An electrode capacitor deionization device, a separation system having the deionization device, and a method of using the separation system.

Abstract

This invention relates to the field of water treatment technology, specifically to an electrode capacitor deionization device, a separation system having the deionization device, and a method of using the separation system. The device includes a fixing mechanism, a conductive mechanism, and a reaction mechanism. The guiding mechanism includes at least two graphite collectors spaced apart and oppositely distributed. The reaction mechanism includes a hollow reaction plate and a hollow concentration plate. The fixing mechanism includes two fixing plates spaced apart and oppositely distributed. The conductive mechanism and the reaction mechanism are distributed in the area between the two fixing plates. A cation exchange membrane is provided between the hollow reaction plate and the hollow concentration plate. The electrode capacitor deionization device disclosed in this invention simplifies the subsequent ion desorption process by adding a hollow concentration plate, thereby reducing subsequent operation steps. Simultaneously, by setting up the cation exchange membrane, when the cation type is limited, the ion sieving function based on the ion hydration radius achieves better ion selective separation.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to an electrode capacitor deionization device, a separation system having the deionization device, and a method of using the separation system. Background Technology

[0002] Lithium batteries are a popular material in new energy research and development today, and they occupy a very important position in the domestic new energy field, especially as power batteries for new energy vehicles.

[0003] However, with the development of my country's new energy vehicle industry, the scrapping of power batteries has become increasingly large-scale. If a large number of scrapped lithium-ion batteries are not disposed of in a timely and proper manner, they will cause serious harm to the environment and human health, and result in a waste of resources.

[0004] Typical automotive lithium-ion battery cathodes contain scarce mineral resources such as lithium (Li), cobalt (Co), and nickel (Ni).

[0005] Lithium accounts for nearly half of the cost of lithium battery cathode materials, making lithium resources as important as strategic resources such as oil.

[0006] In the coming years, the market demand for lithium will see tremendous growth; cobalt is also an important reserve resource with wide applications in commercial, industrial and even military fields. It is widely used in metallurgy, chemical, alloy, battery and mining industries. Whether it is the manufacture of smartphones or aircraft engines, cobalt is one of the indispensable metals.

[0007] Therefore, conducting research on the recycling of lithium and cobalt resources from waste lithium cobalt oxide batteries using relevant technologies is of great significance for alleviating the heavy metal resource crisis.

[0008] After pretreatment, some non-recyclable materials in waste lithium cobalt oxide batteries can be removed, and the cathode material that is of recycling value in the lithium battery can be separated from the other materials. Then, the valuable heavy metals in the cathode material are leached into the solution in ionic form using a leaching agent. Finally, the metal ions in the leaching solution are separated and purified.

[0009] Traditional separation and purification techniques mainly include solvent extraction, ion exchange resin method, chemical precipitation method, and electrodeposition method.

[0010] However, these traditional separation and purification technologies all suffer from problems such as high investment costs, low recovery rates, poor selectivity, poor separation effects, and additional pollution effects.

[0011] Capacitive deionization (CDI) originated in the 1960s and is an electrically driven membrane separation technology that has gradually developed due to its advantages such as simplicity, low energy consumption, and environmental friendliness.

[0012] However, it has problems such as low energy storage efficiency, large co-ion effect, high interfacial resistance between solution and electrode, electrode saturation and need for electrode regeneration, and loss of solution during charge-discharge conversion.

[0013] Therefore, in order to solve or improve at least one problem, a new type of ion separation device or system is needed now. Summary of the Invention

[0014] The purpose of this invention is to provide an electrode capacitor deionization device with a simple structure that can selectively separate lithium ions and cobalt ions.

[0015] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0016] An electrode capacitor deionization device includes a fixing mechanism, a conductive mechanism, and a reaction mechanism;

[0017] The guiding mechanism includes at least two graphite collectors spaced apart and opposite to each other;

[0018] The reaction mechanism includes a hollow reaction plate and a hollow concentration plate;

[0019] At least one reaction mechanism is distributed between the two graphite current collectors;

[0020] The fixing mechanism includes two fixing plates that are spaced apart and opposite to each other;

[0021] The conductive mechanism and the reaction mechanism are distributed in the area between the two fixed plates;

[0022] A cation exchange membrane is provided between the hollow reaction plate and the hollow concentration plate.

[0023] The graphite current collector is provided with electrode channels; the electrode channels are arranged in a meandering manner on the graphite current collector; an anion exchange membrane is provided between the hollow reaction plate or hollow concentration plate and the adjacent graphite current collector.

[0024] The hollow reaction plate includes a reaction plate with a reaction cavity; the hollow concentration plate includes a concentration plate with a concentration cavity; the reaction plate has a first liquid inlet and a first liquid outlet; the first liquid inlet and the first liquid outlet are respectively connected to the reaction cavity; the first liquid inlet and the first liquid outlet are located diagonally on the reaction plate; the concentration plate has a second liquid inlet and a second liquid outlet; the second liquid inlet and the second liquid outlet are respectively connected to the concentration cavity; the second liquid inlet and the second liquid outlet are located diagonally on the concentration plate.

[0025] The two graphite manifolds are respectively bonded to the adjacent hollow reaction plate or hollow concentration plate through sealing rings.

