Device and method for extracting lithium by coupling ion sieve adsorbent and bipolar membrane electrodialysis

Abstract

The invention relates to the technical field of lithium extraction, in particular to a device and a method for extracting lithium by coupling an ion sieve adsorbent and bipolar membrane electrodialysis. A lithium ion sieve adsorbent is respectively embedded into an acid chamber and an alkali chamber of a bipolar membrane electrodialysis device to form a membrane package structure, so that organic combination of an adsorption method and an electrodialysis membrane separation method is realized. In a power-on state, the lithium ion sieve adsorbent in the alkali chamber is in an adsorption state, and the ion sieve in the acid chamber does not adsorb. After a period of time, the lithium ion sieve in the alkali chamber is saturated, and a large amount of acid is generated in the acid chamber. At the moment, the power is cut off to exchange a pipeline, only liquid circulation is carried out in a non-electrified state, at the moment, the saturated ion sieve adsorbent adsorbed in the alkali chamber is desorbed after the acid liquor is introduced, and the non-adsorbed ion sieve adsorbent in the acid chamber is adsorbed after the alkali liquor is introduced, so that a high-purity and high-concentration lithium-containing solution is obtained in the acid liquor storage tank; and the integration level and the efficiency of lithium extraction are improved.

Description

Technical Field

[0001] The invention relates to the technical field of lithium extraction, and in particular to a device and method for lithium extraction by coupling an ion sieve adsorbent with bipolar membrane electrodialysis. Background Art

[0002] At present, the main methods for extracting lithium from salt lake brine include adsorption, membrane separation, precipitation and extraction, but these methods all have certain limitations. Although the adsorption method has high selectivity and adsorption capacity, its recovery process needs to be carried out under specific conditions, which makes the operation difficult; although the electrodialysis membrane separation method is environmentally friendly and efficient, it has high energy consumption and is expensive; the precipitation method is mature in technology, but has poor selectivity for brine with a high magnesium-to-lithium ratio; although the extraction method has excellent separation effect, the organic extraction solvent is prone to cause environmental pollution.

[0003] In the adsorption method, commonly used adsorbents mainly include aluminum-based adsorbents, manganese-based lithium ion sieves and titanium-based lithium ion sieves. Among them, manganese-based and titanium-based lithium ion sieves have become research hotspots due to their high selectivity for lithium, excellent adsorption capacity, regeneration performance and high adsorption capacity. However, their adsorption and desorption processes need to be carried out in alkaline and acidic environments respectively, which limits their scope of application.

[0004] Electrodialysis membrane separation achieves Li + Directed migration and achieving Li + The traditional electrodialysis technology generates Li2CO3 by adding soda ash to the "concentration chamber", but further processing is required to obtain the LiOH required by the lithium battery industry. Summary of the invention

[0005] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide a device and method for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis.

[0006] The first object of the present invention is to provide a device for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis, comprising a three-compartment bipolar membrane electrodialysis device and a liquid storage device: the three-compartment bipolar membrane electrodialysis device comprises a cathode chamber, an anode chamber, and at least one membrane unit, the membrane unit is arranged between the cathode chamber and the anode chamber, the membrane unit comprises an alkali chamber, a dilute chamber, and an acid chamber arranged in sequence along a direction from the cathode chamber to the anode chamber, the alkali chamber and the dilute chamber are separated from each other by at least a cation exchange membrane, the dilute chamber and the acid chamber are separated from each other by at least an anion exchange membrane, and the cathode chamber and the alkali chamber, and the anode chamber and the acid chamber are separated from each other by at least a bipolar membrane; lithium ion sieve adsorbents are arranged in both the alkali chamber and the acid chamber, the lithium ion sieve adsorbents adsorb lithium under alkaline conditions and desorb lithium under acidic conditions; The liquid storage device comprises a dilute chamber storage tank, an alkaline solution storage tank, an acid solution storage tank and a cathode solution storage tank; the dilute chamber storage tank forms a circulation pipeline with the dilute chamber through a first pipeline assembly, and the cathode solution storage tank forms a circulation pipeline with the cathode chamber and the anode chamber through a second pipeline; In the initial state, lithium-containing solution is added to the dilute solution storage tank and the alkali solution storage tank, pure water is added to the acid solution storage tank, and polar solution is added to the polar solution storage tank.

