Method for preparing high-purity ammonium rhenate through hydrothermal single crystal purification

Abstract

The invention belongs to the technical field of high-purity metal preparation through hydrometallurgy, and particularly relates to a method for preparing high-purity ammonium rhenate through hydrothermal single crystal purification. The method comprises the following steps: 1) preparing an ammonia solution, dissolving crude ammonium rhenate in the ammonia solution to prepare a saturated ammonium rhenate solution, taking the saturated ammonium rhenate solution as a substrate solution, adding ammonium rhenate coarse grains into the substrate solution, and carrying out a hydrothermal reaction; and 2) cooling to a recovery temperature after the hydrothermal reaction is finished, and filtering and recovering to obtain the ammonium rhenate single crystal. Crude ammonium rhenate and ammonium rhenate coarse crystals can be directly used as low-cost raw materials, the high-purity ammonium rhenate single crystal is directly obtained by a low-cost, efficient and simple scheme, and meanwhile, the energy consumption and the material utilization rate are relatively high, and the direct recovery rate of the product is extremely high.

Description

Technical Field

[0001] The invention belongs to the technical field of preparing high-purity metals by hydrometallurgy, and in particular relates to a method for preparing high-purity ammonium rhenate by purifying a hydrothermal single crystal. Background Art

[0002] Rhenium is a typical rare metal with a high melting point. Due to its unique physical and chemical properties, it is widely used in aerospace, atomic energy, electronic information, metallurgy, chemical engineering, and other fields. In particular, metallic rhenium has become a core element in the production of high-temperature superalloys for turbine engines and is hailed as a metal that will revolutionize the aviation industry. For example, the article "Effect of rhenium addition on microstructure and mechanical properties of Ti-48Al-2Cr-2Nb alloys [J]. Transactions of Nonferrous Metals Society of China, 2025, 35: 474−485" reports that rhenium addition can improve the mechanical properties and high-temperature resistance of TiAl alloys. Single-crystal blades are key components of aircraft engines, and their manufacturing process is susceptible to interference from impurities and process conditions, which directly affect blade quality and engine performance. Rhenium is a key alloy element, and ensuring its stable supply is of great strategic significance for promoting the development of my country's aerospace blade technology and maintaining national security.

[0003] Because rhenium resources are mostly extracted from associated byproducts, which contain high and complex impurities, crude ammonium rhenate products obtained during metallurgical processes often contain numerous impurity elements. Limited by the solution system and the properties of similar elements, traditional recrystallization methods for ammonium rhenate purification are inefficient and difficult to fully remove. The invention patent application for a method for purifying crude ammonium perrhenate from copper smelting, published by the Patent Office of China on March 25, 2025, is CN116239152B. The method comprises the following steps: slurrying the crude ammonium perrhenate and leaching it to obtain leaching residue and leachate, and part of the leachate is returned to the acid production and adsorption process in an open circuit; slurrying the leaching residue obtained in the previous step, heating and leaching it, and then separating the solid and liquid to obtain leaching residue and leachate, and returning the leaching residue to the system; adding oxidant A to the leachate in the previous step, heating and oxidizing it, and then fine filtering it, and returning the oxidized residue to the system; freezing and crystallizing the oxidized liquid, and separating the solid and liquid to obtain primary crystals and liquid after primary crystallization; adding the primary crystals to the solution, heating and dissolving it, and then controlling the temperature of the filtrate for crystallization, separating the crystals and returning them to dissolve, freezing and crystallizing the liquid after crystallization, and then filtering and washing it to obtain secondary crystals and liquid after secondary crystallization, and drying the secondary crystals to obtain the final product, ammonium perrhenate. The Chinese Patent Office published an invention patent application on March 21, 2025, with application publication number CN119660811A, for a method of preparing high-purity ammonium rhenate from crude rhenate. The patent utilizes calcium hydroxide to separate anions, cationic resin to adsorb cations, and then electrodialysis and ammonia treatment to produce the ammonium rhenate product. Summary of the Invention

[0004] In order to solve the problems in the existing high-purity ammonium rhenate production process, such as the difficulty in effectively removing impurities such as arsenic, sulfur, thallium, and zinc, which makes it difficult to achieve product purity standards, a method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification is provided.

[0005] The main objectives of the present invention are: 1. It can effectively purify crude ammonium rhenate, and the method is simple and efficient; 2. To achieve the purification and removal of impurities and avoid inclusion during crystallization; 3. It can ensure the production of complete ammonium rhenate crystals.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions.

