A method for preparing 4n ammonium rhenate from low concentration rhenium-containing spent acid

Abstract

This invention discloses a method for preparing 4N ammonium permanganate from low-concentration rhenium-containing waste acid, which is divided into a crude refining stage and a refining stage. The crude refining stage includes a rhenium precipitation process, a leaching process, a hydrolysis process, an acidification process, an extraction process, a back-extraction process, and a crystallization process. The refining stage includes a crude ammonium permanganate dissolution process, an ion exchange process, an extraction process, a back-extraction process, a crystallization process, and a nitration-recrystallization process, ultimately obtaining ammonium permanganate with a purity of 99.99%. In the crude refining stage, this invention first prepares 4N ammonium permanganate from low-concentration rhenium-containing waste acid. Rhenium is efficiently and selectively enriched in concentrated waste acid to obtain a 1% grade rhenium precipitate. Then, a weak oxidation leaching process is used to remove impurities from the precipitate, followed by calcium hydroxide hydrolysis, acidification, high-efficiency extraction, back-extraction, and crystallization to obtain a crude ammonium perrhenate product with a grade of ≥99%. In the refining stage, the crude ammonium perrhenate is dissolved a second time, and a resin ion exchange, extraction, back-extraction, and crystallization process is used to obtain a refined ammonium perrhenate with a grade of ≥99.9%. Finally, a nitration-recrystallization process is used to remove impurities from the refined ammonium perrhenate to achieve a 4N grade quality.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically a method for preparing 4N ammonium perrhenate from low-concentration rhenium-containing waste acid. Background Technology

[0002] Rhenium and its compounds have numerous applications, spanning industries such as petrochemicals, defense, aerospace, electrical engineering, and electronics. The development of these industries directly determines the demand for rhenium, especially the increasing demand for high-purity rhenium. Currently, rhenium enrichment raw materials mainly come from two sources. Firstly, in the acidic scrubbing wastewater from copper smelters, rhenium extraction primarily employs a chemical precipitation process using a sulfide precipitation system. The precipitate is then leached, and the leachate is extracted and back-extracted for crystallization, yielding 99% ammonium perrhenate. However, direct sulfide precipitation in a highly acidic environment leads to the precipitation of large amounts of arsenic and lead, resulting in a low rhenium precipitation rate in the sulfide slag and making subsequent processing difficult. Secondly, in the leaching liquid from molybdenum concentrate roasting flue gas, rhenium extraction mainly utilizes a direct extraction process.

[0003] Our company's process for extracting rhenium from waste acid in copper smelters is a direct extraction process. The extractant is an N235 + 2-octanol + sulfonated kerosene system. The ammonia back-extraction-freeze crystallization method yields ammonium perrhenate. However, this method has significant limitations, mainly in the following aspects: (1) The direct extraction process is poorly adaptable to low-concentration rhenium-containing waste acid; (2) The selectivity is poor, and many impurities are extracted, resulting in a high impurity content in the extractant, which continuously reduces the ability to extract rhenium; (3) The impurity content in the waste acid fluctuates greatly, causing the system to be unstable and affecting the service life of the extractant; (4) During the back-extraction process, a large amount of impurity hydrolyzes out, forming a third phase, making back-extraction difficult; (5) The grade of the product ammonium perrhenate cannot meet the requirements of the superior grade 4N ammonium perrhenate specified in YS / T894-2018 "Ammonium Perrhenate". Therefore, it is urgent to develop a new and efficient selective precipitation method to prepare 4N ammonium perrhenate from low-concentration rhenium-containing waste acid. Summary of the Invention

[0004] The purpose of this invention is to address the problems of poor process adaptability and low grade of ammonium perrhenate in traditional direct extraction processes for extracting rhenium from waste acid. This invention provides a method for preparing 4N ammonium perrhenate from low-concentration rhenium-containing waste acid. The method of this invention has strong process adaptability, is simple to operate, has low cost, and produces ammonium perrhenate with a grade that meets the superior grade standard of 4N ammonium perrhenate specified in YS / T894-2018 "Ammonium Perrhenate".

[0005] The present invention provides a method for preparing 4N ammonium rheniumate from low-concentration rhenium-containing waste acid, comprising the following steps:

[0006] (1) Rhenium precipitation process: Rhenium-containing waste acid with a concentration of 5-15 mg / L is pumped into the reactor, heated to 60-65℃, and 2.5-2.8 kg / m³ of sodium thiosulfate is added for efficient and selective rhenium precipitation. The reaction is stirred for 1.5-2.5 h, and the filter residue obtained by pressure filtration is the rhenium precipitate residue. The filtrate is the rhenium precipitate post-precipitation liquid and is sent to the sewage system for treatment.

