JP2007277091A - Tantalum oxide and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high purity tantalum oxide from which fluorine or phosphorus contained as impurities is removed as much as possible in a purification step. <P>SOLUTION: The tantalum oxide is obtained by leaching from tantalum scrap such as a tantalum capacitor used as a raw material with hydrofluoric acid to obtain a tantalum solution, adding an extracting agent of a phosphoric acid ester into the solution to extract tantalum in a solvent as a tantalum complex and successively back extracting the tantalum complex with an ammoniacal aqueous solution, treating the resultant tantalum solution with an adsorbent to remove organic matter, further adding an ammoniacal aqueous solution to obtain tantalum hydroxide which is dried, pulverized and fired to obtain tantalum oxide. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-purity tantalum oxide powder for optical materials, superhard materials, and electronic materials, and a method for producing the same.

When added to an optical material, tantalum oxide (Ta ₂ O ₅ ) increases the refractive index of the optical material and prevents devitrification. When added to tungsten carbide as a tantalum carbide raw material, toughness such as tungsten carbide. It has been used for optical glass, cemented carbide tools, capacitors, etc. because it has characteristics such as improved resistance, chemical stability and high dielectric constant.

In recent years, it has come to be used in the field of electronic materials and the like as a raw material for LiTaO ₃ used for a substrate for a surface wave device. The tantalum oxide used in these fields is usually produced from ore such as tantalite or scraps such as tantalum-containing alloys, capacitors and processed materials.

Conventionally, the following methods and the like have been employed as methods for separating tantalum from these raw materials and removing impurities in the crude tantalum compound.
(1) A solvent extraction method using extraction selectivity such as MIBK.
(2) A fractional crystallization method using the difference in solubility of metal compounds.
(3) Ion exchange separation method using adsorption selectivity of ion exchange resin.
(4) A volatilization method in which anions are volatilized and removed by baking at a high temperature.

  Among these, the method for producing a tantalum compound by the solvent extraction method (1) is disclosed in Patent Documents 1 to 5.

Patent Documents 1 and 2 disclose solvent extraction methods used in the production methods of tantalum halides and alkoxides, respectively. Here, an aqueous solution obtained by dissolving a mixture of tantalite and columbite with a mixed acid of HF and H ₂ SO ₄ (or only HF) is used as a neutral phosphate ester (70% TBP O / A diluted with kerosene = 1/1). ), And the separated organic phase is washed with water or a liquid containing 0.3 mol / liter (hereinafter referred to as L) of NH ₄ F to select Nb ₂ O ₅ , Fe, Mn, Ti, etc. To remove. When the organic phase containing 48.2 g / L of Ta ₂ O ₅ was washed with water (organic phase after washing), the content of Nb ₂ O ₅ was 0.6 g / L, and Fe and Mn were each 0.01 g Similarly, the content of Nb ₂ O ₅ when washed with a 0.3 mol / L NH ₄ F-containing liquid (the organic phase after washing) is 0.2 g / L, and Fe and Mn are Each is less than 0.001 g / L. Next, the organic phase after washing is back-extracted with a 2.0 mol / L NH ₄ F aqueous solution, and the separated aqueous phase is neutralized with a 10% NH ₃ -containing aqueous solution to obtain a precipitate. The content of the precipitate after drying is as follows: Ta ₂ O ₅ 72.4 wt%, Nb ₂ O ₅ 0.02 wt%, Mn, Fe, Ti, Sn, W, Si, Al are all 0.001 wt% %, NH ₃ 5.6% by weight, HF 12.6% by weight.

Patent Documents 3 and 4 disclose solvent extraction methods used in methods for producing fluorine-containing tantalum ammonium salts and metal tantalum, respectively. Here, a neutral phosphate ester (TBP, etc.) or the like is diluted with 2 to 100% (volume) of an aromatic, aliphatic, mixed product or petroleum hydrocarbon such as kerosene, for example, 85% TBP + 15% aromatic The tantalum extract with 60% TBP + 40% aromatic etc. is an F-containing solution containing NH ₄ HF ₂ , NH ₄ F etc. in an amount of 100 to 250 g / L, and shaken at O / A = 1/1 for 10 minutes. Then, after tantalum and tantalum complex ions are transferred to the aqueous phase, crystallization is performed in a crystallization step to obtain a fluorotantalum ammonium salt.

Patent Document 5 discloses a method for producing tantalum chloride having a low SiCl content by chlorinating tantalum oxide obtained from a solution leached with fluorosilicic acid through a solvent extraction method with a chlorine gas flow. Here, a solution obtained by leaching a tantalum mineral and concentrate using fluorosilicic acid (H ₂ SiF ₆ ) at 60 to 80 ° C. under atmospheric pressure is extracted with aliphatic, hydrocarbon-diluted TBP, MIBK, or the like. The separated organic phase is contacted with the aqueous phase and back-extracted. Further, the separated aqueous phase is neutralized with a base to obtain a hydroxide, and the hydroxide is calcined to obtain tantalum oxide. The SiO ₂ content in the obtained oxide is 0.6%.

  The ion exchange separation method (3) is disclosed in Patent Documents 6 and 7.

  Among these, Patent Document 6 discloses a method for recovering tantalum in tantalum-containing scrap by an anion exchange resin. Here, 15N ammonia water was added to a tantalum eluate eluted with a mixed solution of hydrofluoric acid, aqueous ammonia and ammonium salt to adjust the pH to 6.9, and the resulting tantalum hydroxide precipitate was 1000 ° C. To obtain white tantalum oxide powder. As impurities of tantalum oxide, Cu, Mn, Fe, Si, Ca, Al, and Mg are all less than 1 ppm, but Li 2 to 4 ppm, Ag 1 ppm, and Nb are 3 to 30 ppm. , F are not particularly described.

  Patent Document 7 discloses a method for mutually separating niobium and tantalum using a fibrous ion exchanger having an anion exchange group. Here, it is described that niobium and tantalum can be separated. Although it is described that 0.1 to 3 mg of tantalum is contained in a 40 mL fraction of the tantalum eluate by a mixed solution of hydrochloric acid and oxalic acid, the concentration of niobium is contained in the fraction. It is unclear whether this is done.

  Further, other purification methods for tantalum compounds are disclosed in Patent Documents 8 to 11.

Among these, Patent Document 8 discloses a method for separating niobium and tantalum using an adsorbent in which an extractant is immobilized or crosslinked on a porous carrier. Here, it is described that a solvent extraction method using neutral phosphate ester including TBP can be used in the middle of the process. The content in the NH ₄ regeneration solution after the treatment with the porous carrier-supported adsorbent was Ta ₂ O ₅ 124.4 g / L, Mn, Nb ₂ O ₅ , Fe, Ti, and H ₂ SO ₄ were all 0. Less than 001 g / L, NH ₄ 36.0 g / L, HF 96.3 g / L. When Ta ₂ O ₅ is 1, Mn, Nb ₂ O ₅ , Fe, Ti, and H ₂ SO ₄ are all less than 8 ppm. is there.

