Diffusion dialysis lithium selective composite membrane as well as preparation method and application thereof

Abstract

The invention provides a diffusion dialysis lithium selective composite membrane and a preparation method and application thereof, and the diffusion dialysis lithium selective composite membrane comprises an inorganic solid electrolyte and a positively charged organic polymer attached to the inner surface of the inorganic solid electrolyte, the structure of the solid electrolyte comprises a columnar structure perpendicular to the surface of the diffusion dialysis lithium selective composite membrane; the solid electrolyte is provided with a continuous lithium ion transmission channel perpendicular to the surface of the diffusion dialysis lithium selective composite membrane, and the positively charged organic polymer is provided with a continuous anion transmission channel perpendicular to the surface of the diffusion dialysis lithium selective composite membrane. According to the diffusion dialysis lithium selective composite membrane provided by the invention, high Li < + > selectivity of the inorganic solid electrolyte is combined with good flexibility and anion transmission property of the positively charged organic polymer, and the composite membrane has vertical orientation'dual channels', realizes efficient and low-consumption extraction of high-salt brine lithium resources, and is suitable for large-scale application.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium extraction from salt lake brine, and relates to a diffusion dialysis lithium selective composite membrane and a preparation method and application thereof. Background Art

[0002] Lithium is primarily found in lithium ore, salt lake brine, and seawater. While most terrestrial lithium resources exist in liquid form as ions, the majority of my country's lithium resources are found in salt lake brine. Therefore, developing efficient lithium extraction technologies from salt lake brine is crucial. Among new lithium extraction methods, membrane separation is one of the most promising due to its environmental friendliness and ease of continuous production.

[0003] Membrane separation technologies for lithium extraction mainly include electrically driven selective electrodialysis membranes and pressure driven nanofiltration membranes. The high salinity and high impurity ion content in brine pose a huge challenge to lithium extraction from salt lakes. However, the development of concentration difference driven diffusion dialysis (DD) lithium selective membranes has great development prospects by taking advantage of the high salinity of salt lake brine. The lithium selective membrane for diffusion dialysis needs to achieve the co-transmission of anions and cations. On the one hand, it is necessary to construct Li + Selective transport channels, on the other hand, require the construction of anion transport channels.

[0004] Among lithium selective membranes used for diffusion dialysis, two-dimensional material membranes have demonstrated excellent ion screening capabilities due to their designable nanochannels and adjustable screening properties, but their stability is insufficient and the preparation process is complex; covalent organic framework membranes have long-range ordered structures, and their surfaces are modified with different functional groups, which is conducive to the rapid transport of ions, but the microscale thickness of the membrane inevitably leads to high transport resistance; metal organic framework membranes are widely used in Li due to their sub-nanoscale porous structure and adjustable functional groups. + conduction field, but its stability in aqueous solution is poor and it is easy to collapse the framework; the "confinement effect" of the lattice pores in the inorganic solid electrolyte membrane has a great influence on Li + It exhibits high selectivity and is gradually being developed and applied in the field of lithium resource extraction, but it has problems such as strong brittleness and difficulty in large-scale preparation.

[0005] In order to improve the flexibility of solid electrolytes, they are usually compounded with organic polymers. For example, there is currently a technology that uses a blending method to combine solid electrolytes and organic polymers to prepare a composite solid electrolyte membrane. However, in the membrane prepared by the blending method, due to the wrapping of the polymer on the solid electrolyte, a "cage effect" is formed, which makes some Li + The transmission channel is interrupted, causing Li + The flux becomes lower and the resistance becomes larger; moreover, the current composite solid electrolyte membrane only has lithium ion channels but no anion channels, which also limits its application in extracting lithium from salt lake brine using the diffusion dialysis method.

[0006] Therefore, how to provide a "dual-channel" lithium-selective composite membrane that is not affected by the "cage effect" is a technical problem that needs to be solved urgently. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the present invention aims to provide a diffusion dialysis lithium selective composite membrane and its preparation method and application. The diffusion dialysis lithium selective composite membrane provided by the present invention converts the high Li + By combining selectivity with the good flexibility and anion transport properties of positively charged organic polymers, a diffusion-dialysis lithium-selective composite membrane with vertically oriented "dual channels" was constructed, achieving efficient and low-consumption extraction of lithium resources from high-salt brine; moreover, the preparation method provided by the present invention is simple and suitable for large-scale applications.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a diffusion-dialysis lithium selective composite membrane, which comprises an inorganic solid electrolyte and a positively charged organic polymer attached to the inner surface of the inorganic solid electrolyte, wherein the structure of the solid electrolyte comprises a columnar structure perpendicular to the surface of the diffusion-dialysis lithium selective composite membrane; the solid electrolyte has a continuous lithium ion transmission channel perpendicular to the surface of the diffusion-dialysis lithium selective composite membrane, and the positively charged organic polymer has a continuous anion transmission channel perpendicular to the surface of the diffusion-dialysis lithium selective composite membrane.

