Method for extracting lithium carbonate from complex and difficult-to-treat middle-low-grade lithium-containing brine

Abstract

The invention relates to the technical field of lithium salt extraction, and provides a method for extracting lithium carbonate from complex and difficult-to-treat middle-low-grade lithium-containing brine, and the method comprises the following steps: mixing a sodium aluminate solution, acid and lithium-containing brine to obtain a reaction system; the sodium aluminate solution contains NaOH and Al2O3; the sodium aluminate solution and the acid are subjected to acid-base neutralization in the reaction system; when the acid-base neutralization is carried out, lithium in the reaction system enters crystal lattices of aluminum hydroxide generated by the acid-base neutralization to form lithium-rich slag precipitates; mixing the lithium-rich slag precipitate with water, heating, and carrying out solid-liquid separation to obtain a desorption solution and desorption slag; the desorption solution is used for recovering lithium therein; the desorption slag is treated by a redissolution process and is used for preparing the sodium aluminate solution. For specific lithium-containing brine, the lithium precipitation rate can be larger than or equal to 90%, and the lithium precipitation rate exceeds the level which can be achieved by a conventional adsorbent for extracting lithium from a salt lake at present. And desorption slag obtained after lithium precipitation is completely recycled, so that the production cost is greatly optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium salt extraction, and in particular to a method for extracting lithium carbonate from complex and difficult-to-treat medium- and low-grade lithium-containing brine. Background Art

[0002] With the rapid popularization of electric vehicles, the demand for lithium resources will continue to grow rapidly. At present, commercial lithium mining mainly relies on terrestrial salt lakes and high-grade lithium ores. Compared with the cost of lithium extraction from salt lakes, lithium extraction from ore is generally lower in cost and has smaller environmental and ecological costs. In recent years, the technology for lithium extraction from salt lakes has become increasingly mature. The mainstream technologies include traditional solar pond evaporation crystallization, membrane process, and adsorbent-based direct lithium extraction process (DLE). In recent years, domestic and international reports have successively reported that oil and gas field brine, geothermal brine, underground brine salt production (sodium chloride / potassium chloride) mother liquor, seawater salt production concentrated mother liquor, chemical industrial solution / wastewater contain 5~200ppm lithium. Compared with salt lake brine, these lithium-containing solutions can be collectively referred to as unconventional lithium-containing brines, or complex and difficult to handle medium and low-grade lithium-containing brines. This type of unconventional lithium-containing brine is difficult to directly use the mature process technology of lithium extraction from salt lakes, mainly due to the low lithium concentration and the high concentration of Na + Mg 2+ , K + , Ca 2+ Plasma, oil and gas field brines also contain petroleum-based organic matter, making selective extraction difficult. However, these unconventional lithium-containing brines are widely distributed worldwide, and the total amount of lithium is enormous. Developing specialized separation methods and efficient lithium recovery and extraction technologies is of great significance. Summary of the Invention

[0003] The present invention provides a method for extracting lithium carbonate from complex and difficult-to-treat medium- and low-grade lithium-containing brine. For the complex and difficult-to-treat medium- and low-grade lithium-containing brine, an aluminum salt precipitation method is used to quickly and efficiently precipitate lithium in the brine, and the precipitate mainly composed of lithium-containing aluminum hydroxide is collected. The precipitate is further subjected to hydrothermal analysis, purification, concentration, lithium precipitation and other steps to produce battery-grade lithium carbonate. The present invention realizes the direct and high-efficiency extraction of lithium from high-calcium and magnesium, high-organic-matter, medium- and low-grade unconventional lithium-containing brine without chemical pretreatment. The process has the significant advantages of wide adaptability, short process flow and low cost.

