JP2004203694A - Recovery method of tantalum compound and/or niobium compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To recover a highly pure tantalum metal and/or niobium compound from a by-product mixed salt and/or its solution containing at least either sodium fluoride or potassium fluoride and at least one compound selected from among tantalum compounds and niobium compounds. <P>SOLUTION: In a method for recovering the tantalum compound and/or the niobium compound, an ammonia compound and/or a hydrazine compound is added to the by-product mixed salt and/or its solution, followed by solid-liquid separation. The tantalum compound and/or the niobium compound is recovered as tantalum hydroxide and/or niobium hydroxide in a high yield. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
[Industrial applications]
The present invention provides a method for producing a hydroxide by reacting a by-product mixed salt containing sodium fluoride and / or potassium fluoride and / or a tantalum and / or niobium component contained in the solution with an ammonium compound and / or a hydrazine compound. The present invention relates to a method for recovering tantalum and / or niobium hydroxide in high yield.
[0002]
Further, the present invention further comprises dissolving the recovered tantalum hydroxide and / or niobium hydroxide in hydrofluoric acid, and then purifying the impurities to remove impurities. Alternatively, the present invention relates to a method of reusing as a high-purity niobium compound.
[0003]
Also, a method of recovering tantalum and / or niobium raw materials, recovering a fluorine component in a by-product mixed salt as calcium fluoride by adding a calcium compound, and using the recovered calcium fluoride as a raw material for producing hydrofluoric acid. Furthermore, the present invention relates to a method of reacting the added ammonia compound and / or hydrazine compound with a calcium compound, recovering it as ammonium sulfate, and using it as a raw material for chemical fertilizer. Pertaining to a method of causing the
[0004]
[Prior art]
Tantalum is widely used and has excellent corrosion resistance and heat resistance, and is therefore used for various chemical devices such as distillation towers, autoclaves, heat exchangers, and spinning nozzles for chemical fibers for the chemical industry. In general, a tantalum oxide film has a characteristic called a valve action (a characteristic in which the electrode functions as a dielectric when the electrode is a positive electrode, but does not operate as a dielectric when the electrode is a negative electrode, that is, a rectifying characteristic). Therefore, it is used as an electrode material for electrolytic capacitors, and is used in transport equipment, electronic equipment, electronic control equipment, and the like. In addition, a lithium tantalate single crystal wafer is used as a surface acoustic wave (SAW) filter for removing a noise of a mobile phone, and the demand thereof has been greatly increased with the expansion of the mobile communication market. Further, tantalum carbide is used as a material for a carbide cutting tool, and tantalum oxide is used as an additive for an optical lens. Tantalum is extremely important and its demand is increasing.
[0005]
Niobium is used as a steel additive because it has the effect of stabilizing carbon in steel and preventing intergranular corrosion, and this is the largest application. Also, niobium alloy has been put to practical use as a conductive tube associated with a lamp light emitting portion of a high-pressure sodium lamp, and is used as a superconducting material or an additive element of a superalloy.
[0006]
Tantalum (Ta) and niobium (Nb) are usually mined together with each other in an oxide state. Since tantalum is a family of niobium and has very similar properties, industrially the same genus is completely separated by chemical methods before purifying each metal. .
[0007]
An intermediate raw material of metal tantalum and metal niobium purified by this chemical technique is K ₂ TaF ₇ and / or K ₂ NbF ₇ , which is called potassium tantalum fluoride or potassium niobium fluoride. In order to produce metal tantalum and / or niobium metal, a method of reducing this intermediate material using an alkali metal such as sodium or potassium is performed. The reduction reaction is as follows.
K ₂ TaF ₇ + 5Na = Ta + 2KF + 5NaF
K ₂ NbF ₇ + 5Na = Nb + 2KF + 5NaF
[0008]
This reduction reaction is performed at a high temperature of about 1000 ° C. in an atmosphere without air, and is obtained as powdery metal tantalum or metal niobium having a predetermined specific surface area. In the electronics industry, metal tantalum powder and metal niobium powder having various specific surface areas are required. Therefore, it is necessary to adjust the specific surface area, and as a method, potassium tantalum fluoride or potassium niobium fluoride is used. On the other hand, it has been proposed to use an inorganic salt such as potassium fluoride, potassium chloride or sodium chloride as a diluent (see JP-A-48-43006 and JP-A-62-278210).
