RARE EARTHEN COMPOSITION OBTAINED BY LIQUID / LIQUID EXTRACTION OF SOLUTIONS FROM THE PROCESSING OF XENOTIMIUM, MONAZITE, BASTNAESITE AND / OR IONIC CLAY ORE

Abstract

Rare earth composition obtained by liquid / liquid extraction from an initial aqueous solution of rare earth sulfates or rare earth chlorides from the processing of at least one ore of xenotime, monazite, bastnaesite and / or ionic clays, said rare earth composition having a 227Ac content of less than 0.10 Bq / g of rare earths, preferably less than 0.01 Bq / g of rare earths, the alkaline earth and lead content of said rare earth composition being less than 1000 ppm relative to the amount of rare earths, preferably less than 100 ppm relative to the amount of rare earths, and said rare earth composition being in solid form or in aqueous solution form.

Description

Title of the invention: RARE EARTH COMPOSITION DERIVED FROM LIQUID / LIQUID EXTRACTION OF SOLUTIONS FROM PROCESSING OF XENOTIME, MONAZITE, BASTNAESITE AND / OR IONIC CLAY ORES Field of the invention

[0001] The invention falls within the general field of the treatment of aqueous solutions of rare earths. More specifically, it relates to a composition of rare earths resulting from the liquid / liquid extraction of an initial aqueous solution of rare earth sulfates or rare earth chlorides resulting from the treatment of at least one ore of xenotime, monazite, bastnaesite and / or ionic clays. Prior art

[0002] The ores from which rare earths are extracted may contain radioactive compounds, which must be separated from the rare earths. For example, monazite contains all the radioactive isotopes of the thorium 232 (232Th), uranium 235 (U) and uranium 238 (U) families. The ores first undergo a first processing step which consists of physical concentration (magnetic separation, flotation, etc.). However, during this step, the radioactive isotopes present in the rare earth-bearing minerals are not separated from the rare earths. In a second step, a chemical attack is carried out on the concentrate obtained previously. This chemical treatment makes it possible to separate the radioactive elements present in the rare earth-bearing minerals.

[0003] Some isotopes decay rapidly, while others, which have a half-life greater than a few days, must be eliminated to avoid contamination of rare earths. For example, the following isotopes have a relatively long half-life: - 232Th family: 232Th, 228Th, 228Ra, - 238U family: 238U, 234U, 234Th, 230Th, 226Ra, 210Pb, 210Po, - 235U family: 235U, 231Pa, 227Ac, ​​223Ra.

[0004] Most of these elements have chemical properties sufficiently different from those of the rare earths that their removal can be carried out using conventional hydrometallurgical techniques, such as precipitation and filtration. This is the case, for example, with the isotopes of thorium, uranium, radium (Ra), lead (Pb), polonium (Po) and protactinium (Pa).

[0005] On the other hand, the case of the isotope 227Ac, ​​whose radioactive half-life is 22 years, is unique because its chemical properties are close to those of rare earths, and in particular those of lanthanum. During the separation of rare earths, actinium will follow the lanthanum and it risks accumulating in compounds that include lanthanum. It will then have to be eliminated in the radioactive waste stream, which requires additional costs.

[0006] It is therefore necessary to obtain rare earth compositions which, after liquid / liquid extraction from solutions originating from the processing of ores, have an extremely low content of 227Ac and other radioisotopes.

[0007] These rare earths are intended to be further developed because their specific physical properties, in particular their magnetic properties, allow their use in numerous industries, notably in renewable energies, such as wind turbines and electric vehicles.

[0008] Rare earth compositions resulting from ore processing are described in particular in WO 2019 / 000014, where actinium is precipitated from solutions of rare earth chlorides or sulfates, by adding sulfate salts and significant quantities of alkaline earth salts of the Ca, Sr, Ba and / or Pb type. The composition has a 227Ac content of less than 1.0 Bq / g of rare earths. However, the composition comprises a significant residual quantity (of the order of a hundred g / L) of alkaline earth metals and / or lead not precipitated with the actinium. This residual quantity must be subsequently treated, which generates costs and consumption of additional chemical reagents and energy.

[0009] Furthermore, some methods describe the separation by liquid-liquid extraction of rare earths and actinium. This extraction is carried out using organic solvents comprising molecules selective for rare earths, which are extracted in the organic phase while the actinium remains in the aqueous phase. Indeed, it is known to use as extracting agents, cationic agents which have a strong affinity with rare earths, such as organophosphorus acid derivatives.

[0010] For example, document CN 85100148 describes a process for producing lanthanum oxides, by separating the lanthanum and actinium present in a solution of rare earth nitrates. The liquid-liquid separation is carried out using an organic solvent comprising the mono-2-ethylhexyl ester of 2-ethylhexylphosphonic acid (HEHEHP) or the ester of di(2-ethylhexyl)phosphoric acid (HDEHP or D2EHPA).

