An Alg / M hydrogel composite film and its preparation method and application

Abstract

This invention discloses an Alg / M hydrogel composite membrane, its preparation method, and its application, belonging to the field of membrane preparation technology. The preparation method specifically includes the following steps: (1) surface activation and wetting of a hydrophobic microporous membrane using an activating solution, followed by rinsing the hydrophobic microporous membrane to obtain a hydrophilically modified hydrophobic microporous membrane; (2) uniformly coating the hydrophilically modified hydrophobic microporous membrane with an Alg pregel solution, drying it, then wetting and crosslinking it using an ionic crosslinking solution, and rinsing it after the reaction to obtain the Alg / M hydrogel composite membrane. This invention also discloses the Alg / M hydrogel composite membrane prepared by the above method and its application in membrane distillation processes. The hydrogel composite membrane obtained by this invention exhibits excellent long-term pollution resistance, anti-wetting properties, and efficient volatile organic compound (VOC) retention performance without sacrificing the permeation flux of the original hydrophobic base membrane. Furthermore, it is green, economical, and environmentally friendly, which is conducive to industrial production.

Description

Technical Field

[0001] This invention belongs to the field of membrane preparation technology, and particularly relates to an Alg / M hydrogel composite membrane, its preparation method and application. Background Technology

[0002] Membrane distillation (MD) is a desalination technology that couples thermal and membrane methods. Driven by the vapor pressure difference caused by the temperature difference between the solutions on both sides of a hydrophobic microporous membrane, volatile substances (such as water vapor) pass through the hydrophobic membrane pores and are condensed on the permeate side to obtain permeate, while non-volatile components (such as salts) are repelled and retained in the feed solution. Compared with other desalination processes (including reverse osmosis and conventional distillation), MD has significant advantages such as insensitivity to feed solution salt concentration, utilization of low-grade heat sources, high effluent quality, simple equipment, and modularity, making it highly promising for high-salinity wastewater treatment. However, the hydrophobic microporous membrane, acting as a barrier for liquid water transport and a medium for water vapor diffusion, is a core component of MD technology. When treating complex high-salinity wastewater, MD faces challenges such as membrane fouling and wetting, resulting in a significant decrease in salt rejection and flux, limiting the practical engineering application of MD technology. Membrane fouling refers to the phenomenon where, when the MD process treats feed solutions containing a large amount of hydrophobic contaminants (such as oils, hydrophobic organic compounds, etc.), the contaminants adhere to the surface of the hydrophobic membrane due to hydrophobic-hydrophobic interactions, clogging the membrane pores and leading to a significant reduction in water vapor flux. Membrane wetting, on the other hand, occurs when the MD process treats feed solutions containing amphiphilic molecules (such as surfactants and other amphiphilic organic compounds). The hydrophobic tails of these molecules adhere to the surface of the hydrophobic membrane pores, exposing the hydrophilic heads and causing a hydrophilic conversion of the hydrophobic membrane pores. This leads to membrane wetting, causing the feed brine solution to directly permeate to the permeate side and significantly reducing the salt rejection rate. In addition, the MD process also suffers from low separation efficiency of water and volatile organic compounds (VOCs). Specifically, because VOCs have a high Henry's constant and molecular dynamics size similar to that of water molecules, and the existing MD microporous membranes can only separate volatile and non-volatile components through phase change, these small molecule volatile organic compounds (VOCs) can evaporate with water vapor and be collected and enriched by condensation on the permeate side, thus seriously reducing the quality of the produced water.

