JP2018204088A - Recovery method of scandium - Google Patents

Abstract

To provide a recovery method of scandium that can efficiently remove impurities as a neutralized precipitate from a solution containing scandium and can simply and efficiently recover high-purity scandium.SOLUTION: The recovery method of scandium includes a concentration step which has: a first neutralization step of adding a neutralizing agent to a solution containing scandium and subjecting the solution to neutralization treatment to form a first neutralization slurry and performing solid-liquid separation to produce a first neutralized precipitate and a neutralization filtrate; a second neutralization step of adding a neutralizing agent to the first neutralization filtrate and subjecting the filtrate to neutralization treatment to form a second neutralization slurry and performing solid-liquid separation to produce a second neutralized precipitate and a second neutralization filtrate; and a hydroxide dissolution step of adding an acid to the second neutralized precipitate to produce a hydroxide solution. In the solid-liquid separation in the first neutralization step, the first neutralization slurry is subjected to filtration treatment using a filtration membrane as a filter medium to separate the first neutralized precipitate and the first neutralization filtrate.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a scandium recovery method, and more particularly to a method capable of recovering high purity scandium by efficiently separating and removing impurity components.

  Scandium is an extremely useful element as an additive for high-strength alloys and as an electrode material for fuel cells. However, since its production volume 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 nickel and a small amount of scandium. In recent years, nickel oxide ore has become industrially available as a nickel raw material, and methods for industrially recovering scandium from nickel oxide ore have also been studied.

  As a method of using nickel oxide ore as a raw material, the raw material 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 form a solid liquid into a leaching solution containing nickel and a leaching residue. The separating HPAL process has been put into practical use. In this HPAL process, impurities are separated by adding a neutralizing agent to the obtained leachate, and then nickel is recovered as nickel sulfide by adding a sulfiding agent to the leachate from which impurities have been separated. And electric nickel and nickel salt can be obtained by processing this nickel sulfide by the existing nickel smelting process.

  In such an HPAL process, scandium contained in the nickel oxide ore is contained in a poor liquid remaining after recovering the nickel sulfide. As a technique for recovering scandium from this poor solution, for example, there is a method disclosed in Patent Document 1.

  Specifically, the method disclosed in Patent Document 1 is obtained by passing a poor solution through an ion exchange resin and then adding an eluent eluted from the ion exchange resin (or adding a neutralizing agent to the eluent). The re-dissolved liquid obtained by adding acid to the neutralized starch (secondary neutralized starch)) is subjected to solvent extraction to separate the extraction residue and the extraction agent after extraction. The solution is subjected to an oxalate treatment to obtain a scandium oxalate precipitate, and the precipitate is roasted to obtain scandium oxide.

  In the method described above, impurities such as iron and chromium can be removed as neutralized starch (primary neutralized starch) by preliminarily neutralizing the eluent eluted from the ion exchange resin. As a result, scandium having a higher basicity remains in the eluent, and the process can proceed to solvent extraction (or further neutralization).

  In such a method, for example, the primary neutralized starch obtained by neutralizing the eluent tends to be fine particles and difficult to remove. In addition, when a filter cloth made finer in accordance with the size of the primary neutralized starch to be produced is used, the filter cloth is clogged, the processing capacity is lowered, and the replacement frequency is increased. is there.

Japanese Patent No. 5967284

  The present invention has been proposed in view of the above-described circumstances, and efficiently removes impurities as a neutralized starch from a solution containing scandium, and easily and efficiently recovers high-purity scandium. An object of the present invention is to provide a method for recovering scandium.

  The inventors of the present invention have made extensive studies in order to solve the above-described problems. As a result, the solution containing scandium is subjected to a two-step neutralization treatment, and the neutralization slurry obtained by the first-step neutralization treatment is subjected to a filtration treatment using a filter membrane as a filter medium. As a result, it was found that the impurities can be separated and removed more efficiently by separating into neutralized starch and neutralized filtrate, and the present invention has been completed.

  (1) In the first invention of the present invention, a neutralizing agent is added to a solution containing scandium and neutralized to produce a primary neutralized slurry, and the primary neutralized starch is obtained by solid-liquid separation. A secondary neutralization slurry is obtained by adding a neutralizing agent to the primary neutralization filtrate and neutralizing the resulting primary neutralization filtrate. , A second neutralization step of obtaining a secondary neutralized starch and a secondary neutralized filtrate by solid-liquid separation, and adding a hydroxide solution to the obtained secondary neutralized starch A method of recovering scandium comprising a concentration step having a hydroxide dissolution step to be obtained, and in the solid-liquid separation in the first neutralization step, a filtration membrane is used as a filter medium for the primary neutralization slurry. This is a scandium recovery method in which the used neutralization starch and the primary neutralized filtrate are separated by performing the filtration treatment used.

  (2) The second invention of the present invention is the scandium recovery method according to the first invention, wherein the filtration membrane is a hollow fiber membrane.

  (3) The third invention of the present invention is the scandium recovery method according to the first or second invention, wherein the filtration membrane has a fractional particle size of 0.01 μm to 0.05 μm.

  (4) According to a fourth aspect of the present invention, in the first or second aspect, the filtration membrane has a median diameter of solid particles constituting the primary neutralized starch in the primary neutralized slurry. This is a method for recovering scandium comprising a through hole having a diameter corresponding to a size of 1/500 to 1/50.

  (5) According to a fifth invention of the present invention, in any one of the first to fourth inventions, in the first neutralization step, a plurality of filtration processes are performed using a plurality of the filtration membranes, and at least, In the first-stage filtration treatment, the primary neutralized starch is adhered to the surface of the first filtration membrane by filtering the primary neutralized slurry using the first filtration membrane. In the second-stage filtration process, the primary neutralized starch separated from the first filtration membrane is filtered using a second filtration membrane, and this is a scandium recovery method.

  (6) According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the primary neutralization slurry is subjected to a filtration treatment on the primary neutralization slurry using the filtration membrane. This is a scandium recovery method in which water or air is circulated through the filtration membrane from a direction opposite to the filtration direction.

  (7) According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the flow rate of the primary neutralized filtrate passing through the filtration membrane is measured, and the use of the filtration membrane is started. This is a scandium recovery method in which the filtration membrane is subjected to a washing treatment with sulfuric acid when the flow rate corresponds to a ratio of 60% to 90% of the flow rate.

  According to the present invention, it is possible to provide a method for recovering scandium that can efficiently and efficiently recover scandium of high purity by efficiently removing impurities as neutralized starch from an aqueous solution containing scandium. .

It is a flowchart for demonstrating the collection method of a scandium. It is a flow figure for explaining an example of the whole flow to which the recovery method of scandium is applied. It is a flowchart for demonstrating the flow of a neutralization process. It is a graph which shows the ratio (precipitation rate) of each element precipitated from the pH of a solution when a neutralizer is added to a scandium eluent, and the solution.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment, In the range which does not change the summary of this invention, it can add and change suitably. In the present specification, the notation “X to Y” (X and Y are arbitrary numerical values) means “X or more and Y or less”.

