JP2012087085A - Method of producing high-purity niobium solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a high-purity niobium solution, in which the high-purity niobium solution having lower impurities can be obtained by a simple operation.SOLUTION: The method of producing the high-purity niobium solution includes: a step of distilling niobium chloride in the presence of chlorine gas to obtain niobium chloride that does not contain substantially sodium, aluminum, tantalum and iron; a step of mixing the obtained niobium chloride with water to obtain a slurry that contains niobium acid; a step of separating a solid content from the obtained slurry and thereafter cleaning the solid content by using the water; a step of drying the cleaned solid content in a temperature condition of 0-50°C; and a step of mixing the dried solid content with an aqueous solution that contains a complexing agent.

Description

  The present invention relates to a method for producing a high-purity niobium solution with few impurities.

  Niobium is known as an additive element for various metals, and is mainly used as an additive for improving the corrosion resistance, heat resistance, impact resistance, and the like of steel materials. In recent years, attention has been focused on applications as a catalyst or a dielectric for capacitors. In order to further expand the range of applications of niobium having such functions, it is desirable that niobium can be made into a solution by a stable and simple method. However, since the surface of niobium metal is quickly covered with a stable oxide film in the air, it is not easy to make it into a solution using an acid or the like.

  In general, the preparation of niobium solution involves using niobium powder or niobium oxide as a starting material, and therefore involves operations such as dissolution treatment with hydrofluoric acid or melting treatment by adding potassium disulfate or the like. In many cases, the solution is a solution in which alkali metals such as potassium and sodium, fluorine and sulfate ions coexist. When a product is manufactured using a niobium solution containing such a large amount of impurities as a raw material, there is a possibility that problems such as deterioration in performance and safety occur. For this reason, attempts have been made to remove these impurities.

For example, as a method for removing fluorine which is an impurity that may be generated when it is made into a solution with hydrofluoric acid, a method is disclosed in which after dissolving with ammonia, crystallization is performed to separate and remove fluorine ions (patent) Reference 1). In addition, a method of separating and removing fluorine ions by crystallization using an aqueous alkali solution containing CO ₂ is also disclosed (see Patent Document 2).

Japanese Patent Laid-Open No. 51-10197 Japanese Patent Laid-Open No. 1-115820

  However, since hydrofluoric acid is toxic, there are many problems in terms of safety and management for industrial use in large quantities. It is also possible to purify the niobium solution prepared by the above method through an ion exchange resin to obtain a high-purity niobium solution with few impurities. However, providing such a purification step requires a great deal of time. Not only is it necessary, but the load for treating the generated wastewater increases, which is not an economical method. Thus, it was not easy to easily produce a niobium solution with few impurities.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing a high-purity niobium solution capable of obtaining a high-purity niobium solution with few impurities by a simple operation. That is.

  As a result of extensive research, the inventors of the present invention used niobium chloride as a starting material, purified the niobium chloride by distillation, and then obtained a crystal containing no chloride, and then dissolved the crystal. As a result, it was found that a high-purity niobium solution with few impurities can be obtained, and the present invention has been completed. Specifically, the following are provided.

  (1) Niobium chloride is distilled in the presence of chlorine gas to obtain niobium chloride substantially free of sodium, aluminum, tantalum and iron, and the resulting niobium chloride and water are mixed to contain niobic acid. A step of obtaining a slurry to be separated, a step of separating the solid content from the obtained slurry, a step of washing the solid content with water, a step of drying the solid content after washing under a temperature condition of 0 to 50 ° C., and drying A method for producing a high-purity niobium solution, comprising a step of mixing a later solid content and an aqueous solution containing a complexing agent.

  (2) The complexing agent has a carboxyl group, and the content of the complexing agent contained in the aqueous solution is a molar ratio with respect to 1 mol of niobium contained in the solid content after the carboxyl group is dried. The method for producing a high-purity niobium solution according to (1), wherein the amount is 5 or more.

  (3) The method for producing a high-purity niobium solution according to (1) or (2), wherein the complexing agent is oxalic acid.

  According to the production method of the present invention, a high-purity niobium solution with few impurities can be obtained by a simple operation.

  Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. be able to.

