An extraction agent and a method for extracting lithium from a lithium-containing solution

Abstract

This invention relates to the field of chemical technology, and more particularly to an extractant and a method for extracting lithium from lithium-containing solutions. The extractant comprises a phosphorus oxide compound and a halogen. The phosphorus oxide compound is a neutral phosphorus extractant; the halogen is at least one selected from chlorine, bromine, and iodine. The extractant selected in this invention forms [Li·S] when extracting lithium ions from lithium-containing solutions. + [X·(Y2) n ] ‑ The complex can effectively achieve selective extraction of lithium salts from various lithium-containing solutions, thus exhibiting highly efficient selectivity for lithium ions, accurately identifying and extracting lithium, and maximizing the extraction of lithium elements from lithium-containing solutions, providing an extremely effective technical means for the recovery and utilization of lithium resources.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to an extractant and a method for extracting lithium from a lithium-containing solution. Background Technology

[0002] Lithium is a metallic element of significant strategic importance. Its role is increasingly prominent in the development of modern science and technology and industry. With the rapid growth of global demand for clean energy, lithium-ion batteries, as high-efficiency energy storage devices, are widely used in electric vehicles, mobile electronic devices, and renewable energy storage systems, becoming a key factor in driving energy transition. In terms of resource distribution, lithium is mainly found in mineral resources such as salt lake brines, spodumene, and lepidolite. Among these, lithium extraction from salt lake brines has attracted considerable attention due to its abundant reserves and relatively low cost.

[0003] Currently, the most commonly used industrial method for extracting lithium from salt lake brine is solvent extraction. This process involves extracting lithium from both lithium-containing acidic and neutral brines. In 1987, Huang Shiqiang et al. disclosed a method for extracting lithium chloride from lithium-containing brine in patent CN87103431A and proposed TBP-FeCl3-200. # The solvent-kerosene extraction system uses a high concentration of tributyl phosphate (TBP), which is highly corrosive to equipment. Furthermore, during long-term operation, phosphorus oxides are severely degraded in water, and TBP is prone to degradation in acidic media, thus limiting its large-scale industrial development. In 2012, Yuan Chengye et al. proposed an amide compound-neutral phosphorus oxide compound-diluent-FeCl3 extraction system in patent CN103055538A for extracting lithium salts from lithium-containing brine. In 2014, Ji Lianmin et al. proposed an N,N-di(2-ethylhexyl)-3-butanone acetamide-TBP-FeCl3-kerosene extraction system in patent CN104372181A for lithium extraction. This system improved the corrosiveness of high-concentration TBP to equipment. However, all of the above extraction systems require strong acid conditions, directly adding large amounts of concentrated acid to the brine, leading to brine pollution. Subsequent brine discharge causes environmental pollution, and the back-extraction process requires even stronger acid to adjust the system's acidity. In 2017, Meng Qingfen et al. disclosed an extraction system for lithium in patent CN106498184A, which involved a pyrrole-based hexafluorophosphate ionic liquid, a co-extractant (amide, diketone, phosphate ester), and a diluent. This system avoids the use of the co-extractant FeCl3, thus eliminating the need to adjust the pH of the brine. However, ionic liquids are expensive, and their preparation process can be complex, requiring regeneration and treatment of the ionic liquid during extraction.

[0004] The extraction of lithium from lithium-containing alkaline and neutral brine has been discussed in several patents. In 1974, the U.S. Atomic Energy Commission disclosed a fluorinated β-diketone + TRPO extraction system for extracting lithium from neutral or near-neutral brine (pH range 6-9) in patent US3793433A. In 2017, Li Lijuan et al. disclosed furanoyltrifluoroacetone-TBP and furanoyltrifluoroacetone-TRPO extraction systems in patents CN107937734B (based on a mixed clarification tank) and CN108004420B (based on a centrifugal extractant). In 2019, Qi Tao, Zhu Zhaowu et al. proposed a TBP, TOPO + ketoxime (LIX84, LIX54, LIX860, etc.) extraction system in patent CN110656239 (a method for extraction-back-extraction separation and purification of lithium). Lithium products are obtained by extraction, gas (SO2, CO2)-liquid-liquid three-stage back extraction, heat treatment, and separation of lithium-containing solutions under pH conditions of 10-13. This method has a large processing capacity, simple process and equipment, low investment, effective utilization of industrial waste gas, energy saving and environmental protection, and continuous production. In 2020, Zhu Zhaowu et al. disclosed a TRPO+β-diketone extraction system in patent CN111057848A, a method for extracting lithium from lithium-containing solutions by solvent extraction.

[0005] In the current technological landscape, based on the aforementioned existing patent information, it is known that for lithium extraction processes from acidic and neutral brine, commonly used extraction systems largely rely on tributyl phosphate and ferric chloride. Although attempts have been made to introduce amide-based and ionic liquid extractants, the former generally suffers from drawbacks such as high cost, complex process flow, and difficulty in regeneration, while ionic liquid extractants also exhibit insufficient stability. Trialkylphosphine oxide (TRPO) and diketone extractants, commonly used in alkaline brine lithium extraction processes, either alone or in combination, present difficulties in application to acidic brine lithium extraction.

[0006] In summary, developing an extractant that is safe, environmentally friendly, non-toxic, pollution-free, highly stable, and mild, capable of highly selective and efficient lithium extraction at low cost, and possessing a simple process flow suitable for large-scale industrial production, for lithium extraction and impurity removal from acidic and neutral brine, has become a major key technological challenge urgently needing to be overcome and resolved in the current lithium resource development field. A breakthrough in this area is expected to completely revolutionize the existing lithium extraction technology landscape from salt lake brine, providing strong technical support and guarantees for the efficient and sustainable development and utilization of global lithium resources, and possessing profound scientific significance and broad application prospects. Summary of the Invention

[0007] To address the problems of complex processes, high requirements for equipment materials, low lithium selectivity in high magnesium-to-lithium ratio brines, brine contamination due to strong acid extraction conditions, excessively high back-extraction acidity, high production costs, and high energy consumption in existing methods for extracting lithium from lithium-containing solutions, this invention provides an extractant and a method for selectively extracting lithium from lithium-containing solutions. The extractant is safe, environmentally friendly, pollution-free, highly stable, mild, stable, and low-cost; the lithium extraction and impurity removal process is simple and has low energy consumption. The technical solution includes the following content.

