A lithium composite extractant and a method for extracting lithium

Abstract

The present invention belongs to the field of selective extraction of lithium, and provides a lithium composite extractant and a method for extracting lithium. The composition of the composite extractant includes a carbonyl compound 1A, a salicylate compound 1B, an organophosphorus compound 1C, phenylbiguanide, and a diluent. The composite extractant provided by the present invention has low water solubility, is stable under acidic and alkaline conditions, has a fast phase separation speed, does not emulsify, has high selectivity, has a low total organic carbon (TOC) in the raffinate, the raffinate can be discharged after simple treatment, and the extractant can be recycled repeatedly with basically no decrease in extraction performance. The high-purity lithium-containing solution after extraction can be used to prepare high-purity lithium carbonate, realizing the short-process preparation of battery-grade lithium carbonate.

Description

Technical Field

[0001] The present invention belongs to the field of selective extraction of lithium, and particularly relates to a lithium composite extractant and a method for extracting lithium. Background Art

[0002] In recent years, as an important raw material for lithium-ion batteries, the demand for lithium has been increasing day by day. At present, the sources of lithium mainly include lithium ores, salt lake brines, and lithium battery recycling, and all three systems involve the separation of three similar ions, namely lithium, sodium, and potassium. Due to its advantages such as large processing capacity, high selectivity, and low cost, the extraction method has become one of the most important lithium extraction technologies. However, there are still many problems with lithium extractants on the market in terms of high efficiency, selectivity, and environmental friendliness. The β-diketone extractant, which has a good separation effect on the three monovalent ions of lithium, sodium, and potassium, is prone to emulsification during use, seriously affecting continuous operation. In addition, the acidity of the extractant is relatively low (pKa > 8), requiring a strong alkaline environment, resulting in large losses of the extractant, affecting the extraction stability, and possibly causing secondary pollution. These all limit the application of such extractants in the field of industrial lithium extraction. Using a single extraction system can no longer meet the current extraction requirements for lithium, and many multi-component extraction systems have been disclosed in the prior art.

[0003] CN115821040A discloses an extraction system for extracting lithium, including a carbonyl enol, a phosphate ester, and a polar hydrophobic additive; CN117965890A discloses a composite extraction system, whose first component is LIX54 and / or LIX54-100, the second component is a carbonyl compound shown in Formula I, and the third component is a phosphate ester; CN104404269A discloses an extraction organic phase for extracting lithium, including a composite extractant mixed by the following components: 1) tributyl phosphate; 2) N,N-bis(2-ethylhexyl)-3-butanone acetamide; wherein the volume ratio of tributyl phosphate to N,N-bis(2-ethylhexyl)-3-butanone acetamide is 3-8:2-7. CN118880059A discloses a system for extracting and purifying lithium, including extraction solution A and extraction solution B in different extraction stages. The extraction solution A is prepared from a salicylic acid ester extractant, a co-extractant, and a diluent. The extraction solution B is prepared from a diketone extractant, a co-extractant, and a diluent. The salicylic acid ester extractant in the extraction solution A is selected from any one or more of butyl salicylate, isooctyl salicylate, n-octyl salicylate, isoamyl salicylate, and propyl salicylate, and the concentration of the salicylic acid ester extractant is 10%-30% (V); the co-extractant is selected from any one or more of trialkyl phosphine oxide, trioctyl phosphine oxide, triphenyl phosphine oxide, tributyl phosphate, and trioctyl phosphate, and the concentration of the co-extractant is 5%-25% (V); the rest is a diluent, and the diluent is selected from any one of sulfonated kerosene, light kerosene, aviation kerosene, dodecane, toluene, and ethyl acetate; the diketone extractant in the extraction solution B is selected from any one or more of 4-methyl-1-phenylpentane-1,3-pentanedione (CAS No.: 13988-65-3), 1-phenyltetradecane-1,3-dione (CAS No.: 55846-69-0), 2,2,6,6-tetramethyl-3,5-heptanedione (CAS No.: 1118-71-4), 1-phenyl-1,3-decanedione (CAS No.: 68892-13-7), dibenzoylmethane (CAS No.: 120-46-7), and 1-benzoyl-2-nonanone (CAS No.: 112405-99-9), and the concentration of the diketone extractant is 3%-10% (V); the co-extractant is selected from any one or more of trialkyl phosphine oxide, trioctyl phosphine oxide, triphenyl phosphine oxide, tributyl phosphate, and trioctyl phosphate, and the concentration of the co-extractant is 3%-10% (V); the rest is a diluent, and the diluent is selected from any one of sulfonated kerosene, light kerosene, aviation kerosene, dodecane, toluene, and ethyl acetate.

