Application and preparation method of a novel degradable material-based adsorption film

Abstract

The application provides application and a preparation method of a novel degradable material-based adsorption membrane, and relates to the technical field of functional nanofiber membranes.The adsorption membrane is prepared by the following steps: constructing a CA-CS / PVA / PVP-CA three-layer precursor through single-needle step-by-step electrospinning, removing part of PVA / PVP through water bath etching at 90 DEG C, and then soaking in a chitosan acetic acid solution and vacuum drying; thanks to the introduction of active amino groups and hydroxyl groups in chitosan, the membrane has excellent heavy metal adsorption property; the three-dimensional structure of the membrane makes the two acetic cellulose support layers and the middle chitosan functional layer synergistically act, the complex smelting wastewater environment is adapted, and the active layer is prevented from being damaged by suspended matters. Moreover, the synthesis process of the membrane is simple and efficient, raw materials are widely sourced, the price is low, the membrane can be naturally degraded, has both interception and adsorption performance, conforms to the green and sustainable development concept, and has the potential for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of functional nanofiber membrane technology, specifically to the application and preparation method of a novel biodegradable material-based adsorption membrane. Background Technology

[0002] Copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn) are typical heavy metal elements with wide applications in electroplating, metallurgy, chemical industry, battery manufacturing, and electronics. Copper, due to its excellent electrical conductivity and corrosion resistance, is widely used in wire and cable, electronic components, and alloy manufacturing; lead is widely used in storage batteries, lead salts, and radiation shielding materials; nickel is an important raw material for stainless steel, electroplating, and catalysts; and zinc is mainly used for galvanizing corrosion protection, zinc alloys, and dry cell battery manufacturing.

[0003] However, the production and use of these metals generate large amounts of wastewater containing heavy metals. Direct discharge without effective treatment not only results in a severe waste of metal resources but also poses a lasting threat to the ecological environment and human health through water bioaccumulation and food chain transmission. Therefore, developing efficient, economical, and recyclable heavy metal wastewater treatment technologies to achieve the simultaneous removal and resource recovery of heavy metals such as Cu, Pb, Ni, and Zn has become a critical technological issue urgently needing to be addressed in the fields of environmental protection and resource recycling. Furthermore, with the increasing emphasis on sustainable green development by the state, stricter adherence to environmental regulations, and rising demands for drinking water quality, the treatment of heavy metals in industrial wastewater, particularly those with copper and nickel as the surface layer, is receiving increasing attention.

[0004] Traditional heavy metal wastewater treatment technologies have some shortcomings. For example, while chemical precipitation is simple, low-cost, and widely applicable, it also easily generates a large amount of hazardous sludge, causing secondary pollution. Coagulation, while simple in equipment and easy to operate, is effective in removing suspended solids and colloids, but has limited effectiveness in removing soluble heavy metals and requires large amounts of reagents. Ion exchange produces high-quality effluent and can recover heavy metals, making it suitable for advanced treatment, but its core resin is prone to poisoning, has high regeneration costs, and is poorly adaptable to complex water conditions. Traditional membrane separation technologies (such as ultrafiltration and nanofiltration membranes), while achieving efficient solid-liquid separation, also suffer from problems such as membrane fouling, poor shock resistance, and the inability to recover wastewater, resulting in limited application.

[0005] In contrast, adsorption methods, due to their simple operation, wide applicability, low energy consumption, and ability to rapidly reduce the concentration of high-concentration heavy metal wastewater, have become one of the mainstream technologies for treating heavy metal wastewater, particularly copper and nickel. Traditional adsorption materials, such as clay, activated carbon, and zeolite, as well as emerging nanoparticle adsorbents, suffer from problems such as easy aggregation, difficulty in recovery, low adsorption capacity, poor treatment efficiency, poor regeneration and resource recovery capabilities, and high costs, limiting their industrialization prospects. On the other hand, fiber membrane adsorbents, due to their high specific surface area and porous structure, exhibit significant advantages in the adsorption and removal of heavy metals, particularly copper, in terms of treatment efficiency, adsorption capacity, multi-functional applications, resource recycling, and greater compatibility with existing wastewater treatment systems.

