EP3749641A1 - Amphiphilic asymmetrical diglycolamides and use thereof for extracting rare earth metals from acidic aqueous solutions - Google Patents

Abstract

The invention relates to new optimized amphiphilic asymmetrical diglycolamides suitable for use as rare earth metal extracting agents. Said diglycolamides have general formulae (I) and (II), where: R1 = a linear or branched C2 to C4 alkyl group; R2 = a linear or branched C9 to C14 alkyl group; except for the diglycolamide of general formula (I) where R1 = n-butyl group and R2 = n-dodecyl group, and the diglycolamide of general formula (II) where R1 = ethyl group and R2 = n-dodecyl group. The invention also relates to the use of said diglycolamides for extracting rare earth metals from acidic aqueous solutions. The invention applies to the production of rare earth metals from urban ore concentrates, natural ore concentrates having a high rare earth content, or concentrates of natural ore residues.

Description

 AMPHIPHILIC DISSYMMETRIC DIGLYCOLAMIDES AND THEIR USE FOR EXTRACTING RARE EARTHS FROM AQUEOUS ACID SOLUTIONS

DESCRIPTION

TECHNICAL AREA

The invention relates to the field of extraction of rare earths present in aqueous acid solutions from natural or urban ores.

 More specifically, the invention relates to new dissymmetric diglycolamides with optimized amphiphilic character, suitable for use as extractants of rare earths.

 It also relates to the use of these diglycolamides to extract rare earth acid aqueous solutions.

 The invention finds particular applications in the production of rare earths from concentrates from "urban ores", that is to say "mines" consisting of industrial and domestic waste including rare earths and, in particular, in recycling rare earth present:

 - in waste electrical and electronic equipment (also known as "WEEE" or "D3E") and, more specifically, in used or scraped permanent magnets of the Neodymium-Iron-Boron (or NdFeB) or Samarium-Cobalt (or Sm-Co); and

 - in used electrochemical cells (or batteries) of the Nickel-Hydride Metallic (or Ni-MH) type.

However, it can also be used to produce rare earths from concentrates from natural ores including rare earths such as monazites, bastnaesites, apatites or xenotimes, or from concentrates from natural mineral residues. like, for example, tin slag. STATE OF THE PRIOR ART

The rare earths (hereinafter "TR") include metals that are characterized by neighboring properties, namely scandium (Sc), yttrium (Y) and all the lanthanides, the latter corresponding to the 15 elements listed in the periodic table of Mendeleyev elements from atomic number 57 for lanthanum (La) to atomic number 71 for lutetium (Lu). In this group, we distinguish the "light" TRs, that is to say of atomic number at most equal to 61 (scandium, yttrium, lanthanum, cerium, praseodymium and neodymium), and the "heavy" TRs, c ' that is to say, of atomic number at least equal to 62 (samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium and ytterbium).

 The particular electronic configuration of the TRs, and in particular their unsaturated 4f electronic sublayer, gives them unique chemical, structural and physical properties. These properties are used in industrial applications as varied as sophisticated: glass and ceramics industries, polishing, catalysis (in particular oil and automotive), manufacturing of high-tech alloys, permanent magnets, optical devices (devices photos and cameras), phosphors, rechargeable batteries for electric or hybrid vehicles, alternators for wind turbines, etc.

 The TRs are, therefore, part of the so-called "technological" metals whose supply is strategic.

 World demand for rare earths continues to grow (around 9% to 15% per year). However, as the number of rare earth producing countries remains limited - China currently provides more than 90% of the world's rare earth production alone - there is a long-term risk of a rare earth supply breakdown, hence the need to optimize all the ways to produce them.

However, the recycling of TRs present in post-consumer waste and in manufacturing waste, still in its infancy today, is one of the TR's production pathways. One of the first markets, in terms of volume and potential market value, to recycle TRs is the NdFeB permanent magnets found in electric or hybrid vehicles, wind turbines, hard drives, induction motors, or other electrical devices. This resource for the recycling of TRs is particularly interesting to value because these magnets contain a significant amount of light TR (about 30% by weight of a neodymium / praseodymium mixture) and a smaller amount of heavy TR with high economic value (dysprosium and, sometimes, terbium). In addition to containing iron in large quantities, NdFeB permanent magnets are usually covered with a protective anticorrosive coating based on nickel and copper or other transition metals (cobalt, chromium, etc.).

 Another interesting resource for TR recycling concerns Ni-MH batteries that are mainly used in electric or hybrid vehicles but also in various portable devices and that contain a mixture of lanthanum, cerium, neodymium and praseodymium, as well as iron, nickel and cobalt.

 Recycling TRs present in post-consumer waste or manufacturing scrap therefore implies being able to effectively separate them from other metallic elements present in this waste and scrap and, in particular, iron.

 The hydrometallurgical route, based on the liquid-liquid extraction technique, is commonly considered as one of the most appropriate ways to extract the TR from the medium in which they are located and separate them from each other.