[0010] In the present invention, the surface of the diffusion-dialysis lithium selective composite membrane refers to the active surface of the membrane, that is, the surface perpendicular to the thickness direction of the membrane. The inorganic solid electrolyte has a columnar structure perpendicular to the surface of the diffusion-dialysis lithium selective composite membrane. The "confinement effect" of its lattice pores makes it highly selective for lithium ions. Therefore, this inorganic solid electrolyte with a specific structure can provide a vertically oriented continuous lithium ion transmission channel; the positively charged organic polymer can enhance the flexibility and mechanical properties of the membrane on the one hand. On the other hand, because the positively charged organic polymer contains positively charged groups, it has material ion exchange capacity and adsorption capacity for negatively charged substances. And because it is attached to the internal surface of the solid electrolyte with a vertical columnar structure, the anion channel it provides is also vertically oriented and continuous. The lithium ion transmission channel and the anion transmission channel cooperate with each other, enabling the lithium selective composite membrane to achieve efficient and low-consumption extraction of lithium resources in a high-salinity system in the diffusion-dialysis driven by salinity difference energy.

[0011] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0012] Preferably, the configuration of the inorganic solid electrolyte includes any one of perovskite type, NASICON type or garnet type, or a combination of at least two of them.

[0013] It is understood that NASICON type refers to a crystal configuration having a sodium superion conductor structure. The present invention does not limit the specific types of perovskite type, NASICON type or garnet type. For example, perovskite type such as Li 3x La 2 / 3-x TiO3, NASICON type such as Li 1.3 Al 0.3 Ti 1.7 (PO4)3、Li 1+x Al y Ge 2-y (PO4)3 or Li 1+x+y Al x Ti 2- x Si y P 3-y O 12 , garnet type such as Li7La3Zr2O 12 or Li 6.4 La3Zr 1.6 Ta 0.6 O 12 .

[0014] Preferably, the positively charged organic polymer includes fluororesin and quaternized high molecular polymer.

[0015] In the present invention, the fluororesin can enhance the flexibility and mechanical properties of the membrane, and the quaternized polymer chain can provide anion channels.

[0016] Preferably, based on the mass of the diffusion dialysis lithium selective composite membrane as 100wt%, the mass proportion of the solid electrolyte is 85wt% to 95wt%, for example, 85wt%, 86wt%, 87wt%, 88wt%, 89wt%, 90wt%, 91wt%, 92wt%, 93wt%, 94wt% or 95wt%, etc., and the mass proportion of the positively charged organic polymer is 5wt% to 15wt%, for example, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0017] In the present invention, the content of solid electrolyte and positively charged organic polymer in the diffusion dialysis lithium selective composite membrane will affect the performance of the composite membrane. By controlling its content and mass ratio within the above-mentioned preferred range, the flux of lithium ions and anions in the membrane can be within a more appropriate range, which is more conducive to improving the efficiency of lithium extraction from the composite membrane. If the proportion of positively charged organic polymer in the membrane is too high, the corresponding proportion of solid electrolyte will be low, and it will not be able to provide sufficient lithium ion channels, resulting in a low lithium flux; if the proportion of positively charged organic polymer in the membrane is too low, it will not be able to provide sufficient anion channels, which is not conducive to the diffusion dialysis process.

[0018] Preferably, the mass ratio of the fluororesin to the quaternized high molecular weight polymer is (50-90):(10-50), for example, 50:50, 60:40, 70:30, 80:20 or 90:10, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0019] Preferably, the thickness of the diffusion dialysis lithium selective composite membrane is 300um to 500um, for example, 300um, 350um, 400um, 450um or 500um, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0020] In the present invention, by controlling the parameters of the diffusion dialysis lithium selective composite membrane within the above range, it is more conducive to the transmission of lithium ions and anions in the composite membrane, ensuring that the ion diffusion proceeds rapidly.

[0021] In a second aspect, the present invention provides a method for preparing the diffusion dialysis lithium selective composite membrane as described in the first aspect, the preparation method comprising:

[0022] (1) mixing an inorganic solid electrolyte and a water-soluble polymer to obtain a first casting solution, applying a scraping film on a first substrate, sequentially performing directional freezing and drying, and calcining after film removal to obtain an inorganic solid electrolyte membrane;

[0023] (2) mixing a fluororesin, a halogenated methyl polymer, and an organic solvent, and then reacting the mixture with a cross-linking agent to form a quaternary ammonium reaction to obtain a second casting solution, and applying a scraping film on a second substrate to obtain a positively charged organic polymer liquid film;

[0024] (3) Compounding the positively charged organic polymer liquid membrane of step (2) and the inorganic solid electrolyte membrane of step (1), and drying them to obtain the diffusion dialysis lithium selective composite membrane.

