Electrically-controlled adsorption and separation membrane for lithium ions, and preparation method therefor and use thereof

Abstract

Provided in the present application are an electrically-controlled adsorption and separation membrane for lithium ions, and a preparation method therefor and the use thereof. The electrically-controlled adsorption and separation membrane for lithium ions comprises an electrochemical adsorption layer and an ion exchange membrane layer, wherein the electrochemical adsorption layer comprises a composite membrane electrode layer and a two-dimensional material supporting layer, which are sequentially stacked, the two-dimensional material supporting layer being connected to the ion exchange membrane layer, and the composite membrane electrode layer being obtained by compounding an electrode active material and a two-dimensional material. The electrically-controlled adsorption and separation membrane constructed in the present application integrates electrically-controlled adsorptive enrichment of Li+ and SED concentration of Li+; and efficient enrichment is achieved by strengthening a continuous, rapid, selective and electrically-controlled adsorption-desorption process of Li+ by means of electric field coupling, and the concentration of Li+ at an ion exchange membrane interface is increased by effectively utilizing an Li+ enrichment area at an electrode interface during electronically-controlled desorption so as to alleviate / eliminate the effect of SED concentration polarization and improve the concentration and purification efficiency of lithium, thereby achieving the efficient enrichment, concentration and purification of low-grade lithium.

Description

A lithium ion electrically controlled adsorption separation membrane and its preparation method and application Technical Field

[0001] The present application relates to the technical field of ion exchange membranes, for example, a lithium ion electrically controlled adsorption separation membrane and its preparation method and application. Background Art

[0002] In recent years, global lithium consumption has grown rapidly, with my country's consumption increasing by more than 20% annually. Currently, China's lithium resource development mostly uses salt lake brine as raw material, which has a long extraction cycle and a large amount of lithium loss. With the continuous development of salt lake resources, direct extraction of lithium resources using raw brine as raw material has become a research hotspot, but low-grade raw brine Li + The low content and high content of coexisting impurity ions make the development of efficient and low-consumption extraction technology for low-grade lithium resources face huge challenges.

[0003] Adsorption and electrochemical adsorption technologies hold great promise for the development of low-grade lithium resources. Adsorption has rapidly developed for lithium extraction from salt lakes. Aluminum-based adsorbents, for example, have been used industrially on a large scale. However, these methods suffer from low adsorption capacity, high freshwater consumption, and high overall investment costs. Manganese- and titanium-based adsorbents also face challenges such as decreased adsorption capacity after granulation, the need for acid washing and regeneration, and poor cyclic stability. Electrochemical adsorption, driven by potential difference, overcomes the concentration equilibrium limitations of traditional adsorption methods, offering advantages such as rapid insertion-extraction rates, no need for chemical regeneration, and low energy consumption. However, its intermittent operation can lead to the carryover of small amounts of feed liquid, impacting overall efficiency and the lithium purity of the recovered solution. Furthermore, the lithium-rich solutions obtained by adsorption and electrochemical adsorption methods generally require further concentration and purification using other technologies (such as reverse osmosis, electrodialysis, and selective electrodialysis (SED)) to obtain a lithium concentrate suitable for lithium precipitation. Among these, the stepwise coupling of adsorption and selective electrodialysis for the separation and enrichment of low-grade lithium resources has attracted considerable attention. Li in the raw material solution + The concentration and purity are key factors affecting the SED concentration efficiency and energy consumption. Affected by the high ion transfer coefficient of the ion exchange membrane, an "ion depletion zone" is easily formed on the surface of the ion exchange membrane on the raw liquid side during the SED operation, causing a "concentration polarization" phenomenon, thereby affecting the lithium extraction process.

[0004] Therefore, how to improve the Li content of SED feed solution + Concentration and purity, and reducing / suppressing the impact of "concentration polarization" are key issues in achieving lithium concentration and purification.

[0005] Summary of the Invention

[0006] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0007] The purpose of this application is to provide a lithium ion electrically controlled adsorption separation membrane and its preparation method and application. This application constructs an electrically controlled adsorption separation membrane with a stable structure and efficient lithium ion transmission channel. The electrically controlled adsorption separation membrane is an electrically controlled adsorption enrichment membrane. + Li enrichment with SED + Integrates the Li + The continuous and rapid selective electric-controlled adsorption-desorption process achieves efficient enrichment, and effectively utilizes the Li + The enriched area increases the Li + concentration, in order to slow down / eliminate the influence of SED concentration polarization, improve the efficiency of lithium concentration and purification, and achieve efficient enrichment, concentration and purification of low-grade lithium.

[0008] In a first aspect, the present application provides a lithium ion electrically controlled adsorption separation membrane, wherein the lithium ion electrically controlled adsorption separation membrane comprises an electrochemical adsorption layer and an ion exchange membrane layer;

[0009] The electrochemical adsorption layer comprises a composite membrane electrode layer and a two-dimensional material support layer stacked in sequence, wherein the two-dimensional material support layer is connected to the ion exchange membrane layer;

[0010] The composite membrane electrode layer is obtained by compounding electrode active materials and two-dimensional materials.

[0011] This application constructs an electrically controlled adsorption separation membrane with a stable structure and efficient lithium ion transmission channel. The electrically controlled adsorption separation membrane collects lithium ions through electrically controlled adsorption. + Li enrichment with SED + Integrates the Li + The continuous and rapid selective electric-controlled adsorption-desorption process achieves efficient enrichment, and effectively utilizes the Li + The enriched area increases the Li + concentration, in order to slow down / eliminate the influence of SED concentration polarization, improve the efficiency of lithium concentration and purification, and achieve efficient enrichment, concentration and purification of low-grade lithium.

