WO2018043704A1

WO2018043704A1 - Method for producing high-purity scandium oxide

Info

Publication number: WO2018043704A1
Application number: PCT/JP2017/031570
Authority: WO
Inventors: 達也檜垣; 小林　宙
Original assignee: 住友金属鉱山株式会社
Priority date: 2016-09-05
Filing date: 2017-09-01
Publication date: 2018-03-08
Also published as: JP6358299B2; PH12019500477A1; JP2018040020A

Abstract

Provided is a method for efficiently obtaining high-purity scandium oxide from a solution containing scandium.　This method for producing high-purity scandium oxide comprises: a first firing step S12 in which an oxalate conversion process is carried out using oxalic acid in a solution containing scandium, and scandium oxalate crystals thereby obtained are fired at a temperature of 400°C to 600°C; a dissolution step S13 in which sulfuric acid is added to the scandium compound obtained by firing to obtain a solution; a reprecipitation step S14 in which an oxalate conversion process is carried out using oxalic acid in the solution, and a reprecipitation product of scandium oxalate is generated; and a second firing step S15 in which the reprecipitation product of scandium oxalate that was obtained is fired to obtain scandium oxide.

Description

Method for producing high purity scandium oxide

The present invention relates to a method for producing scandium oxide, and more particularly to a method for producing high-purity scandium oxide with reduced impurity quality.

In recent years, scandium, which has attracted attention as a high-performance alloy with aluminum and a material for fuel cells, has been mainly purified from leachate obtained by leaching titanium refining residue and nickel oxide ore with sulfuric acid. Is being collected.

In such conventional scandium recovery, high-purity products are mainly produced through a liquid purification process for separating impurities. In other words, scandium is present in a low concentration in the solution (for example, leachate) in the main processes as described above, and therefore, it is gradually concentrated by carrying out a method such as an ion exchange method or a solvent extraction method in multiple stages. It is necessary to increase the concentration in the solution. Using these methods, the grade required for the alloy, for example, a grade of 99.9% (3N product) or higher is refined, but it takes a lot of work and the cost for refining remains high. It is a factor.

For example, in Patent Document 1, low-grade scandium oxide is heated and dissolved with nitric acid, the nitric acid solution is brought into contact with an anion exchange resin to adsorb impurities dissolved in the liquid, and hydrochloric acid is added to the solution. A method of separating scandium and impurities by bringing them into contact with an anion exchange resin and adsorbing other impurities on the resin is disclosed. In this method, it is shown that oxalic acid or hydrofluoric acid is further added, and the obtained precipitate is fired to obtain high-purity scandium oxide.

However, the method of Patent Document 1 separates impurities present in the same amount as scandium or in a much larger amount than scandium, which increases the labor and cost required for impurity separation, and completely separates impurities. There is a problem that I can not finish.

As a method for separating impurities, a method of refining by re-dissolving and precipitating once purified is known and widely used industrially. However, even if such a method is used for scandium oxide, scandium oxide is hardly soluble in an aqueous solution of an acid or the like, and it is necessary to use a high concentration acid to dissolve it.

Furthermore, even if the scandium oxide can be dissolved, since the acid concentration is high, only a solution having a scandium concentration of about 1 g / L to 3 g / L can be obtained. Moreover, even if it is attempted to oxidize again, since the acid concentration is high, it is necessary to add about 12 equivalents of oxalic acid in order to obtain an actual yield of about 80%.

As described above, in the conventional method, when obtaining high-purity scandium oxide, there is a problem that it takes a lot of labor and costs, and further, there is a problem of safety due to handling a high concentration of acid. .

JP-A-8-232026

The present invention has been proposed in view of such circumstances, and an object thereof is to provide a method for efficiently obtaining high-purity scandium oxide from a solution containing scandium.

The present inventors have made extensive studies to solve the above-described problems. As a result, it was found that a scandium compound having a high solubility in an aqueous solution of an acid or the like can be obtained by firing the crystal of scandium oxalate at a specific temperature condition, and the easily soluble scandium compound It was found that high-purity scandium oxide can be obtained efficiently by preparing a re-dissolved liquid using sinter, and firing scandium oxalate produced from the re-dissolved liquid to produce scandium oxide. The invention has been completed.