Hydrometallurgical processes, which are currently used industrially to recover TR 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 (2-trimethyl) acid , 4,4-pentyl) phosphinic (or Cyanex ™ 272), neodecanoic acid (or Versatic ™ 10) and tri-n-butyl phosphate (or TBP). However, the use of these extractants is not adapted to the recovery of TR present in an acidic aqueous phase resulting from the treatment of post-consumer waste or manufacturing scrap since they all have the disadvantage of strongly extracting the metals from transition and, in particular, iron. Their use would therefore require removing these transition metals from the aqueous phase before extracting the TR, which would lead to a heavy process to implement and therefore not industrially interesting.

 The diglycolamides (hereinafter "DGA") represent a family of extractants that was developed by a Japanese team in studies on the treatment of spent nuclear fuels in order to co-extract trivalent actinides and lanthanides from a refiner of the PUREX process but which has recently given rise to a number of studies on their use in the recycling of TRs.

The DGAs correspond to the general formula RR'NC (O) CH ₂ OCH ₂ C (O) NR "R '" in which R, R', R "and R '" represent hydrocarbon groups, which are typically alkylated.

 They are called "symmetrical" when R, R ', R "and R" "are identical to each other and" asymmetrical "when this is not the case.

 Among the dissymmetrical DGAs, two subtypes can be distinguished:

 the asymmetric type I DGAs, in which R and R 'are identical to each other, R "and R'" are identical to one another but different from R and R ', and

 the asymmetric DGAs of type II, in which R and R "are identical to each other, R 'and R'" are identical to one another but different from R and R ";

As regards the use of symmetrical DGA as extractants in the recycling of TR, it has been shown in PCT International Application WO 2016/046179, hereinafter reference [1], that symmetrical lipophilic DGAs containing 24 or more carbon atoms, such as / V, / V, / V ', / V'-tetraoctyl-3-oxapentanediamide (or TODGA), make it possible to recover dysprosium, praseodymium and neodymium from an acidic aqueous phase resulting from the treatment of permanent magnets NdFeB, not only quantitatively but also selectively vis-à-vis other metal elements present in this phase, in particular vis-à-vis iron and boron. Concerning the use of dissymmetric DGA as extractants in the recycling of TR, the data of the literature are, on the other hand, much less convincing.

 Thus, Mowafi and Mohamed (Sep. Sci Technol., 2017, 52 (6), 1006-1014, hereinafter reference [2]) have used the / V, / V-dihexyl- / V ', / V'- didecyldiglycolamide (or (DH-DD) -DGA) to recover several TRs from three acidic aqueous media: nitric, sulfuric and hydrochloric. In addition to the fact that the selectivity of this DGA for TRs with respect to iron, nickel, cobalt and cesium has only been evaluated in aqueous nitric media, the concentrations of metallic elements used in this study, namely 0.002 mol / L, are much lower than those expected for an aqueous phase resulting from the treatment of a waste or a manufacturing waste; this is particularly true for iron whose concentration in waste and scrap manufacturing is an essential problem of the recycling of TR.

 Narita and Tanaka (Solvent Extraction Research and Development, Japan, 2013, 20, 115-121, hereinafter reference [3]) have themselves been interested in the use of L /, L / '- dimethyl-L / , L '' - di-n-octyldiglycolamide (or MODGA), as an extractant for recovering TR from acidic aqueous media from the processing of NdFeB permanent magnet manufacturing scrap. These authors show that it is possible to separate neodymium and dysprosium from iron and nickel with this DGA, as well as neodymium dysprosium in an aqueous nitric or sulfuric medium. However, their work relies solely on aqueous acidic phases which contain only 0.001 mol / L of dysprosium, neodymium, iron and nickel, which, again, are very far from those expected in an aqueous acid phase resulting from the treatment. permanent magnets NdFeB. Thus, no test has been performed on aqueous acidic phases simulating those actually obtained from the treatment of permanent magnets. In addition, the latter do not specify the behavior and impact of other metal elements also present in an acidic aqueous phase from the treatment of NdFeB permanent magnets such as, for example, praseodymium or cobalt.

Finally, it is important to mention the work of Ravi et al. (Radiochem Acta 2014, 102 (7), 609-617, hereinafter reference [4]) which, although not related to the field of recycling of TRs from waste and scrap manufacturing but falling within the field of spent nuclear fuel treatment, have shown that the extraction of europium from a nitric aqueous phase, of molarity greater than 1, by DGAs asymmetric compounds of formula RR 'CN (O) CH 2 OCH 2 C (O) N ((CH 2) n CH 3) 2 in which R and R' represent a n-butyl, n-hexyl, n-octyl or n-decyl group, does not vary from significantly when the number of carbon atoms of the alkyl groups R and R 'decreases from 8 to 6, then from 6 to 4.

 In view of the major challenge posed by the recycling of TRs present in post-consumer waste and manufacturing scrap and, in particular, in used or discarded NdFeB permanent magnets and used Ni-MH batteries and batteries, the Inventors considered that it was desirable to increase the range of extractants suitable for use for the purposes of this recycling.

 They have therefore set themselves the goal of providing new extractants that make it possible to efficiently extract TRs from acidic aqueous solutions derived from natural or urban ores, with good selectivity towards other metallic elements that are susceptible to be also present in these aqueous solutions and, in particular, vis-à-vis iron, cobalt and nickel.

