A method for purifying ammonium perrhenate

Abstract

The present application belongs to the technical field of purification of dispersed metal salt, and particularly relates to a method for purifying ammonium perrhenate. The existing methods for purifying ammonium perrhenate mainly include recrystallization, solvent extraction and ion exchange. The recrystallization method has the problems of low purification efficiency, high cost and limited deep removal of impurities. The solvent extraction method has the problems of great environmental pressure, serious emulsification and high residual organic solvent in ammonium perrhenate. The ion exchange method has the problems of small processing capacity, easy deactivation of resin and frequent regeneration. The present application discloses a method for purifying ammonium perrhenate. In the presence of a surfactant, impurity metals in ammonium perrhenate are separated by gas floating in an aqueous organic solvent, and high-content ammonium perrhenate is prepared. The purification method has the characteristics of simple purification process, high purification efficiency and low solvent residue.

Description

Technical Field

[0001] This invention belongs to the field of rare and dispersed metal salt purification technology, specifically relating to a purification method for ammonium perrhenate. Background Technology

[0002] Ammonium perrhenate (NH4ReO4) is an important rhenium compound, a white or colorless crystalline powder, readily soluble in water. It is mainly produced from metallic rhenium or rhenium-containing materials through oxidation, dissolution, and crystallization. Ammonium perrhenate is a core intermediate product in the rhenium industry chain, and high-purity ammonium perrhenate is directly linked to high-end manufacturing and high-tech fields. Especially in aerospace, advanced catalysis, and cutting-edge scientific research, there are stringent requirements for the purity of ammonium perrhenate. Existing purification methods for ammonium perrhenate mainly include recrystallization, solvent extraction, and ion exchange. Among these, recrystallization utilizes the characteristic that the solubility of ammonium perrhenate in water changes significantly with temperature, purifying it through multiple dissolution-crystallization processes. However, recrystallization suffers from low purification efficiency, high cost, and limited depth of impurity removal. Solvent extraction utilizes the selective complexation or association of perrhenate ions with the extractant to transfer perrhenate ions from the aqueous phase to the organic phase, followed by back-extraction with ammonia to enrich and purify ammonium perrhenate. Solvent extraction suffers from several drawbacks: significant environmental impact, severe emulsification, and high levels of residual organic solvents in the ammonium perrhenate. Ion exchange utilizes the selective adsorption of perrhenate ions by anion exchange resins, separating perrhenate ions from other metals. Ion exchange methods suffer from several drawbacks: low throughput, easy resin deactivation, and frequent regeneration.

[0003] In 2020, CN110885098A disclosed a method for purifying ammonium perrhenate. Specifically, crude ammonium perrhenate is first dissolved in ultrapure water, then filtered through a three-stage sieve to obtain a crude ammonium perrhenate solution. Hydrogen peroxide and ammonia are then added, and the solution is stirred. After adsorption through two cation exchange resins connected in series, the solution is evaporated and concentrated, then frozen to crystallize, filtered, and dried to obtain ammonium perrhenate. This preparation method suffers from problems such as complex processes and high energy consumption.

[0004] In 2025, CN119387599A disclosed a method for preparing high-purity rhenium bars. First, crude ammonium perperurate is dissolved in deionized water, and an organic solvent is added to precipitate a colloidal substance. Then, the colloidal substance is separated by centrifugation, and the precipitate is evaporated and crystallized to obtain refined ammonium perperurate. Next, the refined ammonium perperurate is reduced with hydrogen to obtain high-purity rhenium powder. Finally, the high-purity rhenium powder is subjected to cold isostatic pressing and sintering to obtain high-purity rhenium bars. While this method can ultimately produce high-purity rhenium bars by purifying ammonium perperurate, it suffers from low centrifugal sedimentation efficiency and high energy consumption during evaporation and crystallization. Summary of the Invention

[0005] To address the problems of complex processes, low purification efficiency, and high costs in existing ammonium perrhenate purification methods, this invention proposes a purification method for ammonium perrhenate, specifically comprising the following steps:

[0006] (1) The crude ammonium perrhenate is pulverized by a pulverizer to form fine ammonium perrhenate powder;

[0007] (2) Ammonium perrhenate fine powder is separated by air flotation in an aqueous organic solvent to form an ammonium perrhenate suspension;

[0008] (3) The ammonium perrhenate suspension is filtered, washed with anhydrous organic solvent, and dried to form a high-quality ammonium perrhenate;

[0009] The content of the crude ammonium perrhenate is ≥99%.

