Method for extracting decay daughter of thorium

Abstract

The present application provides a method for extracting a decay daughter of thorium, wherein the method comprises: a leaching step of mixing thorium hydroxide particles with a leaching solution to dissolve decay daughters of thorium in the thorium hydroxide particles into the leaching solution; and a solid-liquid separation step of separating the thorium hydroxide particles mixed with the leaching solution from the liquid to obtain a solution containing the decay daughters of thorium. The present application can achieve high leaching efficiency, with multiple extractions reaching a leaching efficiency as high as 88%.

Description

A method for extracting decay daughters of thorium Technical Field

[0001] The present application relates to the field of radioactive elements, and in particular to a method for extracting decay daughters of thorium, and more particularly to a method for extracting decay daughters through thorium hydroxide particles. Background Art

[0002] In recent years, the field of α-type therapeutic isotope radiopharmaceuticals has rapidly grown, and many research projects on α-type radiopharmaceuticals and their preparation have been widely carried out. 212 Pb( 212 Bi) is an important representative of the emerging α nuclides, and its daughter 212 Bi(6.05MVe) and 212 Po (8.78 MeV) is the alpha emitter that ultimately produces toxicity (pharmaceutical efficacy) and exhibits excellent cytotoxicity. Furthermore, the production of this nuclide does not rely on long-term national nuclide reserves and can be extracted from natural thorium. 232 The natural decay chain of Th, in which 212 Pb and 212 Reason 232 Th is produced through continuous decay.

[0003] in, 232 Th is the main isotopic component of natural thorium. 228 Th is also distributed in natural thorium or obtained through other enrichment methods. 212 From the perspective of Pb production methods, 232 Preparation of nuclides in the Th decay chain by step-by-step extraction 212 Pb is the most important 212 Pb production method. However, due to 232 Th half-life is very long (1.4×10 10 5 years storage period 232 Th contains only 2×10 -10 (w / w) 228 Ra. So how to 232 Th extraction 228 Ra is all 212 The starting point of Pb production is also the most critical technical difficulty. 232 Th extraction 228 Methods for extracting Ra include barium co-precipitation and selective radium resin extraction. These existing methods each have their strengths and weaknesses. For example, the barium co-precipitation method produces a high volume of wastewater per run; the selective radium resin extraction method requires expensive selective resins. Furthermore, both methods require the long-term storage of large quantities of strongly acidic Th(IV) solutions. Summary of the Invention

[0004] The technical problem to be solved by this application is the deficiency in the background technology, and a method for extracting decay daughters of thorium is provided.

[0005] The technical solution of this application is as follows:

[0006] A method for extracting decay daughters of thorium, wherein the method comprises:

[0007] Leaching step: mixing thorium hydroxide particles with a leachate so that decay daughters of thorium in the thorium hydroxide particles are dissolved in the leachate;

[0008] Solid-liquid separation step: separating the thorium hydroxide particles mixed with the leaching liquid from the liquid to obtain a solution containing decay daughters of the thorium element.

[0009] In some embodiments, an aging treatment is performed before the leaching step, wherein the aging step includes: placing the thorium hydroxide particles for a period of time to enrich the decay daughters of the thorium element.

[0010] In some embodiments, the leaching solution is selected from one or more of water, nitrate solution, hydrochloride solution, sodium salt solution, potassium salt solution, calcium salt solution, and ammonium salt solution.

[0011] In some embodiments, the nitrate is selected from one or more of sodium nitrate, potassium nitrate, silver nitrate, magnesium nitrate, calcium nitrate, copper nitrate, iron nitrate, zinc nitrate, barium nitrate, aluminum nitrate, cesium nitrate, ammonium nitrate and ferrous nitrate;

[0012] The hydrochloride is selected from one or more of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, copper chloride, ferric chloride, zinc chloride, barium chloride, aluminum chloride, cesium chloride, ammonium chloride and ferrous chloride;

[0013] The sodium salt is selected from one or more of sodium chloride, sodium bicarbonate, sodium bisulfate, sodium nitrate, sodium hydrogen phosphate, sodium dihydrogen phosphate, sodium sulfide, sodium sulfite, sodium bisulfite, sodium nitrite, sodium ferrate, sodium fluoride, sodium bromide, sodium iodide, sodium formate, sodium acetate and sodium oxalate;

[0014] The potassium salt is selected from one or more of potassium chloride, potassium bicarbonate, potassium bisulfate, potassium nitrate, potassium hydrogen phosphate, potassium dihydrogen phosphate, potassium sulfide, potassium sulfite, potassium bisulfite, potassium nitrite, potassium ferrate, potassium fluoride, potassium bromide, potassium iodide, potassium formate, potassium acetate and potassium oxalate;

[0015] The calcium salt is selected from one or more of calcium chloride, calcium bicarbonate, calcium bisulfate, calcium nitrate, calcium hydrogen phosphate, calcium dihydrogen phosphate, calcium bisulfite, calcium nitrite, calcium bromide, calcium iodide, calcium formate and calcium acetate;

[0016] The ammonium salt is selected from one or more of ammonium chloride, ammonium bicarbonate, ammonium bisulfate, ammonium nitrate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium sulfide, ammonium sulfite, ammonium bisulfite, ammonium nitrite, ammonium ferrate, ammonium fluoride, ammonium bromide, ammonium iodide, ammonium formate, ammonium acetate and ammonium oxalate.

