A method for removing thorium and uranium from high purity rare earth compounds

Abstract

The application discloses a method for removing thorium and uranium from high-purity rare earth compounds, which comprises the following steps: dissolving the rare earth compound containing trace thorium and uranium with inorganic acid or water to adjust the element complex form and obtain a rare earth solution; using a solid adsorbent to adsorb and separate thorium and uranium in the rare earth solution to obtain a first rare earth solution and a solid adsorbent adsorbing thorium and uranium; using an eluent to stepwise resolve and separate the adsorbed thorium, uranium and a small amount of rare earth elements on the solid adsorbent to obtain a second rare earth solution and a thorium and uranium solution, and the eluted solid adsorbent is reused after regeneration; and performing precipitation, solid-liquid separation, washing and roasting treatment on the first rare earth solution and the second rare earth solution to obtain a rare earth compound with low thorium and uranium content. The effective acid radical ion concentration in the rare earth compound solution is adjusted through element form adjustment, the selective adsorption performance of the solid adsorbent to thorium and uranium is enhanced, and the removal effect is improved when the concentration difference between the rare earth compound and thorium and uranium is large.

Description

Technical Field

[0001] This invention relates to the field of rare earth preparation and purification technology, and in particular to a method for removing thorium and uranium from high-purity rare earth compounds. Background Technology

[0002] Rare earth compounds are the material basis for high-performance rare earth magnetic, optical, and electrical functional materials, and are widely used in strategic emerging industries such as national defense, petrochemicals, glass and ceramics, new energy vehicles, integrated circuits, and 5G communications.

[0003] The presence of trace amounts of thorium and uranium in rare earth compounds directly affects the performance and lifespan of downstream high-tech materials. For example, thorium can form undesirable intermetallic compounds in some magnetocaloric materials; in high-tech fields such as integrated circuits, 5G communications, and sputtering targets for displays, the presence of radioactive nuclides such as thorium and uranium can release alpha particles, easily causing soft breakdown of devices; in rare earth-doped optical glasses, the presence of thorium and uranium can cause fluorescent contamination. All of these can seriously affect the performance of the products. However, because impurity elements such as thorium and uranium are usually associated with rare earth elements and have similar physical and chemical properties, separation and purification are extremely difficult. This results in some rare earth oxides, such as lanthanum oxide and scandium oxide, exceeding the limits for radioactive nuclides, which seriously affects the performance of materials used in downstream applications. For example, domestically produced high-purity scandium oxide products contain 10ppm-100ppm of thorium and 0.1ppm-5ppm of uranium, and the radioactive elements in these products directly affect the performance and lifespan of chips made from aluminum-scandium alloy targets. Domestically produced high-purity lutetium oxide products contain 0.5ppm-20ppm of thorium and 0.1ppm-5ppm of uranium. The presence of trace radioactive elements directly affects the optical performance of downstream lutetium-based scintillation crystals.

[0004] Currently, solvent extraction remains one of the main methods for removing radioactive impurities such as thorium and uranium during the production of high-purity rare earths. However, solvent extraction has problems such as easy emulsification of the solution, large solvent loss, and easy environmental pollution caused by the organic phase. Moreover, it is difficult to remove the content of radioactive impurities such as thorium and uranium to a low level, which cannot meet the product requirements of rare earth compounds for high-tech materials.

[0005] Existing technologies disclose a method for preparing scandium oxide, which can remove thorium and uranium to a low level. However, the separation process requires the use of organic extractants, and the acidity during back-extraction / desorption is relatively high. In the subsequent precipitation control process, a large amount of precipitant is consumed to neutralize this acid. Another method for removing thorium and uranium impurities from rare earth products is disclosed, which involves preparing an adsorbent by heating and stirring 2,4-di-tert-butylphenol, sodium hydroxide, and sodium halocarboxylate, followed by acidification with an inorganic acid. This adsorbent absorbs thorium and uranium, and has a good effect on the removal of thorium. However, the removal rate of uranium is only about 86%, which is insufficient to remove uranium from high-purity rare earth products to below 0.01 ppm. Furthermore, this adsorbent has a certain degree of water solubility, and some of it will remain in the rare earth solution after adsorption.

[0006] Ion exchange technology is an early-developed, common, and effective separation technique, widely used in the nuclear industry for the enrichment and purification of thorium and uranium. Although some studies have explored the separation and enrichment of thorium and uranium from mixed solutions of rare earth elements (RE(III), uranium (U(VI), and thorium (Th(IV))) using adsorbent materials with different functional groups, these studies were conducted in systems with similar concentrations of rare earth elements and thorium / uranium. However, in practical applications, it has been found that as the concentration ratio of rare earth elements to thorium / uranium increases, the adsorption rate and selective separation coefficient of the adsorbent materials for thorium and uranium decrease significantly, failing to meet practical requirements. Summary of the Invention

[0007] The purpose of this invention is to provide a method for removing thorium and uranium from high-purity rare earth compounds. By adjusting the elemental speciation, the effective concentration of acid radicals in the rare earth compound feed solution is regulated, thereby enhancing the selective adsorption performance of the solid adsorbent for thorium and uranium. This method improves the removal efficiency of thorium and uranium when the concentration difference between the rare earth compounds and thorium / uranium is large. Through the selection of effective functional groups and the design of the adsorbent material structure, a solid adsorbent with high selectivity for trace / ultra-trace thorium and uranium in rare earth compounds is developed.

[0008] To address the aforementioned technical problems, embodiments of the present invention provide a method for removing thorium and uranium from high-purity rare earth compounds, comprising the following steps:

[0009] S1: Dissolve the rare earth compound containing trace amounts of thorium and uranium with a first inorganic acid or water, adjust the element complexation form, and obtain a rare earth solution.

[0010] S2: Use a solid adsorbent to adsorb and separate thorium and uranium elements in the rare earth solution to obtain a first rare earth solution and a solid adsorbent adsorbed with thorium and uranium elements. The solid adsorbent contains two or more functional groups from carboxylic acids, amines, amides, nitro compounds, aldehydes, ethers, pyridines, phosphoric acids, and sulfonic acids.

[0011] S3: Use an eluent to separate the thorium, uranium and a small amount of rare earth elements adsorbed on the solid adsorbent in steps to obtain a second rare earth solution and a thorium and uranium solution. The eluted solid adsorbent is regenerated and reused.

[0012] S4: The first rare earth solution and the second rare earth solution are subjected to precipitation, solid-liquid separation, washing, and calcination to obtain rare earth compounds with low thorium and uranium content.

[0013] Furthermore, the rare earth compounds containing trace amounts of uranium and thorium include one or more of the following: rare earth oxides, rare earth carbonates, rare earth nitrates, rare earth chlorides, and rare earth sulfates.

