Dual-channel capacitive deionization device and method for extracting lithium from salt lake

Abstract

The invention relates to the technical field of salt lake lithium extraction, in particular to a dual-channel capacitive deionization device and method for salt lake lithium extraction. The invention provides a dual-channel capacitive deionization device for extracting lithium from a salt lake. The dual-channel capacitive deionization device comprises a first slurry channel plate, a first anionic membrane, a feeding liquid channel plate, a selective membrane, a recovery liquid channel plate, a second anionic membrane and a second slurry channel plate which are arranged in sequence, the first slurry channel plate and the second slurry channel plate adopt conductive structures; a first slurry channel is formed in one side, close to the first anionic membrane, of the first slurry channel plate; a second slurry channel is formed in one side, close to the second anionic membrane, of the second slurry channel plate; a feeding cavity communicated with the first anionic membrane and the selective membrane is formed in the feeding liquid channel plate, and a feed liquid inlet and a feed liquid outlet are formed in the feeding liquid channel plate; a recovery cavity communicated with the second anionic membrane and the selective membrane is formed in the recovery liquid channel plate; a recovery liquid inlet and a recovery liquid outlet are formed in the recovery liquid channel plate. The dual-channel capacitive deionization device for salt lake lithium extraction can separate and recover Li < + > ions at the same time, can work under the voltage of 0.8 V, can achieve the lowest energy consumption of 0.06 kWh mol <-1 >, has the charge efficiency as high as 96.71%, achieves low-energy-consumption and high-efficiency salt lake lithium extraction, and overcomes the defect that in the prior art, an FCDI device cannot be directly used for salt lake lithium extraction.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium extraction from salt lakes, and in particular to a dual-channel capacitive deionization device and method for extracting lithium from salt lakes. Background Art

[0002] Lithium is known as the energy metal of the 21st century and has been widely used in many fields such as batteries, glass and ceramics. With the rapid expansion of the electric vehicle market, the demand for lithium-ion batteries has also shown an explosive growth trend. Faced with the current shortage of lithium resources, it is urgent to explore more efficient lithium resource mining methods to ensure a stable, efficient and environmentally friendly supply of lithium resources.

[0003] Up to 85% of lithium resources are in the form of Li + Lithium exists in the form of ions in salt lake brine, so lithium extraction from salt lakes has become an urgent need. There are various methods for extracting lithium from salt lakes, including adsorption, precipitation, solvent extraction, membrane technology and electrochemical methods. Despite this, these technologies still have some disadvantages, such as poor cycle stability, high energy consumption and environmental pollution, which limit their application and promotion. As a new electrochemical method, capacitive deionization (CDI) technology has received widespread attention in the field of lithium extraction from salt lakes due to its high selectivity, low energy consumption and environmental protection. However, traditional CDI systems also face some limitations, such as low processing capacity and complicated reverse discharge steps.

[0004] In order to deal with the problem of insufficient processing capacity of traditional desalination methods, a new type of mobile electrode capacitive deionization (FCDI) technology has emerged. Its mobile electrode is composed of carbon or composite materials, which greatly enhances the ion adsorption capacity and improves the overall efficiency. FCDI system is mainly used in seawater desalination and other resource recovery. However, its Mg 2+ / Li + It should be pointed out that the traditional FCDI system is limited by its single-channel design and cannot achieve ion separation and recovery at the same time, and Li + The extraction and recovery processes of ions are discontinuous and need to be operated separately, which hinders the application of FCDI system in lithium extraction from salt lakes. Summary of the invention

[0005] In order to overcome the defect that the FCDI device in the above-mentioned prior art cannot be directly used for lithium extraction from salt lakes, the present invention proposes a dual-channel capacitive deionization device for lithium extraction from salt lakes, which can simultaneously separate and recover Li+ ions with low energy consumption and high efficiency.

