Novel poly(ether-phosphoramide) polymer and method for extracting a rare earth from a liquid medium implementing such a polymer

Abstract

The invention relates to a poly(ether-phosphoramide) polymer, a repeating unit of which comprises an isosorbide unit and a phosphoramide function, and which has a high affinity for rare earths, in particular lanthanum and cerium. This polymer is particularly useful for extracting a rare earth from an aqueous liquid medium containing same, such as a mining effluent, by using a solid-liquid extraction method.

Description

[0001]NEW POLY(ETHER-PHOSPHORAMIDE) TYPE POLYMER AND METHOD FOR EXTRACT OF A RARE EARTH FROM A LIQUID MEDIUM USING SUCH A POLYMER The present invention relates to the field of rare earth recovery. More particularly, the present invention relates to a polymer particularly suitable for the solid-phase extraction of a rare earth contained in a liquid medium, as well as a composite material containing such a polymer on a solid support. The invention also relates to the use of such a polymer or such a composite material for extracting a rare earth from a liquid medium containing it. Another subject of the invention is a method for extracting a rare earth from a liquid medium containing it, using such a polymer or such a composite material. Rare earths, and in particular lanthanum, are used for numerous industrial applications.Examples include the manufacture of glass, particularly lenses for cameras and telescopes, the production of steel and nodular cast iron, the manufacture of fuel cells, batteries, particularly rechargeable hydride batteries used in hybrid vehicles, chemical catalysis for oil refining, the preparation of light alloys, particularly to improve their mechanical characteristics, etc. Rare earths are also important elements in the new technology industry, for the manufacture of electronic components for computers and mobile phones, in which they are used in particular in the composition of light-emitting diodes and magnets. The supply of these high value-added raw materials is difficult, particularly due to their low availability in nature.Lanthanum, for example, does not exist as a free element. Mining effluents, particularly from phosphate deposits such as those in Tunisia, currently constitute one of the common sources of rare earths. The ore present in these deposits, of the sedimentary phosphorite type, contains several thousand ppm of rare earth oxides, the most abundant of which are cerium and lanthanum. This phosphate ore is commonly used for the industrial production of phosphoric acid, through its reaction with sulfuric acid in water. This reaction typically leads to the formation of phosphoric acid H3PO4, hydrofluoric acid HF and hydrated calcium sulfate CaSO4,xH2O, where x = 0.5 or 2. Two main phases are obtained at the end of the reaction: a liquid phase, containing the phosphoric acid, and a solid phase, comprising the hydrated calcium sulfate.The liquid phase in particular is rich in rare earths. Currently, rare earths are extracted from it using a liquid-liquid extraction technique, such as that described in the publication by Agarwal et al., 2021, Mineral Processing and Extractive Metallurgy, 130(2): 90-97. However, this technique uses a significant amount of organic solvent, particularly from petrochemicals, for example kerosene, the subsequent disposal of which is environmentally problematic. In order to overcome this drawback, and to avoid or at least limit the use of polluting organic solvents, several solid-liquid extraction techniques have been proposed by the prior art to recover rare earths from a liquid medium containing them. However, none of these techniques offers satisfactory extraction performance.The present invention aims to overcome the drawbacks of the methods proposed by the prior art for extracting rare earths from aqueous media containing them, in particular the drawbacks set out above, by proposing a material that can be used in a solid-liquid type extraction method, and that makes it possible to carry out such extraction efficiently. Additional objectives of the invention are that this material can be obtained, and that the extraction method using it can be implemented, in the most environmentally friendly manner possible. The invention also aims to ensure that the rare earths can be easily recovered at the end of the method, and in such a way that the material that allowed their extraction can be reused.It has been discovered by the present inventors that these objectives are achieved by a polymer of specific structure, from the poly(ether-phosphoramide) family, which has a particularly high affinity for rare earths, in particular lanthanum and cerium, as demonstrated in particular by electrochemical impedance measurements at the interface of the polymer and rare earth solutions. This affinity is notably, particularly surprisingly, much higher than that of other polymers of very similar structure. Implemented in a solid phase extraction process, this polymer thus makes it possible to extract with a high extraction rate the rare earths contained in a liquid medium. The adsorption of rare earths on this polymer is also reversible, and their desorption is simple to carry out, which is moreover advantageously in the aqueous phase.In the present description, by rare earths, in a conventional manner in itself, scandium, yttrium, and the 15 lanthanides, that is to say lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. Thus, according to a first aspect, there is provided according to the present invention a polymer particularly useful for the solid phase extraction of a rare earth from a liquid medium containing it. This polymer comprises a repeating unit of general formula (I):. in which R1 and