JP2021127514A - Method for recovering scandium - Google Patents

Abstract

To provide a method for recovering scandium, the method capable of efficiently recovering high-purity scandium from a solution that contains impurities together with scandium.SOLUTION: The present invention is a method for recovering scandium, the method comprising: a neutralization step S3 wherein a solution containing scandium is passed through an ion exchange resin, an eluent eluted from the ion exchange resin is neutralized by adding a neutralizing agent and dimethylglyoxime thereto, and subsequently a neutralized sediment and a neutralized filtrate are obtained by means of solid-liquid separation; a solvent extraction step S4 wherein the eluent after neutralization is subjected to a solvent extraction treatment; and a scandium recovery step S5 wherein scandium oxide is recovered from an extraction residue that is separated by means of the solvent extraction treatment.SELECTED DRAWING: Figure 3

Description

The present invention relates to a scandium recovery method, and more particularly to a scandium recovery method for efficiently recovering scandium from a scandium-containing solution obtained from a raw material such as nickel oxide ore.

Scandium is extremely useful as an additive for high-strength alloys and as an electrode material for fuel cells, but it has not been widely used due to its low production volume and high cost.

Nickel oxide ores such as laterite ore and limonite ore contain trace amounts of scandium. However, nickel oxide ore has a low nickel grade and has not been industrially used as a nickel raw material for a long time. Therefore, the industrial recovery of scandium from nickel oxide ore has also been rarely studied.

However, in recent years, the HPAL process in which nickel oxide ore is charged into a pressure vessel together with sulfuric acid and heated to a high temperature of about 240 ° C. to 260 ° C. to solid-liquid separation into a nickel-containing leachate and a leachate residue has been put into practical use. ing. In the HPAL process, impurities are separated by adding a neutralizing agent to the obtained leachate, and then nickel is recovered as nickel sulfide by adding a sulfide agent to the leachate from which the impurities have been separated. Then, by treating the recovered nickel sulfide in an existing nickel smelting process, an electronickel or a nickel salt compound can be obtained.

When such an HPAL process is carried out, scandium contained in nickel oxide ore will be contained in the leachate together with nickel (see Patent Document 1). Then, when a neutralizing agent is added to the obtained leachate to separate impurities and then a sulfide agent is added, nickel is recovered as nickel sulfide, while scandium is an acidic solution after the addition of the sulfide agent ( It will be contained in the post-sulfurization solution). Therefore, nickel and scandium can be effectively separated by using the HPAL process.

There is also a method of separating scandium using a chelate resin (see Patent Document 2). Specifically, in the method shown in Patent Document 2, first, nickel and scandium are selectively leached into an acidic aqueous solution under a high temperature and high pressure in an oxidizing atmosphere, and then the obtained acidic solution is prepared. After adjusting the pH to the range of 2-4, nickel is selectively precipitated and recovered as a sulfide by using a sulfide agent. Next, scandium is adsorbed by contacting the obtained solution after recovering nickel with a chelate resin, the chelate resin is washed with a dilute acid, and then the washed chelate resin is brought into contact with a strong acid to remove the scandium from the chelate resin. Elute scandium.

Further, as a method for recovering scandium from the post-sulfurization liquid (acidic solution), a method for recovering scandium by using solvent extraction has also been proposed (see Patent Documents 3 and 4).

Specifically, in the method shown in Patent Document 3, first, in addition to scandium, an aqueous scandium-containing solution containing at least one of iron, aluminum, calcium, yttrium, manganese, chromium, and magnesium is prepared in 2 -Ethylhexyl sulfonic acid-Mono-2-ethylhexyl diluted with kerosine is added to the organic solvent, and the scandium component is extracted into the organic solvent. Then, in order to separate ittium, iron, manganese, chromium, magnesium, aluminum, and calcium extracted together with scandium in an organic solvent, they were removed by adding an aqueous hydrochloric acid solution and scrubbing, and then in the organic solvent. An aqueous NaOH solution is added to make scandium remaining in the organic solvent _{into a slurry containing Sc (OH) 3} , and this is filtered to _{dissolve Sc (OH) 3} in hydrochloric acid to obtain an aqueous scandium chloride solution. Then, oxalic acid is added to the obtained scandium chloride aqueous solution to form a scandium oxalate precipitate, and the precipitate is filtered to separate iron, manganese, chromium, magnesium, aluminum, and calcium into the filtrate. High-purity scandium oxide is obtained by baking.

Further, Patent Document 4 describes a method of selectively separating and recovering scandium from a scandium-containing supply liquid by bringing the scandium-containing supply liquid into contact with an extractant at a constant ratio by batch treatment.

It is known that the grade of scandium recovered by these methods has a purity of about 95% to 98% in terms of scandium oxide. However, although it is of sufficient quality for applications such as addition to alloys, it has higher purity for applications such as fuel cell electrolytes, for which demand has been increasing in recent years, in order to exhibit good characteristics. For example, a quality of about 99.9% is required.

Nickel oxide ore contains various impurity elements such as manganese and magnesium in addition to iron and aluminum, although the type and amount vary depending on the region of production. When scandium is used as an electrolyte for fuel cells, it has an acceptable upper limit depending on the impurity element, and it is necessary to separate and remove each element to the allowable upper limit or less.

However, in the chelate resins and organic solvents disclosed in Patent Documents 2 and 3 described above, some impurity elements behave similarly to scandium, making it difficult to effectively separate and recover scandium. In addition, impurities such as iron and aluminum contained in the leachate of nickel oxide ore have a much higher concentration than scandium, and due to the influence of these large amounts of impurities, high-purity scandium can be industrially produced from nickel oxide ore. No suitable method has been found for recovery.

In this way, even if an attempt is made to recover scandium from nickel oxide ore, it is difficult to effectively separate a wide variety of impurities such as iron and aluminum contained in a large amount and efficiently recover high-purity scandium. Met.

Here, Patent Document 5 proposes a method for separating scandium and impurity elements by adding a neutralizing agent to an eluent in which scandium is eluted from a chelate resin and controlling the pH in two steps. .. However, depending on the type of nickel oxide ore and the conditions of the previous process, it is necessary to neutralize an acidic solution with a high nickel concentration. Further, if the aluminum concentration is high, there is a problem that the amount of nickel coprecipitated in the second stage neutralization treatment increases and the nickel grade in scandium oxide increases.

Japanese Unexamined Patent Publication No. 3-173725 Japanese Unexamined Patent Publication No. 9-194211 Japanese Unexamined Patent Publication No. 9-291320 International Publication No. 2014/11216 Japanese Unexamined Patent Publication No. 2017-13350

The present invention has been proposed in view of such circumstances, and an object of the present invention is to provide a method for recovering scandium capable of efficiently recovering high-purity scandium from a solution containing impurities together with scandium. do.

The present inventors have made extensive studies to solve the above-mentioned problems. As a result, the eluate obtained by passing an acidic solution containing scandium through an ion exchange resin was subjected to a neutralization treatment including the addition of a neutralizing agent and dimethylglioxime, and after neutralization obtained. We have found that high-purity scandium can be easily and efficiently recovered from nickel oxide ore by subjecting the eluate to solvent extraction, and have completed the present invention.

(1) In the first invention of the present invention, a solution containing a scandium is passed through an ion exchange resin, and a neutralizing agent and dimethyl glyoxime are added to the eluent eluted from the ion exchange resin for neutralization treatment. A neutralization step of obtaining a neutralized starch and a neutralized filtrate by solid-liquid separation, a solvent extraction step of performing a solvent extraction treatment on the eluent after neutralization, and a drawing separated by the solvent extraction treatment. It is a solvent recovery step for recovering the solvent oxide from the residual liquid, and a method for recovering the solvent.

(2) The second invention of the present invention is a method for recovering scandium, wherein the scandium-containing solution is a solution obtained by leaching a raw material containing nickel with an acid in the first invention.

(3) In the third invention of the present invention, in the first or second invention, in the neutralization step, the dimethylglyoxime is added in an amount of 3 to 50 equivalents with respect to the amount of nickel contained in the eluent. This is a method for recovering scandium, which is added in proportion.

