Method for extracting decay daughter of thorium

Abstract

The present application provides a method for extracting a decay daughter of thorium. The method comprises: a leaching step, involving: mixing a thorium solid with a leaching solution to enable the decay daughter of thorium in the thorium solid to be dissolved in the leaching solution; and a solid-liquid separation step, involving: separating the thorium solid mixed with the leaching solution from a liquid, so as to obtain a solution containing the decay daughter of thorium. The method involves a simple operation process of extraction, and is beneficial for large-scale production; and thorium oxide is easy to store.

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 elements, and more particularly to a method for extracting decay daughters through thorium solids. 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 decay 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 recovering Th(IV) include barium co-precipitation and selective radium resin extraction. Each method has its strengths and weaknesses. For example, barium co-precipitation suffers from low single-shot recovery efficiency and high waste volume, while selective radium resin extraction 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 the thorium solid and the leachate so that the decay daughters of the thorium element in the thorium solid are dissolved in the leachate;

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

[0009] In some embodiments, the thorium solid is thorium oxide or a solid containing thorium oxide.

[0010] In some embodiments, the pH of the leachate is <13.

[0011] In some embodiments, the pH of the leachate is 0-7.

[0012] In some embodiments, the leaching solution is selected from one or more of water, an aqueous solution containing an acid, an aqueous solution containing an alkali, a soluble salt solution, and a soluble organic ligand solution.

[0013] In some embodiments, the acid is selected from one or more of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, and phosphoric acid;

[0014] The base is selected from one or more of ammonia, sodium hydroxide, calcium hydroxide and potassium hydroxide;

[0015] The soluble salt is selected from one or more of nitrate, hydrochloride, sodium salt, potassium salt, calcium salt and ammonium salt;

[0016] The soluble organic ligand is selected from aminotriacetic acid (or NTA) or its salt, ethylenediaminetetraacetic acid (or EDTA) or its salt, diethylenetriaminepentaacetic acid (or DTPA) or its salt, preferably one or more of ethylenediaminetetraacetic acid or its salt.

[0017] In some embodiments, the leachate is selected from a mixture of an aqueous acid solution and a soluble salt solution.

[0018] 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;

[0019] 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;

[0020] 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;

[0021] 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;

[0022] 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;

[0023] 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.

[0024] In some embodiments, the volume of the leachate is 0.2 to 20 volumes relative to 1 volume of thorium solid.

[0025] In some embodiments, the volume of the leachate is 0.5 to 3 volumes relative to 1 volume of thorium solid.

[0026] In some embodiments, the leaching step and the solid-liquid separation step are repeated to further extract decay daughters.

[0027] In some embodiments, the thorium solid is pre-treated before leaching so that the particle size of the thorium solid is less than 1 mm.

[0028] In some embodiments, the thorium solid is pre-treated before leaching so that the particle size of the thorium solid is less than 1000 nm.

[0029] In some embodiments, the thorium solid is heated before leaching, and the heating temperature is greater than 100°C.

[0030] In some embodiments, the heating temperature is greater than 800°C.

[0031] In some embodiments, the solid-liquid separation method is selected from one or more of filtration, centrifugal separation, decantation and natural sedimentation.

[0032] In some embodiments, the solid-liquid separation is performed by filtration.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] Existing technologies include Ra / Th separation methods that utilize special crown ether resins to selectively adsorb Ra(II) while excluding Th(IV) (Ra selective adsorption resin method), or methods that utilize co-precipitation of Ba(II) and Ra(II) from Th(IV) (BaSO4 co-precipitation method). These existing methods each have their strengths and weaknesses. For example, the barium co-precipitation method produces a high amount of waste liquid per single 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.

[0035] In order to solve these problems, the applicant of this application has made a lot of attempts and innovations, and concluded from practice that the decay daughters of thorium are more easily dissolved in aqueous solution, while the thorium ions (Th 4+ ) has a poor solubility, allowing decay daughters to be selectively extracted into aqueous solutions. This principle differs from existing technologies. The natural thorium in this application is in the form of a neutral wet solid or dry solid powder, which is convenient for storage and long-term decay to produce decay daughters.

[0036] Furthermore, the applicant of this application found that thorium oxide has high density and high thorium content (the measured bulk density is about 3-5 g / cm 3 , containing 87.8% thorium, w / w) solid, this feature can make the storage volume of the present application reach 0.2-0.3m when storing a large amount of thorium oxide for a long time 3 / t, which is very conducive to the aging step in large-scale production that requires long-term and large-scale storage.