[0011] Similarly, document KR 100351554 details a method for liquid-liquid separation of rare earths and actinides contained in solutions of rare earth nitrates, originating from radioactive liquid waste. The method involves the use tributyl phosphate and phosphoric acid esters in the form of metal salts.

[0012] Another problem related to the presence of actinium in rare earth solutions concerns their transport. Indeed, an ore with a uranium content of 6000 ppm compared to the rare earths contained in the ore, produces a rare earth concentrate whose 227Ac content generates an activity equivalent to approximately 2.9 Bq / g of rare earths. Thus, if the concentrate contains 40% rare earths, it will have an activity of 1.2 Bq / g. However, beyond 1 Bq / g, the transport of such a mixture is subject to strict regulations concerning the transport of radioactive materials, known as "class 7". This requires the use of specialized transporters, which constitutes a constraint and additional costs. It is therefore necessary to limit the stages of transport of such solutions, in particular by directly treating the solutions from the ores, without resorting to intermediate stages. Statement of the invention

[0013] One of the aims of the invention is to provide a rare earth composition resulting from the liquid / liquid extraction of an initial aqueous solution of rare earth sulfates or rare earth chlorides resulting from the processing of at least one ore, the rare earth composition having a very low 227Ac content, namely less than 0.100 Bq / g of rare earths, preferably less than 0.010 Bq / g of rare earths.

[0014] Thus, the invention relates to a rare earth composition resulting from the liquid / liquid extraction of an initial aqueous solution of rare earth sulfates or rare earth chlorides resulting from the treatment of at least one ore of xenotime, monazite, bastnaesite and / or ionic clays,

[0015] said rare earth composition having a 227Ac content of less than 0.10 Bq / g of rare earths, preferably less than 0.01 Bq / g of rare earths, the alkaline earth and lead content of said rare earth composition being less than 1000 ppm relative to the quantity of rare earths, preferably less than 100 ppm relative to the quantity of rare earths, and

[0016] said rare earth composition being in the form of a solid or in the form of an aqueous solution. Rare earth composition

[0017] In practice, the rare earth composition has a total activity of less than 0.10 Bq / g of rare earths, preferably less than 0.01 Bq / g of rare earths. The total activity is related to the content of radioelements, for example, 226Ra, 228Ra, 232Th, 238U or 231Pa, and their descendants in the composition.

[0018] This composition advantageously has a 227Ac content of less than 0.10 Bq / g of rare earths.

[0019] Preferably, the rare earths belong to the group comprising La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y.

[0020] According to one embodiment of the invention, the rare earth composition is in the form of a solid belonging to the group comprising carbonates, hydroxycarbonates, hydroxides, oxides, oxalates, crystallized nitrates, anhydrous nitrates, crystallized chlorides and anhydrous chlorides of rare earths.

[0021] In practice, rare earth carbonates, hydroxycarbonates, hydroxides, and oxalates are precipitates. The oxides are obtained by calcining one of the precipitates. Crystallized nitrates and crystallized chlorides are generally obtained by crystallization of solutions of rare earth nitrates or chlorides, while anhydrous nitrates and anhydrous chlorides are obtained by casting concentrated solutions of rare earth nitrates or chlorides at high temperature, preferably between 110°C and 150°C at atmospheric pressure, and then cooling them.

[0022] Preferably, the precipitation is obtained using precipitating agents chosen from the group comprising: sodium carbonate, ammonium bicarbonate, sodium hydroxide, ammonia and oxalic acid.

[0023] According to another embodiment of the invention, the rare earth composition is in the form of an aqueous solution belonging to the group comprising aqueous solutions of rare earth sulfates, chlorides or nitrates.

[0024] For example, the concentration of rare earths in the aqueous solution is between 10 g / L and 500 g / L. Preferably, the concentration of rare earths is between 5 and 30 g / L in an aqueous solution of sulfates, between 50 and 200 g / L in an aqueous solution of chlorides and between 50 and 450 g / L in a solution of nitrates.

[0025] Preferably, the rare earth composition is obtained by a process for removing the actinium contained in said initial aqueous solution of rare earth sulfates or rare earth chlorides.

[0026] The method comprises the following steps: - contacting and mixing the initial aqueous solution with a water-immiscible organic solvent, said organic solvent comprising at least one cationic extraction agent, and - separation by liquid-liquid extraction of rare earths and actinium, to produce the rare earth composition.

