Purification method for ruthenium from technetium and metal impurities in aqueous nitric acid solution

Abstract

The invention relates to a method for purifying ruthenium from an aqueous solution of nitric acid in which ruthenium is present together with technetium and metallic impurities at a concentration at least ten times lower than that of technetium. The invention also relates to a method for producing ruthenium-97 from a technetium-99 target previously irradiated with protons, comprising carrying out a purification method. Application: Production of radiopharmaceuticals based on ruthenium-97 used in the diagnosis of cancer by imaging in nuclear medicine and in its treatment by targeted radiotherapy.

Description

[Technical field]

[0001] The present invention relates to the field of separation and purification of metallic elements in solution.

[0002] More specifically, the present invention relates to a method for purifying ruthenium from an aqueous solution of nitric acid in which ruthenium is present along with technetium and metallic impurities at a concentration at least ten times lower than the concentration of technetium.

[0003] The present invention also relates to a method for producing ruthenium-97 from a proton-irradiated technetium-99 target, including the implementation of this purification method.

[0004] In particular, the invention finds application in the manufacture of ruthenium-97 based radiopharmaceuticals, which are useful in the diagnosis of cancer by imaging in nuclear medicine and in its treatment by targeted radiotherapy. [Background technology]

[0005] Ruthenium-97 is a radioisotope of ruthenium, with a half-life of 2.9 days, which has been the subject of promising research for the last few years in the treatment by targeted radiotherapy, also the so-called vectored radiotherapy, of small sized tumors such as peritoneal carcinomatosis of ovarian or colorectal origin, other possible applications may result in metastatic or residual disease in other pathological situations.

[0006] Ruthenium-97 also forms part of the radioisotopes that have proven important in medical imaging, particularly for carrying out examinations by single photon emission computed tomography (or SPECT).

[0007] In either case, the use of ruthenium-97 can mean that it is administered to the patient in the form of a radiopharmaceutical, i.e. a product in which ruthenium-97 is attached to a vector, i.e. a molecule, such as an antibody, that can very specifically target cancer cells so that they can be destroyed (in the case of targeted radiotherapy) or detected (in the case of medical imaging).

[0008] To do that, the ruthenium-97 must meet radiological purity requirements, ideally greater than 99.00%.

[0009] Ruthenium-97 is usually produced by bombarding natural molybdenum targets (containing molybdenum-95) with alpha particles, but it is also produced by the nucleation of molybdenum in natural molybdenum. 95 Mo is a low-abundance, long-lived isotope that is harmful for medical use. 103 The yield is low due to the formation of Ru.

[0010] Ruthenium-97 can also be produced by proton bombardment of a technetium-99 target, more specifically by nuclear reactions in the proton energy range of 20 MeV to 100 MeV, as described, for example, by N. G. Zaitseva et al. in Radiochimica Acta 1992, 56, 59-68, hereafter ref. [1] and in Applied Radiation and Isotopes 1996, 47(2), 145-151, hereafter ref. [2]. 99 Tc(p,3n) 97 This production route is certainly interesting because its yields are much higher than those of irradiation of natural molybdenum targets, and it offers the possibility of preserving the value of technetium-99, which may be recovered during the processing of spent nuclear fuel.

[0011] In this case, ruthenium-97 is produced together with technetium-97 and molybdenum-97.

[0012] To recover the ruthenium-97 thus produced, the most commonly used method involves dissolving the irradiated target in concentrated nitric acid, replacing the nitric acid medium with a sulfuric acid medium by distillation, and then oxidizing the ruthenium to the volatile ruthenium tetroxide form, RuO4. This oxidation is carried out with a strong oxidizing agent (such as potassium periodate or ammonium persulfate) and by heating to reflux. The volatile oxide is then recovered by trapping in hydrochloric acid or a mixture of hydrochloric acid and hydrogen peroxide, and ruthenium(VIII) is reduced to ruthenium(III) (see reference [2]).

[0013] This method has significant limitations, especially with regard to yield, due to gas leakage in the equipment and losses of ruthenium due to sorption and reduction of RuO4 on the reactor walls and the associated formation of ruthenium dioxide, RuO2. Moreover, the reduction of ruthenium(VIII) in the trap can be partial, leading to species with a poorly defined degree of oxidation, which further reduces the recovery of ruthenium-97, creates problems of radioactive contamination and complicates the step of ruthenium-97 vectorization required for the preparation of radiopharmaceuticals. Finally, the phenomenon of entrainment of pertechnetate, HTcO4, during the reflux affects the separation of ruthenium relative to technetium, resulting in a low separation factor FS Ru / Tc decreases.

[0014] In another technical field, namely the processing of spent nuclear fuel, a method for separating ruthenium from technetium and palladium from aqueous nitric acid solutions containing a large excess of ruthenium relative to technetium (more than 13 times) and many other metallic elements (Te, Ru, Pd, Zr, Ce, U, Pu, Am, Mo) has been proposed in European Patent Application No. 0 347 625, hereinafter reference [3].

[0015] In this method, diethylthiourea (or DEHT) is added to the aqueous solution to be treated, reducing the metal species contained therein. Palladium precipitates in the form of Pd(0), which can be separated by filtration, whereas ruthenium and technetium form cationic complexes, [Ru(NO)-DETH x ]2+と3+ and Tc(IV)O 2+ The ruthenium and technetium are then separated from the other metal species by passing the solution through a cation exchange resin that selectively retains these two metallic elements. The technetium is then recovered by elution with a solution composed of hydrogen peroxide and nitric acid, where it can be oxidized to technetium(VII). The ruthenium is then recovered by elution of the resin with a highly concentrated aqueous solution of nitric acid. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] European Patent Application No. 0 347 625 [Non-patent literature]

[0017] [Non-Patent Document 1] N. G. Zaitseva et al., Radiochimica Acta 1992, 56, 59-68 [Non-Patent Document 2] NG Zaitseva et al., Applied Radiation and Isotopes 1996, 47(2), pp. 145-151 Summary of the Invention [Problem to be solved by the invention]

[0018] In light of the above, the inventors aimed to provide a method for the highly efficient purification of ruthenium from aqueous nitric acid solutions in which ruthenium is present together with technetium and metal impurities at a concentration at least ten times lower than that of technetium, while not being subject to the limitations of the method described in reference [2].