  Patent Document 9 discloses a method of removing fluorine by baking a small amount of fluorine contained in a tantalum compound under the flow of air containing water vapor. Here, tantalum hydroxide having an average particle size of 0.5 or 1 μm containing 1418 ppm of F as tantalum pentoxide is heat-treated in a steam-containing air stream, and the residual F content in tantalum pentoxide is less than 1 ppm. It is described.

  Patent Document 10 discloses a method for purifying tantalum hydroxide which is washed with a mineral acid present in an amount of 0.1 to 2% by weight of boron (boric acid). Here, the impurity content of tantalum hydroxide after washing treatment after drying at 120 ° C. for 20 hours is 1.0 ppm, Fe8 to 10 ppm, Ca6 to 12 ppm, Mg0.9 for Ni, Co, and Ti, respectively. It is described that ˜1.4 ppm, Na 9 to 12 ppm, K1.8 to 2.5 ppm, B is less than 1 ppm, and Cl is less than 1 ppm (burned).

Further, Patent Document 11 discloses a method for producing a tantalum hydroxide having a low fluorine content by reusing ammonia water for cleaning from a fluoride-containing aqueous solution of tantalum (aqueous solution of hydrofluoric acid containing tantalum). . Here, an aqueous solution of tantalum in hydrofluoric acid is added to the aqueous ammonia solution obtained from the first washing step of the preceding step, and an aqueous ammonia solution is further added to adjust the pH to at least 9 or more. After the oxide precipitate is filtered off, it is first washed with a 1 to 10% ammonia solution and secondly with pure water. It is described that the content of F in the tantalum hydroxide obtained after washing is 0.20 to 0.28%.

In addition, as non-patent document 1, as tantalum oxide for high purity, Ta ₂ O ₅ > 99.99%, Nb ₂ O ₅ <0.002%, SiO ₂ <0.001%, Fe ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , NiO, Cr ₂ O ₃ and MnO are all <0.0005%, loss on ignition <0.1%, tantalum oxide for optical use, Ta ₂ O ₅ > 99.9%, Nb ₂ O ₅ <0.03%, SiO ₂ <0.01%, Fe ₂ O ₃ , Al ₂ O ₃ and TiO ₂ are all <0.001%, NiO, Cr ₂ O ₃ and MnO are all <0. 0005%, loss on ignition <0.1%, tantalum oxide for ceramics, components are the same as optical tantalum oxide, loss on ignition <0.2%, various tantalum oxides with an average particle size of 0.6 to 1.0 μm Are listed.

JP-A 63-236716 JP-A-64-45325 Japanese Patent Laid-Open No. 60-195019 JP 60-21343 A JP-A-3-502116 Japanese Patent Laid-Open No. 56-114831 JP-A-2-212318 JP-A-64-31937 JP-A-63-156013 JP-A 63-295431 JP-A-4-270122 "New Metal Data Book" (Edited by Metal Time Review, February 1, 1996)

  However, tantalum hydroxide or tantalum oxide obtained by such a conventional manufacturing method has a defect that P and F as impurities can be removed only to some extent, and high purity products for optical materials and electronic materials are demanded. In spite of this, until now, no powder has been obtained that satisfies this requirement.

  For these reasons, in the above conventional solvent extraction method, the selectivity of tantalum is good, but since the solvent is easily volatilized, it is ignitable and has a high handling risk, and the solubility in water is high. In addition to the problems of the loss of raw materials at the same time as the above solvents, the efficiency is poor and the production cost is high, and since hydrofluoric acid is usually used to dissolve tantalum compounds, it is inevitably avoided to contain fluorine. The waste liquid treatment was necessary. Alternatively, the organic solvent is inevitably mixed during the solvent extraction, and there is a problem that components of the organic solvent such as phosphorus remain up to the final product and cannot be removed as impurities.

Specifically, Patent Documents 1 and 2 disclose that the back extract is an NH ₄ F aqueous solution, so that the resulting precipitate contains HF. Further, Patent Documents 3 and 4 disclose that the back extract is a back extract. NH ₄ H
A process of obtaining a fluorotantalum ammonium salt using a liquid containing a large amount of F ₂ , NH ₄ F, etc., 100 to 250 g / L is disclosed. Of course, F is contained in the final product.

Patent Document 5 discloses that tantalum oxide is obtained by a solvent extraction method from a solution leached with fluorosilicic acid, but the SiO ₂ content in tantalum oxide is 0.6%.

  In addition, in the conventional fractional crystallization method, although a strict treatment condition and a large number of repeated treatments are required, only a low-purity product is obtained. Similarly, in the conventional ion exchange separation method, The processing speed is slow, and a large-scale facility is required to perform a large amount of processing.

  In Patent Document 6, the Nb content in the obtained tantalum oxide is 3 to 30 ppm, and F is not particularly described, but it is considered that F from hydrofluoric acid in the eluent is included. In Patent Document 7, the niobium concentration in the tantalum eluate fraction is unknown.

  Further, in the above conventional volatilization method, an anion gas is generated at the time of firing, and not only the inside of the firing furnace is corroded, but it is necessary to provide a treatment facility for the generated gas.

Further, in Patent Document 8, HF is contained in the obtained NH ₄ regeneration solution, and it is considered that tantalum hydroxide and tantalum oxide containing F can be obtained by neutralization as it is. It is considered necessary to appropriately treat the gas containing F.

  In Patent Document 10, although the content of F is not described, the Fe content in the tantalum hydroxide is 8 to 10 ppm, and in Patent Document 11, F in the tantalum hydroxide obtained after washing. Is 0.20 to 0.28%.

  Non-patent document 1 describes several metal element contents of tantalum oxide, but does not describe P and F.

  Therefore, the present invention is simpler than the conventional one without separation of tantalum compounds and purification without requiring strict treatment conditions and numerous repeated treatments, and without introducing large-scale treatment facilities or gas treatment facilities. It is an object of the present invention to provide a separation and purification method capable of efficiently separating a tantalum compound and removing impurities in a simple process.

  In order to solve the above-mentioned problems, the present inventors conducted extensive research. As a result, in order to obtain tantalum hydroxide, the tantalum concentration, the selection of the neutralizing agent, the concentration, and the addition in the neutralization step (fourth step) It was found that tantalum hydroxide and tantalum oxide having a low content of anions, particularly F, can be obtained by optimizing the speed, liquid temperature, stirring speed and the like. The present invention has been made based on the results of the elucidation, and the first invention is a tantalum hydroxide characterized in that the F content is 0.1 wt% or less.