[0014] The first inorganic acid includes: hydrochloric acid, nitric acid, sulfuric acid or phosphoric acid, preferably nitric acid or sulfuric acid;

[0015] The pH of the rare earth feed solution is ≤5, preferably, the pH range is 0 to 3.5;

[0016] The rare earth ion concentration of the rare earth feed solution is 0.01 mol / L to 1.8 mol / L; preferably 0.05 mol / L to 1.0 mol / L.

[0017] Furthermore, the reagents used in the elemental speciation adjustment process include at least one of sodium nitrate, sodium sulfate, potassium nitrate, potassium sulfate, ammonium nitrate, ammonium sulfate, sulfuric acid, and nitric acid; preferably sodium sulfate, potassium sulfate, sulfuric acid, and / or nitric acid.

[0018] Wherein, when the pH of the solution after the rare earth compound is dissolved is 1 to 5, the concentration of added anions in the solution after adding the reagent during the elemental speciation adjustment process is 0.02 mol / L to 0.6 mol / L, preferably 0.1 mol / L to 0.4 mol / L; when the pH of the solution is < 1, the concentration of added anions in the solution after adding the reagent during the elemental speciation adjustment process is 0.01 mol / L to 0.5 mol / L, preferably 0.05 mol / L to 0.3 mol / L.

[0019] Furthermore, the solid adsorbent comprises two or more functional groups selected from primary amino, secondary amino, tertiary amino, quaternary amino, imino, carboxyl, phosphate, sulfonic acid, crown ether, and pyridine.

[0020] Furthermore, the solid adsorbent is a porous adsorbent material;

[0021] The solid adsorbent has a particle size of 40μm-100μm, a pore size of 10nm-100nm, and a specific surface area of ​​10m². 2 / g-500m 2 / g.

[0022] Furthermore, the adsorption and separation of thorium and uranium elements in the rare earth feed solution using a solid adsorbent includes:

[0023] Thorium and uranium in the feed solution are adsorbed and separated by a reaction device filled with a solid adsorbent. The reaction device includes: a plurality of columns connected in series, each column being filled with an equal amount of the solid adsorbent.

[0024] Optionally, the number of columnar bodies is 1-10, preferably 3-8.

[0025] Furthermore, the flow rate of the rare earth liquid through the reaction device is 0.1 BV / h to 10 BV / h, preferably 0.5 BV / h to 5 BV / h;

[0026] The adsorption temperature of the rare earth liquid as it passes through the reaction device is 10℃~90℃, preferably 20℃~50℃.

[0027] When the rare earth feed solution passes through the reaction device, the feed solution corresponding to 1 BV to 48 BV is selected as the first rare earth solution, preferably 2 BV to 20 BV.

[0028] Where BV is the cylinder volume.

[0029] Furthermore, the adsorption and separation of thorium and uranium elements in the rare earth feed solution using a solid adsorbent includes:

[0030] Thorium and uranium are adsorbed and separated by mixing and oscillating the solid adsorbent with the rare earth liquid.

[0031] The solid-liquid ratio of the solid adsorbent to the liquid feed is 0.01 g / 20 mL to 0.4 g / 20 mL;

[0032] The reaction time ranges from 1 hour to 48 hours, preferably from 12 hours to 24 hours.

[0033] Furthermore, the eluent comprises at least one of a second inorganic acid, an inorganic salt, and an organic complexing agent;

[0034] Optionally, the second inorganic acid includes at least one of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid; preferably hydrochloric acid, nitric acid, and / or sulfuric acid; with a concentration of 0.5 mol / L to 3 mol / L.

[0035] Optionally, the inorganic salt includes at least one of ammonium chloride, ammonium sulfate, sodium chloride, calcium chloride, sodium nitrate, and sodium sulfate; preferably ammonium sulfate, sodium chloride, sodium nitrate, and / or sodium sulfate; with a concentration of 0.01 mol / L to 1 mol / L.

[0036] Optionally, the organic complexing agent includes one or more of the following: citric acid, hypozinotriacetic acid, N-hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, disodium ethylenediaminetetraacetic acid, and 2-hydroxyisobutyric acid; preferably, one or more of hypozinotriacetic acid, N-hydroxyethylethylenediaminetriacetic acid, disodium ethylenediaminetetraacetic acid, and 2-hydroxyisobutyric acid, with a concentration of 0.01 mol / L to 0.5 mol / L.

[0037] The above-described technical solutions of the embodiments of the present invention have the following beneficial technical effects:

[0038] 1. By selecting effective functional groups and designing the structure of adsorbent materials (small particle size, large pore size and high specific surface area), develop solid adsorbents with high selectivity for trace / ultra-thorium and uranium in rare earth compounds;

[0039] 2. By adjusting the effective concentration of anions in the dissolved solution, the speciation distribution of different elements is controlled, ensuring that rare earth elements in the raw material solution exist as cations, while thorium and uranium exist as anions complexed with anions. This increases the difference in speciation between rare earth elements and thorium / uranium. This enhances the selective adsorption performance of the solid adsorbent for thorium and uranium, and improves the removal efficiency of thorium and uranium when the concentration difference between rare earth compounds and thorium / uranium is large.

[0040] 3. Thorium and uranium are removed through two steps: adsorption separation and elution separation, which improves the removal efficiency and rare earth recovery rate.

[0041] 4. The solid adsorbent is stable and the solid adsorption device adopts a purification and regeneration recycling process, which can be reused multiple times, so that the whole system can operate continuously and stably with low cost. Attached Figure Description

[0042] Figure 1 This is a flowchart of a method for removing thorium and uranium from high-purity rare earth compounds, provided in an embodiment of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0044] Please refer to Figure 1 This invention provides a method for removing thorium and uranium from high-purity rare earth compounds, comprising the following steps:

[0045] Step S1: Dissolve the rare earth compound containing trace amounts of thorium and uranium with a first inorganic acid or water, adjust the element complexation state, and obtain a rare earth solution.

[0046] Specifically, the rare earth compounds containing trace amounts of uranium and thorium include one or more of the following: rare earth oxides, rare earth carbonates, rare earth nitrates, rare earth chlorides, and rare earth sulfates; the first inorganic acid includes: hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid, preferably nitric acid or sulfuric acid; the pH of the rare earth solution is ≤5, preferably in the range of 0 to 3.5; the rare earth ion concentration of the rare earth solution is 0.01 mol / L to 1.8 mol / L, preferably 0.05 mol / L to 1.0 mol / L.

