Composite extraction agent and application thereof in separation and recovery of lithium from lithium precipitation mother liquor

Abstract

The invention provides a composite extraction agent and application thereof in separation and recovery of lithium from lithium precipitation mother liquor. Relates to the technical field of composite extraction. The composite extraction agent comprises an extraction agent, a synergistic extraction agent and a diluent, the extraction agent comprises one or more of 1, 3-bis (4-fluorophenyl)-1, 3-propanedione, 2, 2-difluoro-1, 3-diphenyl-1, 3-propanedione, 1-phenyl-3-isoheptyl-1, 3-propanedione and benzoyl trifluoroacetone, and the diluent comprises one or more of 1, 3-bis (4-fluorophenyl)-1, 3-propanedione, 2, 2-difluoro-1, 3-diphenyl-1, 3-propanedione, 2, 2-difluoro-1, 3-diphenyl-1, 3-propanedione, 1-phenyl-3-isoheptyl-1, 3-propanedione and benzoyl trifluoroacetone. The synergistic extraction agent is prepared from one or more of tributyl phosphate, triisobutyl phosphate, triamyl phosphate, tributyl phosphine oxide and bis (4-fluorophenyl) phosphine oxide; the diluent comprises one or more of kerosene, sulfonated kerosene, tetradecane and tetradecanol. The composite extraction agent adopted by the invention has low requirement on pH, better acid and alkali resistance stability, small solution loss and good selective effect on lithium, the lithium recovery cost is reduced, and the comprehensive lithium extraction efficiency can reach 97.0% or above.

Description

Technical Field

[0001] The invention relates to the technical field of composite extraction, in particular to a composite extractant and application thereof in separation and recovery of lithium from lithium precipitation mother liquor. Background Art

[0002] Lithium is a key element in the strategic development of the new energy industry and the nuclear industry. Nowadays, lithium-powered batteries are developing at a rapid pace. At present, no other metal has been found to replace lithium in batteries. Therefore, the reserve of lithium resources and its separation and extraction technology are very important.

[0003] The lithium precipitation mother liquor is a saturated aqueous salt solution mainly composed of sodium sulfate and coexisting lithium and sodium. + The content is 1-3 g / L, while Na + The content is as high as 50-60g / L, with typical high sodium and low lithium characteristics, while other typical salt lake impurity elements K + , Ca 2+ Mg 2+ , B + The concentration of CO3 in lithium precipitation mother liquor is low due to the pretreatment and impurity removal process. At the same time, the industry adopts the method of adding excessive sodium carbonate to ensure the efficiency of lithium precipitation. 2- The residual amount is as high as 20g / L, and the pH of the solution is greater than 10, so the actual lithium precipitation mother solution is Na + , Li + 、CO3 2- 、SO4 2- , a high-salinity alkaline brine system mainly composed of H2O. Therefore, the key to extracting lithium from lithium precipitation mother liquor lies in the efficient separation of lithium and sodium.

[0004] At present, the extraction systems for extracting and separating lithium from lithium precipitate mother liquor mainly include phosphate extraction systems and β-diketone extraction systems. Among them, the phosphate extraction system needs to form an iron-lithium coordination compound and is only applicable to the chloride system. Its stripping effect is not good, and it corrodes the equipment severely, making it difficult to achieve large-scale application. In contrast, the β-diketone extraction system has a more significant advantage in lithium resource recovery, and its overall recovery rate of lithium extraction from brine can reach more than 90%, but the extraction system usually needs to be carried out under strong alkaline conditions, and the dissolution loss of the extractant under acidic conditions is relatively high, resulting in increased extraction and separation costs.

