JP2016065283A - Method for recovering scandium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recovering scandium capable of easily and efficiently recovering high quality scandium from nickel oxide ore.SOLUTION: There is provided a method for recovering scandium where nickel oxide ore containing scandium (Sc) is subjected to sulfuric acid leaching at high temperature under high pressure (S1), a leachate is subjected to neutralization treatment with a neutralizer (S2), a sulfurizing agent is added to the neutralized liquid solution, and is subjected to sulfurization treatment (S3), next, after the sulfurized liquid solution is contacted with a chelate resin, and Sc in the sulfurized liquid solution is adsorbed on the chelate resin to obtain a scandium eluate (S4), the Sc eluate is neutralized to obtain the precipitates of Sc hydroxide, and thereafter, a sulfuric acid solution is added to the Sc hydroxide to obtain an Sc nitric acid solution (S5), next, the Sc nitric acid solution is contacted with a neutral extraction agent, solvent extraction is performed, and impurity elements other than Sc are subjected to extraction separation (S6), the Sc in the extraction residual liquid obtained by the solvent extraction is made into a salt, the Sc salt is roasted, and Sc oxide is obtained to recover Sc (S7).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a scandium recovery method, and more particularly, to a scandium recovery method that efficiently recovers scandium contained in nickel oxide ore using treatment with a chelate resin and solvent extraction with a neutral extractant.

  Scandium is extremely useful as an additive for high-strength alloys and as an electrode material for fuel cells. However, since the production amount is small and expensive, it has not been widely used.

  By the way, nickel oxide ores such as laterite or limonite ore contain a small amount of scandium. However, since nickel oxide ore has a low nickel-containing grade, it has not been used industrially as a nickel raw material for a long time. Therefore, there has been little research on industrially recovering scandium from nickel oxide ore.

  However, in recent years, an HPAL process has been put into practical use, 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 separate the solid and liquid into a leachate containing nickel and a leach residue. ing. In this HPAL process, impurities are separated by adding a neutralizing agent to the obtained leachate, and then nickel can be recovered as nickel sulfide by adding a sulfurizing agent. And the nickel nickel compound can be obtained by processing the obtained nickel sulfide in the existing nickel smelting process.

  When the HPAL process as described above is used, scandium contained in the nickel oxide ore is contained in the leachate together with nickel (see Patent Document 1). And when neutralizing agent is added to the leachate obtained by the HPAL process to separate impurities, and then sulfurizing agent is added, nickel is recovered as nickel sulfide, while scandium is added after the sulfurizing agent is added. Since it comes to be contained in an acidic solution (liquid after sulfidation), nickel and scandium can be effectively separated by using the HPAL process.

  As a method for recovering scandium from the acidic solution described above, a method has been proposed in which scandium is adsorbed onto a chelating resin or the like having iminodiacetate as a functional group, separated from impurities, and concentrated to recover (patent document). 2-4).

On the other hand, a method of recovering scandium from an acidic solution obtained by a hydrometallurgical treatment of nickel oxide ore by a solvent extraction process has also been proposed (see Patent Document 5). In the method described in Patent Document 5, first, in addition to scandium, 2-ethylhexyl sulfone is added to a scandium-containing solution in an aqueous phase containing at least one of iron, aluminum, calcium, yttrium, manganese, chromium, and magnesium. An organic solvent obtained by diluting acid-mono-2-ethylhexyl with kerosene is added, and the scandium component is extracted into the organic solvent. Next, in order to separate yttrium, iron, manganese, chromium, magnesium, aluminum and calcium extracted together with scandium in an organic solvent, they are removed by adding scrubbing with an aqueous hydrochloric acid solution, and then in the organic solvent. by adding NaOH solution, scandium remaining in the organic solvent to prepare a slurry containing Sc (OH) _3, which by the Sc (OH) ₃ obtained by filtration was dissolved in hydrochloric acid, to obtain the chloride scandium solution. Then, oxalic acid is added to the obtained scandium chloride aqueous solution to form a scandium oxalate precipitate. The precipitate is filtered to separate iron, manganese, chromium, magnesium, aluminum, and calcium into the filtrate, followed by calcination. Thus, high-purity scandium oxide is obtained.

JP-A-3-173725 JP-A-1-133920 JP-A-9-176756 JP-A-9-194211 Japanese Patent Laid-Open No. 9-291320

  However, if the chelate resin is used alone, the distribution of iron, aluminum, chromium, etc. into the eluent is very small, but these impurities are contained in a large amount in the raw material. Requires multiple adsorption and elution operations. In addition, although the adsorption and elution behavior of a plurality of impurities contained in a very small amount is inferior to that of scandium, separation is very difficult due to high distribution in the eluent.

  In the recovery process by solvent extraction, since the scandium quality contained in the nickel oxide ore is very small, it is difficult to process the process liquid directly because the recovery rate and equipment capacity increase.

  Thus, no suitable method has been found for industrial recovery of scandium from nickel oxide ore.

  Therefore, the present invention has been proposed in view of the above-described circumstances, and provides a scandium recovery method that enables simple and efficient recovery of high-quality scandium from nickel oxide ore. With the goal.

  The present inventors have intensively studied to solve the above-described problems. As a result, scandium contained in nickel oxide ore was separated with chelate resin, and scandium nitric acid solution obtained by dissolving hydroxide precipitate obtained from scandium eluate with nitric acid solution was subjected to solvent extraction and produced by solvent extraction. It was found that high-quality scandium can be obtained easily and efficiently by roasting the scandium-containing material obtained from the extracted residual liquid, and the present invention has been completed. That is, the present invention provides the following.

