USE OF LIPOPHILIC DERIVATIVES OF AMINOPOLYCARBOXYL ACIDS FOR THE EXTRACTION OF RARE EARTHS FROM AN ACID AQUEOUS SOLUTION

Abstract

The invention relates to the use of a lipophilic derivative of an aminopolycarboxylic acid as an extractant for extracting at least one rare earth element from an acidic aqueous solution. Applications: production of rare earth elements from concentrates derived from urban ores and, in particular, from concentrates of waste electrical and electronic equipment such as used or discarded NdFeB permanent magnets; production of rare earth elements from concentrates derived from natural ores or from concentrates derived from natural ore residues.

Description

Title of the invention: Use of lipophilic derivatives of amino-polycarboxylic acids for the extraction of rare earths from an acidic aqueous solution technical field

[0001] The invention relates to the field of extraction and recovery of rare earths present in acidic aqueous solutions, with a view to recycling these rare earths.

[0002] More specifically, the invention relates to the use of a lipophilic derivative of an aminopolycarboxylic acid as an extractant, to extract one or more rare earths from an acidic aqueous solution.

[0003] The invention finds applications in particular in the production of rare earths from concentrates from "urban ores", that is to say from "mines" made up of industrial and domestic waste including rare earths and, in particular, in the recycling of rare earths present in waste electrical and electronic equipment (also called "WEEE" or "D3E").

[0004] More particularly, the invention finds application in the recycling of rare earths contained in used or discarded permanent magnets, and, in particular, in Neodymium-Iron-Boron (or NdFeB) type permanent magnets.

[0005] However, it can also be used to produce rare earths from concentrates derived from natural ores such as monazites, bastnaesites, apatites or xenotimes, or from concentrates derived from residues of natural ores such as, for example, tin slags. Prior art

[0006] The particular physical and chemical properties of rare earths (scandium, yttrium and lanthanides) currently make them indispensable chemical elements in many industrial fields: glass and ceramics industries, catalysis, metallurgy, manufacture of permanent magnets, optical devices, phosphors etc.

[0007] Rare earths are therefore among the so-called "technological" metals whose supply is strategic.

[0008] Global demand for rare earths is constantly growing and is estimated to increase by 50% over the next ten years. However, as the number of rare earth producing countries remains limited – with China currently dominating global rare earth production – there is a significant risk of a disruption in the supply of rare earths in the long term, hence the need to optimize all the ways in which they can be produced.

[0009] Recycling rare earth elements present in used materials is increasingly preferred. Recycling makes it possible to reconcile reducing supply risks with the environmental challenges associated with mining activities.

[0010] One of the largest markets, in terms of both volume and market value, for rare earth recycling concerns NdFeB permanent magnets found in a number of WEEE (Waste Electrical and Electronic Equipment) items (computer hard drives, audio and video speakers, magnetic devices, etc.). This resource for rare earth recycling has the advantage of containing significant and valuable rare earth elements, typically around 30% by mass. The composition of NdFeB permanent magnets varies depending on the application and the manufacturer, but they typically contain highly valuable heavy rare earth elements (dysprosium and, to a lesser extent, gadolinium and terbium) as well as light rare earth elements (notably neodymium and praseodymium).

[0011] The hydrometallurgical route, based on the liquid-liquid extraction technique, is commonly considered one of the most commercially suitable routes for recovering rare earths from the environment in which they are found.

[0012] Hydrometallurgical processes, which are currently used industrially to recover rare earths from an acidic aqueous solution, preferentially employ organophosphorus extractants such as phosphoric acids, phosphonic acids, phosphinic acids, carboxylic acids and alkyl phosphates. These include, for example, di-2-ethylhexylphosphoric acid (or HDEHP), 2-ethylhexylphosphonic acid (or HEH[EHP]), bis(trimethyl-2,4,4-pentyl)phosphinic acid (or CyanexTM 272), neodecanoic acid (or VersaticTM 10) and tri-n-butyl phosphate (or TBP).

[0013] The use of other types of extractants has been proposed in recent years such as N,N-dibutylacetamide (see European patent application 3,323,899, hereinafter reference [1]), lipophilic symmetric diglycolamides such as N,N,N',N'-tetraoctyl-3-oxapentanediamide (or TODGA) (see international application PCT WO 2016 / 046179, hereinafter reference [2]) and amphiphilic asymmetric diglycolamides (see international application PCT WO 2019 / 197792, hereinafter reference [3]).

