OA19961A - Separation of actinium from process liquors - Google Patents
Separation of actinium from process liquors Download PDFInfo
- Publication number
- OA19961A OA19961A OA1201900505 OA19961A OA 19961 A OA19961 A OA 19961A OA 1201900505 OA1201900505 OA 1201900505 OA 19961 A OA19961 A OA 19961A
- Authority
- OA
- OAPI
- Prior art keywords
- ions
- actinium
- sulfate
- solution
- métal
- Prior art date
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- 229910052767 actinium Inorganic materials 0.000 title claims abstract description 141
- QQINRWTZWGJFDB-UHFFFAOYSA-N actinium Chemical compound [Ac] QQINRWTZWGJFDB-UHFFFAOYSA-N 0.000 title claims abstract description 100
- 238000000034 method Methods 0.000 title claims abstract description 38
- 238000000926 separation method Methods 0.000 title 1
- 150000002500 ions Chemical class 0.000 claims abstract description 155
- -1 rare earth ions Chemical class 0.000 claims abstract description 107
- 239000002244 precipitate Substances 0.000 claims abstract description 44
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 42
- QAOWNCQODCNURD-UHFFFAOYSA-L sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 71
- 230000000694 effects Effects 0.000 claims description 50
- 239000012141 concentrate Substances 0.000 claims description 32
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 27
- 239000000203 mixture Substances 0.000 claims description 26
- TZCXTZWJZNENPQ-UHFFFAOYSA-L Barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 claims description 24
- 238000005336 cracking Methods 0.000 claims description 16
- 229910001422 barium ion Inorganic materials 0.000 claims description 11
- 229910052938 sodium sulfate Inorganic materials 0.000 claims description 10
- 235000011152 sodium sulphate Nutrition 0.000 claims description 10
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 claims description 10
- 229910052712 strontium Inorganic materials 0.000 claims description 10
- 229910001427 strontium ion Inorganic materials 0.000 claims description 10
- 239000002253 acid Substances 0.000 claims description 9
- PMZURENOXWZQFD-UHFFFAOYSA-L na2so4 Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 9
- 229910001426 radium ion Inorganic materials 0.000 claims description 9
- 229910052770 Uranium Inorganic materials 0.000 claims description 5
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 claims description 3
- 239000006259 organic additive Substances 0.000 claims 1
- 229910052751 metal Inorganic materials 0.000 abstract description 2
- 239000002184 metal Substances 0.000 abstract 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 85
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 25
- HCWPIIXVSYCSAN-UHFFFAOYSA-N radium Chemical compound [Ra] HCWPIIXVSYCSAN-UHFFFAOYSA-N 0.000 description 24
- 229910052705 radium Inorganic materials 0.000 description 24
- QQINRWTZWGJFDB-IGMARMGPSA-N actinium-227 Chemical compound [227Ac] QQINRWTZWGJFDB-IGMARMGPSA-N 0.000 description 22
- 150000002910 rare earth metals Chemical class 0.000 description 18
- UBXAKNTVXQMEAG-UHFFFAOYSA-L Strontium sulfate Chemical compound [Sr+2].[O-]S([O-])(=O)=O UBXAKNTVXQMEAG-UHFFFAOYSA-L 0.000 description 16
- ZSLUVFAKFWKJRC-FTXFMUIASA-N thorium-227 Chemical compound [227Th] ZSLUVFAKFWKJRC-FTXFMUIASA-N 0.000 description 12
- 239000007787 solid Substances 0.000 description 11
- AHBGXTDRMVNFER-UHFFFAOYSA-L Strontium chloride Chemical compound [Cl-].[Cl-].[Sr+2] AHBGXTDRMVNFER-UHFFFAOYSA-L 0.000 description 10
- 239000012527 feed solution Substances 0.000 description 10
- HCWPIIXVSYCSAN-OIOBTWANSA-N radium-223 Chemical compound [223Ra] HCWPIIXVSYCSAN-OIOBTWANSA-N 0.000 description 10
- 239000000047 product Substances 0.000 description 9
- 229910001631 strontium chloride Inorganic materials 0.000 description 9
- WDIHJSXYQDMJHN-UHFFFAOYSA-L Barium chloride Chemical compound [Cl-].[Cl-].[Ba+2] WDIHJSXYQDMJHN-UHFFFAOYSA-L 0.000 description 8
- 229910001626 barium chloride Inorganic materials 0.000 description 8
- VEXZGXHMUGYJMC-UHFFFAOYSA-M chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 8
- 238000000638 solvent extraction Methods 0.000 description 7
- 229940013553 strontium chloride Drugs 0.000 description 7
- 229910052788 barium Inorganic materials 0.000 description 6
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium(0) Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 6
- HWSZZLVAJGOAAY-UHFFFAOYSA-L Lead(II) chloride Chemical compound Cl[Pb]Cl HWSZZLVAJGOAAY-UHFFFAOYSA-L 0.000 description 5
- 238000001730 gamma-ray spectroscopy Methods 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N HCl Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 239000000654 additive Substances 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- 229910052727 yttrium Inorganic materials 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000005755 formation reaction Methods 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 230000002285 radioactive Effects 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 241000894007 species Species 0.000 description 3
- 229910052684 Cerium Inorganic materials 0.000 description 2
- 229910052692 Dysprosium Inorganic materials 0.000 description 2
- 229910052691 Erbium Inorganic materials 0.000 description 2
- 229910052693 Europium Inorganic materials 0.000 description 2
- 229910052688 Gadolinium Inorganic materials 0.000 description 2
- 229910052689 Holmium Inorganic materials 0.000 description 2
- RLJMLMKIBZAXJO-UHFFFAOYSA-N Lead(II) nitrate Chemical compound [O-][N+](=O)O[Pb]O[N+]([O-])=O RLJMLMKIBZAXJO-UHFFFAOYSA-N 0.000 description 2
- 229910052765 Lutetium Inorganic materials 0.000 description 2
- 229910052779 Neodymium Inorganic materials 0.000 description 2
- 229910052777 Praseodymium Inorganic materials 0.000 description 2
- 229910052772 Samarium Inorganic materials 0.000 description 2
- 229910052771 Terbium Inorganic materials 0.000 description 2
- 229910052775 Thulium Inorganic materials 0.000 description 2
