An environmentally friendly method for extracting lanthanide elements

Abstract

The present invention relates to a method for extracting at least one first lanthanide element, preferably a lanthanide element selected from lanthanum (La), praseodymium (Pr), neodymium (Nd), europium (Eu), dysprosium (Dy) and ytterbium (Yb), from a solid material comprising said first lanthanide element, at least one waste element such as (Fe), and / or one or more other lanthanide elements, implementing a leaching composition comprising water, at least one organic aprotic solvent and at least one charged hydrotrope, the use of said composition for recycling lanthanide elements, more particularly WEEE, and the use of said composition for decontamination of eluates.

Description

[Technical field]

[0001] The present invention relates to a method for extracting at least one lanthanide element, preferably selected from lanthanum (La), praseodymium (Pr), neodymium (Nd), europium (Eu), dysprosium (Dy) and ytterbium (Yb), from said lanthanide element, one or more waste elements such as iron (Fe) and / or one or more other lanthanide elements, from a solid material, which implements a composition comprising water, at least one organic aprotic solvent and at least one charged hydrotrope, and further to the use of said composition for recycling lanthanide elements, more particularly WEEE, and for decontamination of eluates. [Background technology]

[0002] The present invention deals more particularly, but not exclusively, with the recycling of permanent magnets from waste electrical and electronic equipment (WEEE).

[0003] Rare earths are metals characterized by similar properties, namely scandium (Sc), yttrium (Y) and all of the lanthanides, which correspond to the 15 chemical elements listed in Mendeleev's Periodic Table of the Elements and have atomic numbers ranging from 57 for lanthanum (La) to 71 for lutetium (Lu).

[0004] The properties of rare earth elements (REEs) are related to their special electronic configurations, in particular their unsaturated 4f electronic sublayer, which give them unique chemical, structural and physical properties. These properties are used in a wide range of advanced industrial applications, including metallurgy, catalysis, glass, optics, ceramics, luminescence, magnetism and electronics. Many applications are highly dependent on the physical properties of the REEs. REEs are particularly essential in applications related to green energy technologies, such as wind turbines and electric vehicle batteries. They are also used in most consumer electronics products, such as computers and household appliances. The REEs are therefore part of a group of so-called "technical" metals, whose importance increases with technological evolution and whose supply is strategic.

[0005] However, REEs are at risk due to the increasing global demand for these particular metals. Moreover, as there are few primary REE deposits in European countries, these elements are considered critical metals. Therefore, taking into account the economic importance of REEs and the risks associated with their supply, the European Commission designated REEs as critical elements in 2010.

[0006] Since rare earths are used in the manufacture of many technical devices, industrial and household waste from these devices, especially electrical and electronic equipment (also known as WEEE), represents a source of rare earths that could, at least in part, make up for the shortage of REE resources in European countries. Therefore, there is a great deal of interest in the treatment of waste with the aim of selectively recovering rare earths.

[0007] This e-waste comes from urban mines, i.e. from post-consumer waste recovery, or is industrial waste. Permanent magnets are the application that consumes the largest tonnage of REEs and produces the highest market value. Permanent magnets are used in wind turbine generators, computer hard drives, air conditioner compressors, etc. NdFeB type magnets are the most widely used type of REE magnets due to their high magnetic performance. These magnets contain neodymium (Nd), praseodymium (Pr), and dysprosium (Dy) as REEs, to which scandium, cerium, lanthanum, gadolinium, etc. may be added. In addition, they also contain boron, iron, and several transition metals such as cobalt, aluminum, copper, titanium, chromium, vanadium, and / or nickel. In these magnets, the total content of the first three elements is about 30%, which is much higher than the content found in natural ores of REEs.

[0008] Various methods have been investigated to recycle REEs from NdFeB permanent magnets. These methods can be classified as direct recycling, decrepitation, pyrometallurgy, hydrometallurgy, and solvent metallurgy, or a combination of these. Some of them are described in Yang et al., 2017, J. Sustain. Metall., 3, 122-149.

[0009] Of particular interest is the hydrometallurgical process, which involves oxidative roasting of NdFeB magnets by treating them at 950°C under ambient conditions, leaching (dissolving) the roasted NdFeB magnets in hydrochloric acid (1.7M) to remove Fe, followed by separation of metal cations in the leachate by liquid-liquid extraction technique using trihexyl(tetradecyl)phosphonium chloride ionic liquid to remove Co, and precipitation by addition of oxalic acid to the leachate and heat treatment of the oxalate to produce mixed oxides of REEs that can be reused for the production of NdFeB magnets. The benefit of oxidative roasting is to improve the recovery selectivity of REEs (Nd and Dy) relative to Fe during the leaching process. In addition to improving the selectivity of the process, oxidative roasting of magnets can also limit hydrogen evolution during the leaching process.

[0010] However, it is also useful to separate the REEs from each other in order to obtain high purity REEs or their oxides. For example, didymium (a mixture of Nd and Pr) and Dy have a high market value and are very valuable. In fact, Dy2O3 is used in many applications. Examples include the manufacture of NdFeB permanent magnets, glasses, ceramics, luminaires, and metal halide lamps. As for didymium, in addition to being recycled into NdFeB magnets, it is used in the manufacture of protective glasses for glassblowers, in photographic filters, as a calibration material for spectrometers, and in the manufacture of catalysts used in petroleum cracking.

[0011] Liquid-liquid extraction is often used to separate REEs from leachates. This technique relies on ion distribution between two immiscible phases: an aqueous or water-rich phase (the leachate from NdFeB magnets) and a solvent or solvent-rich phase (the so-called organic phase). The solvent phase contains the selective extractant (often dissolved in a suitable organic diluent). The ions of interest are extracted into the solvent phase and can then be recovered in the clean aqueous phase using a similar technique called back-extraction.