[0007] The alkali solution storage tank forms a circulation pipeline with the alkali chamber or the acid chamber through a third pipeline assembly, and the acid solution storage tank forms a circulation pipeline with the acid chamber or the alkali chamber through a fourth pipeline assembly.

[0008] Furthermore, the lithium ion sieve adsorbent is prepared by the following method: coating a slurry containing ion sieve powder on a support net, and then coating the support net surface by gel cross-linking to form a coating layer.

[0009] Furthermore, the supporting net is a nylon mesh, a polyester mesh or a metal mesh material.

[0010] Furthermore, the ion sieve powder is a manganese-based ion sieve powder, a titanium-based ion sieve powder or a composite metal-based ion sieve powder.

[0011] Furthermore, it comprises a plurality of membrane units, and the plurality of membrane units are connected in series or in parallel.

[0012] Furthermore, the slurry also includes binder powder and N,N-dimethylformamide, and the binder powder includes polyvinyl chloride and polyacrylonitrile in a mass ratio of 9-2:1.

[0013] Furthermore, the first pipeline assembly, the second pipeline assembly, the third pipeline assembly, and the fourth pipeline assembly all include pipelines and circulation pumps arranged on the pipelines.

[0014] The second object of the present invention is a method for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis, using the above-mentioned device.

[0015] Further, the specific method is as follows: In the initial state, lithium-containing solution is added to the dilute chamber storage tank and the alkali solution storage tank, pure water is added to the acid solution storage tank, and the polar solution storage tank is added to the polar solution; the alkali solution storage tank forms a circulation pipeline with the alkali chamber through the third pipeline assembly, and the acid solution storage tank forms a circulation pipeline with the acid chamber through the fourth pipeline assembly; The bipolar membrane electrodialysis device is started, the alkali chamber adsorbs lithium ions, and the acid chamber generates an acidic environment; when the alkali chamber is saturated with adsorption and the pH of the acid chamber drops to a preset threshold, the bipolar membrane electrodialysis device is turned off, and the pipeline is switched. The alkali solution storage tank forms a circulation pipeline with the acid chamber through a third pipeline assembly, and the acid solution storage tank forms a circulation pipeline with the alkali chamber through a fourth pipeline assembly, so that the acid solution flows through the alkali chamber to desorb lithium ions, and the alkali solution flows through the acid chamber for adsorption; the above steps are repeated to continuously collect a high-concentration lithium-containing solution from the acid solution storage tank.

[0016] Furthermore, the lithium-containing solution is obtained by filtering, removing impurities or concentrating at least one of a salt lake lithium-containing solution, seawater, oilfield water, geothermal water, and industrial wastewater. Furthermore, the preset threshold value of the pH value of the acid chamber is 1-2.

[0017] The present invention is a device for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis. The lithium ion sieve adsorbent is respectively embedded in the acid chamber and the alkali chamber of the bipolar membrane electrodialysis device to form a membrane package structure, thereby realizing an organic combination of adsorption method and electrodialysis membrane separation method. The present invention makes full use of the characteristics of the acid chamber and the alkali chamber of the bipolar membrane electrodialysis: the acidic environment of the acid chamber is conducive to the Li in the lithium ion sieve adsorbent. + elution, while the alkali chamber can effectively concentrate the lithium-containing solution and increase its alkalinity, thereby enhancing the adsorption performance of the lithium ion sieve adsorbent. When powered on, the lithium ion sieve adsorbent in the alkali chamber is in an adsorption state, while the ion sieve in the acid chamber is not adsorbed. After a period of time, the lithium ion sieve in the alkali chamber is saturated with adsorption, and a large amount of acid is generated in the acid chamber. At this time, the power is turned off and the pipeline is "swapped". Only liquid circulation is carried out when the power is not turned on. At this time, the saturated ion sieve adsorbent in the alkali chamber is desorbed after the acid solution is passed in, and the unadsorbed ion sieve adsorbent in the acid chamber is adsorbed after the alkali solution is passed in. A high-purity and high-concentration lithium-containing solution is obtained in the acid storage tank, which improves the integration and efficiency of lithium extraction. Moreover, the obtained lithium-containing solution is lithium hydroxide, avoiding secondary treatment.