[0026] A lithium-cobalt ion separation system includes a flowing electrode supply mechanism, a power supply mechanism, a concentration and circulation mechanism, and a solution to be treated supply mechanism; the flowing electrode supply mechanism, the solution to be treated supply mechanism, and the concentration and circulation mechanism are respectively connected to the electrode capacitor deionization device through a pipeline mechanism.

[0027] The power supply mechanism is connected to the graphite current collector in the electrode capacitor deionization device. The power supply mechanism includes a DC power supply box, which is connected to the two graphite current collectors respectively through wires.

[0028] The flowing electrode supply mechanism is connected to the graphite collector plate in the electrode capacitor deionization device via a pipeline mechanism; the concentration and circulation mechanism is connected to the hollow concentration plate in the electrode capacitor deionization device via a pipeline mechanism; and the solution to be treated supply mechanism is connected to the hollow reaction plate in the electrode capacitor deionization device via a pipeline mechanism.

[0029] The separation system includes two flowing electrode supply mechanisms; each flowing electrode supply mechanism includes an electrode liquid supply tank, in which flowing electrode liquid is arranged, and the flowing electrode liquid contains magnesium citrate carbonized material.

[0030] The piping system includes an inlet pipe and an outlet pipe, both of which are silicone tubes. A peristaltic pump is installed on the inlet pipe. The flowing electrode supply mechanism, the solution to be treated supply mechanism, and the concentration and circulation mechanism are respectively connected to the electrode capacitor deionization device through the inlet pipe. The electrode capacitor deionization device is respectively connected to the flowing electrode supply mechanism, the solution to be treated supply mechanism, and the concentration and circulation mechanism through the outlet pipe.

[0031] A method of using the lithium-cobalt ion separation system, the method comprising the following steps:

[0032] Step 1: Prepare two flow electrode cups; one cup as the anode electrode solution and the other cup as the cathode electrode solution; at the same time, add the solution to be treated to the treatment solution supply mechanism;

[0033] Step 2: Use a peristaltic pump to deliver the anolyte and cathode electrolyte to the corresponding graphite manifolds; use a peristaltic pump to deliver the liquid to be treated to the hollow reaction plate; use a peristaltic pump to pump the circulating liquid into the hollow concentrator.

[0034] Step 3: The power supply provides an electric field force to adsorb and separate ions in the liquid to be treated.

[0035] The advantages of this invention are:

[0036] This invention discloses an electrode capacitor deionization device, a separation system having the deionization device, and a method of using the separation system.

[0037] The motor capacitor deionization device disclosed in this invention simplifies the subsequent ion desorption process by adding a hollow concentration plate, thereby reducing subsequent operation steps.

[0038] In addition, by setting up a cation exchange membrane, the present invention can achieve ion sieving based on the ion hydration radius by limiting the cation type, thereby making the ion selective separation effect better.

[0039] Meanwhile, the present invention uses magnesium citrate carbonized material to prepare the flow electrode solution, which makes the flow electrode solution a material with large specific surface area, high mesoporous ratio and negative surface charge, thus greatly improving the adsorption efficiency. Since no additional carbon source and pretreatment process are required, it is very simple and economical. Attached Figure Description

[0040] The following is a brief explanation of the contents of each of the accompanying drawings and the markings in the drawings:

[0041] Figure 1 This is a schematic diagram of the electrode capacitor deionization device of the present invention.

[0042] Figure 2 This is a schematic diagram of the overall structure of the separation system of the present invention.

[0043] The markings in the above figures are all:

[0044] 1. Conductivity meter; 2. Piping mechanism; 3. Solution supply mechanism; 4. Peristaltic pump; 5. Flow electrode supply mechanism; 6. Power supply mechanism; 7. Electrode capacitor deionization device; 8. Fixing plate; 9. Graphite current collector; 10. Hollow core reaction plate; 11. Concentration and circulation mechanism; 12. Anion exchange membrane; 13. Sealing ring; 14. Cation exchange membrane; 15. Hollow core concentrator. Detailed Implementation

[0045] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and the description of the preferred embodiments.

[0046] An electrode capacitor deionization device 7 includes a fixing mechanism, a conductive mechanism, and a reaction mechanism; the electrode capacitor deionization device 7 disclosed in this invention can achieve ion separation of the solution to be treated through the arrangement of the fixing mechanism, the conductive mechanism, and the reaction mechanism.

[0047] In addition, the guiding mechanism described in this invention includes at least two graphite current collectors 9 spaced apart and relatively distributed; the arrangement of the two graphite current collectors 9 facilitates the introduction of flow electrodes during subsequent use. At the same time, the graphite current collectors 9 are connected to the power supply mechanism 6, so that the graphite current collectors 9 are energized, thereby realizing the separation of corresponding ions in the solution to be treated.

[0048] Meanwhile, the reaction mechanism described in this invention includes a hollow reaction plate 10 and a hollow concentration plate 15; the hollow reaction plate 10 is configured as a reaction chamber, and in subsequent use, the solution to be treated is introduced into the hollow reaction plate 10; under the action of the current connected to the power supply mechanism 6, the separation operation of corresponding ions in the solution to be treated is realized.

[0049] In addition, the hollow thickening plate 15 serves to collect the corresponding cations in the solution to be treated, and its basic function is to concentrate ions.

