WO2012132107A1

WO2012132107A1 - Method for producing and method for isolating/purifying niobium

Info

Publication number: WO2012132107A1
Application number: PCT/JP2011/077009
Authority: WO
Inventors: 龍太郎黒田
Original assignee: 三井金属鉱業株式会社
Priority date: 2011-03-31
Filing date: 2011-11-24
Publication date: 2012-10-04
Also published as: JP2012211048A; WO2012132107A9; JP5103541B2

Abstract

Provided is a processing method for recovering a highly pure niobium starting material from glass scraps containing niobium and boron. The method for isolating/purifying niobium has: a first step for extracting niobium into an organic solvent by contacting the organic solvent, which dilutes a phosphoryl-based extraction agent using a petroleum hydrocarbon diluting agent, to a starting material aqueous solution containing niobium, hydrofluoric acid, and sulfuric acid; a second step for further decreasing the impurities present in the organic solvent by cleaning the post-extraction organic solvent using water or sulfuric acid; and a third step for obtaining a purified niobium liquid by using an aqueous solvent to back extract the niobium contained in the organic solvent from which the impurities have been decreased. The method for isolating/purifying niobium is characterized by the free hydrofluoric acid concentration in the starting material aqueous solution in the first step being 2-10 mol/L, and the amount of contained boron, an impurity, in the purified niobium liquid being no greater than 10 ppm with respect to niobium oxide obtained from the purified niobium liquid.

Description

Niobium separation and purification method and production method

The present invention relates to a separation and purification method and a production method for obtaining niobium, and in particular, to a separation and purification technique of niobium that can reduce boron.

Niobium (hereinafter referred to as Nb in some cases) is frequently used as a steel additive because it has the effect of stabilizing carbon in steel and preventing intergranular corrosion. Niobium oxide is also used for single crystals containing niobium such as optical, electronic ceramic, and lithium niobate (LN). A niobium alloy is used as a conductive tube of a lamp light emitting part in a high-pressure sodium lamp, and is also used as an additive element such as a superconducting material or a superalloy.

By the way, niobium is usually obtained from raw materials such as ore and scrap. However, since such raw materials contain a lot of impurities, it is necessary to separate and purify them. As this separation and purification method, for example, a hydrofluoric acid dissolution-solvent extraction method is generally known (see Patent Documents 1 and 2). In this separation and purification method, raw materials such as ore and scrap are pulverized and dissolved with hydrofluoric acid, and then sulfuric acid is added to adjust the solution concentration. Then, the adjustment liquid is filtered with a filter press to obtain a clean solution, and niobium is extracted into MIBK by solvent extraction with MIBK (methyl isobutyl ketone). At this time, impurities such as iron (Fe), manganese (Mn), silicon (Si), etc. contained in the raw material remain in the extraction residual liquid, thereby removing these impurities.

Then, MIBK containing niobium is washed with dilute sulfuric acid and further back-extracted with water to obtain a pure niobium aqueous solution. Ammonia water is added to the niobium aqueous solution thus obtained to precipitate a hydroxide precipitate, the precipitate is filtered and dried, and finally calcined to obtain niobium oxide.

In recent years, niobium is a rare product, has many uses, and the demand has increased significantly, and the supply of niobium cannot keep up with the demand. For this reason, niobium is reused by using waste such as glass scrap as a raw material.

Boron exists as an impurity in the raw material, and this boron has not been noticed so far. As a result of the study by the present inventors, when boron-based glass scrap is used as a raw material, boron-based glass scrap raw material is separated by solvent extraction using MIBK that is generally used as described above. From this, it was found that it was difficult to obtain high-purity niobium.

JP-A-5-2614 Japanese Patent No. 3634747

The present invention provides a technology capable of separating and purifying high-purity niobium from which raw materials containing a large amount of boron, such as boron-based glass scrap, are reliably separated and removed, and other impurities are removed. Objective.

The present invention provides a phosphoryl-based extractant having the following general formula in a raw material aqueous solution containing niobium and containing hydrofluoric acid and sulfuric acid;

(Wherein R is hydrogen, or an alkyl group or aryl group having 1 to 20 carbon atoms) is brought into contact with an organic solvent diluted with a petroleum hydrocarbon diluent to convert niobium A first step of extraction into an organic solvent;
A second step of further reducing impurities remaining in the organic solvent by washing the organic solvent after the extraction with water or sulfuric acid, and back-extracting niobium contained in the organic solvent in which the impurities are reduced with an aqueous solvent A niobium separation and purification method comprising a third step of obtaining a niobium purification solution, wherein the concentration of free hydrofluoric acid in the raw material aqueous solution in the first step is 2 to 10 mol / L; The boron content of liquid impurities is 10 ppm or less with respect to niobium oxide obtained from the niobium refined liquid.