[0006] Therefore, nanofiber membrane adsorption technology is currently receiving much attention. For example, patent CN120393777A discloses a polyurethane / cellulose acetate composite fiber membrane and its preparation method. By grafting polyethyleneimine segments onto the surface of the composite fiber membrane, the membrane's high mass transfer efficiency, high specific surface area, and regular membrane structure are ensured, while significantly improving the adsorption capacity of the fiber membrane for heavy metal ions, thereby achieving efficient adsorption of heavy metals. For example, patent CN118007275A discloses a method for preparing MOF nanofiber membranes for water treatment. MOF is used as a filler, and it is mixed and modified with an environmentally friendly water-soluble polymer. The MOF@polymer nanofiber membrane is prepared using electrospinning and steam crosslinking methods. Glutaraldehyde crosslinking is used to stably load the MOF onto the fiber membrane. The interface structure between MOF and the polymer matrix is ​​optimized to ensure a low dissolution rate in the water environment. The large specific surface area of ​​the polymer fiber membrane is combined with the excellent pore structure and adsorption performance of MOF to synergistically construct a MOF nanofiber membrane with excellent adsorption performance for heavy metals and dyes. Another example is patent CN109364891A, which discloses a method for preparing modified polyacrylonitrile for treating antimony-containing wastewater. By immersing a polyacrylonitrile substrate in an aqueous solution of hydroxylamine hydrochloride to induce in-situ oxime formation, followed by drying and vacuum dehydration, a fiber membrane with strong antimony adsorption capacity, large maximum adsorption capacity, good desorption effect, and recyclability is prepared.

[0007] However, existing fiber membrane preparation technologies also have inherent shortcomings, such as complex processes and difficulty in balancing strength and flux, stability and multifunctional integration. In addition, due to defects in their own materials and production processes, they often have certain deficiencies in process controllability, mass production efficiency and biodegradability, which also limit their practical application value and sustainable development potential. Their poor adaptability to the complex environment in actual production processes also indirectly limits their application prospects.

[0008] In summary, the application of fiber membrane materials in environmental remediation still faces many bottlenecks and inherent limitations that urgently need to be overcome. The core issues lie not only in the difficulty of achieving synergistic and deep removal of heavy metals and multiple coexisting pollutants, and insufficient adaptability to complex water quality conditions and harsh operating environments; but also in the fact that current mainstream membrane materials are mostly based on polymers such as polyacrylonitrile, polyvinylidene fluoride, and polyester, which possess excellent mechanical and thermal stability. These materials generally suffer from inherent defects such as insufficient hydrophilicity, a lack of surface active sites, poor biodegradability, cumbersome preparation processes, and stringent conditions for functional modification. These defects severely restrict the large-scale production, industrial application, and sustainable development potential of these materials.

[0009] Therefore, how to provide a fiber membrane material with a simple preparation process and good heavy metal adsorption and removal effect is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0010] To address the shortcomings of existing technologies, this invention provides a novel method for the application and preparation of a biodegradable material-based adsorption membrane. The membrane synthesis process is simple and efficient, the raw materials are widely available and inexpensive, and it is biodegradable. It combines retention and adsorption properties, conforms to the concept of green and sustainable development, and has the potential for large-scale production.

[0011] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a novel biodegradable material-based adsorption membrane includes the following steps: S1. Dissolve cellulose acetate CA in a mixed solvent of acetone / ethanol to obtain solution A; S2. Dissolve chitosan CS in a high-concentration acetic acid solution to obtain solution B; S3. Add the mixed powder of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) to deionized water and heat it in a water bath at 60°C to dissolve it and obtain the spinning aid solution C. S4. Finally, solution B and solution C are mixed in proportion to obtain spinning solution D. Stepwise spinning method: spinning solution A, spinning solution D and spinning solution A are spun continuously to obtain CA-CS / PVA / PVP-CA three-layer fiber membrane precursor. S5. The standard three-layer fiber membrane precursor was immersed in deionized water and boiled in a water bath at 90°C for a period of time to obtain a CA-CS / PVA / PVP-CA etched three-layer fiber membrane. S6. Finally, the CA-CS / PVA / PVP-CA etched three-layer fiber membrane is directly immersed in a diluted chitosan acetate solution, stirred rapidly for a short time, removed and vacuum dried to obtain the novel biodegradable material-based adsorption membrane.