[0004] Previous multi-component extraction systems mainly focused on the extraction rate of lithium and the separation of lithium / sodium. However, in actual production applications, the loss of the organic phase and the phase separation time also need to be considered. The above multi-component extraction system also has the following defects: on the one hand, the loss of the organic solvent is large. During extraction, the organic phase will enter the aqueous phase, resulting in the loss of the organic phase and the pollution of the aqueous phase, which is difficult to treat. On the other hand, when the lithium ion concentration in the aqueous phase to be extracted is high, phase separation is difficult, the organic phase is prone to emulsification, the phase separation time is long, and it takes a long time to stand to achieve a better phase separation situation. Therefore, it is necessary to develop an extraction system and an extraction method with excellent extraction performance, low loss of organic solvent, and short extraction time. Summary of the Invention

[0005] Aiming at the deficiencies of the existing extraction system for extracting lithium, such as high loss of organic solvent and long extraction time, which are not conducive to industrial production, the present invention provides a novel composite extractant system, including carbonyl compounds, salicylic acid esters, organophosphorus compounds, phenylbiguanide, and diluents. The composite extractant system of the present invention has the advantages of high selectivity, no alkali consumption, fast phase separation, and no emulsification, and can be recycled repeatedly, which is very suitable for large-scale industrial lithium extraction. To achieve this purpose, the present invention adopts the following technical solutions:

[0006] A lithium composite extractant, comprising the following components:

[0007] 0.1 - 1 mol / L of the carbonyl compound shown in Formula 1A, 0.1 - 1 mol / L of the salicylic acid ester compound shown in Formula 1B, 0.5 - 2 mol / L of the organophosphorus compound shown in Formula 1C, 0.02 - 0.05 mol / L of phenylbiguanide, and a diluent;

[0008] 1A

[0009] Wherein, R 1 , R 2 , R 3 , R 4 are independently C1-10 alkyl, C1-10 alkoxy, C6-20 aryl, C5-15 heteroaryl;

[0010] 1B

[0011] Wherein, R 5 is C4-C18 alkyl, C6-20 aryl; the alkyl is such as butyl, hexyl, octyl, dodecyl, tetradecyl;

[0012] 1C

[0013] Wherein, R 6 , R 7, R 8 independently is C1-10 alkyl, C1-10 alkoxy, C6-20 aryl, C5-15 heteroaryl; R 6 , R 7 , R 8 at least one of them is C1-10 alkoxy;

[0014] The phenylbiguanide has the following chemical formula: .

[0015] The inventors unexpectedly found that adding a small amount of the compound phenylbiguanide to the extraction system can simultaneously improve the extraction selectivity, shorten the phase separation time, and can be recycled repeatedly with basically no loss, and will not cause an increase in cost, and can be used in the industrial extraction process of lithium.

[0016] Furthermore, among them, R 1 , R 2 , R 3 , R 4 independently is C1-6 alkyl, C1-6 alkoxy, C6-12 aryl, C5-15 heteroaryl, the C5-15 heteroaryl contains 5-15 C atoms and 1-3 heteroatoms including O, S, N, P; among them, R 5 is C4-C14 alkyl, C6-12 aryl; among them, R 6 , R 7 , R 8 independently is C1-6 alkyl, C1-6 alkoxy, C6-12 aryl, C5-15 heteroaryl, the C5-15 heteroaryl contains 5-15 C atoms and 1-3 heteroatoms including O, S, N, P. C1-10 alkyl such as alkyl is selected from methyl, ethyl, propyl, butyl, pentyl, hexyl; C1-10 alkoxy is selected from methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy; C6-20 aryl such as phenyl, biphenyl, naphthyl, anthryl; C5-15 heteroaryl such as pyrrolyl, pyrazolyl, pyridyl, thienyl; C4-C18 alkyl is selected from butyl, hexyl, octyl, dodecyl, tetradecyl.

[0017] Furthermore, the H atoms in the above alkyl, alkoxy, aryl, and heteroaryl are optionally substituted by substituents, and the substituents are selected from at least one of trifluoromethyl, nitro, hydroxyl, amino, and mercapto.

[0018] Furthermore, R 2 and R 3 , or R 3 and R 4 can be connected to form cycloalkane or N-containing heterocycle, and the heteroatoms on the heterocycle are selected from at least one of nitrogen, oxygen, and sulfur. For example, R 2 and R 3They are connected to form pyrazolone, 2H-pyrrol-2-one, imidazolone, thiazolidinone, pyridone, oxazolidinone, etc.