[0010] This invention uses crude ammonium perrhenate as raw material. The content of the crude ammonium perrhenate needs to be ≥99%, otherwise the purification is not economically viable. The crude ammonium perrhenate can be purified to a content of ≥99% first using methods such as recrystallization, and then purified using the method described in this invention. This invention pulverizes the crude ammonium perrhenate into fine powder using a pulverizer, increasing the specific surface area of ​​the ammonium perrhenate and fully exposing any entrained impurities for subsequent separation. When separating non-ammonium perrhenate impurities, this invention employs air flotation. By selecting suitable air flotation solvents and surfactants, impurities in the ammonium perrhenate are separated and removed as much as possible. The air flotation solvent needs to have relatively low solubility for both ammonium perrhenate and impurities; otherwise, the air flotation process cannot proceed. Unlike existing air flotation separation methods, this invention performs the air flotation process in an aqueous organic solvent. This reduces the solubility of ammonium perrhenate and impurities without affecting the solubility of the surfactant, facilitating a smooth air flotation process.

[0011] The above describes the basic technical solution of the present invention. As a supplement and improvement to the basic technical solution, the present invention also includes the following preferred solutions:

[0012] Preferably, the pulverizer in step (1) is one of an air jet mill, a vibratory mill, a ball mill, a hammer mill, an impact mill, or a centrifugal mill. All of these pulverizers can thoroughly pulverize crude ammonium perrhenate into fine ammonium perrhenate powder. The difference lies in the particle size distribution and pulverization efficiency of the fine ammonium perrhenate powder obtained from different pulverizers. Before pulverization, the moisture content of the crude ammonium perrhenate needs to be controlled to avoid adhesion problems during the pulverization process.

[0013] More preferably, the pulverizer is one of an air jet mill, a vibratory mill, or a ball mill. These three types of pulverizers can produce fine ammonium perrhenate powder with a narrower particle size distribution when pulverizing crude ammonium perrhenate, and can also produce relatively more spherical fine powder, which is very beneficial for improving the subsequent air flotation separation effect.

[0014] Preferably, the particle size D50 of the ammonium perrhenate fine powder in step (1) is ≤10 μm. The particle size of the ammonium perrhenate fine powder directly affects the effect of air flotation separation. If the particle size of the ammonium perrhenate fine powder is too large, the impurities entrained in it cannot be fully exposed and cannot be removed by air flotation separation; if the particle size of the ammonium perrhenate fine powder is too small, the proportion of ammonium perrhenate separated during air flotation increases, increasing the load on subsequent recycling. Generally, controlling the particle size D50 of the ammonium perrhenate fine powder to ≤10 μm is sufficient to meet the requirements of subsequent air flotation separation. It is best to simultaneously control the particle size D50 of the ammonium perrhenate fine powder to >5 μm, otherwise the subsequent filtration process will be slow, affecting efficiency.

[0015] Preferably, the organic solvent in step (2) and / or step (3) is at least one of ethanol, n-propanol, isopropanol, acetone, and butanone. Unlike existing flotation technologies, this invention performs the flotation process in an aqueous organic solvent. In this aqueous organic solvent, ammonium perperate and impurities have low solubility, reducing the surface tension between ammonium perperate and impurities and the organic solvent, thus facilitating the separation of impurities from ammonium perperate via flotation.