[0009]
The production method of the metal tantalum powder and the metal niobium powder is performed in a batch system, and when the reaction is completed, the product is cooled. After cooling, metal tantalum powder or niobium metal powder having a high specific gravity precipitates at the bottom of the reactor, and inorganic salts having a low specific gravity are taken out in a state of being deposited at the top of the reactor. At this time, potassium fluoride, sodium fluoride, and the inorganic salt used as a diluent gather when cooled, forming a lump of about 10 to 1000 mm. At this time, in addition to the metal tantalum powder and the metal niobium powder, about 0.01 to 10 wt% of potassium tantalum fluoride and / or potassium niobium fluoride used as a raw material is taken in. When these are washed, potassium tantalum fluoride and potassium niobium fluoride dissolve in water and flow out into wastewater.
[0010]
Thus, the demand for such a tantalum compound and / or niobium compound has been greatly increased in recent years, despite being rare. Several years ago, the supply of tantalum compounds and / or niobium compounds could not keep up with demand. For this reason, in recent years, it has been attempted to reuse waste materials and unnecessary products generated in the production process of tantalum and niobium as raw materials.
[0011]
For example, Japanese Patent Application Laid-Open No. 2000-7339 discloses that a tantalum-containing waste as a raw material is roasted, thereby removing organic substances in the tantalum-containing waste, and converting metal tantalum and impurities into oxides. A method for performing dissolution by acid is disclosed. Japanese Patent Application Laid-Open No. 2000-7338 discloses a method in which a tantalum oxide-containing sludge is used as a raw material, and the sludge is subjected to an acid treatment or an alkali treatment to increase the tantalum quality and then subjected to a hydrofluoric acid dissolving step. .
[0012]
However, the method of treating and reusing the tantalum compound and / or the niobium compound differs greatly depending on the type of the sludge (waste) containing the tantalum compound and / or the niobium compound or the used auxiliary material. Therefore, these methods cannot be directly applied as a method for recycling a tantalum compound and / or a niobium compound from a waste containing tantalum fluoride and / or niobium fluoride and / or the solution.
[0013]
As an example of the waste containing tantalum fluoride and / or niobium fluoride and / or the solution, by-product mixture generated from a metal tantalum and / or niobium metal reduction process using potassium tantalum fluoride and / or niobium potassium fluoride Salts and their by-product mixed salt solutions (eg, washing solutions) and wastewater.
[0014]
Among them, a method considered to be feasible by the present inventor as a method for recycling by-product mixed salts generated from a reduction process of metal tantalum and / or niobium metal using potassium tantalum fluoride and / or potassium niobium fluoride is actually described. I tried to go. This method is as follows.
[0015]
That is, as a method for recycling the metal tantalum using the potassium tantalum fluoride and / or potassium niobium fluoride and / or the by-product mixed salt generated from the metal niobium reduction step, metal tantalum, potassium tantalum potassium fluoride, // After once completely dissolving niobium metal, potassium niobium fluoride, and by-product mixed salts such as potassium fluoride and sodium fluoride used as diluents in an acidic aqueous solution, neutralize the mixture with sodium hydroxide, potassium hydroxide, etc. It is a method of summing.
[0016]
At this time, mainly precipitation Ta (OH) ₅ and / or Nb (OH) _5, although it recovered as part tantalum compound and / or niobium _{compound, Na 2 TaF 7, K 2} TaF 7, Na x Ta ( SO ₄ ) _y , K _x Ta (SO ₄ ) _y and / or solubilities such as Na ₂ NbF ₇ , K ₂ NbF ₇ , Na _x Nb (SO ₄ ) _y , K _x Nb (SO ₄ ) _y It turned out to be difficult. It was also found that when dissolving the by-product mixed salt, it was necessary to dissolve NaF having the lowest solubility other than the tantalum compound and / or the niobium compound to such an extent that NaF remained undissolved.