[0050] Meanwhile, in this invention, at least one reaction mechanism is distributed between the two graphite current collectors 9; the fixing mechanism includes two fixed plates 8 that are spaced apart and opposite to each other; the conductive mechanism and the reaction mechanism are distributed in the area between the two fixed plates 8; through the setting of the fixed plates 8, the two fixed plates 8 are arranged opposite to each other, and the two fixed plates 8 press and fix the conductive mechanism and the reaction mechanism; thereby realizing the fixed connection between the fixing mechanism, the conductive mechanism and the reaction mechanism.

[0051] In addition, a cation exchange membrane 14 is provided between the hollow reaction plate 10 and the hollow concentration plate 15 in this invention; in subsequent use, by limiting the type of exchange membrane, the separation of different ions can be achieved. That is, in actual operation, the separation of corresponding ions can be achieved inside the electrode capacitor deionization device 7, thereby achieving ion concentration and simplifying the subsequent ion desorption process.

[0052] Furthermore, the graphite current collector 9 described in this invention is provided with electrode channels 91; the setting of electrode channels 91 facilitates the flow of the flowing electrode on the graphite current collector 9; in addition, the electrode channels 91 described in this invention are arranged in a meandering manner on the graphite current collector 9; this arrangement increases the flow path of the flowing electrode on the graphite current collector 9, optimizes the adsorption and separation of ions in the solution to be treated, and at the same time, the aforementioned meandering arrangement in this invention is generally S-shaped, equivalent to the arrangement of condenser tubes in a traditional refrigerator. Additionally, an anion exchange membrane 12 is provided between the hollow reaction plate 10 or hollow concentration plate 15 and the adjacent graphite current collector 9; the setting of the anion exchange membrane 12 facilitates the subsequent passage of anions, and during subsequent use, the retention of cations in the hollow concentration plate 15 can be better ensured by the barrier of the anion exchange membrane 12, while the setting of the anion exchange membrane 12 facilitates the adsorption and removal of anions in the solution to be treated.

[0053] Furthermore, in this invention, the hollow reaction plate 10 includes a reaction plate with a reaction cavity 101; the hollow concentration plate 15 includes a concentration plate with a concentration cavity 151. The presence of the reaction cavity 101 facilitates the entry of the solution to be treated into the hollow reaction plate 10, thereby facilitating subsequent electro-separation of the solution. The concentration cavity 151 facilitates the collection of the separated cations within the concentration cavity 151, thereby achieving concentration and collection of the corresponding cations within the concentration cavity 151. This simplifies the subsequent ion desorption process and makes the operation more convenient.

[0054] Meanwhile, the reaction plate in this invention is provided with a first inlet hole and a first outlet hole; the first inlet hole and the first outlet hole are respectively connected to the reaction cavity 101; the first inlet hole facilitates the entry of the solution to be treated into the hollow reaction plate 10, and the first outlet hole facilitates the discharge of the solution from the hollow reaction plate 10. In addition, the concentration plate in this invention is provided with a second inlet hole and a second outlet hole; the second inlet hole and the second outlet hole are respectively connected to the concentration cavity 151; the second inlet hole facilitates the entry of the concentrated liquid into the concentration plate and facilitates the collection of cations in the concentrated liquid in the concentration cavity 151 after separation; the second outlet hole facilitates the discharge of the concentrated aqueous solution.

[0055] Meanwhile, in this invention, the first inlet and the first outlet are located diagonally on the reaction plate; generally, the first inlet is located at the lower end of the hollow reaction plate 10, and the first outlet is located at the upper end of the hollow reaction plate 10; the second inlet and the second outlet are located diagonally on the concentration plate; generally, the second inlet is located at the lower end of the hollow concentration plate 15, and the second outlet is located at the upper end of the hollow concentration plate 15. This arrangement increases the flow path of the solution to be treated and the concentrated solution to a certain extent, better ensuring the secondary processing efficiency of the solution to be treated, and also better ensuring the accumulation of cations in the concentrated solution.

[0056] Furthermore, in this invention, the two graphite current collectors 9 are respectively bonded to the adjacent hollow reaction plate 10 or hollow concentration plate 15 by sealing rings 13; the sealing rings 13 ensure the sealing between the plates and better guarantee the overall sealing of the entire electrode capacitor deionization device 7.

[0057] A lithium-cobalt ion separation system includes a flowing electrode supply mechanism 5, a power supply mechanism 6, a concentration and circulation mechanism 11, and a solution supply mechanism 3. The flowing electrode supply mechanism 5, the solution supply mechanism 3, and the concentration and circulation mechanism 11 are respectively connected to an electrode capacitor deionization device 7 via a pipeline mechanism 2. This invention, through the above separation system, can process the salt solution to be treated. In this invention, the flowing supply mechanism mainly includes an electrode liquid supply tank, which provides the flowing electrode for adsorption. The power supply mechanism 6 is connected to a graphite current collector 9 in the electrode capacitor deionization device 7. The source mechanism 6 includes a DC power supply box, which is connected to two graphite current collectors 9 via wires. Meanwhile, the concentration and circulation mechanism 11 mainly includes a concentration supply tank, which stores the concentrated solution, typically pure water. The circulation of the concentrated solution allows the separated cations to accumulate within it. Simultaneously, the solution-to-be-treated supply mechanism 3 mainly includes a feed tank containing the solution to be treated. Under the action of the peristaltic pump 4, the solution to be treated can repeatedly enter the hollow reaction plate 10, better ensuring the separation of ions in the solution to be treated.

