A photothermal driven ion separation device, its fabrication method and application

Abstract

This invention discloses a photothermal-driven ion separation device, comprising a porous substrate, a photothermal layer, and an ion separation membrane. The photothermal layer is disposed on a first surface of the porous substrate, and the ion separation membrane is disposed on a second surface of the porous substrate. The internal pore structure of the porous substrate connects the first and second surfaces. In use, the ion separation membrane comes into contact with a solution containing ions to be separated. Through the internal pore structure of the porous substrate, capillary forces drive water and permeable ions in the solution through the ion separation membrane and into the pore structure within the porous substrate. Water evaporates upon contact with the photothermal layer, while the remaining ions are deposited in the porous structure. This invention is effectively used to separate ions with different charge states in a solution, utilizing the photothermal effect for driving the process without external power, exhibiting high energy efficiency and environmental performance. Furthermore, it can simultaneously separate lithium ions and various other ions in a salt lake solution in one step, achieving selective recovery of lithium ions.

Description

Technical Field

[0001] This invention relates to membrane technology, and more particularly to a photothermal driven ion separation device, its preparation method, and its application. Background Technology

[0002] Lithium (Li), as an important non-renewable resource, is facing an increasingly serious supply shortage. According to statistics, approximately 70% of the world's extractable lithium is found in salt lake brines; however, these brines typically contain high levels of magnesium ions, making lithium extraction difficult. Although China's salt lake reserves account for 80% of the world's available lithium reserves, traditional lithium extraction methods are ineffective in practice due to the high magnesium / lithium ratio. Currently, only a few salt lake resources with low magnesium / lithium ratios have been developed and utilized.

[0003] To address the lithium shortage, researchers are increasingly focusing on technologies for extracting lithium from brines with high magnesium / lithium ratios. Several methods have been developed for lithium extraction, including tributyl phosphate / FeCl3 extraction, sodium metasilicate nonahydrate precipitation, and lithium ion sieving. While these methods effectively reduce the magnesium / lithium ratio in brine, practical applications still face challenges such as lithium resource loss, wastewater treatment, and environmental impact. Furthermore, electrochemical recovery technology shows good selectivity and recovery rates in high-concentration magnesium / lithium mixtures, but its large-scale application is limited by high equipment costs, complex operation, and relatively low recovery stability. Membrane separation technology is considered an effective solution for extracting lithium from high magnesium / lithium ratio brines. Nanofiltration membranes, combining size sieving and charge repulsion principles, hold promise as a replacement for traditional methods. However, while existing nanofiltration technologies can effectively separate magnesium and lithium ions, they cannot effectively separate sodium and potassium ions, which have similar hydration radii and charge properties. This necessitates additional post-processing steps to purify the collected lithium product. Furthermore, high-concentration brine poses a challenge to membrane separation technology because its high osmotic pressure differential requires applying pressure exceeding the membrane's capacity. Therefore, traditional treatment processes often require diluting the high-concentration brine, and this pretreatment increases operational complexity. Simultaneously, the lithium-rich solution obtained after nanofiltration membrane separation still needs further concentration through energy-intensive processes to achieve effective lithium resource utilization. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a photothermal driven ion separation device that uses only sustainable energy to obtain high-purity lithium from salt lake brine, simultaneously separates all interfering impurity ions in one step, is environmentally friendly, and reduces energy consumption and operating costs; another purpose of this invention is to provide a method for preparing and applying this photothermal driven ion separation device.

[0005] Technical Solution: The photothermal driven ion separation device of the present invention includes a porous substrate, a photothermal layer, and an ion separation membrane; the photothermal layer is disposed on a first surface of the porous substrate; the ion separation membrane is disposed on a second surface of the porous substrate; the internal pore structure of the porous substrate connects the first surface and the second surface. The photothermal layer can absorb light energy and generate heat energy; the ion separation membrane has the function of selectively permeating different ions in the solution.

[0006] The relative positions of the first surface and the second surface are not limited, but preferably the first surface is on top and the second surface is on the bottom.

[0007] When the inner wall of the pore structure is itself a hydrophilic material, the pore structure functions as a water transport channel. When the hydrophilicity of the inner wall of the pore structure is insufficient, a hydrophilic material is filled inside the pore structure, and the pore structure filled with hydrophilic material then functions as a water transport channel. The water transport channel uses capillary forces to drive water and permeable ions in the solution through the ion separation membrane and into the pore structure of the porous matrix. During use, the water evaporates under the heating effect of the photothermal layer, and the remaining ions are deposited within the pore structure of the porous matrix.

[0008] The hole structure can be designed in the following two ways:

[0009] Method 1: The porous matrix itself is a water-absorbing material, or the inner wall of the pore structure is made of a hydrophilic material. The size of the pore structure is micropore or nanopore. Water can be transported to the lower surface within the pore structure through capillary action.

[0010] Method 2: Fill the porous structure of the porous matrix with a hydrophilic material. The material has micropores or nanoscale water transport channels. The capillary force is the main driving force for water transport. Under this action, water passes through the ion separation membrane to reach the photothermal layer and evaporates in the photothermal layer. The ions that pass through the membrane are deposited in the water transport channels.

[0011] Preferably, the photothermal layer is a polymer light-absorbing material.

[0012] Preferably, the photothermal layer is a polypyrrole, a light-absorbing gel, or a blended polymer containing a black material, formed into a porous film through phase inversion or electrospinning, or formed directly in situ on the first surface of a porous substrate. The black material can be an organic polymer (such as polyaniline, PANI) or an inorganic material, such as carbon nanotubes (CNTs), carbon black, carbon powder, graphene, or MXene. The photothermal layer can also be a gel in which photothermal nanomaterials are dispersed, such as a hydrogel or aerogel.

[0013] Preferably, the light-absorbing polymer material is polypyrrole or polyaniline.

[0014] Preferably, when the inner wall of the pore structure is itself a hydrophilic material, the hydrophilic material is a sand core with a pore size of G1 to G6, preferably G6. When the hydrophilicity of the inner wall of the pore structure is insufficient, a hydrophilic material is filled inside the pore structure. The hydrophilic material is at least one of polyethersulfone (PES), polyvinylidene fluoride (PVDF), polyimide (PI), polyester (PP), polytetrafluoroethylene (PTFE), cellulose acetate (CA), polysulfone (PSF or PSU), polyacrylonitrile (PAN), and hydrogel. The nanoscale water transport channels of the hydrophilic material can generate pressure at the level of hundreds of megapascals to ensure effective water transport.