[0016] Preferably, to improve the effect of air flotation separation, the relative permittivity of the aqueous organic solvent in step (2) is μ; and 25≦μ≦35. Through extensive experimental research, the inventors have determined that to achieve the best separation effect in air flotation separation, the relative permittivity of the aqueous organic solvent must be strictly controlled. Specifically, the relative permittivity μ of the aqueous organic solvent needs to be controlled within the range of 25 to 35; otherwise, the air flotation separation effect will deteriorate. In specific operation, water can be slowly added to the organic solvent, and the relative permittivity of the aqueous organic solvent can be continuously monitored and controlled within the above-mentioned range. Alternatively, organic solvent or water can be added to the aqueous organic solvent to control its relative permittivity within the above-mentioned range.

[0017] Preferably, the air flotation separation process in step (2) is carried out according to the following steps:

[0018] S1. Add an aqueous organic solvent and a surfactant to the flotation tank;

[0019] S2. Add fine ammonium perrhenate powder to the flotation tank;

[0020] S3. Nitrogen microbubbles are introduced into the flotation tank through a microbubble generator to perform flotation.

[0021] S4. Scrape off the foam layer on the upper part of the liquid surface in the flotation tank to obtain ammonium perrhenate suspension.

[0022] This invention describes the flotation separation process in a flotation tank. First, an aqueous organic solvent and a surfactant are added to the flotation tank and thoroughly mixed. Then, fine ammonium perrhenate powder is added and fully suspended in the aqueous organic solvent. Next, nitrogen microbubbles are introduced into the flotation tank through a microbubble generator. The microbubble generator disperses the nitrogen into tiny nitrogen bubbles ranging from a few micrometers to tens of micrometers and introduces them into the flotation tank. Under the action of the surfactant, some impurities adhere to the surface of the nitrogen microbubbles and float to the surface of the flotation tank, accumulating into foam. Finally, the foam on the upper part of the liquid surface in the flotation tank is manually or automatically skimmed off, leaving an ammonium perrhenate suspension at the bottom. Microbubble generators include vortex aerators, pressurized solvent degassing generators, Venturi generators, membrane dispersion generators, and ultrasonic generators, which can be selected according to the type of flotation tank. However, nitrogen must be used as the gas source; using air as the gas source poses safety risks.

[0023] Preferably, the mass ratio of the surfactant in step S1 to the ammonium perrhenate fine powder in step S2 is 0.002–0.02:1; the surfactant is at least one selected from polysorbate 80, polysorbate 20, fatty alcohol polyoxyethylene 9 ether, fatty alcohol polyoxyethylene 7 ether, sodium dodecyl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, hexadecyltrimethylammonium bromide, and dodecyl dimethyl betaine. Through systematic screening experiments, the inventors determined that using at least one of polysorbate 80, polysorbate 20, fatty alcohol polyoxyethylene 9 ether, fatty alcohol polyoxyethylene 7 ether, sodium dodecyl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, hexadecyltrimethylammonium bromide, and dodecyl dimethyl betaine as the surfactant for air flotation separation can efficiently separate impurities from ammonium perrhenate in the above-mentioned aqueous organic solvent. The amount of surfactant should not be too large to avoid introducing it into the ammonium perrhenate and affecting product quality.

[0024] More preferably, the surfactant is at least one selected from polysorbate 80, polysorbate 20, fatty alcohol polyoxyethylene 9 ether, and fatty alcohol polyoxyethylene 7 ether. Among these surfactants, fatty alcohol polyoxyethylene 9 ether and fatty alcohol polyoxyethylene 7 ether are both composed of C, H, and O elements. Polysorbate 80 and polysorbate 20 are composed of C, H, O, and N elements. This minimizes the impact on the quality of the rhenium derivative during the subsequent preparation of rhenium derivatives using ammonium perrhenate, and avoids any issues that could reduce the quality of the rhenium derivative.

[0025] This invention discloses a method for preparing high-content ammonium perrhenate by separating impurity metals from ammonium perrhenate through flotation in an aqueous organic solvent in the presence of a surfactant. This purification method is characterized by its simplicity, high efficiency, and low solvent residue. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments, but the present invention is not limited to these embodiments.

