A method for preparing a virus-removing cellulose membrane based on a bio-based solvent and in-situ cross-linking and a product thereof

Abstract

The application provides a preparation method of a virus-removing cellulose membrane based on a bio-based solvent and in-situ cross-linking and a product thereof, and the preparation method comprises the following steps: dissolving cellulose acetate with a bio-based solvent to prepare a cellulose acetate solution; mixing the cellulose acetate solution with tannic acid and a metal salt in sequence to prepare a casting solution; coating the casting solution on a support after defoaming, immersing in a coagulation bath for non-solvent induced phase inversion, and peeling off from the support after solidification to obtain the virus-removing cellulose membrane. In the application, a green bio-based solvent is used to replace a traditional toxic solvent to prepare the cellulose acetate membrane, and health hazards and environmental pollution are eliminated from the source; in combination with an in-situ cross-linking strategy, the high-throughput and high-virus retention rate are synergistically improved, the tensile strength and elongation at break are significantly improved compared with those of a traditional membrane, and the strict working condition requirements of high-pressure differential filtration and repeated steam sterilization are met.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, specifically relating to a method for preparing a virus-removing cellulose membrane based on a bio-based solvent and in-situ crosslinking, and the resulting product. Background Technology

[0002] Cellulose acetate is abundant and possesses advantages such as renewability, strong hydrophilicity, and good biocompatibility, making it widely used in microfiltration, ultrafiltration, nanofiltration, and even blood purification. Virus-removing membranes based on cellulose acetate are key consumables for removing pathogens such as parvoviruses and prions in downstream biopharmaceutical purification processes. Currently, mainstream virus-removing cellulose acetate membrane products worldwide are generally prepared using petroleum-based toxic solvents such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone. These solvents exhibit reproductive toxicity, hepatotoxicity, and potential carcinogenicity, seriously threatening the health of operators. Furthermore, they present problems such as volatile organic solvent emissions and high recycling costs, increasingly becoming a bottleneck for the green transformation of the industry.

[0003] At the same time, traditional virus-removing cellulose acetate membranes still face the following technical contradictions: (1) It is difficult to balance virus retention and flux: In order to improve the virus retention rate, it is often necessary to sacrifice membrane porosity or thicken the dense skin layer, resulting in a significant decrease in pure water flux and filtration efficiency. (2) Insufficient mechanical properties and hydrophilicity decay: The mechanical strength and tensile strength are low, and it is easy to compact, deform or even break during high pressure differential filtration, multiple steam sterilization and long-term operation; during use, due to molecular chain segment rearrangement and hydrophobic groups migrating to the surface, the hydrophilicity gradually decays, which leads to the intensification of adsorption of pollutants such as proteins on the membrane surface, resulting in structural densification, faster flux decay, increased cleaning frequency and shortened membrane service life. (3) Poor stability and complicated steps of traditional modification processes: The main means of hydrophilization or crosslinking modification of cellulose acetate membranes in the existing technology are surface coating, layer-by-layer self-assembly or post-treatment crosslinking after the finished membrane is soaked. Such post-processing methods, on the one hand, introduce additional steps due to the complexity of the process, prolonging the production cycle and increasing the risk of batch-to-batch inconsistency; on the other hand, the modified layer only adheres to the membrane surface and surface pore walls, and is easily detached or lost during long-term use, chemical cleaning and steam sterilization, resulting in a gradual degradation of retention performance and anti-fouling performance. (4) Color pollution of traditional metal cross-linked membranes: After introducing some metal ions into the membrane material, the membrane exhibits a distinctly dark appearance, which poses two major concerns in the fields of biomedicine and food processing. Dark membrane materials may be misjudged as containing impurities or degradation products, reducing user acceptance; trace metal ions may dissolve when in contact with liquids for a long time, introducing additional metal residue verification burden and potential biosafety risks.

