Electrochemical atomic hydrogen decrepitation of rare earth-containing materials.

Abstract

Provided herein is an apparatus for electrolytic atomic hydrogen decrepitation and a method for its use.

Description

[Technical field]

[0001] Provided herein is an apparatus for electrolytic atomic hydrogen decrepitation and methods of use thereof. [Background technology]

[0002] Rare earth magnets based on neodymium-iron-boron (NdFeB) are employed in many clean energy and high tech applications, such as hard disk drives (HDDs), motors in electric vehicles, and generators in wind turbines. In recent years, the supply of rare earth metals has come under considerable strain. This has resulted in dramatic price fluctuations for rare earth metals, especially neodymium, praseodymium, and dysprosium, the rare earth components of NdFeB magnets. According to the European Critical Materials List (2010, 2014) and the U.S. Department of Energy's Energy Critical Elements List (2010), rare earth metals are classified as at highest risk of supply shortage compared to all other materials used for clean energy technologies.

[0003] There are several ways these material shortages can be addressed, including: (a) opening more rare earth mines; (b) using alternative technologies that do not contain rare earths; (c) reducing the amount of rare earth metals used in certain applications such as magnets; or (d) recycling existing stocks of magnets that contain rare earth metals using various types of equipment. However, with regard to option (a), mining, beneficiation and separation of rare earth elements is energy intensive, results in toxic by-products from the acid leaching process, and primary ores are almost always contaminated with radioactive elements such as thorium. When alternative technologies are used, as in option (b), or reducing the amount of rare earth metals, as in option (c), this often leads to reduced efficiency and performance compared to permanent magnet machines.

[0004] Recycling of magnet scrap from waste consists of several steps, including the following preliminary steps; separation of magnets from waste, demagnetization by heat treatment at 300-350°C, decarburization by combustion under air or oxygen flow at 700-1000°C (to remove resin), and deoxidization by hydrogen reduction. The main process (separation of rare earth metals and iron) starts after these preliminary steps. Several wet processes are also used for recovery of neodymium: acid dissolution, solvent extraction, and oxalate method. In these wet chemical methods, the yield from acid dissolution and wastewater treatment steps is insufficient, and multi-step processes are required, resulting in high costs. It is important that the recovery process for rare earth metals from magnet scrap has as low cost and few steps as possible, since the recovery of magnetic materials from products is itself a multi-step process.

[0005] Grinding / milling of Nd-magnet alloys accounts for more than 10% of the total recycling cost, while the risk of the resulting fine powder being contaminated with grinding media and / or lining materials of the milling equipment (jet mill, ball mill) is not negligible. Decrepitation protocols developed to recycle Nd magnets generally used dry hydrogen gas at moderately high gas pressures and / or temperatures to produce powder alloys.

[0006] One of the biggest challenges associated with magnet recycling is how to efficiently separate the magnetic material from other components, specifically, how to perform decrepitation of ferromagnetic alloys at low cost. Summary of the Invention

[0007] In one embodiment, the presently disclosed subject matter provides an electrolytic apparatus for atomic hydrogen decrepitation of at least one rare earth-containing material, the apparatus comprising: a cathode in which at least one rare earth material is the cathode itself; anode; The electrolyte in the tank; and The electrolytic device is configured to carry out an electrolytic reaction and decrepitate the at least one rare earth-containing material.

[0008] In some embodiments, the cathode and the ferromagnetic alloy comprise the same material. In one embodiment, the cathode and the ferromagnetic alloy are the same material. In one embodiment of the device, the at least one rare earth-containing material comprises any of the following elements selected from the following: cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd), praseodymium (Pr), promethium (Pm), samarium (Sm), scandium (Sc), terbium (Tb), thulium (Tm), ytterbium (Yb), and yttrium (Y).

[0009] In one embodiment of the device, the at least one rare earth-containing material comprises a ferromagnetic alloy or a rare earth magnet. In another embodiment, the rare earth magnet is selected from the list including: NdFe 14 B, SmCO5, Sm(Co,Fe,Cu,Zr)7, Sr-ferrite, iron bar magnets or combinations thereof. In one embodiment, the iron-containing material is subjected to further treatment processes as detailed herein to separate the rare earth materials from the iron-containing material. In some embodiments, further pre-treatment processes can include crushing, grinding, crushing, pulverizing the ferromagnetic alloy prior to the electrolytic atomic hydrogen decrepitation process.

[0010] In one embodiment, the cathode of the device further comprises copper, nickel, steel, titanium, or any combination thereof. In one embodiment, the electrolyte of the device is a hydroxide. In another embodiment, the electrolyte is an aqueous KOH or NaOH solution. In one embodiment, the cathode further comprises at least one grid adapted to allow the decrepitated fragments to pass therethrough. In one embodiment, the grid has holes having a size in the range of 1-100 μm in diameter. In one embodiment, the at least one grid is comprised of copper, nickel, steel, titanium, a ferromagnetic alloy, or any combination thereof. In one embodiment, the device further comprises at least one additional cathode.

[0011] In one embodiment, the presently disclosed subject matter provides a method for electrolytic atomic hydrogen decrepitation of at least one rare earth-containing material, the method comprising: providing an electrolysis device of any of the devices disclosed herein configured to carry out an electrolysis reaction in an electrolyte; and Providing an applied electrical potential between the anode and the cathode to carry out an electrolytic reaction to produce atomic hydrogen at the cathode.

[0012] In one embodiment, the presently disclosed subject matter provides a method for electrolytic atomic hydrogen decrepitation of at least one rare earth-containing material, the method comprising: providing an electrolysis device comprising an anode, a cathode and an electrolyte, the electrolysis device configured to conduct an electrolysis reaction and decrepitate the at least one rare earth-containing material; disposing the at least one rare earth-containing material on the cathode; and Providing an applied electrical potential between the anode and the cathode to carry out an electrolytic reaction to produce atomic hydrogen at the cathode.

[0013] In one embodiment of the method, the cathode and the ferromagnetic alloy are different materials. In some embodiments of the method, the cathode and the ferromagnetic alloy comprise the same material. In one embodiment of the method, the cathode and the ferromagnetic alloy are the same material. In one embodiment of the method, the electrolysis reaction is carried out at room temperature. In one embodiment of the method, the electrolysis reaction is carried out at an elevated temperature. In one embodiment of the method, the applied potential is between 4 and 10 V. In one embodiment of the method, atomic hydrogen is transferred from the cathode to 2H + (aq)+2e - →2H(g) reduction reaction releases H+. In one embodiment of the method, H+ is the result of electrolysis of water (H2O) in the cell. In one embodiment of the method, the electrolyte comprises a hydroxide. In one embodiment of the method, the electrolyte comprises an aqueous solution of KOH or NaOH.

[0014] In one embodiment of the method, the cathode further comprises at least one grid adapted to allow the decrepitated fragments to pass therethrough. In one embodiment of the method, the at least one grid is comprised of copper, nickel, steel, titanium, a ferromagnetic alloy, or any combination thereof.

