Method for recovering high-purity uranium

Abstract

The present invention relates to a recovery method capable of recovering high-purity uranium from uranium-containing soil, minerals, and the like and, more specifically, to a method for recovering high-purity uranium, wherein the method is highly excellent in terms of environment due to less discharge of environmental pollutants in a uranium recovery process and is very advantageous in terms of process efficiency due to the recovery of high-purity uranium through a simple process.

Description

Method for recovering high-purity uranium

[0001] The present invention relates to a recovery method capable of recovering uranium with high purity from uranium-containing soil and minerals, and more specifically, to a high-purity uranium recovery method that is excellent in environmental aspects because it emits less environmental pollutants during the uranium recovery process, and at the same time, it is excellent in process efficiency because it can recover uranium with high purity through a simple process.

[0002]

[0003] The price of uranium, currently used as nuclear fuel, has risen significantly. With the increase in nuclear reactors under construction and planned around the world, demand for uranium is expected to surge, further driving up prices. Accordingly, active development of technologies to recover uranium is underway, and research is also underway to recover trace amounts of uranium from seawater, a resource known for its infinite potential.

[0004] Facilities and areas that handle uranium, such as uranium mines and uranium conversion facilities, generate uranium-contaminated soil. Furthermore, uranium-containing soils exist in uranium-contaminated or uranium-containing soil. Uranium can leach from contaminated or uranium-containing soil, flowing into surrounding groundwater or being incorporated into crops, potentially posing a radiological threat to humans. Residents in these areas are also exposed to higher levels of natural radiation compared to other areas. Even low-level natural radiation, if exposed long-term, can increase the risk of developing diseases such as lung cancer, bone marrow suppression, and immune system suppression. Therefore, developing technologies to remove uranium from uranium-containing or contaminated soil using low-concentration acid solutions to prevent radiation exposure and to simplify the separation of high-purity uranium from the resulting uranium-containing waste liquid would significantly contribute to the protection of local residents and the social and economic security of resources.

[0005] In general, uranium is recovered from minerals mined from uranium mines through extraction using a strong acid of high concentration (2-4M) and a separation process using an organic solvent. However, in order to recover relatively high contents of uranium, a complex separation step is required in the mineral extraction solution, so it is economically very disadvantageous to apply this process to minerals or soil containing low concentrations of uranium. In addition, even if uranium is recovered through this process, there is a problem that uranium cannot be recovered with high purity.

[0006] In addition, there were also environmentally unfavorable problems, such as the generation of a large amount of acid waste liquid in the complex separation process and the generation of a large amount of hazardous liquid waste that is difficult to process using organic solvents.

[0007] Therefore, there is an urgent need for research on a high-purity uranium recovery method that can be applied to minerals and soils containing low concentrations of uranium, while recovering uranium with a much higher purity than before, and at the same time minimizing the generation of waste such as organic waste liquid, thus being excellent from an environmental perspective.

[0008]

[0009] [Prior Art Literature]

[0010] [Patent Document]

[0011] (Patent Document 1) Korean Patent No. 10-1290151

[0012]

[0013] The present invention was designed to solve the above problems, and the purpose of the present invention is to provide a method for recovering high-purity uranium, which is excellent in economic terms because it can economically recover uranium even when uranium is contained in a low concentration in a uranium-containing material, and also can recover uranium with a very high purity, and at the same time, the generation of waste such as organic waste liquid is minimized during the uranium recovery process, so that it is also excellent in environmental terms.

[0014]

[0015] In order to solve the above-described problem, the present invention,

[0016] A method for recovering high-purity uranium is provided, comprising: (1) a step of adding an acid solution to a uranium-containing material to extract uranium and form a uranium extraction solution; and (2) a step of adding hydrogen peroxide and a basic hydrogen nitride compound to the uranium extraction solution to precipitate uranium and form uranium peroxide hydrate.

[0017] Additionally, the basic hydrogen nitride compound may be at least one selected from the group consisting of hydrazine (N2H4) and ammonia water (NH4OH).

[0018] In addition, the step (2) may include: (2-1) a step of forming a mixture by mixing hydrogen peroxide into the uranium extraction solution; and (2-2) a step of forming a uranium peroxide hydrate by adding a basic hydrogen nitride compound while adjusting the pH of the mixture so that it does not exceed 4.

[0019] Additionally, the concentration of hydrogen peroxide in the mixture in step (2-1) may be 0.5 to 5 M.

[0020] In addition, in the above step (2-2), the basic hydrogen nitride compound is a 1 to 5 M solution at 10 to 50 ml / m 2 -It may be administered at a rate of -min.

[0021] Additionally, the acid solution of step (1) may contain a strong acid.

[0022] In addition, the acid solution of step (1) may include at least one selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, and hydrofluoric acid.

[0023] Additionally, the acid solution of step (1) may contain sulfuric acid.

[0024] Additionally, the concentration of the acid solution in step (1) may be 0.025 to 0.2 M.