- 229910052769 Ytterbium Inorganic materials 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- PWHCIQQGOQTFAE-UHFFFAOYSA-L barium chloride dihydrate Chemical compound O.O.[Cl-].[Cl-].[Ba+2] PWHCIQQGOQTFAE-UHFFFAOYSA-L 0.000 description 2
- IKNAJTLCCWPIQD-UHFFFAOYSA-K cerium(3+);lanthanum(3+);neodymium(3+);oxygen(2-);phosphate Chemical compound [O-2].[La+3].[Ce+3].[Nd+3].[O-]P([O-])([O-])=O IKNAJTLCCWPIQD-UHFFFAOYSA-K 0.000 description 2
- 238000000975 co-precipitation Methods 0.000 description 2
- 230000000875 corresponding Effects 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 229910052746 lanthanum Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052590 monazite Inorganic materials 0.000 description 2
- UXBZSSBXGPYSIL-UHFFFAOYSA-N phosphoric acid;yttrium(3+) Chemical compound [Y+3].OP(O)(O)=O UXBZSSBXGPYSIL-UHFFFAOYSA-N 0.000 description 2
- 229910052706 scandium Inorganic materials 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- JFALSRSLKYAFGM-OIOBTWANSA-N uranium-235 Chemical compound [235U] JFALSRSLKYAFGM-OIOBTWANSA-N 0.000 description 2
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 2
- 229910000164 yttrium(III) phosphate Inorganic materials 0.000 description 2
- KEQXNNJHMWSZHK-UHFFFAOYSA-L 1,3,2,4$l^{2}-dioxathiaplumbetane 2,2-dioxide Chemical compound [Pb+2].[O-]S([O-])(=O)=O KEQXNNJHMWSZHK-UHFFFAOYSA-L 0.000 description 1
- 230000036499 Half live Effects 0.000 description 1
- NGWKGSCSHDHHAJ-YPFQVHCOSA-N Liquoric acid Chemical compound C1C[C@H](O)C(C)(C)C2CC[C@@]3(C)[C@]4(C)C[C@H]5O[C@@H]([C@](C6)(C)C(O)=O)C[C@@]5(C)[C@@H]6C4=CC(=O)C3[C@]21C NGWKGSCSHDHHAJ-YPFQVHCOSA-N 0.000 description 1
- OTYBMLCTZGSZBG-UHFFFAOYSA-L Potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 description 1
- HCWPIIXVSYCSAN-IGMARMGPSA-N Radium-226 Chemical compound [226Ra] HCWPIIXVSYCSAN-IGMARMGPSA-N 0.000 description 1
- HCWPIIXVSYCSAN-NJFSPNSNSA-N Radium-228 Chemical compound [228Ra] HCWPIIXVSYCSAN-NJFSPNSNSA-N 0.000 description 1
- 229910052776 Thorium Inorganic materials 0.000 description 1
- 150000001258 actinium compounds Chemical class 0.000 description 1
- 229910001423 beryllium ion Inorganic materials 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 150000003841 chloride salts Chemical class 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000002059 diagnostic imaging Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005188 flotation Methods 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 229910000376 lead(II) sulfate Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 229910052939 potassium sulfate Inorganic materials 0.000 description 1
- 235000011151 potassium sulphates Nutrition 0.000 description 1
- 238000001959 radiotherapy Methods 0.000 description 1
- 230000001105 regulatory Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- AMGRXJSJSONEEG-UHFFFAOYSA-L strontium dichloride hexahydrate Chemical compound O.O.O.O.O.O.Cl[Sr]Cl AMGRXJSJSONEEG-UHFFFAOYSA-L 0.000 description 1
- ZSLUVFAKFWKJRC-UHFFFAOYSA-N thorium Chemical compound [Th] ZSLUVFAKFWKJRC-UHFFFAOYSA-N 0.000 description 1
Abstract
The present specification relates to a method for removing actinium from process liquors comprising ions of interest (which may be, for example, rare earth ions) and actinium ions. In this method, a low solubility metal sulfate salt is caused to precipitate from a solution comprising ions of interest and actinium ions. Actinium ions become associated with the precipitate causing them to be removed from the solution. The method allows actinium to be removed from the solution selectively i.e. without the concurrent removal of substantial amounts of the ions of interest present in the solution
Description
The présent application claims priority from AU 2017902476, the entire contents of which are incorporated herein by cross-reference.
Background
Actinium-227 is frequently présent in minerai processing circuits. Its presence is the resuit of the decay of uranium-235, which may be associated, for example, with rare earth minerai deposits, either occurring in the rare earth minerai itself or otherwise associated with the process feed.
Actinium-227 is radioactive, with a half-life of approximately 22 years. It decays through β émission to thorium-227, which gives rise to further decay products.
Actinium contamination is a problem in minerai processing. While standard processing methods remove the majority of the sources of radioactivity présent in minerai process feeds, due to its Chemical similarity to, for example, the rare earth éléments, actinium is not easily removed.
Furthermore, regulatory authorities set restrictive limits on the amount of actinium activity that may be présent in materials (for example the International Atomic Energy Agency sets a limit of 0.1 Bq/g (or 1.0 Bq/g), depending on the circumstances) for actinium activity, see e.g. IAEA Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards, Sériés No. GSR Part 3, 19 July 2014).
In the context of rare earths processing, rare earth processing feeds may be processed either into individual rare earth products, which typically requires the use of solvent extraction, or into a mixed minerai concentrate, which typically does not require solvent extraction. Solvent extraction can be used to remove actinium from rare earth process streams, however, as it is a costly step and involves extensive additional processing, it is best avoided if possible. Using previously available technology, if a mixed concentrate is to be produced from a feedstock that is contaminated with actinium, it must be processed using solvent extraction, which would not otherwise be required for the production of a mixed concentrate.
Additionally, there is interest in processing high uranium content ores, monazite and xenotime ores, and minerai concentrâtes to produce mixed concentrâtes. These ores may be contaminated with actinium.
Therefore, there is a need for a method of selectively removing actinium from processing streams which does not involve solvent extraction. An object of the présent invention is the provision of a method of at least partially removing actinium from a feed solution which does not require solvent extraction.