(1) In the first invention of the present invention, a solution containing scandium is subjected to an oxalic acid treatment using oxalic acid, and the obtained scandium oxalate crystals are fired at a temperature of 400 ° C. or higher and 600 ° C. or lower. 1 calcination step, a dissolution step to obtain a solution by adding sulfuric acid to the scandium compound obtained by calcination, and oxalic acid is used to oxalate the solution to produce a reprecipitate of scandium oxalate A high-purity scandium oxide production method, comprising: a reprecipitation step to be performed; and a second calcining step of calcining the obtained scandium oxalate reprecipitate to obtain scandium oxide.

(2) The second invention of the present invention is the high-purity scandium oxide according to the first invention, wherein in the reprecipitation step, the temperature of the solution is adjusted to 40 ° C. or more and less than 100 ° C. to perform an oxidation treatment. It is a manufacturing method.

(3) The third invention of the present invention is a method for producing high-purity scandium oxide in the first or second invention, wherein in the second firing step, firing is performed at a firing temperature of 900 ° C. or higher.

(4) According to a fourth aspect of the present invention, in any one of the first to third aspects, the solution containing scandium is subjected to an ion exchange treatment and / or a solvent extraction treatment on the solution containing scandium. This is a method for producing high-purity scandium oxide, which is obtained by application.

According to the present invention, highly pure scandium oxide can be efficiently obtained from a solution containing scandium.

It is process drawing which shows an example of the flow of the manufacturing method of a scandium oxide.

Hereinafter, a specific embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, A various change is possible in the range which does not change the summary of this invention. In this specification, the notation “X to Y” (X and Y are arbitrary numerical values) means “X or more and Y or less”.

<< 1. Overview >>
The method for producing scandium oxide according to the present embodiment is a method for obtaining scandium oxide from crystals of scandium oxalate obtained by subjecting a solution containing scandium to oxalic acid treatment using oxalic acid. In this production method, scandium oxalate obtained by oxalic acid treatment from a solution containing scandium is calcined in two stages to obtain high-purity scandium oxide with few impurities. .

Specifically, in the method for producing scandium oxide according to the present embodiment, a solution containing scandium is subjected to oxalic acid treatment using oxalic acid, and the obtained scandium oxalate crystals are fired at a predetermined temperature. 1 calcination step, a dissolution step in which sulfuric acid is added to the scandium compound obtained by calcination to obtain a solution, and an oxalic acid treatment is performed on the solution using oxalic acid to generate a reprecipitate of scandium oxalate A reprecipitation step, and a second firing step in which the obtained scandium oxalate reprecipitate is fired to obtain scandium oxide.

In such a method, in the first firing step, a scandium compound that is readily soluble in an aqueous solution of an acid or the like can be obtained by firing the crystals of scandium oxalate under specific temperature conditions. Then, using the readily soluble scandium compound thus obtained, specifically, a dissolved solution (re-dissolved solution) is obtained by dissolving in sulfuric acid, and reprecipitation of scandium oxalate from the re-dissolved solution. A high-purity scandium oxide from which impurities are efficiently separated can be obtained by producing a product and subjecting the re-precipitate to a firing treatment at a predetermined temperature condition.

Here, as a raw material solution containing scandium (hereinafter, also referred to as “scandium-containing solution”), nickel is separated by sulfiding the leachate obtained by high-pressure acid leaching (HPAL) treatment of nickel oxide ore. A solution (sulfuric acid acidic solution) obtained by separating impurities by ion exchange treatment and / or solvent extraction treatment and then concentrating scandium can be used for the post-sulfurized solution.

The ion exchange treatment for the scandium-containing solution such as the post-sulfurization solution obtained through the HPAL process of nickel oxide ore is not particularly limited. For example, a treatment using a resin having iminodiacetic acid as a functional group may be used as the chelate resin. As a specific processing step, for example, when a post-sulfurized solution is to be treated, an adsorption step of contacting the post-sulfurized solution with the chelate resin to adsorb scandium to the chelate resin, and contacting the chelate resin with sulfuric acid. An aluminum removal process for removing aluminum adsorbed on the chelate resin, a scandium elution process for obtaining a scandium eluate by contacting sulfuric acid with the chelate resin that has undergone the aluminum removal process, and a sulfuric acid being brought into contact with the chelate resin that has undergone the scandium elution process. And a chromium removal step of removing chromium adsorbed on the chelate resin in the adsorption step.

