A method for purifying potassium iodide containing perfluoroorganic impurities

Abstract

The present application relates to the technical field of potassium iodide, and provides a purification method of potassium iodide containing perfluorinated organic impurities, wherein the impurities in the potassium iodide crude product are perfluorinated organic compounds with the number of C atoms being greater than or equal to 6 and the mass content being greater than or equal to 20%, and the purification method comprises: adding the potassium iodide crude product into an alcohol lye to perform heating reflux to degrade the perfluorinated organic compounds; the alcohol lye is obtained by dissolving an alkaline compound containing an alkali metal or an alkaline earth metal in alcohol, and the mass concentration of the alkaline compound in the alcohol lye is less than or equal to 20%. The method of the present application is not only simple in operation and suitable for industrialization, but also can make the purity of the purified potassium iodide reach more than 98%, and the highest recovery rate can reach 97%, and the whole process does not produce three wastes, has low energy consumption and small risk, which is specifically reflected in that the amount of foam entraining particles during boiling is reduced, the risk of equipment and pipeline blockage is greatly reduced, the safety is high, and the presence of the alkali greatly increases the solubility of the perfluorinated organic impurities, and the purification efficiency is high.

Description

Technical Field

[0001] This invention relates to the field of potassium iodide technology, and more particularly to a method for purifying potassium iodide containing perfluorinated organic impurities. Background Technology

[0002] To purify potassium iodide from perfluoroalkyl ethyl acrylate byproducts, patent CN110002470B describes a method where the perfluoroalkyl ethyl acrylate byproducts are first added to a stirred tank, followed by 1-2 times their weight of anhydrous ethanol. The mixture is then stirred and refluxed for 0.5-2 hours to obtain a crude potassium iodide mixture. This mixture is then subjected to multiple cooling and filtration processes to separate the solid potassium iodide. Perfluoroalkyl ethylene and perfluorinated high-boiling compounds from the perfluoroalkyl ethyl acrylate byproducts are recovered and reused. While this method reduces energy consumption and the generation of gaseous fluorides compared to traditional calcination methods, and allows for continuous purification, research has revealed that some perfluoroalkyl ethyl acrylate byproducts exhibit excessive foaming in the stirred tank, resulting in low potassium iodide recovery and purity when purified using this method.

[0003] Therefore, this invention is proposed. Summary of the Invention

[0004] In response to the above phenomena, this invention has conducted an in-depth study on the byproducts of perfluoroalkyl ethyl acrylate. The crude potassium iodide used in the purification process is mainly produced during the production of fluorinated alkyl ester surfactants. Due to the encapsulation of organic polymers and the presence of residual surfactants, the various properties of the crude potassium iodide are significantly altered, such as water solubility, solution surface tension, and viscosity. When the impurities in the crude potassium iodide during purification are perfluorinated organic compounds with a low number of carbon atoms (<6) and their content is low, the method in patent CN110002470B can achieve a good purification effect. However, as the number of carbon atoms of the perfluorinated organic compounds in the crude potassium iodide during purification gradually increases, and their content also gradually increases, the amount of foam generated in the stirred tank used in patent CN110002470B will increase significantly, resulting in low potassium iodide recovery rate and low purity. Further research and analysis revealed that this method fails to break down the organofluorine coating on the particle surface, resulting in some KI remaining mixed with fluorides and reducing the purity of potassium iodide. While some organic matter dissolves in the solution during the ethanol reflux boiling process, some remains in the potassium iodide solid, further degrading the quality of the recovered potassium iodide. During the boiling reflux process, the solution produces abundant and large amounts of foam, consistent with the characteristics of surfactants. This foam carries potassium iodide solids, impacting the condenser and causing equipment and pipeline blockages. This prevents timely reflux, increases pressure within the reactor, and poses safety hazards. These issues make this method difficult to operate and increase the challenge of large-scale industrial purification.

