Preparation method of composite polyelectrolyte solvent-resistant gel film based on electrostatic self-assembly

Abstract

The invention provides a preparation method of a composite polyelectrolyte solvent-resistant gel membrane based on electrostatic self-assembly, which comprises the following steps: by taking a non-woven fabric as a support layer, coating a layer of negatively charged polyelectrolyte on the non-woven fabric, crosslinking by metal ions to obtain a gel membrane, taking the gel membrane as a base membrane, and forming a positively charged polyelectrolyte layer on the base membrane through electrostatic self-assembly to obtain the composite polyelectrolyte solvent-resistant gel membrane based on electrostatic self-assembly. And crosslinking the composite layer through metal ions to obtain the composite polyelectrolyte solvent-resistant gel film based on electrostatic self-assembly. According to the invention, the pore structure and the charge property of the gel membrane are adjusted by regulating and controlling the interaction between positive and negative charge polyelectrolytes by utilizing a self-assembly method of electrostatic interaction, the tolerance of the gel membrane in an organic solvent is improved, and new functional characteristics (such as interface regulation and control, molecular recognition and the like) can be introduced into the membrane. The gel film prepared by the method has a wide application prospect in the aspects of solute separation and solvent recovery in various organic solvents.

Description

Technical Field

[0001] The invention belongs to the technical field of functional materials, and in particular relates to a method for preparing a composite polyelectrolyte solvent-resistant gel film based on electrostatic self-assembly. Background Art

[0002] The separation and purification of organic solvents are crucial steps in industrial production. Currently, separation methods primarily include evaporation, distillation, crystallization, and extraction. However, these techniques are not only energy-intensive and costly, but can also denature and render pharmaceutical proteins ineffective during heating. In contrast, organic solvent nanofiltration (OSN) is an emerging technology for molecular separation and solvent purification in organic solvents. The emergence of OSN not only significantly reduces the energy consumption of phase change separation methods but also prevents the degradation of heat-sensitive molecules during the separation process, offering promising applications for drug concentration and organic solvent purification.

[0003] At present, nanofiltration membrane materials used in organic solvent systems mainly include inorganic materials and polymer materials. Inorganic materials (such as ceramics and silica) have good chemical stability, but they have challenges such as high brittleness, high cost, and complex preparation process. Although polymer materials (such as polyetherimide, polyacrylonitrile, etc.) have the advantages of low density and easy processing, they will undergo physical aging when used in highly polar organic solvents, causing the polymer to swell or even dissolve, thereby leading to a decrease in membrane performance. Therefore, it is very important to develop a nanofiltration membrane that can be applied to organic solvent systems for a long time.

[0004] Polyelectrolytes (sodium alginate, polydopamine, tannic acid, etc.) are easily soluble in water and environmentally friendly. They can form high molecular polymers with a three-dimensional network structure through chemical or ionic crosslinking. Polyelectrolytes contain more hydrophilic functional groups, which can attract water molecules to quickly enter the network system to form a hydrogel. As the gel system absorbs water and expands, the molecular chains in the network extend into the three-dimensional space. During the extension process, they will reach a swelling equilibrium under the influence of molecular elastic contraction, thereby forming a gel film. Natural gel films have excellent properties such as low cost, non-toxicity, strong adhesion ability, and insolubility in most polar aprotic solvents, making them a potential material for preparing gel films resistant to organic solvents. Zhao Kongyin et al. used sodium alginate as a film-forming material and subjected it to Ca 2+Calcium alginate gel membranes are prepared by cross-linking and exhibit good membrane properties in aqueous systems [Journal of Membrane Science, 2015, 492:536-546]. However, calcium alginate gel membranes have a simple network structure and weak ionic bonding, which results in poor internal gel stability. Long-term use in organic solvents can cause changes in the original pore structure of the gel membrane. Self-assembly methods based on electrostatic interactions, which modulate the interactions between positively and negatively charged polyelectrolytes, can enhance the overall structural stability and tolerance of composite gel membranes in organic solvents. They can also introduce new functional properties (such as interface regulation and molecular recognition) to the membrane surface.

