A method and apparatus for selectively extracting lithium from lithium-containing alkaline aqueous solutions.

Abstract

A method and apparatus for selectively extracting lithium from lithium-containing alkaline aqueous solutions. A naphthenic acid compound, an alkylphenoxycarboxylic acid derivative, or a mixture thereof, is added to a lithium-containing alkaline aqueous solution or a high-temperature leaching solution from lithium-rich bauxite via the Bayer process, at a specific molar ratio to lithium. The mixture is stirred and mixed to obtain a liquid-solid two-phase mixture. This mixture is then pumped into a hollow straight-tube column, followed by pumping an anionic surfactant of a specific concentration into the column and introducing air bubbles. The solid-liquid mixture overflowing from the top of the hollow straight-tube column is collected, filtered, or centrifuged to obtain a solid. The obtained solid is stirred and mixed with a back-extraction agent at a temperature of 20–80°C. After cooling to room temperature, lithium is enriched in the lower liquid phase after back-extraction or in the filtrate after solid-liquid separation. This invention enables the selective extraction, precipitation, and flotation capture of low-concentration lithium in alkaline aqueous solutions. It is simple to operate, the extractant can be repeatedly recycled, it is low-cost, and has a wide range of applications.

Description

Technical Field

[0001] This invention belongs to the field of rare metal lithium enrichment and extraction technology, and relates to a method and apparatus for selectively extracting lithium from lithium-containing alkaline aqueous solutions. In particular, it relates to a method and apparatus for selectively extracting lithium from concentrated sodium aluminate alkaline solution obtained after high-temperature leaching of lithium-rich bauxite by the Bayer process using air flotation flocculation extraction. 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 CN107500318B 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 CN106950413B 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, 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. Only a portion of the alumina is dissolved, allowing for further enrichment of 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 CN109761249B 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 CN110627095B 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 CN113277539A 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 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 CN115807169A 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 CN108421539A, 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 CN108421539A, 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 by Chinese patent CN102631897B, 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, one of the objectives of this invention is to provide a method for selectively extracting lithium from lithium-containing alkaline aqueous solutions. In particular, it provides a method for selectively extracting lithium from a concentrated alkaline sodium aluminate solution obtained after high-temperature leaching of lithium-rich bauxite using the Bayer process via air flotation flocculation extraction. 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] A method for selectively extracting lithium from a lithium-containing alkaline aqueous solution includes the following steps:

[0015] (1) At room temperature, a certain mass of cycloalkanoic acid compound, alkylphenoxycarboxylic acid derivative, or a mixture of the two in a certain mass ratio is added to a lithium-containing alkaline aqueous solution and stirred for 5 minutes to 1 hour to obtain a liquid-solid two-phase mixture. Then, the liquid-solid two-phase mixture is pumped into the straight tube column from the first inlet on the side wall of the middle part of the hollow straight tube column containing a lithium-containing alkaline aqueous solution at a certain volume flow rate.

[0016] (2) At room temperature, a certain mass of anionic surfactant and a certain mass of pure water are premixed to prepare an aqueous solution of anionic surfactant, and then pumped into the straight column at a certain volume flow rate from the second inlet of the distributor at the bottom of the hollow straight column containing lithium alkaline aqueous solution.

[0017] (3) Air is pumped into the hollow straight tube column at a certain volume flow rate from the air inlet of the distributor at the bottom of the column containing a lithium alkaline aqueous solution.

[0018] (4) Collect the solid-liquid mixture flowing out of the overflow outlet at the top of the hollow straight tube column containing an alkaline aqueous solution of lithium, and obtain the solid by filtration or centrifugation.

[0019] (5) Wash the solid obtained in step (4) with deionized water until the filtrate is neutral, then add the back-extraction agent aqueous solution according to 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;

[0020] (6) Centrifuge the liquid-liquid two-phase mixture obtained in step (5) 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 and repeat steps (1) to (6) for use. Alternatively, filter or centrifuge the liquid-solid two-phase mixture obtained in step (5). Wash the obtained solid 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 and repeat steps (1) to (6) for use.

[0021] (7) Collect the lower liquid phase obtained after centrifugation and phase separation of the liquid-liquid two-phase mixture in step (6), 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 (6), and determine the lithium concentration and impurity ion concentration therein.

[0022] According to a specific embodiment of the present invention, the cycloalkanoic acid compound in step (1) is any one of cycloalkanoic acid, octylcyclopentylpropionic acid, nonylcyclopentylbutyric acid or nonylcyclopentylhexanoic acid.

[0023] According to a specific embodiment of the present invention, the source of the cycloalkanoic acid compound 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 cycloalkanoic acid or its derivative is greater than 98%.

[0024] 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 ’ -(1,4-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.

[0025] 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.

[0026] 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%.

[0027] 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).

[0028] 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.

[0029] According to a specific embodiment of the present invention, when the naphthenic acid compound, alkylphenoxycarboxylic acid derivative, or mixture thereof is premixed with the lithium-containing alkaline aqueous solution in step (1), the molar ratio of the naphthenic acid compound, alkylphenoxycarboxylic acid derivative, or mixture thereof to the lithium ions in the lithium-containing alkaline aqueous solution is 1:1 to 5:1.

[0030] According to a specific embodiment of the present invention, the volumetric flow rate of the liquid-solid two-phase mixture pumped into the first inlet of the middle side wall of the hollow straight tube column in step (1) is 1 to 100 L / h.

[0031] According to a specific embodiment of the present invention, the anionic surfactant pumped into the second inlet of the distributor at the bottom of the hollow straight tube column in step (2) is any one of potassium, sodium, ammonium salts or triethanolamine salts of higher fatty acids with a carboxyl group as the hydrophilic group, or is a sulfonate-type anionic surfactant, including but not limited to any one of alkylbenzene sulfonates, α-olefin sulfonates, alkyl sulfonates, α-sulfonyl monocarboxylic esters, fatty acid sulfonyl esters, succinate sulfonates, alkylnaphthalene sulfonates, and lignin sulfonates. Preferably, the anionic surfactant is any one of sodium stearate, sodium oleate, sodium laurate, sodium alkyl polyoxyethylene ether carboxylate, sodium dodecylbenzene sulfonate, anionic polyacrylamide, and sodium dodecyl sulfate.

