法国专利FR3026099A1 METHODS FOR SELECTIVE RECOVERY OF RARE EARTHS IN AQUEOUS ACID PHASES RESULTING FROM THE TREATMENT OF

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The invention relates to a hydrometallurgical process for selectively recovering at least one rare earth "heavy", that is to say of atomic number at least equal to 62, being in an acidic aqueous phase resulting from the treatment of used or rejected permanent magnets. It also relates to a hydrometallurgical process for selectively recovering, at first, at least one heavy rare earth present in an aqueous acid phase resulting from the treatment of used or discarded permanent magnets, and then, at a second stage, at least one rare earth "light", that is to say, atomic number at most equal to 61, also being in this aqueous acid phase. The invention finds particular application in the recycling of rare earths present in used or rejected scraped Neodymium-Iron-Boron permanent magnets (or NdFeB) and, in particular, dysprosium, praseodymium and neodymium, as well as in recycling Samarium present in permanent magnets Samarium-Cobalt type (or SmCo) used or rejected.
公开号:FR3026099A1
申请号:FR1459023
申请日:2014-09-24
公开日:2016-03-25
发明作者:Manuel Miguirditchian；Victor Haquin；Vincent Pacary；Richard Laucournet
申请人:Commissariat a lEnergie Atomique CEA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
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[0001] TECHNICAL FIELD The invention relates to the field of the recovery of rare earths present in used magnets used or discarded for recycling. BACKGROUND OF THE INVENTION of these rare earths. More specifically, the invention relates to a hydrometallurgical process for selectively recovering at least one rare earth "heavy", that is to say of atomic number at least equal to 62 (samarium, europium, gadolinium, terbium , dysprosium, holmium, erbium, thulium and / or ytterbium), being in an aqueous acid phase resulting from the treatment of used or discarded permanent magnets. It also relates to a hydrometallurgical process for selectively recovering, at first, at least one heavy rare earth present in an aqueous acid phase resulting from the treatment of used or discarded permanent magnets, and then, at a second stage, at least one rare earth "light", that is to say, atomic number at most equal to 61 (scandium, yttrium, lanthanum, cerium, praseodymium and / or neodymium), also being in this acidic aqueous phase. The invention finds a particularly advantageous application in the recycling of rare earths contained in used or unworn Neodymium-Fer-Bore permanent-type magnets (or NdFeB) and, in particular, dysprosium (which is the heavy rare earth present in this invention). the type of magnet that is the most economically interesting), praseodymium and neodymium (which are the rare earths most abundant in this type of magnets), as well as in the recycling of samarium contained in permanent magnets of the Samarium type. Cobalt (or SmCo) used or discarded. STATE OF THE PRIOR ART The particular physical and chemical properties of rare earths (scandium, yttrium and lanthanides) make it currently essential chemical elements in many industrial fields: glass and ceramics industries, catalysis, metallurgy, manufacture of permanent magnets , optical devices, phosphors, etc. This specificity, combined with growth in global demand for rare earths and a limited number of rare earth producing countries, creates market risks for these metals.
[0002] Diversification in the production of rare earths is currently receiving a lot of attention from stakeholders. The recycling of rare earths present in used or discarded materials is more and more preferred. Until 2011, less than 1% of these rare earths was recycled. Recycling reconciles reduced supply risks and environmental challenges related to mining activities. One of the first markets in volume and market value of rare earth recycling concerns NdFeB permanent magnets. This resource for recycling rare earths has the advantage of understanding rare earth proportions that are interesting and valuable. In fact, the rare earth mass contents of these magnets are of the order of 30% for about 70% of iron. The composition of the NdFeB magnets varies according to the applications and the manufacturers, but they typically contain rare earths (dysprosium and, to a lesser degree, gadolinium, terbium) which are highly valuable as well as light rare earths (praseodymium and neodymium in particular). In addition to containing iron and boron, NdFeB magnets are generally covered with a protective anticorrosive coating based on nickel and copper or other transition metals (cobalt, chromium, etc.). The problem is therefore to recover, from permanent magnets containing a large proportion of iron, boron and various impurities (cobalt, nickel, copper, titanium, manganese, chromium, etc.) in amounts by weight, rare earths such as than dysprosium, praseodymium and neodymium, with final purities sufficient to allow the recycling of these rare earths (whether in the form of magnets or in other applications) and ideally above 99.5%. The hydrometallurgical route, based on the liquid-liquid extraction technique, is commonly considered as one of the most commercially appropriate ways to recover rare earths from the medium in which they are located and especially to separate them from each other. The hydrometallurgical processes, which are currently used industrially to recover rare earths from an aqueous acidic phase, preferentially employ organophosphorus extractants such as phosphoric acids, phosphonic acids, phosphinic acids, carboxylic acids and alkyl phosphates. . It is, for example, di-2-ethylhexylphosphoric acid (or HDEHP), 2-ethylhexyl-2-ethylhexylphosphonic acid (or HEH [EHP]), bis (trimethyl) -2-acid. , 4,4-pentyl) phosphinic (or Cyanex 272), neodecanoic acid (or Versatic 10) and tri-n-butyl phosphate (or TBP).
[0003] However, the use of these extractants is not suitable for the recovery of the rare earths present in an aqueous acidic phase resulting from the treatment of NdFeB permanent magnets because they all have the disadvantage of strongly extracting the iron and the others. transition metals. Their use therefore requires removing the transition metals from the aqueous phase before extracting the rare earths, which would lead to a heavy process to implement and therefore not industrially interesting. The diglycolamides represent a family of extractants which was developed by a Japanese team in the study of the treatment of spent nuclear fuel with the aim of co-extracting trivalent actinides and lanthanides from a process raffinate. Purex.
[0004] Studies on the extraction of many elements of Mendeleiev's Periodic Table have also been published, but the use of diglycolamides as extractants remains closely linked to the treatment of spent nuclear fuels and, in particular, to the recovery of trivalent actinides (americium and curium) present in these fuels.
[0005] The use of a diglycolamide, in this case N, N'-dimethyl-N, N'-di-noctyldiglycolamide (or MODGA), as an extractant for recovering rare earths from aqueous acidic solutions from waste products. However, NdFeB permanent magnets have been considered very recently in an article published by Narita and Tanaka (Solvent Extraction Research and Development, Japan, 2013, 20, 115-121, reference [1]). This article shows that it is possible to separate neodymium and dysprosium from iron and nickel and dysprosium from neodymium in a nitric or sulfuric medium by means of an organic phase comprising MODGA. However, the work on which it is based is based solely on synthetic aqueous solutions containing only 0.001 mol / L of dysprosium, neodymium, iron and nickel, ie concentrations far removed from those expected in an aqueous solution resulting from the treatment. used or rejected permanent magnets. Thus, no test has been carried out on aqueous solutions actually obtained from permanent magnets and, therefore, capable of containing up to 600 times more iron or 60 times more neodymium, for example, than synthetic aqueous solutions. they used. Moreover, this article does not specify the behavior and impact of the other metallic elements that may also be in an aqueous acid solution resulting from the treatment of NdFeB permanent magnets such as praseodymium, boron, cobalt and copper.
[0006] Finally, no scheme of a process that would make it possible to recover, on an industrial scale, dysprosium and, possibly, praseodymium and it, both quantitatively and selectively, is proposed in this article which is confined to tube experiments only. . In view of the foregoing, the inventors have therefore set themselves the goal of providing a method which makes it possible to recover one or more rare earths present in an acidic aqueous phase resulting from the treatment of used or discarded permanent magnets and, in particular, permanent magnets NdFeB, and this, selectively vis-à-vis non-rare earth elements may also be present in this aqueous phase so that the rare earth or so recovered can present, together or separately, a high degree of purity, ideally above 99.5%.
[0007] They have also set themselves the goal that this process will make it possible to recover this rare earth or these rare earths with a high recovery efficiency, ideally greater than 99.5%. They also set themselves the goal that this process be applicable to aqueous phases resulting from the treatment of permanent magnets whose acidity can be part of a wide range. They further set out that this process should be sufficiently simple to implement so that its exploitation on an industrial scale can be reasonably envisaged.