[0025] In the present invention, an ice template method is first used to prepare a solid electrolyte membrane, which can enable the solid electrolyte to grow along a specific vertical structure. Then, a positively charged organic polymer liquid membrane is prepared. Finally, the positively charged organic polymer liquid is uniformly distributed in the pores of the solid electrolyte membrane through diffusion and adheres to the internal surface of the solid electrolyte after drying. In the present invention, since the solid electrolyte is not prepared by mixing with the fluororesin, the halogenated methyl polymer, the cross-linking agent and the organic solvent, the mutual interference between the lithium transmission channel of the solid electrolyte and the anion channel of the quaternized polymer can be reduced as much as possible, thereby improving the lithium extraction efficiency.

[0026] Preferably, based on the mass of the first casting solution in step (1) being 100 wt%, the mass of the solid electrolyte accounts for 40 wt% to 55 wt%, for example, 40 wt%, 42 wt%, 45 wt%, 48 wt%, 50 wt%, 53 wt% or 55 wt%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0027] Preferably, the water-soluble polymer in step (1) includes any one or a combination of at least two of poly(N-vinyl pyrrolidone) (PVP), poly(N-acryloylmorpholine) (PACMO), polyethylene glycol (PEG) or polyvinyl alcohol (PVA).

[0028] Preferably, the mixing method in step (1) includes ultrasonication first and then stirring.

[0029] Preferably, in step (1), the first substrate comprises an acrylic plate.

[0030] Preferably, the drying in step (1) comprises freeze-drying.

[0031] Preferably, the freeze-drying time is 10 h to 13 h, for example, 10 h, 10.5 h, 11 h, 11.5 h, 12 h, 12.5 h or 13 h, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0032] Preferably, the calcination temperature in step (1) is 700°C to 900°C, for example, 700°C, 730°C, 750°C, 780°C, 800°C, 820°C, 850°C, 880°C or 900°C, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0033] In the present invention, by controlling the calcination temperature within the above-mentioned preferred range, on the one hand, it is possible to ensure that the water-soluble polymer in the casting solution is completely removed; on the other hand, the prepared solid electrolyte can have a smaller grain boundary resistance, which is more conducive to the transmission of lithium ions in the solid electrolyte lattice.

[0034] Preferably, the calcination time in step (1) is 1 h to 3 h, such as 1 h, 1.5 h, 2 h, 2.5 h or 3 h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0035] Preferably, the calcination atmosphere in step (1) includes an air atmosphere.

[0036] Preferably, the fluororesin in step (2) includes any one of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF) or ethylene-tetrafluoroethylene copolymer (ETFE) or a combination of at least two thereof.

[0037] Preferably, the halogenated methyl polymer in step (2) comprises any one or a combination of at least two of para-chloromethylstyrene (MSDS), polyvinylbenzyl chloride (PVBC), 1,4-dichloromethoxybutane (BCMB) or polyepichlorohydrin (PECH).

[0038] Preferably, the organic solvent in step (2) comprises any one or a combination of at least two of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAC) or N,N-dimethylformamide (DMF).

[0039] Preferably, the cross-linking agent in step (2) includes a tertiary amine cross-linking agent.

[0040] Preferably, the cross-linking agent in step (2) includes any one of trimethylamine (TMA), diethylamine (DEA), diethylenetriamine (DETA) or triethylenediamine (DABCO), or a combination of at least two thereof.

[0041] Preferably, the cross-linking agent in step (2) is dissolved in an organic solvent before use.

[0042] Preferably, the mixing in step (2) includes stirring.

[0043] Preferably, the total concentration of the halogenated methyl polymer and the cross-linking agent in the second casting solution in step (2) is 30 g / L to 50 g / L, for example, 30 g / L, 35 g / L, 40 g / L, 45 g / L or 50 g / L, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0044] Preferably, the mass ratio of the halogenated methyl polymer to the cross-linking agent in step (2) is (1-2):1, for example, 1:1, 1.2:1, 1.5:1, 1.8:1 or 2:1, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0045] In the present invention, by controlling the mass proportion of the solid electrolyte in the first casting solution, or controlling the total concentration of the halomethyl polymer and the cross-linking agent in the second casting solution and the mass ratio between the two, the content of the final solid electrolyte or quaternized high molecular polymer in the composite membrane can be controlled. In practical applications, the appropriate content can be selected as needed.

[0046] Preferably, the temperature of the mixing and the quaternization reaction in step (2) is 50°C to 90°C, for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, etc., but is not limited to the listed values, and other values not listed within this numerical range are also applicable.

[0047] Preferably, in step (2), the second substrate comprises a glass plate and a nylon mesh placed on the glass plate.

