Method for extracting lithium through back extraction by using CO2

Abstract

The invention relates to a method for extracting lithium through back extraction by using CO2. The method comprises the following steps: providing a lithium-loaded extraction phase; cO2, water, a stabilizer and the lithium-loaded extraction phase are mixed for reverse extraction, reverse extraction liquid and no-load extraction liquid are obtained after phase splitting, and the stabilizer is selected from at least one of ketones, esters, ethers, C8-C16 saturated alkanes and C8-C16 saturated cyclic hydrocarbons; continuously carrying out phase splitting on the strip liquor to obtain a lithium-rich solution and a stabilizer recovery solution; and carrying out heat treatment on the lithium-rich solution to obtain lithium carbonate. The stabilizer provided by the invention can improve the retention time and retention amount of CO2, so that the unit concentration of CO2 in a back extraction system is improved, the utilization rate of CO2 can be further improved, and the actual consumption of CO2 when 1 ton of Li2CO3 is produced is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium extraction, and particularly to a method for extracting lithium by counter-extraction using CO2. Background Art

[0002] CN110240183A, CN110656239A, etc. have all disclosed the use of CO2 to replace traditional hydrochloric acid, etc. for counter-extraction of lithium. Although the introduction methods of CO2 are different, essentially, it is the H generated by introducing CO2 into water + exchanging with Li + for exchange.

[0003] Theoretically, when extracting lithium by counter-extraction using CO2, 594 kg of CO2 is required to produce 1 ton of Li2CO3. However, due to the low solubility of CO2, as disclosed in the method of CN110240183A, CO2 is first introduced into water and then mixed with the lithium-loaded extraction phase for counter-extraction. When producing 1 ton of Li2CO3, the actual consumption of CO2 reaches more than 4 tons. As disclosed in the method of CN110656239A, a gas-liquid-liquid continuous three-phase reaction is carried out among the lithium-loaded extraction phase, water, and CO2, and CO2 is continuously introduced. When producing 1 ton of Li2CO3, the actual consumption of CO2 reaches more than 3 tons. Therefore, in the current methods for extracting lithium by counter-extraction using CO2, the consumption of CO2 is relatively high and the effective utilization rate is relatively low. Summary of the Invention

[0004] Based on this, it is necessary to provide a method for extracting lithium by counter-extraction using CO2 to effectively reduce the actual consumption of CO2 when producing 1 ton of Li2CO3 for the above problems.

[0005] A method for extracting lithium by counter-extraction using CO2 includes the following steps:

[0006] S1, providing a lithium-loaded extraction phase;

[0007] S2, mixing CO2, water, a stabilizer with the lithium-loaded extraction phase for counter-extraction, and after phase separation, obtaining a counter-extraction solution and an empty extraction solution, wherein the stabilizer is selected from at least one of ketones, esters, ethers, saturated alkanes with C8-C 16 and saturated cycloalkanes with C8-C 16 ;

[0008] S3, further separating the counter-extraction solution to obtain a lithium-rich solution and a stabilizer recovery solution;

[0009] S4, performing heat treatment on the lithium-rich solution to obtain lithium carbonate.

[0010] In one embodiment, in the step of performing back extraction by mixing CO2, water, a stabilizer with the lithium-loaded extraction phase, water and the stabilizer are first mixed, then CO2 is introduced, and then it is mixed with the lithium-loaded extraction phase for back extraction.

[0011] In one embodiment, in the step of performing back extraction by mixing CO2, water, a stabilizer with the lithium-loaded extraction phase, CO2 is first introduced into water, then the stabilizer is added, and then it is mixed with the lithium-loaded extraction phase for back extraction.

[0012] In one embodiment, in the step of performing back extraction by mixing CO2, water, a stabilizer with the lithium-loaded extraction phase, CO2, water, the stabilizer and the lithium-loaded extraction phase are mixed simultaneously for back extraction.

[0013] In one embodiment, the ketones are selected from at least one of β-diketones, aliphatic ketones, alicyclic ketones, and aromatic ketones;

[0014] And / or, the ethers are selected from at least one of polyethers, glycol ethers, block ethers, and crown ethers;

[0015] And / or, the esters are selected from phosphate esters.