[0017]
On the other hand, since the content of the tantalum compound and / or niobium compound is about 0.01 to 10 wt%, Na ₂ TaF ₇ , K ₂ TaF ₇ , Na _x Ta (SO ₄ ) _y , K _x Ta The dissolution of (SO ₄ ) _y and / or Na ₂ NbF ₇ , K ₂ NbF ₇ , Na _x Nb (SO ₄ ) _y , K _x Nb (SO ₄ ) _y is at a sufficiently possible level. Therefore, it has become clear from the study of the present inventors that it is still difficult to achieve a high recovery of the tantalum compound and / or the niobium compound by this method.
[0018]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to eliminate the disadvantages of the above method. More specifically, a by-product mixed salt containing at least one of sodium fluoride and / or potassium fluoride and at least one of a tantalum compound and a niobium compound and / or the solution, and an ammonium compound and / or a hydrazine compound A means for recovering tantalum hydroxide and / or niobium hydroxide in a high yield by reacting. After further dissolving the recovered tantalum hydroxide and / or niobium hydroxide in hydrofluoric acid, a purification operation is performed to obtain a high-purity tantalum compound and / or a high-purity niobium compound suitable for efficient production of various products. Means of reuse. Another object of the present invention is to solve the problem by employing effective means that can reuse calcium fluoride and ammonium sulfate recovered at the same time.
[0019]
[Means for solving the problem]
The present invention reacts a by-product mixed salt containing at least one of sodium fluoride and / or potassium fluoride and at least one of a tantalum compound and a niobium compound and / or the solution with an ammonium compound and / or a hydrazine compound. By doing so, tantalum hydroxide and / or niobium hydroxide can be recovered in a high yield. Further, after the recovered tantalum hydroxide and / or niobium hydroxide is dissolved again in hydrofluoric acid, impurities can be removed by performing a refining operation, and can be reused as a high-purity tantalum compound and / or a niobium compound. In addition, calcium fluoride and ammonium sulfate recovered at the same time have a great feature that they can be reused.
[0020]
In the following, the method of the present invention is shown in a simple flow sheet as shown in FIG.
The by-product mixed salt of the present invention is generated as a result of alkali metal reduction of potassium tantalum fluoride and / or potassium niobium fluoride, and has a main composition of potassium fluoride, potassium chloride, and sodium fluoride. Contains metallic impurities and moisture. More specifically, the fluorine component is about 10 to 40% by weight, the chlorine component is about 10 to 25% by weight, the sodium component is about 10 to 40% by weight, and the potassium component is about 10 to 40% by weight. The metal impurities include Fe <50 ppm, Ni <50 ppm, Cr <40 ppm, Mg <10 ppm, and Si <100 ppm. The main composition may include sodium chloride in addition to the above. Furthermore, the solution is also included, and a solution of a mixed salt by-produced after the reaction can be usually exemplified.
[0021]
The by-product mixed salt is dissolved in water to obtain a slurry. During this dissolution treatment, metal tantalum and / or niobium metal may remain without being dissolved. At this time, the metal tantalum and / or niobium metal can be recovered by filtration, but the insoluble component may be dissolved by adding hydrofluoric acid or sulfuric acid. Also, these solvents may be used for dissolution.
[0022]
The concentration and addition amount of hydrofluoric acid or sulfuric acid may be appropriately determined according to the amount of the raw material, the desired purity, and the like, and are not particularly limited, but are usually used in an amount necessary for dissolution. The conditions for dissolving hydrofluoric acid or sulfuric acid are not particularly limited, but can be preferably performed by stirring and mixing for a predetermined time.
An alkali is added to the resulting solution to cause precipitation. Here, as the alkali, ammonia, aqueous ammonia, or an ammonium compound such as ammonium carbonate or ammonium bicarbonate, or a hydrazine compound such as hydrazine or an aqueous hydrazine hydrate solution is used.