 However, as part of their work, the inventors found that, contrary to the teaching of reference [4], the degree of amphiphilicity of an asymmetrical DGA - which is a function of the number of carbon atoms that show the hydrocarbon groups borne by two amide nitrogens - has an impact on its ability to extract TRs from acidic aqueous solutions and on the selectivity of this extraction and that, therefore, it is possible to have dissymmetrical DGAs with extremely good properties. interesting in terms of extraction capacity of the TRs as well as extraction selectivity by optimizing the amphiphilarity of these DGAs.

 In particular, they found that these properties are at least equivalent and even superior to those presented by the TODGA which is used in reference [1].

And it is on these findings that the invention is based. STATEMENT OF THE INVENTION

These objects are achieved by the invention, which firstly relates to a diglycolamide which corresponds to one of the general formulas (I) and (II):

 (I) (N)

in which :

R ¹ represents a linear or branched alkyl group comprising from 2 to 4 carbon atoms; and

R ² represents a linear or branched alkyl group comprising from 9 to 14 carbon atoms;

with the exception, however, of the diglycolamide of the general formula (I) in which R ¹ represents an n-butyl group and R ² represents an n-dodecyl group and diglycolamide of the general formula (II) in which R ¹ represents an ethyl group and R ² represents an n-dodecyl group.

 Thus, whether it meets the general formula (I) or the general formula (II), the DGA of the invention has the characteristics to include:

on the one hand, two hydrophilic groups identical to each other, each comprising 2 to 4 carbon atoms and corresponding to the radicals R ¹ ; and

on the other hand, two lipophilic groups that are identical to each other, each comprising 9 to 14 carbon atoms and corresponding to the radicals R ² .

 In what precedes and what follows, one understands:

 "linear or branched alkyl group comprising 2 to 4 carbon atoms" means any group selected from ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl;

"linear or branched alkyl group of 9 to 14 carbon atoms" means any straight or branched chain alkyl group which comprises 9, 10, 11, 12, 13 or 14 carbon atoms such as a group n- nonyl, isononyl, n-decyl, isodecyl, n-undecyl, isoundecyl, n-dodecyl, isododecyl, n-tridecyl, isotridecyl, n-tetradecyl, isotetradecyl, 2-methyloctyl, 2-methylnonyl, 2-methyldecyl, 2-methylundecyl, 2-methylldodecyl, 2-methyltridecyl, 2- ethylheptyl, 2-ethyloctyl, 2-ethylnonyl, 2-ethyldecyl, 2-ethylundecyl, 2-ethyldodecyl, 2-propylhexyl, 2-propylheptyl, 2-propyloctyl, 2-propylnonyl, 2-propyldecyl, 2-propylundecyl, 2-butylhexyl, 2-butylheptyl, 2-butyloctyl, 2-butyldecyl, 2-hexyloctyl, 3,7-dimethyloctyl, 2,4,6-trimethylheptyl, etc.

 In addition, the terms "aqueous medium", "aqueous solution" and "aqueous phase" are equivalent and interchangeable, just as the terms "organic solution" and "organic phase" are equivalent and interchangeable.

 Also, the expressions "from .... to ...." and "understood (e) between .... and ...." are equivalent and mean to mean that the bounds are included.

According to the invention, R ¹ advantageously represents an ethyl, n-propyl, isopropyl, n-butyl or isobutyl group, while R ² advantageously represents a linear alkyl group.

In addition, it is preferred that R ² comprise from 10 to 14 carbon atoms, or in other words, that R ² is selected from n-decyl, n-undecyl, n-dodecyl, n-tridecyl and n-tetradecyl, preferably among all being given to the n-dodecyl group.

 Thus, as examples of preferred DGAs, mention may be made of:

the DGA of general formula (I) in which R ¹ represents an ethyl group and R ² represents an n-dodecyl group, hereinafter referred to as (DE-DDd) -DGA;

the DGA of general formula (I) in which R ¹ represents an n-propyl group and R ² represents an n-dodecyl group, hereinafter referred to as (DP-DDd) -DGA;

the DGA of general formula (I) in which R ¹ represents an isopropyl group and R ² represents an n-dodecyl group, hereinafter referred to as (DiP-DDd) -DGA;

the DGA of general formula (II) in which R ¹ represents an n-propyl group and R ² represents an n-dodecyl group, hereinafter referred to as DPDDdDGA;

the DGA of general formula (II) in which R ¹ represents an n-butyl group and R ² represents an n-dodecyl group, hereinafter referred to as DBDDdDGA; and the DGA of general formula (II) in which R ¹ represents an isobutyl group and R ² represents an n-dodecyl group, hereinafter referred to as DiBDDdDGA.

 Among these DGAs, preference is given:

 - to (DE-DDd) -DGA because of its particularly good performance in extracting all the TRs from a nitric aqueous medium, with distribution coefficients of the TRs which are, according to the extracted TR, 8 to 15 times higher than those obtained under the same operating conditions with TODGA;

 - DPDDdDGA because it is particularly efficient for extracting dysprosium from an aqueous sulfuric medium, with a distribution coefficient of dysprosium that is 110 times higher than that obtained under the same operating conditions with TODGA; and

 - to DBDDdDGA because of its high performance in extracting all TRs from an aqueous hydrochloric medium, with distribution coefficients that are, according to the extracted TR, 2 to 4 times higher than those obtained in the same conditions with the TODGA.