[0019] In particular, the inventors aimed to provide a method that does not involve any oxidation or reduction reactions, is simple to perform, can be automated and does not require the consumption of large amounts of solvents, including toxic solvents. [Means for solving the problem]

[0020] These objects are achieved by the present invention by a method for purifying ruthenium from an aqueous solution of nitric acid A1, which contains, in addition to ruthenium in a concentration C1, technetium in a concentration C2 at least ten times higher than C1, and metal impurities, comprising at least the following successive steps: a) extracting ruthenium from an aqueous solution of nitric acid using a cation exchange resin which retains ruthenium selectively with respect to technetium when ruthenium and technetium are contained in the aqueous solution at a molarity comprised between a first value M1 and a second value M2 higher than M1, said extraction comprising contacting the aqueous solution A1 with the cation exchange resin in a chromatographic column, the molarity of the aqueous solution A1 being comprised between M1 and M2; b) washing the cation exchange resin at least once with an aqueous nitric acid solution A2 having a molar concentration between M1 and M2; and c) eluting ruthenium from the cation exchange resin with an aqueous solution A3 of nitric acid or hydrochloric acid having a molality higher than M2 or an aqueous solution A4 of nitric acid or hydrochloric acid containing nitrates or metal chlorides having a molality lower than or equal to M2, thereby obtaining an aqueous solution A5 containing ruthenium The present invention mainly provides a method including:

[0021] In the present invention, a decontamination factor of ruthenium is obtained relative to technetium that is at least equal to 400, this decontamination factor corresponding to the ratio of the concentrations of ruthenium and technetium in aqueous solution A1 to the ratio of the concentrations of these two elements in aqueous solution A5.

[0022] Above and below, metal impurities are understood to be metals that are present in the aqueous solution A1 in a concentration that is at least 20 times lower than the concentration C1 of ruthenium and therefore at least 200 times lower than the concentration C2 of technetium.

[0023] In the present invention, the metal impurities may in particular be molybdenum and rhodium.

[0024] Moreover, the term "molarity" applied to an aqueous solution of an acid, such as nitric acid or hydrochloric acid, is to be understood in its ordinary sense, i.e. it denotes the molar concentration of this acid in said aqueous solution.

[0025] Furthermore, the expressions "from ... to ..." and "comprised between ... and ..." applied to a concentration range are equivalent and mean that the limits of the range are included.

[0026] According to the invention, the metal nitrates or chlorides present in the aqueous solution A4 may in particular be nitrates or chlorides of alkaline earth metals, transition metals, lanthanides or aluminium.

[0027] Of these, nitrates or chlorides of calcium, magnesium, strontium, zinc, strontium, iron or aluminum are preferred, with calcium or magnesium nitrate being more preferred.

[0028] As mentioned above, in step a), the aqueous solution A1 should contain a molarity between M1 and M2 that defines the range of molarity of the nitric acid, the cation exchange resin retaining ruthenium selectively with respect to technetium.

[0029] The method may also comprise, prior to step a), adjusting the molarity of the aqueous solution A1, if necessary, to a value comprised between M1 and M2, which adjustment comprises: - dilute the aqueous solution A1 with nitric acid, advantageously at a very low concentration, if the molarity of nitric acid in this solution is higher than M2; - Or if the molar concentration of nitric acid in this solution is lower than M1, add concentrated nitric acid to the aqueous solution A1. This can be achieved by

[0030] According to the invention, the cation exchange resin may be any cation exchange resin having a molar concentration between M1 and M2, capable of retaining ruthenium selectively relative to technetium when contacted with an aqueous nitric acid solution in the presence of the two metallic elements ruthenium and technetium.

[0031] In particular, this resin may be a porous organic resin made of a poly(meth)acrylate or polystyrene-based matrix, preferably a polystyrene-based matrix, crosslinked and functionalized with sulfonic acid groups, -SO3H.

[0032] For example, resins of this type are the resin AG MP-50 from BioRad, the resins Dowex 50W-X8, Dowex® Marathon C-10, Dowex® HCR-W2, Dowex® Monosphere® C-400 from Dow, the resins AmberLite® HPR1200 H, Amberlite® IRN77 and Amberlite® IR122 Na from DuPont, the resins Purolite® C100E and Purolite® C145 from Purolite, the resins Diaion® PK208 and Diaion® SK1B from Mitsubishi Chemical Corporation, or even the resin Lewatit® MonoPlus S 200 KR from Lanxess.

[0033] Of these, resin AG MP-50 formed from a styrene / divinylbenzene copolymer having sulfonic acid groups is preferred.

[0034] These resins contain the metallic elements ruthenium and technetium, and when contacted with an aqueous nitric acid solution having a nitric acid concentration of 0.01 mol / L to 0.5 mol / L, selectively retain ruthenium relative to technetium, at a concentration at which ruthenium is retained by the resin in the form of a nitrated ruthenium-nitrosyl complex.

[0035] In this case, the aqueous solutions A1 and A2 preferably contain 0.01 mol / L to 0.5 mol / L, and more preferably 0.1 mol / L, of nitric acid.

[0036] Also in that case, step c) aimed at eluting ruthenium from the cation exchange resin comprises: using an aqueous solution A3 which advantageously contains at least 2 mol / L, and even more preferably at least 4 mol / L, for example 6 mol / L, of nitric acid or hydrochloric acid; or with an aqueous solution A4 advantageously containing 0.01 mol / L to 0.5 mol / L nitric acid or hydrochloric acid, for example 0.01 mol / L nitric acid or hydrochloric acid, at least 1 mol / L, more preferably at least 2 mol / L of metal nitrates or chlorides. It will be implemented.

[0037] According to the invention, step b) comprises washing the cation exchange resin at least once with an aqueous solution A2 which, like aqueous solution A1, comprises nitric acid.

[0038] This step is primarily aimed at removing technetium from the cation exchange resin, in particular from its void volume, which may have been retained by this resin in step a).

[0039] Thus, the washing of step b) is carried out with an aqueous solution A2 of nitric acid, the molarity of which, in addition to being comprised between M1 and M2, is preferably lower than or equal to the molarity of the aqueous solution A1 of step a).

[0040] According to the invention, the process may, after completion of step c), optionally comprise an additional purification of the ruthenium present in aqueous solution A5 in order to remove metal impurities that may still be present in said aqueous solution A5.

[0041] Advantageously, this further purification is carried out using a chelating organic resin.

[0042] The resin may be primarily a resin containing diglycolamide as a chelating agent, and the resin may be a diglycolamide-impregnated resin or a diglycolamide-grafted resin.

[0043] It should be recalled that the term "diglycolamide" refers to the family of compounds of formula (I) or formula (II) below: R 1 (R 2 )NC(O)-CH2-O-CH2-C(O)-N(R 3 )R 4 (I) R 1 (R 2 )NC(O)-CH2-O-CH2-COOH (II) In the formula, R 1 , R 2 , R 3 and R 4 is typically a straight or branched alkyl group.

[0044] Preferably, the resin comprising diglycolamide is a resin made of a poly(meth)acrylate or polystyrene-based matrix, preferably a polystyrene-based matrix, which is crosslinked and impregnated with a lipophilic diglycolamide, i.e. a diglycolamide containing at least 24 carbon atoms, such as N,N,N',N'-tetra-n-octyl-3-oxapentanediamide (or TODGA), N,N,N',N'-tetra(2-ethylhexyl)-3-oxapentanediamide (or TEHDGA), N,N,N',N'-tetra-n-decyl-3-oxapentanediamide (or TDDGA) or N,N,N',N'-tetra-n-dodecyl-3-oxapentanediamide (or TdDDGA).

[0045] In particular, this type of resin is the resin DGA N (for Normal) from the company Triske, which is made of a styrene / divinylbenzene copolymer impregnated with TODGA and is available in the form of particles packed in flasks, but also in the form of ready-to-use chromatography columns or cartridges.

