A method for separating Li and Na in a mixed solution and its application

Abstract

The present invention discloses a method for separating Li and Na in a mixed solution and its application, which belongs to the technical field of lithium extraction. The separation method provided by the present invention comprises the following steps: S1. extracting the mixed solution with an organic phase; the organic phase comprises a mixed extractant formed by HBTA and a primary amide extractant; the concentration of HBTA in the organic phase is 0.01~0.1M; the molar ratio of HBTA to the primary amide extractant is 1:1~5; the pH of the mixed solution is limited to 13~14; S2. back-extracting the loaded organic phase obtained in step S1 with a lithium chloride solution to obtain a Na-containing aqueous phase and a Li-loaded organic phase; S3. back-extracting the Li-loaded organic phase obtained in step S2 with an acid solution; the concentration of the acid solution is 0.3~3M. The separation method provided by the present invention can significantly improve the separation efficiency of lithium and sodium, improve the recovery rate of lithium and the purity of the lithium-containing compound finally obtained. The present invention also provides an application of the above separation method.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium extraction, and in particular to a method for separating Li and Na in a mixed solution and application thereof. Background Art

[0002] The development and utilization of salt lake brine faces severe challenges: Generally, salt lakes contain not only Li but also abundant Na. For example, the concentration of Na in some salt lakes can be as high as 650 mmol L -1 In addition, when the precipitation method is used to recover Li from lithium-rich solution, Na2CO3 is usually used as a precipitant to produce Li2CO3. This process will produce a large amount of Li2CO3 precipitation mother liquor with a high Na / Li ratio. It is estimated that about 25m3 of Li2CO3 will be produced per ton of Li2CO3. 3 The mother liquor of Li2CO3 precipitation with high Na / Li ratio, in which the concentrations of Li(I) and Na(I) are 1.4 g L -1 ~2.0 g L -1 and 110g L -1 ~124g L -1 Within this range, the Li / Na mass ratio can reach up to 1:100. This high sodium-lithium ratio leads to three major challenges for traditional separation technologies: 1. Poor selectivity of precipitation methods: Li + (0.076nm) and Na + (0.102 nm) have similar hydrated ionic radius (Li + : 3.82Å, Na + :3.58Å), meanwhile, Li(I) and Na(I) have the same valence in solution and both are alkali metals, so they have similar chemical properties, which leads to the presence of Na becoming a factor that hinders Li separation. If precipitation is used, existing precipitation methods (such as carbonate precipitation) are not very effective for Li + 1. The selectivity coefficient is less than 5, resulting in a lithium recovery rate of less than 60%. 2. Energy consumption bottleneck: Separating lithium from high-sodium environments typically requires evaporation and concentration. Evaporation and concentration consumes 300-500 kWh of energy to process one ton of brine, and the lithium loss rate exceeds 20%. 3. Environmental pressure: Related technologies also use solvent extraction for lithium enrichment. The current solvent extraction method uses a large amount of tributyl phosphate (TBP)-kerosene system, generating 3-5 tons of organic phase waste per ton of lithium product, posing a risk of secondary pollution. Therefore, solving the separation and recovery of lithium from high-sodium / Li ratio salt lake brines is crucial.