 The subject of the invention is also the use of a DGA as defined above for extracting at least one rare earth from an acidic aqueous solution.

 According to the invention, said at least one rare earth is preferably extracted from the acidic aqueous solution by liquid-liquid extraction, in which case this aqueous solution is brought into contact with a water-immiscible organic solution, which comprises DGA in an organic diluent and then separated from the organic solution.

 The concentration of the DGA in the organic solution is advantageously between 0.05 mol / l and 0.5 mol / l and is preferably equal to 0.1 mol / l.

 The organic solution may furthermore comprise a phase modifier capable of increasing the loading capacity of the DGA, that is to say the maximum concentration of metallic elements that can present the organic solution without the occurrence of the formation of a third phase by demixing when this organic solution is brought into contact with an aqueous solution loaded with metal elements.

The phase modifier may especially be chosen from trialkyl phosphates such as tri-n-butyl phosphate (or TBP) or tri-n-hexyl phosphate (or THP), alcohols such as n-octanol, n-decanol or isodecanol, and monoamides such as L /, / V-dihexyloctanamide (or DHOA), L /, V-dibutyldecanamide (or DBDA), N, N-di (2-ethylhexyl) acetamide (or D2EHAA), N, N-di (2-ethylhexyl) -propionamide (or D2EHPA), N, N-di (2-ethylhexyl) isobutyramide (or D2EHÎBA) or / V, / V-dihexyldecanamide (or DHDA).

 Moreover, this phase modifier preferably represents not more than 15% by volume of the volume of the organic solution, or not more than 10% by volume of the volume of this solution when it is an alcohol. like n-octanol.

 As for the organic diluent, it may be any non-polar organic diluent whose use has been proposed for carrying out liquid-liquid extractions such as a hydrocarbon or a mixture of hydrocarbons, for example n-dodecane, hydrogenated tetrapropylene (TPH), kerosene, Isane ™ IP-185T or Isane ™ IP-175T, preferably being given to n-dodecane.

 According to the invention, the acidic aqueous solution from which the at least one rare earth is extracted preferably comprises a mineral acid, which is advantageously nitric acid, sulfuric acid, hydrochloric acid or a mixture of those -this.

However, it goes without saying that said acidic aqueous solution may comprise a mineral acid other than HNO ₃ , H ₂ SO ₄ and HCl, or a mixture of mineral acids other than a mixture of these acids.

 In any case, the concentration of the mineral acid or mixture of mineral acids in the acidic aqueous solution is preferably between 0.1 mol / L and 5 mol / L.

 This acidic aqueous solution may be, in the first place, a solution resulting from the dissolution in acid medium of a concentrate of urban ore and, in particular, a concentrate of a waste D3E.

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). NdFeB or Sm-Co permanent magnets used or discarded. Alternatively, it may also be a solution resulting from the dissolution in acid medium of a material in a divided form (powder, fragments, etc.) and resulting from a treatment (for example, heat treatment + grinding) of used Ni-MH batteries or batteries.

 In another variant, it may also be a solution resulting from the dissolution in an acidic medium of a natural ore comprising rare earths such as monazite, bastnaesite, apatite or xenotime, or dissolution in an acidic environment. a residue of a natural ore such as a tin slag.

 In any event, the rare earth is preferably selected from lanthanum, praseodymium, neodymium, dysprosium and mixtures thereof.

 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 only as an illustration of the subject of the invention and should in no way be interpreted as a limitation of this object. DETAILED PRESENTATION OF PARTICULAR METHODS OF IMPLEMENTATION

I - SYNTHESIS OF DIGLYCOLAMI OF THE INVENTION:

 1.1 - DGA of general formula (I):

 The DGAs of general formula (I) can be obtained by the synthesis process represented below:

In this synthesis process, a solution comprising, on the one hand, 0.2 mol / L (1 eq) of diglycolic anhydride, denoted 1, and, on the other hand, 0.2 mol / L (1 eq. of an amine, denoted 2, of formula (R ² ) ₂ -NH in which R ² is as defined in general formula (I), in an apolar aprotic solvent such as 2-methyltetrahydrofuran (or 2- MeTHF), is stirred for 6 hours to yield dialkyldiglycolamic acid, noted 3.

Then, a coupling reagent such as 1-cyano-2-ethoxy-2-oxoethylidenaminooxy) dimethylamino-morpholino-carbenium hexafluorophosphate (or COMU-1,2 eq.) And a tertiary amine such as / V, / V-diisopropylethylamine (or DIPEA-2 eq.) Are added to the medium and this is stirred for 5 minutes before the addition of an amine (1.1 eq.), Denoted 4, of formula (R ^ -NH wherein R ¹ is as defined in general formula (I) The medium is stirred overnight at room temperature.