[0004] Specifically, in a first aspect, the present invention provides a method for treating lithium-containing brine, the method comprising: Mixing a sodium aluminate solution, an acid and the lithium-containing brine to obtain a reaction system; the sodium aluminate solution contains NaOH and Al2O3; and neutralizing the sodium aluminate solution and the acid in the reaction system; While the acid-base neutralization is being carried out, the lithium in the reaction system enters the crystal lattice of the aluminum hydroxide generated by the acid-base neutralization to form a lithium-rich slag precipitate; The lithium-rich slag precipitate and water are mixed and heated, followed by solid-liquid separation to obtain an elution solution and an elution slag; The analytical solution is used to recover lithium therein; The decomposed slag is processed through a re-dissolution process to prepare the sodium aluminate solution.

[0005] After the reaction system forms a lithium-rich slag precipitate, solid-liquid separation is performed to obtain the lithium-rich slag precipitate and brine after lithium precipitation; wherein, the lithium-rich slag precipitate also contains impurities because some impurities enter the aluminum hydroxide.

[0006] The lithium-rich slag precipitate and water are mixed and heated, and then solid-liquid separation is performed to obtain an analyte solution and an analyte slag.

[0007] After lithium precipitation, the brine is discharged or reused.

[0008] The researchers discovered that during the acid-base neutralization, the lithium in the reaction system enters the aluminum hydroxide lattice generated by the neutralization to form a lithium-rich precipitate, which plays a crucial role in achieving a lithium precipitation rate of ≥90%. This is because the newly generated aluminum hydroxide nuclei are extremely reactive and strongly adsorb ions.

[0009] According to the method for treating lithium-containing brine provided by the present invention, the NaOH content in the sodium aluminate solution is ≥15%, and the Al2O3 content is ≥12%; The acid is a hydrochloric acid solution with a mass concentration of 5-15%; When forming the lithium-rich slag, the pH value of the reaction system is 5-8, the temperature is 20-80° C., and the reaction time is 1-20 hours; Further preferably, the hydrochloric acid is derived from an industrial salt electrolysis process.

[0010] The method for treating the lithium-containing brine provided by the present invention comprises: The lithium-containing brine is placed in a reactor, and sodium aluminate solution and acid are added thereto in proportion; The sodium aluminate solution and the acid are subjected to acid-base neutralization in the reaction system; While the acid-base neutralization is being carried out, the lithium in the reaction system enters the crystal lattice of the aluminum hydroxide generated by the acid-base neutralization to form a lithium-rich slag precipitate; The lithium-rich slag precipitate is washed with water and then subjected to hydrothermal analysis and solid-liquid separation to obtain an analysis liquid and an analysis slag.

[0011] Preferably, the lithium content in the analytical solution is greater than 300 mg / L.

[0012] Preferably, the lithium content in the decomposed slag is less than 0.08%.

[0013] Further preferably, the washing liquid from the water washing of the lithium-rich slag precipitation is refluxed into the lithium precipitation reactor for reuse.

[0014] According to the method for treating the lithium-containing brine provided by the present invention, the re-dissolution process comprises: mixing the analytical slag and liquid alkali to dissolve the aluminum oxide therein to form aluminate ions, and then performing solid-liquid separation to obtain the sodium aluminate solution (i.e., returning the solution to the reactor containing the lithium-containing brine); Preferably, aluminum hydroxide or ground bauxite is added to the mixed dissolution process of the analytical slag and the alkali solution to supplement the aluminum element.

[0015] Further preferably, the concentration of the liquid caustic soda is 12% to 32%.

[0016] Further preferably, the temperature for mixing and dissolving the analytical slag and liquid alkali is 145-240° C. and the time is 30-120 min.

[0017] Further preferably, the liquid caustic soda is derived from an industrial salt electrolysis process. The industrial salt electrolysis in the present invention can be carried out using an ion-exchange membrane electrolysis process or a bipolar membrane electrolysis process according to actual conditions. The ion-exchange membrane electrolysis process can produce 32% liquid caustic soda and >30% hydrochloric acid, while the bipolar membrane electrolysis process can produce >8% liquid caustic soda and >6% hydrochloric acid.

[0018] The main component of the analytical slag is hydrated alumina, and the impurities are mainly a small amount of calcium, magnesium and iron. Alkali solution is used to redissolve the alumina in a high-temperature reactor to make sodium aluminate solution, and the insoluble slag is separated and discharged.

