JP2021014618A - Scandium recovery method - Google Patents

Abstract

To provide a method for effectively separating and removing manganese from an acidic solution containing scandium and the manganese.SOLUTION: A method for collecting scandium from an acidic solution containing the scandium, in which the acidic solution contains at least manganese as an impurity element, includes a concentration process of: adding alkali to the acidic solution; applying a neutralization treatment to generate scandium hydroxide; and condensing scandium. In the concentration process, the alkaline is added while maintaining so that a liquid surface of the acidic solution housed in a reaction vessel avoids a contact with oxygen at the neutralization treatment.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for recovering scandium.

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

By the way, in recent years, as described in Patent Document 1, for example, an HPAL process capable of recovering a trace amount of scandium contained in nickel oxide ore such as laterite ore and limonite ore has been proposed. In the HPAL process, nickel oxide ore is charged into a pressure vessel together with sulfuric acid, heated to a high temperature of about 240 ° C. to 260 ° C., solid-liquid separated into a nickel-containing leachate and a leachate residue, and alkali with respect to the leachate. The impurities are separated by precipitation by adding a neutralizing agent such as, and then nickel is recovered as a nickel sulfide starch by adding a sulfide agent. In this HPAL process, scandium does not become a precipitate even when a sulfurizing agent is added, so that it remains in the acidic solution after sulfurization. Thus, by using the HPAL process, nickel and scandium can be effectively separated.

However, nickel oxide ore contains various impurity elements such as iron, aluminum, manganese, and magnesium, although the type and amount thereof vary depending on the region of production. Therefore, it is necessary to concentrate the dilute scandium and effectively separate and purify these impurities.

As a method for concentrating scandium while separating it from impurities, for example, Patent Document 2 discloses a method using a chelate resin. In the method disclosed in Patent Document 2, a scandium-containing solution (scandium-containing solution) after separating nickel through an HPAL process is brought into contact with a chelate resin to adsorb scandium, and then the adsorbed chelate resin is adsorbed. It is washed with a dilute acid, and then the washed chelate resin is brought into contact with a strong acid to elute scandium.

Further, in addition to the method of adsorbing scandium on the chelate resin, for example, Patent Documents 3 and 4 disclose a method of recovering scandium by using solvent extraction. For example, Patent Document 3 discloses a method for extracting scandium into an organic solvent using an organic solvent obtained by diluting 2-ethylhexylsulfonic acid-mono-2-ethylhexyl with kerosene. Further, Patent Document 4 discloses a method of selectively separating and recovering scandium from a scandium-containing solution by bringing the scandium-containing solution into contact with an extractant at a constant ratio by batch treatment.

The scandium recovered by each of the methods described above has a purity of about 95 to 98% by weight in terms of scandium oxide (Sc ₂ O ₃ ), and is added to an alloy with aluminum. It is of sufficient quality for the purpose of. However, for applications such as fuel cell electrolytes, for which demand has been increasing in recent years, high-purity grades of about 99.9% or more are required in order to exhibit the characteristics of fuel cells, and depending on specific elements. May be set to even stricter standards.

For example, manganese is known to have an effect of deteriorating the characteristics of the electrolyte, and it is said that it is preferable to suppress the manganese concentration in scandium oxide to 50 ppm or less.

Therefore, in addition to purification using a chelate resin or solvent extraction, an alkali is added to neutralize the mixture to obtain a hydroxide of scandium. By obtaining the scandium hydroxide in this way, impurities can be separated, and the obtained hydroxide can be dissolved again with an acid or the like to obtain a redissolved solution having an arbitrary scandium concentration. Then, by re-applying this redissolved solution to the above-mentioned chelate resin or solvent extraction, purification and concentration can be efficiently performed.

In addition, a method for separating impurities by performing a shu oxidation treatment as disclosed in Patent Document 5 can also be used in combination. By using such a method, it is possible to recover high-purity scandium oxide of 99.9% or more.

In this way, various techniques for recovering high-purity scandium oxide have been proposed, but since scandium is derived from oxide ore, the components of the solution such as the after-sulfide liquid obtained by treating the oxide ore and the components of the solution It is inevitable that the concentration will vary.

