Preparation method of high-purity ammonium paratungstate

Abstract

This invention provides a method for preparing high-purity ammonium paratungstate, belonging to the technical field of tungsten metallurgy. This invention utilizes the F in fluorides... ‑ It forms stable fluoride complex anions with Si and / or Al in ammonium paratungstate solution, and precipitates and removes them; the high-valence, easily soluble Cr is removed using the first reducing agent. 6+ and Mo 6+ Reduced to a lower valence state, it is more easily hydrolyzed to form hydroxide precipitates or captured by subsequent chelating agents; utilizing organic chelating agents with Ti 4+ V 4+ / V 5+ A chelation reaction occurs, forming a precipitate for removal. The coordination ability of a metal chelating agent with soft acid metal ions is used to "mask" impurity ions in the solution, preventing them from entering the product lattice during subsequent crystallization. Polyquaternary ammonium salts are used to remove colloidal particles such as phosphate and sulfate ions. A second reducing agent is used to remove impurities such as selenium. Ammonium salts are used to promote the crystallization and precipitation of high-purity ammonium paratungstate, increasing the yield. The method provided by this invention can obtain 5N high-purity ammonium paratungstate.

Description

Technical Field

[0001] This invention relates to the technical field of tungsten metallurgy, and more particularly to a method for preparing high-purity ammonium paratungstate. Background Technology

[0002] High-purity tungsten (99.999%) or ultra-high-purity tungsten (99.9999%) possesses advantages such as high electrical conductivity, high-temperature stability, and the ability to form stable silicides, making it widely used in the electronics industry. Ammonium paratungstate is the raw material for preparing high-purity tungsten, and controlling the impurity content in ammonium paratungstate is the source and fundamental factor in controlling the purity of high-purity tungsten materials.

[0003] Currently, the tungsten metallurgical industry requires ultra-high purity ammonium paratungstate (APS) with impurities <10 ppm. Therefore, deep purification of industrial APS is necessary to obtain ultra-high purity APS (5N). However, existing technologies for preparing ultra-high purity APS have the following problems: Traditional purification methods for APS rely on multi-step recrystallization or ion exchange, which are complex, inefficient, and costly. Furthermore, in industrial APS, metallic impurities such as Mo and Cr have properties similar to tungsten, making deep separation difficult, resulting in residual impurity metals in the purified APS >50 ppm. In addition, commonly used single impurity removers cannot effectively remove multiple impurities, leading to the purified APS product not meeting the purity requirements for ultra-high purity APS.

[0004] Therefore, how to prepare 5N high-purity ammonium paratungstate is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a simple method for preparing 5N high-purity ammonium paratungstate.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing high-purity ammonium paratungstate, comprising the following steps: (1) Dissolve industrial ammonium paratungstate in ammonia water to obtain an ammonium paratungstate solution; (2) The ammonium paratungstate solution obtained in step (1) is mixed with fluoride to carry out the first chelation reaction, and the first filtrate is obtained after the first solid-liquid separation; The first filtrate is mixed with the first reducing agent to carry out the first reduction reaction, resulting in a reduced solution. The reduced solution is mixed with an organic chelating agent to carry out a second chelation reaction, followed by a second solid-liquid separation to obtain a second filtrate. The second filtrate was mixed with a metal chelating agent to carry out a coordination reaction, resulting in a solution after coordination treatment. The solution after coordination treatment is mixed with polyquaternium salt, and after flocculation and precipitation, a third solid-liquid separation is performed to obtain a third filtrate. The third filtrate is mixed with the second reducing agent to carry out a second reduction reaction, followed by a fourth solid-liquid separation to obtain the fourth filtrate. The fourth filtrate was mixed with ammonium salt and salting was performed. After a fifth solid-liquid separation, high-purity ammonium paratungstate was obtained.

[0007] Preferably, the concentration of the ammonium paratungstate solution in step (1) is 100~300g / L.

[0008] Preferably, the ratio of the amount of fluoride in step (2) to the total amount of Si and Al in the ammonium paratungstate solution is 1.5~2.5:1.

[0009] Preferably, the ratio of the amount of the first reducing agent in step (2) to the total amount of Cr and Mo in the ammonium paratungstate solution is 2.0~3.0:1.

[0010] Preferably, the ratio of the amount of organic chelating agent in step (2) to the total amount of Ti and V in the ammonium paratungstate solution is 1.0~1.8:1.

[0011] Preferably, the ratio of the amount of metal chelating agent in step (2) to the total amount of Cr and Mo in the ammonium paratungstate solution is 0.5~1.2:1.

[0012] Preferably, the mass percentage of the polyquaternary ammonium salt in step (2) is 0.1-0.5% of the total mass of P and S in the ammonium paratungstate solution.

[0013] Preferably, the ratio of the amount of the second reducing agent in step (2) to the total amount of Se and As in the ammonium paratungstate solution is 0.3~0.8:1.

[0014] Preferably, the mass percentage of the ammonium salt in step (2) is 10-20% of the mass percentage of industrial ammonium paratungstate in the ammonium paratungstate solution.

[0015] Preferably, the salting-out temperature in step (2) is 25~30℃ and the salting-out time is 2~4h.

