JPH09157769A - Method for recovering compound containing reutilizable rare-earth element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recovering a compd. contg. reutilizable rare- earth element such as rare-earth oxide, rare-earth fluoride or rare-earth metal inexpensively, efficiently and effectively in terms of safety from the rare-earth metal-contg. scrap alloy such as the scrap alloy, defective product, slag, etc., generated when a product is produced from a rare-earth metal-contg. alloy. SOLUTION: The rare-earth metal-contg. scrap alloy is hydrogenated at the least to crush the scrap alloy, and the crushed scrap alloy is heated to obtain the oxide. The oxide is brought into contact with an acid soln. to exude the rare-earth element as its ion, the soln. contg. the rare-earth element ion is filtered to obtain a filtrate, and a precipitate contg. the rare-earth element is deposited from the filtrate.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for recovering reusable rare earth-containing compounds such as rare earth oxides, rare earth fluorides or rare earth metals from rare earth metal-containing alloy scraps.

[0002]

2. Description of the Related Art In recent years, various alloys containing rare earth metals have been developed and used for various purposes. For example, as a high-performance permanent magnet, about 30% by weight rare earth metal, about 65 iron
Rare earth metal-iron based alloys have been utilized which contain wt.%, About 2 wt.% Boron and other components. In manufacturing such a permanent magnet, alloy scraps and defective products corresponding to about 10 to 30% by weight of the product weight, and alloy scrap such as slag are generated. About 3 for these alloy scraps
It contains 0% by weight of rare earth metals. Further, for example, as a nickel-hydrogen secondary battery electrode, a rare earth metal-nickel alloy containing about 30% by weight of rare earth metal, about 65% by weight of nickel, 3.5% by weight of cobalt and other components is used. Even when such a secondary battery electrode is manufactured, alloy scrap corresponding to about 3 to 10% by weight of the product weight is generated. This alloy scrap contains about 30% by weight of rare earth metals.

The rare earth metal contained in such alloy scrap is a scarce resource and is expensive and valuable.
However, even if the conventional alloy scrap having a lump shape or the like can be crushed without considering the risk of ignition, the crushed alloy scrap is undergoing oxidation and is used as a magnet alloy powder, a hydrogen alloy powder, or the like. However, it is impossible to re-use as it is because the desired performance cannot be expected. Therefore, it is considered difficult to recover the rare earth metal from the viewpoint of performance, economy and safety, and an effective recovery method has not been studied. Therefore, alloy scrap is currently disposed of as industrial waste after taking safety measures.

By the way, as a method for separating a rare earth element from an alloy containing a rare earth metal, a strong acid dissolution method has been conventionally known. According to this strong acid dissolution method, first, the entire amount of the rare earth metal alloy is completely dissolved with a strong acid such as hydrochloric acid, nitric acid or sulfuric acid, and then the pH of the solution is adjusted with an alkali such as sodium hydroxide, potassium hydroxide or ammonium hydroxide. Then, iron, nickel, cobalt, etc. in the solution are precipitated and filtered. Then, oxalic acid, ammonium bicarbonate, sodium carbonate, etc. are added to the filtrate to precipitate a rare earth element, and the precipitate is filtered, dried and fired to obtain a rare earth oxide. Therefore, with such a separation method, it is considered possible to recover rare earth elements and the like even from alloy scrap having a lump form or the like. However, in the above strong acid dissolution method,
An extremely large amount of acid is required to completely dissolve the entire amount of the rare earth metal-containing alloy with a strong acid, and then a large amount of alkali is also required to precipitate and separate iron, nickel, cobalt and the like. If this method is applied to alloy scrap, the recovery cost becomes very expensive, and a special facility etc. for post-treatment of separated hydroxides of iron, nickel, etc. is also required, which is economical. It is advantageous to discard the alloy scrap.

