Method for recovering rare earths from rare earth-containing magnets

Abstract

By using solid aqua regia when recovering rare earths from rare earth-containing magnets, rare earths can be recovered safely. [Solution] This process involves a crushing step (S5) in which neodymium magnets extracted from waste products are crushed; the crushed neodymium magnets are placed in solid aqua regia, a composite molten salt, and heated to chlorinate the rare earths and Fe (S11); the rare earth chlorides are cooled to room temperature to solidify the molten salt (S12); the solidified solid aqua regia containing the rare earth chlorides is crushed, and the rare earth chlorides are recovered in a first leaching step (S13); oxalic acid (COOH)2 is added to a solvent containing the rare earth chlorides, FeCl2, and NaCl, and only the rare earth oxalates are selectively precipitated and recovered in a second leaching step (S15).

Description

[Technical Field]

[0001] The present invention relates to a method for recovering rare earths from rare earth-containing magnets such as neodymium magnets used in precision equipment components such as smartphones and hard disks that convert electrical energy into sound or vibration, as well as drive motors and electric power steering for hybrid and electric vehicles. [Background technology]

[0002] Rare earth magnets, such as neodymium magnets, are primarily composed of neodymium (Nd), iron (Fe), and boron (B) and are known as permanent magnets with the strongest magnetic force. Neodymium magnets have a high magnetic force per unit volume, so they can maintain a satisfactory magnetic force even when miniaturized, fully meeting the demand for miniaturized components and are used in a variety of industrial fields.

[0003] Neodymium magnets, which have such strong magnetic force, are used in precision equipment such as smartphones and hard disks, as well as in the drive motors of electric vehicles (EVs, HVs), etc. A method has been proposed to extract neodymium magnets from discarded hard disks and electric vehicle motors and recover rare earth elements from them.

[0004] Techniques for recovering rare earth elements from used rare-earth-containing magnets have been proposed. For example, Patent Document 1 (JP 2017-115175 A) entitled "Method for recovering rare earth elements from rare-earth magnets" proposes a method for recovering rare earth elements from rare-earth magnets, which includes a first step of immersing the rare-earth magnet in water, adding nitric acid, and maintaining the liquid temperature at 50 to 95°C to dissolve the rare-earth magnet to produce a solution; a second step of adjusting the pH of the solution to a range of 1.5 to 2.5 and heating it to 65 to 95°C to produce iron compounds, and recovering and washing out a supernatant liquid containing rare-earth magnet components; a third step of contacting the supernatant with an extractant to extract the rare-earth magnet components into an organic phase; and a fourth step of extracting the rare-earth magnet components from the organic phase into the nitric acid, crystallizing them, and then calcining them to produce rare-earth oxides. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-115175 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the "method for recovering rare earth elements from rare earth magnets" in Patent Document 1 uses acutely toxic nitric acid as a dissolving solution. Nitric acid can cause chemical burns if it comes into contact with the skin, and can cause blindness if it gets into the eyes. Furthermore, this method for recovering rare earth elements involves heating the dissolving solution, which generates harmful fumes (solid fine particles) and gases that, if inhaled by workers, can damage the mucous membranes of the throat and respiratory tract, posing the risk of dental corrosion and pulmonary edema.

[0007] Furthermore, because rare earth-containing magnets such as neodymium magnets have a strong magnetic force, injuries can occur if hands or fingers are pinched between the magnets or between a magnet and a magnetic body such as a piece of iron. Therefore, if processing work is performed while the neodymium magnet's magnetic force is maintained, there is a problem that the magnets are likely to be attracted to processing containers, reaction tanks, handling tools, etc., making the work more complicated. Furthermore, crushing magnets with such properties into fine powder can be an even more complicated process.

