PROCESS FOR PURIFYING RADIUM WITH RESPECT TO BARIUM AND IMPURITIES IN AQUEOUS SOLUTION

Abstract

METHOD FOR PURIFYING RADIUM FROM BARIUM AND IMPURITIES IN AQUEOUS SOLUTION. The present invention relates to a method for separating radium from barium by selective chromatographic separation. Figure for abstract: None

Description

Title of the invention: METHOD FOR PURIFYING RADIUM WITH RESPECT TO BARIUM AND IMPURITIES IN AQUEOUS SOLUTION technical field

[0001] The invention relates to the field of separation and purification of metallic elements in solution. More specifically, the invention relates to a process for purifying radium from a solution in which it is present together with barium and optionally metallic or non-metallic impurities.

[0002] The invention finds particular application for the recovery of the radium-226 isotope which makes it possible to produce actinium-225, useful in nuclear medicine for the treatment of cancers by targeted alpha-therapy. PREVIOUS STATE OF THE ART

[0003] Radium can occur naturally in various ores. It can also be present in processing residues resulting from the contact of an acidic leaching solution with an ore containing uranium.

[0004] In all cases, radium is generally present in conjunction with other elements such as barium and impurities.

[0005] Separations of radioisotopes, for example using ethylenediaminetetraacetic acid (EDTA), have been described. They generally demonstrate low selectivity in the separation of radium with respect to other elements and / or are difficult to implement.

[0006] Thus, US2,554,649 describes a process for separating radium from a sample also containing barium, by chromatographic separation using a single eluent. However, the chromatographic separation described is carried out using a sample with a very high concentration of radium present in a mass equal to that of barium; moreover, the eluent used is concentrated and therefore does not guarantee good selectivity for the separation of radium, particularly when the starting sample contains small amounts of radium compared to the other elements, such as barium.

[0007] The state of the art therefore does not allow for a high concentration of radium from the very low initial concentrations in the sample.

[0008] It is therefore necessary to make available a process for purifying radium from samples in which radium is present in small quantities alongside other elements, in particular metallic impurities.

[0009] It is therefore particularly interesting to isolate the radium present in these residues in order to valorize it.

[0010] The Inventors have therefore set themselves the goal of making available a process for isolating radium from other elements, in particular from barium and other impurities that may be present.

[0011] More specifically, they aimed to purify radium from a sample in which it is present in low concentrations, for example, an ore extraction residue, such as an extraction residue resulting from contacting an acidic leaching solution with an ore containing uranium. Description of the invention

[0012] These goals are achieved by the invention which proposes a chromatographic separation process of radium with respect to barium, allowing a first selective elution of barium, then the elution of radium.

[0013] To this end, the invention relates to a method for separating radium from a sample S comprising radium and barium, said method comprising a chromatographic separation step SC comprising:

[0014] - loading the sample S onto a column C comprising a phase stationary PS cation exchanger capable of retaining radium and barium;

[0015] - the circulation of an eluent El in said phase PS, El selectively eluting the barium vis-à-vis radium, leading to an ELBa eluate enriched in barium; then

[0016] - the circulation of an eluent E2 in said PS phase, E2 eluting radium; and leading to a radium-enriched ELRa eluate;

[0017] E1 and E2 each comprising a complexing agent, identical or different;

[0018] characterized in that the concentration of said agent in the eluent El ([El]) is lower than the concentration of said agent in the eluent E2 ([E2]).

[0019] It was thus discovered that it was possible to selectively elute barium from radium, under certain conditions of eluent concentration.

[0020] The separation process according to the invention makes it possible to recover radium while maximizing its concentration and / or purity.

[0021] In the context of the subsequent production of actinium-225, the process of the invention therefore makes it possible to limit the generation of irradiation products, which would be difficult to separate subsequently and which would therefore risk impacting the radiological purity of the actinium-225 produced.

[0022] According to other advantageous aspects of the invention, the method comprises one or more of the following features, taken individually or in all technically possible combinations:

[0023] In the foregoing and the following, radium may be in the form of one of its isotopes, in particular radioactive, particularly radium-226.

[0024] The term “radium” used here therefore also refers to radium-226.

[0025] The process according to the invention allows the separation of radium from a sample S comprising in particular radium and barium.

[0026] Said sample S may in particular be a solution, such as an aqueous solution.

[0027] Typically, said solution may be weakly concentrated in radium with a radium concentration of less than 102 g / L, in particular less than 104 g / L, and jointly a barium concentration greater than 103, in particular greater than 102 g / L of solution.

[0028] Said sample S may include in addition to radium and barium one or more metallic or non-metallic impurities.

[0029] Metallic impurities may include impurities selected from among the poor metals, alkaline earth metals, actinides, metalloids, such as lead, uranium, arsenic.

[0030] Said stationary phase PS can be any cation exchange stationary phase material which is capable of retaining radium and barium.