[0012] In this application, the composite of electrode active materials and two-dimensional materials can effectively enhance the conductivity of the composite membrane electrode layer, improving its lithium extraction rate and cycling stability. By regulating the interlayer spacing and surface properties of the two-dimensional material, nano-confined water transport channels can be constructed, inhibiting the free permeation of the feedstock liquid or water.

[0013] In this application, a stable and precisely separated ion exchange membrane layer can be constructed on a two-dimensional material support layer. The membrane layer has the characteristics of high density of charged groups, controllable pore size, low resistance, etc. It is a "charged channel" for rapid transfer of lithium ions, which can improve the efficiency of lithium ion transmission and achieve high selectivity, low energy consumption and continuous extraction of lithium.

[0014] As an optional technical solution of the present application, the thickness ratio of the electrochemical adsorption layer and the ion exchange membrane layer is (1-10):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc.

[0015] In this application, if the thickness ratio of the electrochemical adsorption layer to the ion exchange membrane layer is too small, that is, the thickness of the ion exchange membrane layer is too large, the ion flux becomes small; if the thickness ratio of the electrochemical adsorption layer to the ion exchange membrane layer is too large, that is, the thickness of the ion exchange membrane layer is too small, its long-term operation stability cannot be guaranteed.

[0016] As an optional technical solution of the present application, the electrode active material includes LiMn2O4, LiNi x Co y Mn z Any one of O2, Li2MnO3, MnO2 or LiFePO4, or a combination of at least two thereof.

[0017] It should be noted that for LiNi x Co y Mn z As for O2, the values ​​of x, y and z are not limited, and it only needs x+y+z=1.

[0018] In one embodiment, the electrode active material has a multi-level pore structure.

[0019] In the present application, the electrode active material with a multi-level pore structure can increase the contact area between the material and the solution, accelerate the lithium ion transfer rate, increase the adsorption capacity and thus enhance the concentration effect of the electrically controlled adsorption separation membrane.

[0020] In one embodiment, the particle size D50 of the electrode active material is 50-400 nm, for example, 50 nm, 100 nm, 200 nm, 300 nm or 400 nm.

[0021] In the present application, electrode active materials of appropriate size can match the size of the two-dimensional material during the self-assembly process, thereby enhancing the dispersibility and stability of the electrode active material.

[0022] In one embodiment, the mass ratio of the electrode active material to the two-dimensional material support layer is (1-10):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc.

[0023] In this application, if the mass ratio of the electrode active material to the two-dimensional material support layer is too small, that is, the amount of electrode active material added is too small, the interface Li + If the mass ratio of the electrode active material and the two-dimensional material support layer is too large, that is, too much electrode active material is added, the flexibility of the membrane electrode layer will be reduced and the mechanical properties will be degraded.

[0024] In one embodiment, the material of the two-dimensional material and the material of the two-dimensional material support layer are independently reduced graphene oxide or Mxene.

[0025] As an optional technical solution of the present application, the thickness ratio of the composite membrane electrode layer and the two-dimensional material support layer is (1-5):1, for example, it can be 1:1, 2:1, 3:1, 4:1 or 5:1.

[0026] In this application, if the thickness ratio of the composite membrane electrode layer and the two-dimensional material support layer is too small, that is, the thickness of the two-dimensional material support layer is too large, the transmembrane transmission resistance increases and the ion flux decreases; if the thickness ratio of the composite membrane electrode layer and the two-dimensional material support layer is too large, that is, the thickness of the two-dimensional material support layer is too small, the uniform distribution of the polyamide layer cannot be guaranteed, affecting the experimental reproducibility.

[0027] As an optional technical solution of the present application, the ion exchange membrane layer is a polyamide separation layer.

[0028] In the present application, the polyamide separation layer has a stable structure, uniform pores and an efficient lithium ion transmission channel.

[0029] In one embodiment, the average pore size of the ion exchange membrane layer is 0.2-1.5 nm, for example, 0.2 nm, 0.5 nm, 1 nm or 1.5 nm.

[0030] In a second aspect, the present application provides a method for preparing the lithium ion electrically controlled adsorption separation membrane as described in the first aspect, the preparation method comprising the following steps:

[0031] (1) coating a two-dimensional material solution on a base film to form a two-dimensional material support layer on the base film;

[0032] (2) coating a two-dimensional material solution containing an electrode active material on the two-dimensional material support layer to obtain an electrochemical adsorption layer having a composite membrane electrode layer;

[0033] (3) Mixing the aqueous phase monomer material, the oil phase monomer material and the electrochemical adsorption layer, and performing an interfacial polymerization reaction to obtain a lithium ion electrically controlled adsorption separation membrane having an ion exchange membrane layer.

[0034] In this application, with the help of aqueous phase monomers with higher charge density, the charge of the separation layer and its electrostatic repulsion to multivalent heteroions can be enhanced, breaking the "trade-off" effect and reducing the overall membrane resistance.

[0035] As an optional technical solution of the present application, the material of the base film in step (1) is selected from any one of cellulose acetate, polyethersulfone or polyacrylonitrile, or a combination of at least two of them.

[0036] In one embodiment, the coating method in step (2) includes vacuum filtration.

[0037] In one embodiment, after the coating in step (2) is completed, the composite membrane electrode layer is irradiated by ultraviolet light source.

