Electrochemical lithium-magnesium separation device for salt lake brine

Abstract

The utility model relates to an electrochemical lithium-magnesium separation device for salt lake brine, which comprises a brine tank, a cathode and an anode, and further comprises a single-chamber electrolytic bath, the single-chamber electrolytic bath is connected with the bottom of the brine tank through a pipeline and a first peristaltic pump, and two overflow liquid outlets are symmetrically formed in the side wall close to the top of the single-chamber electrolytic bath along a vertical shaft; brine containing magnesium ions and lithium ions is continuously fed into the single-cavity electrolytic bath through a first peristaltic pump to serve as electrolyte, catholyte in the single-cavity electrolytic bath can flow out from overflow liquid outlets, and an anode and a cathode are arranged in the single-cavity electrolytic bath and connected with a power source through wires. The anolyte collecting tank is connected with an anolyte outlet formed in the top of the single-chamber electrolytic bath through a pipeline and a second peristaltic pump, and is used for collecting an acidic electrolyte; and the catholyte collecting tank is communicated with the overflow liquid outlet through a pipeline and is used for collecting the alkaline electrolyte. The device realizes green and efficient separation of lithium and magnesium.

Description

Technical Field

[0001] This utility model relates to the technical field of lithium-magnesium directional separation equipment, specifically an electrochemical lithium-magnesium separation device for salt lake brine. Background Technology

[0002] Lithium, the first metallic element in the periodic table and the element with the smallest relative molecular mass, is often referred to by researchers as "metallic MSG." Lithium is widely used in aerospace, medicine, nuclear energy, and new energy fields. In recent years, with the rapid development of new energy technologies, the market demand for lithium has increased significantly, putting immense pressure on the sustainable development of lithium resources. Currently, lithium resources are mainly stored in salt lake brines, which account for approximately 60% of the world's proven lithium resources. However, lithium in salt lake brines coexists with alkali metal ions (potassium, calcium, sodium, magnesium, etc.), making the separation and extraction of lithium resources difficult. Therefore, there is an urgent need to develop a green and environmentally friendly device for efficiently separating lithium resources from salt lake brines.

[0003] Currently, the main technology for lithium and magnesium separation in salt lake brine is membrane separation. Membrane separation requires a membrane separation device, which includes a brine tank, an anode, and a cathode. The brine to be electrolyzed is fed into an electrolytic cell equipped with an ion exchange membrane through the brine tank. The brine is then electrolyzed by the anode and cathode located on either side of the ion exchange membrane. A drawback of this membrane separation device is that the ion exchange membrane is susceptible to fouling, resulting in poor lithium and magnesium separation efficiency. Therefore, there is an urgent need for a green and efficient electrochemical lithium-magnesium separation device. Utility Model Content

[0004] The purpose of this invention is to overcome the aforementioned problems in the prior art and to provide an electrochemical lithium-magnesium separation device for salt lake brine. This invention can achieve green and efficient separation of lithium and magnesium.

[0005] This utility model provides an electrochemical lithium-magnesium separation device for salt lake brine, comprising: a brine tank, a cathode, and an anode, and further comprising:

[0006] A single-chamber electrolytic cell is connected to the bottom of a brine tank via pipelines and a first peristaltic pump. Two overflow outlets are symmetrically opened along the vertical axis on the side wall near the top of the single-chamber electrolytic cell. The first peristaltic pump continuously feeds brine containing magnesium and lithium ions into the single-chamber electrolytic cell as electrolyte, and allows the cathode liquid in the single-chamber electrolytic cell to flow out from each overflow outlet. The anode and cathode are both located in the single-chamber electrolytic cell and are both connected to the power supply via wires.

[0007] The anolyte collection tank is connected to the anolyte outlet at the top of the single-chamber electrolyzer via pipelines and a second peristaltic pump, and is used to collect acidic electrolyte.

[0008] The cathode liquid collection tank is connected to the overflow outlet via a pipeline and is used to collect alkaline electrolyte.

[0009] Preferably, the cathode liquid collection tank is connected to the brine tank via a pipeline and a third peristaltic pump, which is used to send the alkaline electrolyte after in-situ deposition back into the brine tank to participate in the electrolysis reaction, so as to further remove the magnesium ions that are not completely precipitated in the alkaline electrolyte.

[0010] Preferably, the cathode liquid collection tank is equipped with a microfiltration membrane, which is used for in-situ deposition of magnesium hydroxide.

[0011] Preferably, the single-chamber electrolytic cell has a circular cross-section, with the anode located at the center of the single-chamber electrolytic cell and the cathode located inside the single-chamber electrolytic cell.