[0005] This invention provides a method for purifying potassium iodide containing perfluorinated organic impurities. This method can not only achieve similar or even better technical effects than those in patent CN110002470B in a shorter time, but also solves the technical problems of low potassium iodide recovery rate and low purity caused by the significant increase in the amount of foam generated in the stirred tank of the above method when the impurities in crude potassium iodide are perfluorinated organic compounds with more than 6 carbon atoms and their mass content is more than 20%.

[0006] Specifically, the present invention provides a purification method for crude potassium iodide, wherein the impurities in the crude potassium iodide are perfluorinated organic compounds with 6 or more carbon atoms and their mass content is 20% or more. The purification method includes: adding the crude potassium iodide to an alcohol-alkali solution and heating and refluxing to degrade the perfluorinated organic compounds; the alcohol-alkali solution is obtained by dissolving an alkaline compound containing an alkali / alkaline earth metal in alcohol, and the mass concentration of the alkaline compound in the alcohol-alkali solution is less than 20%.

[0007] Through extensive testing, this invention has discovered that when the above-mentioned alcohol-alkali solution is used to heat and reflux crude potassium iodide, the perfluorinated organic compounds in the crude potassium iodide can be further degraded during the process of fully dissolving them. Moreover, the control of the mass concentration of the alkaline compound in the alcohol-alkali solution is crucial. If the mass concentration of the alkaline compound in the alcohol-alkali solution is too high, it will lead to excessively high viscosity in the reflux system, which will adversely affect the filtration rate, thereby reducing the purity and recovery rate of potassium iodide, and will also corrode equipment and pipelines, causing safety hazards.

[0008] Experiments revealed that the average content of perfluorinated organic impurities with more than 10 carbon atoms in crude potassium iodide, a byproduct of perfluoroalkyl ethyl acrylate, was approximately 8%. In practice, this content fluctuates due to variations in operating conditions, averaging 10-15%. Generally, the average content of perfluorinated organic impurities with more than 6 carbon atoms is over 20%. The technical advantages of the method of this invention become more significant when the average content of perfluorinated organic impurities with more than 6 carbon atoms in the crude potassium iodide gradually increases. When the average content of perfluorinated organic impurities with more than 6 carbon atoms in the crude potassium iodide is over 30%, the purification effect of the method of this invention is even better, manifested in high purity and high recovery rate of the obtained potassium iodide. Furthermore, the efficiency of vacuum filtration is significantly improved during the purification process, greatly enhancing the purification efficiency.

[0009] Preferably, in the purification method for crude potassium iodide provided by the present invention, the mass concentration of the alkaline compound in the alcohol-alkali solution is 3% to 10%.

[0010] Although a certain effect can be achieved even when the mass concentration of the alkaline compound in the alcohol-alkali solution is low, experimental verification shows that the purification effect and purification efficiency of crude potassium iodide are best when the mass concentration of the alkaline compound is within the above-mentioned range, especially when the mass concentration of the alkaline compound in the alcohol-alkali solution is 4% to 6%.

[0011] Preferably, in the purification method for crude potassium iodide provided by the present invention, the alkaline compound includes one or more of the bases or basic salts of lithium, sodium, potassium and calcium; preferably, the alkaline compound includes a potassium-containing alkaline compound, such as potassium hydroxide.

[0012] Preferably, in the purification method for crude potassium iodide provided by the present invention, the alcohol comprises a straight-chain and / or branched alkyl alcohol having 6 or fewer carbon atoms; preferably, the alcohol comprises one or more of methanol, ethanol, and tert-butanol.

[0013] Preferably, in the purification method for crude potassium iodide provided by the present invention, the weight ratio of the added alcohol-alkali solution to the crude potassium iodide is 1:1 to 2:1.

[0014] Preferably, the purification method for crude potassium iodide provided by the present invention includes: heating the crude potassium iodide in an alcohol-alkali solution at 60-90°C for 0.5-2 hours to degrade the perfluorinated organic compounds and until the foam in the system disappears, to obtain a mixture;

[0015] The mixture was vacuum filtered to obtain a filter cake and a first filtrate;

[0016] The filter cake was dissolved in deionized water and then filtered under vacuum to obtain a second filtrate.

