Biological material based salicin composite nanofiltration membrane as well as preparation method and application thereof

Abstract

The invention discloses a novel biological material based salicin composite nanofiltration membrane as well as a preparation method and application thereof, the nanofiltration membrane takes a biological material as a support membrane, and an ultrathin separation layer is formed on the surface of the support membrane by a water-phase monomer (including salicin) and an organic-phase monomer (such as trimesoyl chloride and TMC) through interfacial polymerization reaction. Wherein Isopar G is adopted as the organic phase solvent. The salicin is introduced, so that the nanofiltration membrane is endowed with excellent antibacterial and anti-pollution performance; meanwhile, Isopar G is used as an organic phase solvent, so that the environmental friendliness of the preparation process is effectively improved, and the structure of the separation layer is optimized. The aperture, surface characteristics and separation performance of the nanofiltration membrane can be effectively regulated and controlled by adjusting preparation parameters such as the pH value of a water-phase solution. The nanofiltration membrane has the advantages of high flux, high retention rate, environmental friendliness, biocompatibility and excellent antibacterial and anti-pollution performance, and is suitable for the fields of water treatment (especially scenes sensitive to microbial pollution), medicine separation, environmental protection and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of nanofiltration membrane preparation, and particularly relates to a biomaterial-based salicin composite nanofiltration membrane and a preparation method and application thereof. Background Art

[0002] The accumulation of trace heavy metal ions (such as lead, cadmium, and mercury) and antibiotic contaminants (such as sulfonamides and tetracyclines) in water bodies poses a threat to the ecological environment and human health. Trace heavy metal ions are highly toxic and bioaccumulative. Even at extremely low concentrations in water, they can accumulate through the food chain, ultimately harming human health. The widespread use of antibiotic contaminants has led to significant environmental residues, potentially inducing bacterial resistance and causing long-term impacts on aquatic ecosystems. Currently, commonly used water treatment technologies include chemical precipitation, adsorption, ion exchange, and membrane separation. Membrane separation technology, due to its high efficiency, energy conservation, and ease of operation, has become a research hotspot in the water treatment field. Nanofiltration membranes, a membrane separation technology between ultrafiltration and reverse osmosis, offer high separation precision and throughput, effectively removing trace heavy metal ions and organic contaminants from water.

[0003] Interfacial polymerization (IP) is a mainstream method for preparing high-performance composite nanofiltration membranes. It forms an ultrathin separation layer via a polymerization reaction at the interface between aqueous and organic phases, enabling high separation accuracy and high flux. However, conventional IIP nanofiltration membranes, particularly polyamide (PA) membranes, are typically prepared using petroleum-based monomers and organic solvents (e.g., n-hexane). This process is environmentally unfriendly (high volatility and toxicity), resource-unsustainable, and susceptible to chlorine oxidation and biofouling, limiting their application and long-term stability in certain applications. In recent years, to address these challenges, the membrane science community has focused on developing environmentally friendly nanofiltration membranes. On the one hand, the use of natural biomaterials (e.g., chitosan, cellulose, and polylactic acid) as support membranes or modifiers has attracted widespread attention due to their wide availability, renewable nature, and excellent biocompatibility, effectively reducing membrane preparation costs and environmental pollution. On the other hand, the introduction of bioactive molecules with specific functionalities to modify nanofiltration membranes to impart additional functions such as antibacterial and antifouling properties has also become an important research direction. For example, there have been some attempts in the prior art to introduce natural products to improve membrane performance, but there is still room for optimization in the introduction method and the organic solvents used.