[0016] This invention provides a method for preparing high-purity ammonium paratungstate, comprising the following steps: dissolving industrial ammonium paratungstate in ammonia water to obtain an ammonium paratungstate solution. This invention further involves mixing the ammonium paratungstate solution with a fluoride to perform a first chelation reaction, utilizing the F in the fluoride. - It forms stable fluoride complex anions (such as [SiF6]) with oxygen-containing anions of Si and / or Al in ammonium paratungstate solution. 2- [AlF6] 3-These fluoride anions combine with cations in fluorides to form insoluble fluorosilicate or fluoroaluminate precipitates. These precipitates are removed by a first solid-liquid separation process to obtain a first filtrate. The first filtrate is then mixed with a first reducing agent to carry out a first reduction reaction, which can remove highly oxidized, easily soluble Cr. 6+ (chromate) and Mo 6+ (Molybdate) is reduced to a lower valence state (Cr). 3+ Mo 4+ / 5+ After forming a low-valence metal, it is more prone to hydrolysis to form hydroxide precipitates or to be captured by subsequent chelating agents. In this invention, the reduced solution is mixed with an organic chelating agent to carry out a chelation reaction. The coordinating atoms in the organic chelating agent molecule provide lone pairs of electrons, which can react with Ti. 4+ V 4+ / V 5+ A chelation reaction occurs, forming a poorly water-soluble internal complex salt precipitate. This precipitate has a stable structure and can be removed by a second solid-liquid separation to obtain a second filtrate. In this invention, the second filtrate is mixed with a metal chelating agent, utilizing the metal chelating agent's ability to chelate soft acid metal ions (such as Cr). 3+ Mo 4+ The coordination ability of the complex forms a stable water-soluble complex; this effect "masks" impurity ions in the solution, preventing them from entering the product lattice during subsequent crystallization. In this invention, the coordinated solution is mixed with a polyquaternary ammonium salt. As a cationic polymer, the polyquaternary ammonium salt's positively charged groups neutralize the charge of negatively charged colloidal particles such as phosphate and sulfate ions, disrupting their stability. Through the "adsorption bridging" effect of the polymer chains, the particles agglomerate to form large flocs, which are then removed by a third solid-liquid separation to obtain a third filtrate. In this invention, the third filtrate is mixed with a second reducing agent to remove easily soluble oxygen-containing anions (SeO4). 2- (Selenates) and AsO4 3- Arsenate is reduced to insoluble elemental selenium (Se). 0 Precipitates such as selenium dioxide (SeO2) and arsenic oxide (As2O3) are removed by a fourth solid-liquid separation process to obtain a fourth filtrate. In this invention, the fourth filtrate is mixed with an ammonium salt, which provides a large amount of NH4+. +The method significantly reduces the solubility of ammonium paratungstate, promotes its crystallization, and improves the yield. High ionic strength also reduces the dielectric constant of the medium in the solution, causing some impurity colloids to become unstable and precipitate, and reduces the activity of impurity ions, inhibiting their co-crystallization with the product. After a fifth solid-liquid separation, high-purity ammonium paratungstate is obtained. The method provided by this invention, by adding a directional impurity remover, can deeply remove impurity elements such as Al, Si, P, S, Ti, V, Cr, and Mo from industrial ammonium paratungstate, reducing the total impurity amount to below 10 ppm. It is applicable to ammonium paratungstate raw materials of different grades, and the obtained ammonium paratungstate has a purity ≥99.999%, meeting the requirements of high-end tungsten products (such as semiconductor targets). Furthermore, by inhibiting impurity co-precipitation through directional crystallization, this invention can improve the morphological uniformity of high-purity ammonium paratungstate crystals. Detailed Implementation

[0017] This invention provides a method for preparing high-purity ammonium paratungstate, comprising the following steps: (1) Dissolve industrial ammonium paratungstate in ammonia water to obtain an ammonium paratungstate solution; (2) The ammonium paratungstate solution obtained in step (1) is mixed with fluoride to carry out the first chelation reaction, and the first filtrate is obtained after the first solid-liquid separation; The first filtrate is mixed with the first reducing agent to carry out the first reduction reaction, resulting in a reduced solution. The reduced solution is mixed with an organic chelating agent to carry out a second chelation reaction, followed by a second solid-liquid separation to obtain a second filtrate. The second filtrate was mixed with a metal chelating agent to carry out a coordination reaction, resulting in a solution after coordination treatment. The solution after coordination treatment is mixed with polyquaternium salt, and after flocculation and precipitation, a third solid-liquid separation is performed to obtain a third filtrate. The third filtrate is mixed with the second reducing agent to carry out a second reduction reaction, followed by a fourth solid-liquid separation to obtain the fourth filtrate. The fourth filtrate was mixed with ammonium salt and salting was performed. After a fifth solid-liquid separation, high-purity ammonium paratungstate was obtained.

[0018] This invention involves dissolving industrial ammonium paratungstate in ammonia water to obtain an ammonium paratungstate solution.

[0019] The present invention does not have any special limitation on the source of the industrial paratungstic acid, and any conventional commercially available product can be used.

[0020] This invention does not impose a specific concentration on the ammonia solution; any conventional ammonia solution can be used. In this invention, since alkaline solutions have good solubility for industrial ammonium paratungstate, ammonia solutions of conventional concentrations can be used. In embodiments of this invention, the ammonia solution can be prepared by mixing commercially available concentrated ammonia solution (25-28% by mass) with deionized water at a volume ratio of 1:1.

[0021] In this invention, the preferred method for dissolving industrial ammonium paratungstate in ammonia water is to mix industrial ammonium paratungstate with ammonia water under heating until the industrial ammonium paratungstate is completely dissolved. In this invention, the heating temperature is preferably 60-90°C, more preferably 60-80°C. In this invention, the heating is preferably reflux heating. This invention, by using reflux heating, can prevent the ammonia water from evaporating.

[0022] In this invention, the concentration of the ammonium paratungstate solution is preferably 100-300 g / L, more preferably 150-250 g / L. Controlling the concentration of the ammonium paratungstate solution within this range in this invention is more conducive to the thorough removal of impurities in subsequent reactions.

[0023] After obtaining the ammonium paratungstate solution, the present invention mixes the ammonium paratungstate solution with fluoride to carry out a first chelation reaction, and then performs a first solid-liquid separation to obtain a first filtrate.

[0024] In this invention, the fluoride is preferably ammonium fluoride or sodium fluoride. This invention mixes the ammonium paratungstate solution with the fluoride to perform a first chelation reaction, which utilizes the F in the fluoride. - It forms stable fluoride complex anions (such as [SiF6]) with oxygen-containing anions of Si and / or Al in ammonium paratungstate solution. 2- [AlF6] 3- These fluoride anions react with cations in fluorides (such as NH4+). + The precipitate is formed by combining with the insoluble ammonium fluorosilicate ((NH4)2SiF6) or fluoroaluminate, and the precipitate is removed by the first solid-liquid separation.

[0025] In this invention, the ratio of the amount of fluoride to the total amount of Si and Al in the ammonium paratungstate solution is preferably 1.5 to 2.5:1, more preferably 2.0 to 2.5:1. By controlling the ratio of the amount of fluoride to the total amount of Si and Al in the ammonium paratungstate solution within the above range, this invention can effectively remove Si and Al from the ammonium paratungstate solution.

[0026] In this invention, the temperature of the first chelation reaction is preferably 60-75°C, more preferably 65-70°C; the time of the first chelation reaction is preferably 30-60 min, more preferably 40-50 min. The present invention enables a more complete chelation reaction at the above-mentioned temperature and time.

[0027] In this invention, the first chelation reaction is preferably carried out under stirring, and the stirring speed is preferably 200-300 rpm, more preferably 250-300 rpm. Stirring promotes mass transfer, which in turn facilitates the thorough removal of impurities such as Si and Al.

[0028] In this invention, the pH value of the first chelation reaction is preferably 5.0 to 6.0. This invention conducts the chelation reaction under weakly acidic conditions, which is more conducive to promoting a more complete chelation reaction.