[0003] Traditional lithium extraction technologies include evaporation crystallization, adsorption, membrane separation (electrodialysis) and solvent extraction. However, the above technologies have obvious defects in the main separation technologies currently used in industry: (1) The evaporation crystallization process is mature but has high energy consumption and is suitable for brine with high lithium concentration. The production cycle is as long as 12 to 18 months; (2) Although the adsorption method has good selectivity, it can only achieve Li + Selective adsorption, but aluminum-based adsorbents are not suitable for Na + When the concentration is >50g / L, the adsorption capacity decreases by more than 40%, and membrane separation is environmentally friendly but requires a large investment and is easily contaminated by impurities in brine; (3) Electrodialysis technology is limited by the selectivity of ion exchange membranes, and the Li / Na separation coefficient is usually <50, and the nanofiltration membrane method is easily contaminated by Ca in brine. 2+ Mg 2+ The membrane life is less than 6 months due to pollution. In contrast, solvent extraction technology has significant advantages: first, it has strong adaptability and can process Li + The brine concentration is 0.1~5g / L, and the recovery rate of brine with a Na / Li ratio of up to 1000 is still maintained at more than 90%; secondly, the selectivity is excellent, and the Li / Na separation coefficient of the TBP-FeCl3 system can reach more than 300, and the product purity meets the battery-grade standard; thirdly, the efficiency is high, and 3~5-stage countercurrent extraction can complete lithium enrichment within 24 hours, which is 95% shorter than the evaporation method. With the development of new extractants and the application of intelligent control, extraction technology is becoming the mainstream choice for lithium extraction from salt lakes, especially in dealing with low-grade, high-impurity brines. It shows irreplaceable advantages. According to the global salt lake lithium extraction data in 2023, the average lithium recovery rate of existing technologies is only 65~75%. Although the new extraction process used in the Atacama Salt Lake in Chile has increased the recovery rate to 85%, the Na content of each ton of lithium product is 25%. + The residual content is still as high as 500ppm, which cannot meet the requirements of battery-grade lithium carbonate (Na + The purity requirement is <100ppm. This inefficient separation method results in an estimated 25,000 tons of lithium resource loss worldwide each year, equivalent to a reduction in the battery supply for 300,000 electric vehicles. Therefore, in this context, the development of highly selective, energy-efficient, and environmentally friendly Li / Na separation technologies has become crucial for breaking through the bottlenecks in the salt lake lithium extraction industry. However, as the above analysis demonstrates, conventional technologies are less adaptable to environments with high Na / Li ratios, and lithium recovery rates need to be further improved.

[0004] To solve the problem of insufficient lithium recovery, some technologies use electrochemical methods to convert chloride in the raw solution into sulfate system, which is then separated from the lithium hydroxide solution by sodium sulfate crystallization. This method is completely ineffective for nitrate / carbonate salt lakes and is only applicable to hydrochloric acid and sulfate salt lakes, and relies on high concentrations of SO4 2- The addition of SO4 not only increases the pretreatment cost, but also 2-This will cause the sulfur content in subsequent lithium products to exceed the standard, increasing environmental treatment difficulties. At the same time, Na2SO4 crystals are easy to wrap Li + , resulting in a 5-8% lithium loss. Furthermore, the formation of sodium sulfate decahydrate (glauber's salt) can easily lead to equipment scaling, increasing equipment costs. In particular, the entire process requires significant electricity for electrolysis operations and temperature control, which not only has limitations in application environments but also generates significant energy consumption. There are also attempts to optimize the extraction system to increase lithium recovery (lithium-sodium separation efficiency) in high Na / Li ratios; however, the results remain suboptimal.

[0005] Therefore, it is very important to provide an extraction method suitable for high Na / Li ratios to achieve efficient sodium and lithium separation through simple steps. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for separating Li and Na in a mixed solution, which can effectively improve the recovery rate of lithium and the purity of the recovered lithium-containing product.

[0007] The present invention also provides the application of the above separation method

[0008] According to an embodiment of the first aspect of the present invention, a method for separating Li and Na in a mixed solution is provided, wherein the mixed solution contains Li + and Na + , and the pH is 13-14; the separation method comprises the following steps:

[0009] S1. extracting the mixed solution using an organic phase;

[0010] The organic phase includes a mixed extractant; the mixed extractant includes HBTA and a primary amide extractant shown in the following formula; the concentration of HBTA in the organic phase is 0.01 to 0.1 M; the molar ratio of HBTA (CAS: 2754-40-7) to the primary amide extractant (CAS: 15672-96-5) is 1:1 to 5;

[0011] ;

[0012] S2. The loaded organic phase obtained in step S1 is stripped with a lithium chloride solution to obtain an aqueous phase containing Na and a Li-loaded organic phase;

[0013] S3. The Li-loaded organic phase obtained in step S2 is stripped with acid; the concentration of the acid is 0.3~3M (in the present invention, the concentration unit M represents mol / L).

[0014] The mechanism of the separation method is as follows:

[0015] In step S1, almost all lithium and a very small amount of sodium are extracted by the organic phase;

[0016] In step S2, lithium chloride is used for back extraction, and the lithium therein replaces the sodium in the loaded organic phase, that is, the sodium is back extracted and the lithium is enriched in the Li-loaded organic phase.

[0017] In step S3, lithium is stripped from the Li-loaded organic phase to achieve separation of lithium and sodium.

