Process for separating rare-earth metals in admixture in aqueous solution

Abstract

To address the following problem that: separating rare-earth elements from metals in columns 4 to 14 of the Periodic Table of the Elements is a challenge for the coming years.SOLUTION: Provided is a process for separating one or more elements among the rare-earth elements from other metals in columns 4 to 14 of the Periodic Table of the Elements, in admixture in aqueous solution. The process uses a polyethyleneimine-CS2 adduct in the form of a salt.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for separating rare earth metals admixed with other metals in aqueous solutions. [Background technology]

[0002] Rare earth metals are formed from 17 elements, namely the 15 lanthanides: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, as well as scandium and yttrium. The light rare earth metals are used for their exceptional magnetic properties, while the heavy rare earth metals (the most valuable) are used to raise the temperature point at which magnets lose their magnetism.

[0003] They are widespread, particularly in four industrial sectors representing 10% of the world economy: digital (mobile phones, hard disks, screens), energy (offshore wind turbines, electric and hybrid car engines), medicine (instruments, robots) and weapons.

[0004] Their uses are diverse, primarily (31%) permanent magnets (used in generators, flywheels, alternators, toy and watch motors), catalysts (18%) (used in catalytic converters in cars), metallurgical alloys (18%) (used in aeronautical, military and medical constructions, etc.), abrasives (13%) (used on the surfaces of many industrial products), glass and ceramics (11%), and the remaining 9%.

[0005] Permanent magnets are experiencing unstoppable growth. Wind power and low-carbon mobility consume 35% of the global market, with China accounting for 91% of manufacturing. Their rapid growth (wind power consumption is expected to triple by 2030, and electric vehicles tenfold) could challenge the finite supply of rare earth metals.

[0006] The recovery of these rare earth metals is a major goal in the coming years (battery recycling) in order to facilitate the transition to a circular economy (sharing, reusing, repairing, restoring and recycling existing products and materials so that they retain their value for as long as possible) and ensure the availability of viable products. Summary of the Invention [Problem to be solved by the invention]

[0007] Separating rare earth metals from metals in groups 4 to 14 of the periodic table will be a challenge for the next few years. [Means for solving the problem]

[0008] The applicant has discovered and developed a simple, low-cost method that allows for the separation of rare earth metals admixed with other metals in aqueous solutions.

[0009] More precisely, the invention relates to a method for separating one or more elements of the rare earth elements from other metals of groups 4 to 14 of the periodic table of the elements, admixed in an aqueous solution AS, comprising at least the following successive steps: a) adding at least one polyethyleneimine-CS2 adduct (PEI-CS2) in salt form to an aqueous solution AS; b) stirring the aqueous solution obtained in step a) for at least 1 minute; c) stopping the stirring and waiting for at least 5 minutes for the formation of a suspension S; d) performing solid-liquid separation on the suspension S to obtain an aqueous solution L containing mainly elements from the rare earth elements originally present in the aqueous solution AS; The method includes:

[0010] The solution AS subjected to the method of the invention contains at least one element from among the 17 rare earth metals, which include the 15 lanthanides: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, and also scandium and yttrium.

[0011] Advantageously, the rare earth metals in the solution AS are chosen from the following elements: neodymium, dysprosium, lanthanum, gadolinium, europium, yttrium, cerium and samarium.

[0012] According to a preferred embodiment of the invention, the solution AS contains at least two elements of the rare earth group.

[0013] In particular, the total concentration of elements from rare earth elements that are originally present in the solution AS is in the range of 1 to 10,000 ppm by mass.

[0014] The solution AS also contains at least one other metal from groups 4 to 14 of the periodic table of the elements. The metals from groups 4 to 14 of the periodic table are preferentially iron, copper, chromium, manganese, cobalt, nickel, zinc, cadmium, mercury, tin, lead, vanadium, aluminum, gallium, selenium and molybdenum.

[0015] "Periodic Table of the Elements" refers to Mendeleev's table (updated by IUPAC in 2016).

[0016] In particular, the total concentration of other metals from groups 4 to 14 of the periodic table that are initially present in the solution AS is in the range of 1 to 10,000 ppm by mass.

[0017] The term "polyethyleneimine-CS2 adduct" means the product obtained from the reaction of polyethyleneimine with carbon disulfide.

[0018] In particular, the reaction may be carried out in the presence of a base to directly obtain the polyethyleneimine-CS2 adduct in the form of a salt, for example, the reaction may be carried out in the presence of sodium hydroxide (NaOH) or potassium hydroxide (KOH) to obtain the polyethyleneimine-CS2 adduct (PEI-CS2) in the form of a salt, respectively.

[0019] Preferentially, the polyethyleneimine from which the polyethyleneimine-CS2 adduct in salt form used in step a) of the process of the invention is derived contains between 15% and 65% primary amine functional groups, between 25% and 60% secondary amine functional groups, and between 10% and 60% tertiary amine functional groups.More preferentially, the polyethyleneimine contains between 25% and 45% primary amine functional groups, between 35% and 55% secondary amine functional groups, and between 20% and 40% tertiary amine functional groups.

[0020] Advantageously, the polyethyleneimine from which the polyethyleneimine-CS2 adduct in salt form used in step a) of the process of the invention is derived has a molecular weight between 300 and 70,000 daltons.

[0021] The salt of the polyethyleneimine-CS2 (PEI-CS2) adduct is an alkali metal salt, in particular a potassium or sodium salt. Preferentially, this salt is a sodium salt. In particular, the salt form of the polyethyleneimine-CS2 adduct (PEI-CS2) is such that all CS2 functional groups are in salified form.

[0022] Advantageously, a composition containing two different polyethyleneimine-CS2 adducts (PEI-CS2) in the form of salts may be used in step a) of the method, in other words, the composition contains two (PEI-CS2) salts that differ in that they are obtained from different polyethyleneimines, but whose counterions, i.e., alkali metal cations, may be the same.

[0023] Preferentially, for carrying out step a) of the method of the invention, the polyethyleneimine-CS2 adduct (PEI-CS2) in the form of a salt is at a concentration of between 0.5% and 60% by weight in an aqueous solution, said aqueous solution having a pH of between 10 and 14. The salt is added to the solution AS in particular in this form.

