A method for selectively extracting boron from a solution resulting from acid attack on a permanent magnet containing rare earth elements using an organic solvent.

Abstract

The present invention relates to a method for extracting boron contained in an aqueous solution A1 containing a rare earth element, comprising contacting and mixing the aqueous solution A1, obtained by dissolving machined scrap from the manufacture of powdered NdFeB magnets or permanent magnets, with an organic solvent, wherein the organic solvent contains at least one extraction compound consisting of an alcohol having 6 to 18 carbon atoms, being aliphatic or aromatic, linear or branched, and the boron is transferred from the aqueous solution A1 to the organic solvent by contacting and mixing the aqueous solution A1 with the organic solvent.

Description

[Technical Field]

[0001] This invention belongs particularly to the general field of recycling boron obtained from used or discarded permanent magnets. More specifically, this invention relates to a method for solvent extraction of boron contained in a solution obtained from the acid attack of a permanent magnet containing rare earth elements. [Background technology]

[0002] The use of rare-earth magnets is increasing due to applications in electric vehicle motors, electric scooters, and even wind turbines. The most commonly used rare-earth magnets include neodymium-iron-boron (NdFeB) permanent magnets. However, the scarcity of the chemical elements that make up these magnets and the pollutants released during their extraction make their recycling a significant challenge.

[0003] Therefore, recovering the rare earth elements used in the composition of magnets, or those still present in the manufacturing waste of these magnets, when the magnets reach the end of their lifespan, becomes a crucial factor, given the scarcity of conventional rare earth element resources.

[0004] To recover these rare earth elements, it is essential to separate them from boron during the magnet reprocessing operation. Therefore, recycling boron and then returning it to the market is a crucial operation. Furthermore, since boron is a toxic element, this operation avoids the high cost of managing boron-containing residues generated during magnet recycling.

[0005] Current recycling technologies are essentially based on two processes: One method is the so-called "short-loop" process, in which the permanent magnet is pulverized and then reformed directly from this powder. The other method is the so-called "long loop" process, which consists of dissolving the magnet and then separating the various elements that make up the magnet.

[0006] This invention falls within the framework of this second category of processes.

[0007] First, the recycling process begins by demagnetizing the permanent magnets recovered from end-of-life equipment by heating them to a temperature above the Curie temperature. Next, the permanent magnets are pulverized into powder and then thermally oxidized.

[0008] Next, the oxidized powder is attacked with an acid, such as nitric acid, hydrochloric acid, or sulfuric acid, to dissolve all or part of the elements.

[0009] Therefore, the acid attack solution obtained in this manner contains the components of a permanent magnet, namely, in the case of an NdFeB magnet, neodymium, iron, boron, and trace amounts of other trace components, such as other rare earth elements and / or elements such as iron, aluminum, cobalt, copper, and zinc.

[0010] Boron is recovered from this solution using liquid-liquid extraction technology.

[0011] This dissolution method is described, for example, in international publication No. 96 / 000698, in which the magnet is oxidized by heat treatment and then dissolved in a hydrochloric acid solution.

[0012] On the other hand, given the current state of technology, a process is known for extracting boron from an aqueous solution that does not contain rare earth elements using an organic solvent consisting of at least one alcohol or diol and diluted with a liquid hydrocarbon mixture.

[0013] Such a method is described, for example, in the paper "Boron extraction from aqueous medium using novel hydrophobic deep eutectic solvents" by Almustafa et al., 2020, which details the extraction of boron from aqueous solutions derived from wastewater that does not contain rare earth elements or iron, using a eutectic solvent containing diols and monoalcohols.

[0014] Similarly, in the literature "Recovery of boron from unacidified salt lake brine by solvent extraction with 2,2,4-trimethyl-1,3-pentanediol", Peng et al., 2021, boron extraction is performed from an aqueous solution obtained from brine without rare earth elements and iron using 2,2,4-trimethyl-1,3-pentanediol.

[0015] Such a diol-based extraction system is applied to the reprocessing of magnets. After dissolution, the boron extraction step is carried out, and before that, the rare earth elements present in the magnet attack solution are recovered.

[0016] This method is described in the literature "Recovery and separation of rare earths and boron from spent Nd-Fe-B magnets", Liu et al., 2020. In this literature, after completely precipitating the rare earth elements in the solution in the form of oxalates, it is described that boron is extracted using a solvent consisting of 2-ethyl-1,3-hexanediol and sulfonated kerosene.

[0017] This boron extraction method is applied to solutions that do not contain rare earth elements.

[0018] In the literature "Separation of fission and corrosion products from boric acid solutions by solvent extraction", Narbutt J. et al., 1979, a method for liquid-liquid extraction of boric acid dissolved in an aqueous solution obtained from radioactive corrosion and fission products is described. This literature is not related to the extraction of boron from used or discarded permanent magnets.

Prior Art Documents

Patent Documents

[0019]

Patent Document 1

[0020] [Non-Patent Document 1] “Boron extraction from aqueous medium using novel hydrophobic deep eutectic solvents”, Almustafa et al., 2020 [Non-Patent Document 2] “Recovery of boron from unacidified salt lake brine by solvent extraction with 2,2,4-trimethyl-1,3-pentanediol”, Peng et al., 2021 [Non-Patent Document 3] “Recovery and separation of rare earths and boron from spent Nd-Fe-B magnets”, Liu et al., 2020 [Non-Patent Document 4] "Separation of fission and corrosion products from boric acid solutions by solvent extraction", Narbutt J. et al., 1979 [Overview of the project] [Problems that the invention aims to solve]

[0021] Therefore, there is a need to develop a method for selectively extracting boron from aqueous solutions obtained from magnetic attacks, which mainly contain rare earth elements and trace amounts of other elements.

[0022] According to the present invention, boron is extracted from an attack solution containing rare earth elements, thereby providing greater flexibility in subsequent processes for recovering and separating the rare earth elements without potential interference caused by the presence of boron. In fact, some processes in the prior art carry the risk of contamination of rare earth elements with boron, and furthermore, the lower solubility of boric acid compared to rare earth element salts in these solutions can limit the parameters of such processes. [Means for solving the problem]

[0023] This invention makes it easier to manage solid residues generated during the recycling of rare-earth magnets by removing boron, which is considered toxic. Therefore, it greatly contributes to compliance with environmental constraints.

[0024] The present invention relates to a method for extracting boron contained in an aqueous solution A1 containing a rare earth element, wherein the aqueous solution A1 is obtained by dissolving powder of NdFeB magnet powder or machining scrap generated from the manufacture of permanent magnets. In the method of the present invention, the aqueous solution A1 is brought into contact with and mixed with an organic solvent containing at least one extraction compound made of aliphatic or aromatic, linear or branched alcohol containing a chain of 6 to 18 carbon atoms, and boron is transferred from the aqueous solution A1 to the organic solvent by contact and mixing of the aqueous solution A1 and the organic solvent.

[0025] The present invention can only be carried out using compounds containing 6 or more or 18 or fewer carbon atoms. In fact, hydrocarbons with fewer than 6 carbon atoms are gaseous, while hydrocarbons with more than 18 carbon atoms are solid waxes or tars.

[0026] The process of bringing aqueous solution A1 into contact with and mixing it with an organic solvent brings about the transfer of boron from aqueous solution A1 to the organic solvent.

[0027] "Boron" includes any compound containing at least one boron atom present in an aqueous or organic phase. For example, boric acid is included in the definition of "boron" according to the present invention.

[0028] In this invention, "alcohol" refers to all compounds containing at least one alcohol functional group, and this includes monoalcohols and diols.

[0029] In this invention, "borate" refers to a molecular compound containing at least one boron atom and at least one oxygen atom. For example, but not limited to, metaborate ion BO2 - and tetraborate ion B4O7 2- Ions are borates.

[0030] The term "boron salt" includes borate salts. For example, although not limited to these, sodium metaborate (NaBO2) and sodium tetraborate (Na2B4O7) are boron salts. Sodium tetraborate pentahydrate (Na2B4O7·5H2O) or decahydrate (Na2B4O7·10H2O) is also called borax and is a boron salt.

[0031] Preferably, the extracted compound is: - 1,3-diols, preferably 2-ethyl-1,3-hexanediol (EHD), 2-butyl-2-ethylpropane-1,3-diol (BEPD), 2,2,4-trimethyl-1,3-pentanediol (TMPD), 2-chloro-4-(1,1,3,3-tetramethylbutyl)-6-methylolphenol (CTMP), and from among mixtures thereof, - Monoalcohols having branched or linear aliphatic chains with 6 to 18 carbon atoms, preferably from among 2-ethylhexanol (2-EH), 2-propylheptanol (2-PH), 2-butyloctanol, isodecanol, octanol, and mixtures thereof. It is selected from the group that includes it.

[0032] A "1,3-diol" refers to a compound containing two alcohol functional groups supported by two carbon atoms separated by other carbon atoms. These compounds are also known as "β-diols."

[0033] A "monoalcohol" refers to a compound that contains a single alcohol functional group.

