Use of lipophilic derivatives of aminopolycarboxylic acids for the extraction of rare earths from an acidic aqueous solution

Abstract

The invention 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. Applications: production of rare earths from concentrates derived from urban ores and, in particular, from concentrates from waste electrical and electronic equipment such as used or discarded NdFeB permanent magnets; production of rare earths from concentrates derived from natural ores or from concentrates derived from residues of natural ores.

Description

[0001]USE OF LIPOPHILIC DERIVATIVES OF AMINOPOLYCARBOXYLIC ACIDS FOR THE EXTRACTION OF RARE EARTH ELEMENTS FROM AN ACID AQUEOUS SOLUTION Description TECHNICAL FIELD 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. More specifically, the invention relates to the use of a lipophilic derivative of an aminopolycarboxylic acid as an extractant, for extracting one or more rare earths from an acidic aqueous solution. The invention finds applications in particular in the production of rare earths from concentrates derived from “urban ores”, i.e. “mines” consisting of industrial and domestic waste comprising rare earths and, in particular, in the recycling of rare earths present in waste electrical and electronic equipment (also called “WEEE” or “D3E”).More particularly, the invention finds an application in the recycling of rare earths contained in used or discarded permanent magnets, and, in particular, in permanent magnets of the Neodymium-Iron-Boron (or NdFeB) type. 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 slag. STATE OF THE PRIOR ART The particular physical and chemical properties of rare earths (scandium, yttrium and lanthanides) currently make them essential chemical elements in many industrial fields: glass and ceramics industries, catalysis, metallurgy, manufacture of permanent magnets, optical devices, luminophores, etc.Rare earths are therefore among the so-called "technological" metals whose supply is strategic. Global demand for rare earths continues to grow and it is estimated that this demand will increase by 50% over the next ten years. However, as the number of rare earth producing countries remains limited – China currently dominates the global production of rare earths – there is a significant risk of a shortage of rare earth supplies in the long term, hence the need to optimize all the ways in which they can be produced. Recycling rare earths present in used materials is increasingly favored. Recycling makes it possible to reconcile the reduction of supply risks with the environmental challenges associated with mining activities.One of the leading markets in terms of volume and market value for rare earth recycling concerns NdFeB permanent magnets found in a number of WEEE wastes (computer hard drives, audio or video equipment speakers, magnetic devices, etc.). This resource for rare earth recycling has the advantage of containing interesting and recoverable proportions of rare earths, typically around 30% by mass. The composition of NdFeB permanent magnets varies depending on the applications of these magnets and the manufacturers, but they typically contain heavy rare earths (dysprosium and, to a lesser extent, gadolinium, terbium) which are very recoverable as well as light rare earths (neodymium and praseodymium in particular).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 medium in which they are found. 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 Cyanex ^ 272), neodecanoic acid (or Versatic ^ 10) and tri-n-butyl phosphate (or TBP).The use of other types of extractants has been proposed in recent years, such as N,N-dibutylacetamide (see European patent application 3323899, hereinafter reference [1]), lipophilic symmetrical diglycolamides such as N,N,N',N'-tetraoctyl-3-oxapentanediamide (or TODGA) (see PCT international application WO 2016 / 046179, hereinafter reference [2]) and amphiphilic dissymmetrical diglycolamides (see PCT international application WO 2019 / 197792, hereinafter reference [3]). Furthermore, the idea of ​​developing lipophilic derivatives of aminopolycarboxylic acids emerged in the mid-1970s and then spread in the following years, mainly with the aim of providing compounds for medical imaging. Contrast agents for medical magnetic resonance imaging have thus been proposed, comprising a paramagnetic ion, for example Mn. 2+, complexed with a lipophilic derivative of ethylenediaminetetraacetic acid (or EDTA) in US patent 5,762,910, hereinafter reference [4], and with a lipophilic derivative of trans-1,2-diaminocyclohexanetetraacetic acid (or CyDTA) in international application PCT WO 2016 / 135523, hereinafter