[0048] Preferably, the composite in step (3) comprises: placing the inorganic solid electrolyte membrane in step (1) on the positively charged organic polymer liquid membrane in step (2) to perform intra-membrane diffusion.

[0049] In the present invention, the volume of the positively charged organic polymer liquid film is excessive relative to the maximum adsorption capacity that the solid electrolyte membrane can bear. During the composite process, when the inorganic solid electrolyte membrane fully adsorbs the positively charged organic polymer liquid, it reaches a saturated state and cannot continue to adsorb. Therefore, the present invention can control the content of the final quaternized high molecular polymer in the composite membrane by controlling the total concentration of the halomethyl polymer and the cross-linking agent in the second casting solution and the mass ratio between the two.

[0050] Preferably, the drying method in step (3) includes vacuum drying.

[0051] Preferably, the vacuum drying temperature is 60°C to 90°C, for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0052] In the present invention, during the vacuum drying process, some unreacted organic polymers will continue to undergo cross-linking reaction. By controlling the vacuum drying temperature within the above preferred range, the cross-linking reaction is more conducive to proceeding.

[0053] Preferably, the vacuum drying time is 10 h to 13 h, for example, 10 h, 10.5 h, 11 h, 11.5 h, 12 h, 12.5 h or 13 h, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0054] In a third aspect, the present invention also provides an application of a diffusion dialysis lithium selective composite membrane, which includes extracting lithium from salt lake brine using diffusion dialysis, and the diffusion dialysis lithium selective composite membrane includes the diffusion dialysis lithium selective composite membrane as described in the first aspect or the diffusion dialysis lithium selective composite membrane prepared by the preparation method described in the second aspect.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] The diffusion dialysis lithium selective composite membrane provided by the present invention can convert the high Li + By combining selectivity with the good flexibility and anion transport properties of positively charged organic polymers, a vertically oriented "dual-channel" lithium-selective composite membrane was constructed, which is very suitable for extracting lithium from high-salt brine using diffusion dialysis. In addition, the preparation method provided by the present invention is simple and suitable for large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a SEM surface image of the diffusion dialysis lithium selective composite membrane provided in Example 1.

[0058] Figure 2 This is a SEM surface image of the diffusion dialysis lithium selective composite membrane provided in Example 1.

[0059] Figure 3 This is a SEM cross-sectional view of the diffusion dialysis lithium selective composite membrane provided in Example 1.

[0060] Figure 4 This is a SEM cross-sectional view of the diffusion dialysis lithium selective composite membrane provided in Example 1.

[0061] Figure 5 1 and 2 are XRD diagrams of the diffusion dialysis lithium selective composite membranes provided in Examples 1 and 4.

[0062] Figure 6 1 is a photograph of the inorganic solid electrolyte membrane and the diffusion dialysis lithium selective composite membrane prepared in Example 1.

[0063] Figure 7 This is a schematic diagram of the preparation process of the diffusion dialysis lithium selective composite membrane provided in Example 1.

[0064] Figure 8 This is a schematic diagram of the structure of the DD test device used in Application Example 1.1.

[0065] Figure 9 This is the performance test diagram of Application Examples 1.1 to 1.4.

[0066] Figure 8Middle: 1-raw material chamber; 2-lithium selective composite membrane; 3-recovery chamber; 4-DD test cell. DETAILED DESCRIPTION

[0067] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0069] Example 1

[0070] This embodiment provides a diffusion dialysis lithium selective composite membrane, comprising an inorganic solid electrolyte and a positively charged organic polymer attached to the inner surface of the inorganic solid electrolyte, wherein the inorganic solid electrolyte has a vertical columnar structure, the positively charged organic polymer comprises a fluororesin and a quaternized high molecular polymer, the inorganic solid electrolyte has a vertically oriented continuous lithium ion transmission channel, the positively charged organic polymer has a vertically oriented continuous anion transmission channel, the inorganic solid electrolyte accounts for 90wt% of the composite membrane by weight, and the positively charged organic polymer accounts for 10wt% of the composite membrane by weight. The preparation method is as follows: Figure 7 The specific process is as follows:

[0071] (1) Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP) and PVA aqueous solution were mixed in a mass ratio of 1:1, PEG and anhydrous ethanol were introduced and stirred evenly, ultrasonicated for 20 minutes, stirred at 80℃ for 1.5 hours to obtain the first casting solution, which was then scraped onto an acrylic plate, directionally frozen with liquid nitrogen, freeze-dried for 12 hours, and after demolding, calcined at 800℃ in a muffle furnace for 2 hours to obtain an inorganic solid electrolyte membrane.

[0072] (2) PECH and PVDF were dissolved in DMAC and stirred on a turntable at 80°C for 3 h. DABCO was then dissolved in DMAC and added to the above solution for quaternization reaction to obtain a second casting solution. A nylon mesh was placed on a glass plate and a doctor blade was applied to obtain a positively charged organic polymer liquid film. The total concentration of PECH and DABCO in the second casting solution was 40 g / L.

