JP5368834B2 - Method for producing ammonium tungstate aqueous solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an ammonium tungstate aqueous solution extremely efficiently by using an anion exchange resin without precipitating salt even via a polytungstate ion. <P>SOLUTION: The method for producing the ammonium tungstate aqueous solution includes: a first step of producing an alkali metal polytungstate aqueous solution by adjusting the pH of an alkali metal tungstate aqueous solution to 3.5-8; a second step of adsorbing the polytungstate ion on the anion exchange resin by bringing the alkali metal polytungstate aqueous solution into contact with the anion exchange resin; a third step of recovering the liquid discharged at the second step; and a fourth step of decomposing the polytungstate ion to elute a tungstate ion by bringing ammonia water containing &ge;8 mol/L ammonia into contact with the polytungstate ion-adsorbed anion exchange resin. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for producing an aqueous solution of ammonium tungstate.

  Cemented carbide with tungsten carbide (WC) as the main component, cobalt (Co), nickel (Ni), etc. as the binding metal and Ti or Ta carbide added to improve the performance is hard and wear resistant. Therefore, it is widely used in various fields as cutting tools, wear-resistant tools, mining tools, etc. Currently, a large amount of scraps of used tools in various fields are generated, and their recycling is attracting attention.

Among them, tungsten is a rare resource and is contained in about 80% by mass in such a tool. Therefore, various methods for recovering tungsten from tool scrap have been proposed. For example, such a scrap is dissolved with sodium nitrate to obtain sodium tungstate (Na ₂ WO ₄ ) as a water-soluble salt and then converted to ammonium tungstate ((NH ₄ ) ₂ WO ₄ ). Finally, tungsten carbide is recovered.

  Ammonium tungstate is highly purified by crystallization from an aqueous solution. Tungsten carbide can be easily obtained by calcining, reducing, and carbonizing the crystal, and therefore, it is an important substance in the recycling process as described above.

  As a method for producing such an ammonium tungstate, for example, an aqueous solution of ammonium tungstate is obtained by contacting an aqueous solution of sodium tungstate with a Cl-type strongly basic anion exchange resin and then eluting with an aqueous solution containing ammonium chloride and ammonia. A manufacturing method has been proposed (Patent Document 1).

JP 2008-150251 A

Tungstate ion (WO ₄ ^2- ) is an anion exchange resin in an aqueous solution of the same concentration as compared with polytungstate ion (generally referred to as HW ₆ O ₂₁ ^5- in the present invention as described later). Since the through-flow capacity in the case of adsorption is low, various conditions during adsorption must be strictly controlled, and the exchange efficiency is low. Moreover, the tungstate ion is much more dependent on the solution concentration than the polytungstate ion, and the adsorbed amount up to the pour point is reduced at a high concentration exceeding 100 g / L, which is about 30 to 50 g / L. It was necessary to adsorb at a relatively low concentration. For this reason, when tungstate ions are adsorbed on an anion exchange resin and brought into contact with an eluent containing ammonium ions to obtain ammonium tungstate, there is a problem that the amount of water used becomes extremely large.

On the other hand, polytungstate ion has the advantage over the tungstate ion as described above, and also has an exchange group equivalent of anion exchange resin (mol number of tungsten that can be adsorbed to a predetermined number of exchange groups). 2.4 times the tungstate ions Comparatively (if poly tungstate ions of HW ₆ O ₂₁ ^5-, way in the case of H ₂ W ₁₂ O ₄₀ ^6- quadrupled) capable of adsorbing tungsten Therefore, it can be expected that the exchange efficiency by the anion exchange resin is greatly improved.

  However, after the polytungstate ion is adsorbed on the anion exchange resin and eluted with an eluent containing ammonium ion, there is a problem that a large amount of ammonium salt of the polytungstate ion precipitates. When such a salt (crystal) precipitates in the anion exchange resin tower (resin packed tower) filled with the anion exchange resin, the anion exchange resin and the tower are damaged or the inside of the tower is blocked (so-called so-called). Therefore, polytungstate ions are expected to have the above-mentioned various merits, but it is considered extremely difficult to obtain ammonium tungstate by anion exchange resin using them industrially. It was.

  The present invention has been made in view of the above situation, and the object of the present invention is to produce polytungsten in the production of an aqueous solution of ammonium tungstate from an aqueous solution of alkali metal tungstate using an anion exchange resin. An object of the present invention is to provide a method for producing an ammonium tungstate aqueous solution extremely efficiently without precipitation of a salt (crystal) despite passing through an acid ion.

The method for producing an aqueous solution of ammonium tungstate ((NH ₄ ) ₂ WO ₄ ) according to the present invention is a method for producing an aqueous solution of ammonium tungstate from an aqueous solution of alkali metal tungstate, wherein the pH of the aqueous solution of alkali metal tungstate is adjusted. The first step of producing an alkali metal tungstate metal salt aqueous solution by adjusting to 3.5 to 8, and contacting the polytungstate alkali metal salt aqueous solution with an anion exchange resin, The concentration is 8 mol / L (moles) with respect to the second step of adsorbing the anion exchange resin, the third step of collecting the effluent after the second step, and the anion exchange resin adsorbed with polytungstate ions. Polytongues by contacting ammonia water containing more than ammonia) To decompose the phosphate ions, and a fourth step of eluting the tungstate ions separated from the anion-exchange resin, characterized in that it comprises a.

  In the production method of the present invention, the effluent collected in the above three steps is repeatedly brought into contact with the anion exchange resin while maintaining the pH at 3.5 to 8 while adjusting the pH before performing the above fourth step. Thus, the polytungstate ion in the effluent can be adsorbed to the anion exchange resin.

Here, the production method of the present invention is the polytungstic acid obtained in the first step with respect to the anion exchange resin that has undergone the fourth step after the elution with the ammonia water in the fourth step. using an alkali metal salt aqueous solution, you shall further repeatedly performing the same operation as the second step - the fourth step in this order.

  In addition, after the elution with the ammonia water in the fourth step is finished, the production method of the present invention is after the anion exchange resin is brought into contact with the anion exchange resin after being brought into contact with the ammonia water. A fifth step of adsorbing polytungstate ions in the effluent to the anion exchange resin, a sixth step of recovering the effluent after the fifth step, and By contacting ammonia water containing ammonia having a concentration of 8 mol / L or more with the anion exchange resin on which polytungstate ions are adsorbed in 5 steps, polytungstate ions are decomposed to elute tungstate ions. The seventh step can be repeated one or more times in this order.

