A method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium

Abstract

The application provides a method for preparing high-purity lithium hydroxide monohydrate and recycling rubidium and cesium, comprising the following steps: (1) mixing, ball-milling and roasting lithium ore, a sulfate and an additive at high temperature to obtain clinker; (2) crushing and grinding the clinker in step (1) and using water to obtain a leaching solution; (3) adding the leaching solution in step (2) into a three-chamber electrolytic cell for constant-current electrolysis to obtain an anode liquid, an intermediate liquid and a cathode liquid; (4) obtaining sulfuric acid from the anode liquid, evaporating and concentrating the intermediate liquid, step-by-step cooling and crystallization to obtain rubidium sulfate, cesium sulfate and sodium-potassium sulfate for roasting in step (1), and evaporating and concentrating the cathode liquid to obtain high-purity lithium hydroxide monohydrate. The high-purity lithium hydroxide monohydrate can be obtained through high selectivity of lithium ion solid-state electrolyte thin film to lithium, the utilization rate of potassium, rubidium and cesium is improved, the whole process is green and environmentally friendly, the comprehensive utilization rate of lithium ore is improved, and the product value is high.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium. Background Technology

[0002] Lithium, due to its unique electrochemical properties, has become a key material in primary and secondary batteries for various portable devices and electric vehicles. Currently, high-nickel ternary cathode materials are considered the most promising cathode materials for power batteries due to their high specific energy. In recent years, as the production capacity of high-nickel ternary cathode materials has gradually increased, the demand for lithium hydroxide, one of the raw materials for synthesis, has also grown rapidly, with high purity requirements. Currently, the main methods for preparing high-purity lithium hydroxide monohydrate include the limestone method, the causticization method, and the bipolar membrane electrodialysis method.

[0003] The limestone process involves mixing and grinding lithium ore and calcium oxide, then calcining the mixture in a rotary kiln at 800-900℃ to obtain clinker. The clinker is then water-quenched, finely ground, leached, and separated by sedimentation to obtain a leachate. Evaporation of the leachate yields lithium hydroxide monohydrate. This method is simple, but it has low extraction rates for lithium and rubidium / cesium, resulting in low purity lithium hydroxide monohydrate.

[0004] The causticization method is a process for preparing lithium hydroxide using the metathesis reaction of lithium salts and hydroxides. It typically involves the metathesis reaction of lithium carbonate and calcium hydroxide, as well as lithium sulfate and barium hydroxide. Patent document CN108821313B discloses a method for preparing lithium hydroxide monohydrate using lithium carbonate. In this method, a suspension of lithium carbonate and calcium oxide in water is stirred and reacted under pressure and heating. After filtration, purification, dissolution and crystallization, and drying, lithium hydroxide monohydrate is obtained. This method uses industrial-grade lithium carbonate to prepare lithium hydroxide monohydrate, resulting in high product purity and ease of industrialization. However, the purity is limited by the cost of the raw materials, which are expensive.

[0005] Bipolar membrane electrodialysis is a method that uses a bipolar membrane system to electrolyze a refined lithium salt solution, obtaining a highly concentrated lithium hydroxide solution on the cathode side, and then evaporating and crystallizing it to obtain lithium hydroxide monohydrate. Patent document CN111235591B discloses a method for preparing lithium hydroxide monohydrate from spodumene sulfuric acid leachate. This method utilizes a bipolar membrane system to electrolyze a purified and multi-stage filtered lithium sulfate solution, evaporates the cathode solution to obtain lithium hydroxide monohydrate, and recycles the anolyte. This method produces lithium hydroxide with high purity and does not require the addition of external hydroxides for causticization; however, it requires high purity of the refined lithium salt solution and cannot effectively recover the valuable metals rubidium and cesium.

[0006] Therefore, in view of the shortcomings of existing technologies, it is necessary to provide a method for preparing high-purity lithium hydroxide monohydrate from green and efficient purified lithium ore leaching solution and recovering rubidium and cesium, which is of great significance to the development of my country's new energy industry. Summary of the Invention

[0007] Based on this, the purpose of the present invention is to provide a method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium, so as to provide a method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium from green and efficient purified lithium ore leachate.

