Process for the preparation of 5n cesium iodide

Abstract

The application provides a preparation method of 5N cesium iodide and belongs to the technical field of inorganic material preparation. A cesium carbonate solution is purified to remove insoluble substances, and then cations such as calcium and magnesium are removed by using a cation exchange resin to obtain a purified cesium carbonate solution; the purified cesium carbonate solution is evaporated and concentrated, cooled and crystallized, and dried to obtain dry cesium carbonate; elemental iodine is added into water, carbon tetrachloride is added, and the carbon tetrachloride solution containing the elemental iodine is distilled to obtain refined elemental iodine; the dry cesium carbonate, the refined elemental iodine and hydrazine hydrate are mixed to obtain a cesium iodide solution, which is evaporated and concentrated, cooled and crystallized, and dried to obtain 5N cesium iodide. The application selects a low-cost and high-yield method to purify raw materials from the perspective of raw materials, and 5N cesium iodide is prepared, so that multiple recrystallizations are avoided, and the method has the characteristics of low cost and high yield.

Description

Technical Field

[0001] This invention relates to the field of inorganic material preparation technology, and in particular to a method for preparing 5N cesium iodide. Background Technology

[0002] The primary application of cesium iodide in medical imaging is in X-ray flat panel detectors. Its core function is to significantly improve image quality and diagnostic accuracy by efficiently absorbing X-rays and converting them into light signals. Cesium iodide can also have its scintillation properties adjusted by doping with trace elements to suit different imaging needs.

[0003] Cesium iodide plays a crucial role in optoelectronics and optics. At normal temperatures, cesium iodide exhibits excellent optical transparency, capable of absorbing and radiating energy from the visible to the mid-infrared wavelengths. In the laser field, cesium iodide can be used as a flash lamp medium to enable infrared laser emission. Simultaneously, cesium iodide can also be fabricated into optical components such as lenses, prisms, and windows, used in assemblies and parts of various optical devices. In electronics, cesium iodide possesses high electrical conductivity and low noise characteristics, making it suitable for fabricating various devices such as field-effect transistors, relays, and signal amplifiers.

[0004] Cesium iodide, as an inorganic salt, plays an important role in scientific research and industry due to its unique scintillation crystal properties. Currently, the main methods for preparing cesium iodide both domestically and internationally include: direct reaction method, solution reaction method, redox method, cesium carbonate conversion method, and precipitation separation method. The direct reaction method involves reacting metallic cesium with iodine vapor under certain conditions to produce cesium iodide. This method produces cesium iodide with high purity, but the operation is relatively complex. The solution reaction method involves dissolving metallic cesium in hydrogen iodide solution to generate cesium iodide solution, and finally obtaining solid cesium iodide through evaporation and crystallization. This method is relatively simple, but safety precautions are necessary. The redox method uses an oxidizing agent to oxidize metallic cesium to produce cesium iodide. This reaction is relatively fast, but safety precautions are still necessary. The cesium carbonate conversion method involves reacting cesium carbonate with elemental iodine in the presence of hydrazine hydrate to produce cesium iodide. This method can prepare high-purity cesium iodide, and the operation process is relatively controllable. The precipitation separation method utilizes a precipitant to form a water-insoluble precipitate with cesium ions, and then separates the cesium iodide through processes such as acid washing and alkali dissolution. This method can effectively separate impurities from the raw materials, obtaining high-grade cesium iodide products.

[0005] Existing literature reports the following methods for preparing high-purity cesium iodide: The first method involves purifying cesium nitrate and reacting it with oxalic acid to produce cesium hydrogen oxalate, which undergoes secondary decomposition to generate cesium carbonate. Recrystallization only yields 4N cesium iodide, and this method requires heating to above 157°C, making it energy-intensive. The second method utilizes the characteristic that the solubility of cesium iodide in alcoholic organic solvents increases with temperature. Using this method, high-purity cesium iodide can be produced with only one recrystallization. Although alcoholic organic solvents can be recovered through distillation, it is difficult to achieve a 5N purity level with only one recrystallization, and alcohols are flammable. The third method uses a cesium iodide purification device, including an electric furnace, vacuum tank, material container, cooling collector, condenser, and insulation layer. This device is mostly made of titanium and requires high-temperature evaporation of cesium iodide, resulting in high energy consumption. The fourth method involves synthesizing cesium iodide using an aqueous solution, evaporating and concentrating it to obtain a concentrated cesium iodide solution, and then using ethanol as an antisolvent to precipitate cesium iodide. This method consumes a large amount of ethanol, and like the second method, it has high energy consumption and low yield.

