Process for obtaining se oxides

Abstract

The invention relates to a process for obtaining SE oxides from a starting material comprising one or more SE compounds of formula SEFeB, said process comprising the following steps: comminuting the starting material by means of hydrogen hydrogenation (HPMS); treating the comminuted starting material with an aqueous solution of a carboxylic acid or a mixture of a plurality of carboxylic acids; precipitating the SE oxides from the carboxylic acid solution by adding a precipitant which has an alcohol or a mixture of a plurality of alcohols. The invention further relates to the SE oxides per se and to the use thereof.

Description

[0001] Process for the extraction of rare earth oxides

[0002] Description

[0003] The present invention relates to a process for obtaining rare earth oxides and to the rare earth oxides themselves produced by the process. Furthermore, the invention relates to the use of such rare earth oxides.

[0004] Rare earths or rare earth metals, abbreviated SE, are elements of the 3rd subgroup: scandium (Sc) and yttrium (Y) as well as lanthanum (La) and the following fourteen elements 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).

[0005] The two terms "rare earths" or "rare earth metals" are somewhat misleading. Firstly, the compounds are exclusively metals, and secondly, these metals are not rare but rather fairly evenly distributed throughout the Earth's crust. These terms have a historical origin. When these elements were first discovered, they could initially only be found in rare minerals and isolated only in oxide forms, then called "earths." Today, they can be extracted in highly pure form and are found in many places throughout the Earth's crust.

[0006] The estimated average concentration of rare earths in the Earth's crust, a mantle thickness of about 17 km, is about 150 to 220 ppm. The proportions of the individual elements vary considerably. The most common element is cerium, at about 40-60 ppm. The "rarest" of the rare earths is thulium, which is still about as abundant as the element bismuth in the Earth's crust, but 30 times less abundant than cerium. In some regions, the concentrations of rare earths are considerably higher. If the rock has a concentration of approximately > 0.1% of rare earths, which corresponds to 1000 ppm, or 1 kg of rare earths per ton of rock, such cases are referred to as a rare earth deposit (RE deposit). However, for a mineral deposit to be prospected as a mineable deposit, additional economic, ecological, and political criteria must be met.

[0007] Due to ever-increasing requirements and criteria, the extraction of rare earths from natural sources is becoming increasingly complicated and expensive. At the same time, however, the consumption of these special metals is increasing year after year. The sharp increase in the consumption of selected rare earth elements is interesting. While it was around 100 [t / a] until 1995, it increased a hundredfold for some rare earths from 2000 onwards.

[0008] In 2012, 95% of rare earths were processed in seven major application areas:

[0009] Magnets for wind turbines, hybrid engines and electric drives;

[0010] Catalysts for the chemical industry;

[0011] Alloys for steel castings, batteries, flints, fuel cells and lightweight constructions;

[0012] polishing agents;

[0013] - Glasses: color and UV filters; phosphors such as LEDs and LCS; ceramics for stabilizers and capacitors.

[0014] The remaining 5% was distributed across various, but sometimes no less important, applications. The very strong increase in consumption since 2000, as described above, cannot be attributed to the expansion of existing application areas such as ceramics, glass production, polishing agents, or catalysts, but rather to the emergence of new fields of application, primarily in the production of magnetic materials, but also in their use as luminescent materials. One rapidly growing application for rare earths is in batteries. Mischmetal (a mixture of rare earths) is a component of nickel-hybrid batteries, which are gradually replacing nickel-cadmium batteries in the power supply of portable electronic devices such as laptops and cell phones. A growing use of rare earths is in the production of permanent magnets.Permanent magnets made of samarium cobalt are used in industry, the military, and aerospace. More powerful yet less expensive neodymium iron boron magnets are used in a variety of actuators in cars (window regulators, power steering, headlight range control, seat adjustment, etc.), in medical magnetic resonance imaging devices, industrial motors, wind turbines, CD players, and stereo systems. Rapidly growing application areas include traction motors for hybrid and electric vehicles, as well as stepper motors and sensors in automation and robotics. In addition, approximately 6% of rare earth elements are required for doping phosphors in the lighting and display industries, as well as in oxygen sensors.