[0016] In one embodiment, the ketones are selected from at least one of benzoyltrifluoroacetone, thenoyltrifluoroacetone, furanoyltrifluoroacetone, p-toluoyltrifluoroacetone, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, 1-phenyl-3-methyl-4-octanoyl-5-pyrazolone, 1-phenyl-3-methyl-4-valeryl-5-pyrazolone, octylphenyl-methyl-β-diketone, nonylphenyl-methyl-β-diketone, dodecylphenyl-methyl-β-diketone, tetradecylphenyl-methyl-β-diketone, decylphenyl-ethyl-β-diketone;

[0017] And / or, the ethers are selected from at least one of 12-crown-4, 15-crown-5, 18-crown-6, benzo-12-crown-4, benzo-15-crown-5, benzo-18-crown-6;

[0018] And / or, the esters are selected from at least one of diisopentyl methylphosphonate, dimethylheptyl methylphosphonate, tributyl phosphate, trioctyl phosphate, trialkyl phosphate, dialkyl phosphate, dibutyl butylphosphate, methylene tetrabutyl bisphosphate;

[0019] And / or, the alkylphosphine oxides are selected from at least one of trioctylphosphine oxide, trihexylphosphine oxide, trinonylphosphine oxide, tridecylphosphine oxide;

[0020] And / or, the C8-C 16The saturated alkanes are selected from at least one of n-dodecane, n-decane, isomeric tetradecane, and isomeric hexadecane;

[0021] And / or, the C8-C 16 The saturated cycloalkanes are selected from at least one of cyclooctane, cyclodecane, cycloundecane, cyclododecane, cyclotetradecane, and cyclohexadecane.

[0022] In one embodiment, the volume ratio of the stabilizer to water is 0.01:1 - 0.5:1;

[0023] And / or, the pressure when CO2 is introduced is 0.1 MPa - 1.6 MPa.

[0024] In one embodiment, the volume ratio of the stabilizer to water is 0.01:1 - 0.2:1;

[0025] And / or, the pressure when CO2 is introduced is 0.1 MPa - 0.8 MPa.

[0026] In one embodiment, the volume ratio of the stabilizer to water is 0.01:1 - 0.1:1;

[0027] And / or, the pressure when CO2 is introduced is 0.2 MPa - 0.6 MPa.

[0028] In one embodiment, the stabilizer recovery liquid in step S3 is recycled to step S2 for use.

[0029] When the present invention uses CO2 for back extraction, by using a specific stabilizer, the residence time and residence amount of CO2 can be increased, thereby increasing the unit concentration of CO2 in the back extraction system. Furthermore, not only can the utilization rate of CO2 be increased, reducing the actual consumption of CO2 per ton of Li2CO3 produced, but also the production efficiency can be improved and the production cycle can be shortened.

[0030] In addition, the stabilizer of the present invention has different water solubilities and phase separation speeds from the extractant, so the stabilizer can be recovered and reused by phase separation, which neither affects the recycling of the extractant nor affects the preparation of lithium carbonate by heat treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1Schematic process flow diagram for extracting lithium by back-extraction using CO2 in the present invention. Detailed implementation manners

[0033] To facilitate the understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, these embodiments or examples are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments or examples and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of the related listed items. The any and all combinations include any two related listed items, any more related listed items, or the combination of all related listed items.

[0035] In the present invention, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to an integer, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0036] As Figure 1 shown, the method for extracting lithium by back-extraction using CO2 provided by the present invention includes the following steps:

[0037] S1, providing a lithium-loaded extraction phase;

[0038] S2, mixing CO2, water, a stabilizer with the lithium-loaded extraction phase for back-extraction, and after phase separation, obtaining a back-extraction solution and an empty extraction solution. Among them, the stabilizer is selected from at least one of ketones, esters, ethers, C8-C 16 saturated alkanes, C8-C 16 saturated cycloalkanes;

[0039] S3, continuing to perform phase separation on the back-extraction solution to obtain a lithium-rich solution and a stabilizer recovery solution;

[0040] S4, performing heat treatment on the lithium-rich solution to obtain lithium carbonate.

[0041] The present invention does not impose special requirements on the lithium-loaded extraction phase in step S1, and the lithium-loaded extraction phase is obtained by phase separation after extracting a lithium-containing solution with an extractant.

[0042] For example, the lithium-loaded extraction phase is obtained by phase separation after extracting a lithium-containing solution such as salt lake brine, lithium ore leaching solution, lithium battery waste leaching solution, lithium precipitation mother liquor, etc. with an extractant. Among them, the lithium-containing solution is an alkaline lithium-containing solution, and further preferably has a pH of 10-13, such as pH 10, 11, 12 or 13, etc., or a range composed of any two of these values.