[0008] An extractant for extracting lithium from a lithium-containing solution, the extractant comprising a phosphorus oxide compound and a halogen.

[0009] Furthermore, the phosphorus oxide compound is a neutral phosphorus extractant; the halogen is at least one of chlorine, bromine, and iodine.

[0010] Furthermore, the neutral phosphorus extractant includes at least one of phosphate esters, phosphonates, and trialkylphosphine oxides.

[0011] More preferably, the phosphate ester includes at least one selected from trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triisobutyl phosphate, and triphenyl phosphate; the phosphonate includes at least one selected from dimethyl methylphosphonate and dimethylheptyl methylphosphonate (P350); and the trialkylphosphine oxide includes at least one selected from trialkylphosphine oxide (TRPO), trihexylphosphine oxide, trioctylphosphine oxide, and triphenylphosphine oxide.

[0012] More preferably, the neutral phosphate ester is a phosphate ester or a trialkylphosphine ester.

[0013] Furthermore, the mass concentration of halogen in the extractant is 0.01 mol / L to 2 mol / L.

[0014] Furthermore, the extractant also includes a diluent, the diluent comprising C4 to C64... 16 Alkanes, C1-C 16 Haloalkanes, C6-C 12 Halogenated aromatics, C8-C 12 Ethers, C4-C 10 Alcohols, C4-C 10 At least one of esters and sulfonated kerosene.

[0015] More preferably, C4~C 16 Alkanes include any one of n-pentane, n-heptane, octane, and n-dodecane, wherein the C1-C1... 16 Halogenated alkanes include any one of dichloromethane and 1-chlorodecane, wherein the C6-C6... 12 Halogenated aromatic hydrocarbons include any one of bromobenzene and chlorobenzene, wherein the C8-C9 ratio is 100- ... 12Ethers include diethylene glycol butyl ether, C4~C5 10 The alcohol includes any one of n-butanol, n-pentanol, isoamyl alcohol, n-octanol, isooctanol, and isodecanol, wherein the C4-C5 group is C6-C7-C ... 10 Esters include either ethyl acetate or butyl acetate.

[0016] Furthermore, the volume percentage of the phosphorus oxide compound in the extractant is 30% to 90%, and the volume percentage of the diluent is 10% to 70%.

[0017] A method for extracting lithium from a lithium-containing solution includes the following steps: mixing the above-mentioned extractant with a lithium-containing solution at room temperature, wherein the lithium-containing solution is a neutral or acidic solution, and obtaining a raffinate and a loaded organic phase after phase separation; adding the loaded organic phase to a reverse extraction solution and stirring, and obtaining a loaded aqueous phase and an organic phase after phase separation; adding the loaded aqueous phase to an alkaline solution and stirring, and obtaining a lithium-loaded solution after filtration.

[0018] Furthermore, the extractant is mixed with the lithium-containing solution at room temperature for 5 to 20 minutes; the supported organic phase is added to the back-extraction solution at 20°C to 60°C and mixed and stirred for 5 to 20 minutes.

[0019] More preferably, the supported organic phase is mixed with the back-extraction solution at 40°C to 60°C for 5 min to 20 min.

[0020] Furthermore, the volume ratio of the extractant to the lithium-containing solution is 1:10 to 10:1; the volume ratio of the supported organic phase to the back-extraction solution is 1:5 to 10:1.

[0021] Furthermore, the lithium-containing solution is a neutral or acidic lithium-containing solution (pH range of 0-7), including any one of salt lake brine, seawater and concentrated seawater, lithium extraction water from ore, underground brine, oilfield water, lithium-containing water from lithium battery recovery, and industrial lithium-containing wastewater; the lithium-containing solution contains Li + The mass concentration is 0.01 g / L to 5 g / L; the organic phase is recycled as an extractant.

[0022] Furthermore, the back-extraction solution includes any one of acid, water-soluble salt solution, and pure water.

[0023] More preferably, the back-extraction solution is pure water, and the lithium ion concentration in the loaded aqueous phase obtained by back-extraction when the pure water temperature is at room temperature is 0.01 g / L to 1 g / L, and the lithium ion concentration in the loaded aqueous phase obtained when the pure water temperature is above 40°C is 1 g / L to 5 g / L, which can achieve the purpose of enrichment.

[0024] More preferably, the acid solution is any one of hydrochloric acid, sulfuric acid, nitric acid, formic acid, and acetic acid; and the hydrogen ion concentration in the acid solution is 0.01 mol / L to 6 mol / L.

[0025] More preferably, the water-soluble salt solution is a sodium chloride aqueous solution.

[0026] Furthermore, the alkaline solution is any one of sodium hydroxide aqueous solution, ammonium sulfate aqueous solution, ammonium carbonate aqueous solution, and ammonium bicarbonate aqueous solution.

[0027] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0028] 1. This invention discloses an extractant for selectively extracting lithium from lithium-containing solutions. The selected phosphorus oxides are mixed with halogens, including at least one of chlorine, bromine, and iodine, dissolved in a neutral phosphate ester compound to form a complex that greatly enhances the selectivity for lithium, thereby enabling the extraction of lithium ions from lithium-containing solutions to form [LiS]. + [X(Y2) n ] - (Where S is a neutral phosphate ester, X is a halide ion, Y2 is a molecular halogen, and n = 1-2) complex. The extractant has unique advantages; it does not have specific requirements regarding the magnesium-to-lithium ratio of the brine, and can effectively achieve selective extraction of lithium salts from a variety of lithium-containing solutions. These lithium-containing solutions cover a wide range, including but not limited to salt lake brine, seawater and concentrated seawater, lithium-containing water from ore extraction, underground brine, oilfield water, lithium-containing water from battery recovery, and industrial lithium-containing wastewater. Whether the solution has an extremely low or extremely high magnesium-to-lithium ratio, the extractant can effectively extract lithium. During the extraction process, it exhibits highly efficient selectivity, accurately identifying and extracting lithium, while also possessing a high extraction rate, maximizing the extraction of lithium from lithium-containing solutions, providing a highly effective technical means for the recovery and utilization of lithium resources.