[0015] The rapidly growing new application areas mean that neodymium, praseodymium, dysprosium, and terbium are currently among the rare earth metals with the highest demand. This is primarily due to their diverse applications in high-performance permanent magnets for efficient motors, generators, sensors, acoustics, and optics. Due to the ever-increasing importance of electric drives and generators (e-mobility, wind power), coupled with the simultaneous scarcity of these rare earths as raw materials on the global market, an efficient, environmentally friendly, and cost-effective recycling process for rare earths is required, especially since the current global recycling rate is only approximately 1-3%.

[0016] There are already known methods that address this topic and pursue different approaches. Most of them concern the recycling of neodymium, as neodymium is of greatest technological interest. However, the state-of-the-art methods described in detail below can be adapted to all rare earths. To recover neodymium from pure NdFeB material, powder metallurgical processes such as hydrogen embrittlement (HPMS) have been used in the production of NdFeB magnets to date, as described in US 2012 / 0137829 A1. This process has the advantage of being highly environmentally friendly, as it requires low energy consumption and does not produce any chemical waste. However, powder metallurgical processes require the raw material to be recycled to be of very high purity.In the case of impure starting material, the purity of the recovered Nd compound becomes insufficient, and the Nd compounds recovered from this process cannot be used to manufacture high-quality magnets. Furthermore, the recycling of high-performance magnets (N48, N50, etc.) using the HPMS process requires a complex prior removal of oxide and hydroxide layers, e.g., by cyclone separation, which only allows for a very low yield. Furthermore, sintered NdFeB magnets are usually coated with a protective layer of tin, nickel, aluminum, or a spray or dip coating. This can impose stringent process requirements for recycling due to hydrogen embrittlement and complicates the recycling process for magnetic material of different origins and compositions.

[0017] Other recovery processes compared to powder metallurgical processes are various hydrometallurgical recycling processes, which inherently offer better possibilities for material separation through wet chemical processes.

[0018] WO 94 / 26665 A1 discloses a process in which the digestion of the starting material to be recycled, comprising NdFeB, is carried out, for example, by superficial oxidation of NdFeB using NaOH to form an oxide Nd2O3, which is then dissolved in acetic acid, selectively crystallized as neodymium acetate by concentration, fluorinated, and subsequently reduced to elemental neodymium. However, this process has proven disadvantageous in that only superficial oxidation of the NdFeB to Nd2O3 is possible. This results in a very slow digestion rate and the need for continuous mechanical comminution during the digestion process with simultaneous magnetic separation of elemental iron. US Pat. No. 5,129,945 B1 discloses that the digestion of process waste from rare earth magnet production can be carried out with 2M H2SO4. The double salt NaNd(SC>4)2- H2O or NaOH is selectively isolated from the solution by adding NaOH or NH4OH.NH4Nd(SO4)2' H2O is precipitated. The double salt is then fluorinated by the addition of hydrofluoric acid to NdFs, which, after careful drying, is then reduced calciothermally to elemental Nd. However, this procedure is problematic due to the use and release of hydrogen fluoride (HF). As an alternative to HF, US Pat. No. 5,129,945 B1 describes a reaction of the double salt with an oxalic acid solution to form neodymium oxalate, which can be decomposed into Nd2O3, CO2, and H2O by thermal treatment at 900°C. A disadvantage, however, is the additional salt metathesis step required, coupled with the loss of the oxalic acid used.