[0027] Example 1

[0028] (1) Airflow pulverization:

[0029] Take 150.00g of crude ammonium perrhenate (content: 99.07%, moisture content: 0.08%, particle size D50=124.256μm), and pulverize it into fine ammonium perrhenate powder with a particle size D50=8.514μm in an air jet mill under controlled air pressure of 0.7MPaG, to obtain approximately 147g of fine ammonium perrhenate powder.

[0030] (2) Air flotation separation:

[0031] Add 850g of n-propanol and 150g of deionized water to the flotation tank, maintaining the temperature at 20℃. After thorough mixing, the relative permittivity μ of the n-propanol aqueous solution is measured to be 30.5. Add 1.2g of polysorbate 20 to the flotation tank and mix thoroughly. Add 140.00g of fine ammonium perrhenate powder to the flotation tank. Use a vortex aerator to break high-purity nitrogen into microbubbles and introduce them into the flotation tank for flotation. During the flotation process, trace amounts of solid matter adhere to the surface of the microbubbles and accumulate as foam at the liquid surface in the flotation tank. Use a spoon to scrape the accumulated foam into a beaker. After 20 minutes of flotation, when there are virtually no microparticles on the surface of the foam layer, flotation is stopped.

[0032] (3) Filtration, washing, and drying:

[0033] The material in the flotation tank was filtered through a Buchner funnel. After filtration, the filter cake was washed three times with 200 ml of n-propanol. The washed filter cake was transferred to a single-necked flask and dried for 2 hours in a rotary evaporator at a water bath temperature of 90°C and a pressure of 1000 PaA, yielding 135.42 g of purified ammonium perrhenate, with a purity of 99.94%. 50 ml of n-propanol was added to the beaker containing the impurities, and the mixture was filtered, washed with n-propanol, and the filter cake was dried, yielding 3.40 g of impurities, with a purity of 76.33%. The filtrate and washing liquid were combined, and the n-propanol was recycled.

[0034] Example 2

[0035] In Example 2, the airflow pressure was increased to 0.8 MPaG during the preparation of ammonium perperurate fine powder, which reduced the particle size of the ammonium perperurate fine powder to D50 = 6.327 μm. Other processes and parameters were the same as in Example 1.

[0036] Finally, 134.26 g of purified ammonium perrhenate was obtained, with a purity of 99.96%. 50 ml of n-propanol was added to the beaker containing the impurities, filtered, washed with n-propanol, and the filter cake was dried to obtain 4.50 g of impurities, with a purity of 81.62%.

[0037] Example 3

[0038] In Example 3, the airflow pressure was reduced to 0.6 MPa during the preparation of ammonium perperurate fine powder, thereby increasing the particle size of the ammonium perperurate fine powder to D50 = 9.916 μm. Other processes and parameters were the same as in Example 1.

[0039] Finally, 135.71g of purified ammonium perrhenate was obtained, with a purity of 99.91%. 50ml of n-propanol was added to the beaker containing the impurities, filtered, washed with n-propanol, and the filter cake was dried to obtain 3.12g of impurities, with a purity of 75.42%.

[0040] Example 4

[0041] In Example 4, when preparing aqueous n-propanol, 950g of n-propanol and 50g of water were added. At this time, the relative permittivity of the n-propanol aqueous solution was constant μ=25.0. Other processes and parameters were the same as in Example 1.

[0042] Finally, 136.72 g of purified ammonium perrhenate was obtained, with a purity of 99.91%. 50 ml of n-propanol was added to the beaker containing the impurities, filtered, washed with n-propanol, and the filter cake was dried to obtain 2.15 g of impurities, with a purity of 66.75%.

[0043] Example 5

[0044] In Example 5, when preparing aqueous n-propanol, 750g of n-propanol and 250g of water were added. At this time, the relative permittivity of the n-propanol aqueous solution was constant μ=35.0. Other processes and parameters were the same as in Example 1.