As another method for separating rare earth elements, Japanese Patent Publication No.
No. 14777, a powdered rare earth metal-iron alloy is air-oxidized to make components such as iron hardly-acid-soluble oxides, and then a strong acid leaching method using strong acids such as hydrochloric acid, nitric acid and sulfuric acid. Dissolves rare earth metals, precipitates oxides such as iron by filtration,
A method is disclosed in which an acid such as oxalic acid is added to the filtrate to form a rare earth-containing precipitate, and the precipitate is filtered, dried and calcined to obtain a rare earth oxide. Since this strong acid leaching method is applied to a powdery alloy, it has an advantage that the amount of acid or the like used can be extremely reduced as compared with the above strong acid dissolution method. However, if the particle size distribution of the alloy powder varies, the air oxidation does not proceed uniformly, which causes a problem that the elution rate of rare earth elements during leaching with strong acid decreases. Therefore, it has not been considered to apply such a strong acid leaching method to alloy scrap having a lump form or the like. In particular, when pulverizing a massive alloy containing rare earth metal and pulverizing it in the atmosphere using a normal pulverizer such as a ball mill or a jet mill, there is a risk of ignition in the device and a fire. Even if it is crushed in a large-scale airtight atmosphere apparatus, there is a risk of explosion when taken out, and it is difficult to carry out industrially.

As described above, in order to recover the reusable rare earth-containing compound from the rare earth metal-containing alloy scrap on an industrial scale, there are problems regarding economy and safety, and the current situation is to discard it. Is. However, the demand for rare earth metal-containing alloys such as permanent magnets and nickel-hydrogen secondary batteries has expanded with the expansion of the use in the electronics field in recent years, and the amount of alloy scrap generated during the manufacturing process is also expected to increase. Therefore, from the viewpoint of effective use of resources, development of a technique for recovering rare earth metals contained in alloy scrap is being demanded.

[0007]

DISCLOSURE OF THE INVENTION An object of the present invention is to produce an alloy scrap produced when a product is manufactured from an alloy containing a rare earth metal,
To provide a recovery method for recovering reusable rare earth-containing compounds such as rare earth oxides, rare earth fluorides or rare earth metals from defective products and rare earth metal-containing alloy scraps such as slag at low cost and efficiently. is there. Another object of the present invention is to provide a method of recovering a reusable rare earth-containing compound from a rare earth metal-containing alloy scrap, which is also effective in terms of safety.

[0008]

According to the present invention, (a) a step of crushing a rare earth metal-containing alloy scrap by at least hydrotreating the alloy scrap,
(b) a step of heating the crushed alloy scrap to obtain an oxide, (c) contacting the oxide with an acid solution to leach the rare earth element as an ion, and filtering the solution containing the rare earth ion to obtain a filtrate There is provided a method for recovering a reusable rare earth-containing compound, which comprises the steps of: (d) forming a precipitate containing a rare earth element from the filtrate.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the recovery method of the present invention, for example, rare earth metals such as lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, dysprosium, erbium, and yttrium, rare earth oxides of these oxides or rare earth fluorides of these fluorides. And the like to recover a reusable rare earth-containing compound. Alloy scrap for recovering a reusable rare earth-containing compound by the recovery method of the present invention, in addition to the rare earth metal, usually contains iron, nickel, etc., and further cobalt, boron in some cases,
It has a form such as a lump containing manganese, aluminum and the like.

In the recovery method of the present invention, first, (a) a step of crushing the rare earth metal-containing alloy scrap is performed by at least hydrotreating the alloy scrap. The crushing of the alloy scrap by the hydrogenation treatment can be performed by heating the alloy scrap in a hydrogen pressure atmosphere, for example. Specifically, the alloy scrap is loaded into an atmosphere heating furnace such as a vacuum high-frequency heating furnace and the temperature is set to 10 ⁻³ T.
After evacuating above orr, introduce hydrogen gas and
A hydrogen pressure atmosphere of 5 atm is used, and the temperature is higher than room temperature, preferably 1
Treatment at a temperature of 00 to 800 ° C., particularly preferably 200 to 500 ° C., for 1 to 10 hours, preferably 3 to 5 hours,
It can be performed by a method of absorbing hydrogen in alloy scrap. When hydrogen is absorbed in the rare earth metal-containing alloy scrap as described above, a rapid volume expansion of 20 to 25% occurs, so that fine cracks are formed in the rare earth metal-containing alloy crystal and the alloy crystal can be uniformly crushed. In order to allow the alloy to absorb hydrogen at a sufficient rate to cause a rapid volume expansion, it is desirable that the hydrogen pressure be 1 atm or higher and the temperature be normal temperature or higher.