(4) In the fourth invention of the present invention, in any one of the first to third inventions, the neutralization step is neutralized by adding a neutralizing agent and dimethylglioxime to the eluent. , The first neutralization step of obtaining the primary neutralized starch and the primary neutralization filtrate by solid-liquid separation, and the neutralization treatment by further adding a neutralizing agent to the primary neutralization filtrate to solidify. A method for recovering scandium, which comprises a second neutralization step of obtaining a secondary neutralized starch and a secondary neutralized filtrate by liquid separation.

(5) A fifth invention of the present invention is a method for recovering scandium, wherein in the first neutralization step, the pH of the eluent is adjusted to the range of 3.8 to 4.5 in the fourth invention. Is.

(6) In the sixth aspect of the present invention, in the fourth or fifth invention, in the second neutralization step, the pH of the primary neutralization filtrate is adjusted to the range of 5.5 to 6.5. This is a method for recovering scandium.

(7) In the seventh invention of the present invention, in any one of the first to sixth inventions, an acid is further added to the neutralized starch obtained in the neutralization step to provide a hydroxide solvent solution. This is a method for recovering scandium, which comprises a hydroxide dissolution step of obtaining the above-mentioned product, and in the solvent extraction step, the hydroxide solution is subjected to the solvent extraction treatment as the eluent after neutralization.

(8) The eighth invention of the present invention further comprises a recovery step of recovering dimethylglyoxime from the neutralization filtrate obtained in the neutralization step in any one of the first to seventh inventions. It is a collection method of.

(9) In the ninth invention of the present invention, in the eighth invention, the neutralization step is performed by adding a neutralizing agent and dimethylglioxime to the eluent to perform a neutralization treatment, and by solid-liquid separation 1 The first neutralization step of obtaining the secondary neutralized starch and the primary neutralization filtrate, and the neutralization treatment by further adding a neutralizing agent to the primary neutralization filtrate are performed, and the secondary neutralization is performed by solid-liquid separation. It has a second neutralization step of obtaining a Japanese starch and a secondary neutralization filtrate, and in the recovery step, the secondary neutralization obtained through the second neutralization step in the neutralization step. This is a method for recovering scandium, which recovers dimethylglioxime from the filtrate.

(10) The tenth invention of the present invention is a scandium in which the dimethylglyoxime recovered in the recovery step is repeatedly reused in the neutralization treatment in the neutralization step in the eighth or ninth invention. It is a collection method.

According to the present invention, impurities can be effectively separated from a solution containing impurities together with scandium, and high-purity scandium can be efficiently recovered.

It is a process drawing which shows an example of the scandium recovery method. It is a process drawing which shows an example of the scandium recovery method. It is a process diagram which shows the flow at the time of performing a two-step neutralization treatment in a neutralization step.

Hereinafter, a specific embodiment of the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments, and can be carried out with appropriate modifications without changing the gist of the present 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 of scandium recovery method ≫
FIG. 1 is a process diagram showing an example of a scandium recovery method according to the present embodiment. This scandium recovery method separates scandium and impurities from an acidic solution containing scandium obtained by leaching nickel oxide ore with an acid such as sulfuric acid to easily and efficiently obtain high-purity scandium. It is to be collected.

The scandium-containing acidic solution, which is the target of the scandium recovery method, is not limited to the solution obtained by acid leaching using nickel oxide ore as a raw material. For example, an acidic solution obtained from a raw material containing impurities such as nickel together with scandium can be a suitable target for this recovery method.

Specifically, in this scandium recovery method, an eluent (scandium) obtained by passing an acidic solution containing scandium through an ion exchange resin to adsorb scandium, and then bringing the acid solution into contact with the ion exchange resin (scandium). The eluent) is subjected to a neutralization treatment including the addition of dimethylglioxime. This separates impurities and concentrates scandium. Then, the acidic solution in which scandium is concentrated is subjected to solvent extraction using an extractant such as an amine-based extractant to extract impurities contained in the acidic solution into the extractant, and after the extraction, the acidic solution (drawing residue). Separates from the scandium that will remain in the liquid).

For scandium that has become contained in the extraction residue due to solvent extraction, for example, a method of obtaining a hydroxide precipitate by adding an alkali and performing a neutralization treatment, or oxalate formation using oxalic acid. By a method such as recovery as a precipitate of oxalate by treatment, a solid shape suitable for product use is formed, and residual impurities are also separated. As a result, scandium is recovered as crystals of high-purity scandium hydroxide or scandium oxalate.

The obtained crystals of scandium hydroxide and scandium oxalate are calcined by a known method to obtain the form of scandium oxide. The scandium oxide thus produced can be used as a material for an electrolyte of a fuel cell. Further, it can be used for applications such as obtaining scandium metal by a method such as molten salt electrolysis and then adding it to aluminum to alloy it.

As described above, in the scandium recovery method according to the present embodiment, when the scandium is separated and recovered, dimethylglyoxime is added to the scandium-concentrated solution (eluent) through the ion exchange treatment. It is characterized by performing a neutralization treatment including. As a result, scandium is concentrated, and then a solvent extraction treatment using a solvent extractant is performed. According to such a method, impurities can be separated more effectively, and high-purity scandium can be efficiently produced under stable operation even from a raw material containing many impurities such as nickel oxide ore. Can be recovered.

≪2. About each process of scandium recovery method ≫
More specifically, as shown in FIG. 1, the method for recovering scandium is the wet smelting treatment step S1 of nickel oxide ore to obtain an acidic solution containing scandium by leaching the nickel oxide ore with an acid such as sulfuric acid. , A scandium elution step S2 in which impurities are removed from the acidic solution to obtain a scandium eluent in which scandium is concentrated, and a solution containing a high concentration of scandium by neutralizing the scandium eluent (eluent after neutralization). ), A solvent extraction step S4 in which the obtained neutralized eluent is subjected to solvent extraction with an amine-based extractant or the like, and a scandium recovery step S5 for recovering scandium from the extraction residue. ..

<2-1. Wet smelting process of nickel oxide ore ＞
As the scandium-containing acidic solution to be treated for scandium recovery, an acidic solution obtained by treating nickel oxide ore with sulfuric acid can be used.

Specifically, the acidic solution includes a leaching step S11 in which nickel oxide ore is leached with an acid such as sulfuric acid under high temperature and high pressure to obtain a leaching solution, and a neutralized starch containing impurities by adding a neutralizing agent to the leaching solution. Wet smelting treatment of nickel oxide ore having a neutralization step S12 for obtaining a solution after neutralization and a sulfurization step S13 for obtaining a nickel sulfide and a solution after sulfurization by adding a sulfurizing agent to the solution after neutralization. The post-sulfurization solution obtained in step S1 can be used. Hereinafter, the flow of the wet smelting treatment step S1 of nickel oxide ore will be described.

[Leaching process]
In the leaching step S11, for example, using a high-temperature pressure vessel (autoclave) or the like, sulfuric acid is added to the slurry of nickel oxide ore and agitated at a temperature of 240 ° C. to 260 ° C. to form a leachate and a leaching residue. Form a leachate slurry. The treatment in the leaching step S11 may be performed according to a conventionally known HPAL process.

Nickel oxide ores mainly include so-called laterite ores such as limonite ore and saprolite ore. The nickel content of the laterite ore is usually 0.8% by weight to 2.5% by weight, and is contained as a hydroxide or a magnesium silicate mineral. In addition, these nickel oxide ores contain scandium.

In the leaching step S11, the leaching slurry composed of the obtained leaching liquid and the leaching residue is washed and solid-liquid separated into the leaching liquid containing nickel, cobalt, scandium and the like and the leaching residue which is hematite. In the solid-liquid separation treatment, for example, after mixing the leachate slurry with the cleaning liquid, the solid-liquid separation treatment is performed by a solid-liquid separation facility such as a thickener using a coagulant supplied from a coagulant supply facility or the like. Specifically, first, the leachate slurry is diluted with a washing liquid, and then the leachate residue in the slurry is concentrated as a thickener sediment. In the solid-liquid separation treatment, it is preferable to use a solid-liquid separation tank such as a thickener connected in multiple stages and perform solid-liquid separation while washing the leachate slurry in multiple stages.

