JP2021055153A - Method for producing high-purity scandium oxide - Google Patents

Abstract

To provide a method for efficiently obtaining high-purity scandium oxide from a scandium-containing solution.SOLUTION: The method for producing high-purity scandium oxide according to the present invention includes: a first calcination step S12 in which a scandium-containing solution is subjected to oxalation treatment and the scandium oxalate crystal is calcined at a temperature of 400°C or higher and 800°C or lower; a first dissolution step S13 in which the scandium compound obtained by calcination is dissolved in mineral acid to yield a dissolution liquid; a neutralization step S14 in which neutralization treatment is performed by adding a neutralization agent to the dissolution liquid to produce scandium hydroxide; a second dissolution step S15 in which the scandium hydroxide is dissolved in sulfuric acid to yield a dissolution liquid; an extraction step S16 in which the dissolution liquid and an extraction agent are brought into contact with each other to extract impurity elements; a re-oxalation step S17 in which oxalation treatment is performed by adding oxalic acid to the extraction residue liquid to produce scandium oxalate; and a second calcination step S18 in which the scandium oxalate is calcined to yield scandium oxide.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing scandium oxide, and more specifically, to a method for producing high-purity scandium oxide in which the grade of impurities is reduced.

In recent years, scandium, which has been attracting attention as a high-performance alloy with aluminum and as a material for fuel cells, is mainly purified from the leachate obtained by acid leaching titanium purification residue and uranium ore, and is used as a by-product. Recovery is in progress.

In such conventional recovery of scandium, high-purity products are mainly produced through a purification treatment for separating impurities. That is, since scandium is present at a low concentration in the solution (for example, leachate) in the main steps as described above, it is gradually concentrated by carrying out methods such as an ion exchange method and a solvent extraction method in multiple steps. It is necessary to increase the concentration in the solution. Using these methods, the grade required for alloys, for example, 99.9% (3N product) or higher, is refined, but it takes a considerable amount of time and effort, and the cost required for purification remains high. It is one of the causes.

For example, in Patent Document 1, low-grade scandium oxide is dissolved by heating with nitric acid, the nitric acid solution is brought into contact with an anion exchange resin to adsorb impurities dissolved in the solution, and hydrochloric acid is further added to the solution. A method for separating scandium and impurities by contacting with an anion exchange resin and adsorbing other impurities on the resin is disclosed. In this method, it has been shown that high-purity scandium oxide is obtained by further adding oxalic acid or hydrofluoric acid and calcining the obtained precipitate.

However, in the method of Patent Document 1, since impurities coexisting in the same amount as scandium or in a much larger amount than scandium are separated, it takes time and cost to separate the impurities, and the impurities cannot be completely separated. There is a problem that there is no such thing.

As a method for separating impurities, a method of purifying by re-dissolving and precipitating what has been purified once is known, and it is widely used industrially. However, even if such a method is used for scandium oxide, scandium oxide is sparingly soluble in an aqueous solution such as an acid, and it is necessary to use a high-concentration acid for dissolution.

Further, even if scandium oxide can be dissolved, only a solution having a scandium concentration of about 1 g / L to 3 g / L can be obtained because the acid concentration is high. Further, even if oxalic acid is attempted to be oxidized 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%, which causes a problem that the drug cost increases.

As described above, in the conventional method, in order to obtain high-purity scandium oxide, a lot of labor and cost are required, and further, there is a problem that a safety problem arises because a high concentration of acid is handled.

Japanese Unexamined Patent Publication No. 8-232026

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

The present inventors have made extensive studies to solve the above-mentioned problems. As a result, it was found that a scandium compound that is easily soluble in an aqueous solution such as an acid can be obtained by firing the crystals of scandium oxalate under specific temperature conditions, and the easily soluble scandium compound is obtained. Scandium hydroxide was generated by neutralizing the solution in which scandium hydroxide was dissolved, and the impurity component was removed from the solution in which the scandium hydroxide was dissolved by a solvent extraction method to produce scandium oxalate. It was found that high-purity scandium oxide can be efficiently obtained by producing scandium oxide by firing the above, and the present invention has been completed.