[0017] The second filtrate is concentrated by vacuum evaporation to obtain a saturated potassium iodide solution (the vacuum evaporation concentration can be stopped when a small amount of crystals begin to precipitate).

[0018] The process parameters for vacuum evaporation concentration include: temperature of 70℃~90℃ and pressure of 0.01~-0.1MPa.

[0019] Preferably, the purification method for crude potassium iodide provided by the present invention includes: recrystallizing and drying the saturated potassium iodide solution to obtain the finished potassium iodide product.

[0020] The recrystallization includes: mixing the saturated potassium iodide solution with a recrystallization solvent, allowing it to stand, cooling it to -20 to 10°C, filtering it, and obtaining solid potassium iodide and a third filtrate.

[0021] The recrystallization solvent is ethanol, methanol, or dichloromethane;

[0022] The volume ratio of the potassium iodide saturated solution to the recrystallization solvent is 0.8:1 to 1:0.5;

[0023] The drying process includes drying the potassium iodide solid at 100–120°C under an inert gas environment for 2–5 hours to obtain potassium iodide crystals, which are the finished potassium iodide products.

[0024] Preferably, in the purification method of crude potassium iodide provided by the present invention, the crude potassium iodide is protected by an inert gas during the purification process to prevent iodide ions from being oxidized. Preferably, the inert gas is helium, argon or nitrogen, more preferably nitrogen.

[0025] Preferably, in the purification method for crude potassium iodide provided by the present invention, the first filtrate and / or the third filtrate are each independently distilled to recover the solvent therein.

[0026] If the first filtrate is sent to an enamel-lined distillation kettle for distillation to recover the solvent, the temperature is set to the solvent boiling point temperature, and the fraction below this temperature is collected. Both the bottom liquid and the filter cake are perfluorinated organic compounds, which can be further recycled upstream.

[0027] If the third filtrate is sent to an enamel distillation kettle for distillation to recover the solvent, the temperature is set to the solvent boiling point temperature, and the fraction below this temperature is collected. Since the water content in the recovered solvent is relatively high after the recrystallization solvent is mixed with water, it needs to be dehydrated before recycling. The solvent is sent to a molecular sieve for drying and dehydration to obtain a solvent with a water content of less than 100 ppm, which can be directly pumped into the solvent preparation tank for continued use in this invention.

[0028] Preferably, according to the purification method of crude potassium iodide provided by the present invention, the mixture is vacuum filtered and the filter cake is obtained within 200 minutes, wherein the potassium iodide content of the filter cake is more than 90%.

[0029] The experiment found that the method in patent CN110002470B requires multiple cooling and filtration processes. Due to the presence of a large amount of perfluorinated organic compounds, the transparent gelatinous substance on the filter cake will significantly reduce the filtration efficiency during filtration. The mixed liquid obtained by heating and reflux in this invention has strong permeability during filtration, and the filtrate can be directly concentrated and crystallized, which greatly simplifies the process.

[0030] This invention provides a method for purifying potassium iodide containing perfluorinated organic impurities. The method involves adding crude potassium iodide to an alcohol-alkali solution formed by an alkaline compound containing an alkali / alkaline earth metal, followed by heating and reflux. The mass concentration of the alkaline compound in the alcohol-alkali solution is controlled to be below 20%, thereby further degrading the perfluorinated organic compounds during dissolution. This method is not only simple to operate and suitable for industrial application, but also achieves a purity of over 98% for the purified potassium iodide, with a maximum recovery rate of 97%. Furthermore, the entire process generates no waste, has low energy consumption, and low risk. Specifically, it significantly reduces foam generation during boiling, preventing particle entrainment and greatly reducing the risk of equipment and pipeline blockage, ensuring high safety. The presence of alkali also significantly increases the solubility of perfluorinated organic impurities, resulting in good filtration and high purification efficiency.

[0031] The method of this invention can also separate the outer organic coating, i.e., perfluorinated organic compounds and their high-boiling components. Through further purification, high-purity perfluorinated organic raw materials (purity can reach more than 97%) can be obtained, which can also be directly sold for recycling, realizing resource recycling and reuse, and avoiding waste and pollution.