Here, in particular, when the manganese concentration is relatively high in a solution containing scandium, in the process having a neutralization step of concentrating scandium as scandium hydroxide as described above, not only scandium but also manganese is precipitated. There is a problem that the amount of precipitation is increased, the manganese grade is increased, and the concentration of scandium is inhibited.

As described above, in particular, it is not easy to efficiently concentrate scandium and separate manganese from a solution containing scandium and manganese, and it is difficult to industrially recover high-purity scandium. It was.

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. 2016-108664

The present invention has been proposed in view of such circumstances, and it is possible to effectively separate and remove manganese from an acidic solution containing scandium containing manganese as an impurity element to concentrate scandium. It is an object of the present invention to provide a method for recovering scandium that can be obtained.

The present inventors have made extensive studies to solve the above-mentioned problems. As a result, when an alkali is added to an acidic solution containing scandium and manganese to perform a neutralization treatment, manganese is added by adding the alkali while maintaining the liquid surface of the acidic solution so that oxygen does not come into contact with it. We have found that manganese separation performance can be effectively suppressed by effectively suppressing the formation of precipitates due to oxidation of manganese, and that scandium can be effectively concentrated, and the present invention has been completed.

(1) The first invention of the present invention is a method for recovering scandium from an acidic solution containing scandium, wherein the acidic solution contains at least manganese as an impurity element, and the acidic solution contains at least manganese. A concentration step of generating scandium hydroxide and concentrating the scandium by adding an alkali and performing a neutralization treatment is included. In the concentration step, the liquid level of the acidic solution contained in the reaction vessel is raised during the neutralization treatment. This is a method for recovering scandium, in which the alkali is added while maintaining the contact with oxygen.

(2) In the second invention of the present invention, in the first invention, in the concentration step, an acid dissolution treatment is performed in which an acid is added and dissolved in the precipitate of scandium hydroxide obtained by the neutralization treatment. , A method for recovering scandium.

(3) In the first or second invention, the third invention of the present invention is to blow an inert gas onto the liquid surface of the acidic solution contained in the reaction vessel during the neutralization treatment. This is a method for recovering scandium, in which the liquid surface is sealed with the inert gas.

(4) The fourth invention of the present invention is the method for recovering scandium in the third invention, in which an inert gas is further blown into the solution of the acidic solution during the neutralization treatment.

(5) In the fifth aspect of the present invention, in any one of the first to fourth inventions, scandium is added with the alkali so that the pH of the acidic solution is in the range of 5.1 to 5.7. It is a collection method of.

(6) In the sixth aspect of the present invention, in any one of the first to fifth inventions, the scandium-containing acidic solution is a solution of scandium obtained by acid leaching nickel oxide ore. It is a collection method.

According to the scandium recovery method according to the present invention, manganese, which is an impurity element, can be efficiently separated and removed, scandium can be effectively concentrated, and high-purity scandium can be recovered.

It is a process drawing which shows an example of the recovery method of scandium. It is a graph which shows the analysis result of the Mn / Sc ratio of the scandium hydroxide precipitate obtained under each pH condition (neutralization treatment condition) in Example 1 and Comparative Example 1.

Hereinafter, specific embodiments of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail, but the present invention is not limited to the following embodiments, and the gist of the present invention is changed. It can be implemented with appropriate changes within the range that does not apply. In this specification, the notation "X to Y" (X and Y are arbitrary numerical values) means "X or more and Y or less".

≪1. About removal of manganese ≫
The method for recovering scandium according to the present invention is a method for recovering scandium from an acidic solution containing scandium, and in particular, manganese contained as an impurity element in the acidic solution is efficiently removed, and scandium is effectively concentrated. This is a method for recovering high-purity scandium.

For example, a solution obtained by leaching a scandium-containing ore material such as nickel oxide ore with an acid such as sulfuric acid (an acidic solution containing scandium) contains manganese as an impurity element. There is. The method for recovering scandium according to the present invention is, for example, to effectively recover high-purity scandium by separating and removing manganese, which is an impurity element, from such an acidic solution containing scandium from a raw material.