[0008] One embodiment of the present invention provides a method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium, comprising the following steps:

[0009] Step (1), high temperature roasting: lithium ore, sulfate and additives are ball-milled and mixed evenly in a certain proportion to obtain ball milling material, and the ball milling material is roasted at high temperature to obtain clinker;

[0010] Step (2), water immersion: The cooked material obtained in step (1) is immersed in water and filtered to obtain the leachate;

[0011] Step (3), electrolysis: The leachate from step (2) is added to a three-chamber electrolytic cell for constant current electrolysis to obtain anolyte, intermediate liquid and catholyte;

[0012] Step (4), catholyte evaporation: the catholyte is evaporated and concentrated to obtain high-purity lithium hydroxide monohydrate;

[0013] Step (5), intermediate liquid stepwise crystallization: the intermediate liquid is evaporated and concentrated and then cooled and crystallized stepwise to obtain sodium potassium sulfate, rubidium sulfate and cesium sulfate in sequence, and the sodium potassium sulfate is returned to step (1) for roasting.

[0014] The beneficial effects of this invention are:

[0015] 1. This invention does not involve the use of chemical products such as concentrated sulfuric acid, chlorides, and nitrates, which are highly harmful to the environment. It has low requirements for equipment corrosion prevention and is environmentally friendly. At the same time, the sulfuric acid, hydrogen, and oxygen produced by electrolysis can also be collected and sold.

[0016] 2. This invention utilizes the high selectivity and high conductivity of lithium solid electrolyte thin film for Li+ to construct a corresponding double-film three-chamber electrolysis system, which can obtain a high-purity lithium hydroxide solution in the cathode chamber, and then produce a high-purity lithium hydroxide monohydrate product by evaporation.

[0017] 3. This invention utilizes anion exchange membranes to prevent acidification of the cathode chamber, thereby improving the overall current efficiency. The sodium, potassium, rubidium, and cesium sulfates obtained in the intermediate chamber can be further concentrated and crystallized in steps to obtain the sodium, potassium sulfates, rubidium sulfate, and cesium sulfate products required for calcination.

[0018] 4. This invention has high extraction and utilization rates of lithium, sodium, potassium, rubidium, and cesium, and can produce high-purity lithium hydroxide monohydrate products. The by-product sodium and potassium sulfate can be returned to the roasting step, and rubidium and cesium can be recycled. The whole process is green and environmentally friendly, with high product value and broad industrial application prospects.

[0019] Preferably, the sulfate in step (1) is sodium sulfate or potassium sulfate, the additive is calcium oxide, the ratio of lithium ore: sodium sulfate: potassium sulfate: additive is 1:0.4-0.6:0.05-0.2:0.05-0.1, the particle size of the ball milling material is 100-200 mesh, the calcination temperature is 750-950℃, and the calcination time is determined according to the material ratio.

[0020] Preferably, the three-chamber electrolytic cell described in step (3) consists of an anode chamber, an intermediate chamber, and a cathode chamber, wherein an anion exchange membrane is used to separate the anode chamber and the intermediate chamber, and a lithium solid electrolyte membrane is used to separate the intermediate chamber and the cathode chamber.

[0021] Preferably, in the electrolysis process described in step (3), the pH value of the anode chamber is 0-2, and the Li content of the cathode chamber is 0.5-40 g / L.

[0022] Preferably, the current density of the electrolysis is 200-300 A / m2; the initial pH value of the anode chamber is 1-2, and the initial Li content of the cathode chamber is 0.5-5 g / L; during the electrolysis process, when the pH value of the anode chamber reaches 0-1, the anolyte is discharged; when the Li content of the cathode chamber reaches 30-40 g / L, the catholyte is discharged, evaporated and concentrated to obtain lithium hydroxide monohydrate product; when the Li content of the intermediate chamber is less than 0.005 g / L, the intermediate liquid is discharged, evaporated and concentrated, and then crystallized stepwise to obtain sodium potassium rubidium cesium sulfate.