  The method for producing a high-purity niobium solution of the present invention includes a step of distilling niobium chloride in the presence of chlorine gas to obtain niobium chloride substantially free of sodium, aluminum, tantalum and iron, and the obtained niobium chloride and water. And a step of obtaining a slurry containing niobic acid, separating the solid content from the obtained slurry, washing the solid content with water, and setting the solid content after washing to a temperature condition of 0 to 50 ° C. The method comprises a step of drying underneath, and a step of mixing a solid content after drying and an aqueous solution containing a complexing agent. In the present invention, in order to obtain niobic acid in the form of a solution with few impurities by a simple operation, impurities such as alkali metals such as potassium, fluorine and sulfate ions can be generated in the preparation of the niobium solution as in the conventional method. A method that does not require a dissolution treatment with hydrofluoric acid or a melting treatment in which potassium disulfate or the like is added was adopted. This eliminates the safety and management concerns that arise from the use of highly toxic hydrofluoric acid, and eliminates the need for a purification process using an ion exchange resin to remove impurities. And it does not take much time. In the present invention, the niobium solution includes not only a solution in which a solid is completely dissolved, but also a solution containing a solid that does not cause a practical problem in various applications. Hereinafter, each process will be described in detail.

  In the present invention, niobium chloride is used as a starting material in order to enable easy separation and removal of various metal elements as impurities. This is because, if niobium is in the form of niobium chloride, a high-purity product with few impurities can be obtained by a simple purification method such as distillation. Niobium chloride used as a starting material can be produced, for example, by a conventionally known method in which chlorine gas is reacted with niobium metal or niobium oxide. Here, it is preferable to use niobium oxide purified from the concentrate by solvent extraction. This is because higher purity niobium chloride can be obtained. In the present invention, niobium chloride is first distilled in the presence of chlorine gas to obtain niobium chloride substantially free of sodium, aluminum, tantalum and iron. Here, the distillation temperature condition is preferably 250 ° C. or more, which is the boiling point of niobium chloride, and more preferably in the range of 250 to 400 ° C. If it is 400 degrees C or less, the sublimation of the niobium oxychloride which may be contained in a small amount can be minimized. In addition, by strictly controlling the distillation temperature, the impurities such as sodium, aluminum, tantalum, and iron can be fractionated to obtain a high yield of niobium chloride. In the present invention, through this step, it is possible to remove the mineral-derived sodium, aluminum, tantalum and iron from the starting material to an extent that does not substantially contain them. Here, “substantially not contained” means that the contents of sodium, aluminum, tantalum and iron in niobium chloride are all less than 5 ppm. The purity of niobium chloride can be measured by ICP emission spectroscopy using, for example, a commercially available inductively coupled plasma emission spectrometer (ICP-AES). Niobium chloride is highly hygroscopic and, for example, it is hydrolyzed by absorbing moisture in the air just by leaving it in the air for a short time, so it is preferable to handle it in a dry atmosphere.

  In the present invention, after mixing niobium chloride purified by the distillation and water to obtain a slurry containing niobic acid, the solid content which is a crystal of niobic acid is separated from the slurry, and the solid content is separated from water. Wash with. In niobium chloride purified by the above distillation, various metal elements as impurities have been removed, but niobium is present in the form of a chlorine compound, so depending on the application, it can be an impurity that has a significant impact on the performance of the product. . For example, when using niobium as a raw material for battery materials, if a chlorine compound is present in the electrolyte, problems such as a decrease in battery discharge capacity, an increase in internal resistance, and a decrease in life may be caused. There is sex. For this reason, niobium is preferably not in the form of a chlorine compound. In the present invention, niobium chloride purified by distillation is hydrolyzed by mixing with water to produce niobic acid crystals and hydrogen chloride, and then the niobic acid crystals and the solution containing hydrogen chloride are solid-liquid. The niobic acid crystals from which chloride ions have been removed can be obtained by separating and washing the niobic acid crystals with water. The number of washings is not particularly limited, and most of the chloride ions adhering to the niobic acid crystals can be removed by repeating washing and solid-liquid separation several times. The method for solid-liquid separation of the solid niobic acid crystals and the solution containing hydrogen chloride is not particularly limited. Conventionally known filtration means can be used.

  In the present invention, the solid content after washing is dried under a temperature condition of 0 to 50 ° C., and then the solid content after drying and an aqueous solution containing a complexing agent are mixed to obtain a niobium solution. . The present invention provides a niobic acid crystal obtained by removing impurities such as various metal elements and chloride ions from niobium chloride, and then dissolving the crystal to form a solution, thereby obtaining a high-purity niobium solution with less impurities. It is characterized in that Here, the temperature which dries the solid content after the said washing | cleaning is in the range of 0-50 degreeC, Preferably it is 20-40 degreeC. Drying under temperature conditions exceeding 50 ° C. is not preferable because part of niobic acid becomes niobium oxide and the solubility in an aqueous solution containing a complexing agent is lowered. The dried solid is dissolved in an aqueous solution containing a complexing agent to form a solution. In the present invention, the complexing agent is not particularly limited, but preferably has a carboxyl group, and examples thereof include oxalic acid, citric acid, tartaric acid, etc. Among these, oxalic acid is the simplest carboxyl group. This is particularly preferable in that a high-purity niobium solution can be obtained. The purity of the niobium solution can be measured by ICP emission spectroscopy using, for example, a commercially available inductively coupled plasma emission spectrometer (ICP-AES).