[0027] Actinium is extracted in the form of an aqueous raffinate which may include a portion of the rare earths La and Ce contained in the initial aqueous solution. Organic solvent

[0028] According to the invention, the organic solvent comprises at least one cationic extraction agent which is an organophosphorus acid.

[0029] Preferably, the cationic extracting agent is an organophosphorus acid selected from the group comprising: - phosphoric acid esters, of formula I: [Chem.l] - phosphonic acid esters, of formula II: [Chem. 2] - phosphinic acids, of formula III: [Chem. 3] O R 2

[0030]

[0031] and their mixtures, where R1 and R2 are the same or different, independently chosen from the group comprising linear or branched, aliphatic or aromatic alkyl or aryl radicals of 1 to 20 carbon atoms, preferably of 4 to 20 carbon atoms, and hydrogen atoms. These compounds are particularly effective for complexing trivalent cations, such as rare earth cations. According to the invention, the rare earths are chosen from the group comprising: scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and mixtures thereof. Advantageously, the cationic extraction agent may be chosen from the group consisting of di(2-ethylhexyl)phosphoric acid ester, mono-2-ethylhexyl ester of 2-ethylhexylphosphonic acid, bis(2,4,4-trimethylpentyl) phosphinic acid (known under the trade name CYANEX®272), CYANEX®572 (mixture of phosphonic acid and phosphinic acid), and mixtures thereof.

[0032] Additionally, the organic solvent may comprise a diluent compound, selected from the group consisting of hydrocarbons of 5 to 16 carbon atoms, linear or branched, aliphatic or aromatic.

[0033] For example, the diluent compound is chosen from the group comprising: decane and its isomers, dodecane and its isomers, kerosene, toluene, aliphatic hydrocarbons having between 10 and 14 carbon atoms, hydrocarbons of 10 carbon atoms comprising at least one aromatic function, and mixtures thereof.

[0034] As diluting compound, we can cite for example, Shellsol®D70 (aliphatic hydrocarbon), Solvesso®150 (aromatic hydrocarbon).

[0035] The diluting compound allows the cationic extraction agent, and optionally the modifying compound, to be dissolved. It is in the liquid state and does not modify the chemical properties of the compounds it solubilizes. It is different from the cationic extraction agent.

[0036] In addition to the cationic extraction agent and the diluting compound, the solvent may comprise at least one modifying compound, chosen from the group consisting of phosphoric acid esters and linear or branched fatty alcohols, the total number of carbon atoms of which is between 6 and 12.

[0037] Preferably it is chosen from the group comprising: tributyl phosphate, decan-1-ol, octan-1-ol, isodecan-1-ol, hexan-1-ol, dodecan-1-ol, 2-ethylhexanol and mixtures thereof.

[0038] For the purposes of the invention, the term "modifying compound" means a chemical species other than the cationic extraction agent and the diluting compound, capable of modifying certain properties of the organic solvent. For example, the modifying compound can delay the appearance of a third phase or aid decantation.

[0039] According to a particular embodiment, the organic solvent comprises at least one cationic extraction agent and at least one diluting compound.

[0040] Alternatively, the organic solvent may comprise at least one cationic extractant, at least one diluent compound and at least one modifying compound.

[0041] Preferably, the organic solvent has a concentration of cationic extracting agent of between 0.1 and 2 mol / L, preferably between 0.5 and 1.5 mol / L. Such a concentration allows the solvent to retain a viscosity of less than 20 cP at room temperature.

[0042] In a particular embodiment of the invention, the organic solvent comprises: - from 15% to 55% of at least one cationic extraction agent, - from 45% to 85% of at least one diluting compound, by weight relative to the total weight of the organic solvent, the total being equal to 100%.

[0043] In another embodiment of the invention, the organic solvent comprises: - from 15% to 55% of at least one cationic extraction agent, - from 45% to 85% of at least one diluting compound, - from 0% to 10% of at least one modifying compound, by weight relative to the total weight of the organic solvent, the total being equal to 100%. Aqueous solution of rare earths

[0044] According to the invention, the term "aqueous solution of rare earths" denotes the "initial aqueous solution of rare earth sulfates or rare earth chlorides originating from the treatment of at least one ore of xenotime, monazite, bastnaesite and / or ionic clays".

[0045] The concentration of rare earths in the aqueous solution of rare earth sulfates or in the aqueous solution of rare earth chlorides may be between 100 mg / L and 250 g / , or between 0.001 and 1.8 mol / L. The concentration of rare earths in an aqueous solution of sulfates is preferably between 100 mg / L and 40 g / L. The concentration of rare earths in an aqueous solution of chlorides is preferably between 100 mg / L and 250 g / L.