[0017] In some embodiments, the leachate is a sodium chloride solution and / or a sodium nitrate solution.

[0018] In some embodiments, the pH of the leachate is 4-12.

[0019] In some embodiments, the pH of the leachate is 6-8.

[0020] In some embodiments, the volume of the leachate is 0.5 to 20 volumes relative to 1 volume of the thorium hydroxide particles.

[0021] In some embodiments, the volume of the leachate is 1 to 3 volumes relative to 1 volume of the thorium hydroxide particles.

[0022] In some embodiments, the leaching step and the solid-liquid separation step are repeated to further extract decay daughters.

[0023] In some embodiments, thorium hydroxide particles are prepared as follows:

[0024] A base containing hydroxide or its aqueous solution is added to a solution containing thorium ions to obtain a mixed solution, the pH of the mixed solution is adjusted to 4-14, and thorium hydroxide particles are obtained after solid-liquid separation.

[0025] In some embodiments, the thorium hydroxide particles have a diameter of 100 nm to 1 mm.

[0026] In some embodiments, the pH of the mixed solution is 4-10.

[0027] In some embodiments, the hydroxide-containing base is selected from one or more of ammonia water, sodium hydroxide, calcium hydroxide, potassium hydroxide, barium hydroxide, and cesium hydroxide.

[0028] In some embodiments, the hydroxide-containing base is sodium hydroxide.

[0029] In some embodiments, the solid-liquid separation method is selected from one or more of filtration, centrifugal separation, decantation or natural sedimentation.

[0030] In some embodiments, the solid-liquid separation is performed by filtration.

[0031] The existing technologies include Ra / Th separation methods that use special crown ether resins to selectively adsorb Ra(II) without adsorbing Th(IV) (Ra selective adsorption resin method), or methods that use the same family of Ba(II) and Ra(II) co-precipitation method to enrich Ra(II) from Th(IV) (BaSO4 co-precipitation method). These existing methods each have their own strengths and weaknesses. For example, the barium co-precipitation method has a high amount of waste liquid per single use; the selective radium resin extraction method requires expensive selective resins, and both methods require long-term storage of large amounts of strongly acidic Th(IV) solutions.

[0032] In order to solve these problems, the applicant of this application has made a lot of attempts and innovations, and concluded from practice that thorium decay daughters are more easily dissolved in aqueous solution, while thorium ions (Th 4+ ) due to its poor solubility, the decay daughters are selectively extracted into aqueous solution.

[0033] Furthermore, the applicant of this application discovered during the screening of a large number of thorium solids that thorium hydroxide contains a relatively high proportion of water. This property can greatly increase the migration speed of decay daughters and quickly complete the migration of decay daughters from the solid phase to the liquid phase.

[0034] In addition, since the extraction process does not affect the chemical form and morphology of thorium hydroxide, the thorium hydroxide particles can be stored in the aqueous solution for a long time, and decay daughters can be repeatedly extracted from the thorium hydroxide.

[0035] At the same time, in order to increase the contact area between thorium hydroxide and the leaching solution, the present application prepares thorium hydroxide into particles to further improve the leaching efficiency.

[0036] The existing methods (Ra selective adsorption resin method and BaSO4 co-precipitation method) require long-term storage of strongly acidic Th(IV) solution. The thorium hydroxide particles stored for a long time in this application are in the form of neutral wet solids, which are easier to store on a large scale.

[0037] The extraction method of the present application is simple in operation, conducive to large-scale production, and easy to store. Most importantly, the method is highly efficient in extracting decay daughters and produces low thorium residues.

[0038] This application is applicable to the direct extraction of thorium from natural 228 Ra, from containing 228 Extraction of Th from natural thorium 224 Ra; from containing 228 Extraction of Th from natural thorium 224 Ra.

[0039] The method described in this application is used to extract radium ions (Ra 2+ ) when radium ions (Ra 2+ ) is easier to dissolve in aqueous solution and can quickly complete the migration from solid phase to liquid phase with high efficiency and low thorium residue. For example, a single step operation can be performed to obtain thorium from natural thorium. 228 / 224 Ra solution 232 The ratio of Th increased to 10 -4 ~10 -2 (w / w). The thorium hydroxide particles of the present application have a high water content, which can effectively realize the radium ion (Ra 2+ ) In the migration of the solid phase, a high efficiency leaching rate is achieved. For example, the leaching rate of the first leaching can reach 52% and above, and the leaching efficiency of multiple leaching can reach 88% and above.