R2, identical or different, each represent a hydrogen atom, or a linear, branched and / or cyclic, saturated and / or unsaturated, aromatic or unaromatic, optionally substituted hydrocarbon radical, which may comprise a single cycle or several cycles, optionally condensed, optionally interrupted by one or more heteroatoms, such as oxygen, sulfur or nitrogen, and preferably comprising from 1 to 12 carbon atoms, or R1 and R2 together form, with the nitrogen atom to which each is attached, a 3- to 8-membered, preferably 4- to 6-membered, saturated or unsaturated, optionally aromatic heterocycle, comprising one or more heteroatoms in the cycle, such as an oxygen atom, optionally substituted by one or more linear, branched and / or cyclic alkyl radicals, each of these alkyl radicals preferably being C1-C12, preferably C1-C6 and more preferably C1-C6 C1-C3,said heterocycle being optionally fused to one or more rings or heterocycles, each with 3 to 8 members, preferably with 4 to 6 members, saturated or unsaturated, optionally aromatic, optionally comprising one or more heteroatoms in the ring, and optionally substituted by one or more linear, branched and / or cyclic alkyl radicals, each of these alkyl radicals being preferably C1-C12, preferably C1-C6 and more preferably C1-C3. The polymer according to the invention preferably comprises 10 to 50 repetitions of the repeating unit of general formula (I). It is furthermore preferably linear. Preferably, the repeating unit of general formula (I) is the only repeating unit of the polymer. In preferred embodiments of the invention, the structure of the polymer can thus be expressed by the general formula (II):, in which n is a positive integer greater than or equal to 2, preferably greater than or equal to 10, and preferably between 10 and 50, and R1 and R2 are as defined with reference to general formula (I). The polymer according to the invention may for example correspond to formula (IIa): n is a positive integer greater than or equal to 2, preferably greater than or equal to 10, and preferably between 10 and 50, R1 and R2 are as defined with reference to general formula (I), and A represents a fluorine atom, a chlorine atom, a hydrogen atom or a hydroxyl group. The polymer according to the invention advantageously incorporates an isosorbide unit in its composition. Thus, its synthesis uses an isosorbide synthon, of general formula (III): compound derived from agro-resources. Thus, the polymer according to the invention is advantageously at least partially biosourced. As indicated above, this polymer, in particular in its embodiments corresponding to general formulas (II) and (IIa), has a particularly high affinity for rare earths, and in particular for the two most abundant rare earths in nature, lanthanum and cerium. This affinity is much greater than that of polymers of similar structure, and in particular of polymers corresponding to a similar formula, but in which: - the oxygen atom linked to the phosphorus atom is replaced by a sulfur atom, - and / or the nitrogen atom linked to the phosphorus atom is replaced by a carbon atom, - and / or the isosorbide unit is replaced by a unit derived from bisphenol A, of formula (IV): We will not prejudge here the mechanisms explaining the particularly high affinity of the polymer according to the invention with respect to rare earths. We can only note that it seems specifically linked to the combination, within the structure of the polymer, of the oxygen atom and the nitrogen atom respectively linked to the phosphorus atom, the whole forming a phosphoramide function, and of the isosorbide unit. Nothing in the prior art suggested that such a specific combination would be associated with an affinity with respect to rare earths much higher than that of polymers not comprising this specific combination, even with very similar structures.In particularly preferred embodiments of the invention, in general formula (I), as well as in general formulas (II) and (IIa), R1 and R2 together form, with the nitrogen atom to which each is attached, a saturated heterocycle with 3 to 8 members, preferably with 6 members, comprising one or more heteroatoms in the cycle, optionally substituted by one or more linear, branched and / or cyclic alkyl radicals, each of these alkyl radicals preferably being C1-C12, preferably C1-C6 and more preferably C1-C3.Preferably, in general formula (I), as well as in general formulas (II) and (IIa), R1 and R2 together form, with the nitrogen atom to which each is attached, a morpholine nucleus, optionally substituted by one or more linear, branched and / or cyclic alkyl radicals, each of these alkyl radicals preferably being C1-C12, preferably C1-C6 and more preferably C1-C3. In particular embodiments of the invention, the morpholine nucleus is not substituted. Thus, the polymer according to the invention may comprise a repeating unit of general formula (V):. The polymer may in particular correspond to the general formula [VI): in which n is a positive integer greater than or equal to 2, preferably greater than or equal to 10, and preferably between 10 and 50. The polymer corresponding to this general formula (VI) has an affinity for rare earths, in particular lanthanum and cerium, which is particularly important. The polymer according to the invention may, for example, correspond to formula (VIa): in which n is a positive integer greater than or equal to 2, preferably greater than or equal to 10, and preferentially between 10 and 50, and A represents a fluorine atom, a chlorine atom, a hydrogen atom or a hydroxyl group. In alternative embodiments of the invention, in general formula (I), as well as in general formulas (II) and (IIa), R1 and R2, identical or different, each represent a hydrogen atom or a linear