Preparation method of anhydrous lithium iodide

Abstract

According to an existing preparation method of anhydrous lithium iodide, a high-temperature water removal product is subjected to high-temperature decomposition and oxidative deterioration, and the purity of the product is reduced, the invention provides the preparation method of anhydrous lithium iodide, which comprises the following steps: preparing lithium resin, pre-treating the activated strong-acid cation exchange resin, adding a lithium-containing alkaline solution into the pre-treated strong-acid cation exchange resin for lithiation to obtain a lithium resin crude product, and leaching the lithium resin crude product by using an organic solvent to obtain lithium resin; and preparing the anhydrous lithium iodide: adding a mixed solution containing an organic solvent and potassium iodide into the lithium resin, carrying out ion exchange to obtain a lithium iodide crude product, and carrying out post-treatment on the lithium iodide crude product to obtain the anhydrous lithium iodide. According to the preparation method of the anhydrous lithium iodide provided by the invention, the organic solvent participates in ion exchange, so that the water content of the lithium iodide is reduced, long-time high-temperature water removal is avoided, and the quality and yield of the product are improved.

Description

Technical Field

[0001] The invention relates to the technical field of anhydrous lithium iodide preparation, and in particular to a method for preparing anhydrous lithium iodide. Background Art

[0002] The current synthesis methods of anhydrous lithium iodide can be divided into the following three types.

[0003] The first neutralization method: lithium carbonate or lithium hydroxide is used as raw material to react with hydroiodic acid. This method does not produce any waste, but the resulting product is lithium iodide trihydrate. The dehydration process of this method has no solvent or gas protection. If air enters the disperser at high temperature, the product is easily oxidized and deteriorated, and the sealing and operation requirements of the dispersion process are high. At the same time, the dehydration method adopts direct evaporation method, without impurity removal process, and has high requirements on the quality and cost of raw materials.

[0004] The second method is to mix water, elemental iodine particles and excess iron powder, add lithium hydroxide, separate the solid and liquid, obtain lithium iodide solid containing crystal water, dissolve it in an organic solvent, and perform constant voltage electrolysis to obtain anhydrous lithium iodide solid, refer to the existing patent CN103137981B.

[0005] The third method is the liquid ammonia method; ammonium iodide and metallic lithium are reacted in liquid ammonia to prepare lithium iodide, and then the crystalline hydrate of lithium iodide is dried in a hydrogen iodide atmosphere. At the same time, dry hydrogen is introduced above the molten salt to decompose the generated iodine, or the crystalline hydrate is heated in a vacuum to dehydrate and sublime.

[0006] The water content of lithium iodide obtained by the latter two methods is generally greater than 0.02%, the synthesis process is complex, the process conditions are harsh, the operation is difficult to control, the cost is high, and a large amount of harmful gases will be generated during the synthesis process.

[0007] The anhydrous lithium iodide prepared by the above-mentioned preparation method contains a small amount of water. The high-temperature dehydration causes the product to be decomposed and oxidized and deteriorated, and the purity of the product is reduced.

[0008] Therefore, the industry urgently needs to find a simple and efficient method for synthesizing high-purity anhydrous lithium iodide. Summary of the invention

[0009] In view of the problem that the existing method for preparing anhydrous lithium iodide contains a small amount of water, and high-temperature water removal causes the product to be decomposed and oxidized by high temperature, thereby reducing the purity of the product, the present application provides a method for preparing anhydrous lithium iodide.

[0010] In one aspect, the present invention provides a method for preparing anhydrous lithium iodide, comprising the following steps: Preparation of lithium resin: activating a strongly acidic cation exchange resin, pre-treating the activated strongly acidic cation exchange resin, adding a lithium-containing alkaline solution to the pre-treated strongly acidic cation exchange resin for lithiation to obtain a crude lithium resin product, and eluting the crude lithium resin product with an organic solvent to obtain a lithium resin; Preparation of anhydrous lithium iodide: adding a mixed solution containing the organic solvent and potassium iodide to the lithium resin to perform ion exchange to obtain a crude lithium iodide product, and post-treating the crude lithium iodide product to obtain anhydrous lithium iodide.

[0011] Preferably, activating the strongly acidic cation exchange resin comprises the following steps: The cations in the strongly acidic cation exchange resin include potassium ions; Adding an acidic solution to the strongly acidic cation exchange resin to activate the strongly acidic cation exchange resin, and when the content of potassium ions in the acidic solution that has activated the strongly acidic cation exchange resin is less than 50 ppm, the activation is completed; The concentration of the acidic solution is 10% to 50%.

[0012] Preferably, the acidic solution includes at least one of sulfuric acid and hydrochloric acid; The concentration of the acidic solution is 25% to 35%; And / or, when the content of potassium ions in the acidic solution after activating the strongly acidic cation exchange resin is less than 2 ppm, the activation is completed.