(1) The first invention of the present invention is a first method in which a solution containing scandium is subjected to a sulphurization treatment using oxalic acid, and the obtained scandium oxalate crystals are fired at a temperature of 400 ° C. or higher and 800 ° C. or lower. A firing step, a first dissolution step of dissolving the scandium compound obtained by firing in mineral acid to obtain a solution, and a neutralization treatment by adding a neutralizing agent to the solution to generate scandium hydroxide. A neutralization step, a second dissolution step of dissolving the scandium hydroxide in sulfuric acid to obtain a solution, and an extraction step of contacting the solution obtained in the second dissolution step with an extractant to extract impurity elements. , A re-neutralization step of adding oxalic acid to the extraction residual solution obtained through the extraction step and subjecting it to a oxalic acid treatment to produce scandium oxalate, and a second step of firing the scandium oxalate to obtain scandium oxide. A method for producing high-purity scandium oxide, which comprises a firing step.

(2) The second invention of the present invention is a method for recovering high-purity scandium oxide, wherein in the neutralization step, the pH of the solution is adjusted to the range of 5.5 to 6.8 in the first invention. Is.

(3) In the third invention of the present invention, in the first or second invention, in the re-oxidation step, the temperature of the extraction residual liquid is adjusted to 20 ° C. or higher and lower than 100 ° C. to perform the oxalic oxidation treatment. , A method for producing high-purity scandium oxide.

(4) In the fourth invention of the present invention, in any one of the first to third inventions, the extractant used in the extraction step is an alkylamine-based extractant or an alkylamine-based extractant as a diluent. This is a method for producing high-purity scandium oxide, which is a diluted extractant.

(5) Fifth invention of the present invention, in the first to fourth any one of the, in the extraction step, the concentration of SO ₄ component included in the lysis solution is contacted with the extraction agent 0.1mol It is a method for producing high-purity scandium oxide having a concentration of / L to 2.0 mol / L.

According to the present invention, high-purity scandium oxide can be efficiently obtained from a scandium-containing solution.

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

Hereinafter, a specific embodiment of the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made without changing the gist of the present invention. Further, in the present 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 in which a solution containing scandium is subjected to oxalic acid treatment with oxalic acid to obtain scandium oxide from the obtained crystals of scandium oxalate.

In this production method, scandium oxalate obtained by oxalic acid treatment is made easily soluble by low-temperature firing from a scandium-containing solution, impurities in the scandium solution obtained by dissolution are removed by extraction treatment, and shu is performed again. It is oxidized and fired. As a result, high-purity scandium oxide with few impurities can be efficiently obtained.

Specifically, the method for producing scandium oxide according to the present embodiment is a first method in which a scandium-containing solution is subjected to a scandium oxidation treatment using oxalic acid, and the obtained scandium oxalate crystals are fired at a predetermined temperature. A firing step, a first dissolution step of dissolving a scandium compound obtained by firing in mineral acid to obtain a solution, and a neutralization treatment of the solution to generate scandium hydroxide as a neutralized starch. A neutralization step of dissolving scandium hydroxide in sulfuric acid to obtain a solution, an extraction step of contacting the solution with an extractant to extract an impurity element into an extractant, and an extraction process. It has a re-neutralization step of adding oxalic acid to the obtained extraction residual solution and subjecting it to a oxalic acid treatment to produce scandium oxalate, and a second firing step of calcining scandium oxalate to obtain scandium oxide.

In this production method, a scandium compound exhibiting easy solubility in an acid can be obtained by firing scandium oxalate crystals under specific temperature conditions in the first firing step. Next, the obtained easily soluble scandium compound is used and dissolved in a mineral acid to obtain a dissolved solution (redissolved solution).

In particular, in this production method, a neutralization step is performed in which the obtained solution is neutralized, and scandium hydroxide, which is a neutralized starch obtained by the neutralization treatment, is dissolved in sulfuric acid. It is characterized in that a lysate is obtained, and then the lysate is brought into contact with an extractant to perform an extraction process for removing impurity elements. Then, a reprecipitate of scandium oxalate is produced from the obtained extract residue.

