Preparation method and application of bacterial cellulose based modified forward osmosis membrane

Abstract

The invention provides a preparation method of a bacterial cellulose-based modified forward osmosis membrane, which comprises the following steps: S1, inoculating activated bacterial strains into a seed culture medium for culture to obtain a seed solution, and inoculating the seed solution into a fermentation culture medium for fermentation to obtain a bacterial cellulose membrane; s2, cleaning, purifying and drying the bacterial cellulose membrane obtained in the step S1; s3, carrying out a co-deposition reaction on the bacterial cellulose membrane treated in S2, chitosan and tannic acid in an aqueous solution system; s4, taking out the bacterial cellulose membrane obtained after the co-deposition reaction in S3, cleaning and drying to obtain a bacterial cellulose membrane with a chitosan and tannic acid intermediate layer; and S5, performing interfacial polymerization reaction on the bacterial cellulose membrane in the step S4 in an organic solvent, and drying after the reaction to obtain the bacterial cellulose based modified forward osmosis membrane with the middle layer. According to the invention, the use energy consumption is reduced, and good pollution resistance and long-period usability are shown in water treatment.

Description

Technical Field

[0001] The invention relates to the technical field of osmotic membrane preparation, in particular to a preparation method of a bacterial cellulose-based modified forward osmosis membrane and application thereof. Background Art

[0002] Membrane separation technology uses the selective permeability of natural or synthetic membranes to separate, grade, purify and other operations on different components in liquids. This process depends on the membrane characteristics, its pore size and the applied pressure difference. It can be applied to the separation of different substances according to the different membrane pore sizes. Forward osmosis (FO) technology is a membrane separation technology based on the osmotic pressure difference on both sides of the membrane as the driving force, which is different from traditional membrane technology. In this process, water molecules spontaneously migrate from the low osmotic pressure feed liquid (FS) to the high osmotic pressure draw liquid (DS) through the semipermeable membrane. There is no need to apply external pressure to drive the concentration process, so the energy consumption and cost are relatively low. In addition, since the osmotic pressure difference of FO itself can bring a greater driving force than other general pressure-driven membrane concentration processes, it has the advantage of producing high-concentration concentrates. FO can also be carried out at room temperature and atmospheric pressure, and shows a lower tendency to membrane fouling than pressure-driven membranes. Therefore, the FO process is increasingly used in seawater desalination, heavy metal concentration and recovery, drinking water preparation, seawater desalination, wastewater treatment and food processing.

[0003] A traditional method for preparing forward osmosis membranes. The manufacture of separation membranes relies on petrochemical-based polymers. In addition, the production of these membranes usually consumes a large amount of organic solvents. Therefore, traditional FO membranes rely on petroleum-based polymers (such as polyamide and polysulfone), which have two major defects:

[0004] During the use phase, 0.1-5μm microplastics are released, which harm human health through bioaccumulation;

[0005] The manufacturing process requires a large amount of organic solvents (such as NMP), which is not in line with the principles of green chemistry.

[0006] Therefore, there is an increasing need to develop a green and sustainable forward osmosis membrane manufacturing process to reduce the harm to the environment and human body. Summary of the invention

[0007] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for preparing a bacterial cellulose-based modified forward osmosis membrane and its application, which can solve the existing problems.

[0008] In order to achieve the above object, the technical solution of the present invention is as follows:

[0009] The present invention is achieved through the following technical solution: a method for preparing a bacterial cellulose-based modified forward osmosis membrane, comprising:

[0010] S1. Inoculate the activated bacterial strain into a seed culture medium for cultivation to obtain a seed solution, and then inoculate the seed solution into a fermentation culture medium for fermentation to obtain a bacterial cellulose membrane.

[0011] S2. Wash, purify, and dry the bacterial cellulose membrane obtained in S1.

[0012] S3. Conduct a co-deposition reaction on the bacterial cellulose membrane treated in S2 with chitosan and tannic acid in an aqueous solution system.