  (1) The first invention of the present invention is a leaching step of leaching a nickel oxide ore containing scandium with sulfuric acid under high temperature and high pressure to obtain a leaching solution and a leaching residue, and adding a neutralizing agent to the leaching solution. A neutralization step for obtaining a Japanese starch and a post-neutralization solution; a sulfurization step for adding a sulfide to the post-neutralization solution to obtain nickel sulfide and a post-sulfurization solution; and By contacting the scandium in the solution after sulfidation to the chelate resin by contact, an ion exchange step for obtaining a scandium eluate, and adding a scandium eluate to obtain a scandium hydroxide precipitate, A dissolution process for obtaining a scandium nitrate solution by adding a nitric acid solution to the scandium hydroxide and dissolving the acid, and contacting the scandium nitrate solution with a neutral extractant to extract impurity elements other than scandium. Scandium having a solvent extraction step of separating and obtaining a scandium-containing extract, and a scandium recovery step of producing a scandium salt contained in the extract and roasting the scandium salt to obtain scandium oxide It is a collection method.

  (2) According to a second aspect of the present invention, in the first aspect, the chelate resin is a resin having iminodiacetic acid as a functional group, and the ion exchange step converts the post-sulfurization solution into the chelate resin. An adsorption process for adsorbing the scandium to the chelate resin in contact with the chelate resin having adsorbed scandium in the adsorption process, and a sulfuric acid solution of 0.1 N or less brought into contact with the chelate resin adsorbed to the chelate resin in the adsorption process. An aluminum removal step to be removed, a scandium elution step in which a sulfuric acid solution of 0.3N or more and less than 3N is brought into contact with the chelate resin that has undergone the aluminum removal step, and 3N is added to the chelate resin that has undergone the scandium elution step. Contact the above sulfuric acid solution to remove chromium adsorbed on the chelate resin in the adsorption process That scandium recovery method comprising the chromium removal process.

  (3) According to a third aspect of the present invention, in the first or second aspect of the invention, the solvent extraction step mixes the scandium nitric acid solution and an organic solvent containing the neutral extractant, other than scandium. An extraction step of separating the extracted impurity element into an extracted organic solvent and a residual extraction solution, a nitric acid solution having a concentration of 1 mol / l to 5 mol / l mixed with the extracted organic solvent, and the extracted organic solvent A scrubbing step of recovering scandium from the organic solvent to obtain an organic solvent after washing, a back extraction step of adding a back extractant to the organic solvent after washing, and back-extracting impurity elements from the organic solvent after washing to obtain a back-extraction solution; Is a scandium recovery method.

  (4) According to a fourth aspect of the present invention, in any one of the first to third aspects, the scandium recovery step adds oxalic acid to the extraction residue obtained in the solvent extraction step. A scandium recovery method comprising a step of obtaining scandium oxalate crystals and a step of firing the scandium oxalate crystals.

  (5) According to a fifth aspect of the present invention, in the first to third aspects of the invention, the scandium recovery step is performed at a rate of 5.0 mol / l or more in the extraction residual liquid obtained in the solvent extraction step. It is obtained by adding sodium hydroxide at a concentration of 8.0 mol / l or less to obtain a scandium hydroxide precipitate, and dissolving the obtained scandium hydroxide precipitate with sulfuric acid or hydrochloric acid. The scandium recovery method includes a step of adding oxalic acid to the dissolved solution to obtain scandium oxalate crystals and a step of firing the scandium oxalate crystals.

  According to the present invention, high-quality scandium can be easily and efficiently recovered from nickel oxide ore.

It is a figure for demonstrating the collection method of the scandium which concerns on this invention.

  Hereinafter, specific embodiments of the scandium recovery method according to the present invention (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. However, the present invention can be implemented with appropriate modifications within a range not changing the gist of the present invention.

<< 1. Overview of scandium recovery methods »
FIG. 1 is a flowchart for explaining a scandium recovery method according to the present embodiment. As shown in FIG. 1, this scandium recovery method is a method of recovering scandium from nickel oxide ore containing components such as aluminum and chromium in addition to valuable metals such as nickel and scandium.

  Specifically, the scandium recovery method according to the present embodiment includes a leaching step S1 in which a nickel oxide ore containing scandium is leached with an acid such as sulfuric acid under high temperature and high pressure to obtain a leaching solution and a leaching residue. A neutralization step S2 to obtain a neutralized starch and a neutralized solution by adding a neutralizing agent; and a sulfurization step S3 to obtain a nickel sulfide and a post-sulfurized solution by adding a sulfiding agent to the neutralized solution; , By contacting the post-sulfurization solution with the chelate resin, the scandium in the post-sulfurization solution is adsorbed on the chelate resin, and an ion exchange step S4 to obtain a scandium eluate, and alkali is added to the scandium eluate and the scandium hydroxide After the precipitate is obtained, a nitric acid solution is added to the scandium hydroxide to dissolve the acid to obtain a scandium nitric acid solution, and the scandium nitric acid solution is brought into contact with a neutral extractant. Extraction and separation of impurity elements other than scandium, a solvent extraction step S6 for obtaining an extraction residue containing scandium, and generating a scandium salt contained in the extraction residue, roasting the scandium salt to obtain scandium oxide And a scandium recovery step S8.

  Thus, in the present embodiment, in recovering and purifying scandium, ion exchange (ion exchange step) and solvent extraction (solvent extraction step) are used in combination, and after ion exchange, prior to solvent extraction. To produce a scandium-containing starch from the scandium eluent, dissolve the starch with nitric acid to obtain a scandium nitric acid solution (dissolution step), and subject the nitric acid solution to solvent extraction It is characterized by. According to such a method, impurities can be separated with higher quality, and even from a raw material containing many impurities such as nickel oxide ore, a simple and stable scandium recovery operation can be performed with a compact facility. It can be carried out.

≪2. About each step of the scandium recovery method >>
Hereinafter, each step of the scandium recovery method will be described in more detail with reference to the flowchart shown in FIG.