[0013] Preferably, adding a lithium-containing alkaline solution to the pretreated strongly acidic cation exchange resin for lithiation comprises the following steps: The alkaline solution containing lithium is added to the pretreated strong acid cation exchange resin for lithiation. When the pH of the alkaline solution containing lithium after the lithium cation exchange resin is greater than 11, the lithiation is completed.

[0014] Preferably, the lithium-containing alkaline solution includes one or more of a lithium carbonate solution, a lithium bicarbonate solution, and a lithium hydroxide solution; The concentration of the lithium-containing alkaline solution is 5% to 20%.

[0015] Preferably, before the crude lithium resin product is eluted with an organic solvent, the following steps are further included: eluting the crude lithium resin product with water until the conductivity of the eluted water is less than 20 μS / cm, and the water elution is completed; The crude lithium resin product is eluted with an organic solvent, comprising the following steps: adding an organic solvent to the crude lithium resin product after water elution for elution, until the water content of the organic solvent after elution is less than 20000 ppm, and the elution of the organic solvent is finished; The organic solvent includes one or more of alcohol solvents, nitrile solvents, ether solvents, and carbonate solvents.

[0016] Preferably, the ether solvent includes ethylene glycol dimethyl ether; The nitrile solvent includes acetonitrile; The carbonate solvent includes dimethyl carbonate.

[0017] Preferably, in the mixed solution, the concentration of potassium iodide is 1% to 50%; Adding a mixed solution containing the organic solvent and potassium iodide to the lithium resin for ion exchange to obtain a crude lithium iodide product comprises the following steps: Adding a mixed solution of the organic solvent and potassium iodide to the lithium resin for ion exchange to obtain an effluent containing crude lithium iodide; when the lithium ion content in the effluent containing crude lithium iodide is less than 1000 ppm, the reaction is terminated, and the steps of preparing the lithium resin and preparing the anhydrous lithium iodide are repeated; The flow rate of the mixed solution is 30-80 mL / h. The organic solvent in the mixed solution is the same as the organic solvent in the step of eluting the crude lithium resin product with an organic solvent.

[0018] Preferably, before activating the strong acid cation exchange resin, the strong acid cation exchange resin is also pre-treated, and the pre-treatment includes the following steps: rinsing the strong acid cation exchange resin with water, and the conductivity of the water after rinsing is less than 20 μS / cm, and the pre-treatment is completed; And / or, pre-treating the activated strong acid cation exchange resin comprises the following steps: rinsing the activated strong acid cation exchange resin with water, wherein the conductivity of the rinsed water is less than 20 μS / cm, and the content of anions in the acidic solution in the rinsed water is less than 2 ppm.

[0019] Preferably, post-processing the crude lithium iodide to obtain the anhydrous lithium iodide comprises the following steps: Concentrating the crude lithium iodide under reduced pressure to obtain the anhydrous lithium iodide; The reduced pressure concentration temperature is 70-150°C.

[0020] The preparation method of anhydrous lithium iodide provided in the present application adopts a cationic resin exchange method to synthesize anhydrous lithium iodide, uses an organic solvent to elute a crude lithium resin product to remove water in the resin, and adds a mixed solution containing an organic solvent and potassium iodide to the lithium resin. The organic solvent participates in ion exchange, thereby reducing the water content of lithium iodide and reducing the process difficulty. In addition, since long-term high-temperature water removal is avoided, the product will not be decomposed and oxidized by high temperature, thereby improving the quality and yield of the product. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] In order to illustrate the technical solution of the present invention, specific embodiments are provided below for illustration.

[0023] In one embodiment of the present invention, a method for preparing anhydrous lithium iodide comprises the following steps: Preparation of lithium resin: activating a strongly acidic cation exchange resin, pre-treating the activated strongly acidic cation exchange resin, adding a lithium-containing alkaline solution to the pre-treated strongly acidic cation exchange resin for lithiation to obtain a crude lithium resin product, and eluting the crude lithium resin product with an organic solvent to obtain a lithium resin; Preparation of anhydrous lithium iodide: adding a mixed solution containing the organic solvent and potassium iodide to the lithium resin to perform ion exchange to obtain a crude lithium iodide product, and post-treating the crude lithium iodide product to obtain anhydrous lithium iodide.

[0024] Specifically, the strong acid cation exchange resin is activated, and hydrogen ions replace the original cations in the strong acid cation exchange resin to obtain an exchange resin containing hydrogen ions. An alkaline solution containing lithium is added to perform lithiation, that is, lithium ions are exchanged with hydrogen ions to obtain an exchange resin containing lithium ions, that is, lithium resin. A mixed solution containing potassium iodide is added to the lithium resin to perform an ion exchange reaction, that is, potassium ions are exchanged with lithium ions, potassium ions replace the lithium ions in the lithium resin, and lithium ions and iodide ions combine to form a new compound lithium iodide.