[0006] However, whether cesium iodide is purified by recrystallization or mechanical equipment, the purification is carried out after the synthesis of cesium iodide, which requires the use of organic solvents with high boiling points, making it difficult to obtain a purity of 5N. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing 5N cesium iodide. From the perspective of raw materials, a low-cost and high-yield method is selected to purify the raw materials, and 5N grade cesium iodide can be prepared.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing 5N cesium iodide, comprising the following steps: Cesium carbonate is mixed with water and purified. The resulting cesium carbonate solution is then mixed with a cation exchange resin for adsorption to obtain a purified cesium carbonate solution. The cesium carbonate purified liquid was subjected to a first evaporation concentration, a first cooling crystallization and a first drying process in sequence to obtain dry cesium carbonate. Iodine, water, and carbon tetrachloride are mixed and extracted. The resulting extract is then distilled to obtain purified iodine. The cesium carbonate dry material, refined iodine and hydrazine hydrate are mixed and subjected to a redox reaction to obtain a cesium iodide solution. The cesium iodide solution was subjected to a second evaporation concentration, a second cooling crystallization, and a second drying process to obtain 5N cesium iodide.

[0009] Preferably, the mass ratio of cesium carbonate to water is 1:1 to 3; the purification method is vacuum filtration.

[0010] Preferably, the cation exchange resin is in the hydrogen form or calcium form; the volume ratio of the cation exchange resin to the cesium carbonate solution is 1:2~5.

[0011] Preferably, the adsorption temperature is 20~50℃ and the time is 2~4h.

[0012] Preferably, the temperature of the first evaporation and concentration is 100~110℃; the rate of the first cooling and crystallization is 5~10℃ / h; and the temperature of the first drying is 120~150℃, and the time is 6~8h.

[0013] Preferably, the carbon tetrachloride is of chromatographic purity or analytical grade; the mass ratio of carbon tetrachloride to water is 1:1 to 3:1, and the mass ratio of elemental iodine to carbon tetrachloride is 1.2 to 1.8:100.

[0014] Preferably, the extraction temperature is 20~25℃ and the time is 10~15min; the distillation temperature is 77~90℃.

[0015] Preferably, the mass ratio of the cesium carbonate dry material, refined iodine element and hydrazine hydrate is 10~15:8~12:1; the redox reaction temperature is 90~110℃ and the time is 1~2h.

[0016] Preferably, the temperature of the second evaporation and concentration is 100~110℃; the rate of the second cooling and crystallization is 2~5℃ / h; and the temperature of the second drying is 120~160℃, and the time is 6~8h.

[0017] The beneficial effects of this invention are: This invention provides a method for preparing 5N cesium iodide. The method involves purifying a cesium carbonate solution to remove insoluble matter, then using a cation exchange resin to remove cations such as calcium and magnesium, resulting in a purified cesium carbonate solution. This purified solution is then evaporated, concentrated, cooled, crystallized, and dried to obtain dry cesium carbonate. Iodine is added to water, followed by carbon tetrachloride. The carbon tetrachloride solution containing dissolved iodine is distilled to obtain purified iodine. The dry cesium carbonate, purified iodine, and hydrazine hydrate are mixed and reacted to obtain a cesium iodide solution, which is then evaporated, concentrated, cooled, crystallized, and dried to obtain 5N cesium iodide. This invention, by purifying cesium carbonate and iodine separately, allows for the direct one-step preparation of 5N cesium iodide. High impurity content in the raw materials of cesium iodide can lead to high impurity content in the final product, necessitating multiple recrystallizations. This invention purifies the raw materials of cesium iodide, reducing impurities at the source, thus avoiding multiple recrystallizations and offering advantages such as low cost and high yield. Detailed Implementation

[0018] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0019] This invention provides a method for preparing 5N cesium iodide, comprising the following steps: Cesium carbonate is mixed with water and purified. The resulting cesium carbonate solution is then mixed with a cation exchange resin for adsorption to obtain a purified cesium carbonate solution. The cesium carbonate purified liquid was subjected to a first evaporation concentration, a first cooling crystallization and a first drying process in sequence to obtain dry cesium carbonate. Iodine, water, and carbon tetrachloride are mixed and extracted. The resulting extract is then distilled to obtain purified iodine. The cesium carbonate dry material, refined iodine and hydrazine hydrate are mixed and subjected to a redox reaction to obtain a cesium iodide solution. The cesium iodide solution was subjected to a second evaporation concentration, a second cooling crystallization, and a second drying process to obtain 5N cesium iodide.