[0047] Furthermore, the reagents used in the elemental speciation adjustment process include at least one of sodium nitrate, sodium sulfate, potassium nitrate, potassium sulfate, ammonium nitrate, ammonium sulfate, sulfuric acid, and nitric acid; preferably sodium sulfate, potassium sulfate, sulfuric acid, and / or nitric acid.

[0048] When the pH of the solution after the rare earth compound is dissolved is 1 to 5, the concentration of added anions in the solution after adding reagents during the element speciation adjustment process is 0.02 mol / L to 0.6 mol / L, preferably 0.1 mol / L to 0.4 mol / L; when the pH of the solution is < 1, the concentration of added anions in the solution after adding reagents during the element speciation adjustment process is 0.01 mol / L to 0.5 mol / L, preferably 0.05 mol / L to 0.3 mol / L.

[0049] By adjusting the effective concentration of anions in the dissolved solution, the speciation of different elements is controlled, ensuring that rare earth elements in the raw material solution exist as cations, while thorium and uranium exist as anions complexed with anions. The reaction equation is as follows:

[0050]

[0051] Where A is an anion, x is the charge of the anion, and n is the number of possible anions.

[0052] Step S2: Thorium and uranium elements in the rare earth solution are adsorbed and separated using a solid adsorbent to obtain a first rare earth solution and a solid adsorbent containing thorium and uranium elements. The solid adsorbent contains two or more functional groups from carboxylic acids, amines, amides, nitro compounds, aldehydes, ethers, pyridines, phosphoric acids, and sulfonic acids.

[0053] Furthermore, the solid adsorbent includes two or more functional groups from primary amino, secondary amino, tertiary amino, quaternary amino, imino, carboxyl, phosphate, sulfonic acid, crown ether, and pyridine. These functional groups can adsorb thorium and uranium in the form of ion exchange or in the form of chelation to adsorb complexes formed by the combination of thorium and uranium with acid radicals. They exhibit good selective adsorption of thorium and uranium, and can selectively adsorb and remove thorium and uranium cations or their anionic complexes from rare earth feed solutions.

[0054] Step S3: Use an eluent to separate the thorium, uranium and a small amount of rare earth elements adsorbed on the solid adsorbent in a stepwise manner to obtain a second rare earth solution and a thorium and uranium solution. The eluted solid adsorbent is then regenerated and reused.

[0055] In one embodiment of the present invention, the eluent comprises at least one of a second inorganic acid, an inorganic salt, and an organic complexing agent. Optionally, the second inorganic acid comprises at least one of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid; preferably hydrochloric acid, nitric acid, and / or sulfuric acid; with a concentration of 3 mol / L to 6 mol / L. Optionally, the inorganic salt comprises at least one of ammonium chloride, ammonium sulfate, sodium chloride, calcium chloride, sodium nitrate, and sodium sulfate; preferably ammonium sulfate, sodium chloride, sodium nitrate, and / or sodium sulfate; with a concentration of 0.01 mol / L to 1 mol / L. Optionally, the organic complexing agent comprises one or more of citric acid, hypozoxytriacetic acid, N-hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, disodium ethylenediaminetetraacetate, and 2-hydroxyisobutyric acid; preferably one or more of hypozoxytriacetic acid, N-hydroxyethylethylenediaminetriacetic acid, disodium ethylenediaminetetraacetate, and 2-hydroxyisobutyric acid, with a concentration of 0.01 mol / L to 0.5 mol / L.

[0056] In another embodiment of the present invention, the eluent includes: an acidic eluent, a salt eluent, or an organic complexing eluent. The concentration range of the acidic eluent is 0.1 mol / L to 6 mol / L, the pH range of the salt eluent is 5 to 8, and the pH range of the organic complexing eluent is 2 to 10. The selection of the eluent type and its concentration allows for selective separation of rare earth elements and thorium-uranium adsorbed on the solid adsorbent during the elution process. This allows thorium-uranium to be eluted before or after the rare earth elements, or selectively eluted only the rare earth elements without eluting thorium-uranium, thereby achieving a further efficient separation during the elution process.

[0057] Specifically, by controlling the concentration range or pH value of the various types of eluents mentioned above, and using them in solid adsorbents, rare earth elements adsorbed in the solid adsorbents can be separated.

[0058] Step S4 involves precipitation, solid-liquid separation, washing, and calcination of the first and second rare earth solutions to obtain rare earth compounds with low thorium and uranium content.

[0059] Optionally, the precipitant includes at least one of oxalic acid, ammonium bicarbonate, sodium bicarbonate, sodium carbonate, sodium hydroxide, and ammonia water, preferably at least one of oxalic acid, sodium carbonate, and sodium bicarbonate.

[0060] After the above treatment process, the removal rate of thorium and uranium in rare earth compounds can reach more than 90%.

[0061] The above technical solution first detects the acidity of the dissolved rare earth compounds and adjusts the reagent dosage according to the acidity range to regulate the elemental speciation, ensuring the anion concentration of the solution falls within the range corresponding to the acidity. Then, a solid adsorbent is used to adsorb and separate thorium and uranium from the rare earth solution. At this stage, most of the thorium and uranium in the solution, after elemental speciation adjustment, can be adsorbed by the solid adsorbent. Additionally, trace amounts of rare earth compounds remain on the solid adsorbent. Therefore, an eluent is used to separate the trace rare earth compounds and thorium / uranium adsorbed on the solid adsorbent, resulting in a second rare earth solution containing rare earth compounds and the thorium / uranium remaining on the solid adsorbent. This achieves complete separation of thorium / uranium and rare earth compounds, improving the rare earth recovery rate. Finally, the first rare earth solution containing most of the rare earth compounds and the second rare earth solution containing trace amounts of rare earth compounds were subjected to precipitation, separation, washing, and calcination treatments, respectively. The contents of thorium and uranium in the obtained rare earth compounds were extremely low, thus achieving the purpose of separating thorium and uranium.

[0062] Furthermore, the synthesis of the aforementioned solid adsorbent may include: direct synthesis and / or graft polymerization. The matrix raw materials for the graft polymerization of the solid adsorbent include at least one of: polystyrene resin, polyacrylic acid resin, silica gel, silica particles, and hydroxymethyl cellulose.

[0063] The polymerization method of the adsorption functional group of the solid adsorbent with the synthetic matrix material and / or grafted matrix raw material is at least one of bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization, and sol-gel polymerization; preferably, solution polymerization, emulsion polymerization, or sol-gel polymerization. The initiator of the polymerization process is at least one of potassium persulfate, benzoyl peroxide, azobisisobutyronitrile, dimethyl azobisisobutyrate, magnetic, light, heat, electricity, and radiation; preferably, at least one of potassium persulfate, azobisisobutyronitrile, benzoyl peroxide, and radiation.