[0025] Additionally, the above step (1) may be performed at a temperature of 10 to 50˚C.

[0026] Additionally, the uranium content of the uranium-containing material of step (1) may be 500 to 10,000 ppm.

[0027] In addition, a method for recovering high-purity uranium, characterized in that the uranium-containing material is soil or mineral having an average particle diameter in the range of 10 μm to 2 mm.

[0028] In addition, the step (1) above may include: (1-1) a step of adding an acid solution to a uranium-containing material and then measuring the pH to obtain a graph of pH over time; and (1-2) a step of determining the end point of extraction based on the graph.

[0029] In addition, after the step (2), a step (3) of separating and recovering the uranium peroxide hydrate of the step (2) using a filter may be further performed.

[0030] In addition, the present invention provides a method for recovering high-purity uranium, comprising the steps of (1) adding an acid solution to a uranium-containing material to extract uranium to form a uranium extraction solution; and (2) adding hydrogen peroxide and a precipitation additive to the uranium extraction solution to precipitate uranium to form uranium peroxide hydrate, wherein the precipitation additive reacts with uranium and hydrogen peroxide, and the Gibbs free energy of the reaction is -350 kcal or less.

[0031] In addition, the present invention provides uranium peroxide hydrate recovered through the above-described method in order to solve the above-described problem.

[0032]

[0033] Through the present invention, uranium can be recovered economically even when uranium is contained in a low concentration in a uranium-containing material, so that it is excellent in economic terms, and uranium can be recovered with a very high purity, and at the same time, the generation of waste such as organic waste liquid is minimized during the uranium recovery process, so that a method for recovering high-purity uranium can be provided that is also excellent in environmental terms.

[0034]

[0035] Figure 1 shows the change in pH over time after a sulfuric acid solution was added to a uranium-containing material in Example 1.

[0036] Figure 2 is a photograph of a metal filter used to obtain uranium peroxide hydrate in Example 1.

[0037] Figure 3 is a photograph showing the sequential occurrence of precipitation after hydrazine was added to the uranium extraction solution in Example 1.

[0038] Figure 4 shows the results of XRD analysis of the sediment in Example 1 compared with the XRD spectrum of UO4.

[0039]

[0040] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0041]

[0042] As described above, conventional uranium recovery methods use very high concentrations of strong acid, which makes it economically disadvantageous to use them on soils containing low concentrations of uranium, or because they extract a large amount of impurities together, making it impossible to extract uranium with high purity. In addition, during the uranium recovery process, a large amount of environmentally unfriendly waste, such as organic waste liquid, is generated, which presents many problems from an environmental perspective.

[0043] Accordingly, the present invention provides a method for recovering high-purity uranium, comprising the steps of (1) adding an acid solution to a uranium-containing material to extract uranium and form a uranium extraction solution; and (2) adding hydrogen peroxide and a basic hydrogen nitride compound to the uranium extraction solution to precipitate uranium and form uranium peroxide hydrate, thereby solving the above-described problem. Through this, uranium can be recovered economically even when uranium is contained in a low concentration in a uranium-containing material, so that it is excellent in economic terms, and uranium can be recovered with a very high purity, and at the same time, the generation of waste such as organic waste liquid is minimized during the uranium recovery process, so that a method for recovering high-purity uranium is also excellent in environmental terms.

[0044]

[0045] First, as step (1), an acid solution is added to a uranium-containing material to extract uranium, thereby forming a uranium extraction solution.

[0046] More specifically, when an acid solution is added to a uranium-containing material, uranium is converted to UO2. 2+ It is extracted in the form of. At this time, uranium contained in the uranium-containing material can exist in various forms of compounds and is not limited to a specific form. In addition, during the uranium extraction process, H contained in the acid solution + It reacts with uranium and is consumed.

[0047]

[0048] More specifically, the concentration of the acid solution may be 0.025 to 0.2 M.

[0049] Traditionally, strong acids were used in very high concentrations, such as 2 to 4 M, to extract uranium. This high concentration of acid generated during the uranium extraction process resulted in a large amount of acid waste, requiring additional processing steps. This was disadvantageous from an efficiency standpoint, and the resulting waste was also environmentally detrimental. Furthermore, the use of such highly concentrated acids resulted in the extraction of large quantities of non-uranium materials along with the uranium, making it difficult to recover uranium with high purity. Furthermore, the use of such highly concentrated acid solutions made it impossible to precisely measure pH, making it difficult to gauge the progress of the uranium extraction reaction and, consequently, to accurately determine the end point of the process. Consequently, the extraction process became excessively prolonged, increasing process costs, or was shortened, resulting in inadequate uranium extraction, leading to inefficient processes.