[0023]
The amount of the alkali used is preferably from 10 to 100,000 parts by weight, particularly preferably from 10 to 1,000 parts by weight, based on 100 parts by weight of the (acidic) filtrate. The pH at this time is preferably pH> 7, but since the solubility of the tantalum compound and / or the niobium compound is increased by becoming a strong alkali, the pH is particularly preferably 8 to 10.
The temperature at the time of neutralization is not particularly limited, but is preferably 40 to 90 ° C. After neutralization, cooling and crystallization may be performed. As a crystallization operation, a cooling method, a concentration method (for example, an evaporation concentration method), an adiabatic evaporation method, or another method is used. In the case of the cooling method, the temperature at the time of cooling is not particularly limited, but a preferable temperature is -10 to 30C.
[0024]
The time for the neutralization and the subsequent cooling is not particularly limited, but is preferably about 0.01 to 48 hours. However, 0.01 to 3 hours are particularly preferable industrially. The reaction may be performed under normal pressure, under vacuum, or under pressure.
[0025]
Thus, by using an ammonium compound or a hydrazine compound, Ta (OH) ₅ and / or Nb (OH) ₅ can be obtained at a high recovery rate. These recovered Ta (OH) ₅ and / or Nb (OH) ₅ are purified in a later purification step and then recycled as a high-purity tantalum compound and / or a niobium compound.
[0026]
Here, calcium fluoride is obtained as a precipitate by reacting the aqueous solution of ammonium fluoride and the aqueous solution of ammonium sulfate obtained by the above reaction with a calcium compound. Examples of the calcium compound used here include calcium sulfate, calcium hydroxide, calcium carbonate, calcium chloride and the like. When calcium hydroxide, calcium carbonate, or calcium chloride is used to recover the ammonium compound as ammonium sulfate, it is preferable to react with the calcium compound after adding sulfuric acid.
[0027]
Further, ammonium sulfate crystals can be taken out by concentrating the aqueous solution of ammonium sulfate obtained as a filtrate. The calcium fluoride thus obtained can be reused as a hydrofluoric acid production raw material, and ammonium sulfate can be reused as a chemical fertilizer.
[0028]
The reaction conditions of the aqueous ammonium fluoride solution, the aqueous ammonium sulfate solution and the calcium compound are not particularly limited, and the temperature is particularly preferably from 15 to 90 ° C., and may be carried out under any conditions of normal pressure, vacuum, and pressure. . The amount of the calcium compound is 10 to 100,000 parts by weight, preferably 100 to 1,000 parts by weight, based on 100 parts by weight of ammonium fluoride. Further, the amount of sulfuric acid to be used is not particularly limited, and is 10 to 100,000 parts by weight, preferably 100 to 1,000 parts by weight, based on 100 parts by weight of ammonium fluoride.
[0029]
Further, by purifying the recovered Ta (OH) ₅ and / or Nb (OH) ₅ after dissolving it in hydrofluoric acid, a high-purity tantalum compound and / or a niobium compound suitable for efficient production of various products are obtained. It becomes possible. The purification method is not particularly limited, and a general method can be used. For example, the following method can be exemplified.
[0030]
A method for extracting and separating a tantalum compound and / or a niobium compound with an organic solvent, a method for separating a tantalum compound and / or a niobium compound from other impurity metals using an F-type anion exchange resin, a salting-out agent concentration and a hydrogen ion concentration Separation using a difference, a method of absorbing and removing a tantalum compound and / or a niobium compound from a solution by using an absorbent in which an organic solvent is fixed or crosslinked, crystallization from a solution of a tantalum compound and / or a niobium compound Although a method of purifying by operation and the like may be mentioned, any method may be used.
[0031]
[Action]
As described above, the present invention relates to a method for preparing a tantalum hydroxide and / or water from a by-product mixed salt containing at least one of sodium fluoride and potassium fluoride and at least one of a tantalum compound and a niobium compound and / or the solution. Niobium oxide can be obtained at a high recovery rate. Further, after the recovered tantalum hydroxide and / or niobium hydroxide is dissolved again in hydrofluoric acid, impurities can be removed by performing a purification operation, and it is very important to reuse the tantalum hydroxide and / or niobium compound as a high-purity tantalum compound and / or niobium compound. Features.