[0019] According to the method for treating the lithium-containing brine provided by the present invention, the analytical solution is refined, concentrated, crystallized, solid-liquid separated, and dried to obtain lithium carbonate.

[0020] According to the method for treating the lithium-containing brine provided by the present invention, the refining includes at least one of the following operations: (1) using an ultrafiltration membrane to remove suspended matter in the analytical solution; (2) Using nanofiltration membrane and / or weak acid cationic resin to remove Ca in the analytical solution 2+ and / or Mg 2+ ; Preferably, the Ca of the purified analytical solution is 2+ and / or Mg 2+ The content is less than 2mg / L; (3) Using a boron removal resin to remove boron ions in the analytical solution.

[0021] Preferably, the boron ion content of the purified analytical solution is less than 5 mg / L.

[0022] Preferably, the pH of the purified analytical solution is 6-7.

[0023] According to the method for treating lithium-containing brine provided by the present invention, the purified analytical solution is concentrated so that the lithium concentration therein is ≥20 g / L.

[0024] Preferably, the concentration is carried out by combining a reverse osmosis membrane, an electrodialysis membrane and an MVR evaporator.

[0025] According to the method for treating the lithium-containing brine provided by the present invention, the concentrated analytical solution is subjected to a replacement reaction with carbonate to crystallize into lithium carbonate; the analytical solution containing the lithium carbonate is subjected to solid-liquid separation (such as separation by a centrifuge) to obtain crude lithium carbonate and lithium precipitation mother liquor.

[0026] Further preferably, the lithium content of the lithium precipitation mother solution is 1-2 g / L.

[0027] According to the method for treating the lithium-containing brine provided by the present invention, the lithium content in the lithium-containing brine is 5 to 200 ppm; And / or, the calcium content in the lithium-containing brine is 50-100000 ppm; And / or, the Mg content in the lithium-containing brine is 50-20000 ppm; and / or, the total organic carbon in the lithium-containing brine is 50 to 5000 ppm; And / or, the suspended matter content in the lithium-containing brine is 10-1000 mg / L; And / or, the sulfate content in the lithium-containing brine is 50-50000 ppm.

[0028] In a second aspect, the present invention also provides a method for extracting lithium carbonate from lithium-containing brine, comprising the above-mentioned method for treating lithium-containing brine, wherein the lithium carbonate is battery-grade lithium carbonate.

[0029] The present invention provides a method for extracting lithium carbonate from complex and difficult-to-process medium- and low-grade lithium-containing brine, comprising: mixing a sodium aluminate solution, an acid, and the lithium-containing brine to obtain a reaction system; subjecting the sodium aluminate solution and the acid to acid-base neutralization in the reaction system; while the acid-base neutralization is being carried out, lithium in the reaction system enters the crystal lattice of aluminum hydroxide generated by the acid-base neutralization to form a lithium-rich slag precipitate; and can achieve the following purposes: 1. For low-grade lithium-containing brines with high calcium and magnesium content, high organic matter content, and complex and difficult-to-treat characteristics, the above-mentioned direct precipitation method can achieve high-efficiency lithium precipitation, with a lithium precipitation rate of ≥90%, exceeding the level currently achievable by conventional adsorbents for lithium extraction from salt lakes.

[0030] 2. The lithium-rich slag is hydrothermally analyzed, with a lithium analysis rate of ≥90%, and the lithium content of the obtained analysis liquid is >300mg / L. High-quality lithium carbonate products can be produced through further refining, concentration, crystallization and other processes, achieving the goal of producing high-quality lithium carbonate from unconventional lithium-containing brine.

[0031] 3. The analytical residue obtained after lithium precipitation is completely dissolved in liquid alkali to reuse the aluminum hydroxide in it, which greatly reduces material loss and optimizes production costs.