In the method for separating and purifying niobium in the present invention, a raw material aqueous solution containing niobium and containing hydrofluoric acid and sulfuric acid is used. The raw material aqueous solution is not particularly limited as long as it is an aqueous solution containing niobium. For example, raw material ore containing niobium (eg, tantalite, columbite, pyrochlore, etc.) is hydrofluoric acid or fluoride. It can be obtained by dissolving with a mixed acid of hydrogen acid and sulfuric acid, filtering if necessary, and adjusting the concentration with hydrofluoric acid, sulfuric acid and / or water as appropriate. Therefore, such a raw material aqueous solution contains hydrofluoric acid and sulfuric acid.

In addition to raw ores, raw materials that can be used include niobium compounds with low solubility in liquids, such as waste silos and scraps containing fluorosilicates, fluorotantalates, and fluoroniobates, niobium ferroalloys, niobium Examples thereof include metal scrap and LiNbO ₃ (LN) scrap. More specifically, potassium fluoride tantalate, flux cleaning water when producing niobium powder from potassium fluoride niobate, and neutralization waste generated from surface treatment liquid, waste liquid discharged from target material manufacturers, etc. And waste such as low-grade niobium products that cannot be used for the production of niobium powder.

In the present invention, it is possible to reduce impurities contained in the raw material prior to the preparation of the aqueous raw material solution. A method for removing impurities from the raw material in advance may be performed in accordance with a known method, and can be preferably performed by, for example, the following alkali decontamination treatment. That is, the raw material is stirred and mixed with a strong alkali solution (for example, sodium hydroxide solution) while being appropriately heated to obtain a sparse slurry, which is then filtered. Next, the residue obtained by filtration is washed with a mineral acid other than hydrofluoric acid (for example, sulfuric acid), and the mineral acid is filtered off. The cake with reduced impurities obtained by this filtration separation is dissolved with hydrofluoric acid or the like in the same manner as the above-mentioned ordinary raw materials. In particular, in this alkali disaggregation treatment, fluoroniobate (K ₂ NbF _{7 and the} like) and oxyfluoroniobate (K ₃ Nb ₂ F ₁₁ O and the like) have low solubility in hydrofluoric acid as they are. It is effective to carry out alkali lysis treatment. In addition, since niobium oxide is not alkaline decontaminated below 100 ° C., it will not be necessary to perform alkaline decontamination on the raw material ore of the oxide. In the case of ferroalloys, it is effective to perform alkaline lysis because impurities mainly composed of iron are reduced.

In the present invention, prior to the above-mentioned dissection or hydrofluoric acid dissolution, the raw material can be appropriately pulverized with a ball mill or the like according to the form of the raw material. Thereby, resolving or hydrofluoric acid dissolution can be performed efficiently. In particular, when the raw material is not a powder but a lump, it is more preferable to coarsely pulverize with a jaw crusher or the like and further finely pulverize with a ball mill or the like.

In the present invention, when tantalum (Ta) is contained in the raw material, the following pretreatment is preferably performed when the raw material aqueous solution used in the first step is used. When Ta is contained in the raw material solution in which the raw material is dissolved, the free hydrofluoric acid concentration and sulfuric acid concentration of the raw material solution are adjusted as appropriate, and then the organic solvent (phosphoryl-based extractant and carbonization) used in the present invention is used. Contact with 4-diethyl-2-pentanone (methyl isobutyl ketone / MIBK) to extract and remove Ta, and then adjust the free hydrofluoric acid concentration and sulfuric acid concentration. Thus, a raw material aqueous solution used in the first step of the present invention can be obtained. The concentration of free hydrofluoric acid in the raw material solution when removing Ta is preferably 0.1 mol / L or more and less than 2.0 mol / L, and more preferably 0.2 mol / L to 1.8 mol / L. . The sulfuric acid concentration is preferably 0.2 mol / L to 3.0 mol / L, and more preferably 0.5 mol / L to 2.0 mol / L. If the free hydrofluoric acid concentration and the sulfuric acid concentration are too low, extraction of Ta into the organic solvent becomes insufficient, and if it is too high, Nb is easily extracted into the organic solvent together with Ta, resulting in loss of Nb.