Summary of Invention
In a first aspect of the invention there is provided a method of removing actinium from a solution comprising actinium ions and ions of interest, the method comprising adding métal ions to said solution, a sulfate sait of which has a solubility in water at 20 °C of less than about 0.3 g/100 mL; wherein if the sulfate concentration of the solution is insufficient to cause the sulfate sait of the métal ions to precipitate, a water soluble source of sulfate ions is added to said solution until the sulfate sait of the métal ions précipitâtes; whereby a precipitate comprising actinium and the sulfate sait of the métal ions is formed and wherein a sufficient amount of métal ions is added to cause at least 40% of the actinium ions to precipitate.
The following options may be used in conjunction with the first aspect, either individually or in any suitable combination.
The métal ions may be added in an amount of 0.01-100 mmol per Bq/L of activity of the solution. This may therefore be considered to be a sufficient amount of the métal ions.
The ions of interest may be rare earth ions. The concentration of the ions of interest in the solution may be essentially unchanged by the method.
The actinium ions may be Ac-227 ions. The actinium activity of the total dissolved ions of interest contained in said solution may be greater than about 1.0 Bq/g.
The métal ions may be divalent métal ions. The métal may be selected from the group consisting of calcium, strontium, barium or lead. It may be strontium, or it may be lead, or it may be barium. The métal ions may comprise a mixture of different métal ions, such as a mixture of barium ions and strontium ions.
The solution comprising actinium ions and ions of interest may be produced as a resuit of the processing of an ore or minerai concentrate containing the ions of interest. The ions of interest may be of one or more rare earth éléments selected from the group consisting of Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Y, Tb, Dy, Ho, Er, Tm, Yb, and Lu. In this case, the ore may comprise, or may be, monazite, xenotime, or a mixture thereof. The ore or minerai concentrate may be such that if a mixed rare earth concentrate were to be produced from it without the removal of actinium, the actinium activity of the mixed rare earth concentrate would be greater than 1.0 Bq/g. Altematively, the ions of interest may not be rare earth ions, in this case, the ore or minerai concentrate may be, for example, an ore containing uranium.
The method may comprise a step of processing an ore or minerai concentrate using an acid cracking process so as to produce the solution comprising actinium ions and ions of interest. In this event, the métal ions may be lead(II). The lead(II) may be in the form of lead(II) chloride or lead(II) nitrate.
The method may altematively comprise a step of processing an ore or minerai concentrate using an alkaline cracking process so as to produce the solution comprising actinium ions and ions of interest. In this event, the métal ions may be strontium or barium, or a mixture thereof, which may be in the form of barium chloride and/or strontium chloride. A water soluble source of sulfate ions may be added to said solution until the sulfate sait of the métal ions précipitâtes. The water soluble source of sulfate ions may be selected from the group consisting of sulfuric acid, sodium sulfate, magnésium sulfate, or a combination of any two or ail of these. The molar ratio of sulfate ions to métal ions may be in the range of about 1:1 to about 1000:1.
In the situation where the method comprises processing an ore or minerai concentrate using an alkaline cracking process, the solution may further comprise radium ions. In this case, the métal ions are barium ions, or a mixture of strontium and barium ions. Strontium ions and barium ions may also be added sequentially, in either order. The métal ions may be in the form of barium chloride and/or strontium chloride, and a precipitate comprising actinium ions, radium ions, and barium sulfate and/or strontium sulfate, may be formed. A sufficient amount of métal ions may be added to cause at least 40% of the actinium ions to precipitate and at least 99% of the radium ions to precipitate.
The métal ions may be added to the solution in the fonn of a solid. They may be added in the form of an aqueous solution. The water soluble source of sulfate ions may be added to the solution in the form of a solid. It may be added in the form of an aqueous solution.
The method may further comprise separating the precipitate from the solution. Following this, the solution may hâve a reduced concentration of actinium or its actinium activity may be reduced or both.
Where the ions of interest are rare earth ions, the method may further comprise obtaining a solid mixed rare earth concentrate from the solution. The solid rare earth concentrate may hâve an actinium activity of less than or equal to 1.0 Bq/g.
In one embodiment there is provided a method of removing actinium from a solution comprising actinium-227 ions and rare earth ions, the method comprising adding to the solution lead chloride or strontium chloride; wherein if the sulfate concentration of the solution is insufficient to cause the sulfate sait of the lead or strontium to precipitate, a water soluble source of sulfate ions such as sodium sulfate, sulfuric acid, magnésium sulfate, or a combination of any two or ail of these, is added to the solution until the sulfate sait of the lead or strontium précipitâtes; whereby a precipitate comprising actinium and the sulfate sait of the métal ions is formed. In this embodiment a sufficient amount of métal ions is added to cause at least 40% of the actinium ions to precipitate.
In another embodiment there is provided a method of removing actinium from a solution comprising actinium-227 ions and rare earth ions, the method comprising processing an ore or minerai concentrate using an acid cracking process so as to provide the solution comprising actinium ions and rare earth ions and adding to the solution lead(II) chloride, whereby a precipitate comprising lead(II) sulfate and actinium is formed. In this embodiment a sufficient amount of métal ions is added to cause at least 40% of the actinium ions to precipitate. The method may further comprise separating the precipitate from the solution. Following said séparation, the solution may hâve a reduced actinium activity and the concentration of rare earth ions in said solution may be essentially unchanged.
In another embodiment there is provided a method of removing actinium from a solution comprising actinium-227 ions and rare earth ions, the method comprising processing an ore or minerai concentrate using an alkaline cracking process so as to provide the solution comprising actinium ions and rare earth ions; adding to the solution strontium chloride and, a water soluble source of sulfate ions such as sodium sulfate, sulfuric acid or magnésium sulfate; whereby a precipitate comprising strontium sulfate and actinium is formed. In this embodiment a sufficient amount of métal ions is added to cause at least 40% of the actinium ions to precipitate. The method may further comprise separating the precipitate from the solution. Following said séparation, the solution may hâve a reduced actinium activity and the concentration of rare earth ions in said solution may be essentially unchanged.
