to step (3). The concentration of lithium sulfate and sodium sulfate solution obtained by stripping was detected, and the lithium ion purification effect diagram of different acid concentration stripping agent was drawn (Fig. 4). Figure 6 It can be seen from the figure that the lithium ion purification effect increases significantly with the increase of the concentration of sulfuric acid used as stripping agent within a certain range.

[0067] The above examples only represent some preferred cases, and the present application is not limited to the above examples. For those skilled in the art, the technical solutions listed in the present application can still be modified or replaced equivalently, and any modification, equivalent replacement or improvement made within the spirit and principles of the present application is protected by the present application.

Claims

1. A method for preparing a β-diketone functionalized plant oil extractant, characterized in that: The following steps are involved: (1) Hydrolysis of vegetable oils: unsaturated vegetable oils are mixed with a strong base solution, heated to 60-70°C for hydrolysis for 5-60 minutes, and then acidified to obtain unsaturated fatty acids. The vegetable oils are selected from sunflower oil, rapeseed oil, peanut oil or palm oil, and the strong base is sodium hydroxide or potassium hydroxide. The molar ratio of the vegetable oil to the strong base is 1:(1-4); (2) Synthesis of unsaturated fatty acids with hydroxyl groups: the unsaturated fatty acids obtained in step (1) are esterified with ethylene glycol in chloroform at a temperature of 50 to 60°C for a reaction time of 3 to 6 hours. The molar ratio of the unsaturated fatty acid to the ethylene glycol is 1:(0.5 to 1.5). Concentrated sulfuric acid is added as a catalyst. The molar ratio of the unsaturated fatty acid to the concentrated sulfuric acid is 1:(0.05 to 0.2). (3) Modification of esterified fatty acid by diethylene ketone: The hydroxyl-containing unsaturated fatty acid obtained in step (2) is reacted with diethylene ketone in chloroform, and triethylamine is added as an acid-binding agent. The molar ratio of the hydroxyl-containing unsaturated fatty acid to triethylamine is 1:(0.5-2.0). The reaction temperature is 35-45°C, and the reaction time is 12-24 hours. After purification by chromatography column method, a β-diketone functionalized plant oil extractant is obtained. The chromatography solvent is a mixed solvent of petroleum ether and ethyl acetate, and the volume ratio is 1:(0.5-1).

2. The preparation method according to claim 1, characterized in that The unsaturated fatty acids obtained by hydrolyzing the vegetable oil in step (1) are one or more of oleic acid, linoleic acid, linolenic acid, α-linolenic acid, and arachidonic acid.

3. The preparation method according to claim 1, characterized in that In step (3), the molar ratio of diketene to the unsaturated fatty acid with a hydroxyl group is 1:(0.1-2.0).

4. A β-diketone functionalized plant oil extractant prepared by the method according to any one of claims 1 to 3, characterized in that: Its general structural formula is as follows: in, It is a C10-C24 straight-chain or branched unsaturated alkane, and the value of x is an integer between 10 and 24.

5. Use of the extractant according to claim 4 for extracting lithium ions in a lithium-containing solution, characterized in that: The following steps are involved: (a) preparing an extraction organic phase: mixing the extractant with a diluent such as kerosene or dichloromethane to obtain an extraction organic phase having a concentration of 0.1 to 1.1 mol / L, and adding tributyl phosphate (TBP) as a co-extractant at a concentration ratio of 1:1 to the extractant; (b) Lithium extraction: The lithium-containing solution and the extracted organic phase are mixed in a volume ratio of 1:10 to 10:1, the solution pH is controlled to be 1 to 14, the lithium ion concentration is 0.01 to 10 g / L, and the sodium ion concentration is 10 to 30 times the lithium ion concentration. After extraction at 5 to 75°C, the loaded organic phase is separated; (c) Stripping and releasing lithium: The loaded organic phase is stripped with hydrochloric acid or sulfuric acid solution with a concentration of 0.1 to 10 mol / L at a stripping temperature of 35 to 55°C and a volume ratio of the stripping agent to the loaded organic phase of 1:10 to 10:1 to obtain a lithium ion-rich solution.

6. The use according to claim 5, characterized in that In step (b) of extracting lithium, the pre-extraction solution contains sodium ions.

7. The use according to claim 5, characterized in that The extractant is recycled for no less than 10 times, the lithium extraction efficiency is maintained above 80%, and the lithium / sodium separation factor is ≥286.5.

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