[Neutralization process]
In the neutralization step S12, a neutralizing agent is added to the leachate obtained in the leaching step S11 to adjust the pH, and a neutralized starch containing an impurity element and a neutralized liquid are obtained. By this neutralization treatment, valuable metals such as nickel, cobalt, and scandium are contained in the liquid after neutralization, and most of the impurities such as iron and aluminum become neutralized starch.

As the neutralizing agent, conventionally known ones can be used, and examples thereof include calcium carbonate, slaked lime, sodium hydroxide and the like.

In the neutralization treatment in the neutralization step S12, it is preferable to adjust the pH to the range of 1 to 4 while suppressing the oxidation of the separated leachate, and it is more preferable to adjust the pH to the range of 1.5 to 2.5. preferable. If the pH is less than 1, neutralization may be insufficient and the neutralized starch and the neutralized liquid may not be separated. On the other hand, when the pH exceeds 4, not only impurities such as aluminum but also valuable metals such as scandium and nickel may be contained in the neutralized starch.

[Sulfurization process]
In the sulfurization step S13, a sulfurizing agent is added to the post-neutralizing liquid obtained in the neutralization step S12 to obtain nickel sulfide and a post-sulfurization liquid. By this sulfurization treatment, nickel, cobalt, zinc and the like become sulfides, and scandium and the like are contained in the post-sulfurization liquid.

More specifically, in the sulfurization step S13, a sulfurizing agent such as hydrogen sulfide gas, sodium sulfide, and sodium hydride sulfide is added to the obtained after neutralization liquid, and a sulfide containing nickel with a small amount of impurity components (sulfide). Nickel sulfide) and a post-sulfide liquid containing scandium and the like are produced by stabilizing the nickel concentration at a low level.

In the sulfurization treatment, the nickel sulfide slurry is subjected to a sedimentation separation treatment using a sedimentation separator such as a thickener, and the nickel sulfide is separated and recovered from the bottom of the thickener. On the other hand, the post-sulfurization liquid, which is an aqueous solution component, is recovered by overflowing.

In the scandium recovery method according to the present embodiment, the post-sulfurized solution obtained through each step of the hydrometallurgy step S1 as described above contains scandium and other impurities to be subjected to the scandium recovery treatment. It can be used as an acidic solution.

<2-2. Scandium (Sc) elution step>
As described above, the post-sulfurization liquid obtained through each step of the hydrometallurgy step S1 can be applied as an acidic solution which is a target solution for the scandium recovery treatment. However, in addition to scandium, the acidic solution contains, for example, aluminum, chromium, and various other impurities that remain in the solution without being sulfurized by the sulfurization treatment in the above-mentioned sulfurization step S13. From this, when the obtained acidic solution was subjected to solvent extraction, scandium (Sc) was concentrated by removing impurities contained in the acidic solution in advance as a scandium elution step S2, and a scandium eluent (scandium-containing solution) was used. ) Is preferably generated.

In the scandium elution step S2, for example, by a method of ion exchange treatment using a chelate resin, impurities such as aluminum contained in the acidic solution can be separated and removed to obtain a scandium-containing solution in which scandium is concentrated. ..

FIG. 2 is a process diagram showing an example of a scandium recovery method. The process diagram of FIG. 2 shows an example of a method (ion exchange treatment step) performed by an ion exchange reaction using a chelate resin as a method of removing impurities contained in an acidic solution to concentrate and elute scandium. It is a thing. In this step, scandium is adsorbed by contacting the post-sulfurized liquid obtained in the sulphurization step S13 in the hydrometallurgical treatment step S1 of nickel oxide ore with a chelate resin to obtain a scandium (Sc) eluate. The ion exchange treatment step as an example of the scandium elution step S2 is referred to as “ion exchange treatment step S2”.

Specifically, the ion exchange treatment step S2 includes an adsorption step S21 in which the post-sulfurized liquid is brought into contact with the chelate resin to adsorb scandium to the chelate resin, and a chelate resin is brought into contact with sulfuric acid of 0.1 N or less to form the chelate resin. A chelate through an aluminum removal step S22 for removing adsorbed aluminum, a scandium elution step S23 for contacting a chelate resin with sulfuric acid of 0.3 N or more and 3 N or less to elute scandium to obtain a scandium eluent, and a chelate elution step S23. An example thereof includes a chromium removing step S24 in which 3N or more of sulfuric acid is brought into contact with the resin to remove the chromium adsorbed on the chelate resin. Hereinafter, each step will be outlined, but the ion exchange processing step S2 is not limited to this.

[Adsorption process]
In the adsorption step S21, the post-sulfurized liquid is brought into contact with the chelate resin, and scandium in the post-sulfurized liquid is adsorbed on the chelate resin. The type of chelate resin is not particularly limited, and for example, a resin having iminodiacetic acid as a functional group can be used.

[Aluminum removal process]
In the aluminum removal step S22, the chelate resin adsorbed with scandium in the adsorption step S21 is brought into contact with sulfuric acid of 0.1 N or less to remove the aluminum adsorbed on the chelate resin. When removing aluminum, the pH of the sulfuric acid solution is preferably maintained in the range of 1 or more and 2.5 or less, and more preferably 1.5 or more and 2.0 or less.

[Scandium elution process]
In the scandium elution step S23, sulfuric acid of 0.3N or more and less than 3N is brought into contact with the chelate resin that has undergone the aluminum removal step S22 to obtain a scandium eluent in which scandium is eluted from the chelate resin. When obtaining a scandium eluent, it is preferable to maintain the normality of the sulfuric acid solution used as the elution liquid in the range of 0.3N or more and less than 3N, and more preferably in the range of 0.5N or more and less than 2N. preferable.

[Chromium removal process]
In the chromium removing step S24, sulfuric acid of 3N or more is brought into contact with the chelate resin that has undergone the scandium elution step S23, and the chromium adsorbed when adsorbed on the chelate resin in the adsorption step S21 is removed. When removing chromium, if the normality of the sulfuric acid solution is less than 3N, chromium is not properly removed from the chelate resin, which is not preferable.

<2-3. Neutralization process>
As described above, in the scandium elution step (ion exchange treatment step) S2, scandium and impurities are separated by the selectivity of the chelate resin, and the scandium separated from the impurities is recovered as a scandium eluent. However, due to the characteristics of the chelate resin used, not all impurities can be completely separated from scandium. Therefore, by using the scandium eluate recovered in the scandium elution step S2 as the extraction starting liquid in the solvent extraction step S4, which will be described later, and subjecting it to a solvent extraction treatment, the separation of scandium and impurities can be further promoted.

However, in the solvent extraction treatment, in general, the higher the concentration of the target component in the extraction starting liquid, the better the separation performance from the impurities other than the target. Further, if the amount of scandium to be treated is the same, the amount of the extraction starting liquid containing scandium at a higher concentration requires a smaller amount of liquid to be subjected to the solvent extraction treatment, and as a result, the amount of the extractant to be used is also increased. Can be reduced. Further, there are various merits such as improvement of operation efficiency such that the equipment required for the solvent extraction process can be made more compact.

Therefore, in the scandium recovery method according to the present embodiment, a neutralizing agent is added to the scandium eluent in order to increase the scandium concentration in the scandium eluent, that is, to concentrate the scandium. The pH is adjusted to form a scandium hydroxide precipitate, and an acid is added to the obtained scandium hydroxide precipitate to dissolve it again. This makes it possible to obtain a solution having a high scandium concentration (extraction starting solution).

As described above, by subjecting the scandium eluate to a neutralizing treatment to concentrate the scandium prior to the solvent extraction step S4, the processing efficiency of the solvent extraction can be improved. In addition, by performing such a neutralization treatment, a scandium-containing precipitate is once formed from the scandium eluent and solid-liquid separation is performed, so that the effect of separating impurities that did not become a precipitate is also expected. can.

Specifically, as shown in FIG. 2, the neutralization step S3 was obtained as a neutralization step S31 in which the scandium eluent was neutralized to obtain a neutralized starch and a neutralized filtrate. It has a hydroxide dissolution step S32, which dissolves the neutralized starch by adding an acid to obtain a redissolved solution (hydroxide solution) containing a high concentration of scandium.