According to such a method, impurities remaining in the solution obtained by dissolving the scandium compound after firing in the first firing step can be more effectively separated and removed, and can be obtained through a neutralization treatment. Scandium can be effectively concentrated in the solution obtained by dissolving scandium hydroxide in the second dissolution step. Furthermore, since impurities are removed by performing an extraction treatment on the solution in which scandium is concentrated, the concentration of scandium can be further increased. Then, a reprecipitate in the form of scandium oxalate is obtained from a solution in which scandium is effectively concentrated (extraction residual liquid), and the reprecipitate is subjected to a firing treatment under predetermined temperature conditions. High-purity scandium oxide can be obtained by efficiently separating and removing impurities.

Here, as a scandium-containing solution (hereinafter, also referred to as “scandium-containing solution”) as a raw material, for example, a leachate obtained by subjecting nickel oxide ore to a high-pressure acid leaching (HPAL) treatment is sulfurized. The post-sulfurization solution after separating nickel can be used. Further, a solution (sulfuric acid acidic solution) in which impurities are separated by ion exchange treatment and / or solvent extraction treatment with respect to the post-sulfurized liquid and scandium is concentrated can be used.

The ion exchange treatment for a scandium-containing solution such as a post-sulfurization liquid obtained through the HPAL process of nickel oxide ore is not particularly limited. For example, as the chelate resin, a treatment using a resin having iminodiacetic acid as a functional group can be mentioned. As specific treatment steps, for example, when the post-sulfurized liquid is to be treated, a step of contacting the post-sulfurized liquid with the chelate resin to adsorb scandium to the chelate resin and a step of contacting the chelate resin with sulfuric acid to form the chelate resin. An example thereof includes a step of removing adsorbed aluminum, a step of contacting a chelate resin with sulfuric acid to obtain a scandium eluent, and a step of contacting the chelate resin with sulfuric acid to remove chromium adsorbed on the chelate resin. it can.

The solvent extraction treatment is also not particularly limited, and the scandium eluate obtained through the ion exchange treatment as described above is subjected to a solvent extraction treatment using an amine-based extractant, a phosphoric acid-based extractant, or the like. be able to. For example, an extraction step of mixing a scandium eluent and an extractant to extract impurities and separating the extract into an organic solvent containing scandium and a drawing residue containing scandium, and mixing a hydrochloric acid solution or a sulfuric acid solution with the organic solvent after extraction. A scrubbing step for separating a trace amount of scandium contained in the organic solvent after extraction, and a back-extraction step for mixing the back-extraction starting solution with the organic solvent after washing and back-extracting impurities from the organic solvent after washing to obtain a back-extract. Can be exemplified.

In the scandium-containing solution obtained by performing the ion exchange treatment or the solvent extraction treatment in this way, the impurity components are reduced and the scandium is concentrated in the solution, so that the scandium-containing solution can be used as a raw material for oxidation. Scandium has an even higher scandium quality.

The scandium-containing solution is not limited to the solution obtained by leaching the nickel oxide ore as a raw material as described above, as long as it is a solution obtained from a raw material containing nickel and other impurities together with scandium. It can be applied effectively.

≪2. About each process of manufacturing method of scandium oxide ≫
FIG. 1 is a process diagram showing an example of a flow of a method for producing scandium oxide.

Specifically, as shown in FIG. 1, the method for producing scandium oxide according to the present embodiment includes a oxalation step S11 in which a scandium-containing solution is subjected to a oxalation treatment, and a crystal of scandium oxalate is fired at a predetermined temperature. In the first firing step S12 to obtain a solution by dissolving the scandium compound as a fired product in mineral acid, and in the first dissolution step S13 to neutralize the solution to generate scandium hydroxide. With respect to the sum step S14, the second dissolution step S15 in which scandium hydroxide is dissolved in sulfuric acid to obtain a dissolution solution, the extraction step S16 in which the dissolution solution and the extractant are brought into contact with each other to perform an extraction treatment, and the extraction residual liquid. It has a re-dissolution step S17 for obtaining a reprecipitate of scandium oxalate crystals by subjecting a oxalate treatment, and a second firing step S18 for calcining the reprecipitate of scandium oxalate to obtain scandium oxide.