Also, the solvent extraction treatment is not particularly limited, and a solvent extraction treatment using an amine-based extractant, a phosphate-based extractant, or the like is performed on the scandium eluent obtained through the ion exchange treatment as described above. be able to. For example, an extraction process in which scandium eluent and an extractant are mixed to separate impurities into an extracted organic solvent and extracted residue containing scandium, and after extraction, a hydrochloric acid solution or a sulfuric acid solution is mixed with the organic solvent. A scrubbing process for separating scandium contained in a trace amount in the organic solvent after extraction, and a back extraction process for mixing the back-extraction starting solution in the organic solvent after washing and back-extracting impurities from the organic solvent after washing to obtain a back-extraction liquid; Can be exemplified.

As described above, in the scandium-containing solution obtained by performing the ion exchange treatment or the solvent extraction treatment, since the impurity component is reduced and the scandium is concentrated in the solution, the oxidation obtained using the scandium-containing solution as a raw material. Scandium has an even higher scandium quality.

≪2. About each process of the manufacturing method of scandium oxide >>
FIG. 1 is a process diagram showing an example of the flow of a method for producing scandium oxide. As shown in FIG. 1, this manufacturing method includes an oxidation step S11 for performing an oxidation treatment on a scandium-containing solution, and a first baking step for baking the obtained scandium oxalate crystals at a predetermined temperature. S12, dissolution step S13 for obtaining a solution by dissolving a scandium compound as a fired product in sulfuric acid, and reprecipitation step S14 for obtaining a reprecipitate of scandium oxalate crystals by subjecting the solution to an oxalic oxidation treatment And a second firing step of firing the scandium oxalate reprecipitate to obtain scandium oxide.

[Oxidation process]
The oxidation step S11 is a step of applying an oxidation treatment to the scandium-containing solution. Specifically, in the oxalic oxidation step S11, the scandium-containing solution is caused to react with oxalic acid (scandium oxalate) using oxalic acid.

Thus, by using scandium as an oxalate, handling properties such as filterability can be improved, and scandium can be efficiently recovered. Moreover, the impurities in the solution can be separated by this oxidation treatment.

The scandium-containing solution is not particularly limited, but is preferably adjusted so that the scandium concentration is 5 g / L to 10 g / L, more preferably about 5 g / L, and an acid such as sulfuric acid is used. The pH is adjusted to about 0.

As a method for the oxalic oxidation treatment, a method in which oxalic acid is added to a scandium-containing solution and a solid crystal of scandium oxalate is precipitated based on the scandium in the scandium-containing solution can be used. At this time, the oxalic acid used may be a solid or a solution. In this method of oxalic oxidation treatment, when divalent iron ions are contained as an impurity component in the scandium-containing solution, in order to prevent precipitation of iron (II) oxalate, prior to the oxalic oxidation treatment, It is preferable to add an oxidizing agent and control the oxidation-reduction potential (ORP, reference electrode: silver / silver chloride) within a range of about 500 mV to 600 mV for the oxidation treatment.

Alternatively, as a method of oxalic oxidation treatment, a method in which a scandium-containing solution is gradually added into an oxalic acid solution filled in a reaction vessel to precipitate and produce scandium oxalate solid crystals. At this time, it is preferable to adjust the pH of the scandium-containing solution to a range of −0.5 or more and 1 or less prior to the oxidation treatment. According to such an oxidation treatment method, precipitation of iron (II) oxalate and the like can be prevented, and higher-purity scandium can be recovered without using an expensive oxidizing agent or the like. .

In the oxidation treatment, the temperature of the scandium-containing solution to be treated is preferably adjusted to a range of 10 ° C. to 30 ° C., more preferably adjusted to a range of 15 ° C. to 25 ° C.

Further, as the oxalic acid used for the treatment, it is preferable to use an amount in the range of 1.05 to 1.2 times the equivalent amount required for precipitating scandium in the scandium-containing solution as oxalate. If the amount used is less than 1.05 times the required equivalent, there is a possibility that the entire amount of scandium cannot be recovered effectively. On the other hand, if the amount used exceeds 1.2 times the required equivalent, the solubility of scandium oxalate increases, so that scandium is redissolved and the recovery rate decreases, and excessive oxalic acid is decomposed. This is not preferable because the amount of the oxidizing agent such as hypochlorous soda increases.

The scandium oxalate crystals obtained by such an oxidation treatment can be recovered by filtration and washing treatment.

