Method for removing radionuclide ions from low-level radioactive waste liquid and electro-deionization device

Abstract

The embodiment of the application relates to the technical field of wastewater treatment by an electric desalting device, and particularly relates to a method for removing radionuclide ions in low-radioactivity waste liquid and an electric ion removal device, the method comprising the following steps: turning on the power supply of the electric ion removal device to form a first electric field between the cathode and the anode of the electric ion removal device; under the action of the first electric field, making cations in the radioactive waste liquid migrate to the cathode of the electric ion removal device, and removing the cations in the migration process by using an ion adsorption module of the electric ion removal device to form a clean water zone; under the action of the first electric field, making anions in the radioactive waste liquid migrate to the anode of the electric ion removal device, and stopping the anions in the migration process by using the ion adsorption module to form an anion enrichment zone; separating and collecting the liquid in the clean water zone and the liquid in the anion enrichment zone to obtain the liquid from which the radionuclide ions are removed. The method can effectively remove the radionuclide ions and has high efficiency.

Description

Technical Field

[0001] The embodiments of this application relate to the field of wastewater treatment technology using electro-desalination devices, specifically to a method for removing radionuclide ions from low-radioactivity waste liquid and an electro-deionization device. Background Technology

[0002] The statements herein are provided merely as background information in connection with this application and do not necessarily constitute prior art.

[0003] Nuclear facilities generate 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 from radioactive wastewater.

[0004] Currently, commonly used methods for treating radioactive wastewater mainly include chemical precipitation, ion exchange, evaporation and concentration, and electrochemical treatment. However, these methods still have many shortcomings. Summary of the Invention

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

[0006] In a first aspect, embodiments of this application provide a method for removing radionuclide ions from low-level radioactive waste liquid, applicable to an electrostatic ionization device, comprising the following steps: S1, turning on the power supply of the electrostatic ionization device to form a first electric field between the cathode and anode of the electrostatic ionization device; S2, under the action of the first electric field, causing cations in the radioactive waste liquid to migrate towards the cathode of the electrostatic ionization device, and using the ion adsorption module of the electrostatic ionization device to remove cations during the migration process, thereby forming a clean water zone within a first predetermined range near the anode of the same polarity ion exchange membrane, wherein the ion adsorption module includes multiple same polarity ion exchange membranes and a porous medium, and the porous medium is located between two adjacent same polarity ion exchange membranes; S3, under the action of the first electric field, causing anions in the radioactive waste liquid to migrate towards the anode of the electrostatic ionization device, and using the ion adsorption module to prevent anions during the migration process, thereby forming an anion enrichment zone within a second predetermined range near the cathode of the same polarity ion exchange membrane; S4, separating the liquid in the clean water zone and the liquid in the anion enrichment zone, and collecting the separated liquid in the clean water zone to obtain a liquid from which radionuclide ions have been removed.

[0007] The method provided in the embodiments of this application utilizes multiple homopolar ion exchange membranes and porous media to adsorb cations migrating towards anions in radioactive waste liquid, while simultaneously preventing anions from migrating towards the anode. Since the porous media with a weak charge is filled between the homopolar ion exchange membranes, under the action of a first electric field, the migration and diffusion rates of different radionuclide ions in the radioactive waste liquid are different in the porous media. Under normal circumstances, the migration rate of ions is faster than the diffusion rate during migration, which can avoid the diffusion restriction encountered during the electro-ion removal process. Thus, a clean water zone and an anion enrichment zone can be formed near the homopolar ion exchange membranes, respectively. By separating and collecting the liquid in the clean water zone and the liquid in the anion enrichment zone, a purified liquid that effectively removes radionuclide ions from the radioactive waste liquid can be obtained with high removal efficiency.

[0008] Secondly, embodiments of this application also provide an electro-deionization device for removing radionuclide ions from low-level radioactive waste liquid using the method provided in the embodiments of this application. The device includes: a power supply, an electrode module, an ion adsorption module, and a separation module. The power supply powers the electrode module. The electrode module forms an electric field when the power is switched on, driving ion migration under the influence of the electric field. The electrode module includes a cathode and an anode. The ion adsorption module removes cations and prevents anion migration during ion migration, forming a clean water zone and an anion enrichment zone around the ion adsorption module, respectively. The separation module separates the liquid in the clean water zone and the liquid in the anion enrichment zone, and collects the separated liquid in the clean water zone to obtain a liquid free of radionuclide ions.