[0019] Furthermore, compound 1A is selected from at least one of N,N-bis(2-ethylhexyl)-3-oxobutanamide, N,N-dihexyl-3-oxobutanamide, 2-ethyl-N,N-dimethyl-3-oxohexanamide, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone; compound 1B is selected from at least one of isopentyl salicylate, 2-ethylhexyl salicylate, p-chlorophenyl salicylate, 2-carboxyphenyl 2-hydroxybenzoate, isooctyl salicylate, isopentyl salicylate; compound 1C is selected from at least one of trioctyl phosphate, tributyl phosphate, trihexyl phosphate, triheptyl phosphate, tripentyl phosphate, diisooctyl methylphosphonate, triphenoxyphosphine oxide.

[0020] Furthermore, 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 kerosene, sulfonated kerosene, D80, 260# solvent oil, Escaid 110, butyl benzoate, heptyl acetate, octanol, dodecanol, 4-methyl-2-pentanone, diisobutyl ketone, S150, toluene, etc., and a combination that can be miscible in any volume ratio of one or more than two.

[0021] The second object of the present invention is to provide a method for extracting lithium, which includes the following steps:

[0022] (S1) Add the carbonyl compound shown in formula 1A, the salicylate compound shown in formula 1B, the organophosphorus compound shown in formula 1C, and phenylbiguanide to the diluent, and mix evenly to obtain an organic phase;

[0023] (S2) Adjust the pH value of the lithium-containing aqueous solution to alkaline to obtain an aqueous phase;

[0024] (S3) Add the organic phase and the aqueous phase to an extraction device for countercurrent extraction to obtain a lithium-loaded organic phase;

[0025] (S4) Subject the lithium-loaded organic phase to acid solution countercurrent washing and acid solution countercurrent stripping in sequence to obtain a stripped organic phase and a high-purity lithium-containing solution. The stripped organic phase is returned to the initial extraction device and reused again.

[0026] In step (2), if the initial aqueous phase is alkaline, there is no need to add an alkali solution for adjustment. If the alkalinity is insufficient, one or more of sodium hydroxide, potassium hydroxide, ammonia water, etc. can be added to adjust the pH to alkaline, such as pH = 10 - 12.

[0027] In step (3), the extraction equipment described can use 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.

[0028] In step (4), the acid in the acid solution is at least one of hydrochloric acid, sulfuric acid, and nitric acid. When performing countercurrent washing, the concentration of the acid is 0.01 - 0.5 mol / L, preferably 0.1 - 0.3 mol / L. When the acid solution is used for countercurrent stripping, the concentration of the acid is 0.5 - 3 mol / L, preferably 1 - 2 mol / L. When performing 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.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The composite extractant provided by the present invention has low water solubility, is stable under acidic and alkaline conditions, has a fast phase separation speed, does not emulsify, has high selectivity, has a low total organic carbon (TOC) in the raffinate, and the raffinate can be discharged after simple treatment. The composite extractant can be recycled repeatedly, and its extraction performance basically does not decline, still maintaining a very high extraction efficiency and phase separation speed. The composite extractant of the present invention can be used under weakly alkaline conditions, thus greatly reducing the alkali consumption and shortening the production process. The high-purity lithium-containing solution obtained after extraction can be used to prepare high-purity lithium carbonate with a purity ≥ 99.9%, realizing the short-process preparation of battery-grade lithium carbonate. The composite extractant provided by the present invention can be used for the efficient and rapid extraction of lithium in various scenarios such as salt lake brine, geothermal brine, oilfield brine, ore leaching solution, waste lithium battery leaching solution, lithium precipitation mother liquor, and lithium-containing wastewater. Description of the Drawings

[0031] Figure 1 is the first-phase separation photo of Example 1;

[0032] Figure 2 is the first-phase separation photo of Comparative Example 1;

[0033] Figure 3 is the XRD pattern of the battery-grade lithium carbonate obtained in Example 1. Detailed Embodiments

[0034] The technical solutions of the present invention will be further described below through specific embodiments.

[0035] Example 1

[0036] The composition of the organic phase composite extractant is N, N - bis(2 - ethylhexyl) - 3 - butanone acetamide (content 0.5 mol / L), isoamyl salicylate (content 0.5 mol / L), trioctyl phosphate (content 1 mol / L), phenylbiguanide (content 0.02 mol / L), and the diluent is sulfonated kerosene. In the aqueous phase to be treated, the lithium content is 3.7 g / L, sodium 82 g / L, potassium 16 g / L, and pH is 11.3.