[0004] Therefore, there is an urgent need for a method to construct a uniform cross-linked network through in-situ cross-linking using a green solvent system, which can be applied to a virus-removing cellulose acetate ultrafiltration membrane with high virus rejection rate, high filtration flux, high mechanical strength, and is completely green. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing a virus-removing cellulose membrane based on bio-based solvents and in-situ crosslinking, and the product thereof. This invention aims to solve the following core technical problems: (1) Replacing traditional toxic solvents with green bio-based solvents to eliminate health hazards and environmental pollution at the source, and to achieve green manufacturing of virus-removing membranes. (2) Constructing a uniform crosslinking network through in-situ crosslinking of the membrane body, and controlling the porosity and thickness of the crosslinking network to balance virus rejection rate and pure water flux. (3) Constructing a stable crosslinking network inside the membrane body without sacrificing the inherent biocompatibility of cellulose acetate, significantly improving the mechanical strength, flexibility and long-lasting hydrophilicity of the membrane from a structural perspective, so as to adapt to the harsh working conditions of high pressure differential operation and repeated sterilization cycles. (4) Moving the crosslinking modification from the "surface" to the "body", and achieving in-situ crosslinking through process simplification, so that the crosslinking network is uniformly distributed throughout the entire membrane thickness direction, ensuring that the rejection capacity, hydrophilicity and mechanical strength have long-term stability and consistency, and without the need for additional post-processing steps. (5) Use colorless or light-colored metal ions to construct a tannic acid-metal crosslinking network. While ensuring the crosslinking enhancement and hydrophilicity effect, the resulting membrane product has a light yellow to nearly colorless appearance, eliminating the risk of color pollution and metal ion residue, and broadening its applicability in fields such as medical devices where appearance and cleanliness are strictly required.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a virus-removing cellulose membrane based on a bio-based solvent and in-situ crosslinking. The preparation method includes: dissolving cellulose acetate in a bio-based solvent to prepare a cellulose acetate solution; mixing the cellulose acetate solution sequentially with tannic acid and a metal salt to prepare a casting solution; degassing the casting solution and coating it onto a support, immersing it in a coagulation bath for solvent-induced phase transformation, and then peeling it off from the support after solidification to obtain the virus-removing cellulose membrane.

[0007] This invention uses green bio-based solvents to replace traditional toxic solvents in the preparation of cellulose acetate membranes, eliminating health hazards and environmental pollution at the source. By directly adding tannic acid and metal ions to the casting solution, a three-dimensional cross-linked network uniformly distributed throughout the membrane is constructed in situ using the confinement effect of polymer chains during phase inversion. This single coating-phase inversion process replaces the traditional multi-step surface modification process involving surface coating and post-immersion cross-linking, significantly simplifying the production process, shortening the cycle time, and improving batch-to-batch consistency. Thanks to the effective confinement of cellulose acetate molecular chain movement and nanoscale control of membrane pore structure by the bulk cross-linked network, the membrane product achieves a synergistic improvement in high flux and high virus rejection rate. Tensile strength and elongation at break are significantly improved compared to traditional cellulose acetate membranes, meeting the stringent requirements of high-pressure differential filtration and repeated steam sterilization. The residual phenolic hydroxyl groups in the cross-linked network endow the membrane surface with durable hydrophilicity and antifouling ability, effectively mitigating flux decay during use, extending membrane life, and reducing cleaning frequency and operating costs. The internal cross-linked network structure is stable, avoiding the potential biosafety risks of trace ion leaching, and has multiple comprehensive advantages such as green manufacturing, simplified process, high performance and appearance applicability.

[0008] The Hansen solubility parameter of the bio-based solvent is well-matched with cellulose acetate, enabling it to dissolve cellulose acetate under mild conditions and form a homogeneous solution with molecular-level dispersion. Tannic acid dissolves in the cellulose acetate solution, and the phenolic hydroxyl groups of tannic acid undergo hydrogen bonding with the hydroxyl and acetyl groups on the cellulose acetate chains, resulting in a uniform distribution between the polymer chains. Subsequently, metal ions are slowly added dropwise under low-speed stirring to coordinate with the tannic acid molecules. However, due to the confinement effect and steric hindrance of the tannic acid macromolecular chains, the cross-linking reaction is restricted to the nanoscale, forming only uniformly dispersed oligomeric tannic acid-metal complex nanoparticles without forming macroscopic gel precipitation. The resulting casting solution exhibits good fluidity and homogeneity, with no precipitation after standing, allowing for smooth film coating. Upon immersion in the coagulation bath, polymer solidification and liquid-liquid phase separation occur rapidly as non-solvent water diffuses into the casting solution and solvent exchanges outwards. In this process, tannic acid-metal nanoparticles are "frozen" within a solidified cellulose acetate matrix. Simultaneously, due to localized concentration increases and pH gradient induction, further coordination or hydrogen bonding occurs between particles and between particles and cellulose acetate chains, ultimately forming a semi-interpenetrating three-dimensional cross-linked network across the entire membrane thickness, rather than being limited to the surface. This cross-linked network effectively restricts stress relaxation and swelling of the tannic acid molecular chains, significantly improving the membrane's tensile strength and pressure resistance. The residual phenolic hydroxyl groups of the tannic acid molecules endow the membrane surface with durable hydrophilicity and resistance to protein contamination. Product color can be controlled by metal ions, avoiding color contamination, while the ions themselves possess certain antibacterial properties, facilitating long-term humid storage. By precisely controlling the ratio and total amount of tannic acid and metal ions, the cross-linking density can be adjusted at the nanoscale, thereby controlling the effective pore size and its distribution, achieving efficient retention of virus particles (20-30 nm) while maintaining high throughput.