[0019] DE 10 2012 0174 18 B4 discloses a process for obtaining the double salt NaNd(SO4)2' H2O from a pre-crushed starting mixture containing NdFeB. The process involves magnetic separation and fine comminution, followed by hydrometallurgical digestion with the addition of sulfuric acid, while simultaneously determining the hydrogen volume flow released during the hydrometallurgical digestion or the total hydrogen volume released. The released hydrogen volume flow or the total hydrogen volume is used as a control variable for the amount of sulfuric acid to be added and / or to determine the completion of the hydrometallurgical digestion. Subsequently, the sparingly soluble double salt NaNd(SO4)2' H2O is precipitated after the hydrometallurgical digestion by adding a sodium-containing salt solution, a sodium-containing salt, and / or NaOH.However, the solution disclosed here has proven disadvantageous in that the addition of sulfuric acid and the subsequent addition of a sodium-containing salt solution, a sodium-containing salt, and / or NaOH, the sparingly soluble double salt NaNd(SO4)2'H2O, must be precipitated after hydrometallurgical digestion. This is complex and expensive both in terms of application and the processing of the resulting chemicals. In summary, one of the main obstacles to the effective recycling of rare earths from magnetic scrap materials using hydrometallurgical processes is the lack of, or inadequate, control of the digestion of magnetic materials of different origins with varying properties and compositions. As a result, the time required for digestion is very long, depending on the composition and properties of the material to be recycled (e.g.,through passivation and agglomeration, but also inert foreign materials that cannot be separated otherwise) and both the digestion itself and the subsequent precipitation require an unnecessarily high use of chemicals.

[0020] Furthermore, it is problematic that NdFeB-containing scrap / waste from different sources can contain various contaminants that are not present in the sorted process waste from magnet manufacturing – this includes, for example, other rare earth magnets such as SmCo. In such a case, only the precipitation of a mixed double salt such as NaNdl- x Sm(SO4)2' H2O followed by solvent extraction or ion exchange is used to separate the rare earths. However, this procedure is very complex and prevents a simple recycling process. Other separation methods during digestion, such as hydrogen flotation processes (US 5,238,489 B 1 ), are not possible or difficult to implement in scrap materials due to other contaminants (e.g., plastics).

[0021] Furthermore, none of the known recycling processes can efficiently recycle mixed, non-pure magnetic materials that are subject to fluctuations in composition and properties.

[0022] In view of this, the object of the present invention is to provide possibilities for the effective recovery of rare earth oxides, which on the one hand enable efficient recovery from unsorted waste / scrap with reduced effort and on the other hand are environmentally friendly with regard to the chemicals used.

[0023] This object is achieved by a process for obtaining rare earth oxides having the features of independent claim 1. Advantageous embodiments of this process can be found in dependent claims 2 to 13. Furthermore, the object underlying the invention is also achieved by the rare earth oxides produced by the process and by the use of the rare earth oxides.

[0024] The process according to the invention for obtaining rare earth oxides from a starting material comprising one or more rare earth compounds of the formula SEFeB comprises the following steps: a) comminuting the starting material by means of hydrogen hydrogenation (HPMS); b) treating the comminuted starting material with an aqueous solution of a carboxylic acid or a mixture of several carboxylic acids; c) precipitating the rare earth oxides from the carboxylic acid solution by adding a precipitant comprising an alcohol or a mixture of several alcohols.

[0025] The term “RE oxides” in the sense of the present invention refers to oxides of the rare earths or the 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).

[0026] For the purposes of the present invention, the term “starting material” refers to materials comprising one or more RE compounds of the formula SEFeB and consisting of sorted magnetic waste, mixed magnetic waste, unsorted scrap or waste.

[0027] The process for obtaining rare earth oxides according to the present invention has the significant advantage over the methods and processes known from the prior art that it is characterized by high variability and flexibility in its possible applications. Above all, the process according to the invention enables the recycling of non-pure starting materials comprising rare earth compound(s) of the formula SEFeB, such as scrap or waste, since its flexibility allows the process to be very quickly adapted to the starting materials and their mixtures with variable compositions and properties. Furthermore, the process according to the invention avoids the use of highly hazardous or toxic chemicals, thereby significantly increasing the environmental compatibility of the process according to the invention.

[0028] In the first step a) of the process according to the invention, starting material comprising one or more RE compounds of the formula SEFeB is subjected to a hydrogen treatment according to US 2012 / 0137829 A1, wherein the material can be comminuted beforehand depending on the initial state.

[0029] The resulting powder, so-called HPMS powder, can be separated from impurities such as adhesives, coatings, fixings, casing residues, etc., for example, by sieving or other suitable methods. This step and the method can be easily adapted depending on which starting material or starting material mixture is subjected to the inventive recycling process.

[0030] According to one embodiment, the HPMS powder obtained in step a) has a particle size in the range of 1 pm to 1000 pm. Preferably, the comminuted starting material has a particle size in the range of 1 pm to 125 pm. More preferably, the comminuted starting material has a particle size in the range of 1 pm to 63 pm. Most preferably, the comminuted starting material has a particle size in the range of 1 pm to 25 pm.