[Shu oxidation process]
The sucrose oxidation step S11 is a step of subjecting a scandium-containing solution to sulphate oxidation treatment. Specifically, in the scandium oxidation step S11, a reaction of using oxalic acid to convert scandium to oxalate (scandium oxalate) is caused in a scandium-containing solution.

The scandium-containing solution is not particularly limited, but is preferably adjusted so that the scandium concentration is 5 g / L to 50 g / L, more preferably 10 g / L to 20 g / L, and sulfuric acid or the like. The pH is adjusted to about 0 using the acid of.

As a method for the oxalic acid treatment, a method can be used in which oxalic acid is added to the scandium-containing solution to precipitate and generate solid crystals of scandium oxalate based on the scandium in the scandium-containing solution. At this time, the oxalic acid used may be a solid or a solution. In the method of oxalis oxidation treatment, when the scandium-containing solution contains ferrous iron ions as an impurity component, in order to prevent the precipitation formation of iron (II) oxalate, prior to the oxalate oxidation treatment, It is preferable to add an oxidizing agent to control the oxidation-reduction potential (ORP, reference electrode: silver / silver chloride) in the range of 500 mV or more to perform the oxidation treatment.

As the oxalic acid used for the treatment, it is preferable to use an amount in the range of 1.05 times to 1.2 times the equivalent amount required for precipitating scandium in the scandium-containing solution as an oxalate. If the amount used is less than 1.05 times the required equivalent, it may not be possible to effectively recover the entire amount of scandium. On the other hand, if the amount used exceeds 1.2 times the required equivalent, the solubility of scandium oxalate may increase and the scandium may be redissolved and the recovery rate may decrease. In addition, it is not preferable because the amount of an oxidizing agent such as sodium hypochlorite used increases due to the decomposition of excess oxalic acid.

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

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

The first firing step S12 is characterized in that firing is performed with the firing temperature in the range of 400 ° C. to 800 ° C. As a result, a scandium compound that is easily soluble in an aqueous solution such as an acid can be obtained as a fired product.

The easily soluble scandium compound thus obtained has a weight loss rate of 53% to 65%, preferably 55% to 65%, more preferably 55% to 60, based on the weight of the scandium oxalate crystals before the firing treatment. It is in the range of%. The weight loss rate refers to the rate of weight loss due to firing, and can be expressed by the following formula [1] based on the weight before and after firing.
Weight loss rate (%) = (1-quantity after firing / quantity before firing) x 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 theoretical. The target is (1-137.92 / 353.92) × 100 = 61%. However, in the easily soluble scandium compound obtained by performing the firing treatment under the condition of 400 ° C. to 800 ° C., the weight loss rate varies in the range of 55% to 65%, so that it is poorly soluble. When scandium oxalate is heated and decomposed into poorly soluble scandium oxide, there is a region that exhibits an easily soluble form.

In other words, this easily soluble scandium compound is not one in which the crystals of scandium oxalate, which is the raw material, are completely decomposed by firing to become scandium oxide in its entirety, and scandium oxalate remains partially. Or, it is considered that the compound is in a state in which _{CO 2} , CO, etc. produced by decomposition remain. In fact, the easily soluble scandium compound obtained by firing under temperature conditions in the range of 400 ° C. to 800 ° C. contains a large amount of carbon (C) as compared with the conventional scandium oxide obtained by firing at a high temperature. There is.

Further, even if the scandium compound exhibiting this easily soluble property is subjected to X-ray diffraction analysis, it does not show a peculiar diffraction peak, especially on the temperature side of the lower limit showing the more easily soluble property, and it is difficult to identify the morphology of the compound. Is. Therefore, compounds in the easily soluble region are simply collectively referred to as "scandium compounds". Specifically, in the easily soluble scandium compound obtained by firing under a temperature condition in the range of 400 ° C. to 800 ° C., no peak of scandium oxalate is observed, and the peak intensity corresponding to the peak of scandium oxide is 11000 counts or less. It becomes. From this, it is considered that the scandium compound obtained by firing at a temperature of 400 ° C. to 800 ° C. has a low crystallinity and has an easily soluble property.