<Leaching process>
In the leaching step S1, nickel oxide ore containing scandium is charged together with an acid such as sulfuric acid into a high-temperature pressurized container (autoclave) or the like, and subjected to a stirring process at a high temperature of 240 ° C. to 260 ° C. under a high pressure environment. While leaching the nickel oxide ore with acid, a leaching slurry containing a leaching solution and a leaching residue is generated. In addition, what is necessary is just to perform the process in leaching process S11 according to the conventionally known HPAL process, for example, it describes in patent document 1. FIG.

  Here, examples of the nickel oxide ore include so-called laterite ores such as limonite ore and saprolite ore. Laterite ore usually has a nickel content of 0.8 to 2.5% by weight, and is contained as a hydroxide or siliceous clay (magnesium silicate) mineral. These nickel oxide ores contain a large amount of components such as aluminum, chromium and iron in addition to valuable metals such as nickel, cobalt and scandium.

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

<Neutralization process>
In the neutralization step S2, a neutralizing agent is added to the leachate obtained in the above-described leaching step S1 to adjust the pH, thereby obtaining a neutralized starch containing an impurity element and a post-neutralization solution. Due to the neutralization treatment in this neutralization step S2, valuable metals such as scandium and nickel are contained in the post-neutralization solution, and most of the impurities including iron and aluminum become neutralized starch.

  A conventionally well-known thing can be used as a neutralizer, For example, a calcium carbonate, slaked lime, sodium hydroxide etc. are mentioned.

  In the neutralization process in neutralization process S2, it is preferable to adjust pH to the range of 1-4, suppressing the oxidation of the isolate | separated leachate, and adjusting to the range of 1.5-2.5 more. preferable. If the pH is less than 1, neutralization becomes insufficient, and there is a possibility that the neutralized starch and the liquid after neutralization cannot 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 sulfiding step S3, a sulfiding agent is added to the post-neutralized solution obtained in the neutralizing step S12 to obtain nickel sulfide and a post-sulfurized solution. By the sulfiding treatment in the sulfiding step S13, nickel, cobalt, zinc and the like become sulfides, and scandium and the like are included in the solution after sulfiding.

  Specifically, in the sulfiding step S13, a sulfurizing agent such as hydrogen sulfide gas, sodium sulfide, sodium hydrogen sulfide is blown into the obtained post-neutralized liquid, and sulfide containing nickel and cobalt having a small amount of impurity components. Product (nickel / cobalt mixed sulfide) and the nickel concentration are stabilized at a low level, and a post-sulfurization solution containing scandium or the like is produced.

  In the sulfiding treatment in the sulfiding step S13, the nickel / cobalt mixed sulfide slurry is settled and separated using a sedimentation apparatus such as a thickener, and the nickel / cobalt mixed sulfide is separated and recovered from the bottom of the thickener, while the aqueous solution component The post-sulfurization solution is overflowed and recovered.

<Ion exchange process>
In the ion exchange step S4, by contacting the post-sulfurization solution obtained by the above-described hydrometallurgical treatment of nickel oxide ore with the chelate resin, the scandium contained in the post-sulfurization solution is adsorbed on the chelate resin, and the impurity component A scandium eluent from which is removed is obtained.

  Although it does not specifically limit as an aspect of ion-exchange process S4, For example, as shown in an example in FIG. 1, adsorption | suction process S41 which makes a post-sulfurization liquid contact chelate resin, and adsorb | sucks scandium on chelate resin, and adsorb | sucked scandium A 0.1N or lower sulfuric acid solution is brought into contact with the chelate resin, an aluminum removal step S42 for removing the aluminum adsorbed on the chelate resin in the adsorption step S41, and a sulfuric acid of 0.3N or more and 3N or less on the chelate resin that has undergone the aluminum removal step S42. Scandium elution step S43 for obtaining a scandium eluent by contacting the solution, and removal of chromium adsorbed on the chelate resin in the adsorption step S41 by bringing a sulfuric acid solution of 3N or more into contact with the chelate resin that has undergone the scandium elution step S43 It is preferable that step S44 is included.

[Adsorption process]
In the adsorption step S41, the sulfidized solution is brought into contact with the chelate resin to adsorb scandium to the chelate resin. Although it does not specifically limit as chelate resin, For example, it is preferable to use resin which has iminodiacetic acid as a functional group.

  Here, when the scandium is adsorbed to the chelate resin in the adsorption step S41, the lower the pH range of the solution, the smaller the amount of impurities contained in the nickel oxide ore. Therefore, the adsorption | suction to the chelate resin of an impurity can be suppressed by letting the liquid of the pH range as low as possible pass through a chelate resin. However, when the pH of the solution is less than 2, not only the amount of impurities adsorbed but also the amount of scandium adsorbed decreases. For this reason, it is not preferable to allow a solution in an extremely low pH range to pass through the resin to be adsorbed.

[Aluminum removal process]
In the aluminum removal step S42, a 0.1N or lower sulfuric acid solution is brought into contact with the chelate resin having adsorbed scandium in the adsorption step S41, and the aluminum adsorbed on the chelate resin is removed in the adsorption step S41.

  When removing the aluminum adsorbed on the chelate resin, it is preferable to maintain the pH of the sulfuric acid solution in the range of 1 to 2.5, and more preferably in the range of 1.5 to 2.0. If the pH of the sulfuric acid solution is less than 1, not only aluminum but also scandium may be removed from the chelate resin. On the other hand, if the pH of the sulfuric acid solution exceeds 2.5, aluminum may not be properly removed from the chelate resin.

[Scandium elution step]
In the scandium elution step S43, a sulfuric acid solution of 0.3N or more and less than 3N is brought into contact with the chelate resin that has undergone the aluminum removal step S42 to obtain a scandium eluent.