or branched C1-C6 alkyl radical, preferably a methyl radical or an ethyl radical. In this configuration, preferentially, R1 and R2, identical or different, each represent a methyl radical or an ethyl radical.In variants of the invention, in general formula (I), as well as in general formulas (II) and (IIa), R1 and R2, identical or different, each represent a hydrogen atom or an aromatic cyclic group preferably comprising from 1 to 12 carbon atoms, comprising a single ring or several rings, optionally fused, optionally containing one or more heteroatoms in the ring(s), and optionally substituted by one or more linear, branched and / or cyclic alkyl radicals, each of these alkyl radicals preferably being C1-C6 and preferentially C1-C3. In particular, R1 and R2, identical or different, may then each represent a ring chosen from a benzene ring and a naphthalene ring, this ring being optionally substituted by one or more linear, branched and / or cyclic alkyl radicals, preferably C1-C6 and preferentially C1-C3.Generally, when they do not form a cycle together, R1 and R2 are preferably both different from a hydrogen atom. They are also preferably identical. Thus, in particular embodiments of the invention, in general formula (I) and general formulas (II) and (IIa) above, R1 and R2 each represent, simultaneously: - a methyl radical, - an ethyl radical, - a benzene nucleus, - or a naphthalene nucleus. The polymer according to the invention can be prepared according to any synthetic route within the competence of a person skilled in the art. It can for example be prepared from the isosorbide synthon, of formula (III) above, and a synthon of general formula (VII):. in which A, R1 and R2 are as defined above, in particular of formula (VIIa): by an aromatic nucleophilic substitution reaction (SnAr). The synthon of formula (VII) or (VIIa) can be obtained by any conventional method in itself, in particular by an oxidation reaction of the corresponding thiophosphoryl compound of formula (VIII) or (VIIIa) respectively: in which A, R1 and R2 are as defined above, An example of a process for synthesizing such a thiophosphoryl compound is described in particular in the publication by Chabbah et al., 2022, Talanta, 247: 123550. The polymer according to the invention can be used as such, in powder form, for the extraction of a rare earth from a liquid medium containing it. The powder form of the polymer can be obtained from a solution of the polymer in a solvent in which it is soluble, for example dimethylformamide, dimethylsulfoxide or N-methylmorpholine, by precipitation in a solvent or mixture of solvents in which it is insoluble, such as a water / methanol mixture, then drying the precipitate formed by evaporation of the solvents, this drying being optionally followed by sieving through a sieve, for example with a mesh size of 50 µm to 200 µm.The polymer according to the invention can otherwise be used, for the extraction of a rare earth from a liquid medium containing it, in a form in which it is integrated into a composite material, within which it is supported by a solid support. Thus, another aspect of the invention relates to a composite material comprising a polymer according to the invention on a solid support in divided form. By solid support in divided form, it is meant that the solid support is in the form of a set of distinct individual elements, preferably identical. The solid support is preferably inert with respect to the rare earths, and more generally with respect to the liquid medium containing the rare earth that it is desired to extract therefrom. It is preferably in the most divided form possible, so as to maximize the contact surface between the polymer according to the invention and the liquid medium containing the rare earth to be extracted.The solid support may in particular be in the form of fibers, beads or particles of irregular shape. As fibers that may form the solid support of the composite material according to the invention, mention may be made, for example, of hydrophilic fibers, preferably of natural origin, such as cellulose fibers, in particular with a diameter of between 10 and 50 µm, or carbon fibers, in particular with a diameter of between 5 and 20 µm. Such fibers may advantageously be easily impregnated with the polymer according to the invention, by any technique for impregnating a solid support that is conventional in itself, in particular by immersing the fibers in a solution of the polymer, ultrasonication and heating, then controlled evaporation under vacuum. The composite material may then, for example, be implemented in a chromatography column, through which the medium containing the rare earth to be extracted is circulated.The solid support may otherwise, for example, be in the form of particles, in particular in the form of beads, in particular with a diameter of between 200 and 2000 nm, or of particles of irregular shape. Such particles may, for example, be formed from inorganic oxide(s), for example silicon oxide or metal oxide, in particular copper, nickel, zinc, iron oxide, etc., such a list being in no way limiting of the invention. The solid support may advantageously be in the form of beads with magnetic properties, such as magnetite-type beads, combining the advantages of a large contact surface and great ease of separation from liquid media, and particularly suitable for the treatment of large volumes of liquid media. These magnetite beads may, for example, have a diameter of between 200 and 2000 nm.Such beads, or other solid particles in the form of beads or irregular shapes, can advantageously be easily coated with a layer of polymer according to the invention, by any technique for coating a solid support which is conventional in itself, for example by immersion