[0008] PRESENTATION OF THE INVENTION These and other objects are achieved by the invention, which firstly proposes a process (hereinafter referred to as "first process") for the selective recovery of at least one rare earth TR1, with a number atomic at least equal to 62, from an aqueous acidic phase A1 derived from the treatment of used or discarded permanent magnets and comprising one or more rare earth (s) TR1, transition metals and an acid concentration strong ranging from 0.2 to 6 mol / L, which process comprises: a) extracting the rare earth (s) TR1 from the aqueous phase Al, by contacting the aqueous phase Al with a water immiscible organic phase which comprises a lipophilic diglycolamide, that is to say having a total number of carbon atoms of at least 24, as extractant, in an organic diluent, and then separation aqueous and organic phases; 131) washing the organic phase obtained at the end of step a1), by contacting the organic phase with an aqueous acidic phase A2, which comprises a strong acid identical to the strong acid of the aqueous phase Al, at a concentration at most equal to the strong acid concentration of the aqueous phase Al, and then separation of the aqueous and organic phases; and ci) the desextraction of the rare earth (s) TR1 from the organic phase obtained at the end of step 131), by contacting the organic phase with an aqueous acidic phase A3 which has a pH at least equal to 1, then separation of the aqueous and organic phases. In the foregoing and the following, "used" permanent magnets are all permanent magnets that can be recovered from industrial or domestic post-consumer waste and, in particular, waste electrical and electronic equipment (again so-called "WEEE" or "D3E") such as computer hard drives, electric motors, magnetic devices (scanners, television speakers, etc.), etc. while permanent magnets are called "rejected" , all the rejects of the manufacture of permanent magnets and this, be it powders, chips or more massive elements. Moreover, in what precedes and what follows, the expressions "from .... to ....", "from .... to ...." and "understood (e) between ... and .... "are equivalent and mean to mean that the bounds are included. Similarly, the terms "solution" and "phase" are equivalent and perfectly interchangeable. According to the invention, the diglycolamide is advantageously chosen from diglycolamides which correspond to formula (I) below: R1 (R2) NC (O) -CH2-O-CH2-C (O) -N (R3) R 4 (I) in which R 1, R 2, R 3 and R 4 represent, independently of one another, linear or branched alkyl groups each comprising at least 5 carbon atoms and preferably at least 8 carbon atoms, such as n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl and the like. Among these diglycolamides, the diglycolamides of formula (I) above in which R 1, R 2, R 3 and R 4 represent identical alkyl groups and comprising from 8 to 12 carbon atoms are more particularly preferred. Examples of such diglycolamides include N, N, Al'Artetraoctyl-3-oxapentanediamide (or TODGA), N, N, AP, Ar-tetra (2-ethylhexyl) -3-oxapentanediamide (or TEHDGA), N, N, AP1Ar-tetradecyl-3-oxapentanediamide (or TDDGA) or else N, N, AP1Ar-tetradodecyl-3-oxapentanediamide (or TdDDGA).
[0009] According to a particularly preferred embodiment of the invention, the diglycolamide is chosen from TODGA, TEHDGA and TdDDGA and, more preferably, from TODGA and TdDDGA. Be that as it may, diglycolamide is present in the organic phase at a concentration typically ranging from 0.05 to 0.4 mol / L, for example 0.2 mol / L. The organic phase may furthermore comprise a phase modifier capable of increasing their charge capacity, that is to say the maximum concentration of metallic elements that this phase may present without the formation of a third phase by demixing. when it is brought into contact with an aqueous phase loaded with metallic elements. Such a charge modifier will generally be indicated in the case of an organic phase comprising a diglycolamide of formula (I) above in which R1 to IV represent alkyl groups having less than 12 carbon atoms, such as TODGA or TEHDGA. . This phase modifier can in particular be chosen from trialkyl phosphates such as tri-n-butyl phosphate (or TBP) or tri-n-hexylphosphate (or THP), alcohols such as n-octanol, n-octanol and the like. -decanol or isodecanol, and monoamides such as N, N-dihexyloctanamide (or DHOA), N, N-dibutyldecanamide (or DBDA), N, N-di (2-ethylhexyl) acetamide (or D2EHAA) , N, N-di (2-ethylhexyl) -propionamide (or D2EHPA), N, N-di (2-ethylhexesobutyramide (or D2EHiBA) or N, N-dihexyldecanamide (or DHDA). of phase is preferably not more than 15% by volume of the volume of the organic phase, or not more than 10% by volume of the volume of this phase when it is an alcohol such as n-octanol As for the organic diluent, it may be any non-polar aliphatic organic diluent whose use has been proposed for performing liquid-liquid extractions such as a linear or branched dodecane, such as nd odecane or hydrogenated tetrapropylene (or TPH), or a kerosene such as that sold by TOTAL under the trade name Isane IP-185. As previously indicated, the aqueous phase A2 has a strong acid concentration at most equal to the strong acid concentration of the aqueous phase Al, which means that it may be less than or equal to this concentration. However, for reasons of efficiency of the washing, use is preferably made of an aqueous phase A2 whose concentration of strong acid is lower than that of the aqueous phase Al and is typically between 0.1 and 4 mol / L and more preferably between 0.1 and 2 mol / L of strong acid. According to the invention, the strong acid present in the aqueous phase A1 and, consequently, in the aqueous phase A2 (since, as previously mentioned, the latter comprises the same strong acid as the aqueous phase Al), is preferably , nitric acid. However, it goes without saying that it could equally well be sulfuric acid, hydrochloric acid or phosphoric acid, or even a mixture of several strong acids as mentioned above. The aqueous phase A3 can comprise, as acid, a strong acid and, moreover, the same strong acid as that present in the aqueous phases A1 and A2, for example nitric acid, in which case this aqueous phase typically comprises 0, 0001 to 0.1 mol / L and more preferably 0.0005 to 0.002 mol / L of this strong acid. However, it is also possible for the aqueous phase A3 to comprise, as acid, a weak acid, for example a mono-, di- or tricarboxylic acid such as glycolic acid, malonic acid or mesoxalic acid, in which case this The aqueous phase typically comprises from 0.05 to 1 mol / L and, more preferably, from 0.1 to 0.5 mol / L of this weak acid.
[0010] In order to promote the removal of the rare earth (s) TR1 from the organic phase resulting from step b1), the aqueous phase A3 may also comprise one or more compounds that complex the rare earths in an aqueous medium, which compound (s) can (are) in particular be chosen from hydrophilic diglycolamides, that is to say whose total number of carbon atoms does not exceed 20, such as N, N, N ', N'-tetramethyldiglycolamide (or TMDGA), N, N, N', N'-tetraethyldiglycolamide (or TEDGA) or N, N, N ', N'-tetrapropyldiglycolamide (or TPDGA), polyaminocarboxylic acids as N- (2-hydroxyethyl) ethylene diamine triacetic acid (or HEDTA), nitrilotriacetic acid (or NTA) or diethylene triamine pentaacetic acid (or DTPA), or among mono-, di- or tricarboxylic acids such as glycolic acid, malonic acid or mesoxalic acid in the case, of course, where said aqueous phase A3 does not already include as acid, such an acid. mono-, di- or tricarboxylic. In addition or alternatively, step c1) can also be carried out hot, that is to say typically at a temperature ranging from 40 to 55 ° C.
[0011] Advantageously, the first method further comprises a step of purifying the organic phase resulting from step c1), which purification may comprise, as is well known per se, a washing of this organic phase with one or more acidic aqueous phases. , alkaline and / or complexing, capable of removing the impurities and any degradation products (including hydrolysis products) it contains without de-extracting the diglycolamide. Preferably, this process is carried out in the form of a ring formed by steps a1), 131), ci) and the purification of the organic phase resulting from step c1). According to the invention, the first method, as just described, is preferably implemented to recover the dysprosium (Z = 66) contained in used or discarded NdFeB permanent magnets, in which case the aqueous phase Al is derived from the treatment of permanent magnets of this type and includes dysprosium as a rare earth TR1. However, this method can also be used to selectively recover the samarium (Z = 62) contained in used or discarded SmCo permanent magnets, in which case the aqueous phase Al originates from the treatment of permanent magnets of this type and comprises samarium as a rare earth TR1. It can, moreover, be implemented in a more complete process for selectively recovering, not only one or more heavy rare earths contained in used magnets used or discarded, but also one or more light rare earths contained in these magnets, and therefore be integrated in this process. Also, the subject of the invention is also a process (hereinafter referred to as a "second process") for selective recovery of at least one rare earth TR1, of atomic number at least equal to 62, and of less a rare earth TR2, of atomic number at most equal to 61, from an aqueous acid phase Al resulting from the treatment of used or discarded permanent magnets and comprising one or more rare earth (s) TR1 and a or several rare earth (s) TR2, transition metals and a strong acid concentration ranging from 0.2 to 6 mol / L, which process comprises: - recovery of the rare earth (s) (s) TR1 present (s) in the aqueous phase Al, which recovery comprises the following steps: a) extraction of the rare earth (s) TR1 of the aqueous phase Al, by contacting of the aqueous phase A1 with a first organic phase immiscible with water, which comprises a diglycolamide having a total number of carbon atoms in the ego ns equal to 24 as extractant, in an organic diluent, then separation of the aqueous and organic phases; 131) washing