[0040] This application has completed the extraction of radium ions (Ra) from solid Th compounds for the first time. 2+ ) solution can effectively reduce the storage difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 shows 232 Decay chain of Th. DETAILED DESCRIPTION

[0042] The present application is further described below with reference to examples. It should be understood that the examples are only used to further illustrate and explain the present application and are not intended to limit the present application.

[0043] Unless otherwise defined, technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art. Although methods and materials similar or identical to those described herein may be used in experiments or practical applications, the materials and methods are described herein below. In the event of a conflict, the present specification, including definitions, will prevail. In addition, the materials, methods, and examples are provided for illustrative purposes only and are not intended to be limiting. The present application is further described below with reference to specific examples, which are not intended to limit the scope of this application.

[0044] This application does not limit the source of thorium hydroxide particles; they can be purchased commercially or prepared independently. Those skilled in the art can select a method for obtaining thorium hydroxide particles based on their needs. For example, in some acquisition methods, thorium hydroxide particles can be obtained through self-preparation, such as by reacting thorium salts with alkali or concentrated ammonia to obtain thorium hydroxide particle precipitation.

[0045] In this application, the decay daughter of thorium element refers to 232 The substance obtained by Th decay is shown in Figure 1, which can be 228 Ac, 228 Ra, 228 Th,224 Ra, 220 Rn, 216 Po, 212 Pb, 212 Bi, 208 One or more of Pb. The decay daughters of thorium have different properties and applications. Those skilled in the art can select an appropriate method to extract the above decay daughters according to actual needs.

[0046] The present application provides a method for extracting decay daughters of the thorium element using thorium hydroxide particles, wherein the method comprises: a leaching step of mixing the thorium hydroxide particles with a leaching liquid so that the decay daughters of the thorium element in the thorium hydroxide particles are dissolved in the leaching liquid; and a solid-liquid separation step of separating the thorium hydroxide particles mixed with the leaching liquid from the liquid to obtain a solution containing the decay daughters of the thorium element.

[0047] In some embodiments of the present application, an aging treatment is performed before leaching, wherein the aging step includes: placing the thorium hydroxide particles for a period of time to enrich the decay daughters of the thorium element, and then leaching the aged thorium hydroxide particles after the decay daughters reach a certain concentration.

[0048] In some embodiments of the present application, the decay daughters may be directly leached without performing the aging treatment.

[0049] In this application, whether or not to perform an aging treatment is primarily determined based on practical needs. Those skilled in the art will appreciate that aging further increases the concentration of decay daughters. However, the method of this application can also effectively extract decay daughters without aging.

[0050] In this application, the inventors found that the decay daughters of thorium element are more easily dissolved in aqueous solution, while the thorium ions (Th 4+ ) is not easily soluble in aqueous solution, so the decay daughters can be selectively extracted into aqueous solution, for example, 228 Ra and / or 224 Ra is selectively extracted into aqueous solution.

[0051] In this application, the leachate refers to a solution that easily dissolves decay daughters of thorium element but does not easily dissolve thorium ions (Th) in thorium hydroxide particles. 4+ ) solution, that is, it is difficult to dissolve Th(IV) in thorium hydroxide particles.

[0052] In this application, the thorium hydroxide particles are in the form of a neutral wet solid containing a high proportion of water, which increases the migration speed of radium ions and allows for rapid migration from the solid phase to the liquid phase. Furthermore, because the extraction process does not affect the chemical form and morphology of the thorium hydroxide, the thorium hydroxide particles can be stored in aqueous solution for long periods of time, allowing for repeated extraction of radium from the thorium hydroxide particles.

[0053] In some embodiments of the present application, the decay daughters are selected from 228 Ac, 228 Ra, 224 Ra, 220 Rn, 212 Pb, 212 One or more of Bi; preferably 228 Ra and / or 224 Ra.

[0054] In this application, 228 Ra and / or 224 Compared with other decay products, Ra has a longer half-life and is easy to be purified in a more complicated process. It is generally used in medical isotopes. 212 Pb / 212 It is used independently as a key intermediate nuclide in the production of Bi.

[0055] In this application, the leaching rate refers to the ratio of decay daughters to be leached dissolved in the leaching solution after the thorium hydroxide particles are mixed with the leaching solution.

[0056] In this application, the leaching rate is calculated as follows:

[0057] 224 Ra content test method: Take an appropriate amount of sample and directly test it with a high purity germanium (HPGe) gamma spectrometer, and determine it by counting the 240.0keV energy peak. 224 Ra content;

[0058] 228 Ra content test method: Take an appropriate amount of sample and place the sample for no less than 24 hours. 228 Ra and its children 228 After Ac reaches equilibrium, it is directly measured using a high-purity germanium (HPGe) gamma spectrometer and determined by counting the 911.1keV energy peak. 228 Ac content, where 228 Ra activity is equal to 228 Ac activity.

