Method for removing radionuclide ions in low-radioactivity waste liquid and electric ion removal device

Abstract

The embodiment of the invention relates to the technical field of wastewater treatment of an electrodeionization device, in particular to a method for removing radionuclide ions in low-radioactivity waste liquid and the electrodeionization device, and the method comprises the following steps: switching on a power supply of the electrodeionization device to form a first electric field between a cathode and an anode of the electrodeionization device; under the action of the first electric field, positive ions in the radioactive waste liquid are migrated to a cathode of the electric deionization device, and the positive ions in the migration process are removed by utilizing an ion adsorption module of the electric deionization device, so that a water purification area is formed; under the action of the first electric field, anions in the radioactive waste liquid are migrated to the anode of the electric deionization device, and the anions in the migration process are stopped by using an ion adsorption module to form an anion enrichment area; and separating and collecting the liquid in the water purification area and the liquid in the anion enrichment area to obtain the liquid in which the radionuclide ions are removed. The method can effectively remove radionuclide ions and is high in efficiency.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of wastewater treatment using an electro-deionization device, and more particularly to a method for removing radioactive nuclide ions from low-level radioactive waste liquid and an electro-deionization device. Background Art

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] Nuclear facilities produce radioactive wastewater during operation, and the treatment and discharge of radioactive wastewater are closely related to the development of the nuclear industry. Therefore, it is very important to effectively remove radioactive nuclide ions in radioactive wastewater.

[0004] At present, the commonly used radioactive wastewater treatment methods mainly include chemical precipitation, ion exchange, evaporation concentration and electrochemical treatment, etc. However, these radioactive wastewater treatment methods still have many shortcomings. Summary of the invention

[0005] A brief overview of the present application is provided below in order to provide a basic understanding of certain aspects of the present application. It should be understood that this overview is not an exhaustive overview of the present application. It is not intended to identify the key or important parts of the present application, nor is it intended to limit the scope of the present application. Its purpose is merely to present certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0006] In a first aspect, an embodiment of the present application provides a method for removing radioactive nuclide ions in low-level radioactive waste liquid, which is suitable for an electrodeionization device, and includes the following steps: S1, turning on the power of the electrodeionization device to form a first electric field between the cathode and the anode of the electrodeionization device; S2, under the action of the first electric field, causing cations in the radioactive waste liquid to migrate toward the cathode of the electrodeionization device, and using the ion adsorption module of the electrodeionization device to remove the cations in the migration process to form a clean water zone within a first predetermined range of the same polar ion exchange membrane close to the anode, wherein the ion adsorption module includes a plurality of same polar ion exchange membranes and a porous medium, and the porous medium is located between two adjacent same polar ion exchange membranes; S3, under the action of the first electric field, causing anions in the radioactive waste liquid to migrate toward the anode of the electrodeionization device, and using the ion adsorption module to prevent the anions in the migration process to form an anion-enriched zone within a second predetermined range of the same polar ion exchange membrane close to the cathode; S4, separating the liquid in the clean water zone and the liquid in the anion-enriched zone, and collecting the separated liquid in the clean water zone to obtain a liquid with radioactive nuclide ions removed.

[0007] The method provided in the embodiment of the present application utilizes multiple homopolar ion exchange membranes and porous media to adsorb cations that migrate toward anions in the radioactive waste liquid, and at the same time can prevent the anions from migrating toward the anode. Since a weakly charged porous medium is filled in the middle of the homopolar ion exchange membrane, under the action of the first electric field, the migration speed and diffusion speed of different radioactive nuclide ions in the radioactive waste liquid in the porous medium are different. Usually, the migration speed of ions is faster than the diffusion during the migration process. This can avoid the diffusion limitation in the electrodeionization process, so that a clean water zone and an anion-enriched zone can be formed near the homopolar ion exchange membrane, respectively. By separating and collecting the liquid in the clean water zone and the liquid in the anion-enriched zone, a purified liquid that effectively removes the radioactive nuclide ions in the radioactive waste liquid can be obtained, and the removal efficiency is high.