[0045] Finally, 133.25g of purified ammonium perrhenate was obtained, with a purity of 99.97%. 50ml of n-propanol was added to the beaker containing the impurities, filtered, washed with n-propanol, and the filter cake was dried, yielding 4.48g of impurities with a purity of 84.68%.

[0046] Example 6

[0047] In Example 6, when preparing an aqueous organic solvent, 850g of isopropanol and 150g of water were added. At this time, the relative permittivity of the isopropanol aqueous solution was μ=27.3. Other processes and parameters were the same as in Example 1.

[0048] Finally, 135.14 g of purified ammonium perrhenate was obtained, with a purity of 99.95%. 50 ml of isopropanol was added to the beaker containing the impurities, filtered, washed with isopropanol, and the filter cake was dried, yielding 3.65 g of impurities with a purity of 77.90%.

[0049] Example 7

[0050] In Example 7, when preparing an aqueous organic solvent, 850g of acetone and 150g of water were added. At this time, the relative permittivity of the acetone aqueous solution was μ=29.4. Other processes and parameters were the same as in Example 1.

[0051] Finally, 135.27g of purified ammonium perrhenate was obtained, with a purity of 99.94%. 50ml of acetone was added to the beaker containing the impurities, the mixture was filtered, washed with acetone, and the filter cake was dried, yielding 3.54g of impurities with a purity of 77.34%.

[0052] Example 8

[0053] In Example 8, polysorbate 80:1.2g was added as a surfactant during air flotation, and other processes and parameters were the same as in Example 1.

[0054] Finally, 134.76 g of purified ammonium perrhenate was obtained, with a purity of 99.96%. 50 ml of n-propanol was added to the beaker containing the impurities, filtered, washed with n-propanol, and the filter cake was dried to obtain 4.04 g of impurities, with a purity of 79.22%.

[0055] Example 9

[0056] In Example 9, 1.2g of fatty alcohol polyoxyethylene 9 ether was added as a surfactant during air flotation, and other processes and parameters were the same as in Example 1.

[0057] Finally, 135.19 g of purified ammonium perrhenate was obtained, with a purity of 99.97%. 50 ml of n-propanol was added to the beaker containing the impurities, filtered, washed with n-propanol, and the filter cake was dried to obtain 3.64 g of impurities, with a purity of 76.42%.

[0058] Example 10

[0059] In Example 10, 1.2g of fatty alcohol polyoxyethylene 7 ether was added as a surfactant during air flotation, and other processes and parameters were the same as in Example 1.

[0060] Finally, 134.97g of purified ammonium perrhenate was obtained, with a purity of 99.94%. 50ml of n-propanol was added to the beaker containing the impurities, filtered, washed with n-propanol, and the filter cake was dried, yielding 3.82g of impurities with a purity of 79.05%.

[0061] Example 11

[0062] In Example 11, sodium dodecyl sulfate (1.2g) was added as a surfactant during air flotation. Other processes and parameters were the same as in Example 1.

[0063] Finally, 133.95g of purified ammonium perrhenate was obtained, with a purity of 99.92%. 50ml of n-propanol was added to the beaker containing the impurities, filtered, washed with n-propanol, and the filter cake was dried to obtain 4.80g of impurities, with a purity of 83.64%.

[0064] Comparative Example 1

[0065] In Comparative Example 1, the airflow pressure was reduced to 0.5 MPa during the preparation of ammonium perrhenate fine powder, thereby increasing the particle size of the ammonium perrhenate fine powder to D50 = 15.367 μm. Other processes and parameters were the same as in Example 1.

[0066] Finally, 135.67 g of purified ammonium perrhenate was obtained, with a purity of 99.45%. 50 ml of n-propanol was added to the beaker containing the impurities, filtered, washed with n-propanol, and the filter cake was dried to obtain 3.16 g of impurities, with a purity of 90.64%.