[0013] S4. Take out the bacterial cellulose membrane obtained after the co-deposition reaction in S3, wash it, and then dry it to obtain a bacterial cellulose membrane with a chitosan and tannic acid intermediate layer.

[0014] S5. Conduct an interfacial polymerization reaction on the bacterial cellulose membrane with a chitosan and tannic acid intermediate layer in S4 in an organic solvent, and dry it after the reaction to obtain a modified forward osmosis membrane based on bacterial cellulose with an intermediate layer.

[0015] Further, it also includes S6. Evaluate the modified forward osmosis membrane based on bacterial cellulose obtained in S5 by microplastic dissolution.

[0016] Further, the bacterial strains in S1 include Acetobacter xylinum or Komagataeibacter xylinus.

[0017] Further, the composition of the seed culture medium in S1 includes: 20 - 40 g / L of glucose, 5 - 10 g / L of yeast extract powder, 5 - 19 g / L of peptone, 1 - 3 g / L of citric acid, 1 - 3 g / L of disodium hydrogen phosphate, 0.5 - 3 g / L of magnesium sulfate, and 0.5 - 3 g / L of potassium dihydrogen phosphate, with a pH value of 5.0 ± 0.5; the seed culture medium is sterilized at 121 °C under high temperature and high pressure for 15 - 20 min before use.

[0018] The composition of the fermentation culture medium includes: 25 - 40 g / L of glucose, 5 - 15 g / L of yeast extract powder, 5 - 15 g / L of peptone, 1 - 3 g / L of citric acid, 1 - 3 g / L of disodium hydrogen phosphate, 0.5 - 3 g / L of magnesium sulfate, and 0.5 - 3 g / L of potassium dihydrogen phosphate, with a pH value of 5.0 ± 0.5; the fermentation culture medium is sterilized at 121 °C under high temperature and high pressure for 15 - 20 min before use; the process conditions for culturing the fermentation culture medium include an inoculation amount of 2% - 3% v / v, a cultivation method of first dynamic fermentation and then static fermentation, a cultivation temperature of 30 °C, and a cultivation time of 5 days.

[0019] Further, the washing in S2 includes: washing the bacterial cellulose membrane with flowing water for 24 h until there are no impurities and culture medium on the surface.

[0020] The purification includes: treating with a 0.1 - 0.5 mol / L NaOH solution at a temperature of 85 - 90 °C for 1 hour to obtain a milky bacterial cellulose membrane, and then rinsing with deionized water until the pH reaches neutral;

[0021] The drying includes: hot air drying at 60 °C for 48 h.

[0022] Furthermore, in the co - deposition reaction of S3, the mass fraction of the chitosan addition is 0.1%, the mass fraction of the tannic acid addition is 0.2%, the aqueous solution system is an acetic acid - sodium acetate solution; the temperature of the co - deposition reaction is at room temperature, and the co - deposition time is 1 h.

[0023] Furthermore, the drying in S4 is hot air drying at 60 °C for 24 h.

[0024] Furthermore, in S5, the organic solvents are 0.2% by mass of m - phenylenediamine and 0.15% by mass of trimesoyl chloride, and the trimesoyl chloride is dissolved in a n - hexane solution.

[0025] Furthermore, the interfacial polymerization reaction conditions in S5 include: the bacterial cellulose membrane with an intermediate layer is first immersed in the aqueous phase for 3 min. After using a rubber roller to remove the bubbles on the membrane surface, it is immersed in the oil phase for 1 min; the drying is that the immersed bacterial cellulose membrane is hot air dried at 60 °C for 8 min.

[0026] The present invention also provides an application of the bacterial cellulose - based modified forward osmosis membrane prepared by the preparation method of the bacterial cellulose - based modified forward osmosis membrane in water pollution treatment.