[0064] Preferably, the solid adsorbent is a porous adsorbent material; wherein the particle size of the solid adsorbent is 40μm-100μm, the pore size is 10nm-100nm, and the specific surface area is 10m². 2 / g-500m 2 / g. Specifically, the solid adsorbent is filled with large pores, allowing the liquid to fill the interior of the adsorbent. Therefore, the small particle size, large pore size, and high specific surface area of ​​the solid adsorbent can increase the contact with the solute, thereby shortening the ion mass transfer distance, improving the mass transfer efficiency, and enhancing the element separation effect. In addition, during the elution process, the appearance time and position of individual elements in the eluent are similar, which greatly reduces the tailing phenomenon and is conducive to better separation of different rare earth elements and thorium and uranium.

[0065] Specifically, step S2 involves using a solid adsorbent to adsorb and separate thorium and uranium elements in the rare earth solution, which includes the following process:

[0066] Step S21: Thorium and uranium in rare earth solution are adsorbed and separated by a reaction device filled with solid adsorbent. The reaction device includes: several columns connected in series, each column being filled with an equal amount of solid adsorbent.

[0067] Optionally, the number of columns in the reaction apparatus is 1-10, preferably 3-8.

[0068] Furthermore, the column diameter ratio of the reaction apparatus is 2:1 to 20:1, preferably 4:1 to 15:1.

[0069] Furthermore, the flow rate of the rare earth solution through the reaction device is 0.1 BV / h to 10 BV / h, preferably 0.5 BV / h to 5 BV / h; the adsorption temperature of the rare earth solution when it passes through the reaction device is 10℃ to 90℃, preferably 20℃ to 50℃; the first rare earth solution is selected from the 1st BV to 48th BV of the solution when it passes through the reaction device, preferably 2BV to 20BV; where BV is the column volume. The elution process selectively separates rare earth elements and thorium-uranium adsorbed on the solid adsorbent. By selecting the eluent system and the eluent elution environment (input flow rate, concentration, temperature, etc.), thorium-uranium can be eluted before or after the rare earth elements, or only the rare earth elements can be selectively eluted without eluting thorium-uranium, thus achieving a further separation of rare earth elements and thorium-uranium during the elution process. Specifically, the flow rate of the eluent through the reaction device is 0.1 BV / h to 5 BV / h, preferably 0.2 BV / h to 3 BV / h; the elution temperature of the eluent through the reaction device is 10℃ to 90℃, preferably 20℃ to 50℃; and the feed solution corresponding to 1 BV to 60 BV of the eluent is selected as the second rare earth solution, preferably 2 BV to 40 BV.

[0070] Further, step S2 involves using a solid adsorbent to adsorb and separate thorium and uranium elements in the rare earth solution, including:

[0071] In step S22, thorium and uranium are adsorbed and separated by mixing and oscillating a solid adsorbent with a rare earth liquid.

[0072] During the above-mentioned mixing and oscillation process, the solid-liquid ratio of the solid adsorbent and the rare earth solution is 0.01 g / 20 mL to 0.4 g / 20 mL; the mixing and oscillation is a constant temperature oscillation, with the oscillation temperature ranging from 10 °C to 80 °C, preferably from 25 °C to 45 °C; the oscillation time ranges from 1 h to 48 h, preferably from 12 h to 24 h.

[0073] Optionally, after obtaining the first and second rare earth solutions, the solid adsorbent in the reaction apparatus is regenerated to enable it to adsorb again. The regenerator used may include one or more of the following: sodium chloride, sodium hydroxide, sodium carbonate, ammonia, hydrochloric acid, and sulfuric acid. The concentration of the regenerator is between 0.1 mol / L and 6 mol / L.

[0074] Through the above technical solution, by adjusting the elemental form, the thorium and uranium content in rare earth compounds can be reduced to below 0.2 ppm, with a removal rate of >90%. This meets the low-content requirements for radioactive thorium and uranium in rare earth compounds used in high-end special fields such as aluminum-scandium alloy target chip manufacturing, scintillation crystals, and high-power laser fibers. Compared to the removal effect of existing technologies, the thorium and uranium removal capacity of this invention is significantly improved.

[0075] The process of removing thorium and uranium from high-purity rare earth compounds described above will be further described below with several comparative examples and embodiments:

[0076] Example 1

[0077] The raw material used was commercially available 3N5 grade scandium oxide, which contained 52 ppm thorium and 13 ppm uranium. First, the scandium oxide sample was dissolved in sulfuric acid; the scandium concentration in the solution was adjusted to 5 g / L and the pH to 3.0; sodium sulfate was added to adjust the elemental complexation speciation, bringing the added sodium sulfate concentration in the system to 0.15 mol / L; a solid adsorbent containing amino and phosphate groups was used to adsorb and separate the rare earth elements from the elemental speciation-adjusted solution; the flow rate of the rare earth solution was 2 BV / h, the adsorption temperature was 45℃, and the purified solution volume was 18 BV, yielding the first rare earth solution. A disodium ethylenediaminetetraacetate solution was used as the eluent to perform stepwise analysis of the thorium, uranium, and trace rare earth elements adsorbed on the solid adsorbent; the concentration of the disodium ethylenediaminetetraacetate solution was 0.05 mol / L, and the collected eluent was the second rare earth solution. The first and second rare earth solutions were precipitated with oxalic acid, and after solid-liquid separation, washing, and calcination, scandium oxide products after thorium and uranium removal were obtained. The scandium oxide obtained from the first and second rare earth solutions was analyzed for impurities using glow discharge mass spectrometry (GDMS). The results showed that the thorium content in the scandium oxide purified from the first rare earth solution was 0.25 ppm, with a removal rate of 99.50%; the uranium content was 0.06 ppm, with a removal rate of 99.54%. The scandium oxide purified from the second rare earth solution showed a thorium content of 0.27 ppm, with a removal rate of 99.48% relative to the raw material; and a uranium content of 0.05 ppm, with a removal rate of 99.61% relative to the raw material.