[0020] In this invention, the mass ratio of cesium carbonate to water is preferably 1:1 to 3, more preferably 1:2 to 2.5; the purification method is preferably vacuum filtration. This invention removes insoluble substances (organic matter or dust particles) from cesium carbonate through purification, and commercially available cesium carbonate is at most 3N level.

[0021] In this invention, the cation exchange resin is preferably in hydrogen form or calcium form; the volume ratio of the cation exchange resin to the cesium carbonate solution is preferably 1:2~5, more preferably 1:3~4.

[0022] The present invention does not have any special limitation on the source of the cation exchange resin; any commercially available product well known in the art is acceptable.

[0023] Before use, the cation exchange resin of the present invention is regenerated with hydrochloric acid of 5-10% by mass for 0.5-6 hours, more preferably 0.5-2 hours.

[0024] In this invention, the adsorption temperature is preferably 20-50°C, more preferably 25-40°C, and even more preferably 30-35°C; the adsorption time is preferably 2-4 hours, more preferably 2-3 hours. This invention removes calcium and magnesium cations from cesium carbonate solution by adsorption using a cation exchange resin.

[0025] After the adsorption is completed, the present invention preferably filters the resulting mixture, and the filtrate is the cesium carbonate purification solution.

[0026] In this invention, the temperature of the first evaporation and concentration is preferably 100~110℃, more preferably 100~105℃; the concentration endpoint is when a small number of crystals appear above the liquid surface, at which point the heat source needs to be turned off and the liquid slowly cooled to allow crystallization.

[0027] In this invention, the first cooling crystallization rate is preferably 5~10℃ / h, more preferably 6~8℃ / h; the first drying temperature is preferably 120~150℃, more preferably 130~150℃, and the time is preferably 6~8h, more preferably 7~8h.

[0028] In this invention, the carbon tetrachloride is preferably chromatographically pure or analytically pure; the mass ratio of carbon tetrachloride to water is 1:1 to 3:1, more preferably 1 to 2:1; the mass ratio of elemental iodine to carbon tetrachloride is preferably 1.2 to 1.8:100, more preferably 1.4 to 1.7:100, and even more preferably 1.5 to 1.6:100.

[0029] In this invention, the extraction temperature is preferably 20-25°C, more preferably 25°C, and the extraction time is preferably 10-15 min, more preferably 10-12 min; the extraction is preferably carried out under shaking conditions. This invention purifies an iodine solution in carbon tetrachloride through extraction, followed by filtration to remove insoluble impurities trapped within the iodine particles.

[0030] In this invention, the distillation temperature is preferably 77~90℃, more preferably 80~85℃.

[0031] In this invention, the mass ratio of the cesium carbonate dry material, refined iodine element and hydrazine hydrate is preferably 10~15:8~12:1, more preferably 13:10:1; the temperature of the redox reaction is preferably 90~110℃, more preferably 95~105℃, even more preferably 100℃, and the time is preferably 1~2h, more preferably 1~1.5h.

[0032] After the redox reaction is completed, the resulting product is filtered, and the filtrate is concentrated by a second evaporation.

[0033] In this invention, the temperature of the second evaporation and concentration is preferably 100~110℃, more preferably 102~105℃; the concentration endpoint is when a small number of crystals appear above the liquid surface, at which point the heat source needs to be turned off and the temperature slowly lowered for crystallization.

[0034] In this invention, the second cooling crystallization rate is preferably 2~5℃ / h, more preferably 3~4℃ / h; the second drying temperature is preferably 120~160℃, more preferably 130~150℃, and the time is preferably 6~8h, more preferably 6~7h. During the second drying process, it is necessary to stir the mixture every half hour for the first 2 hours to prevent cesium iodide from clumping during the drying process.

[0035] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0036] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the reagents and raw materials described below are all commercially available.