[0015] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. However, the invention, both as to organization and method of operation, together with its objects, features, and advantages, may best be understood by reference to the following detailed description taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0016] [Figure 1] 1 shows a ferromagnetic alloy before atomic hydrogen decrepitation. [Diagram 2] 1 shows a ferromagnetic alloy after atomic hydrogen decrepitation. [Diagram 3] 1 is a schematic illustration of one embodiment of the method of the present invention. [Figure 4]4A shows the X-ray diffraction (XRD) of ferromagnetic alloys (initial magnets) before atomic hydrogen decrepitation - FIG. 4A: Sample 1; FIG. 4B: Sample 2. (The contents of Samples 1 and 2 are provided in Example 3, Table 3). [Diagram 5] Characterization of the initial magnets by Energy Dispersive X-ray Fluorescence Spectroscopy is shown, where SEM images of the initial magnet, Sample 1, (FIG. 5A); SEM images of the initial magnet, Sample 2, (FIG. 5B); EDS spectrum of initial magnet-Sample 1 (FIG. 5C); and EDS spectrum of initial magnet-Sample 2 (FIG. 5D) are provided. [Figure 6] Figure 6A shows the laboratory setup for atomic hydrogen decrepitation. 1 - glass container (electrolytic cell) containing 700 ml, 2 - titanium cathode, 3 - intact magnet fragments, 4 - titanium grid, 5 - nickel anode, 6 - 1 M KOH electrolyte, 7 - magnet powder after decrepitation. 4.7 V DC, 13-15 A was applied under ambient conditions for 2 h. Figure 6B shows a photograph of the ferromagnetic alloy as the cathode itself. [Figure 7] 1 shows the powder X-ray diffraction (XRD) pattern of the magnet powder after atomic hydrogen decrepitation. [Figure 8] 1 shows an SEM image of magnet powder after atomic hydrogen decrepitation. [Figure 9] Laboratory setup for chlorination for extraction of rare earth metals from permanent magnets. 1 - chlorine generator; 2 - gas stop; 3 - valve; 4 - flow meter; 5 - tube for chlorine; 6 - place for air addition; 7 - quartz reactor; 8 - furnace with temperature control device; 9 - Pyrex glass crucible; 10 - gas washing bottle, 11 - sublimate collector, 12 - sublimate. [Figure 10] 10A and 10B show characterization of the composition of the materials after chlorine gas treatment by energy dispersive X-ray fluorescence spectroscopy (EDS, LEO Supra) for Sample 1 (FIG. 10A) and Sample 2 (FIG. 10B). [Figure 11]Figure 11A shows the powder X-ray diffraction (XRD) patterns of the sublimate from a neodymium magnet sample after temperature treatment (400°C) with chlorine gas. "1" indicates Fe2O3 and "2" indicates FeOCl. Figure 11B shows the quantitative phase analysis of the sublimate obtained from the XRD patterns in Figure 11A. [Figure 12] Figure 12A shows the fine powder obtained after electrolytic hydrogen decrepitation of a cm-sized Nd-magnet fragment under ambient conditions during 2 hours: Figure 12A - Photograph of the powder in a Petri dish. Figure 12B - EDS spectrum. The carbon peak in the panel (marked with ** to the left of the spectrum) is not due to the powder, but rather to the thin carbon support foil. The rare earth elements show overlapping XRF peaks of rare earth elements (REE). [Figure 13] Figure 1 shows the powder X-ray diffraction (XRD) pattern of the fine-grained, decrepitated magnet powder obtained after 2 hours of room temperature electrolysis in 1M KOH solution and compared to the Nd2Fe14BH1.86 standard powder pattern (ICSD#80973). The XRD pattern of the HD (hydrogen decrepitated) powder did not change after 4 months of storage under ambient conditions in air. [Figure 14] Figures 14A and 14B present SQUID magnetometer VSM measurements of the magnetic properties of HD powder at 300 K as a function of the applied magnetic field, μH [T]: Figures 14A and 14B present the magnetic polarization J [T]; Figure 14C presents the magnetic energy density |BH| [Joules / m3], magnetic induction B [T]. [Figure 15] Figure 1 shows the temperature dependence of saturation magnetization of Nd2Fe14BHx fine particle powder produced by electrolytic hydrogen decrepitation. Temperature dependence of HD powder saturation magnetization at a constant external field of 6 Tesla. No demagnetization correction (assumed to be very small) was applied. Fitting to the modified Bloch method in the form: M(T) = M(0)(1-(T / Tc)α) was successful, giving effective values ​​of parameters M(0) = 136.5 Am2 kg-1, Tc = 936 K and α = 2.35 (R = 0.99959). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

[0018] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the invention.

[0019] The presently disclosed subject matter provides an electrolytic apparatus and method for atomic hydrogen decrepitation of ferromagnetic alloys by electrolysis. In some embodiments, the method of atomic hydrogen decrepitation can further include a pretreatment step.

[0020] In some embodiments, the electrolytic device includes a cathode, an anode, and an electrolyte, and at least one rare earth-containing material is disposed on the cathode. In some embodiments, the terms "ferromagnetic alloy," "rare earth-containing material," and "rare earth magnet" are used interchangeably. In some embodiments, any rare earth-containing material that can be bonded to an electrode for electrolysis can be used for this invention. The rare earth-containing material can include any material that contains any number of rare earth elements and / or other materials, such as minerals, alloys, or magnets. The rare earth elements referred to herein can include any of the following: cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd), praseodymium (Pr), promethium (Pm), samarium (Sm), scandium (Sc), terbium (Tb), thulium (Tm), ytterbium (Yb), and yttrium (Y). In some embodiments, the cathode comprises copper, nickel, steel, titanium, or any combination thereof.

[0021] In some embodiments, the ferromagnetic alloy is attached to a cathode in the electrolytic device. In some embodiments, the ferromagnetic alloy is disposed on the cathode, where the ferromagnetic alloy and the cathode are electronically coupled. In some embodiments, the electrolytic device can include at least one additional cathode.

[0022] In some embodiments, the electrolytic apparatus further comprises a grid containing holes beneath the ferromagnetic alloy / pieces. The size of the holes in the grid can be any suitable size configured to allow the ferromagnetic pieces / fragments to pass therethrough, to achieve a desired particle size of powder at the bottom of the electrolytic cell after electrolytic decrepitation.

[0023] In some embodiments, the size of the holes in the grid ranges from 1 to 100 μm in diameter. In some embodiments, the size of the holes in the grid ranges from 1 to 1000 μm in diameter. In some embodiments, the size of the holes in the grid ranges from 1 to 50 μm in diameter. In some embodiments, the size of the holes in the grid ranges from 50 to 100 μm in diameter. In some embodiments, the size of the holes in the grid ranges from 100 to 500 μm in diameter. In some embodiments, the size of the holes in the grid ranges from 500 to 1000 μm in diameter. In some embodiments, the size of the holes in the grid ranges from 1 mm to 5 mm in diameter.

[0024] In some embodiments, more than one grid connected to the cathode is used. With multiple grids, larger pieces can pass through the upper grid but not the lower grid. The ferromagnetic alloy fragments become smaller as they decrepitate and pass through subsequent grids with progressively smaller hole sizes. Multiple grids can facilitate a larger exposed surface area between the ferromagnetic alloy and the electrolyte as the ferromagnetic alloy decrepitates. In one embodiment, any grid configuration that allows for a higher exposed surface area between the ferromagnetic alloy and the electrolyte is within the scope of the invention.

[0025] In some embodiments, the ferromagnetic alloy, rare earth-containing material, or rare earth magnet itself is the cathode, i.e., atomic hydrogen is released directly on the surface of the ferromagnetic alloy cathode. FIG. 6B shows the ferromagnetic alloy integrated as the cathode itself. In such an arrangement, the cathode itself can include the ferromagnetic alloy and the rare earth magnet. In some embodiments, the cathode itself includes the rare earth-containing material. In some embodiments, the cathode itself includes any of the following: cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd), praseodymium (Pr), promethium (Pm), samarium (Sm), scandium (Sc), terbium (Tb), thulium (Tm), ytterbium (Yb), and yttrium (Y). In some embodiments, there is more than one cathode.

