Extraction system, preparation method and application thereof, and method for extracting lithium from alkaline lithium precipitation mother liquor

Abstract

The invention provides an extraction system, a preparation method and application thereof and a method for extracting lithium from alkaline lithium precipitation mother liquor, and relates to the technical field of lithium ion extraction. The extraction system provided by the invention comprises a hydrophobic deep-eutectic solvent and a non-polar organic diluent, the hydrophobic deep-eutectic solvent comprises a hydrogen bond donor and a hydrogen bond acceptor, the hydrogen bond donor comprises one or more of phenyl salicylate, benzyl salicylate and phenethyl salicylate, and the hydrogen bond acceptor is a neutral phosphorus compound with a Li coordination group. The extraction system provided by the invention can effectively realize extraction separation of lithium and sodium in the alkaline lithium precipitation mother liquor, has excellent lithium ion extraction rate and lithium-sodium selectivity, still shows excellent lithium ion extraction rate and lithium-sodium selectivity after regeneration, has the price far lower than that of a diketone extraction agent and an ionic liquid extraction agent, is low in cost, and is suitable for industrial production. The large-scale industrial application is more facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion extraction, and particularly relates to an extraction system, a preparation method and an application thereof, and a method for extracting lithium from an alkaline lithium precipitation mother liquor. Background Art

[0002] Compared with other energy storage devices, lithium ion batteries (LIBs) have become the mainstream energy storage devices for portable electronic products and electric vehicles due to their high voltage, high energy density, small volume and other characteristics. In recent years, the rapid development of these industries has greatly increased the consumption demand for lithium. Moreover, due to the limited lifespan of lithium batteries, the amount of scrapped batteries has increased year by year, and the resulting resource and environmental problems cannot be ignored.

[0003] In industrial lithium battery resource recovery, whether it is lithium extraction at the front end or at the back end, it mainly relies on the lithium carbonate precipitation method (converting lithium resources into lithium carbonate by adding sodium carbonate). However, due to the certain solubility of lithium carbonate in the aqueous phase, lithium ions cannot be completely precipitated. Therefore, the single-pass recovery rate of lithium carbonate precipitation is only about 80%, that is, at room temperature, about 0.216 - 0.360 mol / L of lithium will remain in the aqueous phase, forming a lithium precipitation mother liquor. To improve the economy of lithium carbonate precipitation, the solution can be concentrated to a certain extent by forced evaporation, but this is a high-energy-consuming process. Using NaF and Na3PO4 as precipitation reagents can obtain a higher lithium recovery effect, but the relatively high price of the reagents limits their application. In contrast, the solvent extraction method has significant advantages in terms of lithium recovery rate and selective separation effect of impurity elements. The overall recovery rate of lithium extraction from the mother liquor can reach more than 80%, and the lithium-sodium separation coefficient can reach more than 100.

[0004] Currently, the extraction systems for lithium extraction from the mother liquor mainly include phosphoric esters, β-diketones, and ionic liquids. Among them, the phosphoric ester extraction system shows excellent lithium ion selectivity and extraction rate in acidic salt lakes with a high Mg / Li ratio. For example, the extraction system of TBP-DIBK-kerosene extracts lithium from lithium-containing brine. After eight full reflux cascade experiments, the lithium extraction rate can reach 99.9%. However, when this system extracts lithium, it requires the solution to be acidic (pH < 5), and ferric chloride must be added as a synergistic extractant. The β-diketone extraction system mainly focuses on lithium extraction from alkaline brine. However, β-diketone extractants have problems such as high toxicity and high water solubility. Moreover, when the pH value of the aqueous phase exceeds 13, a relatively serious emulsification phenomenon occurs during the extraction process, which is not conducive to the extraction process. Ionic liquid extractants can effectively separate lithium and sodium in the lithium precipitation mother liquor and are environmentally friendly. However, due to their high viscosity and high price, they are limited in industrial use. Therefore, there is an urgent need to develop an extraction system with excellent lithium ion extraction effect and low cost to achieve efficient separation of lithium and sodium in the alkaline lithium precipitation mother liquor. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an extraction system, a preparation method and application thereof, and a method for extracting lithium from an alkaline lithium precipitation mother liquor. The extraction system provided by the present invention can effectively achieve the extraction separation of lithium and sodium in the alkaline lithium precipitation mother liquor, with high separation efficiency and low cost.

[0006] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides an extraction system, comprising a hydrophobic deep eutectic solvent and a non-polar organic diluent; the hydrophobic deep eutectic solvent comprises a hydrogen bond donor and a hydrogen bond acceptor, the hydrogen bond donor comprises one or more of phenyl salicylate, benzyl salicylate and phenethyl salicylate, and the hydrogen bond acceptor is a neutral phosphorus compound with a Li coordination group.

[0008] Preferably, the neutral phosphorus compound with a Li coordination group comprises one or more of trialkyl phosphine oxide, tributyl phosphate and trioctyl phosphate.

[0009] Preferably, the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:9 to 9:1; the concentrations of the hydrogen bond donor and the hydrogen bond acceptor in the extraction system are independently 0.1 to 1.0 mol / L.

[0010] Preferably, the non-polar organic diluent comprises one or more of sulfonated kerosene, n-hexane, benzene, toluene, heptane and dodecane.

[0011] The present invention provides a preparation method of the extraction system described in the above technical solutions, comprising the following steps:

[0012] Mix the hydrogen bond donor and the hydrogen bond acceptor to obtain a hydrophobic deep eutectic solvent;

[0013] Mix the hydrophobic deep eutectic solvent with the non-polar organic diluent to obtain the extraction system.

[0014] The present invention provides the application of the extraction system described in the above technical solutions or the extraction system prepared by the preparation method described in the above technical solutions in the extraction separation of lithium and sodium.

[0015] The present invention provides a method for extracting lithium from an alkaline lithium precipitation mother liquor, comprising the following steps:

[0016] Mix the extraction system with the alkaline lithium precipitation mother liquor for extraction to obtain a raffinate and a lithium-rich loaded organic phase; the extraction system is the extraction system described in the above technical solutions or the extraction system prepared by the preparation method described in the above technical solutions; the alkaline lithium precipitation mother liquor contains lithium ions and sodium ions.