Further, the scandium compound exhibiting this easily soluble property has a property of being a fine compound having a BET specific surface area of 70 m ^{2 / g or more.} In particular, the scandium compound obtained at a firing temperature of 400 ° C. has a BET specific surface area of 250 m ² / g or more. As described above, the scandium compound obtained by firing at a temperature condition of 400 ° C. or higher and 800 ° C. ° C. or lower has a large specific surface area, and as a result, a large contact area with the acid solution when dissolved in the acid solution. It is thought that it will show easy solubility. 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.

In the firing treatment in the first firing step S12, the crystals of scandium oxalate obtained by the oxalate oxidation treatment are washed with water, dried, and then fired using a predetermined furnace. The furnace is not particularly limited, and examples thereof include a tube furnace, and industrially, by using a continuous furnace such as a rotary kiln, drying and firing can be continuously performed by the same apparatus.

[First dissolution step]
The first dissolution step S13 is a step of completely dissolving an easily soluble scandium compound, which is a calcined product obtained by the calcining treatment in the first calcining step S12, in mineral acid to obtain a solution.

The dissolution treatment in the first dissolution step S13 is not particularly limited, and can be carried out by adding pure water to the scandium compound, further adding a mineral acid solution to the scandium compound, and stirring the mixture. Further, the temperature condition in the melting treatment can be adjusted in the range of about 20 ° C. to 80 ° C.

As the mineral acid, sulfuric acid, hydrochloric acid, nitric acid and the like can be used.

The pH condition at the time of dissolution is not particularly limited, and for example, a sulfuric acid solution adjusted to about pH 0 to 2 may be used.

As the dissolution liquid obtained in the first dissolution step S13, for example, the scandium concentration can be increased to about 50 g / L and adjusted to an arbitrary value, thereby reducing the amount of the liquid and extending the equipment. The capacity can be reduced.

[Neutralization process]
The neutralization step S14 is a step of neutralizing the solution containing scandium obtained through the first dissolution step S13. By performing such a neutralization treatment, scandium hydroxide can be obtained as a neutralized starch, and nickel, which is a component having a higher basicity than scandium, does not easily precipitate and thus remains in the neutralized filtrate. Thereby, by solid-liquid separation of the obtained neutralized slurry, the neutralized starch, that is, the hydroxide of scandium from which impurities have been separated can be recovered.

In the neutralization treatment in the neutralization step S14, the pH of the solution is preferably in the range of 5.5 to 6.8, more preferably in the range of 6.0 to 6.5 by adding the neutralizing agent. Adjust to. By adding a neutralizing agent so that the pH of the solution is in such a range, a scandium hydroxide precipitate can be produced more efficiently.

The neutralizing agent is not particularly limited as long as the solution can be adjusted to a desired pH range, and examples thereof include sodium hydroxide and the like. The concentration of the neutralizing agent such as sodium hydroxide is not particularly limited and may be appropriately set. For example, when a high concentration neutralizing agent exceeding 4 mol / L is added, the pH in the reaction vessel becomes high. There is a possibility that high-purity scandium cannot be obtained due to adverse effects such as local increase and co-precipitation of impurities. Therefore, the neutralizing agent is preferably a solution diluted to 4 mol / L or less, whereby the neutralization reaction may be uniformly caused. On the other hand, if the concentration of the neutralizing agent such as sodium hydroxide solution is too low, the amount of solution required for addition will increase by that amount, the amount of liquid to be handled will increase, and as a result, the equipment scale will increase and the cost will increase. It is not preferable to cause it. Therefore, it is preferable to use a neutralizing agent having a concentration of 1 mol / L or more.

In addition, like the above-mentioned neutralized starch, the precipitate obtained by the treatment including the addition of an alkaline neutralizing agent such as sodium hydroxide generally has extremely poor filterability. Therefore, at the time of neutralization, seed crystals may be added to improve the filterability. The seed crystal is preferably added in an amount of about 1 g / L or more with respect to the solution before the neutralization treatment.

[Second dissolution step]
The second dissolution step S15 dissolves the neutralized starch containing scandium hydroxide as a main component recovered through the neutralization treatment in the above-mentioned neutralization step S14 by adding sulfuric acid, and prepares the redissolved solution. This is a step of obtaining a hydroxide solution.

