Preparation method of a biological macromolecule bridged alginate solvent-resistant gel membrane

Abstract

The application provides a preparation method of a biological macromolecule bridged alginate salt solvent-resistant gel membrane, selects biological macromolecule blended sodium alginate as a membrane casting liquid, coats the membrane on a non-woven fabric, and then immerses the non-woven fabric in a crosslinking agent solution containing metal ion salt to crosslink and form a membrane, so as to obtain a biological macromolecule bridged alginate salt gel membrane; the application utilizes the physical and chemical action between the biological macromolecule and the alginate salt to change the polymer network structure and improve the crosslinking degree, so that the membrane pore structure is more compact and stable, the gel membrane with high flux, good solvent resistance and strong mechanical property is obtained, and the gel membrane has wide application prospects in solute separation and solvent recovery in various organic solvent systems.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, and in particular relates to a method for preparing a biomacromolecule-bridged alginate solvent-resistant gel membrane. Background Technology

[0002] Traditional methods for separating and purifying organic solvents, such as distillation and extraction, are not only energy-intensive and costly but also prone to secondary pollution. To address the excessive energy consumption and environmental pollution associated with organic solvent purification, organic solvent nanofiltration membranes, capable of separating solutes and recovering solvents in organic solvent systems, have seen rapid development. Organic solvent nanofiltration membranes offer advantages such as energy efficiency and high separation efficiency, providing significant benefits for the purification and recovery of organic solvents in industries such as petrochemicals, pharmaceuticals, and dyeing.

[0003] Nanofiltration membrane materials suitable for organic solvent systems typically include inorganic materials and solvent-resistant polymers. Among them, inorganic materials such as ceramics and silicates possess excellent thermal and chemical stability, but suffer from drawbacks such as high brittleness, high preparation costs, demanding preparation conditions, and large molecular weight cutoffs. In contrast, polymer materials, due to their superior flexibility and plasticity, show greater promise in nanofiltration membrane fabrication. Although some polymer materials, such as polyetheretherketone, polytetrafluoroethylene, polypropylene, and polyethylene terephthalate, are inherently solvent-resistant, their poor solubility, complex film-forming conditions, low flux, and uncontrollable pore size after film formation make them almost unsuitable for preparing high-precision separation membranes. Therefore, the research of novel membrane materials has always been a top priority.

[0004] Hydrogels possess a three-dimensional cross-linked polymer network structure, exhibiting good hydrophilicity, flexibility, and tunable porosity, making them an emerging material for nanofiltration membrane preparation. Sodium alginate, a natural high-molecular polymer material, is a linear anionic polysaccharide isolated from brown algae and other algae. The hydrophilic hydroxyl and carboxyl groups distributed on its main chain endow sodium alginate with strong hydrophilicity. Furthermore, sodium alginate exhibits excellent in-situ gelation properties, water solubility, and biocompatibility. Typically, divalent cations such as calcium ions are used to cross-link sodium alginate to form loose nanofiltration membranes with pore sizes ranging from 2-4 nm. However, single-ion cross-linked alginate gel membranes have weak ionic bonds and a simple network structure, resulting in poor internal gel structure stability. The "eggshell" model indicates that cations bind to sodium alginate polymer blocks in a planar two-dimensional manner, with the degree of binding increasing with increasing ionic radius. Larger ionic radii (Ba...)... 2+ 0.135nm, Sr 2+(0.112nm) can fill more space between sodium alginate polymer blocks, resulting in a more compact arrangement of alginate polymers. Sodium alginate gel membranes have a simple network structure, and their use in organic solvent purification usually causes some degree of swelling on the membrane surface. Doping with polymers and nanomaterials can help improve the network cross-linking structure of the gel membrane, thereby enhancing its structural stability. However, nanomaterials are usually expensive and prone to self-polymerization, making them unsuitable for large-scale production.

[0005] Therefore, it is necessary to provide a new gel membrane to overcome the shortcomings of the existing technology and make it applicable to 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 solvent-resistant gel membrane of alginate bridged by biomacromolecules. The technical problems to be solved are low flux, complex membrane formation conditions, unstable pore structure, easy swelling, and poor solvent resistance of traditional organic solvent nanofiltration membranes.

[0007] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0008] A method for preparing a biomacromolecule-bridged alginate solvent-resistant gel membrane includes the following steps:

[0009] a) Slowly add sodium alginate to deionized water, ultrasonically disperse for 5-20 min and magnetically stir for 30-60 min, then blend with biomacromolecules and stir for 6-24 h. Let the resulting solution stand for 12-24 h to remove bubbles and obtain a homogeneous casting solution, in which the mass percentage of sodium alginate is 1-50% and the mass percentage of biomacromolecules is 0.01-20%.