[0003] Currently, Janus MD membranes with nanofiltration or dense hydrophilic layers have been proven to overcome both membrane fouling caused by hydrophobic organic compounds and membrane wetting induced by amphiphilic molecules, while allowing water vapor to diffuse through the ultrathin nanofiltration layer. However, there is almost no research on the design and development of MD membranes for volatile organic compound (VOC) retention. Although theoretically increasing membrane thickness and reducing pore size can improve VOCs retention efficiency to some extent, it will also further increase mass transfer resistance and reduce permeate flux. For the currently developed Janus composite membranes composed of hydrophilic or superhydrophilic surface layers and hydrophobic substrates, on the one hand, a hydration layer is formed on the hydrophilic surface layer to enhance resistance to oil fouling; on the other hand, the density of the hydrophilic layer is adjusted to mitigate surfactant-induced membrane wetting through mechanisms such as size sieving and capillary forces. However, the Janus MD membrane preparation method and its performance still have the following problems: (1) The construction of the surface hydrophilic layer increases the water vapor mass transfer resistance and reduces the permeation flux; (2) The membrane preparation process is relatively complex, involving complex chemical reactions and strict condition control, etc., and has poor repeatability; (3) The long-term resistance to pollution and anti-wetting ability is limited, and there is almost no research on the interception of small molecule VOCs.

[0004] Therefore, how to provide an MD membrane that combines long-term pollution resistance, anti-wetting properties, and efficient VOCs removal is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes an Alg / M hydrogel composite membrane, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing an Alg / M hydrogel composite membrane includes the following steps:

[0008] (1) After surface activation and wetting of the hydrophobic microporous membrane with an activation solution, the hydrophobic microporous membrane is rinsed to obtain a hydrophilic modified hydrophobic microporous membrane.

[0009] (2) The Alg pregel solution is uniformly coated on the hydrophilic modified hydrophobic microporous membrane and dried. Then, it is impregnated and crosslinked with an ionic crosslinking solution. After the reaction is completed, it is rinsed to obtain the Alg / M hydrogel composite membrane.

[0010] Beneficial Effects: The alginate (Alg) used in this invention, as a natural polysaccharide polymer, possesses advantages such as good ionic crosslinking properties, environmental sustainability, biodegradability, and low cost. It also exhibits strong hydration capacity and good tolerance under high salt and acid / alkaline conditions, demonstrating stable superoleophobicity even under high salt conditions. The Alg / M hydrogel composite membrane prepared in this invention first undergoes hydrophilic modification of the hydrophobic microporous membrane using an activating solution to improve the compatibility and adhesion of the subsequent Alg coating. Then, an Alg pregel solution is coated onto the surface of the hydrophilic modified layer, followed by drying / shrinkage to form an Alg pregel layer. Finally, rehydration / crosslinking is performed in an ionic solution to form a highly crosslinked Alg / M hydrogel layer. Because the Alg / M hydrogel layer contains abundant hydroxyl and carboxyl hydrophilic groups, the formation of a sufficient hydration layer in water reduces the energy consumed by water evaporation, ensuring the smooth passage of water molecules and achieving high permeability. Alg / M hydrogel layers possess both air-hydrophilic and underwater superoleophobic properties, enabling them to form a robust hydration layer in water and prevent contamination by light mineral oils and crude oil. Through cross-linking enhancement with ionic solutions, a highly cross-linked and dense Alg / M hydrogel layer is formed, restricting the passage of small-molecule surfactants and preventing membrane wetting. Furthermore, due to the difference in affinity or interaction between water molecules / small-molecule volatile organic compounds and the highly cross-linked hydrophilic Alg / M hydrogel network, the Alg / M hydrogel layer allows for efficient water molecule permeation while simultaneously achieving efficient retention of small-molecule volatile organic compounds.

[0011] Preferably, the hydrophobic microporous membrane in step (1) includes one of polytetrafluoroethylene, polyvinylidene fluoride, polypropylene and their composite materials;

[0012] The activation solution is obtained by dissolving an activator and an auxiliary agent in a buffer solution, wherein the concentration of the activator in the activation solution is 0.2-5 mg / mL, and the concentration of the auxiliary agent is 0.2-5 mg / mL;

[0013] The buffer solution is a Tris-HCl buffer solution with a concentration of 5-100 mmol / L and a pH of 6-10.