[0005] Therefore, those skilled in the art are in urgent need of providing a composite extractant with less dissolution loss, lower overall cost and conducive to large-scale application. Summary of the invention

[0006] The purpose of the present invention is to provide a composite extractant and its application in separating and recovering lithium from lithium precipitation mother liquor, so as to solve the problems of poor extraction effect, easy corrosion to equipment and high extraction and separation cost caused by high dissolution loss of the extractant in the existing method for extracting lithium from lithium precipitation mother liquor.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a composite extractant, comprising an extractant, a co-extractant and a diluent;

[0009] The extractant includes one or more of 1,3-bis(4-fluorophenyl)-1,3-propanedione, 2,2-difluoro-1,3-diphenyl-1,3-propanedione, 1-phenyl-3-isoheptyl-1,3-propanedione, and benzoyltrifluoroacetone;

[0010] The synergistic extractant includes one or more of tributyl phosphate, triisobutyl phosphate, tripentyl phosphate, tributylphosphine oxide, and bis(4-fluorophenyl)phosphine oxide;

[0011] The diluent includes one or more of kerosene, sulfonated kerosene, tetradecane and tetradecanol.

[0012] Preferably, the molar ratio of the extractant to the co-extractant is 0.25 to 4:1;

[0013] The volume ratio of the extractant to the diluent is 0.15 to 2:1.

[0014] The present invention also provides an application of the composite extractant in separating and recovering lithium from lithium precipitation mother liquor, and the application method comprises the following steps:

[0015] 1) mixing the lithium precipitation mother liquor with liquid alkali to react, and obtaining a lithium precipitation mother liquor with preliminary impurity removal through solid-liquid separation;

[0016] 2) using a composite extractant to perform multi-stage countercurrent extraction, stripping and washing on the preliminarily impurity-removed lithium precipitation mother liquor to obtain a lithium stripping solution;

[0017] 3) The lithium stripping solution is mixed with the sodium carbonate solution, and the mixture is filtered and dried in sequence to obtain battery-grade lithium carbonate.

[0018] Preferably, the concentration of lithium ions in the lithium precipitation mother solution in step 1) is 1-4 g / L, and the concentration of sodium ions is 35-75 g / L.

[0019] Preferably, the pH value of the lithium precipitation mother liquor after mixing with liquid alkali in step 1) is 9.0 to 13.0.

[0020] Preferably, the volume ratio of the total amount of the composite extractant used in the multi-stage countercurrent extraction process in step 2) to the lithium precipitation mother liquor after preliminary impurity removal is 0.5 to 3:1.

[0021] Preferably, the extraction stages of the multi-stage countercurrent extraction in step 2) are 2 to 6 stages, the stripping stages are 2 to 5 stages, and the washing stages are 2 to 5 stages.

[0022] Preferably, the stripping solution of the stripping in step 2) is a sulfuric acid solution;

[0023] The volume ratio of the total amount of the stripping solution used in the stripping to the composite extractant is 1:5-25;

[0024] The concentration of the sulfuric acid solution is 1-4 mol / L.

[0025] Preferably, the molar ratio of lithium ions in the lithium stripping solution to carbonate ions in the sodium carbonate solution in step 3) is 1:0.4-0.8.

[0026] The present invention has at least the following beneficial effects:

[0027] (1) The composite extractant used in the present invention has good acid and alkali stability and can remain stable for a long time.

[0028] (2) The composite extractant used in the present invention has a small dissolution loss, so that during the extraction process cycle, the replenishment of the extractant is small and the organic matter content in the raffinate is low, which can further reduce the extraction process cost and the treatment cost of the raffinate.

[0029] (3) The composite extractant used in the present invention has low requirements for the initial pH of the lithium precipitation mother liquor and can reduce the consumption of alkali.

[0030] (4) The composite extractant used in the present invention has a good selectivity effect on lithium, and the comprehensive lithium extraction efficiency reaches more than 97.0%. DETAILED DESCRIPTION

[0031] The present invention provides a composite extractant, comprising an extractant, a co-extractant and a diluent;

[0032] The extractant includes one or more of 1,3-bis(4-fluorophenyl)-1,3-propanedione, 2,2-difluoro-1,3-diphenyl-1,3-propanedione, 1-phenyl-3-isoheptyl-1,3-propanedione, and benzoyltrifluoroacetone;

[0033] The synergistic extractant includes one or more of tributyl phosphate, triisobutyl phosphate, tripentyl phosphate, tributylphosphine oxide, and bis(4-fluorophenyl)phosphine oxide;

[0034] The diluent includes one or more of kerosene, sulfonated kerosene, tetradecane and tetradecanol.