[0010] b) Add two or more metal ion salts to deionized water to prepare a crosslinking agent solution, wherein the mass percentage of the metal ion salts is 0.1-40%;

[0011] c) Pour the casting solution obtained in step a) evenly onto the nonwoven fabric, and use a coating rod with a thickness of 10-2000 μm to apply the coating solution at a speed of 1-10 cm·s. -1 The casting solution is spread evenly at a certain speed, and then left in the air for 1-600 seconds. The nonwoven fabric coated with the film is then immersed in the crosslinking agent solution prepared in step b) for 1-120 minutes to crosslink, thereby obtaining a biomacromolecule-bridged alginate solvent-resistant gel membrane.

[0012] Preferably, the method further includes step d), in which the biomacromolecule-bridged alginate solvent-resistant gel membrane obtained in step c) is immersed in deionized water for 2-8 hours to clean uncrosslinked ions. After cleaning, the membrane is immersed in deionized water and stored at 4-10°C for later use. Before use, the membrane is immersed in ethanol for 1-5 minutes to remove residual moisture in the pores.

[0013] Preferably, in step a), the biomacromolecule is one or more of the following: tannic acid, caffeic acid, chitosan, cyclodextrin, catechol, cysteine, histidine, β-indoleylalanine, dopamine, and norepinephrine.

[0014] Preferably, in step a), sodium alginate is slowly added to deionized water and ultrasonically dispersed for 8-12 min and stirred for 50-60 min, then the biomolecules are blended and stirred for 12-14 h. The resulting solution is allowed to stand for 12-13 h to remove bubbles, resulting in a homogeneous casting solution; the mass percentage of sodium alginate is 1.5-4%; and the mass percentage of biomolecules is 0.05%-1.5%.

[0015] Preferably, in step b), the metal ion salt is a mixture of two or more of calcium salts, iron salts, copper salts, zinc salts, magnesium salts, and barium salts; wherein the calcium salt is one or more of calcium chloride, calcium sulfate, calcium nitrate, calcium phosphate, and calcium acetate; the iron salt is one or more of ferric chloride, ferric sulfate, ferric carbonate, ferric nitrate, and ferric phosphate; the copper salt is one or more of copper chloride, copper sulfate, copper carbonate, copper iodide, and copper nitrate; the zinc salt is one or more of zinc chloride, zinc iodide, zinc sulfate, and zinc nitrate; the magnesium salt is one or more of magnesium chloride, magnesium sulfate, and magnesium nitrate; and the barium salt is one or more of barium chloride and barium nitrate.

[0016] Preferably, in step b), the mass percentage of the metal ion salt is 0.2-4%.

[0017] Preferably, the metal ion salts are calcium chloride and ferric chloride, and the mass fraction of calcium chloride is 2-3% and the mass fraction of ferric chloride is 0.1-0.3%.

[0018] Alternatively, the metal ion salts may be barium chloride and copper chloride, with calcium chloride having a mass fraction of 2-3% and copper chloride having a mass fraction of 0.5-1.5%.

[0019] Alternatively, the metal salt ions may be calcium nitrate, copper nitrate, and ferric nitrate, with the mass fraction of calcium nitrate being 2-3%, copper nitrate being 1-2%, and ferric nitrate being 0.1-0.3%.

[0020] Alternatively, the metal salt ions may be calcium chloride and magnesium chloride, with the mass fraction of calcium chloride being 2-3% and the mass fraction of magnesium chloride being 0.5-1.5%.

[0021] Preferably, in step c), the nonwoven fabric is one of polypropylene nonwoven fabric or polyethylene terephthalate nonwoven fabric.

[0022] Preferably, in step c), the casting solution obtained in step a) is uniformly poured onto the nonwoven fabric, and a coating rod with a thickness of 500-1000 μm is used to coat it at a speed of 2-5 cm·s. -1 The casting solution is spread evenly at a certain speed, and then left to stand in the air for 2-10 seconds. The nonwoven fabric coated with the film is then immersed in the crosslinking agent solution prepared in step b) for 2-5 minutes to crosslink, thereby obtaining a biomacromolecule-bridged alginate solvent-resistant gel membrane.