[0029] 2. This invention discloses a method for selectively extracting lithium and removing impurities from lithium-containing solutions. This invention directly mixes the lithium-containing solution, such as brine stock solution, with an extractant, eliminating the need for additional strong acids or other substances to adjust the pH value, thus ensuring the brine remains uncontaminated during extraction. The extractant used in this invention effectively avoids emulsification, hydrolysis, and other adverse phenomena, guaranteeing the stability and efficiency of the extraction process. The back-extraction process does not use high-concentration acid washing, reducing the requirements for equipment materials. Addressing the challenge of extracting lithium from brine due to the coexistence of large amounts of sodium and magnesium, the extractant selected in this invention does not have strict requirements on the magnesium-to-lithium ratio in the brine and does not require a high lithium concentration in the stock brine, enabling selective lithium extraction with a high extraction rate and good magnesium-to-lithium separation. This characteristic gives this invention a significant technical advantage in the field of lithium extraction from brine. The extracted organic phase can be recycled and reused, and no waste is generated, avoiding environmental pollution and resource waste. Testing showed that the total lithium ion recovery rate obtained by the extractant selected in this invention and the extraction method based on it reached over 90%.

[0030] 3. This invention discloses a method for selectively extracting lithium and removing impurities from lithium-containing solutions. When applied to water samples with a high magnesium-to-lithium ratio, this method achieves the separation of most magnesium and lithium during the extraction stage, with the extraction agent exhibiting extremely low magnesium extraction rates. The subsequent addition of alkaline solution focuses on deep impurity removal, particularly the removal of magnesium impurities, further enhancing the magnesium-to-lithium separation effect and ensuring the purity of the extracted lithium. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating a method for extracting lithium from a lithium-containing solution according to an embodiment of the present invention. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention provides an extractant and extraction method for selectively extracting lithium from lithium-containing solutions with a high magnesium-to-lithium ratio, such as brine. Figure 1As shown, a complete process flow including extractant preparation, extraction, back-extraction, and impurity removal is presented. Parameters such as mass concentration (phosphorus oxides, halogens), volume ratio (organic extractant to aqueous phase), and temperature (extraction and back-extraction temperatures) for each step have been confirmed. A complete process flow for lithium-containing solutions has been designed, which can efficiently extract lithium salts and deeply remove impurities, significantly improving the recovery rate of lithium resources and the purity of subsequent products. In the embodiments of this specification, O / A1 represents the volume ratio of extractant to lithium-containing solution, and O / A2 represents the volume ratio of lithium-loaded organic phase to back-extraction liquid.

[0034] Example 1

[0035] 1. Lithium-containing solution: A neutral or acidic lithium-containing solution (pH range of 0-7) was used as the extraction aqueous phase. In this embodiment, the lithium-containing solution was brine from a salt lake, i.e., water sample 1 in Table 1, which was weakly acidic and contained Li... + The mass concentration is 0.23 g / L (Mg / Li-360 mass ratio).

[0036] 2. Preparation of the extractant: The extractant comprises 70% phosphorus oxides and 30% diluent by volume, and the halogen concentration in the extractant is 0.3 mol / L; the specific preparation method is to mix and stir 35 mL of trioctyl phosphate, 15 mL of n-dodecane and 3.81 g of iodine (molecular iodine) to obtain the extractant.

[0037] 3. Extraction: Take 50 mL of a salt lake brine sample 1 with a high magnesium-to-lithium ratio as shown in Table 1, add 50 mL of extraction solvent and mix (compared to O / Al = 1:1 volume ratio). The extraction temperature is room temperature (about 20℃), and the extraction time is 10 min. Separate the phases to obtain the raffinate and the loaded organic phase. The extraction solvent is directly mixed with the brine stock solution without the need to add other acids or bases to adjust the pH of the stock solution.

[0038] 4. Back-extraction: Take the organic phase loaded in the extraction step, add 50 mL of pure water (compared to O / A2 = 1:1 volume ratio), mix and stir. The back-extraction temperature is room temperature (about 20℃), and the back-extraction time is 5 min. Separate the phases to obtain the loaded aqueous phase (containing a small amount of magnesium salt) and the organic phase. The organic phase is recycled as an extractant.

[0039] 5. Magnesium precipitation: Take the above-mentioned loaded aqueous phase (containing a small amount of magnesium salt) and add 1 mol / L sodium hydroxide aqueous solution to mix and stir to precipitate a small amount of magnesium salt. After filtration, a lithium-loaded solution is obtained.

[0040] Ion chromatography analysis showed that the extraction rate of lithium in water sample 1 was 93.4%, the reverse extraction rate was 97.8%, and the total recovery rate was 92.7%. In water sample 2, the extraction rate was 94.1%, the reverse extraction rate was 98.1%, and the total recovery rate was 93.6%. In water sample 3, the extraction rate was 94.5%, the reverse extraction rate was 98.6%, and the total recovery rate was 94.1%.

[0041] Table 1 Comparison of water sample extraction with different magnesium-lithium ratios (mass ratio)

[0042]

[0043] Using the above-described extractant and extraction method, the above steps were repeated for "Water Sample 2" and "Water Sample 3" listed in Table 1 as lithium-containing solutions, and lithium-loaded solutions were prepared using the same method. The magnesium and lithium content data in Table 1 of this invention were detected by ion chromatography; the separation coefficient was calculated using the formula: separation coefficient = (lithium salt concentration in organic phase / lithium salt concentration in residual liquid) / (magnesium salt concentration in organic phase / magnesium salt concentration in residual liquid).