  According to a second aspect of the present invention, a tantalum-containing material is leached with hydrofluoric acid or a mixed acid of hydrofluoric acid and another inorganic acid, and then solid-liquid separated to obtain a tantalum-containing aqueous solution. Extract tantalum into the solvent as a tantalum complex salt using a normal phosphate ester extractant from the resulting aqueous solution, and back extract the extracted solution separated from the resulting metal impurities with water or an ammoniacal solution to obtain a tantalum solution. After the porous adsorbent was brought into contact with the solution obtained in 2 steps and the 2nd step, the solid solution was separated to obtain a tantalum solution from which organic components were removed, and the 3rd step was obtained. And a fourth step of obtaining tantalum hydroxide by adding an aqueous ammoniacal basic solution to the solution.

  A third invention is a tantalum oxide characterized in that the content of P is 100 ppm by weight or less.

  A fourth invention is a tantalum oxide characterized in that the content of F is 0.5 ppm by weight or less.

A fifth invention is a tantalum oxide characterized by having a Ta ₂ O ₅ purity of 99.9% by weight or more and a specific surface area of 7.0 m ² / g or less.

  According to a sixth aspect of the present invention, the tantalum-containing material is leached with hydrofluoric acid or a mixed acid of hydrofluoric acid and another inorganic acid, and then solid-liquid separated to obtain a tantalum-containing aqueous solution. Extract tantalum as a tantalum complex salt into the solvent using the orthophosphate ester extractant from the resulting aqueous solution, and back extract the extracted solution separated from the resulting metal impurities with water or an ammoniacal solution to obtain a tantalum solution. After the porous adsorbent was brought into contact with the solution obtained in 2 steps and the 2nd step, the solid solution was separated to obtain a tantalum solution from which organic components were removed, and the 3rd step was obtained. A fourth step for obtaining tantalum hydroxide by adding an ammoniacal basic aqueous solution to the solution, and a fifth step for obtaining tantalum oxide by firing the tantalum hydroxide obtained in the fourth step. Made of tantalum oxide It is a method.

  In the present invention, a tantalum scrap such as a tantalum capacitor is used as a raw material to be leached with hydrofluoric acid to obtain a tantalum solution, and then extracted into a solvent as a tantalum complex salt using a normal phosphate ester extractant. The resulting tantalum solution was treated with an adsorbent to remove organic components. Further, an aqueous ammoniacal solution was added to obtain tantalum hydroxide, which was then dried and ground. Later, by firing to obtain tantalum oxide, it became possible to obtain high-purity tantalum hydroxide and tantalum oxide from which fluorine and phosphorus as impurities contained in the purification process were removed as much as possible. Is.

  The manufacturing method of this invention is demonstrated to process order below.

  (First Step) The first step is a raw material leaching step. As a raw material in the production method of the present invention, ore such as tantalite or a tantalum-containing alloy, a tantalum capacitor, the remainder of the tantalum-containing target material, a scrap of vapor deposition, a scrap such as a processing scrap of a carbide tool material, or the like is used. In this case, the composition of the raw material is preferably a composition containing tantalum as a main component, but is not limited thereto.

  The purity of these tantalum-containing materials is preferably a raw material containing at least 60% by weight of tantalum in terms of Ta from the viewpoint of recovery. Although it is finally possible to efficiently purify and recover high-concentration tantalum hydroxide and tantalum oxide, this is not particularly limited to this raw material concentration.

  This tantalum-containing material is leached with hydrofluoric acid or a mixed acid of hydrofluoric acid and other inorganic acids. In this case, the concentration of hydrofluoric acid to be added is sufficient if the tantalum-containing material can be sufficiently leached. Well, as an example, 55% by weight industrial hydrofluoric acid can be used.

  The amount of hydrofluoric acid may be added so that the total amount of raw materials charged is almost dissolved.

The liquid temperature during the leaching is preferably 80 ° C. or higher. This is because the hydrofluoric acid is activated and more tantalum in the raw material is leached out. In this case, in order to promote leaching, it is preferable to add an inorganic acid as a dissolution aid as appropriate. As the inorganic acid to be added, hydrochloric acid, nitric acid, sulfuric acid or the like can be used. As an example, 68% by weight nitric acid can be used, but is not limited thereto.

  The addition time of the hydrofluoric acid is appropriately adjusted so that the tantalum-containing material is sufficiently leached. However, when the temperature is lowered, a dissolution aid may be appropriately added and the temperature may be maintained at 80 ° C. or higher by reaction heat. .

  Next, the obtained leaching solution (tantalum-containing aqueous solution) and a suspension composed of the insoluble residue are subjected to solid-liquid separation to obtain a tantalum-containing aqueous solution. In this case, the solid-liquid separation is performed by filtration or the like, but the filtration can be any of gravity filtration, pressure filtration, or vacuum filtration.

  In addition to tantalum, the composition of the tantalum-containing aqueous solution contains niobium as an impurity, various metal elements including transition metals, and as an acid, mainly hydrofluoric acid and an inorganic acid as a dissolution aid.

  (Second Step) In the second step, tantalum is extracted with the organic phase from the tantalum-containing aqueous solution that is the aqueous phase obtained in the first step, and then the aqueous phase and the organic phase are separated. Subsequently, the separated organic phase is washed with another aqueous phase, and then the aqueous phase and the organic phase are separated. This is a step of back-extracting the separated organic phase with another aqueous phase.

  First, tantalum is extracted into the organic phase from the leaching solution that is the tantalum-containing aqueous solution obtained in the first step. In this case, the composition of the aqueous phase before the extraction contains hydrofluoric acid and the like in addition to tantalum. ing.

  In the aqueous phase, the acid includes hydrofluoric acid used in the leaching of the first step, and when an inorganic acid is added as a dissolution aid in the first step, the acid is also included. Note that the extraction operation is possible even when the aqueous phase is hydrofluoric acid alone.

  When sulfuric acid is added to the aqueous phase, the tantalum extraction rate increases as the sulfuric acid concentration increases. The extraction rate here is the tantalum content in the organic phase after the extraction operation / the tantalum content in the aqueous phase (exudate) before extraction. Also, the higher the sulfuric acid concentration in the aqueous phase, the higher the niobium extraction rate. At the same time, in the present invention, the extraction rate of tantalum is increased, and the separation efficiency of niobium from tantalum is sufficiently high. Concentration was set.

  The concentration of sulfuric acid in the aqueous phase is preferably 10 to 20% by weight. If the concentration is less than 10% by weight, the extraction efficiency does not increase. Conversely, if the concentration exceeds 20% by weight, the separation efficiency from the metal mainly composed of niobium is improved. By incurring a decline.

  The acid concentration of the aqueous phase is 5 to 15% by weight of hydrofluoric acid and 10 to 20% by weight of sulfuric acid, which makes it possible to efficiently extract tantalum separated from other metals.