[0008] The inventors of the present invention thought that rare earths could be safely recovered from rare earth-containing magnets (neodymium magnets) by using so-called solid aqua regia. Solid aqua regia is a complex molten salt consisting of iron (III) chloride (FeCl3) and an alkali metal (potassium chloride (KCl) or sodium chloride (NaCl)). Both of these chemicals are less toxic and easier to handle than the chemicals used in conventional wet methods. Furthermore, treatment can be carried out at approximately 400°C, which is lower than conventional dry methods. Therefore, the inventors of the present invention focused on using solid aqua regia in rare earth recovery treatments.

[0009] The present invention was devised to fundamentally solve these problems. That is, an object of the present invention is to provide a method for recovering rare earths from rare-earth-containing magnets, which uses solid aqua regia to recover rare earths from rare-earth-containing magnets, thereby enabling safe recovery of rare earths. [Means for solving the problem]

[0010] The method for recovering rare earths from a rare earth-containing magnet of the present invention comprises the steps of: It has a magnet whose main component is iron A method for recovering rare earths from rare earth-containing magnets that are incorporated into waste products, the method comprising: a crushing step (S5) of crushing the rare earth-containing magnets extracted from the waste products; The rare earth-containing magnet pulverized in the pulverization step (S5) is Iron(III) chloride (FeCl 3 ) and alkali metal (potassium chloride (KCl) or sodium chloride (NaCl)a chlorination treatment step (S11) in which the rare earth and Fe are chlorinated by adding them to solid aqua regia, which is a composite molten salt, and heating them; a molten salt solidification step (S12) in which the rare earth chloride treated in the chlorination treatment step (S11) is cooled to room temperature to solidify the molten salt; The solid aqua regia containing rare earth chlorides solidified in the molten salt solidification step (S12) is pulverized and leached with water. do A first leaching step (S13), The solid aqua regia containing rare earth chlorides treated in the first leaching step (S13) By solid-liquid separation solid phase Remove magnet residue, Liquid phase In addition to rare earth chlorides, FeCl2 and KCl or Recover the solvent containing NaCl First solid-liquid separation step (S14a) and, The aforementioned First solid-liquid separation step (S14a) Recovered at Liquid phase Rare earth chlorides and FeCl2 KCl or In a solvent containing NaCl 、 Add oxalic acid (COOH)2 do A second leaching step (S15), Rare earths treated in the second leaching step (S15) Selectively precipitate and recover only oxalate Second solid-liquid separation step (S14b) and, The aforementioned Second solid-liquid separation step (S14b) Recovered at Solid phase Rare Earth Oxalates salt The method is characterized in that the rare earths are recovered by drying the waste.

[0011] The present invention also provides It has a magnet whose main component is iron A method for removing neodymium magnets incorporated in waste products and recovering rare earths from the neodymium magnets, comprising the steps of: a crushing step (S5) of crushing the neodymium magnets extracted from the waste products; The neodymium magnet pulverized in the pulverization step (S5) is Iron(III) chloride (FeCl 3 ) and alkali metal (potassium chloride (KCl) or sodium chloride (NaCl) a chlorination treatment step (S11) in which the rare earth and Fe are chlorinated by adding them to solid aqua regia, which is a composite molten salt, and heating them; a molten salt solidification step (S12) in which the rare earth chloride treated in the chlorination treatment step (S11) is cooled to room temperature to solidify the molten salt; The solid aqua regia containing rare earth chlorides solidified in the molten salt solidification step (S12) is pulverized and leached with water. do A first leaching step (S13), The solid aqua regia containing rare earth chlorides treated in the first leaching step (S13) By solid-liquid separation solid phase Remove magnet residue, Liquid phase In addition to rare earth chlorides, FeCl2 and KCl or Recover the solvent containing NaCl No. 1 Solid-liquid separation process (S14 a )and, The aforementioned No. 1 Solid-liquid separation process (S14 a ) Liquid phase Rare earth chlorides and FeCl2 KCl or In a solvent containing NaCl 、 Add oxalic acid (COOH)2 do A second leaching step (S15), Rare earths treated in the second leaching step (S15) Selectively precipitate and recover only oxalate No. 2 Solid-liquid separation process (S14 b ) and, The aforementioned No. 2 Solid-liquid separation process (S14 b ) solid phase Rare Earth Oxalates salt Dry the neodymium The method is characterized by recovering the following:

[0012] Before the pulverization step (S5), Discarded products Rare earth magnet with attached parts or neodymium magnet It is preferable that the method further comprises a demagnetization step (S3) of demagnetizing the magnetic material. In the chlorination treatment step (S11), chlorination and demagnetization can be carried out simultaneously by heat treatment at a temperature exceeding the Curie temperature. [Effects of the Invention]

[0013] The rare earth recovery method for rare earth-containing magnets of the present invention uses a composite molten salt called solid aqua regia for the treatment, which is less toxic and easier to handle than substances used in conventional wet treatment methods. Compared to conventional wet treatment methods, this method does not substantially dissolve Fe, which reduces chemical consumption and also suppresses the generation of waste liquid, which places a high burden on the environment. Processing can be carried out at around 400°C, which is lower than conventional dry processing methods, reducing energy consumption and simplifying equipment. but Furthermore, since chlorination, pulverization, and demagnetization can be carried out simultaneously, the process itself can be greatly simplified.

[0014] In the rare earth recovery method of the present invention, the chlorination of rare earth and the dissolution of Fe proceed simultaneously, making it possible to efficiently extract rare earth from rare earth-containing magnet scrap without pulverizing. In particular, rare earth-containing magnets contain iron(III) chloride (FeCl 3 ) turns the iron into a salt, allowing the solid aqua regia to act on the rare earth elements such as neodymium contained within the magnet, allowing for efficient extraction of the rare earth elements without having to crush the iron into a fine powder. [Brief explanation of the drawings]

[0015] [Figure 1] This is an Ellingham diagram for chlorides of Fe (iron), Nd (neodymium), and Dy (dysprosium). [Figure 2] FIG. 1 is a ternary phase diagram showing the state of a three-phase molten salt of FeCl2-FeCl3-NaCl. [Figure 3] FIG. 1 is a flow diagram showing chemical reactions in a method for recovering rare earths from a rare earth-containing magnet. [Figure 4] FIG. 1 is a flow chart showing an example of a method for recovering rare earths from neodymium magnets, which are rare earth-containing magnets, and is a work flow chart of the pre-treatment stage. [Figure 5] FIG. 1 is a flow chart showing an example of a rare earth recovery method for neodymium magnets, which are rare earth-containing magnets, illustrating the process flow of the chemical treatment stage. [Figure 6] This is an image showing a molten salt solidified by placing a neodymium magnet in solid aqua regia and cooling the chlorinated rare earth chloride to solidify the molten salt. [Figure 7]1 is an image showing the solvent obtained by first leaching the molten salt coagulate with water and removing magnet residues through first solid-liquid separation. [Figure 8] This is an image showing the magnet residue removed by the first solid-liquid separation in the first leaching, with a magnet brought close from the outside. [Figure 9] This is an image showing the solvent recovered after crushing solid aqua regia containing rare earth chlorides, performing a first leaching with water, and removing magnet residues through a first solid-liquid separation, resulting in a solvent containing rare earth chlorides as well as FeCl2 and NaCl. [Figure 10] This is an image showing a solvent containing rare earth chlorides, FeCl2, and NaCl, to which oxalic acid (COOH)2 is added in the second leaching step, selectively precipitating and recovering only the oxalate salts. [Figure 11] This is an image showing the rare earths recovered by drying the rare earth oxalates recovered in the second leaching step. [Figure 12] This is a table showing images of recovered materials taken with a SEM (scanning electron microscope) after a recovery processing time of 2 hours, and the recovery rates confirmed by analysis with an EDS (energy dispersive X-ray analyzer).The recovered materials are FeCl2-based and FeCl3-based. [Figure 13] This is a table showing images of recovered materials taken with a SEM (scanning electron microscope) after a recovery processing time of 4 hours, and the recovery rates confirmed by analysis with an EDS (energy dispersive X-ray analyzer).The recovered materials are FeCl2-based and FeCl3-based. [Figure 14] This is a table showing the recovery rates confirmed by images taken with a SEM (scanning electron microscope) and analysis with an EDS (energy dispersive X-ray analyzer) of recovered materials after a recovery processing time of 6 hours, for FeCl2-based and FeCl3-based recovered materials. [Figure 15] 10 is a graph showing the correlation between recovery processing time and recovery rate, and an image showing the properties of each recovered material. DETAILED DESCRIPTION OF THE INVENTION