<< 1. Overview >>
In the scandium recovery method according to the present invention, scandium and impurities are separated from a scandium-containing solution to efficiently recover high-purity scandium. Examples of the solution containing scandium include an acidic solution obtained by leaching nickel oxide ore with an acid such as sulfuric acid under high temperature and high pressure.

  Specifically, the method for recovering scandium according to the present invention generates a primary neutralized slurry by adding a neutralizing agent to a solution containing scandium and subjecting it to a neutralization treatment. A first neutralization step for obtaining a Japanese starch and a primary neutralized filtrate, and a secondary neutralized slurry is produced by adding a neutralizing agent to the obtained primary neutralized filtrate and neutralizing it. A second neutralization step of obtaining a secondary neutralized starch and a secondary neutralized filtrate by solid-liquid separation, and adding a hydroxide solution to the resulting secondary neutralized starch by adding an acid. And a concentration step having a hydroxide dissolving step to be obtained.

  And in this collection | recovery method, a primary neutralization starch and primary neutralization are performed by performing the filtration process which used the filtration membrane as a filter medium with respect to a primary neutralization slurry in the 1st neutralization process mentioned above. It is characterized by separating the filtrate. The filtration membrane is not particularly limited, and a porous hollow fiber membrane can be used.

  According to such a method, the impurity component which consists of a fine particle can be efficiently removed from the solution containing scandium, and scandium can be concentrated more effectively. As a result, it is possible to recover scandium having a higher purity than in the prior art.

≪2. Scandium recovery method >>
Hereinafter, a series of flows of the scandium recovery method will be described, and the filtration process in the concentration step described above will be described more specifically.

  FIG. 1 is a flowchart showing an example of a scandium recovery method according to the present embodiment. In this scandium recovery method, scandium and impurities are separated from an acidic solution (post-sulfurization solution) containing scandium obtained by leaching nickel oxide ore with an acid such as sulfuric acid. It is simply and efficiently collected.

  In this scandium recovery method, an acidic solution containing scandium is passed through an ion exchange resin to adsorb scandium, and then an eluent (scandium eluent) obtained by contacting the acid solution with the ion exchange resin is used. On the other hand, impurities are separated and scandium is concentrated by performing a two-step neutralization treatment. Then, by subjecting the acidic solution enriched with the scandium to solvent extraction using an extracting agent such as an amine-based extracting agent, impurities contained in the acidic solution are extracted into the extracting agent, and the acidic solution is extracted after extraction. Separated from scandium that will remain in solution (extracted residue).

  For scandium that is contained in the extraction residue by this solvent extraction, for example, by adding an alkali to neutralize to obtain a precipitate of hydroxide or oxalic acid using oxalic acid By recovering oxalate precipitates by chlorination, solids suitable for product use are separated and residual impurities are separated to convert scandium into highly pure scandium hydroxide and scandium oxalate crystals. to recover.

  The obtained scandium hydroxide and scandium oxalate crystals are made into a form of scandium oxide by firing by a known method. The scandium oxide thus produced can be used as an electrolyte material for fuel cells. Moreover, after obtaining scandium metal by a method such as molten salt electrolysis, it can be used for applications such as addition to aluminum to form an alloy.

  As described above, in the scandium recovery method according to the present embodiment, when separating and recovering scandium, a two-stage neutralization process is performed on a solution (eluent) in which scandium is concentrated through an ion exchange process. It is characterized by further concentrating scandium by applying. At this time, the primary neutralized starch and the primary neutralized starch are obtained by subjecting the primary neutralized slurry obtained by the neutralization treatment in the first stage to filtration using a filter membrane as a filter medium. The filtrate is separated into solid and liquid.

  According to such a method, impurities can be effectively separated by a two-stage neutralization treatment, and transferred to the neutralized filtrate by using a filtration membrane in the solid-liquid separation after the neutralization treatment. Impurity components composed of the fine particles can also be separated and removed efficiently. Therefore, even from a raw material containing many impurities such as nickel oxide ore, highly pure scandium can be efficiently recovered under stable operation.

  More specifically, as shown in FIG. 1, the scandium recovery method according to the present embodiment is a wet nickel oxide ore that obtains an acidic solution containing scandium by leaching the nickel oxide ore with an acid such as sulfuric acid. A smelting treatment step S1, a scandium elution step S2 for obtaining a scandium eluent in which impurities are removed from the acidic solution, and a neutralization treatment is performed by adding a neutralizing agent to the scandium eluate to contain a high concentration of scandium. Concentration step S3 for obtaining a solution, and solvent extraction step S4 for subjecting the obtained solution to solvent extraction with an amine-based extractant or the like to extract impurities into the extractant and separate scandium remaining in the acidic solution after extraction. And a scandium recovery step S5 for recovering scandium from the extracted residual liquid.

<2-1. Nickel oxide ore hydrometallurgical treatment process>
An acidic solution obtained by treating nickel oxide ore with sulfuric acid can be used as the acidic solution containing scandium to be treated for scandium recovery.

  Specifically, as an acidic solution subjected to solvent extraction, a leaching step S11 in which nickel oxide ore is leached with an acid such as sulfuric acid under high temperature and high pressure to obtain a leachate, and a neutralizer is added to the leachate to add impurities. A nickel oxide ore having a neutralization step S12 for obtaining a neutralized starch and a post-neutralization solution, and a sulfidation step S13 for obtaining a nickel sulfide and a post-sulfurization solution by adding a sulfiding agent to the post-neutralization solution The post-sulfurization solution obtained by the hydrometallurgical treatment step S1 can be used. Below, the outline | summary of the flow of the hydrometallurgical treatment process S1 of nickel oxide ore is demonstrated.

(1) Leaching step 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 a stirring treatment is performed at a temperature of 240 ° C to 260 ° C. It is a step of forming a leaching slurry comprising leaching residues. 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 a siliceous clay (magnesium silicate) mineral. These nickel oxide ores contain scandium.

  In the leaching step S11, the leaching slurry composed of the obtained leaching solution and the leaching residue is washed, and solid-liquid separation is performed into the leaching solution 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 the 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.

(2) Neutralization step The neutralization step S12 is a step of adjusting the pH by adding a neutralizing agent to the leachate obtained in the leaching step S11 to obtain a neutralized starch containing an impurity element and a post-neutralization solution. It is. By the neutralization treatment in the neutralization step S12, valuable metals such as nickel, cobalt, and scandium are included in the post-neutralization solution, and most of impurities such as 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 S12, 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.

(3) Sulfurization process Sulfurization process S13 is a process which adds a sulfidizing agent to the post-neutralization liquid obtained by neutralization process S12, performs a sulfidation process, and obtains a nickel sulfide and a post-sulfurization liquid. By the sulfiding treatment in the sulfiding step S13, nickel, cobalt, zinc and the like become sulfides, and scandium and the like are contained in the post-sulfurized solution.

  Specifically, in the sulfidation step S13, a sulfide containing nickel and cobalt with a small amount of impurity components is added to the obtained post-neutralization solution by adding a sulfiding agent such as hydrogen sulfide gas, sodium sulfide, sodium hydrogen sulfide. (Nickel / cobalt mixed sulfide) and a post-sulfurization solution containing scandium and the like by stabilizing the nickel concentration at a low level.