the organic phase obtained at the end of step a1), by contacting the organic phase with an aqueous acidic phase A2, which comprises a strong acid identical to the strong acid of the aqueous phase Al, at a concentration at most equal to the strong acid concentration of the aqueous phase Al, and then separation of the aqueous and organic phases; and ci) the desextraction of the rare earth (s) TR1 from the organic phase obtained at the end of step 131), by contacting the organic phase with an aqueous acidic phase A3 which has a pH of at least 1, followed by separation of the aqueous and organic phases; then - the recovery of the rare earth (s) TR2 present (s) in the aqueous phase obtained at the end of step ai), which recovery comprises the following steps: az) extraction of the rare earth (s) TR2 of the aqueous phase obtained after step a1), by contacting the aqueous phase with a second organic phase, immiscible with water which comprises the same extractant as the first organic phase, in an organic diluent, then separation of the aqueous and organic phases; bz) washing the organic phase obtained at the end of step az), by contacting the organic phase with an aqueous acid phase A4, which comprises a strong acid identical to the strong acid of the aqueous phase Al, at a concentration at most equal to the strong acid concentration of the aqueous phase from step a1), and then separation of the aqueous and organic phases; and cz) the desextraction of the rare earth (s) TR2 from the organic phase obtained at the end of step 132), by contacting the organic phase with an aqueous acidic phase A5 which has a pH at least equal to 1, then separation of the aqueous and organic phases. In this second method, the preferred characteristics of the diglycolamide, the first organic phase and the aqueous phases A2 and A3 are as previously described for the first process. Moreover, all that has been previously mentioned about the organic phase of the first process also applies to the second organic phase of the second process; likewise, all that has been previously mentioned about the aqueous phase A2 of the first process also applies to the aqueous phase A4 of the second process while all that has been previously mentioned about the aqueous phase A3 of the first The method also applies to the aqueous phase A5 of the second process. In the second process, the strong acid is also preferably nitric acid, it being understood that it could equally well be another strong acid such as sulfuric acid, hydrochloric acid or the like. phosphoric acid, or a mixture of several strong acids as mentioned above. Advantageously, the second method further comprises a purification of the organic phases from steps ci) and c2). Preferably, the second process is carried out in the form of a first and a second cycle, the first cycle being formed by steps a1), 131), and the purification of the organic phase resulting from step ci) and the second cycle being formed by steps az), 132), cz) and the purification of the organic phase from step c2). More preferably, it is preferred that this process be carried out in the form of a first and a second ring using the same organic phase, in which case the first cycle comprises steps a1), 131) and c1), the second cycle comprises the steps az), bz) and c2), the first and second cycles having in common to understand the purification of an organic phase formed by the combination of organic phases from steps ci) and cz) and then the division of the organic phase thus purified in said first and second organic phases. According to the invention, the second method, as just described, is advantageously used to selectively recover dysprosium, praseodymium (Z = 59) and neodymium (Z = 60) contained in magnets. NdFeB used or discarded permanent, in which case the aqueous phase Al is derived from the treatment of permanent magnets of this type and comprises dysprosium as rare earth TR1, and praseodymium and neodymium as rare earths TR2. Whether NdFeB permanent magnets or permanent magnets of another type, the aqueous phase Al may in particular be derived from the dissolution of a permanent magnet powder in a strong acid supplemented with an oxidizing agent such as hydrogen peroxide, as described in PCT International Application WO 2014/064587, hereinafter reference [2], the permanent magnet powder which can itself be obtained by demagnetizing and grinding permanent magnets then hydride-dehydriding treatment of the ground material thus obtained, as also described in said reference [2].
[0012] Other features and advantages of the invention will emerge from the additional description which follows. It goes without saying that this additional description is given as an illustration of the subject of the invention and should in no way be interpreted as a limitation of this object.
[0013] BRIEF DESCRIPTION OF THE FIGURES FIG. 1 illustrates the principle of a preferred embodiment of the first method of the invention, applied to the treatment, on an industrial scale, of a nitric aqueous phase resulting from the treatment of NdFeB permanent magnets. used or discarded, with a view to selectively recovering the dysprosium present in this aqueous phase. FIG. 2 illustrates the principle of a preferred embodiment of the second method of the invention, applied to the treatment, on an industrial scale, of a nitric aqueous phase resulting from the treatment of used or discarded NdFeB permanent magnets, to selectively recover the dysprosium, praseodymium and neodymium present in this aqueous phase. FIGS. 3A and 3B illustrate the results of extraction tests carried out on synthetic nitric aqueous phases, comprising boron, iron, praseodymium, neodymium and dysprosium, using organic phases comprising 0.2 mol / L of TODGA, 5% (v / v) n-octanol in n-dodecane; FIG. 3A shows the distribution coefficients, denoted Dm, of the different metallic elements obtained as a function of the nitric acid concentration, expressed in mol / L, of the aqueous phases tested while FIG. 3B shows the separation factors, respectively denoted FSDymd. , FSDy / pr, FSDy / B and FSDy / Fe, between dysprosium and other metallic elements as well as the separation factor, denoted FSNdipr, between neodymium and praseodymium, obtained as a function of the nitric acid concentration, expressed in mol / L, aqueous phases tested. Figures 4A and 4B illustrate in detail an example of the preferred embodiment of the second method of the invention which is shown in Figure 2; FIG. 4A corresponds to the steps of the first cycle of this mode of implementation except the stage of the purification of the organic phase whereas FIG. 4B corresponds to the steps of the second cycle of said mode of implementation except, here also, the purification step of the organic phase.
[0014] In FIGS. 1, 2, 4A and 4B, the rectangles referenced 1 to 7 represent multi-stage extractors such as those conventionally used to carry out liquid-liquid extractions on an industrial scale, such as, for example, extractors consisting of mixer-settler batteries; furthermore, the organic phase flows entering and leaving these extractors are symbolized by a continuous line while the aqueous phase flows entering and leaving said extractors are symbolized by dashed lines. DETAILED DESCRIPTION OF THE INVENTION EXAMPLE 1 Schematic diagram of a preferred embodiment of the first method of the invention Referring to FIG. 1, which illustrates the principle of a preferred embodiment of the first process of the invention, designed to treat, on an industrial scale, a nitric aqueous phase resulting from the treatment of used or discarded NdFeB permanent magnets, with a view to selectively recovering the dysprosium which is heavy rare earth present in this aqueous phase , the most economically interesting. This aqueous phase is, for example, an aqueous phase resulting from the dissolution in a nitric medium, supplemented with an oxidizing agent, of a permanent magnet powder NdFeB as obtained in reference [2] above. Such an aqueous phase, which is hereinafter referred to and in FIG. 1 "aqueous phase Al", can comprise, depending on the type of magnets from which it has been obtained and the conditions in which the magnesium powder has been dissolved in nitric medium: from 0.2 to 6 mol / L of nitric acid, of the order of 200 mg / L of dysprosium, a total concentration of praseodymium and neodymium of the order of 10 to 15 g / L, an iron concentration of the order of 30 to 40 g / L and a number of metal impurities such as boron, nickel, copper, cobalt, chromium, manganese, titanium, etc. This iron and these impurities will be grouped in the following under the term "undesirable elements". In the present embodiment, the method comprises a single cycle which aims to selectively recover the dysprosium present in the aqueous phase Al.
[0015] This cycle comprises: a first step, called "Extraction Dy" in Figure 1, which aims to extract dysprosium from the aqueous phase Al by means of an organic phase, immiscible with water; a second step, called "washing Pr + Nd + undesirable elements" in Figure 1, which aims to wash the organic phase from the "Extraction Dy" by means of an aqueous phase A2 to remove the organic phase elements metal other than dysprosium that may have been partially extracted during "Extraction Dy"; a third step, called "Dyextraction Dy" in Figure 1, which aims to extract dysprosium from the organic phase from "washing Pr + Nd + undesirable elements" by means of an aqueous phase A3; and a fourth step, called "organic phase purification" in Figure 1, which aims to subject the organic phase from the "Dyextraction Dy" to a series of treatments to purify this phase for reuse in a subsequent cycle. Concretely, the "Extraction Dy" is carried out in the extractor 1 by bringing the aqueous phase Al entering this extractor several times in contact, in countercurrent, with the organic phase which comprises a diglycolamide (denoted DGA in FIG. ) in solution in an organic diluent. As previously indicated, the diglycolamide is chosen from lipophilic diglycolamides, that is to say whose total number of carbon atoms is at least 24 and, more particularly, from diglycolamides which correspond to the formula: (R2) NC (O) -CH2-O-CH2-C (O) -N (R3) R4 wherein R1 to IV are linear or branched alkyl groups each having at least 5 carbon atoms and more preferably at least 8 carbon atoms, preferably being given to diglycolamides in which R1 to IV represent alkyl groups identical to each other, comprising from 8 to 12 carbon atoms.