[0046] When such chelating organic resins are used, the further purification of ruthenium preferably comprises at least the following successive steps: d) extracting ruthenium from aqueous solution A5, which comprises contacting aqueous solution A5 with a chelating organic resin in a chromatographic column, aqueous solution A5 comprising up to 4 mol / L of nitric acid or hydrochloric acid, optionally from 0.45 mol / L to 4 mol / L of an amine base; e) washing the chelating organic resin at least once with an aqueous solution A6 containing 4 mol / L or less of nitric acid or hydrochloric acid, and optionally 0.45 mol / L to 4 mol / L of an amine base; and f) eluting ruthenium from the chelating organic resin with an aqueous solution A7 containing at least 0.01 mol / L of nitric acid or hydrochloric acid; Includes.

[0047] Alternatively, the chelating organic resin may also be a resin containing bipyridine or phenanthroline as a chelating agent, which may be a bipyridine or phenanthroline impregnated resin or a bipyridine or phenanthroline grafted resin.

[0048] It should be recalled that the term "bipyridine" refers to a family of compounds formed from two pyridines covalently bonded together, while the term "phenanthroline" refers to a family of compounds formed from three fused aromatic rings in which two opposing rings each contain a nitrogen atom facing each other.

[0049] In particular, organic resins containing this type of chelating agent can be obtained by impregnating bipyridine or phenanthroline into an adsorbent resin having a crosslinked poly(meth)acrylate or polystyrene matrix. For example, an adsorbent resin that can be impregnated in this way is the resin Amberlite® XAD4 from DuPont, which consists of a styrene / divinylbenzene copolymer.

[0050] In that case: the bipyridine with which the resin is impregnated may in particular be any lipophilic derivative of 2,2'-bipyridine, such derivatives being typically 2,2'-bipyridines substituted with one or more hydrocarbon groups, for example alkyl or phenyl, such as 4,4'-dinonyl-2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridine, 5,5'-dimethyl-2,2'-bipyridine, 4,4'-di-tert-butyl-2,2'-bipyridine or 4,4'-diphenyl-2,2'-bipyridine; The phenanthroline with which the resin is impregnated may in particular be any lipophilic derivative of 1,10-phenanthroline, such derivatives being typically 1,10-phenanthroline substituted with one or more hydrocarbon groups, for example alkyl or phenyl, such as 4-methyl-1,10-phenanthroline, 5-methyl-1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, neocuproine (or 2,9-dimethyl-1,10-phenanthroline), bathocuproine (or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) or bathophenanthroline (or 4,7-diphenyl-1,10-phenanthroline).

[0051] Among the bipyridines, 4,4'-dinonyl-2,2'-bipyridine is preferred, while among the phenanthrolines, bathophenanthroline is preferred.

[0052] When such chelating organic resins are used, the further purification of ruthenium preferably comprises at least the following successive steps: d) extracting ruthenium from aqueous solution A5, which comprises contacting aqueous solution A5 with a chelating organic resin in a chromatographic column, aqueous solution A5 comprising up to 4 mol / L of nitric acid or hydrochloric acid, optionally from 0.45 mol / L to 4 mol / L of an amine base; e) washing the chelating organic resin at least once with an aqueous solution A6 containing 4 mol / L or less of nitric acid or hydrochloric acid, and optionally 0.45 mol / L to 4 mol / L of an amine base; and f) eluting ruthenium from the chelating organic resin with an aqueous solution A7 containing at least 0.01 mol / L of nitric acid or hydrochloric acid; Includes.

[0053] Alternatively, the chelating organic resin may be a resin that includes thiourea as a chelating agent, which resin may again be a thiourea impregnated resin or a thiourea grafted resin.

[0054] The term "thiourea" refers to a compound of the formula: 1 R 2 N)(R 3 R 4 Recall that the term refers to the family of compounds of formula R 1 , R 2 , R 3 and R 4 is usually a hydrogen atom or a hydrocarbon group, especially an alkyl group, optionally substituted with one or more heteroatoms, for example one or more sulfur atoms, and the simplest compounds of this family are the thioureas of formula (NH)C=S.

[0055] In particular, organic resins containing this type of chelating agent can be obtained by impregnating thiourea into an adsorbent resin having a crosslinked poly(meth)acrylate or polystyrene-based matrix, such as the aforementioned resin Amberlite® XAD4.

[0056] In that case, the thiourea to be impregnated into the resin may in particular be any lipophilic thiourea, which is typically a thiourea containing at least one C8 to C15 alkyl group, such as 1-dodecyl-3-methylthiourea, 1,3-dioctylthiourea, 1-(2-(dodecylthio)ethyl)-3-methylthiourea, 1-methyl-3-(2-(nonylthio)ethyl)thiourea, 1-methyl-3-(2-(octylthio)ethyl)thiourea, 1-(2-(dodecylthio)-ethyl)-3-ethylthiourea or 1-(2-(dodecylthio)ethyl)-3-propylthiourea.

[0057] Of these thioureas, 1-(2-dodecylthio)ethyl)-3-methylthiourea is preferred.

[0058] When such chelating organic resins are used, the further purification of ruthenium preferably comprises at least the following successive steps: d) extracting ruthenium from aqueous solution A5, which comprises contacting aqueous solution A5 with a chelating organic resin in a chromatographic column, aqueous solution A5 comprising up to 4 mol / L of nitric acid or hydrochloric acid, optionally from 0.45 mol / L to 4 mol / L of an amine base; e) washing the chelating organic resin at least once with an aqueous solution A6 containing 4 mol / L or less of nitric acid or hydrochloric acid, and optionally 0.45 mol / L to 4 mol / L of an amine base; and f) eluting ruthenium from the chelating organic resin with an aqueous solution A7 containing 0.5 mol / L to 2 mol / L of thiourea of ​​formula (NH2)2C=S and 0.01 mol / L to 1 mol / L of hydrochloric acid; Includes.

[0059] It goes without saying that, if in step c) of the process the elution of ruthenium from the cation exchange resin is carried out with an aqueous solution A4 of nitric or hydrochloric acid which contains a nitrate or a metal chloride, then the aqueous solution A5 which undergoes one of the further purifications also contains this metal nitrate or chloride. For the washing in step e) of these purifications it is then possible to use an aqueous solution A6 which, in addition to nitric or hydrochloric acid and, optionally, an amine base, contains the same metal nitrate or chloride as is present in aqueous solution A5.

[0060] Moreover, if in process step c) the elution of ruthenium from the cation exchange resin is carried out with an aqueous solution A3 or A4 of nitric acid or hydrochloric acid having a molarity higher than 4, the process further comprises, between this step c) and any one of the steps d) of the further purification, diluting the aqueous solution A5 to a nitric acid or hydrochloric acid concentration thereof to a value lower than or equal to 4 mol / L, as well as the possibility of adding an amine base in order to partially reduce its acidity whilst maintaining a high content of nitrates or chlorides, if present.

[0061] As is known per se, the amine base may consist of any compound containing one or more nitrogen atoms capable of capturing a proton in an aqueous medium, such as ammonia, guanidine, alkylamines, such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine or triethylamine, or nitrogenated compounds, such as pyridine, imidazole or histidine, provided that the amine base used is water-soluble.