[0050] Accordingly, the high-purity uranium recovery method according to the present invention solves the above-mentioned problem by extracting uranium using an acid solution with a concentration in the range of 0.025 to 0.2 M. When uranium is extracted with an acid solution, uranium is extracted as UO2 as described above. 2+ It is extracted in the form of H +As ions are consumed, the pH rises. Therefore, when the pH no longer increases during the uranium extraction step, the uranium extraction is complete. At this time, when the concentration of the acid solution is used in the range of 0.025 to 0.2 M in the extraction step as in the present invention, the pH will have a value of 0.6 or higher, and this range corresponds to a range in which the pH can be measured with sufficient precision even with a conventional pH measuring device. Therefore, the recovery method according to the present invention can be much superior in terms of process efficiency compared to the conventional method because it is possible to clearly measure the point in time when uranium extraction is complete in the uranium extraction step.

[0051] In addition, since the generation of acid waste liquid is reduced by using a low concentration acid solution, the process cost required to treat it can be saved, so it is excellent in terms of process efficiency, and it is also excellent in terms of the environment due to the reduction in waste generation.

[0052] In addition, since high-concentration strong acid solutions were used in the past, it was difficult to selectively recover uranium. In contrast, the present invention enables the recovery of uranium with high purity using low-concentration acid solutions. Accordingly, while it was previously impossible to extract uranium with high purity from materials containing low concentrations of uranium, the present invention enables the extraction of uranium with high purity even from materials containing low concentrations of uranium. In conclusion, in a situation where the demand for uranium is rapidly increasing, the present invention enables the extraction of uranium with high purity even from materials containing low concentrations of uranium, which were not previously subject to the extraction of high-purity uranium, and therefore, the present invention is very superior in terms of economic and practical applications.

[0053]

[0054] At this time, if the concentration of the acid solution is less than 0.025M, the concentration of the acid solution is too low, and uranium and H +Uranium extraction may not be performed properly due to the reaction between ions not being performed properly. In addition, if the concentration of the acid solution exceeds 0.2 M, impurities other than uranium may be extracted together, making it difficult to extract uranium with high purity. In addition, it may be economically disadvantageous to apply it to materials containing uranium at low concentrations. In addition, since the pH drops to an unmeasurable level, the progress of the uranium extraction step cannot be properly measured, the process cost increases, which may be very disadvantageous in terms of process efficiency.

[0055]

[0056] More specifically, the concentration of the acid solution can be differentiated according to the uranium content of the uranium-containing material. If the uranium-containing material contains 1000 ppm or more of uranium, it can be extracted using an acid solution of 0.05 M to 0.2 M, and if the uranium is contained less than 1000 ppm, it can be extracted using an acid solution of 0.025 to 0.05 M. In this way, if the concentration of the acid solution used for extraction is differentiated according to the uranium content, it is possible to achieve very high economic efficiency by using the acid solution most suitable for the uranium concentration of each uranium-containing material. At this time, the method for measuring the uranium content of the uranium-containing material is not limited as long as it is a method capable of measuring the uranium content in general, but for example, it can be a method of measuring the uranium content by analyzing a sample of the uranium-containing material using XRF (X-Ray Fluorescence spectroscopy).

[0057]

[0058] According to a preferred embodiment of the present invention, the acid solution may contain a strong acid.

[0059] If the above acid solution contains a strong acid, it has a stronger tendency to ionize than a weak acid, so even if it is injected at a low concentration, H is used in the process of extracting uranium.+ The concentration is sufficiently secured so that uranium can be extracted quickly.

[0060] More specifically, the acid solution may contain at least one selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, and hydrofluoric acid. When using an acid, the conjugate base of the acid must be removed in order to purify the waste solution remaining after the uranium is finally recovered. At this time, if the acid solution contains at least one acid selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, and hydrofluoric acid, Cl corresponding to the conjugate base of the acid substances - , NO3 - , SO4 2- Since the back can be removed from the waste liquid, it can be advantageous from an environmental point of view. More preferably, the acid solution may contain sulfuric acid. SO4, the conjugate base of sulfuric acid 2- It can be particularly advantageous from an environmental perspective, as it can be removed very easily by forming a precipitate as BaSO4 using barium (Ba) in the process of purifying the waste liquid after ultimately recovering uranium.

[0061]

[0062] More specifically, the solvent of the acid solution may preferably be water. When the solvent of the acid solution is water, the generation of organic waste liquid is minimized when performing the method for recovering high-purity uranium according to the present invention, which may be very advantageous from an environmental perspective. In particular, the present invention utilizes only inorganic substances, not organic substances, in the uranium recovery process, which may be very advantageous from an environmental perspective.

[0063]

[0064] According to a preferred embodiment of the present invention, the step (1) can be performed at 10 to 50˚C. In this case, if uranium is extracted at a temperature below 10˚C, uranium and H +Because the reaction efficiency is too low, extracting uranium can take too long, which can be detrimental to process efficiency. Furthermore, if uranium is extracted at temperatures exceeding 50˚C, the high temperature can lead to the extraction of large quantities of impurities, which can be detrimental to high-purity uranium extraction.