[0058] Furthermore, in this invention, the flowing electrode supply mechanism 5 is connected to the graphite current collector 9 in the electrode capacitor deionization device 7 via the pipeline mechanism 2; the concentration circulation mechanism 11 is connected to the hollow concentration plate 15 in the electrode capacitor deionization device via the pipeline mechanism 2; and the solution to be treated supply mechanism 3 is connected to the hollow reaction plate 10 in the electrode capacitor deionization device 7 via the pipeline mechanism 2. Through the above design, this invention facilitates the connection and communication between the flowing electrode supply mechanism 5, the power supply mechanism 6, the concentration circulation mechanism 11, the solution to be treated supply mechanism 3, and the electrode capacitor deionization device 7, thus facilitating subsequent use.

[0059] Furthermore, the separation system described in this invention includes two flowing electrode supply mechanisms 5; each flowing electrode supply mechanism 5 includes an electrode liquid supply tank, in which flowing electrode liquid is arranged. Through the arrangement of the flowing electrodes, continuous desalination can be achieved. Additionally, the flowing electrode liquid in this invention contains magnesium citrate carbonized material. The use of magnesium citrate carbonized material to prepare the flowing electrodes significantly improves adsorption efficiency. Since no additional carbon source or pretreatment process is required, it is very simple and economical.

[0060] Furthermore, in this invention, the pipeline mechanism 2 includes an inlet pipeline 21 and an outlet pipeline 22, both of which are silicone tubes. A peristaltic pump 4 is arranged on the inlet pipeline 21. The flowing electrode supply mechanism 5, the solution to be treated supply mechanism 3, and the concentration and circulation mechanism 11 are respectively connected to the electrode capacitor deionization device 7 through the inlet pipeline 21. The electrode capacitor deionization device 7 is respectively connected to the flowing electrode supply mechanism 5, the solution to be treated supply mechanism 3, and the concentration and circulation mechanism 11 through the outlet pipeline 22. The pipeline mechanism 2 in this invention plays a good bridging role, facilitating the connection of the flowing electrode supply mechanism 5, the solution to be treated supply mechanism 3, and the concentration and circulation mechanism 11 to the electrode capacitor deionization device 7. In specific arrangements, the length and diameter of the inlet pipeline 21 and the outlet pipeline 22 are selected as needed.

[0061] A method of using the lithium-cobalt ion separation system, the method comprising the following steps:

[0062] Step 1: Prepare two flow electrode cups; one cup as the anode electrode solution and the other cup as the cathode electrode solution; at the same time, add the solution to be treated to the treatment solution supply mechanism;

[0063] Step 2: Use peristaltic pump 4 to transport the anolyte and cathode electrode solutions to the corresponding graphite manifolds 9; use peristaltic pump 4 to transport the solution to be treated to the hollow reaction plate 10; use peristaltic pump 4 to pump the circulating solution into the hollow concentrator 15.

[0064] Step 3: The power supply mechanism 6 provides an electric field force to adsorb and separate the ions in the liquid to be treated.

[0065] Based on the above-described method, this invention enables ion separation of solutions to be treated in the mining industry.

[0066] specific:

[0067] The separation system disclosed in this invention mainly includes a DC power supply, a conductivity meter 1, a peristaltic pump 4, an electrode capacitor deionization device 7, and a pipeline mechanism 2; the electrode capacitor deionization device 7 includes two graphite current collectors 9, two anion exchange membranes 12, a cation exchange membrane 14, a hollow reaction plate 10, and a hollow concentration plate 15; in addition, the separation system in this invention also includes a solution supply mechanism 3; the solution supply mechanism 3 facilitates the feeding operation to the electrode capacitor deionization device 7.

[0068] In this invention, the cation exchange membrane 14 is a modified MXene monovalent selective cation exchange membrane 14 (MXene-CSO).

[0069] In practical implementation, it is necessary to prepare MXene-CSO thin films.

[0070] Specifically: Prepare a 5 mg / mL MXene colloidal solution. Take 20 mL of the 5 mg / mL MXene colloidal solution in a beaker, add 300 mL of pure water for appropriate dilution, and filter it under vacuum with a monovalent selective cation exchange membrane 14 as the substrate to form a uniform and complete two-dimensional layered MXene-CSO membrane.

[0071] Finally, the prepared MXene-CSO film was dried in a vacuum drying oven at 60°C.

[0072] Simultaneously, it is also necessary to prepare magnesium citrate carbonized materials.

[0073] Magnesium citrate was directly carbonized in a tube furnace under a nitrogen atmosphere at a heating rate of 5°C / min.

[0074] After cooling to room temperature, a magnesium-containing carbon sample was obtained.

[0075] The sample was then placed in 3M HCl and stirred at room temperature for 12 hours to remove MgO particles.

[0076] After thorough washing and air drying, a sample of magnesium citrate carbonized material was obtained.

[0077] Carbonization temperatures of 700℃, 800℃, and 900℃ were set to investigate the effects of carbonization temperature on the morphology and electrochemical performance of high-performance samples.

[0078] Simultaneously, two cups of flow electrode slurry were prepared. The conductive suspension formed by mixing the prepared magnesium citrate carbonized material, carbon black, and pure water under magnetic stirring for 12 hours was used as the anode flow electrode. The conductive suspension formed by mixing high specific surface area activated carbon, carbon black, and pure water under magnetic stirring for 12 hours was used as the cathode flow electrode. The volume of each side of the flow electrode was 50 ml, the mass fraction of carbon material was 10%, and the mass fraction of carbon black was 1%.