[0017] Preferably, the concentration of lithium ions in the alkaline lithium precipitation mother solution is 0.05-10 g / L, the concentration of hydroxide ions is less than or equal to 1 mol / L, and the concentration of sodium ions is 25-65 g / L.

[0018] Preferably, the ratio of the extraction system to the alkaline lithium precipitation mother liquor is 1:20 to 20:1; the extraction temperature is 20 to 70° C., and the extraction time is 0.05 to 5 h.

[0019] Preferably, after obtaining the lithium-rich loaded organic phase, the process further comprises mixing the lithium-rich loaded organic phase with an inorganic acid solution for stripping to obtain an empty organic phase and a lithium-rich aqueous phase.

[0020] The present invention provides an extraction system, including a hydrophobic deep eutectic solvent and a non-polar organic diluent; the hydrophobic deep eutectic solvent includes a hydrogen bond donor and a hydrogen bond acceptor, the hydrogen bond donor includes one or more of phenyl salicylate, benzyl salicylate and phenylethyl salicylate, and the hydrogen bond acceptor is a neutral phosphorus compound with a Li coordination group. The present invention uses salicylate compounds such as phenyl salicylate, benzyl salicylate and phenylethyl salicylate and a neutral phosphorus compound with a Li coordination group as hydrogen bond donors and hydrogen bond acceptors to form a hydrophobic deep eutectic solvent (HDES), which can effectively realize the extraction and separation of lithium and sodium in an alkaline lithium precipitation mother liquor, has the advantages of high separation efficiency, low cost, and easy phase separation, and can be well dissolved in an organic phase (i.e., a non-polar organic diluent) and is easy to strip and regenerate, and recycled, and has high economic benefits; and HDES has the characteristics of low vapor pressure, non-flammability, and good thermal stability, and has the advantages of green environmental protection in the extraction and separation process. In addition, the present invention adds a non-polar organic diluent to the extraction system, which can make the extraction system (extracted organic phase) fully mixed with the alkaline lithium precipitation mother liquor (aqueous phase) and further reduce the cost, and the non-polar organic diluent is used to control the concentration of HDES, so as to avoid too much HDES from extracting more sodium ions into the organic phase due to the low lithium ion concentration in the lithium precipitation mother liquor, which is not conducive to lithium-sodium separation; at the same time, the addition of the non-polar organic diluent can reduce the viscosity of the extraction system, increase the diffusion rate of the extraction system, and thus enhance the extraction effect. The extraction system provided by the present invention can effectively realize the extraction and separation of lithium and sodium in the alkaline lithium precipitation mother liquor, has excellent lithium ion extraction rate and lithium-sodium selectivity, and the price is much lower than that of diketone extractants and ionic liquid extractants, with low cost, and is more conducive to large-scale industrial application.

[0021] The results of the embodiment show that the extraction rate of lithium ions in the alkaline lithium precipitation mother liquor is 56.25-89.90% with the extraction system provided by the present invention, and the selectivity is β Li / Na= 114.13 - 171.19; After 5 cycles of regeneration - extraction - back - extraction, the extraction performance of the extraction system did not decline, and still showed excellent lithium - ion extraction rate and lithium - sodium selectivity.

[0022] The present invention provides a preparation method of the extraction system described in the above technical solutions, which has a simple process, easily available raw materials, and low cost. Detailed implementation manners

[0023] The present invention provides an extraction system, including a hydrophobic deep eutectic solvent and a non - polar organic diluent; the hydrophobic deep eutectic solvent includes a hydrogen - bond donor and a hydrogen - bond acceptor, the hydrogen - bond donor includes one or more of phenyl salicylate, benzyl salicylate and phenethyl salicylate, and the hydrogen - bond acceptor is a neutral phosphorus compound with a Li - coordination group.

[0024] In the present invention, unless otherwise specified, the raw materials involved are well - known commercially available products in the art.

[0025] The extraction system provided by the present invention includes a hydrophobic deep eutectic solvent (HDES). In the present invention, the hydrophobic deep eutectic solvent includes a hydrogen - bond donor (HBD) and a hydrogen - bond acceptor (HBA); the hydrogen - bond donor includes one or more of phenyl salicylate, benzyl salicylate and phenethyl salicylate, the hydrogen - bond acceptor is a neutral phosphorus compound with a Li - coordination group, and the neutral phosphorus compound with a Li - coordination group preferably includes one or more of trialkyl phosphine oxide, tributyl phosphate and trioctyl phosphate. The above neutral phosphorus compounds coordinate with Li through the - P = O group. In the present invention, the molar ratio of the hydrogen - bond donor to the hydrogen - bond acceptor is preferably 1:9 - 9:1, and can be 1:3, 1:2, 1:1.5, 1:1, 2:1 or 3:1. In the present invention, phenyl salicylate, benzyl salicylate and phenethyl salicylate have low costs, but the complexes formed by their individual actions all precipitate at the extraction interface and cannot be applied in the extraction process. The present invention forms HDES by combining phenyl salicylate, benzyl salicylate, phenethyl salicylate with a neutral phosphorus compound, which can reduce its melting point and the HDES has good fluidity.

[0026] In the present invention, the phenolic hydroxyl group (-OH) in the molecular structures of phenyl salicylate, benzyl salicylate and phenethyl salicylate can be used as a hydrogen - bond donor, while the - P = O group contained in the neutral phosphorus compound acts as a hydrogen - bond acceptor. The two can enhance the synergistic effect between extractant molecules through hydrogen - bond interaction, thereby overcoming the deficiencies of a single extractant in terms of solubility, stability and extraction performance.