[0034] The organic solvent may contain at least one dilution compound in addition to the extracted compound. The dilution compound is preferably formed from an aliphatic or aromatic hydrocarbon chain with 6 to 18 carbon atoms.

[0035] Preferably, the dilution compound is selected from the group comprising decane and its isomers, dodecane and its isomers, kerosene, toluene, aliphatic or aromatic hydrocarbons having 6 to 18 carbon atoms, paraffins, cycloparaffins, and mixtures thereof. Examples of dilution compounds include Shellsol® D70 (aliphatic hydrocarbon) and Solvesso® 150 (aromatic hydrocarbon).

[0036] Preferably, the dilution compound is a liquid substance in which the extracted compound is dissolved.

[0037] According to one embodiment, the organic solvent further comprises a modified compound different from the extracted compound. The modified compound preferably consists of an alcohol containing an aliphatic chain with 6 to 18 carbon atoms.

[0038] Preferably, the modified compound is selected from the group including monoalcohols, and is preferably selected from decane-1-ol, octan-1-ol, isodecane-1-ol, hexane-1-ol, dodecane-1-ol, 2-propylheptanol, 2-ethylhexanol, and mixtures thereof.

[0039] In the context of this invention, "modified compound" refers to a chemical species other than the extracted compound and the dilution compound that is likely to alter certain properties of the organic solvent.

[0040] For example, modified compounds may delay the generation of the third phase or accelerate the decantation of organic solvents and aqueous solutions.

[0041] The modified compound can be dissolved in the diluted compound.

[0042] In specific embodiments of the present invention, the organic solvent is - 10% to 100% of at least one extractable compound, - At least one diluted compound in a concentration of 0% to 90% - 0% to 70% of at least one modified compound, It contains in a mass ratio relative to the total mass of the organic solvent, and the total is equal to 100%.

[0043] According to one embodiment, the organic solvent contains at least 5%, or further 20%, or further 30%, or further 40%, or further 50%, of at least one extractable compound. The organic solvent may contain up to 90%, or further 80%, or further 70%, or further 60%, of at least one extractable compound.

[0044] According to one embodiment, the organic solvent contains at least 5%, or further 20%, or further 25%, or further 30%, or further 40%, or further 50% of at least one dilution compound. The organic solvent may contain up to 95%, or further 80%, or further 70%, or further 60%, or further 55% of at least one dilution compound.

[0045] According to one embodiment, the organic solvent contains at least 5%, or further 10%, or further 20%, or further 25%, or further 30%, or further 40% of at least one modified compound. The organic solvent may contain up to 80%, or further 70%, or further 60%, or further 50% of at least one modified compound.

[0046] According to the present invention, an organic solvent is brought into contact with an aqueous solution A1 containing a rare earth element and boron.

[0047] According to the present invention, aqueous solution A1 is a solution obtained from acid attack on a demagnetized neodymium-iron-boron (NdFeB) permanent magnet, or a solution obtained by powdering machining scrap obtained from the manufacture of permanent magnets and oxidizing it. Preferably, the pH is in the range of 0.5 to 3.5.

[0048] "Solution obtained from acid attack of magnets" refers to a solution obtained by dissolving magnetic powder, particularly NdFeB magnets, in an acid, such as nitric acid, hydrochloric acid, or sulfuric acid. This powder is produced by the demagnetization, polishing, and oxidation of permanent magnets.

[0049] "Machining scrap" refers to scrap material generated during the manufacture of permanent magnets. This scrap contains the same components as magnets, namely iron, boron, and rare earth elements.

[0050] In particular, by mass ratio, Nd (14%~26%) is mainly found, followed by Pr (0%~9%), Dy (0%~6%), Tb (0%~1%), and Ce (0%~6%). Sc, Y, Tm, Yb, and Lu are not found in NdFeB magnets. A typical composition of NdFeB magnets is, for example, by mass ratio, Fe 65%, Nd 24%, Pr 2.5%, Dy 4.25%, B 1%, and Co 5%.

[0051] This aqueous solution A1 is preferably, - Rare earth elements in the form of dissolved salts, at concentrations of 20-450 g / L. - Boron in the form of boric acid, at a concentration of 1-9 g / L - Iron in the form of dissolved salts, at concentrations of 0-20 g / L, and - Metal elements belonging to the group including cobalt, aluminum, zinc, copper, manganese, and nickel, in the form of dissolved salts, at concentrations of 0-5 g / L. Includes.

[0052] According to the present invention, these rare earth elements are selected from the group comprising lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, and mixtures thereof.

[0053] In particular, solution A1 may contain, in the form of dissolved salts, cobalt between 0 g / L and 1 g / L, copper between 0 g / L and 1 g / L, aluminum between 0 g / L and 1 g / L, and / or zinc between 0 g / L and 0.5 g / L.

[0054] In particular, dissolved salts of rare earth elements belong to the group that includes rare earth nitrates, rare earth chlorides, rare earth sulfates, and mixtures thereof.

[0055] Ideally, the method according to the present invention includes the step of bringing an organic solvent and an aqueous solution A1 into contact, preferably in a ratio of their respective volumes in the range of 1 to 10.

[0056] Contact and mixing are carried out in a liquid-liquid extraction apparatus. Preferably, the mixing duration is in the range of 1 to 15 minutes, more preferably 3 to 5 minutes.

[0057] After mixing, a separation step is performed, for example, by decantation of aqueous solution A1 and organic solvent.

[0058] Contact and mixing are preferably carried out at a temperature in the range of 20°C to 70°C, preferably 40°C to 60°C.

[0059] In this way, a boron-rich solvent and a boron-depleted aqueous raffinate are obtained.

[0060] Advantageously, the boron concentration in this solvent is in the range of 1 g / L to 14 g / L.

[0061] The selectivity of boron extraction ensures that the concentrations of rare earth elements, iron, aluminum, cobalt, copper, and zinc are less than 10 mg / L.

[0062] This extraction operation is advantageously performed in a multi-stage counterflow, mixer-settler battery, or a stirred column or pulsed column.

[0063] After boron transfer, the boron concentration in the aqueous raffinate is typically less than 30 mg / L. This corresponds to a boron extraction rate of over 95%. The amounts of rare earth elements, iron, aluminum, cobalt, copper, and zinc released into the raffinate are equal to the amounts that flow into the initial aqueous solution A1. The target residual boron content is selected according to environmental constraints.

[0064] If necessary, this method can be adapted so that the boron content in the aqueous solvent is less than 30 mg / L.

[0065] Furthermore, the method includes a step of re-extracting the boron present in the organic solvent after the transfer of boron. Preferably, this boron re-extraction step is carried out by contacting a Brønsted base with the solvent, the base being advantageously selected from the group including NaOH, KOH, LiOH, NH4OH, and mixtures thereof. The boron can then be recovered in the form of an alkaline borate obtained from these solutions.

[0066] Generally, bases have concentrations ranging from 0.1 to 2 mol / L.

[0067] In the context of this invention, "re-extraction" refers to a liquid-liquid extraction process that enables the transfer of boron already extracted by the solvent from the organic solvent to the aqueous phase.

[0068] Here, the boron contained in the organic solvent migrates to the aqueous phase containing the base. Therefore, the recovered solvent is substantially free of boron. Preferably, the recovered solvent has a boron concentration of less than 10 mg / L.

[0069] The method of the present invention may further include a step of recovering boron in the form of a boron salt from boric acid present in an organic solvent. This boron recovery step is a sub-step as follows: a) A step of contacting a basic aqueous solution A2 with an organic solvent to extract boron into the basic aqueous solution A2 in the form of a solubilized borate, b) Distillation of borate-containing basic aqueous solution A2 to concentrate the solution and produce a distillate, c) Crystallization in the form of hydrated boron salts, d) Solid-liquid separation of crystallized hydrated boron salt to produce mother water, e) Reintroduction of distillate and crystallized mother liquor in the step of contacting the basic aqueous solution A2 with an organic solvent, Includes.

[0070] Crystallized hydrated boron salts recovered in solid form can be reused in various industrial fields, such as glass (borosilicate glass), ceramics (boron nitride), metallurgy (steel flux), or pharmaceuticals (disinfectants).

[0071] Steps a) to e) are preferably carried out in a closed loop so that the aqueous solution can be continuously circulated and recycled. In this embodiment, the water introduced into the method flows within the loop. Furthermore, the method does not consume any water other than the water initially introduced and recycled.

[0072] At the same time, all trace amounts of organic solvent present in the aqueous phase are completely recycled and recovered.

[0073] This allows for the advantageous recovery of over 99% of the boron contained in the organic solvent. The resulting solid borate also has an advantageous purity of over 99%.

[0074] Sub-process a) In this section, the organic solvent contains boric acid with a boron concentration generally in the range of 1 mg / L to 14 g / L, preferably 1 g / L to 14 g / L.

[0075] Advantageously, the basic aqueous solution A2 is prepared by diluting a concentrated basic solution or by solubilizing a solid basic compound.

[0076] Preferably, the basic aqueous solution A2 is a solution of NaOH, KOH, LiOH, or NH4OH. The choice of base depends on the boron salt to be produced; for example, a NaOH solution may produce sodium borate. Similarly, a KOH solution is chosen to obtain potassium borate.