[0014] Beneficial effects: Compared with activators alone, the present invention uses an auxiliary agent and an activator in combination to shorten the activation time, improve the hydrophilicity effect and adhesion. The Tri-HCl buffer solution is designed to provide a suitable reaction environment.

[0015] Preferably, the activator is dopamine or tannic acid;

[0016] The auxiliary agent is polyethyleneimine or 3-aminopropyltriethoxysilane.

[0017] Preferably, when the activator is dopamine, the auxiliary agent is polyethyleneimine;

[0018] When the activator is tannic acid, the auxiliary agent is 3-aminopropyltriethoxysilane.

[0019] Preferably, the activation and immersion time in step (1) is 6-24 hours.

[0020] Beneficial effects: The activation and wetting time in this invention is adjusted according to the hydrophobicity of the substrate material, and the activation time increases with the increase of hydrophobicity.

[0021] Preferably, the mass concentration of the Alg pregel solution in step (2) is 1-8%;

[0022] The ion crosslinking solution is an aqueous solution of a polyvalent metal salt, wherein the concentration of metal ions is 0.1-1 mol / L;

[0023] The polyvalent metal salt is one or any combination of calcium chloride, calcium sulfate, copper chloride, copper sulfate, aluminum chloride, aluminum sulfate, ferric chloride, and ferric sulfate.

[0024] Beneficial effects: Alg in this invention is a biomass material extracted from algae. It has advantages such as wide availability, low price, biodegradability and renewability. In addition, the Alg molecular chain contains a large number of hydroxyl (-OH) and carboxyl (-COOH) groups, which provide abundant binding sites for ionic crosslinking and are therefore widely used in the preparation of hydrogels.

[0025] Preferably, in step (2), 8. the method for preparing an Alg / M hydrogel composite membrane according to claim 1, is characterized in that the drying in step (2) is natural air drying or drying at 25-45℃;

[0026] The crosslinking time is 0.5-24h.

[0027] Beneficial effects: During the drying process, the Alg chains in the Alg pregel solution of this invention shrink and form hydrogen bonds with each other, resulting in a physically cross-linked Alg dry gel (which swells and dissolves in water). Further immersion of the Alg dry gel in an ionic cross-linking solution for chemical gelation yields an Alg / M hydrogel with excellent stability and anti-swelling properties.

[0028] An Alg / M hydrogel composite membrane was prepared by a method thereof.

[0029] Application of an Alg / M hydrogel composite membrane in membrane distillation process.

[0030] More preferably, during the application process, the side loaded with the Alg / M hydrogel layer faces the feed liquid.

[0031] More preferably, the feed liquid is a salt solution containing surfactants, surfactant-stabilized oil-water emulsions, and volatile organic compounds, and the permeate is deionized water.

[0032] Beneficial effects: The purpose of adding surfactants to the feed liquid in this invention is to test the anti-wetting performance of the Alg / M hydrogel composite membrane; the purpose of adding surfactants to stabilize the oil-water emulsion in the feed liquid is to test the simultaneous anti-fouling and anti-wetting performance of the Alg / M hydrogel composite membrane; the purpose of adding volatile organic compounds to the feed liquid is to test the ability of the Alg / M hydrogel composite membrane to retain volatile organic compounds.

[0033] This invention discloses an Alg / M hydrogel composite membrane, its preparation method, and its applications. First, an activating solution is used to hydrophilicate the surface of the hydrophobic microporous membrane, improving the compatibility and adhesion of the Alg coating, thereby ensuring the formation of a robust and defect-free hydrogel layer on the hydrophobic substrate. Furthermore, this invention uses an Alg / M hydrogel with abundant hydroxyl and carboxyl hydrophilic groups as the hydrophilic coating. The hydrogen bonding between the polymer network and water molecules reduces the enthalpy of water evaporation, ensuring high permeability. Due to its hydrophilicity in air and superoleophobic properties underwater, it can form a robust hydration layer in water, effectively preventing contamination from light mineral oils and crude oil.

