JP7338283B2 - Scandium recovery method - Google Patents

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, due to its low production volume and high cost, it has not been widely used.

By the way, in recent years, as described in Patent Document 1, for example, an HPAL process has been proposed that can recover a trace amount of scandium contained in nickel oxide ores such as laterite ore and limonite ore. In the HPAL process, nickel oxide ore is charged into a pressurized vessel together with sulfuric acid, heated to a high temperature of about 240° C. to 260° C., and solid-liquid separated into a leachate containing nickel and a leach residue, and alkali is applied to the leachate. A neutralizing agent such as sulfide is added to precipitate and separate impurities, and then a sulfiding agent is added to recover nickel as precipitates of nickel sulfide. In this HPAL process, scandium does not form a precipitate even when a sulfiding agent is added, so it remains in the acidic solution after sulfiding. Thus, nickel and scandium can be effectively separated by using the HPAL process.

However, nickel oxide ore contains various impurity elements such as iron, aluminum, manganese, and magnesium, although the types and amounts vary depending on the region where it is produced. Therefore, it is necessary to concentrate the dilute scandium and to 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 solution containing scandium after nickel has been separated through the HPAL process (scandium-containing solution) is brought into contact with a chelate resin to adsorb scandium, and then the adsorbed chelate resin is used. The chelate resin after washing is washed with a dilute acid, and the washed chelate resin is brought into contact with a strong acid to elute scandium.

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

The scandium recovered by each of the above-described methods has a purity of about 95 to 98% by weight in terms of scandium oxide (Sc ₂ O ₃ ), and can be added to an alloy with aluminum. It is of sufficient quality for the purpose of However, for applications such as electrolytes for fuel cells, for which the 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. may have stricter standards.

For example, manganese is known to have an effect of deteriorating the properties 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, alkali is added for neutralization to obtain scandium hydroxide. By obtaining a scandium hydroxide in this manner, impurities can be separated, and a redissolved solution having an arbitrary scandium concentration can be obtained by dissolving the obtained hydroxide again with an acid or the like. Then, by subjecting this re-dissolved liquid to the above-described chelate resin or solvent extraction again, purification and concentration can be performed efficiently.

In addition, a method of separating impurities by performing an oxalic oxidation treatment, as disclosed in Patent Document 5, can also be used in combination. By using such methods, 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. Variation in density is inevitable.

Here, in particular, when the manganese concentration is relatively high in a solution containing scandium, in the above-described process having a neutralization step of concentrating scandium as scandium hydroxide, not only scandium but also manganese precipitates. , the amount of precipitates increases, the grade of manganese increases, and the concentration of scandium is hindered.

Thus, 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. Ta.

JP-A-3-173725 JP-A-9-194211 JP-A-9-291320 WO2014/110216 JP 2016-108664 A

The present invention has been proposed in view of such circumstances, and is capable of concentrating scandium by effectively separating and removing manganese from an acidic solution containing scandium containing manganese as an impurity element. An object of the present invention is to provide a method for recovering scandium that can be used.

The present inventors have made extensive studies to solve the above-described problems. As a result, when an acid solution containing scandium and manganese is neutralized by adding an alkali, the alkali is added while keeping oxygen out of contact with the liquid surface of the acid solution. The present inventors have found that the formation of precipitates due to the oxidation of manganese can be effectively suppressed, the separation performance of manganese can be improved, and scandium can be effectively concentrated, leading to the completion of the present invention.

(1) A first aspect 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 a concentration step of generating scandium hydroxide and concentrating scandium by adding an alkali and performing a neutralization treatment; A method for recovering scandium, wherein the alkali is added while keeping it out of contact with oxygen.

(2) In a second aspect of the present invention, in the first aspect, in the concentration step, acid dissolution treatment is performed by adding an acid to the precipitate of scandium hydroxide obtained by the neutralization treatment to dissolve it. , a scandium recovery method.

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

(4) A fourth aspect of the present invention is the method for recovering scandium according to the third aspect, further comprising blowing an inert gas into the acidic solution during the neutralization treatment.

(5) A fifth aspect of the present invention is the scandium solution according to any one of the first to fourth aspects, wherein the alkali is added so that the pH of the acidic solution is in the range of 5.1 to 5.7. is the recovery method.

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

According to the method for recovering scandium according to the present invention, manganese, which is an impurity element, can be efficiently separated and removed, scandium can be effectively concentrated, and highly pure scandium can be recovered.