[0065]

[0066] In addition, according to a preferred embodiment of the present invention, the uranium content of the uranium-containing material in step (1) may be 1 ppm or more, preferably 10 ppm or more, more preferably 100 ppm or more, and even more preferably 500 ppm or more, based on the mass of the uranium-containing material. In addition, the uranium content may be 20,000 ppm or less, preferably 15,000 ppm or less, and more preferably 10,000 ppm or less based on the mass of the uranium-containing material. In this case, if the uranium content is less than 500 ppm based on the mass of the uranium-containing material, it may be difficult to recover high-purity uranium from the extraction solution, which may be disadvantageous from an economical perspective. In addition, if the uranium content exceeds 10,000 ppm based on the mass of the uranium-containing material, multiple recovery of uranium may be considered.

[0067]

[0068] In addition, according to a preferred embodiment of the present invention, the uranium-containing material of step (1) may be soil or mineral having an average particle size of 10 μm to 2 mm. In this case, if the average particle size is less than 10 μm, uranium extraction may be efficient, but separation from the extraction solution after extraction may not be easy, resulting in difficulty in recovering high-purity uranium. In addition, if the average particle size exceeds 2 mm, the surface area of ​​the particles may be too small, making uranium extraction difficult.

[0069]

[0070] More specifically, the weight ratio of the uranium-containing material and the acid solution may be 1:4 to 1:10. In this case, if the acid solution is less than 1:4, the acid solution is not sufficient to extract uranium, so that a large amount of uranium remains in the uranium-containing soil even after extraction, which may be disadvantageous in terms of uranium extraction efficiency. In addition, if the acid solution is more than 1:10, the impurity content in the extraction solution increases, which may be disadvantageous in terms of recovering high-purity uranium.

[0071]

[0072] More specifically, the method for extracting uranium in the above step (1) is not limited to a method that can extract uranium using a conventional acid solution, but may be, for example, a method of immersing a uranium-containing material in an acid solution. At this time, after immersing the uranium-containing material in the acid solution, the reaction rate can be increased by stirring it, and the stirring can be performed at, for example, 100 to 300 rpm.

[0073]

[0074] According to a preferred embodiment of the present invention, step (1) according to the present invention may further include: (1-1) a step of adding an acid solution to a uranium-containing material and then measuring the pH to obtain a graph of pH over time; and (1-2) a step of determining the end point of extraction based on the graph.

[0075] More specifically, when an acid solution is added to a uranium-containing material, uranium and H + The ions react to form UO2 2+As a result, the pH of the solution increases. At this time, the pH of the solution is measured from the time of adding the acid solution, and a graph of the pH of the solution over time based on the time of adding the acid solution can be obtained. As described above, the graph shows that the pH gradually increases as uranium is extracted from the uranium-containing material, and then the amount of increase in pH gradually decreases. At this time, when the amount of increase in pH of the graph decreases below a certain level and becomes almost constant, it means that the uranium extraction is almost complete, and therefore, the point in time is determined as the point in time when the uranium extraction ends, and the extraction step can be ended. At this time, the point in time when the extraction ends can be appropriately determined depending on the situation, but for example, the extraction can be ended when the pH no longer changes and is constant, and also, for example, the extraction can be ended after the extraction is continued for 2 minutes or more, or 5 minutes or more from the point in time when the pH is constant.

[0076] As described above, the method for recovering high-purity uranium according to the present invention can accurately measure the end point of uranium extraction, thereby avoiding performing meaningless processes, which can be very advantageous in terms of process efficiency.

[0077]

[0078] Next, as step (2), hydrogen peroxide and a basic hydrogen nitride compound are added to the uranium extraction solution to precipitate uranium and form uranium peroxide hydrate.

[0079] More specifically, in step (1), UO2 2+ Uranium extracted in the form of reacts with hydrogen peroxide as shown in the following reaction formula 1 to form uranium peroxide hydrate in the form of UO4·4H2O(s). UO4·4H2O(s) is in the form of a precipitate, and as uranium is extracted as the uranium peroxide hydrate, uranium can be separated from other nuclides present in the solution.

[0080]

[0081] <Reaction Scheme 1>

[0082]

[0083]

[0084] However, when only hydrogen peroxide is added and reaction is carried out according to equation 1, the absolute value of the Gibbs free energy value is small, so the reaction rate is low, and uranium precipitation does not occur properly, so uranium separation is not performed properly.

[0085] In the past, there were attempts to increase the reaction rate by additionally adding a strong base, but this also did not increase the reaction rate to a satisfactory level because the absolute value of the Gibbs free energy was still low. In addition, when a strong base was added, the conjugate acid remained in the reactant after the reaction, which could lower the purity of the recovered uranium. In addition, since an additional removal process had to be performed to remove the conjugate acid, it was very disadvantageous in terms of process efficiency and the environment. The following reaction formula 2 is an example of a reaction formula when NaOH, a strong base, was used. In this case, the Gibbs free energy was not high enough in absolute value to a satisfactory level, so the reaction rate was not excellent. In addition, the conjugate acid of NaOH, Na + There is a problem that it is very disadvantageous in terms of process efficiency and environment because it remains after the reaction.

