A multi-stage flow electrode capacitive deionization device and method for lithium extraction from salt lakes

Abstract

The application discloses a kind of multistage flow electrode capacitive deionization device and method for extracting lithium from salt lake, the application utilizes the FCDI device comprising multiple levels, when using, the number of flow electrode capacitive module installed or started in FCDI device can be adjusted as needed, the purification intensity is gradually improved in the same production, the purification efficiency of lithium product is improved, the equipment structure is simple, and installation and adjustment are very convenient;Each level of flow electrode capacitive module is connected with external independent pipeline, and multiple levels of lithium products can be obtained simultaneously and continuously, low-purity lithium products can be obtained to meet the product demand of general industry, and high-purity lithium products can be obtained to meet the product demand of battery or nuclear industry;And in the preparation process, the raw materials used are cheap and easy to obtain, the production process is simple and convenient, and industrial expansion is easier.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium extraction from salt lakes, and particularly relates to a multi-stage flow electrode capacitive deionization device and method for lithium extraction from salt lakes. BACKGROUND

[0002] Lithium resources are mostly obtained from ore-type lithium mines, but ore-type lithium mines are scarce and in crisis. Since lithium resources in salt lakes are abundant and the cost of extracting lithium from ore is too high, it is necessary to develop technology for extracting lithium resources from natural salt lakes. In addition, lithium enrichment steps are required when extracting lithium from salt lakes.

[0003] At present, the main processes for lithium extraction from salt lakes in China include ion exchange, solvent extraction, membrane separation, calcination leaching, solar pond and electrochemical methods. Among them, ion exchange and membrane separation have lower environmental costs, and the use of adsorbents, nanofiltration membranes or electrodialysis membranes can effectively separate lithium and magnesium and enrich lithium ions, but the performance of adsorbents and nanofiltration membranes has bottlenecks. This method is generally used for lithium extraction from salt lakes with low magnesium-lithium ratio; the precipitation method is simple and practical, but has high production cost and poor applicability; the adsorption method has high selectivity and high lithium recovery rate, but has poor recyclability, which causes a large amount of resource waste in the lithium extraction process; the extraction method has high selectivity but also has high production cost, and has problems such as organic pollution and poor recyclability. Therefore, it is urgent to develop a reliable technology with low energy consumption, high selectivity and environmental friendliness for lithium extraction from salt lakes.

[0004] Electrode deionization (CDI) is a new technology applied to remove salt in water, which forces ions to move to the electrode with opposite charge by applying an electric field, and after removing the electric field, the attracted ions are released into the bulk solution, so that the solution concentration increases, achieving the effect of "charging enrichment", but when the concentration of the inlet water increases, the energy consumption of CDI also increases sharply, so it can only be applied to low-purity salt lake lithium extraction; Compared with electrode deionization technology, flow electrode capacitive deionization technology, simply referred to as FCDI technology, is an ion removal technology based on electrochemical reaction principle, which uses electrodes to adsorb and remove ions in water, and further strengthens the ion removal effect in traditional CDI technology through the action of external electric field; The FCDI device couples the flow electrode with the ion exchange membrane, which can overcome the technical bottleneck of limited adsorption capacity and long-term continuous operation of traditional CDI technology, and through the FCDI device, the lithium extraction purity and efficiency can be greatly improved, and the production energy consumption can be reduced; The FCDI device can improve the treatment capacity of the traditional CDI device by several orders of magnitude, effectively solving the above problems, but at present in the field of salt lake lithium extraction, few use flow electrode capacitive deionization device (FCDI device) for treatment, and the few that use FCDI technology can basically only realize single lithium purity output, and for the use demand of high-purity lithium products, repeated lithium extraction needs to be realized in the production process, which is difficult to realize industrial application, so it is urgent to solve. SUMMARY

[0005] In order to avoid and overcome the technical problems existing in the prior art, the present application provides a subject. The present application enables the salt lake solution to complete at least two stages of purification treatment in the same treatment process by connecting at least two stages of flow electrode capacitive modules of different sizes in the FCDI device, improves the purification efficiency, and each stage of flow electrode capacitive module has an independent external channel, so that multiple purity lithium products can be obtained at the same time after treatment, and the simultaneous continuous production of multiple levels of products is realized.

[0006] To achieve the above object, the present application provides the following technical scheme:

[0007] A subject, comprising a multi-stage flow electrode capacitive deionization device (FCDI device), the FCDI device comprising at least two stages of flow electrode capacitive modules;

[0008] The voltage applied to each stage of the flow electrode capacitive module is different;

[0009] The flow electrode capacitive modules of adjacent two stages are in communication with each other;

[0010] Each stage of the flow electrode capacitive module is connected to an external barrel module through a pipeline, so that each stage of the flow electrode capacitive module can form an independent external channel.

[0011] As a further aspect of the present application: the FCDI device further comprises a retention body and at least two protective plates, each level of the flow electrode capacitor module comprises two groups of ion modules, and the two groups of ion modules of each level are arranged on the two sides of the retention body, and the ion modules of each level comprise, in sequence from the direction away from the retention body, an ion exchange membrane, a gasket and a current collector, the gasket is also arranged between the adjacent two levels of the flow electrode capacitor module, and the protective plates are located at the outermost side of the FCDI device.

[0012] As a further aspect of the present application: the two groups of ion modules of each level of the flow electrode capacitor module are respectively cation modules and anion modules, the cation modules of each level are arranged on the same side of the retention body, and the anion modules of each level are arranged on the other side of the retention body, so that one side of the retention body is negative and the other side is positive; the ion exchange membrane of the cation module is a cation exchange membrane, and the ion exchange membrane of the anion module is an anion exchange membrane.