[0038] In the present application, the purpose of irradiating the composite membrane electrode layer with an ultraviolet light source is to transform the two-dimensional material made of graphene oxide into a two-dimensional material made of reduced graphene oxide, so as to improve the conductivity of the two-dimensional material.

[0039] As an optional technical solution of the present application, the aqueous phase monomer material in step (3) is an amine polymer, which can be an amine polymer containing a quaternary amine group.

[0040] In one embodiment, the method for preparing the amine polymer containing a quaternary amine group comprises:

[0041] The amine raw material and the halogenation agent are mixed in an aqueous solution and subjected to a quaternization reaction to obtain the amine polymer containing the quaternary amine group.

[0042] In one embodiment, the amine polymer includes any one or a combination of at least two of polyethyleneimine, piperazine, m-phenylenediamine, polyallylamine, p-phenylenediamine, or hexamethylenediamine.

[0043] In one embodiment, the amine polymer containing a quaternary amine group includes quaternized polyethyleneimine and / or quaternized polyallylamine.

[0044] In one embodiment, the halogenating agent comprises ethylamine bromide and / or propylamine bromide.

[0045] In one embodiment, the mass ratio of the halogenating agent to the amine raw material is 1:(8-12), for example, 1:8, 1:9, 1:10, 1:11 or 1:12.

[0046] In one embodiment, the temperature of the quaternization reaction is 60-100°C, for example, 60°C, 70°C, 80°C, 90°C or 100°C.

[0047] In one embodiment, the quaternization reaction time is 4-24 hours, for example, 4 hours, 8 hours, 12 hours, 16 hours, 50 hours or 24 hours.

[0048] In the present application, by regulating the time of the quaternization reaction or the concentration of the halogenation reagent, the charged group density of the amine polymer containing the quaternary amine group can be regulated, thereby increasing the positive charge density of the polyamide separation layer and achieving efficient lithium ion transmission.

[0049] In one embodiment, the oil phase monomer material in step (3) is an acyl chloride compound.

[0050] In one embodiment, the acyl chloride compound includes any one of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride or tetraphthaloyl chloride, or a combination of at least two thereof.

[0051] In one embodiment, the mass ratio of the aqueous phase monomer material to the oil phase monomer material in step (3) is (8-12):1, for example, 8:1, 9:1, 10:1, 11:1 or 12:1.

[0052] As an optional technical solution of the present application, the mixing method in step (3) includes:

[0053] The electrochemical adsorption layer with the composite membrane electrode layer is immersed in the aqueous phase solution containing the aqueous phase monomer material. After the immersion is completed, the oil phase solution containing the oil phase monomer material is placed on the surface of the immersed electrochemical adsorption layer to perform interfacial polymerization reaction.

[0054] In one embodiment, the temperature of the interfacial polymerization reaction in step (3) is 20-25°C, for example, 20°C, 21°C, 22°C, 23°C, 24°C or 25°C.

[0055] In one embodiment, the interfacial polymerization reaction in step (3) lasts for 1-3 minutes, for example, 1 minute, 2 minutes, or 3 minutes.

[0056] In one embodiment, the aqueous solution further contains an aqueous solution additive.

[0057] In the present application, the purpose of adding the aqueous solution additive to the aqueous solution is to regulate the diffusion process of the interfacial polymerization reaction.

[0058] In one embodiment, the aqueous solution additive includes organic additives and / or inorganic additives.

[0059] In one embodiment, the inorganic additive includes LiCl and / or MgCl2.

[0060] In one embodiment, the organic additive is an amphoteric organic additive, and the amphoteric organic additive includes any one of nonylphenol polyoxyethylene ether, dodecasodium phytic acid, sodium lauryl sulfonate or cetyltrimethylammonium bromide.

[0061] In one embodiment, the mass concentration of the aqueous solution additive in the aqueous solution is 0.1-1%, for example, 0.1%, 0.5%, 0.7%, 0.8%, 0.9% or 1%.

[0062] In the present application, by regulating the amount of additives added to the aqueous solution, the diffusion behavior of the amine polymer can be inhibited by utilizing the hydrogen bonding between the inorganic additives and the amine polymer, or the diffusion behavior of the aqueous monomer material into the oil phase solution can be uniformly regulated by utilizing the amphiphilic molecular layer formed at the water-oil interface by the amphiphilic organic additives, and the interaction and diffusion path between the additives and the aqueous monomer can be simulated in combination with molecular dynamics to construct a stable and precisely separated ion exchange membrane layer.

[0063] In a third aspect, the present application provides an application of the lithium ion electrically controlled adsorption separation membrane as described in the first aspect in the development of low-grade lithium resources.

[0064] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to limited space and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0065] Compared with the related art, this application has the following beneficial effects:

[0066] (1) This application constructs an electrically controlled adsorption separation membrane with a stable structure and efficient lithium ion transmission channel. The electrically controlled adsorption separation membrane collects lithium ions through electrically controlled adsorption. + Li enrichment with SED + Integrates the Li + The continuous and rapid selective electric-controlled adsorption-desorption process achieves efficient enrichment, and effectively utilizes the Li + The enriched area increases the Li + concentration, in order to slow down / eliminate the influence of SED concentration polarization, improve the efficiency of lithium concentration and purification, and achieve efficient enrichment, concentration and purification of low-grade lithium.

[0067] (2) In this application, the composite of electrode active materials and two-dimensional materials can effectively enhance the conductivity of the composite membrane electrode layer, improve its lithium extraction rate and cycle stability. By regulating the interlayer spacing and surface properties of the two-dimensional material, nano-confined water transmission channels can be constructed to inhibit the free permeation of the raw material liquid or water.