[0078] Example 2

[0079] The raw material used was commercially available 4N-grade scandium oxide, which contained 11 ppm thorium and 0.5 ppm uranium. First, the scandium oxide sample was dissolved in sulfuric acid; the scandium concentration in the solution was adjusted to 5 g / L and the pH to 3.0; sodium sulfate was added to adjust the elemental complexation speciation, bringing the added sodium sulfate concentration in the system to 0.15 mol / L; a solid adsorbent containing amino and phosphate groups was used to adsorb and separate the rare earth elements from the elemental speciation-adjusted solution; the flow rate of the rare earth solution was 2 BV / h, the adsorption temperature was 45℃, and the purified solution volume was 18 BV, yielding the first rare earth solution. A disodium ethylenediaminetetraacetate solution was used as the eluent to perform stepwise analysis of the thorium, uranium, and trace rare earth elements adsorbed on the solid adsorbent; the concentration of the disodium ethylenediaminetetraacetate solution was 0.05 mol / L, and the collected eluent was the second rare earth solution. The first and second rare earth solutions were precipitated with oxalic acid, and after solid-liquid separation, washing, and calcination, scandium oxide products after thorium and uranium removal were obtained. The scandium oxide obtained from the first and second rare earth solutions was analyzed for impurity content using glow discharge mass spectrometry (GDMS). The results showed that the thorium content in the scandium oxide purified from the first rare earth solution was 0.12 ppm, with a removal rate of 98.91%; the uranium content was <0.01 ppm, with a removal rate >98%. The scandium oxide purified from the second rare earth solution had a thorium content of 0.15 ppm, with a removal rate of 98.64% relative to the raw material; the uranium content was <0.01 ppm, with a removal rate >98% relative to the raw material.

[0080] Example 3

[0081] The raw material used was commercially available 3N-grade scandium oxide, which contained 213 ppm thorium and 55 ppm uranium. First, the scandium oxide sample was dissolved in sulfuric acid; the scandium concentration in the solution was adjusted to 5 g / L and the pH to 3.0; sodium sulfate was added to adjust the elemental complexation speciation, bringing the added sodium sulfate concentration in the system to 0.15 mol / L; a solid adsorbent containing amino and phosphate groups was used to adsorb and separate the rare earth elements from the elemental speciation-adjusted solution; the flow rate of the rare earth solution was 2 BV / h, the adsorption temperature was 45℃, and the purified solution volume was 18 BV, yielding the first rare earth solution. A disodium ethylenediaminetetraacetate solution was used as the eluent to perform stepwise analysis of the thorium, uranium, and trace rare earth elements adsorbed on the solid adsorbent; the concentration of the disodium ethylenediaminetetraacetate solution was 0.05 mol / L, and the collected eluent was the second rare earth solution. The first and second rare earth solutions were precipitated with oxalic acid, and after solid-liquid separation, washing, and calcination, scandium oxide products after thorium and uranium removal were obtained. The scandium oxide obtained from the first and second rare earth solutions was analyzed for impurities using glow discharge mass spectrometry (GDMS). The results showed that the thorium content in the scandium oxide purified from the first rare earth solution was 0.85 ppm, with a removal rate of 99.60%; the uranium content was 0.20 ppm, with a removal rate of 99.64%. The scandium oxide purified from the second rare earth solution showed a thorium content of 0.90 ppm, with a removal rate of 99.58% relative to the raw material; and a uranium content of 0.17 ppm, with a removal rate of 99.69% relative to the raw material.

[0082] Example 4-17

[0083] The rare earth compounds containing trace amounts of thorium and uranium in the following examples are commercially available 4N-grade scandium products, which contain 23 ppm of thorium and 4 ppm of uranium.

[0084] Specifically, Examples 4-17 are the specific implementation methods of steps S1 and S2 in the thorium removal method of the present invention.

[0085] Scandium compounds are dissolved in a first inorganic acid or water to obtain scandium sulfate or scandium nitrate. The rare earth concentration is adjusted and the pH of the feed solution is controlled. The elemental speciation is adjusted using sulfuric acid, sodium sulfate, or nitric acid. The rare earth feed solution is passed through the top of a column containing amino and phosphate functional groups of solid adsorbent at a certain flow rate for adsorption. The adsorbed effluent is collected. After precipitation and calcination, scandium oxide with low thorium and uranium content is obtained, with a thorium and uranium removal rate of 90% to 99.5%.

[0086] Examples 18-23

[0087] The rare earth compounds containing trace amounts of thorium and uranium in the following examples are commercially available lanthanum compound products, which contain 18 ppm of thorium and 4.7 ppm of uranium.

[0088] Specifically, Examples 18-23 are the specific implementation methods of steps S1 and S2 in the thorium removal method of the present invention.

[0089] Lanthanum sulfate was obtained by dissolving lanthanum compounds in sulfuric acid or water. The rare earth concentration was adjusted, and the elemental speciation was adjusted using sodium sulfate. The rare earth solution was passed through the top of a column containing amino and acetic acid functional groups at a flow rate of 3 BV / h for adsorption. The adsorbed effluent was collected. After precipitation and calcination, lanthanum oxide with low thorium and uranium content was obtained, with a thorium and uranium removal rate of 95% to 99.5%.

[0090] Examples 24-28

[0091] The rare earth compounds containing trace amounts of thorium and uranium in the following examples are commercially available europium compound products, which contain 25 ppm of thorium and 3.8 ppm of uranium.

[0092] Specifically, Examples 24-28 are the specific implementation methods of steps S1 and S2 in the thorium removal method of the present invention.

[0093] Europium nitrate was obtained by dissolving europium compounds in nitric acid or water. The rare earth concentration was adjusted and the pH of the feed solution was controlled at 2.0. Nitric acid was used to adjust the elemental speciation. The rare earth feed solution was passed through the top of a column containing a solid adsorbent with thiol, imino, and crown ether functional groups at a certain flow rate for adsorption. The adsorbed effluent was collected. After precipitation and calcination, europium oxide with low thorium and uranium content was obtained, with a thorium and uranium removal rate of 95% to 99.5%.

[0094] Examples 29-32

[0095] The rare earth compounds containing trace amounts of thorium and uranium in the following examples are commercially available lutetium compounds, which contain 30 ppm of thorium and 5.6 ppm of uranium.

[0096] Specifically, Examples 29-32 are the specific implementation methods of steps S1 and S2 in the thorium removal method of the present invention.

[0097] Lutene nitrate was obtained by dissolving lutetium compounds in nitric acid or water. The rare earth concentration was adjusted and the pH of the feed solution was controlled. The elemental speciation was adjusted using nitric acid. The rare earth feed solution was passed through the top of a column containing a solid adsorbent with thiol, imino, and crown ether functional groups at a flow rate of 0.5 BV / h for adsorption. The adsorbed effluent was collected. After precipitation and calcination, lutetium oxide with low thorium and uranium content was obtained, with a thorium and uranium removal rate of 95%–99.5%.

[0098] Examples 33-46

[0099] Specifically, Examples 33-46 are specific implementations of step S3 in the thorium removal method of the present invention.

[0100] Using sulfuric acid or disodium ethylenediaminetetraacetate solution as eluent, the eluent is passed through the top of a column containing amino and phosphate functional groups of a solid adsorbent after scandium adsorption for analysis. The eluent is collected in a distributed manner. After precipitation and calcination, scandium oxide with low thorium and uranium content is obtained, with a thorium and uranium removal rate of 92% to 99.5%.