[0026] In some embodiments, when the ferromagnetic alloy is the cathode itself, the electrolytic device further comprises a grid connected to the cathode and configured to allow the decrepitated fragments to pass therethrough.

[0027] The invention further provides a method for electrolytic atomic decrepitation of at least one rare earth-containing material. "Atomic hydrogen decrepitation" generally refers to a process in which atomic hydrogen is used to break down a rare earth-containing material into smaller pieces, generally small fragments or powder. "Electrolytic atomic hydrogen decrepitation" refers to at least a decrepitation process carried out by electrolysis. In some embodiments, "atomic hydrogen decrepitation" and "electrolytic atomic hydrogen decrepitation" or simply "decrepitation" are used interchangeably. As such, terms such as "decrepitated" and "decrepitated fragments" are understood in light of the definitions herein. In some embodiments, no pretreatment step is required before placing the ferromagnetic alloy into the electrolytic device.

[0028] In some embodiments, a pretreatment step up to atomic hydrogen decrepitation can be included, as detailed below.

[0029] In one embodiment, the ferromagnetic alloy pieces are immediately placed in an electrolytic device and electrolytic atomic hydrogen decrepitation is performed to form an alloy powder. Such alloy powder can be separated by a number of additional methods to recover different materials, such as chlorination to separate iron and rare earth metals, as described herein.

[0030] In some embodiments, a method for electrochemical atomic hydrogen decrepitation of rare earth metals includes: providing any one of the electrolytic devices disclosed herein, which generally include an anode, a cathode, an electrolyte, and a cell; disposing at least one rare earth-containing material on the cathode; and Carrying out an electrolytic reaction by providing an applied potential between the cathode and anode to produce atomic hydrogen at the cathode.

[0031] In some embodiments, the method includes the cathode itself being made of a ferromagnetic alloy piece, strip or material.

[0032] In some embodiments, the method is carried out at room temperature. In some embodiments, the method is carried out at ambient conditions. In some embodiments, the electrolysis is carried out at an elevated temperature. In some embodiments, the elevated temperature is 20-30° C. In some embodiments, the elevated temperature is 20-40° C. In some embodiments, the elevated temperature is 20-50° C. In some embodiments, the elevated temperature is 30-40° C. In some embodiments, the elevated temperature is 40-50° C. In some embodiments, the elevated temperature is 50-100° C.

[0033] In some embodiments, the atomic hydrogen decrepitation comprises an electrolytic reaction and the applied potential is 4-10 V. In other embodiments, the applied potential is 4-8 V. In other embodiments, the applied potential is in the range of any one of the following: 4-5 V, 4-6 V, 4-7 V, 4-8 V, 4-9 V, 4-10 V, 5-6 V, 5-7 V, 5-8 V, 5-9 V, 5-10 V, 6-7 V, 6-8 V, 6-9 V, 6-10 V, 7-8 V, 7-9 V, 7-10 V, 8-9 V, 8-10 V, or 9-10 V.

[0034] In some embodiments, the electrolyte is a hydroxide. In some embodiments, the electrolyte is an aqueous KOH or NaOH solution. In some embodiments, the method further comprises filtering the decrepitated ferromagnetic fragments through a grid. In some embodiments, there is more than one grid.

[0035] One advantage of the present invention is that it does not require a pretreatment or chlorination step, although some embodiments may use these as additional steps in the decrepitation process.

[0036] The invention further provides a method for atomic hydrogen decrepitation of at least one rare earth metal from a ferromagnetic alloy, further comprising a chlorination step, the method comprising: (a) reacting a ferromagnetic alloy with at least one chlorine-containing gas to obtain a volatile iron-containing chloride product and at least one non-volatile rare earth metal chloride; (b) providing an air flow to said volatile iron-containing chloride product, thereby oxidizing the iron-containing chloride product to iron oxide; (c) separating said iron oxide product and non-volatile at least one rare earth metal chloride; (d) cooling the separated non-volatile at least one rare earth metal chloride; (e) electrolyzing the cooled non-volatile at least one rare earth metal chloride; This allows the at least one rare earth metal to be recovered.

[0037] In some embodiments, the method of the present invention includes pre-treating the ferromagnetic alloy by decrepitation prior to reacting the ferromagnetic alloy with at least one chlorine-containing gas in step (a), where an atomic hydrogen decrepitation process is used to form the powder alloy. In other embodiments, the decrepitation is performed at room temperature. In other embodiments, the atomic hydrogen decrepitation process is performed using electrolysis. In other embodiments, the electrolysis is performed using a first electrode (cathode) of copper, nickel, steel, titanium, or combinations thereof; and a second electrode (anode) of lead, nickel, steel, or combinations thereof. In other embodiments, the ferromagnetic alloy is deposited on the first electrode (cathode).

[0038] FIG. 3 illustrates one embodiment of rare earth metal recovery, which includes a chlorination step. In some embodiments, a chlorination step is required to separate iron from the ferromagnetic alloy. In other embodiments, a chlorination step is not required. In one embodiment, if iron is not present in the ferromagnetic alloy, atomic hydrogen decrepitation is performed by electrolysis as described herein.

[0039] In some embodiments, for example as shown in FIG. 3, the present invention provides a method for the recovery of at least one rare earth metal from a ferromagnetic alloy, the method comprising: (a) pretreating a ferromagnetic alloy by electrolytic atomic hydrogen decrepitation as described herein to form a powder alloy; (b) reacting the ferromagnetic powder alloy with at least one chlorine-containing gas to obtain a volatile iron-containing chloride product and at least one non-volatile rare earth metal chloride; (c) providing an air flow to said volatile iron-containing chloride product, thereby oxidizing the iron-containing chloride product to iron oxide; (d) separating said iron oxide product and non-volatile at least one rare earth metal chloride; (e) cooling the separated non-volatile at least one rare earth metal chloride; (f) electrolyzing the cooled non-volatile at least one rare earth metal chloride; This allows the at least one rare earth metal to be recovered.

[0040] In some embodiments, the invention provides a method for the recovery of at least one rare earth metal from a ferromagnetic alloy, the method comprising: (i) electrolytic atomic hydrogen decrepitation of the ferromagnetic alloy to form a powder alloy; (ii) magnetic separation of the powder to form a powder alloy having a lower iron content; (iii) reacting the powder alloy having a lower iron content with at least one chlorine-containing gas to obtain a volatile iron-containing chloride product and at least one non-volatile rare earth metal chloride; (iv) separating the volatile iron-containing chloride product and the at least one non-volatile rare earth metal chloride; (v) cooling the separated at least one non-volatile rare earth metal chloride; (vi) electrolyzing the cooled at least one non-volatile rare earth metal chloride; thereby recovering the at least one rare earth metal.

[0041] In another embodiment, the atomic hydrogen decrepitation is performed at room temperature. In another embodiment, the atomic hydrogen decrepitation is performed using electrolysis. In another embodiment, the electrolysis is performed using a first electrode (cathode) of copper, nickel, steel, titanium, or a combination thereof; and a second electrode (anode) of lead, nickel, steel, or a combination thereof. In another embodiment, a ferromagnetic alloy is attached to the first electrode (cathode).

