Methods for Extracting SE Oxides

Abstract

The present invention relates to a method for extracting SE oxides from a starting material comprising one or more SE compounds of formula SEFeB, comprising the steps of: disintegrating the starting material by hydrogen treatment (HPMS), treating the disintegrated starting material with an aqueous solution of a carboxylic acid or a mixture of carboxylic acids, precipitating the SE oxides from the carboxylic acid solution by adding a precipitating agent comprising an alcohol or a mixture of alcohols. The present invention further relates to the SE oxides themselves and to the use of the SE oxides.

Description

[Technical field]

[0001] The present invention relates to a method for extracting SE oxides and to the SE oxides themselves produced by said method.Furthermore, the present invention relates to the use of such SE oxides. [Background technology]

[0002] Rare earths (Seltene Erden) or rare earth metals, abbreviated as SE, refer to the elements of group 3: scandium (Sc), yttrium (Y) and lanthanum (La) and the 14 elements following lanthanum: cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu).

[0003] Both names, rare earths or rare earth metals, are partly confusing: on the one hand, these compounds are exclusively metallic, on the other hand, these metals are not rare and are fairly evenly distributed in the Earth's crust. These terms have historical reasons: at the time of their discovery, they could only be found in rare minerals and could only be isolated in the form of oxides, which were then called "earth". Today, it is possible to extract the elements in high purity and they can be found in the Earth's crust in many places.

[0004] The estimated average concentration of rare earth elements in the Earth's crust, where the mantle strength is about 17 km, is about 150 to 220 ppm. The proportions of individual elements vary considerably. The most common is elemental cerium, at about 40 to 60 ppm, and the "rarest" rare earth is thulium, which is still about 30 times less common than cerium, although it is as common as elemental bismuth in the Earth's crust.

[0005] In some areas, the concentration of rare earth elements is quite high. If the rocks contain rare earth elements at a concentration of about 0.1% or more, which corresponds to 1000 ppm, i.e. 1 kg of rare earth elements per tonne of rock, then they are called rare earth ore deposits (SE deposits). However, in order for a source to be prospected as a minable deposit, further economic, ecological and even political criteria must be met.

[0006] Due to constantly increasing requirements and standards, the extraction of rare earths from natural sources is becoming more and more complex and expensive. But at the same time, the consumption of these special metals is increasing year by year. What is interesting is the dramatic increase in the consumption of selected SE elements: the increase was 100 [t / a] until 1995, whereas for some rare earths it has increased 100 times since 2000.

[0007] 95% of rare earths were processed in 2012 into seven main application areas: - Magnets for wind turbines, hybrid motors and electric drives, - Catalysts for chemical industry, - Cast steel, alloys for batteries, ignition blocks, fuel cells and lightweight construction, - Abrasives, - Glass, colored and UV filters, - Light-emitting materials such as LEDs and LCS, - Ceramics for stabilizers and capacitors.

[0008] The remaining 5% was quantitatively distributed among a variety of different but no less important applications. The significant increase in consumption since 2000, as mentioned above, is not due to the expansion of traditional application areas such as ceramics, glass production, abrasives, and catalysis, but rather due to the emergence of new application areas, notably the production of magnetic materials and their use as luminescent materials. The use of rare earths in batteries is expanding rapidly. Mixed metals (mixtures of rare earths) are components of nickel-hybrid batteries, which are gradually replacing nickel-cadmium batteries as the power source for portable electronic devices, for example laptops and mobile phones. Furthermore, rare earths are increasingly used in the manufacture of permanent magnets. Permanent magnets made of samarium-cobalt are used in industry, the military and space projects. Neodymium-iron-boron magnets, which are more powerful and at the same time cheaper, are used in numerous servo motors in automobiles (window regulators, power steering, headlight leveling, seat adjustment, etc.), medical magnetic resonance devices, industrial motors, wind turbines, CD players and stereo systems. Fast-growing application areas are traction motors for hybrid and electric vehicles as well as step motors and sensors in automation and robotics. Furthermore, around 6% of rare earths are required for doping luminescent materials in the lighting and display industries as well as in oxygen sensors.