[0086]

[0087] <Reaction Formula 2>

[0088]

[0089]

[0090] Accordingly, the method for recovering high-purity uranium according to the present invention solves the above-mentioned problem by adding a basic hydrogen nitride compound. Hydrogen peroxide and the basic hydrogen nitride compound simultaneously produce UO2. 2+ When applied to UO2, despite the presence of impurities such as other metal ions, 2+It reacts specifically with hydrogen peroxide and basic hydrogen nitride compounds to form a precipitate in the form of UO4·4H2O(s). At this time, the reaction has a high absolute Gibbs energy value, and accordingly, uranium can be recovered with high purity and high recovery rate while hardly precipitating other impurities. In addition, at the same time, when a basic hydrogen nitride compound is used as in the present invention, only H2O and N2 gas are generated as byproducts, so unlike the case in the past when a strong base was used, which was disadvantageous in terms of process efficiency and environment due to the remaining conjugate acid, since only environmentally friendly byproducts are generated, no separate removal process is required, and thus it is very excellent in terms of process efficiency and environment.

[0091]

[0092] The above basic hydrogen nitride compound may preferably be weakly basic. In this case, if the basic hydrogen nitride compound is strongly basic, the formed OH - The problem of lowering the purity of the recovered uranium may arise due to the precipitation of impurities other than uranium by ions.

[0093]

[0094] According to a preferred embodiment of the present invention, the basic hydrogen nitride compound may be at least one selected from the group consisting of hydrazine (N2H4) and ammonia water (NH4OH).

[0095]

[0096] For example, when the basic hydrogen nitride compound is hydrazine, hydrazine and hydrogen peroxide are simultaneously formed into UO2 2+ When applied, it reacts as shown in the following reaction formulas 3 and 4, and ammonia water and hydrogen peroxide simultaneously form UO2 2+ When applied, it reacts as shown in the following reaction formula 5.

[0097]

[0098] <Reaction Formula 3>

[0099]

[0100]

[0101] <Reaction Formula 4>

[0102]

[0103]

[0104] <Reaction Formula 5>

[0105]

[0106]

[0107] Referring to the above reaction formulas 3 to 5, UO2 2+ It reacts specifically with hydrogen peroxide and basic hydrogen nitride compounds to form uranium peroxide precipitate as described above. In particular, in the case of the above reaction formulas 3 to 5, unlike the case where only hydrogen peroxide is added or the case where hydrogen peroxide and a strong base are added, the absolute value of the Gibbs energy is very large, so the reaction occurs very spontaneously. Accordingly, uranium can be precipitated as uranium peroxide hydrate at a very high reaction rate. In addition, since it reacts specifically with uranium, only uranium can be precipitated while other impurities are hardly precipitated, so that uranium can be recovered with very high purity. Therefore, through the above reaction of precipitating uranium with hydrogen peroxide and basic hydrogen nitride compounds, uranium can be recovered with high efficiency and high purity. In addition, at the same time, when a basic hydrogen nitride compound is used as in the present invention, only H2O and N2 gas are generated as byproducts, so unlike the case in the past when a strong base was used, which was disadvantageous in terms of process efficiency and environment due to the remaining conjugate acid, only environmentally friendly byproducts are generated, so no separate removal process is required, making it very excellent in terms of process efficiency and environment.

[0108]

[0109] In addition, the present invention provides a method for recovering high-purity uranium by adding hydrogen peroxide and a precipitation additive to the uranium extraction solution to precipitate uranium to form uranium peroxide.

[0110] At this time, the precipitation additive reacts with uranium and hydrogen peroxide, and the Gibbs free energy of the reaction may be -300 kcal or less, more preferably -350 kcal or less. When the Gibbs energy of the reaction is -350 kcal or less, the reaction among uranium, hydrogen peroxide, and the precipitation additive becomes very spontaneous, so that uranium can be extracted with a very high recovery rate and purity despite the presence of impurities, which is very superior to the conventional method. For example, when the precipitation additive is hydrazine as described above, the Gibbs energy of the reaction between uranium and hydrogen peroxide is -350 kcal or less, and when the precipitation agent is ammonia water, the Gibbs energy of the reaction between uranium and hydrogen peroxide is also -350 kcal or less. Accordingly, compared to the conventional case where a strong base was used, the present invention is very superior in that uranium can be recovered with a very high recovery rate and high purity.

[0111]

[0112] More specifically, the step (2) may include: (2-1) a step of forming a mixture by mixing hydrogen peroxide into a uranium extraction solution; and (2-2) a step of forming a uranium peroxide hydrate by adding a basic hydrogen nitride compound while adjusting the pH of the mixture so as not to exceed 4.