[0014] Furthermore, the idea of ​​developing lipophilic derivatives of aminopolycarboxylic acids emerged in the mid-1970s and then spread in the following years, primarily for the purpose of providing compounds for medical imaging. Contrast agents for magnetic resonance imaging were thus proposed, comprising a paramagnetic ion, for example Mn2+, complexed with a lipophilic derivative of ethylenediaminetetraacetic acid (or EDTA) in U.S. patent 5,762,910, hereinafter referred to [4], and by a lipophilic derivative of trans-l,2-diaminocyclohexanetetraacetic acid (or CyDTA) in international application PCT WO 2016 / 135523, hereinafter referred to [5].

[0015] The use of lipophilic derivatives of EDTA, incorporated in a polymer membrane, has also been proposed for the extraction of alkaline earth metals, calcium and magnesium in particular, by Eme et al., Helv. Chim. Acta 1980, 63(8), 2264-2270, hereinafter reference [6].

[0016] Finally, it was proposed in US patent 8,785,691, hereinafter referred to as [7], to use lipophilic derivatives of EDTA, in solution in 1-octanol, to extract, by liquid-liquid extraction, Tamericium(III) and Curium(III) selectively from lanthanides(III) of a raffinate resulting from the implementation of the PUREX spent fuel reprocessing method. Thus, according to this reference, the lanthanides, which represent 15 of the 17 rare earths, would not be extractable, or only very weakly so, by lipophilic derivatives of EDTA.

[0017] However, in the course of their work, the inventors found that, contrary to the teaching of reference [7], lipophilic derivatives of amino-polycarboxylic acids and, in particular, of EDTA and CyDTA can very efficiently extract rare earths and in particular neodymium, praseodymium and dysprosium from acidic aqueous solutions.

[0018] And it is on these experimental findings that the invention is based. Description of the invention

[0019] The invention therefore relates to the use of a lipophilic derivative of an aminopolycarboxylic acid as an extractant, to extract at least one rare earth from an acidic aqueous solution.

[0020] This derivative corresponds to the general formula (I) or (II) below:

[0021] [Chem.l] 0) (H)

[0022] in which: m is equal to 0 or 1; R1 and R2, identical or different, represent a hydrogen atom, a linear or branched Cl-alkyl group at C40, a C5 or C6 cycloalkyl group, a monocyclic aryl group, or together form a saturated or unsaturated C5 or C6 ring, possibly substituted one or more times by a hydrogen atom, a linear or branched Cl-alkyl group at C40, a C5 or C6 cycloalkyl group, or a monocyclic aryl group; R3, R4, R5, R6, R7 and R8 represent, independently of each other, a hydrogen atom, a linear or branched Cl to C40 alkyl group, a C5 or C6 cycloalkyl group or a monocyclic aryl group; X1 and X2, identical to each other, and X3 and X4, identical to each other but different from X1 and X2, represent either a hydroxyl group or an -NHR or -NRR' group with R and R' representing a linear or branched alkyl group at C6 to C20, a cycloalkyl group at C5 or C6 or a monocyclic aryl group; X5 and X6, identical to each other, represent a -NHR or -NRR' group with R and R' representing a linear or branched alkyl group at C8 to C20, a cycloalkyl group at C5 or C6 or a monocyclic aryl group; R9 represents a linear or branched C40 alkyl group, a C5 or C6 cycloalkyl group, a monocyclic aryl group, a -CH2COOH group, or a -CH2-CONHR or -CH2-CONRR' group, with R and R' representing a linear or branched C40 alkyl group, a C5 or C6 cycloalkyl group, or a monocyclic aryl group; and R10 represents a hydrogen atom or a -COOH group if R9 represents a -CH2COOH group, otherwise R10 represents a -COOH group; as an extradant, to extract at least one rare earth from an acidic aqueous Al solution.

[0023] In the preceding and following, the following are understood to mean: - by "linear or branched alkyl group from C} to C40", any alkyl group whose chain is linear or has one or more branches and which includes at least 1 carbon atom but does not include more than 40 carbon atoms; - by "cycloalkyl group in C5 or C6", a cyclopentyl or cyclohexyl group; - by "monocyclic aryl group", any cyclic hydrocarbon group which comprises only one ring and whose ring complies with Hückel's aromaticity rule and therefore has a number of delocalized ir electrons equal to 4 / 7+2; thus, the monocyclic aryl group can in particular be a phenyl group, a tolyl group, a xylyl group, a mesityl group or a benzyl group; - by "saturated or unsaturated C5 or Cô ring", any ring which comprises 5 or 6 carbon atoms and which can be saturated or, on the contrary, contain one or more double bonds, this ring can then be an aromatic ring or not.

[0024] Furthermore, in the preceding and following text, the expressions "from ... to ..." and "between ... and ..." are equivalent and are intended to mean that the boundaries are included.

[0025] Similarly, the terms "solution" and "phase" are equivalent and perfectly interchangeable.