[0016] This diglycolamide is, for example, TODGA, TEHDGA or TdDDGA which is typically used at a concentration ranging from 0.05 to 0.4 mol / l, for example 0.2 mol / l. The organic phase may furthermore comprise, especially when the alkyl groups R 1 to IV of the diglycolamide comprise less than 12 carbon atoms, a phase modifier suitable for preventing the formation of a third phase, for example n-octanol (CH 3 ( CH2) 6CH2OH), in which case the latter is preferably not more than 10% by volume of the volume of the organic phase. As for the organic diluent, it is, for example, an aliphatic diluent such as n-dodecane, TPH or a kerosene such as Isane IP-185.
[0017] The organic phase emerging from the extractor 1, which is loaded with dysprosium, is directed to the extractor 2 devolved to "Pr + Nd wash + undesirable elements" while the aqueous phase exiting the extractor 1 (called "raffinate" in Figure 1) is directed to an aqueous effluent treatment unit of the method. The "Pr + Nd wash + undesirable elements" is carried out in extractor 2 by bringing the organic phase entering into this extractor several times in contact, countercurrently, with the aqueous phase A2 which comprises nitric acid at a temperature of concentration that is at most equal but, preferably, less than the nitric acid concentration of the aqueous phase Al, each contact being followed by separation of the aqueous and organic phases. Typically, the nitric acid concentration of the aqueous phase A2 is from 0.1 to 4 mol / L depending on the nitric acid concentration of the aqueous phase Al. The organic phase leaving the extractor 2 is directed towards the extractor 3 devolved to the "Dyextraction Dy" while the aqueous phase leaving the extractor 2 is returned to the extractor 1 where it joins the aqueous phase Al and is added to it.
[0018] The "Dyextraction Dy" is carried out in the extractor 3 by bringing the organic phase entering into this extractor several times in contact, countercurrently, with the aqueous phase A3 which comprises a nitric acid concentration ranging from 0.0001 to 0 , 01 mol / L, for example 0.001 mol / L, each contact being followed by separation of the aqueous and organic phases.
[0019] To facilitate the desextraction of dysprosium, the aqueous phase A3 may comprise, in addition to nitric acid, one or more rare earth complexing compounds in an aqueous medium such as a hydrophilic diglycolamide, that is to say the total number of of carbon atoms does not exceed 20, such as TMDGA, TEDGA or TPDGA, a polyaminocarboxylic acid such as HEDTA, NTA or DTPA, or a mono-, di- or tricarboxylic acid such as glycolic acid, malonic acid or mesoxalic acid.
[0020] In addition or alternatively, the extractor 3 can also be heated, typically at a temperature ranging from 40 to 55 ° C. At the end of the "Dyextraction Dy", an aqueous phase is obtained which contains only dysprosium as a metallic element, and an organic phase which is directed towards the extractor 7 devolved to the "Purification phase organic" to undergo a a series of treatments (acid washings, alkaline washings, complexing washes, etc.) suitable for ridding it of any degradation products, in particular hydrolysis products, and residual metal elements contained therein. EXAMPLE 2: Schematic diagram of a preferred embodiment of the second method of the invention Referring now to FIG. 2, which illustrates the principle of a preferred embodiment of the second method of the invention, FIG. invention, wherein this process is designed to treat, on an industrial scale, an aqueous phase Al acid similar to that treated in Example 1 above but to selectively recover not only dysprosium but also praseodymium and neodymium. In the present embodiment, the process comprises two cycles, namely: a first cycle which aims to selectively recover the dysprosium present in the aqueous phase A1 and a second cycle which aims at selectively recovering the praseodymium and the neodymium present in the raffinate of the first cycle.
[0021] The first cycle comprises: a first step, called "Extraction Dy" in Figure 2, which aims to extract dysprosium from the aqueous phase Al by means of a first organic phase, immiscible with water; a second stage, called "Pr + Nd wash + undesirable elements" in FIG. 2, which aims to wash the organic phase resulting from the "Dy extraction" by means of an aqueous phase A2 in order to remove from this organic phase the metallic elements other than dysprosium that may have been partially extracted during "Dy Extraction"; a third step, called "Dyextraction Dy" in Figure 2, which aims to extract dysprosium from the organic phase from "washing Pr + Nd + undesirable elements" by means of an aqueous phase A3; while the second cycle comprises: a first step, called "co-extraction Pr + Nd" in Figure 2, which aims to extract praseodymium and neodymium from the aqueous phase from the "Extraction Dy" by means of a second organic phase, immiscible with water; a second step, called "washing undesirable elements" in Figure 2, which aims to wash the organic phase from the "co-extraction Pr + Nd" with an aqueous phase A4 to remove the organic phase of the metal elements other than praseodymium and neodymium which may have been partially extracted during the 'Pr + Nd co-extraction'; and a third step, called "co-stripping Pr + Nd" in Figure 2, which aims to extract the praseodymium and neodymium from the organic phase of the "washing undesirable elements" by means of an aqueous phase A5. The first and second cycles further comprise a common step, referred to as "organic phase purification" in FIG. 2, which links them to each other and which aims at subjecting the organic phase formed by the joining of the organic phases. derived respectively from the "Dyextraction Dy" and "Co-stripping Pr + Nd" to a series of treatments to purify this phase for reuse, after division in two, in the first and second subsequent cycles. The stages "Extraction Dy", "Pr + Nd wash + undesirable elements", "Dyextraction Dy" and "Purification organic phase" are carried out, respectively in the extractors 1, 2, 3 and 7, in the same way as in the example 1.
[0022] On the other hand, unlike in Example 1, the aqueous phase exiting the extractor 1 is directed towards the extractor 4 dedicated to the "Co-extraction Pr + Nd" instead of being directed to a treatment unit aqueous effluents from the process. The "co-extraction Pr + Nd" is carried out by putting the aqueous phase entering the extractor 4 several times in contact, in countercurrent, with the second organic phase which has the same composition, both qualitative and quantitative, the first organic phase, each contacting being followed by separation of the aqueous and organic phases. An increase in the nitric acid concentration of the aqueous phase resulting from the "Extraction Dy" can be carried out, before the inlet or during the entry of this aqueous phase into the extractor 4, to favor the extraction of the praseodymium and neodymium by diglycolamide. The organic phase leaving the extractor 4, which is loaded with praseodymium and neodymium, is directed to the extractor 5 devoted to "washing undesirable elements" while the aqueous phase leaving the extractor 5 (called "raffinate" on the Figure 2) is directed to an aqueous effluent treatment unit of the process.
[0023] "Washing undesirable elements" is carried out in the extractor 5 by bringing the organic phase entering into this extractor several times in contact, countercurrently, with the aqueous phase A4 which comprises nitric acid at a concentration which is more equal but, preferably, lower than the nitric acid concentration of the aqueous phase from the "Extraction Dy", each contact being followed by separation of the aqueous and organic phases. Typically, the nitric acid concentration of the aqueous phase A4 ranges from 0.1 to 4 mol / L depending on the nitric acid concentration of the aqueous phase resulting from the "Dy extraction". The organic phase leaving the extractor 5 is directed towards the extractor 6 devolved to the "Pr + Nd Desextraction" while the aqueous phase leaving the extractor 5 is returned to the extractor 4 where it joins the aqueous phase of "Extraction Dy" and adds to it. The "Pr + Nd Desextraction" is carried out in the extractor 6 by bringing the organic phase entering into this extractor several times in contact, countercurrently, with the aqueous phase A5 which comprises a nitric acid concentration ranging from 0.0001 at 0.1 mol / L, for example 0.001 mol / L, each contact being followed by separation of the aqueous and organic phases. To promote the desextraction of praseodymium and neodymium, the aqueous phase A5 may comprise, in addition to nitric acid, one or more rare earth complexing agents of the same type as those likely to be used for the "Dyextraction Dy". In addition or alternatively, the extractor 6 can be heated, typically at a temperature ranging from 40 to 55 ° C. At the end of the "Pr + Nd Desextraction", an aqueous phase is obtained which contains only praseodymium and neodymium as metallic elements, and an organic phase which joins the organic phase resulting from the "Dyextraction Dy" and is directed, together with the latter, to Extractor 7, which is dedicated to "Purification of organic phase". EXAMPLE 3: Experimental Validation of the Invention In the following tests, the concentrations of the various metallic elements in the solutions or aqueous phases were all measured by plasma torch atomic emission spectrometry, also known as ICPAES. The concentrations of the metallic elements in the organic phases were estimated after desextracting these elements in a strongly complexing aqueous phase (oxalic acid = 0.5 mol / L, TEDGA = 0.2 mol / L, HNO3 = 1 mol / L; volume ratio 0 / A = 1/5, stirring time = 10 minutes, temperature = 25 ° C.) and after having measured the concentrations of said elements in the aqueous phase obtained after this extraction. Moreover, the coefficients of distribution and the separation factors have been determined in accordance with the conventions of the field of liquid-liquid extractions, namely that: the distribution coefficient of a metal element M, denoted Dm, between two phases, respectively organic and aqueous, is equal to: [M] org. Dm = with: [M] org. = concentration of the metal element in the organic phase at the equilibrium of extraction (in g / L); and [M] aq. = concentration of the metallic element in the aqueous phase at the equilibrium of extraction (in g / L); [M] aq - the separation factor between two metal elements M1 and M2, denoted FSm1lm2, is equal to: FSM1 / M2 = with: Dm '= distribution coefficient of the metal element M1; and Dm2 = distribution coefficient of the metal element M2. 