[0023] Preferably, when the intermediate liquid is evaporated and concentrated to a total Na and K content of 80-100 g / L, sodium and potassium sulfate are crystallized out at a controlled crystallization temperature of 20-50°C. The mother liquor is further concentrated to a Rb content of 200-300 g / L and a Cs content of 100-150 g / L, and rubidium sulfate is crystallized out at a controlled crystallization temperature of -5 to 10°C. Cesium sulfate is crystallized out at a controlled crystallization temperature of -20 to -5°C.

[0024] Preferably, the anion exchange membrane is an AMI-7001 type quaternary ammonium anion exchange membrane, and the cation exchange membrane is a lithium lanthanum titanium oxide (LLTO), lithium lanthanum zirconium oxide (LLZO), or lithium lanthanum zirconium tantalum oxide (LLZTO) solid electrolyte film; the cathode and anode materials are both coated titanium electrodes.

[0025] Preferably, the synthesis process of the LLTO, LLZO, or LLZTO solid electrolyte film involves preparing particles using a high-temperature solid-state method and preparing the film using a casting method. Specifically, the process involves mixing metal sources such as lithium, lanthanum, titanium, zirconium, and tantalum in a certain proportion, ball milling them in isopropanol, synthesizing LLTO, LLZO, or LLZTO particles using a high-temperature solid-state method, mixing the particles with an organic solvent and ball milling them into a slurry, coating the slurry onto a PET (polyethylene terephthalate) release film, drying and peeling it off, and then hot-pressing and high-temperature sintering to obtain a dense solid electrolyte film.

[0026] Preferably, the metal source is a metal oxide or carbonate; the ball milling speed is 250-350 rpm, and the ball milling time is 10-12 h; the high-temperature solid-state method involves holding at 800℃ for 4-6 h and continuously sintering at 1100-1250℃ for 24-30 h; the organic solvent is triethanolamine, polyvinyl butyral (PVP), benzyl butyl phthalate (BBP), or ethanol; the hot pressing is performed at 90-110℃ with a pressure of 8-12 MPa for 5-15 min; and the high-temperature sintering involves pre-sintering at 500-600℃ for 1-3 h and sintering at 1000-1300℃ for 10-12 h.

[0027] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] Figure 1 This is a process flow diagram of a method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium according to an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram illustrating the working principle of a double-membrane three-chamber electrolyzer according to an embodiment of the present invention.

[0030] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0031] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0035] The embodiments provided by this invention aim to provide a method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium from green and efficient purified lithium ore leaching solution, thereby improving the preparation efficiency of lithium hydroxide monohydrate and recovering rubidium and cesium to achieve resource recycling.

[0036] Example 1:

[0037] like Figure 1 As shown, this embodiment prepares high-purity lithium hydroxide monohydrate and recovers rubidium and cesium by purifying lithium ore leaching solution. The method provided in this embodiment specifically includes the following steps:

[0038] (1) Lithium mica with a Li2O content of 5.3% was mixed with sodium sulfate, potassium sulfate and calcium oxide in a ratio of 1:0.4:0.1:0.1 and ball-milled. The mixture was then calcined at 850℃ for 30 minutes to obtain clinker. Calcium salt was added to fix fluorine. The particle size after ball milling was 200 mesh.

[0039] (2) The clinker from step (1) is leached with clean water, filtered to obtain leachate, the leaching temperature is controlled at 25℃, the leaching time is 60min, the liquid-solid ratio is 3:1, the leaching method is one-stage or multi-stage countercurrent leaching, and the leaching residue is discarded after countercurrent washing.

[0040] (3) Figure 2 As shown in the electrolysis principle diagram, the leachate obtained in step (2), dilute sulfuric acid with a concentration of 0.01 mol / L, and dilute LiOH solution with a concentration of 0.1 mol / L are pumped into the middle chamber, anode chamber, and cathode chamber of the three-chamber electrolytic cell, respectively. Constant current electrolysis is performed with an electrolysis current density of 300 A / m2. The anion membrane is AMI-7001 type quaternary ammonium anion membrane, the cation membrane is LLTO solid electrolyte membrane, and the cathode and anode materials are both ruthenium-iridium coated titanium electrodes.