  When obtaining the scandium eluent, it is preferable to maintain the normality of the sulfuric acid solution used as the eluent in the range of 0.3N or more and less than 3N, more preferably in the range of 0.5N or more and less than 2N. preferable. If the normality of the sulfuric acid solution is 3N or more, not only scandium but also chromium may be included in the scandium eluent. On the other hand, if the normality of the sulfuric acid solution is less than 0.3 N, scandium may not be appropriately removed from the chelate resin.

[Chromium removal process]
In the chromium removal step S44, a 3N or higher sulfuric acid solution is brought into contact with the chelate resin that has undergone the scandium elution step S43, and the chromium adsorbed on the chelate resin in the adsorption step S41 is removed.

  When removing chromium adsorbed on the chelate resin, if the normality of the sulfuric acid solution used as the eluent is less than 3N, chromium may not be properly removed from the chelate resin. Therefore, it is preferable to treat the sulfuric acid solution of 3N or more in contact with the chelate resin.

[Iron removal process]
Moreover, although not shown in figure, iron may be contained as an impurity in the leachate obtained from nickel oxide ore. In this case, prior to the aluminum removal step S42, a sulfuric acid solution having a normality smaller than the normality of the sulfuric acid solution used in the aluminum removal step S42 is brought into contact with the chelate resin that has adsorbed scandium in the adsorption step S41, and in the adsorption step S41. It is preferable to remove iron adsorbed on the chelate resin.

  When removing iron adsorbed on the chelate resin, it is preferable to maintain the pH of the sulfuric acid solution in the range of 1 to 3. If the pH of the sulfuric acid solution is less than 1, not only iron but also scandium may be removed from the chelate resin. On the other hand, if the pH of the sulfuric acid solution exceeds 3, iron may not be properly removed from the chelate resin.

<Re-adsorption of scandium eluent on chelate resin>
Moreover, although it is not an essential aspect, it is preferable to perform the process which resorbs the obtained scandium eluent to chelate resin.

  Specifically, a neutralizing agent is added to the scandium eluate obtained in the scandium elution step S43, and the pH is in the range of 2 to 4, preferably in the range of 2.7 to 3.3 centered on pH 3. Adjusted (step S101), then adding a reducing agent (step S102), and then adding sulfuric acid to adjust the pH to a range of 1 to 2.5, preferably 1.7 to 2.3 centered on pH 2. By adjusting to the range (step S103), a solution after the pH adjustment of the scandium eluent is obtained, and the treatment in the ion exchange step S4 described above is performed again using the solution after the pH adjustment.

  Thus, the quality of the collected scandium can be further enhanced by re-adsorbing the obtained scandium eluent to the chelate resin and repeating the treatment in the ion exchange step. In addition, it is possible to reduce the chemical cost and the equipment scale when separating scandium from the scandium eluent.

  In the re-adsorption of the scandium eluent to the chelate resin, in the addition of the reducing agent (step S102), the oxidation-reduction potential (ORP) exceeds 200 mV and becomes 300 mV or less with the silver / silver chloride electrode as the reference electrode. It is preferable to carry out so as to maintain the range. If the ORP is 200 mV or less, the sulfur component derived from the added sulfurizing agent will precipitate as a fine solid, clogging the filter cloth in the filtration process after sulfurization will deteriorate the efficiency of solid-liquid separation, and productivity When the liquid is re-passed through the chelate resin, clogging or uneven liquid flow occurs in the resin tower, and uniform liquid flow cannot be performed. On the other hand, if the ORP exceeds 300 mV, there may be a problem that the remaining iron ions and the like are adsorbed on the resin and inhibit the adsorption of scandium.

  A conventionally well-known thing can be used as a neutralizing agent added to a scandium eluent, For example, calcium carbonate etc. are mentioned. Moreover, conventionally well-known thing can be used also about the reducing agent added after pH adjustment, For example, sulfur dioxide, hydrogen sulfide gas, sodium sulfide, sulfur dioxide gas, hydrazine, metallic iron etc. are mentioned.

  In re-adsorption of the scandium eluent to the chelate resin, as the chelate resin, those already used may be reused or a new chelate resin may be used. From the viewpoint of preventing contamination of impurities, it is preferable to reuse the chelate resin that has undergone the above-described chromium removal step S44 or use a new chelate resin. In particular, by reusing the chelate resin that has undergone the chromium removal step S44, it is possible not only to prevent contamination of impurities, but also to reduce the amount of chelate resin used.

<Purification of scandium eluent>
Further, the scandium eluent obtained in the scandium elution step S43 is treated again in the scandium elution step S43, that is, the treatment in which the obtained scandium eluent is brought into contact with the chelate resin that has undergone the aluminum removal step S42. Do. Thus, the concentration of the scandium eluent can be increased by repeatedly performing the scandium elution step S43 using the scandium eluent.

  The more the scandium elution step S43 is repeated, the higher the concentration of recovered scandium. However, even if the scandium elution step S43 is repeated many times, the degree of increase in the concentration of recovered scandium is reduced. Therefore, industrially, the number of times of repeating the scandium elution step S43 is preferably about 8 times or less.

<Dissolution process>
Next, following the ion exchange step S4 described above, a dissolution step S5 is provided to generate a scandium precipitate contained in the scandium eluent to separate it from impurities, and this precipitate is dissolved in a nitric acid solution. The process which produces | generates the extraction start liquid used for solvent extraction of the following process is performed.

  Specifically, as a method for concentrating scandium in the dissolution step S5, that is, a method for generating a scandium precipitate and separating it from impurities, a method of neutralization with hydroxide can be used.

[Hydrogen neutralization]
In the hydroxide neutralization treatment for the scandium eluent, neutralization treatment is performed by adding a neutralizer to the scandium eluate obtained in the above-described ion exchange step S4. And a neutralized solution containing.

  A conventionally well-known thing can be used as a neutralizing agent added to a scandium eluent, For example, alkalis, such as slaked lime and sodium hydroxide, are mentioned. Among them, when the scandium eluent is a sulfuric acid solution, it is preferable to use sodium hydroxide or the like as the neutralizing agent because gypsum is produced with the neutralizing agent containing Ca.