[0009] Preferably, the bio-based solvent includes γ-valerol and / or dihydro-L-glucanone.

[0010] γ-Valactone, derived from lignocellulose biomass through catalytic conversion, possesses excellent properties such as low toxicity, high boiling point, non-flammability, and biodegradability. It can completely dissolve cellulose acetate and prepare porous membranes via a solvent-inducible phase inversion method. Dihydro-L-glucanone, derived from cellulose pyrolysis, has solubility parameters close to those of N-methylpyrrolidone and is non-mutagenic, exhibiting excellent solubility for various polymers. This invention utilizes γ-valactone and dihydro-L-glucanone to dissolve cellulose acetate, constructing a stable cross-linked network within the membrane matrix. This approach balances virus rejection rate and pure water flux, significantly improving mechanical strength.

[0011] Preferably, the bio-based solvent includes γ-valerolactone and dihydro-L-glucanone.

[0012] The present invention preferably uses a combination of γ-valerolactone and dihydro-L-glucanone to dissolve cellulose acetate. The two have a synergistic effect, and the binary bio-based solvent system can achieve precise control of solvent volatility, avoiding excessively rapid evaporation and skin formation or excessively slow phase separation caused by a single solvent.

[0013] Preferably, the mass ratio of γ-valerolactone to dihydrolevulinolone is (1~9):(9~1).

[0014] The specific point values ​​in (1~9) can be 1, 2, 3, 4, 5, 6, 7, 8, 9, etc.

[0015] The specific point values ​​in (9~1) can be 9, 8, 7, 6, 5, 4, 3, 2, 1, etc.

[0016] Preferably, the mass ratio of γ-valerolactone to dihydrolevulinolone is (3~5):(7~5).

[0017] The specific point values ​​in (3~5) can be 3, 3.2, 3.5, 3.7, 4, 4.3, 4.5, 4.8, 5, etc.

[0018] The specific point values ​​in (7~5) can be 7, 6.8, 6.5, 6.3, 6, 5.7, 5.5, 5.2, 5, etc.

[0019] Preferably, the dissolution temperature is 25~60℃, for example, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, etc.; the time is 12~24 h, for example, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, etc.

[0020] Preferably, the cellulose acetate is dried before use.

[0021] Preferably, the drying temperature is 50~60℃, for example, 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, etc.; the drying time is 12~24 h, for example, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h, 24 h, etc.

[0022] Preferably, the metal salt is an anhydrous metal salt.

[0023] Preferably, the metal salt includes inorganic metal salts and / or organic metal salts.

[0024] Preferably, the metal inorganic salt includes any one or a combination of at least two of metal chlorides, metal nitrates, or metal sulfates.

[0025] Preferably, the organometallic salt includes any one or a combination of at least two of metal lactates, metal acetates, or metal tartrates.

[0026] Preferably, the degree of esterification of the cellulose acetate is 2.2 to 2.8, for example, it can be 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, etc.

[0027] Preferably, the concentration of the cellulose acetate solution is 10-20 wt%, for example, it can be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, etc.

[0028] Preferably, the tannic acid accounts for 1 to 8 wt% of the mass of cellulose acetate, for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, etc.

[0029] Preferably, the molar ratio of the tannic acid to the metal ion in the metal salt is 1:(0.3~2).

[0030] The specific point values ​​in (0.3~2) can be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.5, 1.8, 2, etc.

[0031] Preferably, the metal ions in the metal salt include any one or a combination of at least two of aluminum ions, zinc ions, zirconium ions, or titanium ions.

