A method for selectively extracting and precipitating lithium from a lithium-containing alkaline aqueous solution

Abstract

The application relates to a method for selectively extracting and precipitating lithium enrichment from a lithium-containing alkaline aqueous solution, in particular to a method for selectively extracting and precipitating lithium enrichment from a concentrated sodium aluminate solution obtained after high-temperature leaching of lithium-rich bauxite by a Bayer method. A cycloalkanoic compound, an alkyl phenoxy carboxylic acid derivative or a mixture of both is added into the lithium-containing alkaline aqueous solution or the high-temperature leaching solution of the lithium-rich bauxite by the Bayer method at a certain molar ratio with lithium, and the mixture is stirred at room temperature to obtain a liquid-solid two-phase mixture. After dilution with water, a flocculating agent is added, and solid-liquid separation is carried out to obtain a solid. Then, a stripping agent is added at a certain mass ratio, and stirring and mixing are carried out at a temperature of 20-80 DEG C. After cooling to room temperature, lithium is enriched in the lower liquid phase after stripping or the filtrate after solid-liquid separation. The application can realize selective extraction and precipitation and enrichment of low-concentration lithium in an alkaline aqueous solution, and has the advantages of simple operation, repeated use of the extractant, low cost and wide application range.

Description

Technical Field

[0001] This invention belongs to the field of rare metal lithium enrichment and extraction technology, and relates to a method for selectively extracting and precipitating lithium from lithium-containing alkaline aqueous solutions, and particularly to a method for selectively extracting and precipitating lithium from a concentrated alkaline sodium aluminate solution obtained after high-temperature leaching of lithium-rich bauxite by the Bayer process. Background Technology

[0002] Lithium and its compounds possess many excellent properties and have a wide range of applications. With the rapid development of information technology, high-capacity batteries, nuclear fusion, aluminum-lithium alloys, and especially in recent years in the fields of power batteries, electric vehicles, and green energy, the market demand for lithium and its compounds is surging.

[0003] In central my country, bauxite generally has a high lithium content, with an average lithium oxide grade of approximately 0.05-0.5%, dispersed in minerals such as bauxite, kaolinite, and illite. During the production of alumina from lithium-rich bauxite, lithium accumulates in the concentrated alkaline solution of sodium aluminate produced by the Bayer process. This lithium is then precipitated with aluminum hydroxide during subsequent seeding or carbonization processes, and ultimately enters the finished alumina product after roasting, resulting in a high lithium content (Cao Alin, Li Chunhuan. Research on the Enrichment Mechanism of Lithium in the Bayer Process of Alumina Production. *Nonferrous Metals (Smelting Section)*, 2017, No. 9, pp. 23-26). Based on an average lithium oxide content of 0.1% in lithium-rich bauxite and an annual alumina production of 12 million tons, it is estimated that as much as 12,000 tons of lithium oxide are removed annually during alumina production. This not only leads to the loss of lithium resources, but the high lithium content in alumina products also severely impacts subsequent aluminum electrolysis processes, such as reducing electrolysis temperature, worsening furnace regularity, decreasing electrolysis production stability, reducing current efficiency, and increasing energy consumption. Therefore, existing processes require periodic removal of lithium accumulated in the aluminum electrolyte. On the other hand, lithium-rich bauxite can also be considered a non-traditional lithium resource, and the extraction and recovery of lithium from it is of great significance for compensating for the insufficient lithium production from traditional lithium mines and salt lakes. Currently, the main technologies for extracting lithium from lithium-containing solutions include precipitation, solvent extraction, adsorption, and membrane methods. However, most of the reported methods are only applicable to extracting lithium from acidic and neutral solutions, and it is difficult to extract lithium from alkaline solutions, especially from concentrated alkaline solutions with a total alkali concentration greater than 40 g / L. In the alumina production process, the lithium content in the sodium aluminate solution after leaching is generally 0.05–0.1 g / L, but the total alkali concentration in this leaching solution is as high as 100–200 g / L, the alumina concentration is also high, the caustic solubility is low, and it is mostly an unstable supersaturated solution. In addition, the bauxite leaching solution from the Bayer process in industrial production also contains SiO2 and Na2O. x The presence of impurities such as fluoride ions, chloride ions, sulfate ions, and oxalate ions in the solution results in a complex composition, making selective and preferential separation and extraction of lithium extremely difficult.

[0004] Chinese patent CN 107500318B discloses a method for extracting lithium carbonate from sodium aluminate solution in an alumina plant. First, aluminum hydroxide seed crystals are added to an alkaline lithium-rich concentrate obtained by the Bayer process or sintering process to precipitate aluminum and adsorb and enrich lithium. The amount of seed crystals added and the reaction temperature are controlled to ensure that lithium in the Bayer process concentrate co-precipitates with the solid aluminum hydroxide. After lithium precipitation, high-lithium primary aluminum hydroxide (i.e., aluminum hydroxide) is separated from the concentrate. Then, the obtained high-lithium primary aluminum hydroxide is leached using a hydrothermal method at 180–300°C, allowing lithium to re-enter the solution. Finally, after solid-liquid separation, an inorganic acid such as hydrochloric acid is added to the resulting lithium-containing leachate for neutralization. The resulting brine solution is evaporated and concentrated until the lithium content is greater than or equal to 30 g / L. Then, a saturated sodium carbonate aqueous solution is added to crystallize and precipitate lithium carbonate. This method achieves lithium extraction from concentrated alkaline solutions obtained through the Bayer process. However, the resulting lithium carbonate product, after a series of processes including seed precipitation, hydrothermal dissolution, neutralization, evaporation concentration, and sodium carbonate precipitation, has low purity. The lithium extraction process is lengthy, and the overall lithium yield is low. Furthermore, the lack of specific requirements for aluminum hydroxide seed crystals means that coarser aluminum hydroxide particles are less likely to undergo agglomeration, resulting in unsatisfactory delithiation. In addition, the seed precipitation method is essentially a lithium-aluminum co-precipitation, which cannot selectively and preferentially separate and extract lithium from concentrated sodium aluminate alkaline solutions containing lithium.