  When the above acid concentration is specified, tantalum cannot exceed the equivalent of acid, and since tantalum is dissolved using approximately the same amount of hydrofluoric acid, the equivalent amount of tantalum is also determined. Therefore, in the present invention, the tantalum concentration in the aqueous phase is preferably 40 to 120 g / L in terms of Ta, and in this case, if it is less than 40 g / L or, on the contrary, exceeds 120 g / L, it is separated from the metal mainly composed of niobium. This is due to lower efficiency.

  The organic phase is preferably a normal phosphate ester extractant, particularly tributyl phosphate (TBP). This is because, compared with methyl isobutyl ketone (MIBK), the boiling point is high, the solvent loss is small, and the fire resistance is excellent.

  The extractant may be diluted with a diluent. As the diluent, aliphatic hydrocarbons, aromatic hydrocarbons, mixtures thereof and the like can be used.

  When an extractant having a specific gravity close to 1 such as TBP is used, the use of a hydrocarbon-based diluent having a low specific gravity can improve the separation between the organic phase and the aqueous phase. As such a diluent, for example, kerosene can be used, and the amount of the diluent is an extractant / diluent (V / V), preferably about 1/3 to 1/1.

  In the extraction operation, the organic phase and the aqueous phase are brought into contact with each other, shaken or stirred, and then allowed to stand. In this case, the amount of the extractant that can sufficiently extract tantalum is preferable, but when TBP is used as the extractant, TBP is preferably added in an amount of 1.5 L or more per 100 g of tantalum in terms of Ta. The O / A ratio (volume of the organic phase / volume of the aqueous phase) is not particularly limited as long as the organic phase and the aqueous phase can be sufficiently shaken or stirred.

  The temperature of the organic phase and the aqueous phase at the time of extraction is not particularly specified, but if it is 1 ° C or lower, the viscosity of the organic phase increases and extraction cannot be performed. Since the volatilization amount of the agent increases, 1 to 40 ° C. is preferable.

  The shaking or stirring time may be sufficient to allow tantalum to transfer from the organic phase to the aqueous phase. For example, shake or stir for about 3 to 8 minutes.

  The standing time may be such that the organic phase and the aqueous phase can be sufficiently separated. For example, leave it for about 8 to 12 minutes.

  The composition of the organic phase after extraction contains a slight amount of hydrofluoric acid, sulfuric acid, and other metals as impurities.

  After the extraction operation, the organic phase and the aqueous phase are separated, and the separated organic phase is washed with an aqueous solution as a cleaning agent. In this case, the cleaning agent is preferably an aqueous solution of sulfuric acid, because impurities other than tantalum contained in the organic phase, particularly niobium and other metal elements, are transferred to the aqueous phase to be removed.

  The concentration of sulfuric acid in the aqueous phase as the cleaning agent is preferably 10 to 20% by weight. This is because some impurity metals extracted in the organic phase can be efficiently removed.

  In the washing operation, the organic phase and the aqueous phase are brought into contact with each other, shaken or stirred, and then allowed to stand. In this case, the O / A ratio (ratio of the volume of the organic phase / the volume of the aqueous phase) is not particularly limited as long as the washing water phase and the organic phase can be sufficiently shaken or stirred.

  In this case, the temperature of the organic phase and the aqueous phase at the time of extraction is not particularly specified, but if it is 1 ° C. or lower, the viscosity of the organic phase increases and extraction becomes impossible. In particular, 1 to 40 ° C. is preferable because the volatilization amount of the diluent increases.

  In addition, the shaking or stirring time is not particularly limited as long as the impurities other than tantalum can be sufficiently shaken or stirred to such an extent that impurities from the organic phase can be sufficiently transferred from the organic phase to the aqueous phase. There is no particular limitation as long as the phase and the aqueous phase are separated.

  After the washing operation, the organic phase and the aqueous phase are separated. The separated organic phase is washed with a new cleaning agent (about 8 to 12% by weight sulfuric acid). Although it is preferable to repeat this washing operation as appropriate, this is to remove niobium and other metals remaining in the organic phase.

  The composition of the organic phase before the back extraction is a diluted solution of a tantalum fluoride extractant that excludes impurities such as niobium. In particular, when TBP is used as the extractant and kerosene is used as the diluent, it becomes a kerosene diluted solution of tantalum fluoride-TBP.

  Then, after completion of all washing, the organic phase and the aqueous phase are separated, and tantalum is back-extracted from the separated organic phase into the aqueous phase. In this case, the aqueous solution used is preferably water or aqueous ammonia, This is because tantalum does not sufficiently migrate from the organic phase to the aqueous phase with other inorganic acids and alkalis other than aqueous ammonia, and back extraction cannot be performed. In particular, dilute aqueous ammonia is most effective.

  In this case, the concentration of aqueous ammonia in the aqueous phase during back extraction is preferably 1 to 3% by weight, because tantalum precipitates as tantalum hydroxide when the concentration of aqueous ammonia is high. is there.

  The tantalum salt concentration after back extraction is adjusted by the volume ratio of the organic phase / water phase, and an aqueous phase of 1 to 20 L per 100 g of tantalum in terms of Ta in the organic phase is preferable. Further, the tantalum concentration after back extraction is preferably in the range of 5 to 100 g / L in terms of Ta. This is because precipitation occurs when the tantalum concentration in the aqueous phase after back extraction is high.

  In the back extraction operation, the organic phase and the aqueous phase are brought into contact with each other, shaken or stirred, and then allowed to stand. In this case, the O / A ratio is not particularly limited as long as the organic phase and the aqueous phase can be sufficiently shaken or stirred.

  In this case, the temperature of the organic phase and aqueous phase at the time of back extraction is not particularly specified, but if it is 1 ° C. or lower, the viscosity of the organic phase increases and extraction becomes impossible. Since the volatilization amount of an agent and especially a diluent rises, 1-40 degreeC is preferable.

  In addition, the shaking or stirring time is not particularly limited as long as the tantalum can be sufficiently shaken or stirred so that the tantalum can be sufficiently transferred from the organic phase to the aqueous phase. Similarly, the standing time is not limited to the organic phase and the water phase. There is no particular limitation as long as the phases are separated.

  After the phase separation, the organic phase and the aqueous phase are separated. The composition of the aqueous phase after the separation is an aqueous ammoniacal tantalum fluoride solution excluding impure metal components.

  In the extraction, washing, and back extraction steps, a continuous multistage contact method, a continuous batch method, a countercurrent multistage extraction method, and the like can be applied, and an apparatus such as a mixer settler can also be used. Extraction and purification can be efficiently performed by the method and apparatus as described above.