By dissolving the neutralized starch with a sulfuric acid solution in this way, the redissolved solution becomes a scandium sulfate solution. The concentration of the sulfuric acid solution is not particularly limited, but it is preferable to use a sulfuric acid solution having a concentration of 2N or more in consideration of the industrial reaction rate.

The pH condition at the time of dissolution is not particularly limited, and may be, for example, in the range of 0 to 2, preferably in the range of 0.8 to 1.5, and more preferably in the range of about 1.0. By dissolving so as to maintain the pH range at the time of dissolution, scandium hydroxide can be efficiently dissolved, and the recovery loss of scandium due to undissolved can be suppressed.

Further, the temperature condition at the time of melting is not particularly limited, and can be adjusted to, for example, 20 ° C. to 80 ° C.

As the dissolution liquid obtained in the second dissolution step S15, for example, the scandium concentration can be increased to about 50 g / L and adjusted to an arbitrary value. As a result, it is possible to reduce the amount of liquid and, by extension, the installed capacity.

[Extraction process]
The extraction step S16 is a step of using a dissolution liquid obtained through the second dissolution step S15 and removing impurity elements in the dissolution liquid by an extraction treatment using an extractant. In the extraction process in the extraction step S16, the impurity elements in the solution are extracted by the extractant, while the scandium is not extracted and is transferred to the extraction residual liquid (post-extraction liquid). By such an extraction treatment, scandium and impurity elements can be effectively separated, and the purity of scandium oxide obtained in the subsequent steps can be improved.

The extractant is not particularly limited, but an alkylamine-based extractant or an alkylamine-based extractant diluted with a diluent can be preferably used.

Specifically, the alkylamine-based extractant is not particularly limited, but is an extractant known by trade names such as PrimeneJM-T, AmberliteLA-2, TOA (Tri-n-octylamine), and TIOA (Tri-i-octylamine). Can be used. Among such extractants, it is preferable to select one having excellent separability between the target impurity element to be extracted and scandium. For example, when the impurity element to be extracted is Th or U, it is preferable to use PrimeneJM-T because the separability from scandium is more excellent.

Here, the extraction behavior of the alkylamine-based extractant is affected by the salt concentration in the solution. Therefore, before the extraction process, it is preferable to adjust the SO ₄ concentration in the lysate, thereby increasing the isolation. Specifically, the concentration of SO ₄ components in the lysate, preferably in the range of 0.1mol / L~2.0mol / L. When SO ₄ concentration in the lysate is less than 0.1 mol / L, dissolved liquid requires a large amount of extractant too dilute, also equipment increases in size. On the other hand, when the SO ₄ concentration exceeds 2.0 mol / L, at the same time scandium and an impurity element many be extracted, isolation may be reduced.

After the extraction treatment, static separation or the like is performed to separate the extractant (extract) from which the impurity element has been extracted and the extraction residual liquid, and the extraction residual liquid containing scandium is recovered. The extractant containing an impurity element can be repeatedly used as an extractant used in the extraction treatment after the impurities are separated and recovered by washing and performing a back-extraction treatment.

[Re-oxidation process]
The re-oxalate oxidation step S17 is a step of obtaining a reprecipitate of scandium oxalate crystals by performing the oxalate oxidation treatment again using the extraction residual liquid containing scandium obtained through the extraction step S16.

The method of the oxalis oxidation treatment in the re-oxidation step S17 can be carried out in the same manner as the treatment performed in the oxalis oxidation step S11 described above. In the re-oxidation step S17, elements that do not form oxalate, such as iron, manganese, and nickel, that remain in the extraction residual liquid can be separated and removed, and impurities can be further reduced by undergoing this oxalate oxidation treatment.

Here, in the oxalis oxidation treatment in the re-oxidation step S17, it is preferable to adjust the temperature (liquid temperature) of the extraction residual liquid to a range of 20 ° C. or more and less than 100 ° C. By adjusting the liquid temperature of the extraction residual liquid to such a range, scandium oxalate with higher purity can be produced.

[Second firing step]
The second firing step S18 is a step of firing the reprecipitate of scandium oxalate obtained in the recalcination step S17 at a predetermined temperature. That is, in the second firing step S18, a second firing treatment is performed in which the scandium oxalate crystals obtained in the recalcination step S17 are fired, and scandium oxide is obtained by this firing treatment.