[0059] Extraction rate: Extraction rate = Ra activity in liquid phase / (Ra activity in liquid phase + Ra activity in solid phase).

[0060] In this application, the inventors discovered that the pH of the leachate significantly affects the leaching rate. When the pH does not meet specific conditions, the leaching rate is very low or essentially zero. The pH of the leachate is between 4 and 12; for example, the pH of the leachate can be 4, 5, 6, 7, 8, 9, 10, 11, 12, or any range therebetween.

[0061] In some preferred embodiments of the present application, the pH of the leaching solution is 6 to 8. The inventors found that when the pH of the leaching solution is 6 to 8, the leaching rate is the highest. 228 Ra and / or 224 The leaching rate of Ra is the highest.

[0062] In this application, the inventors found that the choice of leaching liquid can further affect the leaching rate. For example, some insoluble salts or salts that will cause Ra precipitation cannot be used as leaching liquids, such as sodium carbonate, sodium sulfate, sodium phosphate, potassium carbonate, potassium sulfate, potassium phosphate, calcium carbonate, calcium sulfate, calcium phosphate, calcium sulfide, calcium sulfite and calcium oxalate. However, some leaching liquids can help 228 Ra and / or 224 The leaching solution is selected from one or more of water, nitrate solution, hydrochloride solution, sodium salt solution, potassium salt solution, calcium salt solution, and ammonium salt solution.

[0063] In some embodiments of the present application, the nitrate is selected from one or more of sodium nitrate, potassium nitrate, silver nitrate, magnesium nitrate, calcium nitrate, copper nitrate, iron nitrate, zinc nitrate, barium nitrate, aluminum nitrate, cesium nitrate, ammonium nitrate and ferrous nitrate.

[0064] In some embodiments of the present application, the hydrochloride is selected from one or more of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, copper chloride, ferric chloride, zinc chloride, barium chloride, aluminum chloride, cesium chloride, ammonium chloride and ferrous chloride.

[0065] In some embodiments of the present application, the sodium salt is selected from one or more of sodium chloride, sodium bicarbonate, sodium bisulfate, sodium nitrate, sodium hydrogen phosphate, sodium dihydrogen phosphate, sodium sulfide, sodium sulfite, sodium bisulfite, sodium nitrite, sodium ferrate, sodium fluoride, sodium bromide, sodium iodide, sodium formate, sodium acetate and sodium oxalate.

[0066] In some embodiments of the present application, the potassium salt is selected from one or more of potassium chloride, potassium bicarbonate, potassium bisulfate, potassium nitrate, potassium hydrogen phosphate, potassium dihydrogen phosphate, potassium sulfide, potassium sulfite, potassium bisulfite, potassium nitrite, potassium ferrate, potassium fluoride, potassium bromide, potassium iodide, potassium formate, potassium acetate and potassium oxalate.

[0067] In some embodiments of the present application, the calcium salt is selected from one or more of calcium chloride, calcium bicarbonate, calcium bisulfate, calcium nitrate, calcium hydrogen phosphate, calcium dihydrogen phosphate, calcium bisulfite, calcium nitrite, calcium bromide, calcium iodide, calcium formate and calcium acetate.

[0068] In some embodiments of the present application, the ammonium salt is selected from one or more of ammonium chloride, ammonium bicarbonate, ammonium bisulfate, ammonium nitrate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium sulfide, ammonium sulfite, ammonium bisulfite, ammonium nitrite, ammonium ferrate, ammonium fluoride, ammonium bromide, ammonium iodide, ammonium formate, ammonium acetate and ammonium oxalate.

[0069] In some preferred embodiments of the present application, the leaching solution is sodium chloride solution and / or sodium nitrate solution.

[0070] In some embodiments of the present application, the volume of the leachate is 0.5 to 20 volumes, preferably 1 to 3 volumes, relative to 1 volume of thorium hydroxide particles. For example, the volume of the leachate may be 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 volumes, or any range therebetween, relative to 1 volume of thorium hydroxide particles. Further increasing the volume of the leachate does not improve the leaching rate but also increases the cost of the raw materials.

[0071] In some embodiments of the present application, the leaching step and the solid-liquid separation step are repeated to further extract decay daughters. The present application can repeat the above steps multiple times, and the leaching rate can be further improved. Those skilled in the art can select the number of repetitions according to actual needs. Among them, the repeated leaching step and the solid-liquid separation step in the present application can be divided into multiple leaching and multiple rounds of leaching. Among them, multiple rounds of leaching are to repeat the leaching step and the solid-liquid separation step after the aging step to further extract decay daughters. Multiple leaching directly repeats the leaching step and the solid-liquid separation step to further extract decay daughters. Those skilled in the art can understand that multiple leaching can be performed in one round of leaching. Among them, the number of leaching times and rounds can be selected according to actual needs.