[0018] The separation method according to the embodiment of the present invention has at least the following beneficial effects:

[0019] (1) The present invention adopts an innovative extraction process design, which does not require external energy input throughout the entire process, achieving true zero-energy operation. In addition, by optimizing the process flow and the selection of extractants, the amount of waste generated is reduced to a minimum, and all by-products can be recycled or harmlessly treated, significantly reducing the risk of environmental pollution. At the same time, the entire separation process has been simplified and the number of operating steps has been greatly reduced, which significantly improves the operability and stability of the process. The method provided by the present invention can treat a variety of salt lake brines such as chloride type and sulfate type, filling the gap in the application of existing technologies in complex systems. Overall, the separation method provided by the present invention effectively solves the technical problems of high energy consumption, high pollution, and complex process in traditional hydrometallurgical processes, and provides a more economical and environmentally friendly solution for the field of lithium-sodium separation (or the extraction of lithium resources).

[0020] (2) The primary amide (-CONH2) extractant used in the present invention has two active sites, carbonyl oxygen (C=O) and amino hydrogen (NH), which can react with Li + Forming a stable five-membered ring chelate structure, and Na⁺ has a larger ionic radius (Li + : 0.76 Å, Na + : 1.02 Å), it is difficult to form such a compact coordination. The chelation effect significantly improves the stability of the primary amide-Li⁺ complex (ΔG is more negative). The primary amide extractant used in the present invention has no substituents in the -NH2 group and has appropriate steric hindrance, which makes Li + More accessible to the coordination site, while Na + Due to poor spatial matching, it is rejected by the primary amide extractant. Compared with the primary amide extractant used in the present invention, the introduction of an alkyl group (R) on the nitrogen atom increases the steric hindrance, which easily hinders the extraction of Li + Close to the coordination center; at the same time, it will lead to the loss of hydrogen bonding ability, relying only on C=O coordination, the chelating effect is weakened, or the chelating ring cannot be formed, which is very effective for Li +The selectivity is greatly reduced; secondly, due to the strong hydrophobicity, the extractant may have poor solubility in the aqueous phase or form micelles. In terms of the difference in electronic effects, the -NH2 of the primary amide has an electron-donating effect, which can enhance the electron density of the carbonyl oxygen and improve its affinity with Li + The coordination ability of the secondary / tertiary amide is improved; and the alkyl substitution of the secondary / tertiary amide will weaken the basicity of oxygen. + The extraction efficiency of Na + extraction and separation efficiency.

[0021] (3) The present invention innovatively adopts a mixed extractant. By controlling the concentration and ratio of HBTA and primary amide extractant, the β-diketone functional group (provided by HBTA) and the C=O functional group (provided by primary amide extractant) are synergistically reacted with Li + It plays an extraction role by efficiently coordinating lone pair electrons to form an electrically neutral complex.

[0022] During this process, the pH of the mixed solution is adjusted so that Na + He Li + Different lone pair electron characteristics are generated in the aqueous solution, so that the extraction system can selectively bind Na / Li; at the same time, the Na + The extraction of Li + The extraction effect of Li + The single-stage extraction rate is still ≥90%, even ≥95%; Na + The single-stage co-extraction rate is less than 8%; and the purity of the final lithium compound reaches the battery grade standard.

[0023] (4) The present invention significantly improves the Li + The stripping efficiency is improved, which improves the lithium recovery rate.

[0024] In addition, the present invention optimizes the transfer rate and coordination capacity during the extraction process by controlling the ratio of the organic phase to the aqueous phase, thereby achieving efficient and selective separation of Na / Li.

[0025] According to some embodiments of the present invention, in step S1, in the mixed solution, Na + He Li + The mass concentration ratio is ≥10:1. For example, it can be about 20:1, 25:1, 30:1, 35:1 or about 40:1.

[0026] According to some embodiments of the present invention, in step S1, in the mixed solution, Na +The concentration of the hydroxybenzoic acid ester is 0.5 to 10 g / L. For example, it can be about 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L or about 9 g / L.

[0027] According to some embodiments of the present invention, in step S1, in the mixed solution, Li + The concentration is 0.1-1 g / L. For example, it can be about 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L or about 0.9 g / L.

[0028] According to some embodiments of the present invention, in step S1, the pH of the mixed solution is 13.2-13.8; for example, it may be about 13.5.

[0029] According to some embodiments of the present invention, in step S1, the organic phase further includes a diluent.

[0030] According to some embodiments of the present invention, the diluent comprises toluene.