[0032] 4. The new process proposes for the first time the construction of industrial salt electrolysis acid and alkali production equipment in conjunction with the lithium extraction production line, so that the entire production line does not need to purchase acid and alkali chemicals from outside, which is especially suitable for remote areas with energy advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 This is one of the flow diagrams of the method for extracting lithium carbonate from lithium-containing brine provided by the present invention. DETAILED DESCRIPTION

[0035] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0036] The following combination Figure 1 The present invention describes a method for extracting lithium carbonate from complex and difficult to process medium and low-grade lithium-containing brine.

[0037] In a specific embodiment of the present invention, a method for treating lithium-containing brine is first provided, the method comprising: Mixing a sodium aluminate solution, an acid and the lithium-containing brine to obtain a reaction system; the sodium aluminate solution contains NaOH and Al2O3; and neutralizing the sodium aluminate solution and the acid in the reaction system; While the acid-base neutralization is being carried out, the lithium in the reaction system enters the crystal lattice of the aluminum hydroxide generated by the acid-base neutralization to form a lithium-rich slag precipitate; The lithium-rich slag precipitate and water are mixed and heated, followed by solid-liquid separation to obtain an elution solution and an elution slag; The analytical solution is used to recover lithium therein; The decomposed slag is processed through a re-dissolution process to prepare the sodium aluminate solution.

[0038] In some embodiments of the present invention, based on the total amount of lithium in the lithium-containing brine, the precipitation rate of lithium when the lithium-rich slag is formed is ≥90%.

[0039] In some embodiments of the present invention, the sodium aluminate solution has a NaOH content of ≥15% and an Al2O3 content of ≥12%.

[0040] In some embodiments of the present invention, the acid is a hydrochloric acid solution with a mass concentration of 5-15%.

[0041] In some embodiments of the present invention, when the lithium-rich slag is formed, the pH value of the reaction system is 5-8, the temperature is 20-80° C., and the reaction time is 1-20 h.

[0042] In some embodiments of the present invention, the hydrochloric acid is derived from an industrial salt electrolysis process.

[0043] In some embodiments of the present invention, the processing method includes: The lithium-containing brine is placed in a reactor, and sodium aluminate solution and acid are added thereto in proportion; The sodium aluminate solution and the acid are subjected to acid-base neutralization in the reaction system; While the acid-base neutralization is being carried out, the lithium in the reaction system enters the crystal lattice of the aluminum hydroxide generated by the acid-base neutralization to form a lithium-rich slag precipitate; The lithium-rich slag precipitate is washed with water and then subjected to hydrothermal analysis and solid-liquid separation to obtain an analysis liquid and an analysis slag; In some embodiments of the present invention, the lithium content in the analytical solution is greater than 300 mg / L.

[0044] In some embodiments of the present invention, the lithium content in the decomposed slag is less than 0.08%.

[0045] In some embodiments of the present invention, the desorption process includes mixing the lithium-rich slag precipitate after water washing with water at a liquid-to-solid ratio (L / S) of 5 to 40, treating the mixture at a temperature of 120 to 240°C for 30 to 120 minutes, and then separating the solid and liquid to obtain a desorption solution and desorption slag. The temperature of 120 to 240°C is achieved by indirect heating, such as steam heating.

[0046] In some embodiments of the present invention, the calcium content in the analytical solution is greater than 10 mg / L.

[0047] In some embodiments of the present invention, the magnesium content in the analytical solution is greater than 1 mg / L.

[0048] In some embodiments of the present invention, the boron content in the analytical solution is greater than 10 mg / L.

[0049] In some embodiments of the present invention, the pH value of the analytical solution is 7-9.

[0050] In some embodiments of the present invention, the conductivity of the analytical solution is 8000-20000 μs / cm.

[0051] In some embodiments of the present invention, the COD content of the analytical solution is greater than 20 mg / L.

[0052] In some embodiments of the present invention, the desorption rate is ≥97%.

[0053] In some embodiments of the present invention, the washing liquid from the water washing of the lithium-rich slag precipitation is refluxed into the lithium precipitation reactor for reuse.