In another embodiment there is provided a method of removing actinium and radium from a solution comprising actinium-227 ions, radium ions and rare earth ions, the method comprising processing an ore or minerai concentrate using an alkaline cracking process so as to provide the solution comprising actinium ions, radium ions and rare earth ions; adding to the solution barium chloride and a water soluble source of sulfate ions, such as sulfuric acid, sodium sulfate, magnésium sulfate, or a combination of any two or ail of these; whereby a precipitate comprising barium sulfate, radium and actinium is formed, and wherein a sufficient amount of métal ions is added to cause at least 40% of the actinium ions to precipitate and at least 99% of the radium ions to precipitate. In this embodiment, the method may further comprise separating the precipitate from the solution. Following said séparation, the solution may hâve a reduced actinium activity, a reduced radium activity, and the concentration of rare earth ions in said solution may be essentially unchanged.
In a second aspect of the invention there is provided a solid mixed rare earth concentrate obtained by the method of the first aspect of the invention wherein the ions of interest are rare earth ions. The solid mixed rare earth concentrate may hâve an actinium activity of less than 1.0 Bq/g.
In a third aspect of the invention there is provided the use of a métal ion, the sulfate sait of which has a solubility in water at 20 °C of less than about 0.3 g/100 mL, for removing actinium from a solution comprising actinium ions and ions of interest.
In a fourth aspect of the invention there is provided a precipitate comprising a sulfate sait of a métal ion and further comprising actinium-227, said precipitate being obtained by the method of the first aspect of the invention.
In a fifth aspect of the invention there is provided a method of preparing a radioisotope, the method comprising: obtaining a precipitate according to the fourth aspect of the invention; separating the actinium-227 from the precipitate; purifying the actinium-227; allowing a portion of the actinium-227 to decay to a decay product, which is the radioisotope, and purifying the radioisotope.
The radioisotope may be thorium-227 or radium-223.
In one embodiment there is provided a method of preparing thorium-227 or radium-223, the method comprising: obtaining a precipitate according to the fourth aspect of the invention; separating the actinium-227 from the precipitate; purifying the actinium-227; allowing a portion of the actinium-227 to decay to thorium-227 or radium-223 and purifying thorium-227 or radium-223 from the resulting mixture of radioisotopes.
In another embodiment there is provided a method of preparing thorium-227 or radium-223, the method comprising: obtaining a precipitate comprising a sulfate sait of métal ions and actinium227 by providing a solution comprising actinium-227 ions and ions of interest; adding to the solution métal ions, a sulfate sait of which has a solubility in water at 20 °C of less than about 0.3 g/100 mL; wherein if the sulfate concentration of the solution is insufficient to cause the sulfate sait of the métal ions to precipitate, a water soluble source of sulfate ions is added to said solution until the sulfate sait of the métal ions précipitâtes; whereby a precipitate comprising the sulfate sait of the métal ions and actinium-227 is formed and wherein a sufficient amount of métal ions is added to cause at least 40% of the actinium ions to precipitate; separating the actinium-227 from the precipitate; purifying the actinium-227; allowing a portion of the actinium-227 to decay to thorium-227 or radium-223 and purifying thorium-227 or radium-223 from the resulting mixture of radioisotopes.
In a sixth aspect of the invention there is provided use of the precipitate of the fourth aspect of the invention to produce a radioisotope, such as a thorium or radium radioisotope.
Description of Embodiments
The présent spécification relates to a method for removing actinium from process liquors comprising ions of interest (which may be, for example, rare earth ions) and actinium ions. In this method, a low solubility métal sulfate sait is caused to precipitate from a solution comprising ions of interest and actinium ions. Actinium ions become associated with the precipitate causing them to be removed from the solution. The method allows actinium to be removed from the solution selectively i.e. without the concurrent removal of substantial amounts of the ions of interest présent in the solution.
Surprisingly, the inventors hâve found that when the low solubility métal sulfate sait précipitâtes in the presence of actinium ions, the actinium ions become selectively associated with the precipitate, causing them to be removed from the solution. Without wishing to be bound by any particular theory, it is suggested that this association may occur through any one of the following mechanisms: co-précipitation of an actinium sait with the métal sulfate sait, adsorption of actinium into defects in the crystal lattice of the métal sulfate sait, incorporation of actinium ions into the métal sulfate sait crystal or occlusion of actinium into the growing métal sulfate sait crystal. Removal of actinium from the solution may occur through a combination of the above mechanisms or through a mechanism not listed here.
Advantageously, the inventors hâve discovered that if the process liquors dérivé from an alkaline cracking process and contain radium and/or lead ions as well as actinium ions, the method of the invention may resuit in actinium, radium and lead ions becoming associated with the precipitate of the métal sulfate sait. In this way, it is possible to remove a proportion of actinium, radium and lead from process liquors in a single process step. If the removal of radium and/or lead, as well as actinium, is desired, the amount of métal ions required (and corresponding amount of sulfate ions) is greater than that required for the removal of radium alone. An advantage of removing actinium and radium simultaneously is that an additional process step is not required for actinium removal because there is already a radium removal step in the process.
The solution which is used as a feed to the method of the invention comprises water, however it may in some instances also comprise one or more non-aqueous co-solvents, or other organic or inorganic additives. In some instances, there may be no co-solvents or additives. In the event that co-solvents or additives, e.g. organic solvents, are présent, they may be in a proportion of less than about 20% by volume of the solution, or less than about 15%, 10%, or 5%, or in a proportion of about 0-10, 10-20, 5-15, 0-5, 5-10, 10-15, 15-20% by volume of the solution. The co-solvents or additives may be présent in an amount of about 5, 10, 15 or 20% by volume. The solution may be provided as a resuit of the processing of an actinium-containing material, which may be an ore or minerai concentrate containing ions of interest, such as rare earth éléments. Two methods which may be used in the processing of an ore or minerai concentrâtes are acid cracking and alkaline cracking.
In the context of this spécification the term “about” is taken to mean ±10% of the stated value, unless signified otherwise by the context.
In the context of this spécification, the term “comprising” is taken to require the presence of the recited integer(s) but does not preclude the presence of others and does not imply any particular concentration or proportion of the recited integer(s).
The process of acid cracking comprises a step of treating the ore or minerai concentrate with concentrated sulfuric acid at elevated température. The resulting mixture may be leached with water. Thus sulfate ions, which are subsequently precipitated to remove actinium, are présent in the process liquor from the sulfuric acid.