[0062] Of these bases, triethylamine is preferred.

[0063] According to the invention, the aqueous solution A1 is preferably irradiated with protons, more specifically, nuclear reactions in the proton energy range of 20 MeV to 100 MeV. 99 Tc(p,3n) 97 This is the solution resulting from the dissolution of a technetium-99 target in nitric acid by Ru.

[0064] In this case, the aqueous solution A1 contains ruthenium-97, technetium-97, and, as a metal impurity, molybdenum-97. The mass ratio of technetium to ruthenium is usually 2x10 4 ~10 6 and the mass ratio of technetium to molybdenum is 4x10 5 ~2x10 7 The range is.

[0065] Another object of the present invention is to provide a method for producing ruthenium-97 from a proton-irradiated technetium-99 target, comprising at least the following steps: i) preparing an aqueous solution A1 of nitric acid containing ruthenium in a concentration C1, technetium in a concentration C2 at least 10 times higher than C1, and metal impurities by dissolving a target in nitric acid; and ii) purifying the ruthenium-97 present in the aqueous solution A1 by carrying out the purification method defined above; Includes.

[0066] Other characteristics and advantages of the invention will become apparent on reading the following supplementary description of examples which make it possible to experimentally verify the purification method of the invention.

[0067] It should be understood that this supplemental description is provided merely for the purposes of illustration of the invention and is in no way intended to limit the scope of the invention. [Brief description of the drawings]

[0068] [Figure 1] FIG. 1 shows, in the form of histograms, the extraction yields (REX, expressed in %) of ruthenium, rhenium (pseudotechnetium), rhodium and molybdenum obtained during extraction tests carried out by contacting, in centrifuge tubes, aqueous solutions simulating the solution resulting from the dissolution in nitric acid of an irradiated technetium target on a cation exchange resin; these extraction yields are expressed as a function of the nitric acid concentration of the aqueous solution ([HNO3], expressed in mol / L). [Diagram 2] FIG. 1 shows in the form of a curve the variation of the separation factor between ruthenium and rhenium ([FSRu / Re]) as a function of the nitric acid concentration ([HNO3], expressed in mol / L) obtained during extraction tests carried out by contacting in a centrifuge tube an aqueous solution simulating the solution resulting from the dissolution of an irradiated technetium target on a cation exchange resin in nitric acid. [Diagram 3] FIG. 1 shows, in the form of a histogram, the extraction yields of ruthenium (REX, expressed in %) obtained during extraction tests carried out by contacting, in centrifuge tubes, with aqueous solutions containing ruthenium in the concentration range from 1 mg / L to 100 g / L of ruthenium and 0.5 mol / L of nitric acid; these extraction yields are expressed as a function of the ruthenium concentration of the aqueous solution ([Ru], expressed in g / L). [Figure 4]FIG. 1 shows, in the form of histograms, the extraction yields (REX, expressed in %) of ruthenium and rhenium obtained during extraction tests carried out by contacting, in centrifuge tubes, aqueous solutions in which the rhenium concentration is 10, 100 and 1,000 times higher than their ruthenium concentration and which contain 0.5 mol / L nitric acid; these extraction yields are expressed as a function of the ratio of the rhenium to ruthenium concentrations ([Re] / [Ru]). [Diagram 5] FIG. 1 shows, in the form of a histogram, the extraction yields (RELU, expressed in %) of ruthenium, rhenium, rhodium and molybdenum obtained during extraction tests carried out by contacting, in centrifuge tubes, with different types of elution solutions with cation exchange resins preloaded with these metallic elements. [Figure 6] FIG. 1 shows the evolution of the recoveries (TR, expressed in %) of ruthenium and rhenium obtained in a test aimed at purifying ruthenium from an aqueous solution containing 1 g / L rhenium, 0.1 g / L ruthenium and 0.1 mol / L nitric acid using a column containing a cation exchange resin; these recoveries are expressed as a function of the number of bed volumes (BV) used during this test; arrow f1 indicates the start of washing of the resin after loading with the aqueous solution, while arrow f2 indicates the start of elution of ruthenium from the resin. [Figure 7] This is similar to FIG. 6, but differs only in the nature of the solution used to elute ruthenium from the resin for the ruthenium purification test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0069] In the following: - Extraction yield of metal elements (R EXT , expressed in %) corresponds to the ratio of the amount of a metal element retained by the resin to the amount of this metal element present in the solution before the solution was passed through the resin; - Metal element elution yield (R ELU , expressed in %) corresponds to the ratio of the amount of metal element dissolved from the resin to the amount of this metal element previously retained by said resin; - Partition coefficient of metal elements (K d , expressed in mL / g) corresponds to the ratio of the concentration of a metal element retained by the resin (per gram of dry resin) to the concentration of this metal element remaining in the solution after the solution has been passed through the resin (per milliliter of solution); - the recovery rate of a metal element (TR, expressed in %) corresponds to the ratio of the amount of a metal element eluted from the resin to the amount of this metal element present in the solution before passing this solution through the resin; - Separation factor between two metal elements M1 and M2 (FS M1 / M2 , unitless) corresponds to the ratio between the partition coefficients of the two metal elements; - Decontamination factor of metal element M1 with respect to metal element M2 (FD M1 / M2 , unitless) corresponds to the ratio of the concentrations of two metal elements in the solution before purification to the ratio of the concentrations of two metal elements in the solution after purification.

[0070] All values ​​given below are expressed with a relative uncertainty of 10%, taking into account the different experimental and analytical uncertainties together.

[0071] Moreover, in the tests reported below, for reasons related to the radiation protection of the experimenters, technetium has been replaced by rhenium, whose behavior mimics that of technetium, as widely described in the prior art. EXAMPLES

[0072] Example 1: Batch purification of ruthenium using a cation exchange resin This example concerns tests for the extraction of ruthenium by cation exchange resin and the elution of this metallic element from said resin, all carried out in batches in centrifuge tubes.

[0073] The cation exchange resin is BioRad resin AG MP-50.

[0074] The centrifuge tubes are equipped with inserts containing polytetrafluoroethylene (PTFE) filters with a porosity of 0.2 μm, whereby the resins are contacted with the aqueous solutions undergoing extraction or used for elution, after which their separation by filtration can be carried out in the same tube by simple centrifugation.

[0075] 1.1 - Effect of nitric acid concentration on the extraction yield of ruthenium A first series of tests is carried out with the aim of extracting ruthenium by means of a cation exchange resin from aqueous solutions which all contain 1 g / L rhenium, 0.1 g / L ruthenium, 0.1 g / L rhodium and 0.1 g / L molybdenum but differ from each other by their nitric acid concentrations ranging from 0.1 mol / L to 12 mol / L.

[0076] These solutions are prepared by diluting perrhenic acid, HReO4, ruthenium(III) nitrosyl nitrate, Ru(NO)(NO3)3, and rhodium(III) nitrate, Rh(NO3)3, into solution, and by dissolving hydrated molybdenum trioxide, MoO3·H2O, in nitric acid.

