JP5792079B2 - Rare earth element separation and recovery method - Google Patents

Description

  The present invention relates to a technique for separating and collecting rare earth elements, and more particularly to a method for separating and collecting rare earth elements from a composition containing a plurality of types of rare earth elements.

  In recent years, the importance of sustainable global environmental protection has been recognized, and industrial systems and traffic systems that can minimize the use of fossil fuels have been vigorously developed. Examples of such environmentally compatible systems and products include wind power generation systems, railway systems, hybrid vehicles, electric vehicles, energy-saving air conditioners, and the like.

  One of the main devices of these environmentally-friendly systems and products is high-efficiency rotating electrical machines (motors and generators), and magnets containing rare earth elements (so-called rare earth magnets) are widely used in these high-efficiency rotating electrical machines. ing. For example, rare earth magnets used in rotating electrical machines such as drive motors for hybrid vehicles and compressors for air conditioners are required to have a high coercive force even in high temperature environments (eg, about 200 ° C). In addition to neodymium, iron, and boron It contains a lot of expensive and heavy heavy rare earth elements (for example, dysprosium). Rare earth magnets are indispensable now, and demand is expected to increase in the future.

  On the other hand, since rare earth elements are difficult and expensive to separate and purify a single element, development of technologies and alternative materials for reducing the amount of use while maintaining the performance of magnets has been intensively studied. However, it seems that it will take time to put these technologies into practical use. Therefore, it is an important technique to separate and recover rare earth elements from waste materials (for example, rare earth magnets in waste motors, shavings (sludge) generated in the production process of rare earth magnets) and recycle them.

  For example, Patent Document 1 discloses a divalent trivalent mixture in which the average valence of two or more rare earth ions is 2 or more and 3 or less by halogenating a rare earth element in a mixture containing a plurality of rare earth elements or compounds thereof. Producing a mixture containing a rare earth halide which is not dissolved in an aqueous solution or an organic solvent, and then utilizing the difference in properties between the divalent rare earth halide and the trivalent rare earth halide, There has been proposed a rare earth element separation method characterized by separating elements into at least two groups. According to Patent Document 1, it is said that the separation factor between rare earth elements can be dramatically increased, and mutual separation can be performed more efficiently than in the conventional method. Furthermore, when separating from rare earth concentrates such as phosphates, steps such as acid dissolution, filtration, precipitation removal of impurities, concentration, neutralization, and drying, which are essential for conventional wet methods, can be omitted. It is said that the cost can be greatly reduced.

  Patent Document 2 discloses a method for recovering a rare earth element from a material containing a rare earth element and an iron group element, and a rare earth element such as a rare earth magnet scrap or sludge is added to a gaseous or molten iron chloride. Select a rare earth element as a chloride from the substance by contacting a substance containing an iron group element and proceeding the chlorination reaction of the rare earth element in the substance while maintaining the metallic state of the iron group element in the substance. There has been proposed a method for recovering a rare earth element characterized by having a step of recovering automatically. According to Patent Document 2, it is possible to extract and separate only high-purity rare earth components from materials containing rare earth elements and iron group elements, such as rare earth magnet scraps or sludges, especially wastes, and thus lower cost rare earth elements. It is said that the magnet recycling law can be established.

JP 2001-303149 A JP 2003-73754 A

  As mentioned above, the demand for rare earth magnets is expected to increase in the future. On the other hand, rare earth elements such as neodymium and dysprosium, which are rare earth magnet raw materials, are unevenly distributed on the earth, and technologies for separating, recovering and recycling rare earth elements from the viewpoint of ensuring the stability of raw materials and effective use of resources. Is becoming more important than before.

  Accordingly, an object of the present invention is to provide a method capable of separating and recovering rare earth elements in a simpler and higher yield than the prior art.

(I) One aspect of the present invention is a method for separating and recovering multiple types of rare earth elements to achieve the above object,
A step of adding metal M in a predetermined amount to the mixture containing halides of the plurality of rare earth elements (step A), and heating the mixture to which the metal M has been added under atmospheric pressure. A step of reaching a chemical equilibrium state where a divalent halide of rare earth element and a halide of the metal M are formed (Step B), and the system that has reached the chemical equilibrium state is evacuated to evacuate the plurality of types. A step (Step C) of generating a rare earth element metal and a trivalent halide from a rare earth element divalent halide by a disproportionation reaction, and vacuum distillation inside the system. Separating the mixture into a distillate condensate and a residue of the one kind of rare earth element trivalent halide (step D), and the metal M is a metal M in an environment of the chemical equilibrium state. And metal M oxide and metal M There is provided a method for separating and recovering a rare earth element in which the three phases of the rare earth element can coexist and the predetermined amount is more than the chemical equivalent to the halide of the plurality of rare earth elements.

