A composite extraction system and process for extracting lithium from a lithium-containing solution

Abstract

The present invention belongs to the technical field of lithium extraction, and particularly relates to a composite extraction system and process for extracting lithium from a lithium-containing solution. The composite extraction system for extracting lithium from the lithium-containing solution comprises the following components: 0.1-1 mol / L of an N-containing diketone compound shown in Formula 1A, 0.2-0.8 mol / L of a tertiary amide compound shown in Formula 1B, 0.5-2 mol / L of a phosphoric ester compound shown in Formula 1C, 0.05-0.2 mol / L of 2,4,5,6-tetraaminopyrimidine, and a diluent. The composite extractant system and extraction process applicable to a wide pH range provided by the present invention have the advantages of being able to extract lithium in the aqueous phase under weakly alkaline conditions with pH≥9, having high selectivity, no alkali consumption, fast phase separation, and no emulsification, and being applicable to large-scale industrial lithium extraction.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium extraction, and particularly relates to a composite extraction system and process for extracting lithium from a lithium-containing solution. Background Art

[0002] The sources of lithium in China mainly include lithium-containing ores, such as spodumene, lepidolite, etc. With the rise of new energy vehicles, lithium resources have gradually become insufficient and prices have increased. Finding new lithium sources is of great significance for the further development of the new energy industry. China has rich salt lake brine resources, and the resources of lithium in brine in China are abundant, which is an important resource for the future development of the lithium industry. At present, solvent extraction is used to selectively separate Li from Na, K, Mg, Ca, etc., which is a new and promising method. β-diketone compounds have the characteristic of selectively extracting lithium, mainly including acetylacetone, ditertiaryvaleroylmethane, benzoylacetone, benzoyltrifluoroacetone, thenoyltrifluoroacetone, etc., among which fluoroacetone has better effect. However, a problem faced by diketone extractants, especially fluorinated diketones, is that the applicable pH range is relatively narrow, and higher pH conditions are required for smooth extraction. Adjusting the pH of the lithium-containing aqueous solution requires a large amount of alkali, and the highly alkaline solution also needs to be neutralized before discharge; moreover, under strong alkaline conditions, the loss of the extractant is large, and the large loss of the organic phase will lead to a significant increase in cost. Therefore, it is particularly important to develop a system that can effectively extract lithium in a wide pH range in the current environment that emphasizes green environmental protection.

[0003] CN118241039A discloses an extractant for extracting lithium from an alkaline lithium-containing solution, including: a main extractant, a strengthening agent, and a co-extractant; the main extractant is an alkyl diketone compound, the strengthening agent is a fluoro diketone compound, and the co-extractant is a phosphine oxide compound. The alkyl diketone compound and the fluoro diketone compound combine the respective advantages of the two and cooperate with each other synergistically to obtain excellent comprehensive effects, and the pH of the aqueous phase is nearly neutral after extraction and stripping.

[0004] CN116904765A discloses a method for selectively extracting and precipitating lithium from lithium-containing alkaline aqueous solutions, comprising the following steps: (1) Weigh a certain mass of naphthenic acid compounds, alkylphenoxy carboxylic acid derivatives, or a mixture of both in a certain mass ratio, add them to the lithium-containing alkaline aqueous solution, and stir and mix at room temperature for 5 minutes to 1 hour to obtain a liquid-solid two-phase mixture; (2) Dilute the liquid-solid two-phase mixture obtained in step (1) with water by 20 to 50 times, add a flocculant, stir and let stand for a period of time, and then filter or centrifuge to obtain a solid; (3) Wash the solid obtained in step (2) with deionized water until the filtrate is neutral, then add an anti-extraction agent aqueous solution according to a certain mass ratio, stir and mix at a temperature of 20 to 80 °C for 5 minutes to 1 hour, and cool to room temperature to obtain a liquid-liquid two-phase mixture or a liquid-solid two-phase mixture; (4) Centrifuge and separate the liquid-liquid two-phase mixture obtained in step (3), wash the upper liquid phase obtained with deionized water until neutral, and return it to step (1) and add it to the lithium-containing alkaline aqueous solution to repeat steps (1) to (4). Further, or filter or centrifuge the liquid-solid two-phase mixture obtained in step (3), wash the solid obtained with deionized water until the filtrate is neutral, and return it to step (1) and add it to the lithium-containing alkaline aqueous solution to repeat steps (1) to (4).