[First firing step]
The first baking step S12 is a step of baking the scandium oxalate crystals obtained in the oxidation step S11 at a predetermined temperature. By such a firing treatment at a predetermined temperature, a scandium compound that is a fired product can be obtained.

And in this Embodiment, in this 1st baking process S12, baking is performed by making baking temperature into the range of 400 degreeC or more and 600 degrees C or less. Thereby, the scandium compound which shows easy solubility with respect to aqueous solutions, such as an acid, can be obtained as a baked product.

The present inventor has performed a scan treatment on scandium oxalate crystals under conditions in the range of 400 ° C. or more and 600 ° C. or less, which is a lower temperature region than conventional ones, thereby easily dissolving scandium in an aqueous solution such as an acid. It was found that a compound was obtained. Conventionally, in order to obtain scandium oxide by baking scandium oxalate, it was necessary to set the baking temperature to 900 ° C. or higher, preferably about 1100 ° C.

Moreover, the readily soluble scandium compound thus obtained has a weight loss ratio of 53% or more and 65% or less, preferably 55% or more and 65% or less, more preferably, with respect to the weight of scandium oxalate crystals before the firing treatment. It becomes the range of 55% or more and 60% or less. The weight loss rate refers to the rate of weight reduction due to firing, and can be represented by the following formula [1] based on the weight before and after firing.
Weight loss rate (%) = (1−amount after firing / amount before firing) × 100 [1]

Here, when scandium oxide (Sc ₂ O ₃ ; molecular weight 137.92) is obtained by firing scandium oxalate (Sc ₂ C ₆ O ₁₂ ; molecular weight 353.92), the weight loss rate before and after firing is theoretically Specifically, (1-1137.92 / 353.92) × 100 = 61%. However, the present inventor has a range in which the weight loss rate is 55% or more and 65% or less in the easily soluble scandium compound obtained by performing the baking treatment in the range of 400 ° C. or more and 600 ° C. or less. Therefore, it was found that there is a region exhibiting a readily soluble form when the hardly soluble scandium oxalate is heated to be decomposed into the hardly soluble scandium oxide.

In other words, this easily soluble scandium compound is not the one in which the raw material scandium oxalate crystals are completely decomposed by firing and the total amount becomes scandium oxide, and scandium oxalate partially remains. Alternatively, it is considered to be a compound in which CO ₂ , CO, etc. produced by decomposition remain. Actually, a readily soluble scandium compound obtained by firing under a temperature condition in the range of 400 ° C. or more and 600 ° C. or less contains more carbon (C) than the conventional scandium oxide obtained by firing at a high temperature. ing.

In addition, even when X-ray diffraction analysis is performed, this scandium compound exhibiting high solubility does not exhibit a specific diffraction peak, particularly on the lower temperature side indicating higher solubility, and it is difficult to specify the form of the compound. It is. For this reason, compounds in the readily soluble region are simply referred to as “scandium compounds”. Specifically, in a readily soluble scandium compound obtained by firing under a temperature condition in the range of 400 ° C. to 600 ° C., no scandium oxalate peak is observed, and the peak intensity corresponding to the scandium oxide peak is also 11000 counts. It becomes as follows. From this, it is considered that a scandium compound obtained by firing at a temperature of 400 ° C. or higher and 600 ° C. or lower has a low crystallinity and has an easily soluble property.

Further, this easily soluble scandium compound has a property that it has a fine BET specific surface area of 70 m ² / g or more. In particular, the scandium compound obtained at a firing temperature of 400 ° C. is 250 m ² / g or more. Thus, in the scandium compound obtained by firing at a temperature condition of 400 ° C. or more and 600 ° C. or less, the specific surface area increases, and as a result, the contact area with the acid solution at the time of dissolution in the acid solution increases, It is thought that it becomes easily soluble. The specific surface area of the scandium compound, more preferably 100 m ² / g or more, more preferably 200 meters ² / g or more, particularly preferably 250 meters ² / g or more.

And the conditions for producing the easily soluble scandium compound in this way are firing at a temperature condition in the range of 400 ° C. or more and 600 ° C. or less, more preferably in the range of 400 ° C. or more and 500 ° C. or less. It is firing under conditions. In other words, such a readily soluble scandium compound has a weight loss rate by firing of 53% to 65%, preferably 55% to 65%, more preferably 55% to 60%. Can be obtained by firing under various conditions.