[0007] (2) Leaching process: Add industrial-grade hydrogen peroxide to the rhenium precipitate at a ratio of 2.8-3.0 L / kg, heat to 60-80℃, stir and react for 3-4 hours, and filter the filter residue obtained by pressure filtration as leaching residue and filtrate as leaching liquid;

[0008] (3) Hydrolysis process: The leaching liquid is pumped into the reactor, industrial grade calcium hydroxide is added to adjust the pH value to ≥8.5, the reaction is stirred for 1.5-2.5h, the filter residue obtained by pressure filtration is calcium residue, and the filtrate is hydrolyzed liquid;

[0009] (4) Acidification process: Pump the hydrolyzed liquid into the reactor, add industrial grade sulfuric acid to adjust the pH value to <1, stir the reaction for 6-8 hours, and filter the filtrate to obtain the acidified liquid;

[0010] (5) Extraction process: The extractant is a mixed organic phase of N235: 2-octanol: sulfonated kerosene = 20: 20: 60. The acidified liquid is subjected to cross-flow extraction with the freshly prepared mixed organic phase. The extraction phase ratio O / A = 1 / 5, the number of extraction stages is 2, the extraction time of each stage is 0.5h, and then it is allowed to stand for 10min. After the phase separation is clear, the next stage of extraction is carried out. After the 2 stages of extraction are completed, the loaded organic phase and the raffinate are obtained. The raffinate is returned to step (1) as rhenium-containing waste acid.

[0011] (6) Back-extraction process: Select industrial grade ammonia water with a mass fraction of 10-12% to back-extract the loaded organic phase. Compared with O / A=5 / 2, the back-extraction time is 0.5h, and it is left to stand for 1-4h to obtain the back-extraction liquid and the lean organic phase. Add industrial grade sulfuric acid to the lean organic phase to adjust the pH value to <1 to obtain a reusable organic phase extractant, which is returned to step (5) for use.

[0012] (7) Crystallization process: The back-extraction liquid is heated to 85-90℃ and concentrated and then filtered. The crystallization temperature of the filtrate is controlled at -4℃ and the crystallization time is 24h. Then, after redissolution and freeze crystallization, it is repeated 2-3 times to obtain crude ammonium permanganate with a mass fraction ≥99%. The crystallized liquid is returned to step (5) and extracted together with the acidified liquid.

[0013] (8) Dissolution process: Add 10 times the mass of pure water to the crude ammonium rhenium and heat to 50-60℃ and stir to dissolve. After complete dissolution, add 0.5 L / kg of analytical grade hydrogen peroxide to the crude ammonium rhenium at constant temperature for oxidation. Stir and react for 1.5-4 h, continue to heat to 85-90℃ to remove ammonia, keep the temperature constant for 10 min and then cool to room temperature. Filter to obtain rhenium-containing solution.

[0014] (9) Ion exchange process: The rhenium-containing solution is prepared into a pre-ion exchange solution with a rhenium concentration of 4-8 g / L, and the flow rate is controlled at 60-72 L / h to pass through a 732 cation exchange column to obtain a post-ion exchange solution containing rhenium.

[0015] (10) Extraction process: The extractant is a mixed organic phase of N235: 2-octanol: sulfonated kerosene = 20: 20: 60. The freshly prepared mixed organic phase is used to perform cross-flow extraction on the rhenium-containing exchange liquid. The extraction phase ratio O / A = 1 / 5, the number of extraction stages is 2, the extraction time of each stage is 0.5h, and then it is allowed to stand for 10min. After the phase separation is clear, the next stage of extraction is carried out. After the 2 stages of extraction are completed, the loaded organic phase and the raffinate are obtained. The raffinate is returned to step (1) as rhenium-containing waste acid.

[0016] (11) Back-extraction process: Select analytical grade ammonia water with a mass fraction of 10-12% to back-extract the loaded organic phase. Compared with O / A=5 / 2, the back-extraction time is 0.5h, and it is allowed to stand for 1-4h to obtain the back-extraction liquid and the lean organic phase. Add analytical grade sulfuric acid to the lean organic phase to adjust the pH value to <1, and obtain a reusable organic phase extractant to return to step (5) or step (10).

[0017] (12) Crystallization process: After the back-extraction liquid is concentrated at 85-90℃, it is filtered and then the freezing crystallization temperature of the filtrate is controlled at -4℃ and the crystallization time is 24h. Then, after redissolution and freezing crystallization, it is repeated 2-3 times to obtain refined ammonium rhenium with a mass fraction ≥99.9%. The crystallized liquid is returned to step (10) and mixed with the rhenium-containing exchange liquid for extraction.