[0023] This invention also provides the utilization of the gel membrane prepared by the method described above in solute separation and solvent recovery in organic solvent systems, wherein the organic solvent is a dye or drug with a molecular weight greater than 450 Da present in methanol, ethanol, or isopropanol; preferably, the dye includes one or a mixture of several of Congo Red, Acid Cadmium Blue K, Direct Black 38, Coomassie Brilliant Blue R250, Reactive Red 2, Acid Red 66, Victoria Blue, Acid Fuchs Red, Bengal Rose Red, and Eosin Y; the drug includes one or a mixture of several of Vitamin B12, folic acid, oxytetracycline, tetracycline, tetracycline hydrochloride, penicillin-streptomycin, erythromycin, cefaclor, amoxicillin, azithromycin, and benzathine penicillin.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] This invention provides a method for preparing a biomacromolecule-bridged alginate solvent-resistant gel membrane. The method involves forming a gel membrane with high mechanical strength and solvent resistance by bridging biomacromolecules with hydrogel on a nonwoven fabric. Using a nonwoven fabric as the support layer, a polymer framework composed of sodium alginate and biomacromolecules as the film-forming material, and an aqueous solution of various metal ions as a crosslinking agent, a one-step phase inversion reaction yields the biomacromolecule-bridged alginate solvent-resistant gel membrane. This membrane can be used within an operating pressure range of 0.1-1 MPa. This method is simple to prepare, has low production costs, and is suitable for solute separation and solvent recovery in various organic solvent systems.

[0026] Biomolecular materials (tannic acid, chitosan, dopamine, etc.) contain a large number of hydrophilic groups. These materials can promote the internal cross-linking reaction of alginate gels through hydrogen bonding, van der Waals forces, Schiff bases and Michael addition reactions. They are more suitable for bridging to gel network structures to form stable and dense gel structures and improve membrane performance.

[0027] Single-ion crosslinked alginate gel membranes exhibit weak ionic bonds and a simple network structure, resulting in poor internal gel structure stability. The "eggshell" model indicates that cations bind to sodium alginate polymer blocks in a planar, two-dimensional manner, with the degree of binding increasing with increasing ionic radius (Ba). 2+ 0.135nm, Sr 2+ A crosslinking particle size of 0.112 nm can fill more of the space between sodium alginate polymer blocks, resulting in a more compact arrangement of the alginate polymers. Crosslinking with two or more ions helps control the crosslinking rate of the gel membrane, increases the degree of crosslinking, and enhances its structural stability.

[0028] In the membrane fabrication process, this invention controls the gel crosslinking rate through co-crosslinking with multiple metal ions, thereby achieving crosslinking of the internal structure of the gel and improving the membrane pore structure; non-woven fabric is selected as a support layer to enhance the mechanical properties of the membrane; biomacromolecules bridge alginate to improve the single network structure of the gel membrane, increase the degree of crosslinking, and enhance solvent resistance.

[0029] The membrane preparation method of this invention is simple, the membrane formation speed is fast, the membrane flux is high, the separation efficiency is high, and the solvent resistance is strong. It has promising applications in solute separation and solvent recovery in organic solvents.

[0030] This invention utilizes the physical and chemical interactions between biomacromolecules and alginate to alter the polymer network structure and increase the degree of crosslinking, resulting in a more compact and stable membrane pore structure and a gel membrane with high flux, good solvent resistance, and strong mechanical properties. Attached Figure Description

[0031] Figure 1 These are scanning electron microscope (SEM) images of gel films with different tannic acid doping levels in Example 1; where Ca / FeSA(a), TA 0.0625 -Ca / FeSA(b), TA 0.125 -Ca / FeSA(c), TA 0.1875 -Ca / FeSA(d), TA 0.25 -Ca / FeSA(e), where the subscript of TA indicates the mass percentage of tannic acid, in percentages (%).

[0032] Figure 2 These are surface energy dispersive X-ray images of gel films with different tannic acid doping levels in Example 1; where Ca / FeSA(h), TA 0.125 -Ca / FeSA(i), where the subscript of TA is the mass percentage of tannic acid, in %.

[0033] Figure 3 Images showing the surface roughness of gel films with different tannic acid doping levels in Example 1: Ca / FeSA(a), TA 0.125 -Ca / FeSA(b);

[0034] Figure 4 Images of water contact angles on the surface of gel films with different tannic acid doping amounts in Example 1 (a) and Zeta potentials on the surface of gel films with different tannic acid doping amounts (b).

[0035] Figure 5 Pore ​​size distribution (a) and tensile properties (b) of gel films with different tannic acid doping amounts in Example 1.