[0013] As a further aspect of the present application: a plurality of through holes are formed in the protective plates and the flow electrode capacitor modules, the through holes with the same function on the protective plates and the flow electrode capacitor modules are arranged along the same axis to form a plurality of channels in the FCDI device, which are in communication with the outside to realize the flow of liquid into and out of the FCDI device, and the barrel module comprises a solution barrel for placing a salt lake solution and a slurry barrel for placing a flow electrode slurry, the solution barrel is in communication with the retention body, and the slurry barrels of each level are in communication with the flow electrode capacitor modules of the corresponding level.

[0014] As a further aspect of the present application: the through holes comprise a group of water holes and a plurality of slurry holes, at least two water holes are formed in the retention body, the water hole and the adjacent water hole share the same axis, and the water holes are connected by a solution channel formed in the retention body, the water holes, the water holes and the solution channel together form a channel for the flow of a salt lake solution, which is used to realize the flow of the salt lake solution between the solution barrel and the retention body; a slurry current collector channel is formed in the current collector, and the slurry current collector channel is connected to the same group of slurry holes at both ends, and the slurry holes and the slurry current collector channel together form a channel for the flow of a flow electrode capacitor slurry, which is used to realize the flow of the flow electrode slurry between the slurry barrels of each level and the flow electrode capacitor modules.

[0015] As a further scheme of the present application: the FCDI device is externally connected with a power supply system, the power supply system provides voltage for the flow electrode capacitor module, and a control system is used to control the opening and closing of the power supply system; the current collector is further provided with a tab, the tab is used to connect the power supply system, and the pipeline is provided with a power device, and the opening and closing of the power device is also controlled by the control system. As a further scheme of the present application: the method comprises the following steps:

[0016] S1, the activated carbon, the conductive additive, the deionized water and the electrolyte salt are mixed in a set proportion, and at least two barrels of flow electrode slurry are configured after stirring for a certain time, and the salt lake solution adopts simulated salt lake brine or actual salt lake brine;

[0017] S2, the device is started, and the salt lake solution in the solution barrel and the flow electrode slurry in the slurry barrel are respectively introduced into the FCDI device along different pipelines under the driving of the power device;

[0018] S3, the control system starts the power supply system to supply power to the FCDI device, and the voltage connected by each level of flow electrode capacitor module increases in turn along the direction away from the retainer;

[0019] S4, an electrostatic field is formed between each level of flow electrode capacitor module to provide electric field force for the movement of free ions in the salt lake solution, and the anions and cations in the salt lake solution enter the anion module and the cation module respectively and are sequentially adsorbed by each level of flow electrode slurry, and the flow electrode slurry after adsorption flows out of the FCDI device and returns to the slurry barrel for storage, so as to realize multi-stage lithium extraction.

[0020] As a further scheme of the present application: in step S1, the activated carbon, the conductive additive, the deionized water and the electrolyte salt are mixed in a mass ratio of (5-10):(0-5):(40-190):(0.1-0.5), and during preparation, the activated carbon, the conductive additive and the deionized water are mixed first, and then the electrolyte salt is added, and the mixed material is fully stirred by using a magnetic stirrer to obtain the flow electrode slurry.

[0021] As a further scheme of the present application: the specific process of step S2 is as follows:

[0022] S21, the salt lake solution in the solution barrel enters the solution channel through the water channel composed of water hole one and water hole two;

[0023] S22, the flow electrode slurry in the slurry barrels of different levels enters the slurry channel of the corresponding level through the slurry channel composed of the corresponding slurry hole.

[0024] As a further scheme of the present application: after step S4, there is also step S5-step S7;

[0025] S5, the flow electrode slurry after lithium extraction is transported to the corresponding slurry tank of each stage by the power device for reuse to continuously extract lithium;

[0026] S6, after setting a time interval, the flow electrode slurry in each stage slurry tank is sampled and the sample is tested by ICP to measure the ion change concentration in the flow electrode slurry;

[0027] S7, when the ion change concentration measured in step S6 reaches the concentration requirement of each stage, the device is closed.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] 1. The present application uses a multi-stage FCDI device containing at least two stages to realize the function of salt lake lithium extraction. Since the voltage size connected by the flow electrode capacitor module gradually increases in the direction away from the retainer, when the lithium extraction of the flow electrode capacitor module in one stage is completed, the remaining unbound cations and anions can continue to move to the flow electrode capacitor module in the next stage under the action of the electric field force to continue lithium extraction, thereby realizing multi-stage purification lithium extraction in the same process. The multi-stage FCDI device improves the lithium extraction capacity of salt lake lithium extraction, thereby improving the purification efficiency. The flow electrode capacitor module in each stage is connected to the external tank module through a pipeline to form an independent external channel, so that the device can meet the demand of multiple lithium extraction purities at the same time to provide lithium products with different purities for various lithium applications, and the product purity is guaranteed, which has a wider range of industrial application and better cycle stability.

[0030] 2. The present application can flexibly expand the number of stages of the flow electrode capacitor module according to the purity demand of the actual product. For the product demand of general lithium application, only one or two levels of flow electrode capacitor modules are used for lithium extraction treatment to meet the product demand. For high-purity lithium products used in batteries or nuclear industry, three or four levels of flow electrode capacitor modules are used for lithium extraction treatment, so that the purity of the solution obtained in the high-level slurry tank can meet the application of battery grade. The device has better flexibility and better adaptability.

[0031] 3. In the present application, the cation exchange membrane uses a monovalent cation exchange membrane. In the process of lithium extraction, the cation module can gradually reduce the content of magnesium ions, so that the purity of lithium ions gradually increases, and the lithium-magnesium separation performance is good from low magnesium-lithium ratio salt lake solution to high magnesium-lithium ratio salt lake solution.