1) Extraction tests carried out on synthetic nitric aqueous phases comprising boron, iron, praseodymium, neodymium and dysprosium: extraction tests are carried out in tubes, using: as organic phases: phases comprising either 0.2 mol / L of TODGA in n-dodecane, ie 0.2 mol / L of TODGA and 5% (v / v) of n-octanol (as a phase modifier) in n-dodecane; and as aqueous phases: phases obtained by dissolving boric acid and hydrated nitrates of iron, praseodymium, neodymium and dysprosium in an aqueous solution of nitric acid; all these phases have the concentrations of boron, iron, praseodymium, neodymium and dysprosium which are indicated in Table I below but their concentration in nitric acid ranges from 0.1 to 2.6 mol / l. Table I Elements Concentrations (g / L) B 1,3 Fe 43,7 Pr 1,1 Nd 10,3 Dy 1,0 Each organic phase is brought into contact, with stirring, with one of the aqueous phases, volume to volume, for 30 minutes at 25 ° C, and then these phases are separated from each other after centrifugation. Dmi Dm2 The results of these tests show that there is no formation of a third phase when the organic phase used for extraction comprises n-octanol, irrespective of the acidity of the aqueous phase. tested. On the other hand, a third phase is formed in the absence of n-octanol in the organic phase.
[0024] As can be seen in FIG. 3A, which illustrates the coefficients of distribution of the various metallic elements as a function of the nitric acid concentration of the aqueous phases tested, a quantitative extraction of dysprosium (DDy> 100) is obtained for all of these phases. Iron, which is the most abundant element in the aqueous phases, is very little extracted (DFe <0.01). Moreover, as shown in FIG. 3B, which illustrates the separation factors between the dysprosium and the other metallic elements as a function of the nitric acid concentration of the aqueous phases tested, the separation of the dysprosium with respect to the iron and the boron is excellent since the separation factors FSDy / Fe and FSDy / B are greater than 10,000 and 750, respectively. In addition, separation factors FSDyiNd and FSDy / pr greater than 10 are obtained regardless of the acidity of the phases. aqueous tests. These results show that it is therefore possible to easily recover dysprosium from an acidic aqueous phase comprising high concentrations of iron, boron, neodymium and praseodymium using a diglycolamide as extractant. 2) Recovery of dysprosium, neodymium and praseodymium from an aqueous phase resulting from the dissolution of a permanent magnet powder NdFeB in a 5.15 M nitric medium: an aqueous phase is prepared by dissolving a powder permanent NdFeB magnets discarded in a 5.15 M nitric medium supplemented with H 2 O 2 (1% by volume) as described in reference [2] above, the permanent magnet powder having itself been obtained by demagnetizing these magnets by means of a heat treatment in an oven (200 ° C - 5 hours), grinding then hydriding treatmentdéshydruration.
[0025] The metal element concentrations of the aqueous phase thus obtained are shown in Table II below. Table II Elements Concentrations (g / L) B 0.4 Fe 36 Co 0.2 Ni 0.8 Cu 0.5 Pr 2.9 Nd 11 Dy 0.2 * Extraction test: The previously obtained aqueous phase is subject to to an extraction test which is carried out using as organic phase, a phase comprising 0.2 mol / l of TODGA and 5% (v / v) of n-octanol in n-dodecane. To do this, the aqueous phase is brought into contact, with stirring, with this organic phase in a volume ratio 0 / A of 1, for 30 minutes at 25 ° C., and then these phases are separated from each other by decanting. Table III below shows the coefficients of distribution of the various metallic elements, the FSDyim and FSprim separation factors and the concentration of the aqueous phase in equilibrium nitric acid obtained for this extraction test.
[0026] Table III Elements Dm FSDy / M FSPr / M [FIN03] eq. B 0.06 383 8.3 476M Fe <0.004> 5 750> 125 Co <0.02> 1150> 25 Ni <0005> 4600> 100 Cu <0.04> 575> 12.5 Pr 0.5 46 1.0 Nd 1.3 18 0.4 Dy 23 1.0 0.02 This table confirms the quantitative extraction of dysprosium (DDy = 23) previously obtained in the extraction tests carried out in point 1) above. on synthetic nitric aqueous phases. It also confirms the high selectivity that TODGA exhibits for dysprosium compared with other metallic elements, including light rare earths, since the separation factors FSDy / pr and FSDyiNd are respectively 46 and 18. Finally, it shows that it is possible to effectively separate, after having extracted the dysprosium from the aqueous phase, the Pr + Nd didymium from the other metallic elements still present in this aqueous phase by using the same organic phase as that used to extract the dysprosium. * Desextraction tests: The organic phase obtained at the end of the extraction test above is subjected to a series of desextraction tests that are carried out using as aqueous phase, an aqueous solution of nitric acid at 0.001. mol / L (pH 3). For this purpose, aliquots of the aqueous phase are brought into contact a first time (hereinafter "contact 1"), with stirring, with aliquots of the organic phase in a volume ratio 0 / A of 1/5, while 30 minutes at 25 ° C, 40 ° C or 55 ° C, then these aliquots are separated from each other by decantation. The concentrations of metallic elements as well as the pH of the aliquots of aqueous phase thus separated are measured, after which these aliquots are brought back into contact (hereinafter "contact 2") with aliquots of the organic phase under the same conditions as previously. Table IV below presents the distribution coefficients of dysprosium, neodymium and praseodymium obtained for these desextraction tests. Also shown in this table are the pH values of the aliquots of the aqueous phase after each of the contacts 1 and 2. Table IV Dm Desextraction at 25 ° C Desextraction at 40 ° C Desextraction at 55 ° C Contact 1 Contact 2 Contact 1 Contact 2 Contact 1 Contact 2 Elements Dy 20.2 0.9 3.8 0.65 0.73 0.86 Nd 0.60 0.15 0.13 <0.1 0.05 <0.05 Pr 0.36 <0 , 3 0.10 <0.1 0.05 <0.05 pH after 1.2 3.0 1.2 3.0 1.2 3.0 contact This table shows that at 25 ° C, the dysprosium desextraction is effective only at the second contact (DDy <1) when the pH is greater than 1 (pH 3) .11 also shows that it is possible to improve the dysprosium desextraction at first contact by carrying out this desextraction at a higher temperature. Thus, at 55 ° C, a distribution coefficient of less than 1 (DDy = 0.7) is obtained for dysprosium from the first contact at a pH of 1.16 at equilibrium.
[0027] On the other hand, a good desextraction of the Pr + Nd didyme is observed from the first contact and this, whatever the temperature, this de-extraction being however improved by an increase of the temperature. 3) Recovery of the dysprosium from an aqueous phase resulting from the dissolution of a permanent magnet powder NdFeB in a 0.4 M nitric medium: An aqueous phase is prepared by dissolving a powder of NdFeB permanent magnets rejected in 0.4M nitric medium in the same manner as in 2) above, except that the aqueous solution used to dissolve the powder resulting from the hydriding-dehydriding treatment is an aqueous solution of nitric acid 0 , 4M. The metal element concentrations of the aqueous phase thus obtained are shown in Table V below. Table V Elements Concentrations (g / L) B 0.4 Fe 32 Co 0.2 Ni 0.08 Cu 0.1 Pr 2.7 Nd 11 Dy 0.2 Then, from this aqueous phase, a test is carried out extraction followed by a series of desextraction tests under the same conditions as those described in point 2) above. Table VI below presents the coefficients of distribution of the various metallic elements, the FSDyim and FSprim separation factors and the concentration of the aqueous phase in equilibrium nitric acid obtained for the extraction test while Table VII below presents the coefficients of distribution of dysprosium, neodymium and praseodymium obtained for the desextraction tests. Also shown in this table are the pH values of the aliquots of aqueous solution after contact 1.
[0028] Table VI Elements Dm FSDy / M FSPr / M [HNO3] eq. B 0.12 225 14 0.34 M Fe <0.002> 3500> 857 Co <0.02> 1350> 85 Ni <005> 540> 34 Cu <0.17 158 10 Pr 1.7 15.9 1 , 0 Nd 2.1 12.8 0.8 Dy 27 1.0 0.06 Table VII Dm Desextraction at 25 ° C Desextraction at 40 ° C Desextraction at 55 ° C Contact 1 Contact 1 Contact 1 Elements Dy 5.4 0 , 76 0.23 Nd 0.17 0.05 0.02 Pr 0.11 0.04 0.02 pH after contact 2.0 2.0 2.0 Table VI shows that it is also possible to extract and to effectively separate the dysprosium on the one hand, then the Pr + Nd didyme on the other hand, other metallic elements (considering the separation factors FSpriélément as dimensioning for the separation) from a water phase of much lower concentration to that of the aqueous phase used in point 2) above (0.4 M versus 5.15 M).