[0005] Chinese patent CN 106950413B discloses a method and system for enriching lithium from sodium aluminate solution in an alumina plant. First, the lithium-containing sodium aluminate solution from the alumina plant is cooled to 60–85°C. A portion of this solution is diverted and aluminum hydroxide seed crystals are added to prepare aluminum hydroxide adsorbent. Then, the aluminum hydroxide adsorbent is added to the remaining cooled lithium-containing sodium aluminate solution to adsorb and precipitate lithium. The amount of aluminum hydroxide adsorbent added is controlled, and after sufficient reaction, the temperature is raised to 95–105°C, followed by solid-liquid separation. The resulting first filter cake is added to the alumina plant's circulating mother liquor and heated to boiling for redissolution, controlling only partial dissolution of alumina to further enrich lithium in the remaining aluminum hydroxide adsorbent. The redissolved slurry is filtered, and the resulting second filter cake is slurried, filtered again, and washed multiple times countercurrently to finally obtain a lithium-enriched third filter cake. The lithium content in the final aluminum-based lithium-rich slag is 4.0–6.0%. This method also employs the lithium-aluminum co-precipitation approach, but the resulting lithium-rich filter cake has a low lithium grade, requiring further separation and purification. Furthermore, while partial redissolution can partially dissolve high-lithium aluminum hydroxide, achieving some degree of lithium enrichment, the degree of partial dissolution is difficult to control due to the intercalation of lithium within the aluminum hydroxide crystal structure. This compromises efficient lithium dissolution and is energy-intensive.

[0006] Chinese patent CN 109761249B discloses a method and system for desorbing lithium from lithium-rich adsorbents in alumina plants. For lithium-rich adsorbents produced by lithium extraction from sodium aluminate solution using an adsorption method, a high-temperature, high-pressure hydrothermal leaching principle is further employed for lithium desorption. The hydrothermal reactor uses a fully piped slurry-to-slurry heat exchange technology, with a desorption temperature of 160–220℃ and a reaction time of 0.5–2 hours. Multiple countercurrent desorption processes are required to achieve a lithium content greater than 0.5 g / L in the desorbed solution. The hydrothermal desorption process is energy-intensive, especially with the piped treatment resulting in severe scaling and high costs for scaling removal.

[0007] Chinese patent CN 110627095B discloses a method for extracting lithium from the alumina production process and preparing battery-grade lithium carbonate. First, an alkaline lithium-rich concentrate obtained from the Bayer process or sintering process is cooled and neutralized with acidic compounds such as aluminum nitrate, aluminum sulfate, or aluminum chloride to prepare active aluminum hydroxide seed crystals. Then, the active seed crystals are mixed with a concentrated alkaline solution of sodium aluminate for an agglomeration reaction, precipitating and enriching lithium in the sodium aluminate solution. After solid-liquid separation, lithium-rich aluminum hydroxide solid is obtained. Next, the lithium-rich aluminum hydroxide is mixed with organic acids such as formic acid, acetic acid, propionic acid, butyric acid, and valeric acid to form a slurry. A microwave desorption reaction is carried out in a microwave reactor. After the reaction, solid-liquid separation is performed, yielding delithiated aluminum hydroxide as the solid and the filtrate as the lithium-rich desorption solution. Then, alkali is added to adjust the pH of the lithium-rich desorption solution to 2.5–5.0, and lithium purification inhibitors such as ammonium sulfate, ammonium chloride, and ammonium phosphate are added to remove aluminum ions, iron ions, calcium ions, and magnesium ions, obtaining a lithium-rich refined solution. Finally, after evaporation and concentration of the lithium-rich refined solution, a saturated sodium carbonate solution is added to precipitate lithium, yielding the lithium carbonate product. This method for extracting lithium from a concentrated alkaline solution containing lithium aluminate is lengthy and results in a low overall lithium yield.

[0008] Chinese patent CN 113277539A discloses a method for separating lithium and aluminum from the leaching solution of gibbsite monohydrate. First, at least one of lithium sulfate, lithium nitrate, lithium chloride, or lithium carbonate is mixed with at least one of titanium dioxide, titanium trichloride, or titanium tetrachloride in a specific ratio and calcined at 550–850°C for 2–6 hours to obtain lithium titanate. The obtained lithium titanate is then acid-washed and modified with dilute hydrochloric acid to obtain a titanium-based lithium-ion sieve. Next, the prepared titanium-based lithium-ion sieve is added to a concentrated alkaline sodium aluminate solution obtained after high-temperature leaching of gibbsite monohydrate bauxite using the Bayer process and separation of red mud. The temperature is controlled at 80–110°C, and the reaction is carried out for 1–4 hours. The solid and liquid phases are separated by filtration to obtain lithium-rich slag after lithium adsorption and loading, and a purified sodium aluminate solution after lithium removal. Then, the lithium-rich slag is desorbed using 2–10 g / L dilute hydrochloric acid to obtain a lithium-rich desorption solution. The desorbed and regenerated titanium-based lithium-ion sieve is recycled. However, this method is only suitable for lithium-aluminum separation when extracting lithium from concentrated alkaline sodium aluminate solutions. Its efficiency in separating other coexisting impurity ions, especially potassium and sodium ions, has not been reported, and the overall lithium yield is also low. Furthermore, the lithium ion sieve is not sufficiently stable and has poor reusability, especially exhibiting high dissolution rates during acid washing.

[0009] Chinese patent CN 115807169A discloses a method for lithium extraction from alkaline solutions. This method uses an organic polymer cross-linked resin grafted with special functional groups, as provided in Chinese patent CN 108421539A, as the lithium adsorbent material. It selectively adsorbs lithium ions from the alkaline solution, then replaces the lithium loaded on the adsorbent material with an alkaline high-lithium, low-impurity solution, followed by desorption with an acid solution, yielding a high-lithium salt solution with a lithium concentration of approximately 5 g / L. The high-lithium salt solution is then electrolyzed in a bipolar membrane system to prepare an alkaline high-lithium, low-impurity solution and an acid solution, which are used for lithium replacement and desorption from the adsorbent material. The resins used in this method, as provided in Chinese patent CN 108421539A, include weakly acidic phenolic resins with lithium-sodium separation capabilities, carboxyl-containing weakly acidic cation exchange resins, carbonyl-containing weakly acidic cation exchange resins, resins with phosphorus-oxygen double bonds, and resins with sulfur-oxygen double bonds, all capable of selectively adsorbing lithium ions in alkaline solutions. Alternatively, this method also uses the ion-sieve type lithium adsorbent provided in Chinese patent CN 102631897B, performing the same steps described above to selectively adsorb lithium from alkaline solutions. However, the applicable alkaline concentration cannot be too high; it is only suitable for alkaline lithium-containing solutions with a pH of 7–13 and cannot be used to extract lithium from concentrated alkaline solutions with a total alkaline concentration greater than 40 g / L. Furthermore, the alkaline high-lithium, low-impurity solution suitable for this method requires an alkaline solution in which the lithium ion concentration is higher than the concentration of other coexisting ions; it is not applicable to concentrated alkaline sodium aluminate solutions obtained after high-temperature leaching of lithium-rich bauxite using the Bayer process.