[0008] In the second aspect, an embodiment of the present application also provides an electro-ionization device for removing radioactive nuclide ions in low-level radioactive waste liquid by the method provided in the embodiment of the present application, comprising: a power supply, an electrode module, an ion adsorption module and a separation module; the power supply is used to power the electrode module; the electrode module is used to form an electric field when the power is turned on, so as to drive ion migration under the action of the electric field, wherein the electrode module comprises a cathode and an anode; the ion adsorption module is used to remove cations and prevent anion migration during ion migration, so as to form a clean water zone and an anion-rich zone around the ion adsorption module respectively; the separation module is used to separate the liquid in the clean water zone and the liquid in the anion-rich zone, and collect the liquid in the clean water zone after separation to obtain a liquid with radioactive nuclide ions removed.

[0009] These and other advantages of the present application will become more apparent through the following detailed description of the preferred embodiments of the present application in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to further illustrate the above and other advantages and features of the present application, the specific embodiments of the present application are further described in detail below in conjunction with the accompanying drawings. The accompanying drawings together with the following detailed description are included in this specification and form a part of this specification. Elements with the same function and structure are represented by the same reference numerals. It should be understood that these drawings only describe typical examples of the present application and should not be regarded as limiting the scope of the present application.

[0011] Figure 1 is a schematic flow chart of a method for removing radionuclide ions from low-level radioactive waste liquid according to an embodiment of the present application;

[0012] Figure 2 Schematic diagram of an electric deionization device according to an embodiment of the present application.

[0013] It should be noted that the drawings are not necessarily drawn to scale, but are merely shown in a schematic manner that does not affect the reader's understanding.

[0014] Description of reference numerals:

[0015] 210. Power supply;

[0016] 220, electrode module; 221, cathode; 222, anode;

[0017] 230. ion adsorption module; 231. homopolar ion exchange membrane; 232. porous medium;

[0018] 241. Water purification area; 242. Anion enrichment area;

[0019] 251. Radioactive waste liquid; 252. Anolyte; 253. Cathode electrolyte; 254. Purified liquid; 255. Concentrated liquid. DETAILED DESCRIPTION

[0020] Exemplary embodiments of the present application will be described below in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of the actual implementation are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the process of developing any such actual implementation in order to achieve the developer's specific goals, such as meeting those constraints related to the system and business, and these constraints may vary from implementation to implementation. In addition, it should be understood that although the development work may be very complex and time-consuming, it is only a routine task for those skilled in the art who benefit from the content of this application.

[0021] It is also necessary to explain here that, in order to avoid obscuring the present application due to unnecessary details, only the device structure and / or processing steps closely related to the scheme according to the present application are shown in the accompanying drawings, while other details that are not very relevant to the present application are omitted.

[0022] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in this application should have the common meanings understood by persons with ordinary skills in the field to which this application belongs.

[0023] In the description of the embodiments of the present application, “plurality” means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0024] In the related art, the commonly used radioactive wastewater treatment methods are still facing many problems. For example, for the electrodeionization method (EDI), the operating current during the operation needs to be maintained at the limiting current density. This is because once the operating current exceeds the limiting current (i.e., the over-limit current), the dissociation of water in the solution will increase, thereby increasing the ion transport difference between the membrane and the solution, resulting in a decrease in current efficiency, and then causing concentration polarization on the membrane surface. In the case of concentration polarization on the membrane surface, the ion exchange membrane in the electrodeionization device used will be polarized due to the concentration difference, which will lead to a decrease in the effective driving force across the membrane, thereby causing problems such as membrane pollution and membrane scaling, and then leading to a decrease in membrane flux, and the radioactive nuclide ions in the radioactive wastewater cannot be effectively removed. In addition, low-level radioactive waste liquids usually have low electrical conductivity. If these waste liquids are used as raw water for treatment, the resistance in the electrodeionization process will be very large, and the energy consumption will be very high.

[0025] In view of the above technical problems, an embodiment of the present application provides a method for removing radionuclide ions in low-level radioactive waste liquid, which is suitable for an electro-deionization device. Figure 1 is a schematic flow chart of a method for removing radioactive nuclide ions from low-level radioactive waste liquid according to an embodiment of the present application, such as Figure 1 As shown, it includes the following steps S1 to S4.

[0026] S1. Turn on the power of the electric deionization device to form a first electric field between the cathode and anode of the electric deionization device.

[0027] S2. Under the action of the first electric field, the cations in the radioactive waste liquid migrate to the cathode of the electrodeionization device, and the ion adsorption module of the electrodeionization device is used to remove the cations in the migration process to form a clean water zone within a first predetermined range of the same polarity ion exchange membrane close to the anode, wherein the ion adsorption module includes a plurality of same polarity ion exchange membranes and a porous medium, and the porous medium is located between two adjacent same polarity ion exchange membranes.