[0034] This invention utilizes ionic crosslinking to strengthen the formation of a highly crosslinked and dense Alg / M hydrogel layer on the polymer membrane surface. This dense Alg / M hydrogel layer restricts the permeation of amphiphilic surfactants, preventing direct contact with the hydrophobic substrate and thus preventing membrane wetting. Furthermore, due to the difference in affinity or interaction between water molecules / small molecule volatile organic compounds and the highly crosslinked hydrophilic Alg / M hydrogel network, efficient separation of water and volatile organic compounds can be achieved. Secondly, the hydrogel composite membrane prepared by this invention exhibits excellent long-term fouling resistance, anti-wetting properties, and efficient volatile organic compound retention when treating high-salt wastewater containing surfactants, surfactant-stabilized oil-water emulsions, and volatile organic compounds, without sacrificing the permeation flux of the original hydrophobic base membrane. In addition, the hydrophilic coating material used in this invention is the non-toxic, environmentally friendly, and low-cost natural polysaccharide Alg. The hydrogel composite membrane is prepared using a simple and easy-to-operate coating-drying-ionic crosslinking method, which is more green, economical, and environmentally friendly than other processes, facilitating scale-up and industrial production. Attached Figure Description

[0035] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0036] Figure 1 This is an electron microscope image of the original polytetrafluoroethylene film surface in Example 1 of the present invention;

[0037] Figure 2 This is an electron microscope image of the Alg / Fe hydrogel composite film surface in Example 1 of the present invention;

[0038] Figure 3 This is an electron microscope image of the cross-section of the Alg / Fe hydrogel layer in Example 1 of the present invention;

[0039] Figure 4 This is a normalized flux and effluent conductivity diagram of the polytetrafluoroethylene membrane and Alg / Fe hydrogel composite membrane in Example 1 of the present invention.

[0040] Figure 5 This is a normalized flux and rejection rate diagram of the polyvinylidene fluoride membrane and Alg / Al hydrogel composite membrane in Example 3 of the present invention.

[0041] Figure 6 This is a graph showing the phenol rejection rate of the polytetrafluoroethylene membrane and Alg / Al hydrogel composite membrane in Example 4 of the present invention. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] All raw materials used in this invention were purchased through commercial channels.

[0045] Unless otherwise specified, the operating temperature in the embodiments of the present invention is room temperature.

[0046] Example 1

[0047] A method for preparing an Alg / M hydrogel composite membrane includes the following steps:

[0048] (1) Dopamine and polyethyleneimine were dissolved in Tris-HCl buffer solution to obtain an activation solution, wherein the concentration of dopamine and polyethyleneimine in the activation solution was 2 mg / mL, the concentration of Tris-HCl buffer solution was 50 mmol / L, and the pH was 8. Then, the upper surface of the polytetrafluoroethylene membrane was brought into contact with the activation solution, and after standing for 12 hours, the membrane was thoroughly rinsed and allowed to dry naturally to obtain a hydrophilic modified polytetrafluoroethylene membrane;

[0049] (2) Add 3gAlg to 97g deionized water and stir to dissolve, to obtain an Alg pregel solution with a mass fraction of 3%, and then pour it onto the surface of the hydrophilic modified polytetrafluoroethylene membrane prepared in step 1), and use a scraper with a gap of 100 micrometers to coat it evenly. After coating evenly, place it at room temperature to dry for 1 hour to obtain an Alg pregel composite membrane.