[0029] In this invention, the first solid-liquid separation is preferably filtration. This invention does not specifically limit the filtration method; any conventional filtration method that can sufficiently remove the precipitate is acceptable.

[0030] After obtaining the first filtrate, the present invention mixes the first filtrate with a first reducing agent to carry out a first reduction reaction, obtaining a reduced solution. The present invention can remove highly oxidized and easily soluble Cr through the first reduction reaction. 6+ (chromate) and Mo 6+ (Molybdate) is reduced to a lower valence state (Cr). 3+ Mo 4+ / 5+ Once formed in a low-valence state, it is more likely to hydrolyze to form hydroxide precipitates or be captured by subsequent chelating agents.

[0031] In this invention, the first reducing agent preferably includes ascorbic acid or hydrazine hydrate, more preferably ascorbic acid.

[0032] In this invention, the preferred ratio of the amount of the first reducing agent to the total amount of Cr and Mo in the ammonium paratungstate solution is 2.0 to 3.0:1, more preferably 2.5 to 3.0:1. By controlling the ratio of the amount of the first reducing agent to the total amount of Cr and Mo in the ammonium paratungstate solution within the above range, this invention can effectively remove Cr and Mo.

[0033] In this invention, the temperature of the first reduction reaction is preferably 60~75℃, more preferably 65~70℃; the time of the first reduction reaction is preferably 20~40min, more preferably 30~40min.

[0034] In this invention, the first reduction reaction is made more complete at the above-mentioned temperature and time.

[0035] In this invention, the first reduction reaction is preferably carried out under stirring, and the stirring speed is preferably 200-300 rpm, more preferably 250-300 rpm. This invention promotes mass transfer through stirring, thereby facilitating the thorough removal of impurities such as Cr and Mo.

[0036] In this invention, the pH value of the first reduction reaction is preferably 5.0 to 6.0. Conducting the first reduction reaction under weakly acidic conditions in this invention is more conducive to promoting a more complete first reduction reaction.

[0037] After obtaining the reduced solution, this invention mixes the reduced solution with an organic chelating agent to carry out a second chelation reaction, followed by a second solid-liquid separation to obtain a second filtrate. This invention mixes the reduced solution with an organic chelating agent, utilizing the lone pair electrons provided by the coordinating atoms in the organic chelating agent molecule, which can bind with Ti. 4+ V 4+ / V 5+ A chelation reaction occurs, forming an inner complex salt precipitate with extremely poor water solubility. This precipitate has a stable structure and can be removed by a second solid-liquid separation.

[0038] In this invention, the organic chelating agent preferably includes 8-hydroxyquinoline, tannic acid or acetylacetone, more preferably 8-hydroxyquinoline.

[0039] In this invention, the preferred ratio of the amount of the organic chelating agent to the total amount of Ti and V in the ammonium paratungstate solution is 1.0 to 1.8:1, more preferably 1.5 to 1.8:1. By controlling the ratio of the amount of the organic chelating agent to the total amount of Ti and V in the ammonium paratungstate solution within the above range, this invention is more conducive to the thorough removal of impurities such as Ti and V.

[0040] In this invention, the temperature of the second chelation reaction is preferably 60-75°C, more preferably 65-70°C; the time of the second chelation reaction is preferably 30-60 min, more preferably 40-50 min. The present invention enables a more complete chelation reaction at the above-mentioned temperature and time.

[0041] In this invention, the second chelation reaction is preferably carried out under stirring, and the stirring speed is preferably 200-300 rpm, more preferably 250-300 rpm. This invention promotes mass transfer through stirring, thereby facilitating the thorough removal of impurities such as Ti and V.

[0042] In this invention, the pH value of the chelation reaction is preferably 5.0 to 7.0. Conducting the chelation reaction under weakly acidic conditions in this invention is more conducive to promoting a more complete chelation reaction.

[0043] In this invention, the second solid-liquid separation is preferably performed by filtration. This invention does not specifically limit the filtration method; any conventional filtration method that can sufficiently remove the precipitate is acceptable. This invention removes internal complex salt precipitates (such as Ti(C9H6NO)4) through filtration.

[0044] After obtaining the second filtrate, the present invention mixes the second filtrate with a metal chelating agent to carry out a coordination reaction, thereby obtaining a coordinated solution. In the present invention, the metal chelating agent preferably includes one of mercaptoacetic acid, dimercaptosuccinic acid, EDTA, and sodium diethyldithiocarbamate, more preferably mercaptoacetic acid. The present invention mixes the second filtrate with a metal chelating agent, utilizing the metal chelating agent to react with soft acid metal ions (such as Cr...). 3+ Mo 4+ The coordination ability of the impurity ions forms a stable water-soluble complex; this effect "masks" the impurity ions in the solution, preventing them from entering the product lattice during subsequent crystallization.

[0045] In this invention, the preferred ratio of the amount of the metal chelating agent to the total amount of Cr and Mo in the ammonium paratungstate solution is 0.5 to 1.2:1, more preferably 1.0 to 1.2:1. By controlling the ratio of the amount of the metal chelating agent to the total amount of Cr and Mo in the ammonium paratungstate solution within the above range, this invention is more conducive to the thorough removal of Cr and Mo.

[0046] In this invention, the temperature of the coordination reaction is preferably 60-75°C, more preferably 65-70°C; the time of the coordination reaction is preferably 20-40 min, more preferably 30-40 min. This invention enables a more complete coordination reaction at the above-mentioned temperature and time.

[0047] In this invention, the coordination reaction is preferably carried out under stirring, and the stirring speed is preferably 200-300 rpm, more preferably 250-300 rpm. Stirring promotes mass transfer, which in turn facilitates the thorough removal of impurities such as Cr and Mo.

[0048] In this invention, the pH value of the coordination reaction is preferably 5.0 to 7.0. Conducting the coordination reaction under weakly acidic conditions in this invention is more conducive to promoting a more complete coordination reaction.

[0049] After obtaining the coordination-treated solution, the present invention mixes the coordination-treated solution with a polyquaternary ammonium salt, and after flocculation and precipitation, performs a third solid-liquid separation to obtain a third filtrate. The present invention mixes the coordination-treated solution with the polyquaternary ammonium salt. As a cationic polymer, the polyquaternary ammonium salt's positively charged groups neutralize the charge of negatively charged colloidal particles such as phosphate and sulfate ions, disrupting their stability. Through the "adsorption bridging" effect of the polymer chains, the particles agglomerate to form large flocs, which are then removed by the third solid-liquid separation to obtain the third filtrate.

[0050] In this invention, the polyquaternary ammonium salt preferably includes one of polyquaternary ammonium salt-7, polyacrylamide, and polydimethyldiallylammonium chloride, more preferably polyquaternary ammonium salt-7.