[0042] In another embodiment, the present invention also provides a method for recovery of used neodymium magnets by chlorination without the need for pretreatment of the magnets. For example, used magnets without demagnetization, crushing and grinding. After treatment at 400°C, clinker consisting of rare earth metal chlorides, sublimate consisting of iron oxide and iron chloride are obtained. The obtained rare earth metal chlorides are then processed by electrolysis of molten salts for rare earth metal production.

[0043] "Pretreatment" refers to any process or processes that occur before another process. In one embodiment, pretreatment may refer to physical processes such as milling and grinding, but may also refer to non-electrolytic atomic hydrogen decrepitation. Other examples of pretreatment may include, but are not limited to: magnetic separation, degaussing, heating, chemical processes, etc.

[0044] When referring to a "ferromagnetic" (used interchangeably with "ferrimagnetic") alloy, it should be understood to encompass any type of source (including post-consumer) permanent magnet made of a combination of metals that creates its own permanent magnetic field. These metals include, but are not limited to, elemental iron, nickel and cobalt, rare earth metals, naturally occurring minerals (e.g., lodestone), and any combination thereof. In another embodiment, the ferromagnetic alloy is NbFe 14 B, (Nb,Pr)Fe 14 B (with Dy2O3 additive). In some embodiments, the rare earth metal is a ferromagnetic alloy, a rare earth magnet, Nd2Fe 14 Magnet origin including B, SmCO5, Sm(Co,Fe,Cu,Zr)7, Sr-ferrite, iron bar magnets and combinations thereof.

[0045] In some embodiments, the present invention provides for the recovery and / or extraction of rare earth metals from any naturally occurring mineral. In some embodiments, the present invention provides for the recovery and / or extraction of rare earth metals from naturally occurring rare earth element sources, including but not limited to rare earth minerals, aeschynite-(Y or Ce), catullenite, apatite, bastnaesite, brissolite, blockite, cerite, dreisite-(Ce), euxenite, fluorite, fluorite, gadolinite, laterite clay, loparite, monazite, parisite-(Ce or La), stillwellite, syncsite, titanite, wakefieldite, xenotime, zircon, or combinations thereof.

[0046] In some embodiments, the at least one rare earth metal is selected from cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd), praseodymium (Pr), promethium (Pm), samarium (Sm), scandium (Sc), terbium (Tb), thulium (Tm), ytterbium (Yb), and yttrium (Y).

[0047] Atomic hydrogen decrepitation Neodymium magnets absorb gaseous hydrogen. Nd 15 Fe 77 B8 alloy readily absorbs hydrogen at room temperature (provided the surface is not heavily oxidized), resulting in decrepitation of the bulk material into a brittle powder. Friability is the tendency of a solid material to break into smaller pieces under force or contact, especially by friction. Hydrogen absorption is carried out in two stages: hydrogen is first absorbed by the Nd-rich grain boundary material and then by the matrix Nd-Fe-B phase. Due to the large electronegativity difference, hydrogen insertion is favored in the vicinity of the rare earth elements (REEs). Intergranular fracture can produce single crystal particles; however, these particles are nevertheless brittle and can undergo further size reduction by ball milling.

[0048] This invention relates to a method for decrepitation of ferromagnetic alloys using atomic hydrogen (by electrolysis) as opposed to gaseous hydrogen. However, the advantage of using electrolytic atomic hydrogen over gaseous hydrogen is the use of milder conditions, where the reaction is carried out at room temperature, eliminating the need for high pressures of pure hydrogen.

[0049] In some embodiments, the method of the present invention includes atomic hydrogen decrepitation of the ferromagnetic alloy, the method includes electrolytic reaction of the ferromagnetic alloy with atomic hydrogen at room temperature, the atomic hydrogen being released from a cathode in an electrochemical cell and reacted with the ferromagnetic alloy to obtain a ferromagnetic alloy powder having a particle size of ≦50 μm. In some embodiments, the atomic hydrogen is 2H+ (aq)+2e - →2H(g) reduction reaction, and is released from the cathode. In another embodiment, H+ is the result of the electrolysis of water (H2O) in an electrolysis cell.

[0050] In another embodiment, the atomic hydrogen further forms gaseous hydrogen (H2) [2H(g) → H2(g)] in the water electrolyzer. Atomic hydrogen forms on the metal surface of the cathode and reacts with the ferromagnetic alloy. The remainder enters the aqueous solution and forms molecular hydrogen.

[0051] In other embodiments, the cathode comprises copper, nickel, steel, titanium, or any combination thereof, hi another embodiment, the anode comprises lead, nickel, steel, or any combination thereof.

[0052] In some embodiments, the atomic hydrogen decrepitation comprises an electrolytic reaction and the electrolyte is an aqueous KOH or NaOH solution.

[0053] In some embodiments, the atomic hydrogen decrepitation comprises an electrolytic reaction, and the electrolytic reaction is carried out at room temperature. In other embodiments, the electrolytic reaction is carried out at a temperature between 20 and 40° C. In other embodiments, the electrolytic reaction is carried out at a temperature between 20 and 30° C. In other embodiments, the electrolytic reaction is carried out at a temperature between 20 and 35° C.

[0054] In some embodiments, this process eliminates the need for high temperature equipment or a high pressure pure hydrogen atmosphere. The fine particle NdFeB hydride powder can be further processed to form novel magnetic materials or to facilitate the separation of valuable rare earth metals from the iron-bearing components of the magnet.

[0055] In some embodiments, the atomic hydrogen decrepitation comprises an electrolytic reaction, and the electrolytic reaction is carried out for a period of between 30 minutes and 3 hours, hi other embodiments, the electrolytic reaction is carried out for 2 hours.

[0056] In some embodiments, the ferromagnetic alloy powder obtained by the atomic hydrogen decrepitation method of the present invention comprises particles with a size of ≦50 μm. In other embodiments, the ferromagnetic alloy powder obtained by the atomic hydrogen decrepitation method of the present invention comprises particles with a size of 1 μm to 50 μm. In other embodiments, the ferromagnetic alloy powder obtained by the atomic hydrogen decrepitation method of the present invention comprises particles with a size of 10 μm to 50 μm. In other embodiments, the ferromagnetic alloy powder obtained by the atomic hydrogen decrepitation method of the present invention comprises particles with a size of 30 μm to 50 μm. In other embodiments, the ferromagnetic alloy powder obtained by the atomic hydrogen decrepitation method of the present invention comprises particles with a size of 10 μm to 40 μm. In other embodiments, the ferromagnetic alloy powder obtained by the atomic hydrogen decrepitation method of the present invention comprises particles with a size of 10 μm to 30 μm. In some embodiments, the ferromagnetic alloy powder obtained comprises particles having any of the following shapes: spherical, globular, cylindrical, non-uniform, cubic, or combinations thereof. In some embodiments, the grains are smooth, while in other embodiments, the grains are coarse.

[0057] Chlorination In some embodiments, the method for recovery of at least one rare earth metal from a ferromagnetic alloy comprises reacting with at least one chlorine-containing gas, hi other embodiments, the reaction is carried out at a temperature between 400° C. and 450° C.

[0058] In some embodiments, the at least one chlorine-containing gas used in the methods of this invention is present in an amount of 0.5-2.0 kg chlorine / kg ferromagnetic alloy (or powdered alloy).

[0059] In some embodiments, the air flow to the volatile iron-containing chloride product is present in an amount of 0.5-2.0 kg air / kg volatile iron-containing chloride product.

[0060] In other embodiments, the chloride product is a high purity chloride (both purity and yield >95%).