[0077] Each test consisted of contacting 700 μL of one aqueous solution with 100 mg of wet resin (i.e., approximately 48 mg of dry resin) in one centrifuge tube, agitating the tube (in a ThermoMixer™) at 1,500 rpm for 30 minutes at 25° C., and then separating the aqueous solutions by centrifugation at 14,500 rpm for 5 minutes.

[0078] The aqueous solution thus recovered is analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) to determine the concentration of each of the four metal elements remaining in solution after extraction.

[0079] The mass balance is verified by mineralization of the resin, i.e. by decomposition in a microwave reactor, where it is dissolved in 8 mL of a 1:1 (v / v) HNO3 / H2O2 mixture and heated at 200 °C for 1 h. The volume of the solution thus obtained is reset and then also analyzed by ICP-AES.

[0080] The results are shown in Figures 1 and 2, respectively, as the extraction yields, R EX , and the separation factor between ruthenium and rhenium, F.S. Ru / Re This is shown in the form of a change in

[0081] FIG. 1 shows that, depending on the type of cation exchange resin used, low concentrations of nitric acid favor the extraction of ruthenium, whereas rhenium is hardly extracted regardless of the nitric acid concentration.

[0082] Therefore, as shown in Figure 2, the best separation factor between ruthenium and rhenium, F.S. Ru / Re is obtained at a nitric acid concentration of 0.1 mol / L or 0.5 mol / L.

[0083] In particular, when the nitric acid concentration was 0.1 mol / L, the ruthenium extraction yield was higher than 90%, which corresponds to a distribution coefficient of 260 mL / g.

[0084] The separation factor F S obtained under these conditions Ru / Re is 432, reflecting good separation between ruthenium and rhenium.

[0085] This separation factor can be further improved by washing the resin after the extraction is completed with an aqueous solution of low nitric acid concentration, for example, containing 0.01 mol / L to 0.5 mol / L nitric acid, preferably 0.1 mol / L (see item 1.5 below).

[0086] However, ruthenium extraction selectivity is not observed with respect to rhodium and molybdenum, both of which are extracted by the cation exchange resin, the first in amounts comparable to ruthenium and the second in lesser amounts.

[0087] 1.2 - Effect of ruthenium concentration on the extraction yield of this metal A second series of tests is carried out to evaluate the effect of the ruthenium concentration in the aqueous solution from which it is to be extracted on its extraction yield by the cation exchange resin.

[0088] These tests are carried out following an operating protocol similar to that described in section 1.1 above, but using aqueous solutions containing 1 mg / L to 100 g / L ruthenium (supplied in the form Ru(NO)(NO3)3) and 0.5 mol / L nitric acid.

[0089] The extraction yield of ruthenium thus obtained, R EX is shown in Figure 3.

[0090] As shown in this figure, the extraction yield of ruthenium is constant and higher than 90% when the ruthenium concentration is less than 1 g / L.

[0091] The obtained isotherm follows the Langmuir model, which is characterized by a monolayer and uniform adsorption of ruthenium on the particle surface of the resin.

[0092] 1.3 - Effect of Re / Ru concentration ratio on the extraction yield of ruthenium A third series of tests is carried out to evaluate the effect of the concentration ratio of rhenium and ruthenium in the aqueous solution from which ruthenium is to be extracted on its extraction yield by the cation exchange resin.

[0093] These tests are similar to those described in section 1.1 above, but with rhenium concentrations (supplied in the form of HReO4) that are 10, 100 and 1,000 times higher than their ruthenium concentrations (supplied in the form of Ru(NO)(NO3)3), and are carried out according to an operating protocol using an aqueous solution containing 0.5 mol / L nitric acid.

[0094] The extraction yield of ruthenium thus obtained, R EX is shown in Figure 4.

[0095] As shown in this figure, the ratio of rhenium to ruthenium concentrations has little effect on the extraction yield of ruthenium, which remains approximately constant regardless of the excess rhenium present in the solution.

[0096] These results are of particular interest for the application of the method of the invention to the purification of ruthenium produced by irradiation of a technetium target, since in this case the concentration of technetium in the solution resulting from dissolution of the target in nitric acid is in the range of 100,000 times lower than the concentration of ruthenium.

[0097] 1.4 - Elution of ruthenium from a cation exchange resin After carrying out a series of extractions described in the above item 1.1 from an aqueous solution containing 1 g / L rhenium, 0.1 g / L ruthenium, 0.1 g / L rhodium, 0.1 g / L molybdenum and 0.1 mol / L or 0.5 mol / L nitric acid, the resin thus loaded with metal elements (Ru, Rh, Mo and trace amounts of Re as shown in Figure 1) is subjected to elution.

[0098] To do so, 700 μL of the elution solution is added to a centrifuge tube and the resin loaded with metal elements is placed in contact under the same operating conditions as described in item 1.1 above (30 min, 1,500 rpm, 25° C.), and the elution solution is then separated by centrifugation at 14,500 rpm for 5 min.

[0099] The elution solution and resin thus separated are analyzed by ICP-AES (after mineralization of the resin as described above in section 1.1).

[0100] The dissolution solutions tested were as follows: - an aqueous solution containing 0.01 mol / L to 12 mol / L nitric acid or 0.01 mol / L to 6 mol / L hydrochloric acid for extractions carried out from an aqueous solution containing 0.1 mol / L nitric acid, and - An aqueous solution containing 2.12 mol / L magnesium nitrate, Mg(NO3)2 or calcium nitrate, Ca(NO3)2 and 0.01 mol / L nitric acid for extraction carried out from an aqueous solution containing 0.5 mol / L nitric acid.

[0101] The elution yield thus obtained, R ELU is shown in Figure 5.

[0102] This figure shows that the use of highly concentrated aqueous solutions of nitric or hydrochloric acid (6 mol / L or more HNO3 or HCl) as elution solutions leads to very satisfactory recovery of ruthenium (70%-80% ruthenium pre-extracted), but is not selective with respect to rhodium and molybdenum.

[0103] The use of aqueous solutions of metal nitrates as elution solutions also results in good recovery of ruthenium (64% and 70% of the ruthenium is pre-extracted for magnesium nitrate and calcium nitrate, respectively), but again shows no selectivity with respect to rhodium and molybdenum.

[0104] On the other hand, the use of low-concentration aqueous solutions of nitric or hydrochloric acid (e.g. 0.01 mol / L or 0.1 mol / L HNO3 or HCl) results in a quantitative recovery of pre-extracted rhenium (more than 85%, but the amount of pre-extracted rhenium is very small, making analysis difficult, and is subsequently eluted) and some molybdenum (up to 45% of molybdenum is pre-extracted), but with limited leaching of ruthenium from the resin (up to 5% of ruthenium is eluted). Thus, such low-concentration solutions of nitric or hydrochloric acid are used to wash the cation exchange resin to remove traces of technetium (simulated here by rhenium) from the resin, as well as most of the pre-extracted molybdenum, before eluting ruthenium from the resin.