In the step (a), dehydrogenation treatment is performed after hydrogenation treatment is performed according to conditions such as the size of alloy scrap, or these hydrogenation treatment and dehydrogenation treatment are repeated. You can also By controlling the number of times of this hydrogenation treatment and dehydrogenation treatment, it is possible to obtain a powder having an appropriate particle size. For example, when the alloy scrap to be crushed is large, it is possible to obtain a uniform powder having an appropriate particle size by repeating the hydrogenation treatment and the dehydrogenation treatment preferably 2 to 3 times. When these treatments are repeated, the final hydrogenation treatment is preferably carried out so that hydrogen is present in the obtained alloy powder. this
The average particle size of the alloy scrap crushed in step (a) is
The thickness is preferably 200 to 2000 μm.

In the recovery method of the present invention, next, (b) a step of heating the crushed alloy scrap to obtain an oxide is carried out. The heating is performed, for example, by cooling the alloy scrap pulverized with hydrogen in the step (a) to about 50 ° C. or less in an atmosphere heating furnace, replacing the hydrogen gas in the furnace with an inert gas such as argon or nitrogen, and The method can be carried out by, for example, a method in which the alloy powder is taken out after the pressure is returned to the pressure, and the taken out alloy powder is loaded into a heating furnace such as an electric furnace in the air and heated to be air-oxidized. The heating is 200 to 700 ° C., particularly 300 to 600 ° C.,
It is preferably carried out under the conditions of 0.5 to 2 hours, particularly about 1 hour. Further, in order to easily convert the alloy powder into an oxide, for example, by the hydrogenation treatment in the step (a), this heating is performed in a state where hydrogen is absorbed in the alloy, that is, in a state where hydrogen is present in the alloy. It is preferable to carry out. When heated in a hydrogen-containing state, hydrogen burns, highly active steam is generated, the rare earth metal in the alloy powder becomes an acid-soluble oxide, and metals other than rare earth metals such as iron and nickel are resistant to acid. It becomes a soluble oxide. Therefore, in the next step (c), elution of metals other than rare earth elements such as iron and nickel in the alloy powder can be reduced. Further, if a metal other than the rare earth element is leached in the next step (c), hydrogen is generated, which is dangerous. Therefore, in order to prevent hydrogen generation, in order to sufficiently oxidize the alloy powder, the heating temperature is 200 ° C. The above is desirable. Also, without consuming excessive energy,
In order to sufficiently perform the leaching of the rare earth element into the acid solution in the step (c), the heating temperature is preferably 700 ° C or lower.

In the recovery method of the present invention, (c) the oxide obtained in step (b) is brought into contact with an acid solution to leach the rare earth element as an ion, and the solution containing the rare earth ion is filtered to obtain a filtrate. Perform the step of obtaining. For leaching the rare earth element as ions, for example, hydrochloric acid, nitric acid,
It can be carried out by a method of adding an acid solution such as sulfuric acid and bringing them into contact with each other. Specifically, after cooling the oxide obtained in the step (b) to about 50 ° C. or lower, it is put into a stirring tank, water is added to form a slurry, and the slurry preferably has a concentration of 2 to 5 N while stirring. It can be carried out by adding an acid solution such as nitric acid diluted to (normal) and leaching the rare earth element as ions. When the oxide is solidified by baking, after cooling, it is heated to 50 to 20 by a disk mill or the like.
It is preferable to grind it to 0 mesh, preferably 80 to 120 mesh and then slurry it. The addition amount of the acid solution may be calculated in advance by a chemical equivalent amount corresponding to the amount of the rare earth element present in the alloy scrap, and controlled and added according to the leaching rate of the rare earth ion. Preferably, in order to prevent the elution of metals other than rare earth elements, it is desirable to add the acid solution while controlling the final pH of the slurry to which the acid solution has been added so as not to fall below 3. The filtration of the solution containing rare earth ions can be performed by separating and removing insoluble precipitates of oxidized iron, nickel, etc. by a known filtration method. This filtrate, that is, the solution containing rare earth ions is preferably a solution containing only rare earth ions of high purity, but may contain iron, nickel, or the like that could not be separated during filtration.

In the recovery method of the present invention, next, (d) a step of producing a precipitate containing a rare earth element from the filtrate obtained in the step (c) is performed. To form a precipitate containing rare earth elements from the filtrate, for example, add a precipitant such as oxalic acid, ammonium bicarbonate (ammonium hydrogen carbonate), sodium carbonate (sodium carbonate), hydrofluoric acid, or ammonium fluoride to the filtrate. Can be done by. At this time, the amount of the precipitant added is preferably 1.2 to 1.5 times the chemical equivalent, which is sufficient to completely precipitate the rare earth ions present in the filtrate. The precipitate can be collected by a known filtration method. When alloy scrap contains rare earth metals such as cobalt, boron, manganese, and aluminum, and metals other than iron and nickel, these metals remain in the filtrate after the precipitate is filtered off. It can be separated and removed by filtration.