[0061] In some embodiments, a method for recovery of at least one rare earth metal from a ferromagnetic alloy includes electrolyzing the cooled non-volatile at least one rare earth metal chloride. In other embodiments, the electrolysis is carried out using graphite electrodes (cathode, anode). In some further embodiments, the electrolysis is carried out at a temperature range of about 500-1500°C. In other embodiments, the electrolysis is carried out using a potential of 10-15V.

[0062] In some embodiments, the invention provides at least one rare earth metal composition prepared by the method of the invention. The following non-limiting examples are presented to more fully illustrate certain embodiments of the invention. However, they should in no way be construed as limiting the broad scope of the invention. Those skilled in the art can readily devise numerous variations and modifications of the principles disclosed herein without departing from the scope of the invention.

[0063] Working Example Example 1 - Magnet Treatment with Atomic Hydrogen-Decrepitation Decrepitation of the ferromagnetic alloy was carried out in 1 M aqueous sodium hydroxide at room temperature. Electrolysis was carried out using a copper cathode and a lead anode. The current density was 0.1 A / cm 2 The uncrushed ferromagnetic alloy was deposited on a cathode electrode. The atomic hydrogen released at the cathode passed through the ferromagnetic alloy pieces and reacted with them. The ferromagnetic alloy pieces were scattered by the atomic hydrogen reaction, and ferromagnetic alloy powder was produced. Figures 1, 2 and 8 show the ferromagnetic alloy before and after atomic hydrogen decrepitation.

[0064] Initial magnet characterization Spent magnet pieces were used as input material.

[0065] The contents of the ingredients are presented in Table 1. [Table 1]

[0066] A photograph of some magnet pieces is presented in Figure 1. Figure 2 is a photograph of the ferromagnetic powder after atomic hydrogen decrepitation.

[0067] Materials X-ray diffraction (XRD) was performed on an Ultima III diffractometer (Rigaku Corporation, Japan), and quantitative phase analysis was achieved using Jade_10 (MDI, Cal.) software and the ICSD database (Figure 4A).

[0068] The composition of the materials was characterized by energy dispersive X-ray fluorescence spectroscopy (EDS, LEO Supra) (Figures 5A-5D).

[0069] thermodynamic calculations Gibbs energy calculations were performed using a computer program based on standard values ​​for pure substances. Gibbs energies (ΔG) in the temperature range 273-473 K are shown in Table 2 for reactions with hydrogen: Group 1 - reactions with atomic hydrogen; Group 2 - reactions with molecular hydrogen; Group 3 - hydrolysis reactions of metal hydrides in water. [Table 2]

[0070] Under the above conditions shown in Table 2, the Gibbs energies of reactions (1, 2) in Group 1 for rare metals were strongly negative (-520-570 kJ / mole).

[0071] Thermodynamic calculations predicted that the reaction of Nd and Pr from the magnet with atomic hydrogen gas results in the formation of Nd and Pr hydrides in a wide temperature range, including the range of interest 273-373 K. Dysprosium is present in the magnet as an additive in the form of oxide Dy2O3, which reacts with atomic hydrogen to produce metallic dysprosium or DyH2 (reactions 4, 5). Group 2 includes hydrogen processing reactions between magnet components and molecular hydrogen. The possibility of reactions (6, 7) was also ensured over the entire temperature range of interest, with the most negative value for (6) being ΔG = -163 kJ / mol. However, the values ​​of the Gibbs energy for reactions (6, 7) are much lower than for reactions (1, 2). Dy2O3 does not react with molecular hydrogen (reactions 8, 9). Iron from the magnet is practically not involved in reactions with hydrogen under the experimental conditions (reactions 3, 8). Group 3 includes the hydrolysis reactions of neodymium, praseodymium, and dysprosium hydrides in water. Under experimental conditions, the Gibbs energies of hydrolysis reactions (11-16) in group 3 for rare metals are strongly negative (-350-530 kJ / mol). Thermodynamic calculations predict that the hydrolysis reactions of neodymium, praseodymium, and dysprosium hydrides can result in the formation of Nd, Pr, and Dy hydroxides or oxides within a wide temperature range, including the range of interest 273-373 K.

[0072] Chemical decrepitation of magnets is described by reactions (1, 2) which show Gibbs energies of -520-570 kJ / mol, predicting rapid chemical decrepitation of magnets upon atomic hydrogen treatment. Dy2O3 can react with atomic hydrogen to produce metallic dysprosium or DyH2 (reactions 4, 5). These reactions (1, 2, 4, 5) lead to magnet decrepitation, resulting in magnet powder with particle sizes less than 200 mesh.

[0073] Experimental procedure The laboratory setup is depicted in Figure 6A. The test duration was 2-4 hours. The temperature was varied from room temperature to boiling point. The potential was 4.7 V and the current was -13-15 A. The cathodic current density was 0.8-0.9 A / cm.2 It was.

[0074] A glass vessel with 1 mol / liter KOH solution (6) was used as the electrolytic cell (1). Titanium was used as the cathode (2) and a nickel plate - as the anode (5). Pieces of neodymium magnets (30-40 mm) (3) (as is, without demagnetization, crushing or grinding) were placed on a titanium grid (4) connected with the cathode (2). The atomic hydrogen released during electrolysis was released on the surface of the magnet pieces (3) and allowed to decrepitate them, producing powder (7). The magnet powder (7) passed through the grid (4) and was collected at the bottom of the electrolytic cell (1). Figure 7 shows the powder X-ray diffraction (XRD) pattern of the magnet powder after decrepitation, and Figure 8 shows the SEM image of the magnet powder after decrepitation.

[0075] In summary, exposure of as-received Nd-magnet pieces (prepared according to Example 4) to chlorine gas for 2 hours at 673 K leaves high purity REE chlorides (both purity and yield >95%) as clinker in the experimental furnace. These chlorides are hygroscopic and readily form hexahydrates when contacted with ambient humidity. Volatile components - especially those containing Fe or B - are removed from the furnace as sublimed acid chlorides and chlorides. The relative amounts of these products depend on the airflow velocity at the top of the reactor, while unreacted chlorine gas is recoverable. The presence of high melting temperature oxides after Nd-magnet alloy decrepitation does not appear to prevent the formation of REE chlorides.

[0076] Example 2 - Rare Earth Metal Extraction Including an Electrochemical Atomic Hydrogen-Decrepitation Step The ferromagnetic alloy was decrepitated using electrochemical atomic hydrogen decrepitation to produce ferromagnetic alloy powder. The ferromagnetic alloy powder was then treated with chlorine gas at 400-450°C. Chlorination of such powder increases the chlorination rate compared to chlorination of magnet pieces because of the higher surface area. The material was charged to a reactor. Chlorine was pumped into the reactor and heated to a temperature of 400-450°C. After reaction, the iron and boron chlorides were sublimated and removed from the reactor. The iron chloride was collected in a water scrubber and the boron chloride was removed with the gas. The rare earth metal chlorides remained in the reactor. The iron-containing chloride vapor product (FeCl3) was received in the scrubber and the non-volatile neodymium and praseodymium chlorides (NdCl 3、 After this step, the rare earth chlorides can then be used for electrolysis in the methods described herein.