[0072] In the present application, multiple leaching refers to repeatedly performing the leaching step after a single aging step and then performing the solid-liquid separation step, or repeatedly performing the leaching step and then performing the solid-liquid separation step, that is, performing multiple leaching in one round of leaching.

[0073] In this application, multiple rounds of leaching refer to completing the complete aging step, leaching step, and solid-liquid separation step as one round of leaching, or completing the complete leaching step and solid-liquid separation step as one round of leaching. Multiple rounds of leaching are repeated "one round of leaching".

[0074] In some embodiments of the present application, an aging treatment is performed before the leaching step.

[0075] In some embodiments of the present application, thorium hydroxide particles are prepared as follows: a base containing hydroxide or an aqueous solution thereof is added to a solution containing thorium ions to obtain a mixed solution, the pH of the mixed solution is adjusted to 4-14, and thorium hydroxide particles are obtained after solid-liquid separation.

[0076] In the present application, the source of thorium ions is not limited, as long as it is known to those skilled in the art. For example, the solution containing thorium ions can be thorium fluoride, thorium nitrate, thorium oxalate, thorium phosphate or other solutions containing thorium ions.

[0077] In this application, the inventors discovered that the pH of the mixed solution can directly affect the formation of thorium hydroxide particles. When the pH of the mixed solution does not meet specific conditions, it is difficult to produce thorium hydroxide particles. For example, when the acidity rises to a certain level, precipitation cannot be formed. The pH of the mixed solution can be 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or any range therebetween.

[0078] In some preferred embodiments of the present application, the pH of the mixed solution is 4-10.

[0079] In some embodiments of the present application, the diameter of the thorium hydroxide particles is 100 nm-1 mm; for example, the diameter of the thorium hydroxide particles can be 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 0.01 mm, 0.1 mm, 1 mm, or any range therebetween.

[0080] In this application, there is no limitation on the source of the hydroxide-containing base, as long as it is known to those skilled in the art and meets actual needs. The hydroxide-containing base is selected from one or more of ammonia water, sodium hydroxide, calcium hydroxide, potassium hydroxide, barium hydroxide, and cesium hydroxide; preferably sodium hydroxide.

[0081] In some embodiments of the present application, the method of solid-liquid separation is not limited in any way, as long as the purpose is met. Those skilled in the art can select the required solid-liquid separation method according to actual needs, for example, one or more of filtration, centrifugal separation, decantation and natural sedimentation; preferably filtration.

[0082] In a specific embodiment of the present application, thorium hydroxide particles are prepared as follows: thorium nitrate hexahydrate is dissolved in water; sodium hydroxide solution is added dropwise, and the pH value of the solution is tested with a pH meter; samples are taken under different pH conditions, and the pH is adjusted to neutral to prepare thorium hydroxide particles.

[0083] In one embodiment of the present application, the method for extracting decay daughters from thorium hydroxide particles is as follows: sodium nitrate solution is added to the thorium hydroxide particles, mixed, and centrifuged to test the liquid phase and solid phase respectively. 224 Ra content, calculate the leaching rate.

[0084] In one embodiment of the present application, thorium nitrate hexahydrate is dissolved in water; sodium hydroxide solution is added dropwise, and the pH value of the solution is tested with a pH meter; samples are taken under different pH conditions, the pH is adjusted to neutral, and thorium hydroxide particles are prepared. After centrifugation, the liquid phase and the solid phase are tested. 224 Ra content, calculate the first leaching rate; add sodium nitrate solution to the thorium hydroxide particles, mix well, centrifuge and test the liquid phase (combined with the first leaching) and solid phase respectively. 224 Ra content, calculate the second leaching rate; add 1mL of sodium nitrate solution with pH=7 to the thorium hydroxide particles, mix well, centrifuge and test the liquid phase (combined with the first and second leaching) and solid phase respectively. 224 Ra content, calculate the third leaching rate.

[0085] The extraction process of the method of the present application is simple, which is conducive to large-scale production, and thorium hydroxide is easy to store. The method of the present application has high efficiency in extracting radium and low thorium residue. For example, a single step operation can obtain radium from natural thorium. 228 / 224 Ra solution 232 The ratio of Th increased to 10 -4 ~10 -2 (w / w).

[0086] This application is applicable to the direct extraction of thorium from natural 228 Ra, from containing 228 Extraction of Th from natural thorium 224 Ra; from containing 228 Extraction of Th from natural thorium 224 Ra.