[0032] According to a specific embodiment of the present invention, the molar ratio of the amount of anionic surfactant added in step (2) to the lithium ions in the lithium-containing alkaline aqueous solution is 2:1 to 10:1.

[0033] According to a specific embodiment of the present invention, the volumetric flow rate of the anionic surfactant aqueous solution pumped into the second inlet of the liquid distributor at the bottom of the hollow straight tube column in step (2) is 0.1 to 1 L / h.

[0034] According to a specific embodiment of the present invention, the volumetric flow rate of the air pumped into the air inlet of the distributor at the bottom of the hollow straight tube containing the lithium alkaline aqueous solution in step (3) is 100 mL / min to 500 mL / min.

[0035] According to a specific embodiment of the present invention, the purpose of pumping anionic surfactant aqueous solution into the second inlet of the distributor at the bottom of the hollow straight tube column containing lithium alkaline aqueous solution in step (2) is that, upon detection, the insoluble solid particles formed by the combination of the naphthenic acid compound, alkylphenoxycarboxylic acid derivative, or a mixture of both with lithium ions in the alkaline solution have a positively charged surface in the alkaline solution. When anionic surfactant is added to the solution, the anionic surfactant will adsorb onto the surface of the insoluble solid particles, leading to flocculation and particle size growth.

[0036] According to a specific embodiment of the present invention, the purpose of pumping air into the air inlet of the distributor at the bottom of the hollow straight column containing the lithium-containing alkaline aqueous solution in step (3) is that, due to the hydrophobic properties of the bubble surface, the anionic surfactant will be adsorbed and coated on the bubble surface and rise with the bubble. During the rising process, the bubble coated with the anionic surfactant will capture insoluble solid particles formed by the combination of the naphthenic acid compound, alkylphenoxycarboxylic acid derivative, or a mixture of both with lithium ions in the alkaline solution, playing a role similar to flotation for capturing insoluble solid particles. Under the synergistic effect of the anionic surfactant and the bubble, the insoluble solid particles formed by the combination of the naphthenic acid compound, alkylphenoxycarboxylic acid derivative, or a mixture of both with lithium ions are captured by the bubble coated with the anionic surfactant and finally flow out from the overflow outlet at the top of the hollow straight column containing the lithium-containing alkaline aqueous solution with the rising bubble.

[0037] According to a specific embodiment of the present invention, the aqueous solution of the stripping agent in step (5) 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.

[0038] According to a specific embodiment of the present invention, the aqueous solution of the stripping agent in step (5) may also be an aqueous solution of magnesium sulfate with a pH of 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.

[0039] According to a specific embodiment of the present invention, the mass ratio of the back-extraction agent aqueous solution in step (5) to the solid obtained in step (4) is 50:1 to 1:1.

[0040] According to a specific embodiment of the present invention, after adding the back-extraction agent aqueous solution in step (3), the mixture is first stirred and mixed at a temperature of 20-80°C for 5 minutes to 1 hour, and then cooled to room temperature. The purpose of this 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 is a liquid-solid two-phase mixture after cooling to room temperature. Furthermore, the naphthenic acid compound after back-extraction and regeneration is in a liquid state at a temperature of 20-80°C, and remains a liquid state after cooling to room temperature. At this time, the entire system is a liquid-liquid two-phase mixture after cooling to room temperature.

[0041] According to a specific embodiment of the present invention, the lithium-containing alkaline aqueous solution 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.

[0042] According to a specific embodiment of the present invention, the lithium-containing alkaline aqueous solution 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.

[0043] Another object of the present invention is to provide an apparatus for selectively extracting lithium from a lithium-containing alkaline aqueous solution.

[0044] The device comprises a hollow straight tube column and a liquid distributor. The height-to-diameter ratio of the hollow straight tube column is 10:1 to 20:1. The liquid distributor is located at the bottom of the hollow straight tube column and is connected to the column by a flange. The spray head of the liquid distributor consists of a set of hollow straight tubes nested together. The inner tube is an air inlet with a diameter of 0.1 to 0.5 mm, and it communicates with the air inlet of the liquid distributor at the bottom of the hollow straight tube column for pumping in the air bubbles described in this invention. The outer tube has an inner diameter of 0.6 to 1.0 mm, and a slit gap between the inner wall of the outer tube and the outer wall of the inner tube allows liquid to be pumped in. This slit connects to a second liquid inlet at the bottom of the hollow straight tube column for pumping in the aqueous solution of the anionic surfactant described in this invention. A foam baffle is provided at the upper end of the hollow straight tube column, and a foam overflow port is provided on the upper side wall.

[0045] According to a specific embodiment of the present invention, the apparatus for selectively extracting lithium from lithium-containing alkaline aqueous solutions by air flotation flocculation extraction can be used alone or in series in multiple stages. When used in series in multiple stages, the alkaline lithium-containing aqueous solution flowing out of the aqueous phase outlet at the bottom of the hollow straight tube column of the previous stage is pumped into the first inlet on the side wall of the middle of the next hollow straight tube column. The second inlet of the distributor at the bottom of each stage of the series-connected hollow straight tube columns is pumped with a fresh anionic surfactant aqueous solution that has not reacted with insoluble solid particles in the alkaline aqueous solution, and air bubbles are individually pumped into the air distributor at the bottom of each stage to capture insoluble solid particles that could not be adsorbed and captured in time due to excessive flow rate of the lithium-containing alkaline aqueous solution pumped in the previous stage. Therefore, the multi-stage series operation of the apparatus for selectively extracting lithium from lithium-containing alkaline aqueous solutions by air flotation flocculation extraction of the present invention can improve the continuous capture of insoluble solid particles, thereby increasing the total recovery rate of lithium in the alkaline aqueous solution.