[0037] Example 1

[0038] 2 kg of cesium carbonate was dissolved in 4 kg of pure water and purified by filtration using a Buchner funnel to obtain a cesium carbonate solution. The cation exchange resin (hydrogen form, Yinghai Group, 001) was mixed at a volume ratio of 1:1. 7. The ion exchange resin was treated with 10% hydrochloric acid for 30 minutes to obtain a pretreated cation exchange resin. Measure 50 mL of pretreated cation exchange resin using a graduated cylinder and add it to a 2 L beaker. Then add 100 mL of cesium carbonate solution to the beaker and stir at 20 °C for 3 h to adsorb. After adsorption is complete, filter the solution. The filtrate is the cesium carbonate purified solution. Turn on the electric furnace and evaporate and concentrate the cesium carbonate purified solution at 100°C. When the solution temperature is 105°C, turn off the heat source and slowly cool down for crystallization at a rate of 5°C / h. Then dry it at 150°C for 8h to obtain dry cesium carbonate. Add 200 mL of pure water to a separatory funnel, add 2.4 g of elemental iodine to the separatory funnel containing pure water, add 200 g of carbon tetrachloride to the separatory funnel, tighten the glass stopper, and shake at 25 °C for 10 min to dissolve the elemental iodine in the carbon tetrachloride; after extraction, filter the solution, and distill the resulting carbon tetrachloride solution of iodine at 80 °C to obtain purified elemental iodine; 1956g of cesium carbonate dry material, 1524g of refined iodine and 150g of hydrazine hydrate were mixed and reacted at 100℃ for 1h to obtain a cesium iodide solution. After filtration, the solution was evaporated and concentrated at 110℃. When the solution temperature reached 115℃, the heat source was turned off and the solution was slowly cooled to crystallize at a rate of 3℃ / h. Finally, the solution was dried at 140℃ for 6h. During the drying process, the solution was stirred every half hour for the first 2h to obtain 5N cesium iodide.

[0039] Example 2

[0040] 2.5 kg of cesium carbonate was dissolved in 7.5 kg of pure water, and purified by suction filtration using a Buchner funnel to obtain a cesium carbonate solution; 50 mL of cation exchange resin (hydrogen form, Yinghai Group, 001) pretreated according to the method in Example 1 was measured using a graduated cylinder. 7 ion exchange resin), add it to a 2L beaker, then add 150mL of cesium carbonate solution to the beaker, stir and adsorb at 30℃ for 2h, filter after adsorption is complete, and the filtrate is the cesium carbonate purified solution; Turn on the electric furnace and evaporate and concentrate the cesium carbonate purified solution at 105°C. When the solution temperature is 105°C, turn off the heat source and slowly cool down for crystallization at a rate of 8°C / h. Then dry it at 150°C for 7h to obtain dry cesium carbonate. Add 200 mL of pure water to a separatory funnel, add 3 g of elemental iodine to the separatory funnel containing pure water, add 200 g of carbon tetrachloride to the separatory funnel, tighten the glass stopper, and shake at 25 °C for 10 min to dissolve the elemental iodine in the carbon tetrachloride; after extraction, filter the solution, and distill the resulting carbon tetrachloride solution of iodine at 90 °C to obtain purified elemental iodine; 2282g of cesium carbonate dry material, 1778g of refined iodine and 175g of hydrazine hydrate were mixed and reacted at 105℃ for 1.5h to obtain a cesium iodide solution. After filtration, the solution was evaporated and concentrated at 105℃. When the solution temperature reached 110℃, the heat source was turned off and the solution was slowly cooled to crystallize at a rate of 2℃ / h. Finally, the solution was dried at 130℃ for 7h. During the drying process, the solution was stirred every half hour for the first 2h to obtain 5N cesium iodide.

[0041] Example 3

[0042] 2.5 kg of cesium carbonate was dissolved in 7.5 kg of pure water, and purified by suction filtration using a Buchner funnel to obtain a cesium carbonate solution; 50 mL of cation exchange resin (hydrogen form, Yinghai Group, 001) pretreated according to the method in Example 1 was measured using a graduated cylinder. 7 ion exchange resin), add it to a 2L beaker, then add 200mL of cesium carbonate solution to the beaker, stir and adsorb at 35℃ for 3h, filter after adsorption is complete, and the filtrate is the cesium carbonate purified solution; Turn on the electric furnace and evaporate and concentrate the cesium carbonate purified solution at 110°C. When the solution temperature is 105°C, turn off the heat source and slowly cool down for crystallization at a rate of 10°C / h. Then dry it at 150°C for 6h to obtain dry cesium carbonate. Add 200 mL of pure water to a separatory funnel, add 3.6 g of elemental iodine to the separatory funnel containing pure water, add 200 g of carbon tetrachloride to the separatory funnel, tighten the glass stopper, and shake at 25 °C for 15 min to dissolve the elemental iodine in the carbon tetrachloride; after extraction, filter the solution, and distill the resulting carbon tetrachloride solution of iodine at 80 °C to obtain purified elemental iodine; 2282g of cesium carbonate dry material, 1778g of refined iodine and 175g of hydrazine hydrate were mixed and reacted at 95℃ for 2h to obtain a cesium iodide solution. After filtration, the solution was evaporated and concentrated at 102℃. When the solution temperature reached 110℃, the heat source was turned off and the solution was slowly cooled to crystallize at a rate of 4℃ / h. Finally, the solution was dried at 140℃ for 7h. During the drying process, the solution was stirred every half hour for the first 2h to obtain 5N cesium iodide.