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

[0038] The present invention is used to extract radium ions (Ra 2+ ) when radium ions (Ra 2+ ) is more easily dissolved in aqueous solution, with high efficiency and low thorium residue. For example, a single-step operation can be used to obtain natural thorium 228 / 224 Ra solution 232 The Th content is reduced to <0.1ppm, that is, the Ra / Th ratio is increased to 10-4 ~10 -2 (w / w), to achieve a high extraction rate, for example, the extraction rate of the first extraction can reach 57% or more, and the extraction efficiency of multiple extractions can reach 68% or more.

[0039] This application has achieved the first extraction of decay daughters, such as radium ions (Ra) from solid Th compounds. 2+ ) solution can effectively reduce the difficulty of storage; this application can realize the storage of dry thorium compounds. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 shows 232 Decay chain of Th. DETAILED DESCRIPTION

[0041] 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.

[0042] 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.

[0043] In this application, thorium solid refers to a solid material containing thorium oxide. This application does not limit its source and can be obtained commercially or prepared independently. Those skilled in the art can choose a method for obtaining thorium solid based on their needs. In this application, the leaching method utilizes the migration and dissolution of decay products in the solid phase into the leaching solution. Therefore, as long as the following conditions are met: 1) the thorium solid is insoluble, 2) the decay products of the thorium element can effectively migrate, and 3) there is a leaching solution that can dissolve the decay products, leaching can be achieved.

[0044] The "thorium solid" described in this article is represented by thorium oxide, but other solid structures containing insoluble thorium oxide (such as thorium oxide-loaded microparticles, thorium oxide microparticles doped with other metals, etc.) can be leached using the method of this application as long as they meet the above three conditions.

[0045] In some embodiments of the present application, the thorium solid is thorium oxide or a solid containing thorium oxide.

[0046] 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 228Ac, 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.

[0047] The present application provides a method for extracting decay daughters of thorium element from thorium solid, which includes a leaching step: mixing the thorium solid and a leaching liquid so that the decay daughters of thorium element in the thorium solid are dissolved in the leaching liquid; and a solid-liquid separation step: separating the thorium solid mixed with the leaching liquid from the liquid to obtain a solution containing the decay daughters of thorium element.

[0048] In some embodiments of the present application, an aging treatment is performed before leaching, wherein the aging step includes: the thorium hydroxide particles are placed for a period of time to enrich the decay daughters of the thorium element, and after the decay daughters reach a certain concentration, the aged thorium hydroxide particles are leached.

[0049] In some embodiments of the present application, the decay daughters may be directly leached without performing the aging treatment.

[0050] 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.

[0051] 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.

[0052] In this application, the leachate refers to a solution that easily dissolves decay daughters of thorium element but is not easy to dissolve thorium ions (Th in thorium oxide). 4+ ) solution, that is, it is not easy to dissolve Th(IV) in thorium oxide.

[0053] The thorium oxide of this application is high-density and high-thorium content (the measured bulk density is 3-5g / cm 3, containing 87.8% thorium, w / w) solid, which can make the storage volume of the application reach 0.2-0.3m when storing a large amount of thorium oxide for a long time 3 / t.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] The extraction rate is calculated as follows:

[0058] 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;

[0059] 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.

[0060] Extraction rate: Extraction rate = Ra activity in liquid phase / (Ra activity in liquid phase + Ra activity in solid phase).

[0061] In the present 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 substantially zero. The pH of the leachate is <13. For example, the pH of the leachate can be -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or any range therebetween.

[0062] In some embodiments of the present application, the pH of the leaching solution is preferably 0 to 7. The inventors found that when the pH of the leaching solution is 0 to 7, the leaching rate is the highest, and 228 Ra and / or 224 The leaching rate of Ra is the highest.

[0063] 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, an aqueous solution containing an acid, an aqueous solution containing an alkali, a soluble salt solution, and a soluble organic ligand solution.

[0064] In some embodiments of the present application, the acid is selected from one or more of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, and phosphoric acid.

[0065] In some embodiments of the present application, the base is selected from one or more of ammonia water, sodium hydroxide, calcium hydroxide, and potassium hydroxide.

[0066] In some embodiments of the present application, the soluble salt is selected from one or more of nitrate, hydrochloride, sodium salt, potassium salt, calcium salt, and ammonium salt.