The reaction is stopped by adding water, the medium is filtered and the filtrate is washed with a saturated solution of Na ₂ CO 3 and a 10% solution of HCl. The organic phase obtained is dried over MgSO ₄ , filtered and concentrated and the residue obtained is purified by flash chromatography on silica gel using a gradient of the heptane / ethyl acetate mixture. The fractions containing the pure product are combined and concentrated. A DGA of pure general formula (I) is thus obtained in the form of a colorless to yellow oil with a yield of 37% to 71%.

Are thus synthesized:

 1) the (DE-DDd) -DGA, which corresponds to the following particular formula:

¹ H NMR (CDC _3, 400 MHz!): D (ppm): 4.30 (sc, 4H), 3.24 (m, 8H); 1.49 (m, 4H), 1.25 (m, 36H), 1.15 (t, J = 7.1 Hz, 3H), 1.08 (m, 3H), 0.86 (t, J = 7.1 Hz, 6H).

¹³ C NMR (CDC _3, 101 MHz!): D (ppm): 168.44, 168.10, 68.68, 48.80, 45.87, 40.98, 40.21, 31.90, 26.66, 29.60, 29.56, 29.51, 29.44, 29.37, 29.32, 28.82, 27.51 , 27.07, 26.75, 22.65, 14.06, 12.81 HRMS (ESI positive mode): m / z calculated for {MH} ⁺ : 525.4995; found: 525.4996

2) the (DP-DDd) -DGA, which responds to the following specific formula:

¹ H NMR (CDCl 4, 400 MHz): d (ppm): 4.26 (s, 2H), 4.28 (s, 2H), 3.24 (m, 4H), 3.14 (t, 3H, H = 8 Hz, 4H), 1.51 (m, 8H), 1.22 (m, 36H), 0.85 (m, 12H)

¹³ C NMR (CDCl 3, 101 MHz): d (ppm): 168.55, 168.42, 69.10, 69.04, 48.47, 47.32, 46.90, 45.73, 31.89, 29.63, 29.60, 29.56, 29.52, 29.40, 29.34, 29.32, 28.94, 27.58 , 27.01, 26.81, 22.66, 22.06, 20.75, 14.09, 11.35, 11.13

HRMS (ESI positive mode): m / z calcd for {MH} ⁺ : 553.5308; found: 553.5310

3) the (DiP-DDd) -DGA, which responds to the following particular formula:

¹ H NMR (CDCl2, 400 MHz): d (ppm): 4.27 (s, 2H), 4.23 (s, 2H), 3.93 (s, 1H), 3.43 (s, 1H), 3.28 (t, J); = 7.6 Hz, 2H), 3.16 (t, J = 7.6 Hz, 2H), 1.51 (m, 4H), 1.40 (d, J = 5.7 Hz, 6H), 1.25 (m, 37H), 1.17 (d, J). = 6.4 Hz, 6H), 0.87 (t, J = 6.7 Hz, 6H)

¹³ C NMR (CDCl 3, 101 MHz): d (ppm): 168.56, 167.80, 70.96, 69.17, 48.05, 47.07, 46.01, 45.90, 32.04, 29.78, 29.75, 29.74, 29.67, 29.55, 29.48, 29.08, 27.73, 27.17 , 26.95, 22.81, 20.93, 20.57, 14.25

HRMS (ESI positive mode): m / z calcd for {MH} ⁺ : 553.5308; found: 553.5305

1.2 - DGA of general formula (II):

The DGA of general formula (II) can be obtained by the synthesis process represented below:

In this method of synthesis, a solution comprising, on the one hand, 2 mol / L (1 eq.) Of an aldehyde, noted, of formula R ¹ -CHO in which R ¹ has the same meaning as in the general formula (II) and, on the other hand, 2 mol / L (1 eq.) Of an amine, denoted 2 ', of formula R ² -NH ₂ in which R ² has the same meaning as in the general formula (II ), in a protic polar solvent such as ethanol, is stirred for 30 minutes at 40 ° C. After cooling the medium to 0 ° C, ethanol is added (2 mL per mmol). A reducing agent such as sodium borohydride (NaBH ₄ - 2.5 eq.) Is then slowly added to the medium and the latter is stirred overnight at room temperature.

A saturated aqueous solution of NH ₄ Cl and water are then added and the aqueous phase is extracted twice with ethyl acetate. The organic phases are combined, dried over MgSO ₄ , filtered and concentrated. The residue is purified by flash chromatography on silica gel using a gradient of the dichloromethane + 5% NH 4 / isopropanol mixture. The fractions containing the pure product are combined and concentrated.

An amine, denoted 3 ', of formula R ¹ R ² -NH is thus obtained in which R ¹ and R ² have the same meaning as in general formula (I) in the form of a white solid or an oil colorless with a yield of 46% to 61%.

A solution comprising diglycolic acid (1 eq.), A coupling reagent such as COMU (2.2 eq.) And a tertiary amine such as DIPEA (4 eq.) In an apolar aprotic solvent such as 2-MeTHF is stirred for 15 minutes at room temperature room. Then, the 3 'amine (2.2 eq.) Is added to the medium and the medium is stirred overnight at room temperature.

