A method for recovering NdFeB permanent magnet waste using water-co-saltification roasting

Abstract

This invention relates to a method for recovering NdFeB permanent magnet waste using a water-coordinated salting roasting process. The method includes: mixing NdFeB permanent magnet waste with a salting agent, and performing water-coordinated salting roasting in a steam-containing atmosphere to obtain a salting roasting product; leaching the salting roasting product with water to obtain a rare earth leachate and leaching residue; adding a precipitant to the rare earth leachate to induce a precipitation reaction, resulting in a rare earth precipitate; and sequentially calcining and electrolyzing the rare earth precipitate with molten salt to obtain regenerated mixed rare earth elements. This invention utilizes water-coordinated salting roasting instead of high-temperature oxidative roasting, and water leaching instead of acid leaching, achieving efficient extraction of rare earth elements from the waste and realizing high-value utilization of the waste.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, specifically to the recycling and utilization of neodymium iron boron permanent magnet waste, and particularly to a method for recycling neodymium iron boron permanent magnet waste using a water-co-saltification roasting method. Background Technology

[0002] Sintered NdFeB magnets, due to their excellent magnetic properties, are widely used in high-tech industries such as new energy vehicles, wind power generation, humanoid robots, and low-altitude economy, with market demand and production increasing year by year. In recent years, with increasingly stringent requirements for lightweight and miniaturized products in high-tech fields, especially microelectronics, the required magnetic components are becoming smaller and smaller. Extensive machining is required to process sintered NdFeB magnet blanks into the required shapes and sizes, generating a large amount of waste containing rare earth elements, which has significant recycling value. Therefore, research on green, efficient, and high-value recycling technologies for NdFeB permanent magnet waste can not only achieve comprehensive resource utilization and promote the sustainable development of the rare earth industry, but also has important significance for ecological environmental protection.

[0003] Currently, in domestic industrial applications, rare earth elements are mainly separated and extracted from sintered NdFeB permanent magnet waste through traditional hydrometallurgical processes. Specifically, this involves separating impurities from rare earths through acid dissolution, solvent extraction, and precipitation, and further separating individual rare earth elements through solvent extraction to achieve the goal of recycling and reusing rare earths.

[0004] CN111349798A discloses a resource recovery system and method for NdFeB waste, including acid leaching of NdFeB waste with hydrochloric acid, followed by solid-liquid separation to obtain an acid leaching solution; spray pyrolysis of the obtained acid leaching solution to obtain acid-containing flue gas and solid materials; water leaching of the solid materials, followed by solid-liquid separation to obtain a filter cake and a rare earth metal chloride solution; drying of the obtained filter cake to obtain iron oxide red product; and extraction and separation of the obtained rare earth metal chloride solution. The recovery method provided by this invention requires acid leaching and involves a spray pyrolysis process for the acid leaching solution, which requires a large amount of acid and generates acid vapor, easily corroding equipment and hindering environmentally friendly recycling.

[0005] CN104087755A discloses a method for recovering rare earth elements from NdFeB waste, comprising: mixing aluminum fluoride powder and cryolite powder at a mass ratio of 1:1 to 1:10 to obtain a cryolite-aluminum fluoride mixture; crushing the NdFeB waste into particles with a size of 4-6 mm and then embedding them in the cryolite-aluminum fluoride mixture; placing the cryolite-aluminum fluoride mixture containing the NdFeB waste in an electric furnace and reacting it at a temperature of 900-1200℃ for 3-12 hours; and performing solid-liquid separation on the reaction product to obtain a solid residue and a molten salt, wherein the solid residue is scrap steel and the molten salt is a mixture of rare earth fluoride, cryolite, and aluminum fluoride. This invention only relates to extracting rare earth elements from NdFeB waste, but the obtained product is a mixture of rare earth fluoride, cryolite, and aluminum fluoride, which requires further extraction and cannot directly yield recycled mixed rare earth elements.