[0032]
Further, by converting the ammonium compound generated at that time into ammonium sulfate, it can be reused as a chemical fertilizer. Furthermore, calcium fluoride can also be used as a raw material for hydrofluoric acid, which is a method with a recycling system.
[0033]
【Example】
Hereinafter, the present invention will be described more specifically with reference to typical examples. These are merely examples for explanation, and the present invention is not limited to these. The evaluation in the examples was performed by the following methods (1) to (3).
(1) Amount of metal impurities: evaluated by an inductively coupled plasma atomic emission analyzer.
(2) Purity: evaluated with a fluorescent X-ray device.
(3) Crystal structure analysis: evaluated by X-ray diffractometer (XRD).
[0034]
Embodiment 1
1 kg of by-product mixed salt (containing tantalum compound) containing potassium fluoride and sodium fluoride as main components, which is a by-product when producing metal tantalum powder by reducing Na tantalum fluoride with Na, was dissolved in 8 kg of water. Thereafter, in order to dissolve the slightly dissolved tantalum compound, 0.5 kg of 98% sulfuric acid was added and completely dissolved. The tantalum concentration in the solution was 500 ppm.
[0035]
Thereafter, 1.3 kg of an aqueous solution of hydrazine hydrate (80 wt%) was added at room temperature, and the precipitate was suction-filtered and washed with 1.0 kg of hot water at 60 ° C. The recovered material weighed 0.065 kg and the tantalum concentration in the filtrate was <10 ppm (tantalum recovery> 95%).
Thereafter, 0.065 kg of the obtained precipitate was dissolved in 0.1 kg of 50 wt% hydrofluoric acid at 80 ° C., and then crystallization was performed at −20 ° C., followed by suction filtration to separate crystals and a filtrate.
The obtained crystals were dried at 250 ° C. for 3 hours, and the dried crystals were TaO ₂ F. The obtained TaO ₂ F was roasted in an electric furnace at 1000 ° C. for 8 hours in the atmosphere. After that, the crystal was taken out and analyzed by XRD to find that it was Ta ₂ O ₅ . Furthermore, as a result of measuring metal impurities in this Ta ₂ O ₅ , Nb <10 ppm, K <10 ppm, Na <10 ppm, Ti <1 ppm, Fe <1 ppm, Ni <1 ppm, Al <1 ppm, Sb <1 ppm.
Further, 10.5 kg of the filtrate after the reaction with the 80 wt% hydrazine hydrate aqueous solution was reacted with 1 kg of calcium sulfate, and separated by filtration into calcium fluoride and ammonia wastewater. Thereafter, 10.3 kg of the filtrate was concentrated to 4.2 kg, and cooled at −5 ° C. to recover ammonium sulfate.
[0036]
Embodiment 2
10 kg of a by-product mixed salt (containing niobium compound) containing potassium fluoride and sodium fluoride as main components, which is a by-product when producing niobium metal powder by reducing potassium niobium fluoride with Na, was dissolved in 70 kg of water. Thereafter, 8.0 kg of 98% sulfuric acid was added and completely dissolved to dissolve the niobium compound remaining slightly dissolved. The niobium concentration in the solution was 850 ppm.
Thereafter, at room temperature, 4.1 kg of a 40% aqueous ammonia solution was added, and the precipitate was suction-filtered, followed by washing with 5.0 kg of 60 ° C. warm water. The weight of the recovered material was 0.14 kg, and the niobium concentration in the filtrate was <10 ppm (niobium recovery rate> 95%).