In the present invention, the concentration of niobium in the raw material aqueous solution is not particularly limited, but the higher the concentration, the more advantageous the amount of drainage. In general, the concentration of the aqueous raw material solution varies depending on the composition of Nb in the ore (raw material) before separation, and is therefore in a wide range of 30 to 300 g / L. Usually, Nb in the raw material aqueous solution is present in the aqueous solution in the form of a fluoride such as H ₂ NbF ₇ , NbF ₅ · 2HF or H ₂ NbOF ₅ , and in addition to this, the surplus that exists free Hydrofluoric acid is present. In the present specification, the surplus hydrofluoric acid present free is referred to as “free hydrofluoric acid”.

In the method for separating and purifying niobium according to the present invention, the raw material aqueous solution containing niobium and containing hydrofluoric acid and sulfuric acid is contacted with a solvent obtained by diluting a phosphoryl-based extractant with a petroleum-based hydrocarbon diluent. Perform one step. This phosphoryl-based extractant is diluted with a diluent. When the extractant is used alone, particularly when a large amount of metal is extracted in the extractant, the specific gravity difference with the aqueous phase becomes very small. This is because there is an inconvenience that phase separation is difficult. Some extractants are solid at room temperature, and it is necessary to use a diluent that dissolves the extractant. Even in this case, petroleum hydrocarbon diluent is preferred. In addition, the phosphoryl-type extractant and petroleum-type hydrocarbon diluent used in the present invention may each be one kind or a mixture of two or more kinds, and are not particularly limited.

Examples of the phosphoryl-based extractant used in the present invention include the following general formula:

(However, R is hydrogen, or an alkyl group or aryl group having 1 to 20 carbon atoms). Preferred examples of such phosphoryl-based extractants include tri-n-butyl phosphate, triisobutyl phosphate, tri-n-octyl phosphate, tris (2-ethylhexyl) phosphate, tri-n-butylphosphine oxide, tri-n. -Ethylhexylphosphine oxide, tri-n-octylphosphine oxide, tri-n-decylphosphine oxide and the like. The most preferred of these are
Tri-n-octylphosphine oxide (hereinafter also referred to as TOPO) or tri-n-butyl phosphate (hereinafter also referred to as TBP). This is because TOPO has a high ability to separate niobium and boron, and TBP has a slightly lower ability to separate niobium and boron than TOPO, but is relatively inexpensive.

The petroleum hydrocarbon diluent is not particularly limited, and various organic solvents can be used. Examples of the petroleum hydrocarbon diluent include toluene, xylene, cyclohexane, benzene, kerosene, diethylbenzene, Shellzol A (manufactured by Shell Chemical Japan Co., Ltd.), and Ipsol (manufactured by Idemitsu Kosan Co., Ltd.). Benzene and toluene are not preferred because of environmental problems, but can be used.

In the present invention, the mixing ratio of the phosphoryl-based extractant and the petroleum-based hydrocarbon diluent is determined by volume when the extractant is liquid, by mass when the extractant is solid, and extractant: diluent = It is preferably 5:95 to 95: 5, and more preferably extractant: diluent = 10: 90 to 90:10. When the mixing ratio of the extractant is smaller than 5:95, the extraction ability of niobium tends to be lowered, and when the ratio of the extractant is larger than 95: 5, the adverse effect when the diluent is not used. Will be insufficient.

The concentration of free hydrofluoric acid in the aqueous raw material solution in the first step of the niobium separation and purification method of the present invention is 2 to 10 mol / L. The free hydrofluoric acid concentration is more preferably 4 to 8 mol / L, and further preferably 5 to 7 mol / L. When the concentration of free hydrofluoric acid in the raw material aqueous solution is less than 2 mol / L, the phosphoryl-based extractant becomes difficult to extract niobium in the first step, and a lot of niobium tends to remain in the extraction residual liquid. If it exceeds 10 mol / L, not only niobium but also boron will be extracted in the first step, and the boron content in the niobium refined solution will increase rapidly.