[0073] (3) The inorganic solid electrolyte membrane is placed on the positively charged organic polymer liquid membrane for intramembrane diffusion, and then placed in a vacuum oven at 70°C for drying for 12 hours to obtain a diffusion dialysis lithium selective composite membrane.

[0074] Example 2

[0075] This embodiment provides a diffusion-dialysis lithium-selective composite membrane, comprising an inorganic solid electrolyte and a positively charged organic polymer attached to the inner surface of the inorganic solid electrolyte. The inorganic solid electrolyte has a vertical columnar structure, and the positively charged organic polymer comprises a fluororesin and a quaternized high molecular polymer. The inorganic solid electrolyte has vertically oriented continuous lithium ion transport channels, and the positively charged organic polymer has vertically oriented continuous anion transport channels. The inorganic solid electrolyte accounts for 85% by weight of the composite membrane, and the positively charged organic polymer accounts for 15% by weight of the composite membrane. The preparation process is as follows:

[0076] (1) Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP) and PVA aqueous solution were mixed at a mass ratio of 1:1.5, PEG and anhydrous ethanol were introduced and stirred evenly, ultrasonicated for 20 minutes, stirred at 80°C for 1.5 hours to obtain the first casting solution, which was then scraped onto an acrylic plate, directionally frozen with liquid nitrogen, freeze-dried for 10 hours, and after demolding, calcined at 700°C in a muffle furnace for 3 hours to obtain an inorganic solid electrolyte membrane.

[0077] (2) BCMB and PTFE were dissolved in DMF and stirred on a turntable at 50°C for 3 h. TMA was then dissolved in DMF and added to the above solution for quaternization reaction to obtain a second casting solution. A nylon mesh was placed on a glass plate and a doctor blade was applied to obtain a positively charged organic polymer liquid film. The total concentration of BCMB and TMA in the second casting solution was 50 g / L.

[0078] (3) The inorganic solid electrolyte membrane is placed on the positively charged organic polymer liquid membrane for intramembrane diffusion, and then placed in a vacuum oven at 60°C for drying for 13 hours to obtain a diffusion dialysis lithium selective composite membrane.

[0079] Example 3

[0080] This embodiment provides a diffusion-dialysis lithium-selective composite membrane, comprising an inorganic solid electrolyte and a positively charged organic polymer attached to the inner surface of the inorganic solid electrolyte. The inorganic solid electrolyte has a vertical columnar structure, and the positively charged organic polymer comprises a fluororesin and a quaternized high molecular polymer. The inorganic solid electrolyte has vertically oriented continuous lithium ion transport channels, and the positively charged organic polymer has vertically oriented continuous anion transport channels. The inorganic solid electrolyte accounts for 95% by weight of the composite membrane, and the positively charged organic polymer accounts for 5% by weight of the composite membrane. The preparation process is as follows:

[0081] (1) Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP) and PVA aqueous solution were mixed at a mass ratio of 1:0.82, PEG and anhydrous ethanol were introduced and stirred evenly, ultrasonicated for 20 minutes, stirred at 80°C for 1.5 hours to obtain the first casting solution, which was then scraped onto an acrylic plate, directionally frozen with liquid nitrogen, freeze-dried for 13 hours, and after demolding, calcined at 900°C in a muffle furnace for 1 hour to obtain an inorganic solid electrolyte membrane.

[0082] (2) PVBC and PTFE were dissolved in NMP and stirred on a turntable at 90°C for 3 h. DEA was then dissolved in NMP and added to the above solution for quaternization reaction to obtain a second casting solution. A nylon mesh was placed on a glass plate and a doctor blade was applied to obtain a positively charged organic polymer liquid film. The total concentration of PVBC and DEA in the second casting solution was 30 g / L.

[0083] (3) The inorganic solid electrolyte membrane is placed on the positively charged organic polymer liquid membrane for intramembrane diffusion, and then placed in a vacuum oven at 90°C for drying for 10 hours to obtain a diffusion dialysis lithium selective composite membrane.

[0084] Example 4

[0085] The difference between this embodiment and embodiment 1 is that, in this embodiment, the mass proportion of the inorganic solid electrolyte in the composite membrane is 75 wt%, and the mass proportion of the positively charged organic polymer in the composite membrane is 25 wt%; in step (1), the LATP and PVA aqueous solutions are mixed at a mass ratio of 1:1.86;

[0086] The rest of the preparation methods and parameters were the same as those in Example 1.