[0006] The present invention proposes a dual-channel capacitive deionization device for extracting lithium from a salt lake, comprising a first slurry channel plate, a first anion membrane, a feed liquid channel plate, a selective membrane, a recovery liquid channel plate, a second anion membrane and a second slurry channel plate arranged in sequence; the first slurry channel plate and the second slurry channel plate adopt a conductive structure;

[0007] A first slurry channel is provided on the side of the first slurry channel plate close to the first anion membrane, and a second slurry channel is provided on the side of the second slurry channel plate close to the second anion membrane; a feed cavity connected to the first anion membrane and the selective membrane is provided on the feed liquid channel plate, and a feed liquid inlet and a feed liquid outlet are provided on the feed liquid channel plate; a recovery cavity connected to the second anion membrane and the selective membrane is provided on the recovery liquid channel plate, and a recovery liquid inlet and a recovery liquid outlet are provided on the recovery liquid channel plate.

[0008] Preferably, it also includes a slurry storage chamber, a slurry pump, a liquid storage chamber, a liquid pump, a recovery liquid storage chamber and a recovery pump; the recovery chamber is connected to the recovery liquid storage chamber through a recovery liquid inlet and a recovery liquid outlet to form a recovery liquid circulation loop, and the recovery pump is arranged on the recovery liquid circulation loop; the feed chamber is connected to the liquid storage chamber through a liquid inlet and a liquid outlet to form a liquid circulation loop, and the liquid pump is arranged on the liquid circulation loop; the first slurry channel and the second slurry channel are connected in parallel to the slurry storage chamber to form a slurry circulation loop, and the slurry pump is arranged on the slurry circulation loop.

[0009] Preferably, the feed liquid inlet and the feed liquid outlet are arranged on opposite sides of the feed liquid channel plate, and the recovery liquid inlet and the recovery liquid outlet are arranged on opposite sides of the recovery liquid channel plate.

[0010] Preferably, both the first slurry channel and the second slurry channel are serpentine channels.

[0011] Preferably, the first slurry channel plate and the second slurry channel plate are graphite plates.

[0012] Preferably, it also includes a power supply, wherein the positive pole of the power supply is connected to the first slurry path plate, and the negative pole of the power supply is connected to the second slurry path plate.

[0013] A method for extracting lithium from a salt lake proposed by the present invention comprises the following steps:

[0014] S1, filling the slurry storage chamber with activated carbon mobile electrode slurry, the liquid storage chamber with liquid, and the recovery liquid storage chamber with recovery liquid;

[0015] S2, start the slurry pump, liquid pump and recovery pump;

[0016] S3, connect the power supply, add positive electricity to the first slurry plate, and add negative electricity to the second slurry plate.

[0017] Preferably, step S4 is further provided after step S3, detecting the lithium ion concentration in the recovery liquid storage chamber, and when the lithium ion concentration in the recovery liquid storage chamber rises to a set lithium ion recovery threshold, replacing the recovery liquid in the recovery liquid storage chamber.

[0018] Preferably, step S5 is further provided after step S3, detecting the lithium ion concentration in the feed liquid storage chamber, and when the lithium ion concentration in the feed liquid storage chamber drops to a set lithium ion separation threshold, replacing the feed liquid in the feed liquid storage chamber.

[0019] Preferably, in step S1, the activated carbon flowing electrode slurry is composed of a mixture of activated carbon, a conductive additive and deionized water in a ratio of 14.55:0.45:135 by mass; the first slurry plate and the second slurry plate are connected to a power supply in a short-circuit connection manner, and the power supply voltage is 0.8V.

[0020] The advantages of the present invention are:

[0021] (1) The present application proposes a dual-channel capacitive deionization device for extracting lithium from salt lakes, which realizes the separation and recovery of lithium ions. At the same time, through the setting of two anion membranes, anions are increased in the first slurry channel and reduced in the second slurry channel, thereby keeping the ions in the carbon slurry balanced. While recovering lithium ions, the carbon slurry is also regenerated and recycled, reducing environmental pollution.

[0022] (2) The power supply of current FCDI devices is generally high, above 1V. The present application can operate under low voltage power supply conditions, achieving a breakthrough in ultra-low voltage of only 0.8V. This low voltage design not only greatly reduces energy consumption, but also enhances the stability and reliability of the device, effectively avoiding the side effects of activated carbon slurry caused by high voltage; at the same time, it also achieves a very high selective separation coefficient, further improving the lithium ion recovery efficiency.