Subsequently, in the niobium separation and purification method of the present invention, the organic solvent after extraction in the first step is washed with water or sulfuric acid to perform a second step of further reducing impurities remaining in the organic solvent. In removing impurities in the second step, when washing with sulfuric acid, 10 mol / L or less is preferable, 7.5 mol / L or less is more preferable, and 5 mol / L or less is more preferable. When it exceeds 10 mol / L, reduction of impurities becomes insufficient. Although washing with water is possible, washing with a dilute sulfuric acid solution is more efficient. In this case, the sulfuric acid concentration is preferably 0.5 mol / L or more, more preferably 0.7 mol / L or more, and 1.0 mol / L. The above is more preferable.

When washing is performed in a state where the concentration of water or sulfuric acid is low, the effect of washing niobium and impurities increases, so that niobium tends to be lost. Therefore, it is necessary to increase the ratio (O / A ratio) between the flow rate (O) of the organic solvent and the flow rate (A) of water or sulfuric acid in the second step. In this case, care should be taken because even if the flow rate changes slightly, it tends to be over-cleaned or under-cleaned. The O / A ratio in the second step is preferably 1 to 50, more preferably 1.5 to 40, and further preferably 2 to 30. When the O / A ratio is less than 1, the loss of niobium tends to increase, and when it exceeds 50, the reduction of impurities tends to be insufficient. In addition, the value (O / A ratio × sulfuric acid concentration) obtained by multiplying the O / A ratio by the sulfuric acid concentration (g / L) is preferably 100 (g / L) or less, more preferably 80 or less, and even more preferably 60 or less. . If the value obtained by multiplying the O / A ratio by the sulfuric acid concentration exceeds 100, the reduction of impurities tends to be insufficient.

Furthermore, in the niobium separation and purification method of the present invention, the third step of obtaining a niobium purified solution by back-extracting niobium contained in the organic solvent in which impurities are reduced in the second step with an aqueous solvent is performed. In this third step, niobium contained in the organic solvent with reduced impurities in the second step is back-extracted with an aqueous solvent. The purified niobium solution obtained by this back extraction contains niobium with high purity. The aqueous solvent used in the third step of the present invention is not particularly limited, but pure water or an aqueous solution containing ammonia and / or ammonium ions can be used, and these aqueous solvents can sufficiently extract back niobium. Is preferable. Among these, pure water, particularly highly pure water is most preferable because it does not contain impurities and niobium is not easily back-extracted. Examples of the aqueous solution containing ammonia and / or ammonium ions include dilute aqueous ammonia, aqueous ammonium fluoride solution, aqueous ammonium hydrogen fluoride solution, and the like.

In the third step of the present invention, the flow ratio (O / A ratio) of the organic solvent to the aqueous solvent (the aqueous solvent includes the raw material aqueous solution and the solvent in sulfuric acid) is 0.5 to 16. It is preferable. If the O / A ratio is less than 0.5, the concentration of the resulting niobium liquid will be low, resulting in poor production efficiency and an increased amount of waste water. On the other hand, when the O / A ratio exceeds 16, the amount of niobium remaining in the organic solvent increases, and the amount to be newly extracted decreases with repeated use.

The niobium purification solution obtained by the niobium separation and purification method of the present invention has an impurity boron content of 10 ppm or less with respect to niobium oxide.

In the niobium separation and purification method according to the present invention, the sulfuric acid concentration in the raw material aqueous solution in the first step is 8 mol / L or less, and is 0.1 to 1.25 with respect to the hydrofluoric acid concentration in the raw material aqueous solution. It is preferable to be doubled. When the ratio of sulfuric acid concentration to hydrofluoric acid concentration in the raw material aqueous solution is less than 0.1 times, the amount of niobium that is not extracted into the organic solvent in the first step tends to increase. However, the ratio of niobium to be extracted into an organic solvent increases, and the separation of niobium and boron tends to be insufficient.

In the niobium separation and purification method according to the present invention, in the first step, the flow rate (volume) ratio of the organic solvent to the aqueous solvent (herein, the aqueous solvent includes the raw material aqueous solution and the solvent in sulfuric acid). The (O / A ratio) is preferably 0.05 to 3. If the O / A ratio is less than 0.05, niobium extraction tends to be insufficient, the amount of organic solvent extracted per unit volume increases (high load concentration), and the phase separation from the aqueous phase is reduced. Deteriorate. On the other hand, when the O / A ratio exceeds 3, the possibility of causing an emulsion increases, which is not preferable.

The method for separating and purifying niobium according to the present invention includes a step of circulating part or all of the organic solvent after back extraction in the third step as part or all of the organic solvent in the first step. Is preferred. If it does in this way, it will become possible to reduce the usage-amount of an organic solvent.