The process of alkaline cracking comprises a step of treating the ore or minerai concentrate with a concentrated solution of a base such as sodium hydroxide at elevated température. This is followed by solubilisation of the caustic residue in an acid, such as hydrochloric acid, adjusting the pH of the solution to 3-4. As no sulfate is provided during this process, it is commonly necessary to add a source of sulfate ions in order to form a precipitate so as to remove actinium.
Actinium is présent in the feed solution. The actinium may be présent as a resuit of the decay of uranium-235 or it may occur as a resuit of any natural or artificial process. The actinium may be actinium-227. Other isotopes of actinium may also be présent. The method of the invention may be used to successfully remove ail isotopes of actinium présent in the solution. As used in this spécification, “actinium” includes elemental actinium as well as actinium ions in any oxidation state. Commonly the actinium will be présent as Ac3+ ions.
Radium may also be présent in the feed solution. The radium may be présent as a resuit of any natural or artificial process. The radium may be radium-226 or radium-228. Other isotopes of radium may also be présent. The method of the invention may be used to successfully remove ail isotopes of radium présent in the solution.
The feed solution will typically contain ions of interest. The ions of interest are non-actinium ions présent in the solution which the operator of the method of the invention may wish to separate from the actinium ions. A goal of the method may be to obtain the ions of interest free from undesirable levels of actinium activity or with reduced actinium activity. However, a goal of the method may equally be to obtain actinium ions and, optionally, discard the ions of interest. The ions of interest may be rare earth ions. Rare earth ions présent in the solution may be ions (of any oxidation state) of one or more of the following éléments: Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Y, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Altematively, the solution may contain no rare earth ions. Another example of an ion of interest may be a uranium ion. In some instances, the ions of interest may comprise both rare earth ions and non-rare earth ions. Other organic or inorganic components may also be présent in the solution. The concentration of the ions of interest (and their counter ions) may be about 1 to about 200 g/L, or about 1-100, 100-200, 50-150, 1-25, 2575, 75-100, 100-125, 125-150, 150-175 or 175-200 g/L.
In the method of the invention, métal ions are added to the feed solution. The métal ions may be of any metallic element in any oxidation state, provided that the solubility of a sulfate sait of the métal ions in water at 20 °C is less than about 0.3 g/100 mL. The solubility of the sulfate sait of the métal ions in water at 20 °C may be less than about 0.25, 0.2, 0.15, 0.1, 0.05, 0.02, 0.005, 0.002, 0.001, 0.0005 or 0.0001 g/100 mL. It maybe in the range of about 0.0001-0.3, 0.00010.25, 0.0001-0.2, 0.0001-0.15, 0.0001-0.1, 0.005-0.05, 0.0001-0.005, 0.005-0.05 or 0.05-0.3 g/100 mL. It may be about 0.00024, 0.0044, 0.013 or 0.25 g/100 mL. Typically, the métal ions are divalent métal ions such as lead, barium or strontium, or combinations thereof. Where a combination of different divalent métal ions is added, the métal ions may be added simultaneously or sequentially.
The feed solution may comprise sulfate ions. For example, if an ore or minerai concentrate is processed using acid cracking the solution will generally comprise sulfuric acid. The sulfate ions may be présent in a sufficient concentration to cause at least some of a sulfate sait of the métal ions to precipitate on addition of the métal ions. In general, a sufficient concentration of sulfate ions is such that, for the given métal ion concentration, the solubility product of the métal sulfate sait is exceeded by the product of the métal ion and sulfate concentrations. At a sufficient concentration of sulfate in the solution, addition of the métal ions may resuit in formation of at least some precipitate which comprises actinium and the sulfate sait of the métal ions.
Altematively, the concentration of sulfate ions in the solution may be insuffïcient to cause at least some of the sulfate sait of the métal ions to precipitate. This is commonly the case if the processing of the ore or minerai concentrate comprises an alkaline cracking step. In general, an insuffïcient concentration of sulfate ions is one at which the solubility product of the sulfate sait of the métal ions is not exceeded by the product of the métal ions and sulfate concentrations. In this case, it may be necessary to increase the concentration of sulfate ions in the solution in order to precipitate at least some of the sulfate sait of the métal ions so as to remove actinium. This is achieved by adding a water soluble source of sulfate ions. Any water soluble source of sulfate ions may be used, such as sodium sulfate, magnésium sulfate, potassium sulfate, sulfuric acid, or any mixture of these. Sulfuric acid, magnésium sulfate, or a combination thereof, are preferred. The water soluble source of sulfate ions may be added, continuously, intermittently or as a single bolus, until at least some of a precipitate comprising the sulfate sait of the métal ions forms. Once a sufficient concentration of sulfate ions is achieved, at least some of a precipitate comprising the sulfate sait of the métal ions and further comprising actinium forms.
The method of the invention is at least partially sélective, and in some circumstances, substantially or essentially completely, for the removal of actinium over ions of interest from the feed solution. The concentration of ions of interest in the solution may be essentially the same before and after applying the method of the invention. In the context of the spécification “essentially the same” means the concentration of ions of interest is not reduced by more than about 1%, or not reduced by more than about 2, 5, 10 or 15%. The concentration may be reduced by about 0-15%, or about 0-10, 0-5, 5-10, 5-15 or 10-15%. The term “essentially unchanged” has a corresponding meaning. In the context of the spécification the term “the concentration of ions of interest” may refer either to the total concentration of ions of interest or it may refer to the concentration of any or each ion of interest individually.