[0031] Such a material may comprise an inorganic solid support (such as silica or alumina particles or a silica gel), an organic support (such as a polymer) or an inorganic-organic support, which is functionalized, by grafting or impregnation, by organic molecules capable of retaining, by ion exchange, molecular recognition or any other mechanism, the radium (Ra) and barium (Ba) ions present in the sample S.

[0032] This may include a material comprising silica particles grafted with molecules of an organic radium ligand, for example, an oxacryptand. A material particularly well-suited to implementing the process of the invention is, for example, that offered by IBC Advanced Technologies, Inc. under the reference AnaLig® Ra-01. This stationary phase retains radium, regardless of its isotope.

[0033] According to one embodiment, the stationary phase PS also retains barium.

[0034] It has been observed that although the PS phase fixes radium and barium, it is possible to elute, under specific conditions, selectively barium and then radium in order to obtain a radium-purified eluate in barium.

[0035] The sample S is loaded at the top of the column; typically, a sample volume is loaded and fixed by circulation within the stationary phase of the column. The sample volume generally depends on the bed volume of the column (or BV for "Bed Volume").

[0036] Typically, between 1 and 10,000 BV of the sample are engaged. The sample circulation velocity can be adjusted according to the operating conditions and can, for example, be between 1 and 100 BV / h, in particular between 1 and 30 BV / h.

[0037] After fixing, one or more washing steps can be carried out with one or more acidic solutions, typically aqueous solutions of nitric acid, in order to wash the impregnating agent or in other words the interstitial liquid of the resin.

[0038] The nitric acid content of the washing solution(s) is preferably within the range of acidities recommended by the supplier of the stationary phase material, for example from 0.01 mol / L to 4 mol / L of nitric acid for AnaLig® Ra-01 particles.

[0039] The term "eluent" used here refers to the mobile phase capable of transporting the element in question through the stationary phase.

[0040] The eluents El and E2 are in the form of an aqueous solution comprising, as a solute, a complexing or chelating agent of the element to be eluted (the two terms being considered here as synonyms, and will be referred to here as "complexing agent").

[0041] The complexing agent of the eluent El is chosen from among the agents capable of releasing the barium retained by the stationary phase PS, in particular by complexation or chelation (the two terms being considered here as synonyms).

[0042] The complexing agent of the eluent E2 is chosen from among the agents capable of releasing the radium retained by the stationary phase PS, in particular by complexation or chelation.

[0043] The complexing agents, i.e. the solutes, of the eluents El and E2 may be identical or different.

[0044] According to one embodiment, these complexing agents are different.

[0045] According to one embodiment, these complexing agents are identical, the eluents El and E2 differing by the respective concentration of said agent.

[0046] The pH of the eluents El and E2, typically between 4 and 10, can optionally be adjusted by means of a buffering agent

[0047] Advantageously, the pH of the eluent E2 is slightly basic, in particular between 7 and 9.

[0048] According to the invention, the complexing agents of El and E2 are preferably chosen from an aminopolycarboxylic acid or a salt of an aminopolycarboxylic acid such as ethylenediaminetetraacetic acid (or EDTA), or aqueous solutions of citric acid and its ammonium, alkali or alkaline-earth salts; of oxalic acid and its ammonium, alkali or alkaline-earth salts; and mixtures thereof.

[0049] Thus, it may include, in particular, ammonium citrate, EDTA, citric acid, oxalic acid, sodium citrate, magnesium citrate, potassium citrate, calcium citrate, ammonium oxalate, sodium oxalate, magnesium oxalate, potassium oxalate, calcium oxalate, and combinations thereof, preferably ammonium citrate.

[0050] According to one embodiment, the concentration of El in complexing agent (here referred to as [El]) is less than the concentration of E2 in complexing agent (here referred to as [E2]) to allow the selective elution of barium by El, then that of radium by E2.

[0051] Thus, according to one embodiment, the eluent El and the eluent E2 are such that [El] < [E2] / 2, in particular [El] < [E2] / 5, preferably [El] = [E2] / 10.

[0052] By way of illustration, the concentration [El] for elutating barium may be less than 1 M, in particular less than 0.5 M, preferably between 0.01 M and 0.5 M.

[0053] According to one embodiment, the concentration [E2] for eluting radium may be greater than 0.1 M, in particular greater than 1 M, preferably between 0.5 M and 3 M.

[0054] Circulation refers to the passage of the eluent through the stationary phase of the column. Generally, the volume of eluent involved depends on the bed volume of the column.

[0055] Typically, between 1 and 100 BV of each eluent are committed, in particular between 10 and 50 BV.

[0056] Advantageously, the engaged volume of El and the engaged volume of E2 are identical.

[0057] The circulation speed of each eluent can be adjusted according to the operating conditions and can, for example, be between 1 and 100 BV / h, in particular between 1 and 30 BV / h.

[0058] Advantageously, the speed of circulation of El and the speed of circulation of E2 are identical.