(II) Another aspect of the present invention is a method for separating and recovering multiple types of rare earth elements to achieve the above object,
A step of producing a mixture containing chloride by chlorinating the compound containing the plurality of rare earth elements, iron and boron using iron chloride (step E), and for the mixture containing the chloride A step of separating the mixture of the plurality of rare earth element chlorides from the mixture containing the chloride by distillation (Step F), and the metal M is disposed in the mixture of the plurality of rare earth element chlorides. A step of adding quantitatively (step A ′) and a chemistry in which the mixture added with the metal M is heated under atmospheric pressure to produce the dichlorides of the rare earth elements and the chloride of the metal M The step of reaching the equilibrium state (step B ′) and the system that has reached the chemical equilibrium state are evacuated to disproportionately react from one kind of rare earth element dichloride of the plurality of kinds by the disproportionation reaction. One kind of rare earth metal and A step of generating chloride (step C ′), and a step of separating the mixture into a distillation condensate and a residue of the rare earth trichloride of the one kind by performing vacuum distillation in the system (step D ′) The metal M is a metal in which three phases of the metal M, an oxide of the metal M, and a chloride of the metal M can coexist in the environment of the chemical equilibrium state, and the predetermined amount is The present invention provides a method for separating and recovering rare earth elements that are in excess of the chemical equivalent to the chloride of the plurality of types of rare earth elements.

In addition, the present invention can be modified or changed as follows in the rare earth element separation and recovery methods (I) and (II).
(I) The step C and the step D are performed simultaneously.
(Ii) The step C ′ and the step D ′ are performed simultaneously.
(Iii) The oxygen potential of the oxidation reaction of the metal M is lower than that of the plurality of rare earth elements.
(Iv) The halogen potential of the halogenation reaction of the metal M is lower than that of the one kind of rare earth element and higher than that of the other one kind of rare earth element among the plurality of kinds.
(V) The metal M is at least one selected from thulium, terbium, erbium, holmium, and yttrium.
(Vi) The one kind of rare earth element is dysprosium.
(Vii) The plurality of rare earth elements further include at least one selected from neodymium, gadolinium, and samarium.
(Viii) The halogen is chlorine.

  According to the present invention, it is possible to provide a method capable of separating and recovering rare earth elements more easily and with a higher yield than the prior art. As a result, rare earth elements (for example, neodymium, dysprosium, etc.) can be separated from waste materials (for example, non-use, defective products, sludge, etc.) of rare earth magnets at a low cost with high accuracy. Can be played as. This can contribute to effective utilization of resources and stable securing of rare earth materials.

It is a cross-sectional schematic diagram which shows the state immediately after a separation process in an example of the distillation apparatus used for the separation process of rare earth elements and other elements. It is a graph which shows the mass distribution of the condensed phase adhering to the mass of the residue in a crucible after performing the distillation separation process in Example 1, and a division | segmentation inner wall. It is the graph which showed the compositional analysis result by XRF of the residue in a crucible in Example 1 (except Y chip | tip) and the condensed phase of the division | segmentation inner wall 8e-8g. It is a graph which shows Dy ratio and Nd ratio computed from FIG. 3A, Formula (1), and Formula (2). 2 is an XRD chart of a powdery residue in a crucible in Example 1. FIG. 2 is an XRD chart of a molten residue adhering to a crucible bottom in Example 1. FIG. 3 is an XRD chart of a condensed phase of a divided inner wall 8g in Example 1. FIG.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. In addition, this invention is not limited to embodiment taken up here, A combination and improvement are possible suitably in the range which does not change a summary.

[First embodiment of the present invention]
(Basic procedure and principle of rare earth element separation)
The basic procedure and principle of the rare earth element separation method in the present invention will be described. The separation method of the present invention is characterized in that solid-gas separation utilizing disproportionation reaction and solid-solid separation are combined. Here, as an example, separation in the case of using a mixture of neodymium chloride and dysprosium chloride will be described, but the present invention is not limited to this.

First, metal yttrium (Y) is added and mixed as metal M to a mixture of neodymium trichloride (NdCl ₃ ) and dysprosium trichloride (DyCl ₃ ). Although there is no special limitation in the shape of the metal yttrium to add, it is preferable that it is a granular shape, lump shape, and chip shape larger than a rare earth chloride so that it may isolate | separate in a post process easily.

  The mixture is then heated to 700-900 ° C under atmospheric pressure. Then, the mixture of rare earth chlorides to which metal yttrium is added is in a chemical equilibrium state as shown in the following chemical formulas (1) and (2).

  As can be seen from the chemical formulas (1) and (2), metal yttrium acts as a reducing agent. Moreover, a chemical reaction can be further advanced to the right side by adding excessive metal yttrium. In other words, in order to advance the formation of rare earth dichloride, when adding and mixing metal yttrium to the rare earth chloride mixture, an excess amount of metal yttrium is added to the chemical equivalent to the rare earth chloride in the mixture. It is preferable to do.