[0035] In the present invention, the volume ratio of the extractant to the co-extractant is 0.25 to 4:1, preferably 0.5 to 3.5:1, more preferably 1 to 3:1, and more preferably 1.5 to 2.5:1.

[0036] In the present invention, the molar ratio of the extractant to the diluent is 0.15 to 2:1, preferably 0.3 to 1.8:1, more preferably 0.5 to 1.5:1, and more preferably 0.8 to 1.2:1.

[0037] The present invention also provides an application of the composite extractant in separating and recovering lithium from lithium precipitation mother liquor, and the application method comprises the following steps:

[0038] 1) mixing the lithium precipitation mother liquor with liquid alkali to react, and obtaining a lithium precipitation mother liquor with preliminary impurity removal through solid-liquid separation;

[0039] 2) using a composite extractant to perform multi-stage countercurrent extraction, stripping and washing on the preliminarily impurity-removed lithium precipitation mother liquor to obtain a lithium stripping solution;

[0040] 3) The lithium stripping solution is mixed with the sodium carbonate solution, and the mixture is filtered and dried in sequence to obtain battery-grade lithium carbonate.

[0041] Preferably, the concentration of lithium ions in the lithium precipitation mother solution in step 1) is 1-4 g / L, and the concentration of sodium ions is 35-75 g / L.

[0042] In the present invention, the pH value of the lithium precipitation mother liquor after mixing with the liquid alkali in step 1) is 9.0 to 13.0, preferably 10.0 to 12.0, and more preferably 10.5 to 11.0.

[0043] The liquid alkali is a sodium hydroxide solution, and the concentration of the liquid alkali is 30-35wt%.

[0044] In the present invention, the main purpose of adding liquid alkali in step 1) is to preferentially precipitate and remove divalent and trivalent cationic impurities in the lithium precipitation mother liquor, such as calcium ions and magnesium ions.

[0045] In the present invention, the volume ratio of the total amount of the composite extractant used in the multi-stage countercurrent extraction process in step 2) to the preliminarily impurity-free lithium precipitation mother liquor is 0.5-3:1, preferably 1-2.5:1, and more preferably 1.5-2:1.

[0046] In the present invention, the multi-stage countercurrent extraction is preferably carried out in an extraction tank of model SY-7100.

[0047] In the present invention, the extraction level of the multi-stage countercurrent extraction in step 2) is 2 to 6, specifically 2, 3, 4, 5 or 6; the level of stripping is 2 to 5, specifically 2, 3, 4 or 5; the level of washing is 2 to 5, specifically 2, 3, 4 or 5.

[0048] In the present invention, the stripping solution of the stripping in step 2) is a sulfuric acid solution.

[0049] In the present invention, the temperatures of the countercurrent extraction, stripping and washing in step 2) are independently 20 to 40°C, preferably 25 to 35°C, and more preferably 28 to 30°C.

[0050] In the present invention, the residence time of each stage of the countercurrent extraction, stripping and washing is independently 5 to 10 minutes, specifically 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes or 10 minutes.

[0051] In the present invention, the volume ratio of the total amount of the stripping solution used in the stripping to the composite extractant is 1:5-25, preferably 1:8-22, more preferably 1:10-20, and more preferably 1:13-18.

[0052] In the present invention, the concentration of the sulfuric acid solution is 1 to 4 mol / L, preferably 1.5 to 3.5 mol / L, more preferably 2 to 3 mol / L, and even more preferably 2.3 to 2.8 mol / L.

[0053] In the present invention, the molar ratio of lithium ions in the lithium stripping solution to carbonate in the sodium carbonate solution in step 3) is 1:0.4-0.8, preferably 1:0.45-0.75, more preferably 1:0.5-0.7, and more preferably 1:0.55-0.65.

[0054] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0055] Example 1

[0056] (1) Preparation of composite extractant: sulfonated kerosene was used as diluent, and 1,3-bis(4-fluorophenyl)-1,3-propanedione (0.1 mol / L), benzoyltrifluoroacetone (0.3 mol / L) and tributyl phosphate (0.2 mol / L) were added.