The reaction is stopped by adding water and the organic phase is washed with saturated Na ₂ CO 3 solution and 10% HCl solution. The organic phase thus obtained is dried over MgSO ₄ , filtered and concentrated and the residue is purified by flash chromatography on silica gel using a gradient of the dichloromethane / ethyl acetate mixture. The fractions containing the pure product are combined and concentrated. A DGA of pure general formula (II) is thus obtained in the form of a colorless to yellow oil with a yield of 46% to 57%.

Are thus synthesized:

1 °) the DPDDdDGA, which responds to the following specific formula:

¹ H NMR (CDCl 4, 400 MHz): d (ppm): 4.31 (s, 4H), 3.26 (q, J = 7.5 Hz, 4H), 3.10 (q, J = 7.6 Hz, 4H), 1.54 (m, 8H), 1.25 (m, 38H), 0.88 (m, 12H)

¹³ C NMR (CDC _3, 101 MHz!): D (ppm): 168.64, 168.60, 68.52, 68.45, 48.31, 47.55, 46.85, 45.94, 32.05, 29.81, 29.78, 29.72, 29.69, 29.61, 29.53, 29.49, 28.92 , 27.64, 27.20, 26.95, 26.92, 22.82, 22.01, 20.81, 14.25, 11.48, 11.22, 11.19

HRMS (ESI positive mode): m / z calcd for {MH} ⁺ : 553.5308; found: 553.5309

2 °) the DBDDdDGA, which corresponds to the following particular formula:

³ H NMR (CDCl 4, 400 MHz): d (ppm): 4.38 (se, 4H), 3.22 (m, 4H), 3.09 (m, 4H), 1.45 (m, 8H), 1.25 (m). , 42H), 0.93 (t, J = 7.4 Hz, 3H), 0.88 (t, J = 6.8 Hz, 9H) ¹³ C NMR (CDCl 3, 101 MHz): d (ppm): 169.10, 68.53, 46.94, 46.84, 46.28, 45.77, 32.06, 30.83, 29.93, 29.90, 29.88, 29.83, 29.81, 29.77, 29.75, 29.69, 28.83, 27.57 , 27.38, 26.82, 22.82, 20.25, 19.99, 19.96, 14.27, 13.98, 13.92

HRMS (ESI positive mode): m / z calcd for {MH} ⁺ : 581.5621; found: 581.5616

3 °) DiBDDdDGA, which corresponds to the following particular formula:

¹ H NMR (CDC _3, 400 MHz!): D (ppm): 4.32 (m, 4H), 3.29 (t, J = 7.5 Hz, 2H), 3.17 (m, 4H), 3.01 (d, J = 7.5Hz, 2H), 1.93 (m, 2H), 1.51 (m, 4H), 1.25 (m, 36H), 0.88 (m, 18H)

¹³ C NMR (CDCl3, 101 MHz): d (ppm): 169.00, 69.97, 53.85, 52.44, 47.19, 45.97, 31.92, 29.63, 29.61, 29.56, 29.43, 29.38, 29.35, 28.77, 27.49, 27.26, 27.10. , 26.88, 26.69, 22.69, 20.15, 19.90, 14.12

HRMS (ESI positive mode): m / z calcd for {MH} ⁺ : 581.5621; found: 581.5620

EXTRACTANT PROPERTIES OF THE DIGLYCOLAMIDES OF THE INVENTION

In the examples which follow, the concentration measurements were carried out by inductively coupled plasma atomic emission spectrometry (ICP-AES) or by inductively coupled plasma mass spectrometry (ICP-MS).

 In addition, the distribution coefficients and separation factors were determined in accordance with the conventions of the field of liquid-liquid extractions, namely that:

the coefficient of distribution (or partitioning) of a metallic element M, denoted DM, between two phases, organic and aqueous, respectively, is equal to:

with:

[M] _org . = concentration of the metal element in the organic phase at the equilibrium of extraction (in mg / L); and [M] _aq . = concentration of the metallic element in the aqueous phase at the equilibrium of extraction (in mg / L);

the separation factor between two metallic elements M1 and M2, denoted FSMI / M2, is equal to:

with:

 DMI = coefficient of distribution of the metal element M1; and

 DM2 = distribution coefficient of the metal element M2.

11.1 - In a nitric aqueous medium:

 Extractions are carried out using:

 as organic phases: solutions comprising either 0.1 mol / L of a DGA of the invention or 0.1 mol / L of a DGA of the state of the art, namely TODGA, in a mixture TPH / n-octanol (90/10, v: v); and

as aqueous phases: aliquots of an aqueous solution representative of a real leachate, called "solution A", comprising 3 mol / L of nitric acid (to simulate the acidity likely to be presented by an aqueous solution resulting from dissolution of TR-rich fractions in nitric acid) as well as representative light and heavy TRs (La ¹¹¹ , Pr ^m , Nd ^m and Dy ^m ) and representative metal impurities (Fe ^m , Co ", Ni") . The concentrations of these elements in solution A are specified in Table 1 below.

 Table 1

Each of these extractions is carried out by contacting, in tube and with stirring, an organic phase with an aliquot of solution A for 30 minutes at 25 ° C. The volume ratio O / A is 1. No third phase was observed during the extraction phases.