[0010] Xu Xin et al. previously studied the application of lithium-ion sieves in caustic alkali systems (Xu Xin, Design, Preparation and Performance Study of High-Efficiency Lithium-Ion Selective Adsorption Materials, Beijing University of Chemical Technology, Doctoral Dissertation, 2017). They used lithium-ion sieves to adsorb lithium ions from a NaOH solution system at room temperature. However, the alumina concentration in this system was extremely low, only tens of ppm, essentially a stable alkali solution system, not the unstable sodium aluminate solution system commonly used in the alumina industry. Therefore, their results are only applicable to stable caustic alkali solutions with extremely low alumina concentrations.

[0011] In summary, for the sodium aluminate concentrated alkaline solution obtained after high-temperature leaching of lithium-rich bauxite by the Bayer process, due to its complex solution composition, high concentration of coexisting impurity ions, and high total alkali concentration, none of the existing publicly reported methods are applicable. Summary of the Invention

[0012] To address the shortcomings of existing technologies, the present invention aims to provide a method for selectively extracting, precipitating, and enriching lithium from lithium-containing alkaline aqueous solutions. In particular, it provides a method for selectively extracting, precipitating, and enriching lithium from a concentrated alkaline sodium aluminate solution obtained after high-temperature leaching of lithium-rich bauxite using the Bayer process. This method is simple to operate, low in cost, and has a wide range of applications.

[0013] The present invention achieves the above objectives and methods through the following technical solutions:

[0014] The method for selectively extracting and precipitating lithium from a lithium-containing alkaline aqueous solution includes the following steps:

[0015] (1) Weigh a certain mass of cycloalkanoic acid compound, alkylphenoxycarboxylic acid derivative, or a mixture of the two in a certain mass ratio, add it to a lithium-containing alkaline aqueous solution, stir and mix at room temperature for 5 minutes to 1 hour to obtain a liquid-solid two-phase mixture;

[0016] (2) After diluting the liquid-solid two-phase mixture obtained in step (1) with water by 20 to 50 times, add flocculant, stir and let stand for a period of time, then filter or centrifuge to obtain solid matter;

[0017] (3) Wash the solid obtained in step (2) with deionized water until the filtrate is neutral, then add the back-extraction agent aqueous solution at a certain mass ratio, stir and mix at 20-80℃ for 5 minutes to 1 hour, cool to room temperature, and obtain a liquid-liquid two-phase mixture or a liquid-solid two-phase mixture;

[0018] (4) Centrifuge the liquid-liquid two-phase mixture obtained in step (3) to separate the phases. Wash the upper liquid phase with deionized water until neutral, and then return it to step (1) to add it to the lithium-containing alkaline aqueous solution to repeat steps (1) to (4) for use. Alternatively, filter or centrifuge the liquid-solid two-phase mixture obtained in step (3). Wash the solid obtained with deionized water until the filtrate is neutral, and then return it to step (1) to add it to the lithium-containing alkaline aqueous solution to repeat steps (1) to (4) for use.

[0019] (5) Collect the lower liquid phase obtained after centrifugation and phase separation of the liquid-liquid two-phase mixture in step (4), and determine the lithium concentration and impurity ion concentration therein. Further, collect the filtrate obtained after filtration or centrifugation of the liquid-solid two-phase mixture in step (4), and determine the lithium concentration and impurity ion concentration therein.

[0020] According to a specific embodiment of the present invention, the cycloalkanoic acid compound in step (1) includes any one of cycloalkanoic acids or their derivatives.

[0021] The cycloalkanoic acid derivative has the following structural formula:

[0022]

[0023] In formula (1), n ​​is an integer from 0 to 16; R1 can be a straight-chain alkyl group with 1 to 15 carbon atoms or a branched alkyl group with 1 to 15 carbon atoms, preferably an alkyl group with 5 to 10 carbon atoms, and more preferably an octyl or nonyl group.

[0024] According to a specific embodiment of the present invention, the cycloalkanoic acid derivative is preferably octylcyclopentylpropionic acid, nonylcyclopentylbutyric acid, or nonylcyclopentylhexanoic acid.

[0025] According to a specific embodiment of the present invention, the source of the naphthenic acid or its derivative is not particularly limited; it can be purchased from the market or synthesized using compound synthesis methods well known to those skilled in the art. Preferably, the purity of the naphthenic acid or its derivative is greater than 98%.

[0026] According to a specific embodiment of the present invention, the molecular structure of the alkylphenoxycarboxylic acid derivative in step (1) contains at least one phenoxy group and one or more carboxyl groups, including but not limited to sec-octylphenoxyacetic acid, p-tert-butylphenoxyacetic acid, p-tert-octylphenoxyacetic acid, 2-(4-(2,4,4-trimethylpentyl-2-yl)phenoxy)acetic acid, 2-(4-butoxyphenoxy)acetic acid, 4-(4-butoxyphenoxy)butyric acid, 2-(4-benzyloxyphenoxy)acetic acid, 2,2'-(1 Any one of the following: 4-phenylenebis(oxy)dioctanoic acid, 2,2'-(1,2-phenylenebis(oxy)dioctanoic acid, 2,2'-(1,3-phenylenebis(oxy)dioctanoic acid, 2,2'-((cyclohexane-1,1-diylbis(4,1-phenylene))bis(oxy))diacetic acid, 2,2'-((oxybis(4,1-phenylene))bis(oxy))diacetic acid, and 2,2'-((propane-2,2-diylbis(4,1-phenylene))bis(oxy))diacetic acid.

[0027] According to a specific embodiment of the present invention, the alkylphenoxycarboxylic acid derivative in step (1) is preferably any one of p-tert-octylphenoxyacetic acid and 2-(4-(2,4,4-trimethylpentyl-2-yl)phenoxy)acetic acid.

[0028] According to a specific embodiment of the present invention, the source of the alkylphenoxycarboxylic acid derivative is not particularly limited; it can be purchased from the market or synthesized using compound synthesis methods well known to those skilled in the art. Preferably, the purity of the alkylphenoxycarboxylic acid derivative is greater than 95%.

[0029] According to a specific embodiment of the present invention, in the mixture of the cycloalkanoic acid compound and the alkylphenoxycarboxylic acid derivative in step (1), the molar ratio of the cycloalkanoic acid compound to the alkylphenoxycarboxylic acid derivative is (40-90):(10-60), preferably (50-80):(20-50), and more preferably (60-70):(30-40).

[0030] According to a specific embodiment of the present invention, the purpose of adding the mixture of cycloalkanoic acid compound and alkylphenoxycarboxylic acid derivative in step (1) is that both can selectively combine with lithium ions in alkaline solution to form compounds preferentially over other coexisting impurity ions. When both are added simultaneously, their synergistic extraction effect can achieve efficient capture of low-concentration lithium in alkaline aqueous solution.