[0025] The preparation method of anhydrous lithium iodide provided in the present application adopts a cationic resin exchange method to synthesize anhydrous lithium iodide, uses an organic solvent to elute a crude lithium resin product to remove water in the resin, and adds a mixed solution containing an organic solvent and potassium iodide to the lithium resin. The organic solvent participates in ion exchange, thereby reducing the water content of lithium iodide and reducing the process difficulty. In addition, since long-term high-temperature water removal is avoided, the product will not be decomposed and oxidized by high temperature, thereby improving the quality and yield of the product.

[0026] The preparation method of anhydrous lithium iodide provided in the present application has a simple operation method, high yield, high purity, and organic solvents participate in ion exchange, which reduces the water content of lithium iodide and effectively reduces the difficulty of industrial drying of lithium iodide, providing a new idea for the industrial production of anhydrous lithium iodide.

[0027] In some embodiments, the cations in the strongly acidic cation exchange resin include potassium ions.

[0028] Specifically, the cations in the strongly acidic cation exchange resin are potassium ions, which are the same as the cations in the reactant potassium iodide, thereby preventing the introduction of new cationic impurities.

[0029] In some embodiments, activating the strongly acidic cation exchange resin comprises the following steps: Adding an acidic solution to the strongly acidic cation exchange resin to activate the strongly acidic cation exchange resin, and when the content of potassium ions in the acidic solution that has activated the strongly acidic cation exchange resin is less than 50 ppm, the activation is completed; The concentration of the acidic solution is 10% to 50%.

[0030] Specifically, an acidic solution is used to activate a strongly acidic cation exchange resin, and hydrogen ions in the acidic solution replace cations in the original strongly acidic cation exchange resin to obtain an exchange resin containing hydrogen ions.

[0031] The concentration of the added acidic solution is 10%~50%, which can not only quickly activate the strong acid cation exchange resin, but also prevent the precipitation of potassium compounds contained in it due to excessively high acid concentration, thus affecting product quality; at the same time, it prevents excessively high acid concentrations from causing a certain degree of damage to the structure of the cation exchange resin.

[0032] Specifically, the concentration of the acidic solution is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc., as long as the concentration of the acidic solution is within the range of 10% to 50%.

[0033] The criterion for determining the end of activation is that the content of potassium ions in the acidic solution after activating the strongly acidic cation exchange resin is less than 50 ppm.

[0034] In some embodiments, the acidic solution includes at least one of sulfuric acid and hydrochloric acid.

[0035] The acid solution is sulfuric acid or hydrochloric acid, which can reduce costs and activate the strong acid cation exchange resin.

[0036] In some embodiments, the concentration of the acidic solution is 25% to 35%.

[0037] The concentration of the acidic solution is in the range of 25-35%, which can activate the strong acidic cation exchange resin relatively quickly and reduce the process time.

[0038] In some preferred embodiments, the concentration of the acidic solution is 35%.

[0039] In some embodiments, the activation is completed when the potassium ion content in the acidic solution after the activation of the strongly acidic cation exchange resin is less than 2 ppm.

[0040] Specifically, an acidic solution is used to activate a strongly acidic cation exchange resin. When the concentration of the acidic solution is the same, the content of potassium ions in the acidic solution that has activated the strongly acidic cation exchange resin can be effectively reduced by increasing the amount of the acidic solution, and the content can be reduced to 2 ppm at the lowest. This can ensure that the active groups of the resin are effectively replaced by hydrogen ions, thereby ensuring that the resin has good cation exchange performance, can effectively perform ion exchange in subsequent use, and improve the purity of anhydrous potassium iodide.

[0041] In some embodiments, adding a lithium-containing alkaline solution to a pretreated strongly acidic cation exchange resin for lithiation comprises the following steps: The alkaline solution containing lithium is added to the pretreated strongly acidic cation exchange resin for lithiation. When the pH of the alkaline solution containing lithium after the lithium-ion exchange resin is greater than 11, the lithiation is completed.

[0042] Specifically, during the lithiation process, a lithium-containing alkaline solution is used to lithiation the pretreated strongly acidic cation exchange resin, so as to avoid bubbles generated during the lithiation process that affect the ion exchange effect of the resin.

[0043] In some embodiments, the lithium-containing alkaline solution includes one or more of a lithium carbonate solution, a lithium bicarbonate solution, and a lithium hydroxide solution.

[0044] In some preferred embodiments, the lithium-containing alkaline solution is a lithium hydroxide solution.

[0045] In some embodiments, the concentration of the lithium-containing alkaline solution is 5% to 20%.