[0009] These and other advantages of this application will become more apparent from the following detailed description of preferred embodiments in conjunction with the accompanying drawings. Attached Figure Description

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

[0011] Figure 1 This is a schematic flowchart of a method for removing radionuclide ions from low-level radioactive waste liquid according to an embodiment of this application;

[0012] Figure 2 This is a schematic diagram of an electro-deionization apparatus according to an embodiment of this application.

[0013] It should be noted that the accompanying drawings are not necessarily drawn to scale, but are shown only in a schematic manner without affecting the reader's understanding.

[0014] Explanation of reference numerals in the attached figures:

[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 zone; 242. Anion enrichment zone;

[0019] 251. Radioactive waste liquid; 252. Anode electrolyte; 253. Cathode electrolyte; 254. Purified liquid; 255. Concentrated liquid. Detailed Implementation

[0020] Exemplary embodiments of this application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of actual implementations are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the development of any such actual embodiment to achieve the developer's specific goals, such as complying with constraints related to the system and business, and these constraints may vary depending on the implementation. Furthermore, it should be understood that while development work can be very complex and time-consuming, such development work is merely a routine task for those skilled in the art who benefit from the content of this application.

[0021] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the equipment structure and / or processing steps closely related to the solution according to this application are shown in the accompanying drawings, while other details that are not closely related to this application are omitted.

[0022] It should be noted that, unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning as understood by a person with ordinary skills in the field to which this application pertains.

[0023] In the description of the embodiments of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0024] Currently used methods for treating radioactive wastewater still face numerous challenges. For example, in electrodeionization (EDI), the operating current must be maintained below the limiting current density. Exceeding this limit increases water dissociation, increasing the transport difference between the membrane and the solution, leading to reduced current efficiency and concentration polarization at the membrane surface. This concentration polarization reduces the effective driving force across the ion exchange membrane, causing membrane fouling and scaling, ultimately reducing membrane flux and hindering effective removal of radioactive nuclide ions from the wastewater. Furthermore, low-level radioactive wastewater typically has low conductivity. Using such wastewater as raw water results in very high resistance and energy consumption during the electrodeionization process.

[0025] To address the aforementioned technical problems, embodiments of this application provide a method for removing radionuclide ions from low-level radioactive waste liquid, which is applicable to electrostatic ionization devices. Figure 1 This is a schematic flowchart of a method for removing radionuclide ions from low-level radioactive waste liquid according to an embodiment of this application, as shown below. Figure 1 As shown, it includes the following steps S1 to S4.

[0026] S1. Turn on the power supply of the electro-deionization device to create a first electric field between the cathode and anode of the electro-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 electro-deionization device, and the ion adsorption module of the electro-deionization device removes the cations during the migration process, so as to form a clean water zone in a first predetermined range near the anode of the same polarity ion exchange membrane. The ion adsorption module includes multiple 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, anions in the radioactive waste liquid migrate toward the anode of the electro-ionization device, and the anion adsorption module is used to prevent the anions from migrating, so as to form an anion enrichment zone in a second predetermined range near the cathode of the same polarity ion exchange membrane.

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

[0030] The method provided in the embodiments of this application utilizes multiple homopolar ion exchange membranes and porous media to adsorb cations migrating towards anions in radioactive waste liquid, while simultaneously preventing anions from migrating towards the anode. Since the porous media with a weak charge is filled between the homopolar ion exchange membranes, under the action of a first electric field, the migration and diffusion rates of different radionuclide ions in the radioactive waste liquid are different in the porous media. Under normal circumstances, the migration rate of ions is faster than the diffusion rate during migration, which can avoid the diffusion restriction encountered during the electro-ion removal process. Thus, a clean water zone and an anion enrichment zone can be formed near the homopolar ion exchange membranes, respectively. By separating and collecting the liquid in the clean water zone and the liquid in the anion enrichment zone, a purified liquid that effectively removes radionuclide ions from the radioactive waste liquid can be obtained with high removal efficiency.