[0028] S3. Under the action of the first electric field, the anions in the radioactive waste liquid migrate to the anode of the electrodeionization device, and the anions in the migration process are blocked by the ion adsorption module to form an anion enrichment zone within a second predetermined range of the same polarity ion exchange membrane close to the cathode.

[0029] S4. Separate the liquid in the water purification zone and the liquid in the anion enrichment zone, and collect the separated liquid in the water purification zone to obtain liquid with radioactive nuclide ions removed.

[0030] The method provided in the embodiment of the present application utilizes multiple homopolar ion exchange membranes and porous media to adsorb cations that migrate toward anions in the radioactive waste liquid, and at the same time can prevent the anions from migrating toward the anode. Since a weakly charged porous medium is filled in the middle of the homopolar ion exchange membrane, under the action of the first electric field, the migration speed and diffusion speed of different radioactive nuclide ions in the radioactive waste liquid in the porous medium are different. Usually, the migration speed of ions is faster than the diffusion during the migration process. This can avoid the diffusion limitation in the electrodeionization process, so that a clean water zone and an anion-enriched zone can be formed near the homopolar ion exchange membrane, respectively. By separating and collecting the liquid in the clean water zone and the liquid in the anion-enriched zone, a purified liquid that effectively removes the radioactive nuclide ions in the radioactive waste liquid can be obtained, and the removal efficiency is high.

[0031] In some embodiments, the homopolar ion exchange membrane may be a cation exchange membrane.

[0032] In some embodiments, the porous medium may be a porous graphite medium (also referred to as porous medium graphite balls).

[0033] In some embodiments, before step S4, it may also include: adjusting the current of the electrodeionization device to form a second electric field between the cathode and the anode of the electrodeionization device; under the action of the second electric field, the ion concentration of the liquid in the clean water area is reduced to form a concentration difference with the ion concentration of the liquid in the anion-enriched area.

[0034] The method provided in the embodiment of the present application adjusts the current of the electrodeionization device to form concentration difference polarization of the radioactive waste liquid, which is beneficial to separate and collect the liquid in the clean water area and the anion-enriched area, thereby improving the efficiency of obtaining the liquid with the radionuclide ions removed.

[0035] In some embodiments, the surface of the porous medium is weakly electronegative, which can make the migration speed of ions greater than the diffusion speed, so that cations are accelerated to pass through the porous medium and migrate toward the negative electrode, and anions are enriched near the porous medium, thereby forming a concentration gradient.

[0036] In some embodiments, the method provided in the embodiments of the present application is to detect radionuclides in radioactive waste liquid. 137 Cs, 90 Sr and 60 The removal efficiency of Co can reach over 99%, and the radioactive waste liquid can be recycled with a recovery rate of over 40%.

[0037] In some embodiments, adjusting the current of the electrodeionization device may include: increasing the power supply voltage of the electrodeionization device so that the current of the electrodeionization device reaches an over-limit current so that the ion concentration of the liquid in the clean water zone approaches zero.

[0038] The method provided in the embodiment of the present application increases the power supply voltage of the electrodeionization device to make the current of the electrodeionization device reach the over-limit current, which is helpful to make the ion concentration of the liquid in the water purification area approach zero, thereby ensuring that the radioactive nuclide ions in the collected liquid can be fully removed.

[0039] In some embodiments, the diameter of the porous medium is in the range of 1-10 microns, and the surface of the porous medium has good electronegativity, which is beneficial to the separation of cations and anions during ion migration, thereby achieving a better electro-removal effect.

[0040] In some embodiments, in step S4, the separation module of the electro-ionization device is used to continuously separate the liquid in the clean water zone and the liquid in the anion-enriched zone, so as to collect the liquid in the clean water zone in time and avoid ion diffusion.

[0041] In some embodiments, after step S1, the process further includes: adjusting the current of the electrodeionization device according to the valence state of the radioactive nuclide ions to achieve directional removal of the radioactive nuclides, which is beneficial to ensuring the removal efficiency of different radioactive nuclides.

