Extracting agent for extracting lithium, extracting system and method for extracting lithium

Abstract

The invention discloses an extraction agent for extracting lithium, which is characterized in that the extraction agent is an ionic liquid of which the anion is in a form of removing hydrogen ions from enol and the cation is quaternary ammonium salt cation, the structure of the extraction agent is as shown in formula (1), and R1, R2, R3, R4, R5 and R6 are the same or different and are respectively and independently H or C1C15 alkyl or C6-C15 aryl. The extraction agent is high in selectivity, non-emulsifying, low in loss, capable of efficiently extracting lithium from a lithium-containing solution and long in cycle life, and the lithium extraction operation cost is remarkably reduced. The invention further relates to a method for extracting lithium by using the extracting agent. # imgabs0 # (1).

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical separation, and in particular, relates to an extractant capable of efficiently extracting lithium with low loss, and further relates to an extraction system comprising the extractant and a method for extracting lithium using the extractant. Background Art

[0002] Lithium salt is the core raw material of lithium-ion batteries. With the gradual popularization of electric vehicles, the demand for lithium salt in domestic and foreign markets continues to grow. However, lithium is usually associated with a variety of alkali metals and non-metallic impurities, resulting in low lithium extraction yield, low purity of lithium salt products, and high production costs.

[0003] Solvent extraction is a commonly used method for efficient extraction and separation of metals, and is widely used in the smelting of non-ferrous metals such as copper, nickel, cobalt, and rare earth elements. The typical solvent extraction system used to separate lithium from other alkali metals (such as sodium, potassium, rubidium, and cesium) and some non-metallic impurities (such as fluorine and silicon) is a synergistic solvent extraction system based on diketone and alkylphosphine oxide, and the separation coefficient of this extraction system is relatively high. However, due to the structural characteristics of the alkylphosphine oxide itself, the extraction system using alkylphosphine oxide is prone to emulsification; and because the extraction system can only effectively extract lithium under alkaline conditions of pH>11, under such conditions, the diketone molecule is hydrolyzed to form a sodium salt. Since the water solubility of the diketone sodium salt is significantly higher than that of its molecular form, the extractant dissolves more in water, which greatly reduces the cycle life of the extractant. Therefore, it is difficult to promote the use of the diketone-alkylphosphine oxide synergistic extraction system on a large scale.

[0004] In view of the problems of the prior art, the present invention provides an ionic liquid extractant for extracting lithium, which has high extraction selectivity, no emulsification, and low extractant loss. It can efficiently extract lithium from lithium-containing solutions, and the extractant has a long cycle life, which can significantly reduce the operating cost of extracting lithium. Summary of the invention

[0005] In view of the problems of the prior art, the present invention provides an ionic liquid extractant for extracting lithium, which has high extraction selectivity, no emulsification, and low extractant loss. It can efficiently extract lithium from lithium-containing solutions, and the extractant has a long cycle life, which can significantly reduce the operating cost of extracting lithium.

[0006] An extractant for extracting lithium, characterized in that: the extractant is an ionic liquid based on enol and quaternary ammonium salt, the anion of which is in the form of enol dehydrogenated, and the cation of which is a quaternary ammonium salt cation, and the structure of the extractant is shown in formula (1): (1) Where R 1 , R 2 , R 3 , R4 , R 5 , R 6 may be the same or different, and each independently is H or C 1 −C 15 Alkyl or C 6 -C 15 Aryl; for example, the C 1 −C 15 The alkyl group is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, pentyl, 2-methyl-butyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl or pentadecyl; the aryl group can be phenyl, methylphenyl, ethylphenyl, propylphenyl, butylphenyl, hexylphenyl, octylphenyl or nonylphenyl, etc.

[0007] The extractant is one of the following compounds.

[0008] [PhOOC 7 ][N 8881 ], whose structural formula is: , [PhOOPh][N 8881 ], whose structural formula is: , [PhOOC 12 ][N 8881 ], whose structural formula is: , [C 8 OOC 8 ][N 8881 ], whose structural formula is: , [PhOOC 8 ][N 6661 ], whose structural formula is: ,and [PhOOC 8 ][N 6666 ], whose structural formula is: .