[0067] In some embodiments of the present application, the soluble organic ligand is selected from aminotriacetic acid (or NTA) or its salt, ethylenediaminetetraacetic acid (or EDTA) or its salt, diethylenetriaminepentaacetic acid (or DTPA) or its salt, preferably one or more of ethylenediaminetetraacetic acid or its salt.

[0068] In some embodiments of the present application, the soluble organic ligand is ethylenediaminetetraacetic acid or a salt thereof.

[0069] In some embodiments of the present application, the leachate is selected from a mixture of an acid-containing aqueous solution and a soluble salt solution.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] In some embodiments of the present application, the leachate volume is 0.2 to 20 volumes, preferably 0.5 to 3 volumes, relative to 1 volume of thorium solid. For example, relative to 1 volume of thorium solid, the leachate volume may be 0.5 volumes, 1 volume, 2 volumes, 3 volumes, 4 volumes, 5 volumes, 6 volumes, 7 volumes, 8 volumes, 9 volumes, 10 volumes, 11 volumes, 12 volumes, 13 volumes, 14 volumes, 15 volumes, 16 volumes, 17 volumes, 18 volumes, 19 volumes, 20 volumes, or any range therebetween. Further increases in the volume of the leachate not only fail to improve the leaching rate but also increase the cost of the raw materials.

[0077] 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, which can further improve the leaching rate. 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.

[0078] In the present application, multiple leaching refers to repeatedly performing the "solid-liquid separation step after the leaching step" after one formation step, or repeatedly performing the "solid-liquid separation step after the leaching step", that is, performing multiple leaching in one round of leaching.

[0079] 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".

[0080] In some embodiments of the present application, the thorium solid is pretreated before leaching so that the particle size of the thorium solid is less than 1 mm, preferably less than 1000 nm; for example, the particle size of the thorium solid can be 1 mm, 0.1 mm, 0.01 mm, 1000 nm, 950 nm, 900 nm, 850 nm, 800 nm, 750 nm, 700 nm, 650 nm, 600 nm, 550 nm, 500 nm, 400 nm, 300 nm or any range therebetween.

[0081] The inventors of the present application have discovered that treating the particle size of thorium solids before leaching to make the particle size smaller is beneficial to improving the leaching rate.

[0082] In this application, the particle size of nano-scale thorium solids is measured using a nano-laser particle size analyzer. Specifically, a small amount of solid suspension is diluted and dispersed with about 1000 times 1% surfactant solution, and the particle size is measured using a nano-laser particle size analyzer.

[0083] The particle size of micron-sized thorium solids is measured using a microscope built-in measurement method. The maximum diameter of no less than 50 representative particles is tested and the average value is calculated.

[0084] In this application, any method for reducing the particle size of the thorium solid is used, as long as the desired particle size is achieved. For example, grinding, crushing, or other methods that can reduce the particle size of the thorium solid can be used. Those skilled in the art can select an appropriate method based on actual needs, as long as the desired particle size is achieved.

[0085] In some embodiments of the present application, the thorium solid is heat treated before leaching, and the heating temperature is greater than 100°C, preferably, the heating temperature is greater than 800°C; for example, the heating temperature can be 100°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C, 1500°C, 1550°C, 1600°C or any range therebetween.

[0086] In this application, the heating method of the thorium solid is not limited. For example, it can be hydrothermal, sand bath, electric heating, electric furnace heating, tubular furnace heating, or muffle furnace heating. Those skilled in the art can select an appropriate method based on actual needs, as long as the desired temperature is achieved.

[0087] In some embodiments of the present application, the thorium solid may be subjected to pretreatment and heating treatment before leaching.

[0088] In some embodiments of the present application, the solid-liquid separation method is selected from one or more of filtration, centrifugal separation, decantation and natural sedimentation; preferably filtration.

[0089] In the present application, after solid-liquid separation, a recovered liquid is obtained, the pH of the recovered liquid is adjusted to 6-7 with sodium hydroxide, and the precipitate is removed by centrifugation to further remove Th.

[0090] In some embodiments of the present application, the method comprises the following steps:

[0091] (1) Allowing the solid thorium compound to sit for a period of time until the thorium decays and produces radium;

[0092] (2) adding a leaching solution to the thorium solid compound and stirring thoroughly; the volume of the leaching solution is 0.2 to 20 times (w / w) the volume of the thorium solid compound, preferably 0.5 to 3 times;

[0093] (3) removing the liquid to obtain a solution containing radium;

[0094] (4) Repeat steps (1) to (3) to extract radium repeatedly.