It is process drawing which shows an example of the recovery|recovery method of scandium. 2 is a graph showing analysis results of the Mn/Sc ratio of scandium hydroxide precipitates obtained under various pH conditions (neutralization treatment conditions) in Example 1 and Comparative Example 1. FIG.

Hereinafter, specific embodiments of the present invention (hereinafter referred to as "present embodiments") 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 scope of not doing so. In this specification, the notation "X to Y" (X and Y are arbitrary numerical values) means "X or more and Y or less".

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

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

Specifically, this method for recovering scandium involves adding an alkali to an acidic solution containing scandium and manganese (also simply referred to as an "acidic solution") and performing a neutralization treatment to generate scandium hydroxide and concentrate scandium. including a concentration step to In addition, during the neutralization process in the concentration process, the alkali is added while maintaining the liquid surface of the acidic solution accommodated 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 precipitates of manganese contained in the acidic solution can be suppressed, and neutralized by alkali to form scandium hydroxide precipitates. Manganese can be effectively separated and removed from scandium. 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, alkali is added to an acid solution containing scandium and manganese, which is an impurity element, to neutralize the solution, thereby obtaining a precipitate of scandium hydroxide. Neutralize. 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 manner, scandium in the acidic solution can be converted into a precipitate of hydroxide (scandium hydroxide). At this time, by suppressing the formation of precipitates of the impurity element manganese, scandium in the formed precipitates can be effectively concentrated, and scandium and manganese can be effectively separated.

Although the alkali to be added is not particularly limited, for example, calcium carbonate, slaked lime, sodium hydroxide and the like can be used. If the neutralizing agent contains calcium, gypsum (calcium sulfate) may form and be mixed with scandium. Therefore, neutralizing agents that do not produce solids such as sodium hydroxide are preferred.

In the neutralization treatment for the acidic solution, the pH condition is preferably adjusted in the range of 5.0 to 6.0 by adding a neutralizing agent, and in the range of 5.1 to 5.7. Adjustment is more preferable, and adjustment in the range of 5.1 to 5.6 is particularly preferable. If the pH is less than 5.0, the neutralization may be insufficient and a scandium hydroxide precipitate may not be formed sufficiently. On the other hand, if the pH exceeds 6.0, the formation of manganese precipitates will proceed, and manganese may not be separated effectively. For this reason, it is preferable to adjust the pH in the range of 5.0 to 6.0 in the neutralization treatment. By adjusting the pH to 5.6 or less, the precipitation of manganese can be suppressed more effectively.

At this time, the method for recovering scandium according to the present invention is characterized in that the alkali is added while keeping oxygen out of contact with the liquid surface of the acidic solution contained in the reaction vessel. Here, the “oxygen” that prevents contact with the liquid surface includes, for example, oxygen contained in the air. Further, "contact" means to physically touch the oxygen, and for example, air touching the liquid surface (air flowing on the liquid surface) also means that oxygen comes into contact.

As a method for preventing contact between the surface of the acid solution and oxygen, for example, the surface of the acid solution in the reaction vessel is covered with the inert gas by blowing the inert gas toward the surface of the acid solution (solution surface). A sealing method is mentioned. By sealing the liquid surface with an inert gas, contact of the liquid surface with, for example, oxygen in the air can be prevented, effectively suppressing the oxidation of the acidic solution, which oxidizes the manganese and forms precipitates. can be prevented. As a result, it is possible to suppress the contamination of manganese with the precipitate of scandium hydroxide formed by the neutralization treatment, thereby enhancing the manganese separation performance.

The method of sealing the liquid surface of the acidic solution contained in the reaction vessel is not limited to the above-described blowing of inert gas. good too.

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

Examples of the inert gas include, but are not limited to, nitrogen gas, argon gas, etc. Among them, nitrogen gas is preferable because it is inexpensive and can be mass-produced.

Further, in the method for recovering scandium according to the present invention, in the concentration step, an acid dissolution treatment can be performed in which an acid is added to dissolve the precipitate of scandium hydroxide obtained by the neutralization treatment. As described above, by performing the neutralization treatment while keeping oxygen out of contact with the liquid surface of the acidic solution, it is possible to prevent the contamination of manganese and generate a precipitate of scandium hydroxide. can be effectively separated and removed. Then, an acid is added to the thus-obtained precipitate of scandium hydroxide to dissolve it in an acid solution (acid dissolution treatment), thereby containing scandium and removing manganese as an impurity element. , ie a concentrated solution of scandium can be obtained.