[0043] Optionally, the extractant includes an extractant and a diluent, and the volume ratio of the extractant in the extractant is not limited, and is specifically adjusted according to the selection of the extractant and the diluent. Exemplarily, the volume fraction of the extractant in the extractant is 40%-50%. Preferably, the extractant is selected from hydrophobic compounds, including trioxythiophene oxide, 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione, 1,1,1,2,2-pentafluoro-6,6-dimethyl-3,5-heptanedione, 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione, benzoyltrifluoroacetone, 1-phenyl-1,3-butadione, 1-benzoyl-2-nonanone, trialkyl phosphate, trialkyl phosphine oxide, trioctyl phosphine oxide, trihexyl phosphine oxide, dialkyl phosphate, methyl isobutyl ketone, 1-phenylazo-2-naphthol, n-octanol, isooctanol, 2-ethylhexanol, 14-crown-4 ether dibutyl butylphosphonate, dibutyl phosphate butyl ester, methylenetetrabutyl bisphosphonate, trioctylamine oxide, 1,10-phenanthroline, quaternary ammonium salt N 263 , at least one of dimethyldi(N-octadecyl)ammonium chloride, methyl dioctyl sulfonium chloride, 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Among them, the trialkyl phosphate includes tributyl phosphate, etc.; the diluent is selected from at least one of n-hexane, n-dodecane, cyclohexane, D70 special solvent oil, D80 special solvent oil, No. 120 solvent oil, No. 160 solvent oil, No. 200 solvent oil, ordinary kerosene, aviation kerosene, and sulfonated kerosene.

[0044] In step S2, when the present invention performs back extraction with CO2, ketones, esters, ethers, alkyl phosphine oxides, C8-C 16 saturated alkanes, C8-C 16 saturated cycloalkanes are further used as stabilizers.

[0045] First of all, these stabilizers can reduce the resistance between CO2 molecules, which is beneficial to improving the dispersion efficiency and distribution uniformity of CO2.

[0046] Secondly, all these stabilizers can change the solvation environment of water and increase the solubility sites in the back-extraction system through their own polarity and the synergistic effect of the molecular chains. This helps to capture and fix CO2 molecules, improving the solubility and dispersion effect of CO2 in water.

[0047] Therefore, the stabilizers of the present invention can all increase the residence time and residence amount of CO2, thereby increasing the unit concentration of CO2 in the back-extraction system, and further improving the utilization rate of CO2 and reducing the actual consumption of CO2 per ton of Li2CO3 produced.

[0048] Optionally, the ketones are selected from at least one of β-diketones, aliphatic ketones, alicyclic ketones, and aromatic ketones. Among them, β-diketones have two carbonyl groups, and their electronic structures are highly conjugated, which is beneficial to improving the solubility of CO2. Therefore, the ketones are further preferably β-diketones, including at least one of benzoyltrifluoroacetone, thiophenecarbonyltrifluoroacetone, furanoyltrifluoroacetone, p-toluoyltrifluoroacetone, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, 1-phenyl-3-methyl-4-octanoyl-5-pyrazolone, 1-phenyl-3-methyl-4-valeryl-5-pyrazolone, octylphenyl-methyl-β-diketone, nonylphenyl-methyl-β-diketone, dodecylphenyl-methyl-β-diketone, tetradecylphenyl-methyl-β-diketone, and decylphenyl-ethyl-β-diketone.

[0049] Optionally, the ethers are selected from at least one of polyethers, glycol ethers, block ethers, and crown ethers, and are preferably crown ethers, including at least one of 12-crown-4, 15-crown-5, 18-crown-6, benzo-12-crown-4, benzo-15-crown-5, and benzo-18-crown-6.

[0050] Optionally, the esters are preferably phosphoric esters, and further preferably at least one of diisopentyl methylphosphonate, dimethylheptyl methylphosphonate, tributyl phosphate, trioctyl phosphate, trialkyl phosphate, dialkyl phosphate, dibutyl butyl phosphate, and methylene tetrabutyl bisphosphate.

[0051] Optionally, the alkylphosphine oxides are selected from at least one of trioctylphosphine oxide, trihexylphosphine oxide, trinonylphosphine oxide, and tridecylphosphine oxide.

[0052] Optionally, the C8-C 16 saturated alkanes are selected from at least one of n-dodecane, n-decane, isomeric tetradecane, and isomeric hexadecane.