[0059] The SC separation can be carried out as long as the recovery yield of barium and / or radium in the eluate is less than or equal to a threshold value, relative to the respective quantity of said element in the sample used. In other words, either of the elution steps can be stopped as soon as the quantity of barium and / or radium recovered exceeds this threshold value.

[0060] For example, this threshold value can be 80% and, even better, 90%.

[0061] At the end of the SC separation according to the invention, an ELRa eluate enriched in radium is recovered with respect to the sample S loaded on the column C.

[0062] The radium-rich ELRa eluate can then be regenerated with an acidic aqueous solution.

[0063] Advantageously, the separation makes it possible to increase the radium purity by a factor of more than 100, in particular more than 1000, in particular more than 10000.

[0064] Here, "purity" means the mass ratio of radium to the sum of the masses of the elements present in the sample considered.

[0065] The separation may also include the usual steps, generally implemented in chromatography, such as packing the column with the dry or wet stationary phase, washing, conditioning, and possible pH adjustment.

[0066] According to one embodiment, the process according to the invention may include the successive conduct of several SC separations as described above.

[0067] Typically, the separation can be carried out n times, with n between 1 and 10, advantageously 2, 3, 4 or 5 times.

[0068] Each of the n SC separations can be carried out on said column C loaded with the stationary phase PS, by means of the eluents El and E2, as previously described, it being understood that said SC separation is carried out n times successively, with n being an integer between 1 and 10, on said column C loaded with the stationary phase PS, by means of the eluents El and E2, such that the (nl)th SC separation leads to a radium-enriched eluate (ELRa)n_i, and the nth SC separation is carried out with (ELRa)n4 and leads to a radium-enriched eluate (ELRa)n.

[0069] Thus, the eluate (ELRa) obtained at the first separation is used as a sample in the second separation.

[0070] Iteratively, the eluate (ELRa)n_i from the (nl)th separation is committed as a sample in the nth separation.

[0071] Successive SC separations are typically conducted under the conditions described above.

[0072] Advantageously, identical or different conditions can be implemented for each SC separation. Thus, typically the eluents El and E2, respectively, can be identical with similar concentrations at each SC separation.

[0073] Advantageously, the volumes of PS committed and / or the volumes of eluents El, respectively E2 can be different for each SC separation, in particular volumes lower at each successive SC iteration.

[0074] Advantageously, one or more washing steps can be conducted on column C after the loading and fixation of the eluate (ELRa)n_i, prior to the circulation of the eluent EL

[0075] The sample S involved in the process according to the invention can ultimately be derived from a residue of ore extraction, in particular from an ore containing uranium.

[0076] More specifically, the sample S may originate from a residue of uranium extraction from said ore.

[0077] Thus, typically, sample S can be prepared from an extraction residue by processing the residue comprising the following steps: - treatment of said residue by particle size separation, such as by hydrocyclone, to isolate a fraction of fine particles; - treatment by leaching of said fine particle fraction, using one or more acidic solutions resulting in a filtrate F; and - purification of said filtrate F by SC0 chromatography, giving rise to a raffinate R.

[0078] Typically, the sample S comprises said raffinate R, in particular the sample S consists of said raffinate R.

[0079] Typically, the filtrate F is a solution comprising radium, barium and lead.

[0080] Advantageously, the treatment process makes it possible to valorize the ore residue.

[0081] Thus, hydrocyclone treatment makes it possible to obtain a fraction of fine particles enriched in radium, while the fraction of coarse particles can be enriched in other elements, in particular in arsenic.

[0082] The leaching treatment makes it possible to obtain a filtrate F enriched in radium, separated from a filtrate which can be enriched in lead in particular.

[0083] The raffinate R obtained by the purification of the filtrate F by the chromatographic separation SCoest is typically enriched in radium, while the eluate EL0 obtained by said chromatography may be enriched in lead.

[0084] Thus, according to one embodiment, the process according to the invention comprises, prior to the SC separation, a step of isolating said sample S from a solution So comprising radium, barium and lead, by initial chromatographic separation (SC0) comprising: - the loading of said solution So onto a column Co comprising a stationary phase PS0 capable of retaining lead; - the collection as a refiner of sample S comprising radium and barium, S being depleted in lead compared to So.

[0085] Typically, the stationary phase PS0 can be chosen from among the cation exchange stationary phase materials which is capable of retaining lead.

[0086] Such a material may comprise a solid inorganic support (such as silica or alumina particles or a silica gel), an organic support (such as a polymer), or an inorganic-organic support, which is functionalized, by grafting or impregnation, by organic molecules capable of retaining, by ion exchange, recognition molecular or any other mechanism, the lead (Pb) ions present in sample S.

[0087] This may include, in particular, a material comprising silica particles grafted with molecules of an organic lead ligand, for example, a crown ether. Materials that are particularly well suited to implementing the process of the invention include, for example, the Pb resins offered by Triskem™.