Specifically, in this scandium recovery method, scandium hydroxide is generated by adding an alkali to an acidic solution containing scandium and manganese (also simply referred to as "acidic solution") and neutralizing the scandium to concentrate the scandium. Includes a concentration step. During the neutralization treatment in the concentration step, the alkali is added while maintaining the liquid level of the acidic solution contained in the reaction vessel so as not to come into contact with oxygen.

According to such a method, by suppressing the oxidation of the acidic solution, the formation of a manganese precipitate contained in the acidic solution can be suppressed, and the manganese is neutralized by an alkali to become a scandium hydroxide precipitate. Manganese can be effectively separated and removed from scandium oxide. As a result, scandium can be effectively concentrated, and highly pure scandium can be recovered.

As described above, in the concentration step in this scandium recovery method, a scandium hydroxide precipitate is obtained by adding an alkali to an acidic solution containing scandium and manganese, which is an impurity element, and neutralizing the solution. Perform neutralization treatment. In this neutralization treatment, an acidic solution is placed in a reaction vessel and a predetermined amount of alkali is added. By neutralizing the acidic solution in this way, scandium in the acidic solution can be made into a precipitate of hydroxide (scandium hydroxide). At this time, by suppressing the formation of a precipitate of manganese, which is an impurity element, scandium in the produced precipitate can be effectively concentrated, and scandium and manganese can be effectively separated.

The alkali to be added is not particularly limited, but for example, calcium carbonate, slaked lime, sodium hydroxide and the like can be used. If the neutralizing agent contains calcium, gypsum (calcium sulfate) may be generated and mixed with scandium. Therefore, a neutralizing agent that does not produce solid matter such as sodium hydroxide is preferable.

Further, in the neutralization treatment for an acidic solution, the pH condition is preferably adjusted to the range of 5.0 to 6.0 by adding a neutralizing agent, and is preferably in the range of 5.1 to 5.7. It is more preferable to adjust it, and it is particularly preferable to adjust it in the range of 5.1 to 5.6. If the pH is less than 5.0, neutralization may be inadequate and scandium hydroxide precipitates may not be sufficiently produced. On the other hand, if the pH exceeds 6.0, manganese precipitate formation may proceed and manganese may not be effectively separated. For this reason, it is preferable to adjust the pH to the range of 5.0 to 6.0 in the neutralization treatment. Then, by adjusting the pH to 5.6 or less, it is possible to more effectively suppress the precipitation of manganese.

At this time, the scandium recovery method according to the present invention is characterized in that the alkali is added while maintaining the liquid surface of the acidic solution contained in the reaction vessel so that oxygen does not come into contact with it. Here, examples of the "oxygen" that prevents contact with the liquid surface include oxygen contained in the air. Further, "contact" means physical contact with the oxygen, and for example, contact of air with the liquid surface (air flows through the liquid surface) also means contact with oxygen.

As a method of preventing contact between the liquid level of the acidic solution and oxygen, for example, by spraying an inert gas toward the liquid level (solution surface) of the acidic solution in the reaction vessel, the liquid level is made of the inert gas. There is a method of sealing. By sealing the liquid surface with an inert gas, contact between the liquid surface and, for example, oxygen in the air is hindered, and oxidation of the acidic solution can be effectively suppressed, which oxidizes manganese and precipitates. It can be prevented from becoming. As a result, it is possible to suppress the mixing of manganese into the scandium hydroxide precipitate formed by the neutralization treatment and improve the manganese separation performance.

The method of sealing the liquid level of the acidic solution contained in the reaction vessel is not limited to the above-mentioned spraying of the inert gas, and the liquid level is physically sealed on the premise that the neutralization treatment is not hindered. May be good.

Further, in addition to blowing the inert gas on the liquid surface of the acidic solution, the inert gas may be blown into the inside (inside the liquid) of the acidic solution. By blowing the inert gas into the solution in this way, the sealing effect on the liquid surface of the acidic solution can be improved.

The inert gas is not particularly limited, and examples thereof include nitrogen gas and argon gas. Among them, nitrogen gas is preferably used because it is inexpensive and can be mass-produced.