[0005] Therefore, a preparation method of a composite polyelectrolyte solvent-resistant gel membrane based on electrostatic self-assembly was proposed to overcome the shortcomings of existing nanofiltration membranes in organic solvent systems and make them suitable for solute separation and solvent recovery in organic solvent systems. Summary of the Invention

[0006] In view of this, the present invention aims to propose a method for preparing a composite polyelectrolyte solvent-resistant gel membrane based on electrostatic self-assembly, so as to solve the problems of traditional organic solvent nanofiltration membrane chemical cross-linking reagents being toxic, complex preparation process, poor stability of the internal gel structure of the alginate gel membrane, changes in the membrane pore structure, and easy swelling.

[0007] To achieve the aforementioned invention objectives, the implementation architecture of the technical route of this solution is as follows:

[0008] A method for preparing a composite polyelectrolyte solvent-resistant gel film based on electrostatic self-assembly, comprising the following steps:

[0009] a) slowly adding 1-20 g of a negatively charged polyelectrolyte to a beaker containing 50-100 mL of deionized water, stirring the mixture magnetically at 100-1000 rpm for 6-24 hours at room temperature, and then allowing the mixture to stand for 6-24 hours to degas, to obtain a homogeneous casting solution;

[0010] b) adding 2-20% by weight of a metal ion salt as an ionic crosslinking agent to deionized water;

[0011] c) The casting solution obtained in step a) is uniformly poured onto the non-woven fabric, and then a coating rod with a coating height of 50-2000 μm is used at a speed of 2-8 cm s -1 uniformly coating the casting solution on the non-woven fabric, and immediately immersing the non-woven fabric coated with the polyelectrolyte in the ionic crosslinking agent of step b) for 1-60 minutes to perform ionic crosslinking to obtain a negatively charged polyelectrolyte gel-based membrane;

[0012] d) slowly adding 1-10 g of a positively charged polyelectrolyte to a beaker containing 50-100 mL of deionized water, and magnetically stirring for 1-8 hours to obtain a positively charged polyelectrolyte aqueous solution;

[0013] e) preparing a metal ion salt aqueous solution with a mass fraction of 1-10% as an ionic crosslinking agent;

[0014] f) evenly pouring the positively charged polyelectrolyte aqueous solution obtained in step d) onto the negatively charged polyelectrolyte gel base film obtained in step c), allowing the solution to stand for 1-60 minutes for electrostatic self-assembly, rinsing with deionized water, and allowing the solution to stand in air for 1-10 minutes to obtain a polyelectrolyte composite layer;

[0015] g) evenly pouring the metal ion crosslinking agent obtained in step e) onto the composite polyelectrolyte gel membrane obtained in step f), and allowing the membrane to stand for 2-30 minutes for metal ion complexation reaction to obtain a composite polyelectrolyte solvent-resistant gel membrane based on electrostatic self-assembly, and soaking the membrane in deionized water for storage.

[0016] In step a), the negatively charged polyelectrolyte is one or more of sodium alginate, polyacrylic acid, sodium polystyrene sulfonate, polymethacrylic acid, lignin, tannic acid, tea polyphenols, gallic acid, cellulose acetate, carboxymethyl cellulose, polyvinyl alcohol, hyaluronic acid, anionic polyacrylamide, carrageenan, silk fibroin, heparin, and pectin.

[0017] In steps b) and e), the metal ion salt is one or more of magnesium chloride, magnesium sulfate, magnesium nitrate, calcium chloride, calcium sulfate, calcium nitrate, copper chloride, copper sulfate, copper nitrate, barium chloride, barium sulfate, barium nitrate, ferric chloride, ferric sulfate, and ferric nitrate.