[0015] Preferably, the ion separation membrane is a crown ether / graphene oxide inorganic nanofiltration membrane, which is in close contact with the second surface of the porous substrate; the crown ether / graphene oxide inorganic nanofiltration membrane includes graphene oxide nanosheets and crown ether; the crown ether is at least one of benzo9-crown ether-3, benzo12-crown ether-4, and dibenzo14-crown ether-4.

[0016] The method for preparing the photothermal driven ion separation device of the present invention includes the following steps: a photothermal layer is formed on the first surface of a porous substrate by in-situ polymerization, and the ion separation membrane is in close contact with the second surface of the porous substrate; when the hydrophilicity of the inner wall of the pore structure is insufficient, a hydrophilic material is filled into the pore structure of the porous substrate, and the hydrophilic material is formed in the pore structure of the porous substrate by in-situ polymerization.

[0017] As a preferred approach, to improve the performance stability of the device, at least one of the photothermal layer and the hydrophilic material is synthesized in situ to form an integral structure, further enhancing the interlayer adhesion and overall stability. A further preferred approach is to synthesize both the photothermal layer and the hydrophilic material in situ on a sand core, further improving interlayer adhesion and device stability.

[0018] Preferably, the specific preparation method of the photothermal layer is as follows:

[0019] S01 Prepares an aqueous solution of a light-absorbing material monomer; the light-absorbing material monomer is at least one of pyrrole and aniline;

[0020] SO2 is used to prepare an aqueous solution of the oxidant.

[0021] S03 Coating the first surface of the porous matrix with an aqueous solution of the light-absorbing material monomer;

[0022] S04: An aqueous solution of oxidant is coated on the first surface of the porous matrix obtained in S03, and the reaction is allowed to proceed statically.

[0023] S05 Repeat steps S02 and S03 until a photothermal layer (2) with a solar spectral light absorption rate greater than 95% is formed.

[0024] Preferably, the oxidant is one of benzoyl peroxide, ammonium dichromate, hydrogen peroxide, ferric chloride, and ammonium persulfate.

[0025] Preferably, the mass fraction of the light-absorbing material monomer in the aqueous solution is 0.5-2 wt%; and the mass fraction of the oxidant in the aqueous solution is 3.5-10 wt%.

[0026] Further optimization involves forming the photothermal layer by alternating in-situ polymerization of polypyrrole (PPy) on the first surface of the sand core. Polypyrrole possesses excellent light absorption properties, effectively improving the photothermal conversion efficiency of the device and promoting water evaporation. Simultaneously, polypyrrole exhibits good compatibility with the sand core, forming a stable bond strength and ensuring the structural robustness and long-term stability of the device. The specific preparation method is as follows: S01 Prepare an aqueous solution of pyrrole and an aqueous solution of ammonium persulfate, preferably with a mass ratio of pyrrole to ammonium persulfate of (1~2):(2~5); S02 Uniformly coat the pyrrole aqueous solution onto the first surface of the porous substrate (sand core), ensuring uniform liquid coverage and penetration into the surface of the pore structure; S03 Coat the first surface of the porous substrate already coated with the pyrrole solution with the ammonium persulfate aqueous solution and allow it to stand for a sufficient time to allow the pyrrole monomers to undergo a polymerization reaction under the action of an oxidant; S04 Repeat steps S02 and S03, alternately coating with pyrrole and ammonium persulfate solutions until a photothermal layer of the required thickness is formed. Through repeated coating and in-situ polymerization, a uniform and dense photothermal layer can be ensured to cover the substrate surface. In this invention, pyrrole undergoes an oxidative polymerization reaction under the action of the oxidant ammonium persulfate: an electrically neutral pyrrole molecule loses an electron and is oxidized to a cationic free radical. Subsequently, two cationic free radical molecules combine to generate a dication of dimerpyrrole. This dication generates electrically neutral dimerpyrrole through disproportionation. Dipyrrole continues to be oxidized, forming longer polymer chains, gradually developing into chain-like PPy molecules with a degree of polymerization n, and finally forming a stable photothermal layer. The reaction formula is as follows:

[0027] ;

[0028] This reaction process continuously enhances the thickness and performance of the photothermal layer through alternating polymerization.

[0029] As a more specific implementation method, the photothermal layer is prepared as follows: (1) Prepare a pyrrole aqueous solution: the preferred content range of pyrrole in the pyrrole aqueous solution is 0.5-2 wt%, and more preferably 1 wt%. After adding the pyrrole monomer to the aqueous solution, the solution is obtained by magnetic stirring for 10 min; (2) Prepare an ammonium persulfate aqueous solution: the preferred content range of ammonium persulfate in the ammonium persulfate aqueous solution is 3.5-10 wt%. When the content of pyrrole monomer is lower than this range, the self-polymerization reaction time of pyrrole will be significantly prolonged, resulting in a decrease in polymerization efficiency. Furthermore, the polypyrrole layer formed on the surface of the sand core will not be uniformly and completely covered, affecting the performance of the photothermal layer. Conversely, if the content of pyrrole monomer is too high, the polypyrrole generated during the polymerization process will fill the pores of the sand core, resulting in a significant decrease in the porosity of the sand core and a reduction in pore size, ultimately weakening the hydrophilicity of the sand core and thus affecting the overall water transport efficiency of the device. The optimal solution preparation method is as follows: Add 7 g of ammonium persulfate white powder to 100 mL of aqueous solution, stir magnetically for 10 min and set aside; (3) Coating pyrrole solution: Use a dropper to take an appropriate amount of pyrrole aqueous solution according to the surface area of ​​the sand core, and evenly drop it onto the surface of the sand core. Then, use a brush or other suitable tool to evenly coat the pyrrole solution onto the surface of the sand core, ensuring that the entire surface is completely wetted; (4) Use a dropper to take an appropriate amount of ammonium persulfate aqueous solution according to the area of ​​the sand core, and evenly drop it onto the surface of the sand core. Then use a brush to evenly coat the solution, ensuring that the solution and pyrrole solution are in full contact, and let stand for 5-20 min to allow polypyrrole to polymerize in situ; (5) After gently wiping the residual solution on the surface of the sand core with a dust-free paper, use a dropper again to take an appropriate amount of pyrrole solution, evenly drop it onto the surface of the sand core, and ensure that the film layer is completely wetted again. Let stand for 5-20 minutes, the specific time can be adjusted flexibly according to the reaction progress; (6) Continue to repeat the above steps (4) and (5) for a total of three cycles, and the last one ends with the dropwise addition of ammonium persulfate solution. Through this method, after alternating coating with pyrrole solution and ammonium persulfate solution, three cycles are completed, and a photothermal layer for solar photothermal conversion is formed in situ on the surface of the sand core by polymerization.