The selectivity of the method is sensitive to the amount of métal ions added. If an excessive amount of métal sulfate is caused to precipitate, the concentration of ions of interest may be unacceptably reduced. If an insuffïcient amount of the métal ions is added, it may not be effective in removing the desired quantity of actinium. In the method of the invention, the métal ion is added in a sufficient amount so as to remove actinium to an acceptable level, and no more. Altematively, if the removal of radium and/or lead, as well as actinium, is desired, the amount of métal ions added will be greater than that required for the removal of radium alone. A sufficient amount of the métal ions is in the range of about 0.01-100 mmol per Bq/L of actinium activity of the feed solution, or about 0.01-0.1, 0.01-1, 0.01-10, 0.01-50, 1-10, 1-50, 50-100, 0.1-1, 1-10, 10-25, 25-50, 50-75, 75-100 mmol per Bq/L of actinium activity of the feed solution. The amount of métal ions which is sufficient to remove actinium without unacceptably reducing the concentration of ions of interest will dépend on the identity of the métal ions. If the métal ions are Pb ions, a sufficient amount of the métal ions is about 0.01-5 mmol per Bq/L, or about 0.01-0.5, 0.01-1, 0.01-2, 1-5, 2-5, 0.01-0.05, 0.05-0.1, 0.1-0.5, 0.5-1, 1-2, 2-3, 3-4, or 4-5 mmol per Bq/L. If the métal ion are Sr2+ions, a sufficient amount of the métal ions is about 0.1-15 mmol per Bq/L, or about 0.1-1, 0.1-5, 0.1-10, 0.1-0.2, 0.2-0.5, 0.5-1, 1-5, 1-10, 1-15, 5-10, or 515 mmol per Bq/L. If the métal ions are Ca2+ions, a sufficient amount of the métal ions is about 10-100 mmol per Bq/L, or about 10-50, 50-100, 10-20, 20-30, 30-40, 40-50, 50-60, 60-70, 7080, 80-90, or 90-100 mol per Bq/L. If the métal ions are Ba2+ ions, a sufficient amount of the métal ions is about 0.1-15 mmol per Bq/L, or about 0.1-1, 0.1-5, 0.1-10, 0.1-0.2, 0.2-0.5, 0.5-1, 1-5, 1-10, 1-15, 5-10, or 5-15 mmol per Bq/L.
In the context of this spécification, “activity” refers to radioactivity. “Actinium activity” refers to the radioactivity of actinium-227,. Activity is measured in Bq/g or Bq/L, depending on the context. The activity of Ac-227 is typically determined by gamma spectroscopy of in-growth of Th-227.
In order to remove a desired amount of actinium, a sufficient amount of the métal ion that is added to the solution must be caused to precipitate as a sulfate sait. It may be titrated into the solution to a desired actinium activity endpoint. This may be achieved by adjusting the relative amounts of métal ions and sulfate ions such that the stoichiometry allows a sufficient amount of the métal ions to form a sulfate sait. For example, if the processing of the ore or minerai concentrate comprises an alkaline cracking step and thus the métal ions are strontium ions and a water-soluble source of sulfate ions is required, typically an at least equimolar amount of sulfate ions, relative to the amount of strontium or barium ions, will be added. Preferably, an excess of sulfate ions is added relative to the strontium or barium ions. The molar ratio of sulfate ions to the total amount of métal ions (such as strontium ions, or barium ions, or a combination thereof) may be in the range of about 1:1 to 1000:1, or about 1:1 to 2:1, 5:1, 10:1, 100:1, 200:1, 300:1; 400:1, 500:1, 600:1, 700:1, 800:1 or 900:1, or about 10:1 to 100:1, 200:1, 300:1; 400:1, 500:1, 600:1, 700:1, 800:1, 900:1 or 1000:1, or about 100:1 to 200:1, 300:1; 400:1, 500:1, 600:1, 700:1, 800:1, 900:1 or 1000:1, or about 200:1 to , 300:1; 400:1, 500:1, 600:1, 700:1, 800:1, 900:1 or
1000:1. The ratio of sulfate ions to métal ions may be about 1:1, 1.5:1, 2:1, 5:1, 10:1, 50:1,
100:1, 200:1, 300:1; 400:1, 500:1, 600:1, 700:1, 800:1, 900:1 or 1000:1. The skilled person will be able to détermine, by routine trial and error guided by the information disclosed herein, a ratio of sulfate to métal ions which is appropriate to remove actinium from particular process liquors.
The total dissolved ions of interest, for example total dissolved rare earths, contained in the solution may originate from an ore or from a minerai concentrate. The ore or minerai concentrate is processed, resulting in the formation of the solution used as a feed to the method of the invention. The dissolved ions of interest may dérivé from various salts such as carbonates or oxides. The total dissolved ions of interest contained in the solution may be radioactive. The radioactivity may originate from actinium-227. Other radioactive éléments may be présent. The actinium activity of the total dissolved ions of interest may be greater than about 0.1 Bq/g, or about 1, 10, 100 or 500 Bq/g. The actinium activity may be in the range of about 0.1-500 Bq/g, or about 0.1-100, 0.1-10, 0.1-1, 1-10, 10-100 or 100-500 Bq/g. The actinium activity of the total dissolved ions of interest may be about 0.1 Bq/g, or about 1, 10, 100 or 500 Bq/g. Alternatively, the actinium activity may be expressed per unit volume of the feed solution. The actinium activity may be in the range of about 1-500 Bq/L, or about 1-100, 1-250, 100-250, 250-500, 1100, 1-200, 1-300, 1-400 Bq/L. The actinium activity may be about 1 Bq/L or about 2, 5, 10, 20, 50, 100, 150, 200, 250, 300, 350, 400, 450 or 500 Bq/L.
The precipitate may be separated from the solution by any method known to the skilled person. Methods of séparation include, but are not limited to, filtration, gravitational settling, centrifugation or flotation and skimming, or any combination of these. The precipitate may comprise a single Chemical species, or may comprise multiple species. The word ‘precipitate’ is intended to refer to the totality of species caused to precipitate out of solution as a resuit of carrying out the method of the invention.
Following the précipitation, the solution may hâve a reduced concentration of actinium when compared to the concentration of actinium prior to carrying out the method of the invention. The actinium concentration may be reduced by up to 100%, or up to about 95, 90, 85, 80, 70, 60, 50, 40, 30 or 20%. The réduction may be in the range of about 100-20%, or about 100-60, 100-85, 85-20, 60-20, 20-40, 40-60, 60-85, 85-90, 90-95 or 95-100%. The concentration may be reduced by about 100%, or about 95, 90, 85, 80, 70, 60, 50, 40, 30 or 20%. Equivalently, up to 100%, or up to about 95, 90, 85, 80, 70, 60, 50, 40, 30 or 20% of the actinium ions may be caused to precipitate. The proportion of actinium ions caused to precipitate may be in the range of about
100-20%, or about 100-60, 100-85, 85-20, 60-20, 20-40, 40-60, 60-85, 85-90, 90-95 or 95-100%. The amount of actinium ions caused to precipitate may be about 100%, or about 95, 90, 85, 80, 70, 60, 50, 40, 30 or 20%. The degree of réduction (amount of précipitation) may be controlled in part by the quantity of the métal ion, which may be determined with reference to the measured actinium activity of the solution.