Further, in the scandium recovery method according to the present invention, in the concentration step, an acid dissolution treatment can be carried out in which an acid is added to dissolve the scandium hydroxide precipitate obtained by the neutralization treatment. As described above, by performing the neutralization treatment while maintaining the liquid surface of the acidic solution so that oxygen does not come into contact with it, it is possible to generate a precipitate of scandium hydroxide while preventing the mixing of manganese, and manganese can be produced from scandium. Can be effectively separated and removed. Then, an acid is added to the precipitate of scandium hydroxide thus obtained and dissolved to obtain an acid dissolution solution (acid dissolution treatment), thereby containing scandium and removing manganese, which is an impurity element. That is, a concentrated solution of scandium can be obtained.

In the following, each step will be described more specifically while showing an example of the flow of the scandium recovery method.

≪2. Scandium recovery method ≫
FIG. 1 is a process diagram showing an example of a scandium recovery method. This scandium recovery method separates scandium from other impurities from the post-sulfidation solution (acid solution containing scandium) obtained by the hydrometallurgy process (hydrometallurgy) of nickel oxide ore, and has high purity. Scandium is efficiently recovered.

Specifically, the scandium recovery method is a wet smelting step S1 of nickel oxide ore and an ion exchange treatment step of subjecting a scandium-containing solution obtained from the wet smelting step S1 to an ion exchange treatment. S2 and the concentration step S3 in which the scandium eluent is neutralized to obtain a scandium hydroxide precipitate, and then an acid is added to the precipitate to dissolve it to obtain a scandium solution to concentrate the scandium. It has a solvent extraction step S4 in which a scandium solution is subjected to a solvent extraction treatment, and a scandium recovery step S5 in which scandium is recovered in the form of scandium oxide from the obtained extraction residual liquid.

As described above, the method for recovering scandium is high in the process of hydrometallurgy of nickel oxide ore for obtaining a solution as a raw material for recovering scandium (wet smelting step S1) and removing impurities from the raw material solution. It is roughly divided into a scandium recovery treatment process (ion exchange treatment step S2 to scandium recovery step S5) for recovering pure scandium.

<2-1. Wet smelting process of nickel oxide ore (wet smelting step S1)>
As shown in FIG. 1, the hydrometallurgy step S1 of the nickel oxide ore is a leaching step S11 in which the nickel oxide ore is leached with sulfuric acid under high temperature and high pressure to obtain a leaching slurry, and the leaching slurry is solid-liquid separated and leached with the leachate. A solid-liquid separation step S12 for obtaining a residue, a neutralization step S13 for obtaining a neutralized starch containing impurities and a post-neutralized liquid by adding a neutralizing agent to the leachate, and hydrogen sulfide gas in the post-neutralized liquid. It has a nickel recovery step S14 of addition to obtain a nickel sulfide and a post-sulfide liquid.

[Leaching process]
The leaching step S11 is composed of a leachate and a leaching residue after adding sulfuric acid to a slurry of nickel oxide ore and stirring the slurry at a temperature of 240 ° C. to 260 ° C. using, for example, a high-temperature pressure vessel (autoclave). This is a step of forming a leaching 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 laterite ore is usually 0.8% by weight to 2.5% by weight, and is contained as a hydroxide or siliceous earth (magnesium silicate) mineral. In addition, these nickel oxide ores contain scandium.

[Solid-liquid separation process]
The solid-liquid separation step S12 is a step of solid-liquid separation between the leaching liquid containing nickel, cobalt, scandium and the like and the leaching residue which is hematite while washing the leaching slurry obtained in the leaching step S11.

The solid-liquid separation treatment can be performed, for example, by mixing the leaching slurry with the cleaning liquid and then using a coagulant supplied from a coagulant supply facility or the like and using a solid-liquid separation facility such as a thickener.

[Neutralization process]
The neutralization step S13 is a step of adding a neutralizing agent to the leachate obtained by separation to adjust the pH to obtain a neutralized starch containing an impurity element and a neutralized liquid. By the neutralization treatment in the neutralization step S13, 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.