[0088] Typically the concentration of the So solution is between 0.1 and 5 N.

[0089] According to one embodiment, the chromatographic separation SC0 can be carried out without eluent by circulation of the charged So solution, with radium and barium circulating through the stationary phase PS0 and lead being retained by said phase.

[0090] The lead initially present in the sample So can be recovered by eluting the lead retained in the stationary phase PS0 with a suitable eluent.

[0091] Thus, according to one embodiment, the SC0 separation further includes the circulation of a lead complexing agent after collection of the solution S, and the collection of an eluate EL0 enriched in lead.

[0092] Agents capable of releasing the lead retained by the stationary phase PS0, in particular by complexation or chelation (the two terms being considered synonymous here). Advantageously, the lead eluent agent is ammonium acetate, in aqueous solution with a concentration between 0.1 and 1 N, in particular acidified solutions, with a pH between 1 and 7.

[0093] The PS0 phase can then be reconditioned to recover elements that would still be fixed on PS0 after the elution of radium and lead.

[0094] According to one embodiment, the process further comprises, prior to step SCo, an aqueous leaching step leading as filtrate F to said solution So comprising radium, barium and lead.

[0095] Said leaching step can advantageously be carried out on a fraction of an ore extraction residue, such as said fine particle fraction mentioned above and, more specifically, a fraction comprising particles whose average diameter (in number) is less than 25 pm, in particular less than 20 pm, particularly less than 17 pm.

[0096] Typically, the leaching step includes at least two successive acid treatments, and the collection of said filtrate F from the second acid treatment as a solution So.

[0097] Advantageously, the first acid treatment comprises mixing said residue sample with an aqueous hydrochloric acid solution of acidity typically between 0.1N and 8N and collecting a solid, and the second acid treatment includes mixing said solid with an aqueous solution of nitric acid of acidity typically between 0.01 N and ION, and collecting said solution So as filtrate F.

[0098] Advantageously, said fraction of an ore extraction residue mentioned above is a fine particle fraction obtained by particle size separation of an ore extraction residue.

[0099] Advantageously, the solid obtained at the end of the first acid treatment and the liquid filtrate obtained at the end of the second acid treatment are enriched in radium.

[0100] Advantageously, the liquid filtrate also obtained by the first acid treatment is enriched in lead.

[0101] Typically, acidic solutions are engaged in a Liquid / Solid (by mass) ratio greater than 1, in particular approximately equal to 4.

[0102] The acid treatments of the leaching stage are advantageously carried out hot, at a temperature between 25°C and 70°C, in particular at about 60°C.

[0103] According to one embodiment, the process further comprises, prior to the leaching step, a particle size separation step, typically comprising: - one or more hydrocyclone treatments of an ore residue; - the separation of a fraction of fine particles, having an average diameter of less than 25 pm, in particular less than 20 pm, particularly less than 17 pm.

[0104] Advantageously, it has been shown that hydrocyclone separation allows the majority of the radium to be "concentrated," which is therefore found in the fine particle fraction resulting from the particle size separation.

[0105] Thus, the particle size separation of a fines fraction of the ore processing residue makes it possible to multiply the radium content by at least 1.5, advantageously by at least 2.

[0106] Typically, the ore extraction residue comprising a radium content of between 100 and 10000 Bq / g reported to the mass of residue.

[0107] Said ore extraction residue comprises in addition to radium and barium, one or more additional metallic impurities selected from uranium and arsenic, and / or one or more non-metallic impurities such as phosphorus.

[0108] All the steps of the process, which are detailed below, are preferably carried out at room temperature, i.e. at a temperature of 20°C to 25°C.

[0109] According to another object, the present invention also relates to the ELRa eluate obtainable by the process according to the invention, comprising a 226Ra content of between 0.1 and 500 GBq / L, more specifically between 1 and 200 GBq / L. more specifically between 10 and 50 GBq / L, and a purity in 226Ra between 50 and 99% more specifically between 75 and 95% (by mass). BRIEF DESCRIPTION OF THE FIGURES

[0110] [Fig. 1] The [Fig. 1] schematically represents the process of valorizing radium from an ore extraction residue 1, up to a radium-enriched extract (ELRa)2, including the separation process of the invention.

[0111] In the diagram of [Fig. 1], two successive chromatographic separations (SC)i and (SC)2 have been represented, it being understood that a lower or higher number of SC separations may be implemented, if appropriate.

[0112] DETAILED DESCRIPTION OF SPECIFIC IMPLEMENTATION METHODS

[0113] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to [Fig.1], illustrating the separation of radium from an ore extraction residue 1, which residue includes in particular radium, barium, lead, arsenic.

[0114] The residue 1 is first subjected to a particle size separation A.

[0115] As described above, said particle size separation A may include one or more separations by hydrocyclone, in order to collect a fraction 2 of fine particles, in particular of average diameter (in number) less than 17 pm enriched in radium and a fraction 2' of coarse particles of greater average diameter which may for example be enriched in other impurities, for example arsenic.