[0079] The solution to be treated is generally a mixed solution of lithium chloride and cobalt chloride; it serves as the feed solution in subsequent use.

[0080] The feed solution is formed by ultrasonically mixing lithium chloride, cobalt chloride hexahydrate, and pure water for 1 minute. The ultrasonication aims to achieve uniform mixing. The feed solution volume is 100 ml, and the concentrations of lithium ions and cobalt ions are both 5 mM.

[0081] In addition, prepare a 100ml pure water solution as the feed solution for the hollow concentrate plate 15; the concentrated solution flows through the concentration circulation mechanism 11.

[0082] In addition, in this invention, the electrode capacitor deionization device 7 uses screws to fix each fixing plate 8, each graphite current collector 9, each ion exchange membrane, each silicone gasket, and the hollow reaction plate 10 in sequence.

[0083] Silicone gaskets are used to ensure tight contact with the ion exchange membrane and hollow reaction plate 10 to prevent leakage of the feed liquid.

[0084] Meanwhile, in this invention, the pipeline mechanism 2 is a silicone tube, connecting the electrode capacitor deionization device 7 to each peristaltic pump 4, the flowing electrode supply mechanism 5, the concentration circulation mechanism 11, and the solution to be treated supply mechanism 3. Additionally, the hollow reaction plate 10 includes a reaction plate with a reaction cavity 101; the hollow concentration plate 15 includes a concentration plate with a concentration cavity 151; the reaction plate has a first inlet hole and a first outlet hole; the first inlet hole and the first outlet hole are respectively connected to the reaction cavity 101; the first inlet hole and the first outlet hole are located diagonally on the reaction plate; the concentration plate has a second inlet hole and a second outlet hole; the second inlet hole and the second outlet hole are respectively connected to the concentration cavity 151; the second inlet hole and the second outlet hole are located diagonally on the concentration plate. In subsequent connections, the first inlet hole, the first outlet hole, the second inlet hole, and the second outlet hole are respectively connected to silicone tubes, thereby forming an electrode liquid circuit and a solution to be treated circuit.

[0085] Connect the positive terminal of the DC power supply box to the graphite current collector 9 in the cathode chamber, and the negative terminal to the graphite current collector 9 in the anode chamber.

[0086] Meanwhile, in actual use, the speed of the small peristaltic pump 4 is adjusted, the feed flow rate is 10 ml / min, and the flow electrode flow rate is set to 10 ml / min, 15 ml / min, 25 ml / min, 35 ml / min, and 45 ml / min respectively. Based on this design, in actual use, the effect of electrode flow rate on adsorption rate and adsorption performance can be studied.

[0087] The DC power supply voltage was adjusted to 0.8V, 1.2V, 1.5V, 1.8V, and 2.1V to study the effect of voltage on adsorption rate and adsorption performance.

[0088] Conductivity meter 1 is placed in the solution to be treated to detect conductivity. Data is recorded every 10 seconds. The feed flow rate, electrode flow rate and voltage are adjusted by monitoring the data to ensure long-term stable selective deionization effect.

[0089] The anion exchange membrane 12 in this invention is a common commercial anion exchange membrane 12, which simultaneously serves to selectively permeate anions and separate the feed liquid from the flowing electrode liquid; the cation exchange membrane 14 is a modified MXene monovalent selective cation exchange membrane 14 (MXene-CSO), which simultaneously serves to selectively permeate lithium ions while blocking cobalt ions and separating the mixed feed liquid from the concentrate.

[0090] After the electric field force is provided by the DC power supply, the lithium ions in the feed liquid are adsorbed into the concentration chamber (concentration chamber 151) through the MXene-CSO membrane under the ion migration effect generated by the electric field and the adsorption effect of the magnesium citrate carbon electrode. The cobalt ions in the feed liquid are blocked by the MXene-CSO membrane and remain in the original feed solution (original solution to be treated). The chloride ions in the solution to be treated are adsorbed into the cathode electrode chamber.

[0091] In summary, the electrode capacitor deionization device 7 disclosed in this invention can be better applied to separation systems. Through the setting of the separation system, this invention can achieve a long-term, stable and efficient desalination effect. At the same time, by using a modified MXene monovalent selective cation exchange membrane 14, the electrode capacitor deionization device 7 can achieve a selective deionization process for lithium-cobalt mixed solutions.

[0092] In addition, the present invention has a flow electrode adsorption material with large specific surface area, high mesoporosity and negative surface charge, which greatly improves the adsorption efficiency; and adopts an improved electrode capacitor deionization device 7 to simplify the subsequent ion desorption process.

[0093] Furthermore, the electrode capacitor deionization device 7 disclosed in this invention has a relatively simple overall structure, is easy to operate, and is easy to automate and monitor online. The device and electrode liquid preparation costs are low, energy consumption is low, and economic performance is strong, providing an effective approach for the efficient treatment of precious metal ions in waste lithium cobalt oxide batteries.

[0094] This invention provides a system for selectively separating lithium and cobalt ions based on capacitive deionization of a flowing electrode. The separation system disclosed in this invention mainly focuses on the selective separation of lithium and cobalt ions, thereby solving the complex problems of electrode saturation and the need for regeneration in traditional CDI technology, improving deionization efficiency, and using a modified MXene monovalent selective cation exchange membrane 14 (MXene-CSO) to selectively separate lithium and cobalt ions, simplifying the subsequent ion desorption process. Based on the above technology, noble metal ions can be effectively separated, purified, and recovered.