[0051] In this invention, the percentage of the mass of the polyquaternary ammonium salt in the total mass of P and S in the ammonium paratungstate solution is preferably 0.1-0.5%, more preferably 0.3-0.5%. By controlling the percentage of the mass of the polyquaternary ammonium salt in the total mass of P and S in the ammonium paratungstate solution within the above range, this invention can effectively remove impurities such as P and S.

[0052] In this invention, the preferred temperature for flocculation and sedimentation is 40-60°C, more preferably 50-60°C; the preferred time for flocculation and sedimentation is 20-30 minutes, more preferably 25-30 minutes. This invention enables more complete flocculation and sedimentation at the above-mentioned temperature and time.

[0053] In this invention, the flocculation and sedimentation are preferably carried out under stirring, and the stirring is preferably variable speed stirring, with the stirring speed preferably gradually decreasing from 300 rpm to 50 rpm. This invention promotes mass transfer through stirring, thereby facilitating the full formation of sediment.

[0054] In this invention, the pH value for flocculation and precipitation is preferably 5.0 to 7.5. This pH value promotes more complete flocculation and precipitation.

[0055] In this invention, the third solid-liquid separation is preferably filtration. This invention does not specifically limit the filtration method; any conventional filtration method that can sufficiently remove the precipitate is acceptable. This invention removes flocculated precipitates through filtration.

[0056] After obtaining the third filtrate, the present invention mixes the third filtrate with the second reducing agent to carry out a second reduction reaction, followed by a fourth solid-liquid separation to obtain the fourth filtrate. The present invention mixes the third filtrate with the second reducing agent to remove easily soluble oxygen-containing anions SeO4. 2- and AsO4 3- Reduced to insoluble Se 0 Precipitates such as SeO2 and As2O3 are removed by the fourth solid-liquid separation process.

[0057] In this invention, the second reducing agent preferably includes one of dimethylamine borane, sodium borohydride, sulfur dioxide, and sodium sulfide, more preferably dimethylamine borane. The reducing agent used in this invention is a mild reducing agent, which more easily dissolves the readily soluble oxygen-containing anion SeO4. 2- and AsO4 3- Reduced to insoluble Se 0 Or precipitates such as SeO2 and As2O3.

[0058] In this invention, the ratio of the amount of the second reducing agent to the total amount of Se and As in the ammonium paratungstate solution is preferably 0.3 to 0.8:1, more preferably 0.5 to 0.8:1. By controlling the ratio of the amount of the second reducing agent to the total amount of Se and As in the ammonium paratungstate solution within the above range, this invention can effectively remove Se and As.

[0059] In this invention, the temperature of the second reduction reaction is preferably 50-70°C, more preferably 60-65°C; the time of the second reduction reaction is preferably 30-60 min, more preferably 40-50 min. The present invention enables a more complete second reduction reaction at the above-mentioned temperature and time.

[0060] In this invention, the second reduction reaction is preferably carried out under stirring, and the stirring speed is preferably 200 rpm. Stirring promotes mass transfer, which in turn facilitates the thorough removal of impurities such as Se and As.

[0061] In this invention, the pH value of the second reduction reaction is preferably 5.0 to 8.0. At this pH value, the second reduction reaction is more likely to be fully realized.

[0062] In this invention, the fourth solid-liquid separation is preferably filtration. This invention does not specifically limit the filtration method; any conventional filtration method that can sufficiently remove the precipitate is acceptable.

[0063] After obtaining the fourth filtrate, this invention mixes the fourth filtrate with an ammonium salt for salting out, followed by a fifth solid-liquid separation to obtain high-purity ammonium paratungstate. In this invention, the fourth filtrate is mixed with an ammonium salt, which provides a large amount of NH4. + The high ionic strength significantly reduces the solubility of ammonium paratungstate, promotes its crystallization and precipitation, and increases the yield. It can also reduce the dielectric constant of the medium in the solution, causing some impurity colloids to become unstable and precipitate, and reduce the activity of impurity ions, inhibiting their co-crystallization with the product. After the fifth solid-liquid separation, high-purity ammonium paratungstate is obtained.

[0064] In this invention, the mass percentage of the ammonium salt in the ammonium paratungstate solution is preferably 10-20%, more preferably 15-18%. By controlling the mass percentage of the ammonium salt in the ammonium paratungstate solution within the above range, this invention can promote crystallization and increase the yield.

[0065] In this invention, the ammonium salt preferably includes one of ammonium sulfate, ammonium chloride, and ammonium nitrate, and more preferably ammonium sulfate. The addition of the ammonium salt in this invention provides NH4. +It reduces the solubility of ammonium paratungstate, promotes its crystallization and precipitation, and increases the yield. The high ionic strength reduces the dielectric constant of the medium in the solution, causing some impurity colloids to become unstable and precipitate, and reduces the activity of impurity ions, inhibiting their co-crystallization with the product.

[0066] In this invention, the mixing temperature of the fourth filtrate and the ammonium salt is preferably 70-80°C, more preferably 75-80°C. This invention does not have a particular limitation on the mixing time of the fourth filtrate and the ammonium salt, as long as the ammonium salt is completely dissolved in the fourth filtrate. In this invention, the mixing is preferably carried out under stirring, and the stirring speed can be 200 rpm.

[0067] In this invention, the pH value of the mixture of the fourth filtrate and the ammonium salt is preferably 7.0 to 8.0, more preferably 7.5 to 8.0. This invention is weakly alkaline at the above pH value, which promotes the dissolution of the ammonium salt in the fourth filtrate.

[0068] In this invention, the system obtained by mixing the fourth filtrate with the ammonium salt is first filtered, and then the resulting solution is slowly cooled to the salting-out temperature. In this invention, the cooling rate is preferably 0.5~1℃ / min.

[0069] This invention removes insoluble impurities through filtration.

[0070] In this invention, the salting-out temperature is preferably 25~30℃, more preferably 26~28℃; the salting-out time is preferably 2~4h, more preferably 3~4h.

[0071] In this invention, the fifth solid-liquid separation method is preferably centrifugation. This invention collects crystals by centrifugation.

[0072] In this invention, the crystals obtained from the solid-liquid separation are preferably washed and dried to obtain high-purity ammonium paratungstate. In this invention, the washing reagent is preferably deionized water; the drying is preferably vacuum drying, the vacuum drying temperature can be 60°C, and the vacuum drying time can be 6 hours.