in a solution of the polymer, ultrasonication and heating then controlled evaporation under vacuum. The thickness of the polymer coating layer is preferably between 10 nm and 100 nm. In general, the polymer according to the invention is impregnated on, or forms a coating layer on, the solid support, more precisely on the individual elements which compose it. An additional aspect of the invention relates to a method for extracting a rare earth from a liquid medium, in particular from an aqueous liquid medium, containing it.This method comprises bringing this liquid medium into contact with a polymer according to the invention, in solid form, in particular in powder form, or with a composite material according to the invention, comprising this polymer, so as to carry out the adsorption of the rare earth by the latter. It then comprises the separation of the polymer, or of the composite material, comprising the rare earth which has been adsorbed on the polymer, and of this liquid medium. The method according to the invention, which falls within the field of solid-liquid extraction, advantageously avoids the use of the consumption of organic solvents required by the liquid-liquid extraction proposed by the prior art. The contacting step of the method according to the invention is preferably carried out at a pH less than or equal to 3, preferably less than or equal to 2.Thus, the method according to the invention may comprise an initial step of measuring the pH of the liquid medium containing the rare earth, and, if necessary, a step of adjusting this pH to the required value, for example by means of a strong acid, such as sulfuric acid, hydrochloric acid, nitric acid or phosphoric acid. The establishment of such a pH advantageously makes it possible to release the rare earth in ionic form within the medium, thus facilitating its extraction. The duration of the contact is advantageously chosen to allow the adsorption of the largest possible quantity of the rare earth by the polymer according to the invention. This duration may for example be between 1 minute and 2 hours.The contacting may be carried out in any manner known to those skilled in the art, for example by circulating the liquid medium in a chromatography column containing the composite material according to the invention, the solid support of which is then preferably in the form of fibers, or by mixing the liquid medium and the composite material, the solid support of which is then preferably in particulate form, and / or by mixing the liquid medium and particles of the polymer according to the invention in powder form. In the latter two cases, the polymer powder and / or the composite material are preferably dispersed in a substantially homogeneous manner throughout the volume of liquid medium. The contacting step may advantageously be carried out at room temperature.The step of separating the polymer or composite material and the liquid medium can be carried out in any conventional manner, depending in particular on the type of solid support in the composite material and the method of implementing the contacting step of the method. For example, the separation can be carried out by simply flowing the liquid medium out of a chromatography column used in the method, or by any conventional means of solid-liquid separation, such as filtration, centrifugation, etc., or even magnetically in the embodiments in which the solid support of the composite material consists of beads with magnetic properties. This latter embodiment is particularly preferred in the context of the invention.The method according to the invention preferably comprises a final step of separating the rare earth and the polymer or composite material onto which it has been adsorbed during the contacting step of the method. This separation step, called desorption, can be carried out by any method known to those skilled in the art. It can in particular be carried out by washing the particles of the polymer, or of the composite material, with an aqueous solution containing a complexing agent for the rare earth, such as for example tributyl phosphate, or cis-1,3,5-triamino 2,4,6-trihydroxycyclohexane (also called 1,3,5-triamino-1,3,5-trideoxy-cis-inositol), called a regeneration solution. Such washing is preferably carried out for a time sufficient to cause the desorption from the polymer of the entire quantity of rare earth which had been adsorbed therein.After separation of the polymer or composite material and the regeneration solution, this separation being able to be carried out by any solid-liquid separation technique known per se, in particular by one of the techniques described above, an aqueous solution containing the rare earth is advantageously obtained. The polymer or composite material can be advantageously reused, for a new implementation of the method according to the invention on a new liquid medium containing a rare earth to be extracted therefrom. The rare earth, for the extraction of which the method according to the invention is applied, can be either a lanthanide, or scandium or yttrium. It is preferably a lanthanide, and in particular lanthanum or cerium. Of course, the method according to the invention can be used to simultaneously extract a plurality of rare earths from a liquid medium containing them in a mixture.The method according to the invention finds a particularly advantageous application for the extraction of rare earths from mining effluents, such a field of application being however in no way limiting of the invention. Thus, in particular embodiments of the invention, the liquid medium, to which the method according to the invention is applied, is a mining effluent, in particular from a phosphate deposit, for example from a phosphate deposit in Tunisia. This