[0012] Commercially available acidic organophosphorus (HA) extractants are known to be effective for the separation between REEs. For example, the separation between Nd and Dy can be performed from a hydrochloric acid solution using di(2-ethylhexyl) phosphate (HDEHP). Furthermore, the separation of adjacent REEs in the periodic table, such as Nd and Pr, is more efficient using bis-2,4,4-trimethylpentyl phosphinate (known under the trade name Cyanex® 272). However, the extraction yield is still low. Mixtures of extractants have also been considered to ensure efficient separation and high extraction yields. Nevertheless, acidic extracts often aggregate in the non-polar organic phase, and as a result, the REE complexes formed during extraction may contain undissociated acids. Thus, the extraction of rare earths from mixtures containing other rare earths is generally complicated and requires the implementation of many steps. In practice, after liquid-liquid extraction, the REEs must be removed from the acidic extractant by back-extraction, followed by precipitation, filtration, and calcination of the REEs recovered in the aqueous phase.

[0013] Liquid-liquid extraction is currently the primary process for rare earth element separation on an industrial scale and can be carried out as a continuous process. Commercial processes are based on a first liquid-liquid extraction circuit designed to separate the REEs as a group from other impurities. A second circuit is then carried out to produce the REEs individually or in mixtures (usually in pairs or triplicates). Eu, which can have variable valence, 2+ and Ce 4+In contrast, other REEs have a similar oxidation degree (oxidation degree +III) and therefore require multiple mixer-settlers in series in the final separation circuit, especially to produce the elements individually. For example, the Rhodia facility in La Rochelle (France) has more than 1500 mixer-settlers in series to produce the individual REEs. The extractants used are: HDEHP, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEHEHP or PC-88A), branched carboxylic acids (Versatic acids 10 and 9-11), tributyl phosphate (TBP) and trioctylmethylammonium salt (Aliquat 336). However, the group extraction of REEs by HDEHP in the primary circuit interferes with the extraction of Fe, and a prior selective precipitation step is necessary. Furthermore, the REE extraction reaction by HDEHP requires a large acid consumption (≧4M) during the protonation back-extraction of HDEHP dimers. Compared to solvents composed only of carbon (C); oxygen (O); hydrogen (H) and nitrogen (N), organophosphate extractants such as TBP and HDEHP generate complex secondary wastes (containing phosphorus) that require additional processing steps (and dedicated incinerators), which can only be incinerated with an adequate amount of air, and the combustion products are discharged directly to the atmosphere.

[0014] Furthermore, during liquid-liquid extraction with known solvents, the formation of a third phase (i.e., partitioning of the organic phase into a heavy viscous phase rich in metal solvent and a light viscous phase rich in diluent) can occur, which is a major obstacle to an efficient liquid-liquid extraction process. The third phase formation occurs at high concentrations of acids and metals in the solvent. This forces the operator to work at conditions where the acid and metal concentrations are below the limiting organic concentration (also called LOC), which is the loading capacity of commercially available solvents is less than 100 g L. -1The LOC is limited to values ​​below 1000 ppm. To increase the LOC, several methods are used, such as increasing the temperature and polarity of the diluent. However, because the extraction reaction is exothermic in many systems, increasing the temperature increases the LOC of the solute, but also reduces the extraction efficiency. Similarly, increasing the polarity of the diluent in some systems leads to strong interactions between the diluent and the extractant, which is unfavorable for the extraction of REEs. Another method that is widely used to increase the LOC is the use of phase modifiers in the solvent, for example, N,N-dihexyloctanamide (DHOA) in the N,N,N,N-tetraoctyl-3-oxapentanediamide (TODGA)-dodecane system in the TRUEX process, or TBP in the n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO)-dodecane system. It is important to note that DHOA or any other modifier only increases the solubility of the acid and metal complexes in the solvent to avoid the formation of a third phase, but does not extract the REEs.

[0015] All currently known methods require the neutralization of large amounts of acid in the effluent, and also contain large amounts of highly toxic molecules in the extractants, diluents, and modifiers. The extractants are largely recycled, but have low solubility in the effluent and products to handle them.

[0016] Recently, Chen et al., 2019, Green Chemistry, 21, 17, 4748-4756, described the use of an environmentally friendly composition based on carboxylic acids and polyols to separate La and Ce. Summary of the Invention [Problem to be solved by the invention]

[0017] The object of the present invention is therefore to overcome the drawbacks of the prior art and, more particularly, to provide a simple and economical method that makes it possible to extract one or more rare earth metals from a raw solid material, said method being selective so as to separate the rare earth metals from one another, avoiding or at least reducing the use of toxic and / or irritating reagents and / or solvents and using smoother leaching conditions, thereby reducing the risk of equipment degradation and / or safety, environmental and health problems. Another object of the present invention is to provide a method that can be carried out in a closed cycle so as to be able to recycle the main products and / or the solvents used in the method. [Means for solving the problem]

[0018] method

[0019] The first object of the present invention is to provide a method for producing a polymer having a molecular weight M L1 (g / mol) of at least one first lanthanide element, L2 The second lanthanide element with molecular weight M (g / mol) WE (g / mol) and one or more other elements selected from mixtures thereof, comprising the steps of: - M WE ≦100 g / mol, - when said other element is a second lanthanide element and is finally in a mixture with the waste element, M L1 ≧154 g / mol, preferably M L1 ≧160 g / mol, M L2 <154 g / mol; The method comprises at least the following steps: i) preparing a leaching composition comprising an aqueous phase, at least one organic aprotic solvent, and at least one charged hydrotrope; ii) mixing the leach composition with the solid material to form a leach solution comprising the first lanthanide element and a solid residue comprising the one or more other elements; iii) separating the leachate from the solid residue; The method includes:

[0020] The method of the invention is simple, economical and allows to extract at least one first lanthanide element from a solid material containing other elements such as a second lanthanide element and / or waste elements such as iron, copper. The method reduces the risk of equipment degradation and / or safety, environmental and health issues by using non-toxic, non-volatile and low ignition point reactants that are environmentally friendly and allow the reduction of toxic waste liquids in hydrometallurgy, and recycling with smoother leaching conditions. The method allows to extract one or more lanthanide elements from a raw solid material, more particularly WEEE, improving the selectivity and effectiveness of the lanthanide element extraction by the leaching composition adjusted in step i). The method of the invention can be carried out in a closed cycle, so that the main reactants and solvents used in the method can be recycled and reused in further extraction methods.