Specifically, in the firing treatment in the first firing step S12, the scandium oxalate crystals obtained by the oxidation treatment are washed with water and dried, and then fired using a predetermined furnace. Although it does not specifically limit as a furnace, A tubular furnace etc. are mentioned, In order to be able to perform drying and baking continuously with the same apparatus by using continuous furnaces, such as a rotary kiln, it is preferable industrially.

The holding time when firing at a firing temperature of 400 ° C. or higher and 600 ° C. or lower is not particularly limited, but is preferably 0.5 hours or longer and 12 hours or shorter, and is preferably 1 hour or longer and 12 hours or shorter. More preferably, it is 1 hour or more and 6 hours or less. If the holding time is less than 0.5 hours, the firing does not proceed sufficiently, and there is a possibility that much of the poorly soluble scandium oxalate remains. On the other hand, when the holding time exceeds 12 hours, the readily soluble property of the obtained scandium compound is hardly changed or may be gradually lowered, and the heat energy is increased, so that the processing cost is increased.

[Dissolution process]
The dissolution step S13 is a step in which the scandium compound, which is a fired product obtained by the firing treatment in the first firing step S12, is completely dissolved in sulfuric acid to obtain a solution.

As described above, by performing firing at a firing temperature in the range of 400 ° C. or more and 600 or less in the first firing step S12, a scandium compound that is easily soluble in an aqueous solution such as an acid can be obtained. Therefore, in the dissolution step S13, the easily soluble scandium compound obtained in this way is dissolved in a sulfuric acid solution, so that scandium is eluted in the solution, which is a so-called re-dissolution solution, and the scandium is concentrated. A solution can be obtained.

As described above, in the method for producing scandium oxide according to the present embodiment, a re-dissolved solution is prepared by using the readily soluble property of the obtained scandium compound, and the re-dissolved solution is used again in the subsequent process based on the re-dissolved solution. By obtaining crystals of scandium acid and firing the crystals to form scandium oxide, the impurity element can be efficiently separated and removed. Thereby, high purity scandium oxide with reduced impurity quality can be produced.

The dissolution treatment in the dissolution step S13 is not particularly limited, and can be performed by adding pure water to the scandium compound, further adding a sulfuric acid solution thereto, and stirring. Moreover, also as temperature conditions in a melt | dissolution process, it can adjust and adjust in the range of about 40 to 80 degreeC.

The pH condition of the sulfuric acid solution used for dissolution is not particularly limited, and for example, a solution adjusted to about pH 0 to 2 may be used. As described above, the scandium compound dissolved in the sulfuric acid solution is easily soluble in an aqueous solution of an acid or the like, so that it can be easily dissolved even under conditions of pH 0 to 2 and the concentration is increased. It is possible to effectively reduce the drug cost required for

As the redissolved solution obtained in the dissolving step S13, for example, the scandium concentration can be increased to about 50 g / L and can be adjusted to an arbitrary value. The capacity can be reduced.

[Reprecipitation process]
In the reprecipitation step S14, a reprecipitate of scandium oxalate crystals is obtained by subjecting the solution (redissolution solution) obtained by redissolving the scandium compound in the dissolution step S13 to oxalate treatment again. It is a process to obtain.

That is, in the reprecipitation step S14, the second oxidation is performed using the re-dissolved solution as a raw material. Thus, according to the method of re-dissolving the easily soluble scandium compound and regenerating the scandium oxalate crystal from the redissolved solution, it coexists with the scandium oxalate crystal obtained by the second oxalic acid oxidation. The amount of impurities can be significantly reduced.

The method of the oxidation treatment in the reprecipitation step S14 can be performed in the same manner as the treatment performed in the oxidation step S11. For example, the redissolved solution is adjusted so that the scandium concentration is 5 g / L to 10 g / L, more preferably about 5 g / L, and the pH is reduced to about 0 using an acid such as sulfuric acid. Oxidize with the adjusted one.

Moreover, in this second oxalic acid treatment, even if the amount of oxalic acid added in the oxalic acid oxidation treatment is kept within 3.0 equivalents relative to scandium, scandium can be converted into scandium oxalate with a high actual yield. The use cost of oxalic acid can be reduced.