When a fluoride precipitant such as hydrofluoric acid, ammonium fluoride or a mixture thereof is added, a rare earth fluoride can be produced as a precipitate.
This precipitate can be recovered by filtration and then dried at 500 to 900 ° C., particularly 700 to 800 ° C., in order to obtain an anhydrous product. The recovered rare earth fluoride is a reusable rare earth-containing compound, for example,
It can be used as a main component of a molten salt bath used in a usual molten salt fluoride bath electrolysis method.

In the recovery method of the present invention, (e) the step (d) is performed by adding a precipitating agent other than the fluoride precipitating agent such as oxalic acid, ammonium bicarbonate, sodium carbonate, or a mixture thereof. It is also possible to perform a step of firing a precipitate containing a rare earth element to generate a rare earth oxide. In the calcination, the precipitate formed in the step (d) is filtered by a known method, and preferably at 800 to 1000 ° C. for 1 to 1
It can be performed by drying and baking for 0 hours. Said
The rare earth oxide produced in the step (e) may contain a metal other than rare earth elements such as iron and nickel, and can be used as a reusable rare earth-containing compound depending on the purpose and method of reuse. For example, it is most suitable for reuse as a raw material for producing a molten salt fluoride bath electrolytic rare earth metal,
In this case, in order to perform the molten salt electrolysis method treatment with good current efficiency, the content of metals such as iron and nickel is preferably less than 10% by weight, particularly preferably less than 5% by weight. Further, of the rare earth metals contained in the raw material alloy scrap, 80% by weight to
It is preferable to recover 98% by weight as a rare earth oxide.

In the recovery method of the present invention, the step of (f) refining the rare earth oxide recovered in the step (e) to produce a rare earth metal can be performed. The refining of the rare earth oxide can be performed by a known method such as a molten salt fluoride bath electrolysis method. Specifically, preferably lithium fluoride 25
~ 35 wt%, barium fluoride 10-25 wt%, and a rare-earth fluoride such as neodymium fluoride 40-65 wt%, the obtained rare earth oxide is put into a bath composed of a component such as a mixed salt. However, it can be carried out by a method of electrolyzing while melting at a temperature of usually 750 to 1000 ° C, preferably 800 to 950 ° C. As the rare earth fluoride in the mixed salt bath, the rare earth fluoride recovered in the step (d) can be used. By such refining, the rare earth metal contained in the raw material alloy scrap can be finally recovered. The rare earth metal recovered in the step (f) may contain a metal other than the rare earth element such as iron and nickel, and can be used as a reusable rare earth-containing compound depending on the purpose and method of reuse. At this time, the rare earth metal to be recovered is preferably 80% by weight to 95% by weight of the rare earth metal contained in the raw material alloy scrap.

[0018]

Industrial Applicability In the method for recovering a reusable rare earth-containing compound of the present invention, rare earth metal-containing alloy scrap, which has been conventionally discarded as industrial waste, can be easily crushed without risk of ignition to safely perform rare earth oxidation. It can be recovered as a substance, a rare earth fluoride, a rare earth metal, or the like. Further, since the leaching of metals other than rare earth elements such as iron and nickel into the acid solution can be suppressed as much as possible, the required amount of acid can be greatly reduced compared to the conventional strong acid dissolution method, which is economical. Also, a reusable rare earth-containing compound such as a rare earth oxide, a rare earth fluoride or a rare earth metal, which is advantageous in terms of performance and has no problem in performance, can be recovered as an industrially effective method.

[0019]