[0057] (2) The pH of the lithium precipitation mother liquor is adjusted to 11.0 using 32 wt % of liquid alkali, so that divalent and trivalent cations such as calcium, magnesium, and iron in the liquid are precipitated, and then the impurity precipitate is removed by normal pressure filtration.

[0058] (3) The lithium precipitation mother liquor (lithium content: 2.29 g / L, sodium content: 65.48 g / L) after impurity removal was passed into an extraction tank (model: SY-7100) containing a composite extractant, and subjected to 4-stage countercurrent extraction, 3-stage countercurrent stripping and 3-stage countercurrent washing to obtain a lithium stripping solution with a lithium concentration of 22.65 g / L. Among them, in the extraction section process, the volume ratio of the amount of the organic phase composite extractant (O) used in the entire countercurrent extraction stage to the lithium-containing liquid (A) is O / A=1:1, the extraction temperature is controlled to be 25°C, the residence time of the extraction section is 6 minutes, the lithium content in the raffinate obtained by extraction is 0.42 mg / L, and the lithium extraction efficiency is greater than 99.9%; in the countercurrent stripping process, 2 mol / L sulfuric acid solution is used as the stripping solution, the total volume of the stripping solution in the entire stripping process is 1:10 to the total volume of the extracted organic phase composite extractant, the lithium content in the stripping solution obtained is 22.65 g / L, and the residence time of the stripping section is 5 minutes; the washing section uses pure water for washing, the washing temperature is 25°C, the washing residence time is 5 minutes, and the volume ratio of pure water to the organic composite extractant is controlled to be 1:1.

[0059] (4) The lithium stripping solution is mixed with a sodium carbonate solution (concentration of 230 g / L) to precipitate lithium, wherein the amount of sodium carbonate added is 0.6 times the amount of lithium ion substances in the stripping solution. After filtering, washing, and drying at 105° C., battery-grade lithium carbonate (Li2CO3≥99.7%, H2O≤0.2%, Na≤0.02%) is obtained.

[0060] Embodiment 2:

[0061] (1) Preparation of composite extractant: sulfonated kerosene was used as diluent, and 1,3-bis(4-fluorophenyl)-1,3-propanedione (0.1 mol / L), benzoyltrifluoroacetone (0.3 mol / L) and tributyl phosphate (0.2 mol / L) were added.

[0062] (2) The pH of the lithium precipitation mother liquor is adjusted to 11.0 using 32 wt % of liquid alkali, so that divalent and trivalent cations such as calcium, magnesium, and iron in the liquid are precipitated, and then the impurity precipitate is removed by normal pressure filtration.

[0063] (3) The lithium precipitation mother liquor (lithium content of 2.29 g / L, sodium content of 65.48 g / L) after impurity removal was passed into an extraction tank (model SY-7100) containing a composite extractant, and subjected to 4-stage countercurrent extraction, 3-stage countercurrent stripping and 3-stage countercurrent washing to obtain a lithium stripping solution with a lithium concentration of 22.40 g / L. Among them, in the extraction section process, the volume ratio of the amount of the organic phase composite extractant (O) used in the entire countercurrent extraction stage to the lithium-containing liquid (A) is O / A=1.2:1, the extraction temperature is controlled to be 25°C, the residence time of the extraction section is 6 minutes, the lithium content in the raffinate obtained by extraction is 0.27 mg / L, and the lithium extraction efficiency is greater than 99.9%; in the countercurrent stripping process, 2 mol / L sulfuric acid solution is used as the stripping solution, the total volume of the stripping solution in the entire stripping process is 1:12 to the total volume of the extracted organic phase composite extractant, the lithium content in the stripping solution obtained is 22.40 g / L, and the residence time of the stripping section is 5 minutes; the washing section uses pure water for washing, the washing temperature is 25°C, the washing residence time is 5 minutes, and the volume ratio of pure water to the organic composite extractant is controlled to be 1:1.