[0101] Examples 47-52

[0102] Specifically, Examples 47-52 are specific implementations of step S3 in the thorium removal method of the present invention.

[0103] Using N-hydroxyethyl ethylenediamine triacetic acid solution as the eluent, the eluent was passed through the top of a column containing amino and acetic acid functional groups of a solid adsorbent after lanthanum adsorption for analysis. The eluent was collected in a distributed manner. After precipitation and calcination, lanthanum oxide with low thorium and uranium content was obtained, with a thorium and uranium removal rate of 97% to 99.5%.

[0104] Examples 53-57

[0105] Specifically, Examples 53-57 are specific implementations of step S3 in the thorium removal method of the present invention.

[0106] Using diethylenetriaminepentaacetic acid solution as the eluent, the eluent was passed through the top of a column containing a solid adsorbent with thiol, imino, and crown ether functional groups after europium adsorption for elution. The eluent was collected in a distributed manner. After precipitation and calcination, europium oxide with low thorium and uranium content was obtained, with a thorium and uranium removal rate of 92% to 99.5%.

[0107] Examples 58-61

[0108] Specifically, Examples 58-61 are specific implementations of step S3 in the thorium removal method of the present invention.

[0109] Using diethylenetriaminepentaacetic acid solution as the eluent, the eluent was passed through the top of a column containing thiol, imine, and crown ether functional groups of a solid adsorbent after lutetium adsorption for analysis. The eluent was collected in a distributed manner. After precipitation and calcination, lutetium oxide with low thorium and uranium content was obtained, with a thorium and uranium removal rate of 92%–99.5%.

[0110] Example 62

[0111] A novel chelating resin was prepared by grafting glycidyl methacrylate onto the surface of polystyrene resin via surface-initiated atom transfer radical polymerization, followed by reaction with iminodiacetic acid. The polymerization time was 15 h and the grafting amount was 50%.

[0112] Example 63

[0113] Activated silica gel was obtained by acidifying silica gel particles with hydrochloric acid for 24 hours. Bis(4-pyridine)amine, activated silica gel, and ethylene glycol dimethacrylate were dissolved in dimethylformamide and reacted with ammonium persulfate as an initiator for 24 hours to obtain a novel solid adsorbent material.

[0114] Example 64

[0115] The raw material used was commercially available lanthanum oxide, which contained 8 ppm thorium and 0.6 ppm uranium. First, the lanthanum oxide sample was dissolved in sulfuric acid; the lanthanum concentration in the solution was adjusted to 10 g / L and the pH to 1.0; sodium sulfate was added to adjust the elemental complexation speciation, bringing the added sodium sulfate concentration in the system to 0.15 mol / L; a solid adsorbent containing amino and acetic acid groups was used to adsorb and separate the rare earth elements in the solution after elemental speciation adjustment; wherein the solid adsorbent containing amino and acetic acid groups had a particle size of 52 μm, a pore size of 85 nm, and a specific surface area of ​​400 nm. 2 / g; the flow rate of the rare earth feed solution was 3 BV / h, the adsorption temperature was 45℃, and the purification feed solution volume was 15 BV, yielding the first rare earth solution. Thorium, uranium, and trace rare earth elements adsorbed on the solid adsorbent were subjected to stepwise desorption using N-hydroxyethylethylenediaminetriacetic acid solution at a concentration of 0.05 mol / L. The collected eluent was the second rare earth solution. The first and second rare earth solutions were precipitated separately using oxalic acid. After solid-liquid separation, washing, and calcination, lanthanum oxide product with thorium and uranium removed was obtained. The impurity content of lanthanum oxide obtained from the first and second rare earth solutions was detected by glow discharge mass spectrometry (GDMS). The results showed that the thorium content in the lanthanum oxide purified from the first rare earth solution was 0.08 ppm, with a removal rate of 99%; the uranium content was <0.01 ppm, with a removal rate >98%. The thorium content in the lanthanum oxide purified from the second rare earth solution was 0.06 ppm, with a removal rate of 99.25% relative to the raw material; the uranium content was <0.01 ppm, with a removal rate >98% relative to the raw material.

[0116] Example 65

[0117] The raw material used was commercially available lanthanum oxide, which contained 8 ppm thorium and 0.6 ppm uranium. First, the lanthanum oxide sample was dissolved in sulfuric acid; the lanthanum concentration in the solution was adjusted to 10 g / L and the pH to 1.0; sodium sulfate was added to adjust the elemental complexation speciation, bringing the added sodium sulfate concentration in the system to 0.15 mol / L; a solid adsorbent containing amino and acetic acid groups was used to adsorb and separate the rare earth elements in the solution after elemental speciation adjustment; wherein the solid adsorbent containing amino and acetic acid groups had a particle size of 63 μm, a pore size of 76 nm, and a specific surface area of ​​236 nm. 2 / g; the flow rate of the rare earth feed solution was 3 BV / h, the adsorption temperature was 45℃, and the purification feed solution volume was 15 BV, yielding the first rare earth solution. Thorium, uranium, and trace rare earth elements adsorbed on the solid adsorbent were subjected to stepwise desorption using N-hydroxyethylethylenediaminetriacetic acid solution at a concentration of 0.05 mol / L. The collected eluent was the second rare earth solution. The first and second rare earth solutions were precipitated separately using oxalic acid. After solid-liquid separation, washing, and calcination, lanthanum oxide product with thorium and uranium removed was obtained. The impurity content of lanthanum oxide obtained from the first and second rare earth solutions was determined by glow discharge mass spectrometry (GDMS). The results showed that the thorium content in the lanthanum oxide purified from the first rare earth solution was 0.10 ppm, with a removal rate of 98.75%; the uranium content was <0.01 ppm, with a removal rate >98%. The thorium content in the lanthanum oxide purified from the second rare earth solution was 0.08 ppm, with a removal rate of 99% relative to the raw material; the uranium content was <0.01 ppm, with a removal rate >98% relative to the raw material.