Next, the system that has reached the above chemical equilibrium state is evacuated. There is no particular limitation on the method and degree of evacuation. Under reduced pressure environment, the dysprosium dichloride (DyCl ₂ ) generated by the chemical formula (2) becomes unstable, causing a disproportionation reaction as shown in the chemical formula (3) below, and the metal dysprosium (Dy) Decomposes into dysprosium trichloride (DyCl ₃ ). Neodymium dichloride (NdCl ₂ ) has a sufficiently small degree of disproportionation reaction.

Next, the inside of the system is heated to 1000-1100 ° C. and vacuum distilled. Here, NdCl ₂ generated by the chemical formula (1) has a low vapor pressure, chemical formula (1), yttrium trichloride produced in (2) (YCl ₃₎ and vapor pressure and DyCl ₃ generated by the chemical formula (3) Therefore, YCl ₃ and DyCl ₃ are distilled and condensed in a low temperature region. On the other hand, NdCl ₂ , excess Y metal and Dy metal generated by the chemical formula (3) remain as a residue. The above-described step of evacuating the system to cause a disproportionation reaction and the present step of vacuum distillation of the system to separate the distillation condensate and the residue may be performed continuously, You may do it simultaneously. From the viewpoint of simplifying the procedure, it is preferable to perform both steps simultaneously. Note that performing simultaneously includes starting heating (temperature increase) and evacuation at the same time.

As described above, since the Y metal is added in the form of large particles, lumps or chips, it can be easily separated from the residue. Since the Dy metal produced by the chemical formula (3) is also agglomerated, it can be easily separated. Further, when an iron (Fe) crucible is used as the crucible, it reacts with the crucible to produce an Fe—Y alloy or an Fe—Dy alloy. On the other hand, the rare earth chloride is usually in the form of powder or solidified, but even in the latter case, it can be pulverized with a simple impact. Therefore, they can be easily separated mechanically, and Y metal, Dy metal, and NdCl ₂ can be separated and recovered from the residue. Further, DyCl ₃ and YCl ₃ can be recovered from the distillation condensate. DyCl ₃ and YCl ₃ can be separated by a conventional method (for example, a solvent extraction method).

(Guidelines for selecting metal M to be added)
Next, guidelines for selecting the metal M to be added to the rare earth chloride mixture will be described. Table 1 shows the calculation results of the oxygen potential of the oxidation reaction in various metals, and Table 2 shows the calculation results of the chlorine potential of the chlorination reaction in various metals. The units of oxygen partial pressure (pO ₂ ) and chlorine partial pressure (pCl ₂ ) in the table are “atm”, respectively.

  In addition to the action as a reducing agent described above, the metal M to be added desirably has an action as a deoxidizing agent in order to prevent oxidation of rare earth elements to be separated. In other words, a metal that oxidizes at a lower oxygen potential than the rare earth element to be separated is desirable. Looking at Table 1 from that point of view, Tb (terbium), Tm (thulium), Ho (holmium), Ca (calcium), Er (erbium), and other metals that oxidize at a lower oxygen potential than Dy (dysprosium) Sc (scandium), Y (yttrium) are mentioned. By adding a metal that is easier to oxidize than the rare earth element to be separated, the oxidation of the rare earth element to be separated can be suppressed even if oxygen components remain / mixed in the system for separating the rare earth element. .

  On the other hand, when considering the chlorination reaction, the chlorine potential of the chlorination reaction of the metal M to be added is higher than the chlorination potential at which multiple types of rare earth elements to be separated become metals, and multiple types of rare earth elements are trichlorinated. It is desirable that it be lower than the potential to reduce the product to dichloride. From this point of view, Table 2 shows Mg (magnesium), Tm, Tb, Er, Ho, Y, and Gd (gadolinium) as metals that generate chlorination at a chlorine potential higher than both Nd and Dy.

Therefore, as the metal M to be added, Tm, Tb, Er, Ho, and Y that are the common metal elements described above are preferable. In other words, it can be said that the metal M to be added is a metal in which the three phases of the metal M, the oxide of the metal M, and the chloride of the metal M can coexist in the environment of the chemical formulas (1) to ( 2 ). The state in which the three phases of the metal M, the metal M oxide, and the metal M chloride coexist is also referred to as a “triple equilibrium state”.

  Further, as described above, the present invention is not limited to a mixture of neodymium chloride and dysprosium chloride. For example, a mixture of gadolinium chloride and dysprosium chloride, samarium chloride and dysprosium chloride It can also be applied to a mixture thereof. In the above description, a system using chlorine (chloride) as an example of halogen is described. However, the same function and effect are not limited to chloride, but also apply to iodide, fluoride, and bromide. be able to.

[Second Embodiment of the Present Invention]
(Separation of rare earth elements from compounds containing rare earth elements)
Next, a method for separating and collecting rare earth elements from rare earth magnets (compounds of rare earth elements and other elements) that are actual starting materials in separation and collection using the above principle will be described.