[0032] The various solvents used in this invention can be recycled and reused, which greatly saves costs, realizes resource recycling, and avoids waste and pollution. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is one of the flowcharts of a purification method for potassium iodide containing perfluorinated organic impurities provided by the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0036] The following is combined with Figure 1 This invention describes a method for purifying potassium iodide containing perfluorinated organic impurities.

[0037] The object of purification in this invention is crude potassium iodide, which is derived from perfluoroalkyl ethyl acrylate byproducts. Tests have revealed that the impurities in it are perfluoroorganic compounds with more than 6 carbon atoms and their mass content is 32%.

[0038] Experiment 1

[0039] A method for purifying potassium iodide containing perfluorinated organic impurities, the process of which involves thermal degradation is as follows: Figure 1 As shown, the details are as follows:

[0040] (1) Heating degradation: Take 30 kg of the above-mentioned crude potassium iodide, and the potassium iodide content is determined to be 74.6% by argentometric method. Add it to a 200L stainless steel stirred tank equipped with stirring, heating and reflux. Then add 45 kg of prepared potassium hydroxide (mass concentration 5%) ethanol solution. Turn on the stirring and control the speed at 100 r / min. Set the heat transfer oil temperature to 79℃. When reflux occurs in the tank, continue heating, stirring and refluxing for 30 min until most of the foam disappears.

[0041] Experiment 2

[0042] A method for purifying potassium iodide containing perfluorinated organic impurities involves a heating degradation process as follows: It is basically the same as Experiment 1, except that the ethanol solution of potassium hydroxide (5% by mass) is replaced with a methanol solution of potassium hydroxide (5% by mass), and the temperature of the heat transfer oil is set to 60°C. When reflux occurs in the reactor, the heating and stirring are continued for 30 minutes until most of the foam disappears, and then the heating is stopped.

[0043] Experiment 3

[0044] A method for purifying potassium iodide containing perfluorinated organic impurities involves a heating degradation process as follows: It is basically the same as Experiment 1, except that the ethanol solution of potassium hydroxide (5% by mass) is replaced with an alkaline alcohol solution (an ethanol solution of potassium hydroxide (3% by mass) and potassium carbonate (2% by mass). When reflux occurs in the reactor, the mixture is heated and stirred for reflux for 30 minutes until most of the foam disappears, and then the heating is stopped.

[0045] Experiment 4

[0046] A method for purifying potassium iodide containing perfluorinated organic impurities, comprising the following filtration and concentration processes:

[0047] (2) Vacuum filtration:

[0048] When the temperature inside the reactor drops below 60°C after the heating and degradation are complete, the material inside the reactor is transferred to a vacuum filter for vacuum filtration (-0.09MPa) to obtain filter cake and first filtrate.

[0049] (3) Water filtration:

[0050] The filter cake was dissolved by stirring with twice its weight of deionized water, and then vacuum filtered again (-0.09 MPa) to obtain the second filtrate.

[0051] (4) Vacuum evaporation concentration:

[0052] The second filtrate is pumped into a vacuum distillation vessel, nitrogen gas is introduced to replace the air in the vessel, and vacuum evaporation and concentration are carried out at a temperature of 80℃ and a pressure of -0.01MPa. When crystals are about to precipitate, heating is stopped to obtain a saturated solution. The material in the vessel is then discharged into a recrystallization vessel.

[0053] Experiment 5

[0054] A method for purifying potassium iodide containing perfluorinated organic impurities, comprising the following crystallization and drying processes:

[0055] (5) Recrystallization and drying: Add an equal volume of ethanol solution to the saturated liquid of the above examples obtained by vacuum evaporation and concentration in the reactor, stir appropriately, and then let stand and cool to -20℃ for recrystallization. After the solution is clear, filter to obtain the filtrate for solvent recovery. The potassium iodide solid is sent to the converter, the air in the furnace is purged with nitrogen, and then hot nitrogen (105~110℃) is introduced to dry for 4 hours to obtain potassium iodide crystals. The purity is determined by argentometric method, and the recovery rate is calculated.