[0043] Example 4

[0044] 2 kg of cesium carbonate was dissolved in 4 kg of pure water, and purified by suction filtration using a Buchner funnel to obtain a cesium carbonate solution; 50 mL of cation exchange resin (hydrogen form, Yinghai Group, 001) pretreated according to the method in Example 1 was measured using a graduated cylinder. 7. Ion exchange resin) is added to a 2L beaker, and then 100mL of cesium carbonate solution is added to the beaker. The mixture is stirred and adsorbed at 50℃ for 4h. After the adsorption is complete, it is filtered, and the filtrate is the cesium carbonate purified solution. Turn on the electric furnace and evaporate and concentrate the cesium carbonate purified solution at 105°C. When the solution temperature is 105°C, turn off the heat source and slowly cool down for crystallization at a rate of 6°C / h. Then dry it at 150°C for 6h to obtain dry cesium carbonate. Add 200 mL of pure water to a separatory funnel, take 3.3 g of elemental iodine into the separatory funnel containing pure water, add 200 g of carbon tetrachloride to the separatory funnel, tighten the glass stopper, and shake at 25 °C for 15 min to dissolve the elemental iodine in the carbon tetrachloride; after extraction, filter the solution, and distill the resulting carbon tetrachloride solution of iodine at 90 °C to obtain purified elemental iodine; 1956g of cesium carbonate dry material, 1524g of refined iodine and 150g of hydrazine hydrate were mixed and reacted at 105℃ for 1h to obtain a cesium iodide solution. After filtration, the solution was evaporated and concentrated at 110℃. When the solution temperature reached 115℃, the heat source was turned off and the solution was slowly cooled to crystallize at a rate of 3℃ / h. Finally, the solution was dried at 140℃ for 8h. During the drying process, the solution was stirred every half hour for the first 2 hours to obtain 5N cesium iodide.

[0045] Example 5

[0046] 3 kg of cesium carbonate was dissolved in 7.5 kg of pure water and purified by suction filtration using a Buchner funnel to obtain a cesium carbonate solution; 50 mL of cation exchange resin (hydrogen form, Yinghai Group, 001) pretreated according to the method in Example 1 was measured using a graduated cylinder. 7 ion exchange resin), add it to a 2L beaker, then add 250mL of cesium carbonate solution to the beaker, stir and adsorb at 40℃ for 3h, filter after adsorption is complete, and the filtrate is the cesium carbonate purified solution; Turn on the electric furnace and evaporate and concentrate the cesium carbonate purified solution at 110°C. When the solution temperature is 105°C, turn off the heat source and slowly cool down for crystallization at a rate of 10°C / h. Then dry it at 150°C for 6h to obtain dry cesium carbonate. Add 200 mL of pure water to a separatory funnel, add 2.8 g of elemental iodine to the separatory funnel containing pure water, add 200 g of carbon tetrachloride to the separatory funnel, tighten the glass stopper, and shake at 25 °C for 10 min to dissolve the elemental iodine in the carbon tetrachloride; after extraction, filter the solution, and distill the resulting carbon tetrachloride solution of iodine at 80 °C to obtain purified elemental iodine; 2934g of cesium carbonate dry material, 2286g of refined iodine and 225g of hydrazine hydrate were mixed and reacted at 110℃ for 1.5h to obtain a cesium iodide solution. After filtration, the solution was evaporated and concentrated at 105℃. When the solution temperature reached 105℃, the heat source was turned off and the solution was slowly cooled to crystallize at a rate of 5℃ / h. Finally, the solution was dried at 140℃ for 7h. During the drying process, the solution was stirred every half hour for the first 2h to obtain 5N cesium iodide.