(Separation process of rare earth elements and other elements)
First, a procedure for obtaining a mixture of neodymium chloride and dysprosium chloride from rare earth magnet sludge containing neodymium, dysprosium, iron, and boron as main components will be described. Actual rare earth magnet sludge often contains praseodymium, which is another rare earth element, but the physical and chemical behavior of neodymium and praseodymium are very similar, so here praseodymium is on the neodymium side. Think of it as accompanying.

  The separation process (procedure) of rare earth elements and other elements is basically the same as the process disclosed in Patent Document 2, but specifically, is as follows. As described above, it is preferable to use waste (for example, non-use, defective products, sludge, etc.) as the rare earth magnet for element separation, and it should be in powder form from the viewpoint of separation and recovery efficiency (chemical reaction efficiency). Is preferred. In the following, separation of rare earth magnets from sludge powder will be described as an example.

  FIG. 1 is a schematic cross-sectional view showing a state immediately after the separation step in an example of a distillation apparatus used in the separation step of rare earth elements and other elements. As shown in FIG. 1, the distillation apparatus 20 is a cylindrical vertical electric furnace having upper and lower two-stage heaters (upper heater 1, lower heater 2, thermocouples 3, 3 ′) on the outer periphery of a vertical furnace core tube 4. Basic structure. The core tube 4 has an exhaust port 5, a gas introduction port 6, and an upper lid 7 so that the inside can be exhausted and replaced with gas. The exhaust port 5 is connected to a rotary pump or the like (not shown). In addition, in FIG. 1, although the bottomed core tube 4 was illustrated, the structure sealed with a lower cover may be sufficient. Moreover, the installation location of the exhaust port 5 and the gas introduction port 6 is not particularly limited.

  A cylindrical multistage inner wall 8 (divided inner walls 8a to 8m) is disposed inside the core tube 4. A crucible 9 containing a material to be separated by distillation is installed inside the lowermost stage (divided inner wall 8a) of the inner wall 8.

First, the sludge powder dried using a dryer or the like is crushed. Thereafter, the crushed sludge powder, graphite powder, and ferrous chloride (FeCl ₂ ) in excess of the chemical equivalent are mixed and filled in the crucible 9. The crucible 9 is installed inside the lowermost stage (divided inner wall 8a) of the inner wall 8, and the distillation apparatus 20 is set up. The inside of the furnace tube 4 is evacuated and replaced with an inert gas (for example, argon gas), and then heated at 700 to 900 ° C. under atmospheric pressure while flowing the inert gas. As a result of this heat treatment, the mixed material in the crucible 9 chemically reacts, and a mixture of rare earth chloride, unreacted ferrous chloride, iron or an iron group element alloy is obtained in the crucible 9 (including chloride). Producing a mixture). The oxygen component fixed in the rare earth magnet sludge powder is gasified by the graphite powder (carbon component), and the generated gas is discharged out of the system by the flowing inert gas.

  Next, the obtained rare earth chloride, ferrous chloride, iron or alloy of iron group elements is subjected to distillation separation by heating to 900-1100 ° C. while reducing the pressure with a rotary pump or the like. At this time, it is preferable that the temperature of the upper heater 1 is maintained at 400 to 500 ° C. and the temperature of the lower heater 2 is maintained at 700 to 1100 ° C. As a result of this distillation separation, a condensed phase 10 of ferrous chloride is formed on the inner wall 8 in the region of the upper heater 1 (the divided inner walls 8g to 8h in FIG. 1), and the inner wall 8 in the region of the lower heater 2 ( In FIG. 1, a condensed phase 11 of rare earth chloride is formed on the divided inner walls 8d to 8e), and an alloy of iron and an iron group element remains as a residue in the crucible 9 (mixture of a plurality of types of rare earth element chlorides). Step). When the condensed phase 11 of the divided inner walls 8d to 8e is recovered, a mixture of plural kinds of rare earth chlorides is obtained. In the case of this example, specifically, a mixture of neodymium chloride and dysprosium chloride is obtained.

(Separation process of multiple types of rare earth elements)
Next, a process of separating rare earth elements from each other from the collected mixture of a plurality of rare earth chlorides will be described. Also in this step, the distillation apparatus 20 shown in FIG. 1 can be used. A mixture of a plurality of kinds of collected rare earth chlorides and an excess amount of metal yttrium more than the chemical equivalent to the rare earth chlorides are mixed and filled in a crucible 9 made of molybdenum. At this time, since the rare earth chloride is rich in hygroscopicity, it is desirable to quickly weigh, mix and fill in a dry environment (for example, a drying room, a glove box, etc.) in order to avoid excessive moisture absorption. Further, graphite powder may be added for the purpose of removing excess oxygen in the system to be chemically reacted as much as possible.