[0029] However, the selectivity of TODGA for dysprosium compared to praseodymium and neodymium appears to be lower than that observed for the aqueous phase used in point 2) above, so that it seems preferable that the solution resulting from the dissolution of A permanent magnet powder NdFeB from which the dysprosium is extracted has a nitric acid concentration significantly greater than 0.4 M.
[0030] Table VII confirms that it is possible to extract the rare earths comprising TODGA as extractant by means of a very dilute aqueous nitric phase (pH 3) and that this desextraction is improved by an increase in temperature. 4) Influence of the nature of the diglycolamide alkyl chains Extraction tests are carried out in tubes, using: as organic phases: phases comprising 0.2 worlds one of the following diglycolamides: TODGA, TEHDGA or TdDDGA, with or without 5% (v / v) of noctanol (as a phase modifier) in n-dodecane; and as aqueous phases: the aqueous phases resulting from the dissolution of a permanent magnet powder NdFeB in a 5.15 M and 0.4 M nitric medium, respectively prepared in points 2) and 3) above. These extraction tests are carried out under the same conditions as those described in point 2) above.
[0031] Table VIII below presents the distribution coefficients of dysprosium, neodymium, praseodymium, iron and boron as well as the pH values presented by the aqueous phases at equilibrium.
[0032] Table VIII Organic phases TODGA TEHDGA TdDDGA 5% 0% 5% 0% 5% 0% octanol octanol octanol octanol octanol octanol Phase DDy 23 3rd 3rd 3rd 24.9 25.3 aqueous phase phase phase 5.15 M DNd 1.4 3rd 3rd 3rd 1.65 1.65 phase phase phase Dp, 0.5 3rd 3rd 3rd 1.61 1.62 phase phase phase DFe <0.004 3rd 3rd 3rd 0.002 0.002 phase phase phase DB 0.06 3rd 3rd 3rd 0.09 0 , 03 phase phase phase [1-1NO3] eq (M) 4.76 3rd 3rd 3rd 4.71 4.88 phase phase phase Phase DDy 27 3rd 3.08 3rd 29.8 30.1 aqueous phase phase 0.4 M DNd 2.4 3rd 3.90 3rd 2.42 2.55 phase phase Dp, 1.7 3rd 3.54 3rd 1.67 2.02 phase phase DFe <0.002 3rd 0.001 3rd 0.001 <0.001 phase phase DB 0.08 3rd 0.13 3rd 0.17 0.04 phase phase [1-1NO3] eq (M) 0.34 3rd 0.33 3rd 0.31 0.33 phase phase This table shows first of all that a third phase does not form when using TdDDGA as an extractant, even in the absence of a phase modifier in the organic phase. On the other hand, the use of TODGA and TEHDGA leads, in the absence of a phase modifier, to the formation of a third phase. A third phase is also observed with TEHDGA with 5% n-octanol in the case of the aqueous phase with higher acidity (HNO3 5.15 M). As already illustrated in the literature, the loading capacity of the TdDDGA is greater than that of the TODGA and TEHDGA extractants. The use of TdDDGA would therefore have the advantage of avoiding the use of a phase modifier in the implementation of the method of the invention. This table also shows that, in the case of TdDDGA, the distribution coefficients of dysprosium, neodymium, praseodymium, iron and boron are comparable between the tests carried out with and without n-octanol in the organic phases, which highlight the absence of impact of this phase modifier on the distribution coefficients of the metal elements. The distribution coefficients obtained for the same metal element with TODGA and TdDDGA are very close, regardless of the acidity of the aqueous phase. Rare earths are quantitatively extracted with TdDDGA with excellent selectivity towards other metallic elements. TdDDGA has a slightly higher extracting power than TODGA (especially in the case of praseodymium) whereas, in the case of the lower acid aqueous phase (0.4 M HNO3), TEHDGA has a much higher extracting power. lower than the other two diglycolamides and leads to lower rare-earth selectivity (especially Dy / Nd). These results confirm the excellent ability of TODGA, TEHDGA and TdDDGA to separate rare earths from other metallic elements and, in particular, from iron. TdDDGA appears to be particularly suitable for recovering dysprosium, then praseodymium and neodymium, from an acidic aqueous dissolution solution of a permanent magnet powder because of its high extracting power but also because it offers the possibility of avoiding the use of a phase modifier. EXAMPLE 4: Detailed diagram of an example of the preferred embodiment of the second method of the invention A mathematical model for the extraction of rare earths and iron from an aqueous solution resulting from the dissolution of a powder of NdFeB permanent magnets in nitric medium by the preferred embodiment of the second method of the invention illustrated in Figure 2, using an organic phase comprising TODGA as an extractant, and n-octanol as a modifier of phase, has been developed.
[0033] The model accounts for the distribution of the species of interest, here the rare earths, between aqueous phase and organic phase. To optimize the reliability of the model, it is based on a chemical description of the phenomena. On the one hand, the coefficients of activity in the aqueous phase are taken into account so that the range of validity of the model is as wide as possible in terms of concentration of nitric acid in particular, and, on the other hand, the constants of the model are determined by numerical optimization of the experimental data. In this case, the model was developed from the experimental data obtained in points 1) to 3) of Example 3 above with an organic phase comprising 0.2 mol / l of TODGA and 5% (v / v) n-octanol in n-dodecane. It was necessary to model the behavior of nitric acid because the extraction of this acid competes with that of rare earths, then to propose, from the optimization of the experimental data, rare earth complexes. The complexes of type [TR (NO3) 3, TODGAn1 where TR denotes Dy, Pr or Nd and n varies from 1 to 3 are selected. For each species transferred between an aqueous phase and an organic phase, a classical mathematical equation in chemistry has been associated. For nitric acid and rare earths (TR), the mathematical equations are: PiNO3, TODGAnj] Kn =, where n varies from 1 to 3; WHN0 3. [HNO3]) 111. [TODGA] RTR (No,) ,, T0DGAni] K'n = where TR = Dy, Pr or Nd and m varies from 1 to 3. YTKNO3) 3- [TR (NO3) 3] - [TODGA] In these equations, YTR (NO3) 3 and YmN.103 denote the activity coefficients of the rare earth TR and nitric acid respectively and the parameters Kn and are constants thereof. These constants have been optimized to best reproduce the experimental distribution coefficients. The comparison of the experimental data and the data calculated by the model is presented in Table IX below.
[0034] Table IX [1-11 eq. DFe DFe DDy DDy DNd DNd DPr DPr (M) (exp.) (Calc.) (Exp.) (Calc.) (Exp.) (Calc.) (Exp.) (Calc.) Phases 0.109 0.0041 0, 0038 119 104 7.6 4.5 3.4 4.1 Aqueous synthetic nitrite 0.173 0.0032 0.0037 121 92 4.9 3.5 3.1 3.1 0.418 0.0033 0.0033 115 102 4, 6 3.3 2.6 2.8 0.761 0.0031 0.0030 114 116 4.1 3.2 2.1 2.5 1.49 0.0024 0.0027 105 132 3.6 3.2 1, 4 2.0 2.23 0.0019 0.0029 104 108 3.4 3.3 1.2 1.7 Aqueous phases resulting from the dissolution of a magnesium powder in a nitric medium 0.34 0.0014 0 , 0014 37 43 2.3 1.8 1.9 1.6 2.57 0.0018 0.0030 197 139 13.4 3.3 6.8 2.1 4.76 0.0036 0.0037 34 32 1.5 1.2 0.6 0.5 5.04 0.0037 0.0034 32 32 2.4 1.2 0.9 0.5 The mathematical model developed in this way led to the detailed scheme that is illustrated in FIGS. 4A and 4B, in which FIG. 4A corresponds to the first cycle devoted to the selective recovery of dysprosium while FIG. 4B corresponds to the second cycle devoted to the selective recovery of praseodymium and neodymium. In these figures, however, is not shown the common step in the two cycles of purification of the organic phase. According to this scheme, a 7-stage extractor would be necessary, in the first cycle, to extract more than 99.99% of the dysprosium from the aqueous phase Al ("Extraction Dy") whereas a extractor also with 7 stages would make it possible to separate dysprosium of other rare earths and other metallic elements ("Pr + Nd wash + undesirable element") and reach a purity of dysprosium of the order of 99.99%. A 5-stage extractor would be necessary to quantitatively extract the dysprosium from the organic phase resulting from the "Pr + Nd wash + undesirable elements" ("Dyextraction Dy") but, in view of the results presented in Tables IV and VII above, this The number of stages could be reduced if the extractor was heated to 40-55 ° C. In the second cycle, a 7-stage extractor would be required to coextract more than 99.99% of the praseodymium and neodymium present in the aqueous phase from the "Extraction Dy" ("Co-extraction Pr + Nd"). a 3-stage extractor would be sufficient to separate the Nd + Pr mixture from the other metal elements ("washing undesirable elements") and to achieve a purity of the Pr + Nd-plus-I-dyme greater than 99.99%. Since the extraction of neodymium and praseodymium from the organic phase proved to be easier than that of dysprosium, a 3-stage extractor should be sufficient to recover quantitatively the purified Pr + Nd didymium in the aqueous phase ("Co-desextraction Pr + Nd "). The invention is not limited to the embodiments described in the examples above. In particular, it is quite possible to adapt the scheme shown in FIGS. 4A and 4B, which has been defined to treat an aqueous phase Al comprising 5 mol / L of nitric acid, to the treatment of aqueous phases comprising another strong acid and / or having a different acidity and, in particular, a much lower acidity such as, for example, 0.4 mol / L of nitric acid. REFERENCES CITED [1] H. Narita and M. Tanaka, Solvent Extraction Research and Development, Japan, 2013, 20, 115-121 [2] International Application WO 2014/064597