[0012] Furthermore, in solution A, the cellulose acetate is industrial-grade diacetate, specifically, solution A is a 5wt% cellulose acetate acetone / ethanol mixed solution; wherein, the solvent used to prepare mixture A is a 7:3 volume ratio acetone and ethanol mixed solution.

[0013] Further, the mixed solution B is a 5wt% chitosan acetate mixed solution; in the mixed solution C, the mass ratio of polyvinyl alcohol and polyvinylpyrrolidone is 2:1, and the mixed powder accounts for 15% of the total solution; the mass ratio of solution B to solution C contained in solution D is 4:6.

[0014] Furthermore, for solution A, the electrospinning parameters are as follows: temperature 15-25℃, humidity 50%, positive spinning voltage 16kV, negative spinning voltage -1.5kV, spinning rate 0.5-1mm / min, distance between spinneret and receiver 18cm, single spinning time 0.25-0.5h, and cumulative spinning solution A volume of 1.5-3mL on both sides of the support membrane.

[0015] Furthermore, for solution D, the electrospinning parameters are as follows: temperature 25-30℃, humidity 50%, positive spinning voltage 23kV, negative spinning voltage -2.5kV, spinning rate 0.15-0.25mm / min, distance between spinneret and receiver 15cm, single spinning time 2-6h, and single spinning volume of intermediate functional membrane 5-10mL.

[0016] Furthermore, the ratio of chitosan, acetic acid, and water added to solution B is 0.5g:8.55g:0.95g.

[0017] Furthermore, in solution C, the water bath conditions are 60°C for 4 hours, and the mass ratio of added polyvinyl alcohol, polyvinylpyrrolidone, and water is 2g:1g:17g.

[0018] Furthermore, the CA-CS / PVA / PVP-CA three-layer fiber membrane precursor is a standard three-layer fiber membrane precursor with a square membrane sheet of size 5x5cm; it is immersed in 100mL of deionized water and boiled in a water bath at 90℃ for 15-30min.

[0019] Furthermore, the diluted chitosan acetate solution directly immersed in the CA-CS / PVA / PVP-CA etched three-layer fiber membrane is specifically a 1wt% mixed solution of chitosan and low-concentration acetic acid; the stirring time is 5-10 min; the drying conditions are drying at 60℃ in a vacuum drying oven for 12 h; the mixing mass ratio of chitosan, acetic acid and water is 1g:10g:89g.

[0020] Furthermore, an application of a novel biodegradable material-based adsorption membrane in the field of advanced treatment and resource recovery of heavy metal wastewater.

[0021] This invention provides an application and preparation method for a novel biodegradable material-based adsorption membrane. It offers the following advantages: 1. This invention provides a novel method for the application and preparation of biodegradable material-based adsorption membranes. Using biodegradable and environmentally friendly polymers such as cellulose acetate, chitosan, polyvinyl alcohol, and polyvinylpyrrolidone as raw materials, a three-layer sandwich structure fiber membrane with CA-CS / PVA / PVP-CA is constructed by stepwise electrospinning. The cellulose acetate layers on both sides provide excellent mechanical support and dimensional stability, effectively overcoming the defects of pure chitosan membranes, such as low mechanical strength and difficulty in independent molding and use.