[0046] Preferably, the aqueous solution of rare earth sulfates or the aqueous solution of rare earth chlorides is obtained from the chemical treatment of an ore concentrate of the xenotime, monazite, ionic clays and / or bastnaesite type. In practice, this concentrate is obtained by physical concentration of the ores, except in the case of ionic clays. As a method of physical concentration, magnetic separation and flotation may be mentioned as examples, without the present invention being limited to these methods.

[0047] In the case of an aqueous solution of rare earth sulfates, this is obtained by treating a concentrate of xenotime, monazite and / or bastnaesite with sulfuric acid.

[0048] Alternatively, the aqueous solution of rare earth sulfates may be obtained from the treatment of ionic clays with ammonium sulfate, alkali sulfates or magnesium sulfate.

[0049] When it is an aqueous solution of rare earth chlorides, this preferably results from the treatment of ionic clays with chlorides of alkali or alkaline earth metals.

[0050] Depending on the nature of the ore from which the solution is derived, the activity of the aqueous solution linked to the 227Ac content is between 0.1 and 25 Bq / g of rare earths. Liquid-liquid extraction

[0051] In practice, the contacting and mixing of the aqueous solution of rare earth sulfates or rare earth chlorides with the organic solvent can be carried out in a device comprising several stages, for example a battery of mixer-decanters or an extraction column. In this device, the aqueous solution and the organic solvent advantageously circulate in countercurrent.

[0052] Advantageously, the process is carried out at a temperature between 20°C and 60°C, preferably between 30°C and 50°C.

[0053] Preferably, the device comprises an extraction section and a re-extraction section. It may further comprise a washing section. Each section may consist of 1 to 10 stages.

[0054] According to one embodiment, the solvent can be saponified by a basic solution (ammonia, sodium hydroxide, etc.) with an OH ion concentration of between 3 and 10 mol / L.

[0055] According to one embodiment, the organic solvent can be washed in the washing section using an acid solution (hydrochloric, sulfuric, nitric, etc.) with an H+ ion concentration of between 0.2 and 7 mol / L.

[0056] In practice, the rare earth composition according to the invention is obtained at the end of the liquid-liquid extraction, comprising mainly the rare earths La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y.

[0057] In general, an aqueous raffinate is also obtained whose rare earth content is more than 50% and advantageously more than 95% lanthanum. This raffinate comprises more than 99.9% of the 227Ac included in the aqueous rare earth solution. Detailed description of the figures

[0058] [Fig.l] is a schematic representation of the method according to Examples 1 and 2 of the invention, in a liquid-liquid extraction battery consisting of four sections.

[0059] [Fig.2] is a schematic representation of the method according to Example 2 of the invention, in a liquid-liquid extraction battery consisting of four sections.

[0060] [Fig. 3] is a schematic representation of the method according to Example 3 of the invention, in a liquid-liquid extraction battery consisting of four sections.

[0061] [Fig. 4] is a schematic representation of the method according to Example 4 of the invention, in a liquid-liquid extraction battery consisting of three sections. Examples of embodiments of the invention

[0062] The examples below were simulated using software, called “PAREX +”, developed by the Applicant, the basic data necessary for the calculations of which were previously obtained by laboratory tests according to the different chemical systems presented.

[0063] Two types of aqueous solutions resulting from the chemical attack of rare earth ores are considered: - an aqueous solution of rare earths resulting from the treatment of a raw material of the ionic clay type; - an aqueous solution of rare earths resulting from the processing of a xenotime-type raw material.

[0064] The examples below were calculated for a battery-type installation of mixer-decanters operating counter-currently, continuously and having the following performances: - the extraction yield of all rare earths with atomic numbers higher than cerium (Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) as well as that of yttrium is higher than 99.9%, - the purification rate of 227Ac compared to the extracted rare earths (ratio between 227 Ac found in the raffinate and 227Ac present in the initial aqueous solution of rare earths) is greater than 99.9%.

[0065] Example 1: Production of a rare earth composition according to the invention by elimination of 227Ac from a solution of rare earth chlorides obtained by leaching ionic clays with a NaCl solution

[0066] The elimination process is carried out using the following device: a liquid-liquid extraction battery of the mixer-decanter type operating in continuous counter-current, consisting of a one-stage loading section (30), a two-stage extraction section (31), a one-stage washing section (32) and a seven-stage re-extraction section (33), these four sections being connected to each other.

[0067] The extraction section (31) is fed with an aqueous solution (1) comprising a mixture of rare earth chlorides (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) and 227Ac, ​​with a flow rate of 181,200 L / h, the composition of which is detailed in Table 1.

[0068] A solvent SI (4), composed of 67% by volume of aliphatic kerosene and 33% by volume of HEHEHP (where HEHEHP is the cationic extraction agent), is injected at a flow rate of 9,000 L / h into the loading section (30). The solvent SI is saponified by a sodium hydroxide solution (2) with an OH concentration of 8 mol / L, at a flow rate of 396 L / h.