effluent may in particular be a phosphoric acid solution such as produced from a phosphate ore extracted from such a deposit. It may otherwise be a leachate from washing such a phosphate ore. The liquid medium to which the method according to the invention is applied may otherwise be an industrial effluent, for example an effluent from the chemical industry.The invention also relates to the use of a polymer or a composite material according to the invention, meeting one or more of the characteristics described above, for the extraction of a rare earth from a liquid medium, in particular aqueous, containing it. This use may meet one or more of the characteristics described above with reference to the method according to the invention for extracting a rare earth from a liquid medium containing it. In particular, the rare earth may be a lanthanide, in particular lanthanum or cerium. The liquid medium may be a mining effluent, for example from a phosphate deposit, such as a phosphoric acid solution obtained from a phosphate ore or a leachate from washing such an ore. It may otherwise be, for example, an industrial effluent.The characteristics and advantages of the invention will appear more clearly in the light of the following implementation examples, provided for purely illustrative purposes and in no way limiting the invention, with the support of Figures 1 to 7, in which: Figure 1 shows a reaction scheme for the production of phosphorylated monomers with a morpholine unit entering into the composition of a polymer according to the invention or of comparative polymers not in accordance with the invention. Figure 2 shows a reaction scheme for the production of phosphorylated monomers with a methyl phenyl unit entering into the composition of comparative polymers not in accordance with the invention.Figure 3 shows the impedance spectra, in the form of Nyquist diagrams representing the imaginary part of the impedance as a function of the real part of the impedance, obtained in an electrochemical impedance measurement experiment using a polymer-coated electrode in a lanthanum solution at different concentrations between 5.10. -11 M and 5.10 -6M, in a / for a polymer in accordance with the invention, in b / for a comparative polymer not in accordance with the invention. Figure 4 shows a graph representing the sensitivity to lanthanum, defined as the ratio of the relative variation of the polarization resistance to the logarithm of the lanthanum concentration, determined from measurements by electrochemical impedance spectroscopy, for a polymer according to the invention (P8) and comparative polymers not in accordance with the invention (P1 to P7). Figure 5 shows the impedance spectra, in the form of Nyquist diagrams representing the imaginary part of the impedance as a function of the real part of the impedance, obtained in an electrochemical impedance measurement experiment using an electrode coated with a polymer in a cerium solution at different concentrations between 10 -8 M and 10 -3M, in a / for a polymer in accordance with the invention, in b / for a comparative polymer not in accordance with the invention. Figure 6 shows a graph representing the sensitivity to cerium, defined as the ratio of the relative variation of the polarization resistance to the logarithm of the cerium concentration, determined from measurements by electrochemical impedance spectroscopy, for a polymer according to the invention (P8) and comparative polymers not in accordance with the invention (P1 to P7). Figure 7 shows photographs of particles of a polymer in accordance with the invention, under illumination at 482 nm, with reading of the luminescence at 425 nm, in a / , in the initial state, and in b / , after 24 h of incubation in an acidic aqueous medium containing lanthanum. A / Synthesis of polymers A polymer in accordance with the invention P8 and comparative polymers not in accordance with the invention, P1 to P7, are synthesized as indicated below. A.1 / Synthesis of phosphorylated monomers Morpholine-nucleated monomers of formula (4a) and (5a) are synthesized according to the reaction scheme shown in Figure 1. Monomers of formula (2a) and (3a) with a methyl phenyl unit are synthesized according to the reaction scheme shown in Figure 2. A.1.1 / Synthesis of bis(4-fluorophenyl)chloro thiophosphorus (1a) In a 250 mL three-necked flask equipped with a condenser surmounted by an HCl trap (KOH dissolved in water), magnetic stirring, an addition funnel and swept by a stream of nitrogen, are introduced: 11.94 g (0.070 mol) of trichloro thiophosphorus (PSCl3) and 14.00 g (0.105 mol) of anhydrous AlCl3. The mixture is stirred at 40°C and 26.90 g (0.280 mol) of fluorobenzene are added dropwise. The solution is stirred at 85°C for 3 h. The reaction medium is poured into 500 mL of an ice / water mixture, then extracted with ethyl acetate. The organic phase is washed with water and dried over anhydrous sodium sulfate.The solvent is evaporated under vacuum, and 17.20 g, with 85% yield, of a white solid (1a) are obtained. A.1.2 / Synthesis of bis(4-fluorophenyl)(4-methylphenyl)phosphine thiooxide (2a) In a 250 mL three-necked flask equipped with a condenser surmounted by an HCl trap (KOH dissolved in water), magnetic stirring, an addition funnel and swept by a stream of nitrogen, are introduced: 10.00 g (0.034 mol) of bis(4-fluorophenyl)chloro thiophosphorus (1a) and 13.84 g (0.104 mol) of anhydrous AlCl3. The mixture is stirred at 40°C and 12.75 g (0.138 mol) of toluene are added dropwise. The solution is stirred at 110°C for 3 h. The reaction medium is poured into 500 mL of an ice / water mixture, then extracted with ethyl acetate. The organic phase is washed with water and dried over anhydrous sodium sulfate. The solvent is