[0022] 2. This invention provides a novel method for the application and preparation of a biodegradable material-based adsorption membrane. After etching the intermediate functional layer in a 90°C water bath, PVA and PVP partially dissolve, forming a rich porous structure that significantly increases the specific surface area and porosity, providing more adsorption active sites and diffusion channels for heavy metal ions. Further modification by rapid immersion in a chitosan acetate solution introduces a large number of chelating groups such as amino and hydroxyl groups onto the membrane surface and within the pores, enhancing the adsorption capacity of Cu... 2+ Pb 2+ Ni 2+ Zn 2+ Heavy metal ions have strong coordination and capture capabilities, large adsorption capacity, and high removal efficiency.

[0023] 3. This invention provides a novel method for the application and preparation of a biodegradable material-based adsorption membrane. The preparation process parameters are controllable and reproducible. The resulting adsorption membrane has good flexibility, permeability and recyclability. Moreover, it can be naturally degraded after use, avoiding secondary pollution. It has broad application prospects in the field of deep treatment and resource recovery of heavy metal wastewater. Attached Figure Description

[0024] Figure 1 This is a photograph of a novel biodegradable material-based adsorption membrane as described in an embodiment of the present invention. Figure 2 The amount of copper ions adsorbed by the nanofiber membrane material obtained in Example 1 of the present invention in copper solutions of different concentrations; Figure 3 The Langmuir monolayer theoretical adsorption curve of copper ions for the nanofiber membrane material obtained in Example 1 of the present invention is shown. Figure 4 This is a comparison chart showing the different removal rates of the nanofiber membrane materials obtained in Examples 1-4 and Comparative Examples 1-3 of the present invention for solutions containing Cu, Pb, Ni, and Zn at a concentration of 100 mg / L. Figure 5This is a cross-sectional SEM image of a novel biodegradable material-based adsorption membrane obtained in Example 1 of the present invention; Figure 6 This is an SEM image of the surface of a novel biodegradable material-based adsorption membrane obtained in Example 1 of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] To make the above-mentioned objects, features and advantages of the present invention more readily understood, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] like Figures 1-6 As shown, this invention provides a method for preparing a novel biodegradable material-based adsorption membrane, comprising the following steps: S1. Dissolve cellulose acetate CA in a mixed solvent of acetone / ethanol to obtain solution A; In solution A, the cellulose acetate is industrial grade cellulose diacetate. Specifically, solution A is a 5 wt% cellulose acetate acetone / ethanol mixed solution; wherein, the solvent used to prepare mixture A is a 7:3 volume ratio acetone and ethanol mixed solution.

[0028] S2. Dissolve chitosan CS in a high-concentration acetic acid solution to obtain solution B; S3. Add the mixed powder of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) to deionized water and heat it in a water bath at 60°C to dissolve it and obtain the spinning aid solution C. S4. Finally, solution B and solution C are mixed in proportion to obtain spinning solution D. Stepwise spinning method: spinning solution A, spinning solution D and spinning solution A are spun continuously to obtain CA-CS / PVA / PVP-CA three-layer fiber membrane precursor. S5. The standard three-layer fiber membrane precursor was immersed in deionized water and boiled in a water bath at 90°C for a period of time to obtain a CA-CS / PVA / PVP-CA etched three-layer fiber membrane. S6. Finally, the CA-CS / PVA / PVP-CA etched three-layer fiber membrane is directly immersed in a diluted chitosan acetate solution, stirred rapidly for a short time, removed and vacuum dried to obtain the novel biodegradable material-based adsorption membrane.

[0029] Mixed solution B is a 5 wt% chitosan-acetic acid mixture; in mixed solution C, the mass ratio of polyvinyl alcohol and polyvinylpyrrolidone is 2:1, and the mixed powder accounts for 15% of the total solution; solution D contains the mass ratio of solution B to solution C of 4:6.

[0030] For solution A, the electrospinning parameters are as follows: temperature 15-25℃, humidity 50%, positive spinning voltage 16kV, negative spinning voltage -1.5kV, spinning rate 0.5-1mm / min, distance between spinneret and receiver 18cm, single spinning time 0.25-0.5h, and cumulative spinning volume of solution A on both sides of the support membrane is 1.5-3mL.