[0018] (13) Nitration and recrystallization process: Refined ammonium perrylate and pure water are mixed at a solid-liquid ratio of 3:25 (kg:L), heated to 85-90℃, and stirred for 0.5h. After complete dissolution, the mixture is filtered, and the temperature of the filtrate is controlled at 60-65℃. An appropriate amount of analytical grade nitric acid is added, and the mixture is stirred for 2h. After filtration, the filtrate is heated to 85-90℃, and analytical grade ammonia is slowly added to adjust the pH to 5.5-6.5. Then, an appropriate amount of analytical grade hydrogen peroxide is slowly added to adjust the pH. After stirring at a constant temperature for 1 hour, add analytical grade ammonia water slowly to adjust the pH to 9.5-10.5. Stir for another hour, filter, and then control the filtrate to freeze and crystallize at -4℃ for 24 hours. Then, after the first crystallization of ammonium permanganate, redissolve, nitrate and freeze crystallize to obtain the superior grade 4N ammonium permanganate that meets the requirements of YS / T894-2018 "Ammonium Permanganate". The crystallized liquid is returned to step (10) to prepare the pre-ion exchange solution.

[0019] The main chemical reactions involved in this invention are as follows:

[0020] In step (1) of this invention, sodium thiosulfate is used as a rhenium precipitant, and the rhenium precipitation reaction principle is as follows:

[0021] Re₂O₇ + H₂O = 2HReO₄

[0022] HReO4 + Na2S2O3→ NaReO4↓+ Re2S7↓,

[0023] The main reaction principles in steps (2) to (13) of this invention are as follows:

[0024] 2Re2S7 + 20H2O2 = 4HReO4 + 14S↓+ 3O2↑+ 18H2O,

[0025] Cu 2+ + 2OH - = Cu(OH)2↓,

[0026] Tl 3+ + 3OH - = Tl (OH)3↓,

[0027] 2AsO3 3- +3 Ca 2+ = Ca3(AsO3)2↓,

[0028] SO4 2- + Ca 2+ =CaSO4↓,

[0029] R3N (o) + H + (a)+ ReO4 - (a) = [R3N·HReO4](o),

[0030] 2R3N (o) + H + (a)+ ReO4 - (a) = [(R3N)2·HReO4](o),

[0031] [(R3N)2·HReO4](o) + NH4OH (a) = NH4ReO4 (a) + H2O (o) + 2R3N (o).

[0032] This invention uses low-concentration rhenium-containing waste acid as raw material and employs the following steps to prepare 4N ammonium rhenium: rhenium precipitation → leaching → hydrolysis → acidification → extraction → back-extraction → crystallization → crude ammonium rhenium dissolution → ion exchange → extraction → back-extraction → crystallization → nitration recrystallization. This method has the following advantages:

[0033] (1) In the rhenium precipitation process, sodium thiosulfate is added as a new rhenium precipitation agent, which can achieve the complete separation of most impurities from rhenium in one step, reduce the loss of rhenium, and obtain a rhenium slag grade that is much higher than that of traditional processes, which is beneficial to the subsequent refining of rhenium. This method is highly practical and improves the direct recovery rate of rhenium.

[0034] (2) The present invention adopts a weak oxidation leaching-hydration to remove impurities-acidification to remove impurities-extraction back-extraction-crystallization process, which can efficiently obtain crude ammonium rhenium with a purity of ≥99%, thus avoiding the risks of large rhenium consumption, high recycling rate, high consumption cost, and rhenium metal loss in the production system.

[0035] (3) The present invention adopts a crude ammonium peroxide dissolution-732 cation ion exchange impurity removal-extraction back-crystallization process, which can efficiently obtain ≥99.9% refined ammonium peroxide. Compared with 4N ammonium peroxide, it avoids the problem of excessive impurities such as thallium, potassium and calcium in refined ammonium peroxide.

[0036] (4) The ion exchange resin selected in this invention can be recycled under certain conditions, which effectively reduces production costs.

[0037] (5) The present invention adds a nitration-recrystallization process to remove impurities from refined ammonium permanganate, which can efficiently obtain the superior grade 4N ammonium permanganate as specified in YS / T894-2018 "Ammonium Permanganate". This avoids the problem that the total impurity content of 4N ammonium permanganate is >0.01%.

[0038] (6) The whole process of the present invention is highly adaptable to low-concentration rhenium-containing waste acid raw materials, and completely solves the problem of unstable continuous production caused by large fluctuations in the composition of waste acid. Attached Figure Description

[0039] Figure 1 This is a process flow diagram of the present invention. Implementation Example 1

[0040] See Figure 1 This embodiment describes a method for preparing 4N ammonium perrylate from low-concentration rhenium-containing waste acid, comprising the following steps:

[0041] (1) Rhenium precipitation process: 35 m³ of waste acid was pumped into the reactor. The waste acid was tested and found to contain 5 mg / L of rhenium. The temperature was raised to 60°C, and sodium thiosulfate was added at a rate of 2.5 kg / m³ (sodium thiosulfate / waste acid) to precipitate rhenium. The reaction was carried out for 1.5 h. The filter residue obtained by pressure filtration contained 1.15% rhenium and the filtrate contained 0.4 mg / L of rhenium after precipitation.