[0077] Preferably, the basic aqueous solution A2 is introduced in a stoichiometric amount relative to the amount of boron salt produced.

[0078] Therefore, the structure of the final product is determined by the number of moles of alkali or ammonium added. For example, to produce sodium tetraborate (Na₂B₄O₇), 0.5 moles of NaOH are introduced for every 1 mole of boron present in the organic solvent. Similarly, to produce sodium metaborate (Na₂BO₂), 1 mole of NaOH is required for every 1 mole of boron.

[0079] In this way, the basic solution is not introduced in excess. This reduces the consumption of alkaline agents.

[0080] Advantageously, the ratio of the number of moles of alkali or ammonium in the basic solution to the number of moles of boron in the organic solvent is in the range of 0.3 to 1.

[0081] During the process of contacting the basic aqueous solution A2 with an organic solvent, the boric acid present in the solvent moves from the organic phase to the aqueous phase. In this way, a basic aqueous solution containing borate is obtained.

[0082] The sub-step a) of contacting the basic aqueous solution A2 with an organic solvent is preferably carried out in a multi-stage apparatus in which the organic solvent and the basic aqueous solution A2 flow in opposite directions.

[0083] For this purpose, two liquids are circulated at different flow rates, and the ratio of the flow rate of the basic aqueous solution to the flow rate of the organic solvent may be in the range of 0.1 to 2, preferably 0.1 to 1, and more preferably 0.1 to 0.5. These flow rate ratios allow for minimizing the amount of water flowing in the method and optimizing the power consumption of the method.

[0084] In the modified configuration, this process is carried out at a temperature in the range of 20°C to 70°C, preferably 40°C to 60°C. Within this temperature range, the ratio of the flow rate of the basic aqueous solution to the flow rate of the organic solvent is optimized to be in the range of 0.1 to 2.

[0085] Sub-process b) In sub-step b), the basic aqueous solution A2 containing solubilized borate is preferably subjected to a concentration step by distillation to produce a distillate. This step is carried out at a temperature in the range of 20°C to 110°C, preferably 30°C to 105°C, and preferably 2.10 4 Pa~10 5 The test is carried out under absolute pressure in the Pa range. By concentrating the solution, a borate saturated solution can be obtained.

[0086] Sub-process c) The crystallization sub-step c) is preferably carried out by distillation of the borate-concentrated basic aqueous solution A2 or by cooling of the borate-concentrated basic aqueous solution A2.

[0087] Next, the crystallized solid is suspended in a solution. This distillation is carried out to obtain the desired amount of crystallized solid in the suspension. This step is performed at a temperature in the range of 20°C to 110°C, preferably 30°C to 105°C, and preferably 2.10 4 Pa~10 5 It is performed using absolute pressure in the Pa range.

[0088] The degree of hydration of the boron salt produced is determined by the temperature at which the distillation is performed. For example, at temperatures in the range of 20°C to 60°C, borax decahydrate (Na₂B₄O₃.10H₂O) is obtained. However, borax pentahydrate (Na₂B₄O₃.5H₂O) is obtained at temperatures in the range of 60°C to 100°C.

[0089] According to another variant of the present invention, crystallization of the borate is achieved by cooling a concentrated basic aqueous solution of the borate, thereby reducing the solubility of the boron salt in the solution. In this case, the solution is cooled according to a temperature gradient of 10°C to 40°C per hour.

[0090] The borate suspension may be partially redissolved by heating the borate, and then cooled again to form a new borate suspension. This operation forms a crystallization cycle. The crystallization cycle may be performed one to three times, and preferably once to increase the purity of the crystallized borate.

[0091] These two crystallization processes, namely distillation and cooling, make it possible to remove residual solvent traces from the solid into the mother liquor.

[0092] "Solvent traces" refers to small amounts of extracted compounds, and / or modified compounds, and / or diluting compounds.

[0093] Furthermore, distillation performed during the concentration process and, if applicable, the crystallization process generally produces a distillate containing trace amounts of solvent, typically less than 1% by mass.

[0094] This distillate is advantageously recycled in this method during the process of contacting the basic aqueous solution A2 with an organic solvent, and / or mixed with the basic aqueous solution A2. In fact, the distillate is used to dilute the concentrated basic solution or to solubilize the solid basic compound.

[0095] After the crystallization process, the borate crystal suspension can be subjected to a maturation suspension for 30 minutes to 2 hours, preferably 1 hour. This duration allows the solution to reach thermodynamic equilibrium.

[0096] Sub-process d) According to sub-step d), the crystals of the hydrated borate salt are advantageously recovered by performing a solid-liquid separation step. Examples of the solid-liquid separation method include, but are not limited to, distillation, centrifugation, and filtration.

[0097] Advantageously, the crystallized hydrated borate salt is filtered to produce a crystallization mother liquor. This crystallization mother liquor may contain less than 1% by mass of trace amounts of the solvent.

[0098] The filtration may be carried out under vacuum, or in the range of 10 5 ~5.10 5 Pa, preferably under a positive pressure of 10 5 Pa, or under a reduced pressure between 10 4 ~8.10 4 Pa.

[0099] Sub-step e) Advantageously, the crystallization mother liquor is recycled in this method during the step of bringing the basic aqueous solution A2 into contact with the organic solvent. The crystallization mother liquor is mixed with the basic aqueous solution A2 during this contact step.

[0100] According to the present invention, the solid thus recovered is a hydrated borate having a formula that can be NaBO2·yH2O, Na2B4O7·yH2O, Na2B5O8·yH2O, Li2B4O7·yH2O, K2B4O7·yH2O, or (NH4)2B4O7·yH2O (where y ranges from 0 to 11).

[0101] After the solid-liquid separation, the recovered solid may be subjected to washing to wash away trace amounts of the solvent.

[0102] In this case, the crystallized hydrated borate salt is washed with an aqueous solution and / or a distillate obtained by distillation, thereby generating washing water. This washing water may contain less than 1% by mass of trace amounts of the solvent.

[0103] The washing water is advantageously recycled in this method during the step of bringing the basic aqueous solution A2 into contact with the organic solvent. The washing water may be mixed with the basic aqueous solution A2 during this contact step.

[0104] Therefore, the method according to the present invention makes it possible to obtain crystallized boron salts with a very low content of residual carbon derived from organic solvents without causing solvent loss.

[0105] The reuse of distillates, crystallized mother liquor, and / or wash water has the advantage of allowing the recovery of all aqueous streams and all solvents.

[0106] A drying process may be performed after washing. In particular, drying should be carried out at a temperature in the range of 50°C to 150°C for 10 minutes. 4 Pa~10 5 It may also be performed at absolute pressures in the Pa range.

[0107] Depending on the drying temperature, either hydrated borax or anhydrous borax can be obtained. For example, at drying temperatures in the range of 100°C to 150°C, anhydrous borax is produced.

[0108] Methods for carrying out the present invention and the advantages obtained will become clearer from the following embodiments shown as non-limiting examples with reference to the accompanying drawings. [Brief explanation of the drawing]

[0109] [Figure 1] This figure shows a simplified representation of four mixer-settler batteries used in implementing a boron extraction method according to a specific embodiment of the present invention. [Figure 2] This figure shows a simplified representation of a method according to a specific embodiment of the present invention. [Modes for carrying out the invention]

[0110] Detailed description of the drawing Figure 1 schematically shows a specific embodiment of this method implemented in a four-mixer-settler battery.

[0111] This method is performed in a multi-stage apparatus in which organic solvents and basic aqueous solutions flow in opposite directions.

[0112] In particular, this method can be carried out in a mixer-settler battery or a liquid-liquid extraction column. The number of stages in these devices is preferably in the range of 3 to 10, more preferably 5 to 7.

[0113] The apparatus in Figure 1 is a mixer-settler battery (e) having four stages (a, b, c, d) of a known type. The first stage (a) is supplied with an organic solvent (11) containing boric acid and a borax solution (12) obtained from the crystallization mother liquor and optionally from the recycling of wash water.

[0114] Furthermore, an aqueous NaOH solution (13) is supplied to the fourth stage (d) in a countercurrent.

[0115] The distillate (20) obtained during the implementation of the present invention is also supplied to the fourth stage (d) in a countercurrent.

[0116] The boron-containing organic solvent (11) in the first stage (a) is then moved to the second stage (b), then to the third stage (c), and finally to the fourth stage (d), where it is mixed and decanted.

[0117] The aqueous phase, consisting of an aqueous NaOH solution (13), supplied to the fourth stage (d), is moved to the first stage (a) via stages (c) and (b), where it combines with the borax solution (12), and the aqueous phase and solvent phase are mixed and decanted at each stage.

[0118] The alkaline borate aqueous solution (14) is collected at the output of the first stage (a). The extraction solvent (15), which does not contain boron, is discharged from the fourth stage (d).

[0119] Referring to Figure 2, the borate aqueous solution (14) discharged from the mixer-settler battery (e) is recovered and treated to crystallize the borate.