[0105] 1.5 - Simulation of the purification of ruthenium from a solution resulting from the dissolution of a technetium target irradiated with protons... Ch. The tests are carried out under conditions which are close to those of the implementation of the method for purifying ruthenium according to the invention from a solution produced by dissolution in nitric acid of a technetium target irradiated with protons, in particular with regard to the composition of the aqueous solution from which ruthenium must be purified as well as the sequence of steps.

[0106] The test therefore proceeded with the steps of extracting ruthenium by means of a cation exchange resin, washing the resin and eluting the ruthenium from said resin.

[0107] The ruthenium extraction step is performed by contacting 700 μL of an aqueous solution containing 10 g / L rhenium (supplied in the form of HReO4), 1 g / L ruthenium (supplied in the form of Ru(NO)(NO3)3), 40 mg / L molybdenum (supplied in the form of MoO3·H2O) and 0.1 mol / L nitric acid with 100 mg of resin while stirring the tube at 1,500 rpm for 30 minutes at 25 °C, and then separating the solution by centrifugation at 14,500 rpm for 5 minutes.

[0108] The resin washing step is carried out by contacting the resin with 700 μL of an aqueous solution containing 0.1 mol / L nitric acid twice in succession, agitating the tube at 1,500 rpm for 5 minutes at 25° C. after each contact, and then separating the washing solution by centrifugation at 14,500 rpm for 5 minutes after completion of each contact.

[0109] The ruthenium elution step is performed by contacting the resin with 700 μL of a solution containing 500 g / L calcium nitrate and 0.01 mol / L nitric acid while agitating the tube at 1,500 rpm for 30 minutes at 25° C., and then filtering the eluted solution by centrifugation at 14,500 rpm for 5 minutes.

[0110] All solutions obtained by filtration are analyzed by ICP-AES.

[0111] The solution obtained after completion of the elution contained 527 mg / L ruthenium, 0.3 mg / L rhenium and 0.96 mg / L molybdenum, which is: - the distribution coefficient Kd of ruthenium is 578 mL / g; - Decontamination factor FD Ru / Re is 16,870, FD Ru / Mo is 23, and - recovering 50% of the amount of ruthenium present in the starting aqueous solution in one contact step, resulting in a final purity of ruthenium of 99.76% This is equivalent to:

[0112] (Example 2: Continuous purification of ruthenium using a cation exchange resin) This example concerns two tests aimed at purifying ruthenium using a cation exchange resin, carried out successively in a chromatographic column, which differ from each other only in the solution used to elute the ruthenium from the resin.

[0113] The cation exchange resin is BioRad resin AG MP-50.

[0114] The column is a double-jacketed glass column, 1 cm in diameter and 15 cm in height, connected to a thermostatically controlled bath. It is equipped with two sintered glasses, one placed at the base and the other added on top of the resin after the column is filled with the latter. It is also equipped with a tank and a tap at the top and bottom of the column, respectively.

[0115] The column is prepared by introducing an aqueous suspension of 5 g of resin in 0.1 mol / L nitric acid into the top of the column. After being compressed by gravity, the resin bed is deposited to a height of more than 10 cm, which corresponds to a column volume, or bed volume, or more simply called BV (standing for Bed volume), of 7.85 mL.

[0116] The resin was then conditioned by washing with several mL of an aqueous solution containing 0.1 mol / L nitric acid.

[0117] After the column is ready, 50 mL of an aqueous solution containing 1 g / L rhenium (supplied in the form of HReO4), 0.1 g / L ruthenium (supplied in the form of Ru(NO)(NO3)3) and 0.1 mol / L nitric acid is introduced into the top of the column. The aqueous solution is allowed to flow from the column by gravity at room temperature. After this solution is collected at the bottom of the column, the volume is again placed in a 50 mL volumetric flask and analyzed by ICP-AES to determine the content of each of the two metallic elements.

[0118] The resin is then washed with 50 mL of an aqueous solution containing 0.1 mol / L nitric acid, allowed to flow by gravity, and then collected at the bottom of the column and analyzed by ICP-AES.

[0119] The column is then heated to 60° C. by circulating water in the double jacket and 20 mL of elution solution preheated to 60° C. are introduced into the column.

[0120] In the first test, the elution solution was an aqueous solution containing 6 mol / L nitric acid, whereas in the second test, the elution solution was an aqueous solution containing either 2.12 mol / L magnesium nitrate or 0.01 mol / L nitric acid.

[0121] In both cases, after elution of the column volume (i.e., 7.85 mL), the flow of the elution solution was stopped for 1 h, after which the remaining elution solution was allowed to flow. The total volume of elution solution collected at the bottom of the column was again placed in a 25 mL volumetric flask and then analyzed by ICP-AES.

[0122] Figures 6 and 7 show the variation of the obtained ruthenium and rhenium recoveries (TR, expressed in %) as a function of the number of bed volumes (BV) used, Figure 6 corresponding to the first test and Figure 7 corresponding to the second test.

[0123] In these figures, arrow f1 indicates the start of washing of the resin after loading with an aqueous solution containing rhenium and ruthenium, while arrow f2 indicates the start of elution of ruthenium.

[0124] These figures show that the recovery of ruthenium from the resin after completion of the elution was very satisfactory in both tests, with recoveries of 61% and 53%, respectively.

[0125] The purification of ruthenium relative to rhenium (and therefore technetium) was also very satisfactory in both tests, with FD Ru / Re are 418 and 808 respectively.

[0126] (Example 3: Further purification of ruthenium using a chelating organic resin) 3.1 - Batch purification of ruthenium using chelating organic resins containing bipyridine or phenanthroline Tests aimed at assessing the possibility of perfecting the purification of ruthenium previously subjected to purification using a cation exchange resin are carried out using chelating organic resins containing bipyridine or phenanthroline.

[0127] The bipyridine is 4,4'-dinonyl-2,2'-bipyridine while the phenanthroline is bathophenanthroline, both of which are available from Sigma-Aldrich.

[0128] The bipyridine-containing resin (hereinafter referred to as DNPB) and the phenanthroline-containing resin (hereinafter referred to as BPhen) were previously prepared by impregnating the adsorption resin Amberlite™ XAD4 (DuPont) with 4,4′-dinonyl-2,2′-bipyridine in the first test and with bathophenanthroline in the second test, at a ratio of about 1.15 mmol / g of dry resin.

[0129] To do so, the adsorption resin is first washed with water, then with ethanol, then dried for several hours. 500 mg of the dry resin are then mixed in a round-bottom flask with 0.573 mmol of 4,4'-dinonyl-2,2'-bipyridine (i.e. 234 mg) or bathophenanthroline (i.e. 191 mg) and 15 ml of dichloromethane. The mixture is stirred overnight, then the solvent is slowly evaporated in a rotary evaporator. Just before the end of the evaporation, 10 mL of dichloromethane are added to the medium and evaporated to dryness in the same way. The resins thus obtained, DNPB and BPhen, are then placed overnight in a desiccator under high vacuum to remove any traces of solvent.

[0130] Prior to testing, the resin is conditioned by contacting it for 1 hour with an aqueous solution containing 2 mol / L nitric acid and 1.95 mol / L triethylamine.