[0036] Figure 6 TA in Example 1 0.125 - The retention performance of Ca / FeSA membrane for dyes (a) and drugs (b) in ethanol. The subscript of TA is the mass percentage of tannic acid, in %;

[0037] Figure 7 TA in Example 1 0.125 -Ca / FeSA membrane. Ca / FeSA membrane flux tests for different solvents. The subscript of TA is the mass percentage of tannic acid, in %;

[0038] Figure 8 The relationship between membrane flux and solvent parameters in Example 1 is shown in δ. p,s MVs -1 ηs -1 . Detailed Implementation

[0039] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0040] The present invention will be described in detail below with reference to the embodiments.

[0041] Example 1

[0042] a) Slowly add 2.5% sodium alginate to deionized water, ultrasonically disperse for 10 min and stir for 60 min, then slowly add 0.125% tannic acid, stir for 12 h, and let the resulting solution stand for 12 h to remove bubbles, thus obtaining a homogeneous casting solution.

[0043] b) Add 2.5% calcium chloride and 0.2% ferric chloride by mass to deionized water to prepare a crosslinking agent solution;

[0044] c) Pour the casting solution obtained in step a) evenly onto polyethylene terephthalate nonwoven fabric, and use a coating rod with a thickness of 500 μm at a speed of 3 cm·s. -1The casting solution is spread evenly at a certain speed, then left to stand in the air for 2 seconds. It is then placed together with the nonwoven fabric into the crosslinking agent solution prepared in step b) and soaked for 5 minutes to carry out ionic crosslinking.

[0045] d) The gel membrane obtained in step c) was immersed in deionized water for 2 hours to wash away uncrosslinked ions, resulting in a tannic acid-bridged alginate solvent-resistant gel membrane. This membrane exhibited a flux of 48.97 L·m⁻¹ to a 0.05 g / L Congo red anhydrous ethanol solution. -2 ·h -1 ·bar -1 The Congo red rejection rate reached 97.2%, the breaking strength was 3.6 MPa, and the tensile length was 57%.

[0046] The flux and rejection rate of Congo red in ethanol solution with a mass concentration of 0.05 g / L were verified after the gel membrane prepared above was immersed in different reagents for different times.

[0047] Table 1. Flux and Congo red rejection rate of the membrane in Example 1 after immersion in different solvents for different times in a 0.05 g / L Congo red ethanol solution.

[0048]

[0049] To verify the performance of the gel membrane, gel membranes with different tannic acid contents were prepared. Except for the different tannic acid contents, the preparation methods of the gel membranes with other contents were the same as those for the gel membranes with tannic acid content of 0.125% by mass. Among them, Ca / FeSA was a gel membrane without tannic acid.

[0050] Figure 1 These are scanning electron microscope (SEM) images of gel films with different tannic acid doping levels in Example 1; where Ca / FeSA(a), TA 0.0625 -Ca / FeSA(b), TA 0.125 -Ca / FeSA(c), TA 0.1875 -Ca / FeSA(d), TA 0.25 -Ca / FeSA(e), where TA is the mass percentage of tannic acid, expressed as %. The Ca / FeSA film has a smooth surface structure with no obvious granular protrusions and a dense pore structure. After adding tannic acid, as shown in Figures (b) and (c), the film surface structure becomes dense, and regularly sized dot-like protrusions appear. With the increase of tannic acid doping, the regularly sized dot-like protrusions gradually aggregate to form irregular granular polymers. As can be seen from Figures (f) and (g), compared to Ca / FeSA, TA... 0.125 - The Ca / FeSA membrane has a more uniform cross-sectional structure, exhibiting a sponge-like pore structure without stratification.

[0051] Figure 2The images show the surface dispersion X-ray images of gel films with different tannic acid doping levels in Example 1; where Ca / FeSA(h), TA 0.125 -Ca / FeSA(i), where the subscript of TA represents the mass percentage of tannic acid, expressed as %. Except for the difference in tannic acid content, the preparation methods for gel films with other contents are the same as those for films containing 0.125% tannic acid by mass. The film surface shows a uniform distribution of Ca, Fe, C, and O elements, indicating that Ca... 2+ Fe 3+ It can effectively and uniformly crosslink sodium alginate gel membranes. It is worth noting that TA... 0.125 The Ca / FeSA membrane shows more Fe, mainly due to the interaction of tannic acid with Fe. 3+ It is caused by a complexation reaction.