[0056] Experiment 6

[0057] A method for purifying potassium iodide containing perfluorinated organic impurities, comprising the following crystallization and drying processes:

[0058] (5) Recrystallization and drying: Add an equal volume of ethanol solution to the material in the reactor obtained by vacuum evaporation and concentration, stir appropriately, and then let stand and cool down to -10℃ for recrystallization. After the solution is clear, filter to obtain the filtrate for solvent recovery. The potassium iodide solid is sent to the converter, the air in the furnace is purged with nitrogen, and then hot nitrogen (10-110℃) is introduced to dry for 4 hours to obtain potassium iodide crystals. The purity is determined by argentometric method, and the recovery rate is calculated.

[0059] Experiment 7

[0060] A method for purifying potassium iodide containing perfluorinated organic impurities, comprising the following crystallization and drying processes:

[0061] (5) Recrystallization and drying: Add 1.5 times the saturated liquid volume of ethanol solution to the material in the reactor obtained by vacuum evaporation and concentration, stir appropriately, and then let stand and cool down to -10℃ for recrystallization. After the solution is clear, filter to obtain the filtrate for solvent recovery. The potassium iodide solid is sent to the converter, and the air in the furnace is purged with nitrogen. Then hot nitrogen (105~110℃) is introduced and dried for 4 hours to obtain potassium iodide crystals. The purity is determined by argentometric method, and the recovery rate is calculated.

[0062] Experiment 8

[0063] A method for purifying potassium iodide containing perfluorinated organic impurities, comprising the following crystallization and drying processes:

[0064] (5) Recrystallization and drying: Add an equal volume of methanol solution to the material in the reactor obtained by vacuum evaporation and concentration, stir appropriately, and then let stand and cool down to -10℃ for recrystallization. After the solution is clear, filter to obtain the filtrate for solvent recovery. The potassium iodide solid is sent to the converter, and the air in the furnace is purged with nitrogen. Then hot nitrogen (105~110℃) is introduced to dry for 4 hours to obtain potassium iodide crystals. The purity is determined by argentometric method, and the recovery rate is calculated.

[0065] Experiment 9

[0066] A method for purifying potassium iodide containing perfluorinated organic impurities, comprising the following crystallization and drying processes:

[0067] (5) Recrystallization and drying: Add an equal volume of methanol solution to the saturated solution of the above examples, stir appropriately, and then let it stand and cool down to 10°C for recrystallization. After the solution is clear, filter to obtain the filtrate for solvent recovery. The potassium iodide solid is sent to the converter, and the air in the furnace is purged with nitrogen. Then hot nitrogen (105-110°C) is introduced to dry for 4 hours to obtain potassium iodide crystals. The purity is determined by argentometric method, and the recovery rate is calculated.

[0068] Calculation of combination results:

[0069] Example 1: Combinations of experiments 1, 4, and 5 yielded 21.9 kg of potassium iodide crystals. The purity was determined to be 99.3% by argentometric titration, and the recovery rate was 97.17%.

[0070] Example 2: Combinations of experiments 2, 4, and 5 yielded 20.3 kg of potassium iodide crystals. The purity was determined to be 98.3% by argentometric titration, and the recovery rate was 89.16%.

[0071] Example 3: Combinations of experiments 1, 4, and 6 yielded 21.2 kg of potassium iodide crystals. The purity was determined to be 98.9% by argentometric titration, and the recovery rate was 93.69%.

[0072] Example 4: Combinations of experiments 3, 4, and 8 yielded 20.7 kg of potassium iodide crystals. The purity was determined to be 98.1% by argentometric titration, and the recovery rate was 90.74%.

[0073] Example 5: Combinations of experiments 1, 4, and 7 yielded 22.1 kg of potassium iodide crystals. The purity was determined to be 99.8% by argentometric titration, and the recovery rate was 98.55%.