[0018] In step d), the positively charged polyelectrolyte is one or more of chitosan, polydopamine, gelatin, cationic polyacrylamide, cationic guar gum, polyethyleneimine 200, polyethyleneimine 400, polyethyleneimine 600, polyethyleneimine 800, polyethyleneimine 1000, polyethyleneimine 2000, polyethyleneimine 4000, polyethyleneimine 10000, and polyethyleneimine 70000.

[0019] The present invention also provides a composite polyelectrolyte solvent-resistant gel membrane prepared using the above method, which is applied to drug separation and solvent recovery in a polar aprotic solvent system. The polar aprotic solvent includes: dimethyl sulfoxide, N,N-dimethylformamide, acetone, acetonitrile, tetrahydrofuran, ethyl acetate, methanol, ethanol, and isopropanol. The retained drugs include: sulfamethoxazole, vitamin B1, folic acid, bisphenol A, aspirin, tetracycline, oxytetracycline, amoxicillin, rifampicin, vitamin B12, cyclosporine A, vancomycin, penicillin G, oxacillin, erythromycin, azithromycin, roxithromycin, norfloxacin, ciprofloxacin, and levofloxacin, or a mixture of several of them.

[0020] Compared with the prior art, the main advantages of the present invention include:

[0021] A method for preparing a solvent-resistant composite polyelectrolyte gel membrane based on electrostatic self-assembly has been proposed. Using a non-woven fabric as a support layer, a negatively charged polyelectrolyte layer is coated on the non-woven fabric. The resulting gel membrane, cross-linked with metal ions, serves as a base membrane. A positively charged polyelectrolyte layer is deposited on the base membrane via electrostatic self-assembly and then cross-linked with metal ions to form a composite polyelectrolyte gel membrane. This gel membrane boasts a simple preparation process, non-toxic reagents, and low material cost. It exhibits good compatibility with drugs and a stable structure in organic solvents, making it suitable for the purification and solvent recovery of drug solutes in polar aprotic solvents.

[0022] The present invention uses metal ion cross-linked polyelectrolytes to prepare gel membranes. Compared with the existing chemical cross-linking method, this method can adjust the membrane pore structure in harsh and highly polar solvents and will not experience physical aging like polymer membranes.

[0023] The present invention regulates the interaction between positive and negative charged polyelectrolytes through the method of electrostatic self-assembly, ensures the close connection between the composite layers through the interaction of hydrogen bonds, electrostatic forces, ionic bonds, and van der Waals forces, and can regulate the complexation amount of the composite layers to control the membrane pore size, thereby giving the gel membrane the ability of selective screening while ensuring the membrane performance.

[0024] The polyelectrolytes used in the present invention are all insoluble in organic solvents, which ensures that the prepared composite gel film has good solvent resistance.

[0025] The preparation process of the invention is simple, the selected materials are non-toxic, the preparation cost is low, and it conforms to the concept of sustainable development. DETAILED DESCRIPTION

[0026] Unless otherwise specified, the technical terms used in the following examples have the same meanings as those understood by those skilled in the art. The experimental reagents used in these examples are all conventional biochemical reagents, and the experimental methods in the examples, unless otherwise specified, are based on conventional procedures.

[0027] The present invention is illustrated in detail by the following examples.

[0028] Example 1.

[0029] a) Slowly add 2.5 g of sodium alginate and 5 g of triacetin to a beaker containing 92.5 mL of deionized water, stir magnetically at 400 rpm for 12 h at room temperature, and then let stand for 8 h to degas to obtain a homogeneous casting solution;

[0030] b) adding 2.5% by mass of calcium chloride as an ionic crosslinking agent to deionized water;

[0031] c) The casting solution obtained in step a) was uniformly poured onto the non-woven fabric, and then a coating rod with a coating height of 500 μm was used at a speed of 4 cm s -1 The casting solution is applied to the non-woven fabric at a uniform speed, and the non-woven fabric coated with the sodium alginate layer is immediately immersed in the calcium chloride ion crosslinking agent of step b) for 5 minutes to perform ion crosslinking to obtain a calcium alginate gel base film;