[0031] According to some embodiments of the present invention, in step S1, the organic phase is prepared by mixing HBTA solution, primary amide extractant solution and diluent.

[0032] The concentration of the HBTA solution is 0.05-0.3 M; for example, it can be about 0.1 M or about 0.2 M;

[0033] The concentration of the primary amide extractant solution is 0.05-0.3M; for example, it can be about 0.1M or about 0.2M.

[0034] The solvent used for the HBTA solution and the primary amide extractant solution is toluene.

[0035] The volume ratio of the HBTA solution, the primary amide extractant solution and the diluent is 1:1:0.5-3; for example, it can be about 1:1:1 or 1:1:2.

[0036] According to some embodiments of the present invention, in step S1, the concentration of HBTA in the organic phase is 0.02M, 0.03M, 0.04M, 0.05M, 0.06M or about 0.08M.

[0037] According to some embodiments of the present invention, in step S1, the molar ratio of HBTA to the primary amide extractant in the organic phase is 1:1-4; for example, it can be about 1:2 or about 1:3.

[0038] According to some embodiments of the present invention, in step S1, the O / A ratio of the extraction is 4 to 7: 1. For example, it can be about 4.5: 1, 5: 1, 5.5: 1, 6: 1 or about 6.5: 1.

[0039] According to some embodiments of the present invention, in step S1, the extraction includes sequentially performing mixing, centrifugal standing, and liquid separation. The mixing method includes at least one of stirring and shaking; the duration is 40 to 50 minutes, for example, specifically about 45 minutes; and the centrifugal standing time is 3 to 8 minutes, for example, specifically about 5 minutes.

[0040] According to some embodiments of the present invention, in step S1, the number of extraction stages is 2 to 5, for example, specifically 3 or 4 stages.

[0041] According to some embodiments of the present invention, in step S2, the concentration of the lithium chloride solution is 0.5-2 M. For example, it can be about 1 M or about 1.5 M.

[0042] According to some embodiments of the present invention, in step S2, the O / A ratio of the stripping is 1:1 to 5. For example, it can be about 1:2, 1:3 or about 1:4.

[0043] According to some embodiments of the present invention, in step S2, the stripping comprises sequentially performing mixing, centrifugal standing, and liquid separation. The mixing time is 8 to 12 minutes, for example, approximately 10 minutes; and the centrifugal standing time is 3 to 8 minutes, for example, approximately 5 minutes.

[0044] According to some embodiments of the present invention, in step S2, the number of stripping stages is 4 to 5.

[0045] According to some embodiments of the present invention, in step S3, the O / A ratio of the stripping is 1:1 to 5. For example, it can be about 1:2, 1:3 or about 1:4.

[0046] According to some embodiments of the present invention, in step S3, the concentration of the acid solution is 0.5-3 M. For example, it can be about 1 M, 1.5 M, 2 M or about 2.5 M.

[0047] According to some embodiments of the present invention, in step S3, the solute of the acid solution includes at least one of HCl, H2SO4, and HNO3. When the solute is HNO3, the concentration of the acid solution is 1.5-3M, for example, approximately 2M. When the solute is another acid, the concentration of the acid solution is 0.5-3M, for example, approximately 1M, 1.5M, or approximately 2M.

[0048] According to some embodiments of the present invention, in step S3, the stripping comprises sequentially performing mixing, centrifugal standing, and liquid separation. The mixing time is 8 to 12 minutes, for example, approximately 10 minutes; and the centrifugal standing time is 3 to 8 minutes, for example, approximately 5 minutes.

[0049] According to some embodiments of the present invention, in step S3, the number of stripping stages is 2 to 3.

[0050] In steps S1 to S3 , the operating temperature is room temperature, specifically about 25° C. Specifically, during the actual operation, the temperature is not adjusted.

[0051] According to some embodiments of the present invention, the separation method further comprises, after step S3, performing the following steps:

[0052] S4. Adjust the pH of the aqueous phase obtained in step S3 to 10-11, and mix the resulting mixture with an excess of saturated aqueous sodium carbonate solution to precipitate lithium; filter, wash, and dry to obtain lithium carbonate.

[0053] According to some embodiments of the present invention, in step S4, the reagent used to adjust the pH of the aqueous phase is a sodium hydroxide aqueous solution, wherein the concentration of the sodium hydroxide aqueous solution is 1.5-2.5M, for example, specifically about 2M.