[0073] The method provided by this invention, by adding a directional impurity remover, can deeply remove impurity elements such as Al, Si, P, S, Ti, V, Cr, and Mo from industrial ammonium paratungstate, reducing the total impurity amount to below 10 ppm. It is applicable to ammonium paratungstate raw materials of different grades, and the resulting ammonium paratungstate has a purity of ≥99.999%, meeting the requirements of high-end tungsten products (such as semiconductor targets). Furthermore, this invention can improve the morphological uniformity of high-purity ammonium paratungstate crystals by inhibiting impurity co-precipitation through directional crystallization.

[0074] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0075] The industrial ammonium paratungstate used in this embodiment of the invention has an initial total impurity content of about 500 ppm, including Al 80 ppm, Si 120 ppm, P 40 ppm, Mo 60 ppm, Cr 30 ppm, Ti 20 ppm, V 15 ppm, As 5 ppm and Se 5 ppm.

[0076] Example 1 A method for preparing high-purity ammonium paratungstate, comprising the following steps: (1) Mix industrial ammonium paratungstate with ammonia water (prepared with a volume ratio of concentrated ammonia water to water of 1:1) at 75°C and dissolve to obtain an ammonium paratungstate solution with a concentration of 200 g / L; (2) According to the ratio of the amount of ammonium fluoride to the total amount of Si and Al in the ammonium paratungstate solution of 2.5:1, the ammonium paratungstate solution obtained in step (1) is mixed with ammonium fluoride and chelated at 75°C, 200 rpm and pH 5.8 for 45 min, and the first filtrate is obtained by filtration. The ratio of the amount of the first reducing agent to the total amount of Cr and Mo in the ammonium paratungstate solution was 2.0:1. The first filtrate was mixed with the first reducing agent (ascorbic acid), and the first reduction reaction was carried out at 75°C, 200 rpm, and pH 6.2 for 30 min to obtain the reduced solution. The ratio of the amount of organic chelating agent to the total amount of Ti and V in the ammonium paratungstate solution was 1.8:1. The reduced solution was mixed with the organic chelating agent (8-hydroxyquinoline), and the chelation reaction was carried out at 75°C, 200 rpm, and pH 6.5 for 60 min. The solution was then filtered to obtain the second filtrate. The second filtrate was mixed with the metal chelating agent (thioglycolic acid) according to the ratio of the amount of metal chelating agent to the total amount of Cr and Mo in the ammonium paratungstate solution of 1.2:1. The mixture was subjected to a coordination reaction at 75°C, 200 rpm and pH 6.5 for 30 min to obtain the solution after coordination treatment. The polyquaternary ammonium salt was mixed with polyquaternary ammonium salt (polyquaternary ammonium salt-7) according to the percentage of the total mass of P and S in the ammonium paratungstate solution being 0.5%. The mixture was then subjected to flocculation and precipitation at 60°C, 200 rpm, and pH 6.8 for 25 min, and then filtered to obtain the third filtrate. The third filtrate was mixed with the second reducing agent (dimethylamine borane) at a ratio of 0.8:1 to the total amount of Se and As in the ammonium paratungstate solution. The second reduction reaction was carried out at 70°C, 200 rpm, and pH 7.0 for 45 min. The mixture was then filtered to obtain the fourth filtrate. The ammonium salt accounts for 20% of the mass of industrial ammonium paratungstate in the ammonium paratungstate solution. The fourth filtrate is mixed with the ammonium salt (ammonium sulfate), filtered while hot, and then cooled to 28°C at 0.5°C / min for salting out. Crystals are then grown at this temperature for 3 hours. After centrifugation and washing with deionized water, the crystals are dried under vacuum at 60°C for 6 hours to obtain high-purity ammonium paratungstate.

[0077] Tests showed that the total impurities in the high-purity ammonium paratungstate prepared in this embodiment were 8 ppm.

[0078] Example 2 A method for preparing high-purity ammonium paratungstate, comprising the following steps: (1) Mix industrial ammonium paratungstate with ammonia water (prepared with a volume ratio of concentrated ammonia water to water of 1:1) at 70°C and dissolve to obtain an ammonium paratungstate solution with a concentration of 200 g / L; (2) According to the ratio of the amount of ammonium fluoride to the total amount of Si and Al in the ammonium paratungstate solution of 2.0:1, the ammonium paratungstate solution obtained in step (1) is mixed with ammonium fluoride and chelated at 75°C, 200 rpm and pH 6.0 for 35 min, and the first filtrate is obtained by filtration. The ratio of the amount of the first reducing agent to the total amount of Cr and Mo in the ammonium paratungstate solution is 2.5:1. The first filtrate is mixed with the first reducing agent (ascorbic acid), and the first reduction reaction is carried out at 75°C, 200 rpm, and pH 6.0 for 25 min to obtain the reduced solution. The organic chelating agent was mixed with the organic chelating agent (8-hydroxyquinoline) according to a molar ratio of 1.4:1 to the total molar amounts of Ti and V in the ammonium paratungstate solution. The chelation reaction was carried out at 75°C, 200 rpm, and pH 6.0 for 35 min. The solution was then filtered to obtain the second filtrate. The second filtrate was mixed with the metal chelating agent (thioglycolic acid) according to the ratio of the amount of metal chelating agent to the total amount of Cr and Mo in the ammonium paratungstate solution being 0.85:1. The mixture was subjected to a coordination reaction at 75°C, 200 rpm, and pH 6.0 for 25 min to obtain the solution after coordination treatment. The polyquaternary ammonium salt was mixed with polyquaternary ammonium salt (polyquaternary ammonium salt-7) according to the percentage of the total mass of P and S in the ammonium paratungstate solution being 0.3%. The mixture was then subjected to flocculation and precipitation at 60°C, 200 rpm, and pH 6.0 for 25 min, and then filtered to obtain the third filtrate. The third filtrate was mixed with the second reducing agent (dimethylamine borane) at a ratio of 0.55:1 to the total amount of Se and As in the ammonium paratungstate solution. The second reduction reaction was carried out at 70°C, 200 rpm, and pH 6.0 for 35 min. The mixture was then filtered to obtain the fourth filtrate. The fourth filtrate was mixed with ammonium salt (ammonium sulfate) according to the mass percentage of ammonium salt in the ammonium paratungstate solution being 15%. After hot filtration, the mixture was cooled to 25°C at a rate of 0.5°C / min for salting out. Crystals were then grown at this temperature for 3 hours. After centrifugation and washing with deionized water, the mixture was vacuum dried at 60°C for 6 hours to obtain high-purity ammonium paratungstate.

[0079] Tests showed that the total impurities in the high-purity ammonium paratungstate prepared in this embodiment were 10 ppm.