[0031] According to a specific embodiment of the present invention, the amount of cycloalkanoic acid compound, alkylphenoxycarboxylic acid derivative, or a mixture thereof added in step (1) is in a molar ratio of 1:1 to 5:1 with lithium in the lithium-containing alkaline aqueous solution.

[0032] According to a specific embodiment of the present invention, the flocculant in step (2) is any one of polyaluminum chloride, polyaluminum sulfate, polyferric chloride, polyferric sulfate, or polyacrylamide, or a mixture thereof.

[0033] According to a specific embodiment of the present invention, the mass of the flocculant added in step (2) is 0.01 to 0.08% of the mass of the lithium-containing alkaline aqueous solution.

[0034] According to a specific embodiment of the present invention, the purpose of diluting the liquid-solid two-phase mixture obtained in step (2) with water by 20 to 50 times is to promote the flocculation effect of the flocculant and to capture and flocculate the solids in the liquid-solid two-phase mixture in step (1).

[0035] According to a specific embodiment of the present invention, when the particle size of the solid particles in the liquid-solid two-phase mixture obtained in step (1) is greater than 0.1 micrometers, it is not necessary to dilute with water or add flocculant.

[0036] According to a specific embodiment of the present invention, the aqueous solution of the stripping agent in step (3) is an aqueous solution of hydrochloric acid or sulfuric acid, and the concentration of hydrochloric acid or sulfuric acid is 1 mol / L to 6 mol / L.

[0037] According to a specific embodiment of the present invention, the aqueous solution of the stripping agent in step (3) may also be an aqueous solution of magnesium sulfate with pH 1 to 3, or an aqueous solution of aluminum sulfate, or a mixed aqueous solution of both magnesium sulfate and aluminum sulfate. The concentration of magnesium sulfate is 0.1 mol / L to 0.3 mol / L, and the concentration of aluminum sulfate is 0.05 mol / L to 0.1 mol / L.

[0038] According to a specific embodiment of the present invention, the mass ratio of the back-extraction agent aqueous solution in step (3) to the solid obtained in step (2) is 50:1 to 1:1.

[0039] According to a specific embodiment of the present invention, the purpose of adding the back-extraction agent in step (3) and first stirring and mixing it at a temperature of 20-80°C for 5 minutes to 1 hour, and then cooling it to room temperature, is that the alkylphenoxycarboxylic acid derivative after back-extraction and regeneration is in a liquid state at a temperature greater than 40°C and less than 80°C, and then transforms into a solid state after cooling to room temperature. At this time, the entire system obtained after cooling to room temperature is a liquid-solid two-phase mixture. Furthermore, the naphthenic acid compound after back-extraction and regeneration is in a liquid state at a temperature of 20-80°C, and remains in a liquid state after cooling to room temperature. At this time, the entire system obtained after cooling to room temperature is a liquid-liquid two-phase mixture.

[0040] According to a specific embodiment of the present invention, the lithium-containing alkaline aqueous solution in step (1) can be a lithium-containing sodium hydroxide aqueous solution, wherein the mass concentration of lithium is 10-1000 mg / L and the mass concentration of sodium hydroxide is 4-250 g / L.

[0041] According to a specific embodiment of the present invention, the lithium-containing alkaline aqueous solution in step (1) can also be a concentrated alkaline sodium aluminate solution obtained after high-temperature leaching of lithium-rich bauxite using the Bayer process, and its solution composition is Na2O. k Concentration: 160–171 g / L, Al₂O₃ concentration: 180–194 g / L, caustic ratio a k : 1.4~1.5, Li2O concentration: 60~70mg / L, SiO2 concentration: 0.6~1.0g / L, Na2O c Concentration: 5–20 g / L.

[0042] The principle of the method for selectively extracting and precipitating lithium from a lithium-containing alkaline aqueous solution according to the present invention is that the alkylphenoxycarboxylic acid derivative contains phenoxy and carboxyl groups in its molecular structure, and the molecular structure of the cycloalkanoic acid compound is shown in formula (1). In a concentrated alkaline medium, after the carboxyl functional group of the cycloalkanoic acid compound, the alkylphenoxycarboxylic acid derivative, or a mixture of the two ionizes into hydrogen ions, its association ability with various cations follows the Hoffmeister ion sequence, that is: Li + >Na + >K + >Mg 2+ >Ca 2+ Lithium ions have a greater affinity for carboxyl groups than aluminate ions in alkaline solutions. Therefore, the alkylphenoxycarboxylic acid derivatives and naphthenic acid compounds can selectively bind to lithium ions preferentially over other coexisting ions. Furthermore, since the compounds formed after association between the alkylphenoxycarboxylic acid derivatives, naphthenic acid compounds, and lithium ions are insoluble in alkaline aqueous solutions at room temperature, they ultimately precipitate from the alkaline aqueous solution as solid precipitates. Upon addition of the stripping agent aqueous solution, excess hydrogen ions in the stripping agent aqueous solution undergo a cation exchange reaction with lithium ions. Therefore, the carboxyl groups of the alkylphenoxycarboxylic acid derivatives and naphthenic acid compounds are regenerated. By controlling a specific solid-to-mass ratio in the stripping solution, lithium ions are enriched in the final stripping solution.

[0043] Compared with other disclosed technical solutions, the present invention has the following beneficial effects:

[0044] 1) The cycloalkanoic acid compounds, alkylphenoxycarboxylic acid derivatives, or mixtures thereof described in this invention do not require saponification pretreatment before use and can be directly added to a concentrated lithium-containing alkaline solution for the extraction and precipitation of lithium.

[0045] 2) The method provided by this invention can selectively extract and precipitate low-concentration lithium from concentrated alkaline solutions containing sodium hydroxide at a mass concentration of 4–250 g / L. It is particularly suitable for selectively extracting, precipitating, and enriching lithium from concentrated alkaline solutions of sodium aluminate obtained after high-temperature leaching of lithium-rich bauxite using the Bayer process. This method can achieve efficient separation from other coexisting impurity ions in the concentrated alkaline solution, such as sodium, potassium, aluminum, silicon, iron, and calcium. The lithium extraction and precipitation yield is over 90%, while the precipitation rate of other coexisting impurity ions is less than 5%, effectively avoiding the generation of slag in traditional processes.

[0046] 3) The cycloalkanoic acid compounds, alkylphenoxycarboxylic acid derivatives, or mixtures thereof described in this invention combine with lithium in a concentrated alkaline solution to form a small-volume solid extract, which can achieve efficient enrichment of low-concentration lithium in a large volume of concentrated alkaline aqueous solution, with a high enrichment factor and a fast extraction and precipitation reaction rate.