[0027] Compared with the prior art, the beneficial effects of the present invention include:

[0028] For the preparation method of the bacterial cellulose - based modified forward osmosis membrane of the present invention, renewable materials are used to replace traditional petroleum - based materials to prepare the separation membrane, which minimizes the harm to the environment and organisms. At the same time, the hot air drying method is adopted to reduce the energy consumption. The bacterial cellulose - based modified forward osmosis membrane prepared by the present invention shows good anti - fouling performance and long - cycle usability in simulated water treatment, and the flux can be restored to more than 90% through simple in - situ cleaning; moreover, the preparation method of the bacterial cellulose - based modified forward osmosis membrane of the present invention is simple, easy to operate, and has practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The disclosure of the present invention will be described with reference to the accompanying drawings. It should be understood that the drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. Among them:

[0030] Figure 1The present invention provides a flowchart of a bacterial cellulose-based modified forward osmosis membrane preparation process.

[0031] Figure 2 Field emission scanning electron microscope images of the bacterial cellulose membrane before and after modification provided in an embodiment of the present invention; wherein a is the scanning electron microscope image of the bacterial cellulose membrane before modification, and b is the scanning electron microscope image of the cellulose-modified forward osmosis membrane after modification.

[0032] Figure 3 A line graph of a permeability measurement experiment provided in an embodiment of the present invention.

[0033] Figure 4 A line graph of a BSA long-term contamination experiment provided in an embodiment of the present invention.

[0034] Figure 5 A line graph of the SA long-period pollution experiment provided in an embodiment of the present invention.

[0035] Figure 6 A flux recovery rate diagram for a long-period contamination experiment provided in an embodiment of the present invention.

[0036] Figure 7 This is a fluorescence intensity diagram of microplastic dissolution provided in an embodiment of the present invention; wherein a is a fluorescence intensity distribution diagram, and b is a relative fluorescence density distribution diagram.

[0037] Figure 8 The present invention is a flowchart of the preparation process of the bacterial cellulose-based modified forward osmosis membrane. DETAILED DESCRIPTION

[0038] It is easy to understand that according to the technical solution of the present invention, without changing the essential spirit of the present invention, a person skilled in the art can propose mutually replaceable implementation methods. Therefore, the following specific implementation methods are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the whole of the present invention or as a limitation or restriction to the technical solution of the present invention.

[0039] The present invention provides a method for preparing a bacterial cellulose-based modified forward osmosis membrane, such as Figure 1 and 8 As shown, the following steps are included:

[0040] S1, inoculating the activated bacterial strain into a seed culture medium for cultivation to obtain a seed solution, and inoculating the seed solution into a fermentation culture medium for fermentation to obtain a bacterial cellulose membrane;

[0041] Specifically, the bacterial species include Acetobacter xylinum or Komagata xylosus;

[0042] The composition of the seed culture medium includes: glucose 20 - 40 g / L, yeast extract powder 5 - 10 g / L, peptone 5 - 19 g / L, citric acid 1 - 3 g / L, disodium hydrogen phosphate 1 - 3 g / L, magnesium sulfate 0.5 - 3 g / L, and potassium dihydrogen phosphate 0.5 - 3 g / L, with a pH value of 5.0 ± 0.5; the seed culture medium is autoclaved at 121 °C for 15 - 20 min before use;

[0043] The composition of the fermentation culture medium includes: glucose 25 - 40 g / L, yeast extract powder 5 - 15 g / L, peptone 5 - 15 g / L, citric acid 1 - 3 g / L, disodium hydrogen phosphate 1 - 3 g / L, magnesium sulfate 0.5 - 3 g / L, and potassium dihydrogen phosphate 0.5 - 3 g / L, with a pH value of 5.0 ± 0.5; the fermentation culture medium is autoclaved at 121 °C for 15 - 20 min before use; the process conditions for culturing the fermentation culture medium include an inoculation amount of 2% - 3% v / v, a culture method of first dynamic fermentation and then static fermentation, a culture temperature of 30 °C, and a culture time of 5 days. The dynamic fermentation conditions are: dynamic fermentation at a rotation speed of 220 rpm for 3 h and then transfer to static fermentation; the static fermentation conditions are: a fermentation temperature of 30 °C and a fermentation time of 5 days. The mode of first dynamic fermentation and then static fermentation (dynamic / static combination) can effectively increase the yield of bacterial cellulose while obtaining a flat and membranous bacterial cellulose membrane.