[0054] In some embodiments of the present invention, the re-dissolution process includes: mixing the analytical slag and liquid alkali to dissolve the aluminum oxide therein to form aluminum carbonate, and then separating the solid and liquid to obtain the sodium aluminate solution (i.e., returning it to the reactor where the lithium-containing brine is located).

[0055] In some embodiments of the present invention, aluminum hydroxide or ground bauxite is added to the mixed dissolution process of the analytical slag and the alkali solution to supplement the aluminum element.

[0056] In some embodiments of the present invention, the concentration of the liquid caustic soda is 12% to 32%.

[0057] In some embodiments of the present invention, the temperature for mixing and dissolving the analytical slag and liquid alkali is 145-240° C. and the time is 30-120 min.

[0058] In some embodiments of the present invention, the liquid caustic soda is derived from an industrial salt electrolysis process.

[0059] In some embodiments of the present invention, the analytical solution is refined, concentrated, crystallized, solid-liquid separated, and dried to obtain lithium carbonate.

[0060] In some embodiments of the present invention, the refining comprises at least one of the following operations: (1) using an ultrafiltration membrane to remove suspended matter in the analytical solution; (2) Using nanofiltration membrane and / or weak acid cationic resin to remove Ca in the analytical solution 2+ and / or Mg 2+ ; Preferably, the Ca of the purified analytical solution is 2+ and / or Mg 2+ The content is less than 2mg / L; (3) Using a boron removal resin to remove boron ions in the analytical solution.

[0061] In some embodiments of the present invention, the boron ion content of the purified analytical solution is less than 5 mg / L.

[0062] Preferably, the pH of the purified analytical solution is 6-7.

[0063] In some embodiments of the present invention, the specification of the ultrafiltration membrane is Toray HFU-2020AN.

[0064] In some embodiments of the present invention, the boron removal resin may be Lanxiao Seplite or Suqing D403.

[0065] In some embodiments of the present invention, the specification of the nanofiltration membrane is Toray NE4040-40.

[0066] In some embodiments of the present invention, the specification of the weakly acidic cationic resin is Suqing D113.

[0067] In some embodiments of the present invention, nanofiltration membrane is first used to remove Ca 2+ and / or Mg 2+ , and then use weak acid cationic resin to completely remove Ca 2+ and / or Mg 2+ .

[0068] In some embodiments of the present invention, the desorption liquid passes through two glass resin columns in sequence, the first resin column is filled with weak acid cation resin, and the second resin column is filled with boron removal resin. 2+ and / or Mg 2+ The content of iron is less than 1mg / L, and the content of boron is less than 2mg / L.

[0069] In some embodiments of the present invention, the purified analytical solution is concentrated to obtain a lithium concentration ≥ 20 g / L; In some embodiments of the present invention, the concentration may be performed using a reverse osmosis membrane, an electrodialysis membrane, or an MVR evaporator, or a combination of the three.

[0070] In some embodiments of the present invention, the concentrated analytical solution is subjected to a replacement reaction with carbonate to crystallize into lithium carbonate; the analytical solution containing the lithium carbonate is subjected to solid-liquid separation (such as separation by a centrifuge) to obtain crude lithium carbonate and lithium precipitation mother liquor.

[0071] In some embodiments of the present invention, the lithium content of the lithium precipitation mother solution is 1-2 g / L.

[0072] In some embodiments of the present invention, the crystallization temperature is 90-100° C. and the time is 1-4 hours.

[0073] In some embodiments of the present invention, the amount of the carbonate added is 1.05 to 1.2 times the molar number of lithium carbonate.

[0074] In some embodiments of the present invention, the lithium precipitation mother liquor is subjected to lithium adsorption by an adsorption resin, and then subjected to acid desorption to obtain a desorption liquid; the desorption liquid is mixed with the refined analytical solution to perform the concentration.

[0075] In some embodiments of the present invention, the acid desorption uses hydrochloric acid with a concentration of 0.1% to 0.5%.

[0076] In some embodiments of the present invention, the hydrochloric acid is derived from an industrial salt electrolysis process.