[0046] Specifically, the concentration of the alkaline solution containing lithium is 5% to 20%, that is, the mass concentration of the lithium-containing compound in the alkaline solution is 5% to 20%. The concentration of the alkaline solution containing lithium can be 5%, 8%, 10%, 12%, 15%, 17%, 20%, etc., as long as it is within the range of 5% to 20%.

[0047] In some preferred embodiments, the concentration of the lithium-containing alkaline solution is 8-12%.

[0048] In some embodiments, before the crude lithium resin product is eluted with an organic solvent, the following steps are further included: eluting the crude lithium resin product with water until the conductivity of the eluted water is less than 20 μS / cm, and the water elution is completed; The crude lithium resin product is eluted with an organic solvent, comprising the following steps: the crude lithium resin product after water elution is eluted with an organic solvent until the water content of the organic solvent after elution is less than 20000 ppm, and the organic solvent elution is completed.

[0049] Specifically, after the lithiation is completed, the crude lithium resin product is first rinsed with water to remove the remaining alkaline solution containing lithium and improve the purity of the product.

[0050] After the water washing is completed, the crude lithium resin product after the water washing is washed with an organic solvent in order to remove water and reduce the water content in the product lithium iodide.

[0051] In some embodiments, the organic solvent includes one or more of an alcohol solvent, a nitrile solvent, an ether solvent, and a carbonate solvent.

[0052] Specifically, the organic solvent must be able to dissolve potassium iodide; at the same time, the organic solvent must also be miscible with water to facilitate the removal of water introduced during the preparation of lithium iodide and reduce the water content in the system.

[0053] In some embodiments, the ether solvent includes ethylene glycol dimethyl ether.

[0054] In some embodiments, the nitrile solvent includes acetonitrile.

[0055] In some embodiments, the carbonate solvent includes dimethyl carbonate.

[0056] In some embodiments, in the mixed solution, the concentration of potassium iodide is 1% to 50%.

[0057] Specifically, the mass concentration of potassium iodide solution is controlled within the concentration range of 1-50%, which can save the amount of organic solvent used and avoid the occurrence of lithium resin breakage due to excessive concentration, affecting product quality. If the concentration of potassium iodide is lower than 1%, the amount of organic solvent used is large, the cost increases, and the production efficiency decreases. The concentration of potassium iodide can be 1%, 5%, 10%, 15%, 20%, 24%, 29%, 30%, 36%, 38%, 40%, 45%, 50%, etc., as long as the concentration of potassium iodide is within the range of 1-50%.

[0058] In some preferred embodiments, in the mixed solution, the concentration of potassium iodide is 20% to 30%.

[0059] Specifically, the concentration of potassium iodide is in the range of 20% to 30%, which can not only save the amount of organic solvent used, but also improve production efficiency and shorten the ion exchange time.

[0060] In some embodiments, adding a mixed solution containing the organic solvent and potassium iodide to the lithium resin for ion exchange to obtain a crude lithium iodide product comprises the following steps: A mixed solution of the organic solvent and potassium iodide is added to the lithium resin for ion exchange to obtain an effluent containing crude lithium iodide; when the lithium ion content in the effluent containing crude lithium iodide is less than 1000 ppm, the reaction is terminated, and the steps of preparing the lithium resin and preparing the anhydrous lithium iodide are repeated.

[0061] Specifically, the present application adopts a cationic resin exchange method to synthesize anhydrous lithium iodide, a mixed solution containing an organic solvent and potassium iodide is added to a lithium resin, potassium ions and lithium ions in the lithium resin are ion exchanged, lithium ions and iodide ions are combined to form lithium iodide, and an effluent containing crude lithium iodide is obtained; when the lithium ion content in the effluent is less than 1000ppm, the lithium ion content in the lithium resin is reduced, and the lithium ion resin needs to be regenerated, so the ion exchange is terminated, and the lithium resin preparation step and the anhydrous lithium iodide preparation step are re-performed.

[0062] Since the solubility of potassium iodide in various organic solvents is different, the lithium ion content in the same volume of effluent is also different. For example, the ether solvent has a lower solubility for potassium iodide, and the lithium ion contained in the effluent after ion exchange is also less. Therefore, when the ether solvent is used, the lithium ion content in the effluent can reach <200ppm, and the ion exchange is terminated; the alcohol solvent has a higher solubility for potassium iodide, and the lithium ion contained in the effluent after ion exchange is also more, and the lithium ion content of the same volume of effluent is relatively large. Therefore, when the alcohol solvent is used, the lithium ion content in the effluent can reach <1000ppm, and the ion exchange is terminated. When the organic solvent is selected from nitrile solvents and carbonate solvents, the lithium ion content in the effluent is controlled between 1000ppm and 200ppm.