[0047] 4) The naphthenic acid compounds, alkylphenoxycarboxylic acid derivatives, or mixtures thereof described in this invention can be regenerated and repeatedly recycled after extraction and back-extraction, while maintaining their selective extraction and precipitation characteristics for lithium. The extraction process does not use other organic solvents, and no wastewater, waste gas, or waste residue is generated. The process cost is low, the operation is simple and convenient, and it has good prospects for industrial application and promotion value.

[0048] 5) The method provided by this invention has a wide range of applications, a simple process flow, and low cost. Besides being used for the selective extraction, precipitation, and enrichment of lithium from concentrated sodium aluminate solutions obtained after high-temperature leaching of lithium-rich bauxite using the Bayer process, it is also suitable for the selective extraction and recovery of lithium from other alkaline aqueous solutions and wastewater containing low concentrations of lithium. The lithium extraction and precipitation process is not affected by ions such as fluoride, chloride, sulfate, and oxalate in the alkaline solution, making the process widely applicable. Detailed Implementation

[0049] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows. Those skilled in the art should understand that these embodiments are merely illustrative of the present invention and should not be considered as specific limitations thereof.

[0050] Example 1

[0051] Refined naphthenic acid was purchased from Shanghai Laya Chemical Co., Ltd., with a molecular weight of 126.15, a pure acid value of 240 mg KOH / g, and a moisture content of less than 1%. 3.57 mmol of naphthenic acid was weighed and directly added to 500 mL of an alkaline aqueous solution containing 10 mg / L lithium and 4 g / L sodium hydroxide. The mixture was stirred at room temperature for 10 minutes to obtain a liquid-solid two-phase mixture. Then, 10 L of deionized water and 8.4 g of polyaluminum chloride flocculant were added to this liquid-solid two-phase mixture. After slow stirring and standing for 30 minutes, the mixture was filtered to obtain a solid. The obtained solid was washed with deionized water until the filtrate was neutral, and then 50 mL of a 3 mol / L hydrochloric acid aqueous solution was added. The mixture was stirred at room temperature for 10 minutes to obtain a liquid-liquid two-phase mixture. After centrifugation and phase separation, a sample of the lower liquid phase was taken and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the lithium concentration and impurity ion concentration. The results showed that in the final stripped lower liquid phase, the lithium ion concentration was 1.07 g / L, the aluminum ion concentration was below the analytical limit, and the sodium ion concentration was 119 mg / L. The total lithium yield was 89.3%.

[0052] Example 2

[0053] 714 mmol of p-tert-octylphenoxyacetic acid was weighed and directly added to 5 L of an alkaline aqueous solution containing 1000 mg / L lithium and 150 g / L sodium hydroxide. The mixture was stirred at room temperature for 60 minutes to obtain a liquid-solid two-phase mixture. Then, 250 L of deionized water and 25.5 g of flocculant polyacrylamide were added to this liquid-solid two-phase mixture. After slow stirring, the mixture was centrifuged to obtain a solid. The solid was washed with deionized water until the filtrate was neutral, and then 100 mL of 6 mol / L sulfuric acid aqueous solution was added. The mixture was stirred at 80 °C for 30 minutes and then cooled to room temperature to obtain another liquid-solid two-phase mixture. The resulting liquid-solid two-phase mixture was filtered, and the filtrate was sampled and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the lithium and impurity ion concentrations. The results showed that the lithium ion concentration in the final back-extraction filtrate was 27.33 g / L, the aluminum ion concentration was below the analytical limit, and the sodium ion concentration was 82 mg / L. The total lithium yield was 91.2%.

[0054] Example 3

[0055] Weigh 4.2 mmol of octylcyclopentylpropionic acid and 2.8 mmol of p-tert-butylphenoxyacetic acid. Mix them and add them directly to 500 mL of an alkaline aqueous solution containing 100 mg / L lithium and 200 g / L sodium hydroxide. Stir and mix at room temperature for 30 minutes to obtain a liquid-solid two-phase mixture. Then, add 25 L of deionized water and 10.2 g of flocculant polyaluminum sulfate to this liquid-solid two-phase mixture. Stir slowly and let stand for 30 minutes, then filter to obtain a solid. Wash the obtained solid with deionized water until the filtrate is neutral. Add 40 mL of a 0.1 mol / L magnesium sulfate aqueous solution (pH 1). Stir and mix at 40 °C for 30 minutes, then cool to room temperature to obtain a liquid-solid two-phase mixture. Centrifuge the obtained liquid-solid two-phase mixture, and sample the filtrate. Analyze the lithium concentration and impurity ion concentration using inductively coupled plasma mass spectrometry (ICP-MS). The results showed that the concentration of lithium ions in the final back-extraction filtrate was 1.03 g / L, and the concentration of sodium ions was 55.3 mg / L. The total lithium yield was 93.6%.

[0056] Example 4

[0057] Weigh 214 mmol of 2-(4-(2,4,4-trimethylpentan-2-yl)phenoxy)acetic acid and add it directly to 50 liters of concentrated sodium aluminate solution obtained from the Bayer process high-temperature leaching of lithium-rich bauxite. The Na₂O₂ content... k Concentration: 162 g / L, Al2O3 concentration: 182 g / L, caustic ratio a k : 1.46, Li2O concentration: 60 mg / L, SiO2 concentration: 0.71 g / L, Na2O c Concentration: 12 g / L. The mixture was stirred at room temperature for 30 minutes to obtain a liquid-solid two-phase mixture. Then, 1000 L of deionized water and 105 g of flocculant polyacrylamide were added to this mixture. The mixture was slowly stirred and allowed to stand for 30 minutes before filtration to obtain a solid. The solid was washed with deionized water until the filtrate was neutral. Then, 130 mL of 1 mol / L sulfuric acid aqueous solution was added, and the mixture was stirred at 80 °C for 30 minutes. The mixture was then cooled to room temperature to obtain another liquid-solid two-phase mixture. The resulting liquid-solid two-phase mixture was centrifuged, and the filtrate was sampled and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the lithium and impurity ion concentrations. The results showed that in the final back-extraction filtrate, the lithium ion concentration was 1.32 g / L, the aluminum ion concentration was below the analytical limit, and the sodium ion concentration was 177 mg / L. The total lithium yield was 94.1%.