 Then, after centrifugation and separation of the phases, each organic phase loaded with TR is subjected to an extraction for analytical purposes by contacting, in tube and with stirring, with an aqueous solution comprising 1 mol / L of nitric acid, 0, 2 mol / L of L /, L / ', L /, L /' - tetraethyldiglycolamide (or TEDGA) and 0.5 mol / L of oxalic acid for 15 minutes at 25 ° C., with a volume ratio O / A equal to 0.2. The mixture is centrifuged and the phases are separated.

 The concentrations of the different metallic elements are measured in solution A before extraction, in the aqueous phases obtained after extraction and in the organic phases obtained after desextraction.

 The coefficients of distribution and the separation factors TR / impurities obtained from these measurements are respectively presented in Tables 2 and 3 below in which they are compared with those obtained under the same operating conditions with a diglycolamide of the state. of the art, namely TODGA.

Tables 2 and 3 below show respectively the coefficients of distribution and the separation factors TR / impurities as obtained for three DGAs of general formula (I), namely the (DE-DDd) -DGA, the (DP -DDd) -DGA and (DiP-DDd) -DGA, for a DGA of general formula (II), namely DiBDDdDGA, as well as for TODGA.

Table 2

Table 3

These results show that the DGAs of the invention have higher TR extraction properties than those of TODGA in a nitric aqueous medium.

 They also show that these DGAs have a particularly high affinity for heavy TRs such as dysprosium.

(DE-DDd) -DGA, which comprises two ethyl groups carried by the same amide nitrogen, has the best performance, probably because its structure makes it possible, by reducing the steric hindrance, a better accessibility of this DGA around the TRs. and, therefore, better coordination of TRs by this DGA. So, this DGA leads to distribution coefficients of TRs 8 to 15 times higher than those obtained with TODGA.

 A comparison of the respective performances of (DE-DDd) -DGA and the other DGAs of the invention shows that the increase in the length of the hydrophilic alkyl chains substantially reduces the affinity of these DGAs for the TRs, and that the DGA asymmetrical type I or type II.

 Conversely, the presence of branching in the hydrophilic alkyl chains appears to increase the affinity. This is contrary to what has been reported in the literature, for example by Sasaki et al., Solvent Extr. Ion Exch. 2015, 33 (7), 625-641, hereinafter [5], for symmetrical DGAs where the presence of branching decreases the affinity for TRs, in particular by comparing the performances of TODGA and L /, L /, L / '/ V'-tetra (2-ethylhexyl) diglycolamide (or TEHDGA).

 Concerning the extraction of iron, nickel and cobalt impurities, the results indicate, for each of the DGAs of the invention tested, iron distribution coefficients less than or equal to 0.01 and lower nickel and cobalt distribution coefficients. at 0.03. These values correspond to the quantification limits of the analytical devices (ICP-AES and ICP-MS) used for the analyzes.

11.2 - In aqueous sulfuric medium:

 Extractions / de-extractions are carried out according to the same operating procedure as that described in point 11.1 above, except that, for the extractions, aliquots of an aqueous solution called "solution B" are used as aqueous phases. , which is also representative of a real leachate but which comprises 2 mol / L of sulfuric acid (instead of 3 mol / L of nitric acid of solution A).

The concentrations of the metallic elements in solution B are specified in Table 4 below. Table 4

The concentrations of the various metallic elements are measured in solution B before extraction, in the aqueous phases obtained after extraction and in the organic phases obtained after desextraction.

 Tables 5 and 6 below show respectively the distribution coefficients and the separation factors TR / impurities as obtained for three DGAs of general formula (II), namely DPDDdDGA, DBDDdDGA and DiBDDdDGA, as well as for the TODGA.

 Table 5

Table 6

 N.Q ..: not quantifiable

 These results show that the DGAs of the invention also have higher TR extraction properties than TODGA in an aqueous sulfuric medium.

It is known that, in general, the affinity of the DGA for the TR in a sulfuric medium is much lower than in the nitric medium. This is due to the fact that the S0 ₄ ² ions are much more complexing for the TR than the NO3 ions in solution. Thus, in sulfuric acid medium, only heavy TRs such as dysprosium are extracted by TODGA but only very partially (DD _Y = 0.2). The very low extraction of heavy TRs by TODGA and the lack of affinity of TODGA for light TRs in sulfuric media have already been reported in the literature.

Among the DGAs of the invention, the DPDDdDGA leads to a distribution coefficient of dysprosium that is 110 times higher than that obtained with TODGA as well as excellent separation factors vis-à-vis other TR (FS) _Dy / _La > 5,000, FS _Dy / p _r = 350 and FS _Dy / _Nd = 93). This makes it a prime candidate for efficient and selective extraction of dysprosium in an aqueous sulfuric medium, knowing that dysprosium is one of the TRs with higher potential for application.

 As before, the impurity distribution coefficients are less than 0.01 for iron and less than 0.03 for nickel and cobalt. 11.3 - In aqueous hydrochloric medium:

Extractions / de-extractions are carried out according to the same operating procedure as that described in point ll.l above, except that, for the extractions, used as aqueous phases, aliquots of an aqueous solution called "solution C", which is also representative of a real leachate but which comprises 2 mol / L of hydrochloric acid (instead of 3 mol / L of nitric acid solution A).