[0018] The high flow rate of electrodialysis will have high requirements on the structural stability and mechanical strength of the lithium ion sieve. Therefore, the present invention further prepares an adsorption material with high adsorption capacity and high mechanical strength by molding the ion sieve with PVC / PAN, combining it with a support net and then coating it with a gel material. This material is combined with bipolar membrane electrodialysis technology to form an adsorbent-electrodialysis system, which has an excellent extraction effect on low-grade lithium-containing solutions. This technology has the advantages of high energy utilization, high product purity, good material recyclability, etc., showing broad application prospects.

[0019] The invention provides a method with low cost, environmental friendliness, good stability and high lithium extraction efficiency, which can reduce the cost caused by the low initial concentration of lithium-containing solution and pH control during the adsorption and desorption process of lithium ion sieve. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of a device for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis in a power-on state and a power-off state according to the present invention; Figure 2 are the adsorption isotherms of ion sieves of different forms; FIG3 shows the change of lithium ion concentration in the acid chamber; FIG. 4 shows the changes in lithium ion concentration in the alkaline chamber and the dilute chamber. DETAILED DESCRIPTION

[0021] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0022] Example 1 Preparation of manganese-based lithium ion sieve adsorbent ① Weigh polyvinyl chloride (PVC) and polyacrylonitrile PAN in a mass ratio of 5:1 and mix them into a binder powder, where PVC can improve the mechanical strength of the ion sieve and PAN can improve the hydrophilicity of the ion sieve. Then add the binder powder to N,N-dimethylformamide (DMF) in a mass ratio of 1:13.6, seal and stir for 8 hours until the solution is clear and free of bubbles. Finally, add the hydrothermally synthesized Li 1.6 Mn 1.6 O4 manganese ion sieve powder, and seal and stir for 8 hours to form a black slurry.

[0023] ② Cut a certain area of ​​100-mesh nylon mesh, spread it flat on a glass plate, and apply the black slurry on the nylon mesh with a scraper. The nylon mesh provides structural support, and then immerse it in water for 48 hours to form a nylon-PVC / PAN-ion sieve composite material, referred to as NPLMO.

[0024] ③ Prepare 1% sodium alginate (SA) solution, immerse the formed NPLMO in the SA solution, take it out and soak it in 2% CaCl2 solution for 48 hours for cross-linking molding, wherein SA acts as a coating layer to play a physical isolation role, and obtain SNPLOM composite film-like lithium ion sieve adsorbent. The obtained lithium ion sieve adsorbent has good uniformity, high mechanical strength, and high capacity retention rate, which is 78% of the powder adsorption capacity.

[0025] Example 2 The adsorption performance of SNPLMO was tested and compared with the initial powdered Li 1.6 Mn 1.6 O4 ion sieve and granular formed ion sieve particles.

[0026] The detailed operating conditions and processing results are as follows: Li 1.6 Mn 1.6 Three forms of O4: powder, film, and granular were subjected to isothermal adsorption. First, it was acid-washed with 0.1 mol / L HCl, and after acid washing and drying, it was isothermally adsorbed at 30°C in a lithium-containing solution with 200 ppm LiCl and pH adjusted to 13 using KOH.