[Neutralization process]
In the neutralization step S31, the scandium eluate is neutralized and the pH of the eluent is adjusted to a predetermined range to make scandium contained in the scandium eluate a precipitate of scandium hydroxide. .. Then, in the scandium recovery method according to the present embodiment, in this neutralization step S31, a neutralization treatment is performed by adding a neutralizing agent and dimethylglyoxime to the scandium eluent.

As will be described in detail later, in the neutralization step S31, the impurity elements contained in the scandium eluent are more effectively separated by adding dimethylglyoxime in addition to the neutralizing agent to perform the neutralization treatment. Can be done. In particular, in the scandium recovery method, nickel as an impurity can be effectively and efficiently separated.

Here, as the neutralization treatment in the neutralization step S31, it is preferable to perform pH adjustment by neutralization using a neutralizing agent in two steps. This makes it possible to separate impurities more efficiently and concentrate scandium.

FIG. 3 is a process diagram showing a flow when performing a two-step neutralization treatment in the neutralization step S31. As shown in FIG. 3, in the neutralization step S31, a neutralizing agent and dimethylglioxime are added to the scandium eluent to perform a neutralization treatment, and the primary neutralized starch and the primary neutralization are performed by solid-liquid separation. In the first neutralization step S311 to obtain a filtrate, a neutralizing agent is further added to the primary neutralization filtrate to perform a neutralization treatment, and a secondary neutralized starch and a secondary neutralized filtrate are obtained by solid-liquid separation. Can be a step having a second neutralization step S312 and the like.

(First neutralization step)
Specifically, as the first neutralization step S311, a neutralizing agent such as sodium hydroxide is added to the scandium eluent to adjust the pH within a predetermined range, and dimethylglyoxime is added. The first stage of neutralization is performed to produce a precipitate.

By adjusting the pH by this first-stage neutralization treatment, most of the impurity elements such as iron and chromium, which are components having a lower basicity than scandium, become a precipitate in the form of a hydroxide. On the other hand, although nickel is more basic than scandium, it may not produce sufficient precipitates by adjusting the pH with a neutralizing agent such as sodium hydroxide. Therefore, by adding a neutralizing agent and dimethylglyoxime, a precipitate of bis (dimethylglyoximeto) nickel is formed by a chelate reaction between dimethylglyoxime and nickel as shown in the following formula [1]. To cause.

Ni ²⁺ + 2dmgH ₂ → Ni (dmgH) ₂ ↓ + 2H ⁺ ... Equation [1]
(Note that "dmgH ₂ " in the formula indicates dimethylglyoxime (C ₄ H ₈ O ₂ N ₂ ))

By filtering the slurry obtained by such a neutralization treatment, it is separated into a primary neutralized starch and a primary neutralized filtrate. Scandium is concentrated in the primary neutralization filtrate.

In the neutralization treatment in the first neutralization step S311, the pH of the solution (scandium eluent) is adjusted to preferably in the range of 3.8 to 4.5 by adding a neutralizing agent and dimethylglyoxime. do. Further, more preferably, the pH is adjusted to be about 4.0 to 4.2. By adding a neutralizing agent so that the pH of the scandium eluent is in such a range, scandium can be more efficiently concentrated in the primary neutralization filtrate.

With respect to the pH of the solution to be adjusted, it is preferable that it is close to the neutral region in order to promote the rightward reaction in the above formula [1]. From this, if the pH is less than 3.8, there is almost no acid dissociation of dimethylglyoxime, and there is a possibility that a precipitate of bis (dimethylglyoximeto) nickel is not sufficiently formed. On the other hand, when the pH is higher than 4.5, the amount of scandium hydroxide precipitated increases, so that nickel and scandium may not be effectively separated.

The neutralizing agent is not particularly limited as long as the scandium eluate can be adjusted to a desired pH range, and examples thereof include sodium hydroxide and the like.

The amount of dimethylglioxime added is not particularly limited, but is preferably 3 equivalents to 50 equivalents with respect to the amount of nickel contained in the scandium eluent, and 4 equivalents to 40 equivalents. Is more preferable, and the ratio is more preferably 10 equivalents to 35 equivalents. By adding dimethylglyoxime in such a proportion, nickel contained in the scandium eluent can be more effectively separated from scandium.

(Second neutralization step)
Next, as the second neutralization step S312, a neutralizing agent such as sodium hydroxide is further added to the primary neutralization filtrate obtained by the first-stage neutralization, and the pH of the solution is predetermined. The second stage of neutralization is performed so that the range is adjusted.

By this second-stage neutralization treatment, scandium contained in the primary neutralization filtrate can be obtained as a precipitate of scandium hydroxide (secondary neutralized starch). At the same time, manganese, which is a component having a higher basicity than scandium, does not form a precipitate and can be left in the secondary neutralization filtrate. Then, by solid-liquid separation of the obtained neutralized slurry, it is possible to recover the secondary neutralized starch, that is, the hydroxide of scandium from which impurities have been separated.

In the neutralization treatment in the second neutralization step S312, the pH of the primary neutralization filtrate is adjusted to preferably in the range of 5.5 to 6.5 by adding a neutralizing agent. Further, more preferably, the pH is adjusted to be about 6.0. By adding a neutralizing agent so that the pH of the primary neutralizing filtrate is in such a range, a precipitate of scandium hydroxide can be produced more efficiently.

The neutralizing agent is not particularly limited as long as the primary neutralizing filtrate can be adjusted to a desired pH range, and examples thereof include sodium hydroxide solution.

The concentration of the neutralizing agent such as sodium hydroxide solution may be appropriately determined. For example, when a high-concentration neutralizing agent exceeding 4N is added, the pH locally rises in the reaction vessel. A state in which the pH exceeds 4.5 can occur. In such a case, adverse effects such as coprecipitation of scandium and impurities may occur, and high-purity scandium may not be obtained. Therefore, the neutralizing agent is preferably a solution diluted to 4N 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 1N or more.

In addition, like the above-mentioned primary neutralized starch and secondary neutralized starch, the precipitate obtained by adding an alkaline neutralizing agent such as sodium hydroxide has extremely poor filterability. Is common. 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.

[Hydroxide dissolution process]
In the hydroxide dissolution step S32, an acid is added to the neutralized starch (secondary neutralized starch) containing scandium hydroxide as a main component, which is recovered through the neutralization treatment in the above-mentioned neutralization step S31. To obtain a hydroxide solution that dissolves and becomes a re-dissolved solution. In the scandium recovery method according to the present embodiment, the redissolved solution thus obtained is used as the extraction starting solution of the solvent extraction treatment in the solvent extraction step S4 described later.

The acid for dissolving the neutralized starch is not particularly limited, but it is preferable to use a sulfuric acid solution. When a sulfuric acid solution is used, the redissolved solution is a scandium sulfate solution.

For example, when a sulfuric acid solution is used, its concentration is not particularly limited, but it is preferable to dissolve it using a sulfuric acid solution having a concentration of 2N or more in consideration of an industrial reaction rate.

Further, by adjusting the slurry concentration at the time of dissolution with a sulfuric acid solution or the like, an extraction starting solution having an arbitrary scandium concentration can be obtained. For example, when a 2N sulfuric acid solution is added and dissolved, the pH of the solution is preferably maintained in the range of 0.8 to 1.5, more preferably about 1.0. By dissolving so as to maintain the pH in this way, the scandium hydroxide can be efficiently dissolved, and the loss of scandium recovery due to undissolved can be suppressed. Regarding the above-mentioned pH range, if the pH is higher than 1.5, the dissolution of scandium hydroxide may not proceed efficiently. On the other hand, when the pH is as low as less than 0.8, a strongly acidic solution is obtained, and the amount of neutralizing agent added in the wastewater treatment for neutralizing and disposing of the solution after recovering scandium increases. , It is not preferable because it is costly and troublesome.