[0087] Example

[0088] Example 1 Thorium hydroxide particles prepared under different pH conditions

[0089] 1) Dissolve 10.4 g of thorium nitrate hexahydrate in 30 mL of water;

[0090] 2) Stir, add 1.72M sodium hydroxide solution dropwise, and test the pH value of the solution with a pH meter;

[0091] 3) According to Table 1 below (Examples 1-10 differ only in the pH when preparing thorium hydroxide particles), approximately 1.5 mL of sample was taken under different pH conditions, the pH was adjusted to neutral, and thorium hydroxide particles were prepared. After centrifugation, the liquid phase and solid phase were tested. 224 Ra content, calculate the first leaching rate;

[0092] 4) Add 1 mL of sodium nitrate solution with pH = 7 to the solid, mix well, centrifuge and test the liquid phase (combined with the first leaching) and the solid phase respectively. 224 Ra content, calculate the second leaching rate;

[0093] 5) Add 1 mL of sodium nitrate solution with pH = 7 to the solid, mix well, centrifuge and test the liquid and solid phases respectively. 224 Ra content, calculate the third leaching rate;

[0094] 6) Test the combined solution 232 Th residual amount.

[0095] The only difference between Examples 2-10 and Example 1 is the pH value during the preparation of thorium hydroxide particles, as shown in Table 1. The rest is the same as in Example 1.

[0096] In this embodiment, multiple extractions are performed continuously. To more effectively reflect the overall efficiency of multiple extractions, the "second extraction rate" in the following calculation formula includes the "first extraction rate", and the "third extraction rate" includes the "second extraction rate". The extraction rate of multiple extractions is calculated as follows:

[0097] First leaching rate = Ra activity in the liquid phase after the first leaching / (Ra activity in the liquid phase after the first leaching + Ra activity in the solid phase after the first leaching)

[0098] Second leaching rate = Ra activity in the liquid phase after the second leaching / (Ra activity in the liquid phase after the first leaching + Ra activity in the solid phase after the first leaching) + first leaching rate

[0099] The third leaching rate = Ra activity in the liquid phase after the third leaching / (Ra activity in the liquid phase after the first leaching + Ra activity in the solid phase after the first leaching) + the second leaching rate

[0100] Table 1

[0101] As shown in Table 1, thorium ions cannot produce thorium hydroxide particle precipitates at a pH of <3.7, but particle precipitation occurs as the acidity decreases. After three leachings, the leaching efficiency of thorium hydroxide particles obtained at pH 4.77 to 12.2 ranged from 72% to 88%. The leaching efficiency of the thorium hydroxide particle precipitates prepared at a weakly alkaline pH (pH 10.7 and 12.2) was significantly lower in the first leaching, likely due to residual alkali in the thorium hydroxide particles. In the second and third leachings, the leaching efficiency reached similar levels to that of the thorium hydroxide particles prepared in Examples 6-7.

[0102] Examples 11-18

[0103] Example 11

[0104] 1) Weighing the thorium hydroxide particles prepared in Example 7, and adding a leachate in a ratio of 1:1 by weight. The leachate was a sodium nitrate solution. The pH of the leachate is shown in Table 2. (Examples 11-18 differ only in the pH of the leachate, where the pH is adjusted by nitric acid or sodium hydroxide);

[0105] 2) After mixing, centrifuge and test the liquid and solid phases respectively. 224 Ra content, calculate one-round leaching rate;

[0106] 3) Add the same leaching solution as in step 1) to the thorium hydroxide particles, mix well, and let it stand for about 7 days. After centrifugation, test the liquid phase and solid phase respectively. 224 Ra content, calculate the second round leaching rate.

[0107] In this embodiment, the multi-round leaching rate is calculated as follows:

[0108] First round leaching rate = Ra activity in the liquid phase after the first round of leaching / (Ra activity in the liquid phase after the first round of leaching + Ra activity in the solid phase after the first round of leaching)

[0109] Second round leaching rate = Ra activity in the liquid phase after the second round of leaching / (Ra activity in the supernatant after the second round of leaching + Ra activity in the solid phase after the second round of leaching)

[0110] The only difference between Examples 12-18 and Example 11 is the pH of the leaching solution, wherein the pH is adjusted by nitric acid or sodium hydroxide, as shown in Table 2. The rest is the same as Example 11.

[0111] Table 2

[0112] As shown in Table 2, when leaching the thorium hydroxide particles of Example 7 using leachates of different pH values, the leaching efficiency was very low under alkaline conditions (pH 10.76 and 12.08), with leaching being nearly impossible at pH 12.8. The optimal leaching efficiency was achieved at pH 6.35 and pH 6.92, suggesting that the pH range of 6-8 is the optimal leaching solution. As shown in Examples 13-18, the leaching efficiency did not decrease after two rounds of leaching.

[0113] Examples 19-34 Leaching with different salt solutions

[0114] Example 19

[0115] 1) Weigh the thorium hydroxide particles prepared in Example 7, add a leaching solution at a weight ratio of 1:1, the pH of the leaching solution being 6-7, and the leaching solution being the salt solution specified in Table 3, mix well, and allow to stand for one week;

[0116] 2) After mixing, centrifuge and test the liquid and solid phases respectively. 224 Ra content, calculate the leaching rate.