Moreover, the manufacturing method of this invention makes the mixed aqueous solution of ammonium chloride and ammonia contact the said anion exchange resin which passed through this final process after the final process in the manufacturing method in any one of said. Accordingly, it shall include an eighth step of eluting the tungstate ions.

  After the eighth step, the anion exchange resin becomes a Cl-type anion exchange resin, so the state returns to the state of the second step and the polytungstate ion is adsorbed on the anion exchange resin. The subsequent steps may be repeated as appropriate.

  The mixed aqueous solution preferably contains ammonia at a ratio of 0.25 to 5 mol with respect to 1 mol of ammonium chloride.

On the other hand, in the fourth step, the space velocity SV when the ammonia water is brought into contact with the anion exchange resin is preferably 7 hr ⁻¹ or more. In the fourth step, when the ammonia water is brought into contact with the anion exchange resin, the ammonia water is brought into contact with the anion exchange resin by supplying the ammonia water from a plurality of locations. Is preferred.

  The method for producing an aqueous solution of ammonium tungstate according to the present invention has the structure as described above, so that an alkali metal tungstate aqueous solution, that is, precipitation of a salt (crystal) despite passing through a polytungstate ion. It has the outstanding effect that an ammonium tungstate aqueous solution can be manufactured very efficiently without accompanying.

It is the graph which showed the tungsten concentration and elution rate at the time of implementing a 4th process and an 8th process. It is the graph which showed the relationship between the resin height in a resin packed tower, space velocity SV, and the presence or absence of crystal precipitation.

Hereinafter, the present invention will be described in more detail. For convenience, it will be described separately first reference aspect to third reference embodiment and the first embodiment as follows.

<First Reference Aspect>
The method for producing an aqueous solution of ammonium tungstate according to the present invention is a method for producing an aqueous solution of ammonium tungstate from an aqueous solution of alkali metal tungstate and adjusting the pH of the aqueous solution of alkali metal tungstate to 3.5-8. A first step of producing an aqueous alkali metal tungstate salt solution, and a second step of bringing the polytungstic alkali metal salt aqueous solution into contact with the anion exchange resin to adsorb the polytungstate ions to the anion exchange resin. Contacting ammonia water containing ammonia having a concentration of 8 mol / L or more with the step, the third step of collecting the effluent after the second step, and the anion exchange resin adsorbed with polytungstate ions Breaks polytungstate ions into tungstate ions It is characterized in that it comprises a fourth step of eluting the tungstate ions simultaneously when the. The production method of the present invention can include other optional steps as long as at least the first to fourth steps are included. Hereinafter, each step will be described.

<First step>
The first step of the present invention is a step of producing a polytungstic alkali metal salt aqueous solution by adjusting the pH of the alkali metal tungstate aqueous solution as a raw material to 3.5 to 8. In the aqueous solution of alkali metal tungstate salt, tungstate ions can exist stably in a region where the pH exceeds 8, but in the region where the pH is 8 or less, polytungstate ions are stabilized instead of tungstate ions. It becomes an existing area. The first step of the present invention utilizes this characteristic, and is a step of generating polytungstate ions from tungstate ions.

Here, the alkali metal tungstate aqueous solution is an aqueous solution of an alkali metal tungstate and any other ion as long as it contains at least alkali metal ions and tungstate ions (WO ₄ ²⁻ ) as main components. Or a compound may be contained. Examples of the alkali metal tungstate include sodium tungstate and potassium tungstate. Therefore, examples of the alkali metal ions that form the aqueous alkali metal tungstate salt include sodium ions (Na ⁺ ) and potassium ions (K ⁺ ). In addition, the kind of said metal is not restricted only to sodium or potassium.

  The concentration of tungsten contained in such an aqueous alkali metal tungstate salt salt is not particularly limited, but it is usually preferably about 10 to 140 g / L (gram / liter). When the amount is less than 10 g / L, the amount of water used for preparing the alkali metal tungstate aqueous solution becomes large. When the amount exceeds 140 g / L, the length of the resin packed column described later filled with an anion exchange resin is used. This is because it is necessary to lengthen the length, or crystals are precipitated. Such an aqueous alkali metal tungstate salt salt solution is assumed to be generated in a recycling process such as the above-mentioned tool, but is not limited to this, and is generated from a raw material ore containing tungsten. It can be a thing.

On the other hand, the polytungstic alkali metal salt aqueous solution is an aqueous solution of polytungstic alkali metal salt, and contains any other ions or compounds as long as it contains at least alkali metal ions and polytungstate ions as main components. It doesn't matter if it goes out. Examples of the polytungstic alkali metal salt include sodium polytungstate and potassium polytungstate. Therefore, examples of the alkali metal ions contained in the polytungstic alkali metal salt aqueous solution include sodium ions (Na ⁺ ) and potassium ions (K ⁺ ). In addition, the kind of said metal is not restricted only to sodium or potassium.

The “polytungstate ion” in the present invention means a polyacid ion containing tungsten (W), for example, HW ₆ O ₂₁ ⁵⁻ , H ₂ W ₁₂ O ₄₀ ⁶⁻ , W ₁₂ O ₄₁ ^10−. Etc. In such a polytungstate ion, HW ₆ O ₂₁ ⁵⁻ is normally present stably in the pH range of 6-8, and W ₁₂ O ₄₁ ¹⁰⁻ is stable in the pH range of 4-6. It exists, and when the pH is less than 4, H ₂ W ₁₂ O ₄₀ ⁶⁻ tends to exist stably. However, these ions may be included alone or two or more ions may be included. Also good.

  In addition, it is necessary to adjust the said pH to 3.5-8, More preferably, it is suitable to adjust to 6-7.5, More preferably, it adjusts to 6.75-7.25. It is preferable to do. If the pH exceeds 8, it is not preferable because tungstate ions exist stably. On the other hand, if the pH is less than 3.5, it is not preferable because the elution rate with respect to the amount of adsorption decreases in the step of eluting tungstate ions.

  Such pH can be adjusted with hydrochloric acid, nitric acid, sulfuric acid or the like, but is not limited to these compounds as long as it is an acid.

  In the first step of the present invention, when a sodium tungstate aqueous solution is used as the raw material alkali metal tungstate salt solution, a sodium polytungstate aqueous solution is produced by adjusting the pH.

<Second step>
The second step of the present invention is a step of adsorbing polytungstate ions to the anion exchange resin by bringing the aqueous solution of alkali metal tungstate metal salt produced in the first step into contact with the anion exchange resin. . Here, the anion exchange resin used in the present invention can be used without particular limitation as long as it is a conventionally known anion exchange resin. For example, a strong basic anion exchange resin, a weak basic anion exchange resin, etc. can be mentioned, OH type may be sufficient and Cl type may be sufficient. In particular, it is preferable to use a Cl-type strongly basic anion exchange resin because the ion exchange reaction does not affect the pH of the aqueous solution, is harmless, and has an appropriate adsorption order for the resin.