[0041] (4) When the pH value of the anode chamber reaches 0, the anode chamber solution is pumped out to the sulfuric acid storage tank. When the Li content of the intermediate chamber solution is less than 0.001 g / L, the intermediate chamber solution is pumped into the sodium potassium rubidium cesium solution storage tank. When the Li content of the cathode chamber reaches 35 g / L, the cathode chamber solution is pumped into the LiOH solution storage tank. After evaporation and concentration, lithium hydroxide monohydrate product is obtained.

[0042] (5) When the sodium potassium rubidium cesium solution is evaporated and concentrated to a total Na and K content of 100 g / L, it is cooled to 30 °C and allowed to stand to crystallize and precipitate sodium sulfate and potassium sulfate crystals. The sodium sulfate and potassium sulfate crystals are returned to step (1). The crystallization mother liquor is further concentrated to a Rb and Cs content of 280 g / L and 120 g / L, respectively. The crystallization mother liquor is cooled to -5 °C and -15 °C, respectively, to crystallize and precipitate crude rubidium sulfate and crude cesium sulfate crystals, respectively. After filtration, they are recrystallized to obtain refined rubidium sulfate and cesium sulfate products.

[0043] The leaching rates of lithium, rubidium, and cesium in this embodiment were measured to be 97.8%, 93.5%, and 90.1%, respectively. No lithium, rubidium, or cesium was detected in the electrolyte of the cathode chamber after electrolysis. + The purity of the prepared lithium hydroxide monohydrate product was 99.95%, the purity of rubidium sulfate was 99.4%, and the purity of cesium sulfate was 99.3%, in addition to the other cations.

[0044] Example 2:

[0045] The method provided in this embodiment is a method for preparing the LLTO solid electrolyte film in Example 1 above, specifically including the following steps:

[0046] (1) Lithium carbonate (Li2CO3), lanthanum oxide (La2O3), and titanium dioxide (TiO2) were ball-milled in isopropanol at a Li:La:Ti molar ratio of 0.33:0.57:1 at a speed of 300 rpm for 10 h. After drying at 80 °C, the mixture was kept at 800 °C for 4 h and then sintered continuously at 1100 °C for 26 h to obtain LLTO particles. The obtained particles were then ball-milled to obtain nano-LLTO particles.

[0047] (2) The nano-LLTO particles obtained in step (1) are mixed with triethanolamine, PVP, BBP and ethanol in a weight ratio of 50:2:12:6:30 and ball-milled for 12h to prepare a slurry. The slurry is coated on a PET release film with a scraper, dried at room temperature and then peeled off. The film is then hot-pressed at 12MPa at 100℃ for 8min to obtain a green film. The green film is pre-calcined at 500℃ for 2h and sintered at 1200℃ for 12h to obtain an LLTO solid electrolyte film.

[0048] Measurements showed that the average particle size of the nano-LLTO particles in this embodiment was around 200 nm, the thickness of the LLTO solid electrolyte film was 80 μm, and the impedance was 120 Ω.

[0049] Example 3:

[0050] Specifically, in this embodiment, it should be noted that the LLTO film used in this embodiment is the same as the LLTO film in Embodiment 1 above, and the method provided in this embodiment specifically includes the following steps:

[0051] (1) Lithium mica with a Li2O content of 3.0% was mixed with sodium sulfate, potassium sulfate and calcium oxide in a ratio of 1:0.4:0.1:0.1 and ball-milled. The mixture was then calcined at 900℃ for 30 minutes to obtain clinker with a particle size of 200 mesh after ball milling.

[0052] (2) The clinker from step (1) is leached with clean water, filtered to obtain leachate, the leaching temperature is controlled at 60℃, the leaching time is 60min, the liquid-solid ratio is 5:1, the leaching method is one-stage or multi-stage countercurrent leaching, and the leaching residue is discarded after countercurrent washing.

[0053] (3) Figure 2 As shown in the electrolysis principle diagram, the leachate obtained in step (2), dilute sulfuric acid with a concentration of 0.01 mol / L, and dilute LiOH solution with a concentration of 0.1 mol / L are pumped into the middle chamber, anode chamber, and cathode chamber of the three-chamber electrolytic cell, respectively. Constant current electrolysis is performed with an electrolysis current density of 300 A / m2. The anion membrane is AMI-7001 type quaternary ammonium anion membrane, the cation membrane is LLTO solid electrolyte membrane, and the cathode and anode materials are both ruthenium-iridium coated titanium electrodes.