[0095] Furthermore, in this invention, the graphite current collector 9 has an electrode channel 91 engraved on the side of the ion exchange membrane, which is the electrode liquid flow channel. The first inlet hole and the first outlet hole for the flow of electrode liquid are opened on the graphite current collector 9 and the hollow reaction plate 10, located diagonally on the graphite current collector 9, and are inserted into the silicone tube to form electrode liquid circuits respectively.

[0096] Similarly, the concentration plate is provided with a second liquid inlet and a second liquid outlet; the second liquid inlet and the second liquid outlet are respectively connected to the concentration chamber 151; and are inserted into the silicone tube to form a concentration circuit.

[0097] Furthermore, the graphite plate flow channel is closely attached to the anion exchange membrane 12 to form the cathode electrode chamber and the anode electrode chamber. The modified MXene-CSO membrane is closely attached between the two hollow reaction plates 10, and they respectively form the feed chamber (reaction chamber 101) and the concentration chamber (concentration chamber 151).

[0098] Furthermore, in the electrode liquid circuit, the electrode flow direction within the electrode liquid flow channel is upward, and in the solution to be treated circuit, the solution flow direction within the feed chamber and concentration chamber is upward.

[0099] Furthermore, the flowing electrode liquid is a conductive suspension formed by mixing the prepared magnesium citrate carbonized material, carbon black, and pure water under magnetic stirring for 12 hours, and the cathode flowing electrode is a conductive suspension formed by mixing high specific surface area activated carbon, carbon black, and pure water under magnetic stirring for 12 hours.

[0100] The solution to be treated can be a lithium chloride and cobalt chloride feed solution; and the lithium chloride and cobalt chloride feed solution is a feed solution formed by ultrasonic oscillation of lithium chloride, cobalt chloride hexahydrate, and pure water for 1 minute.

[0101] The feed liquid to the concentration chamber is pure water.

[0102] Furthermore, the magnesium citrate carbonization material is produced by directly carbonizing magnesium citrate in a tube furnace at 700℃-900℃ under a nitrogen atmosphere, with a heating rate of 5℃ / min.

[0103] After cooling to room temperature, a magnesium-containing carbon sample was obtained. The sample was then placed in 3M HCl and stirred at room temperature for 12 hours to remove MgO particles.

[0104] After thorough washing and air drying, a sample of magnesium citrate carbonized material was obtained.

[0105] Furthermore, the modified MXene monovalent selective cation exchange membrane 14 (MXene-CSO) was prepared using a vacuum-assisted method. A 5 mg / mL MXene colloidal solution was prepared, and 20 mL of this solution was placed in a beaker and diluted appropriately with 300 mL of pure water. Under vacuum assistance, using the monovalent selective cation exchange membrane 14 as a substrate, a uniform and intact two-dimensional layered MXene-CSO membrane was formed by filtration. Finally, the prepared MXene-CSO membrane was dried in a vacuum drying oven.

[0106] Furthermore, screws are used to fix each fixing plate 8, each graphite current collector 9, each ion exchange membrane, each silicone gasket, and the hollow reaction plate 10.

[0107] Based on the structure of the improved electrode capacitor deionization device 7, a concentration chamber 151 is added. An anion exchange membrane 12 is closely attached between the concentration chamber and the anode electrode chamber, so that the adsorbed cations are directly concentrated in the concentration chamber.

[0108] Finally, peristaltic pump 4 is used to circulate and transport the flow electrode and the solution to be treated.

[0109] Furthermore, a voltage is applied to the experimental setup to achieve deionization.

[0110] The advantages of this invention are:

[0111] 1. Ion removal is performed using flow electrode capacitive deionization technology. Flow electrodes have the advantages of being easy to prepare and capable of continuous desalination.

[0112] 2. An improved electrode capacitor deionization device 7 is adopted. The electrode capacitor deionization device 7 has better electroadsorption adaptability and adds a concentration chamber 151, so that the adsorbed lithium ions are directly concentrated in the concentration chamber, simplifying the subsequent ion desorption process and making the operation process more convenient.

[0113] 3. A modified MXene monovalent selective cation exchange membrane 14 (MXene-CSO) was used to prepare a two-dimensional (2D) nanosheet layered membrane based on the CSO membrane, which realizes the ion sieving function based on the ion hydration radius, resulting in better ion selective separation effect;

[0114] 4. By using magnesium citrate as a carbonization material, a material with a large specific surface area, high mesoporous ratio and negative surface charge was prepared, which greatly improved the adsorption efficiency. Since no additional carbon source or pretreatment process is required, it is very simple and economical.

[0115] In this invention, the anode flow electrode is a conductive suspension formed by mixing magnesium citrate carbonized material, carbon black, and pure water under magnetic stirring for 12 hours.

[0116] The cathode flow electrode is a conductive suspension formed by mixing high specific surface area activated carbon, carbon black, and pure water under magnetic stirring for 12 hours.

[0117] The feed solution to be processed is formed by ultrasonic oscillation of lithium chloride, cobalt chloride hexahydrate, and pure water for 1 minute.