It is preferable to produce niobium oxide by adding ammonia to the niobium purification solution obtained by the niobium separation and purification method of the present invention to precipitate niobium hydroxide, filtering the precipitate, and calcining it. Since the niobium purification solution obtained by the niobium separation and purification method of the present invention is reliably separated and removed of boron and other impurities are also removed, high-purity niobium oxide can be obtained. Ammonia can be added in the form of a gas, but is preferably added in the form of an aqueous ammonia solution (NH ₄ OH). The concentration of the aqueous ammonia solution and the amount added thereof can be appropriately determined according to the amount of niobium in the niobium purified solution.

In the present invention, the niobium recovery rate is preferably 50% or more, more preferably 60% or more, still more preferably 70% or more, and particularly preferably 80% or more. The niobium recovery rate is the amount of niobium calculated by multiplying the niobium concentration of the purified niobium solution obtained in the third step by the volume of the purified niobium solution obtained in the third step. The ratio to the niobium amount calculated by multiplying the niobium concentration by the volume of the raw material aqueous solution used in the first step. If the recovery rate of niobium is low, industrial implementation becomes difficult. Therefore, a niobium recovery rate of 50% or more is preferable.

The niobium oxide obtained by the niobium production method of the present invention has a content of 10 ppm or less in boron, silicon, potassium, tin, antimony, copper, and zinc as impurities, and further, iron as impurities, Each content in titanium and phosphorus is 1 ppm or less.
Such high-purity niobium oxide can greatly improve these characteristics when applied to electronic materials and optical materials.

According to the present invention, even when glass scrap containing a large amount of boron is used as a raw material, it is possible to obtain high-purity niobium that reliably separates and removes boron and reduces other impurities.

Schematic diagram of apparatus related to separation and purification of niobium.

Hereinafter, embodiments of the present invention will be described with reference to examples and comparative examples.

First, the raw material aqueous solution used in this embodiment will be described. As a raw material, 2000 kg of Nb glass scrap was roughly pulverized with a jaw crusher and then finely pulverized with a wet ball mill (2000 L of industrial water) to obtain an Nb glass scrap slurry (1000 g / L). This Nb glass scrap slurry was put into a reaction vessel, and 3100 kg of 48 mass% sodium hydroxide was added over 12 hours. After completion of the addition of sodium hydroxide, stirring was continued for 15 hours while maintaining the liquid temperature at 75 ° C. Thereafter, the entire amount was filtered and separated with a filter press, and washed with water with a filter press to obtain a lysed and washed cake. The obtained lyophilized washed cake was slurried with 3000 L of industrial water, sulfuric acid was added, and the slurry pH was adjusted to pH 2.0. After the sulfuric acid treatment, the slurry was separated by filtration with a filter press to obtain a sulfuric acid-treated cake. And this sulfuric acid treatment cake was melt | dissolved with 80 weight% hydrofluoric acid. This solution was filtered with a filter press to obtain a raw material solution 3030L (Nb ₂ O ₅ 300 g / L, free hydrofluoric acid 1 mol / L).

Next, a raw material aqueous solution used in the first step was prepared from the obtained raw material solution as follows. After adding predetermined amounts of 80 wt% hydrofluoric acid and 98 wt% sulfuric acid to 150 L of raw material solution, industrial water is added to bring the total volume to 450 L, so that the desired hydrofluoric acid concentration and sulfuric acid concentration A raw material aqueous solution was prepared. The sulfuric acid concentration was calculated from the 98 wt% sulfuric acid addition amount and the total liquid amount of 450 L, and for confirmation, the sulfur concentration was measured by ICP emission analysis and converted into the sulfuric acid concentration for comparison. This aqueous raw material solution is Nb ₂ O ₅ 100 g / L, and is the hydrofluoric acid concentration and sulfuric acid concentration of each of Examples and Comparative Examples described below. As a result of measuring other composition of the raw solution as follows, the composition of the raw solution (each element / _Nb 2 _{O 5)} is selected from boron _{_{(B / Nb 2 O 5)}} 3000 mass ppm, silicon (Si / Nb ₂ O ₅ ) 10000 mass ppm, potassium (K / Nb ₂ O ₅ ) 300 mass ppm, tin (Sn / Nb ₂ O ₅ ) 10000 mass ppm, zinc (Zn / Nb ₂ O ₅ ) 20000 mass ppm, iron ( Fe / Nb ₂ O ₅ ) 4000 mass ppm, titanium (Ti / Nb ₂ O ₅ ) 50000 mass ppm, copper (Cu / Nb ₂ O ₅ ) 100 mass ppm, phosphorus (P / Nb ₂ O ₅ ) 800 mass ppm (These compositions were common to the raw material aqueous solutions of the examples and comparative examples).
-Sulfuric acid: Sulfur is measured by ICP emission spectroscopy and converted to sulfuric acid concentration-Free hydrofluoric acid: ion exchange separation, fluorine ion electrode method (standard addition)
-K, Na: Atomic absorption photometry-Others: ICP emission spectroscopy