[0054] According to some embodiments of the present invention, in step S4, the excess coefficient of the saturated sodium carbonate aqueous solution is 1.1-1.2.

[0055] According to some embodiments of the present invention, in step S4, the temperature of the mixed lithium deposition is 75-85°C, for example, about 80°C.

[0056] According to some embodiments of the present invention, in step S4, the mixed lithium precipitation is performed under stirring at a rotation speed of 250-350 rpm, for example, about 300 rpm.

[0057] According to some embodiments of the present invention, in step S4, the duration of the mixed lithium deposition is 1.5 to 2.5 hours, for example, about 2 hours.

[0058] According to some embodiments of the present invention, in step S4, the filtration uses a filter membrane with a specification of 0.45 μm.

[0059] According to some embodiments of the present invention, in step S4, the washing method is water washing, wherein the water temperature used is ≤ 5° C., thereby avoiding the loss of lithium carbonate.

[0060] According to some embodiments of the present invention, in step S4, the drying temperature is 60-100°C, for example, about 70°C, 80°C or about 90°C.

[0061] According to an embodiment of the second aspect of the present invention, there is provided an application of the separation method described in an embodiment of the first aspect of the present invention in the smelting of lithium-containing ores, lithium extraction from brine, and wet recovery of lithium-ion batteries.

[0062] Since the application adopts all the technical solutions of the separation method of the above embodiment, it at least has all the beneficial effects brought by the technical solutions of the above embodiment.

[0063] According to some embodiments of the present invention, in the brine lithium extraction method, the brine includes at least one of salt lake brine, salt lake brine concentrate and salt lake brine precipitation mother liquor.

[0064] Unless otherwise specified, the term “about” in the present invention means that the error is allowed to be within the range of ±2%. For example, about 100 is actually 100±2%×100.

[0065] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0067] Figure 1 Schematic diagram of the separation method in an embodiment of the present invention. DETAILED DESCRIPTION

[0068] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0069] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0070] Example 1

[0071] refer to Figure 1 The process shown in the figure provides a method for separating Li and Na in a mixed solution. The specific steps are as follows:

[0072] S1. Using organic phase mixed solution to perform three-stage extraction, wherein,

[0073] The organic phase was obtained by adding 1 mL of 0.1 M HBTA solution (solvent: toluene) and 1 mL of 0.3 M primary amide extractant solution (solvent: toluene) to a centrifuge tube, and then adding 3 mL of toluene as a diluent, and mixing the three together.

[0074] In this case, a simulation experiment was conducted. The mixed solution was prepared in the laboratory: the solvent in the mixed solution was 2M HCl aqueous solution, and the solutes were sodium chloride and lithium chloride monohydrate. + The concentration is 10g / L, Li + The concentration of 0.3 g / L, the pH of the mixed solution was adjusted to 13 by adding NaOH;

[0075] The O / A ratio of the extraction process was 5:1; the extraction process was as follows: Li + After extraction, the centrifuge tube was placed in a centrifuge for 5 minutes and then taken out to separate the organic phase and the aqueous phase. + and a large amount of Li + of the loaded organic phase; most of the Na + Remain in the raffinate phase.

[0076] S2. The loaded organic phase obtained in step S1 was subjected to 4-stage stripping using a 1M aqueous solution of LiCl; wherein,

[0077] The O / A ratio of stripping is 1:2; the stripping process is as follows: magnetic stirring at room temperature for 10 minutes to add Na + After stripping, the centrifuge tube was placed in a centrifuge and centrifuged for 5 minutes, then taken out and the organic phase and the aqueous phase were separated to obtain the Na +aqueous phase D, and a Li-loaded organic phase.

[0078] S3 using 1M HCl aqueous solution of the Li-loaded organic phase obtained in step S2 was subjected to three-stage stripping; wherein,

[0079] The O / A ratio of stripping is 1:3; the stripping process is as follows: magnetic stirring at room temperature for 10 minutes to carry out Li + After stripping, the centrifuge tube was placed in a centrifuge and centrifuged for 5 minutes, then taken out and the organic phase and the aqueous phase were separated to obtain the Li-containing + of the aqueous phase;

[0080] S4. Lithium precipitation: Use 2M NaOH to adjust the pH of the aqueous phase obtained in step S3 to 10~11, and add an excess of saturated Na2CO3 solution with an excess coefficient of 1.1~1.2. Stir and precipitate at a temperature of 80℃. Set the stirring speed to 300rpm. After stirring for 2h, filter with a 0.45μm filter membrane and wash the precipitate multiple times with ultrapure water pre-cooled to 5℃. Finally, dry at 80℃ to obtain white Li2CO3 powder.