[0012] Preferably, the anode is a graphite rod and graphite particles, the cathode is a stainless steel bucket, the bottom of the stainless steel bucket has a water inlet hole communicating with a single-chamber electrolytic cell, the stainless steel bucket is set on a radius with the anode as the center, and the graphite rod and graphite particles are both placed inside the stainless steel bucket.

[0013] Preferably, the inner wall of the stainless steel barrel is coated with a polyurethane insulating coating.

[0014] Preferably, the system also includes a mixing tank, wherein the anolyte collection tank is connected to the mixing tank via a pipeline and a fourth peristaltic pump, and the brine tank is connected to the mixing tank via a pipeline and a fifth peristaltic pump.

[0015] Preferably, the bottom of the brine tank is provided with multiple water distribution pipes, and the single-chamber electrolytic cell is connected to the multiple water distribution pipes through pipelines and a first peristaltic pump.

[0016] Compared with the prior art, the beneficial effects of this utility model are:

[0017] This invention utilizes a first peristaltic pump to electrolyze brine in a single-chamber electrolytic cell, and a second peristaltic pump to draw in the electrolyzed anolyte. The resulting catholyte is then discharged through an overflow outlet, achieving separation of the electrolyte solutions. This eliminates the need for an ion-exchange membrane within the single-chamber electrolytic cell to prevent acid-base mixing at the electrodes. Furthermore, the separate collection of electrolytes at the electrodes maintains an alkaline environment in the catholyte collection tank. Since the electrolyte in the collection tank also contains magnesium, lithium, and hydroxide ions, magnesium and hydroxide ions are deposited in situ to form magnesium hydroxide, thus achieving magnesium-lithium separation in the catholyte. This creates favorable conditions for magnesium hydroxide precipitation without the need for reagents, making it environmentally friendly.

[0018] In addition, a microfiltration membrane is added to the cathode liquid collection tank, and then the cathode liquid filtered by the microfiltration membrane is sent to the brine tank for further degradation through a third peristaltic pump and pipeline. This can further filter the generated magnesium hydroxide and promote the separation of lithium and magnesium.

[0019] Furthermore, the collected anolyte has an acidic pH, which can be used to clean clogged microfiltration membranes, avoiding the need to add large amounts of chemical reagents during membrane cleaning and preventing secondary pollution.

[0020] The anode electrode used in this invention is a graphite particle electrode, and the cathode electrode is a stainless steel container. These materials are stable, resulting in low electrode cost and reduced overall cost. This invention's device achieves zero addition of acid and alkali reagents and environmental harmlessness by constructing a closed-loop system of single-chamber electrolysis-cathode deposition-microfiltration. Attached Figure Description

[0021] Figure 1 This is a structural diagram of an electrochemical lithium-magnesium separation device for salt lake brine according to the present invention.

[0022] Figure 2 This invention relates to the positional relationship of a single-chamber electrolytic cell, cathode, and anode in an electrochemical lithium-magnesium separation device for salt lake brine.

[0023] Figure 3 This invention relates to the connection relationship between the brine tank, mixing tank, fourth peristaltic pump, and fifth peristaltic pump in an electrochemical lithium-magnesium separation device for salt lake brine.

[0024] Explanation of reference numerals in the attached figures:

[0025] 1. Brine tank; 2. Single-chamber electrolytic cell; 3. First peristaltic pump; 4. Anode; 5. Cathode; 6. Anode liquid collection tank; 7. Second peristaltic pump; 8. Cathode liquid collection tank; 9. Microfiltration membrane; 10. Third peristaltic pump; 11. Fourth peristaltic pump; 12. Fifth peristaltic pump; 13. Mixing tank. Detailed Implementation

[0026] The following is combined with Figure 1 ~Attached Figure 3 The specific embodiments of this utility model are described in detail below, but it should be understood that the protection scope of this utility model is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without inventive effort are within the protection scope of this utility model.

[0027] The inventors discovered that existing electrolyzers use ion exchange membranes, which can become fouled over time, and replacing these membranes is expensive. Their device, however, uses a metal filter cartridge as the microfiltration membrane, which has a long lifespan and is free from fouling issues. By electrolyzing water, the device produces hydroxide and hydrogen ions, with the hydroxide ions being used to remove magnesium ions from brine.