[0052] Figure 3 Images showing the surface roughness of gel films with different tannic acid doping levels in Example 1: Ca / FeSA(a), TA 0.125 -Ca / FeSA(b); Ca / FeSA,TA 0.125 The surface roughness Ra of the Ca / FeSA films are 8.51 nm and 14.80 nm, respectively. TA 0.125 -Ca / FeSA membranes have a higher surface roughness, which can effectively increase the effective filtration area of ​​the membrane.

[0053] Figure 4 Images (a) show the water contact angles of gel films with different tannic acid doping levels in Example 1, and (b) show the zeta potentials of the gel films with different tannic acid doping levels. Figure 4 As shown in (a), the Ca / FeSA membrane has a water contact angle of 28.3°, exhibiting good hydrophilicity. After adding tannic acid, the water contact angle on the membrane surface slightly increases. 0.25 The Ca / FeSA membrane achieved a water contact angle of 32.1°, primarily due to the tannins bridging the gel network structure with Fe. 3+ The formation of metal-linked phenolic complexes may result in a significant amount of these complexes on the membrane surface, and their hydrophilicity is slightly lower than that of alginate. However, overall, the gel membrane doped with tannic acid exhibits better hydrophilicity. Figure 4 As shown in (b), Ca / FeSA and TA were tested. 0.125 -Zeta potential of Ca / FeSA film. Ca / FeSA and TA 0.125 The Ca / FeSA membrane surface is negatively charged within the pH range of 10⁻³, and at pH = 7, the Ca / FeSA and TA membranes exhibit a uniform charge. 0.125The zeta potentials of the Ca / FeSA membrane are -10.22 mV and -7.82 mV, respectively. It can achieve good retention of negatively charged solutes through a combination of size sieving and the Donnan effect.

[0054] Figure 5 The images show the pore size distribution (a) and tensile properties (b) of gel films with different tannic acid doping levels in Example 1. Figure 5 As shown in (a), the maximum probability density pore size distribution of the Ca / FeSA film is around 1.03 nm. After TA doping, TA... 0.0625 -Ca / FeSA, TA 0.125 -The average pore size distribution of the Ca / FeSA membrane decreases to approximately 0.74 nm, and the TA 0.125 -Ca / FeSA films exhibit relatively high pore density. With increasing tannic acid doping concentration, TA... 0.1875 -Ca / FeSA, TA 0.25 The average pore size distribution of the Ca / FeSA membrane increased by approximately 1.03 and 1.21 nm, respectively, while the pore density gradually decreased. This is mainly because excessive tannins are prone to oxidative self-polymerization and react with Fe... 3+ Complexation leads to the formation of complex aggregates, which disrupts the gel membrane structure, resulting in uneven pore size distribution and decreased porosity. As shown in 5(b), the maximum tensile strength increases with increasing TA doping concentration, and the maximum tensile strength increases from 3.0 MPa for the Ca / FeSA membrane to [a higher value] for the TA membrane. 0.25 The 4.4 MPa of Ca / FeSA indicates that TA doping is beneficial for improving the rigidity of the gel film.

[0055] Figure 6 TA in Example 1 0.125 - The retention performance of Ca / FeSA membranes for dyes (a) and drugs (b) in ethanol, where TA is indicated by the mass percentage of tannic acid (%); For example... Figure 6 As shown in (a), T A0.125 The retention rates of the Ca / FeSA membrane for methyl orange, Acid Cadmium Blue K, Acid Red-66, Reactive Red 2, Congo Red, Direct Black-38, Methyl Blue, and Coomassie Brilliant Blue-R250 were 31.64%, 97.62%, 97.88%, 98.25%, 97.25%, 98.28%, 97.97%, and 85.25%, respectively. Figure 6 As shown in (b), TA 0.125 The Ca / FeSA membrane retained 95.9% of folic acid, 96.6% of tetracycline, 97.2% of oxytetracycline, and 98.7% of vitamin B12, respectively.

[0056] Figure 7 TA in Example 1 0.125-Ca / FeSA, Ca / FeSA membrane flux testing with different solvents; the subscript for TA indicates the mass percentage of tannic acid, in %; TA 0.125 The order of flux of the Ca / FeSA membrane for different solvents is as follows: methanol (107.73 L·m⁻¹). -2 ·h -1 ·bar -1 )> Acetone (88.15 L·m -2 ·h -1 ·bar -1 Acetonitrile (78.43 L·m) -2 ·h -1 ·bar -1 N,N-dimethylformamide (62.88 L·m) -2 ·h -1 ·bar -1 Tetrahydrofuran (56.55 L·m) -2 ·h -1 ·bar -1 )> Ethanol (46.64 L·m -2 ·h -1 ·bar -1 Isopropanol (20.26 L·m) -2 ·h -1 ·bar -1 > n-Hexane (2.61 L·m -2 ·h -1 ·bar -1 It consistently has a higher flux than Ca / FeSA membranes.