  (Third step) In the third step, the aqueous tantalum solution obtained in the second step is brought into contact with the porous adsorbent, and the extractant or diluent mixed and dissolved in the tantalum aqueous solution in the porous adsorbent. After adsorbing organic substances such as the above, the organic substance mixed and dissolved in the tantalum aqueous solution is removed from the tantalum aqueous solution by separating the tantalum aqueous solution and the porous adsorbent.

  Thereby, it is possible to prevent an element derived from an extractant or a diluent such as phosphorus (P) in the final product tantalum hydroxide or tantalum oxide from being incorporated in the form of hydroxide or oxide. When an extractant containing phosphorus (P) as an extractant, for example, a normal phosphate ester extractant, particularly TBP, is used, tantalum hydroxide of the final product, phosphorus (P) is a hydroxide in tantalum oxide, Incorporation in the form of an oxide or the like can be prevented.

In the tantalum aqueous solution, the liquid obtained in the second step may be brought into contact with the porous adsorbent as it is, but it is more preferable to add an inorganic acid in advance. Thereby, organic matter (oil) is liberated from the aqueous solution, and the removal efficiency is improved. In this case, the inorganic acid to be added in advance can be nitric acid, sulfuric acid, hydrochloric acid, acetic acid and the like, and nitric acid which is an oxidizing inorganic substance is particularly preferable in terms of oxidative decomposition of oil.

  The concentration of the inorganic acid to be added is not particularly limited, but is preferably 2N or less, which is as dilute as possible, in order not to increase the amount of chemical solution used in the next step.

  The porous adsorbent used can be activated carbon, paper filter, etc., and activated carbon having corrosion resistance against hydrofluoric acid is particularly preferable. This is because activated carbon has the property of more adsorbing metals as impurities. In this case, the amount of the porous adsorbent used is preferably 5 to 15 g with respect to 1 L of the treatment solution. This is because this amount sufficiently adsorbs metal impurities.

  The porous adsorbent to be used may be washed with an inorganic acid in advance before contacting with the tantalum aqueous solution to remove the metal element contained in the porous adsorbent. Thereby, mixing of the metal element from the porous adsorbent into the tantalum aqueous solution can be prevented.

  The inorganic acid used for washing is preferably nitric acid, hydrochloric acid, sulfuric acid or the like, but is not limited thereto.

  The contact between the tantalum aqueous solution and the porous adsorbent is carried out by suspending the porous adsorbent in the tantalum aqueous solution, and the suspension of the porous adsorbent in the tantalum aqueous solution requires a predetermined amount of the porous adsorbent. It puts in the tantalum aqueous solution and stirs the tantalum aqueous solution. In addition, the tantalum aqueous solution and the porous adsorbent may be contacted by passing the tantalum aqueous solution through a filter medium precoated with the porous adsorbent.

  In this case, the temperature at the time of contact between the tantalum aqueous solution and the porous adsorbent is not necessarily limited to a specific temperature, and the contact time between the tantalum aqueous solution and the porous adsorbent is a relatively short time. There is no particular limitation as long as it is present.

  Next, after contact, the tantalum aqueous solution and the porous adsorbent are separated to obtain an aqueous tantalum solution from which organic substances have been removed. In this case, the tantalum aqueous solution and the porous adsorbent can be separated by gravity filtration, pressure filtration, centrifugal separator filtration, or the like.

  For example, when TBP is used as an extractant, the phosphorus concentration in the solution before the above treatment was about 1000 ppm by weight in P / Ta, but after adsorption treatment, 10 ppm by weight or less in P / Ta And it goes down significantly.

  (Fourth Step) The fourth step is a step of neutralizing the tantalum aqueous solution obtained in the third step with a basic aqueous solution to obtain tantalum hydroxide having a low anion content.

  At this time, the fluorine concentration in the solution before the neutralization treatment is about 50% by weight in terms of F / Ta.

The tantalum concentration of the aqueous tantalum solution is preferably 10 to 150 g / L, particularly preferably 10 to 50 g / L, in terms of Ta. This is because if the concentration of tantalum is low, the neutralization rate is reduced, and impurities such as anions due to rapid particle growth are reduced in the particles, which can promote particle coarsening due to particle growth. This is because it is desirable that the tantalum concentration be as low as possible. The temperature of the tantalum aqueous solution during neutralization is preferably 10 to 90 ° C, particularly preferably 50 to 90 ° C. This is because the solubility of the product is lowered and the mixing of impurities such as anions into the particles is reduced due to rapid particle growth, which can promote particle coarsening due to particle growth. Depending on what is desired.

  As the basic aqueous solution used for neutralization, an ammoniacal aqueous solution, a sodium hydroxide aqueous solution, or the like is used, but a sodium hydroxide aqueous solution or the like is likely to contain sodium or the like. An aqueous ammoniacal solution is preferred.

  The concentration of the basic aqueous solution decreases the neutralization rate, reduces the contamination of impurities such as anions due to rapid particle growth, and promotes particle coarsening due to hydroxide particle growth. Therefore, since it is desirable to be as dilute as possible, it is preferably 1 to 25% by weight, particularly preferably 1 to 12% by weight. In addition, the temperature of the basic aqueous solution decreases the solubility of the product, reduces the mixing of impurities such as anions into the particles during rapid particle growth, and can promote particle coarsening due to particle growth. Therefore, a temperature as high as possible is desirable, preferably 10 to 90 ° C, and particularly preferably 50 to 90 ° C.

  In the neutralization operation, a basic aqueous solution is added to the stirring tantalum aqueous solution. In this case, when a tantalum aqueous solution is added to the basic aqueous solution, the neutralization reaction proceeds rapidly, and an anion is involved in the generated hydroxide, and the content of the anion in the tantalum hydroxide increases. Therefore, it is not preferable.

  In the neutralization operation, first, an initial neutralization is performed in which a basic aqueous solution is added until immediately before precipitation of hydroxide occurs. In the initial neutralization, the equivalent amount of the basic aqueous solution necessary for starting the hydroxide precipitation of the solution to be used is previously determined by titration or the like. Then, a basic aqueous solution is added slightly less than the precipitation starting equivalent, to prepare an initial neutralization solution. That is, a nearly saturated solution for the hydroxide is created.

  A basic aqueous solution is added to the obtained initial neutralized tantalum solution. As the basic aqueous solution used at this time, an aqueous ammonia solution, an aqueous sodium hydroxide solution or the like can be used. However, in the case of an aqueous sodium hydroxide solution as described above, there is a possibility that sodium or the like may be mixed. An aqueous ammoniacal solution such as an aqueous ammonium carbonate solution is preferred.

  As described above, the concentration of the basic aqueous solution decreases the neutralization rate, reduces the mixing of impurities such as anions due to rapid particle growth into the particles, and coarsens the particles due to hydroxide particle growth. Since it can be promoted, the concentration is as dilute as possible, preferably 1 to 25% by weight, particularly preferably 1 to 12% by weight. In addition, the temperature of the basic aqueous solution decreases the solubility of the product, reduces the mixing of impurities such as anions due to rapid particle growth into the particles, and can promote particle coarsening due to particle growth. It is desirable that it is as high as possible, preferably 10 to 90 ° C, particularly preferably 50 to 90 ° C.