[0021] solid material

[0022] The invention finds particular application in the treatment of natural and / or industrial wastes to produce lanthanide metals, either from concentrates of lanthanide-rich natural minerals such as bastnaesite, monazite, xenotime, apatite, loparite, clays (ionic minerals), or from concentrates obtained from the processing of natural ores other than lanthanide-rich minerals, such as "urban mine" concentrates of lanthanide-containing industrial and consumer waste, in particular electronic waste, or from concentrates of lanthanide scrap products.

[0023] Said solid material may thus be waste material such as ores or WEEE or permanent magnets (for example of the NdFeB type).

[0024] The mass concentration of the first lanthanide element in the solid material (e.g., before carrying out the method of the present invention) can be in the range of about 0.5% by mass to about 30% by mass, preferably about 1% by mass to about 10% by mass, based on the total mass of the solid material.

[0025] In said solid state material, the first lanthanide element (respectively the second lanthanide element) is preferably in the form of an oxide, carbonate or phosphate compound, more preferably an oxide or phosphate compound, even more preferably in the form of an oxide compound.

[0026] The second lanthanide element is different from the first lanthanide element.

[0027] The mass concentration of the second lanthanide element in the solid material (e.g., before carrying out the method of the present invention) can be in the range of about 1% by mass to about 30% by mass, preferably about 18% by mass to about 26% by mass, based on the total mass of the solid material.

[0028] The mass concentration of the waste element in the solid material (e.g., before carrying out the method of the present invention) can be in the range of about 1 mass % to about 70 mass %, preferably about 10 mass % to about 40 mass %, based on the total mass of the solid material.

[0029] The waste element may be a transition metal or metalloid, such as a transition metal or metalloid selected from iron, copper, cobalt, boron, nickel, aluminum, titanium, chromium, and vanadium. The waste element is preferably iron.

[0030] In a first variant, said solid material comprises as said other elements one or more waste elements.

[0031] The method is therefore directed to selectively separating a first lanthanide element from one or more waste elements.

[0032] According to a first variant, the first lanthanide element is preferably selected from lanthanum (La), praseodymium (Pr), neodymium (Nd), europium (Eu), dysprosium (Dy) and ytterbium (Yb).

[0033] In a second variant, said solid material contains as other elements a second lanthanide element ultimately in admixture with one or more waste elements.

[0034] The method therefore aims to selectively separate a first lanthanide element from a second lanthanide element and from one or more waste elements, if present.

[0035] According to the second variant, the first lanthanide is preferably dysprosium (Dy) or ytterbium (Yb) and the second lanthanide element is preferably selected from lanthanum (La), praseodymium (Pr), neodymium (Nd) and europium (Eu).

[0036] In one preferred embodiment, the solid material comprises as said other elements a mixture of a second lanthanide element and one or more waste elements, preferably a mixture of a second lanthanide element and iron.

[0037] M WE is preferably 40 g / mol≦M WE ≦95 g / mol, more preferably 50 g / mol≦M WE ≦80 g / mol.

[0038] M L1 and M L2 is preferably [M L1 ]-[M L2 ]≧10 g / mol, more preferably ≧15 g / mol.

[0039] Process i)

[0040] Leaching Composition

[0041] The leaching composition is preferably a single-phase composition (i.e., only one phase). Indeed, by virtue of its single-phase nature, selective leaching is performed.

[0042] Charged Hydrotrope

[0043] Hydrotropes are small, water-miscible organic molecules used to solubilize hydrophobic compounds in aqueous solutions by methods other than micellar solubilization. Unlike micelle- and vesicle-forming surfactants, hydrotropes do not have a critical micelle concentration (cmc) or critical vesicle concentration (cvc) above which self-aggregation begins to occur spontaneously. In contrast to surfactants, hydrotropes do not aggregate into ordered structures. Hydrotropes can be uncharged (e.g., ethanol) or charged.

[0044] Leached compositions are in fact distinct from eutectic mixtures, which are defined as a homogeneous mixture of materials that melt or solidify at a single temperature below the melting point of either component.

[0045] In the present invention, the hydrotrope is a charged hydrotrope, the charged property of which allows for better ion exchange.

[0046] In the present invention, the expression "charged hydrotrope" refers to a hydrotrope that has at least one charged bond, in other words, a charged hydrotrope comprises a charged organic molecule with a charged organic or inorganic counterion.

[0047] The charged hydrotropes of the present invention are preferably cationic (positively charged) hydrotropes, in other words, comprise a predominantly negatively charged (or anionic) organic molecule with a positively charged organic or inorganic counterion (or cation).

[0048] The cationic hydrotrope may be selected from salts of substituted benzoic acid, salts of unsubstituted benzoic acid, salts of substituted benzenesulfonic acid, and salts of unsubstituted benzenesulfonic acid.

[0049] The benzoic acid (respectively the benzenesulfonic acid) may be substituted with one or more groups selected from alkyl groups, hydroxy groups, aromatic groups, amine groups, nitro groups, alkenyl groups, and alkoxy groups.

[0050] The alkyl group is preferably a methyl group.

[0051] The cationic hydrotrope may be selected from substituted benzoates, unsubstituted benzoates, substituted benzenesulfonates, or unsubstituted benzenesulfonates of cations selected from alkali metal cations such as sodium, lithium, potassium, and ammonium.

[0052] In one preferred embodiment, the charged hydrotrope is selected from sodium salicylate, sodium xylene sulfonate, sodium cumene sulfonate, and sodium toluene sulfonate.

[0053] The charged hydrotrope may comprise from about 20% to about 50% by weight, preferably from about 35% to about 45% by weight, based on the total weight of the leaching composition.

[0054] Organic Aprotic Solvents

[0055] The organic aprotic solvent is preferably low polarity or medium polarity, in other words, the organic aprotic solvent has a dipole moment (D) preferably in the range of about 0.3 to about 2.5, more preferably about 1.0 to about 2.0.

[0056] In one preferred embodiment, the organic aprotic solvent is selected from ethers, esters, carbonates, and mixtures thereof.

[0057] As examples, ethyl acetate, diethyl carbonate, cyclopentyl methyl ether, 2-methyltetrahydrofuran, gamma-valerolactone, or dihydrol evoglucosenone (Cyrene) may be used.