[0030] As a preferred approach, when the hydrophilicity of the inner wall of the pore structure is insufficient, the pore structure of the porous matrix (1) is filled with a hydrophilic material, which is prepared in situ through synthesis within the pore structure. This setup can effectively regulate the pore size and wettability of the water transport channels by controlling the polymer composition, content, or synthesis conditions. The hydrophilic material can be polymerized from two or more monomers, and the materials suitable for this invention include, but are not limited to, polyethersulfone (PES), polyvinylidene fluoride (PVDF), polyimide (PI), polyester (PP), polytetrafluoroethylene (PTFE), cellulose acetate (CA), polysulfone (PSF or PSU), polyacrylonitrile (PAN), and hydrogels. Polyethersulfone is preferably used as the main hydrophilic material, and the preparation method is as follows: S01 Dissolve polyethersulfone particles, polyethyleneimine, and polyethylene glycol in N,N-dimethylformamide (DMF) to form a uniform polymer solution; S02 Inject the prepared polymer solution into the pore structure of the porous matrix to ensure that the pore structure is completely wetted by the solution. Subsequently, the matrix is ​​sealed and maintained for a set time to allow the polymer to fully penetrate and stabilize; in step S03, the treated porous matrix is ​​removed and placed in deionized water for a solvent-inducible phase inversion process. This step forms a uniformly distributed hydrophilic polymer within the pore structure, ensuring that the water transport channels have good hydrophilicity and adjustable pore size.

[0031] Preferably, the method for preparing the hydrophilic material is as follows:

[0032] S01 Dissolve polyethersulfone particles, polyethyleneimine, and polyethylene glycol in N,N-dimethylformamide to prepare a homogeneous polymer solution;

[0033] S02 The prepared polymer solution is injected into the porous structure of the porous matrix to fully wet the pore structure, ensuring that the inner wall of the pore is completely covered and maintained in a wetted state for a set time.

[0034] S03 involves removing the porous matrix from the polymer solution and placing it in deionized water for a solvent-induced phase transformation, thereby forming a hydrophilic polymer within the porous matrix's pore structure.

[0035] More preferably, the preparation method of the hydrophilic material is as follows: (1) Polyethersulfone (PES) particles, polyethyleneimine (PEI) and polyethylene glycol (PEG) are added sequentially to N,N-dimethylformamide (DMF) solvent to prepare a uniform polymer solution with a certain viscosity. The polymer solution contains 1-10 wt% polyethersulfone particles, 0.5-8 wt% polyethyleneimine, and 1-5 wt% polyethylene glycol. The polymer solution is magnetically stirred at 25-55℃ for 8-16 h to ensure that all components are fully dissolved and form a homogeneous solution. Then, it is left to stand at room temperature for 8-16 h to remove bubbles before use. (2) The prepared polymer solution is slowly added dropwise to the microporous sand core to ensure that the solution completely wets the pore structure of the sand core. In order to ensure that the solution fully diffuses and penetrates in the pores, the sand core is sealed for 24 h. (3) The microporous sand core containing the polymer solution is taken out and quickly placed in deionized water for water bath non-solvent-induced phase transformation. It is then left to stand for 24 h to complete the phase transformation of the polymer. After the phase transformation is completed, the pore structure of the sand core is filled with polymer. (4) The sand core completely wetted with the polymer solution is taken out from the sealed container and quickly transferred to deionized water for water bath non-solvent-induced phase transformation. During the phase inversion, DMF and PEG dissolve in water, causing polyethersulfone to form a three-dimensional macromolecular network gel within the porous structure. After standing for 24 hours to complete the phase inversion, the pores of the sand core are filled with hydrophilic polymers, forming water channels with excellent transport properties.

[0036] Further preferably, the polymer solution in step (1) is obtained by dissolving 7 wt% polyethersulfone (PES) particles, 2.5 wt% polyethyleneimine (PEI), and 1.5 wt% polyethylene glycol (PEG) in DMF solvent. The polymer solution is magnetically stirred at 45°C for 12 h and then allowed to stand for degassing for 12 h. The type (single-chain or branched) and molecular weight of the polyethyleneimine are not limited, but preferably the molecular weight of the polyethyleneimine is 80,000 and the molecular weight of the polyethylene glycol is 1,000. This molecular weight provides more positively charged amino groups in the subsequently formed polymer membrane, which can improve the adhesion of the in-situ polymerized nanofiltration layer, as well as improve the hydrophilicity and water flux of the polymer membrane. The type and molecular weight of the non-solvent additives are not limited, nor are the types of solvents used.

[0037] Preferably, the specific preparation method of the ion separation membrane is as follows:

[0038] S01 Prepare an aqueous solution of graphene oxide as the first solution; prepare a dimethylformamide solution of crown ether as the second solution;

[0039] S02 The first solution and the second solution are mixed and ultrasonicated until they are evenly dispersed to obtain a mixed solution. The mixed solution is then filtered through a filter membrane to obtain an ion separation membrane.

[0040] Preferably, the filter membrane is one of polyethersulfone membrane, cellulose acetate membrane, cellulose nitrocellulose membrane, polycarbonate membrane, polytetrafluoroethylene membrane, and polyvinylidene fluoride membrane.

[0041] More preferably, the filter membrane is a polyethersulfone membrane.

[0042] Preferably, the polyethersulfone membrane has a pore size of 220-450 nm.

[0043] Preferably, the mass concentration of graphene oxide in the first solution is 1-2 mg / ml, and the mass concentration of crown ether in the second solution is 10-200 mg / ml, preferably 50 mg / ml.

[0044] Further preferred, the specific preparation method of the ion separation membrane is as follows: (1) Prepare an aqueous solution of graphene oxide containing 1-2 mg / ml and a dimethylformamide solution of benzo12-crown ether-4 containing 10-200 mg / ml; (2) Stir the two solutions magnetically at 20-40℃ for 1-5 h in a ratio of (10~20):(1~5) to obtain a completely dispersed mixed solution; (3) Use a polyethersulfone membrane as a filter membrane and filter 5-20 ml of the mixed solution through a solvent filter, and dry the filter surface completely; (4) Remove the filtered membrane from the solvent filter and vacuum dry it at 50-60℃ for 4-12 h to obtain the ion separation membrane.