[0016] The method for recovering rare earths from rare-earth-containing magnets of the present invention involves removing rare-earth-containing magnets such as neodymium magnets that are used in precision equipment components such as smartphones and hard disks to convert electrical energy into sound or vibration, and in drive motors and electric power steering systems for hybrid and electric vehicles, and recovering rare earths from the rare-earth-containing magnets using solid aqua regia.

[0017] <Application of "solid aqua regia" to rare earth-containing magnets> Figure 1 is an Ellingham diagram for chlorides of iron (Fe), neodymium (Nd), and dysprosium (Dy). Figure 2 is a ternary phase diagram showing the state of a three-phase molten salt of FeCl2-FeCl3-NaCl. The solid aqua regia used in the present invention is a complex molten salt consisting of iron chloride (III) (FeCl3) and an alkali metal (potassium chloride (KCl) or sodium chloride (NaCl)). As shown in the Ellingham diagram of Fe (iron), Nd (neodymium), and Dy (dysprosium) chlorides in Figure 1, rare earths can be salified not only with FeCl3 but also with FeCl2 (iron(II) chloride). For rare earth-containing magnets, treating them with only iron(II) chloride (FeCl2) allows selective treatment of only the rare earths. Because iron(II) chloride (FeCl2) has a melting point of 950 K (677°C), which is higher than iron(III) chloride (FeCl3), it is necessary to enable treatment at low temperatures. Therefore, in this invention, a composite molten salt including FeCl3, which has a melting point of approximately 300°C, is used, making it possible to melt and salify at low temperatures.

[0018] In Figure 2, the phase diagram of the three-phase molten salt FeCl2-FeCl3-NaCl at 650 K (377°C) shows that compositions in the gray region, such as those indicated by stars (molar ratio FeCL2:FeCL3:NaCl = 0.35...0.1:0.55), will achieve a completely molten state even at 650 K. This temperature makes it possible to simplify processing equipment and reduce energy consumption. Note that molten salt formation at 650 K can also be achieved when KCl is used instead of NaCl.

[0019] In the case of this composite molten salt, the rare earths are salified in the reaction shown in Chemical Formula 1, and the Fe in the magnet is salified in the reaction shown in Chemical Formula 2. The FeCl2 generated in this reaction is consumed in the salification of the rare earths, so the overall reaction proceeds as shown in Chemical Formula 3. The salification of the rare earths and the dissolution of Fe proceed simultaneously, making it possible to efficiently extract rare earths from crushed neodymium magnet powder without having to process the neodymium magnets into fine powder.

[0020] [ka]

[0021] [ka]

[0022] [ka]

[0023] <Each reaction phase> FIG. 3 is a flow diagram showing the chemical reactions in the method for recovering rare earths from rare earth-containing magnets. The rare earth recovery method of the present invention allows treatment under milder conditions than those required for conventional wet methods, and also reduces the generation of waste liquid. The reaction proceeds in the following phases. (1) Chlorination and demagnetization of magnet scrap using solid aqua regia. The crushed magnet scrap is placed in solid aqua regia and heated to 360 to 400°C, and the rare earths and Fe are chlorinated by the reaction shown in Chemical Formula 3. After the treatment, the molten salt is cooled to room temperature to solidify and recover. At this time, the treatment exceeds the Curie temperature, thereby simultaneously carrying out chlorination and demagnetization.