[0006] CN112813264A discloses a method for extracting and recovering valuable elements from NdFeB waste. The method includes a first extraction of the leachate from the NdFeB waste to obtain a first organic phase and a first aqueous phase; the first organic phase is then subjected to a first back-extraction to obtain an iron-containing solution; the first aqueous phase is then subjected to a second extraction to obtain a second aqueous phase and a second organic phase; the second organic phase is then subjected to a second back-extraction to obtain a NdFeB-containing solution. This invention involves a multi-step extraction process and requires the recovery of the organic phase used, making the process complex.

[0007] In summary, although traditional wet recycling processes can yield high-purity rare earth compound products, this method is not only lengthy and consumes large amounts of acid and alkali, but also results in the release of large quantities of ammonia nitrogen wastewater due to the saponification of the extractant, leading to high environmental costs. This does not meet the current requirements for green environmental protection, energy conservation, and sustainable development.

[0008] Therefore, it is of great significance to provide a method that has a short process, low pollution, and can achieve green and efficient recycling and high-value reuse of NdFeB permanent magnet waste. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a method for recovering NdFeB permanent magnet waste using a water-coordinated salting roasting method. This invention utilizes water-coordinated salting roasting instead of high-temperature oxidative roasting, and water leaching instead of acid leaching, achieving efficient extraction of rare earth elements from the waste and realizing high-value utilization of the waste.

[0010] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for recovering NdFeB permanent magnet waste using a water-co-saltification roasting method, the method comprising: Waste NdFeB permanent magnets and a salting agent are mixed and subjected to water-co-salting roasting in a steam atmosphere to obtain a salting roasting product. The salting roasting product is then leached in water to obtain a rare earth leachate and a leachate residue. A precipitant is added to the rare earth leachate to induce a precipitation reaction, resulting in a rare earth precipitate. The rare earth precipitate is then subjected to calcination and molten salt electrolysis to obtain a regenerated mixed rare earth.

[0011] This invention involves salting and roasting in a steam-containing atmosphere. The steam acts as a catalyst during the salting and roasting process, promoting the salting reaction between NdFeB permanent magnet waste and the salting agent. This selectively converts rare earth elements and rare earth oxides in the waste into water-soluble rare earth salts. After water leaching, the rare earth elements are enriched in the leachate, while other impurities such as iron enter the leaching residue in the form of oxides or elemental metals. The rare earth leachate is then subjected to precipitation, calcination, and molten salt electrolysis to obtain high-purity mixed rare earths that can be directly used for the preparation of recycled rare earth permanent magnet materials, thus realizing the high-value reuse of NdFeB permanent magnet waste.

[0012] Compared to traditional salting roasting processes, the water-co-salting roasting process provided by this invention reduces the amount of salting agent used and can improve the recovery rate of rare earth elements and the purity of rare earth elements in the regenerated mixed rare earth at a lower roasting temperature. Simultaneously, it uses water leaching instead of acid leaching, reducing acid consumption, and uses precipitation reaction instead of extraction separation, avoiding the wastewater treatment problems associated with extraction. Therefore, the recovery method provided by this invention has the advantages of a simple process flow, low cost, and environmental friendliness, and has good prospects for industrial production.

[0013] Preferably, in the atmosphere containing water vapor, the water vapor includes water vapor obtained from in-situ water vaporization and / or water vapor introduced from an external gas source.

[0014] Preferably, the atmosphere containing water vapor also includes any one or a combination of at least two of oxygen, nitrogen, or inert gases.

[0015] Preferably, when the water vapor is obtained by in-situ vaporization of water, the amount of water added is 1wt% to 95wt% of the total mass of the NdFeB permanent magnet waste and the salting agent.

[0016] Preferably, when the water vapor is water vapor introduced from an external gas source, the concentration of the introduced water vapor is 5 vol% to 90 vol.

[0017] Preferably, when the water vapor is obtained by in-situ vaporization of water, the amount of water added is 30wt% to 50wt% of the total mass of the NdFeB permanent magnet waste and the salting agent.