[Nickel recovery process]
In the nickel recovery step S15, the after-neutralization liquid (mother liquid for nickel recovery) obtained through the neutralization step S13 is used as a sulfurization reaction starting liquid, and hydrogen sulfide gas, which is a sulfurizing agent, is blown into the sulfurization reaction starting liquid. Sulfide reaction of nickel and cobalt with less impurity components (also simply referred to as "nickel sulfide" for convenience) and a poor liquid (post-sulfide liquid) in which the concentration of nickel is stabilized at a low level. Is the process of generating. The nickel recovery mother liquor is a sulfuric acid solution containing nickel and cobalt.

The sulfurization treatment in the nickel recovery step S15 can be performed using a sulfurization reaction tank or the like, and hydrogen sulfide gas is blown into the gas phase portion in the reaction tank with respect to the sulfurization reaction starting liquid introduced into the sulfurization reaction tank. A sulfurization reaction is caused by dissolving hydrogen sulfide gas in the solution. By this sulfurization treatment, nickel contained in the starting solution of the sulfurization reaction is immobilized as sulfide and recovered.

After the sulfurization treatment, the obtained slurry containing nickel sulfide is charged into a sedimentation separation device such as a thickener and subjected to a sedimentation separation treatment, and only the sulfide is separated and recovered from the bottom of the thickener. On the other hand, the aqueous solution component overflows from the upper part of the thickener and is recovered as a post-sulfurization liquid.

Here, in the sulfurization treatment, as described above, nickel contained in the starting solution of the sulfurization reaction becomes sulfide, while scandium contained in the starting solution does not become sulfide and remains in the after-sulfide solution. It will be. As described above, according to the process in the hydrometallurgy step S1, nickel and scandium can be effectively separated.

<2-2. Scandium recovery process (ion exchange process S2 to scandium recovery step S5)>
In the scandium recovery method, the post-sulfurization liquid obtained through the hydrometallurgy step S1 described above can be used as the target solution for the scandium recovery treatment. As described above, the post-sulfidation solution is an acidic solution containing scandium from which nickel and the like are separated. In the following, a step of recovering scandium using a post-sulfidation solution which is an acidic solution containing scandium as a target solution for scandium recovery treatment will be described in order.

[Ion exchange processing process]
The ion exchange treatment step S2 is a step of obtaining a scandium eluent by subjecting the post-sulfurized liquid to an ion exchange treatment using an ion exchange resin.

In addition to scandium, the post-sulfurization solution, which is an acidic solution containing scandium, contains, for example, aluminum, chromium, and other impurities that remain in the solution without being sulfurized by the sulfurization treatment in the nickel recovery step S15 described above. ing. For this reason, in recovering scandium from the post-sulfidation liquid, it is preferable to remove impurities contained in the post-sulfidation liquid in advance and concentrate scandium (Sc) to generate a scandium eluent.

The ion exchange treatment step S2 is a method by an ion exchange treatment using, for example, a chelate resin as an ion exchange resin, and contains scandium in which impurities such as aluminum contained in the post-sulfurized solution are separated and removed to concentrate scandium. A solution (scandium eluent) can be obtained. Specifically, the ion exchange treatment step S2 includes, for example, an adsorption step in which the post-sulfurized liquid is brought into contact with the chelate resin to adsorb scandium, and aluminum is brought into contact with the chelate resin adsorbed with scandium to a predetermined degree of sulfuric acid. The aluminum removal step of removing the above, the scandium elution step of contacting the chelate resin with sulfuric acid of a predetermined normality to obtain a scandium eluent, and the chromium adsorbed on the chelate resin by contacting the chelate resin with sulfuric acid of a predetermined normality. Can be exemplified with a chromium removing step of removing the above-mentioned.

The type of chelate resin used for the ion exchange treatment is not particularly limited. For example, a resin having iminodiacetic acid as a functional group can be used, and according to this chelate resin, the adsorption selectivity of scandium can be enhanced.

By subjecting the post-sulfurized liquid to an ion exchange treatment in this way, impurities such as aluminum and chromium contained in the post-sulfurized liquid can be removed, and a scandium eluent enriched with scandium can be obtained. ..