The filled crucible 9 is installed inside the lowermost stage (divided inner wall 8a) of the inner wall 8, and the distillation apparatus 20 is set up. The inside of the furnace core tube 4 is evacuated and replaced with an inert gas such as argon gas, and then heated at 700 to 900 ° C. for 6 to 24 hours under atmospheric pressure while flowing an inert gas. As a result of this heat treatment, the mixed material in the crucible 9 chemically reacts to reach the chemical equilibrium state shown in the chemical formulas (1) and (2) (step of reaching the chemical equilibrium state). As described above, since the metal yttrium in excess of the chemical equivalent to the rare earth chloride is mixed, the crucible 9 substantially contains neodymium dichloride (NdCl ₂ ) as a product. , Dysprosium dichloride (DyCl ₂ ) and yttrium trichloride (YCl ₃ ), and metal yttrium (Y) as an unreacted product are obtained.

Next, the inside of the system is evacuated with a rotary pump or the like while maintaining the temperature inside the system. As a result, a disproportionation reaction as shown in chemical formula (3) occurs in dysprosium dichloride, and metal dysprosium (Dy) and dysprosium trichloride (DyCl ₃ ) are decomposed and formed (disproportionation reaction step) ).

Next, distillation separation is performed by further heating while continuing to evacuate the system. At this time, it is preferable that the temperature of the upper heater 1 is maintained at 400 to 500 ° C. and the temperature of the lower heater 2 is maintained at 700 to 1100 ° C. By this vacuum distillation, DyCl ₃ and YCl ₃ with high vapor pressure are sublimated, and a condensed phase 10 is formed on the inner wall 8 (for example, the divided inner walls 8g to 8h) in the region of the upper heater 1 (that is, in the low temperature region). The At the same time, since DyCl ₃ in the crucible 9 decreases, the disproportionation reaction of the chemical formula (3) further proceeds to the right side. In the crucible 9, unreacted Y metal, NdCl ₂ produced by the chemical formula (1) and Dy metal produced by the chemical formula (3) remain as residues (step of solid-gas separation by vacuum distillation).

After the distillation separation, the distillation apparatus 20 is cooled to room temperature. Regarding the residue in the crucible 9, since the shape and size of Y metal, Dy metal and NdCl ₂ are different as described above, they can be mechanically separated and recovered (solid and solid separation depending on the shape and size). Process). Neodymium oxide can be recovered by baking the separated NdCl _{2 at} about 900 ° C. in the atmosphere.

On the other hand, the recovered condensed phase 10 is first charged and stirred in pure water to prepare an aqueous solution of dysprosium chloride and yttrium chloride. After adjusting the pH of the aqueous solution, a precipitant (eg, ammonium carbonate ((NH ₄ ) ₂ CO ₃ ), ammonium hydrogen carbonate (NH ₄ HCO ₃ ), sodium carbonate (Na ₂ CO ₃ ), hydrogen carbonate Addition of sodium (NaHCO ₃ ), oxalic acid ((COOH) ₂ ), sodium oxalate ((COONa) ₂ , ammonium hydroxide (NH ₄ OH), etc.), dysprosium and yttrium salts that are sparingly soluble in water To produce a precipitate. After the precipitate is filtered and dried, a mixture of dysprosium oxide and yttrium oxide can be recovered by baking at about 900 ° C. in the atmosphere.

  Although detailed description is omitted, dysprosium oxide and yttrium oxide can be separated by a conventional method (for example, solvent extraction method) after acid leaching. After the separated dysprosium salt and yttrium salt are dried, dysprosium oxide and yttrium oxide can be recovered by baking in the atmosphere at about 900 ° C.

(Reduction process to rare earth metal)
It can reduce | restore to metallic neodymium, metallic dysprosium, and metallic yttrium by performing molten salt electrolysis using a fluoride bath etc. with respect to each of the collected neodymium oxide, dysprosium oxide, and yttrium oxide. These rare earth metals can be reused as raw materials for rare earth magnets.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited to these.

[Example 1]
Experimental verification of separation and recovery from rare earth chloride mixtures was carried out. Anhydrous neodymium trichloride (NdCl ₃ ) powder and anhydrous dysprosium trichloride (DyCl ₃ ) powder were used as starting materials for the rare earth chloride. As starting powder reagents, 3N grades manufactured by Kojundo Chemical Laboratory Co., Ltd. were used. As the metal M to be added, a metal yttrium (Y) chip (manufactured by Wako Pure Chemical Industries, Ltd., about 5 × about 5 × about 2 mm ³ , purity 99.9%) was used. In addition, since metal yttrium is easily oxidized by an oxygen source in the atmosphere, a metal yttrium stored in oil was prepared and used after removing the oil immediately before use.