[0018] Preferably, when the water vapor is water vapor introduced from an external gas source, the concentration of the introduced water vapor is 5 vol% to 30 vol.

[0019] Preferably, the temperature of the water-co-saltification roasting is 100℃~350℃.

[0020] Preferably, the water-co-salinization roasting time is 1h to 5h.

[0021] Preferably, the heating rate of the water-co-salinization roasting is 5℃ / min to 15℃ / min.

[0022] Preferably, the salifying agent comprises chloride salts and / or sulfate salts; the salifying agent comprises any one or a combination of at least two of the following: NH4Cl, FeCl2, FeCl3, AlCl3, MgCl2, ZnCl2, CaCl2, CuCl2, CoCl2, NaCl, KCl, (NH4)2SO4, FeSO4, FeS2, Fe2(SO4)3, MgSO4, Al2(SO4)3, ZnSO4, CaSO4, CuSO4, CoSO4, Na2SO4, and K2SO4.

[0023] Preferably, the stoichiometric coefficient of the salting agent required to completely convert the rare earth elements in the NdFeB permanent magnet waste into rare earth salts is M1, and the amount of salting agent added is M1~2.5M1, preferably 1.2M1~2M1.

[0024] Preferably, the water immersion temperature is 20℃~80℃.

[0025] Preferably, the immersion time is 10 min to 120 min.

[0026] Preferably, the water immersion is carried out under stirring.

[0027] Preferably, the precipitant comprises oxalic acid and / or ammonium bicarbonate.

[0028] Preferably, the stoichiometric coefficient of the precipitant required for the complete precipitation of rare earth elements in the NdFeB permanent magnet waste is M2, and the amount of the precipitant added is M2~1.5M2.

[0029] Preferably, the pH of the precipitation reaction is 1 to 3.5.

[0030] Preferably, the calcination temperature is 850℃~1000℃.

[0031] Preferably, the calcination time is 1 hour to 3 hours.

[0032] Preferably, the electrolyte system for molten salt electrolysis includes the REF3-LiF electrolyte system, where RE represents rare earth elements.

[0033] Preferably, the temperature of the molten salt electrolysis is 950℃~1050℃.

[0034] Preferably, the electrolysis time of the molten salt is 12h to 24h.

[0035] Compared with the prior art, the present invention has the following beneficial effects: (1) Compared with the traditional salting roasting process, the water-co-salting roasting process provided by the present invention reduces the amount of salting agent used and can improve the recovery rate of rare earth elements and the purity of rare earth in the regenerated mixed rare earth at a lower roasting temperature. At the same time, water immersion is used instead of acid immersion, reducing acid consumption. Precipitation reaction is used instead of extraction separation process, avoiding the wastewater treatment problem caused by extraction.

[0036] (2) The recycling method provided by the present invention has the advantages of simple process flow, low cost and green environmental protection, and has good prospects for industrial production. Attached Figure Description

[0037] Figure 1 This is a process flow diagram of the method for recovering NdFeB permanent magnet waste using water-co-saltification roasting in Example 1. Detailed Implementation

[0038] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0039] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0040] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0041] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0042] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0043] In one specific embodiment, the present invention provides a method for recovering NdFeB permanent magnet waste using a water-co-saltification roasting method, the method comprising: Waste NdFeB permanent magnets and a salting agent are mixed and subjected to water-co-salting roasting in a steam atmosphere to obtain a salting roasting product. The salting roasting product is then leached in water to obtain a rare earth leachate and a leachate residue. A precipitant is added to the rare earth leachate to induce a precipitation reaction, resulting in a rare earth precipitate. The rare earth precipitate is then subjected to calcination and molten salt electrolysis to obtain a regenerated mixed rare earth.