[0027] In the present invention, the hydrophobic deep eutectic solvent has excellent lithium ion extraction rate and lithium-sodium selectivity, can be well dissolved in the organic phase, is easy to be stripped and regenerated for recycling, and has high economic benefits. The raw materials of the hydrophobic deep eutectic solvent are easily available, easy to phase-separate, and the price is much lower than that of diketone extractants, which is more conducive to large-scale industrial application; compared with the disadvantages of difficult recovery, high price, and complex synthesis of ionic liquids (ILs), the hydrophobic deep eutectic solvent is easy to prepare and has low cost. In addition, the viscosity of the hydrophobic deep eutectic solvent is much lower than that of ILs, while maintaining similar properties to ILs (such as low volatility, environmentally friendly, and strong adjustability); the hydrophobic deep eutectic solvent has the characteristics of low vapor pressure, non-flammable, and thermally stable, and is more environmentally friendly in the extraction and separation process. Therefore, the hydrophobic deep eutectic solvent described in the present invention can well replace diketone extractants and ILs. In addition, the hydrophobic deep eutectic solvent has the advantage of being designed in terms of structural properties. For a specific separation system, the structure of the solvent (including adjusting the composition and molar ratio of hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD)) can be regulated to improve the molecular recognition ability of the solvent and achieve the required extraction effect.

[0028] The extraction system provided by the present invention includes a non-polar organic diluent. In the present invention, the non-polar organic diluent preferably includes one or more of sulfonated kerosene, n-hexane, benzene, toluene, heptane, and dodecane; the non-polar organic diluent is selected in the present invention, and the complex formed during the extraction process is easy to enter, resulting in good phase separation. In the present invention, the concentrations of the hydrogen bond donor and the hydrogen bond acceptor in the extraction system are independently preferably 0.1-1.0 mol / L, and can independently be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 mol / L; in the present invention, the concentrations and ratios of the hydrogen bond acceptor (HBA), the hydrogen bond donor (HBD), and the non-polar organic diluent can be adjusted according to specific requirements to ensure extraction efficiency and stability. In order to fully mix the extraction system (extraction organic phase) with the alkaline lithium precipitation mother liquor (aqueous phase) and further reduce costs, the present invention uses a non-polar organic diluent to control the concentration of HDES, because too much HDES will extract more sodium ions into the organic phase due to the low lithium ion concentration in the lithium precipitation mother liquor, which is not conducive to lithium-sodium separation; in addition, the addition of the non-polar organic diluent can reduce the viscosity of the extraction system and increase the diffusion rate of the extraction system, thereby enhancing the extraction effect.

[0029] The extraction system provided by the present invention has good phase separation (when the pH of the aqueous phase ≥ 13, the organic phase and the aqueous phase are clear and not emulsified), can effectively achieve the extraction and separation of lithium and sodium, has excellent lithium ion extraction rate and lithium-sodium selectivity, high lithium recovery rate, and low cost.

[0030] The present invention provides a method for preparing the extraction system described in the above technical solution, comprising the following steps:

[0031] Mix a hydrogen bond donor and a hydrogen bond acceptor (denoted as the first mixing) to obtain a hydrophobic eutectic solvent; mix the hydrophobic eutectic solvent with a non-polar organic diluent (denoted as the second mixing) to obtain the extraction system.

[0032] In the present invention, the temperature of the first mixing is preferably 30 to 70 °C, which can be 30, 40, 50, 60 or 70 °C. The temperature is preferably achieved by water bath heating; the first mixing is preferably carried out under stirring, and the stirring rate is preferably 300 to 800 r / min, which can be 400, 500, 600 or 700 r / min. The stirring can be magnetic stirring; the time of the first mixing is preferably 0.05 to 5 h, which can be 0.05, 0.1, 0.3, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 h, specifically until a completely transparent liquid is obtained. After obtaining the completely transparent liquid, the completely transparent liquid needs to be placed at room temperature overnight. If no recrystallization (i.e., no precipitation phenomenon) occurs, the hydrophobic eutectic solvent is successfully prepared.

[0033] The present invention has no special requirements for the second mixing, and it is only necessary to mix the hydrophobic eutectic solvent and the non-polar organic diluent evenly.

[0034] In the present invention, the hydrophobic eutectic solvent can be prepared by mixing a hydrogen bond acceptor and a hydrogen bond donor. The preparation method provided by the present invention has the advantages of simple preparation, high synthetic atom economy and low cost.

[0035] The present invention provides the application of the extraction system described in the above technical solution or the extraction system prepared by the preparation method described in the above technical solution in the extraction and separation of lithium and sodium. The extraction system provided by the present invention has excellent lithium ion extraction rate and lithium-sodium selectivity, and can be used for the extraction and separation of lithium and sodium in a solution containing lithium and sodium.

[0036] The present invention provides a method for extracting lithium from an alkaline lithium precipitation mother liquor, comprising the following steps:

[0037] Mix the extraction system with the alkaline lithium precipitation mother liquor for extraction to obtain a raffinate and a lithium-rich loaded organic phase; the extraction system is the extraction system described in the above technical solution or the extraction system prepared by the preparation method described in the above technical solution; the alkaline lithium precipitation mother liquor contains lithium ions and sodium ions.

[0038] In the present invention, the alkaline lithium precipitation mother liquor contains lithium ions and sodium ions. The present invention has no special requirements for the source of the alkaline lithium precipitation mother liquor, and the alkaline lithium precipitation mother liquor well-known to those skilled in the art is applicable to the present invention. For example, the alkaline lithium precipitation mother liquor obtained by lithium carbonate precipitation method. When using the lithium carbonate precipitation method to precipitate lithium, since the solubility of Li2CO3 is relatively low, it precipitates from the solution. During the precipitation process of Li2CO3, due to the solubility limitation of the Li2CO3 product and the co-saturation point of the Li / Na solution, lithium cannot be completely precipitated. In the present invention, the concentration of lithium ions in the alkaline lithium precipitation mother liquor is preferably 0.05 - 10 g / L, which can be 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 g / L; the concentration of sodium ions is preferably 25 - 65 g / L, which can be 25, 30, 40, 50, 60 or 65 g / L; the concentration of hydroxide ions is preferably less than or equal to 1 mol / L, which can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9 mol / L. The extraction efficiency is affected by the pH value of the alkaline lithium precipitation mother liquor. The higher the hydroxide concentration, the higher the extraction efficiency. After reaching a certain hydroxide concentration (0.5 mol / L), an inflection point appears, and the growth rate of the extraction rate slows down.