[0028] In view of this, this utility model provides an electrochemical lithium-magnesium separation device for salt lake brine. This device uses a first peristaltic pump to place the brine into a single-chamber electrolytic cell for electrolysis, and a second peristaltic pump to draw in the electrolyzed anolyte, while the electrolyzed catholyte is discharged through an overflow outlet, thus achieving separation of the electrolyte solutions. This eliminates the need for an ion exchange membrane built into the single-chamber electrolytic cell to prevent acid-base mixing at the electrodes. Simultaneously, the electrolyte at the electrodes is collected separately, maintaining an alkaline environment in the catholyte collection tank. The electrolyte in the catholyte collection tank also contains magnesium ions, lithium ions, and hydroxide ions. Magnesium ions can react with hydroxide ions in situ to form magnesium hydroxide, which is then separated from the lithium hydroxide in the catholyte after filtration through a microfiltration membrane. This creates favorable conditions for the formation of magnesium hydroxide precipitate without the need for reagents, making it environmentally friendly. Furthermore, the collected anolyte has an acidic pH, which can be used to clean clogged microfiltration membranes, avoiding the need for adding large amounts of chemical reagents during membrane cleaning and preventing secondary pollution. This invention achieves zero addition of acid and alkali reagents and environmental harmlessness by constructing a closed-loop system of single-chamber electrolysis-cathode deposition-microfiltration.

[0029] like Figures 1-2 As shown, this utility model provides an electrochemical lithium-magnesium separation device for salt lake brine, comprising: a brine tank 1, a cathode 5, and an anode 4, and further comprising:

[0030] The single-chamber electrolytic cell 2 is connected to the bottom of the brine tank 1 via pipelines and a first peristaltic pump 3. Two overflow outlets are symmetrically opened along the vertical axis on the side wall near the top of the single-chamber electrolytic cell 2. The first peristaltic pump 3 continuously feeds brine containing magnesium ions and lithium ions into the single-chamber electrolytic cell 2 as electrolyte, and allows the cathode liquid in the single-chamber electrolytic cell 2 to flow out from each overflow outlet. The anode 4 and cathode 5 are both located in the single-chamber electrolytic cell 2 and are both connected to the power supply via wires.

[0031] The anolyte collection tank 6 is connected to the anolyte outlet at the top of the single-chamber electrolytic cell 2 via pipelines and a second peristaltic pump 7, and is used to collect acidic electrolyte. The anolyte in the anolyte collection tank 6 has a pH of 1.6-1.8 and is highly acidic. When the device is finished or paused, the microfiltration membrane cartridge can be removed and the solid magnesium hydroxide on the microfiltration membrane can be removed with the anolyte.

[0032] The cathode liquid collection tank 8 is connected to the overflow outlet via a pipeline and is used to collect alkaline electrolyte.

[0033] The brine tank 1 is connected to the single-chamber electrolytic cell 2 via pipelines and a first peristaltic pump, supplying brine to the single-chamber electrolytic cell 2 for electrolysis. The two overflow outlets on the single-chamber electrolytic cell 2 are connected to the cathode liquid collection tank 8 via pipelines. After electrolysis, the cathode electrolyte (brine containing hydroxide ions, magnesium ions, and lithium ions) overflows into the cathode liquid collection tank 8. The hydroxide ions combine with the magnesium ions to form magnesium hydroxide, thus achieving magnesium-lithium separation.

[0034] Specifically, the cathode liquid collection tank 8 is connected to the brine tank 1 via pipeline and the third peristaltic pump 10, and is used to send the cathode electrolyte (alkaline electrolyte) after the deposition of magnesium hydroxide back into the brine tank 1 to participate in the electrolysis reaction, so as to further remove the magnesium ions that are not completely precipitated in the alkaline electrolyte.

[0035] Specifically, the cathode liquid collection tank 8 is equipped with a microfiltration membrane 9, which is used for in-situ deposition of magnesium hydroxide. The microfiltration unit of the cathode liquid collection tank 8 is used to deposit magnesium hydroxide in situ, further removing magnesium ions from the electrolyte. The alkaline electrolyte after in-situ deposition is then fed back into the brine tank 1 to participate in the electrolysis reaction, further removing any remaining magnesium ions from the alkaline electrolyte.

[0036] Specifically, the single-chamber electrolytic cell 2 has a circular cross-section, with the anode 4 located at the center of the single-chamber electrolytic cell 2 and the cathode located inside the single-chamber electrolytic cell 2.

[0037] This setup facilitates electrode placement and maximizes the effective electrolysis area of ​​the cathode and anode, resulting in uniform electrolysis of the brine and improved electrolysis efficiency. The central design separates the cathode and anode, thus forming a single-chamber electrolytic cell.