reference [5]. The use of lipophilic derivatives of EDTA, incorporated into a polymer membrane, has also been proposed for the extraction of alkaline earth metals, calcium and magnesium in particular, by Erne et al., Helv. Chim. Acta 1980, 63(8), 2264-2270, hereinafter reference [6]. Finally, it was proposed in US patent 8,785,691, hereinafter reference [7], to use lipophilic derivatives of EDTA, in solution in 1-octanol, to extract by liquid-liquid extraction americium(III) and curium(III) selectively with respect to lanthanides(III) from a raffinate resulting from the implementation of the PUREX spent fuel treatment process.Thus, according to this reference, the lanthanides which represent 15 of the 17 rare earths would not be extractable or only very weakly by lipophilic derivatives of EDTA. However, in the context of their work, the inventors have noted that contrary to the teaching of reference [7], lipophilic derivatives of aminopolycarboxylic acids and, in particular, EDTA and CyDTA can very effectively extract rare earths and in particular neodymium, praseodymium and dysprosium from acidic aqueous solutions. And it is on these experimental observations that the invention is based. DISCLOSURE OF THE INVENTION The subject of the invention is therefore 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. This derivative corresponds to the general formula (I) or (II) below: O R2 R. 1 R10 GOLD 3 R 4 R 9 (I) (II) in which: m is 0 or 1; R1 and R 2 , identical or different, represent a hydrogen atom, a linear or branched C1 to C40 alkyl group, a C5 or C6 cycloalkyl group, a monocyclic aryl group, or together form a saturated or unsaturated C5 or C6 ring, optionally substituted one or more times by a hydrogen atom, a linear or branched C1 to C40 alkyl group, a C5 or C6 cycloalkyl group or by a monocyclic aryl group; R 3 , R 4 , R 5 , R 6 , R 7 and R 8 represent, independently of each other, a hydrogen atom, a linear or branched C1 to C alkyl group 40 , a C5 or C6 cycloalkyl group or a monocyclic aryl group; X 1 and X 2 , identical to each other, and X 3 and X 4 , identical to each other but different from X 1 and X 2, represent either a hydroxyl group or a –NHR or –NRR' group with R and R' representing a linear or branched C6 to C alkyl group 20 , a C5 or C6 cycloalkyl group or a monocyclic aryl group; X 5 and X 6 , identical to each other, represent a group –NHR or –NRR' with R and R' representing a linear or branched C8 to C20 alkyl group, a C5 or C6 cycloalkyl group or a monocyclic aryl group; R 9 represents a straight or branched C1 to 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 straight or branched C1 to C40 alkyl group, a C5 or C6 cycloalkyl group or a monocyclic aryl group; and R 10 represents a hydrogen atom or a –COOH group if R 9 represents a group –CH2COOH, otherwise R 10represents a –COOH group; as an extractant, to extract at least one rare earth from an acidic aqueous solution A1. In the above and the following, the following means: ^ by “linear or branched C1 to C alkyl group 40", any alkyl group whose chain is linear or has one or more branches and which comprises at least 1 carbon atom but which does not comprise more than 40 carbon atoms; ^ by "C5 or C6 cycloalkyl group", a cyclopentyl or cyclohexyl group; ^ by "monocyclic aryl group", any cyclic hydrocarbon group which comprises only one ring and whose ring complies with the Hückel aromaticity rule and therefore has a number of delocalized π electrons equal to 4n+2; thus, the monocyclic aryl group may 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 C6 ring", any ring which comprises 5 or 6 carbon atoms and which may be saturated or, on the contrary, comprise one or more double bonds, this ring then being able to be an aromatic ring or not.Furthermore, in the above and below, the expressions "from ... to ..." and "between ... and ..." are equivalent and are intended to mean that the limits are included. Similarly, the terms "solution" and "phase" are equivalent and perfectly interchangeable. It goes without saying that, in the general formulas (I) and (II) above, the meanings of R. 1 to R 8 , of 1 to X 6 and R 9 may be chosen according to the degree of lipophilicity that one wishes to confer on 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 possible. In general formula (I), it is preferred that m is equal to 0. Furthermore, in general formula (I), it is preferred that R 1 and R 2, identical or different, represent a hydrogen atom, a linear or branched C1 to C40 alkyl group, a C5 or C6 cycloalkyl group, a monocyclic aryl group, or together form a cyclohexyl or phenyl group, optionally substituted one or more times by a hydrogen atom, a linear or branched