[0026] It goes without saying that, in the general formulas (I) and (II) above, the meanings of R1 to R8, X1 to X6, and R9 can be chosen according to the degree of lipophilicity that one wishes to impart to the derivative. Thus, in particular, for a high degree of lipophilicity, the presence in these formulas of one or more alkyl groups comprising from 12 to 40 carbon atoms, preferably from 12 to 36 carbon atoms, and even more so from 18 to 24 carbon atoms, will be entirely feasible.

[0027] In the general formula (I), it is preferred that m be equal to 0.

[0028] Furthermore, in the general formula (I), it is preferred that R1 and R2, identical or different, represent a hydrogen atom, a linear or branched alkyl group in Cl to C40, a cycloalkyl group in C5 or C6, a monocyclic aryl group, or together form a cyclohexyl or phenyl group, possibly substituted one or more times by a hydrogen atom, a linear or branched alkyl group in Cl to C40, a cycloalkyl group in C5 or C6 or by a monocyclic aryl group.

[0029] Therefore, the derivative preferably conforms to the particular formula (la), (Ib) or (le) below:

[0030] [Chem.2]

[0031] in which: R1, R2, R3, R4, R11, R12, R13 and R14 represent, independently of each other, a hydrogen atom, a linear or branched alkyl group at C40, a cycloalkyl group at C5 or C6, or a monocyclic aryl group; and X1, X2, X3 and X4 are as previously defined.

[0032] In these particular formulas, it is preferred that X1 and X2 represent a -NHR or -NRR' group with R and R' representing a linear or branched alkyl group at C8 to C20, a cycloalkyl group at C5 or C6 or a monocyclic aryl group, in which case X3 and X4 represent a hydroxyl group.

[0033] Moreover, it is preferred that X1 and X2 represent a -NRR' group in which R and R' are identical and represent a linear or branched alkyl group in C8 to C20 and, more particularly, in C8 to C12 such as an n-octyl, 2-ethylhexyl, n-decyl or n-dodecyl group.

[0034] Among the derivatives of particular formula (la), (Ib) and (le), preference is given to the derivatives of particular formula (la) or (Ib) as previously defined.

[0035] Such derivatives are, for example: - the derivative of particular formula (la) in which R1 to R4 all represent a hydrogen atom, X1 and X2 represent a -N(C10H21)2 group while X3 and X4 represent a hydroxyl group; - the derivative with the particular formula (Ib) in which R3, R4 and R11 to R14 all represent a hydrogen atom, X1 and X2 represent a -N(C12H25)2 group while X3 and X4 represent a hydroxyl group; and - the derivative of particular formula (Ib) in which R3, R4 and R11 to R14 all represent a hydrogen atom, X1 and X2 represent a -N(C8H17)2 group while X3 and X4 represent a hydroxyl group.

[0036] In the general formula (II), it is preferred that X5 and X6 represent a -NRR' group with R and R' representing a linear or branched alkyl group at C6 to C20, a cycloalkyl group at C5 or C6 or even a monocyclic aryl group.

[0037] Moreover, it is preferred that X5 and X6 represent a -NRR' group in which R and R' are identical and represent a linear or branched alkyl group in C8 to C20 and, more particularly, in C8 to C12 such as an n-octyl, 2-ethylhexyl, n-decyl or n-dodecyl.

[0038] More particularly, it is preferred that X5 and X6 represent a -NRR' group in which R and R' represent a 4-hexyldodecyl group.

[0039] As for R9, it preferentially represents a -CH2COOH group, in which case R10 is advantageously a -COOH group.

[0040] According to the invention, the rare earth is preferably extracted from the aqueous Al solution by a liquid-liquid extraction, in which case this extraction includes at least contacting the aqueous Al solution with an organic solution immiscible with water, comprising the derivative in an organic solvent, and then separating the aqueous Al solution from the organic solution.

[0041] However, it goes without saying that it is also possible to extract the rare earth from the aqueous Al solution by solid-liquid extraction, in which case this extraction may in particular include bringing this aqueous solution into contact with a solid material insoluble in water and previously impregnated with an organic solution immiscible with water, comprising the derivative in an organic solvent, and then separating the aqueous solution from the solid material.

[0042] The aqueous solution Al preferably comprises 0.1 mmol / L to 0.01 mol / L of an inorganic acid, which is advantageously nitric acid or hydrochloric acid. However, it is understood that other inorganic acids such as sulfuric acid or phosphoric acid may also be used.

[0043] As for the organic solution, it can comprise from 0.01 mol / L to 0.1 mol / L of the derivative, it being understood that the most appropriate concentration is likely to vary from one derivative to another and can be easily determined, for the derivative to be used, by carrying out prior extraction tests with different concentrations of this derivative.