[0077] Example 3 - Rare Earth Metal Extraction without Electrochemical Atomic Hydrogen-Decrepitation Pretreatment In this example, the process for rare earth extraction did not require pretreatment of the magnets. The magnets used did not include demagnetization, crushing and grinding pretreatment. This example relates to rare earth metal extraction from magnet pieces, and example 4 to rare earth metal extraction from powder using electrolytic atomic hydrogen decrepitation. In this example, after chlorination treatment of the magnets at 400°C, a clinker consisting of rare earth metal chlorides and a sublimate consisting of iron oxide and iron chloride were obtained. It has been shown that the chlorination rate and the completeness of chlorination (when chlorination is required to separate iron from the rare earth metals) are higher in the process including pretreatment by electrolytic hydrogen decrepitation.

[0078] Initial magnet characterization Used magnet pieces were used as the input material. The contents of the ingredients are presented in Table 3. [Table 3]

[0079] Materials X-ray diffraction (XRD) was performed on an Ultima III diffractometer (Rigaku Corporation, Japan), and quantitative phase analysis was achieved using Jade_10 (MDI, Cal.) software and the ICSD database (Figures 4A and 4B).

[0080] The composition of the materials was characterized by energy dispersive X-ray fluorescence spectroscopy (EDS, LEO Supra) (Table 3 and Figures 4A and 4B).

[0081] Table 3 shows that both magnets are composed of the same elements, but the relationships between the elements are quite different. According to the X-ray diffraction patterns, the first sample (Figure 4A) is a well-crystalline material with an average crystallite size of about 70 nm, while the second one (Figure 4B) is composed of nanocrystals with a size of about 5 nm.

[0082] All the main peaks in Fig. 4A are Nd2Fe 14 B and NdPrFe 14 B (their peaks have almost identical positions), and the remaining peaks correspond to Dy2O3, which accounted for only a few percent. According to the EDS results (Table 3), the two main phases in sample 1 had the same amount. In Figure 4B, Nd2Fe 14 B (or NdPrFe 14 B) peaks were observed, but they were relatively small. The compounds shown above the main peak in FIG. 5B were found and are also provided in Table 3.

[0083] thermodynamic calculations Gibbs energy calculations were performed using a computer program based on standard values ​​for pure substances. The Gibbs energies (ΔG) in the temperature range 373-773 K are shown in Table 4 for the chlorination reaction with chlorine gas. [Table 4]

[0084] Regarding Table 4, under sintering conditions, the Gibbs energies of reactions (1-, 6, 8) were strongly negative within a wide temperature range including the range of interest 573-673 K, with the most negative values ​​being ΔG=-(800-900) kJ / mol for reactions (3 and 5). Thus, the highest probability of reactions (1)-(6, 8) can be predicted immediately after the injection of chlorine gas. Dysprosium was present in the magnet as an additive in the form of the oxide Dy2O3 and did not react with chlorine (reaction 7 in Table 4).

[0085] Experimental procedure Sintering of neodymium magnets with chlorine gas was carried out in a temperature-controlled laboratory furnace at 400° C.: sintering time was 2 h. The laboratory setup is depicted in FIG.

[0086] Pieces (30-40 mm) of neodymium magnets (as is, without demagnetization, crushing or grinding) were placed in the furnace in pyrex glass crucibles 9. Before heating, the quartz reactor 7 was purged under a nitrogen flow of 100 ml / min, after which the furnace 8 was heated to the desired temperature and again placed under a nitrogen flow of 100 ml / min. Chlorine gas was fed into the reactor 7 after the latter had reached the specified temperature. All elements (iron, neodymium, praseodymium and boron) were chlorinated according to reactions (1-6, 8) in Table 4. Dysprosium oxide Dy2O3 did not react with chlorine (reaction 7 in Table 4).

[0087] The chlorides of iron and boron were sublimated (the boiling points of FeCl3 are 316°C and BCl3 are -107°C) and the rare earth chlorides remained in the residual clinker (the boiling points of NdCl3 are 1600°C and PrCl3 are 1710°C). The rare earth chlorides and Dy2O3 were formed from the solid powdered clinker (the melting points of NdCl3 are 758°C, PrCl3 are 786°C and Dy2O3 are 2408°C). Air was added to the top of the reactor for the oxidation of iron chloride according to reaction (7): 2FeCl3+1.5O2=Fe2O3+3Cl2(7)

[0088] Chlorine is obtained by reaction (7) and can be returned to the chlorination stage in pilot or industrial units, thus achieving a chlorine gas circulation. After cooling under nitrogen flow, the crucible 9 was removed from the furnace 7 and broken. The final product 12 (solid NdCl3-PrCl3 clinker) was weighed and analyzed by XRD and EDS. A mixture of iron chloride and iron oxide was collected from the top of the reactor and analyzed by XRD and EDS.

[0089] The composition of the materials was characterized by energy dispersive X-ray fluorescence spectroscopy (EDS, LEO Supra) (Figures 10A-10B and Table 5). [Table 5]

[0090] The resulting rare earth metal chlorides can be readily processed by molten salt electrolysis to produce the metallic rare earth metals.

[0091] Quantitative phase analysis of the X-ray diffraction pattern of the sublimate (Figure 11A) showed that two iron-containing crystalline phases (hematite Fe2O3 and iron(III) oxide chloride FeOCl) were obtained, with hematite dominating (Figure 11B).

[0092] Example 4: Electrolytic hydrogen decrepitation of Nd-based magnets material A fragment of a used rare earth element-Fe-B (REE-Fe-B) alloy magnet was removed from a computer hard disk drive. The magnet was originally coated with aluminum; however, prior to shipping to Israel, the surface was polished, thus corroding some of the surface.

[0093] method Structural characterization X-ray diffraction (XRD) of the as-received magnet fragments was performed on a TTRAX III θ-θ diffractometer, while the patterns of the HD (hydrogen decrepitate) powders were measured on an Ultima III θ-θ diffractometer (both diffractometers are products of Rigaku Corporation, Japan). Phase identification was achieved using Jade_Pro (MDI, CAL.) software and the Inorganic Crystal Structure Database (ICSD). Cu K α X-ray, Bragg-Brentano protocol, diffracted beam monochromator and variable divergence slit width constituted our standard operating procedure on both diffractometers. The elemental content of magnet fragments and HD powder was characterized by energy dispersive (X-ray fluorescence) spectroscopy (EDS) and on a LEO Supra scanning electron microscope (SEM). The mass % metal content was quantified by inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7700s) after dissolution of magnet or HD powder in aqua regia. 0.65 grams of as-received magnet fragments were dissolved in 100 ml aqua regia at room temperature with continuous stirring for 24 hours. This solution was diluted to 1000 ml with deionized water to prepare a stock solution. 2 ml of the stock solution was then diluted to 100 ml with deionized water. 0.86 grams of hydrogen decrepitate powder (after electrolysis, filtration and drying in air at 353 K) was dissolved in 100 ml aqua regia at room temperature with continuous stirring for 24 hours. The solution was then diluted to 200 ml with deionized water. Two powder samples were measured: for sample #1, 2 ml of the stock solution was diluted to 1000 ml, and for sample #2, 5 ml of the stock solution was diluted to 1000 ml, both with deionized water.

[0094] Electrolysis The details of the laboratory-scale electrolysis cell are shown in Figure 6A. A glass vessel containing 700 ml of 1 M / L KOH solution served as the electrolysis cell. A homemade titanium metal cathode, dimensions [3.5 × 3.5] cm 2 , and nickel, plate anode, dimensions [4.0 × 4.0] cm 2served as the electrode. An 18-mesh titanium grid was in electrical contact with the cathode. A potential of 4.7 V and a current of 13-15 A were provided by a Kepco power supply KLP-20-120-1200. The cathode current density was 0.8-0.9 A / cm 2 where the total area included the Ti grid. 30-40 mm pieces of as-received Nd-magnets (without demagnetization, crushing or grinding), total weight 300-500 grams, were placed on the titanium grid. Electrolysis at room temperature for 2 hours produced a decrepitated powder, with particles small enough to easily pass through 1 mm diameter holes in the Ti grid, and collected on the bottom of a glass container. The powder was removed from the electrolyte solution by filtration and then dried in air at 353 K. Subsequent mesh sieving provided an upper limit to the particle size.