[0081] In this example, the amount of solution and other materials used is only for the convenience of description and determination of proportions. In actual production, the amount can be increased proportionally as needed.

[0082] Example 2

[0083] This example provides a method for separating Li and Na in a mixed solution. The specific steps differ from those in Example 1 in that:

[0084] In the method for obtaining the organic phase in step S1, the concentration of the primary amide extractant is 0.2M.

[0085] Example 3

[0086] This example provides a method for separating Li and Na in a mixed solution. The specific steps differ from those in Example 1 in that:

[0087] In the method for obtaining the organic phase in step S1, the volume ratio of HBTA, primary amide extractant and diluent is 2:2:1.

[0088] Example 4

[0089] This example provides a method for separating Li and Na in a mixed solution. The specific steps differ from those in Example 1 in that:

[0090] In step S1, the final pH of the mixed solution is controlled to be 14.

[0091] Example 5

[0092] This example provides a method for separating Li and Na in a mixed solution. The specific steps differ from those in Example 1 in that:

[0093] In step S1, the O / A ratio of the extraction is 6:1.

[0094] Example 6

[0095] This example provides a method for separating Li and Na in a mixed solution. The specific steps differ from those in Example 1 in that:

[0096] In step S3, the 1M HCl aqueous solution is replaced with a 3M HNO 3 aqueous solution.

[0097] Example 7

[0098] This example provides a method for separating Li and Na in a mixed solution. The specific steps differ from those in Example 1 in that:

[0099] In step S2, the concentration of the aqueous solution of LiCl is 0.5M.

[0100] Comparative Example 1

[0101] This example provides a method for separating Li and Na in a mixed solution. The specific steps differ from those in Example 1 in that:

[0102] In step S1, in the method for obtaining the organic phase, the concentration of the primary amide extractant is 0.05M.

[0103] Comparative Example 2

[0104] This example provides a method for separating Li and Na in a mixed solution. The specific steps differ from those in Example 1 in that:

[0105] In step S1, in the method for obtaining the organic phase, the concentration of HBTA is 0.025M; the concentration of the primary amide extractant is 0.075M.

[0106] Comparative Example 3

[0107] This example provides a method for separating Li and Na in a mixed solution. The specific steps differ from those in Example 1 in that:

[0108] In step S1, the final pH of the mixed solution is controlled to be 8.

[0109] Comparative Example 4

[0110] This example provides a method for separating Li and Na in a mixed solution. The specific steps differ from those in Example 1 in that:

[0111] In step S3, the concentration of the HCl aqueous solution is 0.05M.

[0112] For the convenience of comparison, some conditions of the embodiments and comparative examples are listed in Table 1.

[0113] Table 1 Some parameters of Examples and Comparative Examples

[0114]

[0115] Test Case

[0116] This example tests the Li + The extraction rate and purity of the final lithium carbonate were calculated, and the Li + The purity test method is to dissolve the obtained lithium carbonate solid product and use ICP-OES to test the Li + The concentration of the compound is calculated, and the ratio of this concentration to the theoretical concentration is the purity (the purity of the corresponding compound). An example of yield is as follows: the lithium yield is the ratio of the lithium in the lithium carbonate to the lithium in the mixed solution. The results of the above tests are shown in Table 2.

[0117] Table 2 Test results of examples and comparative examples

[0118]

[0119] Comparing the results of the examples and comparative examples, it can be seen that within the scope provided by the present invention, by changing the concentration of the mixed extractant in the organic phase, the ratio of the two extractants, the pH of the mixed solution, the ratio of the first extraction, and the O / A ratio in the stripping process, the type and concentration of the stripping agent used for stripping, etc., a higher purity of lithium carbonate can be obtained, and the corresponding lithium yield is higher; specifically, the purity of lithium carbonate is ≥89.0%, and can actually be as high as 98.5%; the yield of lithium is ≥95.0%, and can actually be as high as 98.2%.