[0009] New and fast-growing application areas mean that neodymium, praseodymium, dysprosium and terbium are now among the rare earth metals with the highest demand. This is due to the diverse applications in permanent magnets, especially for efficient motors, generators, sensors, acoustics or optics, as well as high performance. The ever-increasing importance of electric drives and generators (electromobility, wind power) and the simultaneous shortage of rare earths as raw materials on the global market demand efficient, environmentally friendly and cost-effective recycling processes for rare earths, especially since the current recycling rate is only around 1 to 3% worldwide.

[0010] Methods are already known to address the problem and to carry out various approaches. Most of the methods concern the recycling of neodymium, since it is the rare earth of greatest technological interest. However, the prior art methods detailed below are applicable to all rare earths.

[0011] Regarding the recovery of neodymium from NdFeB material of single origin, in the case of the production of NdFeB magnets, powder metallurgy methods have been mainly used so far, for example hydrogen embrittlement (HPMS process), as described in US Patent Application Publication No. 2012 / 0137829. The method has the advantage of being very environmentally friendly, since it requires little energy and does not produce chemical waste. However, the powder metallurgy method requires that the starting material to be recycled has a very high purity. If the starting material is impure, the purity of the recovered Nd compounds is insufficient, and the Nd compounds recovered by the method cannot be used for the production of high-quality magnets. Furthermore, the recycling of high-performance magnets (N48, N50, etc.) using the HPMS process only gives very low yields, since a laborious prior removal of the oxide and hydroxide layers, for example by cyclone separation, is necessary. In addition, sintered NdFeB magnets are usually coated with a protective layer of tin, nickel, aluminum or spray-painted or immersion paint. This means a high process engineering burden for recycling by hydrogen embrittlement, making the recycling process of magnetic materials of different origins and compositions difficult.

[0012] Other recovery methods compared to powder metallurgical methods include various hydrometallurgical recycling methods, which, in principle, offer better material separation methods due to the wet chemical procedures.

[0013] WO 94 / 26665 discloses a method for digesting starting materials to be recycled, comprising NdFeB, by surface oxidation of NdFeB, for example with NaOH, to form the oxide Nd2O3, then dissolving in acetic acid, selectively crystallizing and fluorinating as neodymium acetate by condensation, and then reducing to elemental neodymium. However, the method has the disadvantage that oxidation of NdFeB to Nd2O3 is only possible on the surface. As a result, the digestion rate is very slow and continuous mechanical crushing is required during the digestion process, simultaneously with magnetic separation of elemental iron.

[0014] US Patent 5,129,945 discloses that the digestion of waste from the manufacture of rare earth magnets can be carried out with 2M H2SO4. The double salts NaNd(SO4)2·H2O or NH4Nd(SO4)2·H2O are selectively precipitated from the solution by adding NaOH or NH4OH. The double salts are then fluorinated to NdF3 by adding hydrofluoric acid, which is then reduced again to elemental Nd by calcific heating after thorough drying. However, the method is problematic due to the use and release of hydrogen fluoride (HF). As an alternative to HF, US Patent 5,129,945 discloses that the double salts can be reacted with oxalic acid solution to obtain neodymium oxalate, which can be decomposed to Nd2O3, CO2 and H2O by thermal treatment at 900 °C. However, the disadvantage here is that an additional salt metathesis step is required, with the loss of the oxalic acid used.