[0027] Figure 2 shows the adsorption isotherms of ion sieves of different forms. It can be seen that the adsorption rate of the composite membrane SNPLOM is equivalent to the adsorption capacity of the granular form, which is 78% of the powder adsorption capacity. This shows that the addition of nylon support material and SA coating layer has almost no effect on the adsorption performance of the ion sieve, while also improving the mechanical strength and resistance to water impact.

[0028] Example 3 like Figure 1 As shown, a device for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis comprises a three-compartment bipolar membrane electrodialysis device and a liquid storage device: the three-compartment bipolar membrane electrodialysis device comprises a cathode chamber, an anode chamber, and at least one membrane unit, the membrane unit is arranged between the cathode chamber and the anode chamber, the membrane unit comprises an alkali chamber, a dilute chamber, and an acid chamber arranged in sequence along a direction from the cathode chamber to the anode chamber, the alkali chamber and the dilute chamber are separated from each other by at least a cation exchange membrane, the dilute chamber and the acid chamber are separated from each other by at least an anion exchange membrane, and the cathode chamber and the alkali chamber, and the anode chamber and the acid chamber are separated from each other by at least a bipolar membrane; lithium ion sieve adsorbents are arranged in both the alkali chamber and the acid chamber, the lithium ion sieve adsorbents adsorb lithium under alkaline conditions and desorb lithium under acidic conditions; The liquid storage device includes a dilute chamber storage tank 1, an alkaline solution storage tank 3, an acid solution storage tank 2 and a cathode solution storage tank 4; the dilute chamber storage tank 1 forms a circulation pipeline with the dilute chamber through a first pipeline assembly, and the cathode solution storage tank 4 forms a circulation pipeline with the cathode chamber and the anode chamber through a second pipeline; In the initial state, lithium-containing solution is added to the dilute solution storage tank 1 and the alkali solution storage tank 3 , pure water is added to the acid solution storage tank 2 , and polar solution is added to the polar solution storage tank 4 .

[0029] When the three-compartment bipolar membrane electrodialysis device is in operation, the alkali solution storage tank 4 forms a circulation pipeline with the alkali chamber through the third pipeline assembly, and the acid solution storage tank 2 forms a circulation pipeline with the acid chamber through the fourth pipeline assembly. After running for a period of time, the alkali solution storage tank 4 forms a circulation pipeline with the acid chamber through the third pipeline assembly, and the acid solution storage tank 2 forms a circulation pipeline with the alkali chamber through the fourth pipeline assembly.

[0030] The first pipeline assembly, the second pipeline assembly, the third pipeline assembly, and the fourth pipeline assembly all include pipelines and circulation pumps disposed on the pipelines. In this embodiment, the circulation pump may be a magnetic pump.

[0031] Embodiment 4: This example shows the application of SNPLOM composite membrane-like lithium ion sieve adsorbent coupled with electrodialysis to simulate lithium extraction from lithium-containing solution.

[0032] Using electrodialysis as a carrier, the lithium ion sieve adsorbent is coupled into the membrane stack and integrated into a system. The high flux of electrodialysis can improve the adsorption and desorption rate of the ion sieve. The electrodialysis bipolar membrane system can provide the best adsorption and desorption environment for the ion sieve adsorbent at low cost and environmentally friendly, thereby improving the adsorption performance of the ion sieve adsorbent, reducing costs and reducing operations. The method of coupling the ion sieve adsorbent with bipolar membrane electrodialysis is as follows: ① First, Figure 1 The assembled electrodialysis membrane stack shown in the figure uses a cationic membrane, anionic membrane, and bipolar membrane, wherein the cationic membrane only allows cations to pass through, the anionic membrane only allows anions to pass through, and the bipolar membrane can generate hydrogen ions and hydroxide ions on both sides of the membrane under the action of an electric field. After power-on operation, the acid chamber is transformed from the original pure water to an acid solution containing HCl and H2SO4, which can provide the best desorption environment required by the ion sieve; the alkali chamber is transformed from the original lithium-containing solution to a high-concentration, alkaline lithium-containing solution, which can provide the best adsorption environment required by the ion sieve.