[0080] Example 3 A method for preparing high-purity ammonium paratungstate, comprising the following steps: (1) Mix industrial ammonium paratungstate with ammonia water (prepared with a volume ratio of concentrated ammonia water to water of 1:1) at 70°C and dissolve to obtain an ammonium paratungstate solution with a concentration of 200 g / L; (2) According to the ratio of the amount of ammonium fluoride to the total amount of Si and Al in the ammonium paratungstate solution of 1.5:1, the ammonium paratungstate solution obtained in step (1) is mixed with ammonium fluoride and chelated at 75°C, 200 rpm and pH 6.0 for 50 min, and the first filtrate is obtained by filtration. The ratio of the amount of the first reducing agent to the total amount of Cr and Mo in the ammonium paratungstate solution was 2.0:1. The first filtrate was mixed with the first reducing agent (ascorbic acid), and the first reduction reaction was carried out at 75°C, 200 rpm, and pH 6.0 for 30 min to obtain the reduced solution. The organic chelating agent was mixed with the organic chelating agent (8-hydroxyquinoline) according to a molar ratio of 1.0:1 to the total molar amounts of Ti and V in the ammonium paratungstate solution. The mixture was then subjected to a chelation reaction at 75°C, 200 rpm, and pH 6.0 for 30 min. The resulting solution was filtered to obtain the second filtrate. The second filtrate was mixed with the metal chelating agent (thioglycolic acid) according to the ratio of the amount of metal chelating agent to the total amount of Cr and Mo in the ammonium paratungstate solution of 0.5:1. The mixture was subjected to a coordination reaction at 75°C, 200 rpm and pH 6.0 for 30 min to obtain the solution after coordination treatment. The polyquaternary ammonium salt was mixed with polyquaternary ammonium salt (polyquaternary ammonium salt-7) according to the percentage of the total mass of P and S in the ammonium paratungstate solution being 0.1%. The mixture was then subjected to flocculation and precipitation at 60°C, 200 rpm, and pH 6.0 for 30 min, and then filtered to obtain the third filtrate. The third filtrate was mixed with the second reducing agent (dimethylamine borane) at a ratio of 0.3:1 to the total amount of Se and As in the ammonium paratungstate solution. The second reduction reaction was carried out at 70°C, 200 rpm, and pH 6.0 for 40 min. The mixture was then filtered to obtain the fourth filtrate. The fourth filtrate was mixed with ammonium salt (ammonium sulfate) according to the mass percentage of ammonium salt in the ammonium paratungstate solution being 10%. After hot filtration, the mixture was cooled to 25°C at a rate of 0.5°C / min for salting out. Crystals were then grown at this temperature for 3 hours. After centrifugation and washing with deionized water, the mixture was vacuum dried at 60°C for 6 hours to obtain high-purity ammonium paratungstate.

[0081] Tests showed that the total impurities in the high-purity ammonium paratungstate prepared in this embodiment were 35 ppm.

[0082] Example 4 A method for preparing high-purity ammonium paratungstate, comprising the following steps: (1) Mix industrial ammonium paratungstate with ammonia water (prepared with a volume ratio of concentrated ammonia water to water of 1:1) at 70°C and dissolve to obtain an ammonium paratungstate solution with a concentration of 200 g / L; (2) According to the ratio of the amount of ammonium fluoride to the total amount of Si and Al in the ammonium paratungstate solution of 2.5:1, the ammonium paratungstate solution obtained in step (1) is mixed with ammonium fluoride and chelated at 75°C, 200 rpm and pH 5.0 for 45 min, and the first filtrate is obtained by filtration. The ratio of the amount of the first reducing agent to the total amount of Cr and Mo in the ammonium paratungstate solution was 2.0:1. The first filtrate was mixed with the first reducing agent (ascorbic acid), and the first reduction reaction was carried out at 75°C, 200 rpm, and pH 5.0 for 30 min to obtain the reduced solution. The ratio of the amount of organic chelating agent to the total amount of Ti and V in the ammonium paratungstate solution was 1.8:1. The reduced solution was mixed with the organic chelating agent (8-hydroxyquinoline) and the chelation reaction was carried out at 75°C, 200 rpm and pH 5.0 for 60 min. The solution was then filtered to obtain the second filtrate. The second filtrate was mixed with the metal chelating agent (thioglycolic acid) according to the ratio of the amount of metal chelating agent to the total amount of Cr and Mo in the ammonium paratungstate solution of 1.2:1. The mixture was subjected to a coordination reaction at 75°C, 200 rpm and pH 5.0 for 30 min to obtain the solution after coordination treatment. The polyquaternary ammonium salt was mixed with polyquaternary ammonium salt (polyquaternary ammonium salt-7) according to the percentage of the total mass of P and S in the ammonium paratungstate solution being 0.5%. The mixture was then subjected to flocculation and precipitation at 60°C, 200 rpm, and pH 5.0 for 20-40 min, and then filtered to obtain the third filtrate. The third filtrate was mixed with the second reducing agent (dimethylamine borane) at a ratio of 0.8:1 to the total amount of Se and As in the ammonium paratungstate solution. The second reduction reaction was carried out at 70°C, 200 rpm, and pH 5.0 for 40 min. The mixture was then filtered to obtain the fourth filtrate. The ammonium salt accounts for 20% of the mass percentage of industrial ammonium paratungstate in the ammonium paratungstate solution. The fourth filtrate is mixed with the ammonium salt (ammonium sulfate), filtered while hot, and then cooled to 25°C at 0.5°C / min for salting out. Crystals are then grown at this temperature for 3 hours. After centrifugation and washing with deionized water, the crystals are dried under vacuum at 60°C for 6 hours to obtain high-purity ammonium paratungstate.

[0083] Tests showed that the total impurities in the high-purity ammonium paratungstate prepared in this embodiment were 25 ppm.