[0069] An aqueous raffinate (5) is obtained with a flow rate of 182,052 L / h. This aqueous raffinate (5) comprises mainly La, as well as almost all of the 227Ac contained in the aqueous solution (1). The measured activity is 28 Bq / g of rare earths.

[0070] The solvent SI is washed with a hydrochloric acid solution (6) at an H+ concentration of 4.5 mol / L, with a flow rate of 400 L / h. This step takes place at the washing section (32).

[0071] An aqueous solution of hydrochloric acid (3) with an H+ concentration of 5.5 mol / L is fed into the re-extraction section (33) with a flow rate of 584 L / h, to enable the re-extraction of the rare earths in the aqueous phase. This allows the solvent to be regenerated, to extract all traces of rare earths.

[0072] The rare earth composition according to the invention (7) comprising mainly the rare earths La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y is obtained with a flow rate of 584 L / h. This rare earth composition according to the invention has a rare earth concentration of 140 g / L and an activity, linked to the 227Ac content, of 1.25.103 Bq / g of rare earths.

[0073] The purification rate of 227Ac relative to the extracted rare earths, which is equal to the ratio between the 227Ac content per gram of rare earths in the aqueous feed (1) and the 227Ac content per gram of rare earths in the rare earth composition according to the invention (7) is, under these conditions, equal to 5070.

[0074] The summary diagram of the process of example 1 according to the invention is shown in [Fig.l].

[0075] The quantities of rare earths and the flow rates are reported in Table 1.

[0076] [Tab.l] Power stage ................. Reex. ...........SA........... Raff. Wash. Ext Flux 1 2 3 4 5 6 7 Nature Aqueous Aqueous Aqueous Organic Aqueous Aqueous Aqueous Flow (IA} 185 200 396 584 9 000 182 052 400 584 Flow TR .......(¾¾¾......, tes 24 32 Lafs / Li 0.21 0.1334 25.1 Ce 0.03 0.0301 8.6 ............. 0.03 <0.0001 10.8 0.10 <0.0061 32.4 Sm (g'L) 0.02 <0.0001 5.1 Eu (géL) <6.961 <0.0001 9.4 Gd (gL) 0.02 <0.0995 4.9 Tbfel) <0.01 <0.0001 0.9 DyfeT; 0.02 <0.0001 4.7 <0.01 <0.0901 1.13 Eî- (g / L) 0.01 <0.0001 3.1 Tsi <0.01 <0.0991 9.4 Ybfel) 0.01 <0.0301 2.5 Lu (g / LJ <0.01 <0.0991 0=4 Y (gL) 0.13 <0.0901 .3¾.^ Ac 6.3 28 1.25.19- ■OH'fmeEL) S (oedï.) 0.001 5.5 4.5 2.1 HEHEHP ............... 33 Kerosene 67

[0077] The abbreviations correspond to the following steps: Feed: feeding of the aqueous solution of rare earths (1) into the extraction section (31) Loading: loading of the sodium hydroxide solution (2) into the loading section (30) Re-extracting: re-extracting the rare earths by adding an aqueous solution of hydrochloric acid (3) into the re-extracting section (33) Raff.: aqueous raffinate (5) from the loading section (30) Wash: washing for solvent regeneration using hydrochloric acid solution (6) in the washing section (32) Ext.: rare earth composition according to the invention (7) from the re-extraction section (33) TR: rare earths Nature: nature of the flow gTR .gram of rare earths kgTR: kilogram of rare earths

[0078] Example 2: Production of a rare earth composition according to the invention by elimination of 227Ac from a solution of rare earth sulfates obtained by leaching of ionic clays by a solution of (NH4)2SO4

[0079] The elimination process is carried out using the following device: a liquid-liquid extraction battery of the mixer-decanter type operating in counter-current, consisting of a one-stage loading section (34), a two-stage extraction section (35), a two-stage washing section (36) and a seven-stage re-extraction section (37), these four sections being connected to each other.

[0080] The extraction section (35) is fed with an aqueous solution (8) comprising a mixture of rare earth sulfates (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) and 227Ac, ​​with a flow rate of 120,800 L / h, the composition of which is detailed in Table 2.

[0081] The SI solvent (11), composed of 67% by volume of aliphatic kerosene and 33% by volume of HEHEHP (where HEHEHP is the cationic extraction agent), is injected at a flow rate of 10,000 L / h into the loading section (34). The SI solvent is saponified by an ammonia solution (9) with an OH concentration of 4 mol / L, at a flow rate of 1,000 L / h.