[0044] This invention involves salting and roasting in a steam-containing atmosphere. The steam acts as a catalyst during the salting and roasting process, promoting the salting reaction between NdFeB permanent magnet waste and the salting agent. This selectively converts rare earth elements and rare earth oxides in the waste into water-soluble rare earth salts. After water leaching, the rare earth elements are enriched in the leachate, while other impurities such as iron enter the leaching residue in the form of oxides or elemental metals. The rare earth leachate is then subjected to precipitation, calcination, and molten salt electrolysis to obtain high-purity mixed rare earths that can be directly used for the preparation of recycled rare earth permanent magnet materials, thus realizing the high-value reuse of NdFeB permanent magnet waste.

[0045] Compared to traditional salting roasting processes, the water-co-salting roasting process provided by this invention reduces the amount of salting agent used and can improve the recovery rate of rare earth elements and the purity of rare earth elements in the regenerated mixed rare earth at a lower roasting temperature. Furthermore, it uses water leaching instead of acid leaching, reducing acid consumption, and uses precipitation reaction instead of extraction separation, avoiding the wastewater treatment problems associated with extraction. Therefore, the recovery method provided by this invention has the advantages of a simple process flow, low cost, and environmental friendliness, and has good prospects for industrial production.

[0046] In some embodiments, the water vapor in the atmosphere includes water vapor obtained from in-situ water vaporization and / or water vapor introduced from an external gas source.

[0047] In some embodiments, the water vapor atmosphere further includes any one or a combination of at least two of oxygen, nitrogen, or inert gases. For example, the water vapor atmosphere, in addition to water vapor, includes any one or a combination of at least two of air, oxygen, inert gases, or nitrogen, preferably air and / or oxygen.

[0048] In some embodiments, when the water vapor is water vapor obtained by in-situ vaporization of water, the amount of water added is 1wt% to 95wt% of the total mass of NdFeB permanent magnet waste and salting agent, for example, it can be 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, or 90wt%.

[0049] In some embodiments, when the water vapor is water vapor introduced from an external gas source, the concentration of the introduced water vapor is 5 vol% to 90 vol%, for example, it can be 5 vol%, 10 vol%, 15 vol%, 20 vol%, 25 vol%, 30 vol%, 35 vol%, 40 vol%, 45 vol%, 50 vol%, 55 vol%, 60 vol%, 65 vol%, 70 vol%, 75 vol%, 80 vol%, 85 vol%, or 90 vol%.

[0050] In some embodiments, when the water vapor is water vapor obtained by in-situ vaporization of water, the amount of water added is 30wt% to 50wt% of the total mass of NdFeB permanent magnet waste and salting agent, for example, it can be 30wt%, 35wt%, 40wt%, 45wt% or 50wt%.

[0051] In some embodiments, when the water vapor is water vapor introduced from an external gas source, the concentration of the introduced water vapor is 5 vol% to 30 vol%, for example, it can be 5 vol%, 10 vol%, 15 vol%, 20 vol%, 25 vol%, or 30 vol%.

[0052] The recycling method provided by this invention utilizes water-co-saltification roasting, using steam catalysis to promote the salting reaction between NdFeB permanent magnet waste and salt agent, which can improve the recovery rate of rare earth elements and the purity of rare earth elements in the regenerated mixed rare earth at a lower roasting temperature.

[0053] In some embodiments, the temperature of the water-co-salinization roasting is 100°C to 350°C, for example, it can be 100°C, 150°C, 200°C, 250°C, 300°C or 350°C.

[0054] In some embodiments, the water-co-salinization roasting time is 1h to 5h, for example, it can be 1h, 2h, 3h, 4h or 5h.

[0055] In some embodiments, the heating rate of the water-co-salinization roasting is 5°C / min to 15°C / min, for example, it can be 5°C / min, 7°C / min, 9°C / min, 11°C / min, 13°C / min or 15°C / min.