  In the sulfiding treatment in the sulfiding step S13, the nickel / cobalt mixed sulfide slurry is subjected to settling separation using a settling separator such as a thickener, and the nickel / cobalt mixed sulfide is separated and recovered from the bottom of the thickener. On the other hand, the post-sulfurization solution that is an aqueous solution component is recovered by overflowing.

  In the scandium recovery method according to the present embodiment, the post-sulfurization solution obtained through each step of the above-described nickel oxide ore hydrometallurgical treatment step S1, scandium and other target for scandium recovery treatment. It can be used as an acidic solution containing impurities.

<2-2. Scandium (Sc) elution step>
As described above, a post-sulfurization solution that is an acidic solution containing scandium obtained by leaching nickel oxide ore with sulfuric acid can be applied as a target solution for scandium recovery treatment. However, in the post-sulfurization solution that is an acidic solution containing scandium, in addition to scandium, for example, aluminum, chromium, and other various impurities that remain in the solution without being sulfided by the sulfurization treatment in the above-described sulfurization step S13. It is included. Therefore, when subjecting this acidic solution to solvent extraction, as a scandium elution step S2, impurities contained in the acidic solution are removed in advance to concentrate scandium (Sc), and a scandium eluent (scandium-containing solution) is used. Preferably, it is generated.

  In the scandium elution step S2, for example, an ion exchange treatment using a chelate resin is used to separate and remove impurities such as aluminum contained in the acidic solution to obtain a scandium-containing solution in which scandium is concentrated. Can do.

  FIG. 2 is a flowchart showing an example of a method (ion exchange step) performed by an ion exchange reaction using a chelate resin as a method for concentrating and eluting scandium by removing impurities contained in an acidic solution. In this step, the post-sulfurization solution obtained in the sulfidation step S13 of the nickel oxide ore hydrometallurgy treatment step S1 is brought into contact with the chelate resin so that scandium in the post-sulfurization solution is adsorbed on the chelate resin, and scandium (Sc) An eluent is obtained. The ion exchange step as an example of the scandium elution step S2 is referred to as “ion exchange step S2.”

  Specifically, as the ion exchange step S2, an adsorption step S21 in which the solution after sulfurization is brought into contact with the chelate resin to adsorb scandium to the chelate resin, and sulfuric acid of 0.1 N or less is brought into contact with the chelate resin in which scandium is adsorbed. The aluminum removal step S22 for removing aluminum adsorbed on the chelate resin, the scandium elution step S23 for obtaining a scandium eluent by contacting the chelate resin with sulfuric acid of 0.3N or more and 3N or less, and the chelate resin subjected to the scandium elution step S23 An example is one having 3N or more sulfuric acid in contact with it and a chromium removal step S24 for removing chromium adsorbed on the chelate resin in the adsorption step S21. Hereinafter, although an outline is demonstrated about each process, as ion exchange process S2, it is not limited to this.

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

[Aluminum removal process]
In the aluminum removal step S22, 0.1 N or less sulfuric acid is brought into contact with the chelate resin that has adsorbed scandium in the adsorption step S21 to remove aluminum adsorbed on the chelate resin. In addition, when removing aluminum, it is preferable to maintain pH in the range of 1 or more and 2.5 or less, and it is more preferable to maintain in the range of 1.5 or more and 2.0 or less.

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

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

<2-3. Concentration process>
As described above, in the scandium elution step S2, scandium and impurities are separated by the selectivity of the chelate resin, and the scandium separated from the impurities is recovered as a scandium eluent. However, due to the characteristics of the chelate resin used, not all impurities can be completely separated from scandium.

  Therefore, the scandium eluent recovered in the scandium elution step S2 is subjected to solvent extraction using it as an extraction start solution in the solvent extraction step S4 described later, whereby the separation of scandium and impurities can be further advanced.

  However, in the solvent extraction step S4, which will be described later, in general, the higher the concentration of the target component in the extraction starting solution used for solvent extraction, the better the separation performance from unintended impurities. In addition, if the amount of scandium to be processed is the same, the higher the concentration of scandium, the smaller the amount of solution used for solvent extraction, the smaller the amount of extractant used as a result. I'll do it. In addition, there are various merits such as improvement in operational efficiency such that the equipment required for the solvent extraction process is more compact.

  Therefore, in the present embodiment, in order to increase the scandium concentration in the scandium eluent, that is, in order to concentrate scandium, the scandium elution eluted from the chelate resin in the scandium elution step S2 (scandium elution step S23). A neutralizing agent is added to the liquid for neutralization to form a scandium hydroxide precipitate. Then, by adding an acid to the obtained scandium hydroxide precipitate and dissolving it again, a solution (extraction starting solution) having a high scandium concentration is obtained. Thus, prior to the solvent extraction step S4, the scandium eluent is neutralized to concentrate scandium, thereby improving the solvent extraction processing efficiency.

  In addition, by performing such neutralization treatment, a precipitate containing scandium is once formed from the scandium eluent, and solid-liquid separation is performed, so that an effect of separating impurities that have not become precipitates can be expected.

  Specifically, in the concentration step S3, as shown in FIG. 2, a neutralizing agent is added to the scandium eluent to adjust to a predetermined pH range to obtain a neutralization residue and a neutralized filtrate 2 A neutralization step S31 composed of steps, and a hydroxide dissolution step S32 that is dissolved by adding an acid to the obtained neutralized starch to obtain a redissolved solution containing a high concentration of scandium. Have.

[Neutralization process]
In the neutralization step S31, a neutralizing agent is added to the scandium eluent to adjust the pH of the solution to a predetermined range, and the scandium contained in the scandium eluent is used as a precipitate of scandium hydroxide. In the neutralization step S31, the neutralized starch composed of scandium hydroxide and the neutralized solution are thus generated.

  The neutralizing agent is not particularly limited, and for example, sodium hydroxide can be used.

  Here, in the present embodiment, as the neutralization process in the neutralization step S31, pH adjustment by neutralization using a neutralizer is performed in two stages. Thereby, an impurity can be isolate | separated more efficiently and scandium can be concentrated. In FIG. 3, the figure for demonstrating the flow of the two-step neutralization process in neutralization process S31 is shown. As shown in the process diagram of FIG. 3, the neutralization step S31 includes a first neutralization step for performing the first-stage neutralization and a second neutralization step for performing the second-stage neutralization.

(First neutralization step)
Specifically, in the neutralization treatment by two-stage pH adjustment, as a first neutralization step, a neutralizing agent such as sodium hydroxide is added to the scandium eluent so that the pH of the solution falls within a predetermined range. The first stage of neutralization is adjusted as follows. By this first-stage neutralization, most of impurities such as iron and chromium, which are components having a lower basicity than scandium, become precipitates in the form of hydroxide. And a primary neutralization starch and a primary neutralization filtrate can be obtained by performing the solid-liquid separation which consists of filtration processing with respect to the primary neutralization slurry containing the precipitate. Scandium is concentrated in the primary neutralized filtrate.