[Dimethylglyoxime recovery process]
In the above-mentioned neutralization step S31, since the neutralization treatment is performed by adding dimethylglyoxime together with the neutralizing agent, the unreacted dimethylglyoxime is dissolved in the obtained neutralization filtrate. Therefore, it is desirable to recover dimethylglyoxime dissolved in the neutralized filtrate in the recovery step.

Therefore, as shown in the process diagram of FIG. 3, the dimethylglyoxime recovery step S33 is provided, and the dimethylglyoxime remaining in the solution is recovered from the neutralization filtrate obtained through the neutralization step S31. can do. In the process diagram of FIG. 3, a flow of performing a two-step neutralization treatment and recovering dimethylglyoxime dissolved in the secondary neutralization filtrate obtained through the treatment in the second neutralization step S312 is illustrated.

The dimethylglyoxime recovery step S33 is not limited to the neutralization filtrate obtained through the two-step neutralization treatment, and is also preferably a treatment step for the neutralization filtrate obtained through the neutralization treatment of only one step, for example. Can be provided.

Specifically, as a method of recovery treatment, for example, a compound containing nickel is added to the neutralized filtrate, and dimethylglyoxime and nickel are reacted to produce a precipitate of bis (dimethylglyoximeto) nickel. The method can be mentioned. Then, by adding an acid and mixing the obtained precipitate so that the pH becomes less than 3.8, only nickel is dissolved in the acid solution, and dimethylglyoxime remains as a precipitate without being dissolved. And can be separated from nickel to recover dimethylglyoxime.

The recovered dimethylglyoxime can be reused as dimethylglyoxime used in the neutralization step S31 (indicated by the arrow R in FIG. 3), and the drug cost can be effectively reduced.

<2-4. Solvent extraction process>
Next, in the solvent extraction step S4, the solvent extraction treatment is performed on the eluent (extraction starting liquid) after neutralization. Here, the neutralized eluent refers to a solution obtained by subjecting the scandium eluent obtained in the scandium elution step S2 to the neutralization treatment in the neutralization step S31. More specifically, a redissolved solution (hydroxide solution) obtained through the neutralization step S3 is used as the eluent after neutralization, and the solution is brought into contact with an extractant to perform solvent extraction treatment. A extraction residue containing scandium is obtained. As described above, the redissolving solution used for solvent extraction is an acidic solution in which scandium is concentrated, and is also referred to as a "scandium-containing solution" below.

The treatment mode in the solvent extraction step S4 is not particularly limited, but as shown in FIGS. 1 and 2, for example, a scandium-containing solution and an extractant which is an organic solvent are mixed to selectively select impurities in the organic solvent. Extraction step S41 to obtain a drawing residue with scandium left, scrubbing step S42 to mix a sulfuric acid solution with an organic solvent after extraction and wash the organic solvent after extraction, and a back extractant to the organic solvent after cleaning. It is preferable to carry out the solvent extraction treatment including the back extraction step S43 in which impurities are back-extracted from the organic solvent after washing by adding the above.

[Extraction process]
In the extraction step S41, an organic solvent containing an extractant and a scandium-containing solution are mixed, impurities are selectively extracted into the organic solvent, and the post-extraction organic solvent containing the impurities and the extract residue liquid containing scandium are left. And get. In the scandium recovery method according to the present embodiment, in the extraction step S41, a solvent extraction treatment using an amine-based extractant is preferably performed. By performing the solvent extraction treatment using the amine-based extractant in this way, impurities can be extracted more efficiently and effectively and separated from scandium.

The amine-based extractant has features such as low selectivity with scandium and no need for a neutralizing agent at the time of extraction. Examples of the amine-based extractant include PrimeneJM-T, which is a primary amine, LA-1, which is a secondary amine, TNOA (Tri-n-octylamine), which is a tertiary amine, and TIOA (Tri-i-octylamine). Those known by the trade name of can be used.

At the time of extraction, it is preferable to dilute the amine-based extractant with, for example, a hydrocarbon-based organic solvent or the like before use. The concentration of the amine-based extractant in the organic solvent is not particularly limited, but is preferably about 1% by volume to 10% by volume in consideration of phase separation during extraction and back-extraction described later. In particular, it is more preferably about 5% by volume.

The volume ratio of the organic solvent to the scandium-containing solution at the time of extraction is not particularly limited, but the amount of organic solvent mol is about 0.01 to 0.1 times the amount of metal in the scandium-containing solution. It is preferable to do so.

[Scrubbing (cleaning) process]
When a small amount of scandium coexists in the organic solvent obtained by extracting impurities from the scandium-containing solution in the extraction step S41, scrubbing (organic phase) with respect to the organic solvent (organic phase) after the extraction before back-extracting the extract. Cleaning) processing is performed. As a result, scandium is separated into an aqueous phase and recovered from the organic solvent (scrubbing step S42).

By providing the scrubbing step S42 in this way to wash the organic solvent and separate a small amount of scandium extracted by the extractant, scandium can be separated in the washing liquid, and the recovery rate of scandium is further increased. be able to.

As the solution (washing solution) used for scrubbing, a sulfuric acid solution, a hydrochloric acid solution, or the like can be used. It is also possible to use water to which soluble chloride or sulfate is added. Specifically, when a sulfuric acid solution is used as the cleaning solution, it is preferable to use a solution having a concentration in the range of 1.0 mol / L to 3.0 mol / L.

The number of cleaning steps (number of times) can be appropriately set depending on the type and concentration of impurity elements, the amine-based extractant used, the extraction conditions, and the like. For example, when the phase ratio O / A of the organic phase (O) and the aqueous phase (A) is O / A = 1, the number of cleaning stages is about 3 to 5, and the scandium in the organic solvent is the lower limit of detection of the analyzer. Can be separated and collected to less than.

[Reverse extraction process]
In the back extraction step S43, the impurities are back extracted from the organic solvent from which the impurities were extracted in the extraction step S41. Specifically, in the back extraction step S43, a back extraction solution (back extraction starting solution) is added to an organic solvent containing an extractant and mixed to cause a reaction opposite to the extraction process in the extraction step S41. The impurities are back-extracted to obtain a post-extraction solution containing the impurities.

As described above, in the extraction process in the extraction step S41, impurities are preferably selectively extracted using an amine-based extractant. From this, considering that impurities are separated from the organic solvent and the extractant is regenerated, the back extraction solution is preferably a solution containing a carbonate such as sodium carbonate or potassium carbonate.

The concentration of the carbonate-containing solution, which is a back-extraction solution, is preferably about 0.5 mol / L to 2 mol / L, for example, from the viewpoint of suppressing excessive use.

When the organic solvent containing the extractant is subjected to the scrubbing treatment in the scrubbing step S42, the back-extraction treatment is similarly performed by adding the back-extraction solution to the scrubbing extractant and mixing it. It can be carried out.

In this way, impurities can be removed from the extractant again by adding a carbonate solution such as sodium carbonate to the extractant after extraction or the extractant after scrubbing and performing the back extraction treatment. , Can be repeated as an extractant used in the extraction process.

<2-5. Scandium recovery process>
Next, in the scandium recovery step S5, scandium is recovered from the extracted residual liquid obtained in the extraction step S41 in the solvent extraction step S4, and when scrubbing is performed in the scrubbing step S42, the scandium is recovered from the cleaning liquid after scrubbing. do.

[Crystallization process]
In the crystallization step S51, scandium contained in the extraction residue or the like is crystallized into a scandium salt precipitate and recovered.

The method for crystallizing and recovering scandium is not particularly limited, and a known method can be used. For example, there is a method in which an alkali is added to perform a neutralization treatment to generate a precipitate of scandium hydroxide and recover it. Alternatively, a method of producing and recovering a oxalate precipitate using an oxalic acid solution (oxalate treatment) can also be used. According to these methods, impurities contained in the extraction residue can be effectively separated to obtain high-purity scandium crystals.

[Roasting process]
In the roasting step S52, the precipitates such as scandium hydroxide and scandium oxalate obtained in the crystallization step S51 are washed with water, dried, and then roasted. By undergoing this roasting treatment, scandium can be recovered as extremely high-purity scandium oxide.