[0004] While existing technologies have made some progress in the development of environmentally friendly nanofiltration membranes, practical applications still face numerous challenges. First, effectively integrating natural bioactive molecules (such as salicin) into the separation layer of nanofiltration membranes and leveraging their antibacterial and antifouling properties, as well as their specific separation or adsorption of specific pollutants (such as trace heavy metal ions and antibiotics) to achieve a multifunctional synergistic effect within the membrane material, remains a topic that requires in-depth research. Second, the toxicity and volatility of organic solvents commonly used in traditional interfacial polymerization, such as n-hexane, not only increase the environmental burden but also pose a potential health threat to operators. Therefore, the development and application of new, safer, and environmentally friendly green organic solvents to achieve green and efficient nanofiltration membrane preparation is particularly urgent. Furthermore, understanding the synergistic mechanism between biomaterial-based support membranes and the separation layer, as well as how to manipulate the membrane's microstructure and surface properties through sophisticated fabrication processes to further improve separation performance, chlorine resistance, and long-term operational stability, remain key and challenging areas of current nanofiltration membrane research. Summary of the Invention

[0005] The present invention addresses the shortcomings of existing technologies by providing a novel biomaterial-based salicin composite nanofiltration membrane, its preparation method, and its application. Based on a biomaterial-based support membrane, the present invention aims to construct a nanofiltration membrane with excellent separation performance, antibacterial and anti-fouling capabilities, and good biocompatibility on the surface of the biomaterial-based support membrane by cleverly introducing the natural bioactive monomer salicin into an interfacial polymerization reaction and using the environmentally friendly solvent Isopar G as the organic phase solvent. This overcomes the challenges of existing nanofiltration membranes in terms of environmental friendliness, long-term stability, and multifunctionality.

[0006] The main purpose of the present invention is to 1. Provide a nanofiltration membrane for efficient separation of trace heavy metal ions and antibiotics, and deeply explore its separation ability and mechanism for heavy metal ions of different valence states and various types of antibiotics.

[0007] 2. Develop a biomaterial-based nanofiltration membrane with the natural bioactive monomer salicin as its functional component to enhance its antibacterial and anti-pollution properties.

[0008] 3. Realize green preparation of nanofiltration membranes, use Isopar G to replace traditional organic solvents, and reduce environmental load.

[0009] 4. Study the chlorine resistance and long-term operational stability of biomaterial-based nanofiltration membranes, and optimize their application potential in water treatment, pharmaceutical separation, and environmental protection.

[0010] To achieve the above object, the present invention adopts the following technical solutions: In one aspect, the present invention provides a method for preparing a biomaterial-based salicin composite nanofiltration membrane, comprising the following steps: (1) Preparation of aqueous solution: dissolve the natural active monomer in deionized water, and adjust the pH value to the desired range using sodium hydroxide solution to obtain aqueous solutions with different pH values; (2) Preparation of organic phase solution: dissolve the acyl chloride in Isopar G as the organic phase solution; (3) Preparation of biomaterial-based salicin composite nanofiltration membrane: immerse the biomaterial-based support membrane in the aqueous solution prepared in step (1), remove excess water from the membrane surface after taking it out, and then immediately immerse it in the organic solution prepared in step (2) to carry out interfacial polymerization reaction; after the reaction is completed, take out the composite membrane and place it in an oven for heat treatment; thoroughly wash the membrane surface with deionized water to remove unreacted monomers and by-products, thereby obtaining a biomaterial-based salicin composite nanofiltration membrane.

[0011] Furthermore, the natural active monomer in step (1) is salicin; The concentration of salicin in the aqueous solution of step (1) is 0.1-0.5 wt%; The pH value of the aqueous phase solution in step (1) is 7-12.

[0012] Furthermore, the acyl chloride in step (2) is trimesoyl chloride (TMC); The concentration of acyl chloride in the organic phase solution in step (2) is 0.1-0.2 wt%.

[0013] Furthermore, the biomaterial-based support membrane in step (3) is a polylactic acid (PLA) membrane.

[0014] Furthermore, the reaction time of the biomaterial-based support membrane in the aqueous solution in step (3) is 10-12 minutes; The reaction time of the organic phase solution in step (3) is 5-8 minutes.

[0015] Furthermore, the oven temperature in step (3) is 60-80°C; The heat treatment time in step (3) is 20-30 minutes.

[0016] Furthermore, before immersing the biomaterial-based support membrane in the aqueous solution in step (3), the biomaterial-based support membrane is also pretreated, specifically, the biomaterial-based support membrane is immersed in an ethanol solution at 70° C. for 30-40 minutes for hydrophilization pretreatment, and then fully washed with deionized water.