[0007] A method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification, The method comprises: 1) preparing an ammonia solution, dissolving crude ammonium rhenate in the ammonia solution to prepare a saturated ammonium rhenate solution, and using the saturated ammonium rhenate solution as a base solution. Adding crude ammonium rhenate crystals to the base solution and performing a hydrothermal reaction; 2) After the hydrothermal reaction is completed, the temperature is lowered to the recovery temperature, and the ammonium rhenate single crystal is recovered by filtration.

[0008] As a preference, Step 1) The ammonia solution is prepared from ammonia gas and / or ammonia water and / or water; In step 1), the ammonia concentration of the ammonia solution is 0.1 to 3.0 mol / L.

[0009] As a preference, Step 1) preheating the ammonia solution before dissolving the crude ammonium rhenate in the ammonia solution; The preheating temperature is controlled to be 45-85°C.

[0010] As a preference, Step 1) The crude ammonium rhenate crystals are added to an ammonia solution at a concentration of 20-150 g / L.

[0011] As a preference, In step 1), the hydrothermal reaction process is controlled at a reaction temperature of 150-200°C, a reaction time of 1-6 h, and a reaction pressure of 1.5-3.0 MPa.

[0012] As a preference, The recovery temperature in step 2) is 25-65°C.

[0013] As a preference, Step 3) The filtration recovery obtains ammonium rhenate single crystal.

[0014] As a preference, The filtrate is tested for ammonia concentration before use to ensure that the ammonia concentration meets the ammonia concentration range required by the substrate solution before it can be recycled.

[0015] The core of the technical solution of the present invention lies in creating a supersaturated crystallization environment for ammonium rhenate through a hydrothermal reaction. By precisely controlling the reaction temperature, pressure, and holding time, directional nucleation and orderly growth of ammonium rhenate crystals are achieved in the hydrothermal system. Simultaneously, the crystal nucleation rate and growth kinetics are optimized to promote the preferred orientation of ammonium rhenate single crystals along specific crystal planes, ultimately yielding large, highly oriented, and high-purity ammonium rhenate single crystals. This method significantly improves crystal purity and quality, providing technical support for the stable, large-scale production of high-purity ammonium rhenate materials.

[0016] The primary purpose of using ammonia in the present invention is to ensure that the rhenium element in the prepared base solution is stably present as rhenate, preventing precipitation or conversion of other forms. The ammonia solution must be preheated to promote the dissolution of the crude ammonium rhenate, but this temperature must be controlled to avoid excessive preheating, which could lead to excessive decomposition and release of ammonia. The high-temperature, concentrated ammonia environment allows some impurity elements such as iron, copper, nickel, cobalt, silver, tungsten, and molybdenum to form soluble complexes, preventing their precipitation and creating an optimal environment for ammonium rhenate crystallization.

[0017] The reason for the choice of hydrothermal temperature is that under the hydrothermal temperature conditions selected by the present invention, ammonium rhenate can obtain sufficient crystal transformation energy in the process, which is the key to driving the crystal purification process. In this process, the crystal transformation of ammonium rhenate crystals causes the crystal to be reconstructed, and impurities are released to achieve purification. However, when the temperature is too high, energy consumption is wasted. In addition, controlling the pressure to a suitable state during the hydrothermal process is also to achieve energy reduction while regulating the solubility level of ammonium rhenate. After the impurities in the coarse crystals are released, the impurities are dissolved in the base solution, and a very small amount of extremely fine ammonium rhenate microcrystals can exist as nucleation points, promoting the formation of refined high-purity single crystals in the subsequent recrystallization process. Finally, the temperature is lowered to a suitable recovery temperature to achieve the precipitation and crystallization of a large amount of ammonium rhenate, thereby realizing the entire reaction process.

[0018] Furthermore, in step (2), the control of the cooling temperature during the hydrothermal single crystal purification process is extremely critical. Due to the high-pressure, closed conditions of the hydrothermal autoclave, the cooling rate is extremely slow, which creates favorable conditions for the precipitation and growth of ammonium rhenate crystals. Generally, the cooling rate in the temperature range of 60-20°C is not greater than 2°C / h. This ensures that ammonium rhenate crystallizes in an orderly manner based on the early nucleation process, allowing impurities to be distributed between the solid and liquid phases, thereby achieving efficient purification.

[0019] The recovery cutoff temperature of single crystal ammonium rhenate is 20°C. When the crystallization temperature is below 20°C, the growth rate of ammonium rhenate crystals will be too fast, resulting in polycrystalline ammonium rhenate, which will lead to the concomitant adsorption of impurities and a decrease in the purity of the product. If the recovery temperature is too high, the yield (direct yield) of ammonium rhenate will also decrease.