[0064] (4) The lithium stripping solution is mixed with a sodium carbonate solution (concentration of 230 g / L) to precipitate lithium, wherein the amount of sodium carbonate added is 0.6 times the amount of lithium ion substances in the stripping solution, and then filtered, washed, and dried to obtain battery-grade lithium carbonate.

[0065] Embodiment 3:

[0066] (1) Preparation of composite extractant: sulfonated kerosene was used as diluent, and 1,3-bis(4-fluorophenyl)-1,3-propanedione (0.1 mol / L), benzoyltrifluoroacetone (0.3 mol / L), tributyl phosphate (0.1 mol / L) and tripentyl phosphate (0.1 mol / L) were added.

[0067] (2) The pH of the lithium precipitation mother liquor is adjusted to 10.5 using 32 wt % of liquid alkali, so that divalent and trivalent cations such as calcium, magnesium, and iron in the liquid are precipitated, and then the impurity precipitate is removed by normal pressure filtration.

[0068] (3) The lithium precipitation mother liquor (lithium content of 2.29 g / L, sodium content of 65.48 g / L) after impurity removal was passed into an extraction tank (model SY-7100) containing a composite extractant, and subjected to 4-stage countercurrent extraction, 3-stage countercurrent stripping and 3-stage countercurrent washing to obtain a lithium stripping solution with a lithium concentration of 22.36 g / L. Among them, in the extraction section process, the volume ratio of the amount of the organic phase composite extractant (O) used in the entire countercurrent extraction stage to the lithium-containing liquid (A) is O / A=1:1, the extraction temperature is controlled to be 25°C, the residence time of the extraction section is 5 minutes, the lithium content in the raffinate obtained by extraction is 0.67 mg / L, and the lithium extraction efficiency is greater than 99.9%; in the countercurrent stripping process, 2 mol / L sulfuric acid solution is used as the stripping solution, the total volume of the stripping solution in the entire stripping process is 1:10 to the total volume of the extracted organic phase composite extractant, the lithium content in the stripping solution obtained is 22.36 g / L, and the residence time of the stripping section is 5 minutes; the washing section uses pure water for washing, the washing temperature is 25°C, the washing residence time is 5 minutes, and the volume ratio of pure water to the organic composite extractant is controlled to be 1:1.

[0069] (4) The lithium stripping solution is mixed with a sodium carbonate solution (concentration of 230 g / L) to precipitate lithium, wherein the amount of sodium carbonate added is 0.6 times the amount of lithium ion substances in the stripping solution, and then filtered, washed, and dried to obtain battery-grade lithium carbonate.

[0070] Embodiment 4:

[0071] (1) Preparation of composite extractant: sulfonated kerosene was used as diluent, and 1,3-bis(4-fluorophenyl)-1,3-propanedione (0.1 mol / L), benzoyltrifluoroacetone (0.3 mol / L), tributyl phosphate (0.1 mol / L) and tripentyl phosphate (0.1 mol / L) were added.

[0072] (2) The pH of the lithium precipitation mother liquor is adjusted to 10.5 using 32 wt % of liquid alkali, so that divalent and trivalent cations such as calcium, magnesium, and iron in the liquid are precipitated, and then the impurity precipitate is removed by normal pressure filtration.

[0073] (3) The lithium precipitate mother liquor (lithium content: 2.29 g / L, sodium content: 65.48 g / L) after impurity removal was passed into an extraction tank (model: SY-7100) containing a composite extractant, and subjected to 4-stage countercurrent extraction, 3-stage countercurrent stripping and 3-stage countercurrent washing to obtain a lithium stripping solution with a lithium concentration of 22.18 g / L. Among them, in the extraction section process, the volume ratio of the amount of the organic phase composite extractant (O) used in the countercurrent extraction stage to the lithium-containing liquid (A) is O / A=1:1.2, the extraction temperature is controlled to be 25°C, the residence time of the extraction section is 5 minutes, the lithium content in the raffinate obtained by extraction is 0.45 mg / L, and the lithium extraction efficiency is greater than 99.9%; in the countercurrent stripping process, 2 mol / L sulfuric acid solution is used as the stripping solution, the total volume of the stripping solution in the entire stripping process is 1:12 to the total volume of the extracted organic phase composite extractant, the lithium content in the stripping solution obtained is 22.18 g / L, and the residence time of the stripping section is 5 minutes; the washing section uses pure water for washing, the washing temperature is 25°C, the washing residence time is 5 minutes, and the volume ratio of pure water to the organic composite extractant is controlled to be 1:1.