[0113] More specifically, if all of the hydrogen peroxide and the basic hydrogen nitride compound are added to the uranium extraction solution at the same time, the pH of the solution may rise rapidly due to the basic hydrogen nitride compound, which may cause other nuclides to precipitate together, thus reducing the purity of the uranium. Therefore, if hydrogen peroxide is first mixed into the uranium extraction solution to form a mixture and then the basic hydrogen nitride compound is added in an adjusted manner, as the uranium reacts with the basic hydrogen nitride compound, a large amount of the basic hydrogen nitride compound will not exist in the solution at once, and accordingly, the pH will not rise excessively, preventing the precipitation of other nuclides, and thus uranium can be precipitated with very high purity.

[0114] At this time, the basic hydrogen nitride compound may be added while adjusting the pH of the mixture so that it preferably does not exceed 4, and more preferably, the basic hydrogen nitride compound may be added while adjusting the pH so that it does not exceed 2 to 3.5. At this time, if the basic hydrogen nitride compound is added so that the pH exceeds 4, the purity of the recovered uranium may be lowered as other nuclides precipitate together with uranium.

[0115] More specifically, the basic hydrogen nitride compound may be introduced in a conventional form, preferably in the form of an aqueous solution of the basic hydrogen nitride compound. At this time, the amount of the basic hydrogen nitride compound introduced may vary depending on the amount of uranium contained in the mixture.

[0116] More specifically, the introduction of the basic hydrogen nitride compound can be terminated when a uranium peroxide hydrate precipitate is formed by introducing the basic hydrogen nitride compound.

[0117] At this time, since uranium peroxide precipitation may not be observed depending on the type and size of the container containing the mixture or the amount of the mixture, the addition of the basic hydrogen nitride compound may be terminated when the target pH is set and the target pH is reached. At this time, the target pH may be 4 or less, preferably 1 to 3.5, more preferably 2 to 3, and even more preferably 2 to 2.5. At this time, even when the target pH is set, if uranium peroxide precipitation is observed before the target pH is reached, the addition of the basic hydrogen nitride compound may be terminated. At this time, after the addition of the basic hydrogen nitride compound is terminated, the basic hydrogen nitride compound reacts with uranium, gradually lowering the pH.

[0118] Additionally, more specifically, after the addition of the basic hydrogen nitride compound has been completed, an additional reaction may be performed to further precipitate uranium peroxide hydrate. The time for performing the additional reaction is not particularly limited, but may be performed for, for example, 0.1 to 24 hours.

[0119]

[0120] Also, preferably, a basic hydrogen nitride compound solution of 1 to 5 M concentration is added at 10 to 50 ml / m 2 -min can be injected at a rate of 10 to 50 ml / m of a basic hydrogen nitride compound solution with a concentration of 1 to 5 M. 2 -When injected at a rate of min, the pH of the mixture can be appropriately controlled so as not to exceed 4, thereby precipitating uranium without precipitating other nuclides together with uranium, and thus recovering uranium with high purity.

[0121] At this time, 10 to 50 ml / m 2-min means the unit cross-sectional area of ​​the container containing the mixture into which the basic hydrogen nitride compound is injected, and 10 to 50 ml of the basic hydrogen nitride compound is injected per unit time.

[0122] More specifically, the concentration of the basic hydrogen nitride compound solution is the concentration of hydrogen peroxide and UO2 contained in the mixture. 2+ The concentration may be appropriately selected depending on the composition of the mixture and the reaction conditions, but may be preferably 1 to 5 M, and more preferably 1.5 to 4 M. At this time, the solvent of the basic hydrogen nitride compound solution may be water.

[0123]

[0124] More specifically, the concentration of hydrogen peroxide in the mixture may be 0.5 to 5 M. At this time, the concentration of hydrogen peroxide may be appropriately selected depending on the amount of uranium contained in the mixture. More specifically, UO2 contained in the mixture 2+ When the concentration of UO2 is less than 1000 ppm, the concentration of hydrogen peroxide can be 0.5 to 1.5 M, and the UO2 contained in the mixture 2+ When the concentration of hydrogen peroxide exceeds 1000 ppm and is less than 2500 ppm, the concentration of hydrogen peroxide may be 1.5 to 3 M, and UO2 contained in the mixture 2+ When the concentration of UO2 exceeds 2500 ppm, the concentration of hydrogen peroxide can be 3 to 5 M. When the concentration of hydrogen peroxide is as above, uranium can be precipitated most efficiently as most of the uranium can be precipitated while leaving almost no hydrogen peroxide remaining. At this time, UO2 in the solution 2+ The concentration of UO2 is usually 2+ There are no restrictions on the method of measuring the concentration, but for example, it can be measured using XRF (X-Ray Fluorescence Spectrometry).

[0125] However, it is not limited to the concentration of hydrogen peroxide as described above, and the concentration of hydrogen peroxide in the mixture can be appropriately selected depending on the reaction conditions such as the type of initial uranium-containing material and the amount of impurities.

[0126]

[0127] More specifically, the present invention can further perform a step (3) of separating and recovering uranium peroxide hydrate using a filter after step (2).