[0015] German Patent No. 102012017418 discloses a method for extracting the double salt NaNd(SO4)2·H2O from a pre-crushed starting mixture containing NdFeB. After magnetic separation and fine crushing, hydrometallurgical digestion is carried out by adding sulfuric acid and simultaneously determining the volumetric flow rate of hydrogen released during hydrometallurgical digestion or the total amount of hydrogen released, which is used as a control variable for the amount of oxalic acid added and / or for determining the end of hydrometallurgical digestion. The sparingly soluble double salt NaNd(SO4)2·H2O is then precipitated after hydrometallurgical digestion by adding a sodium-containing salt solution, a sodium-containing salt and / or NaOH. However, it has been found that the solutions disclosed therein have the drawback of being laborious and expensive both in terms of use and in terms of the preparation of the resulting chemicals, since it is necessary to precipitate the sparingly soluble double salt NaNd(SO4)2·H2O after hydrometallurgical digestion by the addition of oxalic acid and then the sodium-containing salt solution, sodium-containing salts and / or NaOH. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] US Patent Application Publication No. 2012 / 0137829 [Patent Document 2] U.S. Patent No. 5,129,945 [Patent Document 3] German Patent Invention No. 102012017418 [Patent Document 4] U.S. Pat. No. 5,238,489 [Patent Document 5] US Patent Application Publication No. 2012 / 0137829 [Patent Document 6] DE 102018221845 A1 [Patent Document 7] WO 94 / 26665 [Patent Document 8] U.S. Patent No. 5,129,945 Summary of the Invention [Problem to be solved by the invention]

[0017] In summary, one of the main obstacles to efficient recycling of rare earths from magnetic waste by hydrometallurgical processing is the inability or insufficient control of digestion in materials containing magnets of various origins, with different properties and compositions, which, depending on the composition and properties of the materials to be recycled, can result in extremely long digestion times (e.g. due to inert foreign matter that cannot be separated by other means besides passivation and agglomeration) and an unnecessarily large number of chemicals required for both the digestion itself and the subsequent precipitation.

[0018] A further problem is that scrap or waste containing NdFeB may contain various impurities of different origin, e.g. other rare earth metals such as SmCo, which are not present in this form in the case of a single origin processing waste during magnet production. In such cases, only the precipitation of mixed double salts, e.g. NaNd1-xSm(SO4)2·H2O, is carried out, followed by solvent extraction or ion exchange to separate the rare earths. However, this treatment requires a lot of effort, which prevents a simple recycling process. Other separation methods during digestion, e.g. by hydrogen flotation (US Pat. No. 5,238,489), are impossible or difficult to achieve in waste due to other contaminations (e.g. by plastics).

[0019] Additionally, there are no known recycling methods capable of efficiently recycling mixed magnetic materials that are not of a single origin and are subject to further variations in composition and properties.

[0020] In view of this, the object of the present invention is to provide a method for the efficient recovery of SE oxides which, on the one hand, requires little effort and is from unsorted waste or scrap, and, on the other hand, is environmentally friendly in terms of the chemicals used. [Means for solving the problem]

[0021] The problem is solved by a method for extracting SE oxides having the features of the independent claim 1. Advantageous embodiments of the method can be found in the dependent claims 2 to 13.

[0022] Furthermore, the object on which the invention is based is also achieved by the SE oxide produced by the method and by the use of the SE oxide. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The method for extracting SE oxides from a starting material comprising one or more SE compounds of formula SEFeB according to the present invention comprises the following steps: a) disintegrating the starting material by hydrotreating (HPMS); b) treating the disintegrated starting material with an aqueous solution of a carboxylic acid or a mixture of carboxylic acids; c) Precipitating the SE oxide from the carboxylic acid solution by adding a precipitating agent comprising an alcohol or a mixture of alcohols.

[0024] The term "SE oxides" within the meaning of the present invention is understood to be oxides of the following rare earths or rare earth metals: scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu).

[0025] The term "starting material" in the sense of the present invention is understood to be a material comprising one or more SE compounds of formula SEFeB and consisting of single-origin magnetic material, mixed magnetic waste, unsorted scrap or waste.