[0087] Example 5

[0088] The difference between this embodiment and embodiment 1 is that, in this embodiment, the mass proportion of the inorganic solid electrolyte in the composite membrane is 97 wt%, and the mass proportion of the positively charged organic polymer in the composite membrane is 3 wt%; in step (1), LATP and PVA aqueous solution are mixed in a mass ratio of 1:0.65;

[0089] The rest of the preparation methods and parameters were the same as those in Example 1.

[0090] Example 6

[0091] The difference between this embodiment and embodiment 1 is that, in this embodiment, the mass proportion of the inorganic solid electrolyte in the composite membrane is 96 wt%, and the mass proportion of the positively charged organic polymer in the composite membrane is 4 wt%; in step (2), the total concentration of PECH and DABCO in the casting solution is 20 g / L;

[0092] The rest of the preparation methods and parameters were the same as those in Example 1.

[0093] Example 7

[0094] The difference between this embodiment and embodiment 1 is that, in this embodiment, the temperature of vacuum drying in step (3) is 100°C;

[0095] The rest of the preparation methods and parameters were the same as those in Example 1.

[0096] Comparative Example 1

[0097] This comparative example provides a diffusion dialysis lithium selective composite membrane, and the preparation process is as follows:

[0098] PECH and PVDF were dissolved in DMAC and stirred on a turntable at 80°C for 3 hours. 90 wt% LATP was then added and ultrasonically stirred for 1 hour. DABCO was then dissolved in DMSO and added to the above solution for quaternization to obtain a membrane casting solution. A nylon mesh was placed on a glass plate and a doctor blade was applied. The solution was then dried in a vacuum oven at 70°C for 12 hours to obtain a diffusion dialysis lithium-selective composite membrane.

[0099] Comparative Example 2

[0100] This comparative example provides a diffusion dialysis lithium selective composite membrane. The preparation process is different from that of Example 1 in that, after the film is scraped on the acrylic plate in step (1), no liquid nitrogen directional freezing is performed, and the membrane is directly freeze-dried for 12 hours. After the membrane is removed, the membrane is calcined at 800° C. for 2 hours in a muffle furnace to obtain an inorganic solid electrolyte membrane.

[0101] The rest of the preparation methods and parameters were the same as those in Example 1.

[0102] Application Example 1.1

[0103] like Figure 8 As shown, the diffusion dialysis lithium-selective composite membrane 2 prepared in Example 1 was installed in the middle of a DD test tank 4. A 0.05 mol / L mixture of LiCl and NaCl was placed in feed chamber 1 as the feed solution, and a 0.05 mol / L KCl recovery solution was placed in recovery chamber 3. The experiment was conducted using a concentration gradient as the driving force, and the diffusion dialysis experiment was conducted for 1.5 hours.

[0104] Application Example 1.2

[0105] The difference between this application example and application example 1.1 is that in this application example, a mixture of 0.05 mol / L LiCl and 0.25 mol / L NaCl is used as the raw material liquid;

[0106] The rest of the application methods and parameters are consistent with those in Application Example 1.1.

[0107] Application Example 1.3

[0108] The difference between this application example and application example 1.1 is that in this application example, a mixture of 0.05 mol / L LiCl and 0.5 mol / L NaCl is used as the raw material liquid;

[0109] The rest of the application methods and parameters are consistent with those in Application Example 1.1.

[0110] Application Example 1.4

[0111] The difference between this application example and application example 1.1 is that in this application example, a mixture of 0.05 mol / L LiCl and 1 mol / L NaCl is used as the raw material liquid;

[0112] The rest of the application methods and parameters are consistent with those in Application Example 1.1.

[0113] Application Example 2-7

[0114] The difference between this application example and application example 1.1 is that in this application example, the diffusion dialysis lithium selective composite membranes prepared in Examples 2-7 are installed in the middle positions of the DD test tanks respectively;

[0115] The rest of the application methods and parameters are consistent with those in Application Example 1.1.

[0116] Comparative Application Examples 1-2

[0117] The difference between Comparative Application Example 1-2 and Application Example 1.1 is that in this application example, the diffusion dialysis lithium selective composite membranes prepared in Comparative Examples 1-2 are installed in the middle positions of the DD test tanks respectively;

[0118] The rest of the application methods and parameters are consistent with those in Application Example 1.1.

[0119] Structural characterization

[0120] The diffusion dialysis lithium selective composite membrane prepared in Example 1 was subjected to SEM test, and the diffusion dialysis lithium selective composite membranes prepared in Example 1 and Example 4 were subjected to XRD test. The test results are as follows: Figure 1-Figure 5 shown.

[0121] Performance Testing

[0122] The ion content in the recovered liquid in Example 1-7 and Comparative Example 1-2 was detected by TAS-990 atomic absorption spectrophotometer. The test results are shown in Table 1.