[0077] In some embodiments of the present invention, the crude lithium carbonate is subjected to 2-3 times of beating countercurrent washing, the washing temperature is 90-100° C., the washing water multiple is 3-8 times, and the moisture content of the wet lithium carbonate product after washing and centrifugation is ≤15%.

[0078] In some embodiments of the present invention, the carbonate is added in the form of a carbonate solution, which is obtained by dissolving the carbonate in a washing solution after washing the crude lithium carbonate. Preferably, the concentration of the carbonate solution is 200-500 g / L.

[0079] In some embodiments of the present invention, the lithium content in the lithium-containing brine is 5 to 200 ppm; And / or, the calcium content in the lithium-containing brine is 50-100000 ppm; And / or, the Mg content in the lithium-containing brine is 50-20000 ppm; and / or, the total organic carbon in the lithium-containing brine is 50 to 5000 ppm; And / or, the suspended matter content in the lithium-containing brine is 10-1000 mg / L; And / or, the sulfate content in the lithium-containing brine is 50-50000 ppm.

[0080] In some embodiments of the present invention, the lithium-containing brine is selected from one or a combination of two or more of oil and gas field brine, geothermal brine, underground brine (sodium chloride / potassium chloride) mother liquor, seawater salt production concentrated mother liquor, and chemical industrial solution / wastewater.

[0081] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0082] Example 1: Based on process flow Figure 1 , brine is produced by underground vacuum salt mother liquor Brine composition: mg / L Table 1 The specific process of extracting lithium carbonate from complex and difficult to process low-grade lithium-containing brine is as follows: Pour 40L of brine into the reactor, start mechanical stirring, maintain the brine temperature at 50℃, and add sodium aluminate solution and dilute hydrochloric acid into the reactor in parallel to control the brine pH to 7~7.5, wherein: sodium aluminate solution contains NaOH=22%, Al2O3=20%, H2O=57%, Na2CO3=1%, and hydrochloric acid mass concentration=10%; the amount of sodium aluminate solution added is 425g, and the amount of hydrochloric acid used is 1010g; after 30 minutes of addition, stir at a constant temperature for 4 hours; after the reaction is completed, filter the precipitate, and the lithium content of the brine after lithium precipitation is measured to be 3.5mg / L, and the lithium precipitation rate is 94.5%. After washing and drying the precipitate, 132g of dry lithium-rich slag is obtained with a lithium content of 1.75%.

[0083] Take dried lithium-rich slag, add 4350g soft water and place it in a 5L reactor, heat to 200℃ and react for 1h. After the reaction is completed, cool down, take out the slurry, filter to obtain the desorption liquid and analytical slag, and the lithium content of the desorption liquid is 520mg / L, the main impurity calcium content is 30mg / L, the magnesium content is 5mg / L, the boron content is 50mg / L, the pH value is 8.5, the conductivity is 11050us / cm, the lithium content of the analytical slag is 0.05%, and the desorption rate is ≥97%.

[0084] The desorption liquid passes through two φ25×300mm glass resin columns in sequence. The first resin column is loaded with weak acidic cationic resin (Suqing D113) and the second resin column is loaded with boron removal resin (Suqing D403). After treatment, the desorption liquid contains calcium and magnesium <1mg / L and boron content <2mg / L. After evaporation to a lithium content of 25g / L, 300g / L sodium carbonate aqueous solution is added to crystallize lithium carbonate. The amount of sodium carbonate added is 0.55 times the molar number of lithium. The reaction temperature is 95°C and the time is 2 hours. After the reaction, it is filtered and separated. The lithium content in the lithium precipitation mother liquor is 1.2g / L. The lithium carbonate is washed with 5 times hot water and then dried. The composition of the finished lithium carbonate is as follows: Table 2

[0085] The product quality meets the standards of battery-grade lithium carbonate.