[0050] (3) Dissolve anhydrous ferric chloride (FeCl3) completely in deionized water to obtain a 0.3 mol / L FeCl3 ion crosslinking solution; then immerse the Alg pregel layer of the Alg pregel modified composite membrane obtained in step (2) into the obtained FeCl3 ion crosslinking solution. After crosslinking for 1 hour, an Alg / Fe hydrogel layer is formed. Then, pour off the excess ionic liquid and thoroughly rinse the membrane surface with deionized water to obtain an Alg / Fe hydrogel composite membrane.

[0051] Technical effect

[0052] The surface and cross-section of the original polytetrafluoroethylene membrane used in Example 1 and the resulting Alg / Fe hydrogel composite membrane were characterized using scanning electron microscopy.

[0053] Figure 1 This is an electron microscope image of the original polytetrafluoroethylene film. Figure 2 Here is a surface electron microscope image of the obtained Alg / Fe hydrogel composite film. Figure 3 This is an electron microscope image of a cross-section of the Alg / Fe hydrogel layer.

[0054] Depend on Figure 1-3 It can be seen that the original polytetrafluoroethylene membrane exhibits a porous morphology with network fiber nodules. In contrast, the obtained Alg / Fe hydrogel composite membrane shows a dense and smooth surface. The electron micrograph of the cross section shows that the thickness of the Alg / Fe hydrogel layer is about 2.87 micrometers.

[0055] The membrane performance was tested using a direct contact membrane distillation apparatus. A solution containing 3.5 wt.% sodium chloride and 0.4 mmol / L sodium dodecyl sulfate surfactant was used as the feed liquid, and the temperature was set to 65°C. The permeate side was deionized water, and the temperature was set to 20°C. Changes in the mass and conductivity of the permeate side were monitored in real time to test the antiwetting performance of the Alg / Fe hydrogel composite membrane prepared in Example 1.

[0056] Figure 4 This is a graph showing the normalized flux and effluent conductivity of a polytetrafluoroethylene (PTFE) membrane and an Alg / Fe hydrogel membrane. Figure 4 It can be seen that when treating salt solutions containing high concentrations of surfactants, the normalized flux of the original PTFE membrane remained relatively stable over 24 hours, but the effluent conductivity of the original PTFE membrane surged to 4870 μS / cm. In contrast, the normalized flux and effluent conductivity of the Alg / Fe hydrogel composite membrane remained relatively stable for up to 120 hours, and its effluent conductivity remained very low at only 2.65 μS / cm after 120 hours. This indicates that the Alg / Fe hydrogel composite membrane has excellent anti-wetting properties.

[0057] Example 2

[0058] The difference from Example 1 is that the anhydrous ferric chloride (FeCl3) in step (3) is replaced with an equal amount of anhydrous ferric sulfate (Fe2(SO4)3).

[0059] Example 3

[0060] A method for preparing an Alg / M hydrogel composite membrane includes the following steps:

[0061] (1) Tannic acid and 3-aminopropyltriethoxysilane were dissolved in Tris-HCl buffer solution to obtain an activation solution. The concentrations of tannic acid and 3-aminopropyltriethoxysilane in the activation solution were both 2 mg / mL, the concentration of Tris-HCl buffer solution was 50 mmol / L, and the pH was 8. The upper surface of the polyvinylidene fluoride membrane was brought into contact with the activation solution, and after standing for 24 hours, the membrane was thoroughly rinsed and allowed to dry naturally to obtain a hydrophilic modified polyvinylidene fluoride membrane.

[0062] (2) Add 3gAlg to 97g deionized water and stir to dissolve to obtain 3%Alg pregel solution. Then, spray it onto the surface of the hydrophilic modified polyvinylidene fluoride membrane obtained in step 1), wherein the spray gun pressure is 0.5MPa, the spray gun is perpendicular to the membrane surface for 10cm, the spray thickness is 5μm, and then place it in an oven to dry at 30℃ for 1 hour to obtain Alg pregel composite membrane.