[0031] For solution D, the electrospinning parameters are as follows: temperature 25-30℃, humidity 50%, positive spinning voltage 23kV, negative spinning voltage -2.5kV, spinning rate 0.15-0.25mm / min, distance between spinneret and receiver 15cm, single spinning time 2-6h, and single spinning volume of intermediate functional membrane 5-10mL.

[0032] The ratio of chitosan, acetic acid, and water added to solution B is 0.5g:8.55g:0.95g.

[0033] In solution C, the water bath conditions were 60℃ for 4 hours, and the mass ratio of polyvinyl alcohol, polyvinylpyrrolidone and water added was 2g:1g:17g.

[0034] The CA-CS / PVA / PVP-CA trilayer fiber membrane precursor is a standard trilayer fiber membrane precursor, with a square membrane sheet size of 5x5cm. It is immersed in 100mL of deionized water and boiled in a 90℃ water bath for 15-30min.

[0035] The diluted chitosan acetate solution directly immersed in the CA-CS / PVA / PVP-CA etched three-layer fiber membrane is specifically a 1wt% mixture of chitosan and low-concentration acetic acid; the stirring time is 5-10 min; the drying conditions are drying at 60℃ in a vacuum drying oven for 12 h; the mixing mass ratio of chitosan, acetic acid and water is 1g:10g:89g.

[0036] The present invention will be further described below through specific embodiments.

[0037] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels; Unless otherwise specified, room temperature or normal temperature in the embodiments of the present invention refers to 25±3℃.

[0038] Example 1: A method for preparing a novel biodegradable material-based adsorption membrane includes the following steps: S1: Preparation of spinning solution Spinning solution A: 0.7787 g of cellulose acetate and 0.1947 g of polyvinylpyrrolidone powder were added to a homogeneous solution consisting of 10 mL of dichloromethane and 5 mL of acetic acid. After stirring at 300 r / min for 1 h, the mixture was sonicated for 5 min to remove internal air bubbles, resulting in a homogeneous polymer solution (spinning solution A) without obvious precipitates.

[0039] Spinning solution D: Solution C: Add 2g of polyvinyl alcohol granules to 18ml of deionized water and heat in an oil bath at 100r / min and 90℃ for 4h to obtain a polymer solution that is well mixed and free of obvious precipitates. Solution B: Add 0.5g of chitosan powder to 8.55g of acetic acid, stir at 300r / min for 1min, then add 0.95g of deionized water, stir at 300r / min for 4h to obtain a pale yellow, homogeneous, viscous liquid; Take 18g of solution A and 2g of solution A and mix them. Stir at 300r / min for 4h to obtain a polymer solution (spinning solution D) that is uniformly mixed and has no obvious precipitate.

[0040] S2: CA-CS / PVA / PVP-CA three-layer fiber membrane precursor Draw 5 mL of spinning solution A with a 10 mL syringe, replace the 21G spinneret, attach baking paper to the receiver, adjust the distance between the spinneret and the receiver to 15 cm for spinning, and set the spinning temperature and humidity to 15℃ and 50% respectively, adjust the positive and negative voltages to 18 kV and -2.5 kV respectively, the syringe push rate to 0.25 mm / min, and the spinning time to 2 h. After spinning is complete, replace spinning solution D, use a 10mL syringe to draw 10mL of spinning solution 2, replace with a clean 21G spinneret, adjust the positive and negative voltages to 23kV and -2.5kV respectively, keep other conditions unchanged, and spin for 4 hours. After spinning is complete, replace spinning solution A, use a 10mL syringe to draw 5mL of spinning solution 1, replace with a clean 21G spinneret, adjust the positive and negative voltages to 18kV and -2.5kV respectively, keep other conditions unchanged, and spin for 2 hours. After spinning is complete, a CA-CS / PVA / PVP-CA three-layer fiber membrane precursor is obtained.