[0039] In the embodiments of the present invention, the hydroxide ion concentration of the lithium-containing solution is adjusted by an alkaline compound to form an alkaline lithium-containing solution to simulate the alkaline lithium precipitation mother liquor; the alkaline compound can be one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide and sodium carbonate.

[0040] In the present invention, the extraction system serves as the extraction organic phase, and the alkaline lithium precipitation mother liquor serves as the extraction aqueous phase; the ratio of the extraction system to the alkaline lithium precipitation mother liquor (i.e., the extraction ratio O / A) is preferably 1:20 - 20:1, which can be 1:20, 1:10, 1:5, 1:1, 5:1, 10:1 or 20:1. In the present invention, the extraction temperature is preferably 20 - 70 °C, which can be 20, 30, 40, 50, 60 or 70 °C, and the time is preferably 0.05 - 5 h, which can be 0.05, 0.1, 0.3, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 h. In the present invention, the extraction can be carried out by single-stage shaking extraction or multi-stage countercurrent extraction, and the multi-stage countercurrent extraction can be three-stage countercurrent extraction. During the extraction process, the extraction organic phase and the extraction aqueous phase are in full contact, and the lithium ions in the aqueous phase are selectively transferred to the organic phase to form a loaded organic phase. After the extraction reaches equilibrium, it is allowed to stand and separate to obtain the raffinate and the lithium-rich loaded organic phase.

[0041] After obtaining the lithium-rich loaded organic phase, the present invention preferably further includes mixing the lithium-rich loaded organic phase with an inorganic acid solution for back extraction to obtain an empty organic phase and a lithium-rich aqueous phase.

[0042] In the present invention, the inorganic acid solution used for back-extraction preferably includes one or more of sulfuric acid, hydrochloric acid, and nitric acid. The hydrogen ion concentration of the inorganic acid solution is preferably 0.05 - 6 mol / L, and can be 0.5, 1, 2, 3, 4, 5, or 6 mol / L. The phase ratio of the lithium-rich loaded organic phase to the inorganic acid solution (i.e., the back-extraction phase ratio (O / A)) is preferably 1:20 - 20:1, and can be 1:20, 1:10, 1:5, 1:2, 1:1, 2:1, 5:1, 10:1, or 20:1. The time for back-extraction is preferably 0.05 - 5 h, and can be 0.3, 1, 2, 3, or 4 h. In the present invention, the back-extraction (which can also be called stripping) can adopt a single-stage shaking or multi-stage countercurrent back-extraction form. During the back-extraction process, the hydrogen ions in the inorganic acid solution can effectively break the stable complex formed between lithium ions and HDES, forming a lithium salt (such as lithium chloride, etc.) that is soluble in water, thereby transferring all lithium ions from the organic phase to the aqueous solution to obtain an empty organic phase and a lithium-rich aqueous phase.

[0043] After obtaining the empty organic phase, the present invention can regenerate the empty organic phase. The preferred regeneration method is: mixing the empty organic phase with a regenerant for regeneration. In the present invention, the regenerant is preferably water or an alkaline aqueous solution, and the alkaline compound in the alkaline aqueous solution can be a carbonate and / or a hydroxide. The regeneration phase ratio is preferably 1:20 - 20:1, and can be 1:20, 1:10, 1:5, 1:2, 1:1, 2:1, 5:1, 10:1, or 20:1. During the back-extraction process, some acids will enter the organic phase in the form of molecules. The function of the regenerant is to wash away the acids in the organic phase, neutralize the acid-base, and the acid is more likely to dissolve in water. The extraction system provided by the present invention still exhibits excellent lithium ion extraction rate and lithium-sodium selectivity after regeneration.

[0044] To further illustrate the present invention, the extraction system provided by the present invention, its preparation method and application, and the method for extracting lithium from an alkaline lithium precipitation mother liquor will be described in detail below with reference to examples, but they should not be construed as limiting the protection scope of the present invention.

[0045] Example 1

[0046] Prepare the extraction organic phase: Take phenyl salicylate as HBD and trialkyl phosphine oxide as HBA, mix them in a molar ratio of 1:1, heat in a water bath at 30 °C and stir magnetically (400 r / min), with a heating time of 3 h. Let the mixture stand overnight at room temperature without precipitation, indicating that HDES is successfully synthesized. Add the diluent dodecane to HDES to obtain the extraction organic phase. In the extraction organic phase, the concentration of phenyl salicylate is 0.4 mol / L, the concentration of trialkyl phosphine oxide is 0.4 mol / L, and the rest is dodecane.

[0047] Configure the extraction aqueous phase: Take a lithium-containing solution with 2.08 g / L of lithium, 32.19 g / L of sodium, chloride ions, carbonate ions as anions, and a hydroxide ion concentration of 0.5 mol / L as the extraction aqueous phase.

[0048] Extraction: Perform single-stage shaking extraction on the above extraction organic phase and extraction aqueous phase under the condition of extraction phase ratio (O / A) = 1:1, with an extraction temperature of 30 °C and an extraction time of 20 min. After the extraction reaches equilibrium, let the mixture stand, and measure the lithium ion concentration after phase separation. It is measured that the remaining lithium ion concentration in the aqueous phase is 0.21 g / L, and the lithium ion extraction rate is calculated to be 89.90%.

[0049] Back-extraction: Use a hydrochloric acid solution with a concentration of 6 mol / L to perform single-stage shaking back-extraction on the loaded organic phase obtained by extraction. The back-extraction phase ratio (O / A) = 1:2, and the back-extraction time is 20 min. After the back-extraction reaches equilibrium, let the mixture stand, and measure the sodium ion concentration after phase separation. It is measured that the sodium ion concentration in the aqueous phase after back-extraction is 0.95 g / L, and the sodium ion extraction rate is calculated to be 5.90%. Selectivity β Li / Na = 141.96.

[0050] Example 2

[0051] Configure the extraction organic phase: Take benzyl salicylate as HBD and trialkyl phosphine oxide as HBA, mix them in a molar ratio of 1:1, heat in a water bath at 30 °C and stir magnetically (400 r / min) for 3 h. Let the mixture stand overnight at room temperature without precipitation, indicating the successful synthesis of HDES; add diluent dodecane to HDES to obtain the extraction organic phase. In the extraction organic phase, the concentration of benzyl salicylate is 0.4 mol / L, the concentration of trialkyl phosphine oxide is 0.4 mol / L, and the rest is dodecane.