C1 to C40 alkyl group, a C5 or C6 cycloalkyl group or by a monocyclic aryl group. Also, the derivative preferably corresponds to the particular formula (Ia), (Ib) or (Ic) below: O R2 X3 X4 R1 O (Ia) (Ib) (Ic) in which: R 1 , R 2 , R 3 , R 4 , R 11 , R 12 , R 13 and R 14 represent, independently of each other, a hydrogen atom, a linear or branched C1 to C alkyl group 40 , a C5 or C6 cycloalkyl group, or a monocyclic aryl group; and X 1 , X 2 , X 3 and X 4are as previously defined. In these particular formulas, it is preferred that X 1 and X 2 represent a group – NHR or – NRR' with R and R' representing a linear or branched C8 to C alkyl group 20 , a C5 or C6 cycloalkyl group or a monocyclic aryl group, in which case these are X 3 and X 4 which represent a hydroxyl group. Furthermore, it is preferred that X 1 and X 2 represent a group –NRR' in which R and R' are identical and represent a linear or branched C8 to C alkyl group 20 and, more particularly, in C8 to C12 such as an n-octyl, 2-ethylhexyl, n-decyl or n-dodecyl group. Among the derivatives of particular formula (Ia), (Ib) and (Ic), all preference is given to the derivatives of particular formula (Ia) or (Ib) as previously defined. Such derivatives are for example: ^ the derivative of particular formula (Ia) in which R 1 to R 4all represent a hydrogen atom, X 1 and X 2 represent a group –N(C 10 H 21 )2while X 3 and X 4 represent a hydroxyl group; ^ the derivative of particular formula (Ib) in which R 3 , R 4 and R 11 to R 14 all represent a hydrogen atom, X 1 and X 2 represent a group –N(C 12 H 25 )2while X 3 and X 4 represent a hydroxyl group; and ^ the derivative of particular formula (Ib) in which R 3 , R 4 and R 11 to R 14 all represent a hydrogen atom, X 1 and X 2 represent a group –N(C8H17)2 while X 3 and X 4 represent a hydroxyl group. In general formula (II), it is preferred that X 5 and X 6represent a group –NRR' with R and R' representing a linear or branched C6 to C20 alkyl group, a C5 or C6 cycloalkyl group or a monocyclic aryl group. Furthermore, it is preferred that X 5 and X 6 represent a group –NRR' in which R and R' are identical and represent a linear or branched C8 to C alkyl group 20 and, more particularly, in C8 to C 12 such as an n-octyl, 2-ethylhexyl, n-decyl or n-dodecyl group. More particularly, it is preferred that X 5 and X 6 represent a group –NRR' in which R and R' represent a 4-hexyldodecyl group. As for R 9 , it preferentially represents a –CH2COOH group, in which case R 10is advantageously a –COOH group. According to the invention, the rare earth is preferably extracted from the aqueous solution A1 by liquid-liquid extraction, in which case this extraction comprises at least one contacting of the aqueous solution A1 with a water-immiscible organic solution, comprising the derivative in an organic solvent, then a separation of the aqueous solution A1 from the organic solution. However, it goes without saying that it is also possible to extract the rare earth from the aqueous solution A1 by solid-liquid extraction, in which case this extraction may in particular comprise a contacting of this aqueous solution with a solid material insoluble in water and previously impregnated with a water-immiscible organic solution, comprising the derivative in an organic solvent, then a separation of the aqueous solution from the solid material.The aqueous solution A1 preferably comprises from 0.1 mmol / L to 0.01 mol / L of an inorganic acid, which is advantageously nitric acid or hydrochloric acid. However, it goes without saying that other inorganic acids such as sulfuric acid or phosphoric acid may also be used. As for the organic solution, it may 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 that it is desired to use, by first carrying out extraction tests with different concentrations of this derivative. The solvent of the organic solution may 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-1-ol, methyl isobutyl ketone (or MIBK), 3-heptanone, TBP and n-dodecane, alone or mixed with 1-octanol, for example in a volume ratio of 93 / 7. According to the invention, the extraction of the rare earth from the aqueous solution A1 is preferably followed by a back-extraction of this rare earth from the organic solution obtained at the end of its extraction, which back-extraction advantageously comprises at least one 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. This aqueous solution A2 may in particular be an acidic aqueous solution having a pH of between 0 and 3.Furthermore, to promote the de-extraction of the rare earth, the aqueous solution A2 may comprise a metal complexing agent such as an aminopolycarboxylic acid of the nitrilotriacetic acid (or NTA), EDTA, diethylenetriaminepentaacetic acid (or DTPA) type or a salt thereof 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, better still, 0.01 mol / L. In accordance with the invention, the use as just described is preferably implemented to extract neodymium, praseodymium and / or dysprosium from an acidic aqueous solution. 