[0032] 4、The raw materials used in the application are cheap and easy to obtain, the preparation method is simple and convenient, easy to industrialize, has better environmental adaptability compared with other existing salt lake lithium extraction technologies, and has lower energy consumption and stronger expansibility. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of a multi-stage flow electrode capacitive deionization device for extracting lithium from salt lakes in the application.

[0034] Figure 2 It is a structural schematic diagram of the application Figure 1 without a control system and a power supply system.

[0035] Figure 3 It is an explosion schematic diagram of the FCDI device in the application Figure 1 .

[0036] Figure 4 It is a three-dimensional schematic diagram of the retention body in the application Figure 3 .

[0037] Figure 5 It is a three-dimensional structural schematic diagram of the primary current collector in the application Figure 3 .

[0038] Figure 6 It is a three-dimensional schematic diagram of the cation exchange membrane in the application Figure 3 .

[0039] Figure 7 It is a flow schematic diagram of a multi-stage flow electrode capacitive deionization method for extracting lithium from salt lakes in the application.

[0040] Figure 8 It is a variation diagram of lithium / magnesium ions and selectivity coefficients in the adsorption process of the FCDI device in Example 6 of the application when the magnesium / lithium ratio is 1.

[0041] Figure 9 It is a variation diagram of lithium / magnesium ions and selectivity coefficients in the adsorption process of the fourth stage of the FCDI device in Example 7 of the application when the magnesium / lithium ratio is 60.

[0042] Figure 10 It is a schematic diagram of the concentration ratio of various ion types before treatment of the actual salt lake brine used in Example 8 of the application.

[0043] Figure 11 It is a schematic diagram of the concentration ratio of various ion types in the fourth stage of the FCDI device in Example 8 of the application in the adsorption process of the actual salt lake brine.

[0044] In the figure:

[0045] 1, control system; 2, power supply system; 3, FCDI device; 311, first flow electrode capacitor module; 31121, first slurry current collector channel; 31161, first slurry feeding hole; 31162, first slurry discharging hole; 312, second flow electrode capacitor module; 31261, second slurry feeding hole; 31262, second slurry discharging hole; 313, third flow electrode capacitor module; 31361, third slurry feeding hole; 31362, third slurry discharging hole; 314, fourth flow electrode capacitor module; 31461, fourth slurry feeding hole; 31462, fourth slurry discharging hole; 3101, gasket; 3112, first current collector; 3103, cation exchange membrane; 3113, first cation exchange membrane; 3123, second cation exchange membrane; 3133, third cation exchange membrane; 3143, fourth cation exchange membrane; 3104, anion exchange membrane; 3105, water hole one; 31051, water hole one water inlet hole; 31052, water hole one water outlet hole; 31022, tab; 32, retention body; 321, water hole two; 3211, water hole two water inlet hole; 3212, water hole two water outlet hole; 322, solution channel; 33, guard plate; 4, pipe; 5, barrel module; 51, solution barrel; 52, slurry barrel. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0047] Embodiment one:

[0048] Please refer to Figures 1-6In the embodiment of the present application, a multi-stage flow electrode capacitive deionization device for extracting lithium from salt lake includes a multi-stage flow electrode capacitive deionization device (FCDI device 3). The FCDI device 3 includes at least two stages of flow electrode capacitive modules. Each stage of flow electrode capacitive module is connected to a different voltage. Adjacent two stages of flow electrode capacitive modules are connected to each other. Each stage of flow electrode capacitive module is connected to an external tank module 5 through a pipeline 4, so that each stage of flow electrode capacitive module can form an independent external channel. After starting the device, the salt lake solution in the solution tank 51 and the flow electrode slurry in the slurry tank 52 can enter the corresponding solution channel 322 and slurry current collector channel in the FCDI device 3, respectively, to extract lithium from salt lake. Under the action of the gradually increasing electric field force, the anions and cations in the salt lake solution move from the flow electrode capacitive module with a small input voltage (low level) to the flow electrode capacitive module with a large input voltage (high level). With the increase of the level, the passing rate of magnesium ions gradually decreases, so that the purity of lithium gradually increases, and the FCDI device 3 can process multiple purity lithium products at the same time. The flow electrode capacitive modules of each stage form a circulation loop with the pipeline 4 and the slurry tank 52 connected thereto. Under the drive of the power device, the flow electrode slurry that has completed ion combination can be pumped out of the slurry current collector channel, and the flow electrode slurry that has not yet undergone ion combination can be transported into the slurry current collector channel to continue ion combination, realizing the circulation of lithium extraction of flow electrode slurry of each stage without repeated lithium extraction, which is more convenient. After the lithium extraction is completed, the lithium product with corresponding purity can be obtained from the corresponding slurry tank 52 of each stage to meet the demand for multiple lithium products at the same time, which is easier to realize industrialization.

[0049] The FCDI device 3 also includes a retention body 32 and at least two guards 33. Each stage of flow electrode capacitive module includes two groups of ion modules. The two groups of ion modules of each stage are arranged on both sides of the retention body 32. The ion modules sequentially include an ion exchange membrane, a gasket 3101 and a current collector in the direction away from the retention body 32, so that the anions and cations entering the flow electrode capacitive module can first pass through the ion exchange membrane for preliminary screening, and then enter the slurry current collector channel. Since the flow electrode slurry used in the anion module and the cation module of each stage uses the flow electrode slurry in the same slurry tank 52, the activated carbon that completes the cation adsorption and anion adsorption in the FCDI device 3 flows back to the slurry tank 52 under the drive of the power device. According to the principle of opposite charges attracting each other, the cations and anions adsorbed on the activated carbon combine with each other. After combination, the ions on the activated carbon can be released into the flow electrode slurry due to charge neutralization. At this time, the activated carbon can continue to adsorb the next free ion and wait for the next ion combination. Under the circulation of the flow electrode slurry, the flow electrode slurry realizes pseudo-infinite adsorption, so as to achieve greater processing capacity for extracting lithium from salt lake.