Next, the separation and purification of niobium will be described. Niobium was separated and extracted as follows using the prepared raw material aqueous solution and a countercurrent multistage mixer settler. Table 1 shows operating conditions in each of the first to third steps, and FIG. 1 shows a specific apparatus configuration. In addition, a countercurrent multi-stage system is adopted as a method for mixing and contacting the liquid in each process. Specifically, mixing contact is performed by supplying an organic solvent to the first stage and an aqueous solvent to the final stage. It was. First, tri-n-octyl phosphine oxide (manufactured by Hokuko Chemical Co., Ltd.) as an extractant was added to Shellsol A150 (manufactured by Shell Chemical Japan Co., Ltd.) as a diluent at a mass ratio of 35:65 A diluted organic solvent for extraction (hereinafter simply referred to as extraction solvent) was prepared, and niobium was extracted. As the first step (FIG. 1, A: Nb extraction stage), the organic solvent was added to the raw material aqueous solution, and mixed and contacted under the conditions shown in Table 1. Specifically, the free hydrofluoric acid concentration is fixed at 6 mol / L, and the sulfuric acid concentration has a coefficient (ratio of sulfuric acid concentration to free hydrofluoric acid concentration in the raw aqueous solution) of 0.05 to 1.5. (Table 2, Comparative Example 1, Examples 1 to 6, and Comparative Example 6). Next, as a second step (FIG. 1, B: Nb purification stage), 3 mol / L dilute sulfuric acid (aqueous phase) is added to the organic solvent obtained in the first step and mixed under the conditions shown in Table 1. Made contact. This transferred niobium and other impurities to dilute sulfuric acid, leaving pure niobium in the organic solvent. Furthermore, as a third step (FIG. 1, C: Nb strip stage), a 1 mol / L aqueous ammonium fluoride solution (aqueous phase) was added to the organic solvent obtained in the second step, and the conditions shown in Table 1 Then, niobium was extracted and mixed to obtain a purified niobium solution.

While stirring the obtained niobium purified solution, 25 mass% ammonia water was added in about 15 minutes until pH 9.0 was reached, thereby precipitating niobium hydroxide. The precipitate was filtered off, dried, and calcined at 900 ° C. for 5 hours to obtain niobium oxide (Nb ₂ O ₅ ).

Table 2 shows the impurity concentration and the niobium recovery rate for the niobium oxide obtained under each condition. Each impurity concentration (impurity weight concentration with respect to niobium oxide weight) and niobium recovery shown in Table 2 were measured as follows.
-Si: ion exchange separation / molybdenum blue absorptiometry -K: ion exchange separation, atomic absorptiometry -others: ion exchange separation, ICP emission spectroscopy

As shown in Table 2, when the coefficient (ratio of sulfuric acid concentration to free hydrofluoric acid concentration in the raw material aqueous solution) was 0.05 (Comparative Example 1), boron in niobium oxide was less than 0.1 ppm. However, the niobium recovery rate was poor. In Examples 1 to 6 (coefficient 0.1 to 1.25), boron in the niobium oxide was 10 ppm or less, and the niobium recovery rate was 50% or more. Further, when the coefficient is 1.5 (Comparative Example 2), the recovery rate of niobium is high, but the boron in niobium oxide exceeds 10 ppm, the boron separation and removal efficiency is poor, and many other impurities remain. Turned out to be.

Subsequently, the case where the free hydrofluoric acid concentration in the first step is changed will be described. The conditions for separation and purification of niobium are basically the same as those described in Tables 1 and 2 and FIG. 1, with the coefficient fixed at 0.5 and the free hydrofluoric acid concentration of 1.5 to The amount was changed to 12 mol / L (Table 3, Comparative Example 3, Examples 7 to 11 and Comparative Example 4). The niobium oxide production conditions, impurity concentrations, and niobium recovery rate were the same as described above. Table 3 shows the results when the free hydrofluoric acid concentration was changed.