[0042] The embodiments of the present application also provide an electro-ionization device for removing radioactive nuclide ions from low-level radioactive waste liquid using the method of the embodiments of the present application. Figure 2 is a schematic diagram of an electric deionization device according to an embodiment of the present application, such as Figure 2 As shown, the electric deionization device may include: a power supply 210, an electrode module 220, an ion adsorption module 230 and a separation module ( Figure 2 not shown).

[0043] The power source 210 is used to supply power to the electrode module 220 .

[0044] The electrode module 220 is used to form an electric field when the power source 210 is turned on, so as to drive ion migration under the action of the electric field, wherein the electrode module 220 includes a cathode 221 and an anode 222 .

[0045] The ion adsorption module 230 is used to remove cations and prevent anion migration during the ion migration process, so as to form a water purification zone 241 and anion enrichment zone 242 around the ion adsorption module 230 respectively.

[0046] The separation module is used to separate the liquid in the clean water area 241 and the liquid in the anion enrichment area 242, and collect the separated liquid in the clean water area 241 to obtain liquid with radioactive nuclide ions removed.

[0047] The electrodeionization device provided in the embodiment of the present application is filled with a weakly charged porous medium in the middle of the homopolar ion exchange membrane. Under the action of the first electric field, the migration speed and diffusion speed of different radioactive nuclide ions in the radioactive waste liquid are different in the porous medium. Usually, the migration speed of ions is faster than the diffusion during the migration process. This can avoid the diffusion limitation in the electrodeionization process, so that a clean water removal zone and anion enrichment zone can be formed near the homopolar ion exchange membrane respectively. By separating and collecting the liquid in the clean water zone and the liquid in the anion enrichment zone, the radioactive nuclide ions in the radioactive waste liquid can be effectively removed with a high removal efficiency. At the same time, there is no need to worry about the saturation and replacement of the ion exchange resin when removing radioactive nuclide ions using the device provided in the embodiment of the present application, and the service life is long.

[0048] In some embodiments, the electrode module 220 further includes a cathode electrolyte 253 disposed around the cathode 221 and an anode electrolyte 252 disposed around the anode 222 .

[0049] In some embodiments, the ion adsorption module 230 includes multiple like-polarity ion exchange membranes 231 and porous media 232, and the porous media 232 is located between two adjacent like-polarity ion exchange membranes 231; wherein, the clean water zone 241 is located within a first predetermined range of the like-polarity ion exchange membrane 231 close to the anode 222, and the anion enrichment zone 242 is located within a second predetermined range of the like-polarity ion exchange membrane 231 close to the cathode 221.

[0050] In some embodiments, the electric field formed by the electrode module 220 when the power source 210 is turned on includes the first electric field or the second electric field.

[0051] The following describes in detail the process of removing radioactive nuclide ions from radioactive waste liquid using the method and electric deionization device provided in the embodiments of the present application based on specific embodiments.

[0052] Example

[0053] Reference Figure 2, the electrode module 220 can form an electric field when the power supply 210 is turned on. Under the action of the electric field, the radioactive waste liquid 251 to be treated flows through the porous medium 232, and the radioactive cations in the radioactive waste liquid 251 can migrate to the cathode 221 through the same polarity ion exchange membrane 231 under the action of the electric field, and the cations are removed after passing through the same polarity ion exchange membrane 231 during the migration process, and a clean water area 241 is formed near the same polarity ion exchange membrane 231; at the same time, the anions migrate to the anode 222 in the porous medium 232, and the anions are blocked by the same polarity ion exchange membrane 231 and are enriched in the porous medium 232, and an anion enrichment area 242 is formed. When an over-limit current is applied, the ion concentration in the clean water zone 241 approaches zero, and concentration polarization will occur. However, since the surface of the porous medium 232 has weak negative charge, the migration of ions can be faster than the diffusion speed. Therefore, cations will accelerate to migrate to the negative electrode through the porous medium 232, while anions will gather near the same polarity ion exchange membrane 231 in the direction of the anode 222 under the action of the electric field, thereby forming a concentration gradient. At the water outlet of the electric deionization device, the liquid in the anion-enriched zone 242 and the liquid in the clean water zone 241 can be separated by a separation module arranged at the end of the porous medium 232, thereby obtaining a concentrated solution 255 and a purified solution 254 from which radioactive cations have been removed.