[0120] First, a borate aqueous solution (14) is distilled (g) to obtain a borate saturated solution and distillate (20) by increasing the temperature and / or changing the pressure of the medium. Next, crystallization (h) is carried out either by distillation again to produce distillate (20) or by cooling, in either case yielding a crystalline borate suspension.

[0121] Finally, the boron salt suspension can be filtered (i) to recover the crystallized mother liquor (21) and crystallized borate (16). If necessary, the borate can be washed (j) to produce wash water (22). The distillate (20) can also be used to wash the borate.

[0122] The distillate (20) is reused to dilute (f) the basic soda concentrate (17) to obtain an aqueous NaOH solution (13). This aqueous NaOH solution is introduced into a mixer-settler battery (e) and used for liquid-liquid extraction of boron.

[0123] The crystallization mother liquor (21) and washing water (22) are mixed to form a borax solution (12), which is then reintroduced into the battery (e). [Examples]

[0124] Examples 1 to 21 aim to illustrate various embodiments of the present invention. These examples disclose fundamental data used to carry out the boron extraction method according to the present invention in the presence of rare earth elements in solution.

[0125] (Example 1) Boron extraction using EHD / octane-1-ol solvent A 20 mL aqueous solution obtained by dissolving the powder of a permanent magnet oxide in nitric acid was introduced into a 50 mL vial. This solution contains a total of 150 g / L of rare earth elements, with a boron concentration of 4.5 g / L, a neodymium concentration of 110 g / L, a praseodymium concentration of 27 g / L, a dysprosium concentration of 7 g / L, a cerium concentration of 3 g / L, and other rare earth elements at concentrations of less than 1 g / L. The solution also contains an iron concentration of 2 g / L, an aluminum concentration of 0.5 g / L, a cobalt concentration of 0.5 g / L, a copper concentration of 0.2 g / L, and trace amounts of zinc. This solution has a pH of 2.

[0126] This aqueous solution is prepared by demagnetizing a neodymium-iron-boron (NdFeB) permanent magnet, crushing it into a powder, and finally treating it with thermal oxidation. Next, the oxidized powder is dissolved in a nitric acid solution.

[0127] 20 mL of organic extraction solvent, consisting of 30% by mass of 2-ethyl-1,3-hexanediol (EHD) as the extractant compound and 70% by mass of octan-1-ol as the diluent compound, is introduced into the same vial.

[0128] Therefore, the volume ratio of the aqueous phase to the organic phase is 1.

[0129] The medium is vigorously stirred at 60°C for 15 minutes. After this, the aqueous phase and organic phase are separated by decantation.

[0130] The boron concentration in the aqueous phase is 0.25 g / L, and the boron concentration in the organic phase is 4.25 g / L. Therefore, a boron partition coefficient corresponding to 17 is obtained.

[0131] The total final concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0132] (Example 2) Boron extraction using EHD / octane-1-ol solvent The extraction method of Example 1 is repeated, but this time, 40 mL of the acidic aqueous solution obtained by dissolving the permanent magnet oxide powder of Example 1, and 10 mL of the organic extraction solvent of Example 1 are introduced into the vial.

[0133] Therefore, the volume ratio of the aqueous phase to the organic phase is 4.

[0134] Therefore, the partition coefficient of boron corresponding to 5 is obtained.

[0135] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0136] (Example 3) Boron extraction using EHD / Solvesso(registered trademark) 150 / 2-EH solvent A 60 mL acidic aqueous solution, obtained by dissolving the powder of a permanent magnet oxide in nitric acid, was introduced into a 100 mL vial. This solution contains a total of 150 g / L of rare earth elements, with a boron concentration of 4.5 g / L, a neodymium concentration of 110 g / L, a praseodymium concentration of 27 g / L, a dysprosium concentration of 7 g / L, a cerium concentration of 3 g / L, and other rare earth elements at concentrations of less than 1 g / L. The solution also contains an iron concentration of 2 g / L, an aluminum concentration of 0.5 g / L, a cobalt concentration of 0.5 g / L, a copper concentration of 0.2 g / L, and trace amounts of zinc. This solution has a pH of 2.

[0137] A 10 mL organic extraction solvent consisting of 30% by mass of 2-ethyl-1,3-hexanediol (EHD) as the extraction compound, 50% by mass of Solvesso® 150 as the diluent, and 20% by mass of 2-ethylhexanol (2-EH) as the modifying compound is introduced into the same vial.

[0138] Therefore, the volume ratio of the aqueous phase to the organic phase is 6.

[0139] The medium is vigorously stirred at 60°C for 15 minutes. After this, the aqueous phase and organic phase are separated by decantation.

[0140] Therefore, the partition coefficient of boron corresponding to 6 is obtained.

[0141] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0142] (Example 4) Boron extraction using EHD / Solvesso(registered trademark) 150 / 2-EH solvent The extraction method of Example 3 is repeated, but this time, 50 mL of the acidic aqueous solution obtained by dissolving the permanent magnet oxide powder of Example 3, and 50 mL of the organic extraction solvent of Example 3 are introduced into the vial.

[0143] Therefore, the volume ratio of the aqueous phase to the organic phase is 1.

[0144] Therefore, the partition coefficient of boron corresponding to 32 is obtained.

[0145] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0146] (Example 5) Boron extraction using TPMD / kerosene / decanol solvents A 50 mL acidic aqueous solution, obtained by dissolving the powder of a permanent magnet oxide in nitric acid, was introduced into a 100 mL vial. This aqueous solution contains a total of 150 g / L of rare earth elements, with a boron concentration of 4.5 g / L, a neodymium concentration of 110 g / L, a praseodymium concentration of 27 g / L, a dysprosium concentration of 7 g / L, a cerium concentration of 3 g / L, and other rare earth elements at concentrations of less than 1 g / L. The solution also contains an iron concentration of 2 g / L, an aluminum concentration of 0.5 g / L, a cobalt concentration of 0.5 g / L, a copper concentration of 0.2 g / L, and trace amounts of zinc. This solution has a pH of 2.

[0147] A 10 mL organic extraction solvent consisting of 15% by mass of 2,2,4-trimethyl-1,3-pentadiol (TPMD) as the extractant, 25% by mass of kerosene as the diluent, and 60% by mass of decanol as the modifier is introduced into the same vial.

[0148] Therefore, the volume ratio of the aqueous phase to the organic phase is 5.

[0149] The medium is vigorously stirred at 60°C for 15 minutes. After this, the aqueous phase and organic phase are separated by decantation.

[0150] Therefore, a boron partition coefficient equivalent to 1.7 is obtained.

[0151] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0152] (Example 6) Boron extraction using TPMD / kerosene / decanol solvents The extraction process of Example 5 is repeated, but this time, 50 mL of the acidic aqueous solution obtained by dissolving the permanent magnet oxide powder of Example 5, and 50 mL of the organic extraction solvent of Example 5 are introduced into the vial.

[0153] Therefore, the volume ratio of the aqueous phase to the organic phase is 1.

[0154] Therefore, the partition coefficient of boron corresponding to 18 is obtained.

[0155] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0156] (Example 7) Boron extraction using BEPD / kerosene / decanol solvents A 50 mL acidic aqueous solution, obtained by dissolving the powder of a permanent magnet oxide in nitric acid, was introduced into a 100 mL vial. This aqueous solution contains a total of 150 g / L of rare earth elements, with a boron concentration of 4.5 g / L, a neodymium concentration of 110 g / L, a praseodymium concentration of 27 g / L, a dysprosium concentration of 7 g / L, a cerium concentration of 3 g / L, and other rare earth elements at concentrations of less than 1 g / L. The solution also contains an iron concentration of 2 g / L, an aluminum concentration of 0.5 g / L, a cobalt concentration of 0.5 g / L, a copper concentration of 0.2 g / L, and trace amounts of zinc. This solution has a pH of 2.

[0157] A 10 mL organic extraction solvent consisting of 15% by mass of 2-butyl-2-ethylpropane-1,3-diol (BEPD) as the extractant, 25% by mass of kerosene as the diluent, and 60% by mass of decanol as the modifier is introduced into the same vial.

[0158] Therefore, the volume ratio of the aqueous phase to the organic phase is 5.

[0159] The medium is vigorously stirred at 60°C for 15 minutes. After this, the aqueous phase and organic phase are separated by decantation.

[0160] Therefore, a partition coefficient of boron equivalent to 1.65 is obtained.

[0161] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0162] (Example 8) Boron extraction using BEPD / kerosene / decanol solvents The extraction process of Example 7 is repeated, but 50 mL of the acidic aqueous solution obtained by dissolving the permanent magnet oxide powder of Example 7, and 50 mL of the organic extraction solvent of Example 7 are introduced into the vial.

[0163] Therefore, the volume ratio of the aqueous phase to the organic phase is 1.

[0164] Therefore, a partition coefficient for boron equivalent to 2 is obtained.