[0053] Optionally, the C8-C 16 saturated cycloalkanes are selected from at least one of cyclooctane, cyclodecane, cycloundecane, cyclododecane, cyclotetradecane, and cyclohexadecane.

[0054] Specifically, in the step of mixing CO2, water, a stabilizer with the lithium-loaded extraction phase for back extraction, the mixing order is not required. For example: first mix water and the stabilizer, then introduce CO2, and then mix with the lithium-loaded extraction phase for back extraction; or, first introduce CO2 into water, then add the stabilizer, and then mix with the lithium-loaded extraction phase for back extraction; or, mix CO2, water, the stabilizer and the lithium-loaded extraction phase simultaneously for back extraction.

[0055] It can be understood that the step of mixing CO2, water, a stabilizer with the lithium-loaded extraction phase for back extraction in the present invention can be carried out using a static mixer, or can be carried out using a continuous mixing clarifier, an extraction column or a centrifugal extractor, etc. for countercurrent back extraction. The back extraction can be carried out in multiple stages and can be carried out intermittently or continuously.

[0056] Of course, in the step of mixing CO2, water, a stabilizer with the lithium-loaded extraction phase, different mixing orders have different utilization rates of CO2 and different consumption amounts of CO2. For example, when first mixing water and the stabilizer, then introducing CO2, and then mixing with the lithium-loaded extraction phase for back extraction, the actual consumption amount of CO2 can be reduced to about 0.6 - 0.8 tons per ton of Li2CO3 produced; when first introducing CO2 into water, then adding the stabilizer, and then mixing with the lithium-loaded extraction phase for back extraction, the actual consumption amount of CO2 can be reduced to about 2.0 - 2.5 tons per ton of Li2CO3 produced; when mixing CO2, water, the stabilizer and the lithium-loaded extraction phase simultaneously for back extraction, the actual consumption amount of CO2 can be reduced to about 0.8 - 1 ton per ton of Li2CO3 produced.

[0057] In order to improve the solubility and dissolution efficiency of CO2 in water, it is preferred to introduce CO2 under pressure. Preferably, the pressure when introducing CO2 in the present invention is 0.1 MPa - 1.6 MPa, more preferably 0.1 MPa - 0.8 MPa, and even more preferably 0.2 MPa - 0.6 MPa.

[0058] Optionally, the volume ratio of the stabilizer to water is 0.01:1 - 0.5:1, preferably 0.01:1 - 0.2:1, and more preferably 0.01:1 - 0.1:1, which is beneficial to both increasing the residence time and residence amount of CO2 and the dissolution amount of CO2.

[0059] The stabilizer of the present invention has different water solubilities and phase separation rates from the extraction solution. Furthermore, when phase separation is carried out in step S2, a back extraction solution and an empty extraction solution are obtained, and the stabilizer is mixed in the back extraction solution. Therefore, the empty extraction solution can be recycled to step S1 for mixing with the lithium-containing solution for extraction to prepare the lithium-loaded extraction phase.

[0060] Then, in step S3, the phase separation method can be continuously adopted to separate the stabilizer in the stripping solution, obtaining a stabilizer recovery solution and a lithium-rich solution. The stabilizer recovery solution can be recycled to step S2 for use, and the lithium-rich solution can be further processed by heat treatment to obtain lithium carbonate (Li2CO3). Among them, the temperature of the heat treatment is preferably greater than or equal to 50 °C, and considering efficiency and yield, the temperature of the heat treatment is further preferably 70 °C - 100 °C.

[0061] It can be understood that after the heat treatment of the lithium-rich solution in step S4, a mother liquor for lithium precipitation and CO2 are also obtained. Preferably, the CO2 is recycled to step S2 for use in back extraction by mixing with water, a stabilizer, and a lithium-loaded extraction phase. The mother liquor for lithium precipitation can be recycled to step S2 for use in back extraction by mixing with CO2, water, a stabilizer, and a lithium-loaded extraction phase. Alternatively, the mother liquor for lithium precipitation can be recycled to step S1 for use in extraction by mixing with a lithium-containing solution.

[0062] Therefore, when the present invention uses CO2 for back extraction, the utilization rate of CO2 can be improved, and the actual consumption of CO2 per ton of Li2CO3 produced can be reduced. This can not only improve production efficiency, shorten the production cycle, but also reduce the equipment volume and production cost.