Each step will be described below in more detail, showing an example of the flow of the scandium recovery method.

≪2. Scandium recovery method≫
FIG. 1 is a process chart showing an example of a scandium recovery method. This scandium recovery method separates scandium and other impurities from the post-sulfidation solution (acidic solution containing scandium) obtained by the hydrometallurgical process (hydrometallurgical treatment) of nickel oxide ore to obtain high-purity of scandium is efficiently recovered.

Specifically, the method for recovering scandium includes a nickel oxide ore hydrometallurgical process S1, and an ion exchange treatment process in which an ion exchange treatment is performed on a post-sulfidation liquid that is a scandium-containing solution obtained from the hydrometallurgical process S1. S2, and a concentration step S3 of subjecting the scandium eluent to a neutralization treatment to obtain a precipitate of scandium hydroxide, and then adding an acid to the precipitate to dissolve it to obtain a scandium solution, thereby concentrating scandium. and a scandium recovery step S5 for recovering scandium in the form of scandium oxide from the obtained extraction residue.

In this way, the method for recovering scandium includes the process of hydrometallurgical treatment of nickel oxide ore (hydrometallurgical process S1) for obtaining a solution that serves as a raw material for recovering scandium, and the process of removing impurities from the raw material solution to obtain a high and a scandium recovery treatment process (ion exchange treatment step S2 to scandium recovery step S5) for recovering pure scandium.

<2-1. Process of hydrometallurgical treatment of nickel oxide ore (hydrometallurgical process S1)>
As shown in FIG. 1, the nickel oxide ore hydrometallurgy step S1 includes 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 a leaching step S11 in which the leaching slurry is solid-liquid separated to obtain a leaching solution and a leaching solution. a solid-liquid separation step S12 for obtaining a residue, a neutralization step S13 for obtaining a neutralized precipitate containing impurities and a post-neutralization liquid by adding a neutralizing agent to the leachate, and adding hydrogen sulfide gas to the post-neutralization liquid. and a nickel recovery step S14 of adding nickel sulfide and obtaining a post-sulfidation solution.

[Leaching process]
In the leaching step S11, for example, using a high-temperature pressurized container (autoclave) or the like, sulfuric acid is added to a slurry of nickel oxide ore and stirred at a temperature of 240° C. to 260° C. to form a leaching solution and a leaching residue. 2. Forming a leach slurry. The treatment in the leaching step S11 may be performed according to the conventionally known HPAL process.

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

[Solid-liquid separation step]
The solid-liquid separation step S12 is a step of solid-liquid separation into a leaching solution containing nickel, cobalt, scandium, etc. and a leaching residue that is hematite while washing the leaching slurry obtained in the leaching step S11.

In the solid-liquid separation process, for example, after the leach slurry is mixed with the cleaning liquid, a flocculant supplied from a flocculant supply facility or the like can be used, and a solid-liquid separation facility such as a thickener can be used.

[Neutralization step]
The neutralization step S13 is a step of adding a neutralizing agent to the leachate obtained by separation to adjust the pH, thereby obtaining a neutralized sediment containing impurity elements and a post-neutralization liquid. Due to the neutralization treatment in the neutralization step S13, valuable metals such as nickel, cobalt and scandium are included in the post-neutralization liquid, and most of the impurities including iron and aluminum become neutralized precipitates.

Conventionally known neutralizing agents can be used, and examples thereof include calcium carbonate, slaked lime and sodium hydroxide.

[Nickel recovery step]
In the nickel recovery step S15, the post-neutralization solution (mother liquor for recovering nickel) obtained through the neutralization step S13 is used as the starting liquid for the sulfurization reaction, and hydrogen sulfide gas, which is a sulfurizing agent, is blown into the starting liquid for the sulfurization reaction. A sulfide reaction of nickel and cobalt with few impurity components (also simply referred to as “nickel sulfide” for convenience) and a poor solution (post-sulfidation solution) in which the concentration of nickel is stabilized at a low level. is a step 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. For the sulfurization reaction starting liquid introduced into the sulfurization reaction tank, hydrogen sulfide gas is blown into the gas phase portion in the reaction tank, A sulfurization reaction is caused by dissolving hydrogen sulfide gas in the solution. By this sulfurization treatment, the nickel contained in the starting liquid of the sulfurization reaction is fixed as a sulfide and recovered.