[0032] d) adding 1 mL of glacial acetic acid to a beaker containing 99 mL of deionized water, stirring magnetically for 5 min, then slowly adding 0.2 g of chitosan, stirring magnetically for 3 h, to obtain a chitosan acetic acid aqueous solution;

[0033] e) preparing a 0.2% by mass ferric chloride aqueous solution as an ionic crosslinking agent;

[0034] f) evenly pouring the chitosan acetic acid aqueous solution obtained in step d) onto the calcium alginate gel base film obtained in step c), allowing it to stand for 1 minute for electrostatic self-assembly, rinsing it with deionized water, and allowing it to stand in air for 8 minutes to obtain a chitosan-calcium alginate composite gel film based on electrostatic self-assembly;

[0035] g) pouring the ferric chloride aqueous solution obtained in step e) onto the chitosan-calcium alginate composite gel membrane obtained in step f), and letting it stand for 5 minutes for iron ion complexation reaction to obtain an iron ion cross-linked chitosan-calcium alginate composite gel membrane, and soaking the membrane in deionized water for storage.

[0036] h) The iron ion cross-linked chitosan-calcium alginate composite gel membrane obtained according to the above steps was subjected to retention experiments of different drugs in an ethanol solvent system. The ethanol flux was 2.4 L·m -2 ·h -1 bar -1 The retention rates of tetracycline, oxytetracycline, rifampicin, folic acid, and vitamin B12 were all greater than 95%. After the gel membrane was immersed in acetonitrile, acetone, isopropanol, and N,N-dimethylformamide for 28 days, its ethanol flux was greater than 2 L·m -2 ·h -1bar -1 The retention rate of rifampicin in ethanol is greater than 90%.

[0037] In order to verify the performance of iron ion cross-linked chitosan-calcium alginate composite gel membrane, the effects of calcium alginate (CaSA) gel membrane and iron ion cross-linked chitosan-calcium alginate (FeCS) on the performance of iron ion cross-linked chitosan-calcium alginate composite gel membrane were investigated. 0.2 -CaSA) composite gel membrane morphology and pore size comparison.

[0038] Figure 1 The surface morphology (a), surface roughness (b), element distribution (c) and cross-sectional morphology (d) images of the CaSA gel film in Example 1; FeCS 0.2 -CaSA composite gel film surface morphology (e), surface roughness (f, i), element distribution (g) and cross-sectional morphology image (h); As shown in the figure, the surface morphology of the CaSA gel film is smooth, with a microporous structure, and C, O, and Ca elements are evenly distributed on the membrane surface. After the FeCS composite layer is deposited, the microporous structure on the surface of the CaSA gel film is covered, and the FeCS 0.2 -CaSA composite gel membrane has more uniform pore structure and smoother surface morphology.

[0039] Figure 2 For CaSA and FeCS in Example 1 0.2 -CaSA gel membrane surface zeta potential (a), the relationship between the retention rate of polyethylene glycol (PEG) with different molecular weights and the Stokes radius of PEG (b) and the pore size distribution (c); As shown in the figure, after the FeCS composite layer is deposited, FeCS 0.2 -CaSA composite gel membrane's negative charge capacity weakened, and the average membrane pore size distribution decreased from 0.75nm to 0.43nm.

[0040] Example 2.