[0024] Advantageously, in step a) of the method of the invention, the polyethyleneimine-CS2 adduct (PEI-CS2) in salt form is the product of the reaction of polyethyleneimine with carbon disulfide, the molar ratio of carbon disulfide / total of amine groups present in the polyethyleneimine being between 0.5 and 1.1, preferentially between 0.6 and 0.95.

[0025] At the end of step d), the method according to the invention makes it possible to obtain an aqueous solution L containing mainly the rare earth elements originally present in the aqueous solution AS.

[0026] In other words, the aqueous solution L obtained at the end of step d) contains a lower proportion (of other metals / rare earth elements from groups 4 to 14 of the periodic table of the elements) than the proportion (of other metals / rare earth elements from groups 4 to 14 of the periodic table of the elements) in the aqueous solution AS.

[0027] In particular, the ratio (other metals from groups 4 to 14 of the periodic table / elements among rare earth elements) in the aqueous solution L is 0, i.e., it does not contain other metals from groups 4 to 14 of the periodic table.

[0028] The rare earth elements, and also other metals of groups 4 to 14 of the periodic table of the elements, are in particular present in the solution AS in cationic form.

[0029] In addition, the method of the invention may preferentially comprise, between steps b) and c), two successive steps b1) and b2), said steps comprising: b1) adding a water-soluble polymer P having an average molecular weight between 20,000 and 1,000,000 Daltons to the aqueous solution obtained in step a) and stirring for at least 1 minute; b2) adding a water-soluble polymer P' having an average molecular weight of more than 1 million daltons to the solution obtained in step b1) and stirring for at least 1 minute; It consists of:

[0030] One advantage of performing steps b1) and b2) is the reduction in the time required for step c).

[0031] The term "polymer" refers to a natural polymer or a chemically modified natural polymer, or a synthetic homopolymer or copolymer prepared from at least two different monomers.

[0032] Polymer P has a molecular weight between 50,000 and 1 million daltons. Polymer P' has a molecular weight of 1 million daltons or more, preferentially between 1 million and 40 million daltons, more preferentially between 3 million and 30 million daltons. The term "molecular weight" means the weight average molecular weight.

[0033] Molecular weight is determined by the intrinsic viscosity of the polymer, which may be measured via methods known to those skilled in the art and can be calculated from reduced viscosity values ​​for various polymer concentrations by a graphical method consisting of plotting reduced viscosity values ​​(Y-axis) against concentration (X-axis) and extrapolating the curve to zero concentration.

[0034] The intrinsic viscosity value is plotted on the Y-axis or using the least squares method. The molecular weight can then be determined by the Mark-Houink equation: [Number 1] [η]=KM α [η] represents the intrinsic viscosity of the polymer determined via a method for measuring viscosity in solution. K represents an empirical constant. M represents the molecular weight of the polymer. α represents the Mark-Howink coefficient. K and α depend on the particular polymer-solvent system.

[0035] The term "water-soluble polymer" refers to a polymer that is dissolved at 25°C and 10 g.L in deionized water. -1 This indicates a polymer that, when dissolved with stirring at a concentration of 0.1 to 1.25, results in an aqueous solution free of insoluble particles.

[0036] The water-soluble polymer P or P' may be a natural polymer or a chemically modified natural polymer, or a synthetic polymer or a semi-synthetic (or semi-natural) polymer.

[0037] Advantageously, the polymer P is chosen from poly(aluminum chloride), products of the polycondensation reaction of epichlorohydrin with dimethylamine, homopolymers or copolymers of diallyldimethylammonium halides.

[0038] the polymer P' is preferentially synthetic and is composed of at least one anionic hydrophilic monomer and / or at least one cationic hydrophilic monomer and / or at least one non-ionic hydrophilic monomer, nonionic hydrophilic monomers are water-soluble vinyl monomers, such as acrylamide, methacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N,N-dialkylacrylamide (e.g. N,N-dimethylacrylamide or N,N-diethylacrylamide), N,N-dialkylmethacrylamide, alkoxylated acrylic acid esters, alkoxylated methacrylic acid esters, N-vinylpyrrolidone, N-methylol (meth)acrylamide, N-vinylcaprolactam, N-vinylformamide (NVF), N-vinylacetamide, N-vinylimidazole, N-vinylsuccinic acid imide, acryloylmorpholine (ACMO), glycidyl methacrylate, glyceryl methacrylate, diacetone acrylamide, methacrylic anhydride, acrylonitrile, maleic anhydride, itaconic anhydride, itaconamide, vinylpyridine, hydroxyalkyl (meth)acrylate, thioalkyl (meth)acrylate, isoprenol and its alkoxylated derivatives, hydroxyethyl (meth)acrylate and its alkoxylated derivatives, hydroxypropyl acrylate and its alkoxylated derivatives, vinyl acetate, and mixtures thereof, wherein the alkyl group is a C1-C3 hydrocarbon chain; - Anionic hydrophilic monomers include the monomers acrylic acid, methacrylic acid, dimethylacrylic acid, itaconic acid, C1-C3 hemiesters of itaconic acid, acryloyl chloride, crotonic acid, maleic acid, fumaric acid, 3-acrylamido-3-methylbutanoic acid, vinyl sulfonic acid, vinylphosphonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-methylidenepropane-1,3-disulfonic acid, 2-sulfoethyl methacrylate, sulfopropyl methacrylate, sulfopropyl acrylate, allylphosphonic acid, ethylene glycol methacrylate phosphate, styrene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid (ATBS), 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, and diethyl allylphosphonate (diethylallyl phosphonate), carboxyethyl acrylate; water-soluble salts of all these monomers, for example, their alkali metal, alkaline earth metal, or ammonium salts; and mixtures thereof; The cationic hydrophilic monomer is selected from diallyldialkylammonium salts, such as diallyldimethylammonium chloride (DADMAC); acidified or quaternized salts of dialkylaminoalkyl(meth)acrylamido, such as methacrylamidepropyltrimethylammonium chloride (MAPTAC), acrylamidopropyltrimethylammonium chloride (APTAC), acidified or quaternized salts of dialkylaminoalkyl acrylates, such as quaternized or chlorinated dimethylaminoethyl acrylate (ADAME), acidified or quaternized salts of dialkylaminoalkyl methacrylates, such as quaternized or chlorinated dimethylaminoethyl methacrylate (MADAME), and mixtures thereof.