[0095] In some embodiments of the present application, in step (3), after the liquid is removed, the leaching solution can be immediately added again, and steps (2) to (3) can be re-executed, and the leaching solutions can be combined to improve the single leaching rate.

[0096] In some embodiments of the present application, leaching under neutral conditions or adjusting the pH to neutral after leaching can reduce the Th content to <100 ppm, that is, adding acid or alkali to adjust to neutral after step 4.

[0097] The above steps may involve a variety of tests and calculations, including:

[0098] 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;

[0099] 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.

[0100] Extraction rate: Extraction rate = Ra activity in liquid phase / (Ra activity in liquid phase + Ra activity in solid phase)

[0101] (Nanoscale) particle size test: Take a small amount of solid suspension and dilute it with about 1000 times 1% surfactant solution to disperse it, and measure the particle size with a nano laser particle size analyzer.

[0102] The particle size of thorium solids (micrometer level) is measured using the built-in measurement method of a microscope. The maximum diameter of no less than 50 representative particles is tested and the average value is calculated.

[0103] Solid volume: Visually estimate in a graduated centrifuge bottle.

[0104] Examples 1-4

[0105] 1) Add 200 g of water to 200 g of commercially available thorium oxide and mix thoroughly;

[0106] 2) The particle size before grinding was 1080 nm. The particles were continuously ground using a sand mill. The particle sizes after grinding are shown in Table 1. The difference between Examples 1-4 was only in the particle size after grinding. Samples were taken every 1-2 hours, for a total of 4 time points.

[0107] 3) Test particle size;

[0108] 4) Adjust the acidity of the solution to about 0.1 mol / L with 6 mol / L nitric acid solution, mix well, and then leave to soak for at least 2 hours;

[0109] 5) Centrifugation, testing liquid and solid phase 224 The content of Ra is used to calculate the leaching rate.

[0110] Table 1

[0111] It can be seen from Table 1 that as the particle size of thorium oxide decreases, 224 The leaching rate of Ra is improved.

[0112] Example 5-22

[0113] 1) Take about 60g of thorium oxide, put it into a crucible, place it in a muffle furnace, and calcine it at a specified temperature. At the specified calcination time and calcination temperature, take out a small amount of sample for testing;

[0114] 2) Take about 1g of sample and add it to 1mL of leaching solution;

[0115] The only difference between Examples 5-22 is the calcination time, calcination temperature and leaching solution, as shown in Table 2.

[0116] 3) After mixing, let it stand for at least 2 hours;

[0117] 4) Centrifugation, testing liquid and solid phase 224 The Ra content is used to calculate the first leaching rate.

[0118] In Examples 7-10, steps (1)-(4) were repeated once to obtain a second leaching rate.

[0119] 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:

[0120] 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)

[0121] 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

[0122] Table 2

[0123] It can be seen from Table 2 that under the same conditions, different leaching solutions will affect 224 The extraction rate of Ra. When the leaching liquid is nitric acid, 224 The extraction rate of Ra is high. Secondary leaching can improve the overall leaching efficiency.

[0124] Examples 23-54

[0125] 1) About 100 g of thorium oxide was added to 100 g of water and mixed, and then placed in a grinding jar for grinding. After 8 hours, the mixture was removed. The particle size after grinding was about 650 nm, and the solution after grinding was weakly alkaline. Except for Example 23, Examples 24-54 were first neutralized with a small amount of nitric acid to neutrality.

[0126] 2) Taking out 1.5 mL of the mixed solution, adding the specified leachate in Table 3 below, so that the leachate in the solution reaches the acidity or pH specified in Table 3 below, and mixing and standing for at least 2 hours; wherein, the only difference between Examples 23-54 is: the leachate solute and the leachate acidity or pH, as shown in Table 3;

[0127] 3) Centrifugation, testing liquid and solid phase 224 The content of Ra is used to calculate the leaching rate;

[0128] If it is necessary to further test the secondary leaching rate in the current round of testing, add 1.5mL of leaching solution, mix well and let it stand for no less than 2h; centrifuge and test the liquid and solid phases. 224 The content of Ra is used to calculate the leaching rate;

[0129] If multiple rounds of testing are required, add 1.5 mL of the extract after the current round of testing, mix well, and place for 7-14 days. Centrifuge and test the liquid and solid phases. 224 The content of Ra is used to calculate the leaching rate.