[0165] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0166] (Example 9) Boron extraction using BEPD / kerosene / decanol solvents A 100 mL acidic aqueous solution, obtained by dissolving the powder of a permanent magnet oxide in sulfuric acid, was introduced into a 200 mL vial. This aqueous solution contained boron at a concentration of 0.6 g / L, neodymium at 14.7 g / L, praseodymium at 3.6 g / L, dysprosium at 0.9 g / L, cerium at 0.4 g / L, and other rare earth elements at concentrations of less than 0.1 g / L. The solution also contained iron at 0.25 g / L, aluminum, cobalt, and copper at concentrations of less than 0.1 g / L, and trace amounts of zinc. This solution had a pH of 2.

[0167] A 10 mL organic extraction solvent consisting of 15% by mass of 2-butyl-2-ethylpropane-1,3-diol (BEPD) as the extractant, 25% by mass of kerosene as the diluent, and 60% by mass of decanol as the modifier is introduced into the same vial.

[0168] Therefore, the volume ratio of the aqueous phase to the organic phase is 10.

[0169] The medium is vigorously stirred at 60°C for 15 minutes. After this, the aqueous phase and organic phase are separated by decantation.

[0170] Therefore, a boron partition coefficient equivalent to 1.7 is obtained.

[0171] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 5. * 10 -4 The value is less than 0.1, and the distribution coefficient of copper is less than 0.1.

[0172] (Example 10) Boron extraction using 2-PH / kerosene solvent A 50 mL acidic aqueous solution, obtained by dissolving the powder of a permanent magnet oxide in nitric acid, was introduced into a 100 mL vial. This solution contains a total of 150 g / L of rare earth elements, with a boron concentration of 4.5 g / L, a neodymium concentration of 110 g / L, a praseodymium concentration of 27 g / L, a dysprosium concentration of 7 g / L, a cerium concentration of 3 g / L, and other rare earth elements at concentrations of less than 1 g / L. The solution also contains an iron concentration of 2 g / L, an aluminum concentration of 0.5 g / L, a cobalt concentration of 0.5 g / L, a copper concentration of 0.2 g / L, and trace amounts of zinc. This solution has a pH of 2.

[0173] A 10 mL organic solvent consisting of 60% by mass of 2-propylheptanol (2-PH) as the extractant compound and 40% by mass of kerosene as the diluent compound is introduced into the same vial.

[0174] Therefore, the volume ratio of the aqueous phase to the organic phase is 5.

[0175] The medium is vigorously stirred at room temperature for 15 minutes. After this, the aqueous phase and organic phase are separated by decantation.

[0176] Therefore, a partition coefficient of boron equivalent to 0.6 is obtained.

[0177] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0178] (Example 11) Boron extraction using 2-PH / kerosene solvent The extraction process of Example 10 is repeated, but 50 mL of the acidic aqueous solution obtained by dissolving the permanent magnet oxide powder of Example 10, and 50 mL of the organic extraction solvent of Example 10 are introduced into the vial.

[0179] Therefore, the volume ratio of the aqueous phase to the organic phase is 1. Thus, a partition coefficient of boron equivalent to 0.6 is obtained.

[0180] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0181] (Example 12) Boron extraction using pure 2-PH solvent A 50 mL acidic aqueous solution, obtained by dissolving the powder of a permanent magnet oxide in nitric acid, was introduced into a 100 mL vial. This solution contains a total of 150 g / L of rare earth elements, with a boron concentration of 4.5 g / L, a neodymium concentration of 110 g / L, a praseodymium concentration of 27 g / L, a dysprosium concentration of 7 g / L, a cerium concentration of 3 g / L, and other rare earth elements at concentrations of less than 1 g / L. The solution also contains an iron concentration of 2 g / L, an aluminum concentration of 0.5 g / L, a cobalt concentration of 0.5 g / L, a copper concentration of 0.2 g / L, and trace amounts of zinc. This solution has a pH of 2.

[0182] A 10 mL organic extraction solvent, formed from 100% by mass of 2-propylheptanol (2-PH) as the extracting compound, is introduced into the same vial.

[0183] Therefore, the volume ratio of the aqueous phase to the organic phase is 5.

[0184] The medium is vigorously stirred at 60°C for 15 minutes. After this, the aqueous phase and organic phase are separated by decantation.

[0185] Therefore, a partition coefficient of boron equivalent to 0.56 is obtained.

[0186] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0187] (Example 13) Boron extraction using pure 2-PH solvent The extraction method of Example 12 is repeated, but 50 mL of the acidic aqueous solution obtained by dissolving the oxide permanent magnet powder of Example 12, and 50 mL of the organic extraction solvent of Example 12 are introduced into the vial.

[0188] Therefore, the volume ratio of the aqueous phase to the organic phase is 1.

[0189] Therefore, a partition coefficient of boron equivalent to 0.58 is obtained.

[0190] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0191] (Example 14) Boron extraction using pure 2-PH solvent A 50 mL acidic aqueous solution, obtained by dissolving the powder of a permanent magnet oxide in hydrochloric acid, was introduced into a 100 mL vial. This solution contains a total of 150 g / L of rare earth elements, with a boron concentration of 4.5 g / L, a neodymium concentration of 110 g / L, a praseodymium concentration of 27 g / L, a dysprosium concentration of 7 g / L, a cerium concentration of 3 g / L, and other rare earth elements at concentrations of less than 1 g / L. The solution also contains an iron concentration of 2 g / L, an aluminum concentration of 0.5 g / L, a cobalt concentration of 0.5 g / L, a copper concentration of 0.2 g / L, and trace amounts of zinc. This solution has a pH of 2.

[0192] 50 mL of organic extraction solvent, formed from 100% by mass of 2-propylheptanol (2-PH) as the extracting compound, is introduced into the same vial.

[0193] Therefore, the volume ratio of the aqueous phase to the organic phase is 1.

[0194] The medium is vigorously stirred at 50°C for 15 minutes. After this, the aqueous phase and organic phase are separated by decantation.

[0195] Therefore, a partition coefficient of boron equivalent to 0.63 is obtained.

[0196] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0197] (Example 15) Boron extraction using pure 2-PH solvent A 50 mL acidic aqueous solution, obtained by dissolving the powder of a permanent magnet oxide in sulfuric acid, was introduced into a 100 mL vial. This aqueous solution contains a total of 20 g / L of rare earth elements, with a boron concentration of 0.6 g / L, a neodymium concentration of 14.7 g / L, a praseodymium concentration of 3.6 g / L, a dysprosium concentration of 0.9 g / L, a cerium concentration of 0.4 g / L, and concentrations of less than 0.1 g / L for other rare earth elements. The solution also contains an iron concentration of 0.25 g / L, and concentrations of less than 0.1 g / L for aluminum, cobalt, and copper, and a trace amount of zinc. This solution has a pH of 2.

[0198] 50 mL of organic extraction solvent, formed from 100% by mass of 2-propylheptanol (2-PH) as the extracting compound, is introduced into the same vial.

[0199] Therefore, the volume ratio of the aqueous phase to the organic phase is 1.

[0200] The medium is vigorously stirred at 50°C for 15 minutes. After this, the aqueous phase and organic phase are separated by decantation.

[0201] Therefore, a partition coefficient of boron equivalent to 0.30 is obtained.

[0202] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0203] (Example 16) Boron extraction from an aqueous solution with a rare earth element concentration of 250 g / L using a pure 2-PH solvent. A 50 mL acidic aqueous solution, obtained by dissolving the powder of a permanent magnet oxide in nitric acid, was introduced into a 100 mL vial. This solution contains a total of 250 g / L of rare earth elements, with a boron concentration of 4.5 g / L, a neodymium concentration of 183 g / L, a praseodymium concentration of 45 g / L, a dysprosium concentration of 12 g / L, a cerium concentration of 5 g / L, and other rare earth elements at concentrations of less than 5 g / L. The solution also contains an iron concentration of 2 g / L, an aluminum concentration of 0.5 g / L, a cobalt concentration of 0.5 g / L, a copper concentration of 0.2 g / L, and trace amounts of zinc. This solution has a pH of 2.

[0204] A 10 mL organic extraction solvent, formed from 100% by mass of 2-propylheptanol (2-PH) as the extracting compound, is introduced into the same vial.

[0205] Therefore, the volume ratio of the aqueous phase to the organic phase is 1.

[0206] The medium is vigorously stirred at 60°C for 15 minutes. After this, the mixture is centrifuged and the aqueous and organic phases are separated by decantation.

[0207] Therefore, a partition coefficient of boron equivalent to 0.65 is obtained.

[0208] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0209] (Example 17) Boron extraction from an aqueous solution with a rare earth element concentration of 350 g / L using a pure 2-PH solvent. A 10 mL acidic aqueous solution, obtained by dissolving the powder of a permanent magnet oxide in hydrochloric acid, was introduced into a 100 mL vial. This solution contains a total of 350 g / L of rare earth elements, with a boron concentration of 4.5 g / L, a neodymium concentration of 256 g / L, a praseodymium concentration of 63 g / L, a dysprosium concentration of 17 g / L, a cerium concentration of 7 g / L, and other rare earth elements at concentrations of less than 7 g / L. The solution also contains an iron concentration of 2 g / L, an aluminum concentration of 0.5 g / L, a cobalt concentration of 0.5 g / L, a copper concentration of 0.2 g / L, and trace amounts of zinc. This solution has a pH of 2.