[0039] The term "hydrophilic monomer" refers to a monomer having an octanol / water partition coefficient, Kow, characterized by log(Kow) being less than or equal to 1, where the Kow partition coefficient is determined at 25°C in an octanol / water mixture having a volume ratio of 1 / 1 at a pH between 6 and 8. [Number 2]

[0040]

number

[0041] The polymer P' may have a linear, branched, star-branched or comb structure, which can be obtained according to the general knowledge of the person skilled in the art.

[0042] The polymers P and P' may be added during steps b1) and b2) in various forms, in particular in liquid form, for example, independently of one another, as a solution, emulsion, dispersion or suspension, or in solid form. The polymers may be in the form of an aqueous solution, an inverse emulsion (water-in-oil), an aqueous suspension, a powder, or a dispersion of the polymer in oil. The polymer P is preferably in the form of an aqueous solution. The polymer P' is advantageously in the form of a powder or an inverse emulsion.

[0043] Generally, the water-soluble polymers P and P' do not require the development of any particular polymerization method. In particular, they can be obtained via any polymerization technique known to those skilled in the art. These can include, inter alia, solution polymerization, gel polymerization, precipitation polymerization, emulsion polymerization (aqueous or inverse), suspension polymerization, reactive extrusion polymerization, water-in-water polymerization, or micellar polymerization.

[0044] The amount of water-soluble polymers P and P' added during steps b1) and b2) is in particular between 1 and 10 000 ppm by weight, preferentially between 10 and 5 000 ppm by weight, in the solution resulting from step a) or b1) of the process.

[0045] In step b) of the method of the present invention, the aqueous solution obtained in step a) is stirred for at least 1 minute. Preferentially, this solution is stirred for 1 to 5 minutes. A person skilled in the art knows how to select the appropriate stirring means. In steps b1) and / or b2), the stirring time is comparable to that in step b).

[0046] In step c) of the method of the invention, stirring of the solution obtained from step b) is stopped and the waiting time for the formation of suspension S is at least 5 minutes, in particular 10 or 15 minutes. Preferentially, the waiting time for the formation of suspension S is between 5 minutes and 2 hours.

[0047] In step d) of the process of the invention, the skilled person knows how to select a suitable solid-liquid separation method, which may be, by way of example, a filtration or decantation step.

[0048] The method of the invention advantageously comprises, after step d), the following step: e) adding at least one polyethyleneimine-CS2 adduct (PEI-CS2) in salt form to the aqueous solution L; f) stirring the aqueous solution obtained in step d) for at least 1 minute; g) stopping the stirring and waiting for at least 5 minutes for the formation of a suspension S'; h) performing solid-liquid separation on the suspension S' to obtain solid SO containing mainly elements from the rare earth elements originally present in the solution L; may include:

[0049] The stirring time (step f) and waiting time (step g) are comparable to those in steps b) and c). The stirring means in step f) are preferentially the same as those in step b). The method of solid-liquid separation h) is preferentially the same as that in step d).

[0050] In particular, the total amount of rare earth elements in the solid SO is more than 80 mass %, particularly more than 90 mass %, relative to the total amount of rare earth elements originally present in the L solution.

[0051] The amount of polyethyleneimine-CS2 adduct (PEI-CS2) in salt form added in steps a) and e) is determined depending on the cationic charge density of the aqueous solution AS, more precisely, so that the anionic charge of the polyethyleneimine / carbon disulfide salt (PEI-CS2) neutralizes the cationic charge of the metal elements present in the aqueous solution AS.

[0052] Aqueous AS solutions are analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) to determine the content of each metal element that makes up the solution. These contents, weighted by the molecular weight of each metal element, allow the cationic charge density of the solution to be determined.

[0053] This cationic charge density allows the calculation of the amount of polyethyleneimine-CS2 adduct in salt form that is used to neutralize all cationic charges of the metal element to the optimal amount of 100%. The stoichiometric dose thus corresponds to the ratio of the anionic charge density of PEI-CS2 to the cationic charge density of the metal element solution. If necessary, an under- or overdose of this 100% value may be applied.

[0054] Preferentially, in step a) of the method of the invention, the stoichiometric dose, corresponding to the ratio of the anionic charge density of the polyethyleneimine-CS2 adduct (PEI-CS2) in salt form to the total cationic charge density of the metal elements in the solution AS, is between 80% and 120%, and even more preferentially between 95% and 105%.

[0055] In step e) of the method of the invention, the stoichiometric dose, which corresponds to the ratio of the anionic charge density of the polyethyleneimine-CS2 adduct (PEI-CS2) in salt form to the total cationic charge density of the metal elements in the solution AS, is between 200% and 500%, more preferentially between 250% and 400%.

[0056] The invention and its advantages will be more clearly understood in light of the following examples and drawings. [Brief explanation of the drawings]