[0045] The present invention relates to the application of the photothermal-driven ion separation device in ion extraction. This photothermal-driven ion separation device floats on the solution surface and directly contacts the solution through its ion separation membrane, achieving selective permeation and separation of ions.

[0046] Preferably, the specific application method is as follows: During use, the device floats on the surface of the solution to be extracted, with the first surface facing upwards to fully absorb sunlight and generate heat, while the second surface is in contact with the solution to be extracted to promote ion separation and extraction. Water molecules pass through the ion separation membrane from the solution to be extracted into the porous structure of the porous matrix, and after being heated, they are converted into water vapor and escape from above the photothermal layer. At this time, ions are deposited in the pores of the porous matrix. After the device finishes working, by immersing the device in deionized water or rinsing the pore structure with deionized water, the ions deposited in the pores dissolve in the water, thereby completing the ion extraction process.

[0047] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0048] 1. No external energy required: The photothermal driven ion separation device of the present invention relies on sunlight and capillary forces within the porous structure as the power source for the transport of water and ions, achieving the advantages of energy saving and environmental protection, and reducing dependence on external energy.

[0049] 2. Highly controllable: By synthesizing hydrophilic materials within the device, the hydrophilicity and pore size of the materials can be flexibly controlled, thereby adjusting the capillary force to adapt to different application scenarios and needs.

[0050] 3. Improved evaporation efficiency: The photothermal layer formed in situ on the porous substrate ensures efficient heat transfer on the device, further improving the evaporation efficiency of water vapor and enhancing the overall performance of the device.

[0051] 4. High-efficiency filtration: Compared with traditional nanofiltration membranes, crown ethers can specifically identify ions through pore size sieving, which can meet the separation requirements of different ions and improve the overall separation efficiency.

[0052] 5. Sustainable and cost-effective: This invention uses interfacial solar evaporation technology to directly extract high-purity lithium from salt lake brine. This is an environmentally friendly solution that reduces reliance on traditional energy-intensive processes and reduces energy consumption and operating costs.

[0053] 6. Highly Efficient Treatment of Salt Lake Brine: This device can directly recover lithium resources from salt lake brines with high magnesium-to-lithium ratios and numerous interfering impurity ions. Compared with existing salt lake ion extraction technologies, this invention not only enables the cyclic crystallization and collection of lithium salts but also achieves one-step simultaneous separation of lithium ions from all other interfering ions, solving the problem that traditional technologies cannot separate sodium and potassium ions with similar radii and charges. Furthermore, this device ensures both environmental friendliness and economic efficiency in the extraction process. Attached Figure Description

[0054] Figure 1 This is a structural diagram of the photothermal driven ion separation device of the present invention;

[0055] Figure 2 This is a structural diagram of the photothermal-driven ion separation device after being encapsulated in a hollow clamp plate according to the present invention;

[0056] Figure 3 The evaporation rate of pure water in different salt solutions under one sun (1 sun) illumination is measured by the photothermal driven ion separation device in Embodiment 1 of the present invention.

[0057] Figure 4 The lithium-magnesium, lithium-potassium, and lithium-sodium separation factors of the photothermal driven ion separation device in different concentration salt solutions in Example 1 of the present invention;

[0058] Figure 5 The lithium chloride crystallization rate of the photothermal driven ion separation device in different concentration salt solutions in Example 1 of the present invention;

[0059] Figure 6The lithium-magnesium, lithium-potassium, and lithium-sodium separation factors of the photothermal driven ion separation device in Example 1 of the present invention and the photothermal driven ion separation device in Comparative Example 1 of the present invention in a 1 g / L salt solution;

[0060] Figure 7 The lithium chloride crystallization rate in a 1 g / L salt solution is compared between the photothermal driven ion separation device in Example 1 of this invention and the photothermal driven ion separation device in Comparative Example 1 of this invention. Detailed Implementation

[0061] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0062] The photothermal driven ion separation device of the present invention, such as Figure 1 As shown, the device includes a porous substrate 1. The porous substrate 1 has a first surface and a second surface arranged opposite to each other, and a pore structure is uniformly distributed on it, serving as channels connecting the first and second surfaces. A photothermal layer 2, which is a porous membrane, is disposed on the first surface; an ion separation membrane 3, in close contact, is disposed on the second surface. This nanofiltration membrane selectively allows specific ions to pass through, thereby achieving effective separation of the target ion from other ions. The pore structure is filled with a hydrophilic material, and water transport channels are provided on the hydrophilic material. These water transport channels are nanoscale channels, preferably with a size range of 10-220 nm, capable of generating pressures exceeding 18 MPa. During use, the first surface faces upwards as the upper surface, and the second surface faces downwards as the lower surface. The device is suspended in the solution to be extracted, with the lower surface in contact with the solution, while the upper surface is not in contact with the solution. Water and target ions in the solution to be extracted permeate through the nanofiltration membrane to the hydrophilic material and are transported within the hydrophilic material. Under the action of the photothermal layer 2, water absorbs heat and converts into water vapor, which then escapes through the photothermal layer 2. Meanwhile, the ions to be extracted are deposited in the hydrophilic material, eventually forming solid crystals. There are no restrictions on the extraction method for the solid crystals; they can be extracted by immersing the device to dissolve them, or by rinsing the device with deionized water to separate them. Alternatively, other methods can be used to directly separate the solid crystals from the device.

[0063] To achieve stable buoyancy of the device in the solution, the porous substrate 1 in this invention can be made of a material with buoyancy properties. Through its own buoyancy, the device can float on the solution surface; furthermore, buoyancy components can be added to the device to enhance its buoyancy. As shown in Example 2, the embodiment uses a hollow clamping plate 4 with buoyancy, positioned on both sides of the device. Gaskets are placed between the hollow clamping plate 4 and the device to clamp it. The hollow clamping plate 4 has a ring structure, which can form effective support around the device.

[0064] In the embodiment, the porous substrate 1 is a sand core containing micropores, the sand core thickness is 3mm, the sand core pore diameter is G6, and the pore diameter range is 1.2~10μm.