[0046] The working principle of the method and apparatus for selectively extracting lithium from lithium-containing alkaline aqueous solution of the present invention is that the molecular structure of the alkylphenoxycarboxylic acid derivative contains phenoxy and carboxyl groups, and the molecular structure of the cycloalkanoic acid compound is shown in formula (1).

[0047]

[0048] 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.

[0049] In a concentrated alkaline medium, the carboxyl functional groups of the aforementioned cycloalkanoic acid compounds, alkylphenoxycarboxylic acid derivatives, or mixtures thereof, after ionization of hydrogen ions, exhibit association abilities with various cations that follow the Hoffmeister ion sequence, i.e., 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 by the association of the alkylphenoxycarboxylic acid derivatives and naphthenic acid compounds with lithium ions are insoluble in alkaline aqueous solutions at room temperature, they precipitate out in the alkaline aqueous solution, forming solid precipitates. When the anionic surfactant and bubbles are pumped into the lithium-containing alkaline aqueous solution, under the synergistic effect of the anionic surfactant and bubbles, the insoluble solid particles formed by the combination of the naphthenic acid compounds, alkylphenoxycarboxylic acid derivatives, or a mixture of both with lithium ions (i.e., solid insoluble extractants) are captured by bubbles coated with anionic surfactant and ultimately collected by the rising bubbles flowing out from the overflow outlet at the top of the hollow straight column containing the lithium-containing alkaline aqueous solution. After the collected lithium-loaded solid is added to the stripping agent aqueous solution, the excess hydrogen ions in the stripping agent aqueous solution undergo a cation exchange reaction with the lithium ions captured on the surface of the extractant solid particles. Therefore, the carboxyl groups of the alkylphenoxycarboxylic acid derivatives and cycloalkanoic acid compounds are regenerated. By controlling a certain solid-to-liquid mass ratio in the back-extraction solution, lithium ions are enriched in the final back-extraction solution.

[0050] Compared with other disclosed technical solutions, the present invention has the following beneficial effects:

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 6) The apparatus and its multi-stage series connection of the air flotation flocculation extraction for selectively extracting lithium from lithium-containing alkaline aqueous solutions, as described in this invention, can efficiently capture and extract insoluble solid extracts from continuously flowing lithium-containing alkaline aqueous solutions. The apparatus is easy to operate continuously, easy to scale up, and has good prospects for industrial application and promotion value. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the apparatus for selectively extracting lithium from a lithium-containing alkaline aqueous solution using air flotation flocculation extraction, as described in Embodiment 1 of the present invention.

[0058] Figure 2 This refers to the liquid distributor of the apparatus for selectively extracting lithium from lithium-containing alkaline aqueous solution using air flotation flocculation extraction as described in Embodiment 1 of the present invention;

[0059] Figure 3The foam baffle of the apparatus for selectively extracting lithium from lithium-containing alkaline aqueous solution by air flotation flocculation extraction as described in Embodiment 1 of the present invention;

[0060] Figure 4 The image above shows the distributor nozzle of the apparatus for selectively extracting lithium from a lithium-containing alkaline aqueous solution using air flotation flocculation extraction as described in Embodiment 1 of the present invention (top view, bottom view).

[0061] Figure 5 This is a schematic diagram illustrating the working principle of an apparatus for selectively extracting lithium from a lithium-containing alkaline aqueous solution using air flotation flocculation extraction, as described in Embodiment 1 of the present invention.

[0062] Figure 6 This is a schematic diagram of the three-stage series operation principle of the apparatus for selectively extracting lithium from lithium-containing alkaline aqueous solution by air flotation flocculation extraction as described in Embodiment 12 of the present invention.

[0063] In the figure:

[0064] 1: Hollow straight tube column; 2: Foam overflow port; 3: Bubble nozzle of the distributor; 4: Upper flange; 5: Lower flange; 6: Inlet of surfactant aqueous solution of the distributor (i.e., the second inlet of the distributor at the bottom of the hollow straight tube column of the present invention); 7: Air inlet of the distributor; 8: Air chamber of the distributor; 9: Storage chamber of surfactant aqueous solution of the distributor; 10: Outlet of raffinate after extraction; 11: Inlet of lithium-containing alkaline aqueous solution (i.e., the first inlet on the middle side wall of the hollow straight tube column of the present invention); 12: Foam baffle at the upper end of the hollow straight tube column; 13: Outer tube of the bubble nozzle of the distributor; 14: Inner tube of the bubble nozzle of the distributor;

[0065] A: A liquid-solid two-phase mixture containing insoluble solid particles flowing out of the foam overflow port on the upper sidewall of the hollow straight tube column; B: Insoluble solid particles formed by the combination of the naphthenic acid compound, alkylphenoxycarboxylic acid derivative, or a mixture thereof with lithium ions (i.e., the solid insoluble extract of the present invention); C: Insoluble solid particles trapped by bubbles; D: Raffinate phase after extraction; E: Air; F: Anionic surfactant aqueous solution; G: Bubbles coated with anionic surfactant; H: Lithium-containing alkaline aqueous solution; I: Interface between the foam phase and the lithium-containing alkaline aqueous solution phase; J: Anionic surfactant foam; K: Foam with lithium-containing insoluble solid particles adsorbed and loaded on its surface. Detailed Implementation

[0066] 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.