[0023] (3) The present application can achieve simultaneous separation and recovery of lithium, and transform the FCDI device so that it can be used in the field of lithium extraction from salt lakes, thereby achieving higher economic benefits and stronger competitiveness. It can not only improve the performance of lithium extraction from salt lakes, but also effectively reduce energy consumption, providing strong technical support for the sustainable utilization of salt lake resources.

[0024] (4) The method for extracting lithium from salt lakes proposed in this application, combined with the improved FCDI device proposed in this application, achieves efficient, low-energy, and low-pollution lithium extraction from salt lakes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 An exploded diagram of a dual-channel capacitive deionization device for extracting lithium from salt lakes proposed in this application;

[0026] Figure 2It is a schematic diagram of the working principle of the device;

[0027] Illustration: 1. First slurry channel plate; 1-1. First slurry channel; 2. First anion membrane; 3. Feed liquid channel plate; 3-1. Feed cavity; 4. Selective membrane; 5. Recovery liquid channel plate; 5-1. Recovery cavity; 6. Second anion membrane; 7. Second slurry channel plate; 8. Slurry storage chamber; 9. Slurry pump; 10. Feed liquid storage chamber; 11. Feed liquid pump; 12. Recovery liquid storage chamber; 13. Recovery pump;

[0028] FIG3( a ) is a current variation trend in Example 1;

[0029] Figure 3(b) shows the conductivity variation trend in Example 1;

[0030] Figure 3(c) shows the variation trend of the electrosorption efficiency and average electrosorption rate in Example 1;

[0031] FIG3( d ) shows the charge efficiency and energy consumption variation trends in Example 1;

[0032] FIG4( a ) is a graph showing the average current variation trend in Example 2;

[0033] Figure 4(b) shows the conductivity variation trend in Example 2;

[0034] Figure 4(c) shows the variation trend of the electrosorption efficiency and the average electrosorption rate in Example 2;

[0035] FIG4( d ) shows the charge efficiency and energy consumption variation trends in Example 2;

[0036] FIG5( a) is a graph showing changes in ion concentration and selectivity at a voltage of 2.4 V in Example 3;

[0037] FIG5( b ) is a graph showing changes in ion concentration and selectivity at a voltage of 1.2 V in Example 3;

[0038] FIG5( c ) is a graph showing changes in ion concentration and selectivity at a voltage of 0.8 V in Example 3;

[0039] Figure 6 is a graph showing changes in ion concentration and selectivity separation coefficient in Example 4;

[0040] Figure 7 This is a graph showing changes in ion concentration and selectivity in Example 5. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] like Figure 1 , Figure 2 As shown, the present application proposes a dual-channel capacitive deionization device for extracting lithium from salt lakes, comprising: a first slurry channel plate 1, a first anion membrane 2, a feed liquid channel plate 3, a selective membrane 4, a recovery liquid channel plate 5, a second anion membrane 6, a second slurry channel plate 7, a slurry storage chamber 8, a slurry pump 9, a feed liquid storage chamber 10, a feed liquid pump 11, a recovery liquid storage chamber 12 and a recovery pump 13.

[0043] Among them, the first slurry channel plate 1, the first anion membrane 2, the feed liquid channel plate 3, the selective membrane 4, the recovery liquid channel plate 5, the second anion membrane 6 and the second slurry channel plate 7 are arranged in sequence to form a flow electrode capacitor module; the first slurry channel plate 1 and the second slurry channel plate 7 adopt a conductive structure.

[0044] A first slurry channel 1 - 1 is provided on a side of the first slurry channel plate 1 close to the first anion membrane 2 , and a second slurry channel is provided on a side of the second slurry channel plate 7 close to the second anion membrane 6 .

[0045] The feed liquid channel plate 3 and the recovery liquid channel plate 5 both adopt a through structure, and the feed liquid channel plate 3 is provided with a feed liquid inlet and a feed liquid outlet, and the recovery liquid channel plate 5 is provided with a recovery liquid inlet and a recovery liquid outlet.

[0046] The feed liquid channel plate 3 cooperates with the first anion membrane 2 and the selective membrane 4 to form a feed cavity 3-1, and the feed liquid inlet and the feed liquid outlet are both connected to the feed cavity; the recovery liquid channel plate 5 cooperates with the second anion membrane 6 and the selective membrane 4 to form a recovery cavity 5-1, and the recovery liquid inlet and the recovery liquid outlet are both connected to the recovery cavity.