[0117] The difference between Examples 20-34 and Example 19 is only the different leaching solutions, as shown in Table 3. The rest is the same as Example 19.

[0118] Table 3

[0119] Example 35 Single-round multiple leaching of thorium hydroxide particles 228 Ra

[0120] 1) Add 2.2 mol / L sodium hydroxide solution to 1 L of a 200 g / L natural thorium nitrate solution until the pH reaches 6-8. Filter and remove approximately 1 L of the liquid to obtain approximately 0.5 L of thorium hydroxide particles.

[0121] 2) Add 0.5 L of sodium nitrate solution with a pH of 6-7 to the thorium hydroxide particles obtained in step 1), soak, and place for two years (the initial solid-liquid mixture contains 228 Ra 69327Bq);

[0122] 3) Filter to obtain a filtrate containing 228 0.5 L of Ra solution was prepared, which was recorded as solution 1-1; and thorium hydroxide particles were obtained by filtration.

[0123] 4) adding 0.5 L of sodium nitrate solution with a pH of 6-7 to the thorium hydroxide particles obtained by filtration in step 3) and soaking them;

[0124] 5) Filter to obtain a filtrate containing 228 0.5 L of Ra solution was prepared, which was recorded as solution 1-2; at the same time, thorium hydroxide particles were obtained by filtration;

[0125] 6) adding 0.5 L of sodium nitrate solution with a pH of 6-7 to the thorium hydroxide particles obtained by filtration in step 5) and soaking them;

[0126] 7) Filter to obtain a filtrate containing 228 0.5 L of Ra solution was prepared and recorded as solution 1-3.

[0127] After testing, solution 1-1 228 The total Ra content is 38347 Bq, in solution 1-2 228 The total Ra content is 14828 Bq, in solution 1-3 228 The total Ra content is 7481 Bq, the total is 60656 Bq, and the leaching rate is 87%.

[0128] Example 35 shows that the sum of the three leaching rates can reach 87%.

[0129] The calculation of the extraction rate of multiple extractions in this embodiment is as follows:

[0130] Leaching rate = (Ra activity in the liquid phase after the first leaching + Ra activity in the liquid phase after the second leaching + Ra activity in the liquid phase after the third leaching) / Ra activity in the initial solid-liquid mixture.

[0131] In the examples, the unit of activity is Bq, the same below.

[0132] Example 36 Long-term multiple-round leaching of thorium hydroxide particles 224 Ra

[0133] 1) Take 1000mL of 200g / L natural thorium nitrate (which contains about 1600Bq / g of 228 Th) solution, adding 2.2 mol / L sodium hydroxide solution to the solution until the pH of the solution reaches 6-8, centrifuging in a low-speed centrifuge, recovering the liquid, and obtaining about 400 mL of thorium hydroxide particles;

[0134] 2) adding 500 mL of a sodium nitrate solution having a pH of 6-7 to the thorium hydroxide particles obtained in step 1) and soaking them;

[0135] 3) Place for about 1 week (the initial solid-liquid mixture contains 241218Bq 224 Ra);

[0136] 4) Centrifuge in a low-speed centrifuge to recover the liquid, which is recorded as solution 2-1; and filter to obtain thorium hydroxide particles;

[0137] 5) adding 500 mL of sodium nitrate solution having a pH of 6-7 to the thorium hydroxide particles obtained in step 4) and soaking them;

[0138] 6) Place for about 1 week (the initial solid-liquid mixture contains 240678Bq 224 Ra);

[0139] 7) Centrifuge in a low-speed centrifuge to recover the liquid, which is recorded as solution 2-2; and filter to obtain thorium hydroxide particles;

[0140] 8) adding 500 mL of sodium nitrate solution with a pH of 6-7 to the thorium hydroxide particles obtained in step 7) and soaking them;

[0141] 9) Place for about 1 week (the initial solid-liquid mixture contains 220889Bq 224 Ra);

[0142] 10) Centrifuge in a low-speed centrifuge to recover the liquid, which is recorded as solution 2-3; and filter to obtain thorium hydroxide particles;

[0143] 11) adding 500 mL of sodium nitrate solution with a pH of 7 to the thorium hydroxide particles obtained in step 10) and soaking them;

[0144] After testing, solution 2-1 224 The total content of Ra is 123834Bq (the first round of leaching rate is 51%), and the solution 2-2 224 The total content of Ra is 108273 Bq (the second round of leaching rate is 45%), and the solution 2-3 224 The total Ra content is 103532 Bq (the third round leaching rate is 47%).