[0024] [ka]

[0025] (2) Rare earths are recovered by leaching rare earth chlorides and adding oxalic acid (COOH)2. The recovered solid aqua regia is leached with water (first leaching). No. 1 Magnet residues and other materials are removed by solid-liquid separation, and the solvent containing rare earth chlorides, FeCl2, and NaCl is recovered. (3) Oxalic acid (COOH)2 is added to the recovered solvent and leached (secondary leaching). The water solubilities of rare earth, alkali metal, and Fe oxalates (FeC2O4) are as shown in Table 1, which lists the water solubilities of various oxalate compounds. Therefore, by controlling the pH, it is possible to selectively precipitate and recover only the rare earth oxalates.

[0026] [Table 1] [Example]

[0027] Figure 4 shows an example of a rare earth recovery method for neodymium magnets containing rare earths, and is a workflow diagram of the pre-treatment stage. Figure 5 shows an example of a rare earth recovery method for neodymium magnets containing rare earths, and is a workflow diagram of the chemical treatment stage. Next, a method for recovering rare earths from neodymium magnets containing rare earths using the above-mentioned solid aqua regia will be described as a recycling technology. The recovery method of Example 1 uses the above-mentioned solid aqua regia to remove neodymium magnets, which are representative of rare earth-containing magnets incorporated into discarded products such as smartphones, hard disks, and electric vehicles, and recovers rare earths from these neodymium magnets. The rare earth recovery method of Example 1 from rare earth-containing magnets mainly consists of a pretreatment stage and a chemical treatment stage, and has the following treatment steps.

[0028] <Pre-processing stage> The pre-processing stage is a processing method including an image identification process S1, a disassembly and sorting process S2, a demagnetization process S3, a surface treatment process S4, and a crushing process S5 in this order.

[0029] The image identification process S1 is a process in which motors are extracted from discarded smartphones, hard disks, drive motors for electric vehicles such as EVs and HEVs, starters (cell motors) for conventional reciprocating engine automobiles, etc., and the magnets used in the motors are identified as neodymium magnets or other magnets using, for example, deep learning technology in computer AI technology. Neodymium magnets can be identified using an XRF (X-ray fluorescence) analyzer as an analytical device. Of course, the analytical device is not limited to this XRF analyzer.

[0030] In the dismantling and sorting process S2, the neodymium magnet motors identified in the image recognition process S1 are removed and dismantled, the motor housing is separated from the neodymium magnets, and the exterior iron and castings are recycled. These metals can be recycled as they are. In rare cases, neodymium magnets can be recovered through manual dismantling.

[0031] When processing neodymium magnets with attached parts, a demagnetization process S3 is carried out after the dismantling and sorting process S2. The demagnetization process S3 is a process for demagnetizing or demagnetizing the neodymium magnets, in which the motor is held under high-temperature conditions and heated to the Curie temperature. Separating neodymium magnets from motors with attached parts is dangerous due to their high magnetic force. Also, when handling neodymium magnets that still retain their magnetic force, they are attracted to magnetic materials, making the process complicated. Therefore, demagnetizing them at this stage makes the processing work after the crushing process S5 easier.

[0032] In the surface treatment process S4, the neodymium magnets used in motors are coated with plating, oil, and paint. Neodymium magnets are prone to rust, and when they rust, they become easily demagnetized. Therefore, the neodymium magnets are protected with plating, oil, and paint. These must be removed as they will hinder smooth processing in the next chemical treatment stage.