[0047] When the first slurry channel plate 1 and the second slurry channel plate 7 are respectively connected to the positive and negative electrodes of the power supply, the carbon slurry in the first slurry channel 1-1 is positively charged, and the carbon slurry in the second slurry channel is negatively charged; in this way, the anions in the feed chamber 3-1 can pass through the first anion membrane 2 and be adsorbed by the positively charged carbon slurry in the first slurry channel 1-1; and the lithium ions in the feed chamber 3-1 pass through the selective membrane 4 into the recovery chamber 5-1, and the circulation of the recovery liquid is realized through the recovery liquid inlet and the recovery liquid outlet, thereby realizing lithium ion recovery.

[0048] The recovery chamber 5-1 is connected to the recovery liquid storage chamber 12 through the recovery liquid inlet and the recovery liquid outlet to form a recovery liquid circulation loop, and the recovery pump 13 is arranged on the recovery liquid circulation loop; the feed chamber 3-1 is connected to the feed liquid storage chamber 10 through the feed liquid inlet and the feed liquid outlet to form a feed liquid circulation loop, and the feed liquid pump 11 is arranged on the feed liquid circulation loop; the first slurry channel 1-1 and the second slurry channel are connected in parallel to the slurry storage chamber 8 to form a slurry circulation loop, and the slurry pump 9 is arranged on the slurry circulation loop.

[0049] In this way, the recovery chamber 5-1 is used to drive the recovery liquid to circulate between the recovery chamber 5-1 and the recovery liquid storage chamber 12, the feed liquid pump 11 is used to drive the feed liquid to circulate between the feed chamber 3-1 and the feed liquid storage chamber 10, and the slurry pump 9 is used to drive the carbon slurry to circulate between the first slurry channel 1-1 / the second slurry channel and the slurry storage chamber 8.

[0050] In specific implementation, the feed liquid inlet and the feed liquid outlet are arranged on opposite sides of the feed liquid channel plate 3 to extend the flow time of the feed liquid in the feed chamber 3-1 and improve the lithium ion separation rate; the recovery liquid inlet and the recovery liquid outlet are arranged on opposite sides of the recovery liquid channel plate 5 to extend the flow time of the recovery liquid in the recovery chamber 5-1 and improve the lithium ion recovery efficiency.

[0051] When the first slurry channel plate 1 and the second slurry channel plate 7 are energized, the anions in the feed chamber 3-1 pass through the first anion membrane 2 and are adsorbed by the positively charged carbon slurry in the first slurry channel 1-1, and the lithium ions in the feed chamber 3-1 pass through the selective membrane 4 and enter the recovery chamber 5-1; the negatively charged carbon slurry in the second slurry channel repels the anions and passes through the second anion membrane 6 to enter the recovery chamber 5-1; the recovery liquid in the recovery liquid storage chamber 12 circulates through the recovery chamber 5-1 to collect lithium ions and anions;

[0052] The feed liquid in the feed liquid storage chamber 10 circulates through the feed cavity 3-1 to separate lithium ions and anions; the carbon slurry with increased anions in the first slurry channel 1-1 and the carbon slurry with reduced anions in the second slurry channel meet in the slurry storage chamber 8 to ensure the service life of the carbon slurry.

[0053] In order to improve the utilization rate of the carbon slurry, in the present application, the first slurry channel 1-1 and the second slurry channel both adopt serpentine channels to increase the contact area and time between the carbon slurry and the anion membrane, increase the anion flow rate, and thus improve the lithium ion recovery efficiency.

[0054] In this application, when recovering lithium ions, the following conditions need to be met:

[0055] 1. The recovery chamber 5-1 is filled with recovery liquid, the feed chamber 3-1 is filled with feed liquid, and the first slurry channel 1-1 and the second slurry channel are filled with carbon slurry;

[0056] 2. The first slurry plate 1 is positively charged, and the second slurry plate 7 is negatively charged;

[0057] When the above two conditions are met, the lithium ions in the feed chamber 3-1 can be recovered. If the recovery liquid circulation loop, the feed liquid circulation loop and the slurry circulation loop are guaranteed to be unobstructed, the lithium ions in the feed liquid can be continuously recovered. At this time, the slurry pump 9, the feed liquid pump 11 and the recovery pump need to be turned on.