[0084] Comparative Example 1 A method for preparing high-purity ammonium paratungstate, comprising the following steps: (1) Mix industrial ammonium paratungstate with ammonia water (prepared with a volume ratio of concentrated ammonia water to water of 1:1) at 70°C and dissolve to obtain an ammonium paratungstate solution with a concentration of 200 g / L; (2) According to the ratio of the amount of ammonium fluoride to the total amount of Si and Al in the ammonium paratungstate solution of 2.5:1, the ammonium paratungstate solution obtained in step (1) is mixed with ammonium fluoride and chelated at 75°C, 200 rpm and pH 7.5 for 35 min, and the first filtrate is obtained by filtration. The ratio of the amount of the first reducing agent to the total amount of Cr and Mo in the ammonium paratungstate solution was 2.0:1. The first filtrate was mixed with the first reducing agent (ascorbic acid), and the first reduction reaction was carried out at 75°C, 200 rpm, and pH 7.5 for 35 min to obtain the reduced solution. The ratio of the amount of organic chelating agent to the total amount of Ti and V in the ammonium paratungstate solution was 1.8:1. The reduced solution was mixed with the organic chelating agent (8-hydroxyquinoline), and the chelation reaction was carried out at 75°C, 200 rpm, and pH 7.5 for 35 min. The solution was then filtered to obtain the second filtrate. The second filtrate was mixed with the metal chelating agent (thioglycolic acid) according to the ratio of the amount of metal chelating agent to the total amount of Cr and Mo in the ammonium paratungstate solution of 1.2:1. The mixture was subjected to a coordination reaction at 75°C, 200 rpm and pH 7.5 for 25 min to obtain the solution after coordination treatment. The polyquaternary ammonium salt was mixed with polyquaternary ammonium salt (polyquaternary ammonium salt-7) according to the percentage of the total mass of P and S in the ammonium paratungstate solution being 0.5%. The mixture was then subjected to flocculation and precipitation at 60°C, 200 rpm, and pH 7.5 for 25 min, and then filtered to obtain the third filtrate. The third filtrate was mixed with the second reducing agent (dimethylamine borane) according to the ratio of the amount of the second reducing agent to the total amount of Se and As in the ammonium paratungstate solution of 0.8:1. The second reduction reaction was carried out at 70°C, 200 rpm and pH 7.5 for 35 min. The fourth filtrate was obtained by filtration. The ammonium salt accounts for 20% of the mass percentage of industrial ammonium paratungstate in the ammonium paratungstate solution. The fourth filtrate is mixed with the ammonium salt (ammonium sulfate), filtered while hot, and then cooled to 25°C at 0.5°C / min for salting out. Crystals are then grown at this temperature for 3 hours. After centrifugation and washing with deionized water, the crystals are dried under vacuum at 60°C for 6 hours to obtain high-purity ammonium paratungstate.

[0085] Tests showed that the total impurities in the high-purity ammonium paratungstate prepared in this embodiment were 50 ppm.

[0086] Comparative Example 2 A method for preparing high-purity ammonium paratungstate, comprising the following steps: (1) Mix industrial ammonium paratungstate with ammonia water (prepared with a volume ratio of concentrated ammonia water to water of 1:1) at 70°C and dissolve to obtain an ammonium paratungstate solution with a concentration of 200 g / L; (2) According to the ratio of the amount of ammonium fluoride to the total amount of Si and Al in the ammonium paratungstate solution of 2.5:1, the ammonium paratungstate solution obtained in step (1) is mixed with ammonium fluoride and chelated at 75°C, 200 rpm and pH 6.0 for 40 min, and the first filtrate is obtained by filtration. The first filtrate was mixed with the organic chelating agent (8-hydroxyquinoline) at a ratio of 1.8:1 to the total amount of Ti and V in the ammonium paratungstate solution. The mixture was then subjected to a chelation reaction at 75°C, 200 rpm, and pH 6.0 for 35 min. The mixture was then filtered to obtain the second filtrate. The second filtrate was mixed with the metal chelating agent (thioglycolic acid) according to the ratio of the amount of metal chelating agent to the total amount of Cr and Mo in the ammonium paratungstate solution of 1.2:1. The mixture was subjected to a coordination reaction at 75°C, 200 rpm and pH 6.0 for 25 min to obtain the solution after coordination treatment. The polyquaternary ammonium salt was mixed with polyquaternary ammonium salt (polyquaternary ammonium salt-7) according to the percentage of the total mass of P and S in the ammonium paratungstate solution being 0.5%. The mixture was then subjected to flocculation and precipitation at 60°C, 200 rpm, and pH 6.0 for 25 min, and then filtered to obtain the third filtrate. The third filtrate was mixed with the second reducing agent (dimethylamine borane) at a ratio of 0.8:1 to the total amount of Se and As in the ammonium paratungstate solution. The second reduction reaction was carried out at 70°C, 200 rpm, and pH 6.0 for 35 min. The mixture was then filtered to obtain the fourth filtrate. The ammonium salt accounts for 20% of the mass percentage of industrial ammonium paratungstate in the ammonium paratungstate solution. The fourth filtrate is mixed with the ammonium salt (ammonium sulfate), filtered while hot, and then cooled to 25°C at 0.5°C / min for salting out. Crystals are then grown at this temperature for 3 hours. After centrifugation and washing with deionized water, the crystals are dried under vacuum at 60°C for 6 hours to obtain high-purity ammonium paratungstate.

[0087] Tests showed that the total impurities in the high-purity ammonium paratungstate prepared in this embodiment were >100 ppm.

[0088] Comparative Example 3 A method for preparing high-purity ammonium paratungstate, comprising the following steps: (1) Mix industrial ammonium paratungstate with ammonia water (prepared with a volume ratio of concentrated ammonia water to water of 1:1) at 70°C and dissolve to obtain an ammonium paratungstate solution with a concentration of 200 g / L; (2) The ammonium paratungstate solution was mixed with the first reducing agent (ascorbic acid) according to the ratio of the amount of the first reducing agent to the total amount of Cr and Mo in the ammonium paratungstate solution of 2.0:1. The first reduction reaction was carried out at 75°C, 200 rpm and pH 6.0 for 25 min to obtain the reduced solution. The ratio of the amount of organic chelating agent to the total amount of Ti and V in the ammonium paratungstate solution was 1.8:1. The reduced solution was mixed with the organic chelating agent (8-hydroxyquinoline), and the chelation reaction was carried out at 75°C, 200 rpm, and pH 6.0 for 35 min. The first filtrate was obtained by filtration. The first filtrate was mixed with the metal chelating agent (thioglycolic acid) according to the ratio of the amount of metal chelating agent to the total amount of Cr and Mo in the ammonium paratungstate solution of 1.2:1. The mixture was then subjected to a coordination reaction at 75°C, 200 rpm and pH 6.0 for 25 min to obtain the solution after coordination treatment. The polyquaternary ammonium salt was mixed with polyquaternary ammonium salt (polyquaternary ammonium salt-7) according to the percentage of the total mass of P and S in the ammonium paratungstate solution being 0.5%. The mixture was then subjected to flocculation and precipitation at 60°C, 200 rpm, and pH 6.0 for 25 min, and then filtered to obtain the second filtrate. The second filtrate was mixed with the second reducing agent (dimethylamine borane) according to the ratio of the amount of the second reducing agent to the total amount of Se and As in the ammonium paratungstate solution of 0.8:1. The second reduction reaction was carried out at 70°C, 200 rpm and pH 6.0 for 50 min. The third filtrate was obtained by filtration. The third filtrate was mixed with ammonium salt (ammonium sulfate) according to the mass percentage of ammonium salt in the ammonium paratungstate solution being 20%. After hot filtration, the mixture was cooled to 25°C at a rate of 0.5°C / min for salting out. Crystals were then grown at this temperature for 3 hours. After centrifugation and washing with deionized water, the mixture was vacuum dried at 60°C for 6 hours to obtain high-purity ammonium paratungstate.