[0044] Table 1 lists three brine samples from salt lakes with different magnesium / lithium ratios (Mg / Li mass ratios): 360, 37, and 21, respectively. The lithium concentrations in these samples also showed significant differences: 0.23 g / L, 0.51 g / L, and 0.74 g / L, respectively. The extractant used in this invention for extracting lithium from salt lake brine exhibits superior performance. Its unique chemical composition and mechanism of action form [Li·S]. + [X·(I2)2] - The complex (S is a neutral phosphorus extractant, X is a halide ion) enables the system to maintain stable and efficient lithium-ion extraction capabilities when faced with salt lake brines of varying lithium concentrations and diverse magnesium-to-lithium ratios. This extractant specifically identifies and binds to lithium ions, effectively eliminating interference from magnesium ions and other impurity ions, thereby achieving efficient and selective extraction of lithium ions.

[0045] Example 2

[0046] 1. Lithium-containing solution: A neutral or acidic lithium-containing solution (pH range of 0-7) is used as the extraction aqueous phase. In this embodiment, the lithium-containing solution is brine from a salt lake, which is weakly acidic, and its Li... + The mass concentration is 0.23 g / L (Mg / Li-360 mass ratio).

[0047] 2. Preparation of the extractant: The extractant comprises 60% phosphorus oxides and 40% diluent by volume, and the halogen concentration in the extractant is 0.3 mol / L. The specific preparation method is to take 30 mL of tributyl phosphate, 10 mL of isooctanol and 10 mL of isodecanol mixture and 2.4 g of bromine (molecular bromine) and mix and stir to obtain the extractant.

[0048] 3. Extraction: Take 100 mL of a salt lake brine sample 1 with a high magnesium-to-lithium ratio as shown in Table 1, add 50 mL of extraction reagent and mix (compared to O / Al = 1:2 volume ratio). The extraction temperature is room temperature (about 20℃), and the extraction time is 10 min. Separate the phases to obtain the raffinate and the loaded organic phase. The extraction reagent is directly mixed with the brine stock solution without the need to add other acids or bases to adjust the pH of the stock solution.

[0049] 4. Back-extraction: Take the organic phase loaded in the extraction step, add 50 mL of pure water (compared to O / A2 = 1:1 volume ratio), mix and stir. The back-extraction temperature is room temperature (about 20℃), and the back-extraction time is 5 min. Separate the phases to obtain the loaded aqueous phase (containing a small amount of magnesium salt) and the organic phase. The organic phase is recycled as an extractant.

[0050] 5. Magnesium precipitation: Take the above-mentioned loaded aqueous phase (containing a small amount of magnesium salt) and add 1 mol / L sodium hydroxide aqueous solution to mix and stir to precipitate a small amount of magnesium salt. After filtration, a lithium-loaded solution is obtained.

[0051] According to ion chromatography, the extraction agent prepared according to the ratio in Example 2, under a specific O / A ratio, achieved an extraction rate of 92.6%, a reverse extraction rate of 97.6%, and a total recovery rate of 90.4% in this experiment.

[0052] Example 3

[0053] 1. Lithium-containing solution: A neutral or acidic lithium-containing solution (pH range of 0-7) is used as the extraction aqueous phase. In this embodiment, the lithium-containing neutral or acidic aqueous solution is salt lake brine, which is weakly acidic and contains Li... + The mass concentration is 0.23 g / L (Mg / Li-360 mass ratio).

[0054] 2. Preparation of the extractant: The extractant comprises 40% phosphorus oxides and 60% diluent by volume, and the halogen concentration in the extractant is 0.1 mol / L. The specific preparation method is to mix 10 mL of trioctyl phosphate and 10 mL of trioctyl phosphate, mix 15 mL of n-butanol and 15 mL of n-pentanol, and stir 1.27 g of iodine (molecular iodine) to obtain the extractant.

[0055] 3. Extraction: Take 100 mL of a salt lake brine sample 1 with a high magnesium-to-lithium ratio as shown in Table 1, add 50 mL of extraction reagent and mix (compared to O / Al = 1:2 volume ratio). The extraction temperature is room temperature (about 20℃), and the extraction time is 10 min. Separate the phases to obtain the raffinate and the loaded organic phase. The extraction reagent is directly mixed with the brine stock solution without the need to add other acids or bases to adjust the pH of the stock solution.

[0056] 4. Back-extraction: Take the organic phase loaded in the extraction step, add 25 mL of pure water (compared to O / A2 = 2:1 volume ratio), mix and stir. The back-extraction temperature is 35.3℃ and the back-extraction time is 5 min. Separate the phases to obtain the loaded aqueous phase (containing a small amount of magnesium salt) and the organic phase. The organic phase is recycled as an extractant.

[0057] 5. Magnesium precipitation: Take the above-mentioned loaded aqueous phase (containing a small amount of magnesium salt) and add 1 mol / L sodium hydroxide aqueous solution to mix and stir to precipitate a small amount of magnesium salt. After filtration, a lithium-loaded solution is obtained.

[0058] According to ion chromatography, the extraction agent prepared according to the ratio in Example 3, under a specific O / A ratio, achieved an extraction rate of 91.4%, a reverse extraction rate of 98.1%, and a total recovery rate of 90% in this experiment.

[0059] Example 4

[0060] 1. Lithium-containing solution: A neutral or acidic lithium-containing solution (pH range of 0-7) is used as the extraction aqueous phase. In this embodiment, the lithium-containing neutral or acidic aqueous solution is salt lake brine, which is weakly acidic and contains Li... + The mass concentration is 0.23 g / L (Mg / Li-360 mass ratio).

[0061] 2. Preparation of the extractant: The extractant comprises 30% phosphorus oxides and 70% diluent by volume, and the halogen concentration in the extractant is 0.01 mol / L. The specific preparation method is to take 10 mL of a mixture of trioctyl phosphate and 5 mL of triphenyl phosphate, 20 mL of a mixture of bromobenzene and 15 mL of chlorobenzene, and 0.13 g of iodine (molecular iodine) and mix them to obtain the extractant.