The conditions for the roasting treatment are not particularly limited, but for example, they may be placed in a tube furnace and heated at about 900 ° C. for about 2 hours. Industrially, it is preferable to use a continuous furnace such as a rotary kiln because drying and roasting can be performed by the same apparatus.

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

[Example 1]
(Hydrometallurgy step S1)
A pressure acid leaching treatment with sulfuric acid was performed using nickel oxide ore as a raw material, the pH of the obtained leachate was adjusted to remove impurities, and then a sulfurizing agent was added to separate nickel to prepare a post-sulfurized liquid. .. Table 1 below shows the concentrations of scandium (Sc), aluminum (Al), and iron (Fe) in the obtained post-sulfidation liquid.

Even when a neutralizing agent is added to a solution having this composition (post-sulfurization liquid) to generate a precipitate to obtain a hydroxide containing scandium and other impurity components, the hydroxide of scandium is obtained. The quality of the product was only about 0.1% by mass.

(Ion exchange processing step S2)
Next, the obtained after-sulfidation liquid was subjected to ion exchange treatment by a known method using a chelate resin to obtain a scandium eluate having a composition shown in Table 2 below.

(Neutralization step S31)
The obtained scandium eluent is placed in a reaction vessel, and dimethylglyoxime is added at a ratio corresponding to 10 equivalents of the amount of nickel present in the scandium eluent and a sodium hydroxide solution having a concentration of 4 N while stirring to make a solution. The first-stage neutralization treatment was performed to adjust the pH of the mixture to 4.2 (first neutralization step S311).

After the first-stage neutralization treatment, solid-liquid separation was performed using a filter paper and a nutche, and as a result, a primary neutralized starch and a primary neutralized filtrate were obtained. By analysis using ICP, the ratio (distribution) of the amount of precipitate-produced material to the amount of material contained in the scandium eluate shown in Table 2 above was evaluated as the precipitation rate (%). Table 3 below shows the precipitation rate by the first-stage neutralization treatment.

As shown in Table 3, the neutralizing agent is added until the pH of the solution reaches 4.2, and dimethylglyoxime is added to perform the neutralization treatment. Chromium could be effectively precipitated as a neutralizing starch. In particular, nickel could be effectively separated from scandium distributed in the primary neutralization filtrate.

Subsequently, the obtained primary neutralization filtrate was placed in a reaction vessel, a sodium hydroxide solution having a concentration of 4N was added thereto, and a second-stage neutralization treatment was performed to adjust the pH of the solution to 6. (Second neutralization step S312).

After the second-stage neutralization treatment, solid-liquid separation was performed in the same manner as in the first-stage neutralization treatment, and as a result, a secondary neutralized starch and a secondary neutralized filtrate were obtained. By analysis using ICP, the ratio (distribution) of the amount of precipitate-produced material to the amount of material contained in the primary neutralization filtrate was evaluated as the precipitation rate (%). Table 4 below shows the precipitation rate by the second stage neutralization treatment.

As shown in Table 4, most of the scandium that did not precipitate in the first-stage neutralization treatment and remained in the filtrate was a secondary neutralized starch at a rate of almost 100% in the second-stage neutralization treatment. Distributed to. On the other hand, manganese, which is more basic than scandium, remains in the secondary neutralization filtrate without precipitating even by the neutralization treatments of both the first and second stages, and can be effectively separated from scandium. did it.

From the results shown in Table 4, most of the components in the scandium eluate (compositions shown in Table 2) of iron, nickel, and chromium are precipitated even in the second stage of neutralization. appear. However, some or most of these components have already been distributed to the primary neutralized starch and separated from scandium by the first-stage neutralization treatment, and the amount itself distributed to the secondary neutralized starch itself. Is suppressed.

From the above results, most of the impurities (impurities other than aluminum) contained in the scandium eluate were removed by the neutralization treatment including the addition of dimethylglyoxime, preferably by performing the two-step neutralization treatment. , Can be effectively separated from scandium. note that. Table 5 below shows the proportion (precipitation rate) distributed in the secondary neutralized starch obtained by solidifying scandium.

(Hydroxide dissolution step S32)
Next, a sulfuric acid solution having a concentration of 2N was added to the obtained secondary neutralized starch to dissolve the precipitate while maintaining the pH at around 1, and the redissolved solution (hydroxide dissolution) shown in Table 6 below was dissolved. Liquid) was obtained.

(Solvent extraction step S4)
Next, 500 ml of the obtained hydroxide solution was used as the extraction starting solution, and an amine-based extractant (PrimeneJM-T, manufactured by Dow Chemical Co., Ltd.) was used as a solvent (Shellzol A150, manufactured by Shell Chemicals Japan Co., Ltd.). 250 ml of an organic solvent adjusted to 5% by volume was mixed, and the mixture was stirred at room temperature for 60 minutes to perform a solvent extraction treatment (extraction step S41). By this solvent extraction treatment, a extraction residual liquid containing scandium was obtained. At the time of extraction, no clad was formed, and phase separation after standing proceeded rapidly.

The composition of each element contained in the extracted organic phase obtained by extraction was analyzed. In Table 7 below, the percentage of the value obtained by dividing the physical quantity of various elements contained in the extracted organic phase by the physical quantity of each element contained in the pre-extraction base solution (extraction starting solution) is calculated, and the percentage is calculated as the extraction rate (extraction rate). %) Shows the result.

As can be seen from the results of the extraction rates shown in Table 7, most of the scandium contained in the pre-extraction original solution (hydroxide solution) was distributed to the extraction residual solution through the solvent extraction treatment. Although not shown in Table 7, other impurities were extracted into an organic solvent and could be effectively separated from scandium.

Subsequently, a sulfuric acid solution having a concentration of 1 mol / L was added to 250 ml of an organic solvent (extracted organic phase) containing a small amount of scandium obtained after the extraction treatment so that the phase ratio (O / A) was 1. The mixture was mixed in an amount of 250 ml, stirred for 60 minutes and washed. Then, the mixture was allowed to stand to separate the aqueous phase, and the organic phase was washed again by mixing with 250 ml of a new sulfuric acid solution having a concentration of 1 mol / L, and the aqueous phase was separated in the same manner. Such a cleaning operation was repeated a total of 5 times (scrubbing step S42).

By washing the extracted organic phase 5 times in this way, scandium contained in the extracted organic phase could be separated into an aqueous phase and recovered. On the other hand, regarding the impurities contained in the extracted organic phase, only the elution at a low level of 1 mg / L can be achieved, and only the scandium extracted in the organic solvent can be effectively separated into the aqueous phase, and only the impurities can be removed. rice field.

Subsequently, sodium carbonate having a concentration of 1 mol / L was mixed with the extracted organic phase after washing so as to have a phase ratio of O / A = 1/1, and the mixture was stirred for 60 minutes to perform a back extraction treatment. Was back-extracted into the aqueous phase (back-extraction step S43). The composition of various elements contained in the liquid after back extraction obtained by this back extraction operation was analyzed. In Table 8 below, the percentage of the value obtained by dividing the physical quantity of various elements contained in the liquid after back extraction by the physical quantity of various elements extracted into the organic phase by the extraction process is calculated, and this is used as the recovery rate (%). The results are shown.

As can be seen from the recovery rate results shown in Table 8, most of the iron and aluminum could be separated and scandium could be recovered by performing the solvent extraction treatment described above.

(Scandium recovery step S5)
Next, crystals of oxalic acid / dihydrate (manufactured by Mitsubishi Gas Chemicals Co., Ltd.), which is three times the calculated amount of the amount of scandium contained in the extracted residual liquid, are dissolved in the obtained extracted residual liquid. , 60 minutes stirring and mixing to generate a white crystalline precipitate of scandium oxalate (crystallization step S51).

Subsequently, the obtained scandium oxalate precipitate was suction-filtered, washed with pure water, and dried at 105 ° C. for 8 hours. The dried scandium oxalate was placed in a tube furnace and roasted (calcined) at 850 ° C. to 900 ° C. to obtain scandium oxide.

Scandium oxide obtained by roasting was analyzed by luminescence spectroscopy. Table 9 below shows the grade (ppm) of each impurity contained in scandium oxide.