  In the neutralization treatment in the first neutralization step, the pH of the solution is preferably adjusted to a range of 3.5 to 4.5 by adding a neutralizing agent. More preferably, the pH of the solution is adjusted to about 4.0. By adding a neutralizing agent and neutralizing so that the pH of the solution falls within this range, scandium can be more efficiently concentrated in the primary neutralized filtrate.

  Here, in a 1st neutralization process, with respect to the primary neutralization slurry produced | generated by the neutralization process, a primary neutralization starch and a primary medium are obtained by performing the filtration process which used the filtration membrane as a filter medium. It is characterized by separating into a Japanese filtrate. Here, the filtration membrane is distinguished from, for example, a filter cloth obtained by weaving or solidifying fibers, and has a relatively small (for example, submicron or smaller) pore on the surface. It is a formed film.

  Thus, in the first neutralization step, the primary neutralized filtrate and the primary neutralized starch are separated by subjecting the primary neutralized slurry to a filtration treatment using a filtration membrane. Thereby, the impurity which consists of the fine particle produced | generated by neutralization can also be isolate | separated effectively as a primary neutralization starch, and it can suppress moving to a primary neutralization filtrate. For example, iron hydroxide (iron hydroxide) produced by neutralization is likely to be very fine, but by performing filtration using a filtration membrane, fine iron hydroxide particles are also produced. It can be separated and removed effectively as a primary neutralized starch.

  Filtration membranes are generally composed of organic polymers or inorganic substances (eg oxides), but gaps (holes, through holes) that allow aqueous solutions to pass through the material itself without weaving or solidifying the fibers. It is preferable to use a porous membrane provided with a large number of.

  Since the size (pore diameter) of the gap (pore) on the surface of the filtration membrane is a molecular size, it is significantly smaller than the size of a precipitate such as a neutralized starch obtained by neutralization treatment. Therefore, the produced neutralized starch cannot pass through the pores of the filtration membrane, and there is no fear that the neutralized starch is clogged in the pores. In addition, the pores on the surface of the filtration membrane may be capped with neutralized starch, but since the pores are through holes and the inside is not clogged, the lid formed by the convection of the neutralized slurry is easy. Removed. Therefore, the filtration can be continued at a certain flow rate until at least one surface of the filtration membrane is covered with the neutralized starch.

  It is known that the filter cloth is more likely to be clogged as the mesh opening is smaller, but it is unexpectedly difficult to clog if the pore diameter is much smaller in molecular size as in a filtration membrane. In the present embodiment, by utilizing such a phenomenon, by using a filtration membrane in the filtration treatment of the neutralized slurry, the impurity components composed of fine particles are effectively separated and removed, and clogging is performed. It is possible to suppress and perform efficient processing.

  The filter membrane is not formed by weaving or hardening fibers like a filter cloth, etc., and has a through hole unique to itself, so it has a large thickness like overlapping of fibers. It is also an advantage not to accompany. Thus, since the thickness can be reduced as the filter medium by using the filtration membrane, the filtration resistance (pressure loss) is small, and the filtration flow rate can be increased.

  Specifically, the filtration membrane is not particularly limited, but a hollow fiber membrane having a porous property can be suitably used. Specifically, the hollow fiber membrane may be made of an organic polymer material such as polyacrylonitrile resin or polysulfone, or made of an inorganic material such as silica or ceramic. These hollow fiber membranes are commercially available and can be obtained at low cost.

  The pore size (pore diameter) of the filtration membrane can be appropriately adjusted within a range that allows the aqueous solution contained in the neutralized slurry to pass through and does not allow the neutralized starch to pass through. For a neutralized slurry obtained by subjecting a scandium eluent to neutralization, for example, a filtration membrane having a pore size of a fractional particle size (opening) of 0.01 μm to 0.05 μm. For example, it can be preferably used from the viewpoint of filtration flow rate, removal amount of neutralized starch, difficulty of clogging in the medium term, and the like. This is because the size of scandium ions and water molecules is smaller than the range of 0.01 μm to 0.05 μm, while the particle size of the neutralized starch is larger than 0.05 μm.

  Further, from the viewpoint of the difficulty of clogging the pores of the filtration membrane, the pores have a median diameter (D50, volume average diameter by laser diffraction / scattering method) of solid particles constituting the neutralized starch of the neutralized slurry. A through hole having a diameter corresponding to a size of 1/500 to 1/50 is preferable. If the pores have such a size (diameter), even if the surface of the neutralized starch (solid particles) is caught in the pores of the filtration membrane, the entire solid particles do not enter the pores. . Of course, the surface of the filtration membrane is damaged by the neutralized starch, so that the pore diameter is expanded to the same size as the solid particles constituting the neutralized starch, or the pores are about the same size as the solid particles. It may occur anew. However, even if solid particles enter and close the large pores that are generated, if many other pores are of the size described above, there will be a large number of pores that are not clogged as a whole. Can be effectively secured. In addition, from this, even if all of the through-holes of the filtration membrane do not have a diameter corresponding to 1/500 to 1/50 of the median diameter of the solid particles, a sufficient effect is obtained. It can be said that it is possible.

  The pore diameter of the filtration membrane can be measured, for example, by observing with an electron microscope. It can also be confirmed by filtering particles of known size. In addition, although there may be a difference in size between the plurality of holes provided in the filtration membrane, in that case, the size that 90% of the particles cannot practically pass through can be regarded as the diameter of the hole diameter. .

  Since the neutralized starch separated by filtration using a filtration membrane is a hydroxide such as iron or chromium as described above, it can be recovered and used for other purposes. At this time, in the filtration treatment, it is preferable to perform a plurality of stages of filtration treatment using a plurality of filtration membranes. Specifically, at least in the first stage filtration, the primary neutralized slurry is filtered on the surface of the first filtration membrane by filtering the primary neutralized slurry using the first filtration membrane. In the second-stage filtration treatment, the primary neutralized starch separated from the first filtration membrane is filtered using the second filtration membrane.

  Moisture containing scandium adheres to the neutralized starch (primary neutralized starch) obtained by separating the primary neutralized slurry using a filtration membrane. Therefore, the second-stage filtration treatment using the second filtration membrane is performed on the primary neutralized starch separated by the first-stage filtration treatment by performing the two-stage filtration treatment as described above. Do. As a result, the water contained in the primary neutralized starch can be effectively separated from the neutralized starch, and the primary neutralized starch can be recovered in a form from which water has been removed. The water containing scandium can be efficiently recovered.

  Further, in the first neutralization step, by performing a two-stage filtration process using a second filtration membrane, the primary neutralized starch to be separated is one that is moist and contains moisture. It will be good. In such a wet state, in the filtration treatment of the primary neutralized slurry, that is, in separating the primary neutralized starch and the primary neutralized filtrate, clogging of the filtration membrane is less likely to occur, Since the liquid comes into contact with the filtration membrane, the filtration flow rate can be increased at the first unit, and the efficiency of the filtration process is improved overall (total of the first and second units).

  In addition, the water separated and recovered from the primary neutralized starch by the second-stage filtration treatment is combined with the primary neutralized filtrate obtained by the first-stage filtration treatment, and the second middle of the next step. It can be transferred to the sum process. Thereby, the recovery loss of scandium can be effectively reduced.