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

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

[0033] In some embodiments, prior to step S4, the method may further include: adjusting the current of the electro-deionization device to form a second electric field between the cathode and anode of the electro-deionization device; under the action of the second electric field, reducing the ion concentration of the liquid in the purified water zone to form a concentration difference with the ion concentration of the liquid in the anion enrichment zone.

[0034] The method provided in the embodiments of this application uses the current of the electro-deionization device to create a concentration differential polarization in the radioactive waste liquid, which is beneficial for separating and collecting the liquid in the clean water zone and the anion-rich zone, thereby improving the efficiency of obtaining liquid with radionuclide ions removed.

[0035] In some embodiments, the porous medium surface is weakly electronegative, which can make the migration rate of ions greater than the diffusion rate, thereby accelerating the migration of cations through the porous medium towards the negative electrode, and enriching anions near the porous medium, thus forming a concentration gradient.

[0036] In some embodiments, the method provided in this application addresses 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 recovered with a recovery rate of over 40%.

[0037] In some embodiments, adjusting the current of the electro-deionization device may include: increasing the power supply voltage of the electro-deionization device to make the current of the electro-deionization device reach an over-limit current, so that the ion concentration of the liquid in the purified water zone approaches zero.

[0038] The method provided in the embodiments of this application increases the power supply voltage of the electro-deionization device to make the current of the electro-deionization device reach the over-limit current. This helps to make the ion concentration of the liquid in the water purification zone 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 micrometers, and the surface of the porous medium has good electronegativity, which is beneficial for separating cations and anions during ion migration, thereby achieving a better electroremoval effect.

[0040] In some embodiments, in step S4, the separation module of the electro-deionization device is used to continuously separate the liquid in the purified water zone from the liquid in the anion enrichment zone, so as to collect the liquid in the purified water zone in a timely manner and avoid ion diffusion.

[0041] In some embodiments, after step S1, the method further includes: adjusting the current of the electro-ionization device according to the valence state of the radionuclide ions to achieve targeted removal of radionuclides, which helps to ensure the removal efficiency for different radionuclides.

[0042] Embodiments of this application also provide an electro-deionization device for removing radionuclide ions from low-level radioactive waste liquid using the method described in the embodiments of this application. Figure 2 This is a schematic diagram of an electro-deionization device according to an embodiment of this application, as shown below. Figure 2 As shown, the electro-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 in the image).

[0043] Power supply 210 is used to supply power to electrode module 220.

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

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

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

[0047] The electro-ionization device provided in this application fills the middle of the same-polarity ion exchange membrane with a weakly charged porous medium. Under the action of a first electric field, the migration and diffusion rates of different radionuclide ions in the radioactive waste liquid are different in the porous medium. Under normal circumstances, the migration rate of ions is faster than the diffusion rate during migration. This avoids the diffusion restriction encountered during the electro-ionization process, thereby forming a purified water zone and anion enrichment zone near the same-polarity ion exchange membrane. By separating and collecting the liquid in the purified water zone and the liquid in the anion enrichment zone, radionuclide ions in the radioactive waste liquid can be effectively removed with high removal efficiency. At the same time, the device provided in this application does not require concern about the saturation and replacement of ion exchange resin, and has a long service life.

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

[0049] In some embodiments, the ion adsorption module 230 includes a plurality of homopolar ion exchange membranes 231 and a porous medium 232, wherein the porous medium 232 is located between two adjacent homopolar ion exchange membranes 231; wherein, the water purification zone 241 is located within a first predetermined range of the homopolar ion exchange membrane 231 near the anode 222, and the anion enrichment zone 242 is located within a second predetermined range of the homopolar ion exchange membrane 231 near the cathode 221.

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

[0051] The following detailed description, based on specific embodiments, illustrates the process of removing radionuclide ions from radioactive waste liquid using the method and electro-ionization device provided in this application.