[0026] The method for extracting SE oxides according to the invention has the great advantage of being characterized by a high variability and flexibility in terms of possible fields of application with respect to methods and processes known from the prior art. In particular, the method according to the invention allows the recycling of starting materials and scrap or waste materials that are not of mono-origin, comprising SE compounds of formula SEFeB, since the method can be adapted due to its flexibility to starting materials and mixtures of starting materials with compositions and properties that are very rapidly variable. Furthermore, the method according to the invention avoids the use of very problematic or harmful chemicals, which significantly improves the environmental compatibility of the method according to the invention.

[0027] In the first step a) of the method of the invention, the starting material comprising one or more SE compounds of formula SEFeB is subjected to a hydrogen treatment according to US 2012 / 0137829 A1, during which the material can be pre-disintegrated depending on the initial state.

[0028] The resulting powder, the so-called HPMS powder, can optionally be separated from impurities such as adhesives, coatings, fixing agents, housing residues, etc. by e.g. sieving or other suitable methods. The steps and methods are easily adaptable depending on which starting material or mixture of starting materials is subjected to the recycling method according to the invention.

[0029] According to one embodiment, the HPMS powder extracted in step a) has a particle size in the range of 1 μm to 1000 μm. Preferably, the disintegrated starting material has a particle size in the range of 1 μm to 125 μm. More preferably, the disintegrated starting material has a particle size in the range of 1 μm to 63 μm. Most preferably, the disintegrated starting material has a particle size in the range of 1 μm to 25 μm.

[0030] The powder thus prepared and optionally purified is treated in step b) with an aqueous solution of a carboxylic acid or a mixture of carboxylic acids. The hydrometallurgical digestion according to step b) can be carried out in deaerated or non-degassed conditions.

[0031] Depending on the composition of the starting material, it is possible to completely or partially dissolve the powder by adding a carboxylic acid or a mixture of carboxylic acids in step b).

[0032] In step c), the SE oxides in the solution are precipitated by adding a precipitating agent comprising an alcohol or a mixture of alcohols, and the precipitated SE oxides are separated by skimming, filtration or other suitable separation methods.

[0033] The remaining carboxylic acid solution is neutralized, for example with sodium carbonate, and the remaining material is filtered.

[0034] If the powder is only partially dissolved in step b), according to another embodiment, after step b), the undissolved SEFe in the carboxylic acid solution is optionally 14 It is possible to carry out a step b') of separating the hard magnetic φ-phase comprising B from the solution before the precipitation step c).

[0035] After the digestion reaction in step b is completed, the hard magnetic φ phase (SE2Fe 14 B) The undissolved SEFeB powder consisting of single crystal particles is separated from the carboxylic acid solution, washed and dried.

[0036] The carboxylic acid is precipitated from the SE oxide obtained by carrying out step b') followed by step c) by adding a precipitating agent comprising an alcohol or a mixture of alcohols, and the precipitated SE oxide is separated by skimming, filtration or other suitable separation method.

[0037] The remaining carboxylic acid solution is neutralized, for example with sodium carbonate, and the remaining material is filtered.

[0038] The method according to the invention thus makes it possible to rapidly adapt the method depending on the composition of the starting materials to be recycled.

[0039] The high purity SE oxide precipitated from the carboxylic acid solution in step c) can be reduced by known methods to SE metal, which is again fed, for example directly, to the magnet manufacturing process.

[0040] The hard magnetic φ phase (NdFe 14 Since the single crystal powder consisting of B) is completely free of SE oxide and hydroxide layers and the agglomerates of crystals connected by SE-rich phases that may remain after HPMS treatment are separated, the dried powder can be directly used for the production of high performance magnets.

[0041] To produce high performance sintered magnets, the single crystal powder according to the invention can be mixed with a corresponding proportion of SE powder (metal or hydrogenated) and then mechanically alloyed, pressed or subjected to a suitable heat treatment.

[0042] To produce novel magnets, single crystal powders can be provided with suitable single or multiple grain boundary phases consisting of metallic, ceramic or organic layers and converted into magnetic solids by suitable bonding methods.