[0058] Esters, especially ethyl acetate, are preferred.

[0059] The organic aprotic solvent may comprise about 10% to about 40% by weight, preferably about 20% to about 30% by weight, based on the total weight of the leaching composition.

[0060] aqueous phase

[0061] The aqueous phase is preferably water.

[0062] It advantageously has a neutral pH, ie in the range of 6.5 to 7.5.

[0063] The aqueous phase can account for about 20% by mass to about 45% by mass, preferably about 35% by mass to about 40% by mass, based on the total mass of the leaching composition.

[0064] Process ii)

[0065] During step ii), the leach composition prepared in step i) is mixed with the solid material so as to form a leach solution containing the first lanthanide element.

[0066] Step ii) is preferably carried out by mixing the leaching composition with the solid material such that the mass concentration of the solid material is about 1 g to about 20 g, more preferably about 1 g to about 10 g, and even more preferably about 1 g to about 5 g per 100 mL of the leaching composition.

[0067] Step ii) may be carried out at a temperature ranging from about 15°C to about 70°C, preferably from about 20°C to about 50°C.

[0068] More specifically, the temperature in step ii) is in the range of about 15°C to about 30°C, more preferably about 18°C ​​to about 25°C.

[0069] Step ii) is preferably carried out for a time ranging from about 1 hour to about 5 hours, more preferably from about 2 hours to about 4 hours. If the time is less than 1 hour, step ii) does not recover a sufficient amount of the first lanthanide element. If the time exceeds 5 hours, step ii) is not selective enough, especially when the other element is a second lanthanide element.

[0070] During step ii), the first lanthanide element is selectively dissolved in the leaching composition to form a leachate comprising said first lanthanide element, the first lanthanide element being dissolved in the leachate to a degree of more than 85%, more preferably more than 90%, even more preferably more than 95%.

[0071] In contrast, the second lanthanide element and / or waste element dissolves in the leachate to a degree of no more than 25%, more preferably no more than 20%, and even more preferably no more than 15%.

[0072] Thus, substantially all of the first lanthanide element dissolves selectively relative to the second lanthanide element and / or the waste element.

[0073] In one preferred embodiment, the first lanthanide element is selected from Dy and Yb and said other element(s) is a second lanthanide element selected from La, Nd, Pr and Eu, finally in admixture with a waste element.

[0074] Process iii)

[0075] Step iii) is carried out in order to separate the first lanthanide element from the other elements remaining in the solid residue.

[0076] The separation may be carried out by filtration.

[0077] At the end of step iii), a leachate free of solid residues and enriched in the first lanthanide element is obtained.

[0078] Thus, unlike state-of-the-art hydrometallurgical processes which first proceed by selective leaching of lanthanides relative to iron to obtain a liquid mixture of lanthanides and then proceed to specific extraction of the lanthanides from this liquid mixture, the method of the present invention allows selectivity between the lanthanides and simultaneously with selectivity for waste elements such as iron, on a solid mixture comprising a mixture of lanthanides and waste elements, as soon as the leaching step i) is carried out.

[0079] Thus, unlike prior art methods that require the use of numerous reagents such as toxic extractive molecules and organic solvents during a long, complicated and expensive process, the method according to the present invention is simple, rapid and environmentally friendly.

[0080] The leachate may then be treated according to steps iv), v) and vi) as described below, so as to obtain the first lanthanide element in a desired form, such as an oxidized form.

[0081] Process iv)

[0082] The method of the present invention may further comprise, after step iii), step iv) of adding a precipitating agent to the leachate so as to form a solid comprising the first lanthanide element.

[0083] The precipitating agent may be selected from oxalic acid, sodium hydroxide, ammonium hydroxide, sodium sulfate, and mixtures thereof.

[0084] The precipitant may be used at a molar concentration in the range of about 10 to 50 mmol / L, preferably about 20 to 30 mmol / L, relative to the total volume of the leachate.

[0085] In particular, the pH of the leachate is adjusted to around 3.

[0086] Process v)

[0087] The method of the present invention may further comprise, after step iv), a step v) of separating the solid comprising the first lanthanide element from the remaining solution, for example by filtering the solid.

[0088] Process vi)

[0089] The method of the present invention may further comprise, after step v), a step vi) of calcining the solid comprising the first lanthanide element so as to form an oxidized form of the first lanthanide element.

[0090] The method is particularly useful for selectively extracting a first lanthanide element from a solid material containing iron and a second lanthanide element as said other elements.

[0091] When the solid material used in step ii) comprises a first lanthanide element, a second lanthanide element and at least one waste element (such as iron), the solid residue obtained in step iii) comprises the second lanthanide element and a waste element.

[0092] According to said second variant, i.e. when said solid material comprises as other elements a second lanthanide element ultimately in a mixture with one or more waste elements, said method further comprises, after step iii), at least the following steps I), II) and III): I) preparing a leaching composition comprising an aqueous phase, at least one organic aprotic solvent, and at least one charged hydrotrope; II) mixing the leach composition of step I) with the solid residue of step iii) to form a leach solution containing the second lanthanide element and a solid residue containing one or more other elements; III) separating the leachate from the solid residue; may include.

[0093] Steps I), II) and III) make it possible to extract the second lanthanide element from said solid residue obtained in step iii).

[0094] Step I) has the same definition as step i).

[0095] The leaching composition, the aqueous phase, the organic aprotic solvent, and the charged hydrotrope are as defined in the present invention. The composition of the leaching composition prepared in step I) may be the same or different from the composition of the leaching composition prepared in step i).

[0096] In step II), the leach composition prepared in step I) is mixed with the solid residue of step iii) to form a leach solution containing a second lanthanide element.

[0097] Step II) is preferably carried out by mixing the leaching composition of step iii) with the solid residue such that the mass concentration of the solid residue is from about 1 g to about 20 g, more preferably from about 1 g to about 10 g, per 100 mL of the leaching composition.

[0098] Step II) may be carried out at a temperature ranging from about 15°C to about 70°C, preferably from about 20°C to about 50°C.

[0099] More specifically, the temperature in step II) is in the range of about 30°C to about 50°C, more preferably about 35°C to about 45°C.