[0082] An aqueous raffinate (12) comprising mainly La and almost all of the 227Ac is obtained with a flow rate of 126,323 L / h. The measured activity is 27 Bq / g of rare earths.

[0083] The solvent SI is washed with a sulfuric acid solution (13) at an H+ concentration of 0.7 mol / L, with a flow rate of 4,248 L / h in the washing section (36).

[0084] An aqueous solution of nitric acid (10) with an H+ concentration of 3.5 mol / L is fed into the re-extraction section (37) with a flow rate of 2,523 L / h, thus allowing the regeneration of the solvent.

[0085] A rare earth composition according to the invention (14) comprising mainly the rare earths La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y is obtained with a flow rate of 2,636 L / h. This rare earth composition has a rare earth concentration of 31 g / L and an activity, linked to the 227Ac content, of 1.3.10 3 Bq / g of rare earths.

[0086] The purification rate of 227Ac relative to the rare earths, which is equal to the ratio between the 227Ac content per gram of rare earths in the aqueous feed (8) and the 227Ac content per gram of rare earths in the rare earth composition according to the invention (14) is, under these conditions, equal to 4,920.

[0087] The summary diagram of the process of example 2 according to the invention is shown in [Fig.2].

[0088] The quantities of rare earths and the flow rates are reported in Table 2.

[0089] [Tab.2] Alum. Charge. Reex. SI Ref. Lav. Ext Flux 8 9 10 11 12 .13 14 Nature Aqueous Aqueous Aqueous Orgatuque Aqueous Aqueous Aqueous Flow (L / h) 120 800 1 000 ? s?-? 10 000 126 323 4 248 2 636 Flow TF. (kgTF / h) 106 25 SI La (g / L) 0.32 0.20 <0.0001 1.12 Eu (g / L) <0.10 <0.0001 0.08 Gd (g / L) 0.02 <0.0001 1.1 Tbfe'L) <0.01 <0.0001 0.2.1 0.02 <0.0001 1.05 Ho (g / L) 0.01 <0.0001 0.25 Er(g / L) 0.01 <0.0001 0.68 Tmtg / L} <0.001 <0.0001 0.08 Yb Cg-'L) 0.01 <0.0001 0.55 Lu (g / L) <0.001 <0.0001 0.08 Y (g-'L) 0.19 <0.0001 8, S WgTJ.) 6.35 77 1.2910-3 OH(moVL) 4 H* (snoPL) 0.001 3.5 0.00598 0.66 2.32 HEHEHP (%vcd) 33 Kerosene (%vol) 67

[0090] The abbreviations correspond to the following steps: Feed: feeding of the aqueous solution of rare earths (8) into the extraction section (35) Loading: loading the ammonia solution (9) into the loading section (34) Re-ex.: re-extraction of rare earths by adding an aqueous solution of nitric acid (10) in the re-extraction section (37) Raff.: aqueous raffinate (12) from the loading section (34) Wash: washing, regeneration of the solvent using a sulfuric acid solution (13) in the washing section (36) Ext.: rare earth composition according to the invention (14) from the re-extraction section (37) TR: rare earths Nature: nature of the flow gTR .gram of rare earths kgTR: kilogram of rare earths

[0091] Example 3: Production of a rare earth composition according to the invention by elimination of 227Ac from a solution of rare earth sulfates obtained by treatment of a xenotime concentrate with a sulfuric acid solution.

[0092] The elimination process is carried out using the following device: a liquid-liquid extraction battery of the mixer-decanter type operating counter-currently, continuously, consisting of a one-stage loading section (38), a two-stage extraction section (39), a one-stage washing section (40) and a seven-stage re-extraction section (41), these four sections being connected to each other.

[0093] The extraction section (39) is fed with an aqueous solution (15) comprising a mixture of rare earth sulfates (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) and 227Ac, ​​with a flow rate of 7,927 L / h, the composition of which is detailed in Table 3.

[0094] The SI solvent (18), composed of 67% by volume of aliphatic kerosene and 33% by volume of HEHEHP (cationic extraction agent) is injected at a flow rate of 6,650 L / h into the loading section (38). The SI solvent is saponified by an ammonia solution (16) with an OH concentration of 4 mol / L at a flow rate of 665 L / h.

[0095] An aqueous raffinate (19) comprising mainly La and almost all of the 227Ac is obtained with a flow rate of 8,966 L / h. The measured activity is 167 Bq / g of rare earths

[0096] The solvent SI is washed with a sulfuric acid solution (20) at an H+ concentration of 0.4 mol / L with a flow rate of 84 L / h in the washing section (40).

[0097] An aqueous solution of nitric acid (17) with an H+ concentration of 3.5 mol / L is fed into the re-extraction section (41) with a flow rate of 2,671 L / h.