In a drying chamber, 2.5 g of NdCl ₃ powder, 2.5 g of DyCl ₃ powder, and 1.16 g of Y chip were weighed and put into a crucible 9 made of molybdenum (Mo) and mixed. Using the distillation apparatus 20 shown in FIG. 1, a crucible 9 containing a mixed material was installed inside the lowermost stage (divided inner wall 8a) of the inner wall 8, and the inner wall 8 was assembled. The inner wall 8 is a cylindrical multistage type, and is divided into divided inner walls 8a to 8m (made of graphite, each having an inner diameter of 50 mm and a height of 50 mm). Thereby, it becomes easy to collect the distilled condensed phase, and the distribution of the distilled condensed phase can be investigated. The Mo crucible 9 and the graphite divided inner walls 8a to 8m were previously baked in a vacuum at 800 ° C. for 3 hours, and mass measurement was performed.

  After assembling the inner wall 8, the core tube 4 was closed with the upper lid 7, and the inside of the core tube 4 was depressurized with a rotary pump through the exhaust port 5. Next, the mixture was heated at 300 ° C. for 12 hours or more, and the mixed material and the inside of the furnace core tube 4 were vacuum-dried. Then, argon gas was introduced from the gas introduction port 6 to bring the system to atmospheric pressure. In order to remove oxygen components remaining in the core tube 4 and the gas inlet 6 as much as possible, the gas exhausting / introducing operation was repeated five times.

  Then, while flowing argon gas, heat treatment was performed for 6 hours with the temperature of the upper heater 1 in the upper low temperature section set to 400 ° C and the temperature of the lower heater 2 set to 800 ° C, and the chemical formulas (1) and (2) An equilibrium state was reached. Next, with the temperature inside the system maintained, the inside of the system was evacuated with a rotary pump to cause a disproportionation reaction as shown in Chemical Formula (3).

  Next, while continuing to evacuate the system, distillation separation was performed for 3 hours with the temperature of the upper heater 1 in the upper low temperature part set to 500 ° C. and the temperature of the lower heater 2 set to 1000 ° C. By this vacuum distillation, a condensed phase 10 was formed on the inner wall 8 in the low temperature region. After distillation, it was cooled to room temperature while being evacuated.

  After cooling, various evaluations were performed on the samples (residues in the condensed phase 10 and the crucible 9) that were vacuum distilled. First, in order to investigate the distribution of the condensed phase 10, the mass of the condensed phase 10 for each divided inner wall was measured by taking the difference between the masses of the divided inner walls 8a to 8m before and after the experiment. The mass of the residue in the crucible 9 was also measured. In addition, the residue in the crucible 9 and the condensed phase 10 adhering to the inner wall of the division are sampled and subjected to composition analysis by X-ray fluorescence analysis (XRF), and X-ray diffraction (XRD). The identification of the precipitated phase was performed.

The Nd and Dy separation rates and yields were calculated from the residue and aggregate composition obtained by XRF. The Dy amount calculated from the Dy concentration obtained by XRF and the mass of the residue or aggregated phase is expressed as [Dy], and the Nd amount calculated from the Nd concentration obtained by XRF and the mass of the residue or aggregated phase as well. Is expressed as [Nd], and the Dy ratio (R _Dy ) and Nd ratio (R _Nd ) were determined from the following formulas (1) and (2), respectively.

The Dy yield (Yield _Dy ) and the Nd yield (Yield _Nd ) are represented by the following formula (3), formula (Dy) ₀ and [Nd] ₀ , respectively. Obtained from (4).

  FIG. 2 is a graph showing the mass of the residue in the crucible after the distillation separation process in Example 1 and the mass distribution of the condensed phase adhering to the divided inner wall. As shown in FIG. 2, about 3.5 g of residue was confirmed in the crucible 9, and a remarkable mass increase (about 0.7 to 0.9 g) was confirmed on the divided inner walls 8e to 8g.

  More specifically, as the residue of the crucible 9 made of Mo, a molten residue and a powder residue were confirmed. It was also found that the Y chip that was introduced was mixed in the residue while retaining the chip shape. The remaining Y chip could be easily removed. When the remaining Y chip was weighed, it was about 0.7 g. That is, it was considered that about 0.7 g of the Y component added and mixed remained as Y metal, and about 0.4 g was salified and existed in the system.

  3A is a graph showing the result of XRF composition analysis of the residue in the crucible (excluding the Y chip) and the condensed phase of the divided inner walls 8e to 8g in Example 1. FIG. FIG. 3B is a graph showing the Dy ratio and the Nd ratio calculated from FIG. 3A, formulas (1) and (2).

  As shown in FIG. 3A, the residue (excluding the Y chip) in the crucible 9 was mainly composed of Cl, Nd, and Dy, and Y was also detected slightly. Specifically, Cl was 24.3%, Nd was 41.2%, and Dy was 30.4%. Dy metal and Nd chloride were mechanically easily separated because of their different shapes and sizes.