In the firing treatment in the second firing step S18, since all scandium oxalate is converted to scandium oxide, the firing temperature condition is preferably 800 ° C. or higher. By firing under high temperature conditions, it is possible to prevent carbon (C) derived from oxalic acid from remaining.

Then, as described above, the easily soluble scandium compound is redissolved, impurities are removed from the redissolved solution by a neutralization treatment using a neutralizing agent or the like or an extraction treatment using an extractant, and then Shu again. Since crystals of scandium acid are generated and fired, high-purity scandium oxide with effectively reduced impurity grade can be obtained.

Hereinafter, examples of the present invention will be shown and more specifically described. The present invention is not limited to the following examples.

[Example 1]
<Generation of scandium-containing solution>
(Hydrometallurgy process of nickel oxide ore)
Nickel oxide ore was leached with sulfuric acid using an autoclave, and slaked lime was added to the obtained leachate to neutralize it. Next, a sulfurizing agent was added to the obtained neutralized liquid to cause a sulfurization reaction, and nickel, cobalt and the like were separated as sulfides to obtain a scandium-containing post-sulfurized liquid.

(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 an eluent containing scandium eluted from the chelate resin (scandium eluent) is obtained. It was. A neutralizing agent was then added to the scandium eluate to produce a scandium hydroxide precipitate.

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

<Shu oxidation process>
The obtained scandium sulfate solution (scandium-containing solution) was diluted by adding water until the scandium concentration became about 5 g / L, and the pH was adjusted to 0 with sulfuric acid. Then, the prepared solution was used as the starting solution for shu oxidation, and a total of 65 liters was prepared.

Next, in order to react 2.7 equivalents of oxalic acid 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 initial solution was added to the oxalic acid solution at a flow rate of 270 ml / min. After adding the entire amount of the starting solution, the mixture was stirred over 1 hour. The reaction temperature was 25 ° C., the residence time was 5 hours, and the addition time was 4 hours. Table 1 below summarizes the treatment conditions for shu oxidation (first shu oxidation).

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

<First firing process>
Next, 500 g of scandium oxalate crystals was separated, placed in a furnace and fired at a temperature of 400 ° C. for 2 hours to obtain about 215 g of a fired product. Table 2 below shows the firing conditions, the weight of the sample before firing (scandium oxalate) and the sample after firing (scandium oxide), and the weight loss rate calculated from the weight. Table 3 below shows the analysis results of scandium oxide obtained by firing. As shown in Table 3 below, nickel, iron, and thorium were particularly contained as impurities.

<First dissolution step>
Next, 80 g of the calcined product obtained by calcining at a calcining temperature of 400 ° C. was collected, pure water was added thereto, and sulfuric acid was added while mixing to adjust the pH to 1.0. By this operation, a solution having a scandium concentration of 25 g / L was obtained.

<Neutralization process>
Next, a neutralization treatment is performed in which a 4 mol / L sodium hydroxide solution is added as a neutralizing agent to 400 ml of the solution obtained through the first dissolution step to adjust the pH of the solution to 6.0. went. By this neutralization treatment, a scandium hydroxide precipitate (neutralized starch) was produced. After the neutralization treatment, the precipitate was recovered by performing solid-liquid separation.

<Second dissolution step>
Next, 210 g of hydroxide (moisture content of about 90%) obtained through the neutralization step was collected, pure water was added thereto, and sulfuric acid was added and dissolved while mixing to adjust the pH to 1.0. did. By this operation, a solution having a scandium concentration of 25 g / L was obtained.

The obtained scandium solution, SO ₄ concentration in the solution was diluted with pure water so that the 0.35 g / L. The scandium concentration after dilution was 10 g / L.

<Extraction process>
An organic solvent prepared by adding 475 ml of Swazole 1800 as a diluent to 25 ml of PrimeneJM-T as an extractant was prepared. Then, 500 ml of the organic solvent and 500 ml of the diluted solution were mixed for 30 minutes and brought into contact with each other. By performing this extraction treatment, Th of impurities present in the solution at a ratio of 1.7 mg / L before the extraction treatment is reduced to less than 0.1 mg / L in the extraction residual liquid obtained after the extraction treatment. Was.