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.As such, it may in particular be a solution resulting from the dissolution in an acid medium of a material in a 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. Other characteristics and advantages of the invention will emerge from the additional description which follows, which relates to experimental tests which have made it possible to validate the use of an aminopolycarboxylic derivative as previously defined as a rare earth extractant. It goes without saying that this additional description is given only as an illustration of the subject of the invention and must in no case be interpreted as a limitation of this subject.BRIEF DESCRIPTION OF THE FIGURES Figure 1 illustrates the influence of the initial pH of aqueous hydrochloric solutions on the extraction coefficient of neodymium(III), noted E%. Nd, as observed in extraction tests carried out using a lipophilic derivative of EDTA as an extractant, in solution in different solvents. Figure 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 an extractant, in solution in different solvents. Figure 3 illustrates the influence of the initial pH of aqueous nitric 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.Figure 4 illustrates the distribution isotherm of neodymium(III) as obtained following 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. Figure 5 illustrates the influence of the initial pH of aqueous hydrochloric solutions on the extraction coefficient, noted E%M, of neodymium(III), praseodymium(III) and dysprosium(III) as observed in extraction tests having been carried out using a lipophilic derivative of EDTA as an extractant, in solution in 1,3-diisopropylbenzene. Figure 6 illustrates the influence of the initial pH of aqueous nitric solutions on the extraction coefficient, noted E%. M, neodymium(III), praseodymium(III) and dysprosium(III) as observed in extraction tests carried out using a lipophilic derivative of EDTA as an extractant, in solution in 1,3-diisopropylbenzene. Figure 7 illustrates the influence of the concentration, noted [RP2] and expressed in mol / L, of a first lipophilic derivative of CyDTA on the extraction coefficient, noted E% M , 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. Figure 8 illustrates the influence of the concentration, noted [RP4] and expressed in mol / L, of a second lipophilic derivative of CyDTA on the extraction coefficient, noted E% M, 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. DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS The distribution coefficients, extraction coefficients, load capacities and separation factors which are reported in the examples which follow, 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 D M and without unit, is determined by the following formula: ^ [M] ^^,é^ in which: [M] ^^^,é^ is the concentration of M in the organic phase at equilibrium (in g / L or mol / L), and [M] ^^,é^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, noted E%M and without unit, is determined by the following formula: [M] ^% ^^^,é^ ^ = in which: [M] ^^^,é^ has the same meaning as before (in g / L or mol / L), and [M] ^^,^^^^ 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, noted FSM1 / M2 and without unit, is determined by the following formula: ^ ^^ in which: ^ ^^ is the distribution coefficient of M1, and ^ ^^is the distribution coefficient of M2. EXAMPLE 1: Use of a lipophilic derivative of EDTA The liquid-liquid extraction tests reported below were carried out using as extractant a lipophilic derivative of EDTA, namely the derivative of particular formula (Ia) in which R 1 , R 2 , R 3 and R 4 represent a hydrogen atom, X 1 and X 2 represent a group –N(C10H21)2 while X 3 and X 4represent an –OH group. 1 – Synthesis of the derivative: The derivative was previously synthesized by reacting EDTA dianhydride (commercially available) with an excess of didecylamine. To do this, 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 at 90 °C with vigorous stirring for 12 hours. After cooling, the mixture was poured into 330 mL of milli-Q ^ water and the precipitate was collected by vacuum filtration. The solid was washed with 50 mL of milli-Q ^ water then dissolved in 150 mL of methanol and evaporated under reduced pressure to a dry residue. The latter was recrystallized from 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 were thus obtained in the form of a white solid (Yield: 78%). 