[0128] More specifically, after step (2), uranium peroxide in the form of a precipitate, UO4·4H2O(s), is formed, and most other impurities exist in the solution in the form of ions. Accordingly, only solid substances can be filtered out using a filter, allowing uranium to be recovered with very high purity.

[0129] At this time, any filter that can filter out UO4·4H2O(s) from a solution can be used without limitation, but when considering reusability, convenience of sediment separation, and economy, a metal filter may be the most effective.

[0130] At this time, the material of the metal filter is not limited as long as it is a material of a typical metal filter, but it may preferably be stainless steel.

[0131] More specifically, the pores of the filter may vary depending on the particle size distribution of the precipitated uranium peroxide hydrate, but preferably, a filter having pores of 1 μm to 10 μm can be used, and more preferably, a filter having pores of 2 μm to 3 μm can be used.

[0132]

[0133] More specifically, after recovering uranium peroxide hydrate using the above-described filtration filter, a step of washing the recovered uranium peroxide hydrate may be performed. At this time, the washing solution may preferably be water (H2O). In addition, the washing solution may be 200 to 500 parts by weight based on 100 parts by weight of the recovered uranium peroxide hydrate, and the washing may preferably be performed at least once.

[0134]

[0135] In addition, the present invention provides uranium peroxide hydrate recovered through the method for recovering high-purity uranium described above.

[0136]

[0137] The present invention will be described in more detail through the following examples, but the following examples do not limit the scope of the present invention, and should be interpreted as helping to understand the present invention.

[0138]

[0139] <Example 1 - Method 1 for recovering high-purity uranium>

[0140] 20 (g) of soil with a uranium concentration of 4000 ppm was immersed in 100 (g) of a 0.1 M sulfuric acid solution and uranium was extracted while stirring at 200 rpm at 20˚C. At this time, the pH was measured immediately after immersion, and a pH graph over time was obtained, which is shown in Fig. 1. After 30 minutes when there was no more change in pH, uranium was extracted to obtain a uranium extraction solution, and the composition of the main components of the extraction solution was measured by ICP-OES (Inductively coupled plasma atomic emission spectroscopy), and the results are shown in Table 1 below.

[0141] Afterwards, hydrogen peroxide was added to the uranium extraction solution so that the hydrogen peroxide concentration of the uranium extraction solution containing hydrogen peroxide became 1 M, and then a hydrazine solution prepared by diluting 98% hydrazine (N2H4·H2O) 5-fold with water was slowly added so that the pH of the mixture of the uranium extraction solution and hydrogen peroxide did not exceed 3.5. In addition, the mixture was stirred at 200 rpm while adding hydrogen peroxide and hydrazine. At this time, the addition of the hydrazine solution was stopped when 1.05 ml was added, at which point precipitation was visually observed, and the pH at this time was 3.5. Thereafter, the reaction was performed until the pH became 2. After all of the hydrazine was added, the concentration of uranium was measured by the ICP-OES method and is similarly shown in Table 1. After that, the precipitate was obtained by filtering it through a stainless steel metal filter as shown in Fig. 2. At this time, the pores of the filter were 2 to 3 μm.

[0142]

[0143] <Example 2 - Method 2 for recovering high-purity uranium>

[0144] In the above Example 1, uranium was extracted using 180 (g) of a 0.05 M sulfuric acid solution, the hydrogen peroxide concentration of the uranium extraction solution was set to 1.25 M, and an ammonia solution prepared by diluting 25% ammonia water (NH4OH) 5 times with water was added to the uranium extraction solution instead of hydrazine, except that the same procedure as Example 1 was performed.

[0145]

[0146] <Comparative Example 1 - Uranium Recovery Method Using Only Hydrogen Peroxide>

[0147] The same procedure as Example 1 was followed, except that only hydrogen peroxide was added to the uranium extraction solution and the solution was left to stand for 7 days.

[0148]

[0149] <Experimental Example 1 - ICP-OES Analysis>

[0150] The composition of the main components of the extraction solution before and after adding hydrogen peroxide and basic hydrogen nitride compounds to the uranium extraction solution for Examples 1 and 2 was measured using ICP-OES, and the results are shown in Tables 1 and 2 below, respectively.

[0151]

[0152]

[0153]

[0154]

[0155]

[0156] As can be seen in Tables 1 and 2, while the concentrations of other elements were almost constant before and after the addition of hydrogen peroxide and basic hydrogen nitride compounds, most of the uranium was removed by precipitation. This shows that the method for recovering high-purity uranium according to the present invention is excellent in that it can recover uranium with very high purity despite the presence of other impurity nuclides by adding basic hydrogen nitride compounds together with hydrogen peroxide.

[0157]

[0158] <Experimental Example 2 - Confirming Precipitation Formation>

[0159] For Example 1 and Comparative Example 1, the formation of sediment was observed with the naked eye, and the results are shown in Fig. 3.