The method may therefore further comprise measuring the actinium activity of the solution and determining from the measured actinium activity the required quantity of the métal ions to be added. The method may also comprise adding to the solution métal ions, a sulfate sait of which has a solubility in water at 20 °C is less than about 0.3 g/l 00 mL and, if required, a source of water soluble sulfate, whereby a precipitate to form comprising actinium and the sulfate sait of the métal ions is formed; measuring the actinium activity of the solution, and determining from the measured actinium activity if further addition of the métal ions (and water soluble source of sulfate, if required) is needed. This step may be repeated as often as required until an acceptable level of actinium activity is reached. The actinium activity may be measured by gamma spectroscopy of in-growth of thorium-227.
Following séparation of the precipitate, the actinium activity of the solution is reduced when compared to its actinium activity prior to carrying out the method of the invention. The actinium activity may be reduced by up to or about 100%, or about 95, 90, 85, 60, 40 or 20%. The réduction may be in the range of about 100-20%, or about 100-60, 100-85, 85-20, 60-20, 20-40, 40-60, 60-85, 85-90, 90-95 or 95-100%. The actinium activity may be reduced by about 100%, or about 95, 90, 85, 60, 40 or 20%. The same proportional réductions apply, independently, to radium and/or lead.
Following séparation of the precipitate, where the ions of interest are rare earth ions the resulting solution may be processed further to produce a solid mixed rare earth concentrate. A mixed rare earth concentrate is a solid comprising a mixture of rare earth éléments intended for further processing. A mixed rare earth concentrate produced by the method of the invention may hâve an actinium activity of less than or equal to about 1.0, 0.75, 0.5, 0.25, 0.1, or 0.05 Bq/g. The actinium activity may be in the range of about 0-0.05, 0-0.1, 0-0.5, 0-1.0, 0.05-0.1, 0.1-0.25, 0.25-0.5, or 0.5-1 Bq/g. The actinium activity may be about 0.05, 0.1, 0.25, 0.5, 0.75, or 1.0 Bq/g.
The invention also encompasses a method of preparing a radioisotope from the precipitate comprising the sulfate sait of the métal ion and further comprising actinium-227, obtained by the method of the invention. Actinium-227 may be separated from the precipitate by any method known to the skilled person. A suitable method involves treating the precipitate with hydrochloric acid. The liberated actinium-227 may then be purified by any suitable method, e.g. ion exchange or solvent extraction. The resulting purified actinium compound may then be allowed to decay, resulting in the formation of decay products which may be the radioisotope. For example, the decay product may be thorium-227 or radium-223. Since actinium-227 decays to thorium-227, which decays to radium-223, sélection of the desired radioisotope may be accomplished by selecting a suitable time for which the actinium-227 is allowed to decay. Thorium-227 or radium-223 produced by the above method may be used in medical imaging or radiotherapy.
Examples
Example 1: To sulfate containing process liquor containing about 8 Bq/L Ac-227 and rare earths, mainly as yttrium, was added strontium. Strontium chloride was dissolved in a minimal amount of water, added to the actinium containing sulfate liquor at room température, and agitated for 20 hours. The sulfate precipitate was filtered off and the Ac-227 removal determined by gamma spectrometry analysis of the liquor.
| Test ID SrCl2. 6H2O addition (mmol per Bq/L activity) | A-2-13 0.7 | A-2-11 4.7 | A-2-12 9.5 |
| Sr | 59 | Précipitation (%) 95 | 98 |
| Y | <5 | <5 | <5 |
| TRE+Y | <5 | <5 | <5 |
| Ac-227 (% précipitation) | 74 | 97 | >99 |
TRE = total rare earths
Example 2: To sulfate-containing process liquor containing ~ 8 Bq/L Ac-227 and rare earths, mainly as yttrium, was added lead(II) chloride. Lead chloride was dissolved in a minimal amount of water, added to the actinium containing sulfate liquor at room température, and agitated for 20 hours. The sulfate precipitate was filtered off and the Ac-227 removal determined by gamma spectrometry analysis of the liquor. The Ac-227 removal was approximately 70-80%.
| Test ID | A-2-7 | A-2-9 |
| PbCl2 addition (mmol per Bq/L activity) | 0.24 | 0.59 |
| Précipitation (%) | ||
| Pb | >92 | >96 |
| Y | <5 | <5 |
| TRE+Y | <5 | <5 |
| Ac-227 | ~68 | ~79 |
Example 3: To a chloride containing process liquor containing ~70 Bq/L Ac-227 and minimal radium was added strontium. The radium had been previously removed by co-precipitation with barium sulfate by addition of barium chloride and sulfuric acid. Strontium chloride solid was added to the process liquor and dissolved in it. Magnésium sulfate was added as a 250 g/L solution to induce the précipitation of strontium sulfate at room température. The mixture was agitated for 20 hours at room température. The sulfate precipitate was filtered off and the Ac-227 removal determined by gamma spectrometry analysis of the liquor. There was approximately 50% removal of Ac-227 with 2% précipitation of rare earths.
| Test ID SrCl2. 6H2O addition (mmol per Bq/L activity) | 61-2 1.3 |
| SO4/Sr molar ratio | 1.5 |
| Sr LRE (La+Ce+Pr+Nd) TRE+Y | % Précipitation 60 2 2 |
| Ac-227 (% précipitation) | 47 |
LRE = light rare earths
Example 4: To a chloride containing process liquor containing ~90 Bq/L Ac-227 and minimal radium was added lead. The radium had been previously removed by co-precipitation with barium sulfate by addition of barium chloride and sodium sulfate. Lead chloride solid was added to the process liquor and lead chloride that had not dissolved was filtered off (0.98 g PbCL/L feed dissolved). Sodium sulfate was added as a 150 g/L solution and the mixture agitated for 20 hours at room température. The precipitate was filtered off. There was 41% removal of Ac-227.