[0037]
Thereafter, 0.14 kg of the obtained precipitate was dissolved in 0.3 kg of 50 wt% hydrofluoric acid at 80 ° C., and 0.4 kg of 6N sulfuric acid was added. Then, 1.6 kg of cyclohexanone was added, and Nb and Ta were extracted into the organic layer. did. The organic layer was re-extracted with 0.6 kg of a 1N aqueous sulfuric acid solution, mixed for 10 minutes, and allowed to stand. The lower aqueous layer and the upper cyclohexanone layer were separated to obtain an Nb extracted aqueous solution. 0.2 kg of potassium fluoride was added to the Nb extraction aqueous solution, and crystallization was performed at -20 ° C. As a result, 0.3 kg of potassium oxyfluoroniobate monohydrate crystal was obtained. After dispersing the potassium oxyfluoroniobate monohydrate crystals in hydrofluoric anhydride, hydrofluoric acid was removed. Thereafter, drying was performed at 110 ° C. and analysis by XRD revealed that it was K ₂ NbF ₇ . Furthermore, as a result of measuring metal impurities in this K ₂ NbF ₇ , Ta <1 ppm, Ti <1 ppm, Fe <1 ppm, Ni <1 ppm, Al <1 ppm, and Sb <1 ppm.
[0038]
[Comparative Example 1]
A comparison with an ammonia compound and / or a hydrazine compound was performed under the same conditions as in Example 1 except that sodium hydroxide was used.
10 kg of by-product mixed salt (containing tantalum compound) containing potassium fluoride and sodium fluoride as main components, which is a by-product when producing metal tantalum powder by reducing Na tantalum fluoride with Na, was dissolved in 80 kg of water. Thereafter, 5.0 kg of 98% sulfuric acid was added and completely dissolved to dissolve the tantalum compound remaining slightly dissolved. The tantalum concentration in the solution was 500 ppm.
[0039]
Thereafter, 2.5 kg of sodium hydroxide was added at 10 ° C., the mixture was cooled to −2 ° C., and the precipitate was collected by suction filtration. The weight of the recovered material was 0.05 kg, and the tantalum concentration in the filtrate was 150 ppm.
When the obtained precipitate was analyzed, it was a mixture of Ta (OH) ₅ and Na ₂ TaF ₇ . However, the tantalum recovery was as low as 70%.
[0040]
【The invention's effect】
According to the present invention, tantalum hydroxide and / or niobium hydroxide is produced from a by-product mixed salt containing at least one of sodium fluoride and potassium fluoride and at least one of a tantalum compound and a niobium compound and / or the solution. It can be obtained with a high recovery rate. Further, after the recovered tantalum hydroxide and / or niobium hydroxide is again dissolved in hydrofluoric acid, impurities can be removed by performing a purification operation, and the high-purity tantalum compound and / or niobium compound can be reused. .
[0041]
Further, by converting the ammonium compound generated at that time into ammonium sulfate, it can be reused as a chemical fertilizer. Furthermore, calcium fluoride can also be used as a hydrofluoric acid raw material.
As described above, the present invention can be greatly expected as a closed system in consideration of the environment.
[0042]
[Brief description of the drawings]
FIG. 1 is a flow sheet showing a typical example of the method of the present invention.

Claims (6)

An ammonia compound and / or a hydrazine compound are added to a by-product mixed salt containing at least one of sodium fluoride and potassium fluoride and at least one of a tantalum compound and a niobium compound and / or the solution, and solid-liquid separation is performed. And recovering the tantalum compound and / or niobium compound in high yield as tantalum hydroxide and / or niobium hydroxide. A method of dissolving the tantalum hydroxide and / or niobium hydroxide obtained in claim 1 in hydrofluoric acid, followed by purification to recover as a high-purity tantalum compound and / or niobium compound. 2. A method of recovering a fluorine component in a solution by-produced in (1) by solid-liquid separation as calcium fluoride, and reusing the recovered calcium fluoride as a raw material for producing hydrofluoric acid. 2. A method of recovering and reusing a solution by-produced in claim 1 (solid-liquid separation by-produced) as ammonium sulfate. The recovery of the tantalum compound and / or the niobium compound according to any one of claims 1 to 4, wherein the by-product mixed salt is obtained by metal reduction of potassium tantalum fluoride and / or potassium niobium fluoride. Method. The tantalum compound according to any one of claims 1 to 5, wherein as the ammonia compound and / or hydrazine compound, any one of ammonia, aqueous ammonia, ammonium carbonate, ammonium bicarbonate and / or hydrazine, and hydrazine hydrate is used. And / or a method for recovering a niobium compound.

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