[0043] The method according to the invention is particularly suitable for the recovery of rare earths from mixed magnetic scrap, such as occurs in shredding facilities for WEEE recycling. In this case, the unseparated magnetic scrap is subjected to HPMS treatment as an agglomerate according to step a). Since only the SE part of the SEFeB magnets from the magnetic scrap forms the corresponding hydrides and the reaction of carboxylic acids with other substances is very slow, if at all, due to mechanical separation of the HPMS powder produced, the scrap or the entire scrap agglomerate can be subjected to hydrometallurgical digestion according to step b). After the reaction is over, the carboxylic acid solution can be separated and subjected to step c) in order to extract the high-purity SE oxides.

[0044] The method can be used equally well for highly contaminated magnetic scrap of single origin but with a low SE magnet content, such as for example smartphone audio modules. After a suitable shredding method, as described for example in DE 10 2018 221 845 A1, and a further HPMS treatment according to step a), the magnets, which are highly contaminated with housing residues, adhesive residues and coil residues, are subjected to a hydrometallurgical digestion according to step b). After the reaction is over, the carboxylic acid solution is separated and high purity SE oxides can be extracted by step c).

[0045] The process according to the invention also has the great advantage that it is significantly faster than the processes according to the prior art. The efficiency of the process is evident from a direct comparison with the cooking process described, for example, in US Patent No. 5,129,945. As can be seen from the examples, the total cooking time of the present invention is only a few minutes, whereas in the publication, the complete cooking takes 24 hours according to the embodiments.

[0046] In another embodiment of the invention, during step b) the pH value of the solution is readjusted by adding further carboxylic acid or a mixture of carboxylic acids so that it does not exceed a value of 3.5. Preferably, the pH value does not exceed 3. More preferably, the pH value does not exceed 2.5. Most preferably, the pH value does not exceed 1.5. In special cases, the pH value does not exceed 1.

[0047] As has been shown in numerous experiments, in contrast to the prior art, problematic measurements and precise adjustment of the pH value for the precipitation reaction are not necessary in the present invention, since the acid concentration of the carboxylic acids during hydrometallurgical digestion is already in the optimum range with respect to product purity and yield. However, if it is desired to accelerate the step, it is possible to readjust the pH value so that it does not exceed 3.5.

[0048] According to one embodiment, the carboxylic acid is a monocarboxylic acid selected from the group consisting of saturated carboxylic acids, aromatic carboxylic acids, monounsaturated carboxylic acids and polyunsaturated carboxylic acids.

[0049] According to another embodiment, the carboxylic acid is a saturated monocarboxylic acid.

[0050] According to another embodiment, the carboxylic acid is an aromatic monocarboxylic acid.

[0051] According to another embodiment, the carboxylic acid is a monounsaturated monocarboxylic acid.

[0052] According to another embodiment, the carboxylic acid is a polyunsaturated monocarboxylic acid.

[0053] According to another embodiment, the carboxylic acid is selected from the group consisting of formic acid, acetic acid, propionic acid, butyric acid, valeric acid, lauric acid, palmitic acid, stearic acid, arachidic acid, lignoceric acid, benzoic acid, oleic acid, elaidic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid.

[0054] According to another embodiment, the carboxylic acid is formic acid.

[0055] According to another embodiment, the carboxylic acid is acetic acid.

[0056] According to another embodiment, the carboxylic acid is palmitic acid.

[0057] According to another embodiment, the carboxylic acid is stearic acid.

[0058] According to another embodiment, the carboxylic acid is benzoic acid.

[0059] According to another embodiment, the carboxylic acid is a dicarboxylic acid.

[0060] According to another embodiment, the carboxylic acid is a dicarboxylic acid selected from the group consisting of oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid, tartaric acid, adipic acid and phthalic acid.

[0061] According to another embodiment, the carboxylic acid is oxalic acid.

[0062] According to another embodiment, the carboxylic acid is succinic acid.

[0063] According to another embodiment, the carboxylic acid is maleic acid.