[0017] The present invention also provides a biomaterial-based salicin composite nanofiltration membrane prepared by the above preparation method.

[0018] The present invention also proposes the application of the biomaterial-based salicin composite nanofiltration membrane in the separation of trace heavy metal ions and in the desalination of antibiotics.

[0019] The beneficial effects of the present invention are: 1. This invention utilizes interfacial polymerization of the naturally occurring active monomer salicin with trimesoyl chloride (TMC) to prepare a novel composite nanofiltration membrane on the surface of a biomaterial-based support membrane (PLA membrane). Compared to the petroleum-based materials commonly used in the prior art, the biomaterials and naturally occurring active molecules employed in this invention offer significant advantages in environmental friendliness and biocompatibility. During the interfacial polymerization process, the multiple hydroxyl or carboxyl groups (if derivatized) within the salicin molecular structure react with the acyl chloride or, through hydrogen bonding and π-π stacking, stabilize the membrane in the separation layer, imparting unique bioactivity to the membrane, thereby enhancing its hydrophilicity and anti-fouling properties and providing additional functionalization sites. 2. This invention innovatively uses Isopar G as the organic phase solvent for interfacial polymerization, replacing the traditional highly toxic and volatile n-hexane. As an isoparaffin solvent, Isopar G offers advantages such as low toxicity, low odor, high flash point, and low volatility. This significantly reduces environmental risks and operator hazards during the preparation process, complying with the requirements of green chemistry and sustainable development. Furthermore, Isopar G helps optimize the interfacial polymerization process, promoting the formation of a more uniform, less defective selective separation layer, thereby enhancing the overall performance of the membrane. 3. The novel biomaterial-based salicin composite nanofiltration membrane prepared by this invention effectively controls the pore size and surface properties of the separation layer by precisely regulating preparation parameters such as the concentrations of salicin and acyl chloride, as well as the pH value of the aqueous phase. This allows for efficient separation and high retention of trace heavy metal ions (such as lead, cadmium, and mercury) and antibiotic contaminants (such as sulfonamides and tetracyclines) at low operating pressures. Furthermore, due to the incorporation of salicin, the membrane also exhibits excellent antibacterial and anti-fouling properties, significantly extending its service life and reducing operating and maintenance costs. 4. The nanofiltration membrane prepared by this invention exhibits excellent mechanical strength, outstanding chlorine resistance, and long-term operational stability. Combined with its environmental friendliness, biocompatibility, efficient separation, and antibacterial and anti-pollution properties, it has enormous application potential in water treatment (particularly deep purification of drinking water sensitive to microbial contamination and hospital wastewater treatment), pharmaceutical separation (such as biomacromolecule purification and antibiotic recovery), and environmental protection (such as deep treatment of industrial wastewater and removal of environmental micropollutants).

[0020] In summary, the present invention provides a novel composite nanofiltration membrane based on a biomaterial-based support membrane, prepared by introducing the natural bioactive monomer salicin and performing interfacial polymerization using the environmentally friendly organic solvent Isopar G. This membrane not only efficiently separates trace heavy metal ions and antibiotics, but also exhibits excellent antibacterial and anti-fouling properties and good environmental friendliness, providing a new technical approach to addressing current water pollution issues. DETAILED DESCRIPTION

[0021] The present invention is described in further detail below in conjunction with specific embodiments. These embodiments are merely intended to illustrate the present invention and are not to be construed as limiting the scope of the invention. Without departing from the spirit or essential features of the present invention, those skilled in the art may make various modifications and variations, which all fall within the scope of protection of the present invention.