[0118] The magnesium citrate carbonized material described in this invention is produced by directly carbonizing magnesium citrate in a tube furnace at 800°C under a nitrogen atmosphere, with a heating rate of 5°C / min. After cooling to room temperature, a magnesium-containing carbon sample is obtained. The sample is then placed in 3M HCl and stirred at room temperature for 12 hours to remove MgO particles. After thorough washing with water and air drying, the magnesium citrate carbonized material sample is obtained. The temperature setting range of the tube furnace is 700°C-900°C.

[0119] The volume of each side of the flow electrode is 50 ml, the mass fraction of carbon material is 10%, the mass fraction of carbon black is 1%, the volume of the feed liquid is 100 ml, and the concentrations of lithium ions and cobalt ions are both 5 mM.

[0120] The modified MXene monovalent selective cation exchange membrane 14 (MXene-CSO) was prepared by vacuum-assisted MXene film preparation. A 5 mg / mL MXene colloidal solution was prepared. 20 mL of the 5 mg / mL MXene colloidal solution was placed in a beaker and diluted appropriately with 300 mL of pure water. Under vacuum assistance, using the monovalent selective cation exchange membrane 14 as a substrate, a uniform and complete two-dimensional layered MXene-CSO film was formed by vacuum filtration. Finally, the prepared MXene-CSO film was dried in a vacuum drying oven.

[0121] The fixing plates 8, graphite current collectors 9, ion exchange membranes, silicone gaskets, and hollow reaction plates 10 are fixed using screws. The improved device adds a concentration chamber 151 to the traditional FCDI device structure. An anion exchange membrane 12 is closely attached between the concentration chamber and the anode electrode chamber, so that the adsorbed cations are directly concentrated in the concentration chamber, simplifying the subsequent ion desorption process.

[0122] Flow electrode capacitive deionization (FCDI) is a newly emerging electrochemical technology in recent years. It is a special type of CDI. It mainly utilizes the effect of capacitance to cause charged ions in the feed water to migrate directionally to the electrode chamber and be adsorbed in the double electric layer structure on the surface of the electrode material, thereby achieving the removal of charged ions from the feed water.

[0123] Compared to traditional fixed electrode capacitive deionization (CDI) technology, FCDI technology uses a flowable slurry as a flowing electrode instead of a fixed electrode. Compared with fixed electrode CDI, it has key advantages such as simple electrode preparation, continuous desalination, high desalination efficiency, high water recovery rate, and easy scalability.

[0124] The performance of FCDI depends to a large extent on the physical, chemical and electrochemical properties of the electrode.

[0125] Electrode materials have the characteristics of large specific surface area, appropriate porosity, high conductivity, large specific capacitance, and good cycle stability, which are conducive to obtaining high ion adsorption performance.

[0126] Activated carbon is widely used in the desalination and softening of brackish water due to its advantages such as large specific surface area, abundant resources, and low cost.

[0127] However, due to the severe overlap effect of EDL in micropores, its ion adsorption capacity and adsorption kinetics are not ideal.

[0128] In recent years, various organometallic compounds, such as organometallic frameworks with high heteroatom content, have been used as carbon precursors to prepare nanoporous carbon with large specific surface area.

[0129] Magnesium citrate, as a typical organometallic salt, is also an ideal carbon precursor for the production of porous carbon due to its high carbon content and low cost.

[0130] Meanwhile, the abundant carboxyl groups in magnesium citrate alter the surface charge properties of the synthesized porous carbon, which is beneficial for ion adsorption during the FCDI process.

[0131] MXenes are a collective term for two-dimensional transition metal carbides, nitrides, and carbonitrides. Currently, MXenes have demonstrated enormous potential in many fields, including lithium-ion batteries, supercapacitors, membrane separation, and photocatalysis.

[0132] MXene materials possess excellent electrical conductivity, hydrophilicity, and pseudocapacitive ion storage properties. Furthermore, the interlayer spacing of MXene nanosheets can be altered by adjusting the interlayer spacing or the stacking strength of the layers themselves, enabling selective ion transport. These properties make MXene an ideal electrode material for ion-selective adsorption in the field of CDI (Continuous Dioxide).

[0133] In addition to being used as an electrode material in CDI technology to improve the desalination rate of the device, MXene, like graphene oxide, can also be used as a two-dimensional (2D) nanosheet layered membrane to achieve ion sieving function based on ion hydration radius.

[0134] An application of a selective separation system based on an electrode capacitance deionization device 7 includes the following steps:

[0135] Prepare MXene-CSO thin films according to the steps described above;

[0136] Magnesium citrate carbonized material was prepared according to the above steps;

[0137] Two flow electrode solutions were prepared by uniformly dispersing magnesium citrate carbonization material and activated carbon with carbon black in pure water, respectively, and stirring on a magnetic stirrer for 12 hours. One solution was used as the anode electrode solution, and the other as the cathode electrode solution. A mixed solution of lithium chloride and cobalt chloride was prepared as the feed solution.

[0138] A small peristaltic pump 4 is used to transport the anode electrode liquid and the cathode electrode liquid to the anode chamber and cathode chamber of the electrode capacitor deionization device 7 through silicone tubes, the feed liquid is transported to the feed chamber, and the pure water is transported to the concentration chamber.

[0139] An electric field is provided by a DC power supply. Under the influence of the electric field and the adsorption of the magnesium citrate carbide electrode, lithium ions in the feed solution are adsorbed into the concentration chamber through the MXene-CSO membrane. Cobalt ions in the feed solution are blocked by the MXene-CSO membrane and remain in the feed solution. Chloride ions in the feed solution are adsorbed into the cathode electrode chamber. The operating conditions of the electrode capacitor deionization device 7 are: supply voltage 0.8-2.1V, feed flow rate 10ml / min, and flow electrode flow rate 10ml / min-45ml / min.