EXAMPLES The present invention will be described in detail below with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Examples 1 to 6 300 g of neodymium-iron-boron-based magnet scrap containing about 25% by weight of rare earth metal and about 73% by weight of iron was charged in a vacuum heating container, evacuated, and filled with hydrogen gas to 3 atm. Under a hydrogen pressure atmosphere, and heated at a temperature of 100 ° C. for 2 hours so that the magnet scraps absorb hydrogen until saturated to pulverize hydrogen. After cooling the obtained alloy powder to room temperature, the hydrogen gas in the container was replaced with argon gas and the pressure was returned to normal pressure, and then the alloy powder was taken out. The particle size distribution of the obtained alloy powder is indicated by the trade name "MICROTRAC PARTICLE-SIZE ANALYZE
The result measured by "R" (made by Leeds & Northrup) is shown in FIG. 30 g of this alloy powder was placed in each of 6 porcelain boats, and 200 g of each was placed in an open type nichrome heating type electric furnace.
C. (Example 1), 300.degree. C. (Example 2), 400.degree. C. (Example 3), 500.degree. C. (Example 4), 600.degree. C. (Example 5), and 700.degree. C. (Example 6) It was heated and air-oxidized for 1 hour. After cooling each sample to room temperature, 1 in a mortar
It was crushed to 00 mesh, transferred to a beaker equipped with a stirrer, and 100 ml of water was added to make a slurry. 63m of 3N nitric acid was added to each slurry while controlling the pH so as not to fall below 3.
1 was added dropwise over 1 hour, and the stirring was continued for 1 hour, and then the precipitated iron oxide was filtered off to obtain a rare earth ion-containing solution. After adding 47 ml of 2N oxalic acid solution to the obtained solution to precipitate rare earth ions as oxalate, the precipitate was separated by filtration and calcined at 1000 ° C. for 1 hour to obtain a rare earth oxide.

After measuring the weight of the obtained rare earth oxide, the amount of the rare earth element contained in the oxide is determined according to JIS M.
It was analyzed according to the chemical analysis method of 8404. The rare earth metal recovery rate was calculated from the obtained value and the initial amount of rare earth metal in the magnet scraps. Table 1 shows the results. Further, in order to measure the elution degree of iron during the treatment by the acid leaching method, 96 ml of 2N sodium hydroxide was added to the filtrate after separating the rare earth oxalate by filtration to remove the iron ions present in the filtrate. It was precipitated as iron hydroxide, and the precipitate was filtered and calcined to obtain iron oxide. The elution rate of iron was calculated from the obtained amount of iron oxide and the initial amount of iron in the magnet scrap. Table 1 shows the results.

Examples 7 to 12 Rare earth oxides and iron oxides were recovered in the same manner as in Examples 1 to 6 except that the heating temperature during hydrogen pulverization was 300 ° C. The amount of the rare earth element contained in and the amount of the obtained iron oxide were measured in the same manner as in Examples 1 to 6, and the recovery rate of the rare earth metal and the elution rate of iron were calculated. Table 1 shows the results.

Examples 13 to 18 Rare earth oxides and iron oxides were recovered in the same manner as in Examples 1 to 6 except that the heating temperature during hydrogen pulverization was 500 ° C. The amount of the rare earth element contained in and the amount of the obtained iron oxide were measured in the same manner as in Examples 1 to 6, and the recovery rate of the rare earth metal and the elution rate of iron were calculated. Table 1 shows the results.

Comparative Example 1 30 g of the same magnet waste as used in Examples 1 to 6 was directly put into a porcelain boat without crushing with hydrogen and heated and oxidized at 600 ° C. for 2 hours in an open nichrome heating type electric furnace. . After cooling the sample to room temperature, it was ground to less than 100 mesh in a mortar to obtain a rare earth oxide and iron oxide in the same manner as in Examples 1-6. The weight of the obtained rare earth oxide, the amount of the rare earth element contained in the oxide, and the amount of the obtained iron oxide were measured in the same manner as in Examples 1 to 6, and the recovery rate of the rare earth metal and the elution of iron were measured. The rate was calculated. Table 1 shows the results.

[0024]

[Table 1]

Example 19 300 g of neodymium-iron-boron magnet scrap containing about 25% by weight of rare earth metal and about 73% by weight of iron was charged in a vacuum heating vessel, evacuated, and then filled with hydrogen gas to obtain 3 The mixture was heated under a hydrogen pressure atmosphere of atmospheric pressure at a temperature of 300 ° C. for 2 hours, and hydrogen was pulverized by allowing the magnet scraps to absorb hydrogen until saturated. After cooling the obtained alloy powder to room temperature, the hydrogen gas in the container was replaced with argon gas and the pressure was returned to normal pressure, and then the alloy powder was taken out. This alloy powder 30
g was put in a magnetic boat and heated and air-oxidized at a temperature of 500 ° C. for 1 hour in an open nichrome heating type electric furnace. After cooling the sample to room temperature, it was ground to 100 mesh in a mortar, transferred to a beaker equipped with a stirrer, and 100 ml of water was added to make a slurry. 63 ml of 3N nitric acid was added dropwise to each slurry over 1 hour while controlling the pH so as not to fall below 3.
After the stirring was continued for further 1 hour, the precipitated iron oxide was removed by filtration to obtain a rare earth ion-containing solution. 117 ml of a 2N hydrofluoric acid solution was added to the resulting solution to generate a fluoride.
Then, ammonia water was added to pH 3 and the mixture was aged with stirring for 1 hour to precipitate a rare earth fluoride. The precipitate was filtered off and dried at 700 ° C. for 1 hour to give a rare earth fluoride 9.
32 g were obtained.