evaporated under vacuum, the solid obtained is recrystallized from hexane and then washed with petroleum ether.On obtient 7,740 g, avec 65 % de rendement, d’un solide brun (2a). RMN. 1 H : (CDCl3) : δ (ppm) : 7,77-7,68 (m, 4H, H2) ; 7,63-7,56 (m, 2H, H3) ; 7,31-7,27 (m, 2H, H4) ; 7,19-7,12 (m, 4H, H1) et 2,43 (s, 3H, H5) RMN 19 F : (CDCl3) : δ (ppm) : -107, 43 RMN 31P: (CDCl3): δ (ppm): 41, 40 A.1.3 / Synthesis of bis(4-fluorophenyl)(morpholino)phosphine thiooxide (4a) In a 250 mL three-necked flask equipped with a condenser, magnetic stirring, an addition funnel and swept by a stream of nitrogen, 10.0 g (0.034 mol) of bis(4-fluorophenyl)chloro thiophosphorus (1a) and 16 mL of chloroform are mixed in an ice bath for 3 min. Then, 6.64 g of morpholine dissolved in 16.0 mL of chloroform are added for 30 min. Then, 7.71 g of trimethylamine are added to the solution. After completing the addition, the solution is heated at 85°C for 6 h. Finally, the reaction mixture is cooled to room temperature and then filtered. The filtrate is washed with water and then extracted with dichloromethane and dried over anhydrous sodium sulfate. The solvent is evaporated under vacuum.The product (4a) obtained is in the form of a brick-red powder following separation by column with a mixture of 9 / 1 (dichloromethane / Acetonitrile). The yield is 75%. NMR. 1 H: (CDCl3): δ (ppm): 8.02-7.93 (m, 4H, H2); 7.12-7.05 (m, 4H, H1); 3.70-3.66 (m, 4H, H4) and 2.80-2.75 (m, 4H, H3) NMR 19 F: (CDCl3): δ (ppm): -106.94 NMR 31 P: (CDCl3): δ (ppm): 65.43 A.1.4 / Synthesis of monomers (3a) and (5a) In a 100 mL three-necked flask equipped with a condenser, magnetic stirring, and an addition funnel are introduced (0.0155 mol) of (2a) or (4a) and 17.0 mL of glacial acetic acid. The reaction medium is placed at 90°C. 1.67 g (0.0490 mol) of hydrogen peroxide (35% by weight solution in water) are added very slowly and dropwise. After 2 h of reaction, an additional 0.83 g of hydrogen peroxide are added more quickly. The reaction is monitored by NMR 31P. After 3 h of reaction, the reaction medium is cooled and left for 30 min at room temperature without stirring. The mixture is filtered through celite to remove the sulfur formed. The celite is rinsed twice with acetic acid. The filtrate is evaporated under vacuum then extracted with 100 mL of ethyl acetate, neutralized with a saturated solution of sodium carbonate to pH 8-9, washed with distilled water, and dried over sodium sulfate. The solvent is evaporated under vacuum, and the solid obtained is washed with hot petroleum ether. Monomer (3a) is obtained with a 68% yield, and monomer (5a) with a 60% yield, in the form of brown solids. (3a) NMR 1 H: (CDCl3): δ (ppm): 7.68-7.63 (m, 4H, H2); 7.55-7.51 (m, 2H, H3); 7.31-7.28 (m, 2H, H4); 7.18-7.14 (m, 4H, H1) and 2.43 (s, 3H, H5) NMR 19 F: (CDCl3): δ (ppm): -106.57 NMR 31 P: (CDCl3): δ (ppm): 27.71 (5a) NMR 1H : (CDCl3) : δ (ppm) : 7,91-7,85 (m, 4H, H2) ; 7,20-7,16 (m, 4H, H1) ; 3,74-3,71 (m, 4H, H4) et 3,10-3,05 (m, 4H, H3) RMN 19 F: (CDCl3): δ (ppm): -106,43 RMN 31P: (CDCl3): δ (ppm): 27.21 A.2 / Polymer synthesis The experimental protocol applied for the formation of polymers, from the above monomers and, depending on the polymers, bisphenol A or isosorbide, is as follows. In a 50 mL three-necked flask, equipped with mechanical stirring and swept by a nitrogen flow, 5.0 mmol of difluorinated phosphorylated monomer (2a, 3a, 4a or 5a), 5.0 mmol of diol (bisphenol A or isosorbide) and 11 mmol of potassium carbonate are added to dimethylacetamide (DMAC). The solid content in DMAC is 25%. The reaction mixture is stirred at 160 - 165°C for 24 h. The reaction medium is cooled and then precipitated in water. After several rinses with distilled water, the polymer is dried under vacuum at 100°C and then washed several times with methanol. The resulting polymer is separated by filtration and then dried under vacuum to constant mass. It is in the form of a solid powder.This process is applied for the preparation of the following polymer P8 (in accordance with the invention) and polymers P1 to P7 (not in accordance with the invention) (for each of these polymers, the glass transition temperature Tg is measured by thermogravimetric analysis ATG):. NMR 1 H: (CDCl3): δ (ppm): 7.80–7.75 (m, 4H, H8), 7.03–6.98 (m, 4H, H7), 5.00-4.96 (m, 1H, H2), 4.86-4.80 (m, 2H, H5 and H3), 4.64–4.63 (m, 1H, H4), 4.19-4.03 (m, 4H, H1 and H6), 3.69 (s, 4H, H10), 3.05 (s, 4H, H9), NMR 31 P: (CDCl3): δ (ppm): 29.5 Tg = 198°C; NMR 1 H: (CDCl3): δ (ppm): 7.63–7.53 (m, 6H, H8 and H9), 7.25–7.22 (m, 6H, H10 and H2), 7.04–6.95 (m, 8H, H7 and H1), 2.41 (s, 3H, H11), 1.69 (s, 6H, H3) NMR 31 P: (CDCl3): δ (ppm): 28.65 Tg = 184°C; NMR 1H : (CDCl3) : δ (ppm) : 7.62–7.51 (m, 6H, H8 et H9), 7.28–7.26 (m, 2H, H10), 7.04–6.98 (m, 4H, H7), 5.02-4.99 (m, 1H, H2), 4.89-4.82 (m, 2H, H5 et H3), 4.67–4.65 (m, 1H, H4) 4.05-4.04 (m, 4H, H1 et H6), 2.41 (s, 3H, H11) RMN 31 P : (CDCl3) : δ (ppm) : 28.57 Tg = 202°C ; RMN 1 H : (CDCl3) : δ (ppm) : 8.00–7.93 (m, 4H, H8), 7.03–6.96 (m, 4H, H7), 5.00-4.96 (m, 1H, H2), 4.86-4.80 (m, 2H, H5 et H3), 4.64–4.63 (m, 1H, H4), 4.19-4.03 (m, 4H, H1 et H6), 3,65 (s, 4H, H10), 2.75 (s, 4H, H9) RMN 31 P : (CDCl3) : δ (ppm) : 66.05 Tg = 218°C ; RMN 1 H : (CDCl3) : δ (ppm) : 7.82–7.77 (m, 4H, H8), 7.28–7.24 (m, 4H, H2), 7.04-6.95 (m, 8H, H1 et H7), 3.70 (s, 4H, H10), 3.08 (s, 4H, H9), 1.71 (s, 6H, H3) RMN 31 P : (CDCl3) : δ (ppm) : 29.08 Tg = 187°C ; RMN 1H : (CDCl3) : δ (ppm) : 8.02–7.95 (m, 4H, H8), 7.26–7.23 (m, 4H, H2), 7.04-6.94 (m, 8H, H1 et H7), 3.75 (s, 4H, H10), 2.88 (s, 4H, H9), 1.71 (s, 6H, H3) RMN 31P: (CDCl3): δ (ppm): 66.09 Tg = 206°C. B / Affinity measurements with respect to rare earths Affinity measurements are carried out by measurements using the electrochemical