[0100] Step II) is preferably carried out for a time ranging from about 1 hour to about 7 hours, more preferably from about 3 hours to about 6 hours. If the time is less than 1 hour, a sufficient amount of the second lanthanide element cannot be recovered. If the time is more than 7 hours, step II) is not selective enough.

[0101] During step II), the second lanthanide element is selectively dissolved in the leaching composition to form a leachate comprising the second lanthanide element, the second lanthanide element being dissolved in the leachate to a degree of more than 85%, more preferably more than 90%, even more preferably more than 95%.

[0102] In contrast, the waste elements are preferably soluble in the leachate to a degree of no more than 25%, more preferably no more than 20%, and even more preferably no more than 15%.

[0103] Thus, substantially all of the second lanthanide element dissolves selectively relative to the waste element.

[0104] The second lanthanide element is preferably selected from La, Nd, Pr, and Eu.

[0105] Step III) is carried out in order to separate the second lanthanide element from the other elements remaining in the solid residue.

[0106] The separation may be carried out by filtration.

[0107] At the end of step III), a second lanthanide-enriched leachate is obtained, free of said solid residues.

[0108] The leachate is then treated according to steps IV) and V) and VI) (with the same definitions as steps iv), v) and vi) respectively, but applied to the second lanthanide element), so as to obtain the second lanthanide element in the desired form, such as in oxidized form.

[0109] In accordance with a first object of the present invention, the method provides for selective extraction of a first lanthanide element [steps i) to vi)] and, optionally, a second lanthanide element [steps i) to iii), and steps I) to VI)] from a solid material.

[0110] The solid material is M L3 ≧154g / mol (preferably M L3 ≧160g / mol) and M L3 <M L1 Molecular weight M such that L3 The compound may further include a third lanthanide element having the formula:

[0111] The third lanthanide element is different from the first and second lanthanide elements, and either or both of the second and third lanthanide elements may be present in the solid material.

[0112] Said third lanthanide element acts as the first lanthanide as defined above in the present invention, so that the third lanthanide element is leached according to step ii) and separated from the solid residue according to step iii) to form a leachate enriched in the first and third lanthanide elements, in other words the leachate obtained in step iii) comprises the first and third lanthanide elements.

[0113] The method of the present invention further comprises, after step iii), a) mixing a diluent comprising an organic aprotic solvent as defined in the present invention and water with the leachate comprising the first and third lanthanide elements obtained in step iii) so as to result in a two-phase composition comprising an organic-rich phase comprising the first lanthanide element and an aqueous-rich phase comprising the third lanthanide element, b) separating the two phases so as to recover the water-rich phase containing the third lanthanide element; c) mixing the organic-rich phase containing the first lanthanide element with an acidic aqueous solution to result in a two-phase composition containing an aqueous-rich phase (stripping) containing the first lanthanide element, and an organic-rich phase; and d) separating the two phases to recover the water-rich phase containing the first lanthanide element; The method may further comprise the step of selectively extracting the first lanthanide element relative to the third lanthanide element according to

[0114] Thus, according to the method of the present invention, the same system (i.e. a composition comprising a charged hydrotrope, an organic aprotic solvent, and water) is used to carry out leaching (step ii) with said leaching composition) and liquid-liquid extraction (steps a) and b) with said leaching solution and said diluent).

[0115] The diluent may contain about 20% by mass to about 80% by mass of water, and preferably about 50% by mass to about 60% by mass of water, based on the total mass of the diluent.

[0116] The diluent may contain about 20% by mass to about 80% by mass of the organic aprotic solvent, and preferably about 40% by mass to about 50% by mass of the organic aprotic solvent, based on the total mass of the diluent.

[0117] The mass ratio of the diluent to the leachate is preferably in the range of about 3.5 to about 5.

[0118] Step a) is preferably carried out for about 20 minutes to about 180 minutes, preferably about 30 minutes to about 60 minutes.

[0119] Step a) is preferably carried out at a temperature of about 20°C to about 30°C.

[0120] Step a) is preferably carried out with stirring or rotary stirring.

[0121] Step b) is preferably carried out by centrifugation.

[0122] In step c), the pH of the acidic aqueous solution can be adjusted by adding an acidic solution to water to form the aqueous solution, wherein the acidic solution is preferably an about 0.1 M to about 1 M acidic solution of hydrochloric acid, nitric acid, and sulfuric acid, preferably an about 0.1 M to about 0.5 M acidic solution.

[0123] In step c), the volume ratio V(organic rich phase) / V(aqueous solution) is preferably in the range of about 0.7 to about 1.3, more preferably equal to 1.

[0124] Step c) is preferably carried out for about 10 minutes to about 60 minutes, preferably about 20 minutes to about 30 minutes.

[0125] Step c) is preferably carried out at a temperature of about 20°C to about 30°C.

[0126] After step d), the water-rich phase containing the first lanthanide element can be treated according to the following steps e), f) and g) so as to obtain the first lanthanide element in a desired form, such as an oxidized form.

[0127] Process e)

[0128] The method of the present invention may further comprise, after step d), a step e) of adding a precipitating agent to the water-rich phase comprising the first lanthanide element so as to form a solid comprising the first lanthanide element.

[0129] The precipitating agent may be selected from oxalic acid, sodium hydroxide, ammonium hydroxide, sodium sulfate, and mixtures thereof.

[0130] The precipitant may be used at a molar concentration in the range of about 10 to 50 mmol / L, preferably about 20 to 30 mmol / L, relative to the total volume of the leachate.

[0131] In particular, the pH of the leachate is adjusted to around 3.

[0132] Process f)

[0133] The process of the invention may further comprise, after step e), a step f) of separating the solid comprising said first lanthanide element from the remaining solution, for example by filtering said solid.

[0134] Process g)

[0135] After step f), the method may further comprise a step g) of calcining the solid comprising said first lanthanide element so as to form an oxidized form of said first lanthanide element.

[0136] In fact, steps e), f) and g) are similar to steps iv), v) and vi), as defined above, but are applied to an aqueous-rich phase comprising said first lanthanide element instead of a leachate comprising said first lanthanide element.