  Although it does not specifically limit as pH when a neutralizing agent is added, It is preferable that it is 8-9. If the pH is less than 8, neutralization becomes insufficient, and scandium in the scandium eluent may not be sufficiently recovered as a precipitate. On the other hand, when pH exceeds 9, since the usage-amount of a neutralizing agent increases, it is unpreferable at the point which increases cost.

  In order to reduce the iron quality, neutralization in the first stage is performed to precipitate only iron during the neutralization treatment with hydroxide, and the resulting precipitate is filtered and then neutralized in the second stage. It is effective to carry out stage neutralization.

[Dissolution with nitric acid]
Next, in this embodiment, the precipitate is dissolved by adding a nitric acid solution to the scandium hydroxide precipitate obtained by the neutralization treatment as described above, and the scandium is dissolved in nitric acid. A liquid is produced. In the scandium recovery method according to the present embodiment, the scandium nitric acid solution thus obtained is a processing target (extraction starting solution) of the solvent extraction process in the solvent extraction process of the next process.

  Although it does not specifically limit as a density | concentration of a nitric acid solution, It is preferable that it is the range of 2.0 mol / l-5.0 mol / l, and it is more preferable that it is the range of 3.0 mol / l-4.0 mol / l. .

  Further, when the precipitate is dissolved by the nitric acid solution, it is preferable to dissolve the precipitate in the vicinity of the solubility of the obtained precipitate. As a result, the solid can be precipitated once and redissolved to an arbitrary concentration, so that the scandium concentration can be arbitrarily selected, and the amount of liquid in the subsequent solvent extraction step, and hence the scale of equipment can be reduced. Industrially very preferable.

  As described above, in the present embodiment, by providing the dissolution step S5 subsequent to the ion exchange step S4, impurities contained in the scandium eluent can be significantly removed, and the ion exchange step S4 and the next step can be performed. The man-hour concerning the solvent extraction step S6 can be reduced. In addition, since the concentration of the starting liquid used for solvent extraction can be arbitrarily adjusted, the operation can be further improved by reducing capital investment by stabilizing the equipment scale in the solvent extraction step S6 and stabilizing the starting liquid concentration. Can be stabilized.

<Solvent extraction process>
In the solvent extraction step S6, the scandium nitrate solution obtained by dissolving scandium hydroxide with a nitric acid solution in the dissolution step S5 described above is brought into contact with a neutral extractant to perform a solvent extraction process to extract impurities. A solvent and a residual solution containing scandium are obtained. By the solvent extraction process in the solvent extraction step S6, impurities other than scandium can be efficiently and effectively separated from scandium, and the purity of scandium can be increased. In particular, in the present embodiment, since the scandium nitric acid solution obtained as described above is a target for the solvent extraction treatment, impurities can be extracted more effectively by the extractant.

  The mode of the solvent extraction step S6 is not particularly limited. For example, as shown in FIG. 1, for example, a scandium nitric acid solution and an organic solvent containing a neutral extractant are mixed to extract the extracted organic solvent and the residue. An extraction step S61 for obtaining a liquid, a scrubbing step S62 for separating and recovering scandium extracted into the extractant by mixing a nitric acid solution of a predetermined concentration in the organic solvent after this extraction, and back-extraction to the organic solvent after washing It is preferable to include a back extraction step S63 for adding an agent and back-extracting the impurity element from the organic solvent after washing.

[Extraction process]
In the extraction step S61, a scandium nitric acid solution and an organic solvent containing a neutral extractant are mixed to selectively extract impurity elements other than scandium. By the extraction process in this extraction step S61, an organic solvent containing impurities and an extraction residual liquid with increased scandium purity are obtained. Various types of neutral extractants are known and are not particularly limited, but it is preferable to use an extractant containing phosphorus, specifically TBP (tri-n-butyl phosphate).

  In the extraction treatment using a neutral extractant, it is preferable to dilute the extractant with a hydrocarbon-based organic solvent or the like. For example, when the above-described TBP is used as a neutral extractant, the concentration of TBP in the organic solvent is not particularly limited. However, considering points such as phase separation during extraction and back extraction, 10 vol% or more 50% The volume is preferably not more than volume%, and more preferably not less than 15 volume% and not more than 25 volume%, particularly around 20 volume%.

  Further, the volume ratio of the scandium nitric acid solution and the organic solvent at the time of extraction is not particularly limited, but the organic solvent molar amount is 0.4 to 1.0 times the metal molar amount in the scandium nitric acid solution. It is preferable to make it.

[Scrubbing (cleaning) process]
In the above-described extraction step S61, when scandium is slightly present in the organic solvent from which impurities have been extracted, the organic solvent (organic phase) is scrubbed (washed) before back-extracting the extract. It is preferable to separate the scandium into an aqueous phase and recover it from the extractant (scrubbing step S62).

  In this way, the scrubbing step S62 is provided to wash the organic solvent, and by separating the slight scandium extracted by the extractant, scandium can be separated in the washing liquid, and the recovery rate of scandium is further increased. Can be increased.

  The solution (cleaning solution) used for scrubbing is not particularly limited, and for example, a hydrochloric acid solution, a sulfuric acid solution, a nitric acid solution, or the like can be used. The cleaning solution recovered by scrubbing is purified together with the extraction residue after extraction. Since it is used for the recovery of scandium, it is preferable to use a nitric acid solution which is the same liquid type as the cleaning solution. Moreover, it is preferable to use a nitric acid solution as a washing solution from the viewpoint of preventing scandium hydrolysis due to an increase in pH. Specifically, for example, when a nitric acid solution is used as the cleaning solution, it is preferably in the range of 2.0 mol / l to 5.0 mol / l, and the one in the range of 3.0 mol / l to 4.0 mol / l is used. It is preferable to do.