[0033] The crushing step S5 is a step in which the neodymium magnets are crushed to particle sizes of approximately 500 μm to 1 mm. This is to facilitate smooth processing during the chemical treatment stage. Coarse crushing is performed using a hammer, and fine crushing is performed using a ball mill or the like. The rare earth recovery method of the present invention chlorinates the rare earths and Fe during the chemical treatment stage, so processing is possible without crushing, but subsequent processing times tend to be longer. The particle size is preferably between 500 μm and 1 mm, but it is possible to make it finer than this. However, this has the disadvantage of increasing the work cost and time. Furthermore, it is preferable for the particle size to be uniform, so classification is carried out as necessary.

[0034] <Chemical treatment stage> The chemical treatment steps of the method for recovering rare earths from neodymium magnets in Example 1 include a chlorination treatment step S11, a molten salt solidification step S12, a first leaching step S13, No. 1 Solid-liquid separation process S14 a , second leaching step S15, No. 2 Solid-liquid separation process S14 b , a filtering step S16, and a drying step S17 in that order.

[0035] The neodymium magnets pulverized in the pulverization step S5 of the pretreatment stage are first treated in the chlorination step S11. In this chlorination step S11, the pulverized neodymium magnets are placed in a furnace together with powder of solid aqua regia, a composite molten salt, and heat-treated. The rare earth and Fe are chlorinated. The ratio of the pulverized neodymium magnets to the powder of solid aqua regia is, for example, 1:2. The furnace is filled with a nitrogen atmosphere. The heating temperature is 670K and the chlorination treatment is carried out for 6 hours. In the chemical treatment stage, including the chlorination treatment step S11, the reaction vessel must be of an appropriate size and material depending on the treatment volume, as the reaction vessel material, the means of transport to the next step, the method of adding solid aqua regia, etc. are extremely reactive. Safety measures must also be taken to prevent chlorine gas leakage.

[0036] Figure 6 shows an image of the molten salt solidified by placing a neodymium magnet in solid aqua regia and cooling the chlorinated rare earth chloride to solidify the molten salt. Figure 7 shows the molten salt solidified by first leaching with water. No. 1 Figure 8 shows the solvent from which magnet residues have been removed by solid-liquid separation. No. 1 This is an image showing the magnet residue after removal by solid-liquid separation, with a magnet brought close from the outside. The chlorination process S11 is followed by the molten salt solidification process S12, in which the rare earth chlorides treated in the chlorination process S11 are cooled to room temperature to solidify the molten salt. After solidification, the solid aqua regia was separated into black and white areas, as shown in Figure 6.

[0037] Following the molten salt solidification step S12 is the first leaching step S13. This first leaching step S13 is a step in which the solid aqua regia containing rare earth chlorides solidified in the molten salt solidification step S12 is crushed and leached with water. The expressions "first" and "second" are used here not to indicate grade, but simply to indicate the difference between the two leaching steps.

[0038] After the first leaching process S13 No. 1 Solid-liquid separation process S14 a is. No. 1 Solid-liquid separation process S14 a is a process for removing magnet residue and recovering the solvent containing rare earth chlorides as well as FeCl2 and NaCl. No. 1 Solid-liquid separation process S14 a The suction filtration method was used. After solidification, the solid aqua regia separated into black and white parts, as shown in Figure 6. The black parts consisted of small pieces and powder parts, and remained in the solid phase after the first leaching step S13. When a magnet was brought close, it was strongly attracted as shown in Figure 8, so both are thought to be Fe, and based on their shapes, the small pieces are thought to be sample residue, and the powder part is thought to be Fe powder that was produced after the magnet was dissolved via the reaction shown in Chemical Formula 3. Furthermore, since all of the particles had lost their magnetism, treatment with solid aqua regia could simultaneously perform chlorination, pulverization, and demagnetization. On the other hand, the white areas shown in Figure 6 are presumed to be rare earth chlorides produced by the reaction shown in Chemical Formula 3, which are eluted into the liquid phase during the leaching process.