[0120] By comparing the results of Example 1 and Example 7, it can be seen that, within the scope provided by the present invention, reducing the concentration of the lithium chloride solution in step S2 will reduce the purity of the obtained lithium carbonate to a certain extent, that is, the stripping ratio of sodium in step S2 is insufficient, but still has excellent purity and recovery rate.

[0121] Comparing the results of Example 1 and Comparative Example 1, it can be seen that if the concentration ratio of HBTA and primary amide extractant in the organic phase is not within the range required by the present invention, then in the extraction of step S1, the Li + The extraction rate is less than 40%, resulting in the inability to completely separate Li / Na. + The recovery rate and product purity decreased.

[0122] Comparison of Example 1 and Comparative Example 2 shows that if the concentrations of HBTA and primary amide extractant in the organic phase are not within the range required by the present invention, then in the extraction of step S1, the Li + The extraction capacity is only about 40%, which results in the inability to completely separate Li / Na. + The recovery rate and product purity decreased.

[0123] Comparative Example 1 and Comparative Example 3 show that if the pH of the mixed solution in step S1 of the present invention is not within the range required by the present invention, then in the extraction of step S1, the Li + The extraction capacity of Li / Na is reduced, resulting in a decrease in the separation capacity of Li + The recovery rate and product purity decreased.

[0124] Comparative Example 1 and Comparative Example 4 show that if step S3 of the present invention is used to strip Li + The concentration of the stripping agent solution is not within the range required by the present invention, then step S3 cannot completely remove Li + Stripping, resulting in Li + The recovery rate has dropped significantly to less than 60%.

[0125] It can also be seen from the processes of the embodiments and comparative examples that in the separation method provided by the present invention, the implementation temperature of all procedures is less than 100°C, and all steps except lithium precipitation are carried out at room temperature (about 25°C); the process is safe, reliable and highly stable.

[0126] In summary, the separation method provided by the present invention creatively combines HBTA and primary amide extractants through the design of steps and parameters, and realizes the unique coordination between the extractant and the metal ion by utilizing a unique functional group, thereby achieving the separation of Li / Na, and the purity of the recovered Li product is high; In addition, the treatment method provided by the present invention is simple to operate, low in cost, environmentally friendly, safe and reliable, and is expected to be used for the separation and extraction of Li from salt lake brine, which is of great significance for promoting the sustainable utilization of lithium resources. It is precisely because of the above advantages that the separation method provided by the present invention is expected to be widely used in lithium ore smelting and brine lithium extraction.

[0127] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A method for separating Li and Na in a mixed solution, characterized in that: The mixed solution contains Li + and Na + , and the pH is 13-14; the separation method comprises the following steps: S1. extracting the mixed solution using an organic phase; The organic phase includes a mixed extractant; the mixed extractant includes HBTA and a primary amide extractant as shown below; the concentration of HBTA in the organic phase is 0.01 to 0.1 M; the molar ratio of HBTA to the primary amide extractant is 1:1 to 5; ； S2. The loaded organic phase obtained in step S1 is stripped with a lithium chloride solution to obtain an aqueous phase containing Na and a Li-loaded organic phase; S3. The Li-loaded organic phase obtained in step S2 is stripped using acid; the concentration of the acid is 0.3~3M.

2. The separation method according to claim 1, characterized in that In step S2, the concentration of the lithium chloride solution is 0.5~2M.

3. The separation method according to claim 1, characterized in that In the mixed solution, Na + He Li + The mass concentration ratio is ≥10:

1.

4. The separation method according to any one of claims 1 to 3, characterized in that The organic phase also includes a diluent.

5. The separation method according to any one of claims 1 to 3, characterized in that In step S1, the O / A ratio of the extraction is 4-7:

1.

6. The separation method according to any one of claims 1 to 3, characterized in that In step S2, the O / A ratio of the stripping is 1:1-5.

7. The separation method according to any one of claims 1 to 3, characterized in that In step S3, the O / A ratio of the stripping is 1:1-5.

8. The separation method according to any one of claims 1 to 3, characterized in that In step S3, the solute of the acid solution includes at least one of HCl, H2SO4 and HNO3.

9. The separation method according to any one of claims 1 to 3, characterized in that In step S1, the extraction stages are 2 to 5.

10. Use of the separation method according to any one of claims 1 to 9 in lithium-containing ore smelting, lithium extraction from brine, and wet recovery of lithium-ion batteries.

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