[0044] S2. Wash, purify, and dry the bacterial cellulose membrane obtained in S1;

[0045] Specifically, the washing includes: washing the bacterial cellulose membrane with running water for 24 h until there are no impurities and culture medium on the surface;

[0046] The purification includes: treating with 0.1 - 0.5 mol / L NaOH solution at a temperature of 85 - 90 °C for 1 hour to obtain a milky white bacterial cellulose membrane, and then rinsing with deionized water until the pH reaches neutral;

[0047] The drying includes: hot air drying at 60 °C for 48 h.

[0048] After washing and purifying the fermented bacterial cellulose membrane, hot air drying is used to replace the commonly used freeze drying, reducing the manufacturing cost of the separation membrane and reducing the waste of energy efficiency.

[0049] S3. Carry out a co - deposition reaction on the bacterial cellulose membrane treated in S2 with chitosan and tannic acid in an aqueous solution system;

[0050] Specifically, the mass fraction of the chitosan addition amount in the co - deposition is 0.1%, the mass fraction of the tannic acid addition amount is 0.2%, the aqueous solution system is acetic acid - sodium acetate solution; the temperature of the co - deposition reaction is room temperature (25 ± 2 °C), and the co - deposition time is 1 h.

[0051] S4. Take out the bacterial cellulose membrane obtained after the co - deposition reaction in S3, wash it and then dry it to obtain a bacterial cellulose membrane with a chitosan and tannic acid intermediate layer.

[0052] Specifically, the drying is carried out by hot - air drying at 60 °C for 24 h.

[0053] In the co - deposition reaction, the amino - rich chitosan (CS) molecules can interact with the hydroxyl and carboxyl groups of tannic acid (TA) to form a CS / TA complex with strong hydrophilicity. Therefore, the introduction of the intermediate layer can not only improve the hydrophilicity of the bacterial cellulose - based membrane, but also facilitate the formation of a denser and defect - free active layer.

[0054] S5. Carry out an interfacial polymerization reaction on the bacterial cellulose membrane with a chitosan and tannic acid intermediate layer in S4, and dry it after the reaction to obtain a modified forward osmosis membrane based on bacterial cellulose with an intermediate layer. Specifically, immerse the dried bacterial cellulose membrane with chitosan and tannic acid in an aqueous solution containing an aqueous - phase monomer for interfacial polymerization; take out the infiltrated membrane from the aqueous phase, and use a rubber roller or nitrogen purge to remove the excess aqueous - phase monomer on the surface; immerse the membrane in an organic solvent containing an organic - phase monomer. After the reaction is completed, take out the membrane and carry out heat treatment or water washing to remove the unreacted monomers and by - products, and finally form a forward osmosis membrane with a dense separation layer.

[0055] Specifically, the organic solvent is m - phenylenediamine (MPD) with a mass fraction of 0.2% and trimesoyl chloride (TMC) with a mass fraction of 0.15%. The trimesoyl chloride is dissolved in a hexane solution. The interfacial polymerization reaction conditions include: the bacterial cellulose membrane with an intermediate layer is first immersed in the aqueous phase for 3 min. After using a rubber roller to remove the air bubbles on the membrane surface, immerse it in the oil phase for 1 min.

[0056] The drying is that the immersed bacterial cellulose membrane is hot - air dried at 60 °C for 8 min;

[0057] Using renewable resource bacterial cellulose to prepare the separation membrane greatly avoids the damage to the environment and organisms caused by the use of organic reagents, reduces the cost of manufacturing the separation membrane, and saves energy consumption.