[0032] Preferably, the metal ions include aluminum ions and / or zinc ions.

[0033] Preferably, the metal ions include aluminum ions and zinc ions.

[0034] The present invention preferably uses a combination of aluminum ions and zinc ions, which have a synergistic effect and can better regulate the crosslinking network.

[0035] Preferably, the molar ratio of aluminum ions to zinc ions is (1~10):(1~10).

[0036] The specific point values ​​in the first (1~10) can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.

[0037] The specific point values ​​in the second (1~10) can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.

[0038] Preferably, the process of mixing with the metal salt includes: adding the aluminum salt first and then adding the zinc salt; or, adding the zinc salt first and then adding the aluminum salt.

[0039] In this invention, the order in which metal salts are added affects the structural distribution of the three-dimensional cross-linked network.

[0040] Preferably, the thickness of the casting solution coated on the support is 100~400 μm, for example, it can be 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, etc.

[0041] Preferably, the coagulation bath comprises 1-20 wt% of a bio-based solvent aqueous solution, such as 1 wt%, 2 wt%, 5 wt%, 7 wt%, 10 wt%, 13 wt%, 15 wt%, 18 wt%, 20 wt%, etc., or deionized water.

[0042] Preferably, the temperature of the non-solvent-induced phase transition is 4~40℃, for example, it can be 4℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, etc.

[0043] Preferably, the stripping process further includes a purification step.

[0044] Preferably, the purification includes soaking the stripped membrane in water for 24 to 48 hours, for example, 24 hours, 27 hours, 30 hours, 35 hours, 40 hours, 43 hours, 45 hours, 48 ​​hours, etc.

[0045] Preferably, the casting solution also includes a pore-forming agent.

[0046] Preferably, the pore-forming agent accounts for 1 to 30 wt% of the mass of cellulose acetate, for example, it can be 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, etc.

[0047] Other specific point values ​​within the range of the above values ​​can be selected, and will not be elaborated on here.

[0048] Preferably, the pore-forming agent comprises any one or a combination of at least two of polyethylene glycol, polyvinylpyrrolidone, or glycerol.

[0049] In a second aspect, the present invention provides a virus-removing cellulose membrane prepared by the preparation method described in the first aspect.

[0050] Compared with the prior art, the present invention has the following beneficial effects: Using green bio-based solvents to replace traditional toxic solvents in the preparation of cellulose acetate membranes eliminates health hazards and environmental pollution at the source. By directly adding tannic acid and metal ions to the casting solution, a three-dimensional cross-linked network uniformly distributed in the membrane body is constructed in situ using the confinement effect of polymer chains during phase inversion. This single coating-phase inversion process replaces the traditional multi-step surface modification process involving surface coating and post-immersion cross-linking, significantly simplifying the production process, shortening the cycle time, and improving batch-to-batch consistency.

[0051] Thanks to the effective restriction of cellulose acetate molecular chain movement and nanoscale control of membrane pore structure by the bulk cross-linking network, the membrane product achieves a synergistic improvement in high flux and high virus rejection rate. Tensile strength and elongation at break are significantly improved compared to traditional cellulose acetate membranes, meeting the stringent requirements of high-pressure differential filtration and repeated steam sterilization. Residual phenolic hydroxyl groups in the cross-linking network endow the membrane surface with durable hydrophilicity and antifouling capabilities, effectively mitigating flux decay during use, extending membrane lifespan, and reducing cleaning frequency and operating costs. The stable internal cross-linking network structure avoids the potential biosafety risks of trace ion leaching, combining multiple advantages such as green manufacturing, simplified processes, high performance, and aesthetic applicability. Attached Figure Description

[0052] Figure 1 A scanning electron microscope image of the surface structure of the virus-free cellulose membrane provided in Example 1; Figure 2 The image shows a scanning electron microscope image of the cross-sectional structure of the virus-free cellulose membrane provided in Example 1. Detailed Implementation

[0053] To further illustrate the technical means and effects of the present invention, the following describes the technical solution of the present invention in conjunction with preferred embodiments of the present invention. However, the present invention is not limited to the scope of the embodiments.

[0054] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0055] Cellulose acetate was purchased from Beijing Innocare Technology Co., Ltd., model A66697, with an acetyl content of 39.8 wt% and a degree of esterification of 2.45. Before use, the cellulose acetate was vacuum-dried at 55°C for 18 hours to completely remove moisture.