[0210] 40 mL of organic extraction solvent, formed from 100% by mass of 2-propylheptanol (2-PH) as the extracting compound, is introduced into the same vial.

[0211] Therefore, the volume ratio of the aqueous phase to the organic phase is 0.25.

[0212] The medium is vigorously stirred at 60°C for 15 minutes. After this, the mixture is centrifuged and the aqueous and organic phases are separated by decantation.

[0213] Therefore, a partition coefficient of boron equivalent to 2.46 is obtained.

[0214] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0215] (Example 18) Boron extraction from an aqueous solution with a rare earth element concentration of 400 g / L using a pure 2-PH solvent. A 50 mL acidic aqueous solution, obtained by dissolving the powder of a permanent magnet oxide in nitric acid, was introduced into a 100 mL vial. This aqueous solution contains a total of 400 g / L of rare earth elements, with a boron concentration of 4.5 g / L, a neodymium concentration of 293 g / L, a praseodymium concentration of 72 g / L, a dysprosium concentration of 19 g / L, a cerium concentration of 8 g / L, and other rare earth elements at concentrations of less than 8 g / L. The solution also contains an iron concentration of 2 g / L, an aluminum concentration of 0.5 g / L, a cobalt concentration of 0.5 g / L, a copper concentration of 0.2 g / L, and trace amounts of zinc. This solution has a pH of 2.

[0216] 50 mL of organic extraction solvent, formed from 100% by mass of 2-propylheptanol (2-PH) as the extracting compound, is introduced into the same vial.

[0217] Therefore, the volume ratio of the aqueous phase to the organic phase is 1.

[0218] The medium is vigorously stirred at 60°C for 15 minutes. After this, the aqueous phase and organic phase are separated by decantation.

[0219] Therefore, a partition coefficient for boron corresponding to 3 is obtained.

[0220] The total concentration of rare earth elements, iron, aluminum, cobalt, copper, and zinc in the solvent is less than 10 mg / L, and therefore the partition coefficient of neodymium is 10 -4 The value is less than 0.05, and the distribution coefficient of copper is less than 0.05.

[0221] Example 19, described below, demonstrates the advantages of operating with a rare earth element concentrated solution. Example 20 shows an example of operation in a mixer-settler battery, including boron extraction and solvent recycling.

[0222] (Example 19) Boron extraction using pure 2-PH solvent The solubility of boron in the attack solution is limited, and in order to utilize this concentration effect (Examples 13, 16, and 18), extraction must be performed in two steps: first, extraction is performed with an attack solution of rare earth elements at a concentration of approximately 150 g / L, and then the partially boron-depleted solution is re-concentrated to approximately 400 g / L.

[0223] The following are introduced into the reactor at a temperature of 50°C: - 300 mL of organic solvent formed from pure 2-propylheptanol as the extracted compound. - A 75 mL aqueous solution obtained by dissolving the powder of an oxide permanent magnet, the solution having a total of 150 g / L of rare earth elements, with a boron concentration of 4.5 g / L, a neodymium concentration of 110 g / L, a praseodymium concentration of 27 g / L, a dysprosium concentration of 7 g / L, a cerium concentration of 3 g / L, and other rare earth elements at less than 1 g / L, an iron concentration of 2 g / L, an aluminum concentration of 0.5 g / L, a cobalt concentration of 0.5 g / L, and a copper concentration of 0.2 g / L, and containing a trace amount of zinc. The solution has a pH of 2.

[0224] After mixing for 15 minutes and performing phase decantation, collect the following: - 300 mL of organic solvent with a boron concentration of 0.8 g / L. - A 75 mL aqueous phase containing rare earth elements, wherein the solution has a total of 150 g / L of rare earth elements, with a boron concentration of 1.27 g / L, a neodymium concentration of 110 g / L, a praseodymium concentration of 27 g / L, a dysprosium concentration of 7 g / L, a cerium concentration of 3 g / L, and other rare earth elements at concentrations of less than 1 g / L, an iron concentration of 1 g / L, an aluminum concentration of 0.5 g / L, and a cobalt concentration of 0.5 g / L, and contains trace amounts of zinc.

[0225] The boron extraction rate in this first step is 71.1%.

[0226] In the second step, the aqueous phase is concentrated by distillation to obtain a solution with a rare earth element concentration of 400 g / L, i.e., a boron concentration of 3.40 g / L, a neodymium concentration of 293 g / L, a praseodymium concentration of 72 g / L, a dysprosium concentration of 19 g / L, a cerium concentration of 8 g / L, and other rare earth element concentrations of less than 3 g / L, an iron concentration of 2.6 g / L, an aluminum concentration of 1.3 g / L, and a cobalt concentration of 1.3 g / L, containing a trace amount of zinc, with a total solution volume of 28 mL.

[0227] Next, in the second reactor, the following is introduced at a temperature of 50°C: - 56 mL of organic solvent formed from pure 2-propylheptanol as the extracted compound; - The 28 mL concentrated solution obtained earlier.

[0228] The following will be collected: - 56 mL of organic solvent with a boron concentration of 1.37 g / L. - A 28 mL aqueous phase containing rare earth elements, wherein the solution has a boron concentration of 0.62 g / L, a neodymium concentration of 293 g / L, a praseodymium concentration of 72 g / L, a dysprosium concentration of 19 g / L, a cerium concentration of 8 g / L, a concentration of less than 3 g / L for other rare earth elements, an iron concentration of 2.6 g / L, an aluminum concentration of 1.3 g / L, and a cobalt concentration of 1.3 g / L, and contains trace amounts of zinc.

[0229] This series of extraction-concentration-extraction operations completely depletes boron from the aqueous phase, with a typical extraction rate of 95% relative to the initial solution.

[0230] (Example 20) Boron extraction using BEPD / kerosene / decanol solvents in mixer-settler batteries This embodiment represents one aspect of the present invention implemented in a countercurrent extraction battery.

[0231] a) Contact between aqueous solution and organic solvent In a battery of six mixer-settlers operating in countercurrent at a temperature of 50°C, the following is introduced: - In step 1: At a flow rate of 145 mL / hour, an organic solvent formed from 15% by mass of BEPD as the extractant compound, 25% by mass of kerosene as the diluent compound, and 60% by mass of decanol as the modified compound, - In step 5: An acidic aqueous solution obtained by dissolving the powder of the oxide permanent magnet at a flow rate of 145 mL / hour, the solution having a total of 137 g / L of rare earth elements, with a boron concentration of 4.60 g / L, a neodymium concentration of 110 g / L, a praseodymium concentration of 25 g / L, a dysprosium concentration of 6 g / L, a cerium concentration of 3 g / L, and concentrations of less than 1 g / L of other rare earth elements. The solution has an iron concentration of 1 g / L, an aluminum concentration of 0.5 g / L, a cobalt concentration of 0.5 g / L, and contains trace amounts of zinc. This solution has a pH of 1.5. - In stage 6: Water at a flow rate of 7 mL / hour.

[0232] The following will be collected: - In stage 1: At a flow rate of 152 mL / hour, a rare earth element aqueous raffinate is used, having a boron concentration of 16 mg / L, a rare earth element concentration of 131 g / L, an iron concentration of 0.95 g / L, an aluminum concentration of 0.48 g / L, a cobalt concentration of 0.48 g / L, and containing a trace amount of zinc. - In step 6: A boron-containing organic solvent with a boron concentration of 4.58 g / L is dispensed at a flow rate of 145 mL / hour.

[0233] Therefore, the boron extraction rate is 99.6%. This ratio corresponds to the mass of boron recovered in the solvent versus the total mass of boron introduced into the feeder.

[0234] This method allows most of the boron initially contained in the aqueous solution to be transferred to the organic solvent.

[0235] The aqueous raffinate obtained in this way contains less than 30 mg / L of boron.

[0236] Rare earth elements, iron, and other impurities are absent in the solvent and are recovered in the aqueous raffinate.

[0237] b) Re-extraction of boron from boron-containing solvents In the second battery of the four mixer-settler operating in countercurrent at a temperature of 50°C, the following is supplied: - In stage 1: A boron-containing organic solvent, recovered at a flow rate of 145 mL / hour from the output of stage 6 during the previous contact step, is formed from 15% by mass of BEPD, 25% by mass of kerosene, and 60% by mass of decanol, and has a boron concentration of 4.58 g / L, - In stage 4: A solution of NaOH aqueous solution with a concentration of 0.40 mol / L is administered at a flow rate of 79 mL / hour.

[0238] The following will be collected: - In stage 1: A basic solution with a boron concentration of 8.35 g / L and a sodium concentration of 9.2 g / L, i.e., a sodium:boron molar ratio of 0.52, is administered at a flow rate of 79 mL / hour. - In stage 4: A solvent, which is an organic solvent having a boron concentration of 30 mg / L, is dispensed at a flow rate of 145 mL / hour.

[0239] The re-extraction rate of boron is 99.3%. This ratio corresponds to the mass of boron recovered in the basic solution versus the mass of boron contained in the organic solvent.