[0062] 3. Extraction: Take 100 mL of a salt lake brine sample 1 with a high magnesium-to-lithium ratio as shown in Table 1, add 50 mL of extraction reagent and mix (compared to O / Al = 1:2 volume ratio). The extraction temperature is room temperature (about 20℃), and the extraction time is 10 min. Separate the phases to obtain the raffinate and the loaded organic phase. The extraction reagent is directly mixed with the brine stock solution without the need to add other acids or bases to adjust the pH of the stock solution.

[0063] 4. Back-extraction: Take the organic phase loaded in the extraction step, add 10 mL of pure water (compared to O / A2 = 5:1 volume ratio), mix and stir. The back-extraction temperature is 41.4℃ and the back-extraction time is 5 min. Separate the phases to obtain the loaded aqueous phase (containing a small amount of magnesium salt) and the organic phase. The organic phase is recycled as an extractant.

[0064] 5. Magnesium precipitation: Take the above-mentioned loaded aqueous phase (containing a small amount of magnesium salt) and add 1 mol / L sodium hydroxide aqueous solution to mix and stir to precipitate a small amount of magnesium salt. After filtration, a lithium-loaded solution is obtained.

[0065] According to ion chromatography, the extraction agent prepared according to the ratio in Example 4, under a specific O / A ratio, achieved an extraction rate of 91.2%, a reverse extraction rate of 98.7%, and a total recovery rate of 90% in this experiment.

[0066] Example 5

[0067] 1. Lithium-containing solution: A neutral or acidic lithium-containing solution (pH range of 0-7) is used as the extraction aqueous phase. In this embodiment, the lithium-containing neutral or acidic aqueous solution is salt lake brine, which is weakly acidic and contains Li... + The mass concentration is 0.23 g / L (Mg / Li-360 mass ratio).

[0068] 2. Preparation of the extractant: The extractant comprises 80% phosphorus oxides and 20% diluent by volume, and the extractant has a halogen concentration of 0.5 mol / L. The specific preparation method is to take 20 mL of trimethyl phosphate and 20 mL of tributyl phosphate mixture, 10 mL of n-octanol and 6.35 g of iodine (molecular iodine) and mix them to obtain the extractant.

[0069] 3. Extraction: Take 100 mL of a salt lake brine sample 1 with a high magnesium-to-lithium ratio as shown in Table 1, add 50 mL of extraction reagent and mix (compared to O / Al = 1:2 volume ratio). The extraction temperature is room temperature (about 20℃), and the extraction time is 10 min. Separate the phases to obtain the raffinate and the loaded organic phase. The extraction reagent is directly mixed with the brine stock solution without the need to add other acids or bases to adjust the pH of the stock solution.

[0070] 4. Back-extraction: Take the organic phase loaded in the extraction step, add 5 mL of pure water (compared to O / A2 = 10:1 volume ratio), mix and stir. The back-extraction temperature is 48.6℃ and the back-extraction time is 5 min. Separate the phases to obtain the loaded aqueous phase (containing a small amount of magnesium salt) and the organic phase. The organic phase is recycled as an extractant.

[0071] 5. Magnesium precipitation: Take the above-mentioned loaded aqueous phase (containing a small amount of magnesium salt) and add 1 mol / L sodium hydroxide aqueous solution to mix and stir to precipitate a small amount of magnesium salt. After filtration, a lithium-loaded solution is obtained.

[0072] According to ion chromatography, the extraction agent prepared according to the ratio in Example 5, under a specific O / A ratio, achieved an extraction rate of 91.7%, a reverse extraction rate of 99%, and a total recovery rate of 90.8% in this experiment.

[0073] Table 2 Comparison of enrichment effects of back-extraction solutions in Examples 2-5

[0074]

[0075] Based on the data in Table 2, it can be seen that in the lithium extraction process of salt lake brine with a high magnesium-to-lithium ratio, when the temperature of the reverse extraction operation gradually increases, lithium ions are more likely to detach from the organic phase and enter the reverse extraction liquid phase, thereby gradually accumulating the lithium ion concentration in the reverse extraction liquid and ultimately achieving the expected goal of enriching lithium ions.

[0076] Example 6

[0077] 1. Lithium-containing solution: A neutral or acidic lithium-containing solution (pH range of 0-7) is used as the extraction aqueous phase. In this embodiment, the lithium-containing neutral or acidic aqueous solution is brine from a salt lake. + The mass concentration is 0.01 g / L (Mg / Li-106 mass ratio).

[0078] 2. Preparation of the extractant: The extractant comprises 90% phosphorus oxides and 10% diluent by volume, and the halogen concentration in the extractant is 0.2 mol / L. The specific preparation method is to take 20 mL of triethyl phosphate, 10 mL of tributyl phosphate, 15 mL of trioctyl phosphate mixture, 5 mL of diethylene glycol butyl ether and 2.54 g of iodine (molecular iodine) and mix them to obtain the extractant.

[0079] 3. Extraction: Take 500 mL of the above water sample, which is neutral, add 50 mL of extraction solvent and mix (compared to O / A1 = 1:10 volume ratio). The extraction temperature is room temperature (about 20℃) and the extraction time is 5 min. Separate the phases to obtain the raffinate and the loaded organic phase. The extraction solvent is directly mixed with the brine stock solution without the need to add other acids or bases to adjust the pH of the stock solution.

[0080] 4. Back-extraction: Take the organic phase loaded in the extraction step, add 10 mL of pure water (compared to O / A2 = 5:1 volume ratio), mix and stir. The back-extraction temperature is 60℃ and the back-extraction time is 20 min. Separate the phases to obtain the loaded aqueous phase (containing a small amount of magnesium salt) and the organic phase. The organic phase is recycled as an extractant.

[0081] 5. Magnesium precipitation: Take the above-mentioned loaded aqueous phase (containing a small amount of magnesium salt) and add it to a 1 mol / L ammonium carbonate aqueous solution. Mix and stir to precipitate a small amount of magnesium salt. After filtration, obtain a lithium-loaded solution.