  The amount of the complexing agent necessary to make niobic acid into solution may be appropriately adjusted according to the concentration of niobium to be dissolved, but when the complexing agent has a carboxyl group, The content of the complexing agent contained is preferably an amount such that the carboxyl group has a molar ratio of 5 or more with respect to 1 mol of niobium contained in the solid content after the drying. More preferred is an amount, even more preferred is an amount in the range of 5-8, and most preferred is an amount in the range of 5-6. By setting it as the said range, melt | dissolution of the crystal | crystallization of niobic acid which is solid content can be promoted. Use of an excessive amount of complexing agent is not preferable from the viewpoint of cost and environment. For example, when a niobium solution is used as an additive to a battery material, the niobium solution is used after being crystallized with another metal solution under alkaline conditions to form a mixed powder. When oxalic acid is used as the complexing agent, a large amount of oxalic acid is present in the niobium solution. However, since the above crystallization process involves solid-liquid separation, excess oxalic acid remains in the liquid. Discharged. Therefore, there arises a concern that the COD load in the wastewater treatment process is greatly increased.

  The temperature in the step of mixing the solid content after drying and the aqueous solution containing the complexing agent is not particularly limited, and is usually 60 to 90 ° C.

  Since the niobium solution obtained by the present invention has few impurities and high purity, it can be suitably used as, for example, an electrolytic capacitor material, an additive for battery materials, and the like. In particular, since the niobium solution obtained by the present invention does not substantially contain sodium, aluminum, tantalum and iron, the presence of these impurities is useful as an additive for battery materials that may cause a decrease in performance. Here, the effect of niobium as an additive for battery materials is to provide functions such as stability to the battery. For example, as described above, the niobium solution is obtained by crystallizing a niobium solution with another metal solution under alkaline conditions. The mixed powder obtained is used as an additive. As a method of use, a small amount of the mixed powder is added to the positive electrode material of the battery. When niobium segregates in the mixed powder, battery performance may be deteriorated. However, in the present invention, since niobium can be obtained as a solution, when it is crystallized with another metal solution as described above, niobium can be uniformly distributed in the mixed powder, and this occurs. There is no fear.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention does not receive a restriction | limiting at all by these description.

<Production Example 1>
Niobium chloride for industrial use having the composition shown in Table 1 was reacted in a chlorine atmosphere and distilled to obtain niobium chloride.

<Test Example 1>
The niobium chloride obtained in Production Example 1 was purified by distillation at 250 ° C. in the presence of chlorine gas. Here, the obtained niobium chloride was dissolved in concentrated hydrochloric acid, and its purity was measured by ICP emission spectroscopy using an inductively coupled plasma emission spectrometer (ICP-AES). As a result, it was 99.5%. The contents of sodium, aluminum, tantalum, and iron were all less than 5 ppm.

  Next, 87.2 g of the niobium chloride after the above-mentioned distillation purification was weighed in a drying chamber, and this was gradually added into 500 ml of pure water and sufficiently stirred to obtain a slurry. Here, when the chloride ion concentration of the obtained slurry was analyzed by neutralization titration, it was 57 g / L. Next, the slurry was subjected to solid-liquid separation into crystals and a filtrate by centrifuging. The obtained crystals were added with 500 ml of pure water, stirred, and centrifuged again to separate the crystals and the filtrate into solid and liquid. The series of washing with pure water and solid-liquid separation were repeated a total of 5 times.

  Thereafter, the obtained crystals were put in a vacuum dryer and dried at 25 ° C. for 24 hours. 122 g of oxalic acid dihydrate and pure water were added to the dried crystals to form a slurry, and water was further added to a volume of 1 liter. This solution was heated to 80 ° C. and stirred while maintaining the temperature at 80 ° C. to completely dissolve the solution. And when the niobium density | concentration of the obtained solution was measured by ICP emission spectroscopy using ICP-AES, it was 30 g / L. Moreover, it was 0.074 g / L when the chloride ion density | concentration in the obtained solution was analyzed by the ion chromatography. From this, it was confirmed that according to the method of the present invention, a niobium solution having a chloride content reduced by 99% or more can be obtained.