[0058] Therefore, the method for extracting lithium from salt lakes proposed in the present application adopts the above-mentioned FCDI device, first filling the activated carbon flowing electrode slurry into the slurry storage chamber 8, filling the slurry storage chamber 10 with slurry, and filling the recovery liquid storage chamber 12 with recovery liquid; then start the slurry pump 9, the slurry pump 11 and the recovery pump 13, so that the feed liquid, the recovery liquid and the carbon slurry enter a circulating flow state; then connect the power supply, add positive electricity to the first slurry plate 1, and add negative electricity to the second slurry plate 7, so as to realize the ion flow between the chambers, thereby realizing lithium ion recovery.

[0059] The effect of the method for extracting lithium from salt lakes proposed in this application is verified by combining several specific examples below.

[0060] In the following embodiments, the thickness of the feed chamber 3-1 and the recovery chamber 5-1 are both 3 mm, that is, the spacing between the first anion membrane 2 and the selective membrane 4 is 3 mm, and the spacing between the second anion membrane 6 and the selective membrane 4 is 3 mm. Between the first slurry channel plate 1 and the first anion membrane 2, between the feed channel plate 3 and the first anion membrane 2 and the selective membrane 4, between the recovery channel plate 5 and the selective membrane 4 and the second anion membrane 6, and between the second slurry channel plate 7 and the second anion membrane 6, a 1 mm thick silicone pad is used for sealing and leakproofing. The selective membrane 4 specifically selects a monovalent selective ion membrane. The flow electrode capacitor module formed by the first slurry channel plate 1, the first anion membrane 2, the feed channel plate 3, the selective membrane 4, the recovery channel plate 5, the second anion membrane 6 and the second slurry channel plate 7 is arranged in sequence and clamped from the outside with an acrylic plate to ensure the stability and sealing of the overall structure. The feed channel plate 3 and the recovery channel plate 5 are 3D printed with resin materials. The first slurry channel and the second slurry channel are 2 mm wide, 2 mm deep, and the straight section is 50 mm long. The effective area of ​​the first slurry channel plate 1 and the second slurry channel plate 7 as current collectors is 753.9 mm 2 .

[0061] In the following embodiments, a 5V / 2A power supply is used to apply a stable voltage to the first slurry plate 1 and the second slurry plate 7, and the current change is monitored; the first slurry plate 1 and the second slurry plate 7 are connected to the power supply using a short circuit connection (SCC); and a Mettler conductivity meter is used to monitor the concentration change of the feed liquid.

[0062] The carbon slurry used in the following examples is obtained by mixing activated carbon, conductive additives and deionized water according to a set ratio and stirring for more than 24 hours. The recovered liquid is 1000 mg L -1 The sodium chloride concentration, the volume of the feed liquid and the recovery liquid in the experiment are both 50 mL. The conductive additive is Ketjen black, and the first slurry channel plate 1 and the second slurry channel plate 7 are serpentine flow channel graphite plates.

[0063] In the following embodiments, the dual-channel capacitive deionization device for extracting lithium from salt lakes is referred to as an R-FCDI device.

[0064] Example 1

[0065] In this embodiment, carbon slurries with different carbon contents are used for experimental comparison, and the carbon contents are respectively: 0%, 4%, 7% and 10%; the mass proportions of each component of the carbon slurry with different carbon contents are shown in Table 1 below.

[0066] Table 1: Proportions of different carbon slurries in Example 1

[0067] Carbon content Activated carbon Conductive Additives Deionized water Carbon slurry 1 0 0 0 100％ Carbon slurry 2 4％ 3.88％ 0.12％ 96％ Carbon slurry 3 7％ 6.79％ 0.21％ 93％ Carbon slurry 4 10％ 9.7％ 0.3％ 90％

[0068] The carbon slurry with a carbon content of 10% is composed of activated carbon, a conductive additive and deionized water in a ratio of 14.55:0.45:135 by mass.