[0031] The powder thus prepared and, if necessary, purified is treated in step b) with an aqueous solution of a carboxylic acid or a mixture of several carboxylic acids. The hydrometallurgical decomposition according to step b) can be carried out in a degassed or non-degassed state.

[0032] Depending on the composition of the starting material, the powder can be completely or partially dissolved in step b) by adding a carboxylic acid or a mixture of several carboxylic acids. In step c), the rare earth oxides present in solution are precipitated by adding a precipitant comprising an alcohol or a mixture of several alcohols. The precipitated rare earth oxides are removed by skimming, filtering, or other suitable separation methods.

[0033] The remaining carboxylic acid solution is neutralized with soda, for example, and residues are filtered off.

[0034] In the event that the powder was only partially dissolved in step b), according to a further embodiment, a step b') can optionally be carried out after step b), in which the hard magnetic powder undissolved in the carboxylic acid solution <t>-Phase comprising SE2Fei4B is separated from the solution before the precipitation step c).

[0035] After completion of the digestion reaction in step b), the undissolved SEFeB powder, which now consists of single crystal particles of the hard magnetic <t>- phase (SE2Fei4B), separated from the carboxylic acid solution, washed and dried.

[0036] The carboxylic acid solution after step b') is subjected to step c), where the resulting rare earth oxides precipitate by adding a precipitant comprising an alcohol or a mixture of several alcohols. The precipitated rare earth oxides are removed by skimming, filtering, or other suitable separation methods.

[0037] The remaining carboxylic acid solution is neutralized with soda, for example, and residues are filtered off.

[0038] Thus, the process according to the invention ensures that the process can be quickly adapted depending on the composition of the starting material to be recycled.

[0039] The high-purity rare earth oxide precipitated from the carboxylic acid solution in step c) can be reduced to rare earth metals by known methods, which can be directly recycled, for example, into the magnet manufacturing process. The oxide obtained in step b') from hard magnetic <t>-Phase (Nd2Fei4B) single crystal powder is completely freed from RE oxide and hydroxide layers, any agglomerates of crystals connected by the RE rich phase remaining after the HPMS process are separated, so that the dried powder can be used directly for the production of high-performance magnets.

[0040] To produce high-performance sintered magnets, the single-crystal powder according to the invention can be mechanically alloyed, pressed and subjected to a suitable heat treatment with the addition of appropriate amounts of RE powder (metallic or hydrogenated).

[0041] To produce novel magnets, the single-crystal powder can be provided with suitable single- or multi-layer grain boundary phases made of metallic, ceramic, or organic layers and converted into a magnetic solid by means of suitable joining processes.

[0042] The process according to the invention is particularly suitable for the recovery of rare earths from mixed magnetic scrap, such as that generated in shredding plants for WEEE recycling. In this case, the non-separated magnetic scrap is subjected to HPMS treatment as an agglomerate according to step a). Since only the rare earth component of the SEFeB magnets in the magnetic scrap forms corresponding hydrides and a reaction of the carboxylic acid with the other substances, if at all, has much slower reaction kinetics, the resulting HPMS powder can be mechanically separated to subject it or the entire scrap agglomerate to hydrometallurgical digestion according to step b). After the reaction is complete, the carboxylic acid solution can be separated and subjected to step c) to obtain high-purity rare earth oxide.

[0043] In the same way, the process can also be used for heavily contaminated magnetic scrap with pure but low RE magnet content, such as smartphone audio modules. After applying a suitable shredding method, as described, for example, in DE 10 2018 221 845 A1, and an HPMS treatment according to step a), the magnets heavily contaminated with casing, adhesive, and coil residues are subjected to hydrometallurgical digestion according to step b). After the reaction is complete, the carboxylic acid solution can be separated and subsequently subjected to step c) to obtain high-purity RE oxide.

[0044] The process according to the invention also has the significant advantage over prior art processes of being significantly faster. The efficiency of this process is demonstrated, for example, in a direct comparison with the digestion process described in US Pat. No. 5,129,945 B1. There, complete digestion according to the exemplary embodiments requires 24 hours, whereas in the present invention, the total digestion time is only a few minutes, as can be seen from the examples.