[0068] (3) In the present application, a stable and precisely separated ion exchange membrane layer can be synthesized on a two-dimensional material support layer. The ion exchange membrane layer has the characteristics of high density of charged groups, controllable pore size, and low resistance. It is a "charge channel" for rapid transfer of lithium ions, which can improve the lithium ion transmission efficiency and achieve high selectivity, low energy consumption, and continuous extraction of lithium.

[0069] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0071] FIG1 is a physical picture of the electrically controlled adsorption separation membrane prepared in Example 1 of the present application.

[0072] FIG2 is a scanning electron microscope image of the electrically controlled adsorption separation membrane prepared in Example 1 of the present application.

[0073] FIG3 is a Li-ion electrostatic adsorption separation membrane provided in Example 1 of the present application. + Flux and Mg 2+ Histogram of flux.

[0074] FIG4 is a bar chart showing the lithium-magnesium separation coefficient of the electrically controlled adsorption separation membrane provided in Example 1 of the present application under constant current conditions.

[0075] FIG5 is a graph showing the Li of the reduced graphene oxide support layer membrane provided in Comparative Example 1 of the present application. + Flux and Mg 2+ Histogram of flux.

[0076] FIG6 is a graphite oxide support layer / ion exchange membrane layer provided in Comparative Example 1 of the present application, wherein the Li + Flux and Mg 2+ Histogram of flux.

[0077] FIG7 is a bar chart of the lithium-magnesium separation coefficient of the reduced graphene oxide support layer / ion exchange membrane layer provided in Comparative Example 1 of the present application under constant current conditions. DETAILED DESCRIPTION

[0078] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0079] Example 1

[0080] This embodiment provides a lithium ion electrically controlled adsorption separation membrane, as shown in FIG1 , wherein the lithium ion electrically controlled adsorption separation membrane comprises an electrochemical adsorption layer and an ion exchange membrane layer with a thickness ratio of 5:1;

[0081] The electrochemical adsorption layer comprises a composite membrane electrode layer and a two-dimensional material support layer stacked in sequence with a thickness ratio of 2:1, wherein the two-dimensional material support layer is connected to the ion exchange membrane layer;

[0082] The composite membrane electrode layer is obtained by compounding the electrode active material and the two-dimensional material;

[0083] The electrode active material is lithium manganate (LiMn2O4) with a multi-level pore structure, and its particle size D50 is 200 nm. Based on the mass of the composite membrane electrode layer, the mass ratio of the electrode active material to the two-dimensional material support layer is 1:1;

[0084] The material of the two-dimensional material and the material of the two-dimensional material support layer are both reduced graphene oxide;

[0085] The ion exchange membrane is a polyamide separation layer with an average pore size of 1 nm.

[0086] Figure 2 shows a scanning electron microscope image of the lithium ion electrically controlled adsorption separation membrane prepared in this example. As can be seen from the figure, the electrically controlled adsorption separation membrane consists of an ion exchange membrane layer and an electrochemical adsorption layer (Figure 2a). The support layer in the electrochemical adsorption layer is relatively regular as a whole, and the two-dimensional reduced graphene oxide sheets are stacked layer by layer, which serves as a flexible substrate for the polyamide separation layer while providing ordered nanochannels for lithium ion transport (Figures 2b, 2c); the polyamide separation layer has a typical nodular structure, and the nodular structure is uniform in size and evenly distributed, indicating that a relatively complete polyamide structure is formed on the membrane surface (Figure 2d); the electrochemical adsorption layer has a sandwich structure, and lithium manganese oxide is evenly distributed between the reduced graphene oxide sheets. The reduced graphene oxide provides a continuous conductive network for lithium manganese oxide, accelerating charge transfer and ion transport (Figures 2e, 2f).

[0087] This embodiment also provides a method for preparing the above-mentioned lithium ion electrically controlled adsorption separation membrane, the preparation method comprising the following steps:

[0088] (1) filtering the aqueous solution containing graphene oxide onto the cellulose acetate base film, so that a graphene oxide support layer is formed on the base film;

[0089] (2) uniformly dispersing lithium manganate in an aqueous solution containing graphene oxide under mechanical stirring to obtain a mixed solution, and using a vacuum filtration technique to filter the mixed solution onto the graphene oxide support layer to obtain a composite membrane electrode layer, and then irradiating the composite membrane electrode layer with an ultraviolet light source for 4 hours to directionally reduce the graphene oxide layer in the composite membrane electrode layer to form reduced graphene oxide, thereby obtaining an electrochemical adsorption layer having a structure of LiMn2O4@rGO / rGO;

[0090] (3) mixing polyethyleneimine and a halogenating agent in an aqueous solution (the mass ratio of the halogenating agent to polyethyleneimine is 1:10), and performing a quaternization reaction at 80° C. for 4 hours to obtain the quaternized polyethyleneimine as an aqueous phase monomer material;

[0091] Wherein, the halogenating agent is ethylamine bromide;

[0092] (4) Immersing the electrochemical adsorption layer having the structure of LiMn2O4@rGO / rGO in an aqueous solution containing an aqueous monomer material and an aqueous solution additive, taking out the electrochemical adsorption layer after immersion, fixing it on a polytetrafluoroethylene plate with tape, pouring an oil phase solution containing an oil phase monomer material, and then performing an interfacial polymerization reaction at 25°C for 1 min to obtain a lithium ion electrically controlled adsorption separation membrane having an ion exchange membrane layer;

[0093] The oil phase monomer material is trimesoyl chloride, the mass ratio of the water phase monomer material to the oil phase monomer material is 10:1, and the water phase solution additive is sodium dodecyl sulfate, and its mass concentration is 0.5%.