As shown in Table 9, high-purity scandium oxide having a low impurity content could be obtained.

[Example 2]
The post-sulfurized liquid of the same composition shown in Table 1 used in Example 1 was subjected to ion exchange treatment in the same manner as in Example 1 to obtain a scandium eluate having the same composition as in Table 2 above.

The obtained scandium eluent is placed in a reaction vessel, and dimethylglyoxime is added at a ratio corresponding to 5 equivalents of a sodium hydroxide solution having a concentration of 4 N and the amount of nickel present in the scandium eluent while stirring to make a solution. The first-stage neutralization treatment was performed to adjust the pH of the mixture to 4.3.

Other than that, scandium oxide was obtained in the same manner as in Example 1.

Scandium oxide obtained by roasting was analyzed by luminescence spectroscopy. Table 10 below shows the grade (ppm) of each impurity contained in scandium oxide.

As shown in Table 10, high-purity scandium oxide having a low impurity content could be obtained.

[Comparative Example 1]
The post-sulfurized liquid of the same composition shown in Table 1 used in Example 1 was subjected to ion exchange treatment in the same manner as in Example 1 to obtain a scandium eluate having the same composition as in Table 2 above.

The obtained scandium eluent is placed in a reaction vessel, a sodium hydroxide solution having a concentration of 4 N is added with stirring, and a neutralization treatment is performed to adjust the pH of the solution to 6, and a precipitate (neutralized starch) is applied. The product) and the neutralized filtrate were produced. That is, unlike Examples 1 and 2, dimethylglyoxime was not added and only one step of neutralization treatment was performed.

Then, scandium oxide was obtained in the same manner as in Example 1 except that a precipitate of scandium hydroxide was obtained from the neutralized filtrate recovered by solid-liquid separation.

The obtained scandium oxide was analyzed by luminescence spectroscopy. Table 11 below shows the grade (ppm) of each impurity contained in scandium oxide.

As shown in Table 11, the content of nickel was particularly high among the impurity elements. Considering this in comparison with Examples, in Comparative Example 1, in the neutralization treatment for the scandium eluent, only the sodium hydroxide solution as a neutralizing agent was added, and dimethylglyoxime was added to the neutralizing agent. It is probable that nickel was not sufficiently removed as a precipitate because nickel was not added because oxime was not added.

[Example 3]
(Hydrometallurgy step S1)
Using the same nickel oxide ore as in Example 1 above as a raw material, pressure acid leaching is performed using the same method as in Example 1, the pH of the obtained leachate is adjusted to remove impurities, and a sulfurizing agent is added. After addition, nickel was separated to prepare a post-sulfurization liquid (a post-sulfidation liquid having the same composition as in Table 1 above).

(Ion exchange processing step S2)
Next, the obtained after-sulfidation liquid was subjected to ion exchange treatment by a known method using a chelate resin to obtain a candium eluate having a composition shown in Table 12 below.

(Neutralization step S31)
The obtained scandium eluent is placed in a reaction vessel, and dimethylglyoxime is added at a ratio corresponding to 10 equivalents of the amount of nickel present in the scandium eluent and a sodium hydroxide solution having a concentration of 4 N while stirring to make a solution. The first-stage neutralization treatment was performed to adjust the pH of the mixture to 4.0 (first neutralization step S311).

After the first-stage neutralization treatment, solid-liquid separation was performed using filter paper and nutche, and as a result, a primary neutralized starch and a primary neutralized filtrate were obtained. By analysis using ICP, the ratio (distribution) of the amount of precipitate-produced material to the amount of material contained in the scandium eluate shown in Table 12 above was evaluated as the precipitation rate (%). Table 13 below shows the precipitation rate by the first-stage neutralization treatment.

As shown in Table 13, the neutralizing agent was added until the pH of the solution reached 4.0, and dimethylglyoxime was added to perform the neutralization treatment. Chromium could be effectively precipitated as a neutralizing starch. In particular, nickel could be effectively separated from scandium distributed in the primary neutralization filtrate. Further, as compared with Example 1 above (adding a neutralizing agent until the pH reached 4.2. See Table 3 above), scandium, which is a recovery loss, could be halved.

Subsequently, the obtained primary neutralization filtrate was placed in a reaction vessel, a sodium hydroxide solution having a concentration of 4N was added thereto, and a second-stage neutralization treatment was performed to adjust the pH of the solution to 6. (Second neutralization step S312).

After the second-stage neutralization treatment, solid-liquid separation was performed in the same manner as in the first-stage neutralization treatment, and as a result, a secondary neutralized starch and a secondary neutralized filtrate were obtained. By analysis using ICP, the ratio (distribution) of the amount of precipitate-produced material to the amount of material contained in the primary neutralization filtrate was evaluated as the precipitation rate (%). Table 14 below shows the precipitation rate by the second stage neutralization treatment.

As shown in Table 14, most of the scandium that did not precipitate in the first-stage neutralization treatment and remained in the filtrate was a secondary neutralized starch at a rate of almost 100% in the second-stage neutralization treatment. Distributed to. On the other hand, manganese, which is more basic than scandium, remains in the secondary neutralization filtrate without precipitating even by the neutralization treatments of both the first and second stages, and can be effectively separated from scandium. did it.

From the results shown in Table 14, most of the components in the scandium eluate (compositions shown in Table 12) of iron, nickel, and chromium are precipitated even in the second stage of neutralization. appear. However, some or most of these components have already been distributed to the primary neutralized starch and separated from scandium by the first-stage neutralization treatment, and the amount itself distributed to the secondary neutralized starch itself. Is suppressed.

From the above results, most of the impurities (impurities other than aluminum) contained in the scandium eluate were removed by the neutralization treatment including the addition of dimethylglyoxime, preferably by performing the two-step neutralization treatment. , Can be effectively separated from scandium. note that. Table 15 below shows the proportion (precipitation rate) distributed in the secondary neutralized starch obtained by solidifying scandium.

(Hydroxide dissolution step S32)
Next, a sulfuric acid solution having a concentration of 2N was added to the obtained secondary neutralized starch to dissolve the precipitate while maintaining the pH at around 1, and the redissolved solution (hydroxide dissolution) shown in Table 16 below was dissolved. Liquid) was obtained.

(Solvent extraction step S4)
Next, 500 ml of the obtained hydroxide solution was used as the extraction starting solution, and an amine-based extractant (PrimeneJM-T, manufactured by Dow Chemical Co., Ltd.) was used as a solvent (Shellzol A150, manufactured by Shell Chemicals Japan Co., Ltd.). 250 ml of an organic solvent adjusted to 5% by volume was mixed, and the mixture was stirred at room temperature for 60 minutes to perform a solvent extraction treatment (extraction step S41). By this solvent extraction treatment, a extraction residual liquid containing scandium was obtained. At the time of extraction, no clad was formed, and phase separation after standing proceeded rapidly.

The composition of each element contained in the extracted organic phase obtained by extraction was analyzed. In Table 17 below, the percentage of the value obtained by dividing the physical quantity of various elements contained in the extracted organic phase by the physical quantity of each element contained in the pre-extraction original liquid (extraction starting liquid) is calculated, and the percentage is calculated as the extraction rate (extraction rate). %) Shows the result.

As can be seen from the results of the extraction rates shown in Table 17, most of the scandium contained in the pre-extraction original liquid (hydroxide dissolution liquid) was distributed to the extraction residual liquid through the solvent extraction treatment. Although not shown in Table 17, other impurities were extracted into an organic solvent and could be effectively separated from scandium.

Subsequently, a sulfuric acid solution having a concentration of 1 mol / L was added to 250 ml of an organic solvent (extracted organic phase) containing a small amount of scandium obtained after the extraction treatment so that the phase ratio (O / A) was 1. The mixture was mixed in an amount of 250 ml, stirred for 60 minutes and washed. Then, the mixture was allowed to stand to separate the aqueous phase, and the organic phase was washed again by mixing with 250 ml of a new sulfuric acid solution having a concentration of 1 mol / L, and the aqueous phase was separated in the same manner. Such a cleaning operation was repeated a total of 5 times (scrubbing step S42).