  The temperature of the aqueous tantalum solution at the time of neutralization decreases the solubility of the product, reduces the mixing of impurities such as anions due to rapid particle growth into the particles, and promotes particle coarsening due to particle growth. It is desirable that it is as high as possible, preferably 10 to 90 ° C, particularly preferably 50 to 90 ° C. Further, the basic aqueous solution is added to the obtained aqueous solution of tantalum until the aqueous solution of tantalum reaches pH 9.

In this case, the addition rate is desirably as slow as possible because the neutralization rate is decreased and the hydroxide particle growth can be promoted, and is preferably 0.01 to 0.10 eq / min in reaction equivalent / hour. . In this case, the addition rate is not particularly limited until the initial neutralization until a saturated solution of hydroxide is prepared.

Overall, the lower the tantalum concentration, the thinner the ammoniacal aqueous solution, the slower the addition rate, the higher the liquid temperature, the slower the stirring, the slower the tantalum hydroxide formation reaction rate. Anion (especially F ⁻ ) contained therein is less involved in precipitation of tantalum hydroxide, and tantalum hydroxide having a low anion content can be obtained.

  The obtained tantalum hydroxide is subjected to solid-liquid separation. Gravity filtration, pressure filtration, centrifugal filtration, etc. can be used for solid-liquid separation of tantalum hydroxide and other aqueous solutions.

  After filtering off, the tantalum hydroxide is washed. The washing is performed to remove attached anions. This cleaning is performed by bringing a cleaning agent into contact with the filtered tantalum hydroxide during the filtering operation. At this time, the cleaning agent used is water, preferably ion-exchanged water generally called pure water, but the pH of the cleaning agent does not need to be adjusted.

After washing, the cleaning agent and tantalum hydroxide were subsequently solid-liquid separated to obtain tantalum hydroxide. The composition of tantalum hydroxide after drying is
Ta 65.0-67.0 wt%
F 0.1 wt% or less P 60 wtppm or less, preferably 6 wtppm or less Cu 3 wtppm or less Mn 3 wtppm or less Ni 3 wtppm or less Nb 3 wtppm or less. This drying is the same as that performed before firing in the next step. The water content (weight difference between before and after treatment at 100 ° C. for 2 hours) is 3% by weight or less, particularly preferably 0.5% by weight or less, which is suitable for producing tantalum oxide in the next step. The F content is 0.1% by weight or less, and is very suitable as a raw material for obtaining tantalum oxide having a low F content in the next step. Further, the P content is 60 ppm by weight or less, which is also suitable as a raw material for obtaining tantalum oxide having a low P content. At the same time, Cu, Mn, Ni, and Nb are each 3 ppm by weight or less, and are optimal as raw materials for producing very high purity tantalum oxide.

The powder characteristics of the tantalum hydroxide after drying and pulverization are an average particle diameter of 5.0 to 15.0 μm and a specific surface area of 20.0 to 80.0 m ² / g. This drying and pulverization is the same as that performed before firing in the next step, and has a particle size and specific surface area that are very preferable as a raw material for firing tantalum oxide in the next step.

  (Fifth Step) The fifth step is a step of drying and baking the tantalum hydroxide obtained in the fourth step to obtain tantalum oxide.

  In this step, first, the tantalum hydroxide obtained in the fourth step is dried. This drying method is performed by air drying, heat drying, vacuum drying, or the like. In this case, the drying temperature and the drying time are not particularly limited.

  After drying, the obtained dried tantalum hydroxide is pulverized. This pulverization method is preferably a method having a high shearing effect or compression effect, such as a roll mill or a ball mill. By this, tantalum hydroxide can be consolidated and tantalum hydroxide having a high bulk density can be obtained.

When a ball mill is used, it is dry and the medium is preferably a ball made of zirconia, alumina, porcelain, or the like, or a bead or ball made of fluorine resin, fluorine resin lining, or the like, and particularly high in specific gravity, but not particularly limited.

  Next, the ground tantalum hydroxide is fired to obtain tantalum oxide. In this case, the firing temperature is preferably 900 to 1100 ° C. This is because a small amount of remaining fluorine can be volatilized and removed.

  The firing time may be sufficient to promote oxidation, for example 6 to 10 hours. Further, the firing pattern is not particularly defined but may be a normal method. Further, the firing atmosphere is preferably an oxygen atmosphere for the purpose of oxidation, but this is not a problem even in the atmosphere as long as oxygen can be sufficiently supplied.

The composition of tantalum oxide obtained by firing the tantalum hydroxide is:
Ta ₂ O ₅ 99.9% by weight or more (by difference method excluding Nb and transition metal),
F 0.5 wt ppm or less P 100 wt ppm or less, preferably 10 wt ppm or less Cu 5 wt ppm or less Mn 5 wt ppm or less Ni 5 wt ppm or less Nb 5 wt ppm or less. The tantalum oxide obtained in this way has a particularly high purity, which has never been obtained before, and is very suitable for optical materials and electronic materials.

The powder characteristics of tantalum oxide obtained in the firing step are an average particle diameter of 1.0 to 10.0 μm and a specific surface area of 2.0 to 7.0 m ² / g. By making the specific surface area in this range, the powder scattering is remarkably prevented, and by making the average particle size in this range, characteristics such as metrology are improved and suitable for optical materials and electronic materials. Tantalum oxide.

Example 1
(First step) In a reaction vessel, 200 g of tantalum-containing material having a composition of 73.0 wt% Ta, Cu 19100 wt ppm, Mn 102000 wt ppm, Ni 10200 wt ppm, Nb 100 wt ppm in terms of each element was converted to 40 wt% The solution was put into 200 ml of hydrofluoric acid, and the temperature of the aqueous solution was maintained at 80 ° C. while stirring the aqueous solution, so that the tantalum-containing material was dissolved and leached. The obtained suspension containing the tantalum-containing aqueous solution and the insoluble residue was filtered with a qualitative filter paper to obtain 250 mL of a tantalum-containing aqueous solution containing 580 g / L in terms of Ta.

  (Second step) To the tantalum-containing aqueous solution obtained in the first step, appropriate amounts of water and sulfuric acid are added, the tantalum concentration of the aqueous phase is 100 g / L in terms of Ta, hydrofluoric acid is 7% by weight, sulfuric acid concentration Was adjusted to 15% by weight.