[0086] After the analytical slag is dried, it is mixed with liquid alkali with a mass concentration of 32%, and the molecular ratio of NaOH to Al2O3 is 2.75. It is placed in a high-pressure reactor and reacted at 220°C for 1 hour. All the alumina in the analytical slag is dissolved in the alkali solution. After cooling, the solution is filtered to remove the insoluble residue. The mass concentration of NaOH measured in the solution is 23.5%, and the mass concentration of Al2O3 is 21.8%. It can be used for the next batch of lithium precipitation reaction.

[0087] Example 2: Based on process flow Figure 1 , brine is produced from underground brine extracted from petroleum Brine composition: mg / L Table 3 Note: Ct is total organic carbon Pour 4L of brine into the reactor, start mechanical stirring, maintain the brine temperature at 50℃, and add sodium aluminate solution and dilute hydrochloric acid into the reactor in parallel to control the brine pH to 5~5.5, wherein: sodium aluminate solution contains NaOH = 22%, Al2O3 = 20%, H2O = 57%, Na2CO3 = 1%, and hydrochloric acid mass concentration = 10%; the amount of sodium aluminate solution added is 155g, and the amount of hydrochloric acid used is 305g; after 30 minutes of addition, stir at a constant temperature for 16 hours; after the reaction is completed, filter the precipitate, and the lithium mother liquor contains 8.5mg / L of lithium, with a lithium precipitation rate of 95.1%. After washing and drying the precipitate, 49.8g of dry lithium-rich slag is obtained with a lithium content of 1.13%.

[0088] Take dried lithium-rich slag, add 1495g soft water and place it in a 5L reactor, heat to 220℃ and react for 1h. After the reaction is completed, cool down, take out the slurry, filter, and obtain desorption liquid and analytical slag. The lithium content of the desorption liquid is 351mg / L, the main impurity calcium content is 1020mg / L, the magnesium content is 167mg / L, the boron content is 113mg / L, the COD content is 37.5mg / L, pH=7.5, the conductivity is 16050μs / cm, the analytical slag contains 0.055% lithium, and the desorption rate is ≥95%.

[0089] The desorption liquid passes through two φ25×300mm glass resin columns in sequence. The first resin column is loaded with weak acidic cationic resin (Suqing D113) and the second resin column is loaded with boron removal resin (Suqing D403). After treatment, the desorption liquid contains calcium and magnesium <1mg / L, B <2mg / L, and is evaporated to a lithium content of 20g / L. 300g / L sodium carbonate aqueous solution is added to crystallize lithium carbonate. The amount of sodium carbonate added is 0.55 times the molar number of lithium. The reaction temperature is 95°C and the time is 2 hours. After the reaction, it is filtered and separated. The lithium content of the lithium precipitated mother liquor is 1.2g / L. The lithium carbonate is washed with 5 times hot water and then dried. The composition of the finished lithium carbonate is as follows: Table 4

[0090] The product quality meets the standards of battery-grade lithium carbonate.

[0091] After the analytical slag is dried, it is mixed with liquid alkali with a mass concentration of 32%, and the molecular ratio of NaOH to Al2O3 is 2.75. It is placed in a high-pressure reactor and reacted at 240°C for 1 hour. All the alumina in the analytical slag is dissolved in the alkali solution. After cooling, the solution is filtered to remove the insoluble residue. The mass concentration of NaOH measured in the solution is 22.5%, and the mass concentration of Al2O3 is 20.5%. It can be used for the next batch of lithium precipitation reaction.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for treating lithium-containing brine, characterized in that: The processing method comprises: Mixing a sodium aluminate solution, an acid and the lithium-containing brine to obtain a reaction system; the sodium aluminate solution contains NaOH and Al2O3; and neutralizing the sodium aluminate solution and the acid in the reaction system; While the acid-base neutralization is being carried out, the lithium in the reaction system enters the crystal lattice of the aluminum hydroxide generated by the acid-base neutralization to form a lithium-rich slag precipitate; The lithium-rich slag precipitate and water are mixed and heated, followed by solid-liquid separation to obtain an elution solution and an elution slag; The analytical solution is used to recover lithium therein; The decomposed slag is processed through a re-dissolution process to prepare the sodium aluminate solution.