[0056] Example 1 This embodiment provides a virus-removing cellulose membrane, the preparation method of which includes: γ-valerol and dihydro-L-glucanone were mixed in a mass ratio of 4:6 as a solvent. Dry cellulose acetate was placed in the solvent and stirred at 45°C for 16 h to prepare a 15 wt% cellulose acetate solution. Tannic acid (3 wt% of the cellulose acetate mass) was added to the cellulose acetate solution and stirred until completely dissolved. Anhydrous aluminum chloride was added dropwise first, followed by anhydrous zinc chloride (tannic acid, aluminum ions, zinc ions molar ratio 1:0.5:0.5) under low-speed stirring, and stirring was continued for 2 h to obtain a homogeneous and stable casting solution. The solution was allowed to stand for 4 h to remove bubbles. A 250 μm casting solution was scraped onto a glass plate using a doctor blade and then immediately immersed in 15°C deionized water for phase inversion. After membrane formation, it was peeled off and soaked in deionized water for 36 h, with the water changed every 8 h, to obtain a virus-free cellulose membrane. The surface structure scanning electron microscope image is shown below. Figure 1 As shown, the cross-sectional structure scanning electron microscope image is as follows: Figure 2 As shown.

[0057] Example 2 This embodiment provides a virus-removing cellulose membrane, the preparation method of which includes: γ-valerol and dihydro-L-glucanone were mixed in a mass ratio of 3:7 as a solvent. Dry cellulose acetate was placed in the solvent and stirred at 25°C for 24 h to prepare a 10 wt% cellulose acetate solution. Tannic acid (1 wt% of the cellulose acetate mass) was added to the cellulose acetate solution and stirred until completely dissolved. Anhydrous aluminum chloride was added dropwise first, followed by anhydrous zinc chloride (tannic acid, aluminum ions, zinc ions molar ratio 1:0.1:0.2), under low-speed stirring. Stirring was continued for 2 h to obtain a homogeneous and stable casting solution, which was then allowed to stand for 4 h to remove bubbles. A 250 μm casting solution was scraped onto a glass plate using a doctor blade and immediately immersed in deionized water at 25°C for phase inversion. After membrane formation, it was peeled off and soaked in deionized water for 48 h, with the water changed every 8 h, to obtain a virus-free cellulose membrane.

[0058] Example 3 This embodiment provides a virus-removing cellulose membrane, the preparation method of which includes: γ-valerol and dihydro-L-glucanone were mixed in a 5:5 mass ratio as a solvent. Dry cellulose acetate was placed in the solvent and stirred at 60°C for 12 h to prepare an 18 wt% cellulose acetate solution. 8 wt% tannic acid and 5 wt% PEG400 (by weight of cellulose acetate) were added to the cellulose acetate solution and stirred until completely dissolved. Anhydrous aluminum chloride was added dropwise under low-speed stirring, followed by anhydrous zinc chloride (tannic acid, aluminum ions, zinc ions molar ratio 1:1:1), and stirring continued for 2 h to obtain a homogeneous and stable casting solution. The solution was allowed to stand for 4 h to remove bubbles. A 250 μm casting solution was prepared by scraping it onto a glass plate and then immediately immersed in an aqueous solution containing 10 wt% bio-based solvent (γ-valerol and dihydro-L-glucanone mass ratio 5:5) at 4°C for phase inversion. After membrane formation, it was peeled off and soaked in deionized water for 24 h, with the water changed every 8 h, to obtain a virus-free cellulose membrane.

[0059] Example 4 This embodiment provides a virus-removing cellulose membrane, which differs from Embodiment 1 only in that: "adding anhydrous aluminum chloride first and then anhydrous zinc chloride (tannic acid, aluminum ions, and zinc ions in a molar ratio of 1:0.5:0.5)" is replaced with "adding anhydrous zinc chloride first and then anhydrous aluminum chloride (tannic acid, aluminum ions, and zinc ions in a molar ratio of 1:0.5:0.5)", while all other steps remain unchanged.

[0060] Example 5 This embodiment provides a virus-removing cellulose membrane, which differs from Embodiment 1 only in that: anhydrous aluminum chloride is not added, and the reduction is made up by anhydrous zinc chloride; all other steps remain unchanged.