[0056] In some embodiments, the salifying agent comprises chloride salts and / or sulfate salts; the salifying agent comprises any one or a combination of at least two of the following: NH4Cl, FeCl2, FeCl3, AlCl3, MgCl2, ZnCl2, CaCl2, CuCl2, CoCl2, NaCl, KCl, (NH4)2SO4, FeSO4, FeS2, Fe2(SO4)3, MgSO4, Al2(SO4)3, ZnSO4, CaSO4, CuSO4, CoSO4, Na2SO4, and K2SO4.

[0057] In this invention, the water-coordinated salting roasting process effectively reduces the amount of salting agent used. If the amount of salting agent is too large, it is easy to produce side reactions and increase costs; if the amount of salting agent is too small, it will lead to insufficient reaction and fail to fully convert the rare earth elements in the NdFeB permanent magnet waste into rare earth salts.

[0058] In some embodiments, the stoichiometric coefficient of the salicylic agent required to completely convert the rare earth elements in the NdFeB permanent magnet waste into rare earth salts is M1, and the amount of the salicylic agent added is M1 to 2.5M1, for example, it can be M1, 1.2M1, 1.5M1, 1.8M1, 2M1, 2.2M1 or 2.5M1, preferably 1.2M1 to 2M1.

[0059] The recycling method provided by this invention does not specifically limit the solid-liquid ratio of the salt-roasted product to the water during the water immersion process; the water only needs to be in excess and sufficient to completely submerge the salt-roasted product.

[0060] In some embodiments, the water immersion temperature is 20°C to 80°C, for example, it can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C.

[0061] In some embodiments, the immersion time is 10 min to 120 min, for example, it can be 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min or 120 min.

[0062] In some embodiments, the water immersion is carried out under stirring.

[0063] In some embodiments, the precipitant includes oxalic acid and / or ammonium bicarbonate. In this invention, the precipitant can be added directly to the rare earth leachate, or an aqueous solution of the precipitant, such as an oxalic acid solution and / or an ammonium bicarbonate solution, can be prepared first and then added to the rare earth leachate to carry out the precipitation reaction. Appropriate precipitant dosage and pH can ensure sufficient precipitation of rare earth elements while avoiding co-precipitation of non-rare earth impurities, thus reducing the purity of the rare earth mixture.

[0064] In some embodiments, the stoichiometric coefficient of the precipitant required to completely precipitate the rare earth elements in the NdFeB permanent magnet waste is M2, and the amount of the precipitant added is M2 to 1.5M2, for example, it can be M2, 1.1M2, 1.2M2, 1.3M2, 1.4M2 or 1.5M2.

[0065] In some embodiments, the pH of the precipitation reaction is 1 to 3.5, for example, it can be 1, 1.5, 2, 2.5, 3 or 3.5.

[0066] In this invention, the method of adjusting pH is not particularly limited. For example, hydrochloric acid solution and / or sulfuric acid solution can be used as acidic regulators, and sodium hydroxide solution can be used as alkaline regulators.

[0067] In some embodiments, the calcination temperature is 850°C to 1000°C, for example, it can be 850°C, 900°C, 950°C or 1000°C.

[0068] In some embodiments, the calcination time is 1h to 3h, for example, it can be 1h, 1.5h, 2h, 2.5h or 3h.

[0069] In some embodiments, the electrolyte system for molten salt electrolysis includes a REF3-LiF electrolyte system, where RE represents a rare earth element.

[0070] In some embodiments, the temperature of the molten salt electrolysis is 950°C to 1050°C, for example, 950°C, 975°C, 1000°C, 1025°C or 1050°C.

[0071] In some embodiments, the electrolysis time of the molten salt is 12h to 24h, for example, it can be 12h, 13h, 15h, 18h, 21h or 24h.

[0072] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0073] To clearly illustrate the technical solution of this invention, the main phase of the neodymium iron boron permanent magnet waste in the specific embodiments includes Nd2Fe. 14 The main phase consists of B, RE2O3 (RE = Nd, Pr, Ce, Dy, Tb, Gd, etc.), Fe, Fe2O3, etc.

[0074] The above description is only for clearly illustrating the technical solution of the present invention and is not intended to further limit the present invention.