[0069] In this embodiment, the feed solution uses a lithium ion concentration of 1000 mg L -1 In this embodiment, as the power is turned on, the device enters the working state, and the changing trends of the current and conductivity are shown in Figures 3(a) and 3(b), and the statistics of the electrosorption efficiency, average electrosorption rate, charge efficiency and energy consumption are shown in Figures 3(c), 3(d) and Table 2.

[0070] Table 2. Statistics of experimental results in Example 1

[0071]

[0072] The energy consumption in this application refers to the energy consumption required to extract each mole of lithium ions.

[0073] As shown in Figure 3(a), with the increase of carbon content, the average current shows a clear upward trend, and its values ​​are 5.16, 31.75, 47.00 and 67.78 mA, respectively. When the carbon content is zero, the current is almost zero, which indicates that the ion migration is almost stagnant at this time, confirming the significant effect of carbon content on ion migration. As shown in Figure 3(b), with the increase of carbon content, the rate of decrease of the conductivity of the feed liquid gradually accelerates. It can be seen that increasing the carbon content can greatly enhance the dominant role of the electrosorption process in the entire device, thereby improving the lithium ion recovery efficiency of the device.

[0074] Table 2 clearly shows the changes in the key parameters of the R-FCDI device at different carbon contents. Through in-depth analysis of these data, two crucial conclusions can be drawn. First, when the carbon content in the system is zero, the electrosorption efficiency is only 1.41%, accompanied by an energy consumption of up to 0.356 kWh mol-1Li and a charge efficiency as low as 17.59%. With the gradual increase of carbon content, the electrosorption efficiency, average electrosorption rate and charge efficiency all show a significant upward trend, while the energy consumption gradually decreases. It is further proved that by increasing the carbon content, the dominant role of the electrosorption process in the entire R-FCDI device can be enhanced, thereby improving the lithium ion recovery efficiency of the device.

[0075] Example 2

[0076] This example explores the performance of the R-FCDI device proposed in this application at different feed liquid concentrations, which is very important and meaningful for adapting to different types of salt lakes.

[0077] This embodiment uses feed solutions with lithium ion concentrations of 100 mg / L, 400 mg / L, 700 mg / L and 1000 mg / L to conduct comparative tests. After the device enters the working state, the change trends of the average current and the lithium ion concentration in the feed solution are shown in Figure 4 (a) and Figure 4 (b), and the statistics of the electrosorption efficiency, average electrosorption rate, charge efficiency and energy consumption are shown in Figure 4 (c), Figure 4 (d) and Table 3.

[0078] Figure 4(a) shows that when the lithium ion concentration in the feed solution gradually increases from 100 mg / L to 1000 mg / L, the average current increases significantly, from 7.46 mA to 67.78 mA, thereby promoting the accelerated migration of lithium ions in the feed chamber 3-1 to the recovery chamber 5-1. Figure 4(b) shows the real-time change of the lithium ion concentration in the feed solution. It can be seen that the time required for complete ion adsorption increases with the increase in lithium ion concentration. As shown in Figure 4(c), the electrosorption efficiency of the device exceeds 95% at different feed solution concentrations. At the same time, the average electrosorption rate gradually increases from 1.61 μmol cm -2 min -1 increased to 7.77 μmol cm -2 min -1 As shown in Figure 4(d), the charge efficiencies are 79.91%, 93.43%, 96.71%, and 93.44%, respectively, and the energy consumption of the entire experiment is reduced from 0.08 kWh mol -1 Li to 0.06 kWh mol -1As shown in Table 3, as the feed solution concentration increases, the number of ions that can be removed also increases accordingly, thereby effectively reducing the energy consumption of the device. It can be seen that the R-FCDI device in this application exhibits excellent performance at different feed solution concentrations, especially in terms of average electrosorption rate and energy consumption.

[0079] Table 3. Statistics of experimental results in Example 2

[0080]

[0081] Example 3

[0082] In view of Example 1 and Example 2, this example selects a carbon slurry with an activated carbon concentration of 10 wt% and a feed solution with a lithium ion concentration of 1000 mg / L for experiment.

[0083] This example investigates the Li + / Mg 2+ The changes in ion concentration and selectivity are shown in Figure 5(a), Figure 5(b), and Figure 5(c).