2. The method for treating lithium-containing brine according to claim 1, wherein: The sodium aluminate solution contains NaOH content ≥15% and Al2O3 content ≥12%; The acid is a hydrochloric acid solution with a mass concentration of 5-15%; When forming the lithium-rich slag, the pH value of the reaction system is 5-8, the temperature is 20-80° C., and the reaction time is 1-20 hours; Further preferably, the hydrochloric acid is derived from an industrial salt electrolysis process.

3. The method for treating lithium-containing brine according to claim 1 or 2, wherein: include: The lithium-containing brine is placed in a reactor, and sodium aluminate solution and acid are added thereto in proportion; The sodium aluminate solution and the acid are subjected to acid-base neutralization in the reaction system; While the acid-base neutralization is being carried out, the lithium in the reaction system enters the crystal lattice of the aluminum hydroxide generated by the acid-base neutralization to form a lithium-rich slag precipitate; The lithium-rich slag precipitate is washed with water and then subjected to hydrothermal analysis and solid-liquid separation to obtain an analysis liquid and an analysis slag; Preferably, the lithium content in the analytical solution is greater than 300 mg / L; Preferably, the lithium content in the decomposed slag is less than 0.08%.

4. The method for treating lithium-containing brine according to any one of claims 1 to 3, wherein: The re-dissolution process comprises: mixing the decomposed slag and liquid alkali to dissolve the aluminum oxide therein to form aluminate ions, and then separating the solid and liquid to obtain the sodium aluminate solution; Preferably, the temperature for mixing and dissolving the analytical slag and liquid alkali is 145-240° C. and the time is 30-120 min. Further preferably, the liquid alkali is derived from an industrial salt electrolysis process.

5. The method for treating lithium-containing brine according to any one of claims 1 to 4, wherein: The analytical solution is refined, concentrated, crystallized, solid-liquid separated, and dried to obtain lithium carbonate.

6. The method for treating lithium-containing brine according to claim 5, characterized in that: The refining comprises at least one of the following operations: (1) using an ultrafiltration membrane to remove suspended matter in the analytical solution; (2) Using nanofiltration membrane and / or weak acid cationic resin to remove Ca in the analytical solution 2+ and / or Mg 2+ ; Preferably, the Ca of the purified analytical solution is 2+ and / or Mg 2+ The content is less than 2mg / L; (3) removing boron ions from the analytical solution using a boron removal resin; Preferably, the boron ion content of the purified analytical solution is less than 5 mg / L.

7. The method for treating lithium-containing brine according to claim 5 or 6, characterized in that: The purified analytical solution is concentrated to obtain a lithium concentration of ≥20 g / L; Preferably, the concentration is carried out by combining a reverse osmosis membrane, an electrodialysis membrane and an MVR evaporator.

8. The method for treating lithium-containing brine according to any one of claims 5 to 7, wherein: The concentrated analytical solution is subjected to a replacement reaction with a carbonate to crystallize into lithium carbonate; the analytical solution containing the lithium carbonate is subjected to solid-liquid separation to obtain a crude lithium carbonate product and a lithium precipitation mother liquor; Further preferably, the lithium content of the lithium precipitation mother solution is 1-2 g / L.

9. The method for treating lithium-containing brine according to any one of claims 1 to 8, wherein: The lithium content in the lithium-containing brine is 5 to 200 ppm; And / or, the calcium content in the lithium-containing brine is 50-100000 ppm; And / or, the Mg content in the lithium-containing brine is 50-20000 ppm; and / or, the total organic carbon in the lithium-containing brine is 50 to 5000 ppm; And / or, the suspended matter content in the lithium-containing brine is 10-1000 mg / L; And / or, the sulfate content in the lithium-containing brine is 50-50000 ppm.

10. A method for extracting lithium carbonate from lithium-containing brine, characterized in that: The method for treating lithium-containing brine according to any one of claims 1 to 9, wherein the lithium carbonate is battery-grade lithium carbonate.

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