  Such anion exchange resins are generally called “gel type” and “porous type”, but the adsorbed polytungstate ion has a larger molecular weight than tungstate ion. Thus, when a “gel-type” anion exchange resin is used, it tends to be adsorbed only on the surface portion of the resin and difficult to penetrate into the resin. For this reason, in view of adsorption efficiency, it is preferable to use a “porous” anion exchange resin.

  In the second step, an aqueous polytungstate alkali metal salt solution is usually passed through a column packed with an anion exchange resin or a packed tower (hereinafter referred to as “resin packed tower”). Thus, the polytungstic alkali metal salt aqueous solution can be brought into contact with the anion exchange resin. In this case, the resin packed tower may be a single (that is, a single tower) or may be a series of two or more resin packed towers. Moreover, such a resin packed tower can usually be obtained by filling a tube (column) having an inner diameter of 2 to 500 cm with an anion exchange resin at a height (length) of 15 to 1000 cm.

  In the second step of the present invention, after the liquid is passed through the resin packed tower, the liquid that has passed through the resin packed tower is recovered, and the recovered liquid is again passed through the resin packed tower. You may perform operation which repeats operation of carrying out once or twice or more. Of course, it is needless to say that such a mode that does not involve an operation of passing the collected liquid again is included.

Further, the speed at which the aqueous solution of alkali metal tungstate is passed through the anion exchange resin is not particularly limited, but it is preferably supplied at a space velocity SV of 0.5 to 10 hr ⁻¹ . It is more preferable to supply at 8 to 5 hr ⁻¹ .

<Third step>
The third step of the present invention is a step of collecting the effluent that has passed through the second step. Here, the effluent having passed through the second step is a solution after the aqueous solution of alkali metal tungstate metal salt passed through the resin packed tower filled with the anion exchange resin passes through the resin packed tower, It contains polytungstate ions that remain without being adsorbed on the anion exchange resin. In the second step, when the operation of allowing the recovered liquid to flow again is performed, the liquid that finally passed through the resin packed tower after a plurality of times of passing the liquid becomes the effluent. Hereinafter, unless otherwise specified, the effluent in other steps is also used in the same meaning. For example, when a Cl-type anion exchange resin is used as an anion exchange resin, an effluent containing Cl 2 ⁻ ions is recovered at the time of the first flow, but this is particularly affected in the adsorption by polytungstate ions. No.

  Therefore, by collecting such effluent, the polytungstate ion can be more efficiently adsorbed to the anion exchange resin by bringing the effluent into contact with the anion exchange resin again in a later step. Is possible.

In this invention, after adjusting pH with respect to such an effluent, it can be used for the following process. Such pH adjustment can be performed using the same compound as that used in the first step, and is preferably adjusted to pH 3.5 to 8, preferably around pH 7. In the present invention, various effluents are used in each of the reference embodiments described later, and the pH can be adjusted in the same manner as described herein for these effluents.

  In the present invention, after the second step is completed, the anion exchange resin may be washed by passing pure water through the resin packed tower. The solution that flows out by the washing operation is also included in the effluent that has passed through the second step.

<4th process>
In the fourth step of the present invention, polytungstate ions are decomposed by bringing ammonia water containing ammonia having a concentration of 8 mol / L or more into contact with an anion exchange resin on which polytungstate ions are adsorbed. This is a step of eluting acid ions. Therefore, since the solution that has undergone the fourth step contains ammonium ions (NH ₄ ⁺ ) and decomposed tungstate ions (WO ₄ ²⁻ ) contained in the aqueous ammonia, this solution must be recovered. That is, an aqueous solution of ammonium tungstate ((NH ₄ ) ₂ WO ₄ ) is produced. A part of the decomposed tungstate ion (WO ₄ ²⁻ ) is adsorbed on the anion exchange resin. In the present invention, “ammonium tungstate aqueous solution” may contain any other ion or compound as long as it contains at least ammonium ion (NH ₄ ⁺ ) and tungstate ion (WO ₄ ²⁻ ) as main components. There is no problem.

  In the fourth step, ammonia water is passed through the resin-filled tower in which the anion exchange resin has adsorbed polytungstate ions through the second step, so that the ammonia water is removed from the anion. It comes into contact with the exchange resin.

  In the present invention, unless otherwise specified, the operation of bringing the liquid into contact with the anion exchange resin is performed by passing the liquid through the resin packed tower in this way.

  Here, the ammonia water brought into contact with the anion exchange resin to which the polytungstate ion is adsorbed needs to contain ammonia having a concentration of 8 mol / L or more. This provides a pH environment where tungstate ions can exist more stably than polytungstate ions, and allows tungstate ions to elute at the same time as polytungstate ions are decomposed into tungstate ions. It is said.

  Such aqueous ammonia preferably contains 10 mol / L or more of ammonia. When the ammonia concentration of ammonia water is less than 8 mol / L, it is not possible to sufficiently provide a pH environment in which tungstate ions can exist stably, and tungstate ions cannot be stably eluted. Crystals of ammonium polytungstate will be precipitated. The upper limit is not particularly limited, but it is preferably 20 mol / L or less because it is difficult to use due to high vapor pressure of ammonia at room temperature and high volatility.

Further, in the fourth step, the space velocity SV at the time of contacting the aqueous ammonia to the anion exchange resin is preferably 7Hr ^-1 or more, more preferably -8 hr ^-1 or more, 10 hr ^- More preferably, it is ¹ or more. When the space velocity SV is less than 7 hr ^{−1, a} pH environment in which tungstate ions can stably exist cannot be sufficiently provided, and crystals of ammonium polytungstate may be generated. Moreover, the upper limit is not particularly limited, but if the flow rate becomes too high, the concentration of the recovered ammonium tungstate aqueous solution is lowered, so that it is preferably 20 hr ⁻¹ or less.

  In the fourth step, the ammonia water flow rate is preferably 0.3 to 3 times the volume of the anion exchange resin. If it is less than 0.3 times, elution may be incomplete, and if it exceeds 3 times, ammonia water that does not participate in the elution is added to the eluent, and the tungsten concentration in the eluent may decrease.

  In the fourth step, when the ammonia water is brought into contact with the anion exchange resin, the ammonia water is brought into contact with the anion exchange resin by supplying the ammonia water from a plurality of locations. It is preferable. In the present invention, the anion exchange resin is usually in the form of a resin packed tower packed in a column or tower, and various solutions are passed through the resin packed tower. Is preferably supplied to the resin packed tower from a plurality of locations.