[0118] Example 66

[0119] The raw material used was commercially available lanthanum oxide, which contained 8 ppm thorium and 0.6 ppm uranium. First, the lanthanum oxide sample was dissolved in sulfuric acid; the lanthanum concentration in the solution was adjusted to 10 g / L and the pH to 1.0; sodium sulfate was added to adjust the elemental complexation speciation, bringing the added sodium sulfate concentration in the system to 0.15 mol / L; a solid adsorbent containing amino and acetic acid groups was used to adsorb and separate the rare earth elements in the solution after elemental speciation adjustment; wherein the solid adsorbent containing amino and acetic acid groups had a particle size of 82 μm, a pore size of 51 nm, and a specific surface area of ​​158 μm. 2 / g; the flow rate of the rare earth feed solution was 3 BV / h, the adsorption temperature was 45℃, and the purification feed solution volume was 15 BV, yielding the first rare earth solution. Thorium, uranium, and trace rare earth elements adsorbed on the solid adsorbent were subjected to stepwise desorption using N-hydroxyethylethylenediaminetriacetic acid solution at a concentration of 0.05 mol / L. The collected eluent was the second rare earth solution. The first and second rare earth solutions were precipitated separately using oxalic acid. After solid-liquid separation, washing, and calcination, lanthanum oxide product with thorium and uranium removed was obtained. The impurity content of lanthanum oxide obtained from the first and second rare earth solutions was determined by glow discharge mass spectrometry (GDMS). The results showed that the thorium content in the lanthanum oxide purified from the first rare earth solution was 0.12 ppm, with a removal rate of 98.5%; the uranium content was <0.01 ppm, with a removal rate >98%. The thorium content in the lanthanum oxide purified from the second rare earth solution was 0.10 ppm, with a removal rate of 98.75% relative to the raw material; the uranium content was <0.01 ppm, with a removal rate >98% relative to the raw material.

[0120] Example 67

[0121] The raw material used was commercially available lanthanum oxide, which contained 8 ppm thorium and 0.6 ppm uranium. First, the lanthanum oxide sample was dissolved in sulfuric acid; the lanthanum concentration in the solution was adjusted to 10 g / L and the pH to 1.0; sodium sulfate was added to adjust the elemental complexation speciation, bringing the added sodium sulfate concentration in the system to 0.15 mol / L; a solid adsorbent containing amino and acetic acid groups was used to adsorb and separate the rare earth elements in the solution after elemental speciation adjustment; wherein the solid adsorbent containing amino and acetic acid groups had a particle size of 150 μm, a pore size of 20 nm, and a specific surface area of ​​56 m². 2 / g; the flow rate of the rare earth feed solution was 3 BV / h, the adsorption temperature was 45℃, and the purification feed solution volume was 15 BV, yielding the first rare earth solution. Thorium, uranium, and trace rare earth elements adsorbed on the solid adsorbent were subjected to stepwise desorption using N-hydroxyethylethylenediaminetriacetic acid solution at a concentration of 0.05 mol / L. The collected eluent was the second rare earth solution. The first and second rare earth solutions were precipitated separately using oxalic acid. After solid-liquid separation, washing, and calcination, lanthanum oxide product with thorium and uranium removed was obtained. The impurity content of lanthanum oxide obtained from the first and second rare earth solutions was determined by glow discharge mass spectrometry (GDMS). The results showed that the thorium content in the lanthanum oxide purified from the first rare earth solution was 0.55 ppm, with a removal rate of 93.12%; the uranium content was 0.04 ppm, with a removal rate of 93.33%. The thorium content in the lanthanum oxide purified from the second rare earth solution was 0.48 ppm, with a removal rate of 94% relative to the raw material; the uranium content was 0.05 ppm, with a removal rate of 91.67% relative to the raw material.

[0122] For details of the specific parameter changes in the above embodiments, please refer to Tables 1 and 2.

[0123] Table 1

[0124]

[0125]

[0126] Table 2

[0127]

[0128]

[0129] As shown in Table 1 above regarding the removal effects of thorium and uranium, this invention, compared to existing removal methods, exhibits superior selective adsorption and removal rates for thorium and uranium impurities, and demonstrates excellent removal efficiency for trace thorium and uranium impurities in high-purity rare earth compounds. The process of this invention can remove thorium and uranium impurities from rare earth compounds to a low level, while still maintaining excellent selective adsorption for trace thorium and uranium in rare earth compounds. The method of this invention is relatively simple, using a small amount of acid and alkali. Through adsorption and elution steps, almost all rare earth elements are recovered, resulting in a high recovery rate with minimal loss or waste of rare earth elements. The elution process separates thorium and uranium, yielding a high-purity thorium- and uranium-containing solution that can be used for the recycling of thorium and uranium.

[0130] This invention aims to protect a method for removing thorium and uranium from high-purity rare earth compounds, comprising the following steps: S1: Dissolving a rare earth compound containing trace amounts of thorium and uranium with an inorganic acid or water, adjusting the elemental complexation morphology to obtain a rare earth solution; S2: Using a solid adsorbent to adsorb and separate the thorium and uranium elements in the rare earth solution, obtaining a first rare earth solution and a solid adsorbent adsorbed with thorium and uranium elements, wherein the solid adsorbent contains two or more functional groups selected from carboxylic acids, amines, amides, nitro compounds, aldehydes, ethers, pyridines, phosphoric acids, and sulfonic acids; S3: Using an eluent to perform stepwise analytical separation of the thorium, uranium, and a small amount of rare earth elements adsorbed on the solid adsorbent, obtaining a second rare earth solution and a thorium and uranium solution, wherein the eluted solid adsorbent is regenerated and reused; S4: Performing precipitation, solid-liquid separation, washing, and calcination treatment on the first and second rare earth solutions to obtain a rare earth compound with low thorium and uranium content. The above technical solution has the following effects:

[0131] 1. By selecting effective functional groups and designing the structure of adsorbent materials (small particle size, large pore size and high specific surface area), develop solid adsorbents with high selectivity for trace / ultra-thorium and uranium in rare earth compounds;

[0132] 2. By adjusting the effective concentration of anions in the dissolved solution, the speciation distribution of different elements is controlled, ensuring that rare earth elements in the raw material solution exist as cations, while thorium and uranium exist as anions complexed with anions. This increases the difference in speciation between rare earth elements and thorium and uranium. This enhances the selective adsorption performance of the solid adsorbent for thorium and uranium, and improves the removal efficiency of thorium and uranium when the concentration difference between rare earth compounds and thorium / uranium is large.

[0133] 3. Thorium and uranium are removed through two steps: adsorption separation and elution separation, which improves the removal efficiency and rare earth recovery rate.

[0134] 4. The solid adsorbent is stable and the solid adsorption device adopts a cleanable recycling process, which can be reused multiple times, so that the whole system can operate continuously and stably with low cost.