[0045] In a further embodiment of the invention, during step b), the pH of the solution is readjusted by further addition of the carboxylic acid or the mixture of several carboxylic acids so that it does not exceed a value of 3.5. Preferably, the pH does not exceed 3. More preferably, the pH does not exceed 2.5. Most preferably, the pH does not exceed 1.5. In special cases, the pH does not exceed 1.

[0046] As demonstrated in numerous experiments, in contrast to the prior art, the present invention eliminates the need for problematic measurement and targeted pH adjustment for the precipitation reaction, since the acid concentration of the carboxylic acid during hydrometallurgical digestion is already within the optimal range in terms of product purity and yield. However, if this step is to be accelerated, the pH can be readjusted so that it does not exceed 3.5.

[0047] 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.

[0048] According to another embodiment, the carboxylic acid is a saturated monocarboxylic acid. According to another embodiment, the carboxylic acid is an aromatic monocarboxylic acid.

[0049] According to a further embodiment, the carboxylic acid is a monounsaturated monocarboxylic acid.

[0050] According to a further embodiment, the carboxylic acid is a polyunsaturated monocarboxylic acid.

[0051] According to a further 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.

[0052] According to a further embodiment, the carboxylic acid is formic acid.

[0053] According to a further embodiment, the carboxylic acid is acetic acid.

[0054] According to a further embodiment, the carboxylic acid is palmitic acid.

[0055] According to a further embodiment, the carboxylic acid is stearic acid.

[0056] According to a further embodiment, the carboxylic acid is benzoic acid.

[0057] According to a further embodiment, the carboxylic acid is a dicarboxylic acid.

[0058] According to a further 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.

[0059] According to another embodiment, the carboxylic acid is oxalic acid. According to another embodiment, the carboxylic acid is succinic acid.

[0060] According to a further embodiment, the carboxylic acid is maleic acid.

[0061] According to a further embodiment, the carboxylic acid is tartaric acid.

[0062] According to a further embodiment, the carboxylic acid is adipic acid.

[0063] According to a further embodiment, the carboxylic acid is phthalic acid.

[0064] According to a further embodiment, the carboxylic acid is a tricarboxylic acid.

[0065] According to a further 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.

[0066] According to a further embodiment, the carboxylic acid is isocitric acid.

[0067] According to a further embodiment, the carboxylic acid is citric acid.

[0068] According to a further embodiment, the carboxylic acid is aconitic acid.

[0069] According to a further embodiment, the carboxylic acid is agaric acid.

[0070] According to a further embodiment, a mixture comprising several carboxylic acids can also be used. The mixing ratios can vary depending on the acids used.

[0071] In one embodiment of the invention, the mixture comprises two different carboxylic acids in a ratio of 100:1 to 1:100, preferably 50:1 to 1:50, more preferably 10:1 to 1:10. In a further embodiment of the invention, the mixture comprises three different carboxylic acids. In this case, the ratio of the first two carboxylic acids is as described above. The ratio of carboxylic acid 1 to carboxylic acid 3 is 100:1 to 1:100, preferably 50:1 to 1:50, more preferably 10:1 to 1:10.

[0072] According to a further embodiment, the concentration of the aqueous solution of the carboxylic acid or mixture of several carboxylic acids is at least 5% and at most 99%. According to preferred embodiments, the carboxylic acid or mixture of several carboxylic acids is at least 30%, more preferably 60%, most preferably 90%.

[0073] According to one embodiment, the precipitant 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, propan-1,3-diol, glycerin, pentaerythritol.

[0074] Preferably, the precipitant is an alcohol selected from the group consisting of: methanol, ethanol, propan-1-ol, butan-1-ol, butan-2-ol, isobutanol, tert-butanol.

[0075] More preferably, the precipitant is an alcohol selected from the group consisting of: methanol, ethanol, butan-1-ol, tert-butanol.

[0076] According to one embodiment, the alcohol is methanol.

[0077] According to a further embodiment, the alcohol is ethanol.