[0084] As shown in Figure 5(a), under the voltage condition of 2.4V, the selective separation coefficient is only 0.5, which shows that the separation effect under the higher applied voltage is not significant. As shown in Figure 5(b), under the voltage condition of 1.2V, the selective separation coefficient is 1.2, which is still at a low level. As shown in Figure 5(c), under the voltage condition of 0.8V, the selective separation coefficient is 15.93.

[0085] It can be seen that at a voltage of 0.8 V, the monovalent selective membrane is 2+ The ideal balance between the blocking effect of ions and the electric field force is achieved, thus realizing Li + / Mg 2+ effective separation.

[0086] Example 4

[0087] In view of Example 1 and Example 3, in this implementation, a carbon slurry with an activated carbon concentration of 10 wt% and a feed solution with a lithium ion concentration of 1000 mg / L were selected for the experiment, and the power supply voltage was set to 0.8V.

[0088] In this embodiment, the feed solution is configured so that the mass ratio of magnesium to lithium is 20:1 to simulate the salt lake water sample. During the experiment, the changes in lithium and magnesium ion concentrations and the selectivity coefficient change diagram were observed. The results are as follows Figure 6 As shown. It can be seen that in the same period of time, the Li + The concentration of ions is always higher than that of Mg 2+ions. This is because the monovalent selective membrane is sensitive to Mg 2+ The ion hindrance makes Li + Ions can preferentially pass into the recovery liquid. At the same time, the selective separation coefficient of the device is relatively stable in the range of 8.52 to 11.04.

[0089] In this embodiment, the energy consumption is as low as 0.03 kWh·mol Li, that is, the energy consumption required to extract each mole of lithium is only 0.03 kWh, which shows the superiority of the device in terms of economy and energy efficiency. These excellent performances not only demonstrate the strong strength of the R-FCDI device proposed in this application in the field of lithium extraction from salt lakes, but also provide strong support for its wide promotion in practical industrial applications.

[0090] Example 5

[0091] In order to further verify the performance of the R-FCDI device proposed in this application in practical applications, a lithium extraction experiment was carried out in a real salt lake.

[0092] The difference between this embodiment 5 and embodiment 4 is that the feed liquid is natural salt lake brine, wherein Mg 2+ Concentration and Li + The concentration ratio is 36.18. Figure 7 The results show that the Li content in the recovered liquid of the R-FCDI device in this embodiment increases after 8 hours of continuous operation. + / Mg 2+ It is obvious that when the device starts running, the concentration of lithium ions in the recovery liquid is higher than that of magnesium ions. As the device continues to run, the concentration of magnesium ions increases faster than that of lithium ions. However, after 500 minutes of operation, the concentration of magnesium ions increases faster than that of lithium ions. 2+ Concentration and Li + The concentration ratio is only increased to a level close to 4; it can be seen that the ratio of magnesium ion concentration to lithium ion concentration in the recovery liquid is significantly lower than that in the feed liquid, achieving effective recovery of lithium ions.

[0093] During this process, the device showed significant separation selectivity, with selectivity coefficients ranging from 4.13 to 24.94 and energy consumption of 3.03 kWh mol-1Li. This result not only strongly verified the good performance of lithium ion recovery in treating natural salt lake brine, but also established a solid experimental foundation for the application of the device in future selective separation.

[0094] Of course, it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, but also includes the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any reference numerals in the claims should not be regarded as limiting the claims involved.

[0095] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0096] The techniques, shapes, and structural parts not described in detail in the present invention are all well-known techniques.

Claims

1. A dual-channel capacitive deionization device for extracting lithium from salt lakes, characterized in that: It comprises a first slurry channel plate (1), a first anion membrane (2), a feed liquid channel plate (3), a selective membrane (4), a recovery liquid channel plate (5), a second anion membrane (6) and a second slurry channel plate (7) which are arranged in sequence; the first slurry channel plate (1) and the second slurry channel plate (7) are of conductive structure; The first slurry channel plate (1) is provided with a first slurry channel (1-1) on the side close to the first anion membrane (2), and the second slurry channel plate (7) is provided with a second slurry channel on the side close to the second anion membrane (6); the feed liquid channel plate (3) is provided with a feed cavity (3-1) connecting the first anion membrane (2) and the selective membrane (4), and the feed liquid channel plate (3) is provided with a feed liquid inlet and a feed liquid outlet; the recovery liquid channel plate (5) is provided with a recovery cavity (5-1) connecting the second anion membrane (6) and the selective membrane (4), and the recovery liquid channel plate (5) is provided with a recovery liquid inlet and a recovery liquid outlet.