[0037] The prepared organic phase and aqueous phase are subjected to 3 - stage continuous counter - current extraction in a mixer - settler at a volume ratio of 1:1. The lithium - loaded organic phase is washed twice with 0.3 mol / L hydrochloric acid, where the volume ratio of the organic phase to the aqueous phase is 10:1, and phase separation occurs for the first time. Then, it is stripped twice with 4 mol / L hydrochloric acid, where the volume ratio of the organic phase to the aqueous phase is 15:1, and phase separation occurs for the second time. The stripped solution is a LiCl solution with a lithium concentration of 25.7 g / L, and the lithium recovery rate is 99.4%. The organic phase after stripping is returned to the extraction section for recycling. Lithium carbonate of battery grade with a purity > 99.9% is obtained by adding sodium carbonate to the lithium chloride solution for precipitation.

[0038] Figure 3 It is the XRD pattern of the battery - grade lithium carbonate obtained in Example 1.

[0039] Table 1 shows the elemental composition of the battery - grade lithium carbonate obtained in Example 1.

[0040] Table 1 Composition of Lithium Carbonate

[0041] 。

[0042] Example 2

[0043] Other conditions are the same as in Example 1, with the difference that the composition of the organic phase composite extractant is N, N - dihexyl - 3 - butanone acetamide (content 0.6 mol / L), the salicylic acid ester compound is 2 - ethylhexyl salicylate (content 0.4 mol / L), the organophosphorus compound is tributyl phosphate (content 1.5 mol / L), phenylbiguanide (content 0.05 mol / L), and the diluent is D80 solvent oil.

[0044] Example 3

[0045] 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: 0.3 mol / L), the salicylic acid ester compound is 2-ethylhexyl salicylate (content: 0.8 mol / L), the organophosphorus compound is tributyl phosphate (content: 1.2 mol / L), phenylbiguanide (content: 0.04 mol / L), and the diluent is a mixture of 260# solvent oil and S150 (v / v = 1:1).

[0046] Example 4

[0047] 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: 0.6 mol / L), the salicylic acid ester compound is 2-carboxyphenyl 2-hydroxybenzoate (content: 0.8 mol / L), the organophosphorus compound is trioctyl phosphate (content: 0.9 mol / L), phenylbiguanide (content: 0.03 mol / L), and the diluent is a mixture of sulfonated kerosene, S150 and diisobutyl ketone (sulfonated kerosene, S150 and diisobutyl ketone are 25 vol%, 25 vol%, 50 vol% respectively).

[0048] Example 5

[0049] 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: 0.5 mol / L), the salicylic acid ester compound is 2-carboxyphenyl 2-hydroxybenzoate (content: 0.6 mol / L), the organophosphorus compound is trioctyl phosphate (content: 0.7 mol / L), phenylbiguanide (content: 0.02 mol / L), and the diluent is a mixture of D80 solvent oil and dodecanol (v / v = 10:1).

[0050] Comparative Example 1

[0051] Other conditions are the same as those in Example 1, except that the extractant is a commercial lithium extractant Lix54-TRPO composite system.

[0052] Comparative Example 2

[0053] Other conditions are the same as those in Example 1, except that in the organic-phase composite extractant, N,N-bis(2-ethylhexyl)-3-butanone acetamide is replaced with benzoyltrifluoroacetone at an equimolar concentration.

[0054] Comparative Example 3

[0055] Other conditions are the same as those in Example 1, except that phenylbiguanide is not added to the organic-phase composite extractant.

[0056] The extraction systems of the above-mentioned examples and comparative examples were evaluated, and the results are shown in Table 2 below.

[0057] Figure 1 This is the first phase separation photo of Example 1. The phase separation was observed every 10 s to determine the phase separation time.

[0058] Figure 2 This is the first phase separation photo of Comparative Example 1. The phase separation was observed every minute to determine the phase separation time.

[0059] It can be seen that in Comparative Example 1, a commercial extractant was used, and the extraction rate was close to that of the present invention, but the phase separation time was much higher than that of the examples. In the traditional extraction system, emulsification easily occurs during extraction and water washing, and the phase separation time is very slow, making continuous operation difficult. The extraction and phase separation situations of the commercial lithium extraction extractant and the extractant developed in the present invention were compared. It was found that the traditional commercial extractant takes 2 hours to phase separate, and there is still a small amount of emulsified phase at the interface, while the extractant developed in the present invention can be completely phase separated within 1 minute, and both the upper and lower phases are clear, showing great advantages.

[0060] Table 2 Performance Test of Composite Extraction System

[0061] 。

[0062] The composite extraction system of Example 1 was reused 20 times, and the results are shown in Table 3 below.