[0052] Configure the extraction aqueous phase: Take a lithium-containing solution with 2.08 g / L of lithium, 32.19 g / L of sodium, chloride ions, carbonate ions as anions, and a hydroxide ion concentration of 0.5 mol / L as the extraction aqueous phase.

[0053] Extraction: Perform single-stage shaking extraction on the above extraction organic phase and extraction aqueous phase under the condition of extraction phase ratio (O / A) = 1:1, with an extraction temperature of 30 °C and an extraction time of 20 min. After the extraction reaches equilibrium, let the mixture stand, and measure the lithium ion concentration after phase separation. It is measured that the remaining lithium ion concentration in the aqueous phase is 0.30 g / L, and the lithium ion extraction rate is calculated to be 85.58%.

[0054] Back extraction: The loaded organic phase obtained by extraction was subjected to single-stage shaking back extraction using a hydrochloric acid solution with a concentration of 6 mol / L. The back extraction phase ratio (O / A) = 1:2, the back extraction time was 20 min. After the back extraction reached equilibrium, the mixture was allowed to stand, and the sodium ion concentration was measured after phase separation. It was measured that the sodium ion concentration in the aqueous phase after back extraction was 0.67 g / L, and the sodium ion extraction rate was calculated to be 4.16%. Selectivity β Li / Na = 136.60.

[0055] Example 3

[0056] Preparation of extraction organic phase: Take phenethyl salicylate as HBD and trialkyl phosphine oxide as HBA, mix them in a molar ratio of 1:1, heat in a water bath at 30 °C and stir magnetically (400 r / min), the heating time is 3 h. The mixture was left at room temperature overnight without precipitation, indicating the successful synthesis of HDES; Diluent dodecane was added to HDES to obtain the extraction organic phase. In the extraction organic phase, the concentration of phenethyl salicylate is 0.4 mol / L, the concentration of trialkyl phosphine oxide is 0.4 mol / L, and the rest is dodecane.

[0057] Preparation of extraction aqueous phase: Take a lithium-containing solution with a lithium content of 2.08 g / L, a sodium content of 32.19 g / L, anions of chloride ions, carbonate ions, and a hydroxide ion concentration of 0.5 mol / L as the extraction aqueous phase.

[0058] Extraction: The above extraction organic phase and extraction aqueous phase were subjected to single-stage shaking extraction under the condition of an extraction phase ratio (O / A) = 1:1, the extraction temperature was 30 °C, and the extraction time was 20 min. After the extraction reached equilibrium, the mixture was allowed to stand, and the lithium ion concentration was measured after phase separation. It was measured that the remaining lithium ion concentration in the aqueous phase was 0.25 g / L, and the lithium ion extraction rate was calculated to be 87.98%.

[0059] Back extraction: The loaded organic phase obtained by extraction was subjected to single-stage shaking back extraction using a hydrochloric acid solution with a concentration of 6 mol / L. The back extraction phase ratio (O / A) = 1:2, the back extraction time was 20 min. After the back extraction reached equilibrium, the mixture was allowed to stand, and the sodium ion concentration was measured after phase separation. It was measured that the sodium ion concentration in the aqueous phase after back extraction was 0.66 g / L, and the sodium ion extraction rate was calculated to be 4.10%. Selectivity β Li / Na = 171.19.

[0060] Example 4

[0061] Preparation of extraction organic phase: Take phenethyl salicylate as HBD and trialkyl phosphine oxide as HBA, mix them in a molar ratio of 1:1, heat in a water bath at 30 °C and stir magnetically (400 r / min) for 3 h. Let the mixture stand overnight at room temperature without precipitation, indicating the successful synthesis of HDES. Add diluent sulfonated kerosene to the HDES to obtain the extraction organic phase. Among them, in the extraction organic phase, the concentration of phenethyl salicylate is 0.4 mol / L, the concentration of trialkyl phosphine oxide is 0.4 mol / L, and the rest is sulfonated kerosene.

[0062] Preparation of extraction aqueous phase: Take a lithium-containing solution with a lithium content of 2.08 g / L, a sodium content of 32.19 g / L, anions of chloride ions, carbonate ions, and a hydroxide ion concentration of 0.5 mol / L as the extraction aqueous phase.

[0063] Extraction: Perform single-stage shaking extraction on the above extraction organic phase and extraction aqueous phase under the condition of extraction phase ratio (O / A) = 1:1, with an extraction temperature of 30 °C and an extraction time of 20 min. After the extraction reaches equilibrium, let the mixture stand, and measure the lithium ion concentration after phase separation. It is measured that the remaining lithium ion concentration in the aqueous phase is 0.32 g / L, and the lithium ion extraction rate is calculated to be 84.62%.

[0064] Back-extraction: Perform single-stage shaking back-extraction on the loaded organic phase obtained by extraction using a hydrochloric acid solution with a concentration of 6 mol / L. The back-extraction phase ratio (O / A) = 1:2, and the back-extraction time is 20 min. After the back-extraction reaches equilibrium, let the mixture stand, and measure the sodium ion concentration after phase separation. It is measured that the sodium ion concentration in the aqueous phase after back-extraction is 0.74 g / L, and the sodium ion extraction rate is calculated to be 4.60%. Selectivity β Li / Na = 114.13.

[0065] Example 5

[0066] Preparation of extraction organic phase: Take phenethyl salicylate as HBD and tributyl phosphate as HBA, mix them in a molar ratio of 1:1, heat in a water bath at 30 °C and stir magnetically (400 r / min) for 3 h. Let the mixture stand overnight at room temperature without precipitation, indicating the successful synthesis of HDES. Add diluent dodecane to the HDES to obtain the extraction organic phase. In the extraction organic phase, the concentration of phenethyl salicylate is 0.4 mol / L, the concentration of tributyl phosphate is 0.4 mol / L, and the rest is dodecane.