  After the filtration treatment is performed on the primary neutralized slurry using the filtration membrane, when the clogging of the filtration membrane proceeds, the washing treatment is preferably performed. The washing treatment is preferably a back washing treatment performed by circulating water or air from the direction opposite to the filtration direction of the primary neutralized slurry with respect to the filtration membrane, thereby effectively removing clogging. Can do.

  When water is used for the backwash treatment, a suspension in which neutralized starch clogged in the filter membrane is suspended is obtained. However, the concentration of the suspension that varies depending on the amount of water used can be obtained. May affect post-processing. Therefore, it is preferable to adjust the amount of water used for washing while analyzing the slurry concentration of the resulting suspension. For example, when the slurry concentration of the suspension falls below the slurry concentration used for normal filtration, the backwash process is stopped.

  Further, since the filtration process cannot be executed during the cleaning process on the filtration membrane, it is desirable to reduce the frequency and time of the cleaning as much as possible. Regarding the frequency, for example, it is performed when a layer of solid particles constituting the neutralized starch is confirmed on the surface of the filtration membrane. Note that the thickness of the solid particle layer at that time can be determined by the degree of visibility of the layer on the surface of the filtration membrane. If the filtration membrane can be seen through, the filtration flow rate and filtration are possible. Each time can be kept high.

  On the other hand, in order to remove the solid particles clogged in the filtration membrane by backwashing, a process requiring a large flow rate or a long time may be required. As described above, while the cleaning process such as the backwash process is being performed, the filtration process cannot be performed, and the processing efficiency is lowered. Therefore, it is preferable that the backwashing process is completed even if the solid particles remain slightly on the filtration membrane, and the sulfuric acid cleaning is periodically performed when the remaining solid particles increase.

  The sulfuric acid cleaning is a cleaning process performed by immersing the entire filtration membrane in sulfuric acid or flowing sulfuric acid. Specifically, the timing of the sulfuric acid washing is determined based on the time when solid particles remaining on the filtration membrane increased, for example, when filtration is performed with a new (at the start of use) filtration membrane, from the filtration membrane. The flow rate of the primary neutralized filtrate to be passed is measured, and the flow rate of the primary neutralized filtrate is set to a time point corresponding to a ratio of 60% to 90% of the flow rate at the start of use. After washing with sulfuric acid, use is resumed after washing with water to wash away sulfuric acid.

(Second neutralization step)
Next, as a second neutralization step, a neutralizing agent such as sodium hydroxide is further added to the primary neutralized filtrate obtained by the first neutralization, and the pH of the solution is within a predetermined range. The neutralization process of the 2nd stage adjusted so that it may become is performed. A secondary neutralized slurry is produced by this second stage neutralization treatment, and a secondary neutralized starch and a secondary neutralized filtrate are obtained by solid-liquid separation. As a result, scandium hydroxide is obtained as a secondary neutralized starch, and nickel, which is a basic component higher than scandium, does not precipitate, so it remains in the secondary neutralized filtrate, and the scandium from which impurities have been separated is obtained. Hydroxide (secondary neutralized starch) can be obtained.

  In the neutralization treatment in the second neutralization step, the pH of the primary neutralized filtrate is preferably adjusted to a range of 5.5 to 6.5 by adding a neutralizing agent. More preferably, the pH of the primary neutralized filtrate is adjusted to about 6.0. By neutralizing by adding a neutralizing agent so that the pH of the solution falls within this range, a precipitate of scandium hydroxide can be generated more efficiently.

  The concentration of sodium hydroxide or the like used as a neutralizing agent in the neutralization treatment may be determined as appropriate. For example, when a high concentration neutralizing agent exceeding 4 N is added, the pH locally increases in the reaction vessel. In some cases, the pH may partially exceed 4.5. In such a case, adverse effects such as coprecipitation of scandium and impurities may occur, and high-purity scandium may not be obtained. For this reason, it is preferable to use a solution diluted to 4N or less as the neutralizing agent, so that the neutralization reaction in the reaction vessel may occur as uniformly as possible.

  On the other hand, for example, if the concentration of the neutralizing agent such as sodium hydroxide solution is too low, the amount of solution required for the addition increases correspondingly, which increases the amount of liquid to be handled, resulting in an increase in equipment scale and cost It is not preferable because it causes an increase. For this reason, it is preferable to use a neutralizing agent having a concentration of 1N or more.

  The secondary neutralized slurry obtained by this neutralization treatment is subjected to a filtration treatment using a filtration membrane as a filter medium in the same manner as the solid-liquid separation treatment in the first neutralization step. And a secondary neutralized filtrate.

  In addition, like the primary neutralized starch and secondary neutralized starch described above, the precipitate obtained by adding an alkali neutralizing agent such as sodium hydroxide has very poor filterability. Is normal. For this reason, in neutralization, filterability may be improved by adding seed crystals. The seed crystal is preferably added in an amount of about 1 g / L or more with respect to the solution before the neutralization treatment.

[Hydroxide dissolution process]
In the hydroxide dissolution step S32, for the neutralized starch (secondary neutralized starch) mainly composed of scandium hydroxide recovered through the two-step neutralization treatment in the neutralization step S31 described above, It dissolves by adding an acid to obtain a hydroxide solution that becomes a redissolved solution. In the present embodiment, the redissolved solution thus obtained is used as an extraction starting solution for solvent extraction processing in a solvent extraction step S4 described later.

  The acid for dissolving the neutralized starch is not particularly limited, but sulfuric acid is preferably used. When sulfuric acid is used, the redissolved solution becomes a scandium sulfate solution.

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

  An extraction starting solution having an arbitrary scandium concentration can be obtained by adjusting the slurry concentration during dissolution with sulfuric acid or the like. For example, when 2N sulfuric acid is added and dissolved, the pH of the solution is preferably maintained in the range of 0.8 to 1.5, more preferably about 1.0, and this pH is maintained. By dissolving in such a manner, scandium hydroxide can be efficiently dissolved, and loss of scandium recovery due to undissolution can be suppressed. In addition, regarding pH range mentioned above, when pH exceeds 1.5 and there exists a possibility that melt | dissolution of a scandium hydroxide may not advance efficiently. On the other hand, if the pH is low, such as less than 0.8, a strongly acidic solution is obtained, and the amount of neutralizing agent added in the wastewater treatment to neutralize and dispose of the solution after recovering scandium increases. This is not preferable because it is costly and troublesome.

<2-4. Solvent extraction process>
Next, in the solvent extraction step S4, the redissolved solution (hydroxide solution) obtained through the concentration step S3 in which the scandium eluent is neutralized is used as the extraction start solution, and this is contacted with the extractant. To obtain an extraction liquid containing scandium. The redissolved solution used for solvent extraction is an acidic solution containing scandium and other impurity elements as described above, and these are referred to as “scandium-containing solutions”.