2 – Nd(III) extraction tests: A first series of extraction tests was carried out using: ^ 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-1-ol, MIBK, 3-heptanone, TBP as well as an n-dodecane / 1-octanol mixture (93 / 7, v / v). 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) in a tube and subjecting the tube to vigorous shaking (400 rpm) for 30 minutes at room temperature, followed by centrifugation at 11000 g for 5 minutes.Afterwards, 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 (PlasmaCAL ^) at 1004 ± 5 ​​µg / mL. The concentrations of Nd(III) present in the organic solutions were deduced from those obtained for the aqueous solutions after a simple mass balance. The extraction coefficients, E%Nd, and distribution coefficients, DNd, of Nd(III) were calculated from the concentrations thus determined.Figures 1 to 3 illustrate: ^ Figure 1: the Nd(III) extraction coefficients obtained as a function of the initial pH of aqueous hydrochloric solutions; ^ Figure 2: the Nd(III) distribution coefficients obtained as a function of the initial pH of aqueous hydrochloric solutions; and ^ Figure 3: the Nd(III) extraction coefficients obtained as a function of the initial pH of aqueous nitric solutions.Furthermore, Figure 4 illustrates the distribution isotherm of neodymium(III) in the form of a curve which shows the equilibrium relationship existing between the concentration of Nd(III) in organic solution, noted [Nd]org,eq and expressed in g / L, and the initial concentration of this same element in aqueous solution, noted [Nd]aq,init and expressed in g / L, as obtained for the tests in which neodymium(III) was extracted from an aqueous solution comprising 0.01 mol / L of hydrochloric acid or nitric acid (pH 2) using as organic solution, a solution comprising 0.015 mol / L in 1,3-diisopropylbenzene. 3 – Nd(III) back-extraction tests: The back-extraction tests were carried out using: ^ as organic solutions, the solutions loaded with neodymium(III) as obtained following the extraction tests reported in point 2 above; and ^ as aqueous solutions, solutions comprising 0.01 mol / L of DTPA in water.Each test was carried out following an operating protocol similar to that described in point 2 above. The analysis of the Nd(III) concentrations in the aqueous and organic solutions after their separation was also carried out as described in point 2 above. These tests showed that it is possible to back-extract almost all of the neodymium(III) from an organic solution in which it has been previously extracted, using an aqueous solution containing DTPA at a level of 0.01 mol / L.4 – Extraction tests of Nd(III), Pr(III) and Dy(III): In order to get as close as possible to an acid leaching medium for NdFeB permanent magnets, a second series of extraction tests was carried out using: ^ as aqueous solutions, solutions comprising from 0.1 mmol / L to 0.01 mol / L of hydrochloric acid or nitric acid and from 0.01 mol / L to 1.5 mol / L of each of the rare earths (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 / 1-octanol mixture (93 / 7, v / v). Each test was carried out following an operating protocol similar to that described in point 2 above. The analysis of the concentrations of the three rare earths in the aqueous and organic solutions after their separation was also carried out as described in point 2 above.Their extraction coefficients, E%M, and distribution coefficients, DM, were calculated from the concentrations thus determined, then the separation factors of neodymium(III) with respect to praseodymium(III) on the one hand, and dysprosium(III) on the other hand, FSNd / Pr and FSNd / Dy, were calculated from the DMs thus obtained.The results are illustrated in Figures 5 and 6 and in Table I below which show: ^ Figure 5: the extraction coefficients of Nd(III), Pr(III) and Dy(III) obtained as a function of the initial pH of the aqueous hydrochloric solutions for the extractions carried out with the derivative in solution in 1,3-diisopropylbenzene; ^ Figure 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 the 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 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-diisopropyl-benzene or the n-dodecane / 1-octanol mixture (93 / 7, v / v). 