[0044] The solvent for the organic solution can be any non-polar solvent in which the derivative, at the concentration at which it is intended to be used, can be solubilized. Suitable organic solvents include 1,3-diisopropylbenzene, chloroform, 10-undecen-l-ol, methylisobutyl ketone (or MIBK), 3-heptanone, TBP, and n-dodecane, alone or in a mixture with 1-octanol, for example in a volume ratio of 93 / 7.

[0045] According to the invention, the extraction of the rare earth from the aqueous solution Al is preferably followed by a de-extraction of this rare earth from the organic solution obtained at the end of its extraction, which de-extraction advantageously includes at least a contacting of the organic solution obtained at the end of the extraction with an aqueous solution A2, then the separation of the organic solution from the aqueous solution A2.

[0046] This aqueous solution A2 can in particular be an acidic aqueous solution having a pH between 0 and 3.

[0047] Furthermore, to promote the de-extraction of the rare earth, the aqueous solution A2 may include a metal complexing agent such as an aminopolycarboxylic acid of the type nitrilotriacetic acid (or NTA), EDTA, diethylenetriaminepentaacetic acid (or DTPA) or a salt of these such as a salt of an alkali metal (sodium or potassium in particular), for example at a concentration ranging from 0.005 mol / L to 0.05 mol / L and, even better, from 0.01 mol / L.

[0048] According to the invention, the use as just described is preferably implemented to extract neodymium, praseodymium and / or dysprosium from an acidic aqueous solution.

[0049] This acidic aqueous solution may in particular be a solution resulting from the dissolution in an acidic medium of an urban ore concentrate and, in particular, of a WEEE waste concentrate.

[0050] As such, it may in particular be a solution resulting from the dissolution in an acidic medium of a material in divided form (powder, fragments, etc.) and resulting from a treatment (for example, demagnetization + grinding as described in particular in international application PCT WO 2014 / 064587, hereinafter reference [8]) of used or discarded NdFeB permanent magnets.

[0051] Other features and advantages of the invention will become apparent from the following supplementary description, which relates to experimental tests which validated the use of an aminopolycarboxylic derivative as previously defined as a rare earth extractant.

[0052] It goes without saying that this additional description is given only as an illustration of the object of the invention and should in no case be interpreted as a limitation of this object. Brief description of the figures

[0053] [Fig.1] illustrates the influence of the initial pH of aqueous hydrochloric solutions on the extraction coefficient of neodymium(III), denoted E%Nd, as observed in extraction tests carried out using a lipophilic derivative of EDTA as an extractant, in solution in different solvents.

[0054] [Fig.2] illustrates the influence of the initial pH of aqueous hydrochloric solutions on the distribution coefficient of neodymium(III), denoted DNd, as observed in extraction tests carried out using a lipophilic derivative of EDTA as the extractant, in solution in different solvents.

[0055] [Fig.3] illustrates the influence of the initial pH of aqueous nitric solutions on the co efficient extraction of neodymium(III), denoted £%Nd, as observed in extraction tests carried out using a lipophilic derivative of EDTA as the extractant, in solution in different solvents.

[0056] [Fig.4] illustrates the distribution isotherm of neodymium(III) as obtained at the end of tests aimed at extracting this element from an aqueous solution comprising 0.01 mol / L of either hydrochloric or nitric acid and using a lipophilic derivative of EDTA as an extractant, in solution in 1,3-diisopropylbenzene.

[0057] [Fig. 5] illustrates the influence of the initial pH of aqueous hydrochloric acid solutions on the extraction coefficient, noted E%M, of neodymium(III), praseodymium(III) and dysprosium(III) as observed in extraction tests carried out using a lipophilic derivative of EDTA as extractant, in solution in 1,3-diisopropylbenzene.

[0058] [Fig.6] illustrates the influence of the initial pH of aqueous nitric solutions on the co efficient extraction, noted E%M, of neodymium(III), praseodymium(III) and dysprosium(III) as observed in extraction tests carried out using a lipophilic derivative of EDTA as the extractant, in solution in 1,3-diisopropylbenzene.

[0059] [Fig.7] illustrates the influence of concentration, denoted [RP2] and expressed in mol / L, of a first lipophilic derivative of CyDTA on the extraction coefficient, noted E%M, of neodymium(III), praseodymium(III) and dysprosium(III) as observed in tests aimed at extracting these three rare earths from an aqueous nitric solution using this derivative as an extractant, in solution in n-dodecane.

[0060] [Fig.8] illustrates the influence of the concentration, denoted [RP4] and expressed in mol / L, of a second lipophilic derivative of CyDTA on the extraction coefficient, denoted E%M, of neodymium(III), praseodymium(III) and dysprosium(III) as observed in tests aimed at extracting these three rare earths from an aqueous nitric solution using this derivative as an extractant, in solution in n-dodecane.