[0058] Example 5

[0059] Weigh 40.6 mmol of nonylcyclopentylbutyric acid and 17.4 mmol of 2-(4-(2,4,4-trimethylpent-2-yl)phenoxy)acetic acid. Mix them and add them directly to 5 liters of concentrated sodium aluminate solution obtained from the Bayer process high-temperature leaching of lithium-rich bauxite. The Na₂O₂ content is... k Concentration: 171 g / L, Al2O3 concentration: 194 g / L, caustic ratio a k : 1.45, Li2O concentration: 65 mg / L, SiO2 concentration: 0.75 g / L, Na2O c Concentration: 15 g / L. The mixture was stirred at room temperature for 5 minutes to obtain a liquid-solid two-phase mixture. Then, 250 L of deionized water and 25.5 g of flocculant polyferric chloride were added to this mixture. The mixture was slowly stirred and allowed to stand for 30 minutes before filtration to obtain a solid. The solid was washed with deionized water until the filtrate was neutral. Then, 50 mL of a pH 1 aluminum sulfate aqueous solution (0.05 mol / L) was added. The mixture was stirred at 60 °C for 30 minutes and then cooled to room temperature to obtain another liquid-solid two-phase mixture. The mixture was centrifuged, and the lower liquid phase was sampled and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the lithium and impurity ion concentrations. The results showed that the lithium ion concentration in the final lower liquid phase after back-extraction was 1.06 g / L, and the sodium ion concentration was 313 mg / L. The total lithium yield was 90.5%.

[0060] Example 6

[0061] Weigh 562 mmol of 2,2'-(1,4-phenylenebis(oxy)yl)dioctanoic acid and add it directly to 50 liters of concentrated sodium aluminate solution obtained from the Bayer process high-temperature leaching of lithium-rich bauxite. The Na₂O₂ content... k Concentration: 165 g / L, Al2O3 concentration: 186 g / L, caustic ratio a k : 1.46, Li2O concentration: 63 mg / L, SiO2 concentration: 0.73 g / L, Na2O cConcentration: 15 g / L. The mixture was stirred at room temperature for 5 minutes to obtain a liquid-solid two-phase mixture. Then, 1000 L of deionized water and 840 g of flocculant polyferric sulfate were added to this mixture. The mixture was slowly stirred and allowed to stand for 30 minutes before centrifugation to separate the liquid-solid mixture, yielding a solid. The obtained solid was washed with deionized water until the filtrate was neutral. Then, 100 mL of a mixed aqueous solution of magnesium sulfate and aluminum sulfate (pH 3, 0.3 mol / L for magnesium sulfate and 0.1 mol / L for aluminum sulfate) was added. The mixture was stirred at 40 °C for 30 minutes and then cooled to room temperature to obtain another liquid-solid two-phase mixture. The resulting liquid-solid mixture was filtered, and the filtrate was sampled and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the lithium and impurity ion concentrations. The results showed that the lithium ion concentration in the final back-extraction filtrate was 0.93 g / L, and the sodium ion concentration was 219 mg / L. The total lithium yield was 92.8%.

[0062] Example 7

[0063] Weigh 348 mmol of 2,2'-((cyclohexane-1,1-diylbis(4,1-phenylene))bis(oxy))diacetic acid and add it directly to 50 liters of concentrated sodium aluminate solution obtained from the Bayer process high-temperature leaching of lithium-rich bauxite. The Na₂O₂ content... k Concentration: 166 g / L, Al2O3 concentration: 186 g / L, caustic ratio a k : 1.47, Li2O concentration: 65 mg / L, SiO2 concentration: 0.68 g / L, Na2O c Concentration: 13 g / L. The mixture was stirred at room temperature for 10 minutes to obtain a liquid-solid two-phase mixture. Then, 1000 L of deionized water and 105 g of flocculant polyacrylamide were added to this mixture. The mixture was slowly stirred and allowed to stand for 30 minutes before centrifugation to obtain a solid. The solid was washed with deionized water until the filtrate was neutral, and then 100 mL of 6 mol / L hydrochloric acid aqueous solution was added. The mixture was stirred at 40 °C for 30 minutes and then cooled to room temperature to obtain another liquid-solid two-phase mixture. The resulting liquid-solid two-phase mixture was centrifuged, and the filtrate was sampled and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the lithium and impurity ion concentrations. The results showed that the lithium ion concentration in the final back-extraction filtrate was 1.59 g / L, the aluminum ion concentration was below the analytical limit, and the sodium ion concentration was 96 mg / L. The total lithium yield was 88.5%.

[0064] Example 8

[0065] Weigh 57.1 mmol of nonylcyclopentylhexanoic acid and 57.1 mmol of 2,2'-((oxybis(4,1-phenylene))bis(oxy))diacetic acid, mix them, and add them directly to 50 liters of concentrated sodium aluminate solution obtained from the Bayer process high-temperature leaching of lithium-rich bauxite. The Na₂O₂ content is... k Concentration: 171 g / L, Al2O3 concentration: 190 g / L, caustic ratio a k : 1.48, Li2O concentration: 64 mg / L, SiO2 concentration: 0.76 g / L, Na2O c Concentration: 14 g / L. The mixture was stirred at room temperature for 5 minutes to obtain a liquid-solid two-phase mixture. Then, 1500 L of deionized water and 310 g of flocculant polyacrylamide were added to this mixture. The mixture was slowly stirred and allowed to stand for 30 minutes before filtration to obtain a solid. The solid was washed with deionized water until the filtrate was neutral, and then 140 mL of 3 mol / L sulfuric acid aqueous solution was added. The mixture was stirred at 80 °C for 30 minutes and then cooled to room temperature to obtain another liquid-solid two-phase mixture. The resulting liquid-solid two-phase mixture was centrifuged, and the lower liquid phase after separation was sampled and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the lithium and impurity ion concentrations. The results showed that in the final lower liquid phase after back-extraction, the lithium ion concentration was 1.87 g / L, the aluminum ion concentration was below the analytical limit, and the sodium ion concentration was 227 mg / L. The total lithium yield was 82.7%.

[0066] Example 9

[0067] Weigh 1.51 mol of 2,2'-((propane-2,2-diylbis(4,1-phenylene))bis(oxy))diacetic acid, and then add the mixture directly to 50 L of an alkaline aqueous solution containing 530 mg / L lithium and 250 g / L sodium hydroxide. Stir and mix at room temperature for 5 minutes to obtain a liquid-solid two-phase mixture. Then, add 1000 L of deionized water and 315 g of flocculant polyaluminum sulfate to this liquid-solid two-phase mixture, stir slowly, let stand for 30 minutes, and then centrifuge to separate the liquid-solid two-phase mixture to obtain a solid. Wash the obtained solid with deionized water until the filtrate is neutral, add 150 mL of 6 mol / L sulfuric acid aqueous solution, stir and mix at 50 °C for 30 minutes, and then cool to room temperature to obtain a liquid-solid two-phase mixture. The resulting liquid-solid two-phase mixture was centrifuged, and the lower liquid phase after separation was sampled and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the lithium and impurity ion concentrations. The results showed that in the final stripped lower liquid phase, the lithium ion concentration was 1.24 g / L, the aluminum ion concentration was below the analytical limit, and the sodium ion concentration was 116 mg / L. The total lithium yield was 86.9%.