[0089] Tests showed that the total impurities in the high-purity ammonium paratungstate prepared in this embodiment were 80 ppm.

[0090] Comparative Example 4 A method for preparing high-purity ammonium paratungstate, comprising the following steps: (1) Mix industrial ammonium paratungstate with ammonia water (prepared with a volume ratio of concentrated ammonia water to water of 1:1) at 70°C and dissolve to obtain an ammonium paratungstate solution with a concentration of 200 g / L; (2) According to the ratio of the amount of ammonium fluoride to the total amount of Si and Al in the ammonium paratungstate solution of 2.5:1, the ammonium paratungstate solution obtained in step (1) is mixed with ammonium fluoride and chelated at 75°C, 200 rpm and pH 6.0 for 40 min, and the first filtrate is obtained by filtration. The ratio of the amount of the first reducing agent to the total amount of Cr and Mo in the ammonium paratungstate solution was 2.0:1. The first filtrate was mixed with the first reducing agent (ascorbic acid), and the first reduction reaction was carried out at 75°C, 200 rpm, and pH 6.0 for 30 min to obtain the reduced solution. The ratio of the amount of organic chelating agent to the total amount of Ti and V in the ammonium paratungstate solution was 1.8:1. The reduced solution was mixed with the organic chelating agent (8-hydroxyquinoline), and the chelation reaction was carried out at 75°C, 200 rpm, and pH 6.0 for 35 min. The solution was then filtered to obtain the second filtrate. The second filtrate was mixed with the metal chelating agent (thioglycolic acid) according to the ratio of the amount of metal chelating agent to the total amount of Cr and Mo in the ammonium paratungstate solution of 1.2:1. The mixture was subjected to a coordination reaction at 75°C, 200 rpm and pH 6.0 for 25 min to obtain the solution after coordination treatment. The solution after coordination treatment was mixed with the second reducing agent (dimethylamine borane) according to the ratio of the amount of the second reducing agent to the total amount of Se and As in the ammonium paratungstate solution of 0.8:1. The second reduction reaction was carried out at 70°C, 200 rpm and pH 6.0 for 40 min. The solution was then filtered to obtain the third filtrate. The third filtrate was mixed with ammonium salt (ammonium sulfate) according to the mass percentage of ammonium salt in the ammonium paratungstate solution being 20%. After hot filtration, the mixture was cooled to 25°C at a rate of 0.5°C / min for salting out. Crystals were then grown at this temperature for 3 hours. After centrifugation and washing with deionized water, the mixture was vacuum dried at 60°C for 6 hours to obtain high-purity ammonium paratungstate.

[0091] Tests showed that the total impurities in the high-purity ammonium paratungstate prepared in this embodiment were 40 ppm.

[0092] The results above show that the method provided by this invention can obtain high-purity ammonium paratungstate with a total impurity content of less than 10 ppm. This is because the method provided by this invention, by adding a directional impurity remover, can deeply remove key impurity elements such as Al, Si, P, S, Ti, V, Cr, and Mo from industrial ammonium paratungstate, reducing the total impurity content to below 10 ppm. This method is applicable to ammonium paratungstate raw materials of different grades, and the resulting ammonium paratungstate has a purity ≥99.999%, meeting the requirements of high-end tungsten products. Furthermore, this invention improves the morphological uniformity of high-purity ammonium paratungstate crystals by inhibiting impurity co-precipitation through directional crystallization.

[0093] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity ammonium paratungstate, characterized in that, Includes the following steps: (1) Dissolve industrial ammonium paratungstate in ammonia water to obtain an ammonium paratungstate solution; (2) The ammonium paratungstate solution obtained in step (1) is mixed with fluoride to carry out the first chelation reaction, and the first filtrate is obtained after the first solid-liquid separation; The first filtrate is mixed with the first reducing agent to carry out the first reduction reaction, resulting in a reduced solution. The reduced solution is mixed with an organic chelating agent to carry out a second chelation reaction, followed by a second solid-liquid separation to obtain a second filtrate. The second filtrate was mixed with a metal chelating agent to carry out a coordination reaction, resulting in a solution after coordination treatment. The solution after coordination treatment is mixed with polyquaternium salt, and after flocculation and precipitation, a third solid-liquid separation is performed to obtain a third filtrate. The third filtrate is mixed with the second reducing agent to carry out a second reduction reaction, followed by a fourth solid-liquid separation to obtain the fourth filtrate. The fourth filtrate was mixed with ammonium salt and salting was performed. After a fifth solid-liquid separation, high-purity ammonium paratungstate was obtained.

2. The preparation method according to claim 1, characterized in that, The concentration of ammonium paratungstate solution in step (1) is 100~300g / L.

3. The preparation method according to claim 1, characterized in that, In step (2), the ratio of the amount of fluoride to the total amount of Si and Al in the ammonium paratungstate solution is 1.5~2.5:

1.

4. The preparation method according to claim 1, characterized in that, In step (2), the ratio of the amount of the first reducing agent to the total amount of Cr and Mo in the ammonium paratungstate solution is 2.0~3.0:

1.

5. The preparation method according to claim 1, characterized in that, In step (2), the ratio of the amount of organic chelating agent to the total amount of Ti and V in the ammonium paratungstate solution is 1.0~1.8:

1.

6. The preparation method according to claim 1, characterized in that, In step (2), the ratio of the amount of metal chelating agent to the total amount of Cr and Mo in the ammonium paratungstate solution is 0.5~1.2:

1.

7. The preparation method according to claim 1, characterized in that, In step (2), the mass of the polyquaternary ammonium salt accounts for 0.1% to 0.5% of the total mass of P and S in the ammonium paratungstate solution.

8. The preparation method according to claim 1, characterized in that, In step (2), the ratio of the amount of the second reducing agent to the total amount of Se and As in the ammonium paratungstate solution is 0.3~0.8:

1.

9. The preparation method according to claim 1, characterized in that, In step (2), the mass percentage of the ammonium salt in the ammonium paratungstate solution is 10-20% of the mass percentage of industrial ammonium paratungstate.

10. The preparation method according to claim 1, characterized in that, In step (2), the salting-out temperature is 25~30℃ and the salting-out time is 2~4h.