[0041] a) Slowly add 10 g of polyvinyl alcohol to a beaker containing 100 mL of deionized water, stir magnetically at 500 rpm for 18 h at room temperature, and then let stand for 12 h to degas to obtain a homogeneous casting solution;

[0042] b) adding 5% by weight of zinc nitrate as an ionic crosslinking agent to deionized water;

[0043] c) The casting solution obtained in step a) was uniformly poured onto the non-woven fabric, and then a coating rod with a coating height of 1000 μm was used at a speed of 3 cm s -1 The casting solution is uniformly applied to the non-woven fabric, and the non-woven fabric coated with the polyvinyl alcohol layer is immediately immersed in the zinc nitrate ion crosslinking agent of step b) for 60 minutes for ion crosslinking to obtain a polyvinyl alcohol gel base film;

[0044] d) Slowly adding 5 g of polyethyleneimine 70000 to a beaker containing 100 mL of deionized water and stirring under magnetic stirring for 8 h to obtain a polyethyleneimine 70000 aqueous solution;

[0045] e) preparing a 5% by mass aqueous solution of ferric nitrate as an ionic crosslinking agent;

[0046] f) pouring the polyethyleneimine 70000 aqueous solution obtained in step d) onto the polyvinyl alcohol gel base film obtained in step c), allowing it to stand for 10 minutes for electrostatic self-assembly, rinsing it with deionized water, and allowing it to stand in air for 30 minutes to obtain a polyethyleneimine-polyvinyl alcohol composite gel film based on electrostatic self-assembly;

[0047] g) evenly pouring the ferric nitrate aqueous solution obtained in step e) onto the polyethyleneimine-polyvinyl alcohol composite gel membrane obtained in step f), allowing the membrane to stand for 30 minutes for iron ion complexation reaction to obtain an iron ion cross-linked polyethyleneimine-polyvinyl alcohol composite gel membrane, and soaking the membrane in deionized water for storage.

[0048] h) The iron ion cross-linked polyethyleneimine-polyvinyl alcohol composite gel membrane obtained in the above steps was subjected to retention experiments of different drugs in a methanol solvent system. The methanol flux was 5.2 L·m -2 ·h -1 bar -1 The retention rates of tetracycline, oxytetracycline, rifampicin, folic acid, and vitamin B12 were all greater than 92%. After the gel membrane was immersed in acetonitrile, acetone, isopropanol, and N,N-dimethylformamide for 28 days, its methanol flux was greater than 4 L·m -2 ·h -1 bar -1 The retention rate of rifampicin in methanol is greater than 90%.

[0049] Example 3.

[0050] a) 8 g of carboxymethyl cellulose was slowly added to a beaker containing 100 mL of deionized water, and the mixture was magnetically stirred at 600 rpm for 14 h at room temperature, followed by standing for 16 h to degas, to obtain a homogeneous casting solution;

[0051] b) adding 7% by weight of copper chloride as an ionic crosslinking agent to deionized water;

[0052] c) The casting solution obtained in step a) is uniformly poured onto the non-woven fabric, and then a coating rod with a coating height of 800 μm is used to coat the non-woven fabric at a speed of 5 cm·s -1 The casting solution is applied to the non-woven fabric at a uniform speed, and the non-woven fabric coated with the carboxymethyl cellulose layer is immediately immersed in the copper chloride ion crosslinking agent of step b) for 50 minutes for ion crosslinking to obtain a carboxymethyl cellulose gel-based membrane;

[0053] d) slowly adding 3 g of dopamine to a beaker containing 100 mL of deionized water and stirring magnetically for 3 h to obtain a polydopamine aqueous solution;

[0054] e) preparing a 10% by mass aqueous solution of barium chloride as an ionic crosslinking agent;

[0055] f) evenly pouring the polydopamine aqueous solution obtained in step d) onto the carboxymethyl cellulose gel-based membrane obtained in step c), allowing it to stand for 60 minutes for electrostatic self-assembly, rinsing it with deionized water, and allowing it to stand in air for 30 minutes to obtain a polydopamine-carboxymethyl cellulose composite gel membrane based on electrostatic self-assembly;

[0056] g) pouring the barium chloride aqueous solution obtained in step e) onto the polydopamine-carboxymethyl cellulose composite gel membrane obtained in step f), allowing it to stand for 20 minutes for ion complexation reaction to obtain a barium ion cross-linked polydopamine-carboxymethyl cellulose composite gel membrane, and soaking the membrane in deionized water for storage.