[0063] In some preferred embodiments, when the organic solvent used in the mixed solution is selected from ethylene glycol dimethyl ether, the organic solvent used to elute the crude lithium resin product with an organic solvent is selected from ethylene glycol dimethyl ether, and when the content of lithium ions in the effluent is less than 200 ppm, the ion exchange is terminated, the lithium resin can be regenerated, and the yield of anhydrous lithium iodide is also improved.

[0064] In some embodiments, the flow rate of the mixed solution is 30-80 mL / h.

[0065] Specifically, the flow rate of the mixed solution is controlled within the above range to ensure that the ion exchange reaction is fully and stably carried out and to prevent damage to the lithium resin structure. If the flow rate is less than 30mL / h, the production rate is affected. If the flow rate is too large, only the lithium ions on the surface of the lithium resin particles may participate in the exchange, and the lithium ions inside the lithium resin have no chance to exchange with the potassium ions in the potassium iodide solution, which will result in incomplete ion exchange, reduce the ion exchange efficiency and the effective utilization rate of the lithium resin. Specifically, the flow rate of the mixed solution can be 30mL / h, 40mL / h, 50mL / h, 60mL / h, 70mL / h, 80mL / h, etc.

[0066] In some embodiments, the organic solvent in the mixed solution is the same as the organic solvent in the step of eluting the crude lithium resin product with an organic solvent.

[0067] Specifically, the type of organic solvent in the mixed solution is the same as the type of organic solvent used in the step of eluting the crude lithium resin product with an organic solvent, so as to prevent the purity of anhydrous lithium iodide from being reduced due to different types of organic solvents.

[0068] It should be noted that the type of organic solvent in the mixed solution may be the same as or different from the type of organic solvent in the step of eluting the crude lithium resin product with an organic solvent, and is preferably the same. This is because the main impact of the selection of the type of organic solvent is still in the ion exchange reaction part, that is, the selection of the type of organic solvent in the mixed solution will affect the reaction concentration and the ion exchange rate. Using different solvents in the two steps will not have a significant effect on the water content of the product, but it will have a greater impact on the purity of the product, increasing the difficulty of subsequent purification.

[0069] In some embodiments, before activating the strong acid cation exchange resin, the strong acid cation exchange resin is also pre-treated, and the pre-treatment includes the following steps: rinsing the strong acid cation exchange resin with water, and the conductivity of the water after rinsing is less than 20 μS / cm, and the pre-treatment is completed.

[0070] Specifically, water is used to rinse the strongly acidic cation exchange resin to remove impurities in the exchange resin, thereby preventing the impurities from being introduced into the product anhydrous lithium iodide and improving the purity of the product anhydrous lithium iodide.

[0071] In some embodiments, pre-treating the activated strong acid cation exchange resin comprises the following steps: rinsing the activated strong acid cation exchange resin with water, wherein the conductivity of the rinsed water is less than 20 μS / cm, and the content of anions in the acidic solution in the rinsed water is less than 2 ppm.

[0072] Specifically, since the strongly acidic cation exchange resin is activated by using an acidic solution, water is needed to be used to rinse the activated strongly acidic cation exchange resin after the activation to wash away the acidic solution on the surface of the activated strongly acidic cation exchange resin and improve the purity of the product anhydrous lithium iodide; until the conductivity of the rinsed water is less than 20 μS / cm and the content of anions in the acidic solution in the rinsed water is less than 2 ppm, indicating that there is basically no acidic solution on the surface of the strongly acidic cation exchange resin, the water rinsing operation is terminated.

[0073] In some embodiments, post-processing the crude lithium iodide to obtain the anhydrous lithium iodide comprises the following steps: Concentrating the crude lithium iodide under reduced pressure to obtain the anhydrous lithium iodide; The reduced pressure concentration temperature is 70-150°C.

[0074] The reduced pressure concentration temperature can be 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc.

[0075] The anhydrous lithium iodide prepared by the preparation method of anhydrous lithium iodide provided in the present application has high purity and can be directly used in the battery field, such as being used as an electrolyte additive.

[0076] The preparation method of anhydrous lithium iodide provided in the present application can be prepared by loading a strong acidic cation exchange resin into a chromatography column, and then performing the steps of preparing a lithium resin and preparing anhydrous lithium iodide. It is understandable that the strong acidic cation exchange resin can also be loaded into other types of containers, which is not limited in the present application.

[0077] The present invention is further described below by way of examples.

[0078] Example 1 Preparation of lithium resin S11: strongly acidic cation exchange resin filling: the strongly acidic cation exchange resin is filled into the chromatography column, wherein the volume of the strongly acidic cation exchange resin in the chromatography column is 500 ml. The cations of the strongly acidic cation exchange resin are potassium ions and hydrogen ions.

[0079] S12 Pretreatment - Water washing resin: Add 500 ml of pure water to the loaded resin column to elute the strong acid cation exchange resin. The conductivity of the water flowing out of the chromatography column after elution is 13 μS / cm, and the water elution is stopped.