  Since the number of cleaning stages (number of times) depends on the type and concentration of the impurity element, it can be appropriately changed depending on the respective neutral extractant and extraction conditions. For example, when the phase ratio O / A = 1 of the organic phase (O) and the aqueous phase (A) is set to 1, the scan number extracted in the organic solvent is detected by the analyzer by setting the number of stages to about 3 to 5 stages. Separation can be achieved to below the lower limit.

[Back extraction process]
In the back extraction step S63, the impurity element is back extracted from the organic solvent from which the impurity element has been extracted. Specifically, in this back extraction step S63, a reverse extraction solution (back extraction start solution) is added to and mixed with an organic solvent containing an extractant, thereby causing a reaction opposite to the extraction process in the extraction step S61. Thus, an impurity element is back-extracted to obtain a post-extraction solution containing the impurity element.

  As described above, in the extraction process for the scandium nitric acid solution in the extraction step S61, the impurity element is selectively extracted using a neutral extractant such as TBP as the extractant. From this point of view, it is preferable to use, for example, pure water as the back extraction solution from the viewpoint of efficiently and effectively separating the impurity element from the organic solvent containing the extractant to regenerate the extractant.

  In addition, when the scrubbing process is performed on the organic solvent containing the extractant in the above-described scrubbing step S502, similarly, the reverse extraction solution is added to and mixed with the extractant after the scrub. An extraction process can be performed.

  The neutral extractant after separating the impurity elements by adding a back-extraction solution such as pure water to the extractant after extraction or after scrubbing in this way and performing back-extraction treatment is again The extractant used in the extraction process in the extraction step S61 can be used repeatedly.

<Scandium recovery process>
Next, in the scandium recovery step S7, scandium is recovered from the extracted residue containing scandium obtained in the solvent extraction step S6. In this scandium recovery step S7, after the scandium salt contained in the extracted residual liquid is generated, the solid scandium salt is roasted to generate scandium oxide to recover scandium.

  The embodiment of the scandium recovery step S7 is not particularly limited. For example, as shown in FIG. 1, for example, scandium precipitation is obtained by adding oxalic acid to the extracted residue obtained in the solvent extraction step S6 to obtain scandium oxalate crystals. It is preferable to include a step S71 and a roasting step S72 for firing scandium oxalate crystals.

[Scandium precipitation process]
The scandium precipitation step S71 is a step in which oxalic acid is added to the extraction residue (post-extraction solution) obtained in the solvent extraction step S6 to precipitate and precipitate as a white crystalline solid of scandium oxalate.

  The amount of oxalic acid added is not particularly limited, but it is preferably 1.05 times or more and 2.0 times or less the equivalent amount necessary for precipitating scandium in the extraction liquid as oxalate. If the amount added is less than 1.05 times the equivalent amount required for precipitation, there is a possibility that the entire amount of scandium cannot be recovered. On the other hand, when the addition amount exceeds 2.0 times the equivalent amount required for precipitation, the solubility of scandium oxalate increases, so that scandium is re-dissolved to lower the recovery rate or decompose excess oxalic acid. This increases the amount of oxidant such as hypochlorous soda.

  The pH of the extraction residual solution during the oxalation reaction is not particularly limited, but is preferably about 0 or more and 2 or less, and more preferably about 1. If the pH is too low, such as less than 0, the solubility of scandium oxalate increases and the scandium recovery rate may decrease. On the other hand, when the pH exceeds 2, impurities contained in the extraction residual liquid also form a precipitate, which causes a decrease in scandium purity.

  Although not shown in FIG. 1, prior to the oxalate treatment in the scandium precipitation step S71, the extraction solution containing scandium obtained in the solvent extraction step S6 is neutralized to give scandium. The precipitate may be generated to remove impurities.

  Specifically, a predetermined concentration of sodium hydroxide (neutralizing agent) is added to the extraction residue obtained in the solvent extraction step S6 to form a scandium hydroxide precipitate (in the extraction residue). Sum processing). Next, sulfuric acid or hydrochloric acid is added to the obtained scandium hydroxide precipitate to dissolve the precipitate, thereby obtaining a scandium solution (hydrochloric acid dissolution treatment).

  Although it does not specifically limit as a density | concentration of the sodium hydroxide added in a extraction residual liquid neutralization process, It is preferable that it is the range of 5 mol / l or more and 8 mol / l or less. Since scandium hydroxide is produced as a precipitate when the pH of the solution (extracted liquid) is 8 or higher, its hydroxylation is taken into consideration when both the formation of the precipitate and the suppression of excess sodium hydroxide are taken into consideration. It is preferable to add sodium so that the pH of the extraction residual liquid is 8 or more and 9 or less. In such a point, when the concentration of sodium hydroxide to be added is in the range of 5 mol / l or more and 8 mol / l or less, a scandium hydroxide precipitate can be efficiently generated.

  The oxalate treatment (scandium precipitation step S71) described above can be performed on the scandium solution obtained by performing the neutralization treatment in this manner. Thereby, scandium with higher purity can be recovered.

[Roasting process]
In the roasting step S8, the scandium oxalate precipitate obtained in the scandium precipitation step S7 is washed with water, dried and roasted to generate scandium oxide. By performing the roasting treatment in this manner, scandium can be recovered as extremely high-quality scandium oxide.

  The conditions for the roasting treatment in the roasting step S17 are not particularly limited. For example, the dried scandium oxalate precipitate may be placed in a tubular furnace and heated at about 900 ° C. for about 2 hours. In addition, industrially, it is preferable to use a continuous furnace such as a rotary kiln because drying and roasting can be performed in the same apparatus.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all.

[Example 1]
<Leaching step S1>
First, nickel oxide ore is charged into an autoclave together with concentrated sulfuric acid, and a leaching slurry containing valuable metals such as scandium and nickel is produced over a period of 1 hour under a temperature condition of 245 ° C. Solid-liquid separation was performed on the leachate contained and the leach residue.