[0131] The tests are carried out in an aqueous solution containing 10 mg / L ruthenium (supplied in the form Ru(NO)(NO3)3), 10 mg / L rhenium (supplied in the form of perrhenic acid), 10 mg / L molybdenum (supplied in the form MoO3·H2O) and 2 mol / L nitric acid.

[0132] Each test involves the extraction of ruthenium from an aqueous solution by one of the resins DNPB and BPhen, followed by the elution of ruthenium from this resin.

[0133] Extraction of ruthenium consisted of contacting 700 μL of the aqueous solution with 50 mg of one of the resins in an insert centrifuge tube described in Example 1 above while agitating the tube (with ThermoMixer™) at 1,500 rpm for 24 hours, followed by separation of the aqueous solution by centrifugation at 14,500 rpm for 5 minutes.

[0134] Elution of ruthenium is carried out by contacting the resin with 700 μL of an aqueous solution containing 10 mol / L hydrochloric acid while agitating the tube at 1,500 rpm for 24 hours at 25° C., and then filtering the eluted solution by centrifugation at 14,500 rpm for 5 minutes.

[0135] All solutions obtained by filtration are analyzed by ICP-AES.

[0136] These analyses show that under these conditions the two resins give similar results. In fact, regardless of the resin being tested, only ruthenium and molybdenum are extracted by this resin, while rhodium remains in solution during the extraction. The extraction yield of ruthenium is very satisfactory, amounting to 60% after one solution / resin contact.

[0137] Then, ruthenium can be selectively recovered from the molybdenum that remains fixed on the resin by elution with 10 mol / L hydrochloric acid.

[0138] Therefore, the decontamination factor FD of resins DNPB and BPhen Ru / Mo are 20 and 40, respectively, and the decontamination factors FD of the two resins are Ru / Rh becomes about 30.

[0139] However, attention should be paid to the fact that when the tests are carried out in batches and without intermediate washing of the resin, the decontamination factor is significantly reduced relative to the decontamination factor that would be obtained by carrying out intermediate washing of the resin according to the method of the present invention in a chromatography column.

[0140] Therefore, taking these results into consideration, it is possible to perfect the purification of ruthenium using chelating organic resins containing bipyridine or phenanthroline.

[0141] 3.2 - Batch purification of ruthenium using chelating organic resins containing thiourea Tests similar to those described above are carried out to verify the possibility of perfecting the purification of ruthenium that has previously been purified using a cation exchange resin with a chelating organic resin containing thiourea (hereinafter referred to as MTU).

[0142] The thiourea is 1-(2-(dodecylthio)ethyl)-3-methylthiourea. It is previously synthesized from 2-(dodecylthio)ethan-1-amine (1 eq) and methyl isothiocyanate (1.1 eq). To do so, the two reagents are mixed in dichloromethane at 45 °C for 5 h, then the solvent is evaporated under reduced pressure and the product is purified on a silica column with a heptane / ethyl acetate gradient. This synthesis gives a yield of 74%. The purity of the product is analyzed by proton nuclear magnetic resonance (NMR) spectroscopy.

[0143] Resin MTU is prepared in the same manner as resins BNPB and BPhen, except that the impregnation is carried out by impregnation of the adsorption resin Amberlite™ XAD4 with 1-(2-(dodecylthio)ethyl)-3-methylthiourea, with 1.146 mmol of methylthiourea per 1 g of dry resin (i.e. 281 mg).

[0144] The tests are carried out in an aqueous solution containing 10 mg / L ruthenium (supplied in the form Ru(NO)(NO3)3), 10 mg / L rhenium (supplied in the form of perrhenic acid), 10 mg / L molybdenum (supplied in the form MoO3·H2O) and 2 mol / L nitric acid.

[0145] This involves the extraction of ruthenium from an aqueous solution by the resin MTU, followed by a step of elution of the ruthenium from this resin.

[0146] This extraction and this elution are carried out according to the same operating protocol as described in item 3.1 above, except that ruthenium is eluted with an aqueous solution containing 0.5 mol / L of thiourea of ​​formula (NH2)2C=S and 0.01 mol / L of hydrochloric acid.

[0147] All solutions obtained by filtration are analyzed by ICP-AES.

[0148] These analyses show that under these conditions, ruthenium is extracted by the resin MTU, whereas no rhodium is extracted and only a very small amount of molybdenum is extracted.

[0149] They also show that the elution of ruthenium with thiourea / aqueous HCl is not very selective with respect to molybdenum, nevertheless this low selectivity is not a disadvantage since molybdenum is only very poorly extracted by resin MTU.

[0150] The obtained separation factor FD Ru / Mo Since the MTU of the resin is 10, the additional purification of ruthenium relative to molybdenum carried out with the resin is entirely satisfactory, although here again the tests were not carried out under the most favourable conditions (batch tests and no intermediate washing of the resin).

[0151] Example 4: Simulation of ruthenium purification from a solution resulting from the dissolution of a proton-irradiated technetium target using a cation exchange resin and a chelating organic resin containing diglycolamide. This example concerns two tests aimed at purifying ruthenium, first using a cation exchange resin and secondly using a chelating organic resin containing diglycolamide.

[0152] These tests were performed in batches in centrifuge tubes as described in item 1 above and differed from each other only in the solution used to elute the ruthenium from the chelating organic resin.

[0153] The cation exchange resin is BioRad resin AG MP-50.

[0154] The chelating organic resin is resin DGA N (100-150 μm) manufactured by Triskeem.

[0155] The operating protocol is as follows.

[0156] *Purification using cation exchange resin: - extraction of ruthenium by contacting 700 μL of an aqueous solution containing 9 g / L rhenium, 0.9 g / L ruthenium, 38 mg / L molybdenum and 0.1 mol / L nitric acid with 100 mg of cation exchange resin in a centrifuge tube, stirring the tube at 1,500 rpm for 30 minutes at 25 °C and centrifuging at 14,500 rpm for 5 minutes to effect solid / liquid separation; - washing the resin a total of two times by contacting the resin with 700 μL of an aqueous solution containing 0.1 mol / L nitric acid each, agitating the tube at 25°C and 1,500 rpm for 5 minutes, and centrifuging at 14,500 rpm for 5 minutes to allow solid / liquid separation; - Elution of ruthenium by contacting the resin with 700 μL of an aqueous solution containing 2.12 mol / L magnesium nitrate and 0.01 mol / L nitric acid, agitating the tube at 1,500 rpm for 30 minutes at 25 °C, and centrifuging at 14,500 rpm for 5 minutes to effect solid / liquid separation.

[0157] * Purification using chelating organic resins: - extraction of ruthenium by contacting 700 μL of the aqueous solution obtained after the completion of the above elution with 50 mg of chelating resin (previously equilibrated with an aqueous solution of magnesium nitrate) in a centrifuge tube, agitating the tube at 1,500 rpm for 24 hours at 25 °C and centrifuging at 14,500 rpm for 5 minutes to obtain a solid / liquid separation; - washing of the resin by contacting it with 700 μL of an aqueous solution containing 2.12 mol / L magnesium nitrate and 0.01 mol / L nitric acid, agitating the tube at 1,500 rpm for 5 minutes at 25°C and centrifuging at 14,500 rpm for 5 minutes to allow solid / liquid separation; - Dissolution of ruthenium by contacting the resin with 700 μL of an aqueous solution containing 10 mol / L hydrochloric acid in the first test and 10 mol / L nitric acid in the second test, agitating the tube at 1,500 rpm for 24 hours at 25 °C and centrifuging at 14,500 rpm for 5 minutes to effect solid / liquid separation.