[0009] The present invention further relates to an extraction system comprising the extractant of the present invention and a diluent, wherein the content of the extractant is 3 vol%-60 vol%, and the content of the diluent is 97 vol%-40 vol%, based on the total volume of the extraction system.

[0010] The diluent may be selected from any one of alkanes (such as kerosene, D70 solvent oil), aromatic hydrocarbons (such as toluene, S150 solvent oil), or any mixture thereof.

[0011] The present invention further relates to a method for extracting lithium from a lithium-containing solution, characterized in that the method uses the extractant of the present invention and comprises the following steps: (1) dissolving the extractant according to the present invention in a diluent to prepare an organic phase, wherein the volume concentration of the extractant in the organic phase is 3 vol%-60 vol%, based on the total volume of the organic phase; (2) measuring the concentration of lithium in the lithium-containing solution to be tested, adding an appropriate amount of alkali thereto, and obtaining an aqueous phase to be extracted; (3) introducing the organic phase prepared in step (1) and the aqueous phase obtained in step (2) into an extraction device for countercurrent extraction reaction to obtain an organic phase loaded with lithium; (4) counter-currently washing the organic phase loaded with lithium in step (3) with a washing liquid to obtain a washed organic phase; (5) subjecting the organic phase washed in step (4) to countercurrent stripping to obtain a stripped organic phase and a high-purity lithium salt solution; (6) The organic phase after stripping is returned to the organic phase storage tank and recycled for countercurrent extraction of lithium.

[0012] In step (1), the diluent is any one of alkanes (such as kerosene, D70 solvent oil, etc.), aromatic hydrocarbons (such as toluene, S150 solvent oil, etc.), or any mixture thereof.

[0013] In step (2), the base can be selected from sodium hydroxide, potassium hydroxide, ammonia or any mixture thereof. The amount of base added to the solution is such that the concentration of the base is 0.5-3.0 times the molar concentration of lithium, based on the molar concentration of lithium in the lithium-containing solution to be measured.

[0014] In step (3), the extraction equipment may be an extraction clarification tank, an extraction tower or a centrifugal extractor, the extraction stage number is 1-20, and the volume ratio of the organic phase to the aqueous phase is 1:50-50:1.

[0015] In step (4), the washing liquid is any one of water, dilute hydrochloric acid or dilute sulfuric acid, and the concentration of the hydrochloric acid or sulfuric acid solution is 0.01-3.0 mol / L; the volume ratio of the organic phase to the washing liquid is 1:50-50:1, and the washing stage is 1-20.

[0016] In step (5), hydrochloric acid aqueous solution, sulfuric acid aqueous solution, carbonic acid aqueous solution (carbon dioxide is passed into water) or phosphoric acid aqueous solution is used as a stripping solution for stripping, and its concentration is 0.03-6.0 mol / L; the volume ratio of the organic phase to the stripping solution is 1:50-50:1, and the stripping stage is 1-20.

[0017] The lithium recovery rate achieved by the method of the present invention using the extractant of the present invention can reach more than 99%, the lithium purity can reach more than 99.5%, and the loss of the extractant in the raffinate is less than 10 ppm.

[0018] The present invention further relates to the use of the extractant according to the present invention for extracting lithium. The extractant of the present invention can be advantageously used to efficiently extract lithium from a variety of lithium-containing solutions such as salt lake brine, oil field brine, battery leachate, ore leachate, lithium precipitation mother liquor, lithium-containing wastewater, etc.