 The concentrations of the metallic elements in solution C are specified in Table 7 below.

 Table 7

The concentrations of the different metallic elements are measured in solution C before extraction, in the aqueous phases obtained after extraction and in the organic phases obtained after desextraction.

 Tables 8 and 9 below show respectively the coefficients of distribution and the separation factors TR / impurities as obtained for a DGA of general formula (II), namely DBDDdDGA, as well as for TODGA.

 Table 8

Table 9

These results show that DBDDdDGA leads to distribution coefficients for lanthanum, praseodymium and neodymium that are 2 to 4 times higher than those obtained with TODGA. DBDDdDGA has an excellent affinity for praseodymium, neodymium and dysprosium, and a lower but nevertheless satisfactory affinity for lanthanum.

 The nickel and cobalt impurities are not extracted by this DGA (DM <0.03).

 On the other hand, iron is weakly extracted as it is by TODGA.

 However, the better affinity of DBDDdDGA for TRs makes it possible to significantly increase iron selectivity compared to that obtained with TODGA.

REFERENCES CITED

[1] PCT International Application WO 2016/046179

[2] Mowafi and Mohamed, Sep. Sci. Technol. 2017, 52 (6), 1006-1014

 [3] Narita and Tanaka, Solvent Extraction Research and Development, Japan, 2013, 20, 115-121

 [4] Ravi et al., Radiochim. Acta 2014, 102 (7), 609-617

 [5] Sasaki et al., Solvent Extr. Ion Exch. 2015, 33 (7), 625-641

Claims

1. Diglycolamide, which corresponds to one of the general formulas (I) and (II):  (I) (N) in which : R ¹ represents a linear or branched alkyl group comprising from 2 to 4 carbon atoms; and R ² represents a linear or branched alkyl group comprising from 9 to 14 carbon atoms; with the exception, however, of the diglycolamide of the general formula (I) in which R ¹ represents an n-butyl group and R ² represents an n-dodecyl group and diglycolamide of the general formula (II) in which R ¹ represents an ethyl group and R ² represents an n-dodecyl group. 2. Diglycolamide according to claim 1, wherein R ² represents a linear alkyl group. The diglycolamide according to claim 2, wherein R ² is selected from n-decyl, n-undecyl, n-dodecyl, n-tridecyl and n-tetradecyl. The diglycolamide according to claim 3, wherein R ² is an n-dodecyl group. 5. Diglycolamide according to any one of claims 1 to 4, which is selected from: the diglycolamide of general formula (I) in which R ¹ represents an ethyl group and R ² represents an n-dodecyl group; the diglycolamide of general formula (I) in which R ¹ represents an n-propyl group and R ² represents an n-dodecyl group; the diglycolamide of general formula (I) in which R ¹ represents an isopropyl group and R ² represents an n-dodecyl group; the diglycolamide of general formula (II) in which R ¹ represents an n-propyl group and R ² represents an n-dodecyl group; the diglycolamide of general formula (II) in which R ¹ represents an n-butyl group and R ² represents an n-dodecyl group; and the diglycolamide of general formula (II) in which R ¹ represents an isobutyl group and R ² represents an n-dodecyl group. Diglycolamide according to claim 5, which is selected from: the diglycolamide of general formula (I) in which R ¹ represents an ethyl group and R ² represents an n-dodecyl group; the diglycolamide of general formula (II) in which R ¹ represents an n-propyl group and R ² represents an n-dodecyl group; and the diglycolamide of general formula (II) in which R ¹ represents an n-butyl group and R ² represents an n-dodecyl group. 7. Use of a diglycolamide according to any one of claims 1 to 6 for extracting at least one rare earth from an acidic aqueous solution. Use according to claim 7 which comprises contacting the acidic aqueous solution with a water immiscible organic solution which comprises diglycolamide in an organic diluent and then separating the aqueous and organic solutions. 9. Use according to claim 8, wherein the concentration of diglycolamide in the organic solution is between 0.05 mol / L and 0.5 mol / L. Use according to any one of claims 7 to 9, wherein the acidic aqueous solution comprises a mineral acid, preferably nitric acid, sulfuric acid, hydrochloric acid or a mixture thereof. 11. Use according to claim 10, wherein the concentration of the mineral acid or mixture of mineral acids in the acidic aqueous solution is between 0.1 mol / L and 5 mol / L. 12. Use according to any one of claims 7 to 11, wherein the rare earth is selected from lanthanum, praseodymium, neodymium, dysprosium and mixtures thereof. 13. Use according to any one of claims 7 to 12, wherein the acidic aqueous solution is derived from the dissolution in acid medium of a concentrate of urban ore and, in particular, a concentrate of a waste of electrical and electronic equipment. 14. Use according to any one of claims 7 to 12, wherein the acidic aqueous solution is derived from the dissolution in acid medium of a material in a divided form and resulting from a treatment of permanent magnets Neodymium- Used or discarded Iron-Boron or Samarium-Cobalt, or treatment of used nickel-metal hydride batteries or electrochemical accumulators. 15. Use according to any one of claims 7 to 12, wherein the acidic aqueous solution is derived from the dissolution in acidic medium of a natural ore or a residue of a natural ore.