[0137] After step b), the water-rich phase comprising the third lanthanide element may be treated according to steps e'), f') and g') (with the same definitions as steps e), f) and g), respectively, but applied to the water-rich phase comprising the third lanthanide element), so as to obtain the third lanthanide element in a desired form, such as an oxidized form.

[0138] The first lanthanide element is preferably Yb and the third lanthanide element is preferably Dy.

[0139] The solid material is M L4 <154g / mol, M L4 <M L2 Molecular weight M such that L4 The compound may further include a fourth lanthanide element having the formula:

[0140] The fourth lanthanide element is different from the second, third and fourth lanthanide elements. The second, third and fourth lanthanide elements may be present together or only one or two of them in said solid material.

[0141] Since said fourth lanthanide element acts as a second lanthanide as defined above in the present invention, it remains together with the second lanthanide element in the solid residue obtained in step iii) and is leached according to step II) and separated from the solid residue according to step III) to form a leachate enriched in the second and fourth lanthanide elements, in other words, said leachate obtained in step iii) comprises the second and fourth lanthanide elements.

[0142] The method of the present invention further comprises, after step III), the following steps: A) mixing a diluent comprising an organic aprotic solvent as defined in the present invention and water with the leachate comprising the second and fourth lanthanide elements obtained in step III) so as to result in a two-phase composition comprising an organic-rich phase comprising the second lanthanide element and an aqueous-rich phase comprising the fourth lanthanide element, B) separating the two phases so as to recover the water-rich phase containing the fourth lanthanide element; and C) mixing the organic-rich phase containing the second lanthanide element with an acidic aqueous solution to obtain a two-phase composition containing an aqueous phase (stripping) containing the second lanthanide element and an organic-rich phase; and D) separating the two phases so as to recover the water-rich phase containing the second lanthanide element; The method may further include the step of selectively extracting the second lanthanide element relative to the fourth lanthanide element according to the method of the present invention.

[0143] Thus, according to the method of the present invention, the same system (i.e. a composition comprising a charged hydrotrope, an organic aprotic solvent, and water) is used to carry out leaching (step II using said leaching composition) and liquid-liquid extraction (steps A) and B using said leaching solution and said dilution solution).

[0144] The diluent may contain about 20% by mass to about 80% by mass of water, and preferably about 21% by mass to about 31% by mass of water, based on the total mass of the diluent.

[0145] The diluent may contain about 20% by mass to about 80% by mass of the organic aprotic solvent, and preferably about 69% by mass to about 79% by mass of the organic aprotic solvent, based on the total mass of the diluent.

[0146] The mass ratio of the diluent to the leachate is preferably in the range of about 15 to about 20.

[0147] Step A) is preferably carried out with stirring or rotary stirring.

[0148] Step A) is preferably carried out for about 20 minutes to about 180 minutes, more preferably about 30 minutes to about 60 minutes.

[0149] Step A) is preferably carried out at a temperature of about 20°C to about 30°C.

[0150] Step B) is preferably carried out by centrifugation.

[0151] In step C), the pH of the acidic aqueous solution can be adjusted by adding an acidic solution to water to form the aqueous solution, wherein the acidic solution is preferably an about 0.1 M to about 1 M acidic solution of hydrochloric acid, nitric acid, and sulfuric acid, preferably an about 0.1 M to about 0.5 M acidic solution.

[0152] In step C), the volume ratio V(organic rich phase) / V(aqueous solution) is preferably in the range of about 0.7 to about 1.3, more preferably equal to 1.

[0153] Step C) is preferably carried out for about 10 minutes to about 60 minutes, preferably about 20 minutes to about 30 minutes.

[0154] Step C) is preferably carried out at a temperature of about 20°C to about 30°C.

[0155] After step D), the water-rich phase comprising said second lanthanide element can be treated according to steps E), F) and G) (with the same definitions as steps e), f) and g), respectively, but applied to said water-rich phase comprising said second lanthanide element), so as to obtain the second lanthanide element in the desired form, such as in oxidized form.

[0156] After step B), the water-rich phase comprising said fourth lanthanide element can be treated according to steps E'), F') and G') (with the same definitions as steps e), f) and g), respectively, but applied to said water-rich phase comprising said fourth lanthanide element), so as to obtain the fourth lanthanide element in the desired form, such as in oxidized form.

[0157] The second lanthanide element is preferably Eu and the fourth lanthanide element is preferably Pr, Nd, La or a mixture of at least two of them.

[0158] Thus, the composition of the leach solution provides an important parameter for selective leaching and / or selective liquid-liquid extraction of heavier lanthanides relative to lighter lanthanides and iron.

[0159] The process of the invention preferably does not use extractants, which are in fact toxic and expensive (TOA, HDEHP, di- and mono-amides).

[0160] It should be noted that the order of steps I)-III) and a)-d) are independent, and only one or both of them can be performed after step iii).

[0161] In practice, the steps carried out after step iii) will depend on the number of lanthanides present in the solid material used in step ii) and on their respective molecular weights.

[0162] The second, third and fourth lanthanide elements are optional and may be present alone or in combinations of two or three lanthanides.

[0163] The solid material may further comprise a fifth, etc. lanthanide.

[0164] Depending on the type of fifth lanthanide, there may be an appropriate sequence of steps, as previously described.

[0165] In said solid state material, the third lanthanide element (respectively the fourth, fifth, etc. lanthanide element) is preferably in the form of an oxide compound, a carbonate compound or a phosphate compound, more preferably an oxide compound or a phosphate compound, even more preferably in the form of an oxide compound.

[0166] The process of the invention may further comprise, after step d) [respectively after step D)], a step h) [respectively step H)] (also called composition adjustment step) for adjusting the obtained organic-rich phase, which has the purpose of modifying / reforming the leach composition prepared in step i) [respectively step I)].

[0167] Step h) [respectively step H)] is preferably carried out by adding a conditioning composition comprising an appropriate amount of a charged hydrotrope and water to said organic rich phase.

[0168] The conditioning composition preferably contains about 40% by mass to about 70% by mass of water and about 30% by mass to about 60% by mass of the charged hydrotrope, and more preferably about 50% by mass to about 60% by mass of water and about 40% by mass to about 50% by mass of the charged hydrotrope, based on the total mass of the conditioning composition.