[0057] [Figure 1] A diagram of Mendeleev's periodic table. The shaded cells represent elements that can be analyzed using ICP-OES techniques. [Figure 2]FIG. 10 depicts the evolution of europium and copper concentrations in filtrates obtained from solutions treated with PEI-CS2 according to Example 6. The x-axis represents the stoichiometry of added PEI-CS2 (expressed as a percentage), while the y-axis represents the concentration of cations in solution (expressed in ppm). [Figure 3] FIG. 10 represents the evolution of yttrium and iron concentrations in the filtrate obtained from solutions treated with PEI-CS2 according to Example 7. The x-axis represents the stoichiometry of added PEI-CS2 (expressed as a percentage), while the y-axis represents the concentration of cations in solution (expressed in ppm). [Figure 4] FIG. 10 depicts the evolution of neodymium and mercury concentrations in filtrates obtained from solutions treated with PEI-CS2 according to Example 11. The x-axis represents the stoichiometry of added PEI-CS2 (expressed as a percentage), while the y-axis represents the concentration of cations in solution (expressed in ppm). [Figure 5] FIG. 10 depicts the evolution of dysprosium and mercury concentrations in filtrates obtained from solutions treated with PEI-CS2 according to Example 13. The x-axis represents the stoichiometry of added PEI-CS2 (expressed as a percentage), while the y-axis represents the concentration of cations in solution (expressed in ppm). [Figure 6] Figure 14 shows the evolution of europium and copper concentrations in the filtrate obtained from a solution treated with PEI-CS2 by adding two polymers according to Example 14. The x-axis represents the stoichiometry of the added PEI-CS2 (expressed as a percentage), while the y-axis represents the concentration of the cations in the solution (expressed in ppm). [Figure 7] Figure 14 shows the evolution of europium and copper concentrations in the filtrate obtained from a solution treated with PEI-CS2 by adding two polymers according to Example 15. The x-axis represents the stoichiometry of the added PEI-CS2 (expressed as a percentage), while the y-axis represents the concentration of the cations in the solution (expressed in ppm). [Example]

[0058] ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy) Analysis Method: ICP-OES technology is a technique that allows the analysis of most of the elements in Mendeleev's periodic table (Figure 1).

[0059] The principle of ICP-OES consists of introducing a sample containing the analyte of interest, which is then ionized by an argon plasma. By definition, plasma is a fully ionized but electrically neutral gas (free electrons and ions are present). It is sometimes likened to a flame and has a temperature that can be up to 10,000 K.

[0060] The sample first enters the chamber as a liquid in the form of an aerosol. The function of the chamber is to produce a homogeneous aerosol at its exit, which is carried to the torch by a flow of argon. The energy provided by the plasma then allows for the vaporization, atomization, and ultimately ionization of the various elements in the injected sample.

[0061] These various elements (atoms) absorb the photons produced by the plasma, causing electrons in these elements to move to higher energy electron shells. When excited, atoms lose energy by emitting one or more photons depending on the state of excitation. These photons are characterized by an energy that can be related to wavelength λ according to the Planck-Einstein relation: [Number 3]

[0062]

number

[0063] (E: photon energy (unit: joule), h: Planck's constant (6.63 x 10 -34 Js, c: the speed of light in a vacuum, λ: the wavelength (in meters) of the electromagnetic wave associated with the photon under consideration.

[0064] Using the instrument's optical sensors and detectors, these wavelengths are identified, thereby allowing the identification and quantification of compounds present.

[0065] Depending on each element under consideration and taking into account our specific matrix, a protocol has been developed:

[0066] Sample preparation: - Control sample: 1 mL of a solution containing 10 ppm of the salt of the element is diluted with 9 mL of 5% by weight nitric acid in water. - Chelation sample: Add 2 drops of 69% by weight nitric acid to 10 mL of sample.

[0067] The corresponding solutions are injected into an ICP-OES 5800 (Agilent) using the following parameters: - 1.2kW RF ICP power - Carrier gas: Argon flow rate 0.7 L / min

[0068] The elements La, Ce, Pr, Nd, Sm, Gd, Dy, Fe, Hg, and Cu were analyzed by axial observation. The elements Y and Eu were analyzed by lateral observation with a measurement height of 8 mm. Calibration curves were obtained for each element from 0.1 ppm to 5 ppm using standard Agilent solutions.

[0069] Determination of the anionic charge density of the salt obtained from the reaction of polyethyleneimine with carbon disulfide (designated PEI-CS2) The charge density of PEI-CS2 was calculated from the colloidal charge (meq / g), which was determined by a colloidal assay using methyl glycol chitosan (MGC) and potassium polyvinyl sulfate (PVSK).

[0070] Prepare a 5 g / L PEI-CS2 solution by diluting 1.00 g of PEI-CS2 equivalent (dry extract) in a 200 mL beaker with magnetic stirring and adding deionized water in an amount appropriate for the initial PEI-CS2 concentration. Once the 5 g / L PEI-CS2 solution is homogeneous, weigh out 0.25 g of the solution and add 100 mL of deionized water. Adjust the pH to 10.4-10.6 using 0.1 N acid or sodium hydroxide. While stirring, add exactly 5 mL of MGC (1 / 200 N), followed by 3 drops of toluidine blue, and assay with PVSK (1 / 400 N).

[0071] When the blue color changes to purple and remains purple for 20 seconds, the equivalence point is reached, and the amount of PVSK introduced (unit: milliliter) is designated as A.

[0072] The same measurement was carried out without adding PEI-CS2, and the amount of PVSK (unit: milliliter) was designated as B.

[0073] The anionic charge density is calculated using the following formula: [Number 4] C(meq / g)=(BA)×N PVSK / (5×m×10 -3 ) [In the formula, m = mass of PEI-CS2 solution at 5g / L N PVSK = normality of PVSK solution, = f / 400, the factor f is given by the supplier WAKO].

[0074] Stoichiometric assay of aqueous solutions containing metal elements The solution is analyzed by ICP-OES to determine the content of each metal element that makes up the solution, which is weighted by the molecular weight of each metal element, allowing the cationic charge density of the solution to be determined.

[0075] This cationic charge density allows the calculation of the amount of PEI-CS2 polymer to be used to neutralize all cationic charges of the metal elements at an optimal content of 100%. The stoichiometric dose thus corresponds to the ratio of the anionic charge density of PEI-CS2 to the cationic charge density of the metal element solution. If necessary, an under- or overdose of this 100% value may be applied.

[0076] Example to clarify calculation of stoichiometric percentage: For an aqueous solution (1000 g) containing 20 ppm copper(II), the amount of PEI-CS2 (charge density: 2.84 meq / g) with 100% stoichiometry is determined according to the following formula: [Number 5] Q = (TS / 100) * (C 金属 *VAL 金属 ) / (MW 金属 * D / 1000) [In the formula, TS=Target stoichiometry (%) Q = Amount of PEI-CS2 to be added (unit: ppm) C 金属 = Metal concentration (unit: ppm) VAL 金属 = Metal valence MW 金属 : Molecular weight of metal (g / mol) D = charge density of PEI-CS2 polymer (meq / g)].