[0038] Specifically, the anode 4 consists of graphite rods and graphite particles, and the cathode 5 is a stainless steel container. The bottom of the stainless steel container has a water inlet hole communicating with the single-chamber electrolytic cell 2. The stainless steel container is positioned on a radius centered on the anode 4. Both the graphite rods and graphite particles are housed within the stainless steel container; this arrangement aims to improve electrolysis efficiency. The graphite particle electrode, consisting of graphite particles and rods connected to the power supply, possesses excellent conductivity and can be obtained by removing impurities from retired lithium batteries, resulting in low cost.

[0039] Specifically, the inner wall of the stainless steel barrel is coated with a polyurethane insulating coating to prevent short circuits between the anode and cathode.

[0040] Specifically, it also includes a mixing tank 13, an anolyte collection tank 6 connected to the mixing tank 13 via a pipeline and a fourth peristaltic pump 11, and a brine tank 1 connected to the mixing tank 13 via a pipeline and a fifth peristaltic pump 12.

[0041] This mixture, prepared to neutralize the pH of the anolyte, achieves a magnesium removal efficiency of up to 85% compared to the original brine, while remaining near neutral. The treated brine in the unmixed brine tank exhibits a magnesium ion removal rate of up to 99.8%.

[0042] At this point, the liquid in brine tank 1 is electrolyzed brine with a higher pH. Magnesium ions have been largely removed from the treated brine. The purpose of mixing is to neutralize the pH of the acidic anolyte. Compared to the original brine, the mixed solution obtained after mixing the two liquids has a magnesium ion content reduced by at least 85%. The mixed solution in the mixing tank will not be further electrolyzed and is the final product. The brine is continuously fed into the single-chamber electrolytic cell 2 to create a circulation, thereby removing magnesium ions more efficiently.

[0043] Specifically, the bottom of the brine tank 1 is equipped with multiple water distribution pipes, and the single-chamber electrolysis cell 2 is connected to multiple water distribution pipes through pipelines and the first peristaltic pump 3 for uniform water intake, which is conducive to uniform electrolysis.

[0044] Specifically, the current density during electrolysis is 5 mA / cm². 2 ~30mA / cm 2 The brine influent rate and the anolyte acid extraction rate were determined through extensive experiments. The brine influent rate was 50 mL / min to 100 mL / min, and the anolyte acid extraction rate was 15 mL / min to 20 mL / min. There was no limit to the rate at which the catholyte was fed into the brine tank; it could be set to the maximum rate of the peristaltic pump.

[0045] Example

[0046] Brine tank 1 is connected to single-chamber electrolytic cell 2 via pipeline and first peristaltic pump, supplying brine to single-chamber electrolytic cell 2 for electrolysis. In single-chamber electrolytic cell 2, graphite particle (graphite rod) electrodes serve as anode 4, placed in a stainless steel cathode 4 at the center of single-chamber electrolytic cell 2. The inner wall of the stainless steel cylinder is coated with polyurethane insulating material. A stainless steel cylindrical electrode serves as cathode 5, placed outside the center of anode 4. Two overflow outlets on single-chamber electrolytic cell 2 are connected to cathode liquid collection tank 8 via pipeline, allowing electrolyte to overflow into cathode liquid collection tank 8. A filter membrane is installed in the microfiltration unit of cathode liquid collection tank 8 for in-situ deposition of magnesium hydroxide to remove magnesium ions from the electrolyte. The electrolyte is then filtered by the microfiltration unit located in cathode liquid collection tank 8 to remove most of the magnesium ions from the cathode electrolyte, achieving magnesium precipitation and lithium enrichment.

[0047] In the single-chamber electrolytic cell 2, the graphite particle (including graphite rod) electrode is connected to the second peristaltic pump 7 and the anolyte collection tank 6 through pipelines. The second peristaltic pump 7 pumps acidic water into the anolyte collection tank 6 to achieve lithium-magnesium separation. When the microfiltration membrane needs to be cleaned, the acidic anolyte can be used to clean the clogged microfiltration membrane, avoiding the addition of a large amount of chemical reagents during the membrane cleaning process, which would cause secondary pollution.

[0048] After determining the magnesium ion content in the electrolyte in the catholyte collection tank by titration, in order to remove magnesium ions as much as possible, the catholyte collection tank 8 is connected to the brine tank 1 through pipelines and a third peristaltic pump 10. The catholyte electrolyte that still contains magnesium ions is pumped back to the brine tank 1 by the third peristaltic pump 10 for secondary electrolysis.