[0067] Preparation of extraction aqueous phase: Take a lithium-containing solution with a lithium content of 2.08 g / L, a sodium content of 32.19 g / L, anions of chloride ions, carbonate ions, and a hydroxide ion concentration of 0.5 mol / L as the extraction aqueous phase.

[0068] Extraction: The above extraction organic phase and extraction aqueous phase were subjected to single-stage shaking extraction under the condition that the extraction phase ratio (O / A) = 1:1, the extraction temperature was 30 °C, the extraction time was 20 min. After the extraction reached equilibrium, the mixture was allowed to stand, and the lithium ion concentration was measured after phase separation. It was measured that the remaining lithium ion concentration in the aqueous phase was 0.54 g / L, and the lithium ion extraction rate was calculated to be 74.04%.

[0069] Stripping: The loaded organic phase obtained by extraction was subjected to single-stage shaking stripping with a hydrochloric acid solution with a concentration of 6 mol / L. The stripping phase ratio (O / A) = 1:2, the stripping time was 20 min. After the stripping reached equilibrium, the mixture was allowed to stand, and the sodium ion concentration was measured after phase separation. It was measured that the sodium ion concentration in the aqueous phase after stripping was 0.36 g / L, and the sodium ion extraction rate was calculated to be 2.24%. Selectivity β Li / Na = 124.65.

[0070] Example 6

[0071] Preparation of extraction organic phase: Take phenethyl salicylate as HBD and trialkyl phosphine oxide as HBA, mix them in a molar ratio of 1:2, heat in a water bath at 30 °C and stir magnetically (400 r / min), the heating time is 3 h. The mixture was left standing overnight at room temperature without precipitation, indicating the successful synthesis of HDES; diluent dodecane was added to HDES to obtain the extraction organic phase. In the extraction organic phase, the concentration of phenethyl salicylate is 0.3 mol / L, the concentration of trialkyl phosphine oxide is 0.6 mol / L, and the rest is dodecane.

[0072] Preparation of extraction aqueous phase: Take a lithium-containing solution with a lithium content of 2.08 g / L, a sodium content of 32.19 g / L, anions of chloride ions, carbonate ions, and a hydroxide ion concentration of 0.5 mol / L as the extraction aqueous phase.

[0073] Extraction: The above extraction organic phase and extraction aqueous phase were subjected to single-stage shaking extraction under the condition that the extraction phase ratio (O / A) = 1:1, the extraction temperature was 30 °C, the extraction time was 20 min. After the extraction reached equilibrium, the mixture was allowed to stand, and the lithium ion concentration was measured after phase separation. It was measured that the remaining lithium ion concentration in the aqueous phase was 0.44 g / L, and the lithium ion extraction rate was calculated to be 78.85%.

[0074] Stripping: The loaded organic phase obtained by extraction was subjected to single-stage shaking stripping with a hydrochloric acid solution with a concentration of 6 mol / L. The stripping phase ratio (O / A) = 1:2, the stripping time was 20 min. After the stripping reached equilibrium, the mixture was allowed to stand, and the sodium ion concentration was measured after phase separation. It was measured that the sodium ion concentration in the aqueous phase after stripping was 0.42 g / L, and the sodium ion extraction rate was calculated to be 2.61%. Selectivity β Li / Na = 139.11.

[0075] Example 7

[0076] Prepare the extraction organic phase: Take phenethyl salicylate as HBD and trialkyl phosphine oxide as HBA, mix them in a molar ratio of 1:3, heat in a water bath at 30 °C and stir magnetically (400 r / min) for 3 h. Let the mixture stand overnight at room temperature without precipitation, indicating the successful synthesis of HDES. Add the diluent dodecane to the HDES to obtain the extraction organic phase. In the extraction organic phase, the concentration of phenethyl salicylate is 0.2 mol / L, the concentration of trialkyl phosphine oxide is 0.6 mol / L, and the rest is dodecane.

[0077] Prepare the extraction aqueous phase: Take a lithium-containing solution with a lithium content of 2.08 g / L, a sodium content of 32.19 g / L, anions of chloride ions, carbonate ions, and a hydroxide ion concentration of 0.5 mol / L as the extraction aqueous phase.

[0078] Extraction: Perform single-stage shaking extraction on the above extraction organic phase and extraction aqueous phase under the condition of an extraction phase ratio (O / A) = 1:1, with an extraction temperature of 30 °C and an extraction time of 20 min. After the extraction reaches equilibrium, let the mixture stand, and measure the lithium ion concentration after phase separation. It is measured that the remaining lithium ion concentration in the aqueous phase is 0.89 g / L, and the lithium ion extraction rate is calculated to be 57.21%.

[0079] Stripping: Perform single-stage shaking stripping on the loaded organic phase with a hydrochloric acid solution with a concentration of 6 mol / L, with a stripping phase ratio (O / A) = 1:2 and a stripping time of 20 min. After the stripping reaches equilibrium, let the mixture stand, and measure the sodium ion concentration after phase separation. It is measured that the sodium ion concentration in the aqueous phase after stripping is 0.17 g / L, and the sodium ion extraction rate is calculated to be 1.06%. Selectivity β Li / Na = 125.25.

[0080] Example 8

[0081] Prepare the extraction organic phase: Take phenethyl salicylate as HBD and trialkyl phosphine oxide as HBA, mix them in a molar ratio of 2:3, heat in a water bath at 30 °C and stir magnetically (400 r / min) for 3 h. Let the mixture stand overnight at room temperature without precipitation, indicating the successful synthesis of HDES. Add the diluent dodecane to the HDES to obtain the extraction organic phase. In the extraction organic phase, the concentration of phenethyl salicylate is 0.4 mol / L, the concentration of trialkyl phosphine oxide is 0.6 mol / L, and the rest is dodecane.

[0082] Prepare the extraction aqueous phase: Take a lithium-containing solution with a lithium content of 2.08 g / L, a sodium content of 32.19 g / L, anions of chloride ions, carbonate ions, and a hydroxide ion concentration of 0.5 mol / L as the extraction aqueous phase.