[0095] Magnetic properties A SQUID magnetometer (MPMS3, LOT-Quantum Design, Inc.) was used in vibration mode (VSM) with a peak amplitude of 2 mm, a frequency of 13 Hz, and an averaging time of 10 s. The magnetic moment (M, [10 -3 Am 2 ]) at ambient temperature (300K) and magnetic field strength |μ o The temperature dependence of the magnetic moment of the sample was measured using H | ≦ 6 T. o The measurements were performed at H=6 T and fitted to the modified Bloch method using the Levenberg-Marquardt algorithm for nonlinear curve fitting in Origin (OriginLab MA). One piece of the as-received magnet, as well as a fine, electrolytically decrepitated magnet, and a powder sample were measured. The thin, elongated, plate-like magnet piece had a mass of 31.0 mg and approximate dimensions of [5 × 2.8 × 0.3] mm. 3The demagnetization factor was estimated to be D = 0.23, consistent with the size and shape of the powder sample in the standard brass holder.

[0096] Results and Discussion Structural characterization of Nd-magnet fragments before electrolysis The as-received Nd-magnet fragments appeared irregularly shaped, 20-30 mm in size, and had partially etched surfaces. Full pattern fitting of the XRD profiles to ICSD pattern #48143 measured on relatively undamaged surface regions yielded R-factors below about 20%, mainly due to the difficulty of fitting such highly textured alloys. α The radiation could only probe a layer about 10 microns thick at the magnet surface due to the strong absorption at 8 KeV of RE (rare earth) metals and iron. SEM images and EDS spectra of the surface are shown in Figures 5A-5D. Here again only a thin layer (1-2 μm) of the fragment surface is probed. The magnet contained Dy (dysprosium) as an additive in addition to Pr (praseodymium). ICP-MS quantitative elemental analysis (wt%) of the as-received magnet, solubilized as described in section 2, gives the following: Nd, 23.5; Pr, 7.8; Dy, 3.7; Ce, 0.01; Fe, 61.7; Al, 0.6. No boron was identified.

[0097] thermodynamic calculations As a guide to understanding the thermodynamics of the reaction of each of the metal alloy components with hydrogen, the Gibbs energies for reactions with atomic hydrogen or hydrogen gas in the temperature range 273-473 K were calculated. The calculations were performed using a computer program based on standard values ​​for pure substances. The Gibbs energies (ΔG) in the temperature range 273-473 K are shown in Table 6 for reactions with hydrogen: Group 1 - reactions with atomic hydrogen and Group 2 - reactions with hydrogen gas. [Table 6]

[0098] With reference to Table 6, under the conditions of the experiment, the Gibbs energies of reactions (1, 2) in group 1 for rare earth metals were strongly negative (-520 to -570 kJ / mol). Calculations predict that the reaction of Nd and Pr with atomic hydrogen will result in the formation of Nd and Pr hydrides within a wide temperature range, including the range of interest. Metallic dysprosium can react with atomic hydrogen, producing DyH2 (reaction 3). Group 2 includes reactions between magnet components and hydrogen gas. The possibility of reactions (7-9) was similarly confirmed throughout the temperature range of interest. However, the values ​​of Gibbs energies for reactions (7, 8) were much less negative than those for reactions (1, 2). Iron only participates in minor reactions with both atomic hydrogen and hydrogen gas under the conditions of the experiment (reactions 4, 10). Boron is highly reactive with atomic H, but not with hydrogen gas. The resulting B2H6 gas is moderately toxic when inhaled, but it is easily converted to boric acid by hydrolysis. The damaged aluminum coating remaining on the magnet fragments was not expected to react with hydrogen gas, but should be transformed into Al hydride by interaction with atomic hydrogen.

[0099] Table 7 contains the hydrolysis reactions of neodymium, praseodymium, and dysprosium hydrides in water. Under experimental conditions, the Gibbs energies of reactions (1-6) for rare earth metal hydrides were strongly negative (approximately -340 to -500 kJ / mol). Therefore, thermodynamic calculations predicted that the hydrolysis reactions of neodymium, praseodymium, and dysprosium hydrides can result in the formation of Nd, Pr, and Dy hydroxides or oxides within a wide temperature range, including the range of interest 273-473 K. Similarly, hydrolysis can result in the oxidation of iron to hematite as well as other iron oxides (Table 7). [Table 7]

[0100] Electrolytic hydrogen decrepitation As mentioned above, the calculated Gibbs energies of reaction of individual REEs with atomic hydrogen (Table 6) are strongly negative, thus predicting rapid chemical decrepitation of two-phase Nd-magnets within the temperature range of interest. These reactions occur immediately after the onset of atomic hydrogen release at the cathode during electrolysis. As described in the Methods section above, complete magnet decrepitation was observed after 2 hours of electrolysis at room temperature, producing powders with particle sizes of <200 mesh. The powders were filtered from the KOH electrolyte and dried in air at 353 K. Subsequent sieving through various sized meshes gave an upper limit of 44 μm for the particle size of the HD powder (FIGS. 12A, 12B). The HD powders were also characterized for elemental composition and crystal structure.

[0101] Except for the additional X-ray fluorescence (XRF) peaks identified as Si and Ca, the EDS spectrum in Figure 12B closely resembles that of the as-received magnet fragment (Figures 5A-5D). The Si and Ca may have been etched from the electrolytic cell by the alkaline electrolyte. Quantitative ICP-MS analysis (wt%, average of two HD samples) gives: Nd-15.99; Pr-5.98; Dy-3.23; Ce-0.02; Fe-49.87; B-0.95; Si-0.91; Ca-0.03.

[0102] X-ray diffraction phase analysis of fine HD particles Phase identification of X-ray diffraction (XRD) peaks from fine HD particles (Figure 13) revealed that the majority of the HD particles were magnet alloy hydride NdFe 14 BH 1.86 (ICSD#80973). The Nd-magnet hydride has the same tetragonal crystal symmetry as the parent metal alloy, with only a moderate expansion of the unit cell volume. SEM images (Figure 8) show that the powder contains a wide mixture of spherical shapes and sizes. XRD profile fitting using Jade_Pro reveals that the as-received magnets are highly anisotropic (grainy), while the Nd-magnet hydride powder is crystallographically isotropic in nature. ( * ICSD stands for Inorganic Crystal Structure Database, the world's largest database of completely characterized inorganic crystal structures).

[0103] The increase in unit cell dimensions reveals that atomic H can be absorbed into the matrix after being absorbed into the Nd-rich grain boundary phase during electrolysis under ambient conditions (Table 8). [Table 8]

[0104] It is this absorption of H into electron-deficient, intergranular boundary phases that produces decrepitation in sintered magnet alloys. Even in the alloy matrix, H tends to be located near Nd atoms, rather than near Fe or B atoms. X-ray diffraction peaks that cannot be associated with magnet alloy hydrides have been identified as minor phases of Nd-oxide (Ia-3) (ICSD#191535) and Nd-trihydroxide (ICSD#398), as well as Pr-oxide (ICSD#75481) and NdFe2 alloy (ICSD#103548). One or more of the various iron oxide phases, including hematite, may also be present. This multiplicity of possible minor phases makes quantitative analysis of electrolytic HD powder XRD patterns very challenging ( * ICSD stands for Inorganic Crystal Structure Database, the world's largest database of completely characterized inorganic crystal structures).