  More specifically, in the case where only one such resin packed tower is provided, a plurality of supply ports are provided at some intervals in the height (length) direction of the resin packed tower. Ammonia water can be supplied from the supply port. In addition, when a plurality of the resin packed towers are connected and provided, a plurality of supply ports as described above can be provided in each resin packed tower. An embodiment in which such a supply port is provided in the middle of a pipe connecting to another resin packed tower and ammonia water is supplied from a plurality of supply ports as a result.

  By supplying ammonia water from a plurality of locations in this way, polytungstate ions adsorbed on the anion exchange resin can be uniformly decomposed into tungstate ions without local bias, which is extremely efficient. Tungstate ions can be eluted.

  In the present invention, after the fourth step is completed, an operation of washing the anion exchange resin may be performed by passing pure water through the resin packed tower.

<Second Reference Mode>
In the method for producing an ammonium tungstate aqueous solution of the present invention, the same operation as in the second step to the fourth step is further performed on the anion exchange resin that has passed the fourth step after the fourth step. It shall be performed repeatedly in the order. That is, in the second reference embodiment, the n-th second step is performed on the anion exchange resin that has undergone the (n-1) -th fourth step.

  In this case, the polytungstic alkali metal salt aqueous solution used in the second and subsequent second steps uses the one produced in the first step, but the aqueous solution may be produced independently each time, It is also possible to manufacture a batch of batches and use them separately.

As described above, in the second reference embodiment of the present invention, after elution with the ammonia water in the fourth step is completed, the aqueous solution of the alkali metal tungstate metal salt is again brought into contact with the anion exchange resin. An aqueous ammonium acid solution can be produced. Above the time of completion of the elution with aqueous ammonia in the fourth step, the anion exchange resin, (in the case of Cl type anion exchange resin Cl ^- ions) which is attached to the initial state anion instead, tungstate ion (WO ₄ ²⁻ ) is adsorbed. That is, this second reference embodiment uses the property that polytungstate ions are adsorbed on the anion exchange resin in preference to the tungstate ions, so that they are once adsorbed on the anion exchange resin after elution. The tungstate ion is efficiently re-eluted by the polytungstate ion, thereby further improving the production efficiency of the ammonium tungstate aqueous solution. Thereby, tungstate ions are eluted by the adsorption of polytungstate ions, and the effluent contains tungstate ions and polytungstate ions. When adsorbing the effluent again on the anion exchange resin, it is necessary to adjust the pH of the effluent to convert the tungstate ion to polytungstic acid.

Also according to the second reference aspect of the present invention, an ammonium tungstate aqueous solution can be efficiently produced without salt precipitation.

  A cleaning operation with pure water can be performed between each step and the next step, if necessary.

<Third Reference Mode>
In the method for producing an ammonium tungstate aqueous solution of the present invention, after the fourth step, the effluent is brought into contact with the anion exchange resin after being brought into contact with the aqueous ammonia. A fifth step of adsorbing the polytungstate ion to the anion exchange resin, a sixth step of recovering the effluent after the fifth step, and anion exchange in which the polytungstate ion is adsorbed by the fifth step Repeating in this order the seventh step of decomposing polytungstate ions and eluting tungstate ions by contacting ammonia water containing ammonia with a concentration of 8 mol / L or more to the resin. It can be.

  Here, the fifth step is the same operation as the second step except that the effluent is used instead of the polytungstic alkali metal salt aqueous solution produced in the first step. The effluent used in the fifth step not only means the effluent collected in the third step, but also means the effluent collected in the next sixth step. That is, when the fifth step to the seventh step are performed only once, the effluent in the fifth step means the effluent collected in the third step, but the fifth step to the seventh step are performed. In the case of repeating twice or more, the first fifth step uses the effluent collected in the third step, but the fifth and subsequent fifth steps (represented as the nth for convenience) are sequentially (n-1). This means that the effluent collected in the sixth step is used.

  That is, when the fifth to seventh steps are repeated n times, the nth fifth step is an anion exchange after the (n-1) th seventh step and the (n-1) th seventh step. In this step, the effluent collected in the (n-1) th sixth step is brought into contact with the resin. Subsequently, the nth sixth step and the nth seventh step are performed.

  On the other hand, the sixth step is a step of collecting the effluent that has passed through the fifth step, which is the previous step, and is the same operation as the third step. In other words, the effluent here includes a solution that flows out by such a cleaning operation when a cleaning operation with pure water is performed after the fifth step.

  In the seventh step, the polytungstate ions are brought into contact with the anion exchange resin adsorbed with the polytungstate ions in the fifth step by contacting ammonia water containing ammonia having a concentration of 8 mol / L or more. Although it is a step of decomposing and eluting tungstate ions, it is the same operation as in the fourth step, and the same conditions as in the fourth step are adopted for each condition.

Thus, the 3rd reference aspect with respect to this invention can manufacture ammonium tungstate aqueous solution more efficiently by making polyan tungstate ion in an effluent adsorb | suck to an anion exchange resin again. Above the time of completion of the elution with aqueous ammonia in the fourth step, the anion exchange resin, (in the case of Cl type anion exchange resin Cl ^- ions) which is attached to the initial state anion instead, tungstate ion (WO ₄ ²⁻ ) is adsorbed. That is, this third reference embodiment utilizes the property that polytungstate ions are adsorbed on anion exchange resins in preference to tungstate ions, and once adsorbed on anion exchange resins, they are adsorbed again. Thus, the tungstate ion is efficiently re-eluted by the polytungstate ion, thereby further improving the production efficiency of the ammonium tungstate aqueous solution.

  Thereby, tungstate ions are eluted by the adsorption of polytungstate ions, and the effluent contains tungstate ions and polytungstate ions. When adsorbing the effluent again on the anion exchange resin, it is necessary to adjust the pH of the effluent to convert the tungstate ion to polytungstic acid.

<First embodiment>
The method for producing an ammonium tungstate aqueous solution of the present invention is the above- mentioned negative reference after the second reference embodiment, after the final step in the production method according to any of the second reference embodiment and the third reference embodiment, and after the final step. to the ion-exchange resin, by contacting the mixed aqueous solution of ammonium chloride and ammonia, it shall include an eighth step of eluting the tungstate ions.

Here, the final process of each reference aspect means the next process. That is, the final step in the first reference aspect means the fourth step. In addition, the final step in the third reference mode means the seventh step, and when the seventh step is performed twice or more, it means the seventh step that is finally performed. In addition, the final step in the second reference aspect means the fourth step that is finally performed among the fourth steps that are performed a plurality of times.