Here, in the oxidation treatment, the oxalic acid obtained in comparison with the case where the reaction is caused at normal temperature (25 ° C.) by setting the solution temperature (re-dissolved solution) at the time of reaction to 40 ° C. or higher. The scandium particles can be coarsened, and handling at the time of charging into the firing furnace in the next firing step (second firing step) becomes easy. However, there is a concern that the quality is deteriorated simply by coarsening the impurities in the gaps between the particles.

However, as described above, in the present embodiment, the easily soluble scandium compound is redissolved, and the scandium oxalate crystal is generated again from the redissolved solution. Since the impurities coexisting with each other can be remarkably reduced, the particles can be effectively coarsened. From this, handling property can also be effectively improved.

In addition, even as the liquid temperature condition of 100 ° C. or higher, since the influence on the coarsening is small and energy is excessive, the temperature condition in the oxidation treatment is preferably in the range of 40 ° C. or higher and lower than 100 ° C., More preferably, the temperature is in the range of 40 ° C. or more and 60 ° C. or less.

[Second firing step]
The second firing step S15 is a step of firing the scandium oxalate reprecipitate obtained in the reprecipitation step S14 at a predetermined temperature. That is, in the second baking step S15, a second baking process for baking the crystals of scandium oxalate obtained from the re-dissolved solution is performed, and scandium oxide is obtained by this baking process.

In the firing treatment in the second firing step S15, the firing temperature condition is preferably 900 ° C. or higher, more preferably 1000 ° C. or higher, and particularly preferably about 1100 ° C. Thus, in 2nd baking process S15, the compound which has the form of a scandium oxide clearly as a baked material is baked on 900 degreeC or more conditions with respect to the crystal of scandium oxalate. Moreover, it can prevent that carbon (C) derived from oxalic acid remains by baking in such a high temperature condition.

In this way, the easily soluble scandium compound is redissolved, and the scandium oxalate crystal is generated again from the redissolved solution, and the scandium oxalate crystal is fired, thereby reducing the impurity quality. High purity scandium oxide can be obtained.

As a method for the firing treatment in the second firing step S15, the obtained scandium oxalate crystals are washed with water and dried in the same manner as in the first firing step S12. Used and fired.

The holding time when firing at a high firing temperature of 900 ° C. or higher is not particularly limited, but is preferably 0.5 hours or longer and 12 hours or shorter, and more preferably 1 hour or longer and 12 hours or shorter. Preferably, it is 1 hour or more and 6 hours or less. If the holding time is less than 0.5 hours, the firing does not proceed sufficiently, and a fired product in the form of scandium oxide may not be obtained effectively. On the other hand, if the holding time exceeds 12 hours, the heat energy increases and the processing cost increases.

Hereinafter, the present invention will be described in more detail with reference to examples of the present invention. The present invention is not limited to the following examples.

[Example 1]
<Generation of scandium-containing solution>
(Nickel ore hydrometallurgical process)
Nickel oxide ore was leached with sulfuric acid using an autoclave and neutralized by adding slaked lime to the obtained leachate. Subsequently, a sulfiding agent was added to the obtained post-neutralization solution to cause a sulfidation reaction, and nickel, cobalt, and the like were separated as sulfides to obtain a post-sulfurization solution containing scandium.

(Ion exchange treatment, neutralization treatment)
Next, the obtained post-sulfurized solution is subjected to an ion exchange treatment using a chelate resin to separate impurities in the solution and to obtain an eluent (scandium eluent) containing scandium eluted from the chelate resin. It was. Thereafter, a neutralizing agent was added to the scandium eluent to form a scandium hydroxide precipitate.

(Solvent extraction process)
Next, sulfuric acid is added to the scandium hydroxide precipitate and dissolved again to obtain a solution (scandium solution). The scandium solution is subjected to a solvent extraction process using an amine-based extractant and extracted. A scandium sulfate solution (scandium-containing solution) was obtained as the remaining liquid.

<Oxidation process>
The obtained scandium sulfate solution was diluted by adding water until the scandium concentration was about 5 g / L, and the pH was adjusted to 0 with sulfuric acid. And the solution after this adjustment was made into the oxidation starter, and a total of 65 liters was prepared.

Next, in order to make 2.7 equivalents of oxalic acid react with scandium in the starting solution, a total of 27 liters of a solution in which oxalic acid was dissolved at a concentration of 100 g / L was prepared. Then, the oxalic acid solution was placed in a reaction vessel, and the starting solution was added into the oxalic acid solution at a flow rate of 270 ml / min. The whole amount of the starting solution was added and stirred for 1 hour. The reaction temperature was 25 ° C., the residence time was 5 hours, and the addition time was 4 hours. Table 1 below collectively shows the processing conditions for the oxidation of oxalate (the first oxidization of oxalate).