2. The dual-channel capacitive deionization device for extracting lithium from salt lakes according to claim 1, characterized in that: It also includes a slurry storage chamber (8), a slurry pump (9), a liquid storage chamber (10), a liquid pump (11), a recovery liquid storage chamber (12) and a recovery pump (13); the recovery chamber (5-1) is connected to the recovery liquid storage chamber (12) via a recovery liquid inlet and a recovery liquid outlet to form a recovery liquid circulation loop, and the recovery pump (13) is arranged on the recovery liquid circulation loop; the feed chamber (3-1) is connected to the liquid storage chamber (10) via a liquid inlet and a liquid outlet to form a liquid circulation loop, and the liquid pump (11) is arranged on the liquid circulation loop; the first slurry channel (1-1) and the second slurry channel are connected in parallel to the slurry storage chamber (8) to form a slurry circulation loop, and the slurry pump (9) is arranged on the slurry circulation loop.

3. The dual-channel capacitive deionization device for extracting lithium from salt lakes according to claim 2, characterized in that: The feed liquid inlet and the feed liquid outlet are arranged on opposite sides of the feed liquid channel plate (3), and the recovery liquid inlet and the recovery liquid outlet are arranged on opposite sides of the recovery liquid channel plate (5).

4. The dual-channel capacitive deionization device for extracting lithium from salt lakes according to claim 1, characterized in that: Both the first slurry channel (1-1) and the second slurry channel are serpentine channels.

5. The dual-channel capacitive deionization device for extracting lithium from salt lakes according to claim 1, characterized in that: The first slurry channel plate (1) and the second slurry channel plate (7) are made of graphite plates.

6. The dual-channel capacitive deionization device for extracting lithium from salt lakes according to any one of claims 1 to 5, characterized in that: It also includes a power supply, wherein the positive electrode of the power supply is connected to the first slurry channel plate (1), and the negative electrode of the power supply is connected to the second slurry channel plate (7).

7. A method for extracting lithium from a salt lake using the dual-channel capacitive deionization device for extracting lithium from a salt lake as claimed in any one of claims 2 to 6, characterized in that: The following steps are involved: S1, filling the slurry storage chamber (8) with activated carbon flowing electrode slurry, filling the slurry storage chamber (10) with slurry, and filling the recovery liquid storage chamber (12) with recovery liquid; S2, start the slurry pump (9), the liquid pump (11) and the recovery pump (13); S3, connecting the power supply, adding positive electricity to the first slurry channel plate (1), and adding negative electricity to the second slurry channel plate (7).

8. The method for extracting lithium from a salt lake as claimed in claim 7, characterized in that: After step S3, step S4 is further provided, in which the lithium ion concentration in the recovery liquid storage chamber (12) is detected, and when the lithium ion concentration in the recovery liquid storage chamber (12) rises to a set lithium ion recovery threshold value, the recovery liquid in the recovery liquid storage chamber (12) is replaced.

9. The method for extracting lithium from a salt lake according to claim 7, characterized in that: After step S3, step S5 is further provided, in which the lithium ion concentration in the feed liquid storage chamber (10) is detected, and when the lithium ion concentration in the feed liquid storage chamber (10) drops to a set lithium ion separation threshold, the feed liquid in the feed liquid storage chamber (10) is replaced.

10. The method for extracting lithium from a salt lake according to claim 7, 8 or 9, characterized in that: In step S1, the activated carbon flowing electrode slurry is composed of a mixture of activated carbon, a conductive additive and deionized water in a ratio of 14.55:0.45:135 by weight; the first slurry plate (1) and the second slurry plate (7) are connected to a power supply in a short-circuit connection manner, and the power supply voltage is 0.8V.

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