[0240] The boron recovery rate is 98.9%. This ratio corresponds to the mass of boron recovered in the basic solution versus the mass of boron contained in the acidic aqueous solution obtained by dissolving the magnetic powder (i.e., the mass of boron introduced into this method).

[0241] The solvent thus regenerated has a low boron concentration, less than 30 mg / L, and is recycled during extraction.

[0242] (Example 21) Boric acid is present, and boron is regenerated from organic solvents containing BEPD. In a battery of five mixer-settlers operating in countercurrent at a temperature of 50 °C, supply the following: - In stage 1: an organic solvent flowing at a rate of 100 L / hour, consisting of 15% by mass of 2-butyl-2-ethylpropane-1,3-diol (BEPD), 25% by mass of kerosene, and 60% by mass of decan-1-ol, with a boron concentration in the solvent of 4.40 g / L. - In stage 5: a NaOH solution having a sodium concentration of 9.40 g / L flowing at a rate of 50 L / hour.

[0243] Recover the following: - In stage 1: an aqueous boric acid solution flowing at a rate of 50 L / hour, having a boron concentration of 8.78 g / L, a sodium concentration of 9.40 g / L, and 0.1% by mass of BEPD. The Na / B molar ratio is 0.5, which is the stoichiometric value of sodium tetraborate ion Na2B4O7. - In stage 5: an organic solvent having a residual boron concentration of less than 0.01 g / L flowing at a rate of 100 L / hour.

[0244] In this way, 99.8% of the boron present in the extraction solvent is recovered.

[0245] Details of the concentrations and flow rates are given in Table 1.

[0246]

Table 1

[0247] (Example 22) Crystallization of sodium tetraborate pentahydrate, i.e., borax (Na2B4O7·5H2O) from a sodium tetraborate solution An organic extraction solvent consisting of BEPD, kerosene, and decan-1-ol, and a soda solution were used to extract boron, obtaining 4.7 L, i.e., 4.8 kg of an aqueous borax solution.

[0248] This aqueous solution had a boron concentration of 8.78 g / L and a sodium concentration of 9.40 g / L. This aqueous solution contained 0.1% by mass of BEPD, or 4.8 g of residual BEPD.

[0249] The crystallization of borax pentahydrate from an aqueous solution involves the following steps: i. A step of distilling an aqueous solution at 100°C to obtain 0.7 kg of solution and 4.1 kg of distillate having a boron concentration of 6.0% by mass (approximately 60 g / L), ii. The obtained solution is cooled from 100°C to 65°C for 1 hour to crystallize borax pentahydrate. iii. A step in which the crystals are aged at 65°C for 1 hour to bring about the formation of a borax pentahydrate suspension. iv. Dissolve borax pentahydrate in a 10-minute solution. 5 A process of filtration under positive pressure in Pa, v. The process of washing the boron salt with 110g of distilled water at 5°C. vi. A process of drying the boron salt at 65°C in a ventilated stove until it reaches a certain mass. Execute according to the instructions.

[0250] You will get the following: - 0.55 kg of crystallized mother liquor containing 3.8% by mass of boron and less than 50 ppm of solvent. - 4.1 kg of distillate containing 0.12 mass% BEPD, i.e., 4.8 g of BEPD. - 130g of washing water containing 3.6% by mass of boron, - 106g of borax pentahydrate with a purity exceeding 99.8%, - Residual organic carbon content of less than 350 mg / kg in borax, - 24g of borax pentahydrate impregnated water.

[0251] Of the 41.3 g of boron contained in the initial aqueous solution, 15.7 g is recovered in the form of pentahydrate borax. Therefore, 38% of the boron initially contained in the aqueous phase is crystallized. 62% of the borate contained in the mother liquor is recycled in the contact step between the organoboron-containing solvent and the basic aqueous solution.

[0252] Boron-containing solution 10 4 Pa~7.10 4 Similar results can be obtained by distilling under reduced pressure in the range of Pa at 65°C, and having 106 g of pentahydrate borax in the suspension before filtration.

[0253] The 4.1 kg distillate contains over 99% of the BEPD extract compounds that were initially dissolved in the aqueous phase from the solvent. The distillate will be recycled for the production of a basic aqueous solution.

[0254] Borax decahydrate can also be obtained by the same method, that is, by concentrating the initial aqueous solution under vacuum at 60°C and cooling it to 5°C within one hour before filtration.

[0255] The mass is described in detail in Table 2.

[0256] [Table 2]

[0257] (Example 23) Boron regeneration from a 2-propylheptanol (2PH)-based solvent containing boric acid. In a battery for six mixer-settlers operating in countercurrent at a temperature of 50°C, the following is supplied: - In stage 1: an organic solvent containing an extract compound consisting of pure 2-propylheptanol is dispensed at a flow rate of 100 L / hour, with a boron concentration of 1.5 g / L in the solvent. - In stage 6: A NaOH solution with a sodium concentration of 12.28 g / L is used at a flow rate of 10 L / hour.

[0258] The following will be collected: - In stage 1: A borate aqueous solution is prepared at a flow rate of 10 L / hour, with a boron concentration of 14.9 g / L, a sodium concentration of 12.28 g / L, and a 2-propylheptanol concentration of 70 mg / L. The Na / B molar ratio is 0.39. - In stage 6: A solvent having a residual boron concentration of less than 0.01 g / L at a flow rate of 100 L / hour.

[0259] In this way, 99.3% of the boron present in the extraction solvent is recovered.

[0260] The concentration, flow rate, and mass are detailed in Table 3.

[0261]

Table 3

[0262] (Example 24) Recovery of borax pentahydrate (Na2B4O7·5H2O) from BEPD In a battery of five mixer-settlers operating in countercurrent at a temperature of 50°C, supply the following: - In stage 1: An organic solvent consisting of 15% by mass of BEPD, 25% by mass of kerosene, and 60% by mass of decan-1-ol, having a boron concentration of 3.52 g / L and introduced at a flow rate of 576 L / hour, and a borax solution having a boron concentration of 39.7 g / L and a sodium concentration of 42.3 g / L obtained by recycling the crystallization mother liquor of the borax produced hereinafter at a flow rate of 39.6 L / hour. - In stage 5: A NaOH solution having a sodium concentration of 11.5 g / L and introduced at a flow rate of 187.8 L / hour. This solution is composed of 3.76 kg of solid NaOH and 187.8 L of distillate.

[0263] Recover the following: - In stage 1: Since 5.9 L of water is produced when boric acid is converted to borax, an aqueous solution having a boron concentration of 15.4 g / L, a sodium concentration of 16.4 g / L, and containing 0.1% by mass of the solvent at a flow rate of 233.3 L / hour. The Na / B molar ratio is 0.5, which is the stoichiometric value of the tetraborate ion Na2B4O7. - In stage 5: A solvent having a boron concentration of less than 0.01 g / L at a flow rate of 576 L / hour.

[0264] In this way, 99.7% of the boron present in the extraction solvent is recovered.

[0265] The crystallization of borax pentahydrate from the aqueous solution recovered in step 1 is carried out in the following steps: i. The aqueous solution recovered in stage 1 is distilled under vacuum at 65°C. During this distillation, borax pentahydrate precipitates, and a solution with a total boron concentration (solid boron and solubilized boron) of 73.1 g / L and a sodium concentration of 77.9 g / L is obtained at a flow rate of 49.2 L / hour, with a distillate flow rate of 187.8 L / hour. ii. A process in which the crystals are aged for 1 hour, resulting in the formation of a borax pentahydrate suspension. iii. Dissolve borax pentahydrate in a 10-minute solution. 5 A process of filtration under positive pressure in Pa, iv. A process of drying the boron salt at 65°C in a ventilated stove until it reaches a certain mass. Execute according to the instructions.

[0266] You will get the following: - A distillate containing 0.12% solvent, recycled into batteries, at a rate of 187.8 L / hour. - A crystallization mother liquor with a boron concentration of 39.7 g / L and a sodium concentration of 42.3 g / L, at a rate of 39.6 L / hour. - Borax pentahydrate containing 5% by mass of water at a rate of 14.4 kg / hour, i.e., 13.7 kg / hour, with a BEPD of less than 50 ppm, i.e., with residual organic carbon of less than 0.035 g / kg.

[0267] The resulting borax pentahydrate has a purity of over 99.8%.

[0268] The crystallized mother liquor contains 44% of the total boron.

[0269] The distillate contains all the solvents soluble in the aqueous phase of the boron solution recovered in step 1.

[0270] The concentrations and flow rates for liquid-liquid extraction and crystallization are detailed in Tables 4 and 5.

[0271] [Table 4]

[0272] [Table 5]

[0273] (Example 25) Recovery of borax pentahydrate (Na2B4O7·5H2O) from 2-propylheptanol In a battery for five mixer-settlers operating in countercurrent at a temperature of 50°C, the following is supplied: - In stage 1: an organic solvent consisting of 2-propylheptanol having a boron concentration of 1.5 g / L is introduced at a flow rate of 1,352 L / hour, and a borax solution having a boron concentration of 39.7 g / L and a sodium concentration of 42.3 g / L is obtained by recycling the crystallized mother liquor of the borax produced later, at a flow rate of 39.6 L / hour. - In stage 5: A NaOH solution with a sodium concentration of 11.5 g / L is introduced at a flow rate of 187.8 L / hour. This solution consists of 3.76 kg of solid NaOH and 187.8 L of distillate.