[0065] The aforementioned devices can be used to separate ions with different charges or different pore sizes, such as allowing Li to... + Monovalent ions can pass through while blocking other interfering impurity ions, such as SO42-. 2- Ca 2+ and Mg 2+ Divalent ions and Na + K + Monovalent ions. As an application, the device can effectively separate lithium ions from a mixed solution of lithium ions, magnesium ions, sodium ions, and potassium ions, so that lithium ions and lithium salts eventually crystallize and precipitate on the top of the photothermal layer 2, thereby realizing the extraction of lithium ions.

[0066] Example 1

[0067] The device fabrication method includes the following steps:

[0068] Step 1 involves in-situ synthesis of photothermal layer 2 on the first surface of the sand core. The synthesis method is as follows:

[0069] (1) Add 0.5 g of pyrrole (analytical grade) to 99.5 mL of aqueous solution and stir magnetically for 10 min to obtain a pyrrole aqueous solution with a mass fraction of 0.5 wt%;

[0070] (2) Add 7 g of ammonium persulfate powder to 92 mL of aqueous solution and stir magnetically for 10 min to obtain 7 wt% ammonium persulfate aqueous solution;

[0071] (3) Using a dropper, a certain amount of pyrrole aqueous solution (determined according to the area of ​​the selected sand core) is added to the surface of the sand core. The amount of pyrrole aqueous solution on a unit area of ​​sand core is 0.5 mL / m. 2 Then use a brush to apply the coating evenly, ensuring that the entire surface of the sand core is wetted;

[0072] (4) Using a dropper, a certain amount of ammonium persulfate aqueous solution (determined according to the area of ​​the selected sand core) is added to the surface of the sand core. The amount of ammonium persulfate aqueous solution added per unit area of ​​sand core is 0.5 mL / m. 2 Apply the mixture evenly with a brush and let it stand for 2 minutes. During this process, pyrrole undergoes a polymerization reaction to form polypyrrole.

[0073] (5) After wiping the surface of the sand core with lint-free paper to remove any remaining aqueous solution, apply 0.5 mL / m again. 2 Add pyrrole aqueous solution dropwise to the sand core to completely wet the membrane surface, and let it stand for 2 min to react;

[0074] (6) Repeat steps (4) and (5) above for a total of three cycles, and terminate the reaction by adding ammonium persulfate solution dropwise. Thus, a photothermal layer 2 for solar photothermal conversion was prepared by in-situ polymerization reaction on the surface of the sand core.

[0075] Step two involves filling the pore structure of the sand core with a hydrophilic material. The preparation method is as follows:

[0076] (1) Polyethersulfone particles, polyethyleneimine and polyethylene glycol were added to N,N-dimethylformamide (DMF) solvent to prepare a polymer solution with a certain viscosity. The concentration of polyethersulfone particles in the polymer solution was 7 wt%, the molecular weight of polyethyleneimine was 80000 and the concentration was 2.5 wt%, and the molecular weight of polyethylene glycol was 1000 and the concentration was 1.5 wt%. The polymer solution was magnetically stirred at 40°C for 12 h, and then allowed to stand at room temperature for 12 h to remove bubbles before use.

[0077] (2) The prepared polymer solution is slowly dripped into the microporous sand core pore structure from the second surface to completely wet it, and then sealed for 24 h;

[0078] (3) Take out the microporous sand core containing polymer solution that is completely soaked, quickly place it in deionized water for water bath non-solvent-induced phase transformation, and let it stand for 24 h to complete the phase transformation of the polymer.

[0079] (4) Remove the polymer-filled microporous sand core and transfer it to fresh deionized water for storage until use.

[0080] Step 3 involves the preparation of crown ether / graphene oxide inorganic nanofiltration membranes. The preparation method is as follows:

[0081] (1) Prepare an aqueous solution containing 1 mg / ml graphene oxide and stir magnetically at 25°C for 4 h to obtain a completely dispersed and uniformly dispersed aqueous solution of graphene oxide.

[0082] (2) Prepare a dimethylformamide solution containing 50 mg of benzo12-crown ether-4 and stir magnetically at 25°C for 4 h to obtain a completely dissolved benzo12-crown ether-4 dimethylformamide solution;

[0083] (3) Mix the aqueous solution of graphene oxide and the solution of benzo12-crown ether-4-dimethylformamide at a mass ratio of 10:1 and stir magnetically at 25°C for 4 hours to obtain a uniformly mixed solution;

[0084] (4) Take 10 ml of the well-mixed solution and use a polyethersulfone membrane with a pore size of 220 nm as a substrate to perform vacuum filtration in a solvent filter until the surface moisture is completely removed.

[0085] (5) Remove the filtered membrane from the solvent filter and dry it under vacuum at 60°C for 12 h to obtain crown ether / graphene oxide photothermal ion separation membrane 3.

[0086] Example 2

[0087] The device fabrication method includes the following steps:

[0088] Step 1 involves in-situ synthesis of photothermal layer 2 on the first surface of the sand core. The synthesis method is as follows:

[0089] (1) Add 2 g of aniline (analytical grade) to 98 mL of aqueous solution and stir magnetically for 10 min to obtain an aqueous solution of aniline with a mass fraction of 2 wt%;

[0090] (2) Add 3.5 g of ferric chloride powder to 96.5 mL of aqueous solution and stir magnetically for 10 min to obtain a 3.5 wt% ferric chloride aqueous solution;

[0091] (3) Using a dropper, a certain amount of aniline aqueous solution (determined according to the area of ​​the selected sand core) is added to the surface of the sand core. The amount of aniline aqueous solution on a unit area of ​​sand core is 0.5 mL / m. 2 Then use a brush to apply the coating evenly, ensuring that the entire surface of the sand core is wetted;

[0092] (4) Using a dropper, a certain amount of ferric chloride aqueous solution (determined according to the area of ​​the selected sand core) is added to the surface of the sand core. The amount of ammonium persulfate aqueous solution added per unit area of ​​sand core is 0.5 mL / m. 2 Apply the mixture evenly with a brush and let it stand for 2 minutes. During this process, aniline undergoes a polymerization reaction to form polyaniline.

[0093] (5) After wiping the surface of the sand core with lint-free paper to remove any remaining aqueous solution, apply 0.5 mL / m again. 2 Add aniline aqueous solution dropwise to the sand core to completely wet the membrane surface, and let it stand for 2 min to react;

[0094] (6) Repeat steps (4) and (5) above for a total of three cycles, and terminate the reaction by adding ferric chloride solution dropwise. Thus, a photothermal layer 2 for solar photothermal conversion was prepared by in-situ polymerization reaction on the surface of the sand core.