[0080] S13 Sulfuric acid activation: prepare a 35% sulfuric acid aqueous solution, add 250 ml of the sulfuric acid aqueous solution into the chromatography column, activate the strong acid cation exchange resin obtained in step S12, and stop the activation when the potassium ion content in the acidic solution of the activated strong acid cation exchange resin flowing out of the chromatography column is 2 ppm.

[0081] S14 pretreatment - water washing acid: After the S13 step, add 500 ml of pure water to the resin column activated by sulfuric acid for elution. When the conductivity of the eluted water flowing out of the chromatography column is 13 μS / cm and the SO4 2- The content was 2ppm, and water washing was stopped to obtain activated resin.

[0082] S15 lithiation: prepare a 10% lithium bicarbonate aqueous solution, take 800 ml of the lithium bicarbonate aqueous solution and add it to the resin column, and lithiation the activated resin obtained in step 14. When the pH of the outflowing lithium bicarbonate aqueous solution is greater than 11, the lithiation is completed to obtain a crude lithium resin product.

[0083] S16 alkali washing: after step S15 is completed, the crude lithium resin product obtained in step 15 is eluted with water, and the conductivity of the eluted water flowing out of the chromatography column is 13 μS / cm, and the water elution is completed; S17: After step S16 is completed, methanol is added to elute the crude lithium resin product after water elution obtained in step 16. The water content of the methanol solution after elution flowing out of the chromatography column is 6534 ppm. The organic solvent elution is completed to obtain a lithium resin.

[0084] Preparation of anhydrous lithium iodide: S21: Prepare 664 ml of a 25% potassium iodide (1 mol) methanol mixed solution, add it to the lithium resin obtained in step S17 for ion exchange, control the flow rate of the mixed solution to 50 mL / h, and obtain an effluent containing crude lithium iodide. When the lithium ion content in the effluent containing crude lithium iodide is less than 1000 ppm, stop ion exchange, repeat the steps of S11-S17 to prepare lithium resin, and prepare anhydrous lithium iodide according to the step of S21.

[0085] S22: The effluent obtained in step S21 is concentrated under reduced pressure at 80° C. to obtain anhydrous lithium iodide crystals.

[0086] Example 1 prepared 127.16 g of anhydrous lithium iodide crystals with a yield of 95%, a purity of 99.991%, and a water content of 623 ppm.

[0087] Example 2 Most of the steps in this embodiment are the same as those in embodiment 1, except that the concentration of the aqueous sulfuric acid solution in step S13 is 25%. The rest is the same as in embodiment 1.

[0088] Example 3 Most of the steps in this embodiment are the same as those in embodiment 1, except that the concentration of the aqueous sulfuric acid solution in step S13 is 50%. The rest is the same as in embodiment 1.

[0089] Example 4 Most of the steps in this embodiment are the same as those in embodiment 1, except that the concentration of the aqueous sulfuric acid solution in step S13 is 10%. The rest is the same as in embodiment 1.

[0090] Example 5 Most of the steps in this embodiment are the same as those in embodiment 1, except that the concentration of the aqueous sulfuric acid solution in step S13 is 55%. The rest is the same as in embodiment 1.

[0091] Example 6 Most of the steps in this embodiment are the same as those in embodiment 1, except that the concentration of the lithium bicarbonate aqueous solution in step S16 is 20%. The rest is the same as in embodiment 1.

[0092] Example 7 Most of the steps in this embodiment are the same as those in embodiment 1, except that the concentration of the lithium bicarbonate aqueous solution in step S16 is 8%. The rest is the same as in embodiment 1.

[0093] Example 8 Most of the steps of this embodiment are the same as those of Embodiment 1, except that: the organic solvent used in step S17 is ethylene glycol dimethyl ether, and the water content of the ethylene glycol dimethyl ether solution flowing out of the chromatography column is 6678 ppm; S21 prepares 664 ml of a 25% potassium iodide (1 mol) ethylene glycol dimethyl ether mixed solution for ion exchange, and when the lithium ion content in the effluent containing the crude lithium iodide is less than 200 ppm, the ion exchange is stopped, and the steps S11-S17 are repeated to prepare the lithium resin, and the anhydrous lithium iodide is prepared according to the step S21.

[0094] Example 9 Most of the steps in this embodiment are the same as those in Example 1, except that the organic solvent used in step S17 is dimethyl carbonate, and in step S21, 664 ml of a 25% potassium iodide (1 mol) dimethyl carbonate mixed solution is prepared, and the rest is the same as in Example 1.

[0095] Example 10 Most of the steps in this embodiment are the same as those in Embodiment 1, except that the concentration of potassium iodide in the mixed solution in step S21 is 50%, and the rest is the same as in Embodiment 1.