[0068] Example 10

[0069] Weigh 450 mmol of 2-(4-benzyloxyphenoxy)acetic acid and add it directly to 50 liters of concentrated sodium aluminate solution obtained from the Bayer process high-temperature leaching of lithium-rich bauxite. The Na₂O₂ content is... k Concentration: 166 g / L, Al2O3 concentration: 186 g / L, caustic ratio a k : 1.47, Li2O concentration: 63 mg / L, SiO2 concentration: 0.68 g / L, Na2O c Concentration: 13 g / L. The mixture was stirred at room temperature for 5 minutes to obtain a liquid-solid two-phase mixture. Then, 2000 L of deionized water and 205 g of flocculant polyacrylamide were added to this mixture. The mixture was slowly stirred and allowed to stand for 30 minutes before filtration to obtain a solid. The solid was washed with deionized water until the filtrate was neutral. Then, 200 mL of a mixed aqueous solution of magnesium sulfate and aluminum sulfate (pH 1, concentration 0.3 mol / L) and aluminum sulfate (concentration 0.05 mol / L) were added. The mixture was stirred at 40 °C for 30 minutes and then cooled to room temperature to obtain another liquid-solid two-phase mixture. The resulting liquid-solid two-phase mixture was filtered and separated. A sample of the filtrate was taken and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the lithium and impurity ion concentrations. The results showed that the lithium ion concentration in the final back-extraction filtrate was 1.47 g / L, and the sodium ion concentration was 102 mg / L. The total lithium yield was 93.3%.

[0070] Example 11

[0071] Weigh 180 mmol of naphthenic acid and 45 mmol of 2-(4-butoxyphenoxy)acetic acid, mix them, and add them directly to 50 liters of concentrated sodium aluminate solution obtained from the Bayer process high-temperature leaching of lithium-rich bauxite. The Na₂O₂ content... k Concentration: 165 g / L, Al2O3 concentration: 186 g / L, caustic ratio a k : 1.46, Li2O concentration: 63 mg / L, SiO2 concentration: 0.73 g / L, Na2O cConcentration: 15 g / L. The mixture was stirred at room temperature for 10 minutes to obtain a liquid-solid two-phase mixture. Then, 2500 L of deionized water and 510 g of flocculant polyferric chloride were added to this mixture. The mixture was slowly stirred and allowed to stand for 30 minutes before filtration to obtain a solid. The solid was washed with deionized water until the filtrate was neutral. Then, 70 mL of a pH 1 aluminum sulfate aqueous solution (0.1 mol / L) was added. The mixture was stirred at 40 °C for 5 minutes and then cooled to room temperature to obtain another liquid-solid two-phase mixture. The mixture was centrifuged, and the lower liquid phase was sampled and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the lithium and impurity ion concentrations. The results showed that the lithium ion concentration in the final lower liquid phase after back-extraction was 1.68 g / L, and the sodium ion concentration was 22 mg / L. The total lithium yield was 92.5%.

[0072] Example 12

[0073] Weigh 550 mmol of octylcyclopentylpropionic acid and 61 mmol of 2,2'-(1,2-phenylenebis(oxy)yl)dioctanoic acid. Mix them and add them directly to 50 liters of concentrated sodium aluminate solution obtained from the Bayer process high-temperature leaching of lithium-rich bauxite. The Na₂O₂ content is... k Concentration: 165 g / L, Al2O3 concentration: 186 g / L, caustic ratio a k : 1.46, Li2O concentration: 63 mg / L, SiO2 concentration: 0.73 g / L, Na2O c Concentration: 15 g / L. The mixture was stirred at room temperature for 30 minutes to obtain a liquid-solid two-phase mixture. Then, 2500 L of deionized water and 255 g of flocculant polyacrylamide were added to this mixture. The mixture was slowly stirred and allowed to stand for 30 minutes before filtration to obtain a solid. The solid was washed with deionized water until the filtrate was neutral. Then, 100 mL of a pH 1 aluminum sulfate aqueous solution (0.1 mol / L) was added. The mixture was stirred at 80 °C for 60 minutes and then cooled to room temperature to obtain another liquid-solid two-phase mixture. The mixture was centrifuged, and the lower liquid phase was sampled and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the lithium and impurity ion concentrations. The results showed that the lithium ion concentration in the final lower liquid phase after back-extraction was 1.73 g / L, and the sodium ion concentration was 88 mg / L. The total lithium yield was 91.9%.

[0074] Example 13

[0075] Weigh 348 mmol of 2-(4-(2,4,4-trimethylpentan-2-yl)phenoxy)acetic acid and add it directly to 50 liters of concentrated sodium aluminate solution obtained from the Bayer process high-temperature leaching of lithium-rich bauxite. The Na₂O₂ content... kConcentration: 166 g / L, Al2O3 concentration: 186 g / L, caustic ratio a k : 1.47, Li2O concentration: 65 mg / L, SiO2 concentration: 0.68 g / L, Na2O c Concentration: 13 g / L. The mixture was stirred at room temperature for 10 minutes to obtain a liquid-solid two-phase mixture. The particle size of the solid particles in the liquid-solid two-phase mixture was determined to be 0.74 μm. Without dilution with water or flocculant, the resulting liquid-solid two-phase mixture was allowed to stand for 30 minutes and then centrifuged to obtain solids. The solids were then washed with deionized water until the filtrate was neutral, and 135 mL of 6 mol / L sulfuric acid aqueous solution was added. The mixture was stirred at 60 °C for 60 minutes and then cooled to room temperature to obtain another liquid-solid two-phase mixture. The resulting liquid-solid two-phase mixture was centrifuged, and the filtrate was sampled and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the lithium and impurity ion concentrations. The results showed that in the final back-extraction filtrate, the lithium ion concentration was 1.66 g / L, the aluminum ion concentration was below the analytical limit, and the sodium ion concentration was 83 mg / L. The total lithium yield was 91.6%.