After the sulfurization treatment, the obtained slurry containing nickel sulfide is put into a sedimentation 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 initial solution of the sulfurization reaction becomes sulfide, while scandium contained in the initial solution does not become sulfide and remains in the post-sulfidation solution. It will be. Thus, according to the process in the hydrometallurgy step S1, nickel and scandium can be effectively separated.

<2-2. Process of scandium recovery treatment (ion exchange treatment step S2 to scandium recovery step S5)>
In the scandium recovery method, the post-sulfidation liquid obtained through the above-described hydrometallurgical process S1 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. Below, the process of recovering scandium using the post-sulfidation solution, which is an acidic solution containing scandium, as the target solution for the scandium recovery treatment will be described in order.

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

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

In the ion exchange treatment step S2, for example, it is a method by ion exchange treatment using a chelate resin as an ion exchange resin. A solution (scandium eluate) can be obtained. Specifically, the ion exchange treatment step S2 includes, for example, an adsorption step in which the post-sulfurization solution is brought into contact with a chelate resin to adsorb scandium, and an adsorption step in which the chelate resin that has adsorbed scandium is brought into contact with a predetermined normality of sulfuric acid to remove aluminum. a scandium elution step to obtain a scandium eluate by contacting a chelating resin with a predetermined normality of sulfuric acid; can be exemplified by a chromium removal step that removes

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

By subjecting the post-sulfidation solution to the ion exchange treatment in this manner, impurities such as aluminum and chromium contained in the post-sulfidation solution can be removed, and a scandium eluate in which scandium is concentrated can be obtained. .

[Concentration step]
In the concentration step S3, the scandium eluate obtained through the ion exchange treatment in the ion exchange treatment step S2 is neutralized to obtain a precipitate containing scandium hydroxide, and then the precipitate is removed. This is a step of dissolving scandium in a mineral acid such as sulfuric acid to obtain a scandium solution.

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.

Here, the scandium eluent is a solution from which impurities such as aluminum have been removed by ion exchange treatment, but contains manganese, which is an impurity element that cannot be sufficiently removed by ion exchange treatment. That is, the scandium eluent 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-described manganese removal treatment is applied to the neutralization treatment in this concentration step S3. That is, in the concentration step S3, an alkali (neutralizing agent) is added to the scandium eluate, which is an acidic solution, and a neutralization treatment is performed to obtain a precipitate of scandium hydroxide, and the neutralization treatment is performed. At this time, the alkali is added while keeping oxygen out of contact with the liquid surface of the scandium eluate contained in the reaction vessel.

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

As described above, the alkali that is the neutralizing agent is not particularly limited, but for example, calcium carbonate, slaked lime, sodium hydroxide, etc. can be used, and sodium hydroxide is particularly preferred.

The pH condition is preferably adjusted to a range of 5.0 to 6.0, more preferably 5.1 to 5.7, by adding a neutralizing agent. It is particularly preferred to adjust it within the range of 1 to 5.6. By adjusting the pH to 5.6 or less, the precipitation of manganese can be suppressed more effectively.

A method for preventing oxygen from coming into contact with the liquid surface of the scandium eluate in the reaction vessel is, for example, by blowing an inert gas such as nitrogen gas toward the liquid surface to seal the liquid surface with the inert gas. 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 prevented, and oxidation of the acidic solution can be effectively suppressed, thereby oxidizing manganese. Precipitate formation due to In addition to blowing the inert gas onto the liquid surface, the inert gas may be blown into the liquid, thereby improving the sealing effect on the liquid surface.

In the concentration step S3, after the precipitate containing scandium hydroxide is thus obtained, an acid is added to dissolve the precipitate to obtain a scandium solution. The precipitate can be recovered by subjecting the neutralized slurry to solid-liquid separation treatment.

Mineral acids such as hydrochloric acid and sulfuric acid can be used as acids for dissolving the precipitate. By using such a mineral acid, the precipitate can be dissolved efficiently, 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 residue containing scandium. It is a process.

The mode of the solvent extraction step S4 is not particularly limited, but after the extraction of impurities and a small amount of scandium by mixing the scandium solution and the extractant, which is an organic solvent, the organic solvent and the extraction residual liquid in which scandium remains. a scrubbing step of washing the organic solvent after extraction; a back extraction step of adding a back extractant to the organic solvent after washing to back extract impurities from the organic solvent after washing; It is preferable to perform a solvent extraction treatment having

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 residue. Although the extractant is not particularly limited, it is preferable to use an amine-based extractant. For example, primary amine PrimeneJM-T, secondary amine LA-1, and tertiary amine, which have characteristics 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 as a trade name such as TNOA (Tri-n-octylamine) or TIOA (Tri-i-octylamine). By performing an extraction treatment using such an amine-based extractant, impurities can be efficiently and effectively extracted and separated from scandium.