权利要求:
Claims (22)
[0001]
REVENDICATIONS1. Process for the selective recovery of at least one rare earth TR1, of atomic number at least equal to 62, from an aqueous acid phase Al resulting from the treatment of used or discarded permanent magnets and comprising one or more earth (s) rare (s) TR1, transition metals and a strong acid concentration of 0.2 to 6 mol / L, which process comprises: a) extraction of the rare earth (s) TR1 of the aqueous phase Al, by contacting the aqueous phase Al with a water-immiscible organic phase, which comprises a diglycolamide having a total number of carbon atoms of at least 24 as extractant, in a organic diluent, then separation of the aqueous and organic phases; 131) washing the organic phase obtained at the end of step a1), by contacting the organic phase with an aqueous acidic phase A2, which comprises a strong acid identical to the strong acid of the aqueous phase Al, at a concentration at most equal to the strong acid concentration of the aqueous phase Al, and then separation of the aqueous and organic phases; and ci) the desextraction of the rare earth (s) TR1 from the organic phase obtained at the end of step 131), by contacting the organic phase with an aqueous acidic phase A3 which has a pH at least equal to 1, then separation of the aqueous and organic phases.
[0002]
The process according to claim 1, wherein the diglycolamide has the formula: R1 (R2) NC (O) -CH2-O-CH2-C (O) -N (R3) R4 wherein R1 to R4, which may be identical or different, represent alkyl groups, linear or branched, each comprising at least 5 carbon atoms and, more preferably, at least 8 carbon atoms.
[0003]
3. A process according to claim 1 or claim 2, wherein the diglycolamide is N, N, AP1Ar-tetraocty1-3-oxapentanediamide, N, N, AP1Ar-tetra (2-ethylhexyl) -3-oxapentanediamide, N , N, AP, Ar-tetradecyl-3-oxapentanediamide or N, N, AP, Ar-tetradodecyl-3-oxapentanediamide.
[0004]
4. Method according to any one of claims 1 to 3, wherein the organic phase comprises from 0.05 to 0.4 mol / L of diglycolamide.
[0005]
The method of any one of claims 1 to 4, wherein the organic phase further comprises a phase modifier.
[0006]
6. Process according to any one of claims 1 to 5, wherein the aqueous phase A2 comprises from 0.1 to 4 mol / L of strong acid.
[0007]
The process according to any one of claims 1 to 6, wherein the aqueous phase A3 comprises from 0.0001 to 0.1 mol / L of a strong acid or from 0.05 to 1 mol / L of a weak acid.
[0008]
8. Process according to any one of claims 1 to 7, wherein the strong acid is nitric acid.
[0009]
9. Process according to any one of claims 1 to 8, which further comprises a purification of the organic phase from step ci).
[0010]
10. Process according to any one of claims 1 to 9, wherein the aqueous phase Al is derived from the treatment of permanent magnets Neodymium-Iron-Boron in a strong acid and the rare earth TR1 is dysprosium.
[0011]
11. Process for the selective recovery of at least one rare earth TR1, of atomic number at least equal to 62, and of at least one rare earth TR2, of atomic number at most equal to 61, from an aqueous phase Al acid resulting from the treatment of used or discarded permanent magnets and comprising one or more rare earth (s) TR1 and one or more rare earth (s) TR2, transition metals and a strong acid concentration ranging from 0.2 to 6 mol / L, which process comprises: - recovering the rare earth (s) TR1 present in the aqueous phase Al, which recovery comprises the following steps: ) extracting the rare earth (s) TR1 from the aqueous phase Al, by contacting the aqueous phase Al with a first organic phase immiscible with water, which comprises a diglycolamide having a total number of carbon atoms of at least 24 as extractant, in an organic diluent, and then separation of the aqueous and organic ; 131) washing the organic phase obtained at the end of step a1), by contacting the organic phase with an aqueous acidic phase A2, which comprises a strong acid identical to the strong acid of the aqueous phase Al, at a concentration at most equal to the strong acid concentration of the aqueous phase Al, and then separation of the aqueous and organic phases; and ci) the desextraction of the rare earth (s) TR1 from the organic phase obtained at the end of step 131), by contacting the organic phase with an aqueous acidic phase A3 which has a pH of at least 1, followed by separation of the aqueous and organic phases; then - the recovery of the rare earth (s) TR2 present (s) in the aqueous phase obtained at the end of step ai), which recovery comprises the following steps: az) extraction of the rare earth (s) TR2 of the aqueous phase obtained after step a1), by contacting the aqueous phase with a second organic phase, immiscible with water which comprises the same extractant as the first organic phase, in an organic diluent, then separation of the aqueous and organic phases; bz) washing the organic phase obtained at the end of step az), by contacting the organic phase with an aqueous acid phase A4, which comprises a strong acid identical to the strong acid of the aqueous phase Al, at a concentration at most equal to the strong acid concentration of the aqueous phase from step a1), and then separation of the aqueous and organic phases; and c2) the desextraction of the rare earth (s) TR2 from the organic phase obtained at the end of step b2), by contacting the organic phase with an aqueous acidic phase A5 which has a pH at least equal to 1, then separation of the aqueous and organic phases.
[0012]
The process according to claim 11, wherein the diglycolamide has the formula: R1 (R2) NC (O) -CH2-O-CH2-C (O) -N (R3) R4 wherein R1 to R4, which may be identical or different, represent alkyl groups, linear or branched, comprising at least 5 carbon atoms and more preferably still at least 8 carbon atoms.
[0013]
The process according to claim 11 or claim 12, wherein the diglycolamide is N, N, AP, Ar-tetraoctyl-3-oxapentanediamide, N, N, AP, Ar-tetra (2-ethylhexyl) -3- oxapentanediamide, N, N, AP, Ar-tetradecyl-3-oxapentanediamide or N, N, AP, Ar-tetradodecyl-3-oxapentanediamide.
[0014]
The process according to any one of claims 11 to 13, wherein each of the first and second organic phases comprises from 0.05 to 0.4 mol / L of diglycolamide.
[0015]
The method of any one of claims 11 to 14, wherein each of the first and second organic phases further comprises a phase modifier.
[0016]
16. A process according to any one of claims 11 to 15, wherein each of the aqueous phases A2 and A4 comprises from 0.1 to 4 mol / L of strong acid.
[0017]
17. A process according to any one of claims 11 to 16, wherein one and / or other of aqueous phases A3 and A5 comprises (include) from 0.0001 to 0.1 mol / L of an acid or 0.05 to 1 mol / L of a weak acid.
[0018]
18. A process according to any one of claims 11 to 17, wherein the strong acid is nitric acid.
[0019]
19. The method of any one of claims 11 to 18, which further comprises a purification of the organic phases from steps ci) and c2). 10
[0020]
20. Process according to any one of claims 11 to 19, which comprises a first and a second cycle, the first cycle being formed by steps a1), 131), ci) and the purification of the organic phase resulting from step ci), and the second cycle being formed by steps az), 132), cz) and purifying the organic phase from step c2).
[0021]
The method of any one of claims 11 to 19, which comprises a first and a second cycle, the first cycle comprising steps a1, 131 and ci), the second cycle comprising steps az), bz) and c2), the first and second cycles further comprising the purification of an organic phase formed by the joining of the organic phases resulting from steps ci) and cz) and then the division of the organic phase thus purified into said first and second organic phases .
[0022]
22. A process according to any one of claims 11 to 21, wherein the aqueous phase A1 is derived from the treatment of Neodymium-Fer-Boron permanent magnets in a strong acid, the rare earth TR1 is dysprosium and rare earths. TR2 are praseodymium and neodymium.