[0039] [ka]

[0040] The first leaching step S13 is carried out under relatively mild conditions (using only water as the solvent and at room temperature). However, the iron powder recovered as a by-product turns to rust in water and must be removed promptly. It has also been suggested that when an aqueous solution of iron chloride comes into contact with air, iron hydroxide forms, which gels and affects filtration. When treating large quantities at a factory, the treatment process must be carried out in a way that avoids these problems.

[0041] Also, No. 1 Solid-liquid separation process S14 a Currently, this is done by suction filtration, which allows for quick processing. However, this method is not limited to this.

[0042] No. 1 Solid-liquid separation process S14 a Next is the second leaching step S15. This second leaching step S15 is a leaching step in which oxalic acid (COOH)2 is added to the solvent containing the rare earth chlorides, FeCl2, and NaCl recovered in the first leaching step S13, and only oxalates are selectively precipitated and recovered. Next to the second leaching step S15 No. 2 Solid-liquid separation process S14 b This separates the rare earth oxalate (solid phase) from the liquid phase containing FeCl2 and NaCl.

[0043] Figure 9 is an image showing the state after crushing solid aqua regia containing rare earth chlorides, performing the first leaching with water, removing the magnet residue by solid-liquid separation, and recovering the solvent containing rare earth chlorides as well as FeCl2 and NaCl. Figure 10 is an image showing the solvent obtained by adding oxalic acid (COOH)2 to the solvent containing rare earth chlorides, FeCl2, and NaCl in the second leaching, selectively precipitating and recovering only the oxalate salts. Figure 11 is an image showing the rare earths recovered by drying the rare earth oxalates recovered in the second leaching process. Figure 9 shows the state of the solvent obtained in the second leaching step S15 after filtering in the filtration step S16. Figure 10 shows the state after adding oxalic acid (COOH)2 and leaving it to stand for one day. Figure 11 shows the final recovered product. The solvent obtained by removing the residue is pale green. When oxalic acid (COOH)2 is added to this solvent, a white precipitate precipitates. When recovered by filtration, it is pale green, which is due to FeCl2 that remained after processing, or FeC2O4 that precipitated at the same time and became mixed in as an impurity.

[0044] <SEM image of the final recovered material and composition of the final precipitate> Figure 12 shows images of recovered material taken with a scanning electron microscope (SEM) after a two-hour recovery process and a table showing the recovery rates confirmed by EDS (energy dispersive X-ray spectrometry), for FeCl2-based and FeCl3-based recovered material. Figure 13 shows images of recovered material taken with an SEM after a four-hour recovery process and a table showing the recovery rates confirmed by EDS analysis, for FeCl2-based and FeCl3-based recovered material. Figure 14 shows images of recovered material taken with an SEM after a six-hour recovery process and a table showing the recovery rates confirmed by EDS analysis, for FeCl2-based and FeCl3-based recovered material. Figure 15 shows a graph showing the correlation between recovery time and recovery rate, along with images showing the properties of each recovered material. We compared the processing time of the above-mentioned recovery methods and the final recovered precipitate. Figures 12 to 15 show SEM (scanning electron microscope) images and EDS (energy dispersive X-ray analyzer) analysis and confirmed recovery rates. For example, the sample contained approximately 40 wt% Nd and 2 wt% Dy, with Fe and O as the main impurities. However, no chlorine (Cl) was present, suggesting that the sample consisted primarily of a mixture of Nd and Dy oxalates or oxides, with some FeCO and iron oxide (FeO). Since neodymium magnets contain approximately 60 wt% Fe, the recovery method of the present invention can selectively separate and recover rare earth elements to a certain extent.