[Concentration process]
In the concentration step S3, a precipitate containing scandium hydroxide is obtained by neutralizing the scandium eluent obtained through the ion exchange treatment in the ion exchange treatment step S2, and then the precipitate is formed. This is a step of obtaining a scandium solution by dissolving it in a mineral acid such as sulfuric acid.

Specifically, in the concentration step S3, for example, a neutralizing agent such as calcium carbonate, slaked lime, or sodium hydroxide is used and added to the scandium eluent for neutralization treatment.

Here, the scandium eluate is a solution in which impurities such as aluminum are removed by an ion exchange treatment, but contains manganese, which is an impurity element that cannot be sufficiently removed by the ion exchange treatment. That is, the scandium eluate is an acidic solution containing scandium and at least manganese as an impurity element.

Therefore, this scandium recovery method is characterized in that the above-mentioned manganese removal treatment is applied to the neutralization treatment in the concentration step S3. That is, in the concentration step S3, an alkali (neutralizing agent) is added to the scandium eluent which is an acidic solution to perform a neutralization treatment to obtain a scandium hydroxide precipitate, and the neutralization treatment is performed. At this time, alkali is added while maintaining the liquid surface of the scandium eluent contained in the reaction vessel so that oxygen does not come into contact with it.

As a result, it is possible to prevent the formation of a precipitate due to the oxidation of manganese in the neutralization treatment, and it is possible to suppress the mixing of manganese into the precipitate of scandium hydroxide formed by the neutralization treatment. As a result, a scandium solution containing no manganese, which is an impurity, can be obtained, and scandium can be effectively concentrated. That is, the concentration effect can be improved, and high-purity scandium can be more effectively recovered as a method for recovering scandium.

As described above, the alkali as a neutralizing agent is not particularly limited, but for example, calcium carbonate, slaked lime, sodium hydroxide and the like can be used, and sodium hydroxide is particularly preferable.

Further, the pH condition is preferably adjusted to the range of 5.0 to 6.0 by adding a neutralizing agent, and more preferably adjusted to the range of 5.1 to 5.7. It is particularly preferable to adjust to the range of 1 to 5.6. Then, by adjusting the pH to 5.6 or less, it is possible to more effectively suppress the precipitation of manganese.

The method of preventing oxygen from coming into contact with the liquid surface of the Scandium eluent in the reaction vessel is to seal the liquid surface with the inert gas, for example, by blowing an inert gas such as nitrogen gas toward the liquid surface. The method can be used. By sealing the liquid surface with an inert gas in this way, contact between the liquid surface and, for example, oxygen in the air is hindered, and oxidation of the acidic solution can be effectively suppressed, thereby oxidizing manganese. Precipitation formation due to Further, in addition to blowing the inert gas on the liquid surface, the inert gas may be blown into the liquid, whereby the sealing effect on the liquid surface can be improved.

In the concentration step S3, a precipitate containing scandium hydroxide is obtained in this way, and then an acid is added to the precipitate to dissolve it to obtain a scandium solution. The precipitate can be recovered by subjecting the slurry to a solid-liquid separation treatment after neutralization.

Examples of the acid used for dissolving the precipitate include mineral acids such as hydrochloric acid and sulfuric acid. By using such a mineral acid, the precipitate can be efficiently dissolved, and a scandium solution (acid solution) in which scandium is concentrated can be obtained.

[Solvent extraction step]
In the solvent extraction step S4, the scandium solution obtained through the concentration step S3, which is a solution in which scandium is concentrated, is subjected to a solvent extraction treatment and brought into contact with an extractant to obtain an extraction residual liquid containing scandium. It is a process.

The embodiment in the solvent extraction step S4 is not particularly limited, but is an extraction residue obtained by mixing a scandium solution and an extractant which is an organic solvent to extract impurities and a small amount of scandium, and then leaving the organic solvent and scandium. An extraction step of separating into and a scrubbing step of performing a cleaning treatment on an organic solvent after extraction, a back extraction step of adding a back extractant to the organic solvent after cleaning and back-extracting impurities from the organic solvent after cleaning. It is preferable to carry out the solvent extraction treatment having the above.