[0041] S3: Novel biodegradable material-based adsorption membrane Chitosan, acetic acid and water were mixed evenly in a mass ratio of 1g:10g:89g to prepare a dilute chitosan coating solution. Cut the CA-CS / PVA / PVP-CA three-layer fiber membrane precursor into 5x5cm size, immerse it in 100mL of deionized water, and boil it in a 90℃ water bath for 15-30min. The water-etched CA-CS / PVA / PVP-CA three-layer fiber was then removed and directly immersed in a 1wt% chitosan-low-concentration acetic acid mixed solution. The stirring time was 5-10 minutes, and the drying conditions were 60℃ in a vacuum drying oven for 12 hours.

[0042] S4: Static Adsorption Experiment Take 0.1 g of the novel biodegradable material-based adsorption membrane and place it in 100 mL of 25 mg / L Cu. 2+ The simulated wastewater was stirred at 100 r / min for 1 hour.

[0043] Example 2: Compared to Example 1, only the CA-CS / PVA / PVP-CA three-layer fiber membrane precursor was prepared. Subsequent water bath etching and CS coating were not performed, and the static adsorption experiment was conducted in the same manner as in Example 1.

[0044] Example 3: Compared to Example 1, the CA-CS / PVA / PVP-CA three-layer fiber membrane precursor was subjected to only subsequent water bath etching without CS coating, and the static adsorption experiment was performed in the same manner as in Example 1.

[0045] Example 4: Compared to Example 1, the CA-CS / PVA / PVP-CA three-layer fiber membrane precursor will only undergo subsequent CS coating without water bath etching, and the static adsorption experiment will be performed in the same manner as in Example 1.

[0046] Comparative Example 1: The only difference from Example 1 is that the static adsorption experiment was conducted on Cu. 2+ For Pb 2+ The remaining process steps are the same as in Example 1.

[0047] Comparative Example 2: The only difference from Example 1 is that the static adsorption experiment was conducted on Cu. 2+ For Ni 2+ The remaining process steps are the same as in Example 1. Specific data can be found in [link to example]. Figure 4 .

[0048] Comparative Example 3: The only difference from Example 1 is that the static adsorption experiment was conducted on Cu. 2+ Zn2+ The remaining process steps are the same as in Example 1.

[0049] In summary, this invention provides a novel method for the application and preparation of biodegradable material-based adsorption membranes. Using environmentally friendly biodegradable polymers such as cellulose acetate, chitosan, polyvinyl alcohol, and polyvinylpyrrolidone as raw materials, a CA-CS / PVA / PVP-CA three-layer sandwich fiber membrane precursor is constructed through a single-needle stepwise electrospinning process. Then, the precursor is pore-forming by etching in a 90°C water bath and surface-modified with a chitosan acetate solution to finally obtain the target adsorption membrane.

[0050] The cellulose acetate layers on both sides of the membrane provide excellent mechanical support and dimensional stability, effectively solving the bottleneck of low mechanical strength and difficulty in independent use of pure chitosan membranes. After etching, the PVA and PVP in the middle functional layer partially dissolve, forming a rich porous structure that significantly increases the specific surface area and porosity, providing more active sites and diffusion channels for heavy metal ions. Chitosan modification further introduces a large number of chelating groups such as amino and hydroxyl groups, which enhance the chelation of Cu... 2+ Pb 2+ Ni 2+ Zn 2+ Heavy metal ions have strong coordination and capture capabilities, large adsorption capacity, and high removal efficiency.

[0051] The preparation process parameters of this invention are controllable and reproducible. The resulting membrane material has good flexibility, permeability and recyclability. It can also be naturally degraded after use without secondary pollution. It has broad industrial application prospects in the field of deep treatment and resource recycling of heavy metal wastewater and is in line with the concept of green and sustainable development.