[0042] (2) Leaching process: Add hydrogen peroxide to 500 kg of rhenium precipitate (containing 1.15% rhenium) at a rate of 2.8 L / kg (hydrogen peroxide / rhenium precipitate), heat to 60℃, react for 3 h, and filter the filter residue obtained by pressure filtration as leaching residue, and the filtrate as leaching liquid containing 3.82 g / L of rhenium;

[0043] (3) Hydrolysis process: The above leaching liquid is pumped into the reactor, and the pH value is adjusted to 8.5 by adding industrial grade calcium hydroxide. The reaction is carried out for 1.5 hours. The filter residue obtained by pressure filtration is calcium residue, and the filtrate is hydrolyzed liquid containing rhenium 3.65 g / L.

[0044] (4) Acidification process: The above hydrolyzed liquid is pumped into the reactor, and the pH value is adjusted to <1 by adding industrial grade sulfuric acid. The reaction is carried out for 6 hours, and the filtrate obtained by pressure filtration contains 3.35 g / L of rhenium.

[0045] (5) Extraction process: The extractant is a mixed organic phase of N235: 2-octanol: sulfonated kerosene = 20: 20: 60. The above acidified liquid is extracted by cross-flow extraction. The extraction phase ratio O / A = 1 / 5. The number of extraction stages is 2. The extraction time for each stage is 0.5h. After standing for 10min, the next stage of extraction is carried out after the phase separation is clear. After the 2 stages of extraction, the loaded organic phase contains rhenium 16.1g / L. The raffinate is returned to step (1).

[0046] (6) Back-extraction process: Select industrial grade 10% ammonia water to back-extract the above loaded organic phase. Compared with O / A=5 / 2, the back-extraction time is 0.5h, and it is left to stand for 1h to obtain a back-extraction solution containing rhenium 38.84g / L. Add industrial grade sulfuric acid to the lean organic phase to adjust the pH value to <1 to obtain a reusable organic phase, and return to step (5).

[0047] (7) Crystallization process: The above back-extraction liquid is concentrated by heating to 85°C and then filtered. The crystallization temperature of the filtrate is controlled at -4°C and the crystallization time is 24h. Then, after redissolution and freeze crystallization, it is repeated 3 times to obtain 99% crude ammonium perrhenate. The crystallized liquid is returned to step (5).

[0048] (8) Dissolution process: Take 100 kg of 99% crude ammonium peroxide, add 1 m³ of pure water and heat to 50°C to dissolve. At constant temperature, add analytical grade hydrogen peroxide at a rate of 0.5 L / kg (analytical grade hydrogen peroxide / crude ammonium peroxide) for oxidation. React for 1.5 h, continue to heat to 85°C to remove ammonia, maintain constant temperature for 10 min and then cool to room temperature. Filter to obtain filtrate containing 65.43 g / L of rhenium.

[0049] (9) Ion exchange process: The above rhenium-containing solution is prepared into an ion exchange pre-solution with a rhenium concentration of 4 g / L, and the flow rate is controlled at 60 L / h to pass through a 732 cation exchange column. The resulting exchange post-solution contains 3.8 g / L of rhenium.

[0050] (10) Extraction process: The extractant is a mixed organic phase of N235: 2-octanol: sulfonated kerosene = 20: 20: 60. The above rhenium-containing exchange liquid is extracted by cross-flow extraction. The extraction phase O / A = 1 / 5, the number of extraction stages is 2, the extraction time of each stage is 0.5h, and then it is allowed to stand for 10min. After the phase separation is clear, the next stage of extraction is carried out. After the 2 stages of extraction, the loaded organic phase containing rhenium is obtained. The raffinate is returned to step (1).

[0051] (11) Back-extraction process: Select analytical grade 10% ammonia water to back-extract the loaded organic phase. Compared with O / A=5 / 2, the back-extraction time is 0.5h, and it is allowed to stand for 4h. The back-extraction solution contains rhenium 45.62g / L. Add analytical grade sulfuric acid to the lean organic phase to adjust the pH value to <1 to obtain a reusable organic phase, and return to step (10).

[0052] (12) Crystallization process: After the back-extraction liquid is concentrated by heating to 90℃, the freezing crystallization temperature is controlled at -4℃ and the crystallization time is 24h. Then, after redissolution and freezing crystallization, it is repeated twice to obtain 77.12kg of 99.9% refined ammonium perrylate. The crystallized liquid is returned to step (10).