[0058] The present invention also includes S6, specifically, microplastic dissolution. Cut the membrane obtained in S5 into small pieces of 2×2 cm, put them into a beaker containing 100 ml of deionized water, and stir at a speed of 600 rpm at 25 °C for 24 hours. Next, remove the membrane from the aqueous solution, and obtain MPs through a glass microfiber filter with a pore size of 1.2 μm and a diameter of 47 mm. Subsequently, store the filter paper containing MPs in a glass petri dish and dry it in a desiccator until analysis. Immerse the filter paper containing MPs in a 0.01 mg / 1 mL nile red dye solution for 30 minutes to label the MPs. Then observe the samples under a fluorescence microscope equipped with a FITC filter to generate blue light excitation.

[0059] The present invention also provides an application of the bacterial cellulose-based modified forward osmosis membrane in the water treatment process. The bacterial cellulose-based modified forward osmosis membrane includes a support layer and an active layer connected to the support layer, and the active layer is located on one side of the support layer; chitosan and tannic acid are co-deposited on the side of the active layer away from the support layer. The bacterial cellulose-based modified forward osmosis membrane has high surface hydrophilicity and good anti-fouling performance against bovine serum albumin and sodium alginate pollution.

[0060] The pollutants in the simulated water treatment process are bovine serum albumin and sodium alginate. Bovine serum albumin (BSA) is a globulin in bovine serum, containing 607 amino acid residues, with a molecular weight of 66.446 KDa and an isoelectric point of 4.7. BSA is a typical protein, widely present in biological fluids (such as blood, milk) and food processing wastewater. Protein pollution is one of the common pollution types in the membrane separation process. BSA is easily adsorbed on the membrane surface to form a dense pollution layer, simulating the membrane pollution caused by proteins in actual applications. Sodium alginate (SA) Sodium alginate is a natural polysaccharide, widely present in food, medicine, and wastewater treatment. Polysaccharide pollution is another common pollution type in the membrane separation process. Sodium alginate easily forms a gel layer in water, simulating the membrane pollution caused by polysaccharide substances in actual applications.

[0061] By studying the individual and combined fouling behaviors of BSA and SA, the fouling mechanism of the membrane can be more comprehensively understood, and effective anti-fouling strategies can be developed.

[0062] Further conduct long-term experiments on the pollutants of the bacterial cellulose-based modified forward osmosis membrane. Through long-term experiments, the anti-fouling performance of the membrane can be evaluated, and the effectiveness of the cleaning strategy can be verified.

[0063] The anti-fouling performance of the bacterial cellulose-based modified forward osmosis membrane against BSA and SA is improved compared with other forward osmosis membranes. After long-term experiments, after simple in-situ cleaning, the flux recovery rates of BSA and SA can reach more than 90%.

[0064] Specific implementation cases

[0065] In the experimental materials of the following examples, unless otherwise specified, the rest are all commercially available products.

[0066] Experimental strains:

[0067] Gluconacetobacter xylinum: The preservation number is CGMCC 11812, purchased from the laboratory. Komagataeibacter xylinus: The preservation number is CICC 10529, purchased from the laboratory.

[0068] Culture medium:

[0069] Seed medium for Gluconacetobacter xylinum and Komagataeibacter xylinus: Glucose 40 g / L, yeast extract powder 5 g / L, peptone 5 g / L, citric acid 1.5 g / L, disodium hydrogen phosphate 2.7 g / L, magnesium sulfate 0.5 g / L, and potassium dihydrogen phosphate 0.5 g / L, pH value is 5.0 ± 0.5; the seed medium is sterilized at 121 °C under high temperature and high pressure for 15 min before use.

[0070] Fermentation medium for Gluconacetobacter xylinum and Komagataeibacter xylinus: Glucose 40 g / L, yeast extract powder 5 g / L, peptone 5 g / L, citric acid 1.5 g / L, disodium hydrogen phosphate 2.7 g / L, magnesium sulfate 0.5 g / L, and potassium dihydrogen phosphate 0.5 g / L, pH value is 5.0 ± 0.5, the fermentation medium is sterilized at 121 °C under high temperature and high pressure for 20 min before use.

[0071] Among them, the seed medium and the fermentation medium are the media for activating and culturing Gluconacetobacter xylinum and Komagataeibacter xylinus.