[0061] Detailed description of particular embodiments

[0062] Distribution coefficients, extraction coefficients, load capacities and the separation factors reported in the following examples were determined in accordance with the conventions of the field of liquid-liquid extraction, namely that: - the distribution coefficient between two phases, respectively organic and aqueous, of a metallic element M, denoted DM and without units, is determined by the following formula: M [M]aq,q in which: [Math.l] is the concentration of M in the organic phase at equilibrium (in g / L or mol / L), and [M]e is the concentration of M in the aqueous phase after extraction (in g / L or mol / L); - The extraction coefficient of a metallic element M, denoted E%M and dimensionless, is determined by the following formula: [Math 2] in which: [Math.2] MOT&éq has the same meaning as before (in g / L or mol / L), and P^aqjnit is the initial concentration of M in the aqueous phase (in g / L or mol / L); - the separation factor of a metallic element M1 with respect to a metallic element M2, denoted FSM1 / M2 and dimensionless, is determined by the following formula: [Math 3] pç _ PM1 n ÜM2 in which: [Math.3] ^Ml is the distribution coefficient of Ml, and ^M2 is the distribution coefficient of M2.

[0063] Example 1: Use of a lipophilic derivative of EDTA

[0064] The liquid-liquid extraction tests reported below were carried out in using as an extractant, a lipophilic derivative of EDTA, namely the derivative of particular formula (la) in which R1, R2, R3 and R4 represent a hydrogen atom, X1 and X2 represent a -N(C10H21)2 group while X3 and X4 represent a group -OH.

[0065] 1 - Synthesis of the derivative:

[0066] The derivative was previously synthesized by reacting commercially available EDTA dianhydride with an excess of didecylamine.

[0067] To this end, in a 100 mL flask, 1 g (3.9 mmol) of EDTA dianhydride and 2.55 g (8.58 mmol) of didecylamine were dissolved in 33 mL of anhydrous dimethylformamide (or DMF) under nitrogen and heated to 90 °C with vigorous stirring for 12 hours. After cooling, the mixture was poured into 330 mL of milli-QTM water and the precipitate was collected by vacuum filtration. The solid was washed with 50 mL of milli-QTM water and then dissolved in 150 mL of methanol and evaporated under reduced pressure until a dry residue was obtained. This residue was recrystallized in 50 mL of ethyl acetate at 4 °C. The crystals were collected by vacuum filtration, washed with cold ethyl acetate, and dried under high vacuum. 2.6 g of the expected derivative was obtained in the form of a white solid (Yield: 78%).

[0068] 2 - Nd(III) extraction tests:

[0069] A first series of extraction tests was carried out using: - such as aqueous solutions, solutions comprising from 0.1 mmol / L to 0.1 mol / L of hydrochloric acid or nitric acid and 0.01 mol / L of neodymium(III) in the form of chloride (in the case of HCl) or nitrate (in the case of HNO3) in water; and - as organic solutions, solutions comprising 0.01 mol / L of the derivative in one of the following solvents: 1,3-diisopropylbenzene, chloroform, 10-undecen-l-ol, MIBK, 3-heptanone, TBP and an n-dodecane / l-octanol mixture (93 / 7, v / v).

[0070] Each test was carried out by putting 2 mL of an aqueous solution and 2 mL of an organic solution (i.e. an O / A ratio of 1) into a tube and subjecting the tube to vigorous shaking (400 rpm) for 30 minutes at room temperature, then to centrifugation at 11,000 g for 5 minutes.

[0071] After which, the concentrations of Nd(III) remaining in the aqueous solutions were determined by inductively coupled plasma emission spectroscopy (or ICP-OES) on aliquots of these solutions after dilution in 1 M hydrochloric or nitric acid. The calibration range was established from ICP standards (PlasmaCALTM) at 1004 ± 5 ​​pg / mL.

[0072] The concentrations of Nd(III) present in the organic solutions were deduced from those obtained for the aqueous solutions after a simple mass balance.

[0073] The extraction coefficients, E%Nd, and distribution coefficient, DNd, of Nd(III) were calculated from the concentrations thus determined.

[0074] Figures 1 to 3 illustrate: - [Fig.l]: Nd(III) extraction coefficients obtained as a function of the initial pH of aqueous hydrochloric solutions; - [Fig. 2]: the distribution coefficients of Nd(III) obtained as a function of the initial pH of aqueous hydrochloric solutions; and - [Fig.3]: Nd(III) extraction coefficients obtained as a function of the initial pH of aqueous nitric solutions.