impedance spectroscopy technique at the polymer / rare earth salt solution interface. Experiments are carried out for the following rare earths: lanthanum, cerium. For this purpose, each of the polymers P1 to P8 above is deposited on a gold or platinum flat electrode as follows. The electrode is rinsed with acetone for 15 min, rinsed with demineralized water and then dried under a nitrogen flow. Then, the electrode surface is cleaned for about 5 min in a piranha solution (mixture 25% by volume of (H2O235%) and 75% by volume of (H2SO496%)) in order to activate this surface, then rinsed with ultrapure water under ultrasound for 10 min, and finally dried under nitrogen flow.A solution of the polymer in chloroform (5 μL, 1% m / m) is then deposited, by drop deposition, on the surface of the electrode. The solvent is evaporated under nitrogen flow at room temperature. Each electrode is immersed in solutions of the rare earth (lanthanum or cerium) at different concentrations (between 5.10. -11 M and 5.10 -6 M for lanthanum, and between 10 -8 M and 10 -3M for cerium) in water, at room temperature. The measurements are carried out after 20 min of immersion time, to ensure that equilibrium conditions have been reached between the polymer-coated electrode and the solution. The impedance spectroscopy measurements are carried out using a BioLogic EC-Lab® VMP3 multi-channel potentiostat at open circuit potential, by applying a sinusoidal perturbation of 10 mV, in the frequency range of 100 mHz to 100 kHz. The impedance spectra are modeled by a Randles equivalent circuit, to extract the value of the polarization resistance. As an example, Figure 3 shows the spectra obtained, in a / , for the polymer P8 in accordance with the invention, and, in b / for the polymer P5, very close in structure but not in accordance with the invention, for the lanthanum solutions.From these results, the affinity of the different polymers for lanthanum is deduced (in terms of sensitivity, defined as the ratio of the relative variation of the polarization resistance to the logarithm of the lanthanum concentration). The results obtained are shown in Figure 4. It is observed that the polymer P8 in accordance with the invention has a much greater affinity for lanthanum than the comparative polymers tested, even though they have very similar structures. It is deduced from this experiment that the impedimetric sensor obtained from the polymer P8 in accordance with the invention allows detection of lanthanum in a concentration range of 7.2.10. -11 M to 7.2.10 -6 M (lanthanum concentration range for which the relative variation in resistance is linear with the logarithm of the lanthanum concentration), with a detection limit of 7.2.10 -11M, and a sensitivity of 0.112. Figure 5 shows as an example the spectra obtained, in a / , for the polymer P8 according to the invention, and, in b / for the polymer P5, very close in structure but not according to the invention, for the cerium solutions. From these results, the affinity of the different polymers with respect to cerium is deduced (in terms of sensitivity, defined as the ratio of the relative variation of the polarization resistance to the logarithm of the cerium concentration). The results obtained are shown in Figure 6. Here again, it is observed that the polymer P8 according to the invention has a much greater affinity for cerium than the comparative polymers tested, even though they have very similar structures. It is deduced from this experiment that the impedimetric sensor obtained from the polymer P8 according to the invention allows detection of cerium in a concentration range of 1.43.10 -10 M at 1.43.10 -5M (cerium concentration range for which the relative variation in resistance is linear as a function of the logarithm of the cerium concentration), with a detection limit of 5.2.10 -10 M, and a sensitivity of 0.15. C / Rare earth adsorption studies on powdered polymer Adsorption studies are carried out by mixing 100 mg of powdered P8 polymer with aqueous solutions containing lanthanum or cerium (at a concentration of 10 µg / L – 10 ppb), and 0.42% phosphoric acid (10 mL) (4.10 -2M, pH 1.4), then stirring the resulting mixture for 24 h. A sample of the mixture is then taken using a syringe and filtered through a 0.45 µm polytetrafluoroethylene PTFE filter to separate the polymer from the liquid medium. The concentration of lanthanum or cerium in the filtrate is measured by inductively coupled plasma mass spectrometry (CP-MS) using an Agilent 8800 ICP MSMS measuring device. From this measurement, the concentration of lanthanum or cerium that has been adsorbed by the polymer is deduced. This concentration is particularly high: 0.317 ppm for lanthanum (0.317 µg / g of polymer) and 0.321 ppm (0.321 µg / g of polymer) for cerium. The presence of lanthanum on the surface of the polymer P8 according to the invention is further demonstrated by the luminescence properties of lanthanum, as illustrated in Figure 7.A significant luminescence is observed at the end of the contacting step (in b / in the figure), whereas no luminescence was observed for the initial polymer (in a / in the figure). D / Desorption of the rare earth The P8 polymer powders obtained at the end of the above experiment of adsorption of lanthanum or cerium on the powdered polymer are recovered from the liquid medium by filtration. Each of the powders obtained is immersed in an aqueous solution comprising a rare earth complexing agent, tributyl phosphate or cis-1,3,5-triamino 2,4,6-trihydroxycyclohexane, at a concentration of 1 M. After an incubation time of 24 h, the polymer powder devoid of lanthanum or cerium is recovered by filtration, on the one hand, and an aqueous solution loaded with lanthanum or cerium, on the other hand.