[0054] In some embodiments, a solution containing 0.9% NaCl is obtained, and a stable solution containing Co, Sr, and Cs ions is mixed therewith, wherein the ion concentrations of Co, Sr, and Cs are 0.1 mMol / L respectively, and then the Co, Sr, and Cs ions in the mixed solution are removed by the method provided in the embodiment of the present application, and different currents are applied during the removal process, for example, currents of 10 mA, 30 mA, 50 mA, 80 mA, and 100 mA are applied in sequence, and the liquid in the clean water area and the anion enrichment area is separated. By analyzing the liquid in the separated clean water area, it can be determined that the removal rates of the radioactive nuclides Co, Sr, and Cs are all above 99%, and the water recovery rate is above 48%.

[0055] The method provided by the present invention can effectively remove metal ions in low-concentration water, and can be effectively applied to the removal of radioactive nuclides Co, Sr, and Cs in radioactive waste liquid.

[0056] Regarding the embodiments of the present application, it should also be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other to obtain new embodiments.

[0057] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. The protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for removing radioactive nuclide ions from low-level radioactive waste liquid, which is suitable for an electric deionization device, characterized in that: It includes the following steps: S1, turning on the power supply of the electrodeionization device to form a first electric field between the cathode and the anode of the electrodeionization device; S2. Under the action of the first electric field, the cations in the radioactive waste liquid migrate toward the cathode of the electrodeionization device, and the ion adsorption module of the electrodeionization device is used to remove the cations in the migration process, so as to form a clean water zone within a first predetermined range of the homopolar ion exchange membrane close to the anode, wherein the ion adsorption module includes a plurality of the homopolar ion exchange membranes and a porous medium, and the porous medium is located between two adjacent homopolar ion exchange membranes; S3, under the action of the first electric field, the anions in the radioactive waste liquid migrate to the anode of the electrodeionization device, and the anions in the migration process are blocked by the ion adsorption module to form an anion enrichment zone within a second predetermined range of the homopolar ion exchange membrane close to the cathode; S4. Separating the liquid in the water purification zone and the liquid in the anion enrichment zone, and collecting the separated liquid in the water purification zone to obtain a liquid from which the radioactive nuclide ions are removed.

2. The method according to claim 1, characterized in that Before the S4 step, the method further includes: adjusting the current of the electrodeionization device so that a second electric field is formed between the cathode and the anode of the electrodeionization device; Under the action of the second electric field, the ion concentration of the liquid in the water purification zone is reduced to form a concentration difference with the ion concentration of the liquid in the anion-enriched zone.

3. The method according to claim 2, characterized in that The step of adjusting the current of the electrodeionization device comprises: The power supply voltage of the electro-ionization device is increased so that the current of the electro-ionization device reaches an over-limit current, so that the ion concentration of the liquid in the water purification area approaches zero.

4. The method according to any one of claims 1 to 3, characterized in that: The diameter of the porous medium is in the range of 1-10 microns.

5. The method according to any one of claims 1 to 3, characterized in that: In the step S4, The separation module of the electric deionization device is used to continuously separate the liquid in the water purification zone and the liquid in the anion-enriched zone.

6. The method according to any one of claims 1 to 3, characterized in that: After the step S1, the method further includes: According to the valence state of the radioactive nuclide ions, the current of the electrodeionization device is adjusted to achieve directional removal of the radioactive nuclides.

7. An electric deionization device, characterized in that: Used for removing radionuclide ions in low-level radioactive waste liquid by the method according to any one of claims 1 to 6, comprising: a power supply, an electrode module, an ion adsorption module and a separation module; The power supply is used to supply power to the electrode module; The electrode module is used to form an electric field when the power is turned on, so as to drive ion migration under the action of the electric field, wherein the electrode module includes a cathode and an anode; The ion adsorption module is used to remove cations and prevent anion migration during ion migration, so as to form a water purification zone and anion enrichment zone around the ion adsorption module respectively; The separation module is used to separate the liquid in the water purification zone and the liquid in the anion enrichment zone, and collect the separated liquid in the water purification zone to obtain the liquid from which the radioactive nuclide ions are removed.

8. The electric deionization device according to claim 7, characterized in that: The ion adsorption module comprises a plurality of ion exchange membranes of the same polarity and a porous medium, and the porous medium is located between two adjacent ion exchange membranes of the same polarity; The water purification zone is located within a first predetermined range of the homopolar ion exchange membrane close to the anode, and the anion enrichment zone is located within a second predetermined range of the homopolar ion exchange membrane close to the cathode.

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