[0047] Comparative Example 1

[0048] 3 kg of cesium carbonate was dissolved in 7.5 kg of pure water and purified by filtration using a Buchner funnel to obtain a cesium carbonate solution. Turn on the electric furnace and evaporate and concentrate the cesium carbonate solution at 110°C. When the solution temperature is 105°C, turn off the heat source and slowly cool down to crystallize at a rate of 10°C / h. Then dry at 150°C for 6h to obtain dry cesium carbonate. Add 200 mL of pure water to a separatory funnel, add 2.8 g of elemental iodine to the separatory funnel containing pure water, add 200 g of carbon tetrachloride to the separatory funnel, tighten the glass stopper, and shake at 25 °C for 10 min to dissolve the elemental iodine in the carbon tetrachloride; after extraction, filter the solution, and distill the resulting carbon tetrachloride solution of iodine at 80 °C to obtain purified elemental iodine; 2934g of cesium carbonate dry material, 2286g of refined iodine and 225g of hydrazine hydrate were mixed and reacted at 110℃ for 1.5h to obtain a cesium iodide solution. After filtration, the solution was evaporated and concentrated at 105℃. When the solution temperature reached 105℃, the heat source was turned off and the solution was slowly cooled to crystallize at a rate of 5℃ / h. Finally, the solution was dried at 140℃ for 7h. During the drying process, the solution was stirred every half hour for the first 2 hours to obtain cesium iodide.

[0049] The test results of the cesium iodide products obtained in Examples 1-5 and Comparative Example 1 are shown in Table 1.

[0050] Table 1. Components and impurity content of cesium iodide prepared in Examples 1-5 and Comparative Example 1

[0051] As shown in Table 1, when the cesium carbonate solution is not purified, the obtained cesium iodide only meets the 4N standard, with the main ions exceeding the standard being sodium, magnesium, potassium, calcium, iron, and rubidium ions. This invention obtains 5N-grade cesium iodide by purifying the cesium carbonate solution.

[0052] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing 5N cesium iodide, characterized in that, Includes the following steps: Cesium carbonate is mixed with water and purified. The resulting cesium carbonate solution is then mixed with a cation exchange resin for adsorption to obtain a purified cesium carbonate solution. The cesium carbonate purified liquid was subjected to a first evaporation concentration, a first cooling crystallization and a first drying process in sequence to obtain dry cesium carbonate. Iodine, water, and carbon tetrachloride are mixed and extracted. The resulting extract is then distilled to obtain purified iodine. The cesium carbonate dry material, refined iodine and hydrazine hydrate are mixed and subjected to a redox reaction to obtain a cesium iodide solution. The cesium iodide solution was subjected to a second evaporation concentration, a second cooling crystallization, and a second drying process to obtain 5N cesium iodide.

2. The preparation method according to claim 1, characterized in that, The mass ratio of cesium carbonate to water is 1:1 to 3; the purification method is vacuum filtration.

3. The preparation method according to claim 1, characterized in that, The cation exchange resin is in hydrogen form or calcium form; the volume ratio of the cation exchange resin to the cesium carbonate solution is 1:2~5.

4. The preparation method according to claim 1, characterized in that, The adsorption temperature is 20~50℃, and the time is 2~4h.

5. The preparation method according to claim 1, characterized in that, The temperature of the first evaporation and concentration is 100~110℃; the rate of the first cooling crystallization is 5~10℃ / h; the temperature of the first drying is 120~150℃, and the time is 6~8h.

6. The preparation method according to claim 1, characterized in that, The carbon tetrachloride is of chromatographic or analytical grade; the mass ratio of carbon tetrachloride to water is 1:1 to 3:1, and the mass ratio of elemental iodine to carbon tetrachloride is 1.2 to 1.8:

100.

7. The preparation method according to claim 1, characterized in that, The extraction temperature is 20~25℃ and the time is 10~15min; the distillation temperature is 77~90℃.

8. The preparation method according to claim 1, characterized in that, The mass ratio of the cesium carbonate dry material, refined iodine, and hydrazine hydrate is 10~15:8~12:1; the redox reaction is carried out at a temperature of 90~110℃ for 1~2 hours.

9. The preparation method according to claim 1, characterized in that, The second evaporation concentration temperature is 100~110℃; the second cooling crystallization rate is 2~5℃ / h; the second drying temperature is 120~160℃ and the time is 6~8h.

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