[0094] Example 2

[0095] This embodiment provides a lithium ion electrically controlled adsorption separation membrane, which comprises an electrochemical adsorption layer and an ion exchange membrane layer with a thickness ratio of 5:1;

[0096] The electrochemical adsorption layer comprises a composite membrane electrode layer and a two-dimensional material support layer stacked in sequence with a thickness ratio of 2:1, wherein the two-dimensional material support layer is connected to the ion exchange membrane layer;

[0097] The composite membrane electrode layer is obtained by compounding the electrode active material and the two-dimensional material;

[0098] The electrode active material is lithium manganate (LiMn2O4) with a multi-level pore structure, and its particle size D50 is 400nm. Based on the mass of the composite membrane electrode layer, the mass ratio of the electrode active material to the two-dimensional material support layer is 2:1;

[0099] The two-dimensional material and the two-dimensional material support layer are both made of reduced graphene oxide;

[0100] The ion exchange membrane is a polyamide separation layer with an average pore size of 1 nm.

[0101] This embodiment also provides a method for preparing the above-mentioned lithium ion electrically controlled adsorption separation membrane, the preparation method comprising the following steps:

[0102] (1) filtering the aqueous solution containing graphene oxide onto the cellulose acetate base film, so that a graphene oxide support layer is formed on the base film;

[0103] (2) uniformly dispersing lithium manganate in an aqueous solution containing graphene oxide under mechanical stirring to obtain a mixed solution, and using a vacuum filtration technique to filter the mixed solution onto the graphene oxide support layer to obtain a composite membrane electrode layer, and then irradiating the composite membrane electrode layer with an ultraviolet light source for 4 hours to directionally reduce the graphene oxide layer in the composite membrane electrode layer to form reduced graphene oxide, thereby obtaining an electrochemical adsorption layer having a structure of LiMn2O4@rGO / rGO;

[0104] (3) mixing polyethyleneimine and a halogenating agent (the mass ratio of the halogenating agent to polyethyleneimine is 1:8) in an aqueous solution, and performing a quaternization reaction at 80° C. for 8 hours to obtain the quaternized polyethyleneimine as an aqueous phase monomer material;

[0105] Wherein, the halogenating agent is ethylamine bromide;

[0106] (4) immersing the electrochemical adsorption layer having the structure of LiMn2O4@rGO / rGO in an aqueous solution containing an aqueous monomer material and an aqueous solution additive, placing an oily phase solution containing an oily phase monomer material on the surface of the electrochemical adsorption layer after immersion, and performing an interfacial polymerization reaction at 25°C for 1 minute to obtain a lithium ion electrically controlled adsorption separation membrane having an ion exchange membrane layer;

[0107] The oil phase monomer material is trimesoyl chloride, the mass ratio of the water phase monomer material to the oil phase monomer material is 10:1, and the water phase solution additive is sodium lauryl sulfate with a mass concentration of 0.1%.

[0108] Example 3

[0109] This embodiment provides a lithium ion electrically controlled adsorption separation membrane, which comprises an electrochemical adsorption layer and an ion exchange membrane layer with a thickness ratio of 5:1;

[0110] The electrochemical adsorption layer comprises a composite membrane electrode layer and a two-dimensional material support layer stacked in sequence with a thickness ratio of 2:1, wherein the two-dimensional material support layer is connected to the ion exchange membrane layer;

[0111] The composite membrane electrode layer is obtained by compounding the electrode active material and the two-dimensional material;

[0112] The electrode active material is lithium manganate (LiMn2O4) with a multi-level pore structure, and its particle size D50 is 200 nm. Based on the mass of the composite membrane electrode layer, the mass ratio of the electrode active material to the two-dimensional material support layer is 1:1;

[0113] The two-dimensional material and the two-dimensional material support layer are both made of reduced graphene oxide;

[0114] The ion exchange membrane is a polyamide separation layer with an average pore size of 1 nm.

[0115] This embodiment also provides a method for preparing the above-mentioned lithium ion electrically controlled adsorption separation membrane, the preparation method comprising the following steps:

[0116] (1) filtering the aqueous solution containing graphene oxide onto the cellulose acetate base film, so that a graphene oxide support layer is formed on the base film;

[0117] (2) uniformly dispersing lithium manganate in an aqueous solution containing graphene oxide under mechanical stirring to obtain a mixed solution, and using a vacuum filtration technique to filter the mixed solution onto the graphene oxide support layer to obtain a composite membrane electrode layer, and then irradiating the composite membrane electrode layer with an ultraviolet light source for 4 hours to directionally reduce the graphene oxide layer in the composite membrane electrode layer to form reduced graphene oxide, thereby obtaining an electrochemical adsorption layer having a structure of LiMn2O4@rGO / rGO;

[0118] (3) mixing polyethyleneimine and a halogenating agent having a mass fraction of 1% (the mass ratio of the halogenating agent to polyethyleneimine is 1:12) in an aqueous solution, and performing a quaternization reaction at 80° C. for 10 hours to obtain the quaternized polyethyleneimine as an aqueous phase monomer material;

[0119] Wherein, the halogenating agent is ethylamine bromide;

[0120] (4) immersing the electrochemical adsorption layer having the structure of LiMn2O4@rGO / rGO in an aqueous solution containing an aqueous monomer material and an aqueous solution additive, placing an oily phase solution containing an oily phase monomer material on the surface of the electrochemical adsorption layer after immersion, and performing an interfacial polymerization reaction at 25°C for 1 minute to obtain a lithium ion electrically controlled adsorption separation membrane having an ion exchange membrane layer;

[0121] The oil phase monomer material is terephthaloyl chloride, the mass ratio of the aqueous phase monomer material to the oil phase monomer material is 10:1, and the aqueous phase solution additive is phytic acid dodecasodium salt, and its mass concentration is 0.5%.