[0116] Said fraction 2 is then treated by leaching, first by a treatment B with an aqueous solution of hydrochloric acid leading to a filtrate 3' enriched in lead and actinium, and a residual solid 3 enriched in radium.

[0117] The solid 3 is then subjected to a second acid treatment B' by a nitric acid solution leading to a filtrate 4 and a solid residue 4'.

[0118] Filtrate 4 corresponds to filtrate F, respectively the sample referenced above So.

[0119] The filtrate 4 obtained at the end of the HCl then HNO3 leaching steps is generally not pure enough to serve as a radiiferous solution for manufacturing targets for irradiation.

[0120] The radium present in the So solution resulting from the double leaching (B and B') is then isolated by implementing the following steps.

[0121] It is thus subjected to an initial chromatographic separation SC0 to purify it of lead, using a resin comprising a stationary phase PS0 that retains the lead, thereby allowing the recovery of a raffinate R of equivalent radium concentration but purified of lead. Elution of the resin by, for example, ammonium acetate leads to an eluate ELo enriched in lead.

[0122] The raffinate R, corresponding to the sample S above, is then used in the radium separation process according to the invention, which herein consists, by way of illustration, of two successive chromatographic separation steps (SC)i and (SC)2 in series, each being carried out on a column C loaded with a stationary phase retaining radium, such as AnaLig® Ra. Each separation (SC)i and (SC)2 comprises elution with the eluent E1 specifically eluting barium, then with the eluent E2 eluting radium.

[0123] Thus, elution by El leads to a barium-enriched eluate (ELBa)i obtained at the end of separation (SC)i and to a barium-enriched eluate (ELBa)2 obtained at the end of separation (SC)2, respectively.

[0124] Thus, elution by E2 leads to a radium-enriched eluate (ELRa)i obtained at the end of the separation (SC)i and to a radium-enriched eluate (ELRa)2 obtained at the end of the separation (SC)2, respectively.

[0125] Each of the eluents El and E2 is for example made up of an aqueous solution of ammonium citrate, with for example [El]=0.05 M and [E2]=0.5 M.

[0126] The eluate (ELRa)i obtained at the end of (SC)i is committed to the top of the second column C for the second chromatographic separation (SC)2.

[0127] Each SC separation also leads to a raffinate RI and R2, respectively

[0128] The eluate (ELRa)2 can then be used for the valorization of radium, for example in the preparation of radium targets by electrodeposition.

[0129] EXAMPLES

[0130] An ore extraction residue (m = 1149 kg) having the following particle size composition is used to separate radium:

[0131] [Tables 1 D10 D50 D90 Fut 4 3.9 pm 18.8 pm 186.0 pm Fut 5 4.2 pm 24.7 pm 261.0 pm Fut 6 4.1 pm 22.4 pm 195.0 pm Fut 7 3.8 pm 4.5 pm 136.0 pm Fut 8 3.6 pm 4.4 pm 124.0 pm Fut 9 3.6 pm 2.5 pm 117.0 pm Average 3.9 pm 18.9 pm 169.8 pm

[0132] Analysis of the residue indicates that it contains a radium-226 content of approximately 2500 Bq / g of residue. Particle size separation

[0133] A fraction of coarse particles (574 kg) is isolated from the residue by hydrocyclone:

[0134] [Tables2 D10 D50 D90 Fut 4 6.0 pm 76.2 pm 235.0 pm Fut 5 5.7 pm 50.1 pm 208.0 pm Fut 6 6.1 pm 71.7 pm 294.0 pm Fut 7 4.9 pm 28.7 pm 173.0 pm Fut 8 5.9 pm 47.0 pm 151.0 pm Fut 9 5.5 pm 44.6 pm 232.0 pm Average 5.7 pm 53.1 pm 215.5 pm - a fraction of fine particles with a D90 (90% of the particles are smaller than 15.5 pm) for a mass of 574 kg:

[0135] [Tables3 D10 D50 D90 Fut 4 2.1 pm 6.5 pm 18.9 pm Fut 5 2.1 pm 6.1 pm 14.7 pm Fut 6 2.2 pm 6.3 pm 14.9 pm Fut 7 2.2 pm 6.4 pm 15.2 pm Fut 8 2.2 pm 6.3 pm 14.5 pm Fut 9 2.3 pm 6.4 pm 14.9 pm Average 2.2 pm 6.3 pm 15.5 pm

[0136] The fine particle fraction has the following composition:

[0137] [Tables4] Ra (g) 6xl02 Ac (g) 3 xlO5 Pb (g) 19510 U (g) 390 As (g) 362 Ba (g) 121 Th (g) 109 Fe (g) 41764 Cu (g) ​​4391 Dissolution by leaching

[0138] The fine particle fraction is then attacked with hydrochloric acid HCl for 4h, at 60°C, in a Liquid / solid ratio L / S=4, by mixing 1318 L of water and 978 L of 37% HCl (1164 g).