[0049] like Figure 3 As shown, in addition, the brine tank 1, the anolyte collection tank 6 and the mixing tank 13 are connected. The water in the brine tank 1 and the anolyte collection tank 6 is pumped into the mixing tank 13 by the fourth peristaltic pump 11 to neutralize the pH of the acidic water in the anolyte, thereby reducing the magnesium ion content in the mixed solution and achieving the purpose of lithium-magnesium separation.

[0050] In the electrochemical lithium-magnesium separation device for salt lake brine, acidic water is extracted from graphite particle (including graphite rod) electrodes to suppress the mixing of acid and alkali solutions produced by electrolysis of the cathode and anode, and this mixture is used to clean clogged microfiltration membranes, achieving zero reagent addition. The high magnesium ion content of the salt lake brine combines with hydroxide ions in the alkaline water produced by electrolysis to generate a large amount of magnesium hydroxide, which is deposited in situ through the microfiltration unit, further reducing the magnesium ion content in the salt lake brine and achieving highly efficient separation of lithium and magnesium in actual brine. This novel device achieves zero addition of acid and alkali reagents and environmental harmlessness by constructing a closed-loop system of single-chamber electrolysis-cathode deposition-microfiltration.

[0051] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An electrochemical lithium-magnesium separation device for salt lake brine, comprising: The brine tank (1), cathode (5) and anode (4) are characterized in that they further include: The single-chamber electrolytic cell (2) is connected to the bottom of the brine tank (1) via pipelines and a first peristaltic pump (3). Two overflow outlets are symmetrically opened along the vertical axis on the side wall near the top of the single-chamber electrolytic cell (2). The first peristaltic pump (3) continuously feeds brine containing magnesium ions and lithium ions into the single-chamber electrolytic cell (2) as electrolyte, and allows the cathode liquid in the single-chamber electrolytic cell (2) to flow out from each overflow outlet. The anode (4) and cathode (5) are both located in the single-chamber electrolytic cell (2) and are both connected to the power supply via wires. The anolyte collection tank (6) is connected to the anolyte outlet at the top of the single-chamber electrolytic cell (2) via a pipeline and a second peristaltic pump (7) for collecting acidic electrolyte. The cathode liquid collection tank (8) is connected to the overflow outlet through a pipeline and is used to collect alkaline electrolyte.

2. The electrochemical lithium-magnesium separation device for salt lake brine according to claim 1, characterized in that, The cathode liquid collection tank (8) is connected to the brine tank (1) via pipeline and a third peristaltic pump (10) to send the alkaline electrolyte after in-situ deposition back into the brine tank (1) to participate in the electrolysis reaction, so as to further remove the magnesium ions that have not been completely precipitated in the alkaline electrolyte.

3. The electrochemical lithium-magnesium separation device for salt lake brine according to claim 2, characterized in that, The cathode liquid collection tank (8) is equipped with a microfiltration membrane (9), which is used for in-situ deposition of magnesium hydroxide.

4. The electrochemical lithium-magnesium separation device for salt lake brine according to claim 1, characterized in that, The single-chamber electrolytic cell (2) has a circular cross-section, with the anode (4) located at the center of the single-chamber electrolytic cell (2) and the cathode located inside the single-chamber electrolytic cell (2).

5. The electrochemical lithium-magnesium separation device for salt lake brine according to claim 4, characterized in that, The anode (4) is a graphite rod and graphite particles, and the cathode (5) is a stainless steel bucket. The bottom of the stainless steel bucket is provided with a water inlet hole that communicates with the single-chamber electrolytic cell (2). The stainless steel bucket is set on a radius with the anode (4) as the center. The graphite rod and graphite particles are both placed inside the stainless steel bucket.

6. The electrochemical lithium-magnesium separation device for salt lake brine according to claim 5, characterized in that, The inner wall of the stainless steel barrel is coated with a polyurethane insulating coating.

7. The electrochemical lithium-magnesium separation device for salt lake brine according to claim 1, characterized in that, It also includes a mixing tank (13), the anolyte collection tank (6) is connected to the mixing tank (13) via a pipeline and a fourth peristaltic pump (11), and the brine tank (1) is connected to the mixing tank (13) via a pipeline and a fifth peristaltic pump (12).

8. The electrochemical lithium-magnesium separation device for salt lake brine according to claim 1, characterized in that, The bottom of the brine tank (1) is provided with multiple water distribution pipes, and the single-chamber electrolytic cell (2) is connected to the multiple water distribution pipes through pipelines and the first peristaltic pump (3).

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