[0122] Example 4

[0123] The difference between this embodiment and embodiment 1 is that the thickness of the ion exchange membrane is adjusted so that the thickness ratio of the electrochemical adsorption layer to the ion exchange membrane layer is 20:1.

[0124] The rest of the preparation methods and parameters remained the same as in Example 1.

[0125] Example 5

[0126] The difference between this embodiment and embodiment 1 is that the thickness of the ion exchange membrane is adjusted so that the thickness ratio of the electrochemical adsorption layer to the ion exchange membrane layer is 1:3.

[0127] The rest of the preparation methods and parameters remained the same as in Example 1.

[0128] Example 6

[0129] The difference between this embodiment and embodiment 1 is that the mass ratio of the electrode active material to the two-dimensional material support layer is 0.5:1.

[0130] The rest of the preparation methods and parameters remained the same as in Example 1.

[0131] Example 7

[0132] The difference between this embodiment and embodiment 1 is that the mass ratio of the electrode active material to the two-dimensional material support layer is 15:1.

[0133] The rest of the preparation methods and parameters remained the same as in Example 1.

[0134] Example 8

[0135] The difference between this embodiment and embodiment 1 is that the thickness of the two-dimensional material support layer is adjusted so that the thickness ratio of the composite membrane electrode layer to the two-dimensional material support layer is 0.5:1.

[0136] The rest of the preparation methods and parameters remained the same as in Example 1.

[0137] Example 9

[0138] The difference between this embodiment and embodiment 1 is that the thickness of the two-dimensional material support layer is adjusted so that the thickness ratio of the composite membrane electrode layer to the two-dimensional material support layer is 6:1.

[0139] The rest of the preparation methods and parameters remained the same as in Example 1.

[0140] Example 10

[0141] The difference between this embodiment and embodiment 1 is that step (3) is not performed, that is, the polyethyleneimine is not subjected to quaternization treatment.

[0142] The rest of the preparation methods and parameters remained the same as in Example 1.

[0143] Example 11

[0144] The difference between this embodiment and embodiment 1 is that no aqueous solution additive is added to the aqueous solution in step (4).

[0145] The rest of the preparation methods and parameters remained the same as in Example 1.

[0146] Example 12

[0147] The difference between this embodiment and embodiment 1 is that the mass concentration of the aqueous solution additive in step (4) is 0.05%.

[0148] The rest of the preparation methods and parameters remained the same as in Example 1.

[0149] Example 13

[0150] The difference between this embodiment and embodiment 1 is that the mass concentration of the aqueous solution additive in step (4) is 2%.

[0151] The rest of the preparation methods and parameters remained the same as in Example 1.

[0152] Comparative Example 1

[0153] The difference between this comparative example and Example 1 is that steps (2) to (4) are replaced by the following steps:

[0154] a. irradiating the graphene oxide support layer with an ultraviolet light source for 4 h to reduce the graphene oxide support layer to a reduced graphene oxide support layer film;

[0155] b. Immerse the reduced graphene oxide support layer membrane in an aqueous solution containing polyethyleneimine, remove it after 5 minutes, scrape it dry with a rubber roller, and let it stand for 3 minutes. Then, use tape to fix the membrane after standing on a polytetrafluoroethylene plate, pour it into an oil phase solution containing trimesoyl chloride and react for 1 minute. After removing the oil phase solution, heat treat it at 80°C for 5 minutes to obtain a reduced graphene oxide support layer / ion exchange membrane layer.

[0156] The rest of the preparation methods and parameters remained the same as in Example 1.

[0157] Comparative Example 2

[0158] The difference between this comparative example and Example 1 is that lithium manganate is not added in step (2), that is, the composite membrane electrode layer only contains a membrane made of reduced graphene oxide.

[0159] The rest of the preparation methods and parameters remained the same as in Example 1.

[0160] Comparative Example 3

[0161] The difference between this comparative example and Example 1 is that step (1) is not performed, that is, the electrochemical adsorption layer does not contain a two-dimensional material support layer.

[0162] The rest of the preparation methods and parameters remained the same as in Example 1.

[0163] Performance Testing

[0164] The membranes prepared in the above examples and comparative examples were subjected to experiments. The equipment of the experiment included a peristaltic pump, a DC power supply and an electrically controlled adsorption separation membrane device. The polar liquid was a 0.15 mol / L Na2SO4 solution, the initial raw material liquid was a mixed solution of 0.05 mol / L LiCl and 0.05 mol / L MgCl2, and the recovered liquid was a 0.1 mol / L KCl solution. The membranes provided in the above examples and comparative examples were installed in an electrically controlled adsorption separation membrane device for experiments. After ensuring the airtightness of the device, the experiments were carried out. After a period of time, samples were taken for analysis to obtain the Li+ flux and the lithium-magnesium separation coefficient. This application tested the lithium ion electrically controlled adsorption separation membrane prepared in Example 1 according to the above experimental steps at 2 mA·cm -2 The experiment was carried out under the condition of constant current, and samples were taken every 20 minutes for analysis. The analysis results are shown in Figures 3 and 4. It can be seen from the figure that after 1 hour, Li + The flux is 1.40×10 -8 mol·cm -2 ·s -1 , the lithium-magnesium separation coefficient is 16.62, and after 2h, Li + The flux is 1.41×10 -8 mol·cm -2 ·s -1 , the lithium-magnesium separation coefficient is 13.32.