[0067] Example 1

[0068] A single-stage extraction apparatus was used, with a hollow straight column having a height-to-diameter ratio of 10:1. The inner tube of the distributor nozzle had an outer diameter of 0.1 mm, and the outer tube had an inner diameter of 0.6 mm. 3.57 mmol of naphthenic acid was weighed and 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. This mixture was then pumped into the hollow straight column at a flow rate of 1 L / h through the first inlet on the side wall of the middle section containing the lithium-containing alkaline aqueous solution. A 30 mmol / L sodium stearate aqueous solution was prepared and pumped into the hollow straight column at a flow rate of 100 mL / h through the second inlet of the distributor at the bottom of the hollow straight column containing the lithium-containing alkaline aqueous solution. Air was pumped into a hollow straight column containing a lithium-containing alkaline aqueous solution at a flow rate of 100 mL / min through the inlet of the distributor at the bottom. The solid-liquid mixture flowing from the overflow outlet at the top of the hollow straight column containing the lithium-containing alkaline aqueous solution was collected, filtered, and the solid was obtained. The effluent from the raffinate outlet at the bottom of the apparatus was collected, and the lithium residue content was analyzed using inductively coupled plasma mass spectrometry (ICP-MS). The solid effluent from the overflow outlet was washed with deionized water until the filtrate was neutral, and then 50 mL of 3 mol / L hydrochloric acid aqueous solution was added. The mixture was stirred and mixed at room temperature for 10 minutes to obtain a liquid-liquid two-phase mixture. After centrifugation and phase separation, the lower liquid phase was sampled and analyzed using 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 1.18 g / L, the aluminum ion concentration was below the analytical limit, and the sodium ion concentration was 132 mg / L. The total lithium yield was 90.3%.

[0069] Example 2

[0070] A single-stage extraction apparatus was used, with a hollow straight column having a height-to-diameter ratio of 16:1. The inner tube of the distributor nozzle had an outer diameter of 0.1 mm, and the outer tube had an inner diameter of 0.6 mm. 714 mmol of p-tert-octylphenoxyacetic acid was weighed and added to 5 liters 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. This mixture was then pumped into the hollow straight column at a flow rate of 10 L / h through the first inlet on the side wall of the hollow straight column containing the lithium-containing alkaline aqueous solution. A 2.8 mol / L sodium oleate aqueous solution was prepared and pumped into the hollow straight column at a flow rate of 1 L / h through the second inlet of the distributor at the bottom of the hollow straight column containing the lithium-containing alkaline aqueous solution. Air was pumped into a hollow straight column containing a lithium-containing alkaline aqueous solution at a flow rate of 500 mL / min through the inlet of the distributor at the bottom. The solid-liquid mixture flowing from the overflow outlet at the top of the hollow straight column containing the lithium-containing alkaline aqueous solution was collected and centrifuged to obtain the solid. The effluent from the raffinate outlet at the bottom of the apparatus was collected and analyzed for lithium residue content using inductively coupled plasma mass spectrometry (ICP-MS). The solid effluent from the overflow outlet 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 and mixed at 80 °C for 30 minutes, and then cooled to room temperature to obtain a liquid-solid two-phase mixture. The resulting liquid-solid two-phase mixture was filtered, and the filtrate was sampled and analyzed using 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 32.93 g / L, the aluminum ion concentration was below the analytical limit, and the sodium ion concentration was 77 mg / L. The total lithium yield was 91.5%.

[0071] Example 3

[0072] A single-stage extraction apparatus was used, with a hollow straight column having a height-to-diameter ratio of 20:1. The inner tube of the distributor nozzle had an outer diameter of 0.5 mm, and the outer tube had an inner diameter of 1.0 mm. 4.2 mmol of octylcyclopentylpropionic acid and 2.8 mmol of p-tert-butylphenoxyacetic acid were weighed and added to 500 mL of an alkaline aqueous solution containing 100 mg / L lithium and 200 g / L sodium hydroxide. The mixture was stirred at room temperature for 30 minutes to obtain a liquid-solid two-phase mixture. This mixture was then pumped into the hollow straight column from the first inlet on the middle side wall containing the lithium-containing alkaline aqueous solution at a flow rate of 2 L / h. A 0.7 mol / L sodium laurate aqueous solution was prepared and pumped into the hollow straight column from the second inlet on the distributor at the bottom of the lithium-containing alkaline aqueous solution at a flow rate of 200 mL / h. Air was pumped into a hollow straight column containing a lithium-containing alkaline aqueous solution at a flow rate of 200 mL / min through the inlet of the distributor at the bottom. The solid-liquid mixture flowing from the overflow outlet at the top of the hollow straight column containing the lithium-containing alkaline aqueous solution was collected and centrifuged to obtain the solid. The effluent from the raffinate outlet at the bottom of the apparatus was collected and analyzed for lithium residue content using inductively coupled plasma mass spectrometry (ICP-MS). The solid effluent from the overflow outlet was washed with deionized water until the filtrate was neutral, and then 40 mL of a 0.1 mol / L magnesium sulfate aqueous solution (pH 1) was added. The mixture was stirred and mixed at 40 °C for 30 minutes, then cooled to room temperature to obtain a liquid-solid two-phase mixture. The liquid-solid two-phase mixture was centrifuged, and the resulting filtrate was sampled and analyzed using 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 1.09 g / L, and the sodium ion concentration was 68 mg / L. The total lithium yield was 92.6%.

[0073] Example 4

[0074] A single-stage extraction device was used, with a column height-to-diameter ratio of 20:1 for the hollow straight column. The inner tube outer diameter of the distributor nozzle was 0.4 mm, and the outer tube inner diameter was 1.0 mm. 214 mmol of 2-(4-(2,4,4-trimethylpentan-2-yl)phenoxy)acetic acid was weighed and added to 50 liters of concentrated alkaline 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 cConcentration: 12 g / L. The mixture was stirred and mixed at room temperature for 30 minutes to obtain a liquid-solid two-phase mixture. Then, the liquid-solid two-phase mixture was pumped into the hollow straight column containing a lithium-containing alkaline aqueous solution through the first inlet on the middle side wall at a volumetric flow rate of 100 L / h. A 0.64 mol / L sodium dodecylbenzenesulfonate aqueous solution was prepared and pumped into the hollow straight column containing the lithium-containing alkaline aqueous solution through the second inlet of the bottom distributor at a volumetric flow rate of 1 L / h. Air was pumped into the straight column containing the lithium-containing alkaline aqueous solution through the air inlet of the bottom distributor at a volumetric flow rate of 300 mL / min. The solid-liquid mixture flowing out from the top overflow outlet of the hollow straight column containing the lithium-containing alkaline aqueous solution was collected, filtered, and the solid was obtained. The effluent from the raffinate outlet at the bottom of the device was collected, and the lithium residue content was analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The solid residue flowing from the overflow outlet 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. After cooling to room temperature, a liquid-solid two-phase mixture was obtained. The mixture was centrifuged, and the resulting 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 1.87 g / L, the aluminum ion concentration was below the analytical limit, and the sodium ion concentration was 223 mg / L. The total lithium yield was 94.6%.