[0019] In the following, [PhOOC 7 ][N 8881 ] Taking the extraction of lithium from a sulfate solution as an example, the mechanism of extracting lithium from a lithium-containing solution by the extraction system according to the present invention is described, and the reaction is shown in the following equation (1): (1) Among them, two [PhOOC 7 ] - Anion with a Li + The cation coordinates to form a coordinated anion [(PhOOC 7 ) 2 Li] - , and then with a quaternary ammonium cation [N 8881 ] + Formation of ion pairs [(PhOOC 7 ) 2 Li][N 8881 ]. [(PhOOC 7 ) 2 Li] - The coordination structure diagram of is shown in formula (2), where four oxygen atoms and Li + The excess extractant that does not participate in lithium extraction is ionic liquid [PhOOC 7 ][N 8881 ] in the form of ionic liquids. Since this ionic liquid is highly hydrophobic and has very low water solubility, it can avoid the loss of the extractant in an alkaline environment. If the enol is not in the form of an ionic liquid, it will exist in the form of a sodium salt in an alkaline environment, such as Na[PhOOC 7 ], and the water solubility of sodium salt is significantly higher than that of ionic liquid, resulting in serious loss of extractant.

[0020] (2) Lithium loaded in organic phase [(PhOOC 7 ) 2 Li][N 8881 ] can be stripped by acid. Taking sulfuric acid stripping as an example, its mechanism is shown in equation (2): (2) The enol H(PhOOC 7 ) and ammonium sulfate [N 8881 ] 2 SO 4 When lithium is extracted under alkaline conditions, ionic liquid and [(PhOOC 7 ) 2 Li][N 8881 ] and enter the next extraction-stripping cycle.

[0021] Similarly, hydrochloric acid, carbonic acid and phosphoric acid are used for back extraction to obtain lithium chloride solution, lithium carbonate (or lithium bicarbonate) solution and lithium dihydrogen phosphate solution respectively.

[0022] Beneficial Effects The extractant of the present invention is an ionic liquid extraction system composed of carbonyl enol and quaternary ammonium salt, which eliminates the emulsification phenomenon and can extract lithium from a solution containing elements such as lithium, sodium, potassium, rubidium, cesium, silicon, fluorine, and chlorine with high selectivity under alkaline conditions, and the separation coefficients of lithium and the above impurity elements are all > 1000. Since the extractant exists in the form of an ionic liquid under alkaline conditions, the dissolution loss of the extractant under alkaline conditions is significantly reduced, and it can be recycled for a long time, thereby greatly reducing the operating cost of extracting lithium; and the total organic matter content (i.e., COD) in the raffinate is low, and the raffinate treatment is simple. The solvent extraction system of the present invention is used to extract lithium from a lithium-containing solution (for example: lithium, sodium, potassium (rubidium, cesium mixed solution) through the method of the present invention, so that efficient purification and concentration of lithium is achieved, the process flow is shortened, the lithium recovery rate is high, and the raffinate treatment flow is simple. The solvent extraction system and the lithium extraction method of the present invention are of great significance for making full use of low-grade lithium resources. DETAILED DESCRIPTION

[0023] The following embodiments are used to illustrate the present invention in more detail, but the present invention is not limited by these embodiments. Within the technical concept of the present invention, those skilled in the art can make various modifications.

[0024] Example 1 The lithium-containing solution to be treated is the intermediate mother liquor in the lithium hydroxide production process, and the solution contains 21 g / L lithium, 83 g / L sodium, 12 g / L potassium, and 55 g / L hydroxide.

[0025] With 35 vol% [PhOOC 7 ][N 8881] and 65 vol% kerosene to form an organic phase. The organic phase and the aqueous phase are subjected to 4-stage continuous countercurrent extraction in an extraction clarification tank at a volume ratio of 6:1 to obtain an organic phase loaded with lithium, and the lithium extraction rate is measured to be >99%. The organic phase loaded with lithium is continued to be washed with 0.5 mol / L sulfuric acid at a volume ratio of 20:1 in the extraction clarification tank for 3 stages, and the washing liquid is returned to the inlet of the aqueous phase; the washed organic phase is continued to be stripped with a saturated carbonic acid solution (carbon dioxide gas is passed into the water) at a volume ratio of 2:1 in the extraction clarification tank, stripped for 2 stages, and a high-purity lithium bicarbonate solution with a lithium concentration of about 7 g / L is obtained, and its lithium purity is measured to be >99.8%. The lithium bicarbonate solution is heated to 90°C for pyrolysis to obtain a battery-grade lithium carbonate product and a pyrolysis mother liquor. The pyrolysis mother liquor is again passed into carbon dioxide for recycling for stripping the loaded organic phase.