[0052] Example

[0053] Reference Figure 2When the power supply 210 is turned on, the electrode module 220 can generate an electric field. Under the action of the electric field, the radioactive waste liquid 251 to be treated flows through the porous medium 232. 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. During the migration, the cations are removed after passing through the same polarity ion exchange membrane 231, forming a clean water zone 241 near the same polarity ion exchange membrane 231. At the same time, anions migrate to the anode 222 in the porous medium 232. Since the anions are blocked by the same polarity ion exchange membrane 231, they are enriched in the porous medium 232, forming an anion enrichment zone 242. When an excessive current is applied, the ion concentration in the purified water zone 241 approaches zero, resulting in concentration polarization. However, due to the weak negative charge on the surface of the porous medium 232, ion migration is faster than diffusion. Therefore, cations migrate more rapidly through the porous medium 232 towards the negative electrode, while anions accumulate near the ion exchange membrane 231 on the same polarity as the anode 222 under the influence of the electric field, thus forming a concentration gradient. At the outlet of the electro-deionization device, a separation module at the end of the porous medium 232 separates the liquid in the anion enrichment zone 242 from the liquid in the purified water zone 241, thereby obtaining a concentrated solution 255 and a purified solution 254 free of radioactive cations.

[0054] In some embodiments, a solution containing 0.9% NaCl is obtained, and a stable solution containing Co, Sr, and Cs ions is mixed uniformly with it, wherein the ion concentrations of Co, Sr, and Cs are 0.1 mmol / L, respectively. Then, the method provided in this application embodiment is used to remove Co, Sr, and Cs ions from the mixed solution, 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 sequentially, and the liquids in the purified water zone and the anion-rich zone are separated. Analysis of the liquid in the separated purified water zone shows that the removal rates of radioactive nuclides Co, Sr, and Cs all reach over 99%, and the water recovery rate reaches over 48%.

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

[0056] Regarding the embodiments of this application, it should also be noted that, without conflict, the embodiments of this application and the features in the embodiments can be combined with each other to obtain new embodiments.

[0057] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. The scope of protection of this application shall be determined by the scope of the claims.

Claims

1. A method for removing radionuclide ions from low-level radioactive waste liquid, applicable to an electro-ionization device, characterized in that, It includes the following steps: S1. Turn on the power supply of the electro-deionization device to form a first electric field between the cathode and anode of the electro-deionization device; S2. Under the action of the first electric field, the cations in the radioactive waste liquid migrate toward the cathode of the electro-deionization device, and the ion adsorption module of the electro-deionization device removes the cations during the migration process, so as to form a clean water zone in a first predetermined range near the anode of the same polarity ion exchange membrane. The ion adsorption module includes a plurality of the same polarity ion exchange membranes and a porous medium with a weak charge, and the porous medium is located between two adjacent same polarity ion exchange membranes. S3. Under the action of the first electric field, the anions in the radioactive waste liquid migrate toward the anode of the electro-ionization device, and the ion adsorption module is used to prevent the anions from migrating, so as to form an anion enrichment area in the second predetermined range near the cathode of the same polarity ion exchange membrane. S4. Separate the liquid in the purified water zone and the liquid in the anion enrichment zone, and collect the separated liquid in the purified water zone to obtain a liquid in which the radioactive nuclide ions have been removed. Prior to step S4, the following is also included: Adjust the current of the electro-ionization device to create a second electric field between the cathode and anode of the electro-ionization device; Under the action of the second electric field, the ion concentration of the liquid in the purified water zone is reduced, so as to form a concentration difference with the ion concentration of the liquid in the anion enrichment zone. Adjusting the current of the electro-ionization device includes: Increase the power supply voltage of the electro-ionization device so that the current of the electro-ionization device reaches the over-limit current, so that the ion concentration of the liquid in the purified water zone approaches zero.

2. The method according to claim 1, characterized in that, The diameter of the porous medium is in the range of 1-10 micrometers.

3. The method according to claim 1, characterized in that, In step S4, The separation module of the electro-deionization device is used to continuously separate the liquid in the purified water zone and the liquid in the anion enrichment zone.

4. The method according to claim 1, characterized in that, Following step S1, the method further includes: The current of the electro-ionization device is adjusted according to the valence state of the radionuclide ions to achieve targeted removal of the radionuclide.

5. An electro-ionization device, characterized in that, The method for removing radionuclide ions from low-level radioactive waste liquid by means of the method described in any one of claims 1-4 includes: 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 generate 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 an anion enrichment zone around the ion adsorption module, respectively. The separation module is used to separate the liquid in the purified water zone and the liquid in the anion enrichment zone, and collect the separated liquid in the purified water zone to obtain the liquid from which the radioactive nuclide ions have been removed.

Images