[0075] Example 5

[0076] A single-stage extraction device was used, with a column height-to-diameter ratio of 15:1 for the hollow straight column. The inner tube outer diameter of the distributor nozzle was 0.3 mm, and the outer tube inner diameter was 0.8 mm. 40.6 mmol of nonylcyclopentylbutyric acid and 17.4 mmol of 2-(4-(2,4,4-trimethylpent-2-yl)phenoxy)acetic acid were weighed and added to 5 liters of concentrated sodium aluminate alkaline solution obtained from the Bayer process high-temperature leaching of lithium-rich bauxite. The Na₂O content was... 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 cConcentration: 15 g / L. The mixture was stirred and mixed at room temperature for 5 minutes to obtain a liquid-solid two-phase mixture. Then, the liquid-solid two-phase mixture was pumped into the hollow straight column containing a lithium-containing alkaline aqueous solution through the first inlet on the middle side wall at a volumetric flow rate of 30 L / h. A 2.3 mol / L anionic polyacrylamide aqueous solution was prepared and pumped into the hollow straight column containing the lithium-containing alkaline aqueous solution through the second inlet of the bottom distributor at a volumetric flow rate of 300 mL / h. Air was pumped into the straight column containing the lithium-containing alkaline aqueous solution through the air inlet of the bottom distributor at a volumetric flow rate of 300 mL / min. The solid-liquid mixture flowing out from the top overflow outlet of the hollow straight column containing the lithium-containing alkaline aqueous solution was collected and centrifuged to obtain the solid. The effluent from the raffinate outlet at the bottom of the device was collected and analyzed using inductively coupled plasma mass spectrometry to determine the lithium residue content. The solid residue flowing from the overflow outlet was washed with deionized water until the filtrate was neutral. Then, 50 mL of a 0.05 mol / L aluminum sulfate aqueous solution (pH 1) was added. The mixture was stirred at 60 °C for 30 minutes, then cooled to room temperature to obtain a 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 1.07 g / L, and the sodium ion concentration was 364 mg / L. The total lithium yield was 90.3%.

[0077] Example 6

[0078] A single-stage extraction apparatus was used, with a hollow straight column height-to-diameter ratio of 18:1. The inner tube outer diameter of the distributor nozzle was 0.2 mm, and the outer tube inner diameter was 0.8 mm. 562 mmol / L of 2,2-distilled liquid was weighed. ’ 1,4-Phenylidene bis(oxy)dioctanoic acid, when added to 50 liters of concentrated alkaline sodium aluminate solution obtained from the Bayer process high-temperature leaching of lithium-rich bauxite, produces Na₂O 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 and mixed at room temperature for 5 minutes to obtain a liquid-solid two-phase mixture. Then, the liquid-solid two-phase mixture was pumped into the hollow straight column containing a lithium-containing alkaline aqueous solution through the first inlet on the middle side wall at a volumetric flow rate of 80 L / h. A 1.13 mol / L alkyl polyoxyethylene ether sodium carboxylate aqueous solution was prepared and pumped into the hollow straight column containing the lithium-containing alkaline aqueous solution through the second inlet of the bottom distributor at a volumetric flow rate of 800 mL / h. Air was pumped into the straight column containing the lithium-containing alkaline aqueous solution through the air inlet of the bottom distributor at a volumetric flow rate of 500 mL / min. The solid-liquid mixture flowing out from the top overflow outlet of the hollow straight column containing the lithium-containing alkaline aqueous solution was collected and centrifuged to obtain the solid. The effluent from the raffinate outlet at the bottom of the device was collected and analyzed using inductively coupled plasma mass spectrometry to determine the residual lithium content. The solids flowing out of the overflow outlet were 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, then cooled to room temperature to obtain a liquid-solid two-phase mixture. The mixture was filtered to separate the liquid-solid phases, 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 0.96 g / L, and the sodium ion concentration was 229 mg / L. The total lithium yield was 94.8%.

[0079] Example 7

[0080] A single-stage extraction apparatus was used, with a hollow straight column height-to-diameter ratio of 20:1. The inner tube outer diameter of the distributor nozzle was 0.2 mm, and the outer tube inner diameter was 0.8 mm. 348 mmol of 2,2 ’ 1,1-(cyclohexane-1,1-diylbis(4,1-phenylene))bis(oxy))diacetic acid, added to 50 liters of concentrated alkaline sodium aluminate solution obtained from the Bayer process high-temperature leaching of lithium-rich bauxite, produces Na₂O 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 cConcentration: 13 g / L. The mixture was stirred and mixed at room temperature for 10 minutes to obtain a liquid-solid two-phase mixture. Then, the liquid-solid two-phase mixture was pumped into the hollow straight column containing a lithium-containing alkaline aqueous solution through the first inlet on the middle side wall at a volumetric flow rate of 100 L / h. A 0.7 mol / L sodium dodecylbenzenesulfonate aqueous solution was prepared and pumped into the hollow straight column containing the lithium-containing alkaline aqueous solution through the second inlet of the bottom distributor at a volumetric flow rate of 1 L / h. Air was pumped into the straight column containing the lithium-containing alkaline aqueous solution through the air inlet of the bottom distributor at a volumetric flow rate of 400 mL / min. The solid-liquid mixture flowing out from the top overflow outlet of the hollow straight column containing the lithium-containing alkaline aqueous solution was collected, filtered, and the solid was obtained. The effluent from the raffinate outlet at the bottom of the device was collected, and the lithium residue content was determined by inductively coupled plasma mass spectrometry. The solid residue flowing from the overflow outlet was washed with deionized water until the filtrate was neutral. Then, 100 mL of 6 mol / L hydrochloric acid aqueous solution was added, and the mixture was stirred and mixed at 40 °C for 30 minutes. After cooling to room temperature, a liquid-solid two-phase mixture was obtained. The mixture was centrifuged, and the resulting 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 1.65 g / L, the aluminum ion concentration was below the analytical limit, and the sodium ion concentration was 92 mg / L. The total lithium yield was 89.5%.