[0098] The rare earth composition according to the invention (21) comprising mainly the rare earths La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y is obtained with a flow rate of 2,798 L / h. The rare earth composition according to the invention has a rare earth concentration of 37 g / L and an activity, linked to the 227Ac content, of 2.27.10 4 Bq / g of rare earths.

[0099] The 227Ac purification rate, which is equal to the ratio of the 227Ac content per gram of rare earths in the aqueous feed (15) to the 227Ac content per gram of rare earths in the rare earth composition according to the invention (21) is equal to 5,220.

[0100] The summary diagram of the process of example 3 according to the invention is shown in [Fig.3].

[0101] The quantities of rare earths and the flow rates are reported in Table 3.

[0102] [Tab.3] Alinr. Charge. Rees. Solvent SI RÆ Washing Est. rkix 15 16 tT 18 19 29 21 Nature Aqueous Aqueous Aqueous Organic Aqueous Aqueous Aqueous Flow (D'h) '7 027 665 2 671 6 650' 84 2 798 Flow TR {kg-zr / h; 104 1 103 La (gi) 0.29 6.080 0.57 Ce(gL) 0.69 1.95 Fr&L} 0.10 <00003 Ntt (gL) 0.46 <9.0001 1.31 Sm (g <l) 0,30 <0,0031 g,s5 eufe l) 0,07 g,18 gd (gl) 1w <s,ûî®1 2,31 tb(gl) 0,18 <9,0001 ■0,50 dy (g.l) 1,20 3,41 ho 0,26 ■0,73 & (g-l) 0,75 <40®! .2,11 tsn (g 0,10 <s,æ®l 0,29 ybfel) 0,61 1,73 lu (g<l) 0,08 ■0,24 y (g'l'l 7,29 40®l 20,39 1,18 167 qh-(œd:l) 4 0,001 3.5 0,02 0,4 234 hehehp 33 kérosène 6?

[0103] The abbreviations correspond to the following steps: Feed: feeding of the aqueous solution of rare earths (15) into the extraction section (39) Loading: loading of the ammonia solution (16) into the loading section (38) Re-extracting: re-extracting the rare earths by adding an aqueous nitric acid solution (16) into the re-extracting section (41) Raff.: aqueous raffinate (19) from the loading section (38) Ext.: rare earth composition according to the invention (21) from the re-extraction section (41) TR: rare earths Nature: nature of the flow gTR .gram of rare earths kgTR: kilogram of rare earths

[0104] Example 4: Production of a rare earth composition according to the invention by elimination of 227Ac from a solution of rare earth sulfates obtained by treatment of a xenotime concentrate with a sulfuric acid solution.

[0105] The elimination process is carried out using the following device: a liquid-liquid extraction battery of the mixer-decanter type operating counter-currently, continuously, consisting of a four-stage extraction section (42), a four-stage washing section (43) and a seven-stage re-extraction section (44), these three sections being connected to each other.

[0106] The extraction section (42) is fed with an aqueous solution (22) comprising a mixture of rare earth sulfates (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) and 227Ac, ​​with a flow rate of 7,927 L / h, the composition of which is detailed in Table 4.

[0107] A solvent S2 (24), composed of 70% by volume of aliphatic kerosene and 30% by volume of HDEHP, (where HDEHP is the cationic extraction agent), is injected at a flow rate of 56,000 L / h.

[0108] An aqueous raffinate (25) comprising mainly La as well as almost all of the 227Ac, ​​is obtained with a flow rate of 8,298 L / h. The measured activity is 105 Bq / g of rare earths.

[0109] The solvent S2 is washed with a sulfuric acid solution (26) at an H+ concentration of 3.1 mol / L with a flow rate of 162 L / h in the washing section (43).

[0110] An aqueous solution of nitric acid (23) with an H+ concentration of 5 mol / L is fed into the re-extraction section (44) with a flow rate of 36,000 L / h.

[0111] The rare earth composition according to the invention (27) comprising mainly the rare earths La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y, is obtained with a flow rate of 38,775 L / h. This rare earth composition according to the invention has a rare earth concentration of 2.7 g / L and an activity, linked to the 227Ac content, of 7.8.10 3 Bq / g of rare earths.

[0112] The 227Ac purification rate, which is equal to the ratio between the 227Ac content per gram of rare earths in the aqueous feed (22) and the 227Ac content per gram of rare earths in the rare earth composition according to the invention (27) is equal to 150.

[0113] The summary diagram of the process of example 4 according to the invention is shown in [Fig.4],

[0114] The quantities of rare earths and the flow rates are reported in Table 4.