[0158] All solutions obtained by filtration are analyzed by ICP-AES.

[0159] These analyses demonstrate that it is possible to achieve complete purification of ruthenium using a chelating organic resin containing a diglycolamide such as TODGA.

[0160] Indeed, in the case of elution of ruthenium from a chelating organic resin with 10M aqueous hydrochloric acid, a final purity of 99.84% of ruthenium is obtained, with decontamination factors of 9,550 and 85, respectively, for the rhenium (and therefore technetium) and molybdenum initially present in the aqueous solutions subjected to two successive purifications.

[0161] The elution of ruthenium from the chelating organic resin with 10M aqueous nitric acid gives even more interesting results, since a final purity of 99.89% of ruthenium is obtained, with decontamination factors of 14,205 and 118 for rhenium (and therefore technetium) and molybdenum, respectively, that were initially present in the aqueous solutions subjected to two successive purifications.

[0162] (References) [1] NG Zaitseva et al., Radiochimica Acta 1992, 56, 59-68 [2] NG Zaitseva et al., Applied Radiation and Isotopes 1996, 47(2), 145-151 [3] EP-A-0 347 625

Claims

1. A method for purifying ruthenium from an aqueous nitric acid solution A1, which contains, in addition to ruthenium in a concentration C1, technetium in a concentration C2 at least ten times higher than C1, and metal impurities, comprising at least the following successive steps: a) extracting ruthenium from an aqueous solution of nitric acid using a cation exchange resin which retains ruthenium selectively with respect to technetium when ruthenium and technetium are contained in the aqueous solution at a molarity comprised between a first value M1 and a second value M2 higher than M1, said extraction comprising contacting the aqueous solution A1 with the cation exchange resin in a chromatographic column, the molarity of the aqueous solution A1 being comprised between M1 and M2; b) washing the cation exchange resin at least once with an aqueous nitric acid solution A2 having a molar concentration between M1 and M2; and c) eluting ruthenium from the cation exchange resin with an aqueous solution A3 of nitric acid or hydrochloric acid having a molality higher than M2 or an aqueous solution A4 of nitric acid or hydrochloric acid containing a metal nitrate or chloride having a molality lower than or equal to M2, thereby obtaining an aqueous solution A5 containing ruthenium A method comprising:

2. 2. The method according to claim 1, further comprising, prior to step a), adjusting the molarity of the aqueous solution A1 to a value comprised between M1 and M2.

3. 3. The method according to claim 1 or claim 2, wherein the cation exchange resin is a porous resin comprising a crosslinked poly(meth)acrylate or polystyrene-based matrix functionalized with sulfonic acid groups.

4. 4. The method according to claim 1, wherein the aqueous solutions A1 and A2 contain 0.01 mol / L to 0.5 mol / L of nitric acid, preferably 0.1 mol / L of nitric acid.

5. 5. The method according to claim 1, wherein the aqueous solution A3 is an aqueous solution containing at least 2 mol / L, preferably at least 4 mol / L, of nitric acid or hydrochloric acid.

6. 5. The method according to claim 1, wherein the aqueous solution A4 comprises from 0.01 mol / L to 0.5 mol / L of nitric acid or hydrochloric acid, at least 1 mol / L, preferably at least 2 mol / L of a metal nitrate or chloride.

7. 7. The method according to claim 1, further comprising purification of the ruthenium present in the aqueous solution A5 with a chelating organic resin.

8. 8. The method of claim 7, wherein the chelating organic resin is a resin containing diglycolamide, bipyridine, phenanthroline or thiourea as a chelating agent.

9. 9. The method of claim 8, wherein the chelating organic resin is a resin made of a crosslinked poly(meth)acrylate or polystyrene-based matrix impregnated with diglycolamide, bipyridine or phenanthroline.

10. At least the following successive steps: d) extracting ruthenium from aqueous solution A5, which comprises contacting aqueous solution A5 with a chelating organic resin in a chromatographic column, aqueous solution A5 comprising up to 4 mol / L of nitric acid or hydrochloric acid, optionally from 0.45 mol / L to 4 mol / L of an amine base; e) washing the chelating organic resin at least once with an aqueous solution A6 containing up to 4 mol / L of nitric acid or hydrochloric acid, and optionally 0.45 mol / L to 4 mol / L of an amine base; and f) eluting ruthenium from the chelating organic resin with an aqueous solution A7 containing at least 0.01 mol / L of nitric acid or hydrochloric acid; 10. The method of claim 9, comprising:

11. 9. The method of claim 8, wherein the chelating organic resin is a resin made of a crosslinked poly(meth)acrylate or polystyrene-based matrix impregnated with thiourea.

12. At least the following successive steps: d) extracting ruthenium from aqueous solution A5, which comprises contacting aqueous solution A5 with a chelating organic resin in a chromatographic column, aqueous solution A5 comprising up to 4 mol / L of nitric acid or hydrochloric acid, optionally from 0.45 mol / L to 4 mol / L of an amine base; e) washing the chelating organic resin at least once with an aqueous solution A6 containing up to 4 mol / L of nitric acid or hydrochloric acid, and optionally 0.45 mol / L to 4 mol / L of an amine base; and f) Formula (NH) of 0.5 mol / L to 2 mol / L 2 ) 2 A step of eluting ruthenium from the chelating organic resin with an aqueous solution A7 containing C=S thiourea and 0.01 mol / L to 1 mol / L hydrochloric acid.

12. The method of claim 11, comprising:

13. 13. The method according to claim 10 or 12, comprising between steps c) and d) a step of diluting the aqueous solution A5 to a concentration of nitric acid or hydrochloric acid of less than or equal to 4 mol / L and, optionally, adding an amine base.

14. The aqueous solution A1 is irradiated with protons, and preferably undergoes a nuclear reaction in the proton energy range of 20 MeV to 100 MeV. 99 Tc(p,3n) 97 14. The method according to any one of claims 1 to 13, wherein the solution is produced by dissolution of a Technetium-99 target by Ru in nitric acid.

15. 15. The method according to claim 14, wherein the aqueous solution A1 contains ruthenium-97, technetium-97 and, as metal impurities, molybdenum-97.

16. A method for producing ruthenium-97 from a proton irradiated technetium-99 target, comprising at least the following successive steps: i) preparing an aqueous solution A1 of nitric acid containing ruthenium in a concentration C1, technetium in a concentration C2 at least 10 times higher than C1, and metal impurities by dissolving a target in nitric acid; ii) purifying the ruthenium-97 present in the aqueous solution A1 by carrying out the method according to any one of claims 1 to 13. A method comprising:

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