[0050] Each level of the flow electrode capacitor module contains two groups of ion modules, namely cation modules and anion modules. The cation modules of each level are arranged on the same side of the retention body 32, and the anion modules of each level are arranged on the other side of the retention body 32, so that the side of the retention body 32 on which the cation modules are arranged is the negative electrode for the movement of cations, and the side of the retention body 32 on which the anion modules are arranged is the positive electrode for the movement of anions. The ion exchange membrane of the cation module is a cation exchange membrane 3103, and the ion exchange membrane of the anion module is an anion exchange membrane 3104. In this embodiment, the cation exchange membrane 3103 is a monovalent cation exchange membrane, which is used to separate magnesium ions and lithium ions to the greatest extent to improve the purity of lithium ions. The cation exchange membrane 3103 and the anion exchange membrane 3104 used in this scheme are directly purchased, cut to the required size by a membrane cutter, and then used. They are prior art, so they will not be described in detail.

[0051] Gaskets 3101 are arranged between adjacent two levels of the flow electrode capacitor module, and gaskets 3101 are also arranged between the flow electrode capacitor module and the retention body 32 (only the positions of some of the gaskets 3101 are marked in the drawings, and the positions of the remaining gaskets 3101 are not marked, but they can be clearly seen in the drawings, and the positions of the gaskets 3101 are described in detail in the specification). The gaskets 3101 are used to ensure the sealing of the FCDI device 3 to prevent water leakage. The guard plate 33 is located at the outermost side of the FCDI device 3. The guard plate 33 is used to clamp the retention body 32 and each flow electrode capacitor module. In this embodiment, the guard plate 33 is connected by a plurality of bolts and nuts to realize the assembly of the FCDI device 3. The bolts are located outside the retention body 32 and each level of the flow electrode capacitor module. A pipe connector is also installed at the through hole on the outside of the guard plate 33 to realize the connection between the pipe 4 and the FCDI device 3. Since this connection method is a common prior art, it will not be described in detail. In other embodiments, the guard plate 33 can be connected by a variety of methods such as a clamp connection and a pressure connection. The connection method of the guard plate 33 can be changed according to specific use requirements and application scenarios.

[0052] The protective plate 33 and the flow electrode capacitor module are provided with multiple groups of through holes, the through holes with the same function on the protective plate 33 and the flow electrode capacitor module are provided along the same axis, for example, after the FCDI device 3 is assembled, all the first slurry feeding holes 31161 provided on the protective plate 33 and the flow electrode capacitor module share the same axis, so as to form multiple slurry feeding channels in the FCDI device 3 which are in communication with the outside, and through the connection of the pipeline 4 and the corresponding through holes on the outside of the protective plate 33, the flow electrode slurry can enter the slurry current collector channel along the formed feeding channel, and then flow out of the FCDI device 3 from the slurry discharging channel, so as to realize the feeding and discharging of the flow electrode slurry in and out of the FCDI device 3, and in the same way, the salt lake solution can also feed and discharge in and out of the FCDI device 3 through the corresponding channels; the barrel module 5 includes a solution barrel 51 for placing the salt lake solution and a slurry barrel 52 for placing the flow electrode slurry, wherein the solution barrel 51 is in communication with the retainer 32, and the slurry barrels 52 of different levels are in communication with the flow electrode capacitor modules of the corresponding levels.

[0053] The through holes include a group of water holes one 3105 and multiple groups of slurry holes, the current collector is provided with a slurry current collector channel, the slurry current collector channel is connected with the same group of slurry holes at both ends, the retainer 32 is provided with at least two water holes two 321, the water hole one 3105 and the adjacent water hole two 321 share the same axis, the water holes two 321 are connected through the solution channel 322 provided on the retainer 32, and the water hole one 3105, the water hole two 321 and the solution channel 322 jointly form a channel for the flow of the salt lake solution, so as to realize the flow of the salt lake solution between the solution barrel 51 and the retainer 32; the current collector is provided with a slurry current collector channel, the slurry current collector channel is connected with the same group of slurry holes at both ends, and the slurry holes and the slurry current collector channel jointly form a channel for the flow of the flow electrode capacitor slurry, so as to realize the flow of the flow electrode slurry between the slurry barrels 52 of different levels and the flow electrode capacitor modules; it should be noted that in the embodiment, only one through hole is provided on each of the gaskets 3101 on both sides of the retainer 32, the through hole provided on the gasket 3101 on the feeding side of the retainer 32 corresponds to the position of the water inlet hole 3211 of the water hole two, and the through hole provided on the gasket 3101 on the discharging side of the retainer 32 corresponds to the position of the water outlet hole 3212 of the water hole two, and under the cooperation of the gaskets 3101 on both sides, the salt lake solution can flow in and out of the retainer 32 along the same channel, and in the embodiment, in order to achieve better lithium extraction effect, the salt lake solution flows through the retainer 32 in the way of down in and up out, and in other embodiments, the way of up in and down out can also be adopted.

[0054] The FCDI device 3 is externally connected with a power supply system 2, the power supply system 2 provides voltage for the flow electrode capacitor module, the control system 1 is used for controlling the opening and closing of the power supply system 2; the current collector is further provided with a tab 31022, the tab 31022 is used for connecting the power supply system 2, in the embodiment, the tab 31022 is partially protruding, and the tabs 31022 of the current collectors in the flow electrode capacitor modules of different levels are arranged in different positions, so that the plurality of tabs 31022 on the positive side and the plurality of tabs 31022 on the negative side of the FCDI device 3 can be conveniently connected with the shark clamp of the external lead after the FCDI device 3 is assembled (other connection modes with the external lead can also be adopted, the connection mode is the existing conventional technology, and is not specifically described, and is also omitted in the drawings, but does not affect the specific implementation of the scheme), so that the connection of the whole device is more convenient; in the embodiment, the current collector adopts a titanium sheet, and the slurry current collector channel is composed of a serpentine channel with a thickness of 1.5 mm, a length of 100 mm and a width of 3 mm; in other embodiments, the current collector can also be composed of copper, iron and other metal materials, and the slurry current collector channel can also be composed of other size serpentine channels, rectangular channels or parabolic channels.