[0072] Example 1

[0073] Prepare a bacterial cellulose-based modified forward osmosis membrane according to the following steps:

[0074] (1) Inoculate the activated Gluconacetobacter xylinum into the seed medium for culture, and then inoculate it into the Gluconacetobacter xylinum fermentation medium according to an inoculation amount of 2% v / v. After fully mixing evenly, place it in a constant temperature incubator at 30 °C and let it stand and ferment for 1 week to obtain a bacterial cellulose membrane;

[0075] (2) Take out the bacterial cellulose membrane obtained in step (1), wash it, and keep it warm in 0.1 mol / L NaOH solution at 90 °C for 1 h until the bacterial cellulose membrane shows a semi-transparent milky white color. After taking it out, rinse it repeatedly with deionized water until it is neutral;

[0076] (3) soaking the bacterial cellulose film obtained in step (2) in an acetic acid-sodium acetate solution containing 0.1 wt % chitosan and 0.2 wt % tannic acid at 25° C. for 1 h to perform a co-precipitation reaction;

[0077] (4) Immersing the bacterial cellulose membrane obtained in step (3) into an aqueous solution containing 0.2 wt% of m-phenylenediamine (MPD) for interfacial polymerization; taking out the impregnated membrane from the aqueous phase, removing excess aqueous monomers on the surface with a rubber roller or nitrogen purge; immersing the membrane in a solution containing 0.15 wt% of trimesoyl chloride-n-hexane. After the reaction is completed, taking out the membrane and heat treating or washing it with water to remove unreacted monomers and by-products, and finally forming a bacterial cellulose modified forward osmosis membrane with an intermediate layer.

[0078] The field emission scanning electron microscopy images of the cell cellulose membrane in (1) and the bacterial cellulose modified forward osmosis membrane in (4) are shown in FIG. Figure 2 shown.

[0079] Example 2

[0080] The bacterial cellulose-based modified forward osmosis membrane was prepared according to the following steps:

[0081] (1) inoculating the activated Bacillus xylosus into a seed culture medium for cultivation, and then inoculating the activated Bacillus xylosus into a fermentation culture medium of Acetobacter xylinum at an inoculum rate of 3% v / v, mixing the mixture thoroughly, and placing the mixture in a constant temperature incubator at 30° C. for fermentation for 1 week to obtain a bacterial cellulose film;

[0082] (2) taking out the bacterial cellulose membrane obtained in step (1), washing it, and keeping it warm at 90° C. with a 0.1 mol / L NaOH solution for 1 h until the bacterial cellulose membrane becomes translucent milky white, and then taking it out and repeatedly rinsing it with deionized water until it becomes neutral;

[0083] (3) soaking the bacterial cellulose film obtained in step (2) in an acetic acid-sodium acetate solution containing 0.1 wt % chitosan and 0.2 wt % tannic acid at 25° C. for 1 h to perform a co-precipitation reaction;

[0084] (4) Immersing the bacterial cellulose membrane obtained in step (3) into an aqueous solution containing 0.2 wt% of m-phenylenediamine (MPD) for interfacial polymerization; taking out the impregnated membrane from the aqueous phase, removing excess aqueous monomers on the surface with a rubber roller or nitrogen purge; immersing the membrane in a solution containing 0.15 wt% of trimesoyl chloride-n-hexane. After the reaction is completed, taking out the membrane and heat treating or washing it with water to remove unreacted monomers and by-products, and finally forming a bacterial cellulose modified forward osmosis membrane with an intermediate layer.

[0085] In the embodiment of the present invention, the water used is preferably pure water (RO water).

[0086] Examples 1 - 2: Permeation Performance and Long - term Fouling Experiments

[0087] Permeation performance:

[0088] Using 400 mL of 2 mol / L sodium chloride solution as the draw solution (DS), 200 mL of deionized water as the feed solution (FS), at a temperature of 25 °C and a feed flow rate of 22.5 cm / s, until 50 mL of permeate is transferred to DS, the experiment ends, and the change in permeation flux (line graph of water flux and permeate volume) is recorded as shown Figure 3 as follows.