[0077] Thus, for 100% stoichiometry, 222 ppm of PEI-CS2 is required.

[0078] Synthesis of PEI-CS2 polymer

[0079] Example 1 Polymer A 248 g of water, 42 g of sodium hydroxide (50% by weight in water), and 50 g of Epomin® P 1050 (PEI from Nippon Shokubai, molar mass 70,000 Daltons; molar ratio of primary / secondary / tertiary amines: 25 / 50 / 25) are introduced into a 1 L double-jacketed reactor equipped with a motor, a stirring paddle, and a condenser. The resulting mixture is mixed for 15 minutes and maintained at 35° C. using a cold air generator through the double jacket of the reactor.

[0080] The dropping funnel is charged with 44 g of CS2 and attached to a 1 L reactor. CS2 is added dropwise to the reactor in this way over a period of 80 minutes. The temperature of the reaction medium is maintained at 40°C, and water is supplied to the condenser to prevent loss of CS2. The reaction medium acquires a reddish color, which reflects the progress of the reaction. After the addition of CS2, the medium is maintained at 40-50°C for 120 minutes, with stirring.

[0081] A further addition of 7 g of Epomin® P 1050 and 32 g of water is then made into the reaction medium. The medium is maintained at the same temperature for 400 minutes and then cooled to 25°C.

[0082] The pH is then adjusted to a value between 10.0 and 12.0 using sodium hydroxide (50% by weight in water). The resulting solution is an aqueous solution containing 20% ​​by weight of polymer A (PEI-CS2).

[0083] Example 2 Polymer B Following the same protocol as in Example 1, a PEI-CS2 polymer is obtained in a 1 L reactor using 165 g of water, 86 g of sodium hydroxide, and 50 g of Epomin® SP 200 (PEI from Nippon Shokubai, molar mass 10,000 Daltons, molar ratio of primary / secondary / tertiary amines: 35 / 35 / 30). The dropping funnel is charged with 82 g of CS2. The final additions are 3 g of Epomin® SP 200 and 11 g of water. The resulting solution is an aqueous solution containing 40% by weight of polymer B (PEI-CS2).

[0084] Example 3 Polymer C Following the same protocol as in Example 1, a PEI-CS2 polymer is obtained in a 1 L reactor using 165 g of water, 86 g of sodium hydroxide, and 50 g of Epomin® SP 018 (PEI from Nippon Shokubai, molar mass 18,000 Daltons, molar ratio of primary / secondary / tertiary amine: 35 / 35 / 30). The dropping funnel is charged with 82 g of CS2. The final additions are 3 g of Epomin® SP 018 and 11 g of water. The resulting solution is an aqueous solution containing 40% by weight of polymer C (PEI-CS2).

[0085] Example 4 Polymer D Using the same protocol as in Example 1, a PEI-CS2 polymer is obtained in a 1 L reactor using 98 g of water, 121 g of sodium hydroxide, and 50 g of tetraethylenepentamine (TEPA). The dropping funnel is charged with 115 g of CS2. The final additions are 2 g of TEPA and 7 g of water. The resulting solution is an aqueous solution containing 50 wt% of polymer D (PEI-CS2).

[0086] Example 5 Polymer E Using the same protocol as in Example 1, a PEI-CS2 polymer is obtained in a 1 L reactor using 159 g of water, 102 g of sodium hydroxide, 25 g of TEPA, and 50 g of Epomin® P 1050. The dropping funnel is charged with 115 g of CS2. The final additions are 3 g of TEPA and 10 g of water. The resulting solution is an aqueous solution containing 40% by weight of polymer E.

[0087] Treatment of solutions containing metal elements Example 6 To a 2 L volumetric flask containing a Teflon-coated magnetic bar, add 2 L of deionized water containing 40 mg of europium chloride hydrate (EuCl3 6H2O) and 96.4 mg of copper sulfate pentahydrate (Cu(SO4)2 5H2O) to obtain a solution containing 10 ppm europium salts and 10 ppm copper salts. Perform ICP-OES analysis to determine the initial amount of each element in the solution (to avoid variability in hydration between salts due to storage conditions).

[0088] The polymer E solution (Example 5) is diluted to 1% (by weight) by mixing 40 mg with 1.41 g of deionized water.

[0089] The aqueous solution containing europium and copper is gently stirred and the diluted polymer E solution is added (amount adjusted to obtain 100% polymer E stoichiometry).

[0090] The mixture is stirred for 60 seconds and a precipitate appears.

[0091] The stirring is stopped and the suspension is left to settle for 60 minutes. The resulting solution is filtered (0.45 μ Sartorius filter) to separate the solid and liquid.

[0092] The filtrate is analyzed by ICP-OES to determine the concentration of europium and copper elements. The analysis of the filtrate during processing is shown in Figure 2.

[0093] 1998 g of filtrate solution is recovered. The filtrate contains 5.43 ppm of dissolved elemental europium and 0 ppm of copper.

[0094] On the filter, 2 g of solid is recovered, which contains 12000 ppm of copper (analysis by ICP-OES).

[0095] Thus, polymer E enriches copper (very quickly) in the precipitates that form.

[0096] The filtrate is once again supplemented with 300% stoichiometry of polymer E. After precipitation, the resulting suspension is filtered (0.45 μ Sartorius filter).

[0097] 2.5 g of solid is recovered on the filter, which contains 9400 ppm europium (ICP-OES analysis).

[0098] This double treatment with polymer E results in a solid enriched in europium.

[0099] Example 7 To a 2 L volumetric flask containing a Teflon®-coated magnetic bar, add 2 L of deionized water containing 49.5 mg of hydrated yttrium chloride (YCl3·xH2O) and 178 mg of iron chloride (FeCl3) to obtain a solution containing 10 ppm of yttrium salt and 10 ppm of iron salt. Perform ICP-OES analysis to determine the initial amount of each element in the solution (to avoid variability in hydration between salts due to storage conditions).

[0100] The polymer E solution (Example 5) is diluted to 1% (by weight) by mixing 50 mg with 1.91 g of deionized water.