[0081] Example 8

[0082] A single-stage extraction apparatus was used, with a hollow straight column height-to-diameter ratio of 10:1. The inner tube outer diameter of the distributor nozzle was 0.1 mm, and the outer tube inner diameter was 0.7 mm. 57.1 mmol of nonylcyclopentylhexanoic acid was weighed, followed by 57.1 mmol of 2,2 ’ -((oxybis(4,1-phenylene))bis(oxy))diacetic acid, after being mixed, is added to 50 liters of concentrated alkaline sodium aluminate solution obtained from the Bayer process high-temperature leaching of lithium-rich bauxite. The Na₂O 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 cConcentration: 14 g / L. The mixture was stirred and mixed at room temperature for 5 minutes to obtain a liquid-solid two-phase mixture. Then, the liquid-solid two-phase mixture was pumped into the hollow straight column containing a lithium-containing alkaline aqueous solution through the first inlet on the middle side wall at a volumetric flow rate of 100 L / h. A 0.46 mol / L sodium dodecylbenzenesulfonate aqueous solution was prepared and pumped into the hollow straight column containing the lithium-containing alkaline aqueous solution through the second inlet of the bottom distributor at a volumetric flow rate of 1 L / h. Air was pumped into the straight column containing the lithium-containing alkaline aqueous solution through the air inlet of the bottom distributor at a volumetric flow rate of 300 mL / min. The solid-liquid mixture flowing out from the top overflow outlet of the hollow straight column containing the lithium-containing alkaline aqueous solution was collected and centrifuged to obtain the solid. The effluent from the raffinate outlet at the bottom of the device was collected and analyzed using inductively coupled plasma mass spectrometry to determine the residual lithium content. The solid residue flowing from the overflow outlet was washed with deionized water until the filtrate was neutral. Then, 140 mL of 3 mol / L sulfuric acid aqueous solution was added, and the mixture was stirred at 80 °C for 30 minutes. After cooling to room temperature, a liquid-solid two-phase mixture was obtained. The 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 1.75 g / L, the aluminum ion concentration was below the analytical limit, and the sodium ion concentration was 213 mg / L. The total lithium yield was 85.7%.

[0083] Example 9

[0084] A single-stage extraction apparatus was used, with a column height-to-diameter ratio of 18:1 for the hollow straight column. The inner tube outer diameter of the distributor nozzle was 0.2 mm, and the outer tube inner diameter was 0.6 mm. 1.51 mol of 2,2-octylphenoxyacetic acid was weighed, followed by 2.27 mol of 2,2-diethylacetic acid. ’-((propane-2,2-diylbis(4,1-phenylene))bis(oxy))diacetic acid was mixed and then added to 50 liters of an alkaline aqueous solution containing 530 mg / L lithium and 250 g / L sodium hydroxide. The mixture was stirred at room temperature for 5 minutes to obtain a liquid-solid two-phase mixture. This mixture was then pumped into a hollow straight column containing the lithium-containing alkaline aqueous solution through the first inlet on the middle side wall at a flow rate of 100 L / h. A 15.16 mol / L anionic polyacrylamide aqueous solution was prepared and pumped into the hollow straight column containing the lithium-containing alkaline aqueous solution through the second inlet of the distributor at the bottom of the hollow straight column at a flow rate of 1 L / h. Air was pumped into the straight column containing the lithium-containing alkaline aqueous solution through the air inlet of the distributor at the bottom of the hollow straight column at a flow rate of 100 mL / min. A solid-liquid mixture was collected from the overflow outlet of a hollow straight column containing an alkaline aqueous solution of lithium. After centrifugation, the solid was obtained. The effluent from the bottom of the apparatus containing the raffinate was collected, and the residual lithium content was analyzed using inductively coupled plasma mass spectrometry (ICP-MS). The obtained solid effluent from the overflow outlet was washed with deionized water until the filtrate was neutral. Then, 150 mL of 6 mol / L sulfuric acid aqueous solution was added, and the mixture was stirred at 50 °C for 30 minutes. After cooling to room temperature, a liquid-solid two-phase mixture was obtained. The mixture was centrifuged, and the lower liquid phase after separation was sampled and analyzed using 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 1.94 g / L, the aluminum ion concentration was below the analytical limit, and the sodium ion concentration was 104 mg / L. The total lithium yield was 83.6%.