[0026] Example 2 The lithium-containing solution to be treated is taken from the recycled lithium batteries, which are disassembled, crushed, leached and the divalent and trivalent metals are removed, and the solution contains 2.7 g / L lithium, 50 g / L sodium, and trace amounts of cobalt, nickel, magnesium, etc.

[0027] At 30 vol% [C 8 OOC 8 ][N 8881 ] was dissolved in 70 vol% kerosene to form an organic phase. NaOH was added to the lithium-containing solution to make the NaOH concentration 0.45 mol / L to form an aqueous phase. The organic phase and the aqueous phase were subjected to three-stage continuous countercurrent extraction in an extraction clarification tank at a volume ratio of 2:1, and the lithium extraction rate was >99%. The loaded organic phase continued to be washed with 0.2 mol / L sulfuric acid at a volume ratio of 20:1 in the extraction clarification tank to extract the co-extracted sodium and potassium, washed for 2 stages, and the washing liquid was returned to the inlet of the aqueous phase; the washed organic phase continued to be stripped with 2 mol / L sulfuric acid at a volume ratio of 20:1 in the extraction clarification tank, stripped for 2 stages, and a high-purity Li with a lithium concentration of 25-27 g / L was obtained. 2 SO 4 The lithium sulfate solution is precipitated with sodium carbonate at a stoichiometric ratio of 0.8 times the lithium at 80°C to obtain battery-grade lithium carbonate with a purity of 99.8%.

[0028] Example 3 The solution to be treated is lithium-containing wastewater generated during the battery recycling process, with a lithium concentration of 0.6 g / L and a sodium concentration of 48 g / L.

[0029] With 30 vol% [PhOOPh][N 8881] was dissolved in 70 vol% kerosene to form an organic phase. NaOH was added to the lithium-containing solution to make the NaOH concentration 0.10 mol / L to form an aqueous phase. The organic phase and the aqueous phase were subjected to 4-stage continuous countercurrent extraction in an extraction clarification tank at a volume ratio of 1:3, and the lithium extraction rate was measured to be >99%. The loaded organic phase continued to be washed with 1.0 mol / L hydrochloric acid at a volume ratio of 15:1 in the extraction clarification tank to extract the co-extracted sodium for 3 stages, and the washing liquid was returned to the inlet of the aqueous phase; the washed organic phase continued to be stripped with 5.0 mol / L hydrochloric acid at a volume ratio of 20:1 in the extraction clarification tank for 2 stages to obtain a LiCl solution with a lithium concentration of 33-37 g / L and a sodium content of <10 ppm. The LiCl solution was evaporated and crystallized to obtain the LiCl product.

[0030] Example 4 The solution to be treated is the lithium precipitation mother liquor obtained by adding sodium carbonate to lithium sulfate solution to precipitate lithium carbonate, and contains 2.6 g / L lithium and 55 g / L sodium.

[0031] With 35 vol% [PhOOC 8 ][N 6661 ] was dissolved in 65 vol% S150 solvent to form an organic phase. NaOH was added to the lithium precipitation mother liquor to make the NaOH concentration 0.40 mol / L, and the solution was used as the aqueous phase. The organic phase and the aqueous phase were subjected to three-stage continuous countercurrent extraction in the extraction clarification tank at a volume ratio of 1:1, and the lithium extraction rate was measured to be >99%. The lithium-loaded organic phase continued to be washed with 0.2 mol / L sulfuric acid at a volume ratio of 10:1 in the extraction clarification tank to extract the co-extracted sodium for three stages, and the washing liquid was returned to the inlet of the aqueous phase; the washed organic phase continued to be stripped with 3 mol / L phosphoric acid at a volume ratio of 8:1 in the extraction clarification tank for three stages to obtain a lithium dihydrogen phosphate solution with a lithium concentration of 20-22 g / L. The lithium dihydrogen phosphate solution was evaporated and crystallized to obtain a lithium dihydrogen phosphate product with a purity of >99.6%.