[0089] Long - term fouling experiment: In a cross - flow filtration system, bovine serum albumin BSA and sodium alginate SA solutions are used as the feed solution. First, the pure water flux (PWF, Jw) of the original bacterial cellulose - based modified forward osmosis membrane is measured for 2 h, and then, with BSA solution (600 mg / L) and SA solution (1 g / L) as the feed solutions, the flux (Jp) is measured at 25 °C for 2 h. After BSA filtration, the membrane is rinsed with deionized water at a flow rate of 22.5 cm / s for 30 min, and the PWF (Jc) of the membrane after cleaning is measured under the same conditions as Jw. The above fouling - cleaning process is repeated 4 times, and the long - term fouling resistance performance of the membrane is evaluated by calculating the flux recovery rate (FRR) of the membrane during the 4 - cycle process. The results of the line graph of bovine serum albumin BSA and sodium alginate SA flux and time are shown Figure 4 and Figure 5 as follows. After the BSA - and SA - fouled membranes are cleaned, the percentage of the water flux restored to the initial flux (Flux Recovery Rate (FRR)) is shown Figure 6 as follows.

[0090] In summary, the preparation methods of Examples 1 - 2 can achieve good fouling resistance and long - term usability while maintaining the permeation flux to the greatest extent, reducing the harm to organisms and the environment, and lowering production energy consumption and costs.

[0091] Example 3

[0092] Select existing PES - PA (polyethersulfone - polyamide composite membrane), CTA (cellulose triacetate homogeneous membrane), and the BCM - CS / TA3 - PA (bacterial cellulose - based modified forward osmosis membrane) prepared in this invention to conduct micro - plastic dissolution. The fluorescence situation graph is shown Figure 7 as follows, where a is the fluorescence intensity graph, and the gray part in the attached figure is the fluorescence intensity part, and b is the distribution graph of Relative Fluorescence Density.

[0093] The primary objective of the present invention is to provide a novel preparation method for a bacterial cellulose-based modified forward osmosis membrane. Through co-deposition, chitosan and tannic acid are combined on the surface of the active layer of the bacterial cellulose membrane, and then an interfacial polymerization is carried out to obtain a bacterial cellulose-based forward osmosis membrane with an intermediate layer. The modification method is simple and effective. The combination of the intermediate layer and the modified layer of the obtained bacterial cellulose-based forward osmosis membrane makes the membrane more stable and durable, with a long service life.

[0094] Another objective of the present invention is to provide an application of the bacterial cellulose-based modified forward osmosis membrane in the water treatment process. The bacterial cellulose-based modified forward osmosis membrane includes a support layer and an active layer connected to the support layer, and the active layer is located on one side of the support layer; chitosan and tannic acid are co-deposited on the side of the active layer away from the support layer. The bacterial cellulose-based modified forward osmosis membrane has high surface hydrophilicity and good anti-fouling properties against bovine serum albumin and sodium alginate fouling.

[0095] The technical scope of the present invention is not limited to the content described above. Those skilled in the art can make various deformations and modifications to the above embodiments without departing from the technical idea of the present invention, and these deformations and modifications should all fall within the protection scope of the present invention.

Claims

1. A preparation method of a bacterial cellulose-based modified forward osmosis membrane, characterized in that: Including S1: Inoculate the activated bacterial strain into the seed medium for cultivation to obtain a seed solution, and then inoculate the seed solution into the fermentation medium for fermentation to obtain a bacterial cellulose membrane; S2: Wash, purify, and dry the bacterial cellulose membrane obtained in S1; S3: Carry out a co-deposition reaction on the bacterial cellulose membrane treated in S2 with chitosan and tannic acid in an aqueous solution system; S4: Take out the bacterial cellulose membrane obtained after the co-deposition reaction in S3, wash it, and then dry it to obtain a bacterial cellulose membrane with a chitosan and tannic acid intermediate layer; S5: Carry out an interfacial polymerization reaction on the bacterial cellulose membrane with a chitosan and tannic acid intermediate layer in S4 in an organic solvent, and dry it after the reaction to obtain a modified forward osmosis membrane based on bacterial cellulose with an intermediate layer.