[0053] (13) Nitration and recrystallization process: The above-mentioned refined ammonium permanganate and pure water are mixed in a solid-liquid ratio of 3:25 (kg:L), heated to 85°C, reacted for 0.5h, and after complete dissolution, filtered. The temperature of the filtrate is controlled at 60°C, and 77L of analytical grade nitric acid is added. After reacting for 2h, filtered, the filtrate is heated to 85°C, and analytical grade ammonia is slowly added to adjust the pH value to 5.5. Then, 38L of analytical grade hydrogen peroxide is slowly added. After reacting at a constant temperature for 1h, analytical grade ammonia is slowly added to adjust the pH value to 9.5. After stirring and reacting for 1h, filtered, and the temperature of the filtrate is controlled at -4°C. The crystallization time is 24h. Then, the first crystallized ammonium permanganate is redissolved, nitrated, and frozen to obtain the superior grade 4N ammonium permanganate that meets the requirements of YS / T894-2018 "Ammonium Permanganate". The crystallized liquid is returned to step (10). Example 2

[0054] This embodiment provides a method for preparing 4N ammonium rhenium from low-concentration rhenium-containing waste acid, comprising the following steps:

[0055] (1) Rhenium precipitation process: 35 m³ of waste acid was pumped into the reactor. The waste acid was tested and found to contain 10 mg / L of rhenium. The temperature was raised to 65°C, and sodium thiosulfate was added at a rate of 2.7 kg / m³ (sodium thiosulfate / waste acid) to precipitate rhenium. The reaction was carried out for 2 hours. The filter residue obtained by pressure filtration contained 1.65% rhenium and the filtrate contained 0.6 mg / L of rhenium after precipitation.

[0056] (2) Leaching process: Add hydrogen peroxide to 500 kg of rhenium precipitate (containing 1.65% rhenium) at a rate of 2.9 L / kg (hydrogen peroxide / rhenium precipitate), heat to 70℃, react for 3.5 h, filter the filter residue obtained by pressure filtration as leaching residue, and the filtrate as leaching liquid containing 5.35 g / L of rhenium;

[0057] (3) Hydrolysis process: The above leaching liquid is pumped into the reactor, and the pH value is adjusted to 9 by adding industrial grade calcium hydroxide. The reaction is carried out for 2 hours, and the filter residue obtained by pressure filtration is calcium residue. The filtrate is hydrolyzed liquid containing rhenium 5.11 g / L.

[0058] (4) Acidification process: The above hydrolyzed liquid is pumped into the reactor, and the pH value is adjusted to <1 by adding industrial grade sulfuric acid. The reaction is carried out for 7 hours, and the filtrate obtained by pressure filtration contains rhenium 5.03 g / L.

[0059] (5) Extraction process: The extractant is a mixed organic phase of N235: 2-octanol: sulfonated kerosene = 20: 20: 60. The above acidified liquid is extracted by cross-flow extraction. The extraction phase ratio O / A = 1 / 5. The number of extraction stages is 2, and the extraction time for each stage is 0.5h. After standing for 10min, the next stage of extraction is carried out after the phase separation is clear. After the 2 stages of extraction, the loaded organic phase contains rhenium 24.40g / L. The raffinate is returned to step (1).

[0060] (6) Back-extraction process: Select industrial grade 11% ammonia water to back-extract the above loaded organic phase. Compared with O / A=5 / 2, the back-extraction time is 0.5h, and it is left to stand for 2h to obtain a back-extraction solution containing rhenium 59.17g / L. Add industrial grade sulfuric acid to the lean organic phase to adjust the pH value to <1 to obtain a reusable organic phase, and return to step (5).

[0061] (7) Crystallization process: The above back-extraction liquid is concentrated by heating to 90°C and then filtered. The crystallization temperature of the filtrate is controlled at -4°C and the crystallization time is 24h. Then, after redissolution and freeze crystallization, it is repeated twice to obtain 99.5% crude ammonium perrhenate. The crystallized liquid is returned to step (5).

[0062] (8) Dissolution process: Take 100 kg of 99.5% crude ammonium perlite, add 1 m³ of pure water and heat to 55°C to dissolve. At constant temperature, add analytical grade hydrogen peroxide at a rate of 0.5 L / kg (analytical grade hydrogen peroxide / crude ammonium perlite) for oxidation. React for 2 hours, continue to heat to 90°C to remove ammonia, maintain constant temperature for 10 minutes and then cool to room temperature. Filter to obtain filtrate containing 65.76 g / L of rhenium.

[0063] (9) Ion exchange process: The above rhenium-containing solution is prepared into an ion exchange pre-solution with a rhenium concentration of 6 g / L, and the flow rate is controlled at 66 L / h to pass through a 732 cation exchange column. The resulting exchange post-solution contains 5.46 g / L of rhenium.

[0064] (10) Extraction process: The extractant is a mixed organic phase of N235: 2-octanol: sulfonated kerosene = 20: 20: 60. The above rhenium-containing exchange liquid is extracted by cross-flow extraction. The extraction phase O / A = 1 / 5, the number of extraction stages is 2, the extraction time of each stage is 0.5h, and then it is allowed to stand for 10min. After the phase separation is clear, the next stage of extraction is carried out. After the 2 stages of extraction, the loaded organic phase containing rhenium is obtained. The raffinate is returned to step (1).