[0055] The material bucket module 5 comprises a solution material bucket 51 and at least two slurry material buckets 52, at least one pipe 4 is arranged in the solution material bucket 51 and the slurry material bucket 52 and connected with the corresponding water hole 3105 and the slurry hole, the pipe 4 is provided with a power device, in the embodiment, the power device adopts a peristaltic pump, in other embodiments, other power devices can also be adopted according to actual needs (it should be noted that at least one power device is arranged in each pipe 4 corresponding to the solution material bucket 51 and the slurry material bucket 52, since the power device is a conventional means for driving liquid to flow in the pipe 4, the scheme is not improved, therefore, the structure of the power device is omitted in the drawings, and the specific working principle is not described, but in actual use, the power device exists; in the scheme, the control system 1 adopts an existing controller, for example, a blue electricity control APP, which is prior art and is not improved in the application, therefore, detailed description is omitted).

[0056] It should be noted that the attached diagram provided in this solution shows an FCDI device 3 containing four stages of flow electrode capacitor modules. To better understand the working path of each stage of the flow electrode capacitor module, some structures in the FCDI device 3 are further differentiated. Specifically, the first-stage flow electrode capacitor module 311 includes a first-stage current collector 3112 and a first-stage cation exchange membrane 3113. The first-stage slurry current collector channel 31121 on the first-stage current collector 3112 is connected at both ends to the first-stage slurry inlet port 31161 and the first-stage slurry outlet port 31162. The second-stage flow electrode capacitor module 312 includes a second-stage current collector 3122 and a second-stage cation exchange membrane 3123. The second-stage slurry current collector channel on the second-stage current collector 3122 is connected at both ends to the second-stage slurry inlet port 31261 and the second-stage slurry outlet port 31262. The third-stage flow electrode capacitor module... Unit 313 includes a three-stage current collector 3132 and a three-stage cation exchange membrane 3133. The three-stage slurry current collector channel on the three-stage current collector 3132 is connected at both ends to the three-stage slurry inlet port 31361 and the three-stage slurry outlet port 31362. The four-stage flow electrode capacitor module 314 includes a four-stage current collector 3142 and a four-stage cation exchange membrane 3143. The four-stage slurry current collector channel on the four-stage current collector 3142 is connected at both ends to the four-stage slurry inlet port 31461 and the four-stage slurry outlet port 31462. (Since the slurry current collector channels on each stage of the current collector are opened in the same way, only the corresponding slurry ports are different, and this can be visually observed in the attached drawings, the labeling of the other stages of current collectors is omitted. Since the structure of each stage of the flow electrode capacitor module is the same, only the other stages of the flow electrode capacitor module are simply labeled in the attached drawings.) Figure 3 The structure of each flow electrode capacitor module and the assembly position of each module during the assembly of the FCDI device 3 can also be seen intuitively; Water hole 1 3105 includes water hole 1 inlet 31051 and water hole 1 outlet 31052, and water hole 2 321 includes water hole 2 inlet 3211 and water hole 2 outlet 3212. After the FCDI device 3 is assembled, water hole 1 inlet 31051 and water hole 2 inlet 3211 share the same axis, and water hole 1 outlet 31052 and water hole 2 outlet 3212 share the same axis, so as to form an inlet channel and an outlet channel for the salt lake solution in the device. In conjunction with the gasket 3101, which has only one through hole corresponding to water hole 2 321 on each side of the retention body 32, a unique salt lake solution flow channel is formed in the FCDI device 3.

[0057] When the device is started, the salt lake solution in the solution tank 51 enters the retention body 32, and first enters the first flow electrode capacitor module 311 for processing, and then enters the second flow electrode capacitor module 312, the third flow electrode capacitor module 313 and the fourth flow electrode capacitor module 314 in sequence for processing; when the salt lake solution passes through the fourth flow electrode capacitor module 314 and completes the processing, the lithium product obtained by the slurry tank 52 connected with the fourth flow electrode capacitor module 314 has a magnesium ion content that can be ignored compared with the lithium ion content, and the processed lithium product can fully meet the purity requirements of the battery or nuclear industry (it should be noted that the lithium product obtained by the device is a preliminary lithium product, and if it is desired to be used, it needs to be further processed, such as for the lithium product required by the battery industry, sodium carbonate needs to be added to the lithium chloride solution obtained by the fourth processing to obtain battery-grade lithium carbonate), and in actual use, if the processing requirement of such high purity is not required, the high-level flow electrode capacitor module can not be installed or started, since the device containing only the first flow electrode capacitor module, the two-level flow electrode capacitor module and the three-level flow electrode capacitor module only increases or decreases the same structure part during assembly, the installation position, connection relationship and working principle of each module are basically unchanged, therefore, only the FCDI device 3 containing the four-level flow electrode capacitor module is shown in the structure of the schematic diagram.