[0076] The applicant declares that the specific implementation schemes of the present invention are illustrated by the above embodiments, but the present invention is not limited to the above steps, that is, it does not mean that the present invention must rely on the above steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, including equivalent substitutions of the raw materials used in the present invention, the addition of auxiliary components, and the selection of specific methods, all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for selectively extracting and precipitating lithium from a lithium-containing alkaline aqueous solution, characterized in that, Includes the following steps: (1) Weigh a certain mass of cycloalkanoic acid compound, alkylphenoxycarboxylic acid derivative, or a mixture of the two in a certain mass ratio, add it to a lithium-containing alkaline aqueous solution, stir and mix at room temperature for 5 minutes to 1 hour to obtain a liquid-solid two-phase mixture; (2) After diluting the liquid-solid two-phase mixture obtained in step (1) with water by 20 to 50 times, add flocculant, stir and let stand for a period of time, then filter or centrifuge to obtain solid matter; (3) Wash the solid obtained in step (2) with deionized water until the filtrate is neutral, then add the back-extraction agent aqueous solution at a certain mass ratio, stir and mix at 20-80℃ for 5 minutes to 1 hour, cool to room temperature, and obtain a liquid-liquid two-phase mixture or a liquid-solid two-phase mixture; (4) Centrifuge the liquid-liquid two-phase mixture obtained in step (3) to separate the phases. Wash the upper liquid phase with deionized water until it is neutral, and then return to step (1) to add it to the lithium-containing alkaline aqueous solution to repeat steps (1) to (4) for use; or filter or centrifuge the liquid-solid two-phase mixture obtained in step (3). Wash the solid obtained with deionized water until the filtrate is neutral, and then return to step (1) to add it to the lithium-containing alkaline aqueous solution to repeat steps (1) to (4) for use; (5) Collect the lower liquid phase obtained after centrifugation and phase separation of the liquid-liquid two-phase mixture in step (4), and determine the lithium concentration and impurity ion concentration therein; or collect the filtrate obtained after filtration or centrifugation of the liquid-solid two-phase mixture in step (4), and determine the lithium concentration and impurity ion concentration therein.

2. The method for selectively extracting and precipitating lithium from a lithium-containing alkaline aqueous solution as described in claim 1, characterized in that, The cycloalkanoic acid compound in step (1) includes any one of cycloalkanoic acids or their derivatives; the cycloalkanoic acid derivative has the following structural formula: (Equation 1) In formula (1), n ​​is an integer from 0 to 16; R1 is a straight-chain alkyl group with 1 to 15 carbon atoms, or a branched alkyl group with 1 to 15 carbon atoms.

3. The method for selectively extracting and precipitating lithium from a lithium-containing alkaline aqueous solution as described in claim 2, characterized in that, The cycloalkanoic acid derivative is any one of octylcyclopentylpropionic acid, nonylcyclopentylbutyric acid, or nonylcyclopentylhexanoic acid.

4. The method for selectively extracting and precipitating lithium from a lithium-containing alkaline aqueous solution as described in claim 1, characterized in that, The alkylphenoxycarboxylic acid derivative in step (1) contains at least one phenoxy group and one or more carboxyl groups in its molecular structure, including sec-octylphenoxyacetic acid, p-tert-butylphenoxyacetic acid, p-tert-octylphenoxyacetic acid, 2-(4-(2,4,4-trimethylpentyl-2-yl)phenoxy)acetic acid, 2-(4-butoxyphenoxy)acetic acid, 4-(4-butoxyphenoxy)butyric acid, 2-(4-benzyloxyphenoxy)acetic acid, 2,2 ’ -(1,4-phenylenebis(oxy)dioctanoic acid, 2,2 ’ -(1,2-phenylenebis(oxy)dioctanoic acid, 2,2 ’ -(1,3-phenylenebis(oxy)dioctanoic acid, 2,2 ’ -((cyclohexane-1,1-diylbis(4,1-phenylene))bis(oxy))diacetic acid, 2,2 ’ -((oxybis(4,1-phenylene))bis(oxy))diacetic acid, 2,2 ’ Any one of -((propane-2,2-dimethylbis(4,1-phenylene))bis(oxy))diacetic acid.

5. The method for selectively extracting and precipitating lithium from a lithium-containing alkaline aqueous solution as described in claim 1, characterized in that, In step (1), the molar ratio of the cycloalkanoic acid compound to the alkylphenoxycarboxylic acid derivative in the mixture is (40-90):(10-60).

6. The method for selectively extracting and precipitating lithium from a lithium-containing alkaline aqueous solution as described in claim 1, characterized in that, The amount of the cycloalkanoic acid compound, alkylphenoxycarboxylic acid derivative, or a mixture thereof added in step (1) is in a molar ratio of 1:1 to 5:1 with the lithium ions in the lithium-containing alkaline aqueous solution.

7. The method for selectively extracting and precipitating lithium from a lithium-containing alkaline aqueous solution as described in claim 1, characterized in that, The flocculant in step (2) is any one or a mixture of polyaluminum chloride, polyaluminum sulfate, polyferric chloride, polyferric sulfate, or polyacrylamide, and the mass of the flocculant added is 0.01 to 0.08% of the mass of the lithium-containing alkaline aqueous solution.

8. The method for selectively extracting and precipitating lithium from a lithium-containing alkaline aqueous solution as described in claim 1, characterized in that, The stripping agent aqueous solution in step (3) is a hydrochloric acid or sulfuric acid aqueous solution, and the concentration of hydrochloric acid or sulfuric acid is 1 mol / L to 6 mol / L; the stripping agent aqueous solution in step (3) is either a magnesium sulfate aqueous solution with pH 1 to 3, or an aluminum sulfate aqueous solution, or a mixed aqueous solution of magnesium sulfate or aluminum sulfate; the concentration of magnesium sulfate is 0.1 mol / L to 0.3 mol / L, and the concentration of aluminum sulfate is 0.05 mol / L to 0.1 mol / L.

9. The method for selectively extracting and precipitating lithium from a lithium-containing alkaline aqueous solution as described in claim 1, characterized in that, The mass ratio of the back-extraction agent aqueous solution in step (3) to the solid obtained in step (2) is 50:1 to 1:

1.

10. The method for selectively extracting and precipitating lithium from a lithium-containing alkaline aqueous solution as described in claim 1, characterized in that, The lithium-containing alkaline aqueous solution in step (1) is a lithium-containing sodium hydroxide aqueous solution, wherein the mass concentration of lithium is 10-1000 mg / L and the mass concentration of sodium hydroxide is 4-250 g / L; or the lithium-containing alkaline aqueous solution in step (1) is a concentrated alkaline sodium aluminate solution obtained by high-temperature leaching of lithium-rich bauxite using the Bayer process, and its solution composition is Na2O. k Concentration: 160-171 g / L, Al2O3 concentration: 180-194 g / L, caustic ratio a k : 1.4 ~ 1.5, Li₂O concentration: 60 ~ 70 mg / L, SiO₂ concentration: 0.6 ~ 1.0 g / L, Na₂O c Concentration: 5 ~ 20 g / L.

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