[0096] Embodiment 11 Most of the steps in this embodiment are the same as those in Embodiment 1, except that the concentration of potassium iodide in the mixed solution in step S21 is 10%, and the rest is the same as in Embodiment 1.

[0097] Example 12 Most of the steps in this embodiment are the same as those in Embodiment 1, except that the concentration of potassium iodide in the mixed solution in step S21 is 55%, and the rest is the same as in Embodiment 1.

[0098] Comparative Example 1 In the first step, lithium carbonate and iodine in hydroiodic acid are added to the hydroiodic acid at a molar ratio of 1:1, and the mixture is evenly mixed to obtain a first mixed solution; The second step is to add an impurity remover, oxalic acid dihydrate, to the first mixed solution and mix them evenly to obtain a second mixed solution, wherein the amount of the impurity remover, oxalic acid dihydrate, is 0.3% of the mass of lithium carbonate; the second mixed solution is filtered to obtain a filter residue and the first filtrate; The third step is to evaporate and concentrate the first filtrate to 70% of the volume of the first filtrate to obtain a concentrated solution, and the concentrated solution is cooled to room temperature and centrifuged to obtain lithium iodide trihydrate and a mother liquor; The fourth step is to add lithium iodide trihydrate to the organic solvent methanol in a mass ratio of 1:5 to 1:1, and mix the lithium iodide trihydrate evenly to obtain a third mixed solution, and filter the third mixed solution to obtain a filter residue and a second filtrate; In the fifth step, the second filtrate is distilled at a temperature of 60° C. to 150° C. until the distillate is 70% by volume of the organic solvent methanol, and the residue is obtained after distillation. The residue is vacuum dried and then crushed to obtain battery-grade anhydrous lithium iodide with a mass percentage water content of less than 0.015%.

[0099] The anhydrous lithium iodide prepared in the above-mentioned embodiments and comparative examples was tested for yield, purity and water content of anhydrous lithium iodide. The test results are shown in Table 1.

[0100] Table 1 From the test results in Table 1, it can be seen that, compared with Example 1 and Comparative Example 1, the water content of the anhydrous lithium iodide prepared in Example 1 of the present application is much lower than the water content of the lithium iodide in Comparative Example 1, indicating that the present application uses a cationic resin exchange method to synthesize anhydrous lithium iodide, uses an organic solvent to rinse the crude lithium resin product, removes water from the resin, and adds a mixed solution containing an organic solvent and potassium iodide to the lithium resin. The organic solvent participates in ion exchange, which reduces the water content of the lithium iodide, and the purity and yield are also high.

[0101] Compared with Example 1-4 and Example 5, when the concentration of the acidic solution is higher than 10% to 50%, the purity of the anhydrous lithium iodide is low, the water content is high, and the yield is low. It is speculated that the acidic solution with too high a concentration will cause a certain degree of damage to the structure of the cation exchange resin, reduce the purity of the lithium iodide, and reduce the yield; it shows that when the concentration of the acidic solution is in the range of 10% to 50%, the anhydrous lithium iodide obtained has a high yield, high purity, and low water content; further preferably, the concentration of the acidic solution is in the range of 25% to 35%, and the yield of anhydrous lithium iodide is higher, the purity is higher, and the water content is lower.

[0102] Comparison between Example 1 and Examples 6-7 shows that in the S15 lithiation step, the concentration of the added lithium-containing alkaline solution is in the range of 5-20%, and the anhydrous lithium iodide prepared has a higher yield, higher purity, and lower water content.

[0103] The comparison of Examples 1 and 8-9 shows that in the step of eluting with an organic solvent and in the step of adding a mixed solution containing an organic solvent and potassium iodide to the lithium resin, the organic solvent used has the effect of reducing the water content of lithium iodide as long as it meets the requirements of the present application; the water content of anhydrous lithium iodide in Example 9 is higher than that in Example 8, mainly because dimethyl carbonate is used in Example 9, and ethylene glycol dimethyl ether is used in Example 8. The organic solvent used in Example 9 belongs to an ester solvent, and the solubility of the organic solvent in Example 9 in water is slightly worse than that in Example 8, and less water is taken away, so the water content of Example 9 is slightly higher.

[0104] Comparing Examples 1, 10-11 and 12, the concentration of potassium iodide is higher than 1% to 50%. The concentration of potassium iodide is too high, the purity of the anhydrous lithium iodide product is reduced, and the yield is reduced. It is speculated that the excessively high concentration of potassium iodide causes the lithium resin to break, affecting the purity and yield of the anhydrous lithium iodide product; it shows that when the concentration of potassium iodide is in the range of 1% to 50%, the purity and yield of the obtained anhydrous lithium iodide product are high, and the water content of the anhydrous potassium iodide is low.