[0045] It should be noted that the present invention is not limited to the above-described embodiments of the invention, and can of course be modified in various ways without departing from the spirit and scope of the present invention, as long as rare earths can be safely recovered by using solid aqua regia when recovering rare earths from rare earth-containing magnets. [Industrial Applicability]

[0046] The method for recovering rare earths from rare earth-containing magnets of the present invention is not limited to neodymium magnets, but can also recover rare earths from samarium-cobalt magnets, praseodymium magnets, samarium-iron-nitrogen magnets, and the like. [Explanation of symbols]

[0047] S1 Image recognition process S2 Dismantling and sorting process S3 Demagnetization process S4 Surface treatment process S5 Crushing process S21 Demagnetization process S22 Dismantling and sorting process S11 Chlorination process S12 Molten salt solidification process S13 First leaching process S14 a No. 1 Solid-liquid separation process S14 b No. 2Solid-liquid separation process S15 Second leaching process S16 Filtration process S17 Drying process

Claims

1. A method for recovering rare earths from rare earth-containing magnets that are incorporated into discarded products such as hard disks and electric vehicles, comprising the steps of: a pulverization step (S5) of pulverizing the rare earth-containing magnets extracted from the waste products; a chlorination treatment step (S11) in which the rare earth-containing magnet pulverized in the pulverization step (S5) is introduced into solid aqua regia, which is a composite molten salt, and the rare earth and Fe are chlorinated while being heated; a molten salt solidification step (S12) in which the rare earth chloride treated in the chlorination treatment step (S11) is cooled to room temperature to solidify the molten salt; The solid aqua regia containing rare earth chlorides solidified in the molten salt solidification step (S12) is pulverized, and the pulverized aqua regia is leached with water to remove magnet residues by solid-liquid separation, and in addition to rare earth chlorides, FeCl ２ a first leaching step (S13) of recovering a solvent containing NaCl; The rare earth chlorides and FeCl recovered in the first leaching step (S13) ２ Oxalic acid (COOH) in a solvent containing NaCl ２ and a second leaching step (S15) of selectively precipitating and recovering only oxalate, A method for recovering rare earths from a rare earth-containing magnet, comprising drying the rare earth oxalate recovered in the second leaching step (S15) to recover the rare earths.

2. A method for recovering rare earths from neodymium magnets that are incorporated into discarded products such as hard disks and electric vehicles, by removing the neodymium magnets, a crushing step (S5) of crushing the neodymium magnets extracted from the waste products; a chlorination treatment step (S11) in which the neodymium magnet pulverized in the pulverization step (S5) is introduced into solid aqua regia, which is a composite molten salt, and the rare earth and Fe are chlorinated while being heated; a molten salt solidification step (S12) in which the rare earth chloride treated in the chlorination treatment step (S11) is cooled to room temperature to solidify the molten salt; The solid aqua regia containing rare earth chlorides solidified in the molten salt solidification step (S12) is pulverized, and the pulverized aqua regia is leached with water to remove magnet residues by solid-liquid separation, and in addition to rare earth chlorides, FeCl ２ a first leaching step (S13) of recovering a solvent containing NaCl; The rare earth chlorides and FeCl recovered in the first leaching step (S13) ２ Oxalic acid (COOH) in a solvent containing NaCl ２ and a second leaching step (S15) of selectively precipitating and recovering only oxalate, A method for recovering rare earths from a rare earth-containing magnet, comprising drying the rare earth oxalate recovered in the second leaching step (S15) to recover the rare earths.

3. The solid aqua regia is iron(III) chloride (FeCl ３ ) and alkali metal (potassium chloride (KCl)), or iron (III) chloride (FeCl ３ 3. The method for recovering rare earths from a rare earth-containing magnet according to claim 1, wherein the rare earth is a composite molten salt consisting of molten iron (MnO) and sodium chloride (NaCl).

4. 3. The method for recovering rare earths from rare earth-containing magnets according to claim 1 or 2, further comprising a demagnetization step (S3) of demagnetizing the rare earth-containing magnet with attached components prior to the pulverization step (S5).

5. 3. The method for recovering rare earths from a rare-earth-containing magnet according to claim 1 or 2, wherein, in the chlorination treatment step (S11), chlorination and demagnetization are simultaneously carried out by heat treatment above the Curie point.

Images