[0085] Example 10

[0086] A single-stage extraction device was used, with a hollow straight column height-to-diameter ratio of 16:1. The inner tube outer diameter of the distributor nozzle was 0.3 mm, and the outer tube inner diameter was 0.9 mm. 450 mmol of 2-(4-benzyloxyphenoxy)acetic acid was weighed and added to 50 liters of concentrated alkaline 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: 63 mg / L, SiO2 concentration: 0.68 g / L, Na2O cConcentration: 13 g / L. The mixture was stirred at room temperature for 5 minutes to obtain a liquid-solid two-phase mixture. This mixture was then pumped into the hollow straight column containing a lithium-containing alkaline aqueous solution through the first inlet on the middle side wall at a flow rate of 50 L / h. A 2.24 mol / L sodium dodecyl sulfate aqueous solution was prepared and pumped into the hollow straight column containing the lithium-containing alkaline aqueous solution through the second inlet of the distributor at the bottom at a flow rate of 500 mL / h. Air was pumped into the straight column containing the lithium-containing alkaline aqueous solution through the air inlet of the distributor at the bottom at a flow rate of 200 mL / min. The solid-liquid mixture flowing out from the overflow outlet at the top of the hollow straight column containing the lithium-containing alkaline aqueous solution was collected and centrifuged to obtain the solid. The effluent from the raffinate outlet at the bottom of the device was collected and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the residual lithium content. The solids flowing out of the overflow outlet were 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 for magnesium sulfate and 0.05 mol / L for aluminum sulfate) was added. The mixture was stirred at 40 °C for 30 minutes, then cooled to room temperature to obtain a liquid-solid two-phase mixture. The mixture was filtered to separate the phases, 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 1.43 g / L, and the sodium ion concentration was 162 mg / L. The total lithium yield was 91.1%.

[0087] Example 11

[0088] A single-stage extraction device was used, with a hollow straight column height-to-diameter ratio of 12:1. The inner tube outer diameter of the distributor nozzle was 0.2 mm, and the outer tube inner diameter was 0.8 mm. 180 mmol of naphthenic acid and 45 mmol of 2-(4-butoxyphenoxy)acetic acid were weighed, mixed, and added to a 50-liter concentrated alkaline solution of sodium aluminate 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 and mixed at room temperature for 10 minutes to obtain a liquid-solid two-phase mixture. Then, the liquid-solid two-phase mixture was pumped into the hollow straight column containing a lithium-containing alkaline aqueous solution through the first inlet on the middle side wall at a volumetric flow rate of 100 L / h. A 1.35 mol / L sodium dodecyl sulfate aqueous solution was prepared and pumped into the hollow straight column containing the lithium-containing alkaline aqueous solution through the second inlet of the bottom distributor at a volumetric flow rate of 1 L / h. Air was pumped into the straight column containing the lithium-containing alkaline aqueous solution through the air inlet of the bottom distributor at a volumetric flow rate of 400 mL / min. The solid-liquid mixture flowing out from the top overflow outlet of the hollow straight column containing the lithium-containing alkaline aqueous solution was collected and centrifuged to obtain the solid. The effluent from the raffinate outlet at the bottom of the device was collected and analyzed using inductively coupled plasma mass spectrometry to determine the residual lithium content. The solids flowing out of the overflow outlet were washed with deionized water until the filtrate was neutral. Then, 70 mL of a 0.1 mol / L aluminum sulfate aqueous solution (pH 1) was added. The mixture was stirred at 40 °C for 5 minutes, then cooled to room temperature to obtain a 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 1.88 g / L, and the sodium ion concentration was 43 mg / L. The total lithium yield was 92.2%.

[0089] Example 12

[0090] A three-stage tandem extraction apparatus was used, with a column height-to-diameter ratio of 20:1 for the hollow straight column. The inner tube outer diameter of the distributor nozzle was 0.3 mm, and the outer tube inner diameter was 0.8 mm. 348 mmol of 2-(4-(2,4,4-trimethylpentan-2-yl)phenoxy)acetic acid was weighed and added to 50 liters of concentrated alkaline 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 cConcentration: 13 g / L. The mixture was stirred and mixed at room temperature for 10 minutes to obtain a liquid-solid two-phase mixture. Then, the liquid-solid two-phase mixture was pumped into the first-stage hollow straight column containing a lithium-containing alkaline aqueous solution at a volumetric flow rate of 100 L / h through the first inlet on the side wall of the first-stage column. A 1.39 mol / L sodium dodecylbenzenesulfonate aqueous solution was prepared and pumped into the straight column containing a lithium-containing alkaline aqueous solution at a volumetric flow rate of 1 L / h through the second inlet of the distributor at the bottom of each stage hollow straight column. Air was pumped into the straight column containing a lithium-containing alkaline aqueous solution at a volumetric flow rate of 300 mL / min through the air inlet of the distributor at the bottom of each stage hollow straight column. The solid-liquid mixture flowing out from the overflow outlet at the top of each stage hollow straight column was collected and centrifuged to obtain the solid. The effluent from the raffinate outlet at the bottom of the third-stage unit was collected and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the residual lithium content. Then, the solids from each overflow outlet were combined and washed with deionized water until the filtrate was neutral. 135 mL of 6 mol / L sulfuric acid aqueous solution was added, and the mixture was stirred at 60 °C for 60 minutes. After cooling to room temperature, a liquid-solid two-phase mixture was obtained. The mixture was centrifuged, and the resulting 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 1.89 g / L, the aluminum ion concentration was below the analytical limit, and the sodium ion concentration was 55 mg / L. The total lithium yield was 96.2%.