[0095] Step two involves filling the pore structure of the sand core with a hydrophilic material. The preparation method is as follows:

[0096] (1) Polyethersulfone particles, polyethyleneimine and polyethylene glycol were added to N,N-dimethylformamide (DMF) solvent to prepare a polymer solution with a certain viscosity. The concentration of polyethersulfone particles in the polymer solution was 10 wt%, the molecular weight of polyethyleneimine was 100,000 and the concentration was 8 wt%, the molecular weight of polyethylene glycol was 2,000 and the concentration was 5 wt%. The polymer solution was magnetically stirred at 40°C for 12 h, and then allowed to stand at room temperature for 12 h to remove bubbles before use.

[0097] (2) The prepared polymer solution is slowly dripped into the microporous sand core pore structure from the second surface to completely wet it, and then sealed for 24 h;

[0098] (3) Take out the microporous sand core containing polymer solution that is completely soaked, quickly place it in deionized water for water bath non-solvent-induced phase transformation, and let it stand for 24 h to complete the phase transformation of the polymer.

[0099] (4) Remove the polymer-filled microporous sand core and transfer it to fresh deionized water for storage until use.

[0100] Step 3 involves the preparation of crown ether / graphene oxide inorganic nanofiltration membranes. The preparation method is as follows:

[0101] (1) Prepare an aqueous solution containing 1.5 mg / ml graphene oxide and stir magnetically at 25°C for 4 hours to obtain a completely dispersed and uniformly dispersed aqueous solution of graphene oxide.

[0102] (2) Prepare a dimethylformamide solution containing 10 mg of dibenzo-14-crown ether-4 and stir magnetically at 25°C for 4 h to obtain a completely dissolved dibenzo-14-crown ether-4 dimethylformamide solution;

[0103] (3) Mix the aqueous solution of graphene oxide and the solution of dibenzo-14-crown ether-4-dimethylformamide at a mass ratio of 10:5, and stir magnetically at 25°C for 4 hours to obtain a uniformly mixed solution;

[0104] (4) Take 10 ml of the well-mixed solution and vacuum filter it in a solvent filter using a polyethersulfone membrane substrate with a pore size of 220 nm until the surface moisture is completely removed.

[0105] (5) Remove the filtered membrane from the solvent filter and dry it under vacuum at 60°C for 12 h to obtain crown ether / graphene oxide photothermal ion separation membrane 3.

[0106] Example 3

[0107] The device fabrication method includes the following steps:

[0108] Step 1 involves in-situ synthesis of photothermal layer 2 on the first surface of the sand core. The synthesis method is as follows:

[0109] (1) Add 1 g of pyrrole and aniline (analytical grade, mass ratio of 1:1) to 99 mL of aqueous solution, stir magnetically for 10 min to obtain a mixed aqueous solution of pyrrole and aniline with a mass fraction of 1 wt%;

[0110] (2) Add 5 g of ammonium dichromate powder to 95 mL of aqueous solution and stir magnetically for 10 min to obtain 5 wt% ammonium dichromate aqueous solution;

[0111] (3) Using a dropper, a certain amount (determined according to the area of ​​the selected sand core) of pyrrole and aniline mixed aqueous solution is added to the surface of the sand core. The amount of pyrrole and aniline mixed aqueous solution on a unit area of ​​sand core is 0.5 mL / m 2 Then use a brush to apply the coating evenly, ensuring that the entire surface of the sand core is wetted;

[0112] (4) Using a dropper, a certain amount of ammonium dichromate aqueous solution (determined according to the area of ​​the selected sand core) is added to the surface of the sand core. The amount of ammonium dichromate aqueous solution added per unit area of ​​sand core is 0.5 mL / m. 2 Apply the mixture evenly with a brush and let it stand for 2 minutes. During this process, pyrrole and aniline undergo a polymerization reaction to form a pyrrole-aniline copolymer. The reaction formula is as follows:

[0113] (5) After wiping the surface of the sand core with lint-free paper to remove any remaining aqueous solution, apply 0.5 mL / m again. 2 Add the solution of pyrrole and aniline mixed aqueous solution to the sand core dropwise to completely wet the membrane surface, and let it stand for 2 min to react;

[0114] (6) Repeat steps (4) and (5) above for a total of three cycles, and terminate the reaction by adding ammonium dichromate solution dropwise. Thus, a photothermal layer 2 for solar photothermal conversion was prepared by in-situ polymerization reaction on the surface of the sand core.

[0115] Step two involves filling the pore structure of the sand core with a hydrophilic material. The preparation method is as follows:

[0116] (1) Polyethersulfone particles, polyethyleneimine and polyethylene glycol were added to N,N-dimethylformamide (DMF) solvent to prepare a polymer solution with a certain viscosity. The concentration of polyethersulfone particles in the polymer solution was 1 wt%, the molecular weight of polyethyleneimine was 120000 and the concentration was 1 wt%, and the molecular weight of polyethylene glycol was 5000 and the concentration was 5 wt%. The polymer solution was magnetically stirred at 40°C for 12 h, and then allowed to stand at room temperature for 12 h to remove bubbles before use.

[0117] (2) The prepared polymer solution is slowly dripped into the microporous sand core pore structure from the second surface to completely wet it, and then sealed for 24 h;

[0118] (3) Take out the microporous sand core containing polymer solution that is completely soaked, quickly place it in deionized water for water bath non-solvent-induced phase transformation, and let it stand for 24 h to complete the phase transformation of the polymer.

[0119] (4) Remove the polymer-filled microporous sand core and transfer it to fresh deionized water for storage until use.

[0120] Step 3 involves the preparation of crown ether / graphene oxide inorganic nanofiltration membranes. The preparation method is as follows:

[0121] (1) Prepare an aqueous solution containing 2 mg / ml graphene oxide and stir magnetically at 25°C for 4 h to obtain a completely dispersed and uniformly dispersed aqueous solution of graphene oxide.

[0122] (2) Prepare a dimethylformamide solution containing 200 mg of benzo9-crown ether-3 and stir magnetically at 25°C for 4 h to obtain a completely dissolved benzo9-crown ether-3 dimethylformamide solution;

[0123] (3) Mix the aqueous solution of graphene oxide and the solution of benzo9-crown ether-3-dimethylformamide at a mass ratio of 20:5 and stir magnetically at 25°C for 4 hours to obtain a uniformly mixed solution;

[0124] (4) Take 10 ml of the well-mixed solution and use a polyethersulfone membrane with a pore size of 220 nm as a substrate to perform vacuum filtration in a solvent filter until the surface moisture is completely removed.