In the extraction step, impurities are selectively extracted into an organic solvent containing an extractant to obtain an organic solvent containing impurities and an extraction residual liquid. The extractant is not particularly limited, but it is preferable to use an amine-based extractant. For example, PrimeneJM-T, which is a primary amine, and LA-1, which is a secondary amine, which have features such as low selectivity with scandium and no need for a neutralizing agent during extraction. It is preferable to use an amine-based extractant known by a trade name such as TNOA (Tri-n-octylamine) or TIOA (Tri-i-octylamine). By performing the extraction treatment using such an amine-based extractant, impurities can be efficiently and effectively extracted and separated from scandium.

Further, in the scrubbing step, the organic solvent after extraction is subjected to a cleaning treatment by mixing a cleaning initial solution such as a sulfuric acid solution, and a small amount of scandium extracted in the organic solvent after extraction is separated into an aqueous phase. To obtain the liquid after cleaning. The obtained post-washing liquid is subjected to the scandium recovery step S5 of the next step together with the extraction residual liquid from the extraction step. By providing the scrubbing step in this way, the recovery loss of scandium can be reduced.

In the back extraction step, impurities are back extracted from the organic solvent from which the impurities have been extracted through the extraction process. Specifically, by adding a back-extraction solution (back-extraction starting solution) to an organic solvent containing an extractant and mixing the mixture, a reaction opposite to the extraction process is generated to back-extract impurities and contain impurities. Obtain a solution after back extraction. As the back extraction solution, it is preferable to use a solution containing a carbonate such as sodium carbonate and potassium carbonate. By performing the back extraction treatment in this way, the extractant used for solvent extraction can be reused.

[Scandium recovery process]
The scandium recovery step S5 is a step of recovering scandium from the extraction residual liquid obtained by the extraction treatment in the solvent extraction step S4 and, when the scrubbing treatment is performed, the cleaning liquid after scrubbing.

The scandium recovery method is not particularly limited, and a known method can be used. For example, a method of adding an alkali to the extraction residual liquid containing scandium to neutralize it and recovering it as a precipitate of scandium hydroxide, or adding oxalic acid to the extraction residual liquid and recovering it as a precipitate of oxalate. The method (oxalate treatment) can be used. Among them, the method using the oxalate treatment is preferable because impurities can be separated more effectively.

In the recovery method using the oxalate treatment, a precipitate of scandium oxalate is formed by adding oxalic acid to the extraction residual liquid, and then the scandium oxalate is dried and roasted to recover it as scandium oxide. .. In the oxalate treatment, a scandium oxalate precipitate may be formed by adding the extraction residual liquid to the reaction vessel containing the oxalic acid solution.

The roasting treatment is a treatment in which the scandium oxalate precipitate obtained by the oxalate treatment is washed with water, dried, and then roasted. By undergoing this roasting treatment, scandium can be recovered as extremely high-purity scandium oxide. The roasting treatment conditions 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.

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

[Example 1]
2500 liters of the post-sulfurized liquid obtained in the nickel recovery step (sulfurization step) S14 in the hydrometallurgy step S1 in which the nickel oxide ore is subjected to high-pressure acid treatment is passed through an ion exchange resin of a chelate resin having iminodiacetic acid as a functional group. Then, scandium and other impurities in the post-sulfurized solution were adsorbed on the ion exchange resin, and then the scandium was eluted from the on-exchange resin using a sulfuric acid solution of 0.5N to obtain a scandium eluent (ion exchange). Processing step S2).

Next, the scandium eluate is placed in a reaction vessel, and a sodium hydroxide solution diluted to 5% is added to the scandium eluate so that the pH of the solution becomes 5.0 to 5.6. Japanese treatment was performed (concentration step S3). At this time, during the neutralization treatment, nitrogen gas was sprayed toward the liquid surface of the scandium eluate contained in the reaction vessel. In addition, nitrogen gas was blown into the inside (inside) of the scandium eluent through a blow pipe. As a result, the liquid surface was sealed with nitrogen gas to prevent oxygen contained in the air from coming into contact with it.