[0063] (3) Dissolve anhydrous aluminum chloride (AlCl3) fully in deionized water to obtain 0.3 mol / L AlCl3 ion crosslinking solution. Then, immerse the Alg pregel layer of the Alg pregel modified composite membrane obtained in step (2) into the obtained AlCl3 ion crosslinking solution. After crosslinking for 4 hours, an Alg / Al hydrogel layer is formed. Then, pour off the excess ionic liquid and rinse the membrane surface thoroughly with deionized water to finally obtain the Alg / Al hydrogel composite membrane.

[0064] The membrane performance was tested using a direct contact membrane distillation apparatus. A solution containing 3.5% sodium chloride, 1 g / L mineral oil, and 0.1 mmol / L sodium dodecyl sulfate surfactant was used as the feed liquid, with the temperature set at 65°C. The permeate side was deionized water, with the temperature set at 20°C. Changes in the mass and conductivity of the permeate side were monitored in real time. The fouling resistance and antiwetting properties of the Alg / Al hydrogel composite membrane prepared in Example 3 were tested.

[0065] Figure 5 This is a graph showing the normalized flux and rejection rate of the polyvinylidene fluoride membrane and the Alg / Al hydrogel composite membrane. Figure 5 It can be seen that when treating oil-water emulsion salt solutions with surfactant-stable properties, the normalized flux of the original polyvinylidene fluoride membrane decreased to 0.35 and the salt rejection rate decreased to 82.37% after 30 hours, while the normalized flux and rejection rate of the Alg / Al hydrogel composite membrane remained basically stable for up to 120 hours, and its salt rejection rate was still as high as 99.99%. This indicates that the Alg / Al hydrogel composite membrane has both excellent antifouling and antiwetting properties.

[0066] Example 4

[0067] A method for preparing an Alg / M hydrogel composite membrane includes the following steps:

[0068] (1) Dopamine and polyethyleneimine were dissolved in Tris-HCl buffer solution to obtain an activation solution. The concentrations of dopamine and polyethyleneimine in the activation solution were 2 mg / mL and 4 mg / mL, respectively. The concentration of Tris-HCl buffer solution was 100 mmol / L and the pH was 8.5. The upper surface of the polytetrafluoroethylene membrane was brought into contact with the activation solution. After standing for 8 hours, the membrane was thoroughly rinsed and allowed to dry naturally to obtain a hydrophilic modified polytetrafluoroethylene membrane.

[0069] (2) Add 4gAlg to 96g deionized water and stir to dissolve to obtain 4%Alg pregel solution. Then pour it onto the surface of the hydrophilic modified polytetrafluoroethylene membrane prepared in step (1) and coat it evenly with a scraper with a gap of 50 micrometers. After drying at room temperature for 2 hours, Alg pregel modified composite membrane is obtained.

[0070] (3) Dissolve anhydrous aluminum sulfate (Al2(SO4)3) fully in deionized water to obtain 0.5 mol / L Al2(SO4)3 ion crosslinking solution. Then, immerse the Alg pregel layer of the Alg pregel modified composite membrane obtained in step (2) into the obtained Al2(SO4)3 ion crosslinking solution. After crosslinking for 6 hours, an Alg / Al hydrogel layer is formed. Then, pour off the excess ionic liquid and rinse the membrane surface thoroughly with deionized water to finally obtain the Alg / Al hydrogel composite membrane.

[0071] The membrane performance was tested using a direct contact membrane distillation apparatus. A solution containing 3.5% sodium chloride and 100 ppm phenol was used as the feed liquid, and the temperature was set to 65°C. The permeate side was deionized water, and the temperature was set to 20°C. The phenol concentration in the permeate side solution was measured after a certain amount of permeate had accumulated. The volatile organic compound rejection rate of the Alg / Al hydrogel composite membrane prepared in Example 4 was tested.