  The organic phase is a dilute solution of kerosene with a volume ratio of tributyl phosphate of 50%, and the extraction operation is performed by placing the organic phase and the aqueous phase in a separatory funnel at O / A (volume ratio) = 6/1. And shaken at room temperature for 5 minutes. After shaking, the mixture was allowed to stand for at least 10 minutes, and when the organic phase and the aqueous phase were sufficiently separated, the organic phase and the aqueous phase were separated.

  The organic phase after separation was washed with an aqueous phase of 10% by weight sulfuric acid. In this washing operation, the organic phase and the aqueous phase were put into a separatory funnel at O / A (volume ratio) = 6/1, and a shaker was used. And shaken at room temperature for 5 minutes. After shaking, the mixture was allowed to stand for at least 10 minutes, and when the organic phase and the aqueous phase were sufficiently separated, the organic phase and the aqueous phase were separated.

  After the organic phase after separation, a 10% by weight sulfuric acid aqueous phase is newly prepared, and the same washing operation is repeated, and a new 10% by weight sulfuric acid aqueous phase is prepared each time, and a total of 10 washing operations are performed. An organic phase separated from the aqueous phase was obtained.

  The separated organic phase was back-extracted with a 2% by weight aqueous ammonia solution as an aqueous phase. In this back extraction operation, the organic phase and the aqueous phase were placed in a separatory funnel at O / A (volume ratio) = 6/1 and shaken on a shaker at room temperature for 5 minutes. After shaking, the mixture was allowed to stand for at least 10 minutes, and when the organic phase and the aqueous phase were sufficiently separated, the organic phase and the aqueous phase were separated. The obtained aqueous phase had a tantalum concentration of 100 g / L in terms of Ta, and a phosphorus (P) concentration of 2000 ppm by weight in terms of P / Ta.

  (Third step) Next, an appropriate amount of nitric acid and water was added to the aqueous tantalum solution obtained in the second step to obtain 1525 mL of a tantalum aqueous solution having a nitric acid concentration of 1 N and a tantalum concentration of 95 g / L in terms of Ta. .

  As the porous adsorbent, 10 g of activated carbon (powder) was previously stirred and suspended in 100 mL of 1N nitric acid for 5 minutes at room temperature, then filtered and washed with pure water to remove metal impurities. did.

  In this tantalum aqueous solution, 10 g of activated carbon after removing metal impurities was added, stirred and suspended at room temperature for 5 minutes, and then filtered to obtain an aqueous tantalum solution from which the activated carbon adsorbing organic matter was separated. At this time, the fluorine concentration in the aqueous solution was about 50% by weight in terms of F / Ta.

  (Fourth step) Next, an appropriate amount of pure water is added to the tantalum aqueous solution obtained in the third step to obtain a tantalum aqueous solution having a tantalum concentration of 50 g / L in terms of Ta. The tantalum aqueous solution is heated to 60 ° C. and stirred. Then, a 3 wt% aqueous ammonium carbonate solution heated to 60 ° C. was gradually added.

  In this neutralization operation, initial neutralization in which the aqueous ammonium carbonate solution was added until immediately before precipitation of hydroxide was performed. In the initial neutralization, the equivalent amount of the ammonium carbonate aqueous solution necessary for the start of hydroxide precipitation of the tantalum aqueous solution is previously determined by titration, etc., and then the aqueous ammonium carbonate solution is added to the tantalum aqueous solution slightly less than the precipitation start equivalent. An initial neutralization solution was prepared by addition.

  That is, a saturated solution for hydroxide was created.

  A 3% by weight aqueous ammonium carbonate solution heated to 60 ° C. was added as a basic aqueous solution to the aqueous tantalum solution obtained by initial neutralization. The temperature of the aqueous tantalum solution during the neutralization was continuously maintained at 60 ° C., and a 3 wt% aqueous ammonium carbonate solution was added to the aqueous tantalum solution until the pH reached 9. In this case, the addition rate was set to 0.01 eq / min in terms of reaction equivalent / hour.

  The suspension containing the precipitated tantalum hydroxide was filtered, and the tantalum hydroxide separated from the suspension was washed with pure water and filtered to obtain tantalum hydroxide.

The composition after drying of the tantalum hydroxide obtained in the fourth step was subjected to composition analysis by gravimetric method, ICP, atomic absorption spectrophotometry, and liquid chromatograph.
Ta 67.0% by weight
F 0.03% by weight
P 3 ppm by weight
Cu Less than 1 ppm by weight Mn Less than 1 ppm by weight Ni Less than 1 ppm by weight Nb Less than 1 ppm by weight Moisture 0.09% by weight
Met.

The powder characteristics of the tantalum hydroxide obtained in the fourth step after drying and pulverization were an average particle diameter of 12.0 μm and a specific surface area of 30.0 m ² / g.

  (Fifth Step) Next, the tantalum hydroxide obtained in the fourth step was dried with heat at 100 ° C. for 24 hours. After drying, the obtained tantalum hydroxide was pulverized using a ball mill. Then, it baked in the air at 1000 ° C. for 8 hours with a heater to obtain tantalum oxide.

When the composition of the tantalum oxide obtained in the fifth step was analyzed by a gravimetric method, ICP, atomic absorption photometry, and liquid chromatography,
Ta ₂ O ₅ 99.9% by weight
F 0.03 ppm by weight
P Less than 2 ppm by weight Cu Less than 1 ppm by weight Mn Less than 1 ppm by weight Ni Less than 1 ppm by weight Nb Less than 1 ppm by weight.

The powder characteristics of the tantalum oxide obtained in the fifth step were as follows: the average particle size was 3.0 μm and the specific surface area was 3.0 m ² / g.

(Example 2)
(First step) In a reaction vessel, 200 g of tantalum containing a composition of Ta 96.6 wt%, Cu 160 wt ppm, Mn less than 10 wt ppm, Ni 70 wt ppm, Nb 140 wt ppm in terms of each element was added to 55 wt% The solution was put into 200 mL of hydrofluoric acid, and the temperature of the aqueous solution was maintained at 80 ° C. while stirring the aqueous solution, so that the tantalum-containing material was dissolved and leached.

  The obtained suspension containing tantalum-containing aqueous solution and undissolved residue was filtered with a qualitative filter paper to obtain 255 mL of a tantalum-containing aqueous solution containing 760 g / L in terms of Ta.

  (Second Step) Next, an appropriate amount of water and sulfuric acid are added to the tantalum-containing aqueous solution obtained in the first step, the tantalum concentration of the aqueous phase is 70 g / L in terms of Ta, and the hydrofluoric acid concentration is 5% by weight. The sulfuric acid concentration was adjusted to 10% by weight.

  The organic phase is a dilute solution of kerosene with a volume ratio of tributyl phosphate of 50%, and the extraction operation is performed by placing the organic phase and the aqueous phase in a separatory funnel at O / A (volume ratio) = 6/1. And shaken at room temperature for 5 minutes. After shaking, the mixture was allowed to stand for at least 10 minutes, and when the organic phase and the aqueous phase were sufficiently separated, the organic phase and the aqueous phase were separated.