[0061] Example 6 This embodiment provides a virus-removing cellulose membrane, which differs from Embodiment 1 only in that: anhydrous zinc chloride is not added, and the reduction is made up by anhydrous aluminum chloride; all other steps remain unchanged.

[0062] Example 7 This embodiment provides a virus-removing cellulose membrane, which differs from Embodiment 1 only in that: "adding anhydrous aluminum chloride first and then anhydrous zinc chloride (tannic acid, aluminum ions, and zinc ions in a molar ratio of 1:0.5:0.5)" is replaced with "adding anhydrous zirconium tetrachloride (tannic acid and zirconium ions in a molar ratio of 1:1)", while all other steps remain unchanged.

[0063] Example 8 This embodiment provides a virus-removing cellulose membrane, which differs from Embodiment 1 only in that: "adding anhydrous aluminum chloride first and then anhydrous zinc chloride (tannic acid, aluminum ions, and zinc ions in a molar ratio of 1:0.5:0.5)" is replaced with "adding anhydrous ferric chloride (tannic acid and ferric ions in a molar ratio of 1:1)", while all other steps remain unchanged.

[0064] Example 9 This embodiment provides a virus-removing cellulose membrane, which differs from Example 1 only in that "γ-valerolactone and dihydro-L-glucanone are mixed in a mass ratio of 4:6 as a solvent" is replaced with "γ-valerolactone and dihydro-L-glucanone are mixed in a mass ratio of 1:9 as a solvent", while the other steps remain unchanged.

[0065] Example 10 This embodiment provides a virus-removing cellulose membrane, which differs from Example 1 only in that "γ-valerolactone and dihydro-L-glucanone are mixed in a mass ratio of 4:6 as a solvent" is replaced with "γ-valerolactone and dihydro-L-glucanone are mixed in a mass ratio of 9:1 as a solvent", while the other steps remain unchanged.

[0066] Example 11 This embodiment provides a virus-removing cellulose membrane, which differs from Example 1 only in that γ-valerol is not added, and the reduction is made up by dihydro-L-glucanone, while the other steps remain unchanged.

[0067] Example 12 This embodiment provides a virus-removing cellulose membrane, which differs from Example 1 only in that: dihydro-L-glucanone is not added, and the reduction is made up by γ-valerol, while the other steps remain unchanged.

[0068] Example 13 This embodiment provides a virus-removing cellulose membrane, which differs from Example 1 only in that γ-valerolactone is replaced with an equal amount of δ-valerolactone, while the other steps remain unchanged.

[0069] Comparative Example 1 This comparative example provides a virus-removing cellulose membrane, which differs from Example 1 only in that "γ-valerolactone and dihydrolevulinolone mixed in a mass ratio of 4:6 as solvent" is replaced with "N,N-dimethylformamide as solvent", while all other steps remain unchanged.

[0070] Comparative Example 2 This comparative example provides a virus-removing cellulose membrane, which differs from Example 1 only in that "γ-valerolactone and dihydro-L-glucanone mixed in a mass ratio of 4:6 as solvent" is replaced with "N-methylpyrrolidone as solvent", while all other steps remain unchanged.

[0071] Comparative Example 3 This comparative example provides a virus-removing cellulose membrane, the preparation method of which includes: γ-valerol and dihydro-L-glucanone were mixed in a 4:6 mass ratio as a solvent. Cellulose acetate was placed in the solvent and stirred at 45°C for 16 h to prepare a 15 wt% cellulose acetate solution. The solution was then allowed to stand for 4 h to remove bubbles. A 250 μm layer of the cellulose acetate solution was scraped onto a glass plate using a spatula and then immediately immersed in 15°C deionized water for phase inversion. After membrane formation, it was peeled off and soaked in deionized water for 36 h, with the water changed every 8 h, to obtain a virus-free cellulose membrane.

[0072] Test Example 1 The virus-removing cellulose membranes provided in Examples 1-13 and Comparative Examples 1-3 were subjected to the following tests: (1) After pre-compression at 25°C and 0.1 MPa, the pure water flux was measured; (2) A 1.0 g / L BSA (molecular weight approximately 66 kDa) solution was prepared in PBS with a pH of 7.4, and the BSA rejection rate was measured; (3) PP7 bacteriophage (particle size 20-30 nm) was used as a model virus with a titer of approximately 10 7 PFU / mL, after filtration, the filtrate titer was determined by the double-layer agar method, the LRV was calculated, and the phage retention capacity was evaluated; (4) the tensile strength and elongation at break of the wet sample were determined by the universal testing machine; (5) the water contact angle was determined by the water droplet method.