  On the other hand, Cl, Y, and Dy were remarkably detected in the condensed phase of the divided inner walls 8e to 8g, and the Nd content was low. Specifically, in the divided inner wall 8e, Cl was 24.3%, Y was 19.7%, Dy was 29.1%, and Nd was 9.5%. In the divided inner wall 8f, Cl was 41.1%, Y was 20.6%, Dy was 28.2%, and Nd was 10.0%. Moreover, in the divided inner wall 8g, Cl was 49.2%, Y was 25.6%, Dy was 22.4%, and Nd was 2.8%.

As shown in FIG. 3B, the Dy ratio in the condensed phase was 75.5% for the divided inner wall 8e, 73.9% for the divided inner wall 8f, and 89.0% for the divided inner wall 8g. Since the Dy ratio (initial Dy ratio) at the time of preparing the mixed material is 50.0%, it can be seen that the material is well separated by the separation process of the present invention. Further, when the yield of Dy was calculated from the average Dy ratio in the condensed phase of the divided inner walls 8e to 8g, “Yield _Dy = 59.5%” was obtained.

4 is an XRD chart of the powdery residue in the crucible in Example 1. FIG. As shown in FIG. 4, in the powdery residue in the crucible 9, the peak of NdCl ₂ was mainly detected, and other peaks of YOCl, Y ₃ O ₄ Cl (Y ₂ O ₃ .YOCl), and DyOCl were detected. . It was considered that oxychloride was produced due to oxygen components remaining / mixed in the system.

FIG. 5 is an XRD chart of the molten residue adhering to the bottom of the crucible in Example 1. As shown in FIG. 5, in the molten residue adhering to the bottom of the Mo crucible 9, Dy metal and YOCl were detected in addition to the Mo metal caused by the crucible.

6 is an XRD chart of the condensed phase of the divided inner wall 8g in Example 1. FIG. As shown in FIG. 6, DyCl ₃ and YCl ₃ were mainly detected, and some NdCl ₃ was detected.

  From the above measurement / analysis results, it can be said that the chemical reaction and the separation process shown in the first embodiment of the present invention have been demonstrated.

[Example 2]
We investigated the separation and recovery of rare earth elements from waste materials of rare earth magnets (RE ₂ Fe ₁₄ B, RE: rare earth elements) containing neodymium, dysprosium, praseodymium, iron and boron. The mass composition of the rare earth magnet used was 61.2% Fe-23.1% Nd-3.5% Dy-2.0% Pr-1.0% B. The waste magnet is a defective product because cracks, chips, etc. occur after nickel plating in the manufacturing process.

  First, the waste magnet was roughly pulverized by heating at 800 ° C. in a hydrogen atmosphere using an electric furnace. As described above, the waste magnet was nickel-plated. However, since the nickel-plated film can be peeled off by the hydrogen pulverization step, the peeled-off plated film was separated from the magnet powder by sieving.

The obtained magnetic powder was mixed with FeCl ₂ powder as a chlorine source and placed in an iron crucible 9 and placed in the distillation apparatus 20 shown in FIG. The Inconel furnace core tube 4 is evacuated with a rotary pump and then replaced with argon gas. The temperature of the lower heater 2 is set to 800 ° C., the temperature of the upper heater 1 is set to 400 ° C., and maintained for 10 to 15 hours. Reaction was performed. Thereafter, the temperature of the lower heater 2 was raised to 1000 ° C., the temperature of the upper heater 1 was raised to 500 ° C., and vacuum distillation was performed for 3 hours while exhausting with a rotary pump. After vacuum distillation, the furnace core tube 4 was cooled in the furnace while maintaining a vacuum.

  After the furnace was cooled to room temperature, the state of the condensed phase adhering to the inner wall 8 (divided inner walls 8a to 8m) was observed, and light purple powder, light green powder, and white powder were condensed in the 500 to 800 ° C region. However, an orange powdery substance was condensed in the region below 500 ° C. It was observed that these condensed substances absorb moisture in a short time when left in a general room. On the other hand, when these condensed substances were quickly recovered and semi-quantitatively analyzed with an XRF apparatus, the condensed substances in the 500 to 800 ° C region mainly consisted of chlorides of rare earth elements (neodymium, praseodymium, dysprosium), and the content rate was It was confirmed to be 98%.

  If the separation process similar to Example 1 described above is performed on the rare earth chloride mixture recovered above, neodymium, praseodymium and dysprosium can be separated from each other.

1 ... Upper heater, 2 ... Lower heater, 3, 3 '... Thermocouple, 4 ... Core tube, 5 ... Exhaust port,
6 ... Gas inlet, 7 ... Upper lid, 8 ... Inner wall, 8a-8m ... Divided inner wall, 9 ... Crucible,
10, 11 ... condensed phase, 20 ... distillation equipment.