[0101] The aqueous solution containing yttrium and iron is gently stirred and the diluted polymer E solution is added (amount adjusted to obtain 100% polymer E stoichiometry).

[0102] The mixture is stirred for 60 seconds and a precipitate appears.

[0103] The stirring is stopped and the suspension is left to settle for 60 minutes. The resulting solution is filtered (0.45 μ Sartorius filter) to separate the solid and liquid.

[0104] The filtrate is analyzed by ICP-OES to determine the concentrations of yttrium and iron elements. The analysis of the filtrate during processing is presented in Figure 3.

[0105] 1997.5 g of filtrate solution is recovered. The filtrate contains 5.90 ppm dissolved elemental yttrium and 0 ppm iron.

[0106] On the filter, 2.5 g of solid is recovered, which contains 24490 ppm of iron (analysis by ICP-OES).

[0107] In this way, polymer E enriches the iron (very quickly) in the precipitates formed.

[0108] As in Example 6, the addition of 300% stoichiometric polymer E to the filtrate leads, in a second step, to enrichment of yttrium in the solid obtained after precipitation and filtration.

[0109] Example 8 To a 2 L volumetric flask containing a Teflon®-coated magnetic rod, add 2 L of deionized water in which the following metal salts (Table 1) have been dissolved to obtain a mixture containing 10 ppm of each metal salt. ICP-OES analysis is performed to determine the initial amount of each element in solution (to avoid variability in hydration between salts due to storage conditions).

[0110] [Table 1]

[0111] Polymer E solution (Example 5) is diluted to 1% (by weight) by mixing 180 mg with 6.93 g of deionized water.

[0112] The aqueous solution containing various metal elements is gently stirred, and the diluted polymer E solution is added (in an amount adjusted to obtain 100% polymer E stoichiometry).

[0113] The mixture is stirred for 60 seconds and a precipitate appears.

[0114] The stirring is stopped and the suspension is left to settle for 60 minutes. The resulting solution is filtered (0.45 μ Sartorius filter) to separate the solid and liquid.

[0115] The filtrate is analyzed by ICP-OES to determine the concentration of various metal elements. The analysis of the filtrate is listed in Table 2.

[0116] At 100% stoichiometry, the filtrate contains between 4 and 6 ppm of dissolved lanthanide elements and 0 ppm of heavy metals. Polymer E allows for enrichment of heavy metals in the precipitate and enrichment of lanthanides in the filtrate.

[0117] [Table 2]

[0118] Example 9 To a 2 L volumetric flask containing a Teflon®-coated magnetic rod, add 2 L of deionized water in which the following lanthanide salts (Table 3) have been dissolved to obtain a mixture containing 10 ppm of each lanthanide salt. ICP-OES analysis is performed to determine the initial amount of each element in solution (to avoid variability in hydration between salts due to storage conditions).

[0119] [Table 3]

[0120] Polymer E solution (Example 5) is diluted to 1% (by weight) by mixing 480 mg with 18.74 g of deionized water.

[0121] Aqueous solutions containing various lanthanides are gently stirred and diluted polymer E solution is added (amount adjusted to obtain the desired polymer E stoichiometry).

[0122] The mixture is stirred for 60 seconds and a precipitate appears.

[0123] The stirring is stopped and the suspension is left to settle for 60 minutes. The resulting solution is filtered (0.45 μ Sartorius filter) to separate the solid and liquid.

[0124] The filtrate is analyzed by ICP-OES to determine the concentration of various metal elements. The analysis of the filtrate is listed in Table 4.

[0125] At 400% stoichiometry, the filtrate contains between 0.3 and 1.1 ppm of each lanthanide. Polymer E, at high dosages, thus allows for effective chelation of all lanthanides, producing a lanthanide-enriched solid after precipitation and filtration.

[0126] [Table 4]

[0127] Example 10 To a 2 L volumetric flask containing a Teflon®-coated magnetic rod, 2 L of deionized water in which the lanthanide salts (Table 3 in Example 9) have been dissolved is added to obtain a mixture containing 10 ppm of each lanthanide salt. ICP-OES analysis is performed to determine the initial amount of each element in solution (to avoid variability in hydration between salts due to storage conditions).

[0128] Polymer B solution (Example 2) is diluted to 1% (by weight) by mixing 480 mg with 18.74 g of deionized water.

[0129] The aqueous solutions containing the various lanthanides are gently stirred and the diluted polymer B solution is added (amount adjusted to obtain the desired polymer B stoichiometry).

[0130] The mixture is stirred for 60 seconds and a precipitate appears.

[0131] The stirring is stopped and the suspension is left to settle for 60 minutes. The resulting solution is filtered (0.45 μ Sartorius filter) to separate the solid and liquid.

[0132] The filtrate is analyzed by ICP-OES to determine the concentration of various metal elements. The analysis of the filtrate is listed in Table 5.

[0133] At 300% stoichiometry, the filtrate contains between 2 and 3 ppm of each lanthanide. Polymer B, at high dosages, thus allows for effective chelation of all lanthanides, producing a lanthanide-enriched solid after precipitation and filtration.

[0134] [Table 5]

[0135] Example 11 To a 2 L volumetric flask containing a Teflon-coated magnetic bar, add 2 L of deionized water containing 45.1 mg of hydrated neodymium chloride (NdCl3 xH2O) and 33.2 mg of mercury chloride (HgCl2) to obtain a solution containing 10 ppm neodymium salts and 10 ppm mercury salts. Perform ICP-OES analysis to determine the initial amount of each element in the solution (to avoid variability in hydration between salts due to storage conditions).

[0136] Polymer B solution (Example 2) is diluted to 1% (by weight) by mixing 22 mg with 0.85 g of deionized water.

[0137] The aqueous solution containing neodymium and mercury is gently stirred and the diluted polymer B solution is added (amount adjusted to obtain 100% polymer B stoichiometry).

[0138] The mixture is stirred for 60 seconds and a precipitate appears.

[0139] The stirring is stopped and the suspension is left to settle for 60 minutes. The resulting solution is filtered (0.45 μ Sartorius filter) to separate the solid and liquid.

[0140] The filtrate is analyzed by ICP-OES to determine the concentration of elements neodymium and mercury. The analysis of the filtrate during processing is presented in Figure 4.