[0075] Furthermore, [Fig. 4] illustrates the distribution isotherm of neodymium(III) in the form of a curve that shows the equilibrium relationship between the concentration of Nd(III) in organic solution, denoted [Nd]org,eq and expressed in g / L, and the initial concentration of the same element in aqueous solution, denoted [Nd]aq,init and expressed in g / L, as obtained for tests in which neodymium(III) was extracted from an aqueous solution containing 0.01 mol / L of hydrochloric acid or nitric acid (pH 2) using, as the organic solution, a solution containing 0.015 mol / L in the 1,3-Diisopropylbenzene.

[0076] 3 - Nd(III) de-extraction tests:

[0077] The extraction tests were carried out using: - as organic solutions, solutions containing neodymium(III) such as those obtained from the extraction tests referred to in point 2 above; and - such as aqueous solutions, solutions comprising 0.01 mol / L of DTPA in water.

[0078] Each test was carried out following an operating protocol similar to that described in point 2 above.

[0079] The analysis of the concentrations of Nd(III) in aqueous and organic solutions after their separation was also carried out as described in point 2 above.

[0080] These tests have shown that it is possible to extract almost all of the neodymium(III) from an organic solution in which it has been previously extracted, using an aqueous solution comprising DTPA at a level of 0.01 mol / L.

[0081] 4 - Extraction tests for Nd(III), Pr(III) and Dy(III):

[0082] In order to more closely approximate an acidic leaching medium for NdFeB permanent magnets, a second series of extraction tests was carried out using: - as aqueous solutions, solutions comprising 0.1 mmol / L to 0.01 mol / L of hydrochloric acid or nitric acid and 0.01 mol / L to 1.5 mol / L of each of the rare earth elements (neodymium(III), praseodymium(III) and dysprosium(III)) in the form of chlorides (in the case of HCl) or nitrates (in the case of HNO3) in water; and - as organic solutions, solutions comprising 0.01 mol / L of the derivative in 1,3-diisopropylbenzene or an n-dodecane / l-octanol mixture (93 / 7, v / v).

[0083] Each test was carried out following an operating protocol similar to that described in point 2 above.

[0084] The analysis of the concentrations of the three rare earths in aqueous and organic solutions after their separation was also carried out as described in point 2 above.

[0085] Their extraction coefficients, E%M, and distribution coefficient, DM, were calculated from the concentrations thus determined, then the separation factors of neodymium(III) from praseodymium(III) on the one hand, and of dysprosium(III) on the other hand, FSNd / Pr and FSNd / Dy, were calculated from the DM thus obtained.

[0086] The results are illustrated in Figures 5 and 6 and in Table I below, which show: - [Fig.5]: the extraction coefficients of Nd(III), Pr(III) and Dy(III) obtained as a function of the initial pH of aqueous hydrochloric solutions for extractions carried out with the derivative in solution in 1,3-diisopropylbenzene; - [Fig.6]: the extraction coefficients of Nd(III), Pr(III) and Dy(III) obtained as a function of the initial pH of the aqueous nitric solutions for extractions carried out with the derivative in solution in 1,3-diisopropylbenzene; - Table I: Separation factors of neodymium(III) from praseodymium(III) on the one hand, and from dysprosium(III) on the other hand, obtained for extractions carried out on aqueous solutions comprising 0.1 mmol / L of hydrochloric or nitric acid (pH 4) with the derivative in solution in 1,3-diisopropylbenzene or the n-dodecane / l-octanol mixture (93 / 7, v / v).

[0087] [Tables 1] Solvent FS FS Nd / Pr f^Nd / Djl R» Nd / Pr F^Nd / Dy 1,3-diisopropylbenzene 1.38 1.47 1.14 1.37 n-dodecane / l-octanol (93 / 7, v / v) 1.26 1.07 1.27 1.23 Acid of aqueous solutions HCl hnq3

[0088] These results show that the derivative allows the extraction of both neodymium(III), the praseodymium(III) and dysprosium(III) from an aqueous hydrochloric or nitric solution having a pH ranging from 2 to 4.

[0089] They also show that the derivative has more affinity for neodymium(III) than for the other two rare earths, this affinity being in the order: Nd > Pr > Dy for extractions carried out with the derivative in solution in 1,3-diisopropylbenzene whereas it is in the order: Nd > Dy > Pr for extractions carried out with the derivative in solution in the n-dodecane / l-octanol mixture (93 / 7, v / v).

[0090] Example 2: Use of two lipophilic derivatives of CyDTA

[0091] The liquid-liquid extraction tests reported below were carried out using two lipophilic derivatives of CyDTA in n-dodecane as extractants, namely: - the derivative with the particular formula (Ib) in which R3, R4 and R11 to R14 represent a hydrogen atom, X1 and X2 represent a -N(C12H25)2 group while X3 and X4 represent a -OH group, referred to as "RP2 derivative" below; and - the derivative of particular formula (Ib) in which R3, R4 and R11 to R14 represent a hydrogen atom, X1 and X2 represent a -N(C8H17)2 group while X3 and X4 represent a -OH group, called "RP4 derivative" below.