[0083] Extraction: The above extraction organic phase and extraction aqueous phase were subjected to single-stage shaking extraction under the condition of extraction phase ratio (O / A) = 1:1, the extraction temperature was 30 °C, the extraction time was 20 min. After the extraction reached equilibrium, the mixture was allowed to stand, and the lithium ion concentration was measured after phase separation. It was measured that the remaining lithium ion concentration in the aqueous phase was 0.25 g / L, and the lithium ion extraction rate was calculated to be 87.98%.

[0084] Stripping: The loaded organic phase was subjected to single-stage shaking stripping with a hydrochloric acid solution with a concentration of 6 mol / L, the stripping phase ratio (O / A) = 1:2, the stripping time was 20 min. After the stripping reached equilibrium, the mixture was allowed to stand, and the sodium ion concentration was measured after phase separation. It was measured that the sodium ion concentration in the aqueous phase after stripping was 0.88 g / L, and the sodium ion extraction rate was calculated to be 5.47%. Selectivity β Li / Na = 126.56.

[0085] Example 9

[0086] Preparation of extraction organic phase: Take phenethyl salicylate as HBD and trialkyl phosphine oxide as HBA, mix them in a molar ratio of 1:1, heat in a water bath at 30 °C and stir magnetically (400 r / min), the heating time is 3 h. The mixture was left at room temperature overnight without precipitation, indicating the successful synthesis of HDES; Diluent dodecane was added to HDES to obtain the extraction organic phase. In the extraction organic phase, the concentration of phenethyl salicylate is 0.4 mol / L, the concentration of trialkyl phosphine oxide is 0.4 mol / L, and the rest is dodecane.

[0087] Preparation of extraction aqueous phase: Take a lithium-containing solution with a lithium content of 2.08 g / L, a sodium content of 25.26 g / L, anions of chloride ions, carbonate ions, and a hydroxide ion concentration of 0.2 mol / L as the extraction aqueous phase.

[0088] Extraction: The above extraction organic phase and extraction aqueous phase were subjected to single-stage shaking extraction under the condition of extraction phase ratio (O / A) = 1:1, the extraction temperature was 30 °C, the extraction time was 20 min. After the extraction reached equilibrium, the mixture was allowed to stand, and the lithium ion concentration was measured after phase separation. It was measured that the remaining lithium ion concentration in the aqueous phase was 0.91 g / L, and the lithium ion extraction rate was calculated to be 56.25%.

[0089] Example 10

[0090] Preparation of extraction organic phase: Take phenethyl salicylate as HBD and trialkyl phosphine oxide as HBA, mix them in a molar ratio of 1:1, heat in a water bath at 30 °C and stir magnetically (400 r / min) for 3 h. Let the mixture stand overnight at room temperature without precipitation, indicating the successful synthesis of HDES. Add diluent dodecane to HDES to obtain the extraction organic phase. In the extraction organic phase, the concentration of phenethyl salicylate is 0.4 mol / L, the concentration of trialkyl phosphine oxide is 0.4 mol / L, and the rest is dodecane.

[0091] Preparation of extraction aqueous phase: Take a lithium-containing solution with a lithium content of 2.08 g / L, a sodium content of 32.19 g / L, anions of chloride ions, carbonate ions, and a hydroxide ion concentration of 0.5 mol / L as the extraction aqueous phase.

[0092] Extraction: Perform three-stage countercurrent extraction on the above extraction organic phase and extraction aqueous phase under the condition of extraction phase ratio (O / A) = 1:1, with an extraction temperature of 30 °C and an extraction time of 20 min. After the extraction reaches equilibrium, let the mixture stand, and measure the lithium ion concentration after phase separation. It is measured that the remaining lithium ion concentration in the aqueous phase after three-stage countercurrent extraction is 0.009 g / L, and the total extraction rate of lithium ions in three-stage countercurrent extraction is calculated to be 99.57%.

[0093] Example 11

[0094] The regeneration of the extraction phase has two steps:

[0095] (1) Stripping metal ions: Use hydrochloric acid aqueous solution to back-extract all metal ions in the organic phase after extraction in Example 3 into the aqueous phase to avoid the influence of metal impurities on the subsequent extraction performance. Among them, the concentration of hydrochloric acid aqueous solution is 0.5 mol / L, and the back-extraction phase ratio (O / A) = 1:1. (2) Regenerating the extraction system: Wash the organic phase with water to remove excess acid, and the regeneration phase ratio (O / A) = 1:2. Then, perform extraction experiments on the regenerated organic phase under the same conditions as in Example 3. After 5 cycles, the extraction performance of the extractant does not decline, and it still shows excellent lithium ion extraction rate and lithium-sodium selectivity. The lithium ion extraction rate E in each cycle Li ≈87%, and the selectivity β Li / Na ≈170.

[0096] Comparative Example 1

[0097] Replace phenethyl salicylate in Example 1 with 2-ethylhexyl salicylate, and the rest is the same as in Example 1.

[0098] Result: The lithium ion extraction rate is 87.25%. In addition, the synthesis process of 2-ethylhexyl salicylate has higher requirements for reaction conditions and purification steps, and its production cost is much higher than that of phenethyl salicylate.

[0099] Comparative Example 2

[0100] Replace phenyl salicylate in Example 1 with 2 - thenoyltrifluoroacetone, and the rest is the same as in Example 1. After the extraction reaches equilibrium, the remaining lithium ion concentration in the aqueous phase is measured to be 0.61 g / L, and the lithium ion extraction rate is calculated to be 70.67%.

[0101] Comparative Example 3

[0102] Study the effect of a single component on lithium extraction. The extraction aqueous phase is a lithium - containing solution with 2.08 g / L lithium ions, 32.19 g / L sodium ions, anions being chloride ions, carbonate ions, and the hydroxide ion concentration being 0.5 mol / L. An extraction experiment is carried out under the conditions of an oil - to - water ratio O / A = 1:1 and a temperature of 30°C, and the extraction time is 20 min.

[0103] The extraction organic phase is 0.8 mol / L tributyl phosphate dissolved in dodecane. After the extraction reaches equilibrium, the remaining lithium ion concentration in the aqueous phase is measured to be 2.0798 g / L, and the lithium ion extraction rate is calculated to be 0.0096%.