[0005] CN115433830A discloses an extraction system for extracting lithium from alkaline lithium-containing solutions, comprising a mixed solution containing an extractant and a synergistic extractant; wherein, the extractant is selected from any one or more of isooctyl salicylate, n-octyl salicylate, butyl salicylate, propyl salicylate, hexyl salicylate, and isoamyl salicylate, and the synergistic extractant is selected from any one or more of triphenylphosphine oxide, trioctylphosphine oxide, trialkylphosphine oxide, tributyl phosphate, phenylbis(2-ethylhexyl) phosphate, trioctyl phosphate, 2-(diethylhexyl)acetamide, and 2-(dimethylheptyl)acetamide.

[0006] The above patents disclose methods for extracting lithium from alkaline solutions, but all require the initial aqueous phase to be at a relatively high pH for extraction to proceed. Developing a system that can effectively extract lithium within a wide pH range, especially a system with excellent extraction performance at pH≥9, has important significance and commercial value.

[0007] CN110777266A discloses an extraction system for separating calcium and extracting lithium from calcium-containing brines using a secondary amide / alkane composite solvent. The extraction system contains two types of substances, A and B; wherein type A substances are secondary amides composed of a single compound or a mixture of two or more, and type B substances are alkanes. It has excellent extraction performance in the extraction of high calcium-lithium ratio oilfield brines. However, the single-stage extraction efficiency of Li is very low, and it is only applicable to high calcium systems and not applicable to high sodium systems. Summary of the Invention

[0008] In view of the deficiencies of the prior art that the extraction system for extracting lithium from lithium-containing solutions requires relatively high pH conditions, has high losses of organic solvents, long extraction times, and is not conducive to industrial production, the present invention provides a composite extractant system applicable to a wide pH range and an extraction process. The composite extraction system of the present invention includes an N-diketone compound, a tertiary amide compound, a phosphoric acid ester compound, 2,4,5,6-tetraaminopyrimidine, and a diluent. The composite extractant system of the present invention has the advantages of high selectivity, no alkali consumption, fast phase separation, and no emulsification, and is very suitable for large-scale industrial lithium extraction. To achieve this purpose, the present invention adopts the following technical solutions:

[0009] A composite extraction system for extracting lithium from a lithium-containing solution, comprising the following components:

[0010] 0.1 - 1 mol / L of an N-diketone compound represented by Formula 1A, 0.2 - 0.8 mol / L of a tertiary amide compound represented by Formula 1B, 0.5 - 2 mol / L of a phosphoric acid ester compound represented by Formula 1C, 0.05 - 0.2 mol / L of 2,4,5,6-tetraaminopyrimidine, and a diluent;

[0011] 1A

[0012] wherein, R 1 , R 2 , R 3 , R 4 are independently selected from C1-10 alkyl, C1-10 alkoxy, C6-20 aryl, or C5-15 heteroaryl; the C5-15 heteroaryl contains 1 - 3 heteroatoms including O, S, N, and P;

[0013] 1B

[0014] wherein, R 5 is C6-C20 aryl, and R 6 , R 7 are independently selected from C1-C10 alkyl;

[0015] 1C

[0016] wherein, R 8 , R 9 , R 10 are independently selected from C1-10 alkyl, C1-10 alkoxy, C6-20 aryl, C5-15 heteroaryl, wherein at least one of R 8 , R 9 , R 10 is C1-10 alkoxy;

[0017] The chemical formula of the 2,4,5,6 - tetraaminopyrimidine is as follows: .

[0018] Furthermore, the composite extraction system for extracting lithium from the lithium - containing solution provided by the present invention includes the following components: 0.3 - 0.7 mol / L of the N - containing diketone compound shown in Formula 1A, 0.25 - 0.5 mol / L of the tertiary amide compound shown in Formula 1B, 1 - 1.5 mol / L of the phosphoric ester compound shown in Formula 1C, 0.05 - 0.1 mol / L of 2,4,5,6 - tetraaminopyrimidine, and a diluent.