[0063] In addition, after the consumption of CO2 is reduced, the gas flux can also be reduced, which can effectively alleviate problems such as emulsification and mutual entrainment of oil and water, and thus is conducive to continuous production and reduction of the loss of the extraction solution.

[0064] Hereinafter, the method for extracting lithium by back extraction using CO2 will be further described through the following specific examples.

[0065] Example 1

[0066] Dodecylphenyl-methyl-β-diketone and tributyl phosphate are used as extractants, and solvent oil No. 160 is used as a diluent. They are mixed to obtain an extraction solution, and the volume fraction of dodecylphenyl-methyl-β-diketone in the extraction solution is controlled to be 20%, and the volume fraction of tributyl phosphate is 20%. The pH of the salt lake brine with a lithium concentration of 2.5 g / L is adjusted to 12, and then it is mixed with the extraction solution for extraction. The volume ratio of the extraction solution to the salt lake brine is controlled to be 1:1. After phase separation, a lithium-loaded extraction phase with a lithium concentration of 2.49 g / L is obtained.

[0067] First, water and benzoyltrifluoroacetone are mixed at a volume ratio of 1:0.01, then CO2 is introduced (the introduction pressure is 0.3 MPa), and then it is mixed with the above-obtained lithium-loaded extraction phase to form a back extraction system for extraction. After phase separation, a stripping solution with a lithium concentration of 7.4 g / L and an empty extraction solution are obtained. The empty extraction solution is recycled for use in the extraction section.

[0068] The stripping solution obtained above is further phase-separated to obtain a lithium-rich solution and benzoyltrifluoroacetone, and the benzoyltrifluoroacetone is recycled for use in the stripping section.

[0069] The lithium-rich solution obtained above is heated to 80 °C to obtain lithium carbonate products. Through operation statistics, for every 1 ton of lithium carbonate produced in this example, 0.62 tons of CO2 are consumed.

[0070] Examples 2 - 12 and Comparative Examples 1 - 4 are different from Example 1 in terms of the stabilizer, and the results are shown in Table 1.

[0071] Table 1

[0072] Stabilizer <![CDATA[CO2 consumption per ton of lithium carbonate (tons)]]> Example 1 Benzoyltrifluoroacetone 0.62 Example 2 Dodecylphenyl-methyl-β-diketone 0.66 Example 3 12-Crown-4 0.66 Example 4 18-Crown-6 0.65 Example 5 Diisopentyl methylphosphonate 0.71 Example 6 Trioctyl phosphate 0.66 Example 7 Trioctylphosphine oxide 0.68 Example 8 Trinonylphosphine oxide 0.61 Example 9 n-Dodecane 0.74 Example 10 Isotetradecane 0.64 Example 11 Cyclooctane 0.63 Example 12 Cyclodecane 0.68 Comparative Example 1 Dodecylamine 1.56 Comparative Example 2 Lauric aldehyde 2.11 Comparative Example 3 1-Decene 1.92 Comparative Example 4 Neo-decanoic acid 1.56

[0073] Example 13

[0074] Example 13 is different from Example 1 in that: first, CO2 (inlet pressure is 0.5 MPa) is introduced into water, then benzoyltrifluorothiophenone is added, and the volume ratio of benzoyltrifluorothiophenone to water is 0.1:1. Then it is mixed with the obtained lithium-loaded extraction phase to form a back-extraction system for extraction, and phase separation is carried out to obtain a stripping solution with a lithium concentration of 7.5 g / L and an unloaded extraction solution.

[0075] Examples 14 - 24 and Comparative Examples 5 - 8 are different from Example 13 in terms of the stabilizer, and the results are shown in Table 2.

[0076] Table 2

[0077]

[0078]

[0079] Example 25

[0080] Example 25 is different from Example 1 in that: directly, CO2 (inlet pressure is 0.7 MPa), water, decylphenyl-ethyl-β-diketone and the obtained lithium-loaded extraction phase are jointly mixed to form a back-extraction system for extraction. Among them, the volume ratio of decylphenyl-ethyl-β-diketone to water is 0.2:1, and phase separation is carried out to obtain a stripping solution with a lithium concentration of 7.3 g / L and an unloaded extraction solution.

[0081] Examples 26 - 36 and Comparative Examples 9 - 12 are different from Example 25 in terms of the stabilizer, and the results are shown in Table 2.