[0057] Figure 8 The relationship between membrane flux and solvent parameters in Example 1 is shown in δ. p,s MV s -1 η s -1 Clearly, the solute / solvent transport system in organic solvents is more complex than that in water systems. TA 0.125 -Ca / FeSA membrane solvent flux and δ p,s MV s -1 η s -1 (where δ) p,s MV s -1 η s -1 The parameters representing Hansen's solubility (molar volume, dynamic viscosity, etc.) show a strong linear relationship (R0). 2 =0.93585).

[0058] Example 2.

[0059] a) Slowly add 3% sodium alginate to deionized water, ultrasonically disperse for 10 min and stir for 50 min, then slowly add 1% catechol, stir for 14 h, let the resulting solution stand for 12 h to remove bubbles, and obtain a homogeneous casting solution.

[0060] b) Add 2.5% barium chloride and 1% copper chloride by mass to deionized water to prepare a crosslinking agent solution;

[0061] c) Pour the casting solution obtained in step a) evenly onto polyethylene terephthalate nonwoven fabric, and use a coating rod with a thickness of 1000 μm at a speed of 2 cm·s. -1 The casting solution is spread evenly at a certain speed, then left in the air for 10 seconds, and then placed together with the nonwoven fabric into the crosslinking agent solution prepared in step b) for 5 minutes to carry out ionic crosslinking.

[0062] d) The membrane obtained in step c) was immersed in deionized water for 2 hours to wash away uncrosslinked ions, resulting in a catechol-bridged alginate solvent-resistant gel membrane. This membrane exhibited a flux of 28.6 L·m³ for a 0.05 g / L Congo red anhydrous ethanol solution. -2 ·h -1 ·bar -1 The membrane exhibits a 98.3% rejection rate for Congo red. Rejections of Acid Cadmium Blue K, Acid Red-66, Reactive Red 2, Congo red, Direct Black-38, and Methylene Blue in anhydrous ethanol solutions are 98.2%, 98.5%, 98.8%, 97.7%, 99.0%, and 98.9%, respectively. Rejections of folic acid, tetracycline, oxytetracycline, and vitamin B12 in anhydrous ethanol solutions are 96.9%, 97.7%, 98.2%, and 99.2%, respectively. Furthermore, the membrane possesses a tensile strength of 4 MPa and a tensile length of 42%.

[0063] The flux and rejection rate of Congo red in ethanol solution with a mass concentration of 0.05 g / L were verified after the gel membrane prepared above was immersed in different reagents for different times.

[0064] Table 2. Flux and Congo red rejection rate of the membrane in Example 2 after immersion in different solvents for different times in a 0.05 g / L Congo red ethanol solution.

[0065]

[0066] Example 3.

[0067] a) Slowly add 2% sodium alginate to deionized water, ultrasonically disperse for 10 min and stir for 60 min, slowly add 0.5% chitosan, stir for 12 h, let the resulting solution stand for 12 h to degas, and obtain a homogeneous casting solution.

[0068] b) Add 3% calcium nitrate, 2% copper nitrate and 0.2% ferric nitrate by mass percentage to deionized water to prepare a crosslinking agent solution;

[0069] c) Pour the casting solution obtained in step a) evenly onto polyethylene terephthalate nonwoven fabric, and use a coating rod with a thickness of 750 μm at a speed of 5 cm·s. -1 The casting solution is spread evenly at a certain speed, then left to stand in the air for 10 seconds. It is then placed together with the nonwoven fabric into the crosslinking agent solution prepared in step b) and soaked for 4 minutes to carry out ionic crosslinking.

[0070] d) The membrane obtained in step c) was immersed in deionized water for 2 hours to wash away uncrosslinked ions, resulting in a chitosan-bridged alginate solvent-resistant gel membrane. This membrane exhibited a flux of 23.4 L·m³ to a 0.05 g / L Congo red anhydrous ethanol solution. -2 ·h -1 ·bar -1 The membrane exhibits a 98.7% rejection rate for Congo red. The rejection rates for Acid Cadmium Blue K, Acid Red-66, Reactive Red 2, Congo red, Direct Black-38, and Methylene Blue in anhydrous ethanol solutions are 98.5%, 98.9%, 99.2%, 98.2%, 99.4%, and 99.2%, respectively. The rejection rates for folic acid, tetracycline, oxytetracycline, and vitamin B12 in anhydrous ethanol solutions are 97.4%, 98.1%, 98.6%, and 99.7%, respectively. Furthermore, the membrane possesses a tensile strength of 4.2 MPa and a tensile length of 60%.