[0139] Washing with 1613 L of water yields a filtrate (m=3592 g, v=3295 L, d=l.09) enriched in lead and actinium having the following composition:

[0140] [Tables5] g / L g Ra 1.3 xlO 7 4xl04 Ac 8.3 xlO9 3xl05 Pb 1.7 5436 U 0.1 412 As 0.0 113 Ba 0.0 6 Th 0.0 79 Fe 8.1 26654 Cu 0.5 1766

[0141] A residual solid (“cake”) enriched in radium is also obtained, having the following composition:

[0142] [Tableauxô] Wet mass (g) 914 Of which water (g) 525 Dry mass (g) 389

[0143] [Tables?] g / kg g Ra l.5xl04 6xl02 Ac 3.6 xlO 9 106 Pb 36.2 14074 U 0.0 0.0 As 0.6 248 Ba 0.3 114 Th 0.1 30 Fe 38.8 15110 Cu 6.7 2625

[0144] The residual solid obtained is mixed with 525 L of water (m=525 kg) and then undergoes a second attack with nitric acid (604 L of water and 427 L of HNO3 65% (598 kg)) for 4h, at 60°C, in a Liquid / solid ratio L / S=4.

[0145] Washing with 1161 L of water yields a filtrate (m=2251 kg, v=2052 L, d=l,l) enriched in radium having the following composition:

[0146] [Tables8] g / L g Ra 2xl05 5xl02 Ac 6xl012 IxlO8 Pb 1.2 2523 U 0.0 27 As 0.1 172 Ba 0.0 63 Th 0.0 7 Fe 1.9 3816 Cu 1.3 2687

[0147] The radium yield of the dissolution is therefore 78.9%.

[0148] The solid residue also obtained has the following composition:

[0149] [Tables9] g / kg g Ra 3.4 xlO5 102 Ac 3.9 xlO9 106 Pb 32.4 11550 U 0.00 0 As 0.2 76 Ba 0.1 52 Th 0.1 23 Fe 31.7 11294 Cu 0.0 0 Lead purification

[0150] The radium-enriched filtrate obtained above is fixed onto a column loaded with a Triskem™ Pb resin:

[0151] [TableauxlO] Loading (BV) 13 Triskem Pb Resin Flow Rate (BV / h) 1 V (L) m(g) Breakthrough + Elution (days) 1 158 61809

[0152] The following solutions are used:

[0153] Washes:

[0154] [Tables 11] HNO3 2N h2o Volume Vol urn L 158 158 BV 1 1

[0155] Lead elution:

[0156] [Tables 12] Ammonium acetate 0.6M pH=6.4 Volume L 1105 BV 7

[0157] Reconditioning:

[0158] [Tables 13] HNO3 2N Volume L 316 BV 2

[0159] This yields a lead-enriched eluate:

[0160] [Tables 14] Volume (L) 1105 Density g / L g Ra 3.86x10 7 4xl04 Pb 2.22 2452 Ba 0.00 1

[0161] The raffinate and washes, enriched in radium, are collected:

[0162] [Tables 15] Volume (L) 2367 g / L g Ra l.4xl05 3 xlO-2 Pb 0.00 0 Ba 0.02 49

[0163] The radium yield of this separation is therefore 73.1%.

[0164] Purification of radium by successive chromatographic separations

[0165] First purification:

[0166] The radium-enriched solution obtained above is fixed onto a column loaded with AnaLig® Ra resin:

[0167] [Tables 16] Loading (BV) 291 AnaLig® Ra Resin 1st purification AnaLig® Ra Resin Flow rate (BV / h) 20 V (L) m(g) Breakthrough + elution (days) 1 8.1 3186

[0168] The following solutions are used:

[0169] [Tables 17] hno3 2N hno3 0.lN Ammonium citrate 0.05M Ammonium citrate 0.5M pH=8 HNO3 10N regeneration Vol urn (L) Vol urn (L) Volume (L) Volume (L) Volume (L) L 244 244 244 81 81 BV 30 30 30 10 10

[0170] This yields two eluates:

[0171] [Tables 18] Ra-enriched eluate (0.5M citrate) Volume (L) 81.3 g / L g Ra 3.5 xlO4 3xl02 Ba 7.4 xlO3 6x10*

[0172] [Tables 19] Eluat enriched in B a (0.05M citrate) Volume (L) 244 g / L g Ra 1.8 xlO5 4xl03 Ba 2.0 xlO 1 48

[0173] By treating the radium-enriched eluate with 65% nitric acid (18.4 kg), a regenerated eluate is obtained:

[0174] [Tables20] Volume (L) 94.6 g / L g Ra 3.0xl04 03xl02 Ba 6.4xl03 6x10*

[0175] Second purification:

[0176] This regenerated eluate is then subjected to a second chromatographic separation (SC2) on the following column:

[0177] [Tables21] Loading (BV) 12 AnaLig® Ra Resin 2nd purification AnaLig® Ra Resin Flow rate (BV / h) 20 V (L) m(g) Breakthrough + elution (days) 1 8.1 3186

[0178] using the following solutions:

[0179] [Tables22] HNO3 2N HNO3 0, IN Ammonium citrate 0.05M Ammonium citrate 0.5M pH=8 HNO3 10N regeneration Volume (L) Volume (L) Volume (L) Volume (L) Volume (L) L 244 244 244 81 81 BV 30 30 30 10 10

[0180] This yields two eluates:

[0181] [Tables23] Ra-enriched eluate (0.5M citrate) Volume (L) 81.3 g / L g Ra 2.9 xlO4 2xl02 Ba 4.0 xlO4 3xl02

[0182] [Tables24] Eluat enriched in B a (0.05M citrate) Volume (L) 244 g / L g Ra 1.65x10 5 4.03xl03 Ba 2.34x10 3 5.71x10*

[0183] By treating the radium-enriched eluate with 65% nitric acid (18.4 kg), a regenerated eluate is obtained:

[0184] [Tables25] Ra eluate regenerated with HNO3 Volume (L) 94.6 g / L g Ra 2.52lxO4 2lxO2 Ba 3.46lxO4 3lxO2

[0185] Third purification:

[0186] This regenerated eluate is then subjected to a third chromatographic separation (SC3) on the following column:

[0187] [Tables26] Loading (BV) 52 AnaLig® Ra Resin 3rd purification AnaLig® Ra Resin Flow rate (BV / h) 20 V (L) m(g) Breakthrough + elution (days) 1 1.8 717

[0188] And the following solutions:

[0189] [Tables27] HNO3 2N HNO3 O.1N Ammonium citrate 0.05M Ammonium citrate 0.5M pH=8 HNO3 10N regeneration Volume (L) Volume (L) Volume (L) Volume (L) Volume (L) L 55 55 55 18 18 BV 30 30 30 10 10

[0190] This yields two eluates:

[0191] [Tables28] Eluat Ra (0.5M citrate) Volume (L) 18.3 g / L g Ra 1.3 xlO3 2xl02 Ba 1.3 xlO4 102

[0192] [Tables29] Eluat B a (0.05M citrate) Volume (L) 55 g / L g Ra 4.3 xlO6 2xl04 Ba 4.1 xlO4 2xl02

[0193] By treating the radium-enriched eluate with 65% nitric acid (4.1 kg), a regenerated eluate is obtained:

[0194] [Tables30] Eluat Ra regenerated with HNO3 Volume (L) 21.3 g / L g Ra l.lxl03 2xl02 Ba 4.8xl04 102

[0195] Fourth purification:

[0196] This regenerated eluate is then subjected to a fourth chromatographic separation (SC4) on the following column:

[0197] [Tables31] Loading (BV) 131 AnaLig® Ra Resin 4th purification AnaLig® Ra Resin Flow rate (BV / h) 5 V (L) m(g) Breakthrough + elution (days) 2 0.16 64

[0198] And the following solutions:

[0199] [Tables32] HN03 2N HNO3 0.lN Ammonium citrate 0.05M Ammonium citrate 0.5M pH=8 HNO3 10N regeneration Volume (L) Volume (L) Volume (L) Volume (L) Volume (L) L 5 5 5 2 2 BV 30 30 30 10 10

[0200] This yields two eluates:

[0201] [Tables33] Eluat Ra (0.5M citrate) Volume (L) 1.63 g / L g Ra 1.4 xlO2 2xl02 Ba 1.4 xlO4 2xl04

[0202] [Tables34] Eluat B a (citrate 0.05M) Volume (L) 5 g / L g Ra 4.7 xlO5 2xl04 Ba 2xl03 102

[0203] By treating the radium-enriched eluate with 65% nitric acid (0.368 kg), a regenerated eluate is obtained:

[0204] [Tables35] Eluate Ra regenerated with HNO3 Volume (L) 1.891 g / L g Ra l,2xlO2 2,2xlO2 Ba l,2xlO4 2xlO4

[0205] Fifth purification:

[0206] This regenerated eluate is then subjected to a fifth chromatographic separation (SC5) on the following column:

[0207] [Tables36] Loading (BV) 47 AnaLig® Ra Resin 5th purification AnaLig® Ra Resin Flow rate (BV / h) 5 V (L) m(g) Breakthrough + elution (days) 2 0.0407 15.93

[0208] And the following solutions:

[0209] [Tables37] HNO3 2N HNO3 O.1N Ammonium citrate 0.05M Ammonium citrate 0.5M pH=8 HNO3 10N regeneration Volume (L) Volume (L) Volume (L) Volume (L) Volume (L) L 1.2 1.2 1.2 0.4 0.4 BV 30 30 30 10 10