[0105] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents. 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 embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A method for preparing anhydrous lithium iodide, characterized in that: The following steps are involved: Preparation of lithium resin: activating a strongly acidic cation exchange resin, pre-treating the activated strongly acidic cation exchange resin, adding a lithium-containing alkaline solution to the pre-treated strongly acidic cation exchange resin for lithiation to obtain a crude lithium resin product, and eluting the crude lithium resin product with an organic solvent to obtain a lithium resin; Preparation of anhydrous lithium iodide: adding a mixed solution containing the organic solvent and potassium iodide to the lithium resin to perform ion exchange to obtain a crude lithium iodide product, and post-treating the crude lithium iodide product to obtain anhydrous lithium iodide.

2. The method for preparing anhydrous lithium iodide according to claim 1, characterized in that: Activating the strongly acidic cation exchange resin comprises the following steps: The cations in the strongly acidic cation exchange resin include potassium ions; Adding an acidic solution to the strongly acidic cation exchange resin to activate the strongly acidic cation exchange resin, and when the content of potassium ions in the acidic solution that has activated the strongly acidic cation exchange resin is less than 50 ppm, the activation is completed; The concentration of the acidic solution is 10% to 50%.

3. The method for preparing anhydrous lithium iodide according to claim 2, characterized in that: The acidic solution includes at least one of sulfuric acid and hydrochloric acid; The concentration of the acidic solution is 25% to 35%; And / or, when the content of potassium ions in the acidic solution after activating the strongly acidic cation exchange resin is less than 2 ppm, the activation is completed.

4. The method for preparing anhydrous lithium iodide according to claim 1, characterized in that: Adding a lithium-containing alkaline solution to the pretreated strongly acidic cation exchange resin for lithiation includes the following steps: The alkaline solution containing lithium is added to the pretreated strong acid cation exchange resin for lithiation. When the pH of the alkaline solution containing lithium after the lithium cation exchange resin is greater than 11, the lithiation is completed.

5. The method for preparing anhydrous lithium iodide according to claim 1, characterized in that: The lithium-containing alkaline solution includes one or more of a lithium carbonate solution, a lithium bicarbonate solution, and a lithium hydroxide solution; The concentration of the lithium-containing alkaline solution is 5% to 20%.

6. The method for preparing anhydrous lithium iodide according to claim 1, characterized in that: Before the crude lithium resin product is eluted with an organic solvent, the following steps are also included: eluting the crude lithium resin product with water until the conductivity of the eluted water is less than 20 μS / cm, and the water elution is completed; The crude lithium resin product is eluted with an organic solvent, comprising the following steps: adding an organic solvent to the crude lithium resin product after water elution for elution, until the water content of the organic solvent after elution is less than 20000 ppm, and the elution of the organic solvent is finished; The organic solvent includes one or more of alcohol solvents, nitrile solvents, ether solvents, and carbonate solvents.

7. The method for preparing anhydrous lithium iodide according to claim 6, characterized in that: The ether solvent includes ethylene glycol dimethyl ether; The nitrile solvent includes acetonitrile; The carbonate solvent includes dimethyl carbonate.

8. The method for preparing anhydrous lithium iodide according to claim 1, characterized in that: In the mixed solution, the concentration of potassium iodide is 1% to 50%; Adding a mixed solution containing the organic solvent and potassium iodide to the lithium resin for ion exchange to obtain a crude lithium iodide product comprises the following steps: Adding a mixed solution of the organic solvent and potassium iodide to the lithium resin for ion exchange to obtain an effluent containing crude lithium iodide; when the lithium ion content in the effluent containing crude lithium iodide is less than 1000 ppm, the reaction is terminated, and the steps of preparing the lithium resin and preparing the anhydrous lithium iodide are repeated; The flow rate of the mixed solution is 30-80 mL / h. The organic solvent in the mixed solution is the same as the organic solvent in the step of eluting the crude lithium resin product with an organic solvent.

9. The method for preparing anhydrous lithium iodide according to claim 2, characterized in that: Before activating the strong acid cation exchange resin, the strong acid cation exchange resin is pre-treated, and the pre-treatment includes the following steps: rinsing the strong acid cation exchange resin with water, and the conductivity of the water after rinsing is less than 20 μS / cm, and the pre-treatment is completed; And / or, pre-treating the activated strong acid cation exchange resin comprises the following steps: rinsing the activated strong acid cation exchange resin with water, wherein the conductivity of the rinsed water is less than 20 μS / cm, and the content of anions in the acidic solution in the rinsed water is less than 2 ppm.

10. The method for preparing anhydrous lithium iodide according to claim 1, characterized in that: Post-processing the crude lithium iodide to obtain the anhydrous lithium iodide comprises the following steps: Concentrating the crude lithium iodide under reduced pressure to obtain the anhydrous lithium iodide; The reduced pressure concentration temperature is 70-150°C.

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