[0057] h) The barium ion cross-linked polydopamine-carboxymethyl cellulose composite gel membrane obtained in the above steps was subjected to retention experiments of different drugs in an isopropanol solvent system. The isopropanol flux was 1.8 L·m -2 ·h -1 bar -1 The retention rates of tetracycline, oxytetracycline, rifampicin, folic acid, and vitamin B12 were all greater than 95%. After the gel membrane was immersed in acetonitrile, acetone, isopropanol, and N,N-dimethylformamide for 28 days, its flux to isopropanol was greater than 1.5 L·m -2 ·h -1 bar -1 The retention rate of rifampicin in ethanol is greater than 88%.

[0058] Example 4.

[0059] a) Slowly add 6 g of carrageenan to a beaker containing 100 mL of deionized water, stir magnetically at 400 rpm for 12 h at room temperature, and then allow to stand for 12 h to degas to obtain a homogeneous casting solution;

[0060] b) adding 18% by weight of copper nitrate as an ionic crosslinking agent to deionized water;

[0061] c) The casting solution obtained in step a) was uniformly poured onto the non-woven fabric, and then a coating rod with a coating height of 1000 μm was used at a speed of 6 cm s -1The casting solution is uniformly applied to the non-woven fabric, and the non-woven fabric coated with the carrageenan layer is immediately immersed in the copper nitrate ion crosslinking agent of step b) for 60 minutes for ion crosslinking to obtain a carrageenan gel base film;

[0062] d) slowly adding 5 g of cationic polyacrylamide to a beaker containing 100 mL of deionized water, and magnetically stirring for 3 h to obtain a cationic polyacrylamide aqueous solution;

[0063] e) preparing a 10% by mass aqueous solution of ferric chloride as an ionic crosslinking agent;

[0064] f) evenly pouring the cationic polyacrylamide aqueous solution obtained in step d) onto the carrageenan gel base film obtained in step c), allowing it to stand for 30 minutes for electrostatic self-assembly, rinsing it with deionized water, and allowing it to stand in air for 20 minutes to obtain a cationic polyacrylamide-carrageenan gel composite gel film based on electrostatic self-assembly;

[0065] g) evenly pouring the ferric chloride aqueous solution obtained in step e) onto the cationic polyacrylamide-carrageenan gel composite gel membrane obtained in step f), allowing the membrane to stand for 30 minutes for ion complexation reaction to obtain an iron ion cross-linked cationic polyacrylamide-carrageenan gel composite gel membrane, and soaking the membrane in deionized water for storage.

[0066] h) The iron ion cross-linked cationic polyacrylamide-carrageenan gel composite gel membrane obtained in the above steps was subjected to retention experiments of different drugs in an ethanol solvent system. The ethanol flux was 2.1 L·m -2 ·h -1 bar -1 The retention rates of tetracycline, oxytetracycline, rifampicin, folic acid, and vitamin B12 were all greater than 94%. After the gel membrane was immersed in acetonitrile, acetone, isopropanol, and N,N-dimethylformamide for 28 days, its ethanol flux was greater than 1.5 L·m -2 ·h -1 bar -1 The retention rate of rifampicin in ethanol is greater than 90%.