[0130] In this embodiment, the multi-round leaching rate is calculated as follows:

[0131] 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)

[0132] Second round leaching rate = Ra activity in the liquid phase after the second round of leaching / (Ra activity in the liquid phase after the second round of leaching + Ra activity in the solid phase after the second round of leaching)

[0133] The third round of leaching rate = Ra activity in the liquid phase after the third round of leaching / (Ra activity in the liquid phase after the third round of leaching + Ra activity in the solid phase after the third round of leaching)

[0134] Fourth round leaching rate = Ra activity in the liquid phase after the fourth round of leaching / (Ra activity in the liquid phase after the fourth round of leaching + Ra activity in the solid phase after the fourth round of leaching)

[0135] Table 3

[0136] As shown in Table 3, leaching is possible at pH ≤ 13. The leaching rate is higher under acidic or neutral conditions. A wide range of leaching solutions, as long as they do not cause Ra precipitation (such as sodium carbonate), can achieve excellent leaching rates. Furthermore, as shown in Examples 34-36, multiple leaching cycles can improve the leaching rate.

[0137] Example 55

[0138] 1) Take about 800g of natural thorium oxide, add 1200g of water, and test the content of 224 Ra is about 1.69E+6Bq, and after 8h of grinding in a ball mill, the particle size after grinding is about 650nm;

[0139] 2) Add approximately 15 mL of 10 M nitric acid to adjust the pH to 1-2;

[0140] 3) Stir thoroughly, take a small amount of liquid and centrifuge to test the liquid and solid phases. 224 The content of Ra was calculated and the leaching rate was 27.58%;

[0141] 4) The solid-liquid separation was achieved by low-speed centrifugation, and a total of about 1000 mL of liquid was recovered. The Th content in the recovered liquid was tested. 4+ The content is 92ppm;

[0142] 5) adjusting the pH of the recovered liquid in step 4) to 6-7 with sodium hydroxide, and centrifuging to remove the precipitate;

[0143] 6) Then, about 1000 mL of 0.1 M sodium nitrate was added to the precipitate solid in step 5), and the pH was adjusted to 6-7 with a small amount of sodium hydroxide;

[0144] 7) Stir thoroughly, take a small amount of liquid and centrifuge to test the liquid and solid phases. 224 The content of Ra, the combined two leaching rates were 42.54%;

[0145] 8) The solid-liquid separation was achieved by low-speed centrifugation, and a total of about 1000 mL of liquid was recovered. The Th content in the recovered liquid was tested. 4+ Content <0.1ppm;

[0146] 9) The total solid storage volume is approximately 220 mL;

[0147] 10) After the solid of step 9) is left for another 10 days, it is regenerated. 224 Ra;

[0148] 11) Add approximately 1000 mL of 0.1 M sodium nitrate solution to the solid after 10 days of storage and mix thoroughly;

[0149] 12) Stir thoroughly, take a small amount of liquid and centrifuge to test the liquid and solid phases. 224 The content of Ra was calculated and the leaching rate was 30.89%;

[0150] 13) The solid-liquid separation was achieved by low-speed centrifugation, and a total of about 1000 mL of liquid was recovered. The Th content in the recovered liquid was tested. 4+ Content <0.1ppm;

[0151] 14) Then, about 1000 mL of 0.1 M sodium nitrate was added to the precipitate solid in step 13);

[0152] 15) Stir thoroughly, take a small amount of liquid and centrifuge to test the liquid and solid phases. 224 The content of Ra was calculated, and the leaching rate was 18.48%, and the combined leaching rate of the two times was 43.67%;

[0153] 16) The solid-liquid separation was achieved by low-speed centrifugation, and a total of about 1000 mL of liquid was recovered. The Th content in the recovered liquid was tested. 4+ Content <0.1ppm;

[0154] 17) The total solid storage volume is approximately 220 mL.

[0155] As can be seen from Example 55, the processing volume of Example 55 was expanded to 800g. Compared with the small-scale test (e.g., 100g), it can also obtain a similar high leaching rate, indicating that the method of the present application can expand the processing volume. As can be seen from steps 9) and 17), the reserve volume can reach 0.2-0.3L / kg. As can be seen from steps 8) and 16), under neutral conditions, Th 4+ The content is <0.1ppm. It can be seen from steps 3) and 7), steps 12) and 15) that multiple leaching cycles can improve the leaching rate. It can be seen from steps 3) and 12), steps 7) and 15) that multiple leaching cycles can improve the leaching rate.