<Neutralization step S2>
Next, neutralization was performed by adding calcium carbonate (neutralizing agent) to the leachate obtained by separation. By this neutralization treatment, a post-neutralization solution containing valuable metals such as scandium and nickel and a neutralized starch containing most of impurities including aluminum were obtained.

<Sulfurization step S3>
Next, hydrogen sulfide gas (sulfurizing agent) was blown into the obtained post-neutralization liquid to convert nickel, cobalt, and zinc into sulfides, which were separated from the post-sulfurization liquid that was the liquid after this sulfidation treatment.

<Ion exchange step S4>
(Adsorption process S41)
Subsequently, slaked lime was added as a neutralizer to the post-sulfurized solution obtained by separation to adjust the pH of the solution to 1.6. In addition, in order to clarify the behavior of elements that are not contained in the liquid after addition of slaked lime, or even if contained, the contents of the elements are very small. Thus, an adsorption source solution having the composition shown in Table 1 below was obtained.

  The adsorption source solution having the composition shown in Table 1 was passed through a column packed with a chelate resin (product name: Diaion CR11, manufactured by Mitsubishi Chemical Corporation) having iminodiacetic acid as a functional group. The amount of resin in the column was 40 liters, and the flow rate was 5.3 liters per minute so that the SV was 8. The flow rate was 2400 liters (Bed Volume: BV = 60). The liquid temperature at the time of liquid supply was 60 ° C.

(Aluminum removal step S42)
Next, 800 liters of a sulfuric acid solution having a concentration of 0.1 N was passed through the chelate resin after the adsorption treatment (SV becomes 40) at a flow rate of 27 liters per minute. The aluminum-rich cleaning solution discharged from the column was stored as an aluminum cleaning solution, a part of which was sampled and analyzed by ICP. As a result, the analytical values were Ni: 7 mg / l, Mg: 1 mg / l, Mn: 4 mg / l, Fe: 1 mg / l, Al: 84 mg / l, Sc: 3 mg / l. In addition, the analytical value of Cr and Ca was less than the lower limit which can be measured.

(Scandium elution step S43)
Thereafter, 400 liters of a sulfuric acid solution having a concentration of 1 N was passed through the chelate resin (SV was 40) at a flow rate of 80 liters per minute. The eluent discharged from the column was stored as scandium eluent, and a part was sampled and analyzed. Table 2 below shows the analysis results of the scandium eluent. In addition, "-" in a table | surface shows that it was less than the lower limit which is unanalyzed or measurable.

(Chromium removal step S44)
Subsequently, 80 liters of sulfuric acid solution having a concentration of 3N was passed through the chelate resin at a flow rate of 2.6 liters per minute (SV becomes 40). The cleaning liquid discharged from the column was stored as a chromium cleaning liquid, and a part thereof was sampled and analyzed. As a result, analytical values were Fe: 2 mg / l, Cr: 30 mg / l. In addition, the analytical value of Ni, Mg, Mn, Al, Ca, and Sc was less than the lower limit which can be measured.

<Dissolution step S5>
Next, sodium hydroxide was added to the scandium eluent having the composition shown in Table 2 to maintain the pH at 8-9, thereby generating a hydroxide precipitate of scandium. A nitric acid solution was added to the hydroxide precipitate and dissolved to obtain a chelate eluent hydroxide solution (scandium nitric acid solution). Table 3 below shows the results of analyzing the composition of the solution. In addition, "-" in a table | surface shows that it was unanalyzed or less than the lower limit which can be measured, for example, the analytical value of Mg, Cr, Mn, and Ca was less than the lower limit which can be measured.

<Solvent extraction step S6>
(Extraction step S61)
Solvent extraction treatment was performed using 103 liters of scandium solution having the composition shown in Table 3 as an extraction starting solution. Specifically, the extraction start solution, neutral extractant tri-n-butyl phosphate (trade name: TBP, manufactured by Daihachi Chemical Co., Ltd.) and organic solvent Teclean N20 (JX Nippon Mining Corporation) And 20.6 liters of an organic solvent adjusted to 50% by volume with stirring, and stirred at room temperature for 60 minutes, an extracted organic phase containing impurities excluding scandium, and a liquid after extraction (extracted liquid) Got. In this extraction, no clad was formed, and phase separation after standing proceeded rapidly.

  The composition of various elements contained in the extracted organic phase was analyzed. In Table 4 below, the percentage of the value obtained by dividing the amount of each element contained in the extracted organic phase by the amount of each element contained in the original solution before extraction is calculated, and the result is shown as the extraction rate (%). . In addition, "-" in a table | surface shows that it was less than the lower limit which is unanalyzed or measurable.

  From the results of the extraction rates shown in Table 4, it was found that most of the scandium contained in the original liquid before extraction remained in the liquid after extraction and not extracted through the solvent extraction process in the extraction step S61. In addition, uranium and thorium impurity elements were extracted in a high proportion in the extracted organic phase. In addition, it turns out that elements, such as aluminum, nickel, magnesium, chromium, manganese, calcium, cobalt, copper, and zinc, are hardly contained.

(Scrubbing (cleaning) step S62)
Next, with respect to 20.6 liters of organic solvent (extracted organic phase) obtained in the extraction step S61, a nitric acid solution having a concentration of 3 mol / l has a phase ratio (O / A) of 0.3. Mixed in an amount of 6.2 liters, stirred for 10 minutes and scrubbed. Thereafter, the mixture was allowed to stand to separate the aqueous phase, and the organic phase was again mixed with 6.2 liters of a new nitric acid solution having a concentration of 3 mol / l and washed repeatedly, and the aqueous phase was separated in the same manner. Such washing operation was repeated 3 times in total.