[0064] According to another embodiment, the carboxylic acid is tartaric acid.

[0065] According to another embodiment, the carboxylic acid is adipic acid.

[0066] According to another embodiment, the carboxylic acid is phthalic acid.

[0067] According to another embodiment, the carboxylic acid is a tricarboxylic acid.

[0068] According to another embodiment, the carboxylic acid is a tricarboxylic acid selected from the group consisting of isocitric acid, citric acid, aconitic acid, propane-1,2,3-tricarboxylic acid, agaric acid and trimesic acid.

[0069] According to another embodiment, the carboxylic acid is isocitrate.

[0070] According to another embodiment, the carboxylic acid is citric acid.

[0071] According to another embodiment, the carboxylic acid is aconitic acid.

[0072] According to another embodiment, the carboxylic acid is agar acid.

[0073] According to another embodiment, it is also possible to use a mixture comprising several carboxylic acids. The mixing ratio can vary depending on the acid used.

[0074] In one embodiment of the invention the mixture comprises two different carboxylic acids in a ratio of from 100:1 to 1:100, preferably from 50:1 to 1:50, more preferably from 10:1 to 1:10.

[0075] In another embodiment of the invention the mixture comprises three different carboxylic acids, in which the ratio of carboxylic acid 1 to carboxylic acid 2 is as described above, and the ratio of carboxylic acid 1 to carboxylic acid 3 is from 100:1 to 1:100, preferably from 50:1 to 1:50, more preferably from 10:1 to 1:10.

[0076] According to another embodiment, the concentration of the carboxylic acid or mixture of carboxylic acids in the aqueous solution is at least 5% and at most 99%. According to a preferred embodiment, the concentration of the carboxylic acid or mixture of carboxylic acids is at least 30%, more preferably 60%, most preferably 90%.

[0077] According to one embodiment, the precipitating agent is an alcohol selected from the group consisting of methanol, ethanol, propan-1-ol, propan-2-ol, butan-1-ol, butan-2-ol, isobutanol, tert-butanol, glycol, propylene glycol, propane-1,3-diol, glycerol, pentaerythritol.

[0078] The precipitating agent is preferably an alcohol selected from the group consisting of methanol, ethanol, propan-1-ol, butan-1-ol, butan-2-ol, isobutanol, tert-butanol.

[0079] More preferably, the precipitating agent is an alcohol selected from the group consisting of methanol, ethanol, butan-1-ol, tert-butanol.

[0080] In one embodiment, the alcohol is methanol.

[0081] According to another embodiment, the alcohol is ethanol.

[0082] According to another embodiment, the alcohol is butan-1-ol.

[0083] According to one embodiment, the precipitation in step c) is obtained by adding a liquid precipitant.

[0084] According to another embodiment, precipitation is obtained by addition of a liquid precipitating agent.

[0085] In one embodiment, all steps of the process of the invention are carried out at room temperature. In another embodiment, the process is carried out at an elevated temperature of 70 to 90° C. Depending on the starting material used, it may be desirable to heat the carboxylic acid in step b) to increase solubility and thereby reduce reaction time.

[0086] In another embodiment, it is possible to separate the demagnetized SE compounds from the starting material and / or to separate only the magnetized (residual) ferromagnetic and ferrimagnetic compounds by carrying out a magnetic separation after step a).

[0087] The measures contribute to a flexible adaptation of the method according to the invention to the starting materials to be recycled.

[0088] In another embodiment, prior to magnetic separation the SE compound is heated above its Curie temperature and / or demagnetized by using an alternating electromagnetic field.

[0089] Further advantageous features of the present invention are described and explained in more detail below using examples and experiments. EXAMPLES

[0090] Example 1 Extraction of SE oxides from single-source waste magnets from wind turbines 200 g of HPMS powder extracted from a single source of waste magnets from a wind turbine are stirred for 45 min at 80 °C in 1 liter of a mixture of tartaric acid (50%), formic acid (35%) and oxalic acid (15%) with a pH value of 2. The acid solution is then separated from the powder. The weight of the magnetic powder, completely freed from the SE-rich grain boundary phase, is 99.25 g.