  As described above, after the final step, the mixed aqueous solution of ammonium chloride and ammonia is brought into contact with the anion exchange resin that has passed through the final step, so that tungstate ions can be more efficiently removed from the anion exchange resin. Can be eluted. This mechanism is considered as follows.

That is, in the final step of the first reference aspect to third reference embodiment of the above, tungstate ions efficiently eluted. However, the tungstate ion once eluted from the anion exchange resin may be adsorbed on the anion exchange resin again. Since tungstate ions tend to be adsorbed on anion exchange resins in preference to OH ⁻ contained in ammonia water, it is difficult to elute tungstate ions adsorbed on anion exchange resins with OH ⁻ . It is expected that the tungstate ion (WO ₄ ²⁻ ) is adsorbed on the anion exchange resin. Therefore, a mixed aqueous solution of ammonium chloride and ammonia containing chlorine ions (Cl ⁻ ), which has a tendency to adsorb to the anion exchange resin in preference to the tungstate ion, is brought into contact with the anion exchange resin after the final step. Then, it becomes possible to more efficiently elute tungstate ions adsorbed on the anion exchange resin by the action of chlorine ions while providing a pH range for stabilizing tungstate ions. In this case, the polytungstate ion remaining and adsorbed on the anion exchange resin may decompose and elute the tungstate ion, but in any case, it deviates from the scope of the present invention. is not.

  Here, the mixed aqueous solution of ammonium chloride and ammonia preferably contains ammonia in a ratio of 0.25 to 5 mol with respect to 1 mol of ammonium chloride. More preferably, it is preferable to contain ammonia in a ratio of 0.25 to 3 mol with respect to 1 mol of ammonium chloride. Thereby, the tungstate ions adsorbed on the anion exchange resin as described above can be eluted more efficiently. In the above ratio, if the ammonia is less than 0.25 mol, crystals of ammonium tungstate may be precipitated, and if it exceeds 5 mol, there is no change in the elution behavior and the consumption of ammonia may increase.

  In addition, it is preferable that the density | concentration of ammonium chloride in such mixed aqueous solution shall be 1.0-4.7 mol / L. When the concentration is less than 1.0 mol / L, the concentration of the ammonium tungstate aqueous solution recovered in the elution process may decrease. When the concentration exceeds 4.7 mol / L, it takes time to dissolve ammonium chloride, and the temperature decreases. May precipitate.

  In the eighth step, the amount of the mixed aqueous solution of ammonium chloride and ammonia is preferably 0.2 to 2 times the volume of the anion exchange resin. If it is less than 0.2 times, the amount of liquid flow is small, and elution of tungsten may be incomplete. If it exceeds 2 times, ammonia water that does not participate in the elution is added to the eluent, and the tungsten concentration in the eluent is reduced. May decrease.

Such 8th process is a process of producing | generating ammonium tungstate aqueous solution similarly to each final process of said 1st reference aspect-3rd reference aspect. The anion exchange resin subjected to the eighth step is a Cl type anion exchange resin. In the present invention, after the eighth step is completed, an operation of washing the anion exchange resin may be performed by passing pure water through the resin packed tower.

Hereinafter, although a reference example is given and this invention is demonstrated in detail, this invention is not limited to these. In the following preliminary experiments and reference examples , the alkali metal tungstate and the alkali metal polytungstate were those containing sodium tungstate and sodium polytungstate as main components, respectively.

<Preliminary experiment>
Experiments related to the first to third steps of the present invention were conducted.

  That is, a sodium polytungstate aqueous solution was produced (first step), and an experiment was carried out to adsorb it onto a Cl-type strongly basic anion exchange resin. Table 1 below shows the adsorption conditions (that is, the conditions of the second step and the third step).

  In Table 1, the notation “up to the pour point” in the column of “pour method” indicates a method of passing the liquid to the pour point (that is, a method of supplying an aqueous solution of sodium tungstate to the anion exchange resin up to the pour point) When the effluent containing polytungstate ions passed through the pour-through point was collected and subsequently supplied again to the anion exchange resin, it was indicated as “circulation”. More specific description will be given below.

First, the pH was adjusted to 3 to 9 by adding hydrochloric acid to a sodium tungstate aqueous solution having a pH of 9 or more. "PH" described in Table 1 is the pH after the adjustment. Further, the “concentration” (see Table 1) of the aqueous sodium polytungstate solution after pH adjustment is 70 to 140 g-WO ₃ / L-Resin (70 to 140 g per liter of anion exchange resin in terms of WO ₃ ). The concentration was adjusted as described above (first step).

Next, each prepared sodium polytungstate aqueous solution by adjusting the pH and concentration was added to a Cl-type strongly basic anion exchange resin (trade name: IRA900J, manufactured by Rohm Anhud Haas, unless otherwise specified) The same as in the reference example ) was passed through a resin packed tower (a glass column having an inner diameter of 26 mm and 350 ml of the anion exchange resin) packed in a glass column. In the case of “circulation”, the space velocity SV was 6 hr ^−1, and in the case of “up to the flow through point”, the space velocity SV was 2 hr ⁻¹ .

In addition, in the case of “up to the flow-through point”, the flow rate is up to the point where the polytungstate ion concentration contained in the effluent becomes 100 mg / L or more in terms of WO ₃ . I did it. That is, in the case of pH 3 and 3.5, a solution containing 450 g of W in terms of WO ₃ per liter of anion exchange resin was passed, and in the case of pH 6 to 9, 280 g of W in terms of WO ₃ per liter of anion exchange resin. The solution containing was passed through. In the second and subsequent cycles of “circulation”, the recovered effluent was again passed at the same speed.

Table 1 below shows the amount of polytungstate ion adsorbed on the anion exchange resin after performing the first to third steps under the above conditions. The unit of “adsorption amount” (g-WO ₃ / L-Resin) in Table 1 indicates the number of g adsorbed per liter of anion exchange resin in terms of WO ₃ .

  As apparent from Table 1 below, the test condition No. The test was carried out under 10 conditions of 1-10. As a result, in the case of pH 3.5 to 8, it was found that the adsorption by “circulation” is higher than the adsorption to “through point”, and the adsorption amount to the anion exchange resin is high.

  Further, it was found that when the “concentration” of the sodium polytungstate aqueous solution was increased, the adsorption by “circulation” was more efficient than the adsorption “to the flow-through point” (test conditions No. 4, 5, From comparison with test conditions No. 8 and 9).