[0033] ② Spread the ion sieve adsorbent between the membrane and the partition, that is, embed the ion sieve adsorbent into the acid chamber and the alkali chamber respectively.

[0034] ③ Connect the membrane stack embedded with the ion sieve adsorbent to the storage tank through the pipeline. At the same time, introduce an operation of "swap": swap the pipeline connection between the acid storage tank and the alkali storage tank, so that the acid can pass through the alkali chamber and the alkali can pass through the acid chamber.

[0035] In the initial state, Figure 1The lithium-containing solution is added to the storage tank of the medium-water chamber and the alkali storage tank, and pure water is added to the acid storage tank. After the electrodialysis equipment is operated, the lithium ion sieve adsorbent in the alkali chamber is in an adsorption state when the power is on, while the ion sieve in the acid chamber is not adsorbed. After a period of time, the lithium ion sieve in the alkali chamber is saturated with adsorption, and a large amount of acid is generated in the acid chamber. At this time, the power is turned off and the pipelines of the acid storage tank and the alkali storage tank are "swapped", that is, the pipelines of the third pipeline assembly and the fourth pipeline assembly are "swapped". Only liquid circulation is carried out when the power is not turned on. At this time, the saturated ion sieve adsorbent in the alkali chamber is desorbed after the acid is introduced, and the unadsorbed ion sieve adsorbent in the acid chamber is adsorbed after the alkali is introduced. At this time, the acid storage tank contains a high-purity, high-concentration lithium-containing solution, namely, a lithium hydroxide solution, which can be used for subsequent lithium extraction. The above operation is repeated in the subsequent cycle.

[0036] The detailed operating conditions and processing results are as follows: Figure 1 As shown, 2L of simulated lithium solution (Li content 65ppm) was added to the fresh water storage tank and the alkali storage tank, deionized water was added to the acid chamber, and 4%wt Na2SO4 was added to the electrode chamber. Electrodialysis was operated under a constant voltage of 10 V, and the power was stopped when the pH reached about 1. Liquid samples were taken from the acid chamber and the alkali chamber at regular intervals to measure the lithium concentration and pH.

[0037] FIG3 shows the change of lithium ion concentration in the acid chamber, and FIG4 shows the change of lithium ion concentration in the alkali chamber and the dilute chamber; Figure 3 , Figure 4 As shown, after the SNPLOM composite membrane-like lithium ion sieve adsorbent is coupled with electrodialysis in this example, the lithium ion concentration in the acid chamber reaches 130ppm after 1h of power on, and the lithium ion concentration in the dilute chamber gradually decreases to close to 0ppm due to the transfer to the alkali chamber. The lithium ion concentration in the alkali chamber is transferred into the lithium ions. At the same time, as the pH rises, the adsorption rate of the lithium ion sieve adsorbent increases, the lithium ions are adsorbed, and the lithium ion concentration first rises and then falls. Therefore, the lithium in both chambers is adsorbed by the ion sieve. The lithium desorption rate of 75% and the lithium adsorption rate of 96.6% were reached, the comprehensive lithium extraction rate was 75%, and the energy consumption was 117kJ / mol (calculated as the energy consumption per mole of lithium carbonate), which is lower than the traditional lithium extraction method. It can be seen that the SNPLOM composite membrane-like lithium ion sieve coupled with electrodialysis has a high lithium extraction efficiency and energy consumption. A cycle can be completed in 4 hours, and only one-quarter of the time is powered on, with low energy consumption, and has good application and development prospects.

[0038] For matters not mentioned above, the prior art applies.