[0075] Example 1 This embodiment provides a method for recovering NdFeB permanent magnet waste using a water-co-saltification roasting method, such as... Figure 1 The process flow diagram shown indicates that the method includes: (1) Taking the stoichiometric number of NH4Cl required for all rare earth elements in the NdFeB permanent magnet waste to be converted into rare earth salt as M1, NdFeB permanent magnet waste and NH4Cl with a stoichiometric number of 1.5M1 are uniformly mixed and placed in a tube furnace with an air atmosphere. Water vapor is introduced with a concentration of 30 vol%, and the temperature is raised to 200°C at a heating rate of 10°C / min. Water-co-salting roasting is carried out for 3 hours to obtain the salting roasting product. (2) At 60°C, the salt-roasting product obtained in step (1) is stirred and soaked in water for 30 minutes to obtain rare earth leachate and leachate residue. (3) Add oxalic acid solution to the rare earth leachate obtained in step (2), with the stoichiometric number of oxalic acid required for all rare earth elements in the NdFeB permanent magnet waste to precipitate as M2, the amount of oxalic acid in the oxalic acid solution as 1.5M2, adjust the pH to 3, and carry out the precipitation reaction to obtain rare earth precipitate. (4) The rare earth precipitate obtained in step (3) is calcined at 900℃ for 2 hours and then placed in the REF3-LiF electrolyte system for molten salt electrolysis. The temperature of molten salt electrolysis is 1000℃ and the time is 18 hours to obtain regenerated mixed rare earth.

[0076] Example 2 This embodiment provides a method for recovering NdFeB permanent magnet waste using a water-co-saltification roasting method, the method comprising: (1) Taking the stoichiometric number of ZnSO4 required for all rare earth elements in the NdFeB permanent magnet waste to be converted into rare earth salt as M1, the NdFeB permanent magnet waste and ZnSO4 with a stoichiometric number of 2M1 are mixed evenly, and then 35wt% of water of the total mass of NdFeB permanent magnet waste and ZnSO4 is added. The mixture is placed in a tube furnace in an air atmosphere and heated to 100℃ at a heating rate of 5℃ / min. The mixture is then subjected to water-co-salting roasting for 5 hours to obtain the salting roasting product. (2) At 25°C, the salt-roasted product obtained in step (1) is stirred and soaked in water for 120 min to obtain rare earth leachate and leachate residue. (3) Add ammonium bicarbonate to the rare earth leachate obtained in step (2), with the stoichiometric number of ammonium bicarbonate required for all rare earth elements in the NdFeB permanent magnet waste to precipitate as M2, the amount of ammonium bicarbonate added as M2, adjust the pH to 3.5, and carry out the precipitation reaction to obtain rare earth precipitate. (4) The rare earth precipitate obtained in step (3) is calcined at 1000℃ for 1h and then placed in the REF3-LiF electrolyte system for molten salt electrolysis. The temperature of molten salt electrolysis is 950℃ and the time is 24h to obtain regenerated mixed rare earth.

[0077] Example 3 This embodiment provides a method for recovering NdFeB permanent magnet waste using a water-co-saltification roasting method, the method comprising: (1) Using (NH4)2SO4 and FeSO4 in a mass ratio of 1:1 as composite salting agents, and taking the stoichiometric number of the composite salting agent required to convert all rare earth elements in the NdFeB permanent magnet waste into rare earth salts as M1, the NdFeB permanent magnet waste and the composite salting agent with a stoichiometric number of 2M1 are uniformly mixed and placed in a tube furnace with an air atmosphere. Water vapor is introduced, the concentration of water vapor is 15 vol%, and the temperature is raised to 350°C at a heating rate of 15°C / min. Water-co-salting roasting is carried out for 1 hour to obtain the salting roasting product. (2) At 80°C, the salt-roasted product obtained in step (1) is stirred and soaked in water for 10 minutes to obtain rare earth leachate and leachate residue. (3) Add oxalic acid solution to the rare earth leachate obtained in step (2), with the stoichiometric number of oxalic acid required for all rare earth elements in the NdFeB permanent magnet waste to precipitate as M2, the amount of oxalic acid in the oxalic acid solution as 1.5M2, adjust the pH to 3, and carry out the precipitation reaction to obtain rare earth precipitate. (4) The rare earth precipitate obtained in step (3) was calcined at 900℃ for 1.5h and then placed in the REF3-LiF electrolyte system for molten salt electrolysis. The temperature of molten salt electrolysis was 1020℃ and the time was 12h to obtain regenerated mixed rare earth.