[0082] According to ion chromatography, the extraction agent prepared according to the ratio in Example 6, under a specific O / A ratio, achieved an extraction rate of 91.5%, a reverse extraction rate of 98.2%, and a total recovery rate of 90% in this experiment.

[0083] Example 7

[0084] 1. Lithium-containing solution: A neutral or acidic lithium-containing solution (pH range of 0-7) is used as the extraction aqueous phase. In this embodiment, the lithium-containing neutral or acidic aqueous solution is brine from a salt lake. +The mass concentration is 0.23 g / L (Mg / Li-360 mass ratio).

[0085] 2. Preparation of the extractant: The extractant comprises phosphorus oxides and halogens, wherein the halogen concentration in the extractant is 1 mol / L; the specific preparation method is to take 25 mL of tributyl phosphate, 25 mL of trialkylphosphine oxide (TRPO) mixture and 12.7 g of iodine (molecular iodine) and mix and stir to obtain the extractant.

[0086] 3. Extraction: Take 200 mL of a salt lake brine sample with a high magnesium-to-lithium ratio as shown in Table 1. The sample is neutral. Add 50 mL of the extractant and mix (O / Al = 1:4 volume ratio). The extraction temperature is room temperature (about 20℃) and the extraction time is 10 min. Separate the phases to obtain the raffinate and the loaded organic phase. The extractant is directly mixed with the original brine solution without the need to add other acids or bases to adjust the pH of the original solution.

[0087] 4. Back-extraction: Take the organic phase loaded in the extraction step and add 100 mL of 3% hydrochloric acid aqueous solution (O / A2 = 1:2 volume ratio) and mix and stir. The back-extraction temperature is room temperature (about 20℃) and the back-extraction time is 5 min. Separate the phases to obtain the loaded aqueous phase (containing a small amount of magnesium salt) and the organic phase. The organic phase is recycled as an extractant.

[0088] 5. Magnesium precipitation: Take the above-mentioned loaded aqueous phase (containing a small amount of magnesium salt) and add 1 mol / L ammonium sulfate aqueous solution to mix and stir to precipitate a small amount of magnesium salt. After filtration, a lithium-loaded solution is obtained.

[0089] According to ion chromatography, the extraction agent prepared according to the ratio in Example 7, under a specific O / A ratio, achieved an extraction rate of 93.2%, a reverse extraction rate of 98%, and a total recovery rate of 91.3% in this experiment.

[0090] Example 8

[0091] 1. Lithium-containing solution: A neutral or acidic lithium-containing solution (pH range of 0-7) is used as the extraction aqueous phase. In this embodiment, the lithium-containing neutral or acidic aqueous solution is brine from a salt lake. + The mass concentration is 0.23 g / L (Mg / Li-360 mass ratio).

[0092] 2. Preparation of the extractant: The extractant comprises 80% phosphorus oxides and 20% diluent by volume, and the halogen concentration in the extractant is 0.2 mol / L. The specific preparation method is to take 20 mL of dimethyl methylphosphonate, 20 mL of dimethylheptyl methylphosphonate (P350) mixture, 5 mL of n-octane, 5 mL of isooctane mixture and 2.54 g of iodine (molecular iodine) and mix and stir to obtain the extractant.

[0093] 3. Extraction: Take 250 mL of a salt lake brine sample 1 with a high magnesium-to-lithium ratio as shown in Table 1. It is weakly acidic. Add 50 mL of extraction reagent and mix and stir (compared to O / Al = 1:5 volume ratio). The extraction temperature is room temperature (about 20℃) and the extraction time is 20 min. Separate the phases to obtain the raffinate and the loaded organic phase. The extraction reagent is directly mixed with the brine stock solution without the need to add other acids or bases to adjust the pH of the stock solution.

[0094] 4. Back-extraction: Take the organic phase loaded in the extraction step and add 150 mL of 10% sodium chloride aqueous solution (compared to O / A2 = 1:3 volume ratio) and mix and stir. The back-extraction temperature is room temperature (about 20℃) and the back-extraction time is 5 min. Separate the phases to obtain the loaded aqueous phase (containing a small amount of magnesium salt) and the organic phase. The organic phase is recycled as an extractant.

[0095] 5. Magnesium precipitation: Take the above-mentioned loaded aqueous phase (containing a small amount of magnesium salt) and add 1 mol / L sodium hydroxide aqueous solution to mix and stir to precipitate a small amount of magnesium salt. After filtration, a lithium-loaded solution is obtained.

[0096] According to ion chromatography, the extraction agent prepared according to the ratio in Example 8, under a specific O / A ratio, achieved an extraction rate of 90.3%, a reverse extraction rate of 98.5%, and a total recovery rate of 89% in this experiment.

[0097] Example 9

[0098] 1. Lithium-containing solution: A neutral or acidic lithium-containing solution (pH range of 0-7) is used as the extraction aqueous phase. In this embodiment, the lithium-containing neutral or acidic aqueous solution is brine from a salt lake. + The mass concentration is 0.23 g / L (Mg / Li-360 mass ratio).

[0099] 2. Preparation of the extractant: The extractant comprises 70% phosphorus oxides and 30% diluent by volume, and the halogen concentration in the extractant is 0.1 mol / L. The specific preparation method is to take 20 mL of triisobutyl phosphate, 15 mL of trioctyl phosphate mixture, 10 mL of n-pentane, 5 mL of n-heptane mixture and 0.8 g of bromine (molecular bromine) as halogens, mix and stir to obtain the extractant.

[0100] 3. Extraction: Take 5 mL of a neutral brine sample from a salt lake with a high magnesium-to-lithium ratio, add 50 mL of extraction solvent and mix (O / Al = 10:1 volume ratio). The extraction temperature is room temperature (about 20℃) and the extraction time is 20 min. Separate the phases to obtain the raffinate and the loaded organic phase. The extraction solvent is directly mixed with the original brine solution without the need to add other acids or bases to adjust the pH of the original solution.