[0058] The working principle of the present application is:

[0059] In use of the application, first, the device is started, the salt lake solution in the solution tank 51 and the flow electrode slurry in the plurality of slurry tanks 52 are driven by the power device to enter the corresponding solution channel 322 and slurry current collector channel in the FCDI device 3 respectively for processing; the power system 2 is started by the control system 1, the flow electrode capacitive modules at different levels are connected to different constant voltages, so that an electrostatic field is formed in the FCDI device 3, under the action of the electric field force, the anions and cations of the salt lake solution in the solution channel 322 can enter the anion module and the cation module on both sides of the retainer 32 respectively, when the anions and cations reach the slurry current collector channel, the free anions and cations are adsorbed by the activated carbon in the flow electrode slurry, the flow electrode slurry adsorbed with the free ions is driven by the power device to flow back to the initial slurry tank 52, in the short circuit mode, the adsorbed anions and cations can be released into the flow electrode slurry due to the charge neutralization, so that the activated carbon can continue the ion adsorption in the next time, under the circulation of the flow electrode slurry at different levels, the pseudo-infinite adsorption of the free ions can be achieved; since the voltage connected by the flow electrode capacitive modules gradually increases along the direction away from the retainer 32, therefore, the free ions entering the flow electrode capacitive modules at the lower level will enter the flow electrode capacitive modules at the next level for lithium extraction under the action of the electric field force, after reaching the set time interval, the samples can be directly taken from the slurry tanks 52 at different levels for ICP test, when the lithium purity in the detected sample reaches the requirement at different levels, the device is closed, at this time, the slurry tanks 52 at different levels store lithium products with different purities.

[0060] Embodiment two:

[0061] In this embodiment, based on the multi-level flow electrode capacitive deionization device for lithium extraction from salt lake of embodiment one, the following improvements are made:

[0062] The other end of the pipeline 4 connected with the flow electrode capacitive modules at different levels is not arranged in the same slurry tank 52, but one end of the pipeline 4 for feeding is arranged in one slurry tank 52, and the other end of the pipeline 4 for discharging is arranged in another slurry tank 52, that is, each flow electrode capacitive module is connected with at least two slurry tanks 52 outside the FCDI device 3 (the connection mode is not much different from the original structure, and the difference between the two embodiments can be directly obtained according to the description, therefore the schematic of this connection structure is omitted in the drawing).

[0063] When the device is started, the flow electrode slurry in the slurry tank 52 connected with the pipe 4 for feeding is transported into the FCDI device 3, and after the flow electrode slurry completes the adsorption of free ions and is output from the FCDI device 3, it is stored in another slurry tank 52 following the pipe 4 for discharging. When the flow electrode slurry in the slurry tank 52 for feeding is consumed, the positions of the two slurry tanks 52 are exchanged, and the lithium extraction is continued. In the form of single pass, the flow electrode slurry before entering the FCDI device 3 can be distinguished from the flow electrode slurry after entering the FCDI device 3, so that the magnesium-lithium ratio is unchanged during the ion adsorption process, and the test result is more accurate.

[0064] Embodiment three:

[0065] With reference to Figures 1-7 , in the embodiment of the present application, a multi-stage flow electrode capacitive deionization method for lithium extraction from salt lake,

[0066] including the above-mentioned multi-stage flow electrode capacitive deionization device,

[0067] S1, mix active carbon, conductive additive, deionized water and electrolyte salt according to a set ratio, and after stirring for a certain time, configure at least two buckets of flow electrode slurry. The salt lake solution adopts simulated salt lake brine or actual salt lake brine.

[0068] The simulated salt lake brine is prepared by deionized water and lithium chloride and magnesium chloride drugs with different contents. Since the anion in most salt lakes is chloride, lithium chloride is used in the simulated salt lake brine and the slurry to save the step of extracting anions. Since the FCDI device 3 of the device can directly adsorb the brine, whether simulated salt lake brine or actual salt lake brine, other impurity ions in the brine, such as potassium ions, sodium ions and calcium ions, will not affect the experimental results, and they also do not need to be filtered before the experiment. The chemical drugs used in this embodiment are directly purchased from the official website of Aladdin and have not been purified, so specific descriptions of various drugs are not given.

[0069] The active carbon, conductive additive, deionized water and electrolyte salt are mixed according to the mass ratio (5-10) :(0-5) :(40-190) :(0.1-0.5). During preparation, the active carbon, conductive additive and deionized water are mixed first, and then the electrolyte salt is added. The mixed material is fully stirred by a magnetic stirrer to obtain the flow electrode slurry. The main function of the flow electrode slurry is electric adsorption, which can accelerate the ion transmembrane movement.

[0070] In the present embodiment, the conductive additive is Ketjen black or acetylene black, and the experimental environment is at a temperature of 20-25℃ and a humidity of 35-50% RH; the flow rate of the power device when pumping the flow electrode slurry is 30-70 mL·min -1 , and the flow rate of the power device when pumping the salt lake solution is 3-20 mL·min -1 ; after the FCDI device 3 is connected to the power supply system 2, it is operated in a constant voltage mode for 5-12 h; when preparing the flow electrode slurry, the electrolyte salt used is lithium chloride, and the rotational speed of the magnetic stirrer is 500-1000 r·min -1 , and the stirring time is 8-24 h.

[0071] S2, start the device, and under the driving of the power device, the salt lake solution and the flow electrode slurry in the barrel module 5 are respectively introduced into the FCDI device 3 along different pipelines 4;

[0072] The specific process of step S2 is as follows:

[0073] S21, the salt lake solution in the solution barrel 51 enters the solution channel 322 through the water channel composed of the water hole one 3105 and the water hole two 321;

[0074] S22, the flow electrode slurry in the slurry barrel 52 of different levels enters the slurry channel of the corresponding level through the slurry channel composed of the corresponding slurry hole.