By washing the extracted organic phase 5 times in this way, scandium contained in the extracted organic phase could be separated into an aqueous phase and recovered. On the other hand, regarding the impurities contained in the extracted organic phase, only the elution at a low level of 1 mg / L can be achieved, and only the scandium extracted in the organic solvent can be effectively separated into the aqueous phase, and only the impurities can be removed. rice field.

Subsequently, sodium carbonate having a concentration of 1 mol / L was mixed with the extracted organic phase after washing so as to have a phase ratio of O / A = 1/1, and the mixture was stirred for 60 minutes to perform a back extraction treatment. Was back-extracted into the aqueous phase (back-extraction step S43). The composition of various elements contained in the liquid after back extraction obtained by this back extraction operation was analyzed. In Table 18 below, the percentage of the value obtained by dividing the physical quantity of various elements contained in the liquid after back extraction by the physical quantity of various elements extracted into the organic phase by the extraction process was calculated, and the percentage was calculated as the recovery rate (%). The result is shown.

As can be seen from the recovery rate results shown in Table 18, most of the iron and aluminum could be separated and scandium could be recovered by performing the solvent extraction treatment described above.

(Scandium recovery step S5)
Next, crystals of oxalic acid / dihydrate (manufactured by Mitsubishi Gas Chemicals Co., Ltd.), which is three times the calculated amount of the amount of scandium contained in the extracted residual liquid, are dissolved in the obtained extracted residual liquid. , 60 minutes stirring and mixing to generate a white crystalline precipitate of scandium oxalate (crystallization step S51).

Subsequently, the obtained scandium oxalate precipitate was suction-filtered, washed with pure water, and dried at 105 ° C. for 8 hours. The dried scandium oxalate was placed in a tube furnace and roasted (calcined) at 850 ° C. to 900 ° C. to obtain scandium oxide.

Scandium oxide obtained by roasting was analyzed by luminescence spectroscopy. Table 19 below shows the grade (ppm) of each impurity contained in scandium oxide.

As shown in Table 19, high-purity scandium oxide having a low impurity content could be obtained.

[Example 4]
The secondary neutralization filtrate obtained by the same method as in Example 1 above was subjected to the dimethylglyoxime recovery step shown below.

(Dimethylglyoxime recovery step S33)
-First stage neutralization That is, the secondary neutralization filtrate after separating the secondary neutralization starch containing scandium is collected, placed in a container, and while stirring, a sodium hydroxide solution having a concentration of 8N and 1 A process of recovering dimethyl glyoxime by adding nickel sulfate in a ratio corresponding to 9 equivalents of the amount of dimethyl glyoxime added in the stage neutralization treatment to adjust the pH of the solution to 6.0. (Neutralization treatment) was performed.

After the neutralization treatment, solid-liquid separation was performed using a filter paper and a nutche to obtain a neutralized starch and a neutralized filtrate. The analysis was performed using ICP, and the ratio (distribution) of the amount of the substance produced by the precipitate to the amount of the substance contained in the secondary neutralization filtrate was evaluated as the precipitation rate (%). As a result, the precipitation rate of nickel was 88%, and most of the nickel was precipitated and distributed to the neutralized starch.

It was found that the neutralized starch thus obtained was a precipitate of bis (dimethylglyoximeto) nickel, and that dimethylglyoxime could be reused by separating the nickel.

-Second-stage neutralization Next, the neutralized starch (bis (dimethylglioxymato) nickel starch) obtained by the first-stage neutralization is stirred while adding 64% sulfuric acid and pure water. , A lysate and a lysate were obtained. The analysis was performed using ICP, and the ratio (distribution) of the amount dissolved in the filtrate to the amount contained in the neutralized starch was evaluated as the dissolution rate (%). As a result, the dissolution rate of nickel was 82%.

In this way, nickel in the bis (dimethylglyoximeto) nickel starch, which is a neutralized starch, dissolves in the acid and is distributed to the solution, but dimethylglyoxime does not dissolve in the acid. Recovered as starch.

[Example 5]
(Reuse of dimethylglyoxime)
The dimethylglyoxime recovered by the operation of Example 4 was returned to the first neutralization step S311 in the neutralization step S31 and reused.

Specifically, dimethylglyoxime adjusted to 10 equivalents of the amount of nickel present in the scandium eluent to be neutralized by adding new dimethylglyoxime to the recovered dimethylglyoxime is added to the scandium eluent. Then, a sodium hydroxide solution having a concentration of 4N was added with stirring to adjust the pH of the solution to 4.2. By this neutralization treatment, a nickel bis (dimethylglioxymate) precipitate was obtained as the primary neutralized starch.

The obtained precipitate is analyzed using ICP, and the ratio (distribution) of the amount of the precipitate produced to the amount contained in the nickel sulfate solution before the neutralization treatment is evaluated as the precipitation rate (%). bottom. As a result, the precipitation rate of nickel was 99%, and it was confirmed that most of the nickel was precipitated. At the same time, it was confirmed that the recovered dimethylglyoxime can be effectively reused.

As described above, it was found that the cost of using dimethylglyoxime used for the neutralization treatment can be effectively reduced by recovering dimethylglyoxime from the filtrate after the neutralization treatment and repeatedly reusing the recovered dimethylglyoxime. rice field.

Claims (10)

A solution containing scandium is passed through an ion exchange resin, a neutralizing agent and dimethyl glyoxime are added to the eluent eluted from the ion exchange resin to perform a neutralization treatment, and a neutralized starch is obtained by solid-liquid separation. Neutralization step to obtain neutralization filtrate and
A solvent extraction step in which the eluate is subjected to solvent extraction after neutralization,
A scandium recovery step of recovering scandium oxide from the extraction residue separated by the solvent extraction treatment, and a method for recovering scandium. The method for recovering scandium according to claim 1, wherein the scandium-containing solution is a solution obtained by leaching a nickel-containing raw material with an acid. The method for recovering scandium according to claim 1 or 2, wherein in the neutralization step, the dimethylglyoxime is added at a ratio of 3 equivalents to 50 equivalents with respect to the amount of nickel contained in the eluent. The neutralization step
A first neutralization step in which a neutralizing agent and dimethylglyoxime are added to the eluent to perform a neutralization treatment, and a primary neutralizing starch and a primary neutralizing filtrate are obtained by solid-liquid separation.
It has a second neutralization step in which a neutralizing agent is further added to the primary neutralization filtrate to perform a neutralization treatment, and a secondary neutralization starch and a secondary neutralization filtrate are obtained by solid-liquid separation. The method for recovering scandium according to any one of claims 1 to 3. The scandium recovery method according to claim 4, wherein in the first neutralization step, the pH of the eluent is adjusted to the range of 3.8 to 4.5. The method for recovering scandium according to claim 4 or 5, wherein in the second neutralization step, the pH of the primary neutralization filtrate is adjusted to the range of 5.5 to 6.5. Further, it has a hydroxide dissolution step of adding an acid to the neutralized starch obtained in the neutralization step to obtain a hydroxide solution.
The method for recovering scandium according to any one of claims 1 to 6, wherein in the solvent extraction step, the hydroxide solution is subjected to the solvent extraction treatment as the eluent after neutralization. The method for recovering scandium according to any one of claims 1 to 7, further comprising a recovery step of recovering dimethylglyoxime from the neutralization filtrate obtained in the neutralization step. The neutralization step
A first neutralization step in which a neutralizing agent and dimethylglyoxime are added to the eluent to perform a neutralization treatment, and a primary neutralizing starch and a primary neutralizing filtrate are obtained by solid-liquid separation.
A second neutralization step is provided in which a neutralizing agent is further added to the primary neutralization filtrate to perform a neutralization treatment, and a secondary neutralization starch and a secondary neutralization filtrate are obtained by solid-liquid separation. death,
In the recovery step,
The method for recovering scandium according to claim 8, wherein dimethylglyoxime is recovered from the secondary neutralization filtrate obtained through the second neutralization step in the neutralization step. Dimethylglyoxime recovered in the recovery step is repeatedly reused in the neutralization treatment in the neutralization step.
The scandium recovery method according to claim 8 or 9.

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