[0054] (4) When the pH value of the anode chamber reaches 0, the anode chamber solution is pumped out to the sulfuric acid storage tank. When the Li content of the intermediate chamber solution is less than 0.001 g / L, the intermediate chamber solution is pumped into the sodium potassium rubidium cesium solution storage tank. When the Li content of the cathode chamber reaches 35 g / L, the cathode chamber solution is pumped into the LiOH solution storage tank. After evaporation and concentration, lithium hydroxide monohydrate product is obtained.

[0055] (5) When the sodium potassium rubidium cesium solution is evaporated and concentrated to a total Na and K content of 80 g / L, it is cooled to 30°C and allowed to stand to crystallize and precipitate sodium sulfate and potassium sulfate crystals. The sodium sulfate and potassium sulfate crystals are returned to step (1). The crystallization mother liquor is further concentrated to a Rb and Cs content of 250 g / L and 100 g / L, respectively. The crystallization mother liquor is cooled to -5°C and -20°C, respectively, to crystallize and precipitate crude rubidium sulfate and crude cesium sulfate crystals, respectively. After filtration, they are recrystallized to obtain refined rubidium sulfate and cesium sulfate products.

[0056] The leaching rates of lithium, rubidium, and cesium in this embodiment were measured to be 96.4%, 95.5%, and 92.4%, respectively. No lithium was detected in the electrolyte of the cathode chamber after electrolysis, except for Li. + The purity of the prepared lithium hydroxide monohydrate product was 99.95%, the purity of rubidium sulfate was 99.2%, and the purity of cesium sulfate was 99.1%, in addition to the other cations.

[0057] Please refer to Table 1 below, which shows the parameters corresponding to Embodiments 1 and 3 of the present invention.

[0058] Table 1

[0059]

[0060] It should be noted that the above implementation process is only to illustrate the feasibility of this application, but it does not mean that the method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium in this application has only the above-mentioned single implementation process. On the contrary, as long as the method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium in this application can be implemented, it can be included in the feasible implementation scheme of this application.

[0061] In summary, the method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium provided in the above embodiments of the present invention does not involve the use of chemical products such as concentrated sulfuric acid, chloride, and nitrate, which are highly harmful to the environment. It has low requirements for equipment corrosion protection and is environmentally friendly. At the same time, the sulfuric acid, hydrogen and oxygen produced by electrolysis can also be collected and sold.

[0062] A corresponding dual-membrane three-chamber electrolysis system was constructed by utilizing the high selectivity and high conductivity of lithium solid electrolyte thin film for Li+. High-purity lithium hydroxide solution can be obtained in the cathode chamber, and high-purity lithium hydroxide monohydrate product can be obtained by evaporation.

[0063] An anion exchange membrane is used to prevent acidification of the cathode chamber, which improves the overall current efficiency. The sodium, potassium, rubidium, and cesium sulfate obtained in the intermediate chamber can be further concentrated and crystallized in steps to obtain the sodium, potassium sulfate, rubidium sulfate, and cesium sulfate products required for calcination.

[0064] It has high extraction and utilization rates for lithium, sodium, potassium, rubidium, and cesium, and can produce high-purity lithium hydroxide monohydrate products. The by-product sodium and potassium sulfate can be returned to the roasting step, and rubidium and cesium can be recycled. The whole process is green and environmentally friendly, with high product value and broad industrial application prospects.

[0065] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0066] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium, characterized in that, Includes the following steps: Step (1), high temperature roasting: Lithium ore, sulfate and additives are ball-milled and mixed evenly in a certain proportion to obtain ball milling material, and the ball milling material is roasted at high temperature to obtain clinker; Step (2), water immersion: The cooked material obtained in step (1) is immersed in water and filtered to obtain the leachate; Step (3), electrolysis: The leachate from step (2) is added to a three-chamber electrolytic cell for constant current electrolysis to obtain anolyte, intermediate liquid and catholyte; Step (4), catholyte evaporation: the catholyte is evaporated and concentrated to obtain high-purity lithium hydroxide monohydrate; Step (5), intermediate liquid stepwise crystallization: the intermediate liquid is evaporated and concentrated and then cooled and crystallized stepwise to obtain sodium potassium sulfate, rubidium sulfate and cesium sulfate in sequence, and the sodium potassium sulfate is returned to step (1) for roasting; The three-chamber electrolytic cell described in step (3) consists of an anode chamber, an intermediate chamber, and a cathode chamber. An anion exchange membrane is used to separate the anode chamber and the intermediate chamber, and a lithium solid electrolyte membrane is used to separate the intermediate chamber and the cathode chamber.