[0075] S3, the control system 1 turns on the power supply system 2 to supply power to the FCDI device 3, and the voltage connected to the flow electrode capacitor modules in the direction away from the retainer 32 increases in size in turn, so that the flow electrode capacitor modules in the FCDI device 3 are arranged in the order from low level to high level in the direction away from the retainer 32, and the voltage increases in size step by step, so that after the FCDI device 3 is powered on, the electric field force in the direction of the guard plate 33 increases step by step with the retainer 32 as the center, and the electric field force provides a force for the movement of the free ions from the low-level flow electrode capacitor module to the high-level flow electrode capacitor module; the power supply voltage of the power supply system 2 ranges from 0 to 5 V.

[0076] S4, an electrostatic field is formed between each flow electrode capacitor module to provide an electric field force for the movement of the free ions in the salt lake solution, and the anions and cations in the salt lake solution enter the anion module and the cation module, respectively, and are sequentially adsorbed by the flow electrode slurry of each level, and the flow electrode slurry after adsorption flows out of the FCDI device 3 and returns to the initial slurry barrel 52 for storage, so as to realize multi-stage lithium extraction.

[0077] S5, the flow electrode slurry after lithium extraction is transported to each corresponding slurry barrel 52 by the power device for reuse to continuously extract lithium;

[0078] S6, set a time interval, sample the flow electrode slurry in each stage slurry tank 52 and perform ICP test on the sample to measure the ion change concentration in the flow electrode slurry;

[0079] S7, when the ion change concentration measured in step S6 reaches the concentration requirement of each stage, the device is closed, and the required lithium product is obtained from the slurry tank 52 corresponding to the level.

[0080] Example Four:

[0081] The embodiment is based on the preparation method of the simulated salt lake brine provided in the above-mentioned example three, and specifically as follows:

[0082] 4L of deionized water is placed in a 5L beaker, the resistivity of the deionized water is 18.2MΩ·cm; 24.43g of lithium chloride and 15.87g of magnesium chloride are added respectively, and the magnetic stirrer is used for stirring at a speed of 700r·min -1 for 30min at room temperature, and then placed in an ultrasonic cleaning machine for 15min to ensure that the salt lake solution is uniformly dispersed;

[0083] The magnesium-lithium ratio is 1:1, and the concentration of lithium ions is 1000mg·L -1 .

[0084] Example Five:

[0085] The embodiment is based on the preparation method of the flow electrode slurry provided in the above-mentioned example three, and specifically as follows:

[0086] The active carbon, ketchen black and deionized water are mixed in a mass ratio of 9.5:0.5:90, specifically 14.25g of active carbon, 0.75g of ketchen black, 244.29mg of lithium chloride and 135g of deionized water are mixed, and the magnetic stirrer is used for uniform stirring at a speed of 800r·min -1 for 10h at room temperature to ensure uniform dispersion of the active material in the solution and achieve the best effect; the total mass of the prepared flow electrode slurry is 150g, the active material accounts for 10% of the mass of the entire flow electrode slurry, and the concentration of lithium chloride is 200mg·L -1 .

[0087] The flow electrode slurry prepared by the method has good cycle stability, low raw material price, and simple preparation method, and is easy to be industrialized.

[0088] Example Six:

[0089] Referring to Figures 1-3 and Figure 8Based on the performance test and test data of the equipment in the case of the mass ratio of magnesium to lithium being 1:1 provided in Embodiments Three to Five, the embodiment of the present application is as follows:

[0090] The salt lake solution prepared in Embodiment Four is pumped into the solution channel 322 by the power device at a flow rate of 10 mL·min -1 , while the flow electrode slurry prepared in Embodiment Five is uniformly pumped into the corresponding slurry collector channel in communication with each slurry barrel 52 by the power device at a flow rate of 50 mL·min -1 . It should be noted that, in order to better ensure that the positive and negative parts of the flow electrode capacitor module of the same level are pumped at the same speed, in this embodiment, the slurry holes corresponding to the positive part and the slurry holes corresponding to the negative part are connected to the same pipeline 4, and the power device is arranged at the pipeline 4 shared by the positive part and the negative part to realize the synchronous input and output of the flow electrode slurry in the positive part and the negative part of the same flow electrode capacitor module by one power device. In other embodiments, the flow electrode slurries of the positive part and the negative part can be pumped in and out separately.

[0091] During the experiment, the cation module of the FCDI device 3 is connected to negative electricity, the anion module is connected to positive electricity, and the FCDI device 3 is operated in constant voltage mode, in which the first flow electrode capacitor module 311 is connected to a voltage of 1.3 V, the second flow electrode capacitor module 312 is connected to a voltage of 2.0 V, the third flow electrode capacitor module 313 is connected to a voltage of 3.0 V, and the fourth flow electrode capacitor module 314 is connected to a voltage of 3.6 V.

[0092] According to Table 1, the lithium / magnesium ions and the selectivity coefficient change in real time with time at different levels:

[0093] Table 1 Details of Lithium and Magnesium Ion Concentration Changes

[0094]

[0095]

[0096] The calculation formula of the purity is:

[0097] Lithium ion purity (%) = lithium ion concentration / (lithium ion concentration + magnesium ion concentration)

[0098] It can be found that with the gradual increase of the number of stages, the concentration of magnesium ions gradually decreases, and the corresponding selectivity coefficient is also higher and higher, that is, the separation effect of lithium ions and magnesium ions is better and better, and the selectivity coefficient increases from 33.44 of the first stage to 11247.27 of the fourth stage; and the purity of lithium ions increases from 90.52% of the first stage to 99.97% of the fourth stage; wherein, the low-purity lithium product obtained can meet the general demand for lithium products, and the high-purity lithium product obtained can meet the purity demand of the battery or nuclear industry; the device has high selectivity and can also produce extremely high-purity lithium products, has a large product application range, and is suitable for industrial application.