[0073] Table 1 The test results are shown in Table 1: The pure water flux of the virus-removing cellulose membrane prepared in this invention is 115~182 L / (m²). 2 •h•bar), the retention rate of bovine serum albumin is 86.3~97.8%, the logarithmic removal rate (LRV) of PP7 mode phage is ≥4.0, the tensile strength is 3.4~5.4 MPa, the elongation at break is 20.3~29.3%, and the surface static water contact angle is 50~62°.

[0074] As shown in Comparative Examples 1-3, this invention, starting with a bio-based solvent and combining "tannic acid + metal ions" to construct a three-dimensional cross-linked network, has significant advantages over traditional organic solvent systems. It balances various properties such as pure water flux, retention capacity, mechanical strength, and hydrophilicity, effectively avoiding the introduction of colored substances. Metal ions are stably immobilized in the cross-linked network, resulting in an extremely low risk of precipitation. Examples 9-13 show that γ-valerolactone and dihydro-L-glucanone in the bio-based solvent can construct a stable cross-linked network. Examples 4-8 demonstrate that metal ions further influence the construction of the cross-linked network.

[0075] This invention illustrates, through the above embodiments, a method for preparing a virus-removing cellulose membrane based on a bio-based solvent and in-situ crosslinking, and the resulting product. However, this invention is not limited to the above embodiments, meaning that it does not necessarily depend on them for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials, additions of auxiliary components, and selection of specific methods, etc., all fall within the scope of protection and disclosure of this invention.

[0076] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0077] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A method for preparing a virus-removing cellulose membrane based on a bio-based solvent and in-situ crosslinking, characterized in that, The preparation method includes: dissolving cellulose acetate in a bio-based solvent to prepare a cellulose acetate solution; mixing the cellulose acetate solution with tannic acid and a metal salt in sequence to prepare a casting solution; degassing the casting solution and coating it onto a support, immersing it in a coagulation bath for solvent-induced phase transformation, and then peeling it off from the support after solidification to obtain the virus-removing cellulose membrane.

2. The preparation method according to claim 1, characterized in that, The bio-based solvents include γ-valerolactone and / or dihydrolevulinone; Preferably, the bio-based solvent includes γ-valerolactone and dihydro-L-glucanone; Preferably, the mass ratio of γ-valerolactone to dihydrolevulinolone is (1~9):(9~1); Preferably, the mass ratio of γ-valerolactone to dihydrolevulinolone is (3~5):(7~5).

3. The preparation method according to claim 1 or 2, characterized in that, The dissolution temperature is 25~60℃, and the time is 12~24 h.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The degree of esterification of the cellulose acetate is 2.2~2.8; Preferably, the concentration of the cellulose acetate solution is 10-20 wt%.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The tannins comprise 1-8 wt% of the mass of cellulose acetate. Preferably, the molar ratio of the tannic acid to the metal ion in the metal salt is 1:(0.3~2).

6. The preparation method according to any one of claims 1 to 5, characterized in that, The metal salt contains any one or a combination of at least two of aluminum ions, zinc ions, zirconium ions, or titanium ions. Preferably, the metal ions include aluminum ions and / or zinc ions; Preferably, the metal ions include aluminum ions and zinc ions; Preferably, the molar ratio of aluminum ions to zinc ions is (1~10):(1~10).

7. The preparation method according to any one of claims 1 to 6, characterized in that, The thickness of the casting solution coated on the support is 100~400 μm; Preferably, the coagulation bath comprises 1-20 wt% of a bio-based solvent aqueous solution or deionized water; Preferably, the temperature of the non-solvent-induced phase transformation is 4~40℃.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The process after stripping also includes a purification step; Preferably, the purification includes soaking the stripped membrane in water for 24-48 hours.

9. The preparation method according to any one of claims 1 to 8, characterized in that, The casting solution also includes a pore-forming agent; Preferably, the pore-forming agent accounts for 1-30 wt% of the mass of cellulose acetate. Preferably, the pore-forming agent comprises any one or a combination of at least two of polyethylene glycol, polyvinylpyrrolidone, or glycerol.

10. The virus-removing cellulose membrane prepared by any one of claims 1 to 9.

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