[0145] In this embodiment:

[0146] First round leaching rate = Ra activity in the liquid phase after the first round of leaching / Ra activity in the initial solid-liquid mixture in the first round

[0147] Second round leaching rate = Ra activity in the liquid phase after the second round of leaching / Ra activity in the initial solid-liquid mixture in the second round

[0148] The third round of leaching rate = Ra activity in the liquid phase after the third round of leaching / Ra activity in the initial solid-liquid mixture in the third round

[0149] Example 36 shows that the method of the present application can be used for multiple consecutive rounds of radium extraction, with an extraction rate of 45% to 51%, and no significant decrease in extraction efficiency is observed.

[0150] Although the present invention has been disclosed above with reference to the embodiments, they are not intended to limit the present invention. Anyone with ordinary knowledge in the art may make slight changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of the patent application attached hereto.

Claims

1. A method for extracting decay daughters of thorium, wherein the method comprises: Leaching step: mixing thorium hydroxide particles with a leachate so that decay daughters of thorium in the thorium hydroxide particles are dissolved in the leachate; Solid-liquid separation step: separating the thorium hydroxide particles mixed with the leaching liquid from the liquid to obtain a solution containing decay daughters of the thorium element.

2. The method according to claim 1, wherein Before the leaching step, an aging treatment is performed, wherein the aging step includes: placing the thorium hydroxide particles for a period of time to enrich the decay daughters of the thorium element.

3. The method according to claim 1, wherein The leaching solution is selected from one or more of water, nitrate solution, hydrochloride solution, sodium salt solution, potassium salt solution, calcium salt solution, and ammonium salt solution.

4. The method according to claim 3, wherein: The nitrate is selected from one or more of sodium nitrate, potassium nitrate, silver nitrate, magnesium nitrate, calcium nitrate, copper nitrate, iron nitrate, zinc nitrate, barium nitrate, aluminum nitrate, cesium nitrate, ammonium nitrate and ferrous nitrate; The hydrochloride is selected from one or more of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, copper chloride, ferric chloride, zinc chloride, barium chloride, aluminum chloride, cesium chloride, ammonium chloride and ferrous chloride; The sodium salt is selected from one or more of sodium chloride, sodium bicarbonate, sodium bisulfate, sodium nitrate, sodium hydrogen phosphate, sodium dihydrogen phosphate, sodium sulfide, sodium sulfite, sodium bisulfite, sodium nitrite, sodium ferrate, sodium fluoride, sodium bromide, sodium iodide, sodium formate, sodium acetate and sodium oxalate; The potassium salt is selected from one or more of potassium chloride, potassium bicarbonate, potassium bisulfate, potassium nitrate, potassium hydrogen phosphate, potassium dihydrogen phosphate, potassium sulfide, potassium sulfite, potassium bisulfite, potassium nitrite, potassium ferrate, potassium fluoride, potassium bromide, potassium iodide, potassium formate, potassium acetate and potassium oxalate; The calcium salt is selected from one or more of calcium chloride, calcium bicarbonate, calcium bisulfate, calcium nitrate, calcium hydrogen phosphate, calcium dihydrogen phosphate, calcium bisulfite, calcium nitrite, calcium bromide, calcium iodide, calcium formate and calcium acetate; The ammonium salt is selected from one or more of ammonium chloride, ammonium bicarbonate, ammonium bisulfate, ammonium nitrate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium sulfide, ammonium sulfite, ammonium bisulfite, ammonium nitrite, ammonium ferrate, ammonium fluoride, ammonium bromide, ammonium iodide, ammonium formate, ammonium acetate and ammonium oxalate.

5. The method according to claim 1, wherein The pH of the leaching solution is 4-12.

6. The method according to claim 5, wherein: The pH of the leaching solution is 6-8.

7. The method according to claim 1, wherein Compared to 1 volume of thorium hydroxide particles, the leaching solution has 0.5 to 20 volumes.

8. The method according to claim 1 or 2, wherein: Repeat the leaching step and the solid-liquid separation step to further extract decay daughters.

9. The method according to claim 1, wherein Thorium hydroxide particles are prepared as follows: A base containing hydroxide or its aqueous solution is added to a solution containing thorium ions to obtain a mixed solution, the pH of the mixed solution is adjusted to 4-14, and thorium hydroxide particles are obtained after solid-liquid separation.

10. The method according to claim 1, wherein The diameter of the thorium hydroxide particles is 100 nm-1 mm.

11. The method according to claim 9, wherein The pH of the mixed solution is 4-10.

12. The method according to claim 9, wherein The hydroxide-containing base is selected from one or more of ammonia water, sodium hydroxide, calcium hydroxide, potassium hydroxide, barium hydroxide, and cesium hydroxide.

13. The method according to claim 12, wherein: The alkali containing hydroxide is sodium hydroxide.

14. The method according to claim 1, wherein The solid-liquid separation method is selected from one or more of filtration, centrifugal separation, decantation or natural sedimentation.

15. The method according to claim 14, wherein The solid-liquid separation method is filtration.

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