2. The method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium according to claim 1, characterized in that, The sulfates mentioned in step (1) are sodium sulfate and potassium sulfate, the additive is calcium oxide, the ratio of lithium ore: sodium sulfate: potassium sulfate: additive is 1:0.4-0.6:0.05-0.2:0.05-0.1, the particle size of the ball milling material is 100-200 mesh, the calcination temperature is 750-950 ℃, and the calcination time is determined according to the material ratio.

3. The method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium according to claim 1, characterized in that, In step (3), the pH value of the anode chamber is 0-2 and the Li content of the cathode chamber is 0.5-40 g / L during the electrolysis process.

4. The method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium according to claim 1 or 3, characterized in that, The current density of the electrolysis is 200-300 A / m2; the initial pH value of the anode chamber is 1-2, and the initial Li content of the cathode chamber is 0.5-5 g / L; during the electrolysis process, when the pH value of the anode chamber reaches 0-1, the anolyte is discharged; when the Li content of the cathode chamber reaches 30-40 g / L, the catholyte is discharged, evaporated and concentrated to obtain lithium hydroxide monohydrate product; when the Li content of the intermediate chamber is less than 0.005 g / L, the intermediate liquid is discharged, evaporated and concentrated, and then crystallized stepwise to obtain sodium potassium rubidium cesium sulfate.

5. The method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium according to claim 1, characterized in that, When the intermediate liquid is evaporated and concentrated to a total Na and K content of 80-100 g / L, sodium and potassium sulfate are crystallized out at a controlled crystallization temperature of 20-50 ℃. The mother liquor is further concentrated to a Rb content of 200-300 g / L and a Cs content of 100-150 g / L. Rubidium sulfate is crystallized out at a controlled crystallization temperature of -5 to 10 ℃, and cesium sulfate is crystallized out at a controlled crystallization temperature of -20 to -5 ℃.

6. The method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium according to claim 1, characterized in that, The anion exchange membrane is an AMI-7001 type quaternary ammonium anion exchange membrane, and the cation exchange membrane is a lithium lanthanum titanium oxide (LLTO), lithium lanthanum zirconium oxide (LLZO), or lithium lanthanum zirconium tantalum oxide (LLZTO) solid electrolyte film; the cathode and anode materials are both coated titanium electrodes.

7. The method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium according to claim 6, characterized in that, The synthesis process of the LLTO, LLZO, or LLZTO solid electrolyte film involves preparing particles using a high-temperature solid-state method and preparing the film using a casting method. Specifically, the metal source is mixed in proportion, ball-milled in isopropanol, and then LLTO, LLZO, or LLZTO particles are synthesized using a high-temperature solid-state method. The particles and organic solvent are mixed and ball-milled to form a slurry. The slurry is coated onto a PET (polyethylene terephthalate) release film, dried, and then peeled off. After hot pressing and high-temperature sintering, a dense solid electrolyte film is obtained.

8. The method for preparing high-purity lithium hydroxide monohydrate and recovering rubidium and cesium according to claim 7, characterized in that, The metal source is a metal oxide or carbonate; the ball milling speed is 250-350 rpm, and the ball milling time is 10-12 h; the high-temperature solid-state method involves holding at 800 ℃ for 4-6 h and then continuously sintering at 1100-1250 ℃ for 24-30 h; the organic solvent is triethanolamine, polyvinyl butyral (PVP), benzyl butyl phthalate (BBP), or ethanol; the hot pressing is performed at 90-110 ℃ with a pressure of 8-12 MPa for 5-15 min; the high-temperature sintering involves pre-sintering at 500-600 ℃ for 1-3 h and then sintering at 1000-1300 ℃ for 10-12 h.

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