[0101] 4. Back-extraction: Take the organic phase loaded in the extraction step and add 100 mL of 10% sodium chloride aqueous solution (O / A2 = 1:2 volume ratio) and mix and stir. The back-extraction temperature is room temperature (about 20℃) and the back-extraction time is 5 min. Separate the phases to obtain the loaded aqueous phase (containing a small amount of magnesium salt) and the organic phase. The organic phase is recycled as an extractant.

[0102] 5. Magnesium precipitation: Take the above-mentioned loaded aqueous phase (containing a small amount of magnesium salt) and add 1 mol / L sodium hydroxide aqueous solution to mix and stir to precipitate a small amount of magnesium salt. After filtration, a lithium-loaded solution is obtained.

[0103] According to ion chromatography, the extraction agent prepared according to the ratio in Example 9, under a specific O / A ratio, achieved an extraction rate of 91.8%, a reverse extraction rate of 98.4%, and a total recovery rate of 90.3% in this experiment.

[0104] Example 10

[0105] 1. Lithium-containing solution: A neutral or acidic lithium-containing solution (pH range of 0-7) is used as the extraction aqueous phase. In this embodiment, the lithium-containing neutral or acidic aqueous solution is brine from a salt lake. + The mass concentration is 0.23 g / L (Mg / Li-360 mass ratio).

[0106] 2. Preparation of the extractant: The extractant comprises 60% phosphorus oxides and 40% diluent by volume, and the extractant has a halogen concentration of 0.4 mol / L. The specific preparation method is to mix and stir 30 mL of trialkylphosphine oxide (TRPO), 20 mL of n-dodecane and 5.08 g of iodine (molecular iodine) to obtain the extractant.

[0107] 3. Extraction: Take 500 mL of a salt lake brine sample with a high magnesium-to-lithium ratio, which is weakly acidic, add 50 mL of extraction reagent and mix (compared to O / Al = 1:10 volume ratio). The extraction temperature is room temperature (about 20℃) and the extraction time is 20 min. Separate the phases to obtain the raffinate and the loaded organic phase. The extraction reagent is directly mixed with the brine stock solution without the need to add other acids or bases to adjust the pH of the stock solution.

[0108] 4. Back-extraction: Take the organic phase loaded in the extraction step and add 250 mL of 10% sodium chloride aqueous solution (O / A2 = 1:5 volume ratio) and mix and stir. The back-extraction temperature is room temperature (about 20℃) and the back-extraction time is 5 min. Separate the phases to obtain the loaded aqueous phase (containing a small amount of magnesium salt) and the organic phase. The organic phase is recycled as an extractant.

[0109] 5. Magnesium precipitation: Take the above-mentioned loaded aqueous phase (containing a small amount of magnesium salt) and add 1 mol / L sodium hydroxide aqueous solution to mix and stir to precipitate a small amount of magnesium salt. After filtration, a lithium-loaded solution is obtained.

[0110] According to ion chromatography, the extraction agent prepared according to the ratio in Example 10, under a specific O / A ratio, achieved an extraction rate of 93.6%, a reverse extraction rate of 98.1%, and a total recovery rate of 91.8% in this experiment.

[0111] Example 11

[0112] 1. Lithium-containing solution: A neutral or acidic lithium-containing solution (pH range of 0-7) is used as the aqueous phase for extraction. + The mass concentration is approximately 5000 mg / L.

[0113] 2. Preparation of the extractant: The extractant comprises 70% phosphorus oxides and 30% diluent by volume, and the halogen concentration in the extractant is 2 mol / L. The specific preparation method is to mix and stir 20 mL of trioctylphosphine oxide, 11.5 mL of trihexylphosphine oxide, 13.5 mL of n-dodecane and 16 g of bromine (molecular bromine) to obtain the extractant.

[0114] 3. Extraction: Take 10 mL of lithium-containing solution with a pH value of 50 mL, add 50 mL of extractant and mix (compared to O / Al = 5:1 volume ratio). The extraction temperature is 35℃ and the extraction time is 10 min. Separate the phases to obtain the raffinate and the loaded organic phase. The extractant is directly mixed with the brine stock solution without the need to add other acids or bases to adjust the pH of the stock solution.

[0115] 4. Back-extraction: Take the organic phase loaded in the extraction step and add 25 mL of 10% sodium chloride aqueous solution (O / A2 = 1:1 volume ratio) and mix and stir. The back-extraction temperature is 35℃ and the back-extraction time is 10 min. Separate the phases to obtain the loaded aqueous phase (containing a small amount of magnesium salt) and the organic phase. The organic phase is recycled as an extractant.

[0116] 5. Magnesium precipitation: Take the above-mentioned loaded aqueous phase (containing a small amount of magnesium salt) and add 1 mol / L sodium hydroxide aqueous solution to mix and stir to precipitate a small amount of magnesium salt. After filtration, a lithium-loaded solution is obtained.

[0117] According to ion chromatography, the extraction agent prepared according to the ratio in Example 11, under a specific O / A ratio, achieved an extraction rate of 92.6%, a reverse extraction rate of 98.2%, and a total recovery rate of 90.9% in this experiment.

[0118] Experimental example: Comparison experiment of extractants.

[0119] 1. Lithium-containing solution: A neutral or acidic lithium-containing solution (pH range of 0-7) is used as the extraction aqueous phase. In this embodiment, the lithium-containing neutral or acidic aqueous solution is brine from a salt lake. + The mass concentration is 0.23 g / L (Mg / Li-360 mass ratio).

[0120] 2. Preparation of the extraction agent: Prepare the extraction agent according to the phosphorus oxides, halogens and diluents listed in Table 3.

[0121] 3. Extraction: Take 100 mL of a salt lake brine sample 1 with a high magnesium-to-lithium ratio, which is weakly acidic, add 50 mL of extraction reagent and mix (compared to O / Al = 1:2 volume ratio). The extraction temperature is room temperature (about 20℃) and the extraction time is 5 min. Separate the phases to obtain the raffinate and the loaded organic phase. The extraction reagent is directly mixed with the brine stock solution, so there is no need to add other acids or bases to adjust the pH of the stock solution.