[0019] The solvent system for extracting lithium of the present invention, the N - containing diketone compound shown in Formula 1A has an added N atom on the basis of the conventional diketone compound, endows the composite extraction system with good selectivity for extracting lithium without the need for fluoro - substituents, and is not easily emulsified. The cooperative effect of the tertiary amide compound shown in Formula 1B and 2,4,5,6 - tetraaminopyrimidine enables the composite extraction system of the present invention to have excellent extraction performance within a wide pH range, and can effectively and selectively extract lithium under weakly alkaline conditions (pH≥9), completing the good extraction performance that the conventional extractant only has in a higher alkaline environment with pH≥12. The inventors also tried its polyamino compounds, such as chain polyamines like diethylenetriamine and triethylenetetramine, or aromatic polyamino compounds such as tetra - (4 - amino - (1,1 - biphenyl)) ethylene, 3,3'-diaminobenzidine, and 3,3',4,4'-tetraaminodiphenyl ether. However, only 2,4,5,6 - tetraaminopyrimidine can simultaneously improve the extraction performance, phase - separation time of the extraction system and broaden the pH range, and it is necessary to control the concentration of 2,4,5,6 - tetraaminopyrimidine in the composite extraction system. Within the range of 0.05 - 0.2 mol / L, preferably within the range of 0.05 - 0.1 mol / L, it has an improvement effect on the extraction system.

[0020] Furthermore, R 1 , R 2 , R 3 , R 4 , R 8 , R 9 , R 10 are independently selected from C1 - 6 alkyl, C1 - 6 alkoxy, C6 - 12 aryl, C5 - 15 heteroaryl; at least one of R 8 , R 9 , R 10 is C1 - 6 alkoxy; R 5 is C6 - C12 aryl; R 6 , R 7 are independently selected from C1 - 6 alkyl.

[0021] Further, the C1-6 alkyl group is selected from methyl, ethyl, propyl, butyl, pentyl, and hexyl; the C1-6 alkoxy group is selected from methoxy, ethoxy, propoxy, butoxy, pentyloxy, and hexyloxy; the C6-12 aryl group is selected from phenyl, biphenyl, naphthyl, and anthryl; the C5-15 heteroaryl group is selected from pyrrolyl, pyrazolyl, pyridyl, and thienyl; the H atom in the above alkyl, alkoxy, aryl, and heteroaryl groups is optionally substituted by a substituent, and the substituent is selected from at least one of methyl, ethyl, isopropyl, trifluoromethyl, nitro, hydroxy, amino, and mercapto.

[0022] Further, R 2 is connected to R 3 to form a cycloalkane or a nitrogen-containing heterocycle, and the ring may contain heteroatoms of nitrogen, oxygen, and sulfur. For example, R 2 is connected to R 3 to form pyrazolone, 2H-pyrrol-2-one, imidazolone, thiazolidinone, pyridone, or oxazolidinone.

[0023] In a preferred technical solution of the present invention, Compound 1A is selected from at least one of N,N-bis(2-ethylhexyl)-3-butanone acetamide, N,N-dihexyl-3-butanone acetamide, N,N-diisopropyl-3-butanone acetamide, 2-ethyl-N,N-dimethyl-3-oxohexanamide, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, and 1-(4-trifluoromethylphenyl)-3-methyl-4-benzoyl-5-pyrazolone; Compound 1B is selected from at least one of N,N-dimethyl-4-methylbenzamide, N,N-diethyl-4-methylbenzamide, N,N-diisopropyl-4-methylbenzamide, N,N-dihexyl-4-methylbenzamide, and N,N-dibutyl-4-methylbenzamide; Compound 1C is selected from at least one of trioctyl phosphate, tributyl phosphate, trihexyl phosphate, triheptyl phosphate, tripentyl phosphate, diisooctyl methylphosphonate, and triphenoxyphosphine oxide.