[0078] According to a further embodiment, the alcohol is butan-1-ol.

[0079] According to one embodiment, the precipitation in step c) is achieved by adding a liquid precipitant.

[0080] According to another embodiment, precipitation is achieved by adding it to a liquid precipitant. In one embodiment, all steps of the process according to the invention are carried out at room temperature. In another embodiment, the process is carried out at elevated temperatures of 70-90°C. Depending on the starting material used, it may be desirable to heat the carboxylic acid solution in step b) to increase solubility and thus shorten the reaction time.

[0081] In a further embodiment, a magnetic separation takes place after step a), whereby the demagnetized RE compounds are separated from the starting material and / or only magnetized (remanent) ferro- and ferrimagnetic compounds are separated.

[0082] This measure contributes to the fact that the process according to the invention can be flexibly adapted to the starting material to be recycled.

[0083] In a further embodiment, prior to magnetic separation, demagnetization of the RE compounds is carried out by heating to above its Curie temperature and / or the use of alternating electromagnetic fields.

[0084] Further advantageous properties of the invention are described and explained in more detail below using examples and experiments.

[0085] Example 1: Extraction of RE oxides from sorted waste magnets from a wind turbine

[0086] 200 g of HPMS powder, obtained from sorted waste magnets from a wind turbine, is stirred in one liter of a mixture of tartaric acid (50%), formic acid (35%), and oxalic acid (15%) with a pH of 2 for 45 minutes at 80°C. The acid solution is then separated from the powder. The magnet powder, completely free of the rare-earth-rich grain boundary phase, weighs 99.25 g.

[0087] The rare earth oxide dissolved in the acid mixture is precipitated using ethanol and, after drying, has a weight of 272.70 g. Example 2: Extraction of rare earth oxides from magnetic waste from smartphone audio modules

[0088] Shredded magnetic waste from 100 smartphone audio modules is largely separated from polymer residues using magnetic separation and subjected to HPMS treatment. The resulting 40 g of HPMS powder is stirred in 0.5 liters of a mixture of tartaric acid (55%), formic acid (30%), and citric acid (15%) with a pH of 2 for 60 minutes at 80°C. The acid solution is then separated from the powder. The rare earth oxide dissolved in the acid mixture is precipitated using ethanol and, after drying, has a weight of 76.25 g.< / t> < / t> < / t>

Claims

Claims: A process for obtaining SE oxides from a starting material comprising one or more SE compounds of the formula SEFeB, comprising the following steps: a) comminution of the starting material by hydrogen hydrogenation (HPMS); b) treatment of the comminuted starting material with an aqueous solution of a carboxylic acid or a mixture of several carboxylic acids; c) precipitation of the SE oxides from the carboxylic acid solution by adding a precipitating agent comprising an alcohol or a mixture of several alcohols. The process according to claim 1, characterized in that during step b), the pH of the solution is readjusted by further addition of the carboxylic acid or the mixture of several carboxylic acids so that it does not exceed a value of 3.5.A method according to claim 1 or 2, characterized in that, optionally, a step b') is provided after step b) in which the insoluble, hard magnetic O-phase comprising SE2Fei4B in the carboxylic acid solution is separated from the solution before precipitation step c). A method according to any one of the preceding claims, characterized in that the starting material comminuted in step a) has a particle size in the range of 1 pm to 1000 pm. A method according to any one of claims 1 to 4, 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. A process 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. A process according to any one of claims 1 to 4, 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. A process according to any one of claims 1 to 4, 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.A process according to any one of the preceding claims, 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. A process according to claim 9, characterized in that the alcohol is methanol. A process according to claim 9, characterized in that the alcohol is butanol. A process according to any one of the preceding claims, characterized in that, after step a), magnetic separation takes place, whereby the demagnetized SE compounds are separated from the starting material and / or only magnetized (remanent) ferro- and ferrimagnetic compounds are separated. The method of claim 12, characterized in that, prior to magnetic separation, the SE compounds are demagnetized by heating to above their Curie temperature and / or by the application of alternating electromagnetic fields. SE oxides produced according to a method according to claims 1 to 13. Use of the SE oxides produced according to the method according to claims 1 to 13 for the production of magnets.