[0156] In the examples, the unit of activity is Bq, the same below.

[0157] Example 56

[0158] 1) Take about 200g of natural thorium oxide, put it into a muffle furnace, calcine it at 1000℃ for 4h, and test its content. 224 Ra is 4.41E+5Bq;

[0159] 2) Add 200 mL of sodium nitrate solution with a pH of 2;

[0160] 3) Stir thoroughly, separate the solid and liquid by filtration, and wash the solid with about 100 mL of pH 2 solution. 224 Ra is 1.97E+5Bq, and the extraction rate is 44.5%, of which Th 4+ The content is 19ppm;

[0161] 4) Add about 2 mL of 2M sodium hydroxide to the recovered leachate to adjust the pH to neutral to produce thorium hydroxide precipitate. Remove the thorium hydroxide precipitate by filtration and test the liquid phase for the content of thorium hydroxide. 224 Ra is 2.01E+5Bq, and the leaching rate is 45.74%, of which Th 4+ Content <0.1ppm.

[0162] As can be seen from Example 56, the processing volume of Example 56 was expanded to 200g. Compared with the small-scale test (e.g., 60g), it can also obtain a similar high leaching rate, indicating that the method of the present application can expand the processing volume. This Example 56 can be leached under acidic conditions. As can be seen from steps 3) and 4), the solution Th after leaching under acidic conditions is 4+ The content is high, and after adding alkali to adjust to neutral Th 4+ Content <0.1ppm.

[0163] Example 57

[0164] 1) Take about 450g of natural thorium oxide, put it into a muffle furnace, calcine it at 1450℃ for 2h, and test its content. 224 Ra and 228 Ra are 9.45E+5Bq and 2.03E+5Bq respectively;

[0165] 2) Add 450 mL of nitric acid solution with a pH of 2;

[0166] 3) Stir thoroughly and separate the solid and liquid by centrifugation to obtain the liquid phase containing 224 Ra is 6.62E+5Bq, 228 Ra is 1.35E+5Bq, and the leaching rates are 70.0% and 66.6%, respectively;

[0167] 4) Wash the solid with about 250 mL of pH 2 solution, stir thoroughly, and separate the solid and liquid by centrifugation to obtain a liquid phase containing 224 Ra is 1.34E+5Bq and 228 Ra is 3.03E+4Bq.

[0168] After the above two extractions, the total 224 The Ra extraction rate was 74.2%, 228 The Ra extraction rate was 81.6%.

[0169] It can be seen from Example 57 that this Example 57 can be leached after high temperature calcination, and can be leached at the same time 228 Ra and 224 Ra, and 224 Ra and 228 The extraction efficiency of Ra was >80%.

[0170] 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 the thorium solid and the leachate so that the decay daughters of the thorium element in the thorium solid are dissolved in the leachate; Solid-liquid separation step: separating the thorium solid 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 The thorium solid is thorium oxide or a solid containing thorium oxide.

3. The method according to claim 1, wherein The pH of the extract is less than 13.

4. The method according to claim 3, wherein: The pH of the leaching solution is 0-7.

5. The method according to claim 1, wherein The leaching solution is selected from one or more of water, an aqueous solution containing an acid, an aqueous solution containing an alkali, a soluble salt solution, and a soluble organic ligand solution.

6. The method according to claim 5, wherein: The acid is selected from one or more of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, and phosphoric acid; The base is selected from one or more of ammonia, sodium hydroxide, calcium hydroxide and potassium hydroxide; The soluble salt is selected from one or more of nitrate, hydrochloride, sodium salt, potassium salt, calcium salt and ammonium salt; The soluble organic ligand is selected from one or more of aminotriacetic acid or its salt, ethylenediaminetetraacetic acid or its salt, and diethylenetriaminepentaacetic acid or its salt.

7. The method according to claim 6, 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.

8. The method according to claim 1, wherein Compared to 1 volume of thorium solid, the leaching solution has 0.2 to 20 volumes.

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

10. The method according to claim 1, wherein The thorium solid is pre-treated before leaching so that the particle size of the thorium solid is less than 1 mm.

11. The method according to claim 1, wherein The thorium solid is heated before leaching, with the heating temperature being greater than 100°C.

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

13. The method according to claim 12, wherein: The solid-liquid separation method is filtration.

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