[0099] Example seven:

[0100] Referring to Figure 9 Different from the above-mentioned example six, the performance test of the fourth stage of the concentration change of lithium and magnesium ions under the condition that the magnesium-lithium mass ratio of the simulated salt lake solution is changed to 60:1 is provided, and the specific conditions are as follows:

[0101] When the magnesium-lithium mass ratio is 60:1, the selectivity coefficient increases from the initial stage of 40651.31 to the maximum value of 153273.85 after 3h, and with the continuation of the experiment, the selectivity coefficient gradually decreases until it decreases to the final 6019.83. After the experiment, the lithium ion concentration is 2.85 times the initial concentration, at this time, the purity of lithium ions is reduced to 99.71% compared with 99.97% when the magnesium-lithium mass ratio is 1; wherein, the concentration of lithium ions is 90.33mmol·L -1 , the concentration of magnesium ions is 0.1769mmol·L -1 , and the energy consumption is 0.26kWh·molLi, that is, the energy consumption required for extracting each mole of lithium is 0.26kWh.

[0102] When the simulated salt lake solution with a magnesium-lithium mass ratio of 60:1 is used, the selectivity coefficient is reduced, but it is still much higher than 1, therefore, it still shows that using the multi-stage flow electrode capacitor device to selectively extract lithium in high-magnesium-lithium mass ratio salt lake brine has broad application prospects.

[0103] Example eight:

[0104] Referring to Figures 10-11 Different from the above-mentioned example six, the performance test of the fourth stage of the concentration change of lithium and magnesium ions under the condition that the simulated salt lake solution is replaced by actual salt lake brine (Golmud old brine) is provided, and the magnesium-lithium mass ratio of the actual salt lake brine is 79.29:1, and the specific conditions are as follows:

[0105] After the actual salt lake brine completes the experiment, the mass ratio of magnesium to lithium in the fourth-stage flow electrode slurry obtained is 1:79.55, the selectivity coefficient is 6307.17, the purity is 99.64%, the concentration of lithium ions in the flow electrode slurry is 69.55 mmol·L -1 , the concentration of magnesium ions is 0.19 mmol·L -1 , the energy consumption is 0.20 kWh·mol Li, that is, the energy consumption required for extracting each mole of lithium is 0.20 kWh.

[0106] The selectivity coefficient obtained from the data is also always much more than 1, therefore, it is still shown that the selective extraction of lithium in the actual salt lake brine (Golm old brine) using the multi-stage flow electrode capacitive device has broad application prospects, and can be put into actual industrial application.

[0107] Of course, for those skilled in the art, the present application is not limited to the details of the above exemplary embodiments, but also includes the same or similar structures that can be realized in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0108] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description manner of the specification is only for the sake of clarity, those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be properly combined to form other embodiments that those skilled in the art can understand.

[0109] The technologies, shapes, and structural parts not described in detail in the present application are well-known technologies.

Claims

1. A multi-stage flow electrode capacitive deionization device for lithium extraction from salt lakes, characterized in that, The application relates to a multi-stage flow electrode capacitive deionization device (FCDI device), which comprises at least two-stage flow electrode capacitive modules; The voltage applied to each stage of the flow electrode capacitive module is different; The two-stage flow electrode capacitive modules are connected to each other; Each stage of the flow electrode capacitive module is connected to an external tank module through a pipeline, so that each stage of the flow electrode capacitive module can form an independent external channel; The FCDI device further comprises a retention body and at least two protective plates, each stage of the flow electrode capacitive module comprises two groups of ion modules, and the two groups of ion modules of each stage are arranged on the two sides of the retention body; the ion modules sequentially comprise an ion exchange membrane, a gasket and a current collector in the direction away from the retention body; the gasket is arranged between the two-stage flow electrode capacitive modules; and the protective plates are located at the outermost side of the FCDI device. Each stage of the flow electrode capacitive module comprises two groups of ion modules, which are cation modules and anion modules respectively; the cation modules of each stage are arranged on the same side of the retention body, and the anion modules of each stage are arranged on the other side of the retention body, so that one side of the retention body is a negative electrode and the other side is a positive electrode; the ion exchange membrane of the cation module is a cation exchange membrane, and the ion exchange membrane of the anion module is an anion exchange membrane; The protective plates and the flow electrode capacitive modules are provided with a plurality of through holes; the through holes with the same function on the protective plates and the flow electrode capacitive modules are arranged on the same axis, so as to form a plurality of channels in the FCDI device, realize the liquid in and out of the FCDI device, and realize the liquid in and out of the FCDI device; the tank module comprises a solution tank for placing a salt lake solution and a slurry tank for placing a flow electrode slurry; the solution tank is communicated with the retention body; and the slurry tank of each stage is communicated with the flow electrode capacitive module of the corresponding stage. The through holes comprise a group of water holes and a plurality of slurry holes; at least two water holes are arranged on the retention body; the water hole and the adjacent water hole share the same axis; the water holes are connected through a solution channel arranged on the retention body; the water hole, the water hole and the solution channel jointly form a channel for the flow of the salt lake solution, so as to realize the flow of the salt lake solution between the solution tank and the retention body. A slurry current collector channel is arranged on the current collector; the slurry current collector channel is connected with the same group of slurry holes at both ends; and the slurry hole and the slurry current collector channel jointly form a channel for the flow of the flow electrode capacitive slurry, so as to realize the flow of the flow electrode slurry between the slurry tank of each stage and the flow electrode capacitive module.

2. The multi-stage flow electrode capacitive deionization device for lithium extraction from salt lakes according to claim 1, characterized in that, The FCDI device is externally connected with a power supply system, the power supply system provides voltage for the flow electrode capacitive module, and a control system is used for controlling the opening and closing of the power supply system; a tab is further arranged on the current collector, the tab is used for connecting the power supply system, a power device is arranged on the pipeline, and the opening and closing of the power device is also controlled by the control system.

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