[0274] The following will be collected: - In stage 1: 5.9 L of water is produced when boric acid is converted to borax, resulting in an aqueous solution with a flow rate of 233.3 L / hour, a boron concentration of 15.4 g / L, a sodium concentration of 16.4 g / L, and containing 70 ppm by mass of solvent. The Na / B molar ratio is 0.5. - In stage 5: A solvent with a boron concentration of less than 0.01 g / L at a flow rate of 1,352 L / hour.

[0275] In this way, 99.3% of the boron present in the extraction solvent is recovered.

[0276] The crystallization of borax pentahydrate from the aqueous solution recovered in step 1 is carried out in the following steps: i. The aqueous solution recovered in stage 1 is distilled under vacuum at 65°C. During this distillation, borax pentahydrate precipitates, and a solution with a total boron concentration (solid boron and solubilized boron) of 73.1 g / L and a sodium concentration of 77.9 g / L is obtained at a flow rate of 49.2 L / hour, with a distillate flow rate of 187.8 L / hour. ii. A step in which the crystals are aged for 1 hour to bring about the formation of a borax pentahydrate suspension. iii. Dissolve borax pentahydrate in a 10-minute solution. 5 A process of filtering under pressure in Pa, iv. A process of drying the boron salt at 65°C in a ventilated stove until it reaches a certain mass. Execute according to the instructions.

[0277] You will get the following: - A distillate containing 87 ppm solvent, recycled into batteries, at a rate of 187.8 L / hour. - A crystallization mother liquor with a boron concentration of 39.7 g / L and a sodium concentration of 42.3 g / L, at a rate of 39.6 L / hour. - A borax pentahydrate containing 5% by mass of water, at a rate of 14.4 kg / hour, i.e., 13.7 kg / hour, with a pH of less than 50 ppm, i.e., less than 0.037 g / kg of residual organic carbon.

[0278] The resulting borax pentahydrate has a purity exceeding 99.8%. The crystallized mother liquor contains 44% of the total boron.

[0279] The distillate contains all the solvents soluble in the aqueous phase of the boron solution recovered in step 1.

[0280] The concentrations and flow rates for liquid-liquid extraction and crystallization are detailed in Tables 6 and 7.

[0281] [Table 6]

[0282] [Table 7]

[0283] By using the method of the present invention, lithium tetraborate, potassium tetraborate, ammonium tetraborate, and sodium tetraborate decahydrate can be formed.

[0284] The solubility of these salts in water differs from that of sodium tetraborate pentahydrate, and the amounts of distillates, mother liquor, and boron salts produced during crystallization vary accordingly. [Explanation of Symbols]

[0285] 11 Boron-containing organic solvents 12 Borax solution 13 NaOH aqueous solution 14. Alkaline borate aqueous solution 15 Extraction solvent 16. Crystallized borate 17. Concentrated basic soda solution 20 Distillates ( 21 Crystallization mother liquor 22 Washing water a. First paragraph b. Second paragraph c. Third paragraph d Fourth paragraph e Mixer - Settler Battery f Dilution g distillation h crystallization i filtration j Cleaning

Claims

1. A method for extracting boron contained in an aqueous solution A1 containing a rare earth element, wherein the aqueous solution A1 is obtained from the dissolution of powder of NdFeB magnets or machining scrap generated from the manufacture of permanent magnets, and in the method, the aqueous solution A1 is brought into contact with and mixed with an organic solvent, the organic solvent contains at least one extraction compound made of an aliphatic or aromatic, linear or branched alcohol containing a chain of 6 to 18 carbon atoms, and the contact and mixing of the aqueous solution A1 and the organic solvent causes the transfer of boron from the aqueous solution A1 to the organic solvent.

2. The extracted compound is - 1,3-diols, preferably 2-ethyl-1,3-hexanediol (EHD), 2-butyl-2-ethylpropane-1,3-diol (BEPD), 2,2,4-trimethyl-1,3-pentanediol (TMPD), 2-chloro-4-(1,1,3,3-tetramethylbutyl)-6-methylol-phenol (CTMP), and mixtures thereof. - Monoalcohols having branched or linear aliphatic chains with 6 to 18 carbon atoms, preferably from among 2-ethylhexanol (2-EH), 2-propylheptanol (2-PH), 2-butyloctanol, isodecanol, octanol, and mixtures thereof. A method for extracting boron according to claim 1, selected from the group including the following.

3. The method for extracting boron according to claim 1 or 2, wherein the organic solvent further comprises at least one dilution compound formed from an aliphatic or aromatic hydrocarbon chain having 6 to 18 carbon atoms.

4. The method for extracting boron according to claim 3, wherein the dilution compound is selected from the group comprising decane and its isomers, dodecane and its isomers, kerosene, toluene, aliphatic or aromatic hydrocarbons having between 6 and 18 carbon atoms, and mixtures thereof.

5. The method for extracting boron according to any one of claims 1 to 4, wherein the organic solvent further comprises a modified compound different from the extracted compound, and the modified compound is made of an alcohol containing an aliphatic chain of 6 to 18 carbon atoms.

6. The method for extracting boron according to claim 5, wherein the modified compound is selected from the group comprising monoalcohols, preferably from among decane-1-ol, octan-1-ol, isodecane-1-ol, hexane-1-ol, dodecane-1-ol, 2-propylheptanol, 2-ethylhexanol, and mixtures thereof.

7. The aforementioned organic solvent - At least one extractable compound, 10% to 100% - At least one diluted compound in a concentration of 0% to 90%, - 0% to 70% of at least one modified compound, A method for extracting boron according to any one of claims 1 to 6, comprising the above in a mass ratio to the total mass of the organic solvent, with the total being equal to 100%.

8. The aqueous solution A1 is - Rare earth elements in the form of dissolved salts, at concentrations of 20 to 450 g / L - Boron in the form of boric acid, at a concentration of 1 to 9 g / L - Iron in the form of dissolved salts, at concentrations of 0 to 20 g / L - Metallic elements belonging to the group including cobalt, aluminum, zinc, copper, manganese, and nickel, in concentrations of 0 to 5 g / L, A method for extracting boron according to any one of claims 1 to 7, comprising:

9. A method for extracting boron according to any one of claims 1 to 8, wherein the dissolved salt of a rare earth element belongs to the group comprising rare earth nitrates, rare earth chlorides, rare earth sulfates, and mixtures thereof.

10. The method for extracting boron according to any one of claims 1 to 9, wherein the contact and mixing are carried out at a temperature in the range of 20°C to 70°C, preferably 40°C to 60°C.

11. A method for extracting boron according to any one of claims 1 to 10, wherein the method further comprises a step of re-extracting the boron present in the organic solvent after the transfer of boron.

12. Boron re-extraction is carried out by contacting the Brønsted base with the solvent, and the base is NaOH, KOH, LiOH, NH ４ A method for extracting boron according to claim 11, selected from the group comprising OH and mixtures thereof.

13. The process further includes a step of recovering boron in the form of a boron salt from boric acid present in the organic solvent, wherein the boron recovery step is a sub-step: a) A step of contacting a basic aqueous solution A2 with the organic solvent to extract boron into the basic aqueous solution A2 in the form of a solubilized borate, b) Distillation of a borate-containing basic aqueous solution A2 to concentrate the solution and produce a distillate, c) Crystallization of borates in the form of hydrated boron salts, d) Solid-liquid separation of crystallized hydrated boron salt to produce the crystallized mother liquor, e) Reintroduction of the distillate and the crystallized mother liquor in the step of contacting the basic aqueous solution A2 with the organic solvent, A method for extracting boron according to any one of claims 1 to 12, including the following:

14. The method for extracting boron according to claim 13, wherein the crystallization of the borate is achieved by distillation of the borate-concentrated basic aqueous solution A2 or by cooling of the borate-concentrated basic aqueous solution A2.

15. The method for extracting boron according to claim 13 or 14, wherein the step of contacting the basic aqueous solution A2 with the organic solvent is performed in a multi-stage apparatus in which the organic solvent and the basic aqueous solution A2 flow in opposite directions.

16. The method for extracting boron according to any one of claims 13 to 15, wherein the basic aqueous solution A2 is prepared by diluting a concentrated basic solution or by solubilizing a solid basic compound.

17. The method for extracting boron according to claim 16, wherein the distillate dilutes the concentrated basic solution or solubilizes the solid basic compound.

18. The method for extracting boron according to any one of claims 13 to 17, wherein the basic aqueous solution A2 is introduced in a stoichiometric amount relative to the amount of boron salt produced.

19. A method for extracting boron according to any one of claims 13 to 18, wherein the crystalline hydrated boron salt is washed with an aqueous solution and / or the distillate to generate washing water.

20. The method for extracting boron according to claim 19, wherein the washing water is recycled during the step of contacting the basic aqueous solution A2 with the organic solvent.

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