  Although it does not specifically limit as an aspect in solvent extraction process S4, for example, as shown in FIG.1 and FIG.2, extraction which mixed the scandium containing solution and the extractant which is an organic solvent, and extracted a little scandium An extraction step S41 for separating the post-organic solvent and the extraction liquid leaving the scandium, and mixing the sulfuric acid solution with the post-extraction organic solvent to separate the slight scandium extracted into the organic solvent into the aqueous phase. It is preferable to perform a solvent extraction process including a scrubbing step S42 for obtaining a post-washing solution and a back extraction step S43 for back-extracting impurities from the washed organic solvent by adding a back extractant to the washed organic solvent.

(1) Extraction step In the extraction step S41, a scandium-containing solution and an organic solvent containing an extractant are mixed, and impurities are selectively extracted into the organic solvent. Get. In the scandium recovery method according to the present embodiment, a solvent extraction process using an amine-based extractant is preferably performed in the extraction step S41. Thus, by performing a solvent extraction process using an amine extractant, impurities can be more efficiently and effectively extracted and separated from scandium.

  Here, the amine-based extractant has characteristics such as low selectivity with scandium and no need for a neutralizing agent during extraction. For example, Primene JM-T, which is a primary amine, secondary amine. An amine-based extractant known under a trade name such as LA-1, a tertiary amine, TNOA (Tri-n-octylamine), or TIOA (Tri-i-octylamine) can be used.

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

  Further, the volume ratio between the organic solvent and the scandium-containing solution at the time of extraction is not particularly limited, but the organic solvent molar amount is about 0.01 to 0.1 times the metal molar amount in the scandium-containing solution. It is preferable to make it.

(2) Scrubbing (washing) step When the scandium is slightly present in the solvent in which impurities are extracted from the scandium-containing solution in the extraction step S41 described above, the extract obtained in the extraction step S41 is back-extracted. Before that, the organic solvent (organic phase) is subjected to scrubbing (washing) treatment, and scandium is separated into an aqueous phase and recovered from the extractant (scrubbing step S42).

  In this way, the scrubbing step S42 is provided to wash the organic solvent and to separate the slight amount of scandium extracted by the extractant, whereby the scandium can be separated in the washing liquid, and the scandium recovery rate is further enhanced. be able to.

  As a solution (cleaning solution) used for scrubbing, a sulfuric acid solution, a hydrochloric acid solution, or the like can be used. Moreover, what added the soluble chloride and sulfate to water can also be used. Specifically, when a sulfuric acid solution is used as the cleaning solution, it is preferable to use one having a concentration range of 1.0 mol / L or more and 3.0 mol / L or less.

  The number of washing steps (number of times) depends on the type and concentration of the impurity element, and can be appropriately changed depending on the amine-based extractant used, the extraction conditions, and the like. For example, when the phase ratio O / A = 1 of the organic phase (O) and the aqueous phase (A) is set to 1, the scandium extracted into the organic solvent can be extracted from the organic solvent by setting the number of washing steps to about 3 to 5 steps. Separation can be achieved to below the detection limit.

(3) Back extraction process In back extraction process S43, an impurity is back-extracted from the organic solvent which extracted the impurity in extraction process S41. Specifically, in the back extraction step S43, a reverse extraction solution (back extraction start liquid) 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 S41. Impurities are back-extracted to obtain a back-extracted solution containing impurities.

  As described above, in the extraction process in the extraction step S41, preferably, an amine-based extractant is used as an extractant to selectively extract impurities. The extracted impurities can be separated from the organic solvent containing the amine-based extractant using the back extraction solution, and the extractant can be regenerated. In view of such a viewpoint, the back extract solution includes sodium carbonate, It is preferable to use a solution containing a carbonate such as potassium carbonate.

  The concentration of the carbonate-containing solution that is the back extraction solution is preferably about 0.5 mol / L or more and 2 mol / L or less, for example, from the viewpoint of suppressing excessive use.

  In addition, when the scrubbing process is performed on the organic solvent containing the extractant in the above-described scrubbing step S42, back extraction is similarly performed by adding and mixing the back extraction solution to the scrubbing extractant. Processing can be performed.

  Thus, the extractant after adding the carbonate solution such as sodium carbonate to the extractant after extraction or the extractant after scrubbing and performing the back extraction process to separate impurities is again in the extraction step S41. It can be used repeatedly as an extractant.

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

[Crystalling process]
The crystallization step S51 is a step of recovering the scandium contained in the extraction residual liquid by crystallizing it into a scandium salt precipitate.

  A method for crystallizing and recovering scandium is not particularly limited, and a known method can be used. For example, a method of adding and neutralizing an alkali to produce a precipitate of scandium hydroxide and recovering it. There is. Moreover, the method (oxalate-ized process) which produces | generates and collect | recovers the precipitate of an oxalate with an oxalic acid solution can also be used. These methods are preferable because they can more effectively separate impurities and obtain scandium crystals.

  In addition, about crystals, such as scandium hydroxide and scandium oxalate obtained by the above-described method, the solid-liquid separation is followed by washing, and by performing the treatment in the roasting step S52 described later, high purity scandium oxide and can do.

[Roasting process]
The roasting step S52 is a step in which the precipitate such as scandium hydroxide and scandium oxalate obtained in the crystallization step S51 is washed with water and dried, and then roasted. By undergoing such roasting treatment, it can be recovered as scandium oxide containing scandium with extremely high purity.

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

≪Reference example: Examination of pH and precipitation behavior in neutralization treatment≫
Based on a known method such as the method described in Patent Document 1, nickel oxide ore is subjected to pressure acid leaching using sulfuric acid, and the pH of the obtained leachate is adjusted to remove impurities, and then a sulfurizing agent is added. Then, nickel was separated and a solution after sulfidation was prepared. Table 1 below shows the concentrations of scandium, aluminum, and iron in the obtained post-sulfurized solution.

  Even when a neutralizing agent is added to the solution having this composition to form a precipitate, and a hydroxide containing scandium and other impurity components is obtained, the grade of scandium hydroxide is 0. Only about 1% by mass was obtained.

  Next, the post-sulfurized solution shown in Table 1 was subjected to ion exchange treatment by a known method using a chelate resin to obtain a scandium eluent having the composition shown in Table 2 below.

  Next, the obtained scandium eluent (composition of Table 2) was collected and placed in a container, and a 4N sodium hydroxide solution was added with stirring to adjust the pH of the solution to 1. .

  Subsequently, the stirring is stopped, the mixture is left to stand, the amount of the liquid is measured, and the supernatant liquid (primary neutralized filtrate) after the precipitate (primary neutralized starch) has settled is collected, and then the stirring is resumed. Then, a 4N sodium hydroxide solution was added again to adjust the pH of the solution to 2. Then, the stirring is stopped, the liquid is measured, the supernatant is collected (secondary neutralized filtrate), and stirring is repeated, so that each scandium in the range where the pH of the solution is 1 to 6 is obtained. A sample of the eluent was prepared.

  About each prepared sample, components, such as a scandium, iron, aluminum, nickel, were analyzed using ICP. In addition, the quantity calculated from the analysis value of each component and the liquid volume of each sampling is the quantity of the component present in the solution at each pH. The difference between the quantity of the components present in this solution and the initial quantity calculated from the analysis value of the scandium eluent shown in Table 2 above and the initial quantity is the amount of precipitation produced by pH adjustment (neutralization). Equivalent to. A ratio obtained by dividing the amount of precipitation by the initial amount described above was defined as the precipitation rate (%).