[0065] (11) Back-extraction process: Select analytical grade 11% ammonia water to back-extract the loaded organic phase. Compared with O / A=5 / 2, the back-extraction time is 0.5h, and it is allowed to stand for 3h. The back-extraction solution contains rhenium 65.54g / L. Add analytical grade sulfuric acid to the lean organic phase to adjust the pH value to <1 to obtain a reusable organic phase, and return to step (10).

[0066] (12) Crystallization process: After the back-extraction liquid is concentrated at 85°C, the freezing crystallization temperature is controlled at -4°C and the crystallization time is 24h. Then, after redissolution and freezing crystallization, it is repeated twice to obtain 76.03kg of 99.95% refined ammonium perrylate. The crystallized liquid is returned to step (10).

[0067] (13) Nitration and recrystallization process: The above-mentioned refined ammonium permanganate and pure water are mixed in a solid-liquid ratio of 3:25 (kg:L), heated to 90°C, reacted for 0.5h, and after complete dissolution, filtered. The temperature of the filtrate is controlled at 65°C, and 76L of analytical grade nitric acid is added. After reacting for 2h, filtered, the filtrate is heated to 90°C, and analytical grade ammonia is slowly added to adjust the pH value to 6. Then, 38L of analytical grade hydrogen peroxide is slowly added. After reacting at a constant temperature for 1h, analytical grade ammonia is slowly added to adjust the pH value to 10. After stirring and reacting for 1h, filtered, and the temperature of the filtrate is controlled at -4°C. The crystallization time is 24h. Then, the first crystallized ammonium permanganate is redissolved, nitrated, and frozen to obtain the superior grade 4N ammonium permanganate that meets the requirements of YS / T894-2018 "Ammonium Permanganate". The crystallized liquid is returned to step (10). Example 3

[0068] This embodiment provides a method for preparing 4N ammonium rhenium from low-concentration rhenium-containing waste acid, comprising the following steps:

[0069] (1) Rhenium precipitation process: 35 m³ of waste acid was pumped into the reactor. The waste acid was tested and found to contain 15 mg / L of rhenium. The temperature was raised to 60°C, and sodium thiosulfate was added at a rate of 2.8 kg / m³ (sodium thiosulfate / waste acid) to precipitate rhenium. The reaction was carried out for 2.5 h. The filter residue obtained by pressure filtration was the rhenium precipitate residue containing 1.75% rhenium, and the filtrate was the rhenium precipitate liquid containing 0.6 mg / L of rhenium.

[0070] (2) Leaching process: Add hydrogen peroxide to 500 kg of rhenium precipitate (containing 1.75% rhenium) at a rate of 3.0 L / kg (hydrogen peroxide / rhenium precipitate), heat to 80℃, react for 4 h, and filter the filter residue obtained by pressure filtration as leaching residue, and the filtrate as leaching liquid containing 5.42 g / L of rhenium;

[0071] (3) Hydrolysis process: The above leaching liquid is pumped into the reactor, and the pH value is adjusted to 9.5 by adding industrial grade calcium hydroxide. The reaction is carried out for 2.5 hours. The filter residue obtained by pressure filtration is calcium residue, and the filtrate is hydrolyzed liquid containing rhenium 5.17 g / L.

[0072] (4) Acidification process: The above hydrolyzed liquid is pumped into the reactor, and the pH value is adjusted to <1 by adding industrial grade sulfuric acid. The reaction is carried out for 8 hours, and the filtrate obtained by pressure filtration contains rhenium 5.09 g / L.

[0073] (5) Extraction process: The extractant is a mixed organic phase of N235: 2-octanol: sulfonated kerosene = 20: 20: 60. The above acidified liquid is extracted by cross-flow extraction. The extraction phase ratio O / A = 1 / 5. The number of extraction stages is 2. The extraction time for each stage is 0.5h. After standing for 10min, the next stage of extraction is carried out after the phase separation is clear. After the 2 stages of extraction, the loaded organic phase contains rhenium 24.81g / L. The raffinate is returned to step (1).

[0074] (6) Back-extraction process: Select industrial grade 12% ammonia water to back-extract the above loaded organic phase. Compared with O / A=5 / 2, the back-extraction time is 0.5h, and it is left to stand for 1h to obtain a back-extraction solution containing rhenium 60.47g / L. Add industrial grade sulfuric acid to the lean organic phase to adjust the pH value to <1 to obtain a reusable organic phase, and return to step (5).

[0075] (7) Crystallization process: The above back-extraction liquid is concentrated at 85°C and then filtered. The crystallization temperature of the filtrate is controlled at -4°C and the crystallization time is 24 hours. Then, after redissolution and freeze crystallization, it is repeated 3 times to obtain 99.8% crude ammonium perrhenate. The crystallized liquid is returned to step (5).