[0169] In one preferred embodiment, the mass ratio of m(tuning composition) / m(organic rich phase) is in the range of about 2-6.

[0170] Step h) [respectively Step H)] is preferably carried out at a temperature of about 20°C to about 30°C.

[0171] This step h) or H) makes it possible to work in a closed cycle and thus to recycle the solvent and the charged hydrotrope used in the first cycle.

[0172] The method of the invention may further comprise a preliminary step i0) of heat treating the raw solid material under oxidizing conditions, prior to step i), in order to obtain the corresponding oxides of the waste elements and / or lanthanides present in the raw solid material. Indeed, some waste electrical and electronic equipment contains non-oxidized lanthanides.

[0173] The process of the present invention is preferably carried out at atmospheric pressure.

[0174] A second object of the present invention is the use of said leach composition defined in the first object of the present invention for recycling lanthanide elements, more particularly WEEE.

[0175] A third object of the present invention is the use of said leaching composition defined in the first object of the present invention for the decontamination of eluates.

[0176] The present invention will be described in more detail in the following examples, but the present invention is not limited to these examples. [Brief description of the drawings]

[0177] [Figure 1] 1 shows a flow sheet of the all-in-one process. [Diagram 2] A process diagram for recycling permanent magnets is proposed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

[0178] Figure 1 shows the flow sheet of the all-in-one process.

[0179] More specifically, FIG. 1 illustrates a process for extracting a first and a second lanthanide element in accordance with an embodiment of the present invention.

[0180] The solid material defined in the present invention, more specifically comprising La, Nd, Pr, Eu, Dy, Yb and Fe, is leached for 3 hours at 20° C. [step ii)] after preparing a leached single-phase composition comprising, for example, ethyl acetate, water and sodium salicylate [(step i)]. After filtration according to step iii), a leachate rich in Dy and Yb is obtained. This leachate can then be diluted with a diluent comprising, for example, ethyl acetate and water in order to separate Yb from Dy [steps a) and b)]. A back extraction [step c)] is then provided to recover Yb in the aqueous phase [step d)] and then precipitate it in the form of oxalate by adding oxalic acid [step e)]. After filtration [step f)], the oxalate is calcined [step g)] to recover ytterbium oxide at the end of the method.

[0181] Step iii) The solid residue obtained is leached for 5 hours at 40° C. (step II)) after preparing a leaching single-phase composition comprising, for example, ethyl acetate, water and sodium salicylate [step I)]. At the end of the filtration step [step III)], a leachate rich in Nd, Pr and Eu is obtained. This leachate can then be diluted with a diluent comprising, for example, ethyl acetate and water in order to separate Eu from didymium (Pr+Nd) [steps A) and B)]. A back extraction [step C)] is then provided in order to recover Eu in the aqueous phase [step D)] and then precipitate it in the form of oxalate by adding oxalic acid [step E)]. After filtration [step F)], the oxalate is calcined [step G)] to recover europium oxide (EU2O3) at the end of the process.

[0182] The resulting solid residue is mainly Fe in the form of Fe2O3 and can be used for the production of pigments.

[0183] Example 1: Method for extracting at least one first rare earth metal from a permanent magnet powder according to the method of the present invention

[0184] 1.1 Step i) Preparing a leaching composition comprising an aqueous phase, at least one organic solvent, and at least one charged hydrotrope.

[0185] A single-phase leaching composition was prepared containing 40 wt. % water, 21 wt. % ethyl acetate (as the organic solvent), and 39 wt. % sodium salicylate (as the charged hydrotrope).

[0186] 1.2 Leaching process ii)

[0187] The leaching step ii) was carried out in a thermostatically controlled stirred reactor to regulate the temperature.

[0188] As solid material, a powder resulting from the grinding of a permanent magnet was used in the method of the present invention, which has the composition shown in Table 1 below.

[0189] [Table 1]

[0190] 10 mL of the leaching composition prepared in section 1.1 was added to the reactor, and then 0.2 g of solid material was added to the leaching composition.

[0191] The leaching step ii) was carried out at a temperature of 20° C. for 3 hours.

[0192] The leachate was then filtered.

[0193] As a comparative example, the same method as described in section 1.2 was carried out using a comparative leaching composition containing a 5M nitric acid solution.

[0194] The molar concentrations of lanthanides and waste elements in the leachate and control leachate were measured using X-ray fluorescence (XRF) analysis.

[0195] Table 2 below shows: the amount (mol %) of a given element extracted with the leachate of the invention (100 x [molar concentration of a given element in the leachate] / [molar concentration of said given element in the solid material]), the amount (mol%) of a given element extracted in the comparative leachate (100 x [molar concentration of a given element in the comparative leachate] / [molar concentration of said given element in the solid material]), Compare.

[0196] [Table 2]

[0197] In the case of the leaching composition that is not part of the present invention (5M nitric acid solution), the leaching is complete for all elements. It is therefore a non-selective leaching system. The leaching composition defined in the present invention allows selective extraction of Dy relative to Nd, Pr and Fe without the need for adding dedicated extractants, resulting in lower costs and saving time and money.

[0198] 1.3 Other processes

[0199] The process according to the invention produces a leachate rich in Dy and a solid residue rich in Nd, Pr and Fe.

[0200] After filtration, the pH of the leachate is adjusted to 3, and then Dy oxalate is precipitated by adding 25 mmol / L oxalic acid to the leachate. The precipitation is carried out at 20°C under constant stirring. 96 mol% of dysprosium is precipitated to form dysprosium oxalate. The leachate can be reused as a leachate composition for new NdFeB oxide powder. In this way, the loss of rare earths during the precipitation step is also avoided, since the remaining rare earths are returned to the process feed.

[0201] The solid residue rich in Nd, Pr, and Fe was leached using the leaching composition prepared in step 1.1 at a solid / liquid ratio of 1:50 (g mL -1 ) for 5 hours at a temperature of 40 °C. At the end of the filtration step, a leachate rich in Nd and Pr is obtained. In this step, 80 mol% Nd and 84.3 mol% Pr are selectively recovered from the iron in the leachate. Didymium (a mixture of Nd and Pr) is then precipitated with 25 mmol / L oxalic acid under the same operating conditions as in the previous precipitation step. After filtration, 94 mol% Nd and 97.4 mol% Pr are precipitated as didymium oxalate. Didymium oxide can be obtained by calcination. The resulting solid residue contains mainly Fe.