  FIG. 4 shows each pH and the precipitation rate of the components shown in Table 2. As shown in the graph of FIG. 4, it can be seen that the precipitation rate of iron increases in the region where the pH is 3 or more, and almost completely precipitates in the range of 4.5 to 5 or more. It can also be seen that the precipitation rate of aluminum increases when the pH exceeds 4.5. On the other hand, scandium also increases in precipitation rate when the pH exceeds 4.5, but the increase is slower than that of aluminum. Nickel begins to precipitate when the pH starts to exceed 6.

<< Example 1: Two-step neutralization process >>
(First stage neutralization)
According to the results shown in FIG. 4, the scandium eluent having the composition shown in Table 2 above is placed in a container, and a 4N sodium hydroxide solution is added with stirring to adjust the pH of the solution to 1. Stage neutralization was performed.

  After the first stage neutralization treatment, the obtained slurry (primary neutralization slurry) was subjected to solid-liquid separation at a pressure of 0.1 MPa using a hollow fiber membrane which is a filtration membrane made of an organic polymer resin. . As a result, a primary neutralized starch and a primary neutralized filtrate were obtained separately. The primary neutralized slurry subjected to solid-liquid separation was turbid in brown, but the primary neutralized filtrate obtained by separation was colorless and transparent, and no suspended matter was confirmed.

In addition, the filtration flow rate of the primary neutralization slurry per unit filtration area of the used filtration membrane is 400 L / m ² / hr for 30 minutes from the start of use, and backwash treatment with air every 30 minutes after that. When the operation was carried out (treatment time: 2 minutes), the filtration flow rate could be maintained at 350 L / m ² / hr or more until 4 months later.

  Further, the primary neutralized slurry subjected to the filtration treatment in Example 1 was collected, and the particle size of the solid particles contained in the slurry was analyzed by a laser diffraction / scattering method. As a result, the median diameter (D50) of the solid particles was 4.6 μm in terms of volume average diameter.

  By analyzing using ICP, the proportion (distribution) of the amount of precipitate produced in the amount of the scandium eluent whose composition is shown in Table 2 was evaluated as the precipitation rate (%). Table 3 below shows the precipitation rate by the first-stage neutralization treatment.

  As shown in Table 3, by neutralizing by adding a neutralizing agent until the pH of the solution becomes 4, it is possible to effectively precipitate iron and chromium as impurities in the solution as neutralized starch. And can be effectively separated from scandium distributed in the primary neutralized filtrate.

(Second stage neutralization)
Next, the obtained primary neutralized filtrate was put into a container, and 4N sodium hydroxide was added thereto, and a second-stage neutralization treatment was performed to adjust the pH of the solution to 6.

  After this second stage neutralization treatment, the resulting slurry (secondary neutralized slurry) was subjected to solid-liquid separation in the same manner as the first stage neutralization. A sum filtrate was obtained.

  By analyzing using ICP, the ratio (partition) of the quantity of precipitation produced in the quantity contained in the primary neutralized filtrate was analyzed as the precipitation rate (%). Table 4 below shows the precipitation rate due to the second-stage neutralization treatment.

  As shown in Table 4, almost 90% of the scandium remaining in the filtrate without precipitating mostly in the first stage neutralization was distributed to the secondary neutralized starch by the second stage neutralization. On the other hand, nickel, which is more basic than scandium, remained in the secondary neutralized filtrate without being precipitated by neutralization in both the first and second stages, and could be effectively separated from scandium. .

  According to the results shown in Table 4, it appears that most of the components of scandium eluent (composition of Table 2) precipitate iron and chromium even after the second stage neutralization. However, most of these components are already distributed to the primary neutralized starch and separated from scandium by the neutralization of the first stage, and the amount itself distributed to the secondary neutralized starch is suppressed. Yes.

  From the above results, by performing such a two-step neutralization treatment, among the components contained in the scandium eluent, the scandium was distributed into the secondary neutralized starch recovered by solidification. As shown in Table 5 below, the ratio (precipitation rate) was such that aluminum was conspicuous in addition to scandium, and other iron, chromium, nickel, and the like were effectively separated.

≪Scandium recovery≫
(Hydroxide dissolution treatment)
Next, a 2N sulfuric acid solution is added to the obtained secondary neutralized starch and dissolved while maintaining the pH at around 1, thereby obtaining a re-dissolved solution (hydroxide solution) shown in Table 6 below. It was.

(Solvent extraction process)
Next, 100 liters of a redissolved solution having the composition shown in Table 6 was used as an extraction starting solution, and an amine-based extractant (manufactured by Dow Chemical Co., Primene JM-T) was used as a solvent (manufactured by Shell Chemicals Japan Co., Shellsol A150). 50 liters of an organic solvent adjusted to 5% by volume was mixed and stirred at room temperature for 60 minutes for solvent extraction treatment. By this solvent extraction treatment, an extraction residue containing scandium was obtained. During extraction, no clad was formed, and phase separation after standing proceeded rapidly.

  The composition of each element contained in the extracted organic phase obtained by extraction was analyzed. In Table 7 below, the percentage of the value obtained by dividing the amount of each element contained in the extracted organic phase by the amount of each element contained in the original liquid before extraction (extraction start liquid) is calculated, and the percentage is calculated as the extraction rate ( %)).

  As can be seen from the extraction rate results shown in Table 7, most of the scandium contained in the original liquid before extraction was distributed to the extraction residual liquid through the solvent extraction process. Although not described in Table 7, other impurities migrated to the organic solvent and could be effectively separated from scandium.

  Subsequently, a sulfuric acid solution having a concentration of 1 mol / L is added to 50 liters of an organic solvent (extracted organic phase) slightly containing scandium obtained after the extraction treatment so that the phase ratio (O / A) is 1. 50 liters was mixed and stirred for 60 minutes for washing. Thereafter, the mixture was allowed to stand to separate the aqueous phase, and the organic phase was again mixed with 50 liters of a new sulfuric acid solution having a concentration of 1 mol / L and washed, and the aqueous phase was similarly separated. Such washing operation was repeated a total of 5 times.

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

  Subsequently, sodium carbonate having a concentration of 1 mol / L is mixed with the extracted organic phase after washing so as to have a phase ratio of O / A = 1/1, and the mixture is stirred for 60 minutes to perform a reverse extraction process. Was back extracted into the aqueous phase.

  The composition of various elements contained in the liquid after back extraction obtained by this back extraction operation was analyzed. In Table 8 below, the percentage of the value obtained by dividing the amount of various elements contained in the solution after back extraction by the amount of various elements extracted into the organic phase by the extraction treatment is calculated, and this is used as the recovery rate (%). Results are shown.

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

(Oxalate treatment)
Next, oxalic acid dihydrate (manufactured by Mitsubishi Gas Chemical Co., Inc.) crystals, which is twice the calculated amount of scandium contained in the extracted residual liquid, is obtained from the extracted residual liquid. Dissolved and stirred and mixed for 60 minutes to produce a white crystalline precipitate of scandium oxalate.