1.3. n-dodecane / 1-octanol (93 / 7, v / v) 1.26 1.07 1.27 1.23 Acid of aqueous HCl HNO3 solutions These results show that the derivative allows the extraction of neodymium(III), praseodymium(III) and dysprosium(III) from an aqueous hydrochloric or nitric acid solution with a pH ranging from 2 to 4. They also show that the derivative has a greater affinity for neodymium(III) than for the other two rare earths, this affinity being in the order: Nd ^ Pr ^ Dy for the extractions carried out with the derivative in solution in 1,3-diisopropylbenzene while it is in the order: Nd ^ Dy ^ Pr for the extractions carried out with the derivative in solution in the mixture n-dodecane / 1-octanol (93 / 7, v / v). EXAMPLE 2: Use of two lipophilic derivatives of CyDTA The liquid-liquid extraction tests reported below were carried out using as extractant, two lipophilic derivatives of CyDTA, in n-dodecane, namely: ^ the derivative of particular formula (Ib) in which R 3 , R 4 and R 11 to R 14represent a hydrogen atom, X 1 and X 2 represent a group –N(C12H25)2 while X 3 and X 4 represent a –OH group, called “RP2 derivative” hereinafter; and ^ the derivative of particular formula (Ib) in which R 3 , R 4 and R 11 to R 14 represent a hydrogen atom, X 1 and X 2 represent a group –N(C8H 17 )2while X 3 and X 4represent an –OH group, hereinafter referred to as “RP4 derivative”. 1 – Synthesis of the derivatives: The derivatives were previously synthesized by reacting the CyTDA dianhydride with an excess of didodecylamine for the RP2 derivative and dioctylamine for the RP4 derivative. * Synthesis of the CyTDA dianhydride: 12.64 g (36.7 mmol) of trans-1,2-diaminocyclohexane tetraacetic acid monohydrate (CyDTA ^H2O) 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 left stirring overnight. The solution obtained was poured dropwise into 350 mL of diethyl ether and the suspension formed was then filtered through a sintered glass of porosity 3. The precipitate was washed with diethyl ether (3 x 100 mL) and then dried under vacuum. 7.27 g of the expected dianhydride were thus obtained in the form of a yellowish powder (Yield: 69%).* Synthesis of the RP2 derivative: 1 g (3.22 mmol) of the previously obtained CyDTA dianhydride and 2.51 g (2.2 eq., 7.08 mmol) of didodecylamine were introduced into a 100 mL two-necked flask equipped with a septum, topped with a condenser and placed under an argon atmosphere. Then, 40 mL of DMF was added, the mixture was brought to 60 °C and left stirring overnight. The DMF was then evaporated under vacuum and the residual crude was solubilized in 100 mL of dichloromethane (or DCM) and then poured into a 250 mL separating funnel. The organic phase was washed with a 3 M hydrochloric acid solution (2 x 100 mL) and then with deionized water (Milli-Q ^ - 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 reverse-phase flash chromatography (C18 column) and elution by methanol / isopropanol gradient (from 100 / 0 to 80 / 20). 2.19 g of the RP2 derivative were thus obtained in the form of a white paste (Yield: 67%). * Synthesis of the RP4 derivative: 1.43 g of the RP4 derivative in the form of a yellowish oil were obtained by following a protocol similar to that described for the synthesis of the RP2 derivative, except that 1 g (3.22 mmol) of the CyDTA dianhydride was reacted with 1.71 g (2.2 eq., 7.08 mmol) of dioctylamine and that the elution of the C18 column used for purification was carried out by methanol / water gradient from 95 / 5 to 100 / 0 (Yield: 56%).2 – Extraction tests: The extraction tests were carried out using: ^ as aqueous solutions, solutions comprising 1 mmol / L of nitric acid and from 0.01 mol / L to 0.1 mol / L of neodymium(III), praseodymium(III) and dysprosium(III) in nitrate form 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. Each test was carried out following an operating protocol similar to that described in point 2 of Example I above. The analysis of the concentrations of the three rare earths in the aqueous and organic solutions after their separation was also carried out as described in point 2 of Example I above. Their extraction coefficients, E%M, were calculated from the concentrations thus determined.The results are illustrated in Figures 7 and 8, which present the extraction coefficients thus obtained as a function of the concentrations of RP2 (Figure 7) and RP4 (Figure 8) in the organic solutions. 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, have an identical or almost identical affinity for neodymium(III), praseodymium(III) and dysprosium(III). These results are extremely interesting because they mean that the invention offers a panel of extractants capable of carrying out both an extraction of neodymium(III) selective with respect to praseodymium(III) and dysprosium(III) – if such an extraction is sought – and an extraction of all three of these rare earths. CITED REFERENCES [1] EP-A-3323899 [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. Chim.Acta 1980, 63(8), 2264-2270 [7] US-B-8,785,691 [8] WO-A-2014 / 064587.