[0078] Example 4 This embodiment provides a method for recovering NdFeB permanent magnet waste using water-co-saltification roasting. Except for the water-co-saltification roasting temperature of 300°C in step (1), the method is the same as in embodiment 1.

[0079] Example 5 This embodiment provides a method for recovering NdFeB permanent magnet waste using a water-co-saltification roasting method. Except for step (1), where the stoichiometric number of FeCl3 required for all rare earth elements in the NdFeB permanent magnet waste to be converted into rare earth salts is M1, the NdFeB permanent magnet waste is uniformly mixed with FeCl3 with a stoichiometric number of 1.5M1, and the water-co-saltification roasting temperature is 150°C, the rest of the method is the same as in Example 1.

[0080] Example 6 This embodiment provides a method for recovering NdFeB permanent magnet waste using a water-co-saltification roasting method. The method is the same as in Example 1 except that in step (1), water vapor is not introduced, but water of 50wt% of the total mass of NdFeB permanent magnet waste and NH4Cl is added to the mixture of NdFeB permanent magnet waste and NH4Cl.

[0081] Example 7 This embodiment provides a method for recovering NdFeB permanent magnet waste using a water-co-saltification roasting method. The method is the same as in Example 1 except that in step (1), water vapor is not introduced, but water of 20wt% of the total mass of NdFeB permanent magnet waste and NH4Cl is added to the mixture of NdFeB permanent magnet waste and NH4Cl.

[0082] Example 8 This embodiment provides a method for recovering NdFeB permanent magnet waste using a water-co-saltification roasting method. Except for the concentration of water vapor introduced in step (1) being 50 vol%, the method is the same as in Example 1.

[0083] Example 9 This embodiment provides a method for recovering NdFeB permanent magnet waste using a water-co-saltification roasting method. Except for step (1), in which the stoichiometric number of FeCl3 required for all rare earth elements in the NdFeB permanent magnet waste to be converted into rare earth salts is M1, the NdFeB permanent magnet waste is uniformly mixed with FeCl3 with a stoichiometric number of 3M1, and the water-co-saltification roasting temperature is 350°C, the rest of the method is the same as in Example 1.

[0084] Example 10 This embodiment provides a method for recovering NdFeB permanent magnet waste using a water-co-saltification roasting method. The method is the same as in Example 1 except that in step (1), water vapor is not introduced, but water of 95wt% of the total mass of NdFeB permanent magnet waste and NH4Cl is added to the mixture of NdFeB permanent magnet waste and NH4Cl.

[0085] Comparative Example 1 This comparative example provides a method for recovering NdFeB permanent magnet waste by salt roasting. Except for step (1), in which the NdFeB permanent magnet waste is uniformly mixed with NH4Cl with a stoichiometric coefficient of 2.5M1 and no water vapor is introduced, the rest of the method is the same as in Example 4.

[0086] Performance testing: The purity of rare earth in the recycled mixed rare earth obtained from all the above embodiments and comparative examples was tested, and the content of rare earth in the recycled mixed rare earth was measured. The rare earth recovery rate was calculated, and the test results are shown in Table 1.