2. The preparation method of a bacterial cellulose-based modified forward osmosis membrane according to claim 1, characterized in that: It also includes S6: Evaluate the modified forward osmosis membrane based on bacterial cellulose obtained in S5 by microplastic dissolution.

3. The preparation method of a bacterial cellulose-based modified forward osmosis membrane according to claim 1, wherein: The bacterial strain in S1 includes Acetobacter xylinum or Komagataeibacter xylinus.

4. The preparation method of a bacterial cellulose-based modified forward osmosis membrane according to claim 1, characterized in that: The composition of the seed medium in S1 includes: 20 - 40 g / L of glucose, 5 - 10 g / L of yeast extract powder, 5 - 19 g / L of peptone, 1 - 3 g / L of citric acid, 1 - 3 g / L of disodium hydrogen phosphate, 0.5 - 3 g / L of magnesium sulfate, and 0.5 - 3 g / L of potassium dihydrogen phosphate, with a pH value of 5.0 ± 0.5; the seed medium is autoclaved at 121 °C for 15 - 20 min before use; The composition of the fermentation medium includes: 25 - 40 g / L of glucose, 5 - 15 g / L of yeast extract powder, 5 - 15 g / L of peptone, 1 - 3 g / L of citric acid, 1 - 3 g / L of disodium hydrogen phosphate, 0.5 - 3 g / L of magnesium sulfate, and 0.5 - 3 g / L of potassium dihydrogen phosphate, with a pH value of 5.0 ± 0.5; the fermentation medium is autoclaved at 121 °C for 15 - 20 min before use; the process conditions for culturing the fermentation medium include an inoculation amount of 2% - 3% v / v, a culture method of first dynamic fermentation and then static fermentation, a culture temperature of 30 °C, and a culture time of 5 days.

5. The preparation method of a bacterial cellulose-based modified forward osmosis membrane according to claim 1, characterized in that: The washing in S2 includes: washing the bacterial cellulose membrane with running water for 24 h until there are no impurities and medium on the surface; The purification includes: treating with a 0.1 - 0.5 mol / L NaOH solution at a temperature of 85 - 90 °C for 1 hour to obtain a milky white bacterial cellulose membrane, and then rinsing with deionized water until the pH reaches neutral; The drying includes: hot air drying at 60 °C for 48 h.

6. The preparation method of a bacterial cellulose-based modified forward osmosis membrane according to claim 1, characterized in that: In the co-deposition reaction of S3, the mass fraction of the chitosan addition amount is 0.1%, and the mass fraction of the tannic acid addition amount is 0.2%. The aqueous solution system is an acetic acid - sodium acetate solution; the temperature of the co-deposition reaction is normal temperature, and the co-deposition time is 1 h.

7. The preparation method of a bacterial cellulose-based modified forward osmosis membrane according to claim 1, characterized in that: The drying in S4 is hot air drying at 60 °C for 24 h.

8. The preparation method of a bacterial cellulose-based modified forward osmosis membrane according to claim 1, characterized in that: The organic solvent in S5 is 0.2% by mass of m-phenylenediamine and 0.15% by mass of trimesoyl chloride, and the trimesoyl chloride is dissolved in a n-hexane solution.

9. The preparation method of a bacterial cellulose-based modified forward osmosis membrane according to claim 1, characterized in that: The interfacial polymerization reaction conditions in S5 include: the bacterial cellulose membrane with an intermediate layer is first immersed in the aqueous phase for 3 min. After using a rubber roller to remove the bubbles on the membrane surface, it is immersed in the oil phase for 1 min; the drying is that the immersed bacterial cellulose membrane is dried with hot air at 60 °C for 8 min.

10. Application of the bacterial cellulose-based modified forward osmosis membrane with an intermediate layer prepared by the method for preparing a bacterial cellulose-based modified forward osmosis membrane according to any one of claims 1 to 9 in water pollution treatment.

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