[0092] 1 - Synthesis of derivatives:

[0093] The derivatives were previously synthesized by reacting the CyTDA dianhydride with an excess of didodecylamine for the RP2 derivative and of dioctylamine for the RP4 derivative.

[0094] * Synthesis of CyTDA dianhydride:

[0095] 12.64 g (36.7 mmol) of trans-1,2-diaminocyclohexane monohydrate traacetic acid (CyDTA₂H₂O) and 11 mL of pyridine were introduced into a 250 mL single-necked flask. Then, 66 mL of acetic anhydride were added, and the mixture was stirred overnight. The resulting solution was added dropwise to 350 mL of diethyl ether, and the suspension was then filtered through a sintered glass filter with a porosity of 3. The precipitate was washed with diethyl ether (3 x 100 mL) and then dried under vacuum. This yielded 7.27 g of the expected dianhydride as a yellowish powder (yield: 69%).

[0096] * Synthesis of the RP2 derivative:

[0097] 1 g (3.22 mmol) of the previously obtained CyDTA dianhydride and 2.51 g (2.2 eq., 7.08 mmol of didodecylamine was introduced into a 100 mL two-necked flask fitted with a septum, topped with a condenser, and placed under an argon atmosphere. Then, 40 mL of DMF was added, the mixture was heated to 60 °C, and left to stir overnight. The DMF was then evaporated under vacuum, and the remaining crude was dissolved in 100 mL of dichloromethane (or DCM) and then transferred to a A 250 mL separatory funnel was used. The organic phase was washed with a 3 M hydrochloric acid solution (2 x 100 mL) and then with deionized water (Milli-QTM - 2 x 100 mL). The organic phase was then dried over sodium sulfate (Na₂SO₄) and filtered under reduced pressure. The hydrated salts were rinsed with DCM (3 x 40 mL), and the filtrate was evaporated under reduced pressure. The oily residue was purified by reversed-phase flash chromatography (Cl8 column) and methanol / isopropanol gradient elution (from 100 / 0 to 80 / 20). This yielded 2.19 g of the RP2 derivative as a white paste (67% yield).

[0098] * Synthesis of the RP4 derivative:

[0099] 1.43 g of the RP4 derivative in the form of a yellowish oil were obtained by following a protocol to that described for the synthesis of derivative RP2 except that 1 g (3.22 mmol) of the dianhydride from CyDTA was reacted with 1.71 g (2.2 eq., 7.08 mmol) of dioctylamine and that the elution of the C18 column used for the purification was carried out by methanol / water gradient from 95 / 5 to 100 / 0 (Yield: 56%).

[0100] 2 - Extraction tests:

[0101] The extraction tests were carried out using: - as aqueous solutions, solutions comprising 1 mmol / L of nitric acid and 0.01 mol / L to 0.1 mol / L of neodymium(III), praseodymium(III) and dysprosium(III) as nitrate in water; and - as organic solutions, solutions comprising from 0.01 mol / L to 0.1 mol / L of the RP2 derivative or the RP4 derivative, in n-dodecane.

[0102] Each test was carried out following an operating protocol similar to that described in point 2 of example I above.

[0103] The analysis of the concentrations of the three rare earths in aqueous and organic solutions after their separation was also carried out as described in point 2 of Example I above.

[0104] Their extraction coefficients, E%M, were calculated from the concentrations thus determined.

[0105] The results are illustrated in Figures 7 and 8, which show the extraction coefficients thus obtained as a function of the concentrations of RP2 ([Fig.7]) and RP4 ([Fig.8]) of the organic solutions.

[0106] These figures show that, unlike the lipophilic derivative of EDTA tested in Example I above, the two lipophilic derivatives of CyDTA, in solution in n-dodecane, exhibit an identical or almost identical affinity for neodymium(III), praseodymium(III) and dysprosium(III).

[0107] These results are extremely interesting because they mean that the invention offers a range of extractants suitable for carrying out both selective extraction of neodymium(III) with respect to praseodymium(III) and dysprosium(III) - if such extraction is sought - that is, an extraction of all three of these rare earths. References cited

[0108] [1] EP-A-3 323 899 [2] WO-A-2016 / 046179 [3] WO-A-2019 / 197792 [4] US-A-5,762,910 [5] WO-A-2016 / 135523 [6] Erne et al., Helv. Chem. Acta 1980, 63(8), 2264-2270 [7] US-B-8,785,691 [8] WO-A-2014 / 064587