[0020] The crystallization mother liquor can be further cooled deeply to recover the ammonium rhenate therein and transferred to the next batch of purification production as a crude product for subsequent purification.

[0021] For extremely low concentrations of ammonium rhenate after crystallization, extraction or ion exchange can be used for recovery. This is a common industry technology and is not limited here.

[0022] In the technical solution of the present invention, it should be noted that, usually, ammonia gas, ammonia water, etc. need to be pure ammonia or electronic grade ammonia water, and the water used needs to be high-purity water with a conductivity of at least 18 MΩ·cm. At the same time, the hydrothermal process is easy to use a container lined with high-purity polytetrafluoroethylene material. The embodiments of the present invention meet the above requirements to ensure that the introduction of external impurities is avoided.

[0023] The beneficial effects of the present invention are: The present invention can directly use crude ammonium rhenate and coarse ammonium rhenate crystals as low-cost raw materials to directly obtain high-purity single-crystal ammonium rhenate in a low-cost, efficient and simple solution. 5N-grade single-crystal ammonium rhenate products can be stably obtained using 4N ammonium rhenate as the raw material. At the same time, high energy consumption and material utilization rates are ensured, and the direct product yield is extremely high. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The XRD characterization results of the product obtained in Example 1 of the present invention are as follows; Figure 2 This is a morphology characterization diagram of the product obtained in Example 1 of the present invention under an optical microscope. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to specific embodiments and the accompanying drawings. Based on these descriptions, those skilled in the art will be able to implement the present invention. Furthermore, the embodiments of the present invention described below are generally only a portion of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0026] Unless otherwise specified, the raw materials used in the examples of the present invention are all commercially available or available to those skilled in the art; unless otherwise specified, the methods used in the examples of the present invention are all methods known to those skilled in the art.

[0027] Example 1 A method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification, The method comprises: 1) Prepare a 0.1 mol / L ammonia solution with electronic-grade ammonia and high-purity water and preheat to 60°C. Dissolve crude ammonium rhenate in the ammonia solution to prepare a saturated ammonium rhenate solution. This solution is used as the base solution. Add crude ammonium rhenate crystals at a rate of 0.10 g / g of crude ammonium rhenate to the base solution and perform a hydrothermal reaction at 150°C and 2 MPa for 6 h. 2) After the hydrothermal reaction is completed, the temperature is lowered to 25°C and filtered to recover ammonium rhenate single crystals.

[0028] The direct yield of the ammonium rhenate single crystal prepared above was calculated and its purity was characterized. The direct yield is: (actual yield / theoretical yield calculated based on the amount and purity of the ammonium rhenate crude crystal) × 100%.

[0029] Calculation and characterization results show that the direct yield of the above process is 98.87% and the product purity is 99.993%, which meets the 4N standard.

[0030] In addition, the filtrate recovered after filtration was preheated to 60°C and crude ammonium rhenate was added to dissolve until the ammonium rhenate was saturated and then recycled as the base solution. Similarly, the direct yield and product purity were calculated for each preparation result. The results are shown in the following table. Number of cycles Direct yield Product purity 1 time 99.80 % 99.991 % 2 times 99.52 % 99.990 % 3 times 99.15 % 99.992 % 4 times 99.89 % 99.989 % 5 times 99.03 % 99.966 % 6 times 99.10 % 99.920 % 7 times 99.21 % 99.731 %

[0031] From the above characterization results, it can be clearly seen that in the first 7 cycles, a good direct yield of the product can be maintained, indicating that the technical solution of the present invention can at least ensure that the product has an extremely high yield, which can basically be maintained at a relatively stable level. As the number of cycles increases, the purity of the product will gradually show a downward trend, but the level of decline in the first three times is almost negligible, indicating that the effect of the solution is stable and a single prepared solution can be used multiple times. By the end of the sixth cycle, the extent of the decline is still within a controllable range, but at the beginning of the seventh cycle, the purity of the product begins to decline uncontrollably, which indicates that the impurities in the base solution gradually enrich to a threshold as the number of cycles increases, and obvious precipitation inclusions will occur, resulting in a significant decrease in the purity of the target product.

[0032] Therefore, it can be seen that the technical solution of the present invention can effectively achieve the efficient purification of crude products and crude crystals of ammonium rhenate, while having high material utilization, saving energy consumption, and not generating a large amount of environmental pollutants, and has the characteristics of high efficiency, greenness and safety.