[0125] (5) Remove the filtered membrane from the solvent filter and dry it under vacuum at 60°C for 12 h to obtain crown ether / graphene oxide photothermal ion separation membrane 3.

[0126] Example 4

[0127] This embodiment uses a sand core with hydrophilic channels, eliminating the need for further filling with hydrophilic polymers. The device fabrication method includes the following steps:

[0128] Step 1 involves in-situ synthesis of photothermal layer 2 on the first surface of the sand core. The synthesis method is as follows:

[0129] (1) Add 1 g of aniline (analytical grade) to 98 mL of aqueous solution and stir magnetically for 10 min to obtain an aqueous solution of aniline with a mass fraction of 1 wt%.

[0130] (2) Add 5 g of ferric chloride powder to 95 mL of aqueous solution and stir magnetically for 10 min to obtain a 5 wt% ferric chloride aqueous solution;

[0131] (3) Using a dropper, a certain amount of aniline aqueous solution (determined according to the area of ​​the selected sand core) is added to the surface of the sand core. The amount of aniline aqueous solution on a unit area of ​​sand core is 0.5 mL / m. 2 Then use a brush to apply the coating evenly, ensuring that the entire surface of the sand core is wetted;

[0132] (4) Using a dropper, a certain amount of ferric chloride aqueous solution (determined according to the area of ​​the selected sand core) is added to the surface of the sand core. The amount of ammonium persulfate aqueous solution added per unit area of ​​sand core is 0.5 mL / m. 2 Apply the mixture evenly with a brush and let it stand for 2 minutes. During this process, pyrrole undergoes a polymerization reaction to form polyaniline.

[0133] (5) After wiping the surface of the sand core with lint-free paper to remove any remaining aqueous solution, apply 0.5 mL / m again. 2 Add aniline aqueous solution dropwise to the sand core to completely wet the membrane surface, and let it stand for 2 min to react;

[0134] (6) Repeat steps (4) and (5) above for a total of three cycles, and terminate the reaction by adding ferric chloride solution dropwise. Thus, a photothermal layer 2 for solar photothermal conversion was prepared by in-situ polymerization reaction on the surface of the sand core.

[0135] Step 2 involves the preparation of a crown ether / graphene oxide inorganic nanofiltration membrane. The preparation method is as follows:

[0136] (1) Prepare an aqueous solution containing 1 mg / ml graphene oxide and stir magnetically at 25°C for 4 h to obtain a completely dispersed and uniformly dispersed aqueous solution of graphene oxide.

[0137] (2) Prepare a dimethylformamide solution containing 50 mg of dibenzo-14-crown ether-4 and stir magnetically at 25°C for 4 h to obtain a completely dissolved dibenzo-14-crown ether-4 dimethylformamide solution;

[0138] (3) Mix the aqueous solution of graphene oxide and the solution of dibenzo-14-crown ether-4-dimethylformamide at a mass ratio of 10:1, and stir magnetically at 25°C for 4 hours to obtain a uniformly mixed solution;

[0139] (4) Take 10 ml of the well-mixed solution and use a polyethersulfone membrane with a pore size of 220 nm as a substrate to perform vacuum filtration in a solvent filter until the surface moisture is completely removed.

[0140] (5) Remove the filtered membrane from the solvent filter and dry it under vacuum at 60°C for 12 h to obtain crown ether / graphene oxide photothermal ion separation membrane 3.

[0141] Comparative Example 1

[0142] It contains only the ion separation membrane 3, excluding the photothermal layer 2, and no crown ether molecules are introduced into the ion separation membrane 3. The preparation steps are as follows:

[0143] (1) Prepare an aqueous solution containing 1 mg / ml graphene oxide and stir magnetically at 25°C for 4 h to obtain a completely dispersed and uniformly dispersed aqueous solution of graphene oxide.

[0144] (2) Take 10 ml of graphene oxide aqueous solution, use an AAO membrane with a pore size of 100 nm as a substrate, and perform vacuum filtration in a solvent filter until the surface moisture is completely removed.

[0145] (3) Remove the filtered membrane from the solvent filter and dry it under vacuum at 60°C for 12 h to obtain the ion separation membrane 3 of Comparative Example 1;

[0146] (4) The prepared ion separation membrane 3 of Comparative Example 1 is used in close contact with any surface of the sand core.

[0147] test:

[0148] Prepare the following solutions:

[0149] Solution 1: A mixed salt aqueous solution of magnesium chloride, sodium chloride, potassium chloride and lithium chloride with a total concentration of 1 g / L, wherein the mass ratio of each ion is 1:1:1:1.

[0150] Solution 2: A mixed salt aqueous solution of magnesium chloride, sodium chloride, potassium chloride and lithium chloride with a total concentration of 2 g / L, wherein the mass ratio of each ion is 1:1:1:1.

[0151] Solution 3: A mixed salt aqueous solution of magnesium chloride, sodium chloride, potassium chloride and lithium chloride with a total concentration of 3 g / L, wherein the mass ratio of each ion is 1:1:1:1.

[0152] Solution 4: A mixed salt aqueous solution of magnesium chloride, sodium chloride, potassium chloride and lithium chloride with a total concentration of 4 g / L, wherein the mass ratio of each ion is 1:1:1:1.

[0153] Solution 5: A mixed salt aqueous solution of magnesium chloride, sodium chloride, potassium chloride and lithium chloride with a total concentration of 5 g / L, wherein the mass ratio of each ion is 1:1:1:1.

[0154] The device described in Example 1 is encapsulated using a hollow clamp 4 and gaskets, both of which are annular structures fixed around the upper and lower surfaces of the device. The hollow clamp 4 provides buoyancy, allowing the device to float on water. The resulting device was placed in mixed salt solutions of solutions one through five, ensuring that the crown ether / graphene oxide inorganic ion separation membrane 3 was in contact with the solution. Subsequently, the lithium extraction efficiency of the device was tested under a single sunlight intensity for 72 hours.