The amount of rare earth element contained in this rare earth fluoride was analyzed by the chemical analysis method of JIS M8404, and the recovery rate of rare earth metal was calculated from the obtained value and the initial amount of rare earth metal in the magnet scrap. However, the recovery rate was 89%. When the iron as an impurity present in this rare earth fluoride was analyzed, the amount present was 0.15%. On the other hand, in order to measure the elution degree of iron during the treatment by the acid leaching method, 96 ml of 2N sodium hydroxide was added to the filtrate after separating the rare earth fluoride by filtration to remove the iron ions present in the filtrate. It was precipitated as iron hydroxide, and the precipitate was filtered and calcined to obtain iron oxide. The elution ratio of iron was calculated from the obtained amount of iron oxide and the initial amount of iron in the magnet scraps to be 1.7%.

Examples 20 to 25 300 g of misch metal-nickel based hydrogen storage alloy slag containing 28.9% by weight of misch metal and 65.2% by weight of nickel were pulverized with hydrogen in the same manner as in Examples 1 to 6. The particle size distribution of the obtained alloy powder is referred to as "MICROTRAC
Fig. 2 shows the results measured by "PARTICLE-SIZE ANALYZER" (manufactured by Leeds & Northrup). 30 g of this alloy powder was placed in each of 6 porcelain boats to obtain a rare earth oxide in the same manner as in Examples 1-6. The weight of the obtained rare earth oxide and the amount of the rare earth element contained in the oxide were measured in the same manner as in Examples 1 to 6, and the recovery rate of the rare earth metal was calculated. Table 2 shows the results
Shown in Furthermore, in order to measure the elution degree of nickel during the treatment by the acid leaching method, 60 ml of 2N sodium hydroxide was added to the filtrate after the rare earth oxalate was filtered off to hydrate the nickel ions present in the filtrate. It was precipitated as nickel, and the precipitate was filtered and calcined to obtain nickel oxide. The elution rate of nickel was calculated from the obtained amount of nickel oxide and the initial amount of nickel in the slag. Table 2 shows the results
Shown in

Examples 26 to 31 Rare earth oxides and nickel oxides were recovered in the same manner as in Examples 20 to 25 except that the heating temperature during hydrogen pulverization was 300 ° C. The amount of rare earth element contained in and the amount of nickel oxide obtained were measured in the same manner as in Examples 20 to 25, and the recovery rate of rare earth metal and the elution rate of nickel were calculated. Table 2 shows the results.

Examples 32 to 37 Rare earth oxides and nickel oxides were recovered in the same manner as in Examples 20 to 25 except that the heating temperature during hydrogen pulverization was 500 ° C. The amount of rare earth element contained in and the amount of nickel oxide obtained were measured in the same manner as in Examples 20 to 25, and the recovery rate of rare earth metal and the elution rate of nickel were calculated. Table 2 shows the results.

Comparative Example 2 30 g of the same misch metal-nickel hydrogen storage alloy slag as that used in Examples 20 to 25 was put directly into a porcelain boat without crushing with hydrogen, and was placed in an open type nichrome heating type electric furnace to obtain 600 It was heated and oxidized at 2 ° C. for 2 hours. After cooling the sample to room temperature, it was ground to less than 100 mesh in a mortar to obtain a rare earth oxide and nickel oxide in the same manner as in Examples 20-25. The weight of the obtained rare earth oxide, the amount of the rare earth element contained in the oxide, and the obtained amount of nickel oxide were measured in the same manner as in Examples 20 to 25 to recover the rare earth metal and elute nickel. The rate was calculated. Table 2 shows the results.