[0063] Table 3 Extraction Performance Test after Repeated Cycling of the Extraction System of Example 1 for 20 Times

[0064] 。

[0065] From the data in Table 2 and Table 3, it can be seen that the composite extraction system provided by the present invention can efficiently and rapidly extract lithium with high selectivity from the lithium-containing aqueous phase, and the contents of impurity metal ions such as Na, K, Mg, and Ca in the product are low. In particular, the composite extraction system of the present invention can significantly shorten the phase separation time, which is especially convenient for industrial use. Moreover, it can be recycled multiple times. After 10 cycles, the extraction performance basically does not decrease, and the loss of the organic phase is small.

Claims

1. A lithium composite extractant, characterized in that, It comprises the following components: 0.1 - 1 mol / L of the carbonyl compound shown in Formula 1A, 0.1 - 1 mol / L of the salicylate compound shown in Formula 1B, 0.5 - 2 mol / L of the organophosphorus compound shown in Formula 1C, 0.02 - 0.05 mol / L of phenylbiguanide, and a diluent; 1A Wherein, R 1 , R 2 , R 3 , R 4 independently represents a C1-6 alkyl group, a C1-6 alkoxy group, a C6-12 aryl group; or R 2 and R 3 are connected to form a nitrogen-containing heterocycle, and the heteroatom on the heterocycle is selected from at least one of nitrogen, oxygen, and sulfur; 1B Among them, R 5 is a C4-C14 alkyl group or a C6-12 aryl group; 1C Among them, R 6 , R 7 , R 8 are independently C1-6 alkyl, C1-6 alkoxy, C6-12 aryl; R 6 , R 7 , R 8 at least one of which is C1-6 alkoxy; The chemical formula of the phenyl biguanide is as follows: .

2. The lithium composite extractant according to claim 1, wherein C1 - 10 alkyl is selected from methyl, ethyl, propyl, butyl, pentyl or hexyl; C1 - 10 alkoxy is selected from methoxy, ethoxy, propoxy, butoxy, pentyloxy or hexyloxy; aryl is selected from phenyl, biphenyl, naphthyl, anthryl; C4 - C18 alkyl is selected from butyl, hexyl, octyl, dodecyl or tetradecyl.

3. The lithium composite extractant according to claim 1, wherein The H atom in the above alkyl, alkoxy, aryl, heteroaryl is optionally substituted by a substituent, and the substituent is selected from at least one of trifluoromethyl, nitro, hydroxyl, amino, mercapto.

4. The lithium composite extractant according to claim 1, wherein R 2 With R 3 linked to form pyrazolone.

5. The lithium composite extractant according to claim 1, characterized in that, Compound 1A is selected from at least one of N,N - bis(2 - ethylhexyl) - 3 - butanone acetamide, N,N - dihexyl - 3 - butanone acetamide, 2 - ethyl - N,N - dimethyl - 3 - oxohexanamide, 1 - phenyl - 3 - methyl - 4 - benzoyl - 5 - pyrazolone; and / or Compound 1B is selected from at least one of isopentyl salicylate, 2 - ethylhexyl salicylate, p - chlorophenyl salicylate, 2 - carboxyphenyl 2 - hydroxybenzoate, isooctyl salicylate, isopentyl salicylate; and / or Compound 1C is selected from at least one of trioctyl phosphate, tributyl phosphate, trihexyl phosphate, triheptyl phosphate, tripentyl phosphate, diisooctyl methylphosphonate, triphenoxyphosphine oxide.

6. The lithium composite extractant according to claim 1, wherein The diluent is selected from any one or a combination of at least two of alkanes having 4 to 14 carbon atoms, ester compounds having 4 to 14 carbon atoms, alcohol compounds having 4 to 14 carbon atoms, ketone compounds having 4 to 14 carbon atoms, and aromatic compounds.

7. The lithium composite extractant according to claim 1, characterized in that, The diluent is selected from 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, toluene, which are miscible in any volume ratio.

8. A method for extracting lithium, characterized in that, It comprises the following steps: (S1) Add the carbonyl compound shown in Formula 1A, the salicylate compound shown in Formula 1B, the organophosphorus compound shown in Formula 1C, and phenylbiguanide into the diluent, and mix evenly to obtain the lithium composite extractant according to any one of Claims 1 - 7; (S2) Adjust the pH value of the lithium - containing aqueous solution to alkaline to obtain an aqueous phase; (S3) Add the lithium composite extractant and the aqueous phase into an extraction device for counter - current extraction to obtain a lithium - loaded organic phase; (S4) Subject the lithium - loaded organic phase to acid - liquid counter - current washing and acid - liquid counter - current stripping in sequence to obtain a stripped organic phase and a high - purity lithium - containing solution. The stripped organic phase is returned to the initial extraction device for recycling.

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