[0091] The present invention has been illustrated through 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 lithium from a lithium-containing alkaline aqueous solution, characterized in that, The method comprises the following steps: (1) at room temperature, a certain mass of naphthenic acid compound, alkyl phenoxycarboxylic acid derivative, or mixture of both in a certain mass ratio is added into a lithium-containing alkaline aqueous solution and stirred for 5 minutes to 1 hour to obtain a liquid-solid two-phase mixture, and then the liquid-solid two-phase mixture is pumped into a hollow straight pipe column from a first liquid inlet on the side wall of the middle part of the column containing the lithium-containing alkaline aqueous solution at a certain volumetric flow rate; (2) at room temperature, a certain mass of anionic surfactant is mixed with a certain mass of pure water to prepare an anionic surfactant aqueous solution, and then the anionic surfactant aqueous solution is pumped into the hollow straight pipe column from a second liquid inlet at the bottom end of the column containing the lithium-containing alkaline aqueous solution at a certain volumetric flow rate; (3) air is pumped into the hollow straight pipe column from an air inlet at the bottom end of the column containing the lithium-containing alkaline aqueous solution at a certain volumetric flow rate; (4) a solid-liquid mixture flowing out from an overflow outlet at the top end of the column containing the lithium-containing alkaline aqueous solution is collected, and then filtered or centrifuged to obtain a solid; (5) the solid obtained in step (4) is washed with deionized water until the filtrate is neutral, and then a certain mass ratio of anionic surfactant aqueous solution is added, and the mixture is stirred at 20-80°C for 5 minutes to 1 hour, and then cooled to room temperature to obtain a liquid-liquid two-phase mixture or a liquid-solid two-phase mixture; (6) the liquid-liquid two-phase mixture obtained in step (5) is centrifuged to separate the phases, and then the upper liquid phase is washed with deionized water until it is neutral, and then returned to step (1) to be added to the lithium-containing alkaline aqueous solution for repeating steps (1)-(6); or the liquid-solid two-phase mixture obtained in step (5) is filtered or centrifuged to obtain a solid, and then the solid is washed with deionized water until the filtrate is neutral, and then returned to step (1) to be added to the lithium-containing alkaline aqueous solution for repeating steps (1)-(6); (7) the lower liquid phase obtained after centrifugation of the liquid-liquid two-phase mixture in step (6) is collected, and the lithium concentration and impurity ion concentration thereof are determined; or the filtrate obtained after filtration or centrifugation of the liquid-solid two-phase mixture in step (6) is collected, and the lithium concentration and impurity ion concentration thereof are determined.

2. The method of selectively extracting lithium from a lithium-containing alkaline aqueous solution according to claim 1, wherein The naphthenic acid compound in step (1) is any one of octylcyclopentylpropionic acid, nonylcyclopentylbutyric acid or nonylcyclopentylhexanoic acid, and the alkylphenoxy carboxylic acid derivative in step (1) has at least one phenoxy group and one carboxyl group in its molecular structure, including any one of sec-octylphenoxyacetic acid, p-tert-butylphenoxyacetic acid, p-tert-octylphenoxyacetic acid, 2-(4-(2,4,4-trimethylpentan-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'-((propane-2,2-diylbis(4,1-phenylene))bis(oxy))diacetic acid.

3. The method of selectively extracting lithium from a lithium-containing alkaline aqueous solution of claim 1, wherein, The naphthenic acid compound, alkylphenoxy carboxylic acid derivative or mixture of both in step (1) is pre-mixed with the aqueous lithium-containing alkaline solution, and the molar ratio of the amount of the naphthenic acid compound, alkylphenoxy carboxylic acid derivative or mixture of both to lithium ions in the aqueous lithium-containing alkaline solution is 1:1 to 5:

1.

4. The method of selectively extracting lithium from a lithium-containing alkaline aqueous solution according to claim 1, wherein The volume flow rate of the liquid-solid two-phase mixture pumped into the first liquid inlet on the side wall of the middle part of the hollow straight tube column in step (1) is 1 to 100 L / h.

5. The method of selectively extracting lithium from a lithium-containing alkaline aqueous solution according to claim 1, wherein The anionic surfactant pumped into the second liquid inlet of the liquid distributor at the bottom end of the hollow straight tube column in step (2) is any one of a potassium salt of a higher fatty acid, a sodium salt of a higher fatty acid, an ammonium salt of a higher fatty acid or a triethanolammonium salt, or is a sulfonate anionic surfactant, including any one of an alkylbenzenesulfonate, an alpha-olefinsulfonate, an alkylsulfonate, an alpha-sulfo monocarboxylic acid ester, a fatty acid sulfonalkyl ester, a succinate sulfonate, an alkyl naphthalene sulfonate, a lignosulfonate; and the molar ratio of the amount of the anionic surfactant to lithium ions in the aqueous lithium-containing alkaline solution is 2:1 to 10:

1.

6. The method of selectively extracting lithium from a lithium-containing alkaline aqueous solution according to claim 5, wherein The anionic surfactant is any one of sodium stearate, sodium oleate, sodium laurate, sodium alkyl polyoxyethylene ether carboxylate, sodium dodecylbenzenesulfonate, an anionic polyacrylamide or sodium dodecyl sulfate.

7. The method of selectively extracting lithium from a lithium-containing alkaline aqueous solution according to claim 1, wherein The volume flow rate of the aqueous solution of the anionic surfactant pumped into the second liquid inlet of the liquid distributor at the bottom end of the hollow straight tube column in step (2) is 0.1 to 1 L / h.

8. The method of selectively extracting lithium from a lithium-containing alkaline aqueous solution according to claim 1, wherein The volume flow rate of the air pumped into the air inlet of the liquid distributor at the bottom end of the hollow straight tube column in step (3) is 100 mL / min to 500 mL / min.

9. The method of selectively extracting lithium from a lithium-containing alkaline aqueous solution of claim 1, wherein, The stripping agent aqueous solution in step (5) is hydrochloric acid or sulfuric acid aqueous solution, and the concentration of hydrochloric acid or sulfuric acid is 1 mol / L-6 mol / L; the stripping agent aqueous solution in step (5) is selected from the group consisting of magnesium sulfate aqueous solution with pH 1-3, aluminum sulfate aqueous solution, and a mixture of magnesium sulfate and aluminum sulfate; the concentration of magnesium sulfate is 0.1 mol / L-0.3 mol / L, and the concentration of aluminum sulfate is 0.05 mol / L-0.1 mol / L; and the mass ratio of the stripping agent aqueous solution in step (5) to the solid obtained in step (4) is 50:1-1:

1.

10. The method of selectively extracting lithium from a lithium-containing alkaline aqueous solution according to claim 1, wherein The lithium-containing alkaline aqueous solution 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; the lithium-containing alkaline aqueous solution is either a concentrated sodium aluminate solution obtained after high-temperature leaching of lithium-rich bauxite by the Bayer process, or a concentrated sodium aluminate solution obtained after high-temperature leaching of lithium-rich bauxite by the Bayer process, and the solution composition of the concentrated sodium aluminate solution 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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