[0160] In the case of Example 1, as can be seen in Fig. 3, precipitation was observed to occur as hydrazine was added. In contrast, in the case of Comparative Example 1, precipitation did not occur even after waiting for 7 days. Through this, it can be confirmed that Example 1, which added hydrazine, was much better at precipitating uranium than Comparative Example 1.

[0161]

[0162] <Experimental Example 2 - XRD Analysis>

[0163] For the sediment of Example 1, the contents of U and O in the sediment were measured using the SEM-EDS (Scanning Electron microscope-Energy dispersive X-ray spectroscope) method and are shown in Table 3. The structure of the sediment was analyzed using XRD (X-ray diffraction) and the results are shown in Fig. 4.

[0164]

[0165]

[0166]

[0167] As can be seen from Table 3 and Figure 4, it can be confirmed that most of the uranium obtained by the recovery method of Example 1 is in the form of uranium peroxide hydrate (UO4·4H2O). Therefore, the method for recovering high-purity uranium according to the present invention is excellent in that it can recover only uranium in the form of uranium peroxide hydrate without precipitating other nuclides.

[0168]

[0169] The present invention was carried out with the following tasks.

[0170]

[0171] [National Research and Development Project Supporting This Invention]

[0172] [Project ID] 2710007317

[0173] [Assignment Number] 522230-24

[0174] [Ministry Name] Ministry of Science and ICT

[0175] [Name of Project Management (Specialist) Institution] National Research Council for Science and Technology

[0176] [Research Project Name] Korea Atomic Energy Research Institute Research Operations Support (Main Project Expenses)

[0177] [Research Project Name] Expansion of the Radioactive Waste Lifecycle Management System and Processing Infrastructure

[0178] [Name of Project Performing Organization] Korea Atomic Energy Research Institute

[0179] Research Period: January 1, 2024 - December 31, 2024

Claims

1. (1) A step of adding an acid solution to a uranium-containing material to extract uranium and form a uranium extraction solution; and (2) A method for recovering high-purity uranium, comprising the step of adding hydrogen peroxide and a basic hydrogen nitride compound to the uranium extraction solution to precipitate uranium and form uranium peroxide hydrate.

2. In paragraph 1, A method for recovering high-purity uranium, characterized in that the basic hydrogen nitride compound is at least one selected from the group consisting of hydrazine (N2H4) and ammonia water (NH4OH).

3. In paragraph 1, Step (2) above is, (2-1) A step of forming a mixture by mixing hydrogen peroxide into the uranium extraction solution; and (2-2) A method for recovering high-purity uranium, characterized by including a step of forming uranium peroxide hydrate by adding a basic hydrogen nitride compound while adjusting the pH of the above mixture so that it does not exceed 4.

4. In paragraph 3, A method for recovering high-purity uranium, characterized in that the concentration of hydrogen peroxide in the mixture in the above step (2-1) is 0.5 to 5 M.

5. In paragraph 3, In the above step (2-2), the basic hydrogen nitride compound is a 1 to 5 M solution at 10 to 50 ml / m 2 A method for recovering high-purity uranium, characterized by administering at a rate of -min.

6. In paragraph 1, A method for recovering high-purity uranium, wherein the acid solution of step (1) above contains a strong acid.

7. In paragraph 1, A method for recovering high-purity uranium, characterized in that the acid solution of step (1) above contains at least one selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, and hydrofluoric acid.

8. In paragraph 1, A method for recovering high-purity uranium, characterized in that the acid solution of step (1) above contains sulfuric acid.

9. In paragraph 1, A method for recovering high-purity uranium, characterized in that the concentration of the acid solution in step (1) is 0.025 to 0.2 M.

10. In paragraph 1, A method for recovering high-purity uranium, characterized in that the above step (1) is performed at a temperature of 10 to 50˚C.

11. In paragraph 1, A method for recovering high-purity uranium, characterized in that the uranium content of the uranium-containing material of step (1) above is 500 to 10,000 ppm.

12. In paragraph 1, A method for recovering high-purity uranium, characterized in that the uranium-containing material is soil or mineral having an average particle diameter in the range of 10 μm to 2 mm.

13. In paragraph 1, Step (1) above, (1-1) A step of adding an acid solution to a uranium-containing material and measuring the pH to obtain a graph of pH over time; and (1-2) A method for recovering high-purity uranium, characterized by including a step of determining the extraction end point based on the above graph.

14. In paragraph 1, After step (2) above, (3) A method for recovering high-purity uranium, characterized by further performing a step of separating and recovering the uranium peroxide hydrate of step (2) using a filter. 15.(1) A step of adding an acid solution to a uranium-containing material to extract uranium and form a uranium extraction solution; and (2) a step of adding hydrogen peroxide and a precipitation additive to the uranium extraction solution to precipitate uranium and form uranium peroxide hydrate; A method for recovering high-purity uranium in which the above precipitation additive reacts with uranium and hydrogen peroxide, and the Gibbs free energy of the reaction is -350 kcal or less.

16. Uranium peroxide hydrate recovered through any one of the methods in paragraphs 1 to 15.

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