[0076] (8) Dissolution process: Take 100 kg of crude ammonium permanganate with 99.8% purity, add 1 m³ of pure water and heat to 60 °C to dissolve. Under constant temperature, add analytical grade hydrogen peroxide at a rate of 0.5 L / kg (analytical grade hydrogen peroxide / crude ammonium permanganate) for oxidation. React for 4 h, continue to heat to 85 °C to remove ammonia, maintain constant temperature for 10 min and then cool to room temperature. Filter to obtain filtrate containing 65.96 g / L of rhenium.

[0077] (9) Ion exchange process: The above rhenium-containing solution is prepared into an ion exchange pre-solution with a rhenium concentration of 8 g / L, and the flow rate is controlled at 72 L / h to pass through a 732 cation exchange column. The resulting exchange post-solution contains 7.60 g / L of rhenium.

[0078] (10) Extraction process: The extractant is a mixed organic phase of N235: 2-octanol: sulfonated kerosene = 20: 20: 60. The above rhenium-containing exchange liquid is extracted by cross-flow extraction. The extraction phase O / A = 1 / 5, the number of extraction stages is 2, the extraction time of each stage is 0.5h, and then it is allowed to stand for 10min. After the phase separation is clear, the next stage of extraction is carried out. After the 2 stages of extraction, the loaded organic phase containing rhenium is obtained. The raffinate is returned to step (1).

[0079] (11) Back-extraction process: Select analytical grade 12% ammonia water to back-extract the loaded organic phase. Compared with O / A=5 / 2, the back-extraction time is 0.5h, and it is allowed to stand for 4h to obtain a back-extraction solution containing rhenium 87.55g / L. Add analytical grade sulfuric acid to the lean organic phase to adjust the pH value to <1 to obtain a reusable organic phase, and return to step (10);

[0080] (12) Crystallization process: After the back-extraction liquid is concentrated at 85°C, the freezing crystallization temperature is controlled at -4°C and the crystallization time is 24h. Then, after redissolution and freezing crystallization, it is repeated 3 times to obtain 74.28kg of refined ammonium perrhenate with 99.98% purity. The crystallized liquid is returned to step (10).

[0081] (13) Nitration and recrystallization process: The above-mentioned refined ammonium permanganate and pure water are mixed in a solid-liquid ratio of 3:25 (kg:L), heated to 85°C, reacted for 0.5h, and after complete dissolution, filtered. The temperature of the filtrate is controlled at 65°C, and 74L of analytical grade nitric acid is added. After reacting for 2h, filtered, the filtrate is heated to 90°C, and analytical grade ammonia is slowly added to adjust the pH value to 6.5. Then, 37L of analytical grade hydrogen peroxide is slowly added. After reacting at a constant temperature for 1h, analytical grade ammonia is slowly added to adjust the pH value to 10.5. After stirring and reacting for 1h, filtered, and the temperature of the filtrate is controlled at -4°C. The crystallization time is 24h. Then, the first crystallized ammonium permanganate is redissolved, nitrated, and frozen to obtain the superior grade 4N ammonium permanganate that meets the requirements of YS / T894-2018 "Ammonium Permanganate". The crystallized liquid is returned to step (10).

[0082] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for preparing 4N ammonium perrylate from low-concentration rhenium-containing waste acid, characterized in that... Includes the following steps: (1) Rhenium precipitation process: Rhenium-containing waste acid with a concentration of 5-15 mg / L is pumped into the reactor, heated to 60-65℃, and 2.5-2.8 kg / m³ of sodium thiosulfate is added for efficient and selective rhenium precipitation. The reaction is stirred for 1.5-2.5 h, and the filter residue obtained by pressure filtration is the rhenium precipitate residue. The filtrate is the rhenium precipitate post-precipitation liquid and is sent to the sewage system for treatment. (2) Leaching process: Add industrial-grade hydrogen peroxide to the rhenium precipitate at a ratio of 2.8-3.0 L / kg, heat to 60-80℃, stir and react for 3-4 hours, and filter the filter residue obtained by pressure filtration as leaching residue and filtrate as leaching liquid; (3) Hydrolysis process: The leachate is pumped into the reactor, and industrial-grade calcium hydroxide is added to adjust the pH value to ≥ 8.5, stir and react for 1.5-2.5 hours, filter the residue obtained by pressure filtration as calcium residue, and the filtrate as hydrolyzed liquid; (4) Acidification process: Pump the hydrolyzed liquid into the reactor, add industrial grade sulfuric acid to adjust the pH value to <1, stir the reaction for 6-8 hours, and filter the filtrate to obtain the acidified liquid; (5) Extraction process: The extractant is a mixed organic phase of N235: 2-octanol: sulfonated kerosene = 20: 20:

60. The acidified liquid is subjected to cross-flow extraction with the freshly prepared mixed organic phase. The extraction phase ratio O / A = 1 / 5, the number of extraction stages is 2, the extraction time of each stage is 0.5h, and then it is allowed to stand for 10min. After the phase separation is clear, the next stage of extraction is carried out. After the 2 stages of extraction are completed, the loaded organic phase and the raffinate are obtained. The raffinate is returned to step (1) as rhenium-containing waste acid. (6) Back-extraction process: Select industrial grade ammonia water with a mass fraction of 10-12% to back-extract the loaded organic phase. Compared with O / A=5 / 2, the back-extraction time is 0.5h, and it is left to stand for 1-4h to obtain the back-extraction liquid and the lean organic phase. Add industrial grade sulfuric acid to the lean organic phase to adjust the pH value to <1 to obtain a reusable organic phase extractant, which is returned to step (5) for use. (7) Crystallization process: The back-extraction liquid is heated to 85-90℃ and concentrated and then filtered. The crystallization temperature of the filtrate is controlled at -4℃ and the crystallization time is 24h. Then, after redissolution and freeze crystallization, it is repeated 2-3 times to obtain crude ammonium permanganate with a mass fraction ≥99%. The crystallized liquid is returned to step (5) and extracted together with the acidified liquid. (8) Dissolution process: Add 10 times the mass of pure water to the crude ammonium rhenium and heat to 50-60℃ and stir to dissolve. After complete dissolution, add 0.5 L / kg of analytical grade hydrogen peroxide to the crude ammonium rhenium at constant temperature for oxidation. Stir and react for 1.5-4 h, continue to heat to 85-90℃ to remove ammonia, keep the temperature constant for 10 min and then cool to room temperature. Filter to obtain rhenium-containing solution. (9) Ion exchange process: The rhenium-containing solution is prepared into a pre-ion exchange solution with a rhenium concentration of 4-8 g / L, and the flow rate is controlled at 60-72 L / h to pass through a 732 cation exchange column to obtain a post-ion exchange solution containing rhenium. (10) Extraction process: The extractant is a mixed organic phase of N235: 2-octanol: sulfonated kerosene = 20: 20:

60. The freshly prepared mixed organic phase is used to perform cross-flow extraction on the rhenium-containing exchange liquid. The extraction phase ratio O / A = 1 / 5, the number of extraction stages is 2, the extraction time of each stage is 0.5h, and then it is allowed to stand for 10min. After the phase separation is clear, the next stage of extraction is carried out. After the 2 stages of extraction are completed, the loaded organic phase and the raffinate are obtained. The raffinate is returned to step (1) as rhenium-containing waste acid. (11) Back-extraction process: Select analytical grade ammonia water with a mass fraction of 10-12% to back-extract the loaded organic phase. Compared with O / A=5 / 2, the back-extraction time is 0.5h, and it is allowed to stand for 1-4h to obtain the back-extraction liquid and the lean organic phase. Add analytical grade sulfuric acid to the lean organic phase to adjust the pH value to <1, and obtain a reusable organic phase extractant to return to step (5) or step (10). (12) Crystallization process: After the back-extraction liquid is concentrated at 85-90℃, it is filtered and then the freezing crystallization temperature of the filtrate is controlled at -4℃ and the crystallization time is 24h. Then, after redissolution and freezing crystallization, it is repeated 2-3 times to obtain refined ammonium rhenium with a mass fraction ≥99.9%. The crystallized liquid is returned to step (10) and mixed with the rhenium-containing exchange liquid for extraction. (13) Nitration and recrystallization process: Refined ammonium perrylate and pure water are mixed at a solid-liquid ratio of 3:25 (kg / L). The mixture is heated to 85-90℃ and stirred for 0.5 hours. After complete dissolution, it is filtered, and the temperature of the filtrate is controlled at 60-65℃. An appropriate amount of analytical grade nitric acid is added, and the mixture is stirred for 2 hours. After filtration, the filtrate is heated to 85-90℃, and analytical grade ammonia is slowly added to adjust the pH to 5.5-6.

5. Then, an appropriate amount of analytical grade hydrogen peroxide is slowly added to adjust the pH to 5.5-6.

5. After stirring the pH value to 9.5 for 1 hour, continue to slowly add analytical grade ammonia water to adjust the pH value to 9.5-10.

5. After stirring for 1 hour, filter the solution and control the filtrate to freeze crystallize at -4℃ for 24 hours. Then, after the first crystallization of ammonium permanganate, after redissolution, nitration and freeze crystallization, the superior grade 4N ammonium permanganate that meets the requirements of YS / T894-2018 "Ammonium Permanganate" can be obtained. The crystallized solution is returned to step (10) to prepare the pre-ion exchange solution.

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