[0072] Figure 6 This is a graph showing the phenol rejection rates of polytetrafluoroethylene (PTFE) membranes and Alg / Al hydrogel membranes. (Source: [Insert graph here]) Figure 6 It can be seen that when treating salt solutions containing volatile organic compounds such as phenol, the original polytetrafluoroethylene membrane has a phenol rejection rate of only 8.67%, while the Alg / Al hydrogel composite membrane has a phenol rejection rate as high as 99.52%. This indicates that the Alg / Al hydrogel composite membrane has the ability to efficiently retain volatile organic compounds.

[0073] Comparative Example 1

[0074] A method for preparing a PVA-coated composite film differs from Example 1 in that: the pregel solution in step (2) does not use Alg pregel solution, but uses polyvinyl alcohol (PVA) pregel solution. The PVA coating is prepared by traditional high-temperature chemical crosslinking and repeated freeze-thaw method. However, in Example 1, Alg pregel solution is cast onto the film surface and then dried / shrinked-rehydrated / crosslinked, which constructs the Alg / M hydrogel coating in a simpler and greener way.

[0075] Comparative Example 2

[0076] A method for preparing a PVA composite film differs from Example 1 in that the crosslinking agent in step (3) is polyacrylic acid (PAA) and glutaraldehyde (GA), and the PVA layer is crosslinked by heating in air at 100°C. However, in Example 1, Alg dry gel was impregnated with Fe... 3+ Alg / Fe hydrogels are formed at room temperature in ion-crosslinked solutions, and the reagents used are more environmentally friendly and economical, while the operating conditions are milder.

[0077] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing an Alg / M hydrogel composite membrane, characterized in that, Includes the following steps: (1) After surface activation and wetting of the hydrophobic microporous membrane with an activation solution, the hydrophobic microporous membrane is rinsed to obtain a hydrophilic modified hydrophobic microporous membrane. (2) The Alg pregel solution was uniformly coated on the hydrophilic modified hydrophobic microporous membrane and dried. Then, it was impregnated and cross-linked with an ionic cross-linking solution. After the reaction was completed, it was rinsed to obtain the Alg / M hydrogel composite membrane. The hydrophobic microporous membrane mentioned in step (1) includes one of polytetrafluoroethylene, polyvinylidene fluoride, polypropylene and their composite materials; The activation solution is obtained by dissolving an activator and an auxiliary agent in a buffer solution, wherein the concentration of the activator in the activation solution is 0.2-5 mg / mL and the concentration of the auxiliary agent is 0.2-5 mg / mL; The buffer solution is a Tris-HCl buffer solution with a concentration of 5-100 mmol / L and a pH of 6-10. The activator is dopamine or tannic acid; The auxiliary agent is polyethyleneimine or 3-aminopropyltriethoxysilane; When the activator is dopamine, the auxiliary agent is polyethyleneimine; When the activator is tannic acid, the auxiliary agent is 3-aminopropyltriethoxysilane.

2. The method for preparing an Alg / M hydrogel composite membrane according to claim 1, characterized in that, The activation and immersion time in step (1) is 4-24 hours.

3. The method for preparing an Alg / M hydrogel composite membrane according to claim 1, characterized in that, The mass concentration of the Alg pregel solution in step (2) is 1-8%; The ion crosslinking solution is an aqueous solution of a polyvalent metal salt, wherein the concentration of metal ions is 0.1-1 mol / L; The polyvalent metal salt is one or any combination of calcium chloride, calcium sulfate, copper chloride, copper sulfate, aluminum chloride, aluminum sulfate, ferric chloride, and ferric sulfate.

4. The method for preparing an Alg / M hydrogel composite membrane according to claim 1, characterized in that, The drying process described in step (2) is either air drying or drying at 25-45℃. The crosslinking time is 0.5-24h.

5. The Alg / M hydrogel composite membrane prepared by the method for preparing an Alg / M hydrogel composite membrane according to any one of claims 1-4.

6. The application of the Alg / M hydrogel composite membrane as described in claim 5 in membrane distillation process.

Images