  The composition of various elements contained in the cleaning liquid after the cleaning operation was analyzed. In Table 5 below, the percentage of the value obtained by dividing the amount of each element contained in the cleaning liquid by the amount in the extracted organic phase obtained in the extraction step S61 is calculated, and the result is expressed as the recovery rate (%). Show. In addition, "-" in a table | surface shows that it was less than the lower limit which is unanalyzed or measurable.

  By washing the extracted organic phase three times in this manner, a small amount of scandium extracted into the organic solvent can be separated into the aqueous phase, and the scandium concentration in the organic solvent is reduced to a level of less than 10 mg / l. I was able to.

(Back extraction step S63)
Next, the extracted organic phase after washing is mixed with pure water so as to have a phase ratio of O / A = 1 / 0.3, stirred for 20 minutes, and allowed to stand to leave the organic phase after back extraction. Separated into (organic solvent) and reverse aqueous phase (liquid after back extraction).

<Scandium recovery step S7>
(Scandium precipitation step S71)
Next, with respect to the post-extraction liquid (extracted residual liquid) obtained in the solvent extraction step S6 described above, oxalic acid · 2 water that is twice the calculated amount with respect to the amount of scandium contained in the extracted residual liquid Japanese crystals (Mitsubishi Gas Co., Ltd.) were dissolved and mixed with stirring for 60 minutes to form a white crystalline precipitate of scandium oxalate.

(Roasting step S72)
The precipitate of scandium oxalate obtained in the scandium precipitation step S71 was subjected to suction filtration, washed with pure water, and then dried at 105 ° C. for 8 hours. Subsequently, the dried scandium oxalate was put in a tube furnace and maintained at 850 ° C. to 900 ° C. and subjected to roasting (firing) treatment to obtain scandium oxide.

  The obtained scandium oxide was analyzed by emission spectroscopic analysis, and the reduction rate of thorium (Th) as an impurity in scandium oxide recovered through the solvent extraction treatment was examined. Regarding the reduction rate of thorium, the scandium eluate obtained in the ion exchange step S4 was treated in the dissolution step S5 to obtain a scandium nitric acid solution without undergoing the above-described solvent extraction treatment. Calculation was made based on the amount of thorium in scandium oxide obtained by the roasting treatment. Table 6 shows the calculation results of the quality and reduction rate of thorium in scandium oxide.

As can be seen from the results shown in Table 6, through the scandium recovery process described above, thorium as an impurity can be almost completely removed, and scandium is converted to scandium oxide (Sc ₂ O ₃ ) with extremely high purity. It was possible to recover.

Claims (5)

A leaching step of leaching a nickel oxide ore containing scandium with sulfuric acid under high temperature and high pressure to obtain a leachate and a leach residue;
A neutralization step of adding a neutralizing agent to the leachate to obtain a neutralized starch and a post-neutralized solution;
A sulfurization step of adding a sulfide to the post-neutralization solution to obtain nickel sulfide and a post-sulfurization solution;
An ion exchange step of adsorbing the scandium in the post-sulfurization solution to the chelate resin by bringing the post-sulfurization solution into contact with the chelate resin to obtain a scandium eluate;
A dissolution step of obtaining a scandium nitrate solution by adding an alkali to the scandium eluent to obtain a scandium hydroxide precipitate and then adding a nitric acid solution to the scandium hydroxide and dissolving the acid;
A solvent extraction step of bringing the scandium nitrate solution into contact with a neutral extractant to extract and separate impurity elements other than scandium, and obtaining an extraction liquid containing scandium; and
A scandium recovery method comprising: generating a scandium salt contained in the extraction residual liquid and roasting the scandium salt to obtain scandium oxide. The chelate resin is a resin having iminodiacetic acid as a functional group,
The ion exchange step includes
An adsorption step of contacting the post-sulfurized solution with the chelate resin to adsorb the scandium to the chelate resin;
An aluminum removal step of contacting the chelate resin adsorbing scandium in the adsorption step with a sulfuric acid solution of 0.1 N or less to remove aluminum adsorbed on the chelate resin in the adsorption step;
A scandium elution step of contacting the chelate resin that has undergone the aluminum removal step with a sulfuric acid solution of 0.3N or more and less than 3N to obtain the scandium eluent;
The method for recovering scandium according to claim 1, further comprising: a chromium removal step in which a 3N or higher sulfuric acid solution is brought into contact with the chelate resin that has undergone the scandium elution step to remove chromium adsorbed on the chelate resin in the adsorption step. The solvent extraction step includes
An extraction step of mixing the scandium nitrate solution and an organic solvent containing the neutral extractant, and extracting the impurity element other than scandium into an extracted organic solvent and a residue after extraction;
A scrubbing step of mixing a nitric acid solution having a concentration of 1 mol / l or more and 5 mol / l or less with the organic solvent after extraction, recovering scandium from the organic solvent after extraction, and obtaining the organic solvent after washing;
The method for recovering scandium according to claim 1, further comprising: a back extraction step of adding a back extractant to the washed organic solvent and back extracting the impurity element from the washed organic solvent to obtain a back extract. The scandium recovery step includes
Adding oxalic acid to the extraction residue obtained in the solvent extraction step to obtain scandium oxalate crystals;
The method for recovering scandium according to any one of claims 1 to 3, further comprising: firing the scandium oxalate crystal. The scandium recovery step includes
Adding sodium hydroxide having a concentration of 5.0 mol / l or more and 8.0 mol / l or less to the extraction liquid obtained in the solvent extraction step to obtain a scandium hydroxide precipitate;
Dissolving the obtained scandium hydroxide precipitate with sulfuric acid or hydrochloric acid, adding oxalic acid to the solution obtained by dissolving, and obtaining scandium oxalate crystals;
The method for recovering scandium according to any one of claims 1 to 3, further comprising: firing the scandium oxalate crystal.

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