The relatively high précipitation of rare earths is attributed to sodium sulfate addition and précipitation of a sodium sulfate rare earth double sulfate sait.
| Test ID | AMI |
| PbCl2 addition (mmol per Bq/L activity) | 0.041 |
| SO4/Pb molar ratio | 42 |
| % Précipitation | |
| Pb | 23 |
| Nd | 13 |
| TRE+Y | 13 |
| Ac-227 | 41 |
Example 5: To a chloride containing process liquor containing >100 Bq/L Ac-227 and >10,000
Bq/L Ra-228 was added barium. Barium chloride solid was added to the process liquor and dissolved. Sulfùric acid solution was added as the sulfate source to induce précipitation of barium sulfate. The mixture was agitated for 20 hours at room température. The precipitate was fdtered off. Results are presented in the table below.
| Test ID | 56-1 | 56-2 | 56-3 |
| BaCl2.2H2O addition (mmol per Bq/L Ac-227 activity) | 0.4 | 0.7 | 1.4 |
| SO4:Ba molar ratio | 1.1 | 1.1 | 1.1 |
| Dilution of feed volume | 0.80 | 0.80 | 0.80 |
| % Précipitation | |||
| Ba | >99 | >99 | >99 |
| LRE | 0.4 | 0.8 | 2 |
| TRE+Y | 0.4 | 0.8 | 2 |
| Ac-227 (% précipitation) | 27 | 43 | 66 |
| Ra-228 (% précipitation) | >99.9 | >99.9 | >99.9 |
[0001] Example 6: To a chloride containing process liquor containing >100 Bq/L Ac-227 and >10,000 Bq/L Ra-228 was added barium and strontium, as their chloride salts. In one test (test
ID = 59-3), précipitation of barium sulfate and strontium sulfate was carried out simultaneously. Both barium chloride and strontium chloride salts were added to the process liquor and dissolved followed by addition of sulfuric acid solution to initiate barium sulfate and strontium sulfate précipitation. In another test (test ID = 59-4), précipitation of barium sulfate and strontium sulfate was carried out sequentially in the same vessel. Barium chloride was dissolved in the process liquor and sulfuric acid added to initiate barium sulfate précipitation. Without filtration of the barium sulfate, strontium chloride was dissolved in the slurry and more sulfuric acid was added to initiate strontium sulfate précipitation. The Ac-227 removal was slightly higher when précipitation of barium sulfate and strontium sulfate occurred sequentially rather than simultaneously. Radium removal was >99.9% in both cases.
| Test ID | 59-3 | 59-4 |
| BaCl2.2H2O addition (mmol per Bq/L Ac-227 activity) | 0.3 | 0.3 |
| SrCl2.6H2O addition (mmol per Bq/L Ac-227 activity) | 0.3 | 0.3 |
| SO4:(Ba+Sr) molar ratio | 1.6 | 1.6 |
| SO4:Ba molar ratio | 1.1 | |
| SO4:Sr molar ratio | 2.1 | |
| % Précipitation | ||
| Ba | >99 | >99 |
| Sr | 85 | 83 |
| TRE+Y | 1.7 | 1.0 |
| Ac-227 (% précipitation) | 42 | 55 |
| Ra-228 (% précipitation) | >99.9 | >99.9 |
Claims (10)
18 CLAIMS
1. A method of removing actinium ions from a solution comprising actinium ions and ions of interest, the method comprising adding to said solution divalent métal ions, a sulfate sait of which has a solubility in water at 20 °C of less than about 0.3 g/100 mL, wherein if the sulfate concentration of the solution is insufficient to cause the sulfate sait of the divalent métal ions to precipitate, a water soluble source of sulfate ions is added to said solution until the sulfate sait of the divalent métal ions précipitâtes, whereby a precipitate comprising actinium and the sulfate sait of the divalent métal ions is formed and the concentration of the ions of interest in said solution is essentially unchanged, wherein a sufficient amount of divalent métal ions is added to cause at least 40% of the actinium ions to precipitate, and wherein the solution does not contain organic additives.
2. The method of claim 1, wherein the divalent métal ions are added in an amount of 0.01-100 mmol per Bq/L of actinium activity of the solution.
3. The method of claim 1 or claim 2, wherein the actinium activity of the total dissolved ions of interest contained in said solution is greater than about 1.0 Bq/g.
4. The method of any one of claims 1 to 3, wherein the divalent métal ions are strontium or lead or barium ions.
5. The method of any one of claims 1 to 4, wherein the solution comprising actinium ions and ions of interest is produced as a resuit of the processing of an ore or minerai concentrate containing the ions of interest, wherein the ore contains uranium and the ions of interest are uranium ions, or wherein the ions of interest are rare earth ions.
6. The method of any one of claims 1 to 5 comprising the step of processing an ore or minerai concentrate using an acid cracking process so as to produce the solution comprising actinium ions and ions of interest, and wherein the divalent métal ions are lead(II) ions.
7. The method of any one of claims 1 to 5 comprising the step of processing an ore or minerai concentrate using an alkaline cracking process so as to produce the solution comprising actinium ions and ions of interest, and wherein the divalent métal ions are strontium or barium ions or a mixture thereof.
5
8. The method of claim 7, wherein a water soluble source of sulfate ions is added to said solution until the sulfate sait of the métal ion précipitâtes, wherein the water soluble source of sulfate ions is selected from the group consisting of sulfùric acid, sodium sulfate, magnésium sulfate, or a combination of any two or ail thereof.
9. The method of claim 7 or claim 8, wherein the solution further comprises radium ions, 10 wherein the divalent métal ions are barium ions, strontium ions, or a mixture thereof, and whereby a precipitate comprising actinium ions, radium ions and barium sulfate is formed, and wherein a sufficient amount of divalent métal ions is added to cause at least 40% of the actinium ions to precipitate and at least 99% of the radium ions to precipitate.
10. The method of any one of claims 7 to 9, wherein the molar ratio of sulfate ions to divalent 15 métal ions is in the range of about 1:1 to about 1000:1.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2017902476 | 2017-06-27 |
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| OA19961A true OA19961A (en) | 2021-08-10 |
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