[0140] The conductivity of the feed solution and the concentration chamber is monitored by a conductivity meter 1, and the data is recorded every 10 seconds. The feed flow rate, electrode flow rate and voltage are adjusted based on the monitoring data to ensure a long-term stable selective deionization effect.

[0141] The aforementioned separation system is actually used for the efficient separation and recycling of large quantities of high-value cobalt and lithium metals from waste lithium cobalt oxide batteries.

[0142] Obviously, the specific implementation of this invention is not limited to the above-described methods. Any non-substantial improvements made using the inventive concept and technical solution of this invention are within the protection scope of this invention.

Claims

1. A lithium-cobalt ion separation system, characterized in that, It includes a flowing electrode supply mechanism, a power supply mechanism, a concentration and circulation mechanism, and a solution to be treated supply mechanism; the flowing electrode supply mechanism, the solution to be treated supply mechanism, and the concentration and circulation mechanism are respectively connected to the electrode capacitor deionization device through a pipeline mechanism; The electrode capacitor deionization device includes a fixing mechanism, a conductive mechanism, and a reaction mechanism; The conductive mechanism includes at least two graphite current collectors spaced apart and opposite to each other; The reaction mechanism includes a hollow reaction plate and a hollow concentration plate; At least one reaction mechanism is distributed between the two graphite current collectors; The fixing mechanism includes two fixing plates that are spaced apart and opposite to each other; The conductive mechanism and the reaction mechanism are distributed in the area between the two fixed plates; A cation exchange membrane is provided between the hollow reaction plate and the hollow concentration plate; the cation exchange membrane is an MXene-CSO selective membrane; lithium ions and cobalt ions are screened based on the ion hydration radius. The power supply mechanism is connected to the graphite current collector in the electrode capacitor deionization device. The power supply mechanism includes a DC power supply box, which is connected to the two graphite current collectors respectively through wires. The flowing electrode supply mechanism is connected to the graphite collector plate in the electrode capacitor deionization device via a pipeline mechanism; the concentration and circulation mechanism is connected to the hollow concentration plate in the electrode capacitor deionization device via a pipeline mechanism; and the solution to be treated supply mechanism is connected to the hollow reaction plate in the electrode capacitor deionization device via a pipeline mechanism. The separation system includes two flowing electrode supply mechanisms; each flowing electrode supply mechanism includes an electrode liquid supply tank, in which flowing electrode liquid is arranged. Prepare two flow electrodes; One cup is used as the anode electrode solution, and the other cup is used as the cathode electrode solution. The anode electrode solution is a conductive suspension formed by mixing magnesium citrate carbonized material, carbon black, and pure water under magnetic stirring for 12 hours. The cathode flowing electrode solution is a conductive suspension formed by mixing high specific surface area activated carbon, carbon black, and pure water under magnetic stirring for 12 hours.

2. The lithium-cobalt ion separation system according to claim 1, characterized in that, The graphite current collector is provided with electrode channels; the electrode channels are arranged in a meandering manner on the graphite current collector; an anion exchange membrane is provided between the hollow reaction plate or hollow concentration plate and the adjacent graphite current collector.

3. The lithium-cobalt ion separation system according to claim 1, characterized in that, The hollow reaction plate includes a reaction plate with a reaction cavity; the hollow concentration plate includes a concentration plate with a concentration cavity; the reaction plate has a first liquid inlet and a first liquid outlet; the first liquid inlet and the first liquid outlet are respectively connected to the reaction cavity; the first liquid inlet and the first liquid outlet are located diagonally on the reaction plate; the concentration plate has a second liquid inlet and a second liquid outlet; the second liquid inlet and the second liquid outlet are respectively connected to the concentration cavity; the second liquid inlet and the second liquid outlet are located diagonally on the concentration plate.

4. The lithium-cobalt ion separation system according to claim 1, characterized in that, The two graphite manifolds are respectively bonded to the adjacent hollow reaction plate or hollow concentration plate through sealing rings.

5. A lithium-cobalt ion separation system according to claim 1, characterized in that, The piping system includes an inlet pipe and an outlet pipe, both of which are silicone tubes. A peristaltic pump is installed on the inlet pipe. The flowing electrode supply mechanism, the solution to be treated supply mechanism, and the concentration and circulation mechanism are respectively connected to the electrode capacitor deionization device through the inlet pipe. The electrode capacitor deionization device is respectively connected to the flowing electrode supply mechanism, the solution to be treated supply mechanism, and the concentration and circulation mechanism through the outlet pipe.

6. A method of using the lithium-cobalt ion separation system according to any one of claims 1-5, characterized in that, The method of use includes the following steps: Step 1: Prepare two flow electrode cups; one cup as the anode electrode solution and the other cup as the cathode electrode solution; at the same time, add the solution to be treated to the treatment solution supply mechanism; Step 2: Use a peristaltic pump to deliver the anolyte and cathode electrolyte to the corresponding graphite manifolds; use a peristaltic pump to deliver the liquid to be treated to the hollow reaction plate; use a peristaltic pump to pump the circulating liquid into the hollow concentrator. Step 3: The power supply provides an electric field force to adsorb and separate ions in the liquid to be treated.

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