Claims

1. An extractant for extracting lithium, characterized in that: The extractant is an ionic liquid compound, the anion of which is in the form of an enolate stripped of hydrogen ions, and the cation of which is a quaternary ammonium salt cation, and the structure of which is shown in formula (1): （1） Wherein R1, R2, R3, R4, R5, and R6 are the same or different and are each independently H or C1-C 15 Alkyl or C6-C 15 Aryl.

2. The extractant according to claim 1, characterized in that: The C1−C 15 The alkyl group is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, pentyl, 2-methyl-butyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl or pentadecyl; the C6-C 15 Aryl is phenyl, methylphenyl, ethylphenyl, propylphenyl, butylphenyl, hexylphenyl, octylphenyl or nonylphenyl.

3. The extractant according to claim 1 or 2, characterized in that: The extractant is one of the following compounds: [PhOOC7][N 8881 ], whose structural formula is: , [PhOOPh][N 8881 ], whose structural formula is: , [PhOOC 12 ][N 8881 ], whose structural formula is: , [C8OOC8][N 8881 ], whose structural formula is: , [PhOOC8][N 6661 ], whose structural formula is: ,and [PhOOC8][N 6666 ], whose structural formula is: .

4. A method for extracting lithium, characterized in that: The method uses the extractant according to any one of claims 1 to 3, and the method comprises the following steps: (1) dissolving the extractant in a diluent to prepare an organic phase, wherein the volume concentration of the extractant in the organic phase is 3 vol%-60 vol%, based on the total volume of the organic phase; (2) measuring the lithium concentration in the lithium-containing solution to be tested, adding an appropriate amount of alkali thereto, and obtaining an aqueous phase to be extracted; (3) introducing the organic phase prepared in step (1) and the aqueous phase obtained in step (2) into an extraction device for countercurrent extraction reaction to obtain an organic phase loaded with lithium; (4) counter-currently washing the lithium-loaded organic phase of step (3) with a washing liquid to obtain a washed organic phase; (5) subjecting the organic phase washed in step (4) to countercurrent stripping to obtain a stripped organic phase and a high-purity lithium salt solution; (6) The organic phase after stripping is returned to the organic phase storage tank and recycled for countercurrent extraction of lithium.

5. The method according to claim 4, wherein in step (1), the diluent is any one of kerosene, D70 solvent oil, toluene, S150 solvent oil or any mixture thereof; in step (2), the alkali is sodium hydroxide, potassium hydroxide, ammonia water or a mixture thereof; the amount of the alkali added is such that the concentration of the alkali is 0.5-3.0 times the molar concentration of lithium, based on the molar concentration of lithium in the lithium-containing solution to be measured.

6. The method according to claim 4, wherein in step (3), the volume ratio of the organic phase to the aqueous phase is 1:30-30:

1.

7. The method according to claim 4, wherein in step (4), the washing liquid is any one of water, dilute hydrochloric acid or dilute sulfuric acid, and the concentration of hydrochloric acid or sulfuric acid is 0.01-2.0 mol / L; the volume ratio of the organic phase to the washing liquid is 1:30-30:

1.

8. The method according to claim 4, wherein in step (5), hydrochloric acid aqueous solution, sulfuric acid aqueous solution, carbonic acid aqueous solution or phosphoric acid solution is used as the stripping solution for stripping, and its concentration is 0.03-6.0 mol / L; the volume ratio of the organic phase to the stripping solution is 1:50-50:

1.

9. An extraction system, characterized in that: The extraction system comprises a diluent and an extractant according to any one of claims 1 to 3, wherein the content of the extractant is 3 vol%-60 vol%, and the content of the diluent is 97 vol%-40 vol%, based on the total volume of the extraction system; the diluent is selected from any one of kerosene, D70 solvent oil, toluene, S150 solvent oil, or any mixture thereof.

10. Use of the extractant according to any one of claims 1 to 3 or the extraction system according to claim 9 for extracting lithium from salt lake brine, oil field brine, battery leachate, ore leachate, lithium precipitation mother liquor and lithium-containing wastewater.

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