After the stirring, the whole amount was filtered to separate scandium oxalate crystals, and repulp washing using 1 liter of pure water was repeated 3 times for 50 g of the separated crystals.

<First firing step>
Next, a part of scandium oxalate crystals obtained by the oxalic oxidation treatment was fractionated, put in a furnace and baked at a temperature of 1100 ° C. for 2 hours, and the obtained baked products were analyzed. Table 5 below shows the analysis results of the fired product obtained at a firing temperature of 1100 ° C. (“Scandium oxide after first firing treatment in Table 5”).

On the other hand, 60 g of the remaining scandium oxalate crystal was collected, placed in a furnace, and baked at a temperature of 400 ° C. for 2 hours to obtain about 25 g of a fired product. A part of the fired product was analyzed. Table 2 below collectively shows firing conditions at a firing temperature of 400 ° C. Table 5 below shows the analysis results of the fired product (intermediate product) obtained at a firing temperature of 400 ° C. (“Scandium compound after first firing treatment” in Table 5).

<Remelting process>
Next, 16 g of the remainder of the fired product obtained by firing at a firing temperature of 400 ° C. is collected, heated to 60 ° C. while adding pure water thereto and mixed, and further added with sulfuric acid to bring the pH to 0. It was adjusted. By this operation, a scandium solution in which 95% or more of 16 g of scandium oxalate crystals were dissolved was obtained. Table 3 below summarizes the conditions for the dissolution treatment.

The obtained scandium solution was diluted so that the scandium concentration was 5 g / L, and a solution prepared by adding sulfuric acid to adjust the pH to 0 was used as a redissolved solution, and 1.72 liters were prepared for each test condition. .

<Reprecipitation process>
Next, in order to make 2.7 equivalents of oxalic acid react with scandium in the redissolved solution, 0.71 liter of a solution in which oxalic acid was dissolved at a concentration of 100 g / L was prepared for each test condition. And the oxalic acid solution was accommodated in the reaction container, and the redissolved solution was added in the oxalic acid solution. After adding the entire amount of the re-dissolved solution, the stirring state was maintained for 1 hour. The reaction temperature was 25 ° C., the residence time was 2 hours, and the addition time was 1 hour. Table 4 below collectively shows the processing conditions for the oxidation (second oxidation).

<Second firing step>
Next, the washed scandium oxalate crystals were placed in a furnace, and the second firing was performed at a firing temperature of 1100 ° C. for 2 hours to generate scandium oxide. And the scandium oxide taken out from the furnace was analyzed.

The analysis of scandium oxide was performed as follows. That is, for scandium (Sc), the other 69 component impurities were analyzed using an ICP and ICP mass spectrometer (ICP-MS), and the remainder after subtracting these impurity amounts was regarded as scandium for evaluation. Moreover, carbon (C) was measured using the analyzer which combined the high frequency induction heating by LECO, and the non-dispersion type infrared absorption method. The analysis of scandium oxide after the first baking treatment (1100 ° C.) and the analysis of any scandium compound in the first baking treatment (400 ° C.) were performed in the same manner.

Table 5 below shows the analysis results of the obtained scandium oxide (“scandium oxide after the second baking treatment” in Table 5).

As shown in Table 5, the scandium oxalate obtained by the oxalic oxidation treatment was calcined at 400 ° C., the obtained scandium compound was redissolved in sulfuric acid, and the scandium oxalate crystals were re-dissolved from the redissolved solution. The scandium oxide obtained by firing and firing the scandium oxalate at 1100 ° C. has reduced impurity quality and high purity compared to scandium oxide after the first firing treatment (1100 ° C.). became.

[Example 2]
The first oxidation of oxalate was performed under the same conditions as in Example 1, and 170 g to 250 g of the obtained scandium oxalate crystals were fractionated and fired at a firing temperature of 400 ° C. for 7 hours. Was measured to determine the weight loss rate. As a result, calcined products (scandium compounds) having a weight loss rate of 53% to 63% were obtained.