[0141] 1997.5 g of filtrate solution is recovered. The filtrate contains 4.48 ppm dissolved elemental neodymium and 0 ppm mercury.

[0142] On the filter, 2.5 g of solid is recovered, which contains 8000 ppm (by mass) of mercury (analysis by ICP-OES).

[0143] In this way, polymer B allows (very quickly) the enrichment of mercury in the precipitate formed.

[0144] As in Example 6, the addition of 300% stoichiometric Polymer B to the filtrate leads, in a second step, to the enrichment of neodymium in the solid obtained after precipitation and filtration.

[0145] Example 12 To a 2 L volumetric flask containing a Teflon®-coated magnetic bar, 2 L of deionized water in which the lanthanide salts (Table 3 in Example 9) have been dissolved is added to obtain a mixture containing 10 ppm of each lanthanide salt. ICP-OES analysis is performed to determine the initial amount of each element in solution (to avoid variability in hydration between salts due to storage conditions).

[0146] The Polymer C solution (Example 3) is diluted to 1% (by weight) by mixing 480 mg with 18.74 g of deionized water.

[0147] Aqueous solutions containing various lanthanides are gently stirred and diluted polymer C solution is added (amount adjusted to obtain the desired polymer C stoichiometry).

[0148] The mixture is stirred for 60 seconds and a precipitate appears.

[0149] The stirring is stopped and the suspension is left to settle for 60 minutes. The resulting solution is filtered (0.45 μ Sartorius filter) to separate the solid and liquid.

[0150] The filtrate is analyzed by ICP-OES to determine the concentration of various metal elements. The analysis of the filtrate is listed in Table 6.

[0151] At 300% stoichiometry, the filtrate contains between 0.8 and 1.8 ppm of each lanthanide. Polymer C, at high dosages, thus allows for effective chelation of all lanthanides, producing a lanthanide-enriched solid after precipitation and filtration.

[0152] [Table 6]

[0153] Example 13 To a 2 L volumetric flask containing a Teflon®-coated magnetic bar, add 2 L of deionized water containing 40.9 mg of hydrated dysprosium chloride (DyCl3·xH2O) and 33.2 mg of mercury chloride (HgCl2) dissolved therein, resulting in a solution containing 10 ppm of dysprosium salts and 10 ppm of mercury salts. Perform ICP-OES analysis to determine the initial amount of each element in the solution (to avoid variability in hydration between salts due to storage conditions).

[0154] The polymer C solution (Example 3) is diluted to 1% (by weight) by mixing 20 mg with 0.78 g of deionized water.

[0155] The aqueous solution containing dysprosium and mercury is gently stirred and the diluted polymer C solution is added (amount adjusted to obtain 100% polymer C stoichiometry).

[0156] The mixture is stirred for 60 seconds and a precipitate appears.

[0157] The stirring is stopped and the suspension is left to settle for 60 minutes. The resulting solution is filtered (0.45 μ Sartorius filter) to separate the solid and liquid.

[0158] The filtrate is analyzed by ICP-OES to determine the concentrations of elements dysprosium and mercury. The analysis of the filtrate during processing is presented in Figure 5.

[0159] 1998.2 g of filtrate solution is recovered. The filtrate contains 4.3 ppm of dissolved elemental dysprosium and 0 ppm of mercury.

[0160] On the filter, 2.2 g of solid is recovered, which contains 9090 ppm (by mass) of mercury (analysis by ICP-OES).

[0161] In this way, polymer C allows (very quickly) the enrichment of mercury in the precipitate formed.

[0162] As in Example 6, the addition of 300% stoichiometric Polymer C to the filtrate leads, in a second step, to the enrichment of dysprosium in the solid obtained after precipitation and filtration.

[0163] Example 14 To two 2 L volumetric flasks containing Teflon®-coated magnetic bars, add 2 L of deionized water containing 40 mg of europium chloride hydrate (EuCl3·6H2O) and 96.4 mg of copper sulfate pentahydrate (Cu(SO4)2·5H2O) to obtain a solution containing 10 ppm europium salts and 10 ppm copper salts. Perform ICP-OES analysis to determine the initial amount of each element in the solution (to avoid variability in hydration between salts due to storage conditions).

[0164] The polymer E solution (Example 5) is diluted to 1% (by weight) by mixing 40 mg with 1.41 g of deionized water.

[0165] This method is also carried out for the Polymer A solution (Example 1), in which 72 mg is diluted to 1% (by weight) by mixing with 1.37 g of deionized water.

[0166] The aqueous solution containing europium and copper is gently stirred, and the diluted polymer E and polymer A solutions (amounts adjusted to obtain 100% stoichiometry of polymer A or E) are added separately to one of two volumetric flasks.

[0167] The mixture is allowed to continue stirring for 60 seconds and a precipitate is visible forming.

[0168] The stirring is stopped and the suspension is left to settle for 60 minutes. The resulting solution is filtered (0.45 μ Sartorius filter) to separate the solid and liquid.

[0169] The filtrate is analyzed by ICP-OES to determine the concentration of europium and copper elements. The analysis of the filtrate during processing is presented in Figure 6.

[0170] For polymers A and E, copper is effectively removed from the precipitate at 100% and above stoichiometry. The europium content in the filtrate is comparable.

[0171] However, at higher stoichiometry, polymer E results in slightly more europium enrichment in the precipitate.

[0172] Example 15 To two 2 L volumetric flasks containing Teflon®-coated magnetic bars, add 2 L of deionized water containing 40 mg of europium chloride hydrate (EuCl3·6H2O) and 96.4 mg of copper sulfate pentahydrate (Cu(SO4)2·5H2O) to obtain a solution containing 10 ppm europium salts and 10 ppm copper salts. Perform ICP-OES analysis to determine the initial amount of each element in the solution (to avoid variability in hydration between salts due to storage conditions).

[0173] The polymer E solution (Example 5) is diluted to 1% (by weight) by mixing 40 mg with 1.41 g of deionized water.

[0174] This method is also carried out for the Polymer D solution (Example 4), in which 32 mg is diluted to 1% (by weight) by mixing with 1.25 g of deionized water.