[0074] (4) The lithium stripping solution is mixed with a sodium carbonate solution (concentration of 230 g / L) to precipitate lithium, wherein the amount of sodium carbonate added is 0.6 times the amount of lithium ion substances in the stripping solution, and then filtered, washed, and dried to obtain battery-grade lithium carbonate.

[0075] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A composite extractant, characterized in that Including extractants, co-extractants and diluents; The extractant includes one or more of 1,3-bis(4-fluorophenyl)-1,3-propanedione, 2,2-difluoro-1,3-diphenyl-1,3-propanedione, 1-phenyl-3-isoheptyl-1,3-propanedione, and benzoyltrifluoroacetone; The synergistic extractant includes one or more of tributyl phosphate, triisobutyl phosphate, tripentyl phosphate, tributylphosphine oxide, and bis(4-fluorophenyl)phosphine oxide; The diluent includes one or more of kerosene, sulfonated kerosene, tetradecane and tetradecanol.

2. A composite extractant according to claim 1, characterized in that: The molar ratio of the extractant to the co-extractant is 0.25 to 4:1; The volume ratio of the extractant to the diluent is 0.15 to 2:

1.

3. Use of the composite extractant according to any one of claims 1 to 2 in separating and recovering lithium from lithium precipitation mother liquor, characterized in that: The application method comprises the following steps: 1) mixing the lithium precipitation mother liquor with liquid alkali to react, and obtaining a lithium precipitation mother liquor with preliminary impurity removal through solid-liquid separation; 2) using a composite extractant to perform multi-stage countercurrent extraction, stripping and washing on the preliminarily impurity-removed lithium precipitation mother liquor to obtain a lithium stripping solution; 3) The lithium stripping solution is mixed with the sodium carbonate solution, and the mixture is filtered and dried in sequence to obtain battery-grade lithium carbonate.

4. The use of the composite extractant according to claim 3 in separating and recovering lithium from lithium precipitation mother liquor, characterized in that: In step 1), the concentration of lithium ions in the lithium precipitation mother solution is 1-4 g / L, and the concentration of sodium ions is 35-75 g / L.

5. The use of the composite extractant according to claim 4 in separating and recovering lithium from lithium precipitation mother liquor, characterized in that: The pH value of the lithium precipitation mother solution after mixing with the liquid alkali in step 1) is 9.0-13.0; The liquid alkali is a sodium hydroxide solution, and the concentration of the liquid alkali is 30-35wt%.

6. The use of the composite extractant according to claim 5 in separating and recovering lithium from lithium precipitation mother liquor, characterized in that: The volume ratio of the total amount of the composite extractant used in the multi-stage countercurrent extraction process in step 2) to the preliminarily impurity-free lithium precipitation mother liquor is 0.5 to 3:

1.

7. Use of the composite extractant according to any one of claims 3 to 6 in separating and recovering lithium from lithium precipitation mother liquor, characterized in that: The extraction stages of the multi-stage countercurrent extraction in step 2) are 2 to 6 stages, the stripping stages are 2 to 5 stages, and the washing stages are 2 to 5 stages.

8. Use of the composite extractant according to claim 7 in separating and recovering lithium from lithium precipitation mother liquor, characterized in that: The stripping solution of the stripping in step 2) is a sulfuric acid solution; The volume ratio of the total amount of the stripping solution used in the stripping to the composite extractant is 1:5-25; The concentration of the sulfuric acid solution is 1-4 mol / L.

9. Use of the composite extractant according to claim 8 in separating and recovering lithium from lithium precipitation mother liquor, characterized in that: The molar ratio of lithium ions in the lithium stripping solution to carbonate ions in the sodium carbonate solution in step 3) is 1:0.4-0.8.