<Re-oxidation process>
Next, 385 ml of a solution having an oxalic acid concentration of 100 g / L (oxalic acid solution) was added to 475 ml of the extraction residual liquid obtained through the extraction step, and the mixture was mixed for 1 hour to perform oxalic acid treatment. The conditions were such that the liquid temperature (reaction temperature) of the extraction residual liquid was 25 ° C., the residence time was 5 hours, and the addition time was 4 hours.

After the stirring was completed, the whole amount was filtered to separate the scandium oxalate crystals, and the repulp washing using 100 ml of pure water was repeated 3 times for 13 g of the separated crystals.

<Second firing process>
Next, the washed scandium oxalate crystals were placed in a furnace and the second firing was performed at a firing temperature of 900 ° C. for 2 hours to generate scandium oxide. Then, scandium oxide taken out from the furnace was analyzed.

Table 4 below shows the analysis results of the obtained scandium oxide. As shown in Table 4, high-purity scandium oxide having a reduced impurity content could be obtained.

[Example 2]
In the neutralization step, scandium oxide was produced by the same method as in Example 1 except that a 4 mol / L sodium hydroxide solution was added as a neutralizing agent and the pH of the solution was adjusted to 6.5. did.

Table 4 below shows the analysis results of the obtained scandium oxide. As shown in Table 4, high-purity scandium oxide having a reduced impurity content could be obtained.

[Example 3]
In the neutralization step, scandium oxide was produced in the same manner as in Example 1 except that a 4 mol / L sodium hydroxide solution was added as a neutralizing agent and the pH of the solution was adjusted to 7.0. did.

Table 4 below shows the analysis results of the obtained scandium oxide. As shown in Table 4, high-purity scandium oxide having a reduced impurity content could be obtained. 2 ppm of nickel was detected.

[Reference example]
The solution obtained in the first dissolution step, SO ₄ concentration in the solution is diluted with pure water so that 0.35 g / L, in the ready extraction step scandium concentration of a solution of 10 g / L after dilution Scandium oxide was produced in the same manner as in Example 1 except that the neutralization step was omitted in the extraction treatment.

Table 4 below shows the analysis results of the obtained scandium oxide. As shown in Table 4, 6 ppm of nickel was detected in scandium oxide.

Claims (5)

A first firing step in which a scandium-containing solution is subjected to oxalic acid treatment with oxalic acid, and the obtained scandium oxalate crystals are fired at a temperature of 400 ° C. or higher and 800 ° C. or lower.
The first dissolution step of dissolving the scandium compound obtained by firing in mineral acid to obtain a solution, and
A neutralization step of adding a neutralizing agent to the solution to neutralize it to produce scandium hydroxide, and
The second dissolution step of dissolving the scandium hydroxide in sulfuric acid to obtain a solution, and
An extraction step in which the solution obtained in the second dissolution step is brought into contact with the extractant to extract impurity elements, and
A re-oxidation step of adding oxalic acid to the extraction residual liquid obtained through the extraction step and performing a oxalic acid treatment to produce scandium oxalate, and a re-oxidation step of producing scandium oxalate.
The second firing step of firing the scandium oxalate to obtain scandium oxide, and
A method for producing high-purity scandium oxide. In the neutralization step, the pH of the solution is adjusted to the range of 5.5 to 6.8.
The method for recovering high-purity scandium oxide according to claim 1. In the re-oxidation step, the temperature of the extraction residual liquid is adjusted to 20 ° C. or higher and lower than 100 ° C., and the shu-oxidation treatment is performed.
The method for producing high-purity scandium oxide according to claim 1 or 2. The extractant used in the extraction step is an alkylamine-based extractant or an extractant obtained by diluting an alkylamine-based extractant with a diluent.
The method for producing high-purity scandium oxide according to any one of claims 1 to 3. In the extraction step, high-purity oxide according to any concentration of SO ₄ component included in the lysis solution is contacted with the extraction agent is 0.1mol / L~2.0mol / L in which the first to fourth aspects Scandium manufacturing method.

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