[0067] The above contents are merely embodiments of the present invention with better effects and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a composite polyelectrolyte solvent-resistant gel film based on electrostatic self-assembly, characterized in that: The following steps are involved: a) slowly adding 1-20 g of negatively charged polyelectrolyte to a beaker containing 50-100 mL of deionized water, stirring magnetically for 6-24 hours, and then standing for 8-12 hours to degas, to obtain a homogeneous casting solution; b) adding 2-20% by weight of a metal ion salt as an ionic crosslinking agent to deionized water; c) The casting solution obtained in step a) is uniformly poured onto the non-woven fabric, and then a coating rod with a coating height of 50-2000 μm is used at a speed of 2-8 cm s -1 uniformly coating the casting solution on the non-woven fabric, and then immediately immersing the non-woven fabric coated with the negatively charged polyelectrolyte in the ionic crosslinking agent of step b) for 1-60 minutes to perform ionic crosslinking to obtain a negatively charged polyelectrolyte gel-based membrane; d) slowly adding 1-10 g of a positively charged polyelectrolyte to a beaker containing 50-100 mL of deionized water, and magnetically stirring for 1-8 hours to obtain a positively charged polyelectrolyte aqueous solution; e) preparing a metal ion salt aqueous solution with a mass fraction of 1-10% as an ionic crosslinking agent; f) evenly pouring the positively charged polyelectrolyte aqueous solution obtained in step d) onto the negatively charged polyelectrolyte gel base film obtained in step c), allowing the mixture to stand for 1-60 minutes for electrostatic self-assembly, rinsing with deionized water, and allowing the mixture to stand in air for 1-10 minutes to obtain a composite polyelectrolyte gel film; g) evenly pouring the metal ion crosslinking agent obtained in step e) onto the composite polyelectrolyte gel membrane obtained in step f), and allowing the membrane to stand for 2-30 minutes for metal ion complexation reaction to obtain a composite polyelectrolyte solvent-resistant gel membrane based on electrostatic self-assembly, and soaking the membrane in deionized water for storage.

2. The method for preparing a composite polyelectrolyte solvent-resistant gel film based on electrostatic self-assembly according to claim 1, characterized in that: In step a), the negatively charged polyelectrolyte is one or more of sodium alginate, polyacrylic acid, sodium polystyrene sulfonate, polymethacrylic acid, lignin, tannic acid, tea polyphenols, gallic acid, cellulose acetate, carboxymethyl cellulose, polyvinyl alcohol, hyaluronic acid, anionic polyacrylamide, carrageenan, silk fibroin, heparin, and pectin.

3. The method for preparing a composite polyelectrolyte solvent-resistant gel film based on electrostatic self-assembly according to claim 1, characterized in that: In steps b) and e), the metal ion salt is one or more of magnesium chloride, magnesium sulfate, magnesium nitrate, calcium chloride, calcium sulfate, calcium nitrate, copper chloride, copper sulfate, copper nitrate, barium chloride, barium sulfate, barium nitrate, ferric chloride, ferric sulfate, and ferric nitrate.

4. The method for preparing a composite polyelectrolyte solvent-resistant gel film based on electrostatic self-assembly according to claim 1, characterized in that: In step d), the positively charged polyelectrolyte is one or more of chitosan, polydopamine, gelatin, cationic polyacrylamide, cationic guar gum, polyethyleneimine 200, polyethyleneimine 400, polyethyleneimine 600, polyethyleneimine 800, polyethyleneimine 1000, polyethyleneimine 2000, polyethyleneimine 4000, polyethyleneimine 10000, and polyethyleneimine 70000. The composite polyelectrolyte gel membrane obtained by the preparation method according to any one of claims 1 to 4 is used for drug separation and solvent recovery in a polar aprotic solvent system. The polar aprotic solvent comprises: Dimethyl sulfoxide, N,N-dimethylformamide, acetone, acetonitrile, tetrahydrofuran, ethyl acetate, methanol, ethanol, isopropanol. Retained drugs include: sulfamethoxazole, vitamin B1, folic acid, bisphenol A, aspirin, tetracycline, oxytetracycline, amoxicillin, rifampicin, vitamin B12, cyclosporine A, vancomycin, penicillin G, oxacillin, erythromycin, azithromycin, roxithromycin, norfloxacin, ciprofloxacin, levofloxacin, or a mixture of several of them.

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