[0031]

[Table 2]

Example 38 10 kg of neodymium-iron-boron based magnet scrap containing about 25% by weight of rare earth metal and about 73% by weight of iron was charged in a vacuum heating vessel, evacuated, and filled with hydrogen gas to obtain 3 The mixture was heated under a hydrogen pressure atmosphere of atmospheric pressure at a temperature of 300 ° C. for 2 hours, and hydrogen was pulverized by allowing the magnet scraps to absorb hydrogen until saturated. After cooling the obtained alloy powder to room temperature, the hydrogen gas in the container was replaced with argon gas and the pressure was returned to normal pressure, and then the alloy powder was taken out. The obtained alloy powder was heated and air-oxidized at 300 ° C. for 2 hours in an open nichrome heating type electric furnace. After cooling the sample to room temperature, crush it to 100 mesh with a disk mill, transfer it to a stirring tank, and add water 3
0 liter was added to make a slurry. While controlling the pH so as not to become less than 3, 1N 3N nitric acid was added to the slurry.
1 liter was added dropwise over 5 hours, and stirring was continued for further 2 hours, and then the precipitated iron oxide component was removed by filtration to obtain a rare earth ion-containing solution. After adding 14.3 liters of 2N oxalic acid to the resulting solution to precipitate the rare earth ion as an oxalate salt, this precipitate is separated by filtration and calcined at 800 ° C. for 5 hours to obtain a rare earth oxide 2. 68 kg was obtained. Next, this rare earth oxide is electrolyzed at 900 ° C. while being placed in a molten salt bath for electrolysis containing 30% by weight of lithium fluoride, 20% by weight of barium fluoride and 50% by weight of neodymium fluoride, to obtain a rare earth iron master alloy. 2.4 kg was obtained. This rare earth iron master alloy contained 2.0 kg of rare earth metal, and the recovery rate based on the amount of rare earth metal in the initial magnet scrap was 82%. Table 3 shows the results
Shown in

Comparative Example 3 10 kg of the same magnet waste as used in Example 38 was tried to be crushed with a jaw crusher and a jet mill, but when it was put into the jaw crusher, it ignited and could not be crushed. Therefore, this magnet waste was put directly into a porcelain container and heated and air-oxidized at 600 ° C. for 2 hours in an open type nichrome heating type electric furnace. The oxidized magnet waste was treated in the same manner as in Example 38 to obtain 1.49 kg of a rare earth oxide. Then, the obtained rare earth oxide was treated in the same manner as in Example 38 to obtain 1.34 kg of a rare earth iron master alloy. The rare earth iron master alloy contained 1.14 kg of the rare earth metal, and the recovery rate based on the amount of the rare earth metal in the magnet scrap was 45.7%. Table 3 shows the results.

[0034]

[Table 3]

[Brief description of the drawings]

FIG. 1 is a first example to a sixth example, a seventh example to a twelve example, and a first example.
In Nos. 3 to 18, the particle size distribution of the alloy powder when the neodymium-iron-boron-based magnet scraps were pulverized with hydrogen at temperatures of 100 ° C, 300 ° C, and 500 ° C, respectively. It is a graph shown in comparison with.

FIG. 2 shows Misch metal-nickel based hydrogen storage alloy slags of Examples 20 to 25, Examples 26 to 31, and Examples 32 to 37 of 100 ° C., 300 ° C., and 50 ° C., respectively.
It is a graph which shows a particle size distribution of alloy powder at the time of pulverizing with hydrogen at each temperature of 0 ° C.

Claims (4)

[Claims] 1. A step of crushing an alloy scrap containing a rare earth metal at least by hydrotreating the scrap, (b) a step of heating the crushed alloy scrap to obtain an oxide, and (c). A step of leaching the rare earth element as an ion by contacting the oxide with an acid solution, filtering a solution containing the rare earth ion to obtain a filtrate, and (d) forming a precipitate containing the rare earth element from the filtrate. A method for recovering a reusable rare earth-containing compound containing. 2. In the step (d), a precipitate containing a rare earth element is formed by adding to the filtrate a precipitant consisting of oxalic acid, ammonium bicarbonate, sodium carbonate, or a mixture thereof, The recovery method according to claim 1, wherein (e) the step of producing the rare earth oxide by firing the precipitate produced in the step (d) is performed. 3. The step of (f) refining the rare earth oxide produced in the step (e) to produce a rare earth metal.
The collection method described in. 4. In the step (d), a precipitate containing a rare earth element is produced by adding a fluoride precipitant consisting of hydrofluoric acid, ammonium fluoride or a mixture thereof to the filtrate,
The recovery method according to claim 1, wherein a rare earth fluoride is generated.