[0024] Further, the diluent includes any one or a combination of at least two of C4-C 14 alkanes, C4-C 14 ester compounds, C4-C 14 alcohol compounds, C4-C 14 ketone compounds, and aromatic hydrocarbon compounds; preferably, the diluent is one or a combination of two or more of kerosene, sulfonated kerosene, D80, 260# solvent oil, Escaid 110, butyl benzoate, heptyl acetate, octanol, dodecanol, 4-methyl-2-pentanone, diisobutyl ketone, S150, and toluene, which can be miscible in any volume ratio.

[0025] The second object of the present invention is to provide a method for extracting lithium, which includes the following steps:

[0026] (S1) Add the N-diketone compound shown in Formula 1A, the tertiary amide compound shown in Formula 1B, the phosphoric ester compound shown in Formula 1C, and 2,4,5,6-tetraaminopyrimidine into a diluent, and mix evenly to obtain an organic phase;

[0027] (S2) Adjust the pH value of the lithium-containing aqueous solution to 9 - 10 to obtain an aqueous phase;

[0028] (S3) Mix the organic phase and the aqueous phase, and perform countercurrent extraction to obtain an organic phase enriched with lithium;

[0029] (S4) Wash the organic phase enriched with lithium successively by countercurrent washing with an acid solution and countercurrent stripping with an acid solution to obtain a stripped organic phase and a lithium-rich aqueous phase. The stripped organic phase is returned to the initial extraction device for recycling.

[0030] In step (2), if the initial pH of the aqueous phase ≥ 9, no alkali solution needs to be added for adjustment. If the alkalinity is insufficient, one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, ammonia water, etc. can be added to adjust the pH to weakly alkaline, such as pH = 9 - 11.

[0031] In step (3), the extraction equipment described can be a mixer-settler, an extraction column or a centrifugal extractor. The number of extraction stages is 1 - 30, preferably 5 - 20. The volume ratio of the organic phase to the aqueous phase is 1:60 - 60:1, preferably 1:1 - 5.

[0032] In step (4), the acid in the acid solution is at least one of hydrochloric acid, sulfuric acid, and nitric acid. The concentration of the acid during countercurrent washing is 0.01 - 0.5 mol / L, preferably 0.1 - 0.3 mol / L. During countercurrent stripping with the acid solution, the concentration of the acid is 0.5 - 3 mol / L, preferably 1 - 2 mol / L. During countercurrent washing with the acid solution and countercurrent stripping with the acid solution, the volume ratio of the organic phase to the aqueous phase is 5 - 30:1, such as 10 - 20:1.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] The composite extraction system provided by the present invention can be applicable in a relatively wide pH range, especially can have good extraction effects under weakly alkaline conditions, such as under the weakly alkaline conditions of pH = 9 - 10. In addition, during extraction with the composite extraction system of the present invention, emulsification is not likely to occur, the loss of the organic phase is small, and the phase separation time is fast. It can selectively extract lithium from weakly alkaline lithium-containing aqueous solutions at low cost, efficiently and rapidly. The pH of the raffinate is close to neutral and can be discharged after simple treatment. In addition, the loss after extraction with the composite extraction system of the present invention is small, and it can be recycled repeatedly with basically no decline in extraction performance. The high-purity lithium-containing solution obtained after extraction can be used to prepare high-purity lithium carbonate with a purity greater than 99.7%, realizing the short-process preparation of battery-grade lithium carbonate. Brief Description of the Drawings

[0035] Figure 1 is the XRD pattern of the battery-grade lithium carbonate obtained in Example 1;

[0036] Figure 2 is the photo of the first phase separation in Example 1 over time;

[0037] Figure 3 is the photo of the first phase separation in Comparative Example 1 over time. Detailed Description of the Invention

[0038] The technical solution of the present invention will be further described below through specific embodiments.

[0039] Example 1

[0040] The composition of the composite extractant is 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (content 0.5 mol / L), N,N-dihexyl-4-methylbenzamide (content 0.4 mol / L), trioctyl phosphate (content 1 mol / L), 2,4,5,6-tetraaminopyrimidine (content 0.07 mol / L), and the diluent is a mixture of D80 and diisobutyl ketone (v / v = 8:1). The components of the composite extractant are mixed evenly to obtain the organic phase. In the water phase to be treated, the lithium content is 2.6 g / L, sodium 67.7 g / L, potassium 12.3 g / L, magnesium 3.5 g / L, and pH = 9.