[0123] Table 1

[0124]

[0125] Figure 1 and Figure 2 This is a surface diagram of a diffusion-dialysis lithium selective composite membrane. As can be seen from the figure, the surface of the lithium selective composite membrane prepared by the present invention is uniform; Figure 3 and Figure 4 This is a cross-sectional view of a diffusion-dialysis lithium selective composite membrane. As can be seen from the figure, the interior of the diffusion-dialysis lithium selective composite membrane prepared by the present invention has a vertically distributed columnar structure. This structure provides continuous and directional lithium ion channels and anion channels, making it more suitable for extracting lithium from high-salinity brine by using concentration diffusion. At the same time, the bridge structure in the vertical channels of the solid electrolyte is evenly loaded with polymer, which can effectively inhibit the leakage of impurity ions. Figure 5 It can be seen that the preparation method provided by the present invention does not change the crystal structure of the inorganic solid electrolyte in the lithium selective composite membrane. Figure 6 (a) and Figure 6 (b) are photos of the inorganic solid electrolyte membrane and the diffusion-dialysis lithium selective composite membrane, respectively. It can be seen from the figure that the inorganic solid electrolyte membrane and the diffusion-dialysis lithium selective composite membrane prepared by the present invention have smooth surfaces.

[0126] From the application example 1.1 and the comparative application examples 1 and 2 in Table 1, it can be seen that in the comparative application example 1, the selectivity for Li / Na is 21.71, in the comparative application example 2, the selectivity for Li / Na is 59.12, and in the application example 1.1, the selectivity for Li / Na is as high as 220.75, and the Li selectivity is greatly increased. It can be seen that the diffusion dialysis lithium selective composite membrane prepared by the present invention has a vertically oriented inorganic solid electrolyte "lattice confinement" effect and anion channel charge balance, which shortens the transmission path, reduces the transmission resistance, and significantly improves the composite membrane material to Li +The selectivity of the process has shown significant advantages in achieving efficient and low-consumption extraction of lithium resources in low-grade and complex solution systems.

[0127] From the data comparison of Application Example 1.1 and Application Examples 4-6 in Table 1, it can be seen that by changing the content of the solid electrolyte in the first casting solution, or changing the content of the halogenated methyl polymer and the cross-linking agent in the second casting solution, the mass ratio of the solid electrolyte and the positively charged organic polymer in the final diffusion dialysis lithium selective composite membrane can be adjusted. Within a certain range, as the mass ratio of the inorganic solid electrolyte in the composite membrane increases, the Li + The flux and separation coefficient also increase. This is because the content of inorganic solid electrolyte material increases, the pore size of the membrane surface decreases, the pores in the membrane decrease, and the inorganic solid electrolyte Li + The continuous transmission channels increase, making Li + The flux of Na + The flux is at a low level, and the separation coefficient also shows an upward trend; if the mass proportion of the inorganic solid electrolyte in the composite membrane is too high, or the mass proportion of the positively charged organic polymer in the composite membrane is too low, the separation coefficient will decrease. This is because this situation is not conducive to the formation of a continuous anion transport channel, resulting in a decrease in lithium extraction performance.

[0128] From the comparison of the data of Application Example 1.1 and Application Example 7 in Table 1, it can be seen that by controlling the temperature of vacuum drying within the preferred range of the present invention, it is more conducive to improving the separation effect of the composite membrane.

[0129] Depend on Figure 9 As can be seen from the data comparison of application examples 1.1 to 1.4 in Table 1, the Li + The flux and separation coefficient not only increase with increasing inorganic solid electrolyte content, but also show significant improvements in high-salinity systems compared to low-salinity systems. This is because, with the concentration gradient as the driving force, the higher the sodium-to-lithium ratio, the greater the driving force. The synergistic effect of the dual channels enables the diffusion-dialysis lithium-selective composite membrane to highlight the significant advantages of lithium resource enrichment in high-salinity systems.

[0130] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A diffusion dialysis lithium selective composite membrane, characterized in that: The diffusion-dialysis lithium selective composite membrane comprises an inorganic solid electrolyte and a positively charged organic polymer attached to the inner surface of the inorganic solid electrolyte, wherein the structure of the solid electrolyte comprises a columnar structure perpendicular to the surface of the diffusion-dialysis lithium selective composite membrane; The solid electrolyte has a continuous lithium ion transmission channel perpendicular to the surface of the diffusion-dialysis lithium selective composite membrane, and the positively charged organic polymer has a continuous anion transmission channel perpendicular to the surface of the diffusion-dialysis lithium selective composite membrane.

2. The diffusion dialysis lithium selective composite membrane according to claim 1, characterized in that The configuration of the inorganic solid electrolyte includes any one of perovskite type, NASICON type or garnet type or a combination of at least two; Preferably, the positively charged organic polymer includes fluororesin and quaternized high molecular polymer.