[0165] The reduced graphene oxide support layer membrane prepared in Comparative Example 1 was also tested at 2 mA·cm according to the above experimental steps. -2 The experiment was carried out under constant current conditions, and samples were taken for analysis after 0.5h and 1h. The analysis results are shown in Figure 5. It can be seen from the figure that the obtained Li + The flux is 1.75×10 -8 mol·cm -2 ·S -2 , 1.72×10 -8 mol·cm -2 ·S -2 , the lithium-magnesium separation coefficient is 1.02.

[0166] The reduced graphene oxide support layer / ion exchange membrane layer prepared in Comparative Example 1 was subjected to the above-mentioned experimental steps at 2 mA·cm -2The experiment was carried out under the constant current condition, and samples were taken and analyzed after 1h and 2h respectively. The analysis results are shown in Figures 6 and 7. It can be seen from the figure that after 1h, Li + The flux is 1.24×10 -8 mol·cm -2 ·s -1 , the lithium-magnesium separation coefficient is 7.29, and after 2h, Li + The flux is 1.23×10 -8 mol·cm -2 ·s -1 , the lithium-magnesium separation coefficient is 9.46.

[0167] Using the above experimental steps, the membranes provided in the examples and comparative examples were tested at 2 mA·cm -2 The experiment was carried out under constant current conditions. Samples were taken for analysis after 1 hour. The analysis results are shown in Table 1.

[0168] Table 1

[0169] analyze:

[0170] As can be seen from the above table, this application has constructed an electrically controlled adsorption separation membrane with a stable structure and an efficient lithium ion transmission channel. The electrically controlled adsorption separation membrane collects Li + Li enrichment with SED + Integrates the Li + The continuous and rapid selective electric-controlled adsorption-desorption process achieves efficient enrichment, and effectively utilizes the Li + The enriched area increases the Li + concentration, in order to slow down / eliminate the influence of SED concentration polarization, improve the efficiency of lithium concentration and purification, and achieve efficient enrichment, concentration and purification of low-grade lithium.

[0171] It can be seen from the data results of Example 1 and Examples 4-5 that if the thickness ratio of the electrochemical adsorption layer and the ion exchange membrane layer is too small, that is, the thickness of the ion exchange membrane layer is too large, the ion flux decreases; if the thickness ratio of the electrochemical adsorption layer and the ion exchange membrane layer is too large, that is, the thickness of the ion exchange membrane layer is too small, the lithium ion flux increases and the selectivity decreases.

[0172] From the data results of Example 1 and Example 6-7, it can be seen that if the mass content of the electrode active material is too low, Li + The concentration effect is limited and the selectivity decreases; if the mass content of the electrode active material is too high, the water barrier performance of the material is limited, the ion flux increases, and the selectivity decreases.

[0173] It can be seen from the data results of Example 1 and Examples 8-9 that if the thickness ratio of the composite membrane electrode layer and the two-dimensional material support layer is too small, that is, the thickness of the two-dimensional material support layer is too large, the mass transfer resistance increases and the ion flux decreases; if the thickness ratio of the composite membrane electrode layer and the two-dimensional material support layer is too large, that is, the thickness of the two-dimensional material support layer is too small, the ion transfer resistance decreases, the uniformity of the ion exchange membrane decreases, and the selectivity decreases.

[0174] It can be seen from the data results of Example 1 and Example 10 that if polyethyleneimine is not subjected to quaternization treatment, the ion flux and membrane selectivity will decrease.

[0175] It can be seen from the data results of Example 1 and Example 11 that if no aqueous solution additive is added to the aqueous solution in step (4), the uniformity of the polyamide layer is reduced and the lithium-magnesium separation coefficient decreases.

[0176] From the data results of Examples 1 and 12-13, it can be seen that if the concentration of the aqueous solution additive in step (4) is too low, it will not play a significant role; if the concentration of the aqueous solution additive is too high, it will cover the nanopores on the surface of the polyamide layer and reduce the ion flux.

[0177] From the data results of Example 1 and Comparative Example 1, it can be seen that if the reduced graphene oxide support layer / ion exchange membrane layer is used as the membrane, the high Li+ interface concentration provided by the membrane electrode side is lacking, and the flux and selectivity are reduced compared to the integrated membrane.

[0178] From the data results of Example 1 and Comparative Example 2, it can be seen that if the composite membrane electrode layer only contains a membrane made of reduced graphene oxide, there is no obvious selectivity, and the fluxes of lithium and magnesium are similar.

[0179] From the data results of Example 1 and Comparative Example 3, it can be seen that if the electrochemical adsorption layer does not contain a two-dimensional material support layer, the membrane density decreases, and although the lithium-magnesium flux increases significantly, the lithium-magnesium separation coefficient decreases significantly.

[0180] The applicant declares that while the above-mentioned embodiments are used to illustrate the process of the present application, the present application is not limited to the above-mentioned process steps, which does not mean that the present application must rely on the above-mentioned process steps in order to be implemented. Those skilled in the art should understand that any improvements to the present application, equivalent replacements for the raw materials used in the present application, addition of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present application.