[0041] The organic phase and the water phase are subjected to three-stage continuous countercurrent extraction in a mixer-settler at a volume ratio of 1:1 to obtain the organic phase enriched in lithium. The organic phase is washed twice with 0.3 mol / L hydrochloric acid, where the volume ratio of the organic phase to the water phase is 10:1. For the first phase separation, the organic phase is then subjected to two-stage stripping with 4 mol / L hydrochloric acid, and the volume ratio of the organic phase to the water phase is 15:1. For the second phase separation, the concentration of LiCl in the stripping liquid water phase is 30.1 g / L, and the lithium recovery rate reaches 97.5%. The organic phase after stripping is returned to the extraction equipment for continuous recycling. Lithium chloride solution is added with sodium carbonate to precipitate battery-grade lithium carbonate with a purity > 99.9%.

[0042] Figure 1 is the XRD pattern of the battery-grade lithium carbonate obtained in Example 1.

[0043] Table 1 shows the elemental composition of the battery-grade lithium carbonate obtained in Example 1.

[0044] Table 1 Elemental Composition of Lithium Carbonate

[0045] .

[0046] Example 2

[0047] Other conditions are the same as those in Example 1, except that the composition of the organic-phase composite extractant is 1-(4-trifluoromethylphenyl)-3-methyl-4-benzoyl-5-pyrazolone (content: 0.6 mol / L), N,N-dibutyl-4-methylbenzamide (content: 0.4 mol / L), the organophosphorus compound is tributyl phosphate (content: 1.3 mol / L), 2,4,5,6-tetraaminopyrimidine (content: 0.05 mol / L), and the diluent is a mixture of heptyl acetate and octanol (v / v = 4:1).

[0048] Example 3

[0049] Other conditions are the same as those in Example 1, except that the composition of the organic-phase composite extractant is N,N-dihexyl-3-butanone acetamide (content: 0.4 mol / L), N,N-diisopropyl-4-methylbenzamide (content: 0.8 mol / L), the organophosphorus compound is tributyl phosphate (content: 1.2 mol / L), 2,4,5,6-tetraaminopyrimidine (content: 0.04 mol / L), and the diluent is a mixture of Solvent 260# and S150 (v / v = 1:1).

[0050] Example 4

[0051] Other conditions are the same as those in Example 1, except that the composition of the organic-phase composite extractant is N,N-diisopropyl-3-butanone acetamide (content: 0.7 mol / L), N,N-dibutyl-4-methylbenzamide (content: 0.3 mol / L), the organophosphorus compound is trioctyl phosphate (content: 1.1 mol / L), 2,4,5,6-tetraaminopyrimidine (content: 0.1 mol / L), and the diluent is a mixture of sulfonated kerosene and octanol (v / v = 5:1).

[0052] Example 5

[0053] Other conditions are the same as those in Example 1, except that the composition of the organic-phase composite extractant is N,N-bis(2-ethylhexyl)-3-butanone acetamide (content: 0.2 mol / L), N,N-dihexyl-4-methylbenzamide (content: 0.5 mol / L), the organophosphorus compound is trioctyl phosphate (content: 1.5 mol / L), 2,4,5,6-tetraaminopyrimidine (content: 0.2 mol / L), and the diluent is a mixture of S150 and 4-methyl-2-pentanone (v / v = 10:1).

[0054] Example 6

[0055] Other conditions are the same as those in Example 1, except that the pH of the aqueous phase to be treated is 11.7.

[0056] Comparative Example 1

[0057] Other conditions were the same as in Example 1, except that the extractant was a commercial lithium extractant Lix54-P113 composite system.

[0058] Comparative Example 2

[0059] Other conditions were the same as in Comparative Example 1, except that the pH of the aqueous phase to be treated was 11.7.

[0060] Comparative Example 3

[0061] Other conditions were the same as in Example 1, except that in the organic phase composite extractant, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone was replaced with thiobenzoyltrifluoroacetone at an equimolar concentration.