[0135] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for removing thorium and uranium from high-purity rare earth compounds, characterized in that, Includes the following steps: S1: Dissolve the rare earth compound containing trace amounts of thorium and uranium with a first inorganic acid or water, adjust the element complexation form, and obtain a rare earth solution. S2: Use a solid adsorbent to adsorb and separate thorium and uranium elements in the rare earth solution to obtain a first rare earth solution and a solid adsorbent adsorbed with thorium and uranium elements. The solid adsorbent contains two or more functional groups from carboxylic acids, amines, amides, nitro compounds, aldehydes, ethers, pyridines, phosphoric acids, and sulfonic acids. S3: Use an eluent to separate the thorium, uranium and a small amount of rare earth elements adsorbed on the solid adsorbent in steps to obtain a second rare earth solution and a thorium and uranium solution. The eluted solid adsorbent is regenerated and reused. S4: The first rare earth solution and the second rare earth solution are subjected to precipitation, solid-liquid separation, washing, and calcination to obtain rare earth compounds with low thorium and uranium content; The reagents used to adjust the complexation form of the elements include at least one of sodium nitrate, sodium sulfate, potassium nitrate, potassium sulfate, ammonium nitrate, ammonium sulfate, sulfuric acid, and nitric acid. When the pH of the solution after dissolving the rare earth compound is 1-5, the concentration of added anions in the solution after adjusting the elemental complexation form and adding the reagent is 0.02 mol / L-0.6 mol / L. When the pH of the solution is <1, the concentration of added anions in the solution after adjusting the elemental complexation form and adding the reagent is 0.01 mol / L-0.5 mol / L.

2. The method for removing thorium and uranium from high-purity rare earth compounds according to claim 1, characterized in that, The rare earth compounds containing trace amounts of uranium and thorium include one or more of the following: rare earth oxides, rare earth carbonates, rare earth nitrates, rare earth chlorides, and rare earth sulfates. The first inorganic acid includes: hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid; The pH of the rare earth feed solution is ≤5; The rare earth ion concentration of the rare earth feed solution is 0.01 mol / L to 1.8 mol / L.

3. The method for removing thorium and uranium from high-purity rare earth compounds according to claim 2, characterized in that, The first inorganic acid includes: nitric acid or sulfuric acid; The pH range of the rare earth feed solution is 0~3.5; The rare earth ion concentration of the rare earth feed solution is 0.05 mol / L to 1.0 mol / L.

4. The method for removing thorium and uranium from high-purity rare earth compounds according to claim 1, characterized in that, The reagents used to adjust the complexation form of the elements are sodium sulfate, potassium sulfate, sulfuric acid and / or nitric acid; Wherein, when the pH of the solution after the rare earth compound is dissolved is 1 to 5, the concentration of added anions in the solution after adjusting the element complexation form and adding the reagent is 0.1 mol / L to 0.4 mol / L; when the pH of the solution is < 1, the concentration of added anions in the solution after adjusting the element complexation form and adding the reagent is 0.05 mol / L to 0.3 mol / L.

5. The method for removing thorium and uranium from high-purity rare earth compounds according to claim 1, characterized in that, The solid adsorbent comprises two or more functional groups selected from primary amino, secondary amino, tertiary amino, quaternary amino, imino, carboxyl, phosphate, sulfonic acid, crown ether, and pyridine.

6. The method for removing thorium and uranium from high-purity rare earth compounds according to claim 1, characterized in that, The solid adsorbent is a porous adsorbent material; The solid adsorbent has a particle size of 40 μm-100 μm, a pore size of 10 nm-100 nm, and a specific surface area of ​​10 m². 2 / g -500 m 2 / g.

7. The method for removing thorium and uranium from high-purity rare earth compounds according to claim 1, characterized in that, The adsorption and separation of thorium and uranium elements in the rare earth feed solution using a solid adsorbent includes: Thorium and uranium in the feed solution are adsorbed and separated by a reaction device filled with a solid adsorbent. The reaction device includes a plurality of columns connected in series, each column being filled with an equal amount of the solid adsorbent.

8. The method for removing thorium and uranium from high-purity rare earth compounds according to claim 7, characterized in that, The number of columnar bodies is 1-10.

9. The method for removing thorium and uranium from high-purity rare earth compounds according to claim 8, characterized in that, The number of columnar bodies is 3-8.

10. The method for removing thorium and uranium from high-purity rare earth compounds according to claim 7, characterized in that, The flow rate of the rare earth liquid through the reaction device is 0.1 BV / h ~ 10 BV / h; The adsorption temperature of the rare earth solution as it passes through the reaction device is 10 ℃~90 ℃; When the rare earth feed solution passes through the reaction device, the feed solution corresponding to the 1st BV to 48th BV is selected as the first rare earth solution; Where BV is the cylinder volume.

11. The method for removing thorium and uranium from high-purity rare earth compounds according to claim 10, characterized in that, The flow rate of the rare earth liquid through the reaction device is 0.5 BV / h to 5 BV / h; The adsorption temperature of the rare earth solution as it passes through the reaction device is 20 ℃~50 ℃; When the rare earth feed solution passes through the reaction device, the feed solution corresponding to the 2nd BV to 20th BV is selected as the first rare earth solution.

12. The method for removing thorium and uranium from high-purity rare earth compounds according to claim 1, characterized in that, The adsorption and separation of thorium and uranium elements in the rare earth feed solution using a solid adsorbent includes: Thorium and uranium are adsorbed and separated by mixing and oscillating the solid adsorbent with the rare earth liquid. The solid-liquid ratio of the solid adsorbent to the liquid feed is 0.01 g / 20 mL ~ 0.4 g / 20 mL; The reaction time ranges from 1 h to 48 h.

13. The method for removing thorium and uranium from high-purity rare earth compounds according to claim 12, characterized in that, The reaction time ranges from 12 h to 24 h.

14. The method for removing thorium and uranium from high-purity rare earth compounds according to claim 1, characterized in that, The eluent comprises at least one of a second inorganic acid, an inorganic salt, and an organic complexing agent; The second inorganic acid includes at least one of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid; The inorganic salt includes at least one of ammonium chloride, ammonium sulfate, sodium chloride, calcium chloride, sodium nitrate, and sodium sulfate. The organic complexing agent includes one or more of the following: citric acid, hypozinotriacetic acid, N-hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, disodium ethylenediaminetetraacetic acid, and 2-hydroxyisobutyric acid.

15. The method for removing thorium and uranium from high-purity rare earth compounds according to claim 14, characterized in that, The second inorganic acid includes hydrochloric acid, nitric acid, and / or sulfuric acid, with a concentration of 0.5 mol / L to 3 mol / L; The inorganic salts include: ammonium sulfate, sodium chloride, sodium nitrate and / or sodium sulfate, with a concentration of 0.01 mol / L to 1 mol / L; The organic complexing agent includes one or more of the following: hyponitrotriacetic acid, N-hydroxyethylethylenediaminetriacetic acid, disodium ethylenediaminetetraacetic acid, and 2-hydroxyisobutyric acid, with a concentration of 0.01 mol / L to 0.5 mol / L.

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