Claims

CLAIMS 1. Polymer comprising a repeating unit of general formula (I): in which R1 and R2, which may be identical or different, each represent a hydrogen atom, or a linear, branched and / or cyclic, saturated and / or unsaturated, aromatic or unaromatic hydrocarbon radical, which may comprise a single ring or several rings, optionally fused, optionally interrupted by one or more heteroatoms, or R1 and R2 together form, with the nitrogen atom to which each is attached, a saturated or unsaturated, optionally aromatic, 3- to 8-membered heterocycle, comprising one or more heteroatoms in the ring, optionally substituted by one or more linear, branched and / or cyclic alkyl radicals, said heterocycle being optionally fused to one or more saturated or unsaturated, optionally aromatic, 3- to 8-membered rings or heterocycles, optionally comprising one or more heteroatoms in the ring, and optionally substituted by one or more linear, branched and / or cyclic alkyl radicals.Polymer according to claim 1, comprising 10 to 50 repetitions of the repeating unit of general formula (I).

3. Polymer according to claim 1 or 2, which is linear.

4. Polymer according to any one of claims 1 to 3, corresponding to the general formula (IIa):. in which n is an integer between 10 and 50, and A represents a fluorine atom, a chlorine atom, a hydrogen atom or a hydroxyl group.

5. Polymer according to any one of claims 1 to 4, in which R1 and R2 together form, with the nitrogen atom to which each is attached, a morpholine nucleus.

6. Polymer according to any one of claims 1 to 4, in which R1 and R2, which may be identical or different, each represent a hydrogen atom, a methyl radical or an ethyl radical.

7. Polymer according to any one of claims 1 to 4, in which R1 and R2, which may be identical or different, each represent a hydrogen atom, or a nucleus chosen from a benzene nucleus and a naphthalene nucleus, said nucleus being optionally substituted by one or more linear, branched and / or cyclic alkyl radicals.

8. Composite material, comprising a polymer according to any one of claims 1 to 7 on a solid support in divided form. 9.Composite material according to claim 8, wherein said solid support is in the form of fibers, beads or irregularly shaped particles.

10. Composite material according to claim 8 or 9, wherein said polymer is impregnated onto or forms a coating layer on said solid support.

11. Use of a polymer according to any one of claims 1 to 7. or a composite material according to any one of claims 8 to 10, for the extraction of a rare earth from an aqueous liquid medium containing it.

12. A method of extracting a rare earth from an aqueous liquid medium containing it, characterized in that it comprises bringing said liquid medium into contact with a polymer according to any one of claims 1 to 7 or a composite material according to any one of claims 8 to 10, then separating said polymer or said composite material, and said medium.

13. Extraction method according to claim 12, wherein said contacting is carried out at a pH less than or equal to 3.

14. Extraction method according to claim 12 or 13, comprising a final step of separating said rare earth and said polymer or said composite material.

15. Extraction method according to any one of claims 12 to 14, wherein said rare earth is a lanthanide, preferably lanthanum or cerium. 16.Extraction method according to any one of claims 12 to 15, wherein said liquid medium is a mining effluent.

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