[0062] Comparative Example 4

[0063] Other conditions were the same as in Example 1, except that 2,4,5,6-tetraaminopyrimidine was not added to the organic phase composite extractant.

[0064] Comparative Example 5

[0065] Other conditions were the same as in Example 1, except that in the organic phase composite extractant, 2,4,5,6-tetraaminopyrimidine was replaced with triethylenetetramine at an equimolar concentration.

[0066] Comparative Example 6

[0067] Other conditions were the same as in Example 1, except that in the organic phase composite extractant, 2,4,5,6-tetraaminopyrimidine was replaced with 3,3',4,4'-tetraaminodiphenyl ether at an equimolar concentration.

[0068] Application Example 1

[0069] The extraction systems of the above examples and comparative examples were evaluated, and the results are shown in Table 2 below.

[0070] Figure 2 It is a photo of the first phase separation of Example 1 over time. Whether the phase separation was completed was observed every 10 s to determine the phase separation time.

[0071] Figure 3 It is a photo of the first phase separation of Comparative Example 1 over time. Whether the phase separation was completed was observed every minute to determine the phase separation time.

[0072] It can be seen that Comparative Example 1 uses a commercial extractant, and at pH = 9, the extraction rate is very low, basically unable to meet the need for lithium extraction. When the pH is close to 12, the single-stage extraction rate of the commercial extractant for Li can reach the same level as that of the present invention; however, the selection is not good, and the phase separation time is long, taking about 2 hours to reach the degree required for extraction and separation. On the other hand, the composite extraction system of the present invention can complete extraction under lower pH conditions, has a high single-stage extraction rate for Li, good selectivity for Li, and can complete phase separation within 80 s, showing great practical value in industry.

[0073] Table 2 Performance Test of the Composite Extraction System

[0074] 。

[0075] It can be seen from the data in Table 2 that the composite extraction system of the present invention can quickly and efficiently complete the extraction of lithium in the aqueous phase under lower pH conditions (pH = 9), has high extraction efficiency, good selectivity, and fast phase separation time. The commercial extractant cannot extract smoothly at pH = 9, and the pH value needs to be increased, and its selectivity for Li is not as good as that of the composite extraction system of the present invention. The composite extraction system of the present invention can have excellent extraction performance under lower pH conditions, which is attributed to the reasonable compounding of each component, especially 2,4,5,6-tetraaminopyrimidine, but its concentration needs to be reasonably controlled, otherwise it is not conducive to the selective extraction of lithium instead.

[0076] Application Example 2

[0077] The composite extraction system of Example 1 was reused 10 times, and the results are shown in Table 3 below.

[0078] Table 3 Performance Test of the Extraction System of Example 1 after Repeated Cycling 10 Times

[0079] 。

[0080] The composite extraction system provided by the present invention not only has excellent extraction performance, but also can be recycled multiple times, and the extraction performance basically does not decline.

Claims

1. A composite extraction system for extracting lithium from a lithium-containing solution, characterized in that, It comprises the following components: 0.1 - 1 mol / L of the N-containing diketone compound represented by Formula 1A, 0.2 - 0.8 mol / L of the tertiary amide compound represented by Formula 1B, 0.5 - 2 mol / L of the phosphoric ester compound represented by Formula 1C, 0.05 - 0.2 mol / L of 2,4,5,6-tetraaminopyrimidine, and a diluent; 1A Among them, R 1 , R 2 , R 3 , R 4 are independently selected from C1-10 alkyl, C1-10 alkoxy, C6-20 aryl or C5-15 heteroaryl; the C5-15 heteroaryl contains 1-3 heteroatoms including O, S, N, P; or R 2 and R 3 are connected to form a nitrogen-containing heterocycle; 1B Among them, R 5 is a C6-C20 aryl group, and R 6 , R 7 are independently selected from C1-C10 alkyl groups; 1C Among them, R 8 , R 9 , R 10 are independently selected from C1-10 alkyl, C1-10 alkoxy, C6-20 aryl, C5-15 heteroaryl, wherein at least one of R 8 , R 9 , R 10 is C1-10 alkoxy; The chemical formula of the 2,4,5,6 - tetraaminopyrimidine is as follows: .