Next, the obtained fired product was heated to 60 ° C. while being mixed with water, and sulfuric acid was added to adjust the pH to 1 to 1.6. When the slurry concentration was adjusted to about 5% to 8%, the calcined product was completely dissolved, and a high scandium concentration sulfuric acid solution with a scandium concentration of 26 g / L to 45 g / L could be produced.

Table 6 below summarizes the weight loss rate due to firing against scandium oxalate and the results when the fired product was dissolved.

[Comparative Example 1]
In the same manner as in Example 1, from the post-sulfurization solution obtained from the hydrometallurgical process of nickel oxide ore, ion exchange treatment, neutralization treatment, and solvent extraction treatment were performed to obtain a scandium sulfate solution (scandium-containing solution). Obtained.

Further, using the scandium sulfate solution, an oxalic acid oxidation treatment (first oxidization) was performed to obtain scandium oxalate crystals. Specifically, in the oxalic acid treatment, the oxalic acid solution is accommodated in a reaction vessel, and the starting solution is added to the oxalic acid solution at a flow rate of 130 ml / min. Stir. The reaction temperature was 25 ° C., the residence time was 1 hour, and the addition time was 10 hours. Table 7 below collectively shows the processing conditions for the oxidation of oxalic acid (first time of oxidization).

Next, a part of the obtained scandium oxalate crystal was put in a furnace and fired at a temperature of 1100 ° C. for 2 hours, and the obtained fired product was analyzed. In addition, in the following Table 9, the analysis result of the fired product obtained at a firing temperature of 1100 ° C. is shown (“scandium oxide after the first firing treatment in Table 9”).

On the other hand, 22 g of the remaining scandium oxalate obtained was fractioned, and 539 ml of a 64 wt% sulfuric acid solution was added while mixing. Furthermore, when 1452 ml of pure water was additionally added and mixing was continued, the pH became about-(minus) 0.5. The scandium oxalate solution thus obtained was analyzed to obtain a scandium leaching rate of 95% or more. However, the scandium concentration of this solution increased only to 2.3 g / L. Table 8 below collectively shows the conditions for the dissolution treatment and the analysis results of the solution.

Next, 126 g of oxalic acid in an amount of 12 equivalents was added and mixed with 1 liter of the solution in order to perform the second oxidation treatment with the solution of scandium oxalate (second time). After mixing, the crystals of scandium oxalate were separated by filtration and analyzed. As a result, the recovery rate of scandium was 80%.

Next, scandium oxalate crystals obtained from the second (second) oxidation treatment were placed in a furnace and fired at a temperature of 1100 ° C., and the fired products obtained were analyzed. The analysis results of the fired product obtained at a firing temperature of 1100 ° C. are shown in Table 9 below (“Scandium oxide after second firing treatment in Table 9)”.

The obtained scandium oxalate was dissolved again without firing rather than the scandium oxide obtained by the first firing treatment for scandium oxalate (fired at 1100 ° C.) and fired again for scandium oxalate obtained by the oxalate oxidation treatment. Impurities were removed from scandium oxide obtained by the treatment (1100 ° C.), and high-purity scandium having a quality of 99.94% could be purified.

However, the scandium concentration of the scandium oxalate redissolved solution is as low as about 2.3 g / L, and the amount of oxalic acid required for the second oxalic acid treatment is as large as 12 equivalents. Compared with the processing efficiency.

Claims

A first firing step of subjecting the scandium-containing solution to oxalic acid treatment using oxalic acid, and firing the obtained scandium oxalate crystals at a temperature of 400 ° C. to 600 ° C .;
A dissolution step of adding a sulfuric acid to the scandium compound obtained by firing to obtain a solution;
A reprecipitation step in which oxalic acid is used to oxalate the solution to generate a reprecipitate of scandium oxalate;
A second calcining step of calcining the obtained re-precipitate of scandium oxalate to obtain scandium oxide; and a method for producing high-purity scandium oxide.
The method for producing high-purity scandium oxide according to claim 1, wherein in the reprecipitation step, the temperature of the solution is adjusted to 40 ° C. or higher and lower than 100 ° C. to perform an oxidation treatment.
The method for producing high-purity scandium oxide according to claim 1 or 2, wherein in the second firing step, firing is performed at a firing temperature of 900 ° C or higher.
The high-purity oxidation according to any one of claims 1 to 3, wherein the solution containing scandium is obtained by subjecting a solution containing scandium to an ion exchange treatment and / or a solvent extraction treatment. Scandium production method.