[0074] The purity of all other combinations of experiments 1-9 was above 98%, and the recovery rate was above 85%. Furthermore, during vacuum filtration in step (2), Examples 1, 3, and 5 showed higher filtration rates, requiring filtration times of 105 min, 108 min, and 106 min respectively. Example 2 required 122 min, and Example 4 required 185 min. Overall, the filtration efficiency of the ethanol solution of potassium hydroxide (5%) was higher, followed by the methanol solution of potassium hydroxide, while the ethanol solution of the mixed alkali had lower filtration efficiency.

[0075] Compared to soda ash solutions prepared with other alkalis, potassium iodide solutions prepared with ethanol have the highest purity and a higher recovery rate.

[0076] Example 6

[0077] A method for purifying potassium iodide containing perfluorinated organic impurities is basically the same as in Example 1, except that potassium hydroxide is replaced with sodium hydroxide. In the experiment, it was found that during vacuum filtration, the average filtration time was 110 min, the filtrate was clear, and the mass of potassium iodide crystals obtained was 21.1 kg. The purity determined by argentometric titration was 98.1%, and the recovery rate was 92.49%.

[0078] Example 7

[0079] A method for purifying potassium iodide containing perfluorinated organic impurities is basically the same as in Example 1, except that potassium hydroxide is replaced with lithium hydroxide. In the experiment, it was found that during vacuum filtration, the average filtration time was 182 min, the filtrate was clear, and the mass of potassium iodide crystals obtained was 20.4 kg. The purity determined by argentometric titration was 96.3%, and the recovery rate was 87.78%.

[0080] Comparative Example 1

[0081] A method for purifying potassium iodide containing perfluorinated organic impurities is presented, which is essentially the same as in Example 1, except that the mass concentration of potassium hydroxide is increased to 25%. During the experiment, it was found that the average filtration time during vacuum filtration was 241 min, the filtrate was turbid, and the mass of potassium iodide crystals obtained was 19.3 kg. The purity determined by argentometric titration was 94.5%, and the recovery rate was 81.49%.

[0082] Comparative Example 2

[0083] A purification method for potassium iodide containing perfluorinated organic impurities is basically the same as that in Example 1, except that the ethanol solution of potassium hydroxide (5% by mass) during heating degradation is replaced with an equal volume of ethanol. The results showed that the filtration time during vacuum filtration in step (2) was 254 min.

[0084] Comparative Example 3

[0085] A purification method for potassium iodide containing perfluorinated organic impurities is basically the same as that in Example 2, except that the methanol solution of potassium hydroxide (5% by mass) during heating degradation is replaced with an equal volume of methanol. The results showed that the filtration time during vacuum filtration in step (2) was 326 min.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for purifying crude potassium iodide, wherein the crude potassium iodide contains impurities that are perfluorinated organic compounds with 6 or more carbon atoms and whose mass content is 20% or more, characterized in that... The purification method includes: adding the crude potassium iodide to an alcohol-alkali solution and heating under reflux to degrade the perfluorinated organic compounds to obtain a mixture; filtering the mixture under vacuum to obtain a filter cake and a first filtrate; dissolving the filter cake in deionized water and filtering under vacuum to obtain a second filtrate; evaporating and concentrating the second filtrate under vacuum to obtain a saturated potassium iodide solution; recrystallizing and drying the saturated potassium iodide solution to obtain the finished potassium iodide product; wherein the alcohol-alkali solution is obtained by dissolving an alkaline compound containing an alkali / alkaline earth metal in alcohol, and the mass concentration of the alkaline compound in the alcohol-alkali solution is 3-10%.

2. The purification method for crude potassium iodide according to claim 1, characterized in that, The alkaline compound includes one or more of the bases or basic salts of lithium, sodium, potassium, and calcium.

3. The purification method for crude potassium iodide according to claim 2, characterized in that, The alkaline compounds include potassium-containing alkaline compounds.

4. The purification method for crude potassium iodide according to claim 3, characterized in that, The alkaline compound is potassium hydroxide.

5. The purification method for crude potassium iodide according to any one of claims 1 to 4, characterized in that, The alcohols include alkyl straight-chain and / or branched alcohols containing 6 or fewer carbon atoms.