2. The composite extraction system according to claim 1, wherein It comprises the following components: 0.3 - 0.7 mol / L of the N-containing diketone compound represented by Formula 1A, 0.25 - 0.5 mol / L of the tertiary amide compound represented by Formula 1B, 1 - 1.5 mol / L of the phosphoric ester compound represented by Formula 1C, 0.05 - 0.1 mol / L of 2,4,5,6-tetraaminopyrimidine, and a diluent.

3. The composite extraction system according to claim 1, characterized in that, R 1 ,R 2 ,R 3 ,R 4 ,R 8 ,R 9 ,R 10 independently selected from C1-6 alkyl, C1-6 alkoxy, C6-12 aryl, C5-15 heteroaryl; R 8 ,R 9 ,R 10 at least one of which is C1-6 alkoxy; R 5 is C6-C12 aryl; R 6 、R 7 independently selected from C1-6 alkyl.

4. The composite extraction system according to claim 3, wherein The C1-6 alkyl group is selected from methyl, ethyl, propyl, butyl, pentyl, and hexyl; the C1-6 alkoxy group is selected from methoxy, ethoxy, propoxy, butoxy, pentyloxy, and hexyloxy; the C6-12 aryl group is selected from phenyl, biphenyl, naphthyl, and anthryl; the C5-15 heteroaryl group is selected from pyrrolyl, pyrazolyl, pyridyl, and thienyl.

5. The composite extraction system according to claim 1, wherein The H atom in the alkyl group, alkoxy group, aryl group, or heteroaryl group is substituted by a substituent, and the substituent is selected from at least one of methyl, ethyl, isopropyl, trifluoromethyl, nitro, hydroxyl, amino, and mercapto.

6. The composite extraction system according to claim 1, wherein R 2 Connected to R 3 to form a heterocycle containing N, with heteroatoms of oxygen and sulfur on the ring.

7. The composite extraction system according to claim 1, wherein R 2 With R 3 is linked to form pyrazolone.

8. The composite extraction system according to claim 1, wherein Compound 1A is selected from at least one of N,N-bis(2-ethylhexyl)-3-butanone acetamide, N,N-dihexyl-3-butanone acetamide, N,N-diisopropyl-3-butanone acetamide, 2-ethyl-N,N-dimethyl-3-oxohexanamide, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, 1-(4-trifluoromethylphenyl)-3-methyl-4-benzoyl-5-pyrazolone; and / or Compound 1B is selected from at least one of N,N-dimethyl-4-methylbenzamide, N,N-diethyl-4-methylbenzamide, N,N-diisopropyl-4-methylbenzamide, N,N-dihexyl-4-methylbenzamide, N,N-dibutyl-4-methylbenzamide; and / or Compound 1C is selected from at least one of trioctyl phosphate, tributyl phosphate, trihexyl phosphate, triheptyl phosphate, tripentyl phosphate, diisooctyl methylphosphonate, and triphenoxyphosphine oxide.

9. The composite extraction system according to claim 1, wherein The diluent includes alkanes having C4-C 14 , ester compounds having C4-C 14 , alcohol compounds having C4-C 14 , ketone compounds having C4-C 14 , or any combination of one or at least two of aromatic compounds.

10. A method for extracting lithium, characterized in that, It comprises the following steps: (S1) Add the N-containing diketone compound represented by Formula 1A, the tertiary amide compound represented by Formula 1B, the phosphoric ester compound represented by Formula 1C, and 2,4,5,6-tetraaminopyrimidine to a diluent, and mix evenly to obtain the composite extraction system according to any one of claims 1 - 9; (S2) Adjust the pH value of the lithium-containing aqueous solution to 9 - 10 to obtain an aqueous phase; (S3) Mix the organic phase with the aqueous phase and perform countercurrent extraction to obtain an organic phase enriched with lithium; (S4) Subject the organic phase enriched with lithium to acid solution countercurrent washing and acid solution countercurrent stripping in sequence to obtain a stripped organic phase and a lithium-rich aqueous phase. The stripped organic phase is returned to the initial extraction device and reused in circulation.

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