Claims

1. A lithium ion electrically controlled adsorption separation membrane, comprising an electrochemical adsorption layer and an ion exchange membrane layer; The electrochemical adsorption layer comprises a composite membrane electrode layer and a two-dimensional material support layer stacked in sequence, and the two-dimensional material support layer is connected to the ion exchange membrane layer; The composite membrane electrode layer is obtained by compounding an electrode active material and a two-dimensional material.

2. The lithium ion electrically controlled adsorption separation membrane according to claim 1, wherein: The thickness ratio of the electrochemical adsorption layer to the ion exchange membrane layer is (1-10):

1.

3. The lithium ion electrically controlled adsorption separation membrane according to claim 1 or 2, wherein: The electrode active material includes LiMn2O4, LiNi x Co y Mn z Any one of O2, Li2MnO3, MnO2 or LiFePO4, or a combination of at least two thereof.

4. [Corrected 05.02.2024 according to Rule 26] A lithium ion electrically controlled adsorption separation membrane according to any one of claims 1 to 3, wherein: The electrode active material has a multi-level pore structure; Optionally, the particle size D50 of the electrode active material is 50-400 nm.

5. The lithium ion electrically controlled adsorption separation membrane according to any one of claims 1 to 4, wherein: The mass ratio of the electrode active material to the two-dimensional material support layer is (1-10):1; Optionally, the material of the two-dimensional material and the material of the two-dimensional material support layer are independently reduced graphene oxide or MXene.

6. The lithium ion electrically controlled adsorption separation membrane according to any one of claims 1 to 5, wherein: The thickness ratio of the composite membrane electrode layer and the two-dimensional material support layer is (1-5):

1.

7. The lithium ion electrically controlled adsorption separation membrane according to any one of claims 1 to 6, wherein: The ion exchange membrane layer is a polyamide separation layer; Optionally, the average pore size of the ion exchange membrane layer is 0.2-1.5 nm.

8. A method for preparing a lithium ion electrically controlled adsorption separation membrane according to any one of claims 1 to 7, comprising the following steps: (1) coating a two-dimensional material solution on a base film so as to form a two-dimensional material support layer on the base film; (2) coating a two-dimensional material solution containing an electrode active material on the two-dimensional material support layer to obtain an electrochemical adsorption layer having a composite membrane electrode layer; (3) Mixing the aqueous phase monomer material, the oil phase monomer material and the electrochemical adsorption layer to carry out an interfacial polymerization reaction to obtain a lithium ion electrically controlled adsorption separation membrane having an ion exchange membrane layer.

9. The preparation method according to claim 8, wherein: The material of the base film in step (1) is selected from any one of cellulose acetate, polyethersulfone or polyacrylonitrile or a combination of at least two thereof; Optionally, the coating method in step (2) includes vacuum filtration.

10. The preparation method according to claim 8 or 9, wherein: After the coating in step (2) is completed, the composite membrane electrode layer is irradiated by ultraviolet light source.

11. The preparation method according to any one of claims 8 to 10, wherein: The aqueous phase monomer material in step (3) is an amine polymer, which can be an amine polymer containing a quaternary amine group.

12. The preparation method according to any one of claims 8 to 11, wherein: The preparation method of the amine polymer containing quaternary amine groups comprises: The amine polymer and the halogenating agent are mixed in an aqueous solution to carry out a quaternary amination reaction to obtain the amine polymer containing a quaternary amine group; Optionally, the amine polymer includes any one or a combination of at least two of polyethyleneimine, piperazine, m-phenylenediamine, polyallylamine, p-phenylenediamine or hexamethylenediamine; Optionally, the amine polymer containing quaternary amine groups includes quaternized polyethyleneimine and / or quaternized polyallylamine; Optionally, the halogenating agent comprises ethylamine bromide and / or propylamine bromide.

13. The preparation method according to claim 12, wherein: The mass ratio of the halogenating agent to the amine raw material is 1:(8-12); Optionally, the temperature of the quaternization reaction is 60-100°C; Optionally, the quaternization reaction time is 4-24h; Optionally, the oil phase monomer material in step (3) is an acyl chloride compound; Optionally, the acyl chloride compound includes any one of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride or tetraphthaloyl chloride, or a combination of at least two thereof; Optionally, in step (3), the mass ratio of the aqueous phase monomer material to the oil phase monomer material is (8-12):

1.

14. The preparation method according to any one of claims 8 to 13, wherein: The mixing method in step (3) includes: The electrochemical adsorption layer having the composite membrane electrode layer is immersed in the aqueous phase solution containing the aqueous phase monomer material, and after the immersion, the oil phase solution containing the oil phase monomer material is placed on the support layer side of the immersed electrochemical adsorption layer to perform an interfacial polymerization reaction; Optionally, the temperature of the interfacial polymerization reaction in step (3) is 20-25° C.; Optionally, the interfacial polymerization reaction time in step (3) is 1-3 min; Optionally, the aqueous phase solution further contains an aqueous phase solution additive; Optionally, the aqueous solution additive includes an organic additive and / or an inorganic additive; Optionally, the inorganic additive includes LiCl and / or MgCl2; Optionally, the organic additive is an amphoteric organic additive, and the amphoteric organic additive includes any one of nonylphenol polyoxyethylene ether, dodecasodium phytic acid, sodium dodecyl sulfonate or hexadecyltrimethylammonium bromide; Optionally, in the aqueous solution, the mass concentration of the aqueous solution additive is 0.1-1%.

15. Use of the lithium ion electrically controlled adsorption separation membrane according to any one of claims 1 to 7 in the development of low-grade lithium resources.

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