6. The purification method for crude potassium iodide according to claim 5, wherein the alcohol comprises one or more of methanol, ethanol and tert-butanol.

7. The purification method for crude potassium iodide according to any one of claims 1 to 4 and 6, characterized in that, The weight ratio of the added alcohol-alkali solution to the crude potassium iodide is 1:1 to 2:

1.

8. The purification method for crude potassium iodide according to claim 5, characterized in that, The weight ratio of the added alcohol-alkali solution to the crude potassium iodide is 1:1 to 2:

1.

9. The purification method for crude potassium iodide according to any one of claims 1 to 4, 6, and 8, characterized in that, include: The crude potassium iodide is heated in an alcohol-alkali solution at 60-90°C for 0.5-2 hours to degrade the perfluorinated organic compounds, yielding a mixture.

10. The purification method for crude potassium iodide according to claim 5, characterized in that, include: The crude potassium iodide is heated in an alcohol-alkali solution at 60-90°C for 0.5-2 hours to degrade the perfluorinated organic compounds, yielding a mixture.

11. The purification method for crude potassium iodide according to claim 7, characterized in that, include: The crude potassium iodide is heated in an alcohol-alkali solution at 60-90°C for 0.5-2 hours to degrade the perfluorinated organic compounds, yielding a mixture.

12. The purification method for crude potassium iodide according to claim 9, characterized in that, The recrystallization process includes: mixing the saturated potassium iodide solution with a recrystallization solvent, allowing it to stand, cooling it to -20°C to 10°C, filtering it, and obtaining solid potassium iodide and a third filtrate.

13. The purification method for crude potassium iodide according to claim 10 or 11, characterized in that, The recrystallization process includes: mixing the saturated potassium iodide solution with a recrystallization solvent, allowing it to stand, cooling it to -20°C to 10°C, filtering it, and obtaining solid potassium iodide and a third filtrate.

14. The purification method for crude potassium iodide according to any one of claims 1-4, 6, 8, 10-12, characterized in that, The crude potassium iodide is purified using an inert gas to prevent the iodide ions from being oxidized.

15. The purification method for crude potassium iodide according to claim 14, characterized in that, The inert gas is helium, argon, or nitrogen.

16. The purification method for crude potassium iodide according to claim 5, characterized in that, The crude potassium iodide is purified using an inert gas to prevent the iodide ions from being oxidized.

17. The purification method for crude potassium iodide according to claim 16, characterized in that, The inert gas is helium, argon, or nitrogen.

18. The purification method for crude potassium iodide according to claim 7, characterized in that, The crude potassium iodide is purified using an inert gas to prevent the iodide ions from being oxidized.

19. The purification method for crude potassium iodide according to claim 18, characterized in that, The inert gas is helium, argon, or nitrogen.

20. The purification method for crude potassium iodide according to claim 9, characterized in that, The crude potassium iodide is purified using an inert gas to prevent the iodide ions from being oxidized.

21. The purification method for crude potassium iodide according to claim 20, characterized in that, The inert gas is helium, argon, or nitrogen.

22. The purification method for crude potassium iodide according to claim 13, characterized in that, The crude potassium iodide is purified using an inert gas to prevent the iodide ions from being oxidized.

23. The purification method for crude potassium iodide according to claim 22, characterized in that, The inert gas is helium, argon, or nitrogen.

24. The purification method for crude potassium iodide according to claim 12, characterized in that, The solvent in the first filtrate and / or the third filtrate is recovered by distillation independently.

25. The purification method for crude potassium iodide according to claim 13, characterized in that, The solvent in the first filtrate and / or the third filtrate is recovered by distillation independently.

26. The purification method for crude potassium iodide according to claim 9, characterized in that, The mixture is vacuum filtered, and the filter cake is obtained within 200 minutes. The filter cake contains more than 90% potassium iodide.

27. The purification method for crude potassium iodide according to claim 10 or 11, characterized in that, The mixture is vacuum filtered, and the filter cake is obtained within 200 minutes. The filter cake contains more than 90% potassium iodide.

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