<Test Example 2>
20 g of niobium chloride obtained in the above Production Example 1 was weighed in a drying chamber, gradually added to 500 ml of pure water, and sufficiently stirred to obtain a slurry. Here, when the chloride concentration of the obtained slurry was analyzed by neutralization titration, it was 13 g / L. Next, the slurry was subjected to solid-liquid separation into crystals and a filtrate by centrifuging. The obtained crystals were added with 100 ml of pure water, stirred, and centrifuged again to separate the crystals and the filtrate into solid and liquid. The series of washing with pure water and solid-liquid separation were repeated a total of 5 times.

  Thereafter, 2 g of each of the obtained crystals was collected, put in a vacuum dryer, and dried under conditions of 25 ° C., 40 ° C., 50 ° C., 70 ° C., 90 ° C., and 110 ° C. for 24 hours. The dried crystals were added to 100 ml of an aqueous solution in which 0.05 mol of oxalic acid (0.1 mol as a carboxyl group) was dissolved. These solutions were heated to 80 ° C and then stirred for 6 hours while maintaining the temperature at 80 ° C. Thereafter, solid-liquid separation was performed by filtration, and when an undissolved residue was generated, the mixture was further stirred at the same temperature (80 ° C.) for 24 hours.

  As a result, when drying was performed at 70 ° C., 90 ° C., and 110 ° C., undissolved residues were generated, and a solution in which crystals were completely dissolved could not be obtained. From this, it was confirmed that it was appropriate to dry the crystals at 50 ° C. or lower.

<Test Example 3>
2 g of niobium chloride obtained in the above Production Example 1 was weighed in a drying chamber, gradually added to 50 ml of pure water, and sufficiently stirred to obtain a slurry. Here, when the chloride concentration of the obtained slurry was analyzed by neutralization titration, it was 13 g / L. Next, the slurry was subjected to solid-liquid separation into crystals and a filtrate by centrifuging. The obtained crystals were mixed with 50 ml of pure water, stirred, and centrifuged again to separate the crystals and the filtrate into solid and liquid. The series of washing with pure water and the solid-liquid separation operation were repeated a total of 5 times. The obtained crystals were put in a vacuum dryer and dried at 25 ° C. for 24 hours.

  The dried crystals are added to an oxalic acid aqueous solution in which the amount of oxalic acid is adjusted so that the molar amount of carboxyl groups is 3, 4, 5, 6, 8 times the amount of 1 mol of niobium contained in the crystals. Each was added. In addition, the niobium content contained in the crystal after drying was measured by ICP emission spectroscopy using ICP-AES after dissolving the crystal in hydrofluoric acid. These solutions were heated to 80 ° C and then stirred for 2 hours while maintaining the temperature at 80 ° C.

  When the solution after stirring for 2 hours was visually observed, the amount of oxalic acid was adjusted so that the molar amount of the carboxyl group was 3 or 4 times the molar amount of niobium contained in the crystal. Crystals were confirmed when using an acid aqueous solution, but no crystals were observed when using an oxalic acid aqueous solution in which the amount of oxalic acid was adjusted to be 5, 6, or 8 times the amount. . From this, if the amount of oxalic acid is adjusted so that the molar amount of the carboxyl group is 5 times or more with respect to 1 mol of niobium contained in the crystal, the solution in which the crystal is completely dissolved is obtained. It was confirmed that it was obtained.

Claims (3)

Distilling niobium chloride in the presence of chlorine gas to obtain niobium chloride substantially free of sodium, aluminum, tantalum and iron;
Mixing the obtained niobium chloride with water to obtain a slurry containing niobic acid,
A step of separating the solid content from the obtained slurry and then washing the solid content with water;
High purity characterized by comprising a step of drying a solid content after washing at a temperature of 0 to 50 ° C., and a step of mixing the solid content after drying and an aqueous solution containing a complexing agent. A method for producing a niobium solution. The complexing agent has a carboxyl group;
2. The high content according to claim 1, wherein the content of the complexing agent contained in the aqueous solution is an amount such that the carboxyl group is 5 or more in molar ratio with respect to 1 mol of niobium contained in the solid content after the drying. A method for producing a pure niobium solution.   The method for producing a high-purity niobium solution according to claim 1 or 2, wherein the complexing agent is oxalic acid.