3. The diffusion dialysis lithium selective composite membrane according to claim 2, characterized in that Based on the mass of the diffusion dialysis lithium selective composite membrane being 100 wt%, the mass of the solid electrolyte accounts for 85 wt% to 95 wt%, and the mass of the positively charged organic polymer accounts for 5 wt% to 15 wt%; Preferably, the mass ratio of the fluororesin to the quaternized high molecular weight polymer is (50-90):(10-50).

4. The diffusion dialysis lithium selective composite membrane according to any one of claims 1 to 3, characterized in that: The thickness of the diffusion dialysis lithium selective composite membrane is 300um to 500um.

5. A method for preparing a diffusion dialysis lithium selective composite membrane according to any one of claims 1 to 4, characterized in that: The preparation method comprises: (1) mixing an inorganic solid electrolyte and a water-soluble polymer to obtain a first casting solution, applying a scraping film on a first substrate, sequentially performing directional freezing and drying, and calcining after film removal to obtain an inorganic solid electrolyte membrane; (2) mixing a fluororesin, a halogenated methyl polymer, and an organic solvent, and then reacting the mixture with a cross-linking agent to form a quaternary ammonium reaction to obtain a second casting solution, and applying a scraping film on a second substrate to obtain a positively charged organic polymer liquid film; (3) Compounding the positively charged organic polymer liquid membrane of step (2) and the inorganic solid electrolyte membrane of step (1), and drying them to obtain the diffusion dialysis lithium selective composite membrane.

6. The method for preparing a diffusion dialysis lithium selective composite membrane according to claim 5, characterized in that: Based on the mass of the first casting solution in step (1) being 100 wt%, the mass of the solid electrolyte accounts for 40 wt% to 55 wt%; Preferably, the water-soluble polymer in step (1) comprises any one or a combination of at least two of poly (N-vinyl pyrrolidone), poly (N-acryloylmorpholine), polyethylene glycol or polyvinyl alcohol; Preferably, the mixing method in step (1) comprises ultrasonication first and then stirring; Preferably, in step (1), the first substrate comprises an acrylic plate; Preferably, the drying in step (1) comprises freeze drying; Preferably, the freeze-drying time is 10h to 13h; Preferably, the calcination temperature in step (1) is 700° C. to 900° C.; Preferably, the calcination time in step (1) is 1 h to 3 h; Preferably, the calcination atmosphere in step (1) includes an air atmosphere.

7. The method for preparing a diffusion dialysis lithium selective composite membrane according to claim 5 or 6, characterized in that: The fluororesin in step (2) includes any one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride or ethylene-tetrafluoroethylene copolymer, or a combination of at least two thereof; Preferably, the halogenated methyl polymer in step (2) comprises any one or a combination of at least two of p-chloromethylstyrene, polyvinylbenzyl chloride, 1,4-dichloromethoxybutane or polyepichlorohydrin; Preferably, the organic solvent in step (2) comprises any one or a combination of at least two of N-methylpyrrolidone, dimethyl sulfoxide, dimethylacetamide or N,N-dimethylformamide; Preferably, the cross-linking agent in step (2) comprises a tertiary amine cross-linking agent; Preferably, the cross-linking agent in step (2) comprises any one of trimethylamine, diethylamine, diethylenetriamine or triethylenediamine, or a combination of at least two thereof; Preferably, the cross-linking agent in step (2) is dissolved in an organic solvent before use.

8. The method for preparing a diffusion dialysis lithium selective composite membrane according to any one of claims 5 to 7, characterized in that: The mixing in step (2) includes stirring; Preferably, the total concentration of the halogenated methyl polymer and the cross-linking agent in the second casting solution in step (2) is 30 g / L to 50 g / L; Preferably, the mass ratio of the halogenated methyl polymer to the cross-linking agent in step (2) is (1-2):1; Preferably, the temperature of the mixing and the quaternization reaction in step (2) is 50° C. to 90° C.; Preferably, in step (2), the second substrate comprises a glass plate and a nylon mesh placed on the glass plate.

9. The method for preparing a diffusion dialysis lithium selective composite membrane according to any one of claims 5 to 8, characterized in that: The composite of step (3) comprises: placing the inorganic solid electrolyte membrane of step (1) on the positively charged organic polymer liquid membrane of step (2) to perform intra-membrane diffusion; Preferably, the drying method in step (3) includes vacuum drying; Preferably, the vacuum drying temperature is 60°C to 90°C; Preferably, the vacuum drying time is 10 hours to 13 hours.

10. An application of a diffusion dialysis lithium selective composite membrane, characterized in that: The application includes extracting lithium from salt lake brine by diffusion dialysis, and the diffusion dialysis lithium selective composite membrane includes the diffusion dialysis lithium selective composite membrane according to any one of claims 1 to 4 or the diffusion dialysis lithium selective composite membrane prepared by the preparation method according to any one of claims 5 to 9.

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