[0033] Example 2 A method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification, The method comprises: 1) Prepare a 0.1 mol / L ammonia solution with electronic-grade ammonia and high-purity water and preheat to 60°C. Dissolve crude ammonium rhenate in the ammonia solution to prepare a saturated ammonium rhenate solution. This solution is used as the base solution. Add crude ammonium rhenate crystals at a rate of 0.10 g / g of crude ammonium rhenate to the base solution and perform a hydrothermal reaction at 180°C and 2 MPa for 6 h. 2) After the hydrothermal reaction is completed, the temperature is lowered to 25°C and filtered to recover ammonium rhenate single crystals.

[0034] The direct yield of the ammonium rhenate single crystal prepared above was calculated and its purity was characterized. The direct yield is: (actual yield / theoretical yield calculated based on the amount and purity of the ammonium rhenate crude crystal) × 100%.

[0035] Calculation and characterization results show that the direct yield of the above process is 99.12% and the product purity is 99.999%, which meets the 5N standard.

[0036] Example 3 A method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification, The method comprises: 1) Prepare a 1.0 mol / L ammonia solution with electronic-grade ammonia and high-purity water and preheat to 60°C. Dissolve crude ammonium rhenate in the ammonia solution to prepare a saturated ammonium rhenate solution. This solution is used as the base solution. Add crude ammonium rhenate crystals at a rate of 0.10 g / g of crude ammonium rhenate to the base solution and perform a hydrothermal reaction at 150°C and 2 MPa for 6 h. 2) After the hydrothermal reaction is completed, the temperature is lowered to 25°C and filtered to recover ammonium rhenate single crystals.

[0037] The direct yield of the ammonium rhenate single crystal prepared above was calculated and its purity was characterized. The direct yield is: (actual yield / theoretical yield calculated based on the amount and purity of the ammonium rhenate crude crystal) × 100%.

[0038] Calculation and characterization results show that the direct yield of the above process is 99.43% and the product purity is 99.994%, which meets the 4N standard.

[0039] Example 4 A method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification, The method comprises: 1) Prepare a 1.0 mol / L ammonia solution with electronic-grade ammonia and high-purity water and preheat to 60°C. Dissolve crude ammonium rhenate in the ammonia solution to prepare a saturated ammonium rhenate solution. This solution serves as the base solution. Add crude ammonium rhenate crystals at a rate of 0.10 g / g of crude ammonium rhenate to the base solution and perform a hydrothermal reaction at 150°C and 2.5 MPa for 6 h. 2) After the hydrothermal reaction is completed, the temperature is lowered to 25°C and filtered to recover ammonium rhenate single crystals.

[0040] The direct yield of the ammonium rhenate single crystal prepared above was calculated and its purity was characterized. The direct yield is: (actual yield / theoretical yield calculated based on the amount and purity of the ammonium rhenate crude crystal) × 100%.

[0041] Calculation and characterization results show that the direct yield of the above process is 99.39% and the product purity is 99.996%, which meets the 4N standard.

[0042] Example 5 A method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification, The method comprises: 1) Prepare a 1.0 mol / L ammonia solution with electronic-grade ammonia and high-purity water and preheat to 60°C. Dissolve crude ammonium rhenate in the ammonia solution to prepare a saturated ammonium rhenate solution. This solution is used as the base solution. Add crude ammonium rhenate crystals at a rate of 0.10 g / g of crude ammonium rhenate to the base solution and perform a hydrothermal reaction at 150°C and 2 MPa for 3 h. 2) After the hydrothermal reaction is completed, the temperature is lowered to 25°C and filtered to recover ammonium rhenate single crystals.

[0043] The direct yield of the ammonium rhenate single crystal prepared above was calculated and its purity was characterized. The direct yield is: (actual yield / theoretical yield calculated based on the amount and purity of the ammonium rhenate crude crystal) × 100%.

[0044] Calculation and characterization results show that the direct yield of the above process is 99.17% and the product purity is 99.980%, which meets the 3N5 standard.

[0045] Example 6 A method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification, The method comprises: 1) Prepare a 2.0 mol / L ammonia solution with electronic-grade ammonia and high-purity water and preheat to 60°C. Dissolve crude ammonium rhenate in the ammonia solution to prepare a saturated ammonium rhenate solution. This solution is used as the base solution. Add crude ammonium rhenate crystals at a rate of 0.10 g / g of crude ammonium rhenate to the base solution and perform a hydrothermal reaction at 150°C and 2 MPa for 3 h. 2) After the hydrothermal reaction is completed, the temperature is lowered to 25°C and filtered to recover ammonium rhenate single crystals.

[0046] The direct yield of the ammonium rhenate single crystal prepared above was calculated and its purity was characterized. The direct yield is: (actual yield / theoretical yield calculated based on the amount and purity of the ammonium rhenate crude crystal) × 100%.