[0087] Table 1 Based on the test results of Examples 1 to 10 and Comparative Example 1 in Table 1, the present invention utilizes a water-coordinated salting roasting process, which reduces the amount of salting agent compared to the traditional salting roasting process. It can also improve the recovery rate of rare earth elements and the purity of regenerated mixed rare earth elements at a lower roasting temperature. At the same time, it uses water leaching instead of acid leaching, which reduces acid consumption, and uses precipitation reaction instead of extraction separation process, which avoids the wastewater treatment problem caused by extraction.

[0088] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for recovering NdFeB permanent magnet waste using a water-co-saltification roasting process, characterized in that, The method includes: Waste NdFeB permanent magnets and a salting agent are mixed and subjected to water-co-salting roasting in a steam atmosphere to obtain a salting roasting product. The salting roasting product is then leached in water to obtain a rare earth leachate and a leachate residue. A precipitant is added to the rare earth leachate to induce a precipitation reaction, resulting in a rare earth precipitate. The rare earth precipitate is then subjected to calcination and molten salt electrolysis to obtain a regenerated mixed rare earth.

2. The method as described in claim 1, characterized in that, In the atmosphere containing water vapor, the water vapor includes water vapor obtained from in-situ water vaporization and / or water vapor introduced from an external gas source; And / or, the atmosphere containing water vapor also includes any one or a combination of at least two of oxygen, nitrogen, or inert gases.

3. The method as described in claim 2, characterized in that, When the water vapor is obtained by in-situ vaporization of water, the amount of water added is 1wt% to 95wt% of the total mass of NdFeB permanent magnet waste and salting agent; And / or, when the water vapor is water vapor introduced from an external gas source, the concentration of the introduced water vapor is 5 vol% to 90 vol.

4. The method as described in claim 3, characterized in that, When the water vapor is obtained by in-situ vaporization of water, the amount of water added is 30wt%~50wt% of the total mass of NdFeB permanent magnet waste and salting agent. And / or, when the water vapor is water vapor introduced from an external gas source, the concentration of the introduced water vapor is 5 vol% to 30 vol.

5. The method according to any one of claims 1 to 4, characterized in that, The temperature for water-co-salinization roasting is 100℃~350℃; And / or, the water-co-salinization roasting time is 1h~5h; And / or, the heating rate of the water-co-salinization roasting is 5℃ / min to 15℃ / min.

6. The method according to any one of claims 1 to 5, characterized in that, The salifying agent includes chloride salts and / or sulfate salts; the salifying agent includes any one or a combination of at least two of the following: NH4Cl, FeCl2, FeCl3, AlCl3, MgCl2, ZnCl2, CaCl2, CuCl2, CoCl2, NaCl, KCl, (NH4)2SO4, FeSO4, FeS2, Fe2(SO4)3, MgSO4, Al2(SO4)3, ZnSO4, CaSO4, CuSO4, CoSO4, Na2SO4, and K2SO4; And / or, with M1 as the stoichiometric number of the salting agent required to completely convert the rare earth elements in the NdFeB permanent magnet waste into rare earth salts, the amount of the salting agent added is M1~2.5M1.

7. The method according to any one of claims 1 to 6, characterized in that, The water immersion temperature is 20℃~80℃; And / or, the immersion time is 10 min to 120 min; And / or, the water immersion is carried out under stirring.

8. The method according to any one of claims 1 to 7, characterized in that, The precipitant includes oxalic acid and / or ammonium bicarbonate; And / or, with the stoichiometric coefficient of the precipitant required for all rare earth elements in the NdFeB permanent magnet waste to precipitate as M2, the amount of the precipitant added is M2~1.5M2; And / or, the pH of the precipitation reaction is 1 to 3.

5.

9. The method according to any one of claims 1 to 8, characterized in that, The calcination temperature is 850℃~1000℃; And / or, the calcination time is 1h to 3h.

10. The method according to any one of claims 1 to 9, characterized in that, The electrolyte system for molten salt electrolysis includes the REF3-LiF electrolyte system, where RE represents rare earth elements; And / or, the temperature of the molten salt electrolysis is 950℃~1050℃; And / or, the electrolysis time of the molten salt is 12h~24h.

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