[0091] The SE oxide dissolved in the acid mixture was precipitated with ethanol and weighed 272.70 g after drying. Example 2 Extraction of SE oxides from magnetic waste from smartphone audio modules Magnetic waste, shredded from 100 smartphone audio modules, is separated as far as possible from the polymer residues by magnetic separation and then subjected to HPMS treatment. 40 g of the obtained HPMS powder are stirred at 80 °C for 60 min in 0.5 liters of a mixture of tartaric acid (55%), formic acid (30%) and citric acid (15%) with a pH value of 2. The acid solution is then separated from the powder. The SE oxide dissolved in the acid mixture is precipitated with ethanol and weighs 76.25 g after drying.

Claims

1. A method for extracting SE oxides from a starting material comprising one or more SE compounds of the formula SEFeB, comprising the following steps: a) crushing the starting material by hydrogenation (HPMS); b) treating the crushed starting material with an aqueous solution of a carboxylic acid or an aqueous solution of a mixture of several carboxylic acids; and c) precipitating the SE oxides from the carboxylic acid solution by adding a precipitant comprising an alcohol or a mixture of several alcohols.

2. The method according to claim 1, characterized in that, during step b), the pH value of the solution is readjusted so as not to exceed 3.5 by further adding the carboxylic acid or a mixture of multiple carboxylic acids.

3. After step b), the undissolved SE in the carboxylic acid solution is used. ２ Fe １４ The method according to claim 1 or 2, characterized in that a step b') is provided for separating the hard magnetic φ phase containing B from the solution before step c) of precipitation.

4. The method according to claim 1 or 2, characterized in that the starting material crushed in step a) has a particle size in the range of 1 μm to 1000 μm.

5. The method according to claim 1 or 2, characterized in that the carboxylic acid is a monocarboxylic acid selected from the group consisting of saturated carboxylic acids, aromatic carboxylic acids, monounsaturated carboxylic acids, and polyunsaturated carboxylic acids.

6. The method according to claim 5, characterized in that the monocarboxylic acid is selected from the group consisting of formic acid, acetic acid, propionic acid, butyric acid, valeric acid, lauric acid, palmitic acid, stearic acid, arachidic acid, lignoceric acid, benzoic acid, oleic acid, elaidic acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

7. The method according to claim 1 or 2, characterized in that the carboxylic acid is a dicarboxylic acid selected from the group consisting of oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid, tartaric acid, adipic acid, and phthalic acid.

8. The method according to claim 1 or 2, characterized in that the carboxylic acid is a tricarboxylic acid selected from the group consisting of isocitric acid, citric acid, aconitic acid, propane-1,2,3-tricarboxylic acid, agaric acid, and trimesic acid.

9. The method according to claim 1 or 2, characterized in that the alcohol is selected from the group consisting of methanol, ethanol, propan-1-ol, propan-2-ol, butan-1-ol, butan-2-ol, isobutanol, tert-butanol, glycol, propylene glycol, propan-1,3-diol, glycerol, and pentaerythritol.

10. The method according to claim 9, characterized in that the alcohol is methanol.

11. The method according to claim 9, characterized in that the alcohol is butanol.

12. The method according to claim 1 or 2, characterized in that, after step a), magnetic separation is performed to separate the demagnetized SE compound from the starting material and / or separate only the magnetized (residual) ferromagnetic and ferrimagnetic compounds.

13. The method according to claim 12, characterized in that, prior to the magnetic separation, the SE compound is heated to a temperature exceeding the Curie temperature of the SE compound and / or demagnetized by using an alternating electromagnetic field.

14. SE oxide produced by the method described in claim 1 or 2.

15. Use of SE oxide manufactured by the method of claim 1 or 2 for the manufacture of a magnet.