As shown in Table 3, when the free hydrofluoric acid concentration was as low as 1.5 mol / L (Comparative Example 3), boron in niobium oxide exceeded 10 ppm, and the niobium recovery rate was poor. In Examples 7 to 11 (free hydrofluoric acid concentration 2 to 10.0 mol / L), boron in niobium oxide was 10 ppm or less, and the niobium recovery rate was 50% or more. In the case of a free hydrofluoric acid concentration of 12 mol / L (Comparative Example 4), although the niobium recovery rate is high, 50 ppm of boron in niobium oxide remains, the separation and removal efficiency of boron is poor, and other impurities are also present. It was found that many remained.

Furthermore, the case where the extractant in the first step is changed will be described. Examples of the extractant include tri-n-butyl phosphate (TBP: manufactured by Daihachi Chemical Industry Co., Ltd .: Example 12) and tris (2-ethylhexyl) phosphate (TOP: manufactured by Daihachi Chemical Industry Co., Ltd .: Example 13). ), 4-methyl-2-pentanone (MIBK: manufactured by Mitsui Chemicals, Inc .: Comparative Example 5) was used. The niobium separation and purification conditions are basically the same as those in Example 1 described in Tables 1 and 2 and FIG. The mixing ratio of the extractant to the diluent (Shellsol A150) was determined in Examples 12 and 13 in a volume ratio of 35:65, and Comparative Example 5 was 100% extractant without using a diluent. Niobium oxide production conditions, impurity concentrations, and niobium recovery were the same as above. Table 4 shows the results when the extractant is changed. In Table 4, the results of Example 4 are also shown for reference.

As shown in Table 4, when tri-n-butyl phosphate (TBP: Example 12) and tri-n-octyl phosphate (TOP: Example 13) were used as the extracting agent, tri-n-octyl phosphine oxide ( TOPO: As in Example 13), it was found that boron can be separated and removed. In contrast, in the case of 4-methyl-2-pentanone (MIBK: Comparative Example 5), the boron content in niobium oxide was as high as 32 ppm, and it was found that the boron separation and removal efficiency was not so high.

According to the present invention, high-purity niobium can be easily and efficiently obtained from glass scrap containing a large amount of boron, and niobium raw materials suitable for electronic materials and optical materials can be provided to the market.

Claims

A phosphoryl-based extractant having the following general formula in a raw material aqueous solution containing niobium and containing hydrofluoric acid and sulfuric acid;

(Wherein R is hydrogen, or an alkyl group or aryl group having 1 to 20 carbon atoms) is brought into contact with an organic solvent diluted with a petroleum hydrocarbon diluent to convert niobium A first step of extraction into an organic solvent;
A second step of further reducing impurities remaining in the organic solvent by washing the organic solvent after the extraction with water or sulfuric acid;
A third step of obtaining a niobium purified solution by back-extracting niobium contained in the organic solvent in which the impurities are reduced with an aqueous solvent, comprising:
The concentration of free hydrofluoric acid in the aqueous raw material solution in the first step is 2 to 10 mol / L,
A method for separating and purifying niobium, wherein the boron content of impurities in the niobium refined solution is 10 ppm or less with respect to niobium oxide obtained from the niobium refined solution.
The sulfuric acid concentration in the raw material aqueous solution in the first step is 8 mol / L or less, and is 0.1 to 1.25 times the free hydrofluoric acid concentration in the raw material aqueous solution. The method for separating and purifying niobium as described.
The method for separating and purifying niobium according to claim 1 or 2, comprising a step of circulating part or all of the organic solvent after back extraction in the third step as part or all of the organic solvent in the first step.
A niobium purified solution obtained by the method for separating and purifying niobium according to any one of claims 1 to 3 is added with ammonia to precipitate niobium hydroxide, and the precipitate is filtered and calcined. A method for producing niobium, comprising producing niobium oxide.
Niobium oxide obtained by the method for producing niobium according to claim 4, wherein each content in boron, silicon, potassium, tin, antimony, copper, and zinc as impurities is 10 ppm or less,
Furthermore, each content in iron, titanium, and phosphorus as an impurity is 1 ppm or less, and niobium oxide characterized by the above-mentioned.