[0047] Calculation and characterization results show that the direct yield of the above process is 99.46% and the product purity is 99.991%, which meets the 4N standard.

[0048] Example 7 A method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification, The method comprises: 1) Prepare a 0.1 mol / L ammonia solution with electronic-grade ammonia and high-purity water and preheat to 60°C. Dissolve crude ammonium rhenate in the ammonia solution to prepare a saturated ammonium rhenate solution. This solution is used as the base solution. Add crude ammonium rhenate crystals at a rate of 0.10 g / g of crude ammonium rhenate to the base solution and perform a hydrothermal reaction at 180°C and 2 MPa for 6 h. 2) After the hydrothermal reaction, the temperature was lowered to 30°C and filtered to recover ammonium rhenate single crystals.

[0049] The direct yield of the ammonium rhenate single crystal prepared above was calculated and its purity was characterized. The direct yield is: (actual yield / theoretical yield calculated based on the amount and purity of the ammonium rhenate crude crystal) × 100%.

[0050] Calculation and characterization results show that the direct yield of the above process is 96.23% and the product purity is 99.996%, which meets the 4N standard.

[0051] From the comparison of Examples 2 to 7 and Example 1 above, it is obvious that the recovery temperature significantly affects the recovery rate of the product. However, after testing, the recovery temperature was controlled within the range of 25 to 45 ° C, and a direct recovery rate of more than 90% was achieved, which can ensure production efficiency and cost-effectiveness. When the temperature was further increased to 50 ° C, the direct recovery rate dropped sharply to about 82.3%, thus significantly reducing the industrial effectiveness and being unsuitable. When the temperature reached 20 ° C, the purity of the product dropped significantly, reaching only about 99.810, even failing to meet the 3N standard, and the purification effectiveness decreased.

[0052] On the other hand, the hydrothermal temperature also has a certain influence on the purity of the product. For example, the initial preparation of Example 1 and Example 2 and Example 7 are compared horizontally. It can be clearly seen that the hydrothermal temperature increases with the temperature in the range of 150-200 ° C. For example, based on Example 7, the hydrothermal temperature is changed to 200 ° C. The product purity can reach 99.999%, that is, it reaches the 5N level standard. However, as the temperature further rises to 220 ° C, it will cause the direct yield of the product to drop significantly, plummeting to 90.22%, indicating that too high a temperature may increase the difficulty of recrystallization, reduce the product recovery effect, and also increase energy consumption, thus having a poor cost performance. At 130 ° C, the purity of the product drops significantly, and can only reach a purity of 2N level and below. This is mainly due to insufficient energy provided by the crystal transformation and poor actual purification effect.

Claims

1. A method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification, characterized in that: The method comprises: 1) preparing an ammonia solution, dissolving crude ammonium rhenate in the ammonia solution to prepare a saturated ammonium rhenate solution, and using the saturated ammonium rhenate solution as a base solution. Adding crude ammonium rhenate crystals to the base solution and performing a hydrothermal reaction; 2) After the hydrothermal reaction is completed, the temperature is lowered to the recovery temperature, and the ammonium rhenate single crystal is recovered by filtration.

2. The method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification according to claim 1, characterized in that: Step 1) The ammonia solution is prepared from ammonia gas and / or ammonia water and / or water; In step 1), the ammonia concentration of the ammonia solution is 0.1 to 3.0 mol / L.

3. The method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification according to claim 1 or 2, characterized in that: Step 1) preheating the ammonia solution before dissolving the crude ammonium rhenate in the ammonia solution; The preheating temperature is controlled to be 45-85°C.

4. The method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification according to claim 1, characterized in that: In step 1), the amount of crude ammonium rhenate crystals used is 0.01 to 0.20 g / g of crude ammonium rhenate.

5. The method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification according to claim 1, characterized in that: In step 1), the hydrothermal reaction process is controlled at a reaction temperature of 150-200°C, a reaction time of 1-6 h, and a reaction pressure of 1.5-3.0 MPa.

6. The method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification according to claim 1, characterized in that: The recovery temperature in step 2) is 25-45°C.

7. The method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification according to claim 1, characterized in that: Step 3) After the ammonium rhenate single crystal is obtained by filtration and recovery, the filtrate can be recovered and recycled as a base solution for at least three times.

8. The method for preparing high-purity ammonium rhenate by hydrothermal single crystal purification according to claim 7, characterized in that: The filtrate is tested for ammonia concentration before use to ensure that the ammonia concentration meets the ammonia concentration range required by the substrate solution before it can be recycled.

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