Claims

1. Demands Use of a derivative of an aminopolycarboxylic acid, which corresponds to the general formula (I) or (II) below: in which: m is equal to 0 or 1; R1 and R2 together form a saturated or unsaturated C5 or C6 ring, possibly substituted one or more times by a hydrogen atom, a linear or branched Cl-alkyl group at C40, a C5 or C6 cycloalkyl group or a monocyclic aryl group; R3, R4, R5, R6, R7 and R8 represent, independently of each other, a hydrogen atom, a linear or branched Cl-alkyl group at C40, a C5 or C6 cycloalkyl group or a monocyclic aryl group; X1 and X2, identical to each other, and X3 and X4, identical to each other but different from X1 and X2, represent either a hydroxyl group or an -NHR or -NRR' group with R and R' representing a linear or branched alkyl group at C6 to C20, a cycloalkyl group at C5 or C6 or a monocyclic aryl group; X5 and X6, identical to each other, represent a -NHR or -NRR' group with R and R' representing a linear or branched alkyl group at C6 to C20, a cycloalkyl group at C5 or C6 or a monocyclic aryl group; R9 represents a linear or branched alkyl group at C40, a cycloalkyl group at C5 or C6, a monocyclic aryl group, or a -CH2-C0NHR or -CH2-C0NRR' group, with R and R' representing a linear or branched alkyl group at C40, a cycloalkyl group at

2.

3.

4. C5 or C6 or a monocyclic aryl group; and R10 represents a -COOH group; as an extractant, to extract at least one rare earth from an acidic aqueous Al solution. Use according to claim 1, in which m is 0. Use according to claim 1 or claim 2, wherein R1 and R2 together form a cyclohexyl or phenyl group, optionally substituted one or more times by a hydrogen atom, a linear or branched Cl to C40 alkyl group, a C5 or C6 cycloalkyl group, or a monocyclic aryl group. Use according to any one of claims 1 to 3, wherein the derivative corresponds to the particular formula (Ib) or (the) below: [Chem 2]

5.

6.

7. (Ib) (the) in which R3, R4, R11, R12, R13 and R14 represent, independently of each other, a hydrogen atom, a linear or branched Cl to C40 alkyl group, a C5 or C6 cycloalkyl group, or a monocyclic aryl group. Use according to claim 4, wherein X1 and X2 represent an -NHR or -NRR' group with R and R' representing a linear or branched alkyl group at C6 to C20, a cycloalkyl group at C5 or C6 or a monocyclic aryl group, in which case X3 and X4 represent a hydroxyl group. Use according to claim 5, wherein X1 and X2 represent a -NRR' group in which R and R' are identical and represent a linear or branched alkyl group in C8 to C20 and, better still, in C8 to Cl2, preferably n-octyl, 2-ethylhexyl, n-decyl or n-dodecyl. Use according to any one of claims 4 to 6, in in which the aminopolycarboxylic acid derivative is chosen from: - the derivative of particular formula (Ib) in which R3, R4, R11, R12, R13 and R14 represent a hydrogen atom, X1 and X2 represent a -N(C12H25)2 group and X3 and X4 represent a hydroxyl group; - the derivative of particular formula (Ib) in which R3, R4, R11, R12, R13 and R14 represent a hydrogen atom, X1 and X2 represent a -N(C8H17)2 group and X3 and X4 represent a hydroxyl group.

8. Use according to any one of claims 1 to 7, wherein the aqueous solution Al comprises from 0.1 mmol / L to 0.01 mol / L of an inorganic acid, preferably nitric acid or hydrochloric acid.

9. Use according to any one of claims 1 to 8, wherein the extraction of the rare earth comprises at least one contacting of the aqueous Al solution with an organic solution immiscible with water, which comprises the derivative in an organic solvent, and then a separation of the aqueous Al solution from the organic solution.

10. Use according to claim 9, wherein the organic solution comprises from 0.01 mol / L to 0.1 mol / L of the derivative.

11. Use according to claim 9 or claim 10, which further includes a de-extraction of the rare earth from the organic solution obtained at the end of the extraction, the de-extraction comprising at least a contacting of the organic solution obtained at the end of the extraction with an aqueous solution A2, and then the separation of the organic solution from the aqueous solution A2.

12. Use according to claim 11, wherein the aqueous solution A2 comprises a complexing agent, preferably an aminopolycarboxylic acid.

13. Use according to any one of claims 1 to 12, wherein the rare earth is selected from neodymium, praseodymium, dysprosium and mixtures thereof.

14. Use according to any one of claims 1 to 13, wherein the aqueous solution Al is obtained from the dissolution in acidic medium of an urban ore concentrate, preferably a concentrate of waste electrical and electronic equipment.

15. Use according to any one of claims 1 to 13, wherein the aqueous Al solution is obtained from the dissolution in an acidic medium of a material in divided form resulting from the treatment of spent Neodymium-Iron-Boron permanent magnets or repelled.

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