[0067] Comparative Example 2

[0068] In Comparative Example 2, when preparing aqueous n-propanol, 980g of n-propanol and 20g of water were added. At this time, the relative permittivity of the n-propanol aqueous solution was μ=22.5. Other processes and parameters were the same as in Example 1.

[0069] Finally, 137.11 g of purified ammonium perrhenate was obtained, with a purity of 99.39%. 50 ml of n-propanol was added to the beaker containing the impurities, filtered, washed with n-propanol, and the filter cake was dried to obtain 1.78 g of impurities, with a purity of 87.33%.

[0070] Comparative Example 3

[0071] In Comparative Example 3, when preparing aqueous n-propanol, 700g of n-propanol and 300g of water were added. At this time, the relative permittivity of the n-propanol aqueous solution was constant μ=38.5. Other processes and parameters were the same as in Example 1.

[0072] Finally, 133.07 g of purified ammonium perrhenate was obtained, with a purity of 99.58%. 50 ml of n-propanol was added to the beaker containing the impurities, filtered, washed with n-propanol, and the filter cake was dried to obtain 3.60 g of impurities, with a purity of 93.68%.

[0073] Comparative Example 4

[0074] Comparative Example 4 did not use surfactants during air flotation, but other processes and parameters were the same as in Example 1.

[0075] Finally, 136.58 g of purified ammonium perrhenate was obtained, with a purity of 99.42%. 50 ml of n-propanol was added to the beaker containing the impurities, filtered, washed with n-propanol, and the filter cake was dried to obtain 2.29 g of impurities, with a purity of 88.35%.

[0076] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for purifying ammonium perrhenate, characterized in that, The purification method shall be carried out in accordance with the following steps: (1) The crude ammonium perrhenate is pulverized by a pulverizer to form fine ammonium perrhenate powder; (2) Ammonium perrhenate fine powder is separated by air flotation in an aqueous organic solvent to form an ammonium perrhenate suspension; (3) The ammonium perrhenate suspension is filtered, washed with anhydrous organic solvent, and dried to form a high-quality ammonium perrhenate; The content of the crude ammonium perrhenate is ≥99%.

2. The purification method according to claim 1, characterized in that, The pulverizer mentioned in step (1) is one of the following: air jet mill, vibratory mill, ball mill, hammer mill, impact mill, centrifugal mill.

3. The purification method according to claim 2, characterized in that, The pulverizer is one of the following: air jet mill, vibratory mill, or ball mill.

4. The purification method according to claim 1, characterized in that, The particle size of the ammonium perrhenate fine powder in step (1) is D50≦10μm.

5. The purification method according to claim 1, characterized in that, The organic solvent in step (2) and / or step (3) is at least one of ethanol, n-propanol, isopropanol, acetone, and butanone.

6. The purification method according to claim 1, characterized in that, The relative permittivity of the aqueous organic solvent in step (2) is μ; and 25≦μ≦35.

7. The purification method according to claim 1, characterized in that, The air flotation separation process in step (2) is carried out according to the following procedures: S1. Add an aqueous organic solvent and a surfactant to the flotation tank; S2. Add fine ammonium perrhenate powder to the flotation tank; S3. Nitrogen microbubbles are introduced into the flotation tank through a microbubble generator to perform flotation. S4. Scrape off the foam layer on the upper part of the liquid surface in the flotation tank to obtain ammonium perrhenate suspension.

8. The purification method according to claim 7, characterized in that, The mass ratio of the surfactant in step S1 to the ammonium perrhenate fine powder in step S2 is 0.002 to 0.02:1; the surfactant is at least one of polysorbate 80, polysorbate 20, fatty alcohol polyoxyethylene 9 ether, fatty alcohol polyoxyethylene 7 ether, sodium dodecyl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, hexadecyltrimethylammonium bromide, and dodecyl dimethyl betaine.

9. The purification method according to claim 8, characterized in that, The surfactant is at least one of polysorbate 80, polysorbate 20, fatty alcohol polyoxyethylene 9 ether, and fatty alcohol polyoxyethylene 7 ether.