  Next, the separated organic phase is washed with an aqueous phase of 10% by weight sulfuric acid, and the washing operation is carried out by placing the organic phase and the aqueous phase in a separatory funnel at O / A (volume ratio) = 3/1, and applying to a shaker. Shake for 5 minutes at room temperature. After shaking, the mixture was allowed to stand for at least 10 minutes, and when the organic phase and the aqueous phase were sufficiently separated, the organic phase and the aqueous phase were separated.

  After the organic phase after separation, a 10% by weight sulfuric acid aqueous phase is newly prepared, and the same washing operation is repeated, and a new 10% by weight sulfuric acid aqueous phase is prepared each time, and a total of 8 washing operations are performed. An organic phase separated from the aqueous phase was obtained.

  The separated organic phase was back-extracted with a 2% by weight aqueous ammonia solution as an aqueous phase. In this back-extraction operation, the organic phase and the aqueous phase were placed in a separatory funnel at O / A (volume ratio) = 3/1. And shaken on a shaker at room temperature for 5 minutes. After shaking, the mixture was allowed to stand for at least 10 minutes, and when the organic phase and the aqueous phase were sufficiently separated, the organic phase and the aqueous phase were separated. The resulting aqueous phase had a tantalum concentration of 50 g / L in terms of Ta and a phosphorus (P) concentration of 1800 ppm by weight in terms of P / Ta.

  (Third step) Next, an appropriate amount of nitric acid and water was added to the aqueous tantalum solution obtained in the second step to obtain 4290 mL of an aqueous tantalum solution having a nitric acid concentration of 1 N and a tantalum concentration of 45 g / L in terms of Ta. . At this time, the fluorine concentration in the raw solution was about 50% by weight in terms of F / Ta.

  In this tantalum aqueous solution, 50 g of activated carbon after removing metal impurities was added as a porous adsorbent, stirred and suspended at room temperature for 5 minutes, filtered, and separated from the activated carbon adsorbing organic matter. Got. As this porous adsorbent, 50 g of activated carbon (powder) was previously stirred and suspended in 500 ml of 0.5N nitric acid at room temperature for 5 minutes, then filtered and washed with pure water to remove metal impurities. I used something.

  (Fourth Step) Next, an appropriate amount of pure water was added to the tantalum aqueous solution obtained in the third step to obtain a tantalum aqueous solution having a tantalum concentration of 10 g / l. The liquid temperature of this tantalum aqueous solution was 15 ° C., and 12% by weight of aqueous ammonium carbonate heated to 60 ° C. was gradually added to the stirring of the 15 ° C. tantalum aqueous solution.

  In this neutralization operation, initial neutralization in which the aqueous ammonium carbonate solution was added until immediately before precipitation of hydroxide was performed. In the initial neutralization, the equivalent amount of the ammonium carbonate aqueous solution necessary for the start of hydroxide precipitation of the tantalum aqueous solution is previously determined by titration, etc., and then the aqueous ammonium carbonate solution is added to the tantalum aqueous solution slightly less than the precipitation start equivalent. An initial neutralization solution was prepared by addition.

  That is, a saturated solution for hydroxide was created.

  A 3% by weight ammonium carbonate aqueous solution was added as a basic aqueous solution to an aqueous solution of tantalum obtained by initial neutralization. The temperature of the tantalum aqueous solution at the time of neutralization was heated and maintained at 60 ° C., and a 3 wt% ammonium carbonate aqueous solution was added to the tantalum aqueous solution until the pH reached 9. In this case, the addition rate was 0.05 eq / min in terms of reaction equivalent / hour.

  The suspension containing the precipitated tantalum hydroxide was filtered, and the tantalum hydroxide separated from the suspension was washed with pure water and filtered to obtain tantalum hydroxide.

The composition after drying of the tantalum hydroxide obtained in the fourth step was analyzed by gravimetry, ICP, atomic absorption spectrophotometry, and liquid chromatograph.
Ta 67.0% by weight
F 0.10% by weight
P 10wtppm
Cu Less than 1 ppm by weight Mn Less than 1 ppm by weight Ni Less than 1 ppm by weight Nb Less than 1 ppm by weight Water 0.10% by weight
Met.

The powder characteristics after drying of the tantalum hydroxide obtained in the fourth step were an average particle diameter of 7.5 μm and a specific surface area of 71.7 m ² / g.

  (Fifth Step) Next, the tantalum hydroxide obtained in the fourth step was dried with heat at 100 ° C. for 24 hours. After drying, the obtained tantalum hydroxide was pulverized using a ball mill. Then, it baked in the air at 1000 ° C. for 5 hours with a heater to obtain tantalum oxide.

The composition of tantalum oxide obtained in the fifth step was analyzed by gravimetry, atomic absorption photometry, ICP, and liquid chromatograph.
Ta ₂ O ₅ 99.9% by weight
F 0.5 ppm by weight
P 9wtppm
Cu Less than 1 ppm by weight Mn Less than 1 ppm by weight Ni Less than 1 ppm by weight Nb Less than 1 ppm by weight

The powder characteristics of the tantalum oxide obtained in the fifth step were an average particle size of 5.0 μm and a specific surface area of 4.5 m ² / g.

Claims (5)

  A tantalum oxide characterized in that the content of F is 0.5 ppm by weight or less and the content of P is 100 ppm by weight or less.   The tantalum oxide according to claim 1, wherein the content of P is 10 ppm by weight or less. Leaching the tantalum-containing material with hydrofluoric acid or a mixed acid of hydrofluoric acid and another inorganic acid, followed by solid-liquid separation to obtain a tantalum-containing aqueous solution,
Tantalum is extracted as a tantalum complex salt from the aqueous solution obtained in the first step as a tantalum complex salt using an orthophosphoric acid ester extractant, and the extract separated from the resulting metal impurities is washed with a sulfuric acid aqueous solution, The second step to obtain a tantalum solution by back extraction and after the treatment of adding an inorganic acid to the extract extracted with aqueous ammonia obtained in the second step, the porous adsorbent is brought into contact, and then solid-liquid separation is performed. The third step for obtaining a tantalum solution from which the components have been removed, the fourth step for obtaining tantalum hydroxide by adding an ammoniacal basic aqueous solution to the solution obtained in the third step, and the tantalum hydroxide obtained in the fourth step The method for producing tantalum oxide according to claim 1, further comprising a fifth step of obtaining tantalum oxide by firing the material.   The method for producing tantalum oxide according to claim 3, wherein the sulfuric acid concentration in the second step is 10 to 12% by weight.   4. The method for producing tantalum oxide according to claim 3, wherein the ammonia concentration used for back extraction in the first step is 1 to 3 wt%.