[0039] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art to which the present invention belongs may make various modifications or supplements to the specific embodiments described or replace them in a similar manner, but they will not deviate from the direction of the present invention or exceed the scope defined by the attached claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis, characterized in that: It comprises a three-compartment bipolar membrane electrodialysis device and a liquid storage device; the three-compartment bipolar membrane electrodialysis device comprises a cathode chamber, an anode chamber, and at least one membrane unit, the membrane unit is arranged between the cathode chamber and the anode chamber, and the membrane unit comprises an alkali chamber, a dilute chamber, and an acid chamber arranged in sequence in a direction from the cathode chamber to the anode chamber; the alkali chamber and the acid chamber are both provided with a lithium ion sieve adsorbent, the lithium ion sieve adsorbent adsorbs lithium under alkaline conditions and desorbs lithium under acidic conditions; The liquid storage device comprises a dilute chamber storage tank, an alkaline solution storage tank, an acid solution storage tank and a cathode solution storage tank; the dilute chamber storage tank forms a circulation pipeline with the dilute chamber through a first pipeline assembly, and the cathode solution storage tank forms a circulation pipeline with the cathode chamber and the anode chamber through a second pipeline; In the initial state, lithium-containing solution is added to the dilute liquid storage tank and the alkali liquid storage tank, pure water is added to the acid liquid storage tank, and polar liquid is added to the polar liquid storage tank; The alkali solution storage tank forms a circulation pipeline with the alkali chamber or the acid chamber through a third pipeline assembly, and the acid solution storage tank forms a circulation pipeline with the acid chamber or the alkali chamber through a fourth pipeline assembly.

2. The device for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis as claimed in claim 1, characterized in that: The lithium ion sieve adsorbent is prepared by the following method: coating a slurry containing ion sieve powder on a support net, and then coating the support net surface by gel cross-linking to form a coating layer.

3. The device for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis as claimed in claim 2, characterized in that: The coating layer is one of a sodium alginate gel coating layer, a chitosan gel coating layer and a polyvinyl alcohol gel coating layer.

4. The device for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis as claimed in claim 2, characterized in that: The supporting net is a nylon mesh, a polyester mesh or a metal mesh material.

5. The device for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis as claimed in claim 2, characterized in that: The ion sieve powder is manganese-based ion sieve powder, titanium-based ion sieve powder or composite metal-based ion sieve powder.

6. The device for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis as claimed in claim 1, characterized in that: The first pipeline assembly, the second pipeline assembly, the third pipeline assembly and the fourth pipeline assembly all include pipelines and circulation pumps arranged on the pipelines.

7. The device for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis as claimed in claim 1, characterized in that: It comprises a plurality of membrane units, and the plurality of membrane units are connected in series or in parallel.

8. A method for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis, characterized in that: Use the device according to any one of claims 1 to 7; The specific method is as follows: In the initial state, lithium-containing solution is added to the dilute chamber storage tank and the alkali solution storage tank, pure water is added to the acid solution storage tank, and the polar solution storage tank is added to the polar solution; the alkali solution storage tank forms a circulation pipeline with the alkali chamber through the third pipeline assembly, and the acid solution storage tank forms a circulation pipeline with the acid chamber through the fourth pipeline assembly; The bipolar membrane electrodialysis device is started, the alkali chamber adsorbs lithium ions, and the acid chamber generates an acidic environment; when the alkali chamber is saturated with adsorption and the pH of the acid chamber drops to a preset threshold, the bipolar membrane electrodialysis device is turned off, and the pipeline is switched. The alkali solution storage tank forms a circulation pipeline with the acid chamber through a third pipeline assembly, and the acid solution storage tank forms a circulation pipeline with the alkali chamber through a fourth pipeline assembly, so that the acid solution flows through the alkali chamber to desorb lithium ions, and the alkali solution flows through the acid chamber for adsorption; the above steps are repeated to continuously collect a high-concentration lithium-containing solution from the acid solution storage tank.

9. The method for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis as claimed in claim 8, characterized in that: The lithium-containing solution is obtained by filtering, removing impurities or concentrating at least one of a salt lake lithium-containing solution, seawater, oilfield water, geothermal water and industrial wastewater.

10. The method for extracting lithium by coupling an ion sieve adsorbent with bipolar membrane electrodialysis as claimed in claim 8, characterized in that: The preset threshold value of the acid chamber pH is 1-2.

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