[0052] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a novel biodegradable material-based adsorption membrane, characterized in that, Includes the following steps: S1. Dissolve cellulose acetate CA in a mixed solvent of acetone / ethanol to obtain solution A; S2. Dissolve chitosan CS in a high-concentration acetic acid solution to obtain solution B; S3. Add the mixed powder of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) to deionized water and heat it in a water bath at 60°C to dissolve it and obtain the spinning aid solution C. S4. Finally, solution B and solution C are mixed in proportion to obtain spinning solution D. Stepwise spinning method: spinning solution A, spinning solution D and spinning solution A are spun continuously to obtain CA-CS / PVA / PVP-CA three-layer fiber membrane precursor. S5. The standard three-layer fiber membrane precursor was immersed in deionized water and boiled in a water bath at 90°C for a period of time to obtain a CA-CS / PVA / PVP-CA etched three-layer fiber membrane. S6. Finally, the CA-CS / PVA / PVP-CA etched three-layer fiber membrane is directly immersed in a diluted chitosan acetate solution, stirred rapidly for a short time, removed and vacuum dried to obtain the novel biodegradable material-based adsorption membrane.

2. The method for preparing the novel biodegradable material-based adsorption membrane according to claim 1, characterized in that, In solution A, the cellulose acetate is industrial grade cellulose diacetate. Specifically, solution A is a 5 wt% cellulose acetate acetone / ethanol mixed solution; wherein, the solvent used to prepare mixture A is a 7:3 volume ratio acetone and ethanol mixed solution.

3. The method for preparing the novel biodegradable material-based adsorption membrane according to claim 1, characterized in that, The mixed solution B is a 5 wt% chitosan acetate mixed solution; in the mixed solution C, the mass ratio of polyvinyl alcohol and polyvinylpyrrolidone is 2:1, and the mixed powder accounts for 15% of the total solution; the mass ratio of solution B to solution C contained in solution D is 4:

6.

4. The method for preparing the novel biodegradable material-based adsorption membrane according to claim 1, characterized in that, For solution A, the electrospinning parameters are as follows: temperature 15-25℃, humidity 50%, positive spinning voltage 16kV, negative spinning voltage -1.5kV, spinning rate 0.5-1mm / min, distance between spinneret and receiver 18cm, single spinning time 0.25-0.5h, and cumulative spinning solution A volume of 1.5-3mL for both support membranes.

5. The method for preparing the novel biodegradable material-based adsorption membrane according to claim 1, characterized in that, For solution D, the electrospinning parameters are as follows: temperature 25-30℃, humidity 50%, positive spinning voltage 23kV, negative spinning voltage -2.5kV, spinning rate 0.15-0.25mm / min, distance between spinneret and receiver 15cm, single spinning time 2-6h, and single spinning volume of intermediate functional membrane 5-10mL.

6. The method for preparing the novel biodegradable material-based adsorption membrane according to claim 1, characterized in that, The ratio of chitosan, acetic acid, and water added to solution B is 0.5g:8.55g:0.95g.

7. The method for preparing the novel biodegradable material-based adsorption membrane according to claim 1, characterized in that, In solution C, the water bath conditions are 60°C for 4 hours, and the mass ratio of polyvinyl alcohol, polyvinylpyrrolidone, and water added is 2g:1g:17g.

8. The method for preparing the novel biodegradable material-based adsorption membrane according to claim 1, characterized in that, The CA-CS / PVA / PVP-CA three-layer fiber membrane precursor is a standard three-layer fiber membrane precursor, with a square membrane sheet size of 5x5cm; it is immersed in 100mL of deionized water and boiled in a water bath at 90℃ for 15-30min.

9. The method for preparing the novel biodegradable material-based adsorption membrane according to claim 1, characterized in that, The diluted chitosan acetate solution directly immersed in the CA-CS / PVA / PVP-CA etched three-layer fiber membrane is specifically a 1wt% mixed solution of chitosan and low-concentration acetic acid; the stirring time is 5-10 min; the drying conditions are drying at 60℃ in a vacuum drying oven for 12 h; the mixing mass ratio of chitosan, acetic acid and water is 1g:10g:89g.

10. Application of a novel biodegradable material-based adsorption membrane in the field of advanced treatment and resource recovery of heavy metal wastewater.

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