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同族专利:

公开号 | 公开日

US10464819B2|2019-11-05|

FR3026099B1|2017-06-02|

EP3197833A1|2017-08-02|

US20170291827A1|2017-10-12|

JP6650443B2|2020-02-19|

JP2017531097A|2017-10-19|

EP3197833B1|2019-05-08|

WO2016046179A1|2016-03-31|

引用文献:

公开号 | 申请日 | 公开日 | 申请人 | 专利标题

FR2810679A1|2000-06-21|2001-12-28|Japan Atomic Energy Res Inst|Extraction of americium, curium and lanthanides from strongly acidic solutions using a tridentate complexing agent based on diglycol amide in an organic solvent|

FR2907346A1|2006-10-23|2008-04-25|Commissariat Energie Atomique|Separating actinide groups in strong acidic aqueous phase, comprises coextraction of actinides, lanthanides or yttrium and optionally few other fission products and extraction of actinides|

EP2592068A1|2010-07-05|2013-05-15|Shin-Etsu Chemical Co., Ltd.|Method for synthesizing rare earth metal extractant|

FR2997095A1|2012-10-24|2014-04-25|Commissariat Energie Atomique|PROCESS FOR ISOLATING RARE EARTHS AND / OR APPARENT METAL ELEMENT CONTAINED IN THE MAGNETIC PHASE OF PERMANENT MAGNETS.|

FR3080114B1|2018-04-13|2021-10-08|Commissariat Energie Atomique|AMPHIPHILIC DISSYMETRIC DIGLYCOLAMIDES AND THEIR USE TO EXTRACT RARE EARTHS FROM ACIDIC AQUEOUS SOLUTIONS|

WO2019204554A1|2018-04-19|2019-10-24|Warner Babcock Institute For Green Chemistry, Llc|Methods of rare earth metal recovery from electronic waste|

FR3086302B1|2018-09-26|2020-12-25|Commissariat Energie Atomique|USE OF A SYNERGIC MIXTURE OF EXTRACTANTS TO EXTRACT RARE EARTHS FROM AN AQUEOUS MEDIUM CONTAINING PHOSPHORIC ACID|

KR102067606B1|2018-12-20|2020-01-17|전남대학교산학협력단|A method for separation and recovery of Nd and Dy from nitrate leach solution of spent mobile phone camera module|

CN112517602B|2020-11-12|2022-02-01|北京工业大学|Pretreatment method for recycling neodymium iron boron waste with adhesive tape oil sludge|

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优先权:

申请号 | 申请日 | 专利标题

FR1459023A|FR3026099B1|2014-09-24|2014-09-24|METHODS FOR SELECTIVE RECOVERY OF RARE EARTHS IN AQUEOUS ACID PHASES RESULTING FROM THE TREATMENT OF PERMANENT MAGNETS USED OR REBUIDED|FR1459023A| FR3026099B1|2014-09-24|2014-09-24|METHODS FOR SELECTIVE RECOVERY OF RARE EARTHS IN AQUEOUS ACID PHASES RESULTING FROM THE TREATMENT OF PERMANENT MAGNETS USED OR REBUIDED|

PCT/EP2015/071679| WO2016046179A1|2014-09-24|2015-09-22|Processes for selective recovery of rare earth metals present in acidic aqueous phases resulting from the treatment of spent or scrapped permanent magnets|

US15/511,926| US10464819B2|2014-09-24|2015-09-22|Processes for selective recovery of rare earth metals present in acidic aqueous phases resulting from the treatment of spent or scrapped permanent magnets|

EP15771557.4A| EP3197833B1|2014-09-24|2015-09-22|Processes for selective recovery of rare earth metals present in acidic aqueous phases resulting from the treatment of spent or scrapped permanent magnets|

JP2017516072A| JP6650443B2|2014-09-24|2015-09-22|Method for the selective recovery of rare earth metals present in an acidic aqueous phase resulting from the treatment of used or discarded permanent magnets|

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