[0115] [Tab.4] Htâüs Alùn. Reex. S2 Raff. Lav. Est. Flux 22 23 24 75 î 76 77 Nature Aqueous Aqueous Organic Aqueous ; Aqueous Aqueous Flow rate (L / h) 7,927 36,000 56,000 8,298 162 38,775 Flow rate TR.(kg^Æ) 194 1,103 La (gi) 0^9 0.130 0.03 Ce (g / L) 0.69 0.009 0.14 Pr(gT) œio <0.0001 0.02 NdtgTJ 0.46 <0.0001 0.09 Sirs (g / L) 030 <0.0001 0.06 Eu (g.'L) 0.07 <0.0001 ; 0.01 GdfeL) 0.52 <0.0001 0.17 Tb (g / L) 0.1 s <0.0001 0.04 Dy (gL) 1.20 <0.0001 0.2.5 Ho (g / L) 0.26 <0.0001 0.05 Et (g;Lj 0.75 <0.0001 1 0.15 Tm (g / L) 0.10 <0.0001 0.02 Yb(gL) 0.61 <0.0001 0.12 Lu (g / L) 0.08 <0 0001 0.02 Y (g / L) 7.20- <0.0001 1.47 "7Ac (Bq-'gTg) 1.18 105 i 7.83.10-3 (mol / L} 0.001 5 0.40 3.1 4.5 HDEHP 30 .Kerosene {%yd) 70

[0116] The abbreviations correspond to the following steps: Feed: feed of the aqueous solution of rare earths (22) into the extraction section (42)

[0117] Reex.: re-extraction of rare earths by adding an aqueous solution of nitric acid (23) in the re-extraction section (44) Raff.: aqueous raffinate (25) from the extraction section (42) Wash: washing, regeneration of the solvent (24) using a sulfuric acid solution (26) in the washing section (43) Ext.: rare earth composition according to the invention (27) from the re-extraction section (44) TR: rare earths Nature: nature of the flow gTR .gram of rare earths

[0118] In addition to the disadvantages of the state of the art listed above, it appears that certain processes of the prior art, such as that described in the publication “Cleaning rare earth elements from actinium”, Journal of Alloys and Compounds, vol. 225 (1995), pages 320-323, can only be implemented if the initial aqueous solution of rare earths is a solution of rare earth nitrates. This is also the case for the process described in document CN 85100148, which is carried out to purify solutions of lanthanum nitrates only.

[0119] Furthermore, example 3 of document WO 2019 / 000014, which describes a process for purifying actinium by precipitation, applicable to solutions of rare earth sulfates or chlorides, has a precipitation rate of 227Ac for high 227Ac contents (70 Bq / L) of approximately 47%, for a precipitation rate of rare earths of 2%. The purification rate of 227Ac is therefore:

[0120] [Formula 1] (1-2%) / (147%) = 1.85

Claims

Claims

1. A rare earth composition resulting from the liquid / liquid extraction of an initial aqueous solution of rare earth sulfates or rare earth chlorides from the processing of at least one ore of xenotime, monazite, bastnaesite and / or ionic clays, said rare earth composition having a 227Ac content of less than 0.10 Bq / g of rare earths, preferably less than 0.01 Bq / g of rare earths, the alkaline earth and lead content of said rare earth composition being less than 1000 ppm relative to the amount of rare earths, preferably less than 100 ppm relative to the amount of rare earths, and said rare earth composition being in the form of a solid or in the form of an aqueous solution.

2. A rare earth composition according to claim 1, characterized in that the rare earth composition has a total activity of less than 0.10 Bq / g of rare earths, preferably less than 0.01 Bq / g of rare earths.

3. A rare earth composition according to claim 1 or 2, characterized in that the rare earths belong to the group comprising La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y.

4. Rare earth compositions according to claim 1 or 2, characterized in that the rare earth composition is in the form of a solid belonging to the group comprising carbonates, hydroxycarbonates, hydroxides, oxides, oxalates, crystallized nitrates, anhydrous nitrates, crystallized chlorides and anhydrous chlorides of rare earths.

5. Rare earth compositions according to claim 1 or 2, characterized in that the rare earth composition is in the form of an aqueous solution belonging to the group comprising aqueous solutions of rare earth sulfates, chlorides or nitrates.

6. Rare earth composition according to claim 5, characterized in that the concentration of rare earths in the aqueous solution is between 10 g / L and 500 g / L.

7. Rare earth composition according to one of claims 1 to 6, characterized in that it is obtained by a process for removing the actinium contained in said initial aqueous solution of rare earth sulfates or rare earth chlorides, said process comprising the following steps: - contacting and mixing the initial aqueous solution with a water-immiscible organic solvent, said organic solvent comprising at least one cationic extraction agent, and - separation by liquid-liquid extraction of the rare earths and the actinium, to produce the rare earth composition.

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