Claims (15)

A method for separating and recovering multiple types of rare earth elements,
Adding metal M in a predetermined amount to the mixture containing halides of the plurality of rare earth elements (step A);
Heating the mixture to which the metal M is added under atmospheric pressure to reach a chemical equilibrium state in which the divalent halides of the plurality of rare earth elements and the halide of the metal M are formed (step B); ,
By evacuating the system that has reached the chemical equilibrium state, the rare earth element metal and trivalent halide are converted from the rare earth element divalent halide of the plurality of kinds by a disproportionation reaction. A step of generating (step C);
Separating the mixture into distillation aggregates and residues of the one kind of rare earth element trivalent halide by vacuum distillation in the system (Step D),
The metal M is a metal in which the three phases of the metal M, the oxide of the metal M, and the halide of the metal M can coexist in the environment of the chemical equilibrium state,
The method for separating and recovering rare earth elements, wherein the predetermined amount is more than a chemical equivalent to a reaction for reducing the trivalent halides of the plurality of rare earth elements to divalent halides. The method for separating and recovering rare earth elements according to claim 1,
A method for separating and recovering a rare earth element, wherein the step C and the step D are performed simultaneously. The rare earth element separation and recovery method according to claim 1 or 2,
A method for separating and recovering a rare earth element, wherein the oxygen potential of the oxidation reaction of the metal M is lower than that of the plurality of rare earth elements. In the method for separating and recovering rare earth elements according to any one of claims 1 to 3,
Wherein said halogen potential halogenation reaction of the metal M, the plurality of kinds of rare earth elements trivalent halides of di- halides are the lower than that of the reaction reduced to, the plurality of kinds of rare earth elements in metal A method for separating and recovering rare earth elements characterized by being higher than that of the reaction . The rare earth element separation and recovery method according to any one of claims 1 to 4,
The method for separating and recovering rare earth elements, wherein the metal M is at least one selected from thulium, terbium, erbium, holmium, and yttrium. In the method for separating and recovering rare earth elements according to any one of claims 1 to 5,
A method for separating and recovering a rare earth element, wherein the halogen is chlorine. In the method for separating and recovering rare earth elements according to any one of claims 1 to 6,
The method for separating and recovering a rare earth element, wherein the one kind of rare earth element is dysprosium. The method for separating and collecting rare earth elements according to claim 7,
The method for separating and recovering rare earth elements, wherein the plurality of rare earth elements further include at least one selected from neodymium, gadolinium, and samarium. A method for separating and recovering multiple types of rare earth elements,
A step of producing a mixture containing chloride by chlorinating the compound containing the plurality of rare earth elements, iron and boron using iron chloride (step E);
Separating the mixture of the plurality of rare earth element chlorides from the chloride-containing mixture by distilling the chloride-containing mixture (Step F);
Adding a predetermined amount of metal M to the mixture of chlorides of the plurality of rare earth elements (step A ′);
Heating the mixture to which the metal M is added under atmospheric pressure to reach a chemical equilibrium state in which the plurality of rare earth element dichlorides and the metal M chloride are formed (step B ′); ,
By evacuating the system that has reached the chemical equilibrium state, the rare earth element metal and trichloride are converted from the rare earth element dichloride of the plurality of kinds by a disproportionation reaction. A step of generating (step C ′);
Separating the mixture into a distillate aggregate and residue of the one kind of rare earth element trichloride by vacuum distillation in the system (step D ′),
The metal M is a metal in which three phases of the metal M, an oxide of the metal M, and a chloride of the metal M can coexist in the environment of the chemical equilibrium state,
The predetermined amount, method of separating and recovering the rare earth element which is a excess than chemical equivalent for the reaction to be reduced to dichloride trichloride of the plurality of kinds of rare earth elements. The rare earth element separation and recovery method according to claim 9,
A method for separating and recovering a rare earth element, wherein the step C ′ and the step D ′ are performed simultaneously. In the method for separating and recovering rare earth elements according to claim 9 or 10,
A method for separating and recovering a rare earth element, wherein the oxygen potential of the oxidation reaction of the metal M is lower than that of the plurality of rare earth elements. In the method for separating and recovering rare earth elements according to any one of claims 9 to 11,
Chlorine potential of chloride the reaction of the metal M, the plurality of kinds of rare earth element is less than that of the reaction being reduced from trichloride into dichloride, reactions plurality kinds of rare earth elements is a metal A method for separating and recovering rare earth elements, which is higher than that. In the method for separating and recovering rare earth elements according to any one of claims 9 to 12,
The method for separating and recovering rare earth elements, wherein the metal M is at least one selected from thulium, terbium, erbium, holmium, and yttrium. In the method for separating and recovering rare earth elements according to any one of claims 9 to 13,
The method for separating and recovering a rare earth element, wherein the one kind of rare earth element is dysprosium. The method for separating and recovering rare earth elements according to claim 14,
The method for separating and recovering rare earth elements, wherein the plurality of rare earth elements further include at least one selected from neodymium, gadolinium, and samarium.

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