  Furthermore, regarding “pH” in the first step, when tungstate ions are more stable than polytungstate ions when the pH is 9 or more, the pH is 9 or more compared to when the pH is 8 or less. Was found to significantly reduce the amount of tungsten adsorbed on the anion exchange resin (from comparison between test conditions No. 6 and 7 and test conditions No. 8 and 10). That is, it is preferable to set the pH in the first step to 3.5 to 8.

< Reference Example 1>
Experiments were conducted on the first reference embodiment and the eighth step of the present invention. That is, a sodium polytungstate aqueous solution produced by adjusting pH from a sodium tungstate aqueous solution is adsorbed on a Cl-type strongly basic anion exchange resin, and then an eluent containing ammonium ions is passed through to obtain an ammonium tungstate aqueous solution. The test which manufactures was conducted.

First, a sodium polytungstate aqueous solution was prepared by adding hydrochloric acid to a sodium tungstate aqueous solution having a pH of 9 or more to adjust the pH to 3 to 8 (see the “pH” column in Table 2). . The concentration of the aqueous sodium polytungstate solution was adjusted so that the “concentration” after pH adjustment was 70 g-WO ₃ / L-Resin (70 g per liter of anion exchange resin in terms of WO ₃ ) ( First step).

Next, each of the prepared sodium polytungstate aqueous solutions by adjusting the pH and concentration as described above was packed into a resin packed tower in which a glass column was packed with a Cl-type strongly basic anion exchange resin (into a glass column with an inner diameter of 26 mm). The anion exchange resin was filled in 350 ml). This liquid flow was performed until the space velocity SV was 6 hr ⁻¹ and saturated adsorption was performed. In addition, it was set as saturated adsorption when the tungsten concentration of the effluent that passed through the resin packed tower became the same as the tungsten concentration in the sodium tungstate aqueous solution prepared in the first step. Thus, the polytungstate ion was adsorbed to the anion exchange resin by bringing the aqueous sodium polytungstate solution into contact with the anion exchange resin, and the effluent that passed through the resin packed tower was recovered (second step). , Third step).

Next, for the anion exchange resin on which polytungstate ions are adsorbed as described above, ammonia water (“NH” in the “Composition” column) under the conditions described in the “Fourth Step” column of Table 2 below. The concentration indicated in “ ₄ OH” indicates the concentration of ammonia), and the polytungstate ion was decomposed to elute the tungstate ion (fourth step).

Subsequently, in Table 2, the following eighth step was performed for those whose conditions are described in the column of the eighth step. That is, after the fourth step, ammonium chloride and ammonia (in the present invention, “NH” in the condition of the “eighth step” in Table 2 for the anion exchange resin that has undergone the fourth step. ₄ OH + NH ₄ Cl ”and a mixed aqueous solution (the concentration written in“ NH ₄ OH ”in the“ Composition ”column indicates the concentration of ammonia, and the concentration written in“ NH ₄ Cl ”is Further, tungstate ions were eluted by contacting with (indicating ammonium chloride concentration) (eighth step).

FIG. 1 shows an elution operation for performing the eighth step following the fourth step. In FIG. 1, the solid line indicates the elution rate, and the dotted line indicates the tungsten concentration (converted to “WO ₃ ”). The tungsten concentration is the concentration in the eluent after passing through the resin packed tower. In FIG. 1, the left peak indicated by the dotted line indicates the fourth step, the right peak indicates the eighth step, and the flow from the fourth step to the eighth step is around 700 ml. There are points.

  In the fourth step, the ammonia water is passed through 3 times the volume of the anion exchange resin, and in the eighth step, the mixed aqueous solution of ammonium chloride and ammonia is passed 1.5 times the volume of the anion exchange resin. Liquid.

  As a comparative experiment, instead of the fourth step and the eighth step, an experiment was performed in which elution was performed only with a mixed aqueous solution of ammonium chloride (or ammonium sulfate) and ammonia. In Table 2, the elution operation in this comparative experiment is described in the column of “4th step” for convenience.

As described above, the test condition No. 116 is a reference example of the first reference embodiment for the present invention. 102,103,105～109 is reference example was carried out an eighth step after the first reference aspect for the present invention. In contrast, test condition No. Reference numerals 101, 104, and 110 to 115 are comparative examples with respect to the reference example . The details of the comparative example are as follows.

  Test condition No. 101 is a pH of 3 in the first step. In addition, test condition No. No. 104 is an ammonia concentration in the fourth step of 6 mol / L. Test condition No. 110 to 115 relate to comparative experiments in which elution was performed only with a mixed aqueous solution of ammonium chloride (or ammonium sulfate) and ammonia as described above.

  Each test condition No. For each elution operation (steps 4 and 8), the presence or absence of crystal precipitation in the resin packed column and the elution rate (ratio of the amount of tungsten eluted to the amount of tungsten adsorbed on the anion exchange resin) Is shown in Table 2 below. The elution rate was determined by the difference between the total amount of tungsten adsorbed on the resin and the total amount of tungsten eluted. The elution rate could not be determined for the crystals precipitated.

  As apparent from the results in Table 2, test conditions No. 1 and No. 4 in which the elution operation was performed as the fourth step and the eighth step. 102, 103, 105-109 are test conditions No. Compared to 110-115, it was possible to elute tungstate ions efficiently without precipitating crystals in the resin packed tower.

  On the other hand, test condition No. No. 101 showed that since the pH in the first step was 3, the elution rate was low and it was difficult to completely elute. Therefore, it is shown that the lower limit of pH adjustment in the first step needs to be 3.5 or more. In addition, test condition No. In 104, since the ammonia concentration in the fourth step was 6 mol / L, crystals were precipitated after the fourth step. For this reason, it is shown that the ammonia concentration in the fourth step needs to be 8 mol / L or more.

  On the other hand, test condition No. It was confirmed that No. 116 can elute tungstate ions without precipitating crystals, although the elution rate is low.

< Reference Example 2>
Experiments were conducted on the first reference embodiment of the present invention, and the relationship between the resin height in the resin packed tower and the space velocity SV was confirmed.

  The resin height in the resin packed tower and the space velocity SV are changed variously, and the first step to the fourth step are performed under the following conditions, so that the polytungstic sodium aqueous solution is converted into a Cl-type strongly basic anion exchange resin. After the effluent at that time was recovered, ammonia water was passed through to elute tungstate ions, and the eluate was recovered.

  As the resin packed tower, a glass column having an inner diameter of 26 mm was used, and the anion exchange resin was packed so as to have a “resin height” described in Table 3 below. Each glass column was 10 cm longer than the packed “resin height”, and was adjusted so that the distance between the upper end of the glass column and the upper end of the resin-filled portion was 7 cm.