[0071] The flux and rejection rate of Congo red in ethanol solution with a mass concentration of 0.05 g / L were verified after the gel membrane prepared above was immersed in different reagents for different times.

[0072] Table 3. Flux and Congo red rejection rate of the membrane in Example 3 after immersion in different solvents for different times in a 0.05 g / L Congo red ethanol solution.

[0073]

[0074] Example 4.

[0075] a) Slowly add 3% sodium alginate to deionized water, ultrasonically disperse for 10 min and stir for 60 min, slowly add 1% dopamine, stir for 14 h, let the resulting solution stand for 12 h to degas, and obtain a homogeneous casting solution.

[0076] b) Add 2.5% calcium chloride and 1% magnesium chloride by mass to deionized water to prepare a crosslinking agent solution;

[0077] c) Pour the casting solution obtained in step a) evenly onto polyethylene terephthalate nonwoven fabric, and use a coating rod with a thickness of 1000 μm at a speed of 4 cm·s. -1 The casting solution is spread evenly at a certain speed, then left in the air for 10 seconds, and then placed together with the nonwoven fabric into the crosslinking agent solution prepared in step b) for 5 minutes to carry out ionic crosslinking.

[0078] d) The membrane obtained in step c) was immersed in deionized water for 2 hours to wash away uncrosslinked ions, resulting in a dopamine-bridged alginate solvent-resistant gel membrane. This membrane exhibited a flux of 17.8 L·m³ to a 0.05 g / L Congo red anhydrous ethanol solution. -2 ·h -1 ·bar -1 The membrane exhibits a 98.8% rejection rate for Congo red. The rejection rates for Acid Cadmium Blue K, Acid Red-66, Reactive Red 2, Congo red, Direct Black-38, and Methylene Blue in anhydrous ethanol solutions are 98.7%, 99.0%, 99.4%, 98.5%, 99.6%, and 99.5%, respectively. The rejection rates for folic acid, tetracycline, oxytetracycline, and vitamin B12 in anhydrous ethanol solutions are 97.4%, 98.3%, 98.8%, and 99.8%, respectively. The membrane has a tensile strength of 5.2 MPa and a tensile length of 48%.

[0079] The flux and rejection rate of Congo red in ethanol solution with a mass concentration of 0.05 g / L were verified after the gel membrane prepared above was immersed in different reagents for different times.

[0080] Table 4. Flux and Congo red rejection rate of the membrane in Example 4 after immersion in different solvents for different times for a concentration of 0.05 g / L Congo red in an ethanol solution.

[0081]

[0082] The above description is only a preferred embodiment of the present invention and is 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 within the protection scope of the present invention.

Claims

1. A method for preparing a biomacromolecule-bridged alginate solvent-resistant gel membrane, characterized in that: Includes the following steps, a) Slowly add sodium alginate to deionized water, ultrasonically disperse for 5-20 min, and magnetically stir for 30-60 min. Then, blend the biomacromolecules and stir for 6-24 h. Let the resulting solution stand for 12-24 h to remove bubbles and obtain a homogeneous casting solution. The mass percentage of sodium alginate is 1-50%, and the mass percentage of biomacromolecules is 0.01-20%. The biomacromolecules are one or more of the following: tannic acid, caffeic acid, chitosan, cyclodextrin, catechol, cysteine, histidine, β-indoleylalanine, dopamine, and norepinephrine. b) Add two or more metal ion salts to deionized water to prepare a crosslinking agent solution, wherein the mass percentage of the metal ion salt is 0.1-40%; wherein the metal ion salt is a mixture of two or more of calcium salt, iron salt, copper salt, zinc salt, magnesium salt, and barium salt. c) Pour the casting solution obtained in step a) evenly onto the nonwoven fabric, and use a coating rod with a thickness of 10-2000 μm to apply the coating solution at a speed of 1-10 cm·s. -1 The casting solution is spread evenly at a certain speed, and then left in the air for 1-600 seconds. The nonwoven fabric coated with the film is then immersed in the crosslinking agent solution prepared in step b) for 1-120 minutes to crosslink, thereby obtaining a biomacromolecule-bridged alginate solvent-resistant gel membrane.