Claims

Claims 1. Use of a derivative of an aminopolycarboxylic acid, which corresponds to the general formula (I) or (II) below: O X 2 R3 R2 X6 R1 R10 O (I) (II) in which: m is 0 or 1; R 1 and R 2 together form a saturated or unsaturated C5 or C6 ring, optionally substituted one or more times by a hydrogen atom, a linear or branched C1 to C alkyl group 40 , a C5 or C6 cycloalkyl group or by a monocyclic aryl group; R 3 , R 4 , R 5 , R 6 , R 7 and R 8 represent, independently of each other, a hydrogen atom, a linear or branched C1 to C alkyl group 40 , a C5 or C6 cycloalkyl group or a monocyclic aryl group; X 1 and X 2 , identical to each other, and X 3 and X 4 , identical to each other but different from X 1 and X 2, represent either a hydroxyl group or a –NHR or –NRR' group with R and R' representing a linear or branched C6 to C alkyl group 20 , a C5 or C6 cycloalkyl group or a monocyclic aryl group; X 5 and X 6 , identical to each other, represent a group –NHR or –NRR' with R and R' representing a linear or branched C6 to C alkyl group 20 , a C5 or C6 cycloalkyl group or a monocyclic aryl group; R 9 represents a linear or branched C1 to C40 alkyl group, a C5 or C6 cycloalkyl group, a monocyclic aryl group or a –CH2-CONHR or –CH2-CONRR' group with R and R' representing a linear or branched C1 to C alkyl group 40 , a C5 or C6 cycloalkyl group or a monocyclic aryl group; and R 10represents a –COOH group; as an extractant, for extracting at least one rare earth from an acidic aqueous solution A1.

2. Use according to claim 1, in which m is 0.

3. Use according to claim 1 or claim 2, in which R 1 and R 2 together form a cyclohexyl or phenyl group, optionally substituted one or more times by a hydrogen atom, a linear or branched C1 to C alkyl group 40 , a C5 or C6 cycloalkyl group or by a monocyclic aryl group.

4. Use according to any one of claims 1 to 3, in which the derivative corresponds to the particular formula (Ib) or (Ic) below: O X3 X4 O (Ib) (Ic) in which R 3 , R 4 , R 11 , R 12 , R 13 and R 14 represent, independently of each other, a hydrogen atom, a linear or branched C1 to C alkyl group 40, a C5 or C6 cycloalkyl group, or a monocyclic aryl group.

5. Use according to claim 4, wherein X 1 and X 2 represent a group –NHR or –NRR' with R and R' representing a linear or branched C6 to C alkyl group 20 , a C5 or C6 cycloalkyl group or a monocyclic aryl group, in which case X 3 and X 4 represent a hydroxyl group.

6. Use according to claim 5, wherein X 1 and X 2 represent a group –NRR' in which R and R' are identical and represent a linear or branched C8 to C alkyl group 20 and, better still, in C8 to C 12 , preferably n-octyl, 2-ethylhexyl, n-decyl or n-dodecyl.

7. Use according to any one of claims 4 to 6, in which the aminopolycarboxylic acid derivative is chosen from: ^ the derivative of particular formula (Ib) in which R 3 , R 4 , R 11, R 12 , R 13 and R 14 represent a hydrogen atom, X 1 and X 2 represent a group –N(C12H25)2 and X 3 and X 4 represent a hydroxyl group; ^ the derivative of particular formula (Ib) in which R 3 , R 4 , R 11 , R 12 , R 13 and R 14 represent a hydrogen atom, X 1 and X 2 represent a group –N(C8H 17 )2and X 3 and X 4represent a hydroxyl group.

8. Use according to any one of claims 1 to 7, wherein the aqueous solution A1 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 solution A1 with a water-immiscible organic solution, which comprises the derivative in an organic solvent, then a separation of the aqueous solution A1 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 comprises a back-extraction of the rare earth from the organic solution obtained at the end of the extraction, the back-extraction comprising at least one contacting of the solution organic obtained at the end of the extraction with an aqueous solution A2, then the separation of the organic solution from the aqueous solution A2.

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

13. Use according to any one of claims 1 to 12, in which the rare earth is chosen from neodymium, praseodymium, dysprosium and their mixtures.

14. Use according to any one of claims 1 to 13, in which the aqueous solution A1 comes from the dissolution in an acid 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, in which the aqueous solution A1 comes from the dissolution in an acid medium of a material in a divided form and resulting from a treatment of used or discarded Neodymium-Iron-Boron permanent magnets.

Images