[0155] In the above tests, the water evaporation rate, separation factor, and lithium chloride crystallization rate of the device were evaluated. Taking lithium-magnesium ions as an example, the separation factor was calculated as follows: Separation factor = (mass ratio of lithium-magnesium ions after separation) / (mass ratio of lithium-magnesium ions before separation). If the mass ratio of lithium ions to magnesium ions in the salt solution to be extracted is 1:1, and assuming the mass ratio of lithium ions to magnesium ions entering the sand core pore structure is 15:1, then the separation ratio is (15:1) / (1:1) = 15.

[0156] The lithium chloride crystallization rate is calculated as the mass of lithium chloride powder collected per unit area of ​​the device per unit time via solar energy. In this invention, the lithium chloride powder collected by the device is dissolved in a certain volume of aqueous solution, and the mass concentration of lithium ions in the aqueous solution is measured using inductively coupled plasma spectrometry (ICP-SPS) to deduce the mass of the lithium chloride powder. For example, if the lithium ion concentration in the aqueous solution is 5 mg / L and the volume of the aqueous solution is 0.1 L, then the mass of lithium is: Mass of lithium = 5 mg / L × 0.1 L = 0.5 mg

[0157] Test results are as follows Figures 3 to 5 As shown. By Figure 3-4 It can be seen that as the total concentration of the mixed salt solution increases, the water evaporation rate and the separation factor remain basically unchanged. Figure 5 The results show that the lithium chloride crystallization rate increases with increasing concentration of the mixed salt solution, indicating that the device can adapt to salt solutions of various concentrations. This characteristic is particularly beneficial for increasing the crystallization rate in high-concentration salt solutions.

[0158] The separation factor and lithium chloride crystallization rate of Comparative Example 1 were tested using Solution 1, and the results are as follows: Figure 6 and Figure 7 As shown. From Figure 6 It can be seen that, because Comparative Example 1 did not add a crown ether with specific recognition function for lithium ions, it only had a limited separation effect on magnesium ions, and no separation effect on sodium and potassium ions, with a separation factor close to 1. Example 1, on the other hand, showed good separation effects for all ions. Figure 7 It can be seen that, due to the absence of photothermal layer 2, the crystallization rate of lithium chloride in Comparative Example 1 is much lower than that in Example 1.

Claims

1. A photothermally driven ionic separation device, characterized in that, It includes a porous substrate (1), a photothermal layer (2), and an ion separation membrane (3); the photothermal layer (2) is disposed on the first surface of the porous substrate (1); the ion separation membrane (3) is disposed on the second surface of the porous substrate (1); the internal pore structure of the porous substrate (1) connects the first surface and the second surface; The porous matrix (1) is filled with a hydrophilic material inside its pore structure, and the pore structure filled with the hydrophilic material serves as a water transport channel; the hydrophilic material is formed in the pore structure of the porous matrix (1) by in-situ polymerization; The method for preparing the hydrophilic material by in-situ polymerization of the porous matrix (1) is as follows: S01 Dissolve polyethersulfone particles, polyethyleneimine, and polyethylene glycol in N,N-dimethylformamide to prepare a homogeneous polymer solution; S02 The prepared polymer solution is injected into the porous structure of the porous matrix to fully wet the pore structure, ensuring that the inner wall of the pore is completely covered and maintained in a wetted state for a set time. S03 involves removing the porous matrix from the polymer solution and placing it in deionized water for a solvent-induced phase transformation, thereby forming a hydrophilic polymer within the porous matrix's pore structure. The photothermal layer (2) is a high molecular polymer light-absorbing material; the photothermal layer (2) is formed on the first surface of the porous matrix (1) by in-situ polymerization; The ion separation membrane (3) is a crown ether / graphene oxide inorganic nanofiltration membrane, which is in close contact with the second surface of the porous substrate (1); the crown ether / graphene oxide inorganic nanofiltration membrane includes graphene oxide nanosheets and crown ether; the crown ether is at least one of benzo9-crown ether-3, benzo12-crown ether-4, and dibenzo14-crown ether-4.

2. A method of fabricating the photothermally driven ionic separation device of claim 1, wherein, Includes the following steps: The photothermal layer (2) is formed on the first surface of the porous substrate (1) by in-situ polymerization, and the ion separation membrane (3) is in close contact with the second surface of the porous substrate (1); the porous substrate (1) is filled with a hydrophilic material, which is formed in the porous substrate (1) by in-situ polymerization. The method for preparing the hydrophilic material by in-situ polymerization of the porous matrix (1) is as follows: S01 Dissolve polyethersulfone particles, polyethyleneimine, and polyethylene glycol in N,N-dimethylformamide to prepare a homogeneous polymer solution; S02 The prepared polymer solution is injected into the porous structure of the porous matrix to fully wet the pore structure, ensuring that the inner wall of the pore is completely covered and maintained in a wetted state for a set time. S03 involves removing the porous matrix from the polymer solution and placing it in deionized water for a solvent-induced phase transformation, thereby forming a hydrophilic polymer within the porous matrix's pore structure. The specific preparation method of the photothermal layer (2) is as follows: S01 Prepares an aqueous solution of a light-absorbing material monomer, wherein the light-absorbing material monomer is at least one of pyrrole and aniline; SO2 is used to prepare an aqueous solution of the oxidant. S03 The light-absorbing material monomer aqueous solution is coated on the first surface of the porous matrix (1); S04 The oxidant aqueous solution is coated on the first surface of the porous matrix (1) obtained by S03 and allowed to react statically; S05 Repeat steps S03 and S04 until a photothermal layer with a solar spectral light absorption rate greater than 95% is formed (2). The specific preparation method of the ion separation membrane (3) is as follows: prepare an aqueous solution of graphene oxide as the first solution; prepare a dimethylformamide solution of crown ether as the second solution; mix the first solution and the second solution and sonicate until uniformly dispersed to obtain a mixed solution; filter the mixed solution on a filter membrane to obtain the ion separation membrane (3).

3. The method for preparing the photothermal-driven ion separation device according to claim 2, characterized in that, The light-absorbing material monomer aqueous solution has a mass fraction of 0.5-2 wt%; the oxidant aqueous solution has a mass fraction of 3.5-10 wt%.

4. The method for preparing the photothermal driven ion separation device according to claim 2, characterized in that, The mass concentration of graphene oxide in the first solution is 1-2 mg / ml, and the mass concentration of crown ether in the second solution is 10-200 mg / ml.

5. The application of the photothermal driven ion separation device according to claim 1 or the photothermal driven ion separation device prepared by any of the preparation methods in claims 2-4 in ion extraction.

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