(Roasting treatment)
Next, the obtained scandium oxalate precipitate was subjected to suction filtration, washed with pure water, and 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 baked (baked) to obtain scandium oxide.

  Scandium oxide obtained by roasting was analyzed by emission spectroscopy. Table 9 below shows the removal rate (%) obtained by dividing the amount after roasting by the amount before the oxalate treatment.

As can be seen from the removal rate results shown in Table 9, aluminum and iron other than scandium, and other impurities, which are not shown in the table, can be almost completely removed, and the purity as scandium oxide (Sc ₂ O ₃ ). Extremely high purity scandium oxide exceeding 99.9% by weight could be obtained.

«Example 2: Filtration treatment in the neutralization step (about the fractional particle size of the filtration membrane)»
In the filtration treatment (solid-liquid separation) after the first-stage neutralization treatment in Example 1, Example 1 was used except that a filtration membrane having a fractional particle size (opening) of 0.02 μm was used. In the same manner as above, scandium oxide was finally produced.

  The primary neutralized slurry subjected to solid-liquid separation was turbid in brown, but the primary neutralized filtrate obtained by separation was colorless and transparent, and no suspended matter was confirmed.

In addition, the filtration flow rate of the primary neutralization slurry per unit filtration area of the used filtration membrane is 400 L / m ² / hr for 30 minutes from the start of use, and backwash treatment with air every 30 minutes after that. When the operation was carried out (treatment time: 2 minutes), the filtration flow rate could be maintained at 350 L / m ² / hr or more until 4 months later.

<< Example 3: Filtration treatment in the neutralization step (about two-stage filtration) >>
The primary neutralized starch obtained in Example 1 was sent to a filtration membrane (second group) of the same type as that used in the filtration treatment in Example 1 and filtered. That is, after filtering the primary neutralized slurry using the first filtration membrane (Example 1), the separated primary neutralized starch is filtered using the second filtration membrane. Stage filtration was applied.

  One day after the second-stage filtration treatment, the second filtration membrane was backwashed with water, and the obtained backwash waste water was collected to measure the suspended solids concentration. As a result, it was 2310 mg / L. The concentration of suspended matter in the backwash waste water with respect to the first filtration membrane is 335 mg / L, and the primary neutralization is performed by separating and collecting by performing at least two stages of filtration using a plurality of filtration membranes. It was found that the water content of starch can be removed effectively.

<< Comparative Example 1: Neutralization treatment of only one stage >>
The post-sulfurization solution having the same composition shown in Table 1 used in Example 1 was subjected to ion exchange treatment in the same manner as in Example 1 to obtain a scandium eluent having the same composition as in Table 2.

  Based on the results shown in FIG. 4, a 4N sodium hydroxide solution is added to the scandium eluent, and the solution is neutralized so that the pH of the solution falls within the range of 5-6. Generated. Thereafter, solid-liquid separation was performed to obtain a scandium hydroxide precipitate. Thus, unlike Example 1, the neutralization treatment was performed only in one stage. This method is the same as the conventional method.

  Next, sulfuric acid having a concentration of 2N was added to the obtained scandium hydroxide and dissolved while maintaining the pH at around 1, thereby obtaining a redissolved solution having the composition shown in Table 10 below.

  The re-dissolved solution obtained by the conventional method (composition shown in Table 10) and the re-dissolved solution obtained in Example 1, that is, the re-dissolved solution obtained after two-step neutralization treatment (composition shown in Table 6) , The scandium concentration was the same, but there was a large difference in the aluminum concentration and the iron concentration. That is, as in Example 1, it was confirmed that the two steps of neutralization treatment can effectively separate aluminum and iron as impurities.

«Comparative Example 2: Filtration treatment (use of filter cloth) in the neutralization step»
In the filtration treatment (solid-liquid separation) after the first-stage neutralization treatment in Example 1, treatment was performed in the same manner as in Example 1 except that a filter cloth was used instead of the filtration membrane. Tried to manufacture. A filter cloth having an air permeability of 0.33 cc / sec / cm ² was used.

The filtration flow rate of the primary neutralized slurry per unit filtration area of the filter cloth used was remarkably low despite the start of use. Further, even when the pressure was increased to 0.4 MPa, the flow rate increased only to about 113 L / m ² / h, so the filtration treatment was stopped.

«Comparative Example 3: Filtration treatment (use of filter cloth) in the neutralization step»
The treatment was performed in the same manner as in Comparative Example 2 except that the liquid was passed at a pressure of 0.4 MPa from the beginning of the filtration treatment, and finally scandium oxide was produced.

As a result, the initial flow rate was 113 L / m ² / h, but when the change in the flow rate was observed without performing a backwash process, the flow rate gradually decreased and 10 L was reached when one day passed after the start. / M ² / h. Moreover, although the deposit adhering on the filter cloth was removed and filtration was performed again, the recovery of the flow rate was not seen due to clogging.

Claims (7)

A first neutralization slurry is produced by adding a neutralizing agent to a solution containing scandium and subjecting it to a neutralization treatment, and a primary neutralized starch and a primary neutralized filtrate are obtained by solid-liquid separation. A neutralization step of
A neutralization agent is added to the obtained primary neutralized filtrate to carry out a neutralization treatment to produce a secondary neutralized slurry, and a secondary neutralized starch and a secondary neutralized filtrate are obtained by solid-liquid separation. A second neutralization step to obtain
A hydroxide dissolution step of adding an acid to the obtained secondary neutralized starch to obtain a hydroxide solution;
A method for recovering scandium comprising a concentration step having
In the solid-liquid separation in the first neutralization step, the primary neutralized slurry is subjected to a filtration treatment using a filter membrane as a filter medium to obtain a primary neutralized starch and a primary neutralized filtrate. Separate scandium recovery method. The method for recovering scandium according to claim 1, wherein the filtration membrane is a hollow fiber membrane. The method for recovering scandium according to claim 1, wherein the filtration membrane has a fractional particle size of 0.01 μm to 0.05 μm. The filtration membrane includes a through-hole having a diameter corresponding to 1/500 to 1/50 of the median diameter of the solid particles constituting the primary neutralized starch in the primary neutralized slurry. The method for recovering scandium according to 1 or 2. In the first neutralization step, a plurality of filtration processes are performed using a plurality of filtration membranes,
at least,
In the first-stage filtration treatment, the primary neutralized starch is adhered to the surface of the first filtration membrane by filtering the primary neutralized slurry using the first filtration membrane. Separate and
5. The first-stage neutralized starch separated from the first filtration membrane is filtered using a second filtration membrane in the second-stage filtration treatment. 5. Of recovering scandium. The water or air is circulated through the filtration membrane from a direction opposite to the filtration direction of the primary neutralization slurry after the filtration treatment is performed on the primary neutralization slurry using the filtration membrane. The method for recovering scandium according to any one of 1 to 5. When the flow rate of the primary neutralized filtrate passing through the filtration membrane is measured and the flow rate corresponds to a ratio of 60% to 90% of the flow rate when the use of the filtration membrane is started, the filtration membrane The method for recovering scandium according to any one of claims 1 to 6, wherein a washing treatment with sulfuric acid is performed on the catalyst.

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