Then, an aqueous solution of sodium polytungstate adjusted to pH 6 (concentration: 70 g-WO ₃ / L-Resin) was passed through each resin packed tower adjusted as described above. The conditions for passing liquid were adjusted so that the space velocity SV was 6 hr ⁻¹ with respect to the resin capacity of each resin packed column, and the liquid was passed until saturated adsorption was performed as in Reference Example 1. Thereby, the polytungstate ion was made to adsorb | suck to the said anion exchange resin (1st process-3rd process).

  Subsequently, with respect to the anion exchange resin on which the polytungstate ion is adsorbed, ammonia water containing 16 mol / L of ammonia is used at a space velocity described in Table 3 (see the column of “4th step space velocity SV”). By passing the solution, ammonia water was brought into contact with the anion exchange resin to decompose polytungstate ions and elute tungstate ions (fourth step).

  The results are shown in Table 3 and FIG. FIG. 2 shows the relationship between “presence / absence of crystal precipitation in resin packed tower” and “presence / absence of crystal precipitation in liquid feeding pipe”, “resin height” and “space velocity SV” shown in Table 3. It is a graph so that becomes clear.

As apparent from Table 3 and FIG. 2, when the resin height in the resin packed tower is 100 cm or more and 400 cm or less, the space velocity SV when the aqueous ammonia is brought into contact with the anion exchange resin in the fourth step is 7 hr. ^When it was set to ⁻¹ or more, it was confirmed that no crystals were precipitated in the resin packed tower or in the liquid feeding pipe.

In addition, since the resin height of 100 cm or more and 400 cm or less is a standard resin height when the ion exchange resin is used for industrial applications, a space velocity SV of 7 hr ⁻¹ or more is particularly suitable for industrial applications. This is a numerical range. For laboratory applications where the resin height is less than 100 cm, even if ammonia water is contacted at a space velocity SV of less than 7 hr ⁻¹ , crystal precipitation is prevented as long as the ammonia concentration is 8 mol / L or more. can do.

< Reference Example 3>
In carrying out the eighth step of the present invention, when ammonia water is brought into contact with the anion exchange resin in the fourth step, the ammonia water is supplied to the anion exchange resin from a plurality of locations. It was confirmed that it was effective to make the contact.

  Specifically, first, the following resin packed tower was prepared. That is, in the resin packed tower, a liquid supply port (hereinafter referred to as “first supply port”) is provided at the top of the resin packed tower so that liquid can flow downward from the upper part of the resin packed tower in the same manner as a normal one. And a liquid feeding tube is inserted from the outside of the resin packed tower so that the liquid can be supplied also from a portion half as high as the portion filled with the anion exchange resin. The tip of the liquid feeding tube (hereinafter referred to as “second supply port”) was set at a height of 1/2 of that. That is, the resin packed tower has a structure that allows liquid to flow from two places, the first supply port and the second supply port. In the resin packed tower, a glass column (inner diameter 26 mmφ) was packed with a Cl-type strongly basic anion exchange resin so that the resin height was 100 cm.

Then, by adding hydrochloric acid to a sodium tungstate aqueous solution having a pH of 9 or more, a sodium polytungstate aqueous solution (70 g-WO ₃ / L-Resin) adjusted to pH 6 is passed through the first supply port. Thus, the polytungstate ion was adsorbed to the Cl-type strongly basic anion exchange resin and the effluent was collected (first to third steps). In addition, this liquid flow was made into the space velocity SV of 6 hr <-1> with respect to the resin capacity | capacitance of the said resin packed column, and it was made to flow through until saturated adsorption was carried out similarly to the reference example 1.

  Next, ammonia water was passed through the anion exchange resin on which the polytungstate ions were adsorbed in accordance with the conditions of the fourth step in Table 4 to decompose the polytungstate ions and elute the tungstate ions (first step). 4 steps). In Table 4, “Ammonia water concentration” indicates the concentration of ammonia contained therein. “First supply port” and “second supply port” indicate the first supply port and the second supply port of the resin packed tower, respectively, from which ammonia water was allowed to flow at the space velocity SV described in Table 4. Is shown. When the “second supply port” is blank, it means that ammonia water was passed through only the first supply port.

  Then, the 8th process was implemented according to the conditions of Table 4. In this eighth step, tungstate ions were eluted by passing a mixed aqueous solution of ammonium chloride and ammonia through only the first supply port with respect to the anion exchange resin having undergone the fourth step. .

  Then, the presence or absence of crystal precipitation in the resin packed tower and the elution rate were confirmed. The results are shown in Table 4.

  As is apparent from the results in Table 4, when ammonia water is supplied only from the first supply port in the fourth step, the first supply port can be used even under conditions where crystals are precipitated in the resin packed tower. It was confirmed that precipitation of crystals can be prevented by supplying ammonia water to the anion exchange resin from a plurality of locations such as the second supply port and contacting the ammonia water.

  A resin having a resin height of 100 cm as described above may be used in industrial applications. However, when the resin height becomes high, the space velocity SV of ammonia water supply is also important. It becomes a big factor. When the resin height of the resin packed tower is high and the space velocity SV of the ammonia water supply is low in this way, as is apparent from the above results, the ammonia water is hidden in the fourth step. When contacting the ion exchange resin, it is effective to supply ammonia water to the anion exchange resin from a plurality of locations.

< Reference Example 4>
The following test conditions No. Experiments 401 to 404 were conducted. In common with each test condition, as the resin packed tower, a glass column having an inner diameter of 26 mm packed with 350 ml of Cl-type strongly basic anion exchange resin was used.

First, test condition no. 401 is as follows.
That is, an aqueous solution of sodium polytungstate (70 g-WO ₃ / L-Resin) adjusted to pH 7 by adding hydrochloric acid to an aqueous solution of sodium tungstate having a pH of 9 or more was passed through the resin packed tower. The liquid was passed at a space velocity SV of 6 hr ⁻¹ with respect to the resin capacity of the resin packed tower (first step to second step).

  On the other hand, the effluent that passed through the resin packed tower was recovered (third step), and the pH of the effluent was adjusted to 7 with hydrochloric acid. Then, the effluent was again passed through the resin packed tower (the space velocity SV was the same as above). As a result, an anion exchange resin having adsorbed polytungstate ions was obtained. At this time, the tungsten concentration was measured by analyzing the effluent that passed through the resin packed tower by emission spectroscopy (ICP) (hereinafter referred to as “tungsten concentration A”).

Next, the polytungstate ion is decomposed by passing ammonia water containing 16 mol / L ammonia to the anion exchange resin adsorbed with the polytungstate ion at a space velocity SV of 5 hr ^−1. Then, tungstate ions were eluted (fourth step). At this time, the tungsten concentration was measured by analyzing the effluent that passed through the resin packed tower by the same emission spectroscopic analysis (ICP) as described above (hereinafter referred to as “tungsten concentration B”).