[0175] The aqueous solution containing europium and copper is gently stirred, and the diluted polymer E and polymer D solutions (amounts adjusted to obtain 100% stoichiometry of polymer D or E) are added separately to one of two volumetric flasks.

[0176] The mixture is allowed to continue stirring for 60 seconds and a precipitate is visible forming.

[0177] The stirring is stopped and the suspension is left to settle for 60 minutes. The resulting solution is filtered (0.45 μ Sartorius filter) to separate the solid and liquid.

[0178] The filtrate is analyzed by ICP-OES to determine the concentration of europium and copper elements. The analysis of the filtrate during processing is presented in Figure 7.

[0179] For polymers A and D, copper is effectively removed from the precipitate at 100% stoichiometry and above. The europium content in the filtrate is comparable. However, at higher stoichiometries, polymer E is more efficient at enriching the precipitate with europium.

[0180] Example 16 The operating conditions of Example 6 are repeated. The polymer E solution (Example 5) is diluted to 1% (by weight) by mixing 40 mg with 1.41 g of deionized water.

[0181] The europium and copper-containing aqueous solution is gently stirred, and the diluted polymer E solution is added (adjusted to obtain 100% polymer E stoichiometry). The solution is stirred for 1 minute. Next, 0.5 mL of an aqueous solution containing 1% coagulant (PAC 18 (polyaluminum chloride, average molecular weight between 20,000 and 1,000,000 daltons)) is added, and the solution is stirred for 1 minute. Finally, 0.5 mL of a solution containing 0.5 g / L of anionic flocculant (Flopam® AN 934 VHM, average molecular weight greater than 1,000,000 daltons) is added, and the solution is left stirring for 1 minute.

[0182] The mixture is kept stirring at 200 rpm for 60 seconds and then at 50 rpm for 5 minutes, allowing flocs to form.

[0183] The stirring is stopped and the suspension is left to settle for 10 minutes. The resulting solution is filtered (0.45 μ Sartorius filter) to separate the solid and liquid.

[0184] The copper and europium contents in the solid and in the filtrate remain comparable to those obtained in Example 6. However, the processing time (sedimentation, solid-liquid separation) is shorter than in Example 6.

Claims

1. A method for separating one or more elements of rare earth elements from other metals of groups 4 to 14 of the periodic table of the elements, admixed in an aqueous solution AS, comprising at least the following sequential steps: a) adding at least one polyethyleneimine-CS2 adduct (PEI-CS2) in salt form to an aqueous solution AS; b) stirring the aqueous solution obtained in step a) for at least 1 minute; c) stopping the stirring and waiting for at least 5 minutes for the formation of a suspension S; d) performing solid-liquid separation on the suspension S to obtain an aqueous solution L containing mainly elements from the rare earth elements originally present in the aqueous solution AS; A method comprising:

2. Between steps b) and c) the following sequential steps: b1) adding a water-soluble polymer P having an average molecular weight between 20,000 and 1,000,000 Daltons to the aqueous solution obtained in step a) and stirring for at least 1 minute; b2) adding a water-soluble polymer P' having an average molecular weight of more than 1 million daltons to the solution obtained in step b1) and stirring for at least 1 minute; 2. The method of claim 1, comprising:

3. 2. The method of claim 1, wherein the salt of the polyethyleneimine-CS2 adduct is a sodium salt.

4. 4. The method according to claim 1, wherein the polyethyleneimine from which the polyethyleneimine-CS2 adduct in salt form used in step a) is derived contains between 15% and 65% primary amine functional groups, between 25% and 60% secondary amine functional groups, and between 10% and 60% tertiary amine functional groups.

5. 5. The method according to claim 1, wherein the polyethyleneimine from which the polyethyleneimine-CS2 adduct in salt form used in step a) is derived has a molecular weight between 300 and 70,000 daltons.

6. 6. The method according to claim 1, wherein step a) may use a composition containing two different polyethyleneimine-CS2 adducts in the form of salts.

7. 7. The method according to claim 1, wherein the polyethyleneimine-CS2 adduct in salt form is at a concentration of between 0.5% and 60% by weight in the aqueous solution, and the aqueous solution has a pH of between 10 and 14.

8. After step d), at least the following steps: e) adding to the aqueous solution L at least one polyethyleneimine-CS2 adduct (PEI-CS2) in salt form; f) stirring the aqueous solution obtained in step d) for at least 1 minute; g) stopping the stirring and waiting for at least 5 minutes for the formation of a suspension S'; h) performing solid-liquid separation on the suspension S' to obtain solid SO containing mainly elements from the rare earth elements originally present in the solution L; 8. The method according to claim 1, comprising:

9. 9. The method according to claim 1, wherein the solution AS contains at least two elements of the rare earth group.

10. 10. The method according to any one of claims 1 to 9, characterized in that the rare earth metals in the solution AS are selected from the following elements: neodymium, dysprosium, lanthanum, gadolinium, europium, yttrium, cerium and samarium.

11. 11. The method according to claim 1, wherein the metals of groups 4 to 14 of the periodic table are iron, copper, chromium, manganese, cobalt, nickel, zinc, cadmium, mercury, tin, lead, vanadium, aluminum, gallium, selenium, and molybdenum.

12. 12. The method according to claim 1, wherein in step a) the polyethyleneimine-CS2 adduct (PEI-CS2) in salt form is the product of the reaction of polyethyleneimine with carbon disulfide, and the molar ratio of carbon disulfide / total of amine groups present in the polyethyleneimine is between 0.5 and 1.

1.

13. 13. The method according to claim 1, wherein in step a) of the method, the stoichiometric dosage, corresponding to the ratio of the anionic charge density of the polyethyleneimine-CS2 adduct (PEI-CS2) in salt form to the total cationic charge density of the metal elements in the solution AS, is between 80% and 120%.

14. 9. The method according to claim 8, characterized in that in step e) of the method, the stoichiometric dosage, corresponding to the ratio of the anionic charge density of the polyethyleneimine-CS2 adduct (PEI-CS2) in salt form to the total cationic charge density of the metal elements in the solution AS, is between 200% and 500%.

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