[0202] Figure 2 proposes a process diagram for recycling permanent magnets, where the elements can be selectively separated from each other only in the leaching step ii) (no need for liquid-liquid extraction), reducing the number of processing steps.

Claims

1. Molecular weight M Ｌ１ (g / mol) of at least one first lanthanide element, Ｌ２ (g / mol) of the second lanthanide element, molecular weight M ＷＥ 1. A method for extracting from a solid material containing at least one waste element having a % saturation (g / mol) and one or more other elements selected from mixtures thereof, comprising: -M ＷＥ ≦100 g / mol, - when said other element is a second lanthanide element and is ultimately in a mixture with the waste element, M Ｌ１ ≧154 g / mol, preferably M Ｌ１ ≧160 g / mol, and M Ｌ２ < 154 g / mol, The method comprises at least the following steps: i) preparing a leaching composition comprising an aqueous phase, at least one organic aprotic solvent, and at least one charged hydrotrope; ii) mixing the leaching composition with the solid material to form a leachate comprising the first lanthanide element and a solid residue comprising the one or more other elements; iii) separating the leachate from the solid residue; A method comprising:

2. 10. The method of claim 1, wherein the charged hydrotrope is a cationic hydrotrope selected from salts of substituted benzoic acids, salts of unsubstituted benzoic acids, salts of substituted benzenesulfonic acids, and salts of unsubstituted benzenesulfonic acids.

3. 2. The method of claim 1, wherein the charged hydrotrope comprises 20% to 50% by weight of the total weight of the leaching composition.

4. 10. The method of claim 1, wherein the organic aprotic solvent is selected from ethers, esters, carbonates, and mixtures thereof.

5. 2. The method of claim 1, wherein the organic aprotic solvent comprises 10% to 40% by weight, based on the total weight of the leaching composition.

6. 10. The method of claim 1, wherein the aqueous phase has a pH in the range of 6.5 to 7.

5.

7. The method of claim 1 , wherein the solid material is a WEEE or a permanent magnet.

8. 10. The method of claim 1, wherein the waste element is a transition metal or metalloid selected from iron, copper, cobalt, boron, nickel, aluminum, titanium, chromium, and vanadium.

9. 2. The method of claim 1, wherein the solid material comprises one or more waste elements as the other elements, and the first lanthanide element is selected from lanthanum (La), praseodymium (Pr), neodymium (Nd), europium (Eu), dysprosium (Dy), and ytterbium (Yb).

10. 2. The method of claim 1, wherein the solid material contains as another element a second lanthanide element ultimately in a mixture with one or more waste elements, the first lanthanide being dysprosium (Dy) or ytterbium (Yb) and the second lanthanide element being selected from lanthanum (La), praseodymium (Pr), neodymium (Nd), and europium (Eu).

11. After step iii), - adding a precipitating agent to the leachate to form a solid containing the first lanthanide element, step iv); - step v) after step iv), separating the solid containing the first lanthanide element from the remaining solution, and - after step v), a step vi) of calcining said solid containing said first lanthanide element so as to form an oxidized form of said first lanthanide element. The method of claim 1 further comprising:

12. 10. The method of claim 1, - the solid material is M Ｌ３ ≧154 g / mol, M Ｌ３ <M Ｌ１ Molecular weight M Ｌ３ and further comprising a third lanthanide element having the formula: - the leachate obtained in step iii) is enriched in first and third lanthanides, and the method further comprises, after step iii), a) mixing a diluent comprising an organic aprotic solvent and water with the leachate comprising the first and third lanthanides obtained in step iii) so as to result in a two-phase composition comprising an organic-rich phase comprising the first lanthanide and a water-rich phase comprising the third lanthanide; b) separating the two phases so as to recover the water-rich phase containing the third lanthanide element; c) mixing the organic-rich phase containing the first lanthanide element with an acidic aqueous solution to result in a two-phase composition comprising a water-rich phase containing the first lanthanide element and an organic-rich phase; and d) separating the two phases to recover the water-rich phase containing the first lanthanide element; 3. The method of claim 1, further comprising selectively extracting the first lanthanide element relative to the third lanthanide element according to

13. 10. The method of claim 1, The solid material contains as other elements a second lanthanide element which is ultimately in admixture with one or more waste elements, and the method comprises, after step iii), at least the following steps I), II) and III): I) preparing a leaching composition comprising an aqueous phase, at least one organic aprotic solvent, and at least one charged hydrotrope; II) mixing the leach composition of step I) with the solid residue of step iii) to form a leach solution containing the second lanthanide element and a solid residue containing one or more other elements; III) separating the leachate from the solid residue; A method comprising:

14. 14. The method of claim 13, - the solid material is M Ｌ４ <154 g / mol, M Ｌ４ <M Ｌ２ Molecular weight M Ｌ４ and further comprising a fourth lanthanide element having the formula: - the leachate obtained in step III) is enriched in secondary and quaternary lanthanides, and the method further comprises, after step III), A) mixing a diluent comprising an organic aprotic solvent and water with the leachate comprising the second and fourth lanthanides obtained in step III) so as to result in a two-phase composition comprising an organic-rich phase comprising the second lanthanide and a water-rich phase comprising the fourth lanthanide; B) separating the two phases to recover the water-rich phase containing the fourth lanthanide element; and C) mixing the organic-rich phase containing the second lanthanide element with an acidic aqueous solution to result in a two-phase composition containing a water-rich phase containing the second lanthanide element and an organic-rich phase; and D) separating the two phases to recover the water-rich phase containing the second lanthanide element; 3. The method of claim 1, further comprising selectively extracting the second lanthanide element relative to the fourth lanthanide element according to

15. Use of a leaching composition as defined in any one of claims 1 to 6 for recycling lanthanide elements, more particularly WEEE.

16. Use of a leaching composition as defined in any one of claims 1 to 6 for the decontamination of eluates.

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