[0082] Table 2

[0083]

[0084]

[0085] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0086] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for extracting lithium by back-extraction using CO2, characterized in that, It includes the following steps: S1. Provide a lithium-loaded extraction phase; S2, mixing CO2, water, a stabilizer and the lithium-loaded extract phase for stripping, and obtaining a stripping solution and an unloaded extract after phase separation, wherein the stabilizer is selected from ketones, esters, ethers, C8-C 16 Saturated alkanes, C8-C 16 At least one of the saturated cyclic hydrocarbons; S3. Further separate the stripping solution to obtain a lithium-rich solution and a stabilizer recovery solution; S4. Heat-treat the lithium-rich solution to obtain lithium carbonate.

2. The method for extracting lithium by back-extraction using CO2 according to claim 1, characterized in that, In the step of mixing CO2, water, a stabilizer with the lithium-loaded extraction phase for stripping, first mix water and the stabilizer, then introduce CO2, and then mix with the lithium-loaded extraction phase for stripping.

3. The method for extracting lithium by back-extraction using CO2 according to claim 1, characterized in that, In the step of mixing CO2, water, a stabilizer with the lithium-loaded extraction phase for stripping, first introduce CO2 into water, then add the stabilizer, and then mix with the lithium-loaded extraction phase for stripping.

4. The method for extracting lithium by back-extraction using CO2 according to claim 1, characterized in that, In the step of mixing CO2, water, a stabilizer with the lithium-loaded extraction phase for stripping, simultaneously mix CO2, water, the stabilizer with the lithium-loaded extraction phase for stripping.

5. The method for extracting lithium by counter-extraction using CO2 according to any one of claims 1-4, characterized in that, The ketones are selected from at least one of β-diketones, aliphatic ketones, alicyclic ketones, and aromatic ketones; And / or, the ethers are selected from at least one of polyethers, glycol ethers, block ethers, and crown ethers; And / or, the esters are selected from phosphoric acid esters.

6. The method for extracting lithium by back-extraction using CO2 according to claim 5, characterized in that, The ketones are selected from at least one of benzoyltrifluoroacetone, thiophenecarbonyltrifluoroacetone, furancarbonyltrifluoroacetone, p-toluoyltrifluoroacetone, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, 1-phenyl-3-methyl-4-octanoyl-5-pyrazolone, 1-phenyl-3-methyl-4-valeryl-5-pyrazolone, octylphenyl-methyl-β-diketone, nonylphenyl-methyl-β-diketone, dodecylphenyl-methyl-β-diketone, tetradecylphenyl-methyl-β-diketone, and decylphenyl-ethyl-β-diketone; And / or, the ethers are selected from at least one of 12-crown-4, 15-crown-5, 18-crown-6, benzo-12-crown-4, benzo-15-crown-5, and benzo-18-crown-6; And / or, the esters are selected from at least one of diisopentyl methylphosphonate, dimethylheptyl methylphosphonate, tributyl phosphate, trioctyl phosphate, trialkyl phosphate, dialkyl phosphate, dibutyl butylphosphate, and methylene tetrabutyl bisphosphate; And / or, the alkylphosphine oxides are selected from at least one of trioctylphosphine oxide, trihexylphosphine oxide, trinonylphosphine oxide, and tridecylphosphine oxide; and / or, the C8-C 16 saturated alkanes are selected from at least one of n-dodecane, n-decane, isomeric tetradecane, and isomeric hexadecane; and / or, the C8-C 16 saturated cycloalkane is selected from at least one of cyclooctane, cyclodecane, cycloundecane, cyclododecane, cyclotetradecane, and cyclohexadecane.

7. The method for extracting lithium by back-extraction using CO2 according to any one of claims 1-4, characterized in that, The volume ratio of the stabilizer to water is 0.01:1 - 0.5:1; And / or, the pressure when introducing CO2 is 0.1 MPa - 1.6 MPa.

8. The method for extracting lithium by back-extraction using CO2 according to claim 7, characterized in that, The volume ratio of the stabilizer to water is 0.01:1 - 0.2:1; And / or, the pressure when introducing CO2 is 0.1 MPa - 0.8 MPa.

9. The method for extracting lithium by back-extraction using CO2 according to claim 8, wherein The volume ratio of the stabilizer to water is 0.01:1 - 0.1:1; And / or, the pressure when introducing CO2 is 0.2 MPa - 0.6 MPa.

10. The method for extracting lithium by back-extraction using CO2 according to any one of claims 1-4, characterized in that, The stabilizer recovery solution in step S3 is recycled to step S2 for use.

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