[0104] The extraction organic phase is 0.8 mol / L trialkylphosphine oxide dissolved in dodecane. After the extraction reaches equilibrium, the remaining lithium ion concentration in the aqueous phase is measured to be 2.0557 g / L, and the lithium ion extraction rate is calculated to be 1.17%.

[0105] The extraction organic phase is 0.8 mol / L phenyl salicylate / benzyl salicylate / phenethyl salicylate dissolved in dodecane. Among them, phenyl salicylate and phenethyl salicylate are solids at room temperature and have poor solubility in dodecane, while benzyl salicylate is a liquid at room temperature and can be mixed evenly with dodecane; however, when phenyl salicylate, benzyl salicylate, and phenethyl salicylate are used to extract the alkaline lithium - precipitation mother liquor alone, the complex will precipitate at the interface due to containing two water molecules. After adding organophosphine to synthesize HDES, the melting point of the mixture can be reduced, its solubility in the diluent can be increased, and the hydrophobicity of the complex can be improved.

[0106] Comparative Example 4

[0107] Study the effect of different concentrations of alkali on lithium extraction:

[0108] Taking phenethyl salicylate as HBD and trialkyl phosphine oxide as HBA, they were mixed at a molar ratio of 1:1, heated in a water bath at 30 °C and magnetically stirred (400 r / min) for 3 h. The mixture was left overnight at room temperature without precipitation, indicating the successful synthesis of HDES. Diluent dodecane was added to the HDES to obtain the extraction organic phase. Among them, in the extraction organic phase, the concentration of HBD was 0.4 mol / L, the concentration of HBA was 0.4 mol / L, and the rest was diluent dodecane. The extraction aqueous phase was a lithium-containing solution with 2.08 g / L of lithium ions, 32.19 g / L of sodium ions, and anions of chloride ions, carbonate ions, and different concentrations of hydroxide ions.

[0109] Extraction conditions: extraction phase ratio (O / A) = 1:1, extraction temperature 30 °C, extraction time 20 min. Results: The higher the concentration of the alkali in the lithium-containing solution, the better the extraction effect. When the concentration of the alkali exceeded 0.5 mol / L, the growth rate of the extraction efficiency became slower and slower.

[0110] Comparative Example 5

[0111] Study the influence of different diluents on lithium extraction:

[0112] Taking phenethyl salicylate as HBD and trialkyl phosphine oxide as HBA, they were mixed at a molar ratio of 1:1, heated in a water bath at 30 °C and magnetically stirred (400 r / min) for 3 h. The mixture was left overnight at room temperature without precipitation, indicating the successful synthesis of HDES. A diluent was added to the HDES to obtain the extraction organic phase. Among them, in the extraction organic phase, the concentration of HBD was 0.4 mol / L, the concentration of HBA was 0.4 mol / L, and the rest was the diluent. The extraction aqueous phase was a lithium-containing solution with 2.08 g / L of lithium ions, 32.19 g / L of sodium ions, and anions of chloride ions, carbonate ions, and a hydroxide ion concentration of 0.5 mol / L.

[0113] Extraction conditions: extraction phase ratio (O / A) = 1:1, extraction temperature 30 °C, extraction time 20 min. Results: The extraction rates of lithium ions from large to small were: dodecane > sulfonated kerosene > toluene. The complex formed by extraction had poor solubility in polar solvents such as ethyl acetate and dichloromethane.

[0114] The above are only the preferred embodiments of the present invention and do not impose any formal restrictions on the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. An extraction system, characterized in that, It includes a hydrophobic eutectic solvent and a non-polar organic diluent; the hydrophobic eutectic solvent includes a hydrogen bond donor and a hydrogen bond acceptor, the hydrogen bond donor includes one or more of phenyl salicylate, benzyl salicylate and phenethyl salicylate, and the hydrogen bond acceptor is a neutral phosphorus compound with a Li coordination group.

2. The extraction system according to claim 1, wherein The neutral phosphorus compound with a Li coordination group includes one or more of trialkyl phosphine oxide, tributyl phosphate and trioctyl phosphate.

3. The extraction system according to claim 1 or 2, characterized in that, The molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:9 to 9:1; the concentrations of the hydrogen bond donor and the hydrogen bond acceptor in the extraction system are independently 0.1 to 1.0 mol / L.

4. The extraction system according to claim 1, characterized in that, The non-polar organic diluent includes one or more of sulfonated kerosene, n-hexane, benzene, toluene, heptane and dodecane.

5. The preparation method of the extraction system according to any one of claims 1 to 4, characterized in that, It includes the following steps: Mix the hydrogen bond donor and the hydrogen bond acceptor to obtain a hydrophobic eutectic solvent. Mix the hydrophobic eutectic solvent with the non-polar organic diluent to obtain the extraction system.

6. Use of the extraction system according to any one of claims 1 to 4 or the extraction system prepared by the preparation method according to claim 5 in the extraction and separation of lithium and sodium.

7. A method for extracting lithium from alkaline lithium precipitation mother liquor, characterized in that, It includes the following steps: Mix the extraction system with an alkaline lithium precipitation mother liquor for extraction to obtain a raffinate and a lithium-rich loaded organic phase; the extraction system is the extraction system according to any one of claims 1 to 4 or the extraction system prepared by the preparation method according to claim 5; the alkaline lithium precipitation mother liquor includes lithium ions and sodium ions.

8. The method according to claim 7, characterized in that The concentration of lithium ions in the alkaline lithium precipitation mother liquor is 0.05 to 10 g / L, the concentration of hydroxide ions is less than or equal to 1 mol / L, and the concentration of sodium ions is 25 to 65 g / L.

9. The method according to claim 7 or 8, characterized in that, The phase ratio of the extraction system to the alkaline lithium precipitation mother liquor is 1:20 to 20:1; the temperature of the extraction is 20 to 70 °C, and the time is 0.05 to 5 h.

10. The method according to claim 7, characterized in that, After obtaining the lithium-rich loaded organic phase, it further includes mixing the lithium-rich loaded organic phase with an inorganic acid solution for back-extraction to obtain an empty organic phase and a lithium-rich aqueous phase.