In the scrubbing step, the post-extraction organic solvent is washed by mixing a washing starting liquid such as a sulfuric acid solution, and a small amount of scandium extracted by the post-extraction organic solvent is separated into the aqueous phase. to obtain the post-washing liquid. The obtained post-washing liquid is supplied to the scandium recovery step S5 in 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 and mixing a back-extraction solution (initial back-extraction solution) with an organic solvent containing an extractant, a reaction reverse to the extraction process is caused to back-extract impurities, resulting in A liquid after back extraction is obtained. As the reverse extraction solution, it is preferable to use a solution containing a carbonate such as sodium carbonate or potassium carbonate. By performing the reverse extraction process in this manner, the extractant used for the solvent extraction can be reused.

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

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

In the recovery method using oxalation treatment, oxalic acid is added to the extraction residue to form a precipitate of scandium oxalate, and then the scandium oxalate is dried and roasted to recover scandium oxide. . In addition, in the oxalation treatment, the precipitate of scandium oxalate may be generated by adding the extraction residual liquid to the reaction tank containing the oxalic acid solution.

The roasting treatment is a treatment in which the precipitate of scandium oxalate obtained by the oxalation treatment is washed with water, dried, and then roasted. Through 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 tubular furnace and heated at about 900° C. for about 2 hours.

EXAMPLES The present invention will be more specifically described below with reference to Examples, but the present invention is not limited to these Examples.

[Example 1]
2500 liters of the post-sulfurization solution obtained in the nickel recovery step (sulfurization step) S14 in the hydrometallurgy step S1 in which 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-sulfidation solution are adsorbed on the ion exchange resin, and then scandium is eluted from the on exchange resin using a 0.5 N sulfuric acid solution to obtain a scandium eluate (ion exchange process step S2).

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

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

As a result, as shown in Table 1, a precipitate of scandium hydroxide having an extremely low manganese/scandium ratio was obtained. This is due to the fact that, in the neutralization process, the surface of the scandium eluate can be sealed with the nitrogen gas by blowing nitrogen gas onto the surface of the liquid, preventing contact with the air. It is thought that this is because the manganese in the eluent was prevented from being oxidized. Moreover, it was confirmed that the manganese/scandium ratio becomes almost constant and low value, that is, manganese does not increase, by performing the neutralization treatment at least under the condition of pH 5.6 or less.

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

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

[Comparative Example 1]
Comparative Example 1 was the same as Example 1, except that the neutralization process in the concentration step S3 did not include the process of blowing nitrogen gas onto the surface of the scandium eluate or the process 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 precipitate of scandium hydroxide obtained by the neutralization treatment is analyzed by ICP to detect manganese. The (Mn)/scandium (Sc) ratio (weight % ratio) was investigated.

As a result, as shown in Table 2, a precipitate due to oxidation of manganese was formed as the pH increased, and the Mn/Sc ratio of the scandium hydroxide precipitate increased. Moreover, when scandium oxide was produced in the same manner as in Example 1 using the 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 scandium hydroxide precipitates obtained under various pH conditions (neutralization treatment conditions) in Example 1 and Comparative Example 1. As shown in FIG.

Claims (2)

A method for recovering scandium from an acidic solution containing scandium, comprising:
The acidic solution is a solution obtained by acid leaching nickel oxide ore, and contains at least manganese as an impurity element,
A concentration step of adding an alkali to the acidic solution and subjecting it to a neutralization treatment to generate scandium hydroxide and concentrate scandium;
In the concentration step, during the neutralization process , an inert gas is blown onto the liquid surface of the acidic solution contained in a reaction vessel to seal the liquid surface with the inert gas, and the inside of the reaction vessel is adding the alkali so that the pH of the acidic solution is in the range of 5.1 to 5.7 while maintaining the liquid surface of the acidic solution contained in the container so that it does not come into contact with oxygen;
In the concentration step, an acid dissolution treatment is performed by adding an acid to the scandium hydroxide precipitate obtained by the neutralization treatment to dissolve the precipitate. The method for recovering scandium according to claim 1, further comprising blowing an inert gas into the acidic solution during the neutralization treatment.

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