Next, the effluent whose “tungsten concentration A” was measured was passed through the anion exchange resin having undergone the fourth step at a space velocity SV of 6 hr ⁻¹ , and polytungstate ions remaining in the effluent Was adsorbed on an anion exchange resin. Then, the effluent that has passed through the resin packed tower is recovered, the pH of the effluent is adjusted to 7 with hydrochloric acid, and then the effluent is analyzed by emission spectroscopy (ICP) to measure the tungsten concentration. (Hereinafter referred to as “tungsten concentration C”).

Subsequently, the polytungstate ion is decomposed by passing ammonia water containing 16 mol / L of ammonia to the anion exchange resin on which the polytungstate ion is adsorbed at a space velocity SV of 5 hr ^−1. Then, tungstate ions were eluted (fourth step). At this time, the tungsten concentration was measured (hereinafter referred to as “tungsten concentration D”) by analyzing the effluent that passed through the resin packed tower by the same emission spectroscopic analysis (ICP) as described above.

In this way, the total amount of tungsten adsorbed on the ion exchange resin and the ion species of tungsten adsorbed on the resin, calculated from the above “tungsten concentration C” and the tungsten concentration of the solution prepared in the first step, are expressed as W ₁₂ O. ₄₁ Assuming ^10- , the adsorption rate (%) of tungsten was determined from the difference in the amount of tungsten adsorbable calculated from the exchange capacity of the ion exchange resin. Further, the elution rate (%) of tungsten was obtained from the difference between the total amount of eluted tungsten calculated from the “tungsten concentration B” and the total amount of adsorbed tungsten. These results are shown in Table 5.

On the other hand, test condition No. No. 402 is a test condition no. Except that the concentration (70 g-WO ₃ / L-Resin) of the sodium polytungstate aqueous solution in 401 is set to “140 g-WO ₃ / L-Resin”, all other conditions are the same as in test conditions No. Similar to 401, the adsorption rate and elution rate of tungsten were determined. The results are shown in Table 5.

  In addition, test condition No. 403 is a test condition No. 403. Except for adjusting pH 7 of the effluent in pH 401 to pH 6.5, all others were tested under Test Condition No. Similar to 401, the adsorption rate and elution rate of tungsten were determined. The results are shown in Table 5.

  In addition, test condition No. No. 404 is a test condition no. Except for adjusting pH 7 of the effluent in pH 401 to pH 7.5, all others were tested under Test Condition No. Similar to 401, the adsorption rate and elution rate of tungsten were determined. The results are shown in Table 5.

  As is apparent from Table 5, the test condition No. 401 and no. For 402, high values were obtained in both the adsorption rate and the elution rate. On the other hand, the test condition No. 1 in which the pH was adjusted to 6.5. No. 403 has a high adsorption rate but a low elution rate, and test conditions No. 403 in which the pH was adjusted to 7.5. In 404, although the elution rate was high, the adsorption rate was low.

  Therefore, it was confirmed that ammonium tungstate can be efficiently produced using a wide range of sodium polytungstate aqueous solutions as raw materials by carrying out cyclic adsorption while maintaining the pH at around 7.

Although the embodiments and reference examples of the present invention have been described above, the configurations of the above-described embodiments, reference aspects, and reference examples can be combined as appropriate.

This disclosed embodiments, it is to be understood that not restrictive manner illustrative in terms of all. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims (6)

A method for producing an ammonium tungstate aqueous solution for producing an ammonium tungstate aqueous solution from an alkali metal tungstate salt aqueous solution,
A first step of producing a polytungstic alkali metal salt aqueous solution by adjusting the pH of the alkali metal tungstate aqueous solution to 3.5 to 8, and
A second step of adsorbing the polytungstate ion to the anion exchange resin by contacting the aqueous solution of the alkali metal tungstate metal salt with the anion exchange resin;
A third step of collecting the effluent after the second step;
By contacting ammonia water containing ammonia having a concentration of 8 mol / L or more with the anion exchange resin on which the polytungstate ions are adsorbed, the polytungstate ions are decomposed to elute the tungstate ions. A fourth step;
After finishing the elution with ammonia water in the fourth step,
Using the aqueous solution of alkali metal tungstate obtained in the first step, the same operation as in the second to fourth steps is further performed on the anion exchange resin that has undergone the fourth step. Repeat in order,
After the last step of the fourth step performed a plurality of times,
An aqueous ammonium tungstate solution comprising an eighth step of eluting tungstate ions by bringing the mixed aqueous solution of ammonium chloride and ammonia into contact with the anion exchange resin after the elution with the aqueous ammonia is completed. Production method. Prior to performing the fourth step, the effluent collected in the third step is repeatedly brought into contact with the anion exchange resin while maintaining the pH at 3.5 to 8 to adjust the polytungstate ion. The manufacturing method of the ammonium tungstate aqueous solution of Claim 1 made to adsorb | suck to an ion exchange resin. To the anion exchange resin after contacting the pre-Symbol ammonia water, the effluent is repeatedly contacted with an anion exchange resin, by contacting in a state in which the pH was adjusted to 3.5-8, the A fifth step of adsorbing polytungstate ions in the effluent to the anion exchange resin;
A sixth step of recovering the effluent after the fifth step;
The polytungstate ion is decomposed by bringing ammonia water containing ammonia having a concentration of 8 mol / L or more into contact with the anion exchange resin on which the polytungstate ion is adsorbed in the fifth step. rows that have repeated a seventh step of eluting the ions, in this order,
3. The ammonium tungstate according to claim 2, wherein the fifth to seventh steps that are repeatedly performed are performed between the final step of the fourth step that is performed a plurality of times and the eighth step. A method for producing an aqueous solution.   The said mixed aqueous solution is a manufacturing method of the ammonium tungstate aqueous solution in any one of Claims 1-3 which contains the said ammonia in the ratio of 0.25-5 mol with respect to 1 mol of said ammonium chloride. 5. The space velocity SV when the ammonia water is brought into contact with the anion exchange resin in the step of eluting with ammonia water in the fourth step is 7 hr ⁻¹ or more, according to claim 1. A method for producing an aqueous solution of ammonium tungstate.   In the step of eluting with ammonia water in the fourth step, when the ammonia water is brought into contact with the anion exchange resin, the ammonia water is supplied to the anion exchange resin from a plurality of locations, whereby the ammonia The manufacturing method of the ammonium tungstate aqueous solution in any one of Claims 1-5 which makes water contact.

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