After neutralization has progressed to the respective pH conditions shown in Table 1 below, a sample is collected and filtered, and the scandium hydroxide precipitate obtained by the neutralization treatment is analyzed by ICP to produce manganese (Mn). ) / Scandium (Sc) ratio (% by weight ratio) was investigated. Table 1 shows the pH conditions in the neutralization treatment and the analysis results of the Mn / Sc ratio of scandium hydroxide obtained under each condition.

As a result, as shown in Table 1, a scandium hydroxide precipitate having an extremely low manganese / scandium ratio could be obtained. This means that the liquid surface of the scandium eluate can be sealed with the nitrogen gas by performing a treatment such as blowing nitrogen gas onto the liquid surface in the neutralization treatment, which hinders contact with air. It is probable that this was possible because the oxidation of manganese in the eluent could be prevented. Further, it was confirmed that the manganese / scandium ratio became almost constant and low, that is, manganese did not increase by performing the neutralization treatment under the condition of at least pH 5.6 or less.

Here, the scandium hydroxide precipitate neutralized at each pH is dissolved with an acid (concentration step S3), and the obtained scandium solution is subjected to a known solvent extraction treatment (solvent extraction step S4) and then recovered. The final product, scandium oxide, was produced based on the extracted residual liquid (scandium recovery step S5). Then, the manganese grade was analyzed by ICP based on the produced scandium oxide.

As a result, the manganese grade of scandium oxide produced from the product obtained by neutralization under the condition of pH 5.60, which has the highest manganese / scandium ratio, is sufficiently below the standard upper limit of 50 ppm. Was confirmed. That is, it was high-purity scandium oxide from which manganese, which is an impurity element, was sufficiently removed.

[Comparative Example 1]
Comparative Example 1 is the same as that of Example 1 except that the neutralization treatment in the concentration step S3 did not perform the treatment of blowing nitrogen gas on the liquid surface of the scandium eluent or the treatment of blowing nitrogen gas into the liquid. And processed.

Then, when the neutralization progresses to the respective pH conditions shown in Table 2 below, a sample is collected and filtered, and the scandium hydroxide precipitate obtained by the neutralization treatment is analyzed by ICP to perform manganese. The (Mn) / scandium (Sc) ratio (% by weight ratio) was investigated.

As a result, as shown in Table 2, as the pH increased, a precipitate was formed due to the oxidation of manganese, and the Mn / Sc ratio of the scandium hydroxide precipitate increased. Further, when scandium oxide was produced in the same manner as in Example 1 using scandium hydroxide obtained under each of these pH conditions, the manganese grade of any scandium oxide exceeded the standard upper limit of 50 ppm. ..

FIG. 2 is a graph showing the analysis results of the Mn / Sc ratio of the scandium hydroxide precipitate obtained under each pH condition (neutralization treatment condition) in Example 1 and Comparative Example 1.

Claims (6)

A method of recovering scandium from an acidic solution containing scandium.
The acidic solution contains at least manganese as an impurity element.
It comprises a concentration step of producing scandium hydroxide and concentrating scandium by adding an alkali to the acidic solution and performing a neutralization treatment.
In the concentration step, a method for recovering scandium in which the alkali is added while maintaining the liquid level of the acidic solution contained in the reaction vessel so as not to come into contact with oxygen during the neutralization treatment. The method for recovering scandium according to claim 1, wherein in the concentration step, an acid dissolution treatment is carried out in which an acid is added to dissolve the scandium hydroxide precipitate obtained by the neutralization treatment. The scandium according to claim 1 or 2, wherein during the neutralization treatment, the liquid surface of the acidic solution contained in the reaction vessel is sprayed with an inert gas to seal the liquid surface with the inert gas. Collection method. The method for recovering scandium according to claim 3, wherein an inert gas is further blown into the acidic solution during the neutralization treatment. The method for recovering scandium according to any one of claims 1 to 4, wherein the alkali is added so that the pH of the acidic solution is in the range of 5.1 to 5.7. The method for recovering scandium according to any one of claims 1 to 5, wherein the acidic solution containing scandium is a solution obtained by acid leaching nickel oxide ore.

Images