[0210] This yields two eluates:

[0211] [Tables38] Eluat Ra (0.5M citrate) Volume (L) 0.407 g / L g Ra 5.2xl02 2xl02 Ba 104 4xl05

[0212] [Tables39] Eluat B a (0.05M citrate) Volume (L) 1 g / L g Ra 1.8 xlO4 2xl04 Ba 1.5 xlO4 2xl04

[0213] The radium-enriched eluate is then concentrated by evaporation-concentration (FCV=3), leading to the following concentrate:

[0214] [Tables40] Ra concentrate (1.5M citrate) — Volume (L) 0.136 g / L g GBq / L Ra 1.56x10* 2.11x102 5.76 Ba 3.00xl04 4.07xl05

[0215] The concentrate is mixed with 1.220 L of alcohol to form the following target by electrodeposition:

[0216] [Tables41] Thin target Ra g Ra 2.11x102 Ba 4.07xl05

Claims

Demands

1. A process for separating radium from a sample S comprising radium and barium, said process comprising a chromatographic separation step SC comprising: — loading the sample S onto a column C comprising a cation-exchange stationary phase PS capable of retaining radium and barium; — circulating an eluent El in said phase PS, El selectively eluting barium with respect to radium, leading to an eluate ELBa enriched in barium; then — circulating an eluent E2 in said phase PS, E2 eluting radium; and leading to an eluate ELRa enriched in radium; El and E2 each comprising a complexing agent, identical or different; characterized in that the concentration of said agent in the eluent El ([El]) is less than the concentration of said agent in the eluent E2 ([E2]).

2. A method according to claim 1 comprising prior to the SC separation, an isolation step of said sample S from a solution So comprising radium, barium and lead, by initial chromatographic separation SC0 comprising - loading said solution So onto a Co column comprising a stationary phase PS0 suitable for retaining lead; - collecting as a raffinate of the sample S comprising radium and barium, S being depleted in lead compared to So.

3. Process according to claim 2 comprising prior to step SCo an aqueous leaching step leading as a filtrate to said solution So comprising radium, barium and lead.

4. A process according to any one of the preceding claims wherein radium is in the form of the isotope 226Ra.

5. A process according to any one of the preceding claims wherein the eluents El and E2 each contain an identical complexing agent.

6. A process according to any one of the preceding claims wherein the eluent El and the eluent E2 are such that [El] < [E2] / 2, in particular [El] < [E2] / 5, preferably [El] = [E2] / 10.

7. A process according to any one of the preceding claims wherein the eluent El and the eluent E2 are selected from aqueous solutions of citric acid and its ammonium, alkali or alkaline earth salts; of oxalic acid and its ammonium, alkali or alkaline earth salts; EDTA; and mixtures thereof.

8. A process according to any one of the preceding claims wherein the eluent El and the eluent E2 are selected from ammonium citrate, EDTA, citric acid, oxalic acid, sodium citrate, magnesium citrate, potassium citrate, calcium citrate, ammonium oxalate, sodium oxalate, magnesium oxalate, potassium oxalate, calcium oxalate, and combinations thereof, preferably ammonium citrate.

9. A process according to any one of the preceding claims wherein the concentration [El] is between 0.01 M and 0.5 M and the concentration [E2] is between 0.5 M and 3 M.

10. A method according to any one of the preceding claims wherein said SC separation is carried out n times successively, with n being an integer between 1 and 10, on said column C loaded with the stationary phase PS, by means of the eluents El and E2, such that the (nl)th SC separation leads to a radium-enriched eluate (ELRa)ni, and the nth SC separation is carried out with (ELRa)n.iet leads to a radium-enriched eluate (ELRa)n.

11. A process according to claim 2 wherein step SC0 further comprises the circulation of a lead complexing agent after collection of solution S, and the collection of a lead-enriched eluate EL0.

12. A process according to claim 3 wherein the leaching step is carried out on a fraction of an ore extraction residue, said fraction comprising particles whose average diameter (in number) is less than 25 pm.

13. A process according to claim 12 wherein the leaching step comprises at least two successive acid treatments of said fraction, and the collection of said filtrate F from the second acid treatment as a solution So.

14. A process according to claim 13 wherein the first acid treatment comprises mixing said extraction residue sample with an aqueous solution of hydrochloric acid and collecting a solid, and the second acid treatment comprises mixing said solid with an aqueous solution of nitric acid, and collecting said solution So as a filtrate F.

15. A process according to claim 12 or 13 wherein said fraction is a fine particle fraction obtained by particle size separation of an ore extraction residue.

16. Process according to claim 15 wherein said residue comprises a radium content of between 100 and 10000 Bq / g relative to the mass of residue.

17. A process according to claim 15 or 16 wherein said ore extraction residue comprises one or more additional metallic impurities selected from uranium and arsenic, and / or one or more non-metallic impurities such as phosphorus.

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