2. The method for preparing a biomacromolecule-bridged alginate solvent-resistant gel membrane according to claim 1, characterized in that: It also includes step d), immersing the biomacromolecule-bridged alginate solvent-resistant gel membrane obtained in step c) in deionized water for 2-8 hours to clean uncrosslinked ions. After cleaning, the resulting membrane is immersed in deionized water and stored at 4-10℃ for later use. Before use, the membrane is immersed in ethanol for 1-5 minutes to remove residual moisture in the pores.

3. The method for preparing a biomacromolecule-bridged alginate solvent-resistant gel membrane according to claim 1 or 2, characterized in that: In step a), sodium alginate is slowly added to deionized water and ultrasonically dispersed for 8-12 min and stirred for 50-60 min. Then, biomolecules are blended and stirred for 12-14 h. The resulting solution is allowed to stand for 12-13 h to remove bubbles, resulting in a homogeneous casting solution. The mass percentage of sodium alginate is 1.5-4% and the mass percentage of biomolecules is 0.05%-1.5%.

4. The method for preparing a biomacromolecule-bridged alginate solvent-resistant gel membrane according to claim 1 or 2, characterized in that: In step b), the calcium salt is one or more of calcium chloride, calcium sulfate, calcium nitrate, calcium phosphate, and calcium acetate; the iron salt is one or more of ferric chloride, ferric sulfate, ferric carbonate, ferric nitrate, and ferric phosphate; the copper salt is one or more of copper chloride, copper sulfate, copper carbonate, copper iodide, and copper nitrate; the zinc salt is one or more of zinc chloride, zinc iodide, zinc sulfate, and zinc nitrate; the magnesium salt is one or more of magnesium chloride, magnesium sulfate, and magnesium nitrate; and the barium salt is one or more of barium chloride and barium nitrate.

5. The method for preparing a biomacromolecule-bridged alginate solvent-resistant gel membrane according to claim 1 or 2, characterized in that: In step b), the mass percentage of the metal ion salt is 0.2-4%.

6. The method for preparing a biomacromolecule-bridged alginate solvent-resistant gel membrane according to claim 4, characterized in that: The metal ion salts are calcium chloride and ferric chloride, with calcium chloride having a mass fraction of 2-3% and ferric chloride having a mass fraction of 0.1-0.3%. Alternatively, the metal ion salts may be barium chloride and copper chloride, with calcium chloride having a mass fraction of 2-3% and copper chloride having a mass fraction of 0.5-1.5%. Alternatively, the metal salt ions may be calcium nitrate, copper nitrate, and ferric nitrate, with the mass fraction of calcium nitrate being 2-3%, copper nitrate being 1-2%, and ferric nitrate being 0.1-0.3%. Alternatively, the metal salt ions may be calcium chloride and magnesium chloride, with the mass fraction of calcium chloride being 2-3% and the mass fraction of magnesium chloride being 0.5-1.5%.

7. The method for preparing a biomacromolecule-bridged alginate solvent-resistant gel membrane according to claim 1 or 2, characterized in that: In step c), the nonwoven fabric is one of polypropylene nonwoven fabric or polyethylene terephthalate nonwoven fabric.

8. The method for preparing a biomacromolecule-bridged alginate solvent-resistant gel membrane according to claim 1 or 2, characterized in that: In step c), the casting solution obtained in step a) is poured evenly onto the nonwoven fabric, and a coating rod with a thickness of 500-1000 μm is used to coat it at a speed of 2-5 cm·s. -1 The casting solution is spread evenly at a certain speed, and then left to stand in the air for 2-10 seconds. The nonwoven fabric coated with the film is then immersed in the crosslinking agent solution prepared in step b) for 2-5 minutes to crosslink, thereby obtaining a biomacromolecule-bridged alginate solvent-resistant gel membrane.

9. The use of the gel membrane prepared by the preparation method according to any one of claims 1-8 in solute separation and solvent recovery in an organic solvent system, wherein the organic solvent is a dye or drug with a molecular weight greater than 450 Da present in methanol, ethanol or isopropanol.

10. The application of the gel membrane according to claim 9 in solute separation and solvent recovery in organic solvent systems, characterized in that: The dyes include one or a mixture of several of the following: Congo Red, Acid Cadmium Blue K, Direct Black 38, Coomassie Brilliant Blue R250, Reactive Red 2, Acid Red 66, Victoria Blue, Acid Fuchsin, Bengal Rose Red, and Eosin Y; the drugs include one or a mixture of several of the following: Vitamin B12, folic acid, oxytetracycline, tetracycline, tetracycline hydrochloride, penicillin-streptomycin, erythromycin, cefaclor, amoxicillin, azithromycin, and benzathine penicillin.

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