[0105] Magnetic properties of electrolytically decrepitated EoL NdFeB magnets The magnetic properties of the electrolytic HD powder were characterized as described in the Methods section above. The results are summarized in Table 9 (SQUID magnetometer data is presented in Figures 14A-14C, and Figure 15) and compared with those obtained from untreated Nd-magnet fragments. As expected for small particle HD powder that was not degassed at high temperature, a weak remanent magnetic polarization J was observed. rem and coercive field H c Only the magnetic energy density (Fig. 14A, 14B) is detected in the SQUID magnetometer measurement. Therefore, the magnetic energy density of the HD powder (Fig. 14C) is 10 times higher than that of the as-received EoL Nd-magnet. 3 Twice lower. [Table 9]

[0106] Oxidation of HD powder NdFe 14High levels of oxidation (3000-5000 ppm oxygen) in B alloy wastes are a significant obstacle to large-scale recovery and recycling of valuable rare earth metals. Even pristine NdFeB alloys may contain 300-400 ppm oxygen, with most of the oxidation reactions occurring within the Nd-rich grain boundaries. Both confocal microscopy and Raman spectroscopy were used to locate, measure, and identify the growth of surface reaction products at room temperature immediately after exposure to air. These measurements showed that significant growth of Nd2O3 occurs at the triple junctions of the Nd-rich grain boundaries. It was further found that the oxidation triple junctions did not react with hydrogen to form NdH2, leading to poor redistribution of the Nd-rich phase during subsequent resintering. The grain boundary phase no longer melts uniformly due to the very high melting temperatures of the RE (rare earth) metal oxides, and thus full mass density cannot be achieved in the recycled magnets. The dispersed Nd2O3 compounds are responsible for the formation of Nd2Fe 14 B Reduces the coercive force of the alloy.

[0107] HD powders with large surface-to-volume ratios oxidize easily on exposure to air. Very low magnetic coercivity at 300 K, such as that reported by us (Table 9), was also attributed to the presence of metallic α-Fe at the grain boundaries. This soft magnetic phase is formed as a result of localized heterogeneity due to the formation of neodymium hydrides and associated exothermic reactions. With further processing of the powder under ambient conditions, the oxygen content only increases. It is shown that the sinterability and thus the degradation of the magnetic properties can be overcome, at least in part, by blending additional Nd in the form of Nd hydrides into the HD powders.

[0108] conclusion Electrochemical hydrogen decrepitation can be used to safely and economically fabricate cm-sized, sintered NdFe 14Pulverization of NdFeB alloy magnet fragments under ambient conditions using 1M KOH as the selective aqueous electrolyte to a fine powder (particle size <325 mesh, i.e. <44 μm) can be an effective procedure. This process eliminates the need for high temperature equipment or high pressure pure hydrogen atmosphere. The fine particle NdFeB hydride powder can be further processed to form novel magnetic materials or to facilitate the separation of valuable rare earth metals from the iron-bearing components of the magnet.

[0109] All references mentioned ("cited herein"), and all references cited or referenced in this document, are hereby or in any document hereby incorporated by reference herein. Along with any manufacturer's instructions, manuals, product specifications, and product sheets for any of the products listed, they may be incorporated by reference herein and may be used in the practice of the invention. More particularly, all references are incorporated by reference to the extent that each individual reference is specifically and individually indicated to be incorporated by reference.

[0110] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art and it is to be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the invention.

Claims

1. An electrolytic apparatus for atomic hydrogen decrepitation of at least one rare earth-containing material, wherein the electrolytic apparatus is The cathode is a cathode in which at least one of the rare earth-containing materials is a cathode; anode; Electrolyte; Includes, The electrolytic apparatus is configured to carry out an electrolytic reaction to declentiate the at least one rare earth-containing material.

2. The electrolytic apparatus according to claim 1, wherein the at least one rare earth-containing material comprises any of the following elements selected from: cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd), praseodymium (Pr), promethium (Pm), samarium (Sm), scandium (Sc), terbium (Tb), thulium (Tm), ytterbium (Yb), and yttrium (Y).

3. The electrolytic apparatus according to claim 1, wherein the at least one rare earth-containing material includes a ferromagnetic alloy or a rare earth magnet.

4. The rare earth-containing material is selected from the list below, which is the electrolytic apparatus according to claim 1: Nd ２ Fe １４ B, SmCO ５ , Sm(Co, Fe, Cu, Zr) ７ Sr-ferrite, iron bar magnets, or a combination thereof.

5. The electrolytic apparatus according to claim 1, wherein the cathode further comprises copper, nickel, steel, titanium, a rare earth-containing material, or any combination thereof.

6. The electrolytic apparatus according to claim 1, further comprising at least one additional cathode.

7. The electrolytic apparatus according to claim 1, wherein the electrolyte is an aqueous solution of KOH or NaOH.

8. The electrolytic apparatus according to claim 1, wherein the cathode further comprises at least one grid adapted to allow a decleptated fragment to pass through it.

9. The electrolytic apparatus according to claim 8, wherein at least one grid has holes having a size in the range of 1 to 100 μm in diameter.

10. The electrolytic apparatus according to claim 9, wherein the at least one grid is made of copper, nickel, steel, titanium, a ferromagnetic alloy, or any combination thereof.

11. A method for electrolytic atomic hydrogen decrepitation of at least one rare earth-containing material, To provide an electrolytic apparatus according to any one of claims 1 to 10, configured to carry out an electrolytic reaction in an electrolyte; and The electrolytic reaction is carried out by applying a potential between the anode and the cathode, thereby generating atomic hydrogen at the cathode. Methods that include...

12. A method for electrolytic atomic hydrogen decrepitation of at least one rare earth-containing material, To provide an electrolytic apparatus comprising an anode, a cathode, and an electrolyte, configured to carry out an electrolytic reaction and declentiate at least one rare earth-containing material; Placing the aforementioned at least one rare earth-containing material on the cathode; and The electrolytic reaction is carried out by applying a potential between the anode and the cathode, thereby generating atomic hydrogen at the cathode. Methods that include...

13. The method according to claim 12, wherein the cathode comprises copper, nickel, steel, titanium, a rare earth-containing material, or any combination thereof.

14. The method according to claim 11 or 12, wherein the electrolytic reaction is carried out at room temperature.

15. The method according to claim 11 or 12, wherein the electrolytic reaction is carried out at a high temperature.

16. The method according to claim 11 or 12, wherein the applied potential is 4 to 10 V.

17. Atomic hydrogen is 2H from the cathode. ＋ (aq) + 2e － →The method according to claim 11 or 12, wherein 2H(g) is released by a reduction reaction.

18. The H+ is the water (H) inside the cell. ２ The method according to claim 11 or 12, which is the result of electrolysis of O).

19. The method according to claim 11 or 12, wherein the electrolyte comprises an aqueous solution of KOH or NaOH.

20. The method according to claim 11 or 12, wherein the cathode further comprises at least one grid adapted to allow a decleptated fragment to pass through it.

21. The method according to claim 20, wherein the at least one grid is made of copper, nickel, steel, titanium, a ferromagnetic alloy, or any combination thereof.

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