[0122] 4. Back-extraction: Take the organic phase loaded in the extraction step, add 25 mL of pure water (compared to O / A2 = 2:1 volume ratio), mix and stir. The back-extraction temperature is room temperature (about 20℃), and the back-extraction time is 20 min. Separate the phases to obtain the loaded aqueous phase (containing a small amount of magnesium salt) and the organic phase. The organic phase is recycled as an extractant.

[0123] 5. Magnesium precipitation: Take the above-mentioned loaded aqueous phase (containing a small amount of magnesium salt) and add 1 mol / L sodium hydroxide aqueous solution to mix and stir to precipitate a small amount of magnesium salt. After filtration, a lithium-loaded solution is obtained.

[0124] The extraction rates of lithium from lithium-containing solutions were measured using the extractants listed in Tables 3 (numbers 1-15), and the results are detailed in Table 3. Accurate determination revealed that the lithium ion concentration (Li) in water sample 1 was... + The mass concentration of ) was 0.23 g / L, while the magnesium ion (Mg) concentration was 0.23 g / L. 2+ The mass concentration of lithium reached 82.67 g / L. After screening, the preferred extractant was a combination of phosphate ester and / or trialkylphosphine oxide, bromine or iodine, and a diluent, achieving a lithium extraction rate of over 90%.

[0125] Table 3 Comparison of the composition of each extractant group

[0126]

[0127]

[0128] In summary, the extractant screened by this invention has high selectivity for lithium in brine, can accurately identify and extract lithium, and can extract lithium from lithium-containing solutions to the greatest extent, providing an extremely effective technical means for the recovery and utilization of lithium resources.

[0129] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0130] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. An extractant for extracting lithium from a lithium-containing solution, characterized in that: The extractant includes phosphorus oxides and halogens.

2. The extractant for extracting lithium from a lithium-containing solution according to claim 1, characterized in that: The phosphorus oxide compound is a neutral phosphorus extractant; the halogen is at least one of chlorine, bromine and iodine.

3. The extractant for extracting lithium from a lithium-containing solution according to claim 2, characterized in that: The neutral phosphorus extractant includes at least one of phosphate esters, phosphonates, and trialkylphosphine oxides.

4. The extractant for extracting lithium from a lithium-containing solution according to claim 3, characterized in that: The phosphate ester includes at least one of trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triisobutyl phosphate, and triphenyl phosphate; the phosphonate includes at least one of dimethyl methylphosphonate and dimethylheptyl methylphosphonate; and the trialkylphosphine oxide includes at least one of trialkylphosphine oxide, trihexylphosphine oxide, trioctylphosphine oxide, and triphenylphosphine oxide.

5. The extractant for extracting lithium from a lithium-containing solution according to claim 1, characterized in that: The mass concentration of halogen in the extractant is 0.01 mol / L to 2 mol / L.

6. The extractant for extracting lithium from a lithium-containing solution according to any one of claims 1 to 5, characterized in that: The extractant also includes a diluent, which comprises C4 to C6. 16 Alkanes, C1-C 16 Haloalkanes, C6-C 12 Halogenated aromatics, C8-C 12 Ethers, C4-C 10 Alcohols, C4-C 10 At least one of esters and sulfonated kerosene.

7. The extractant for extracting lithium from a lithium-containing solution according to claim 6, characterized in that: The volume percentage of the phosphorus oxide compound in the extractant is 30% to 90%, and the volume percentage of the diluent is 10% to 70%. The C4~C 16 Alkanes include any one of n-pentane, n-heptane, octane, and n-dodecane, wherein the C1-C1... 16 Halogenated alkanes include any one of dichloromethane and 1-chlorodecane, wherein the C6-C6... 12 Halogenated aromatic hydrocarbons include any one of bromobenzene and chlorobenzene, wherein the C8-C9 ratio is 100- ... 12 Ethers include diethylene glycol butyl ether, C4~C5 10 The alcohol includes any one of n-butanol, n-pentanol, isoamyl alcohol, n-octanol, isooctanol, and isodecanol, wherein the C4-C5 group is C6-C7-C ... 10 Esters include either ethyl acetate or butyl acetate.

8. A method for extracting lithium from a lithium-containing solution, characterized in that: Includes the following steps: The extractant according to any one of claims 1 to 7 is mixed with a lithium-containing solution at room temperature, wherein the lithium-containing solution is a neutral or acidic solution. After phase separation, a raffinate and a loaded organic phase are obtained. The loaded organic phase is added to a reverse extraction solution and mixed and stirred. After phase separation, a loaded aqueous phase and an organic phase are obtained. The loaded aqueous phase is added to an alkaline solution and mixed and stirred. After filtration, a lithium-loaded solution is obtained.

9. The method for extracting lithium from a lithium-containing solution according to claim 8, characterized in that: The extractant is mixed with the lithium-containing solution at room temperature for 5 min to 20 min; the loaded organic phase is added to the back-extraction solution at 20℃ to 60℃ and mixed and stirred for 5 min to 20 min; the volume ratio of the extractant to the lithium-containing solution is 1:10 to 10:1; the volume ratio of the loaded organic phase to the back-extraction solution is 1:5 to 10:

1.

10. The method for extracting lithium from a lithium-containing solution according to claim 8, characterized in that: The lithium-containing solution includes any one of the following: salt lake brine, seawater and concentrated seawater, lithium extraction water from ore, underground brine, oilfield water, lithium-containing water from lithium battery recovery, and industrial lithium-containing wastewater. Li in lithium-containing solution + The mass concentration is 0.01 g / L to 5 g / L; The organic phase is recycled as an extractant. The back-extraction solution includes any one of acid solution, water-soluble salt solution, and pure water; The alkaline solution is any one of sodium hydroxide aqueous solution, ammonium sulfate aqueous solution, ammonium carbonate aqueous solution, and ammonium bicarbonate aqueous solution.

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