[0022] Pure water flux (PWP): Using a cross-flow filtration device, under a set pressure, record the pure water permeation per unit time and unit membrane area. The calculation formula is PWP=V / (A×t×P), where V is the permeation water volume (L) and A is the effective membrane area (m 2 ), t is the filtration time (h), ΔP is the operating pressure (bar), the unit is L / (m 2 h bar) Retention rate (R): A simulated solution of a specific concentration was filtered using a cross-flow filtration device at a set pressure. Heavy metal ion concentrations in the influent and effluent were measured by inductively coupled plasma mass spectrometry (ICP-MS), and antibiotic concentrations in the influent and effluent were measured by ultraviolet spectrophotometry (UV). The retention rate was calculated using the formula: R = (1-Cp / Cf) × 100%, where Cp is the permeate concentration and Cf is the feed concentration.

[0023] Chlorine resistance: The prepared nanofiltration membranes were immersed in a 1000 ppm sodium hypochlorite (NaClO) solution, removed periodically, and rinsed thoroughly with deionized water. Changes in the membrane's pure water flux and heavy metal ion rejection before and after immersion were measured to assess the membrane's chlorine resistance.

[0024] Example 1-6: Effect of different aqueous phase pH values ​​on the performance of biomaterial-based salicin composite nanofiltration membrane This series of examples aims to explore the effect of aqueous solution pH on the performance of biomaterial-based salicin composite nanofiltration membranes. The preparation method includes the following steps: (1) Pretreatment of biomaterial-based support membrane: PLA ultrafiltration membrane was prepared as support membrane by wet phase conversion method. The specific preparation process is as follows: first, 15% PLA was dissolved in 80% N,N-dimethylformamide (DMF) to prepare a uniform casting solution, and 5% hydrophilic additive (PEG) was added to regulate the membrane structure; then the casting solution was scraped onto a glass plate and quickly immersed in a coagulation bath to induce the exchange of solvent and non-solvent, causing PLA to phase separate and form an ultrafiltration membrane with a porous structure; finally, the primary membrane was washed with water to remove the residual solvent, and then dried or post-treated to obtain a PLA ultrafiltration membrane with good separation performance and a certain degree of hydrophilicity.

[0025] The PLA ultrafiltration membrane was immersed in an ethanol solution at 70°C for 30 minutes for hydrophilization pretreatment, and then thoroughly washed with deionized water.

[0026] (2) Preparation of aqueous solution: 0.2 wt% salicin was weighed and dissolved in deionized water, and the pH of the aqueous solution was adjusted by adding 0.1 M NaOH solution. In this series of examples, aqueous solutions with pH values ​​of 7.0 (Example 1), 8.0 (Example 2), 9.0 (Example 3), 10.0 (Example 4), 11.0 (Example 5), and 12.0 (Example 6) were prepared and stirred until completely dissolved.

[0027] (3) Preparation of organic phase solution: Weigh 0.18 wt% TMC and dissolve it in Isopar G. Stir until completely dissolved to obtain an organic phase solution.

[0028] (4) Preparation of biomaterial-based salicin composite nanofiltration membrane: The pretreated PLA ultrafiltration membrane was immersed in the aqueous solution prepared in step (2) for 10 minutes. After removal, the excess water on the membrane surface was gently scraped off with a rubber roller. The soaked ultrafiltration membrane was then immediately immersed in the organic solution prepared in step (3) and reacted for 5 minutes.

[0029] (5) Post-treatment: After the reaction is completed, the composite membrane is removed and placed in an oven at 60°C for heat treatment for 20 minutes. Finally, the membrane surface is thoroughly washed with deionized water to remove unreacted monomers and by-products, thereby obtaining a biomaterial-based salicin composite nanofiltration membrane.

[0030] Example 7-11: Effect of salicin concentration on the performance of biomaterial-based salicin composite nanofiltration membrane This series of examples aims to investigate the effect of salicin concentration on the performance of biomaterial-based salicin composite nanofiltration membranes. The preparation method is similar to that of Examples 1-6, but the aqueous phase pH is fixed at 9.0, the organic phase TMC concentration is 0.18 wt%, and the salicin concentration in the aqueous phase is varied.

[0031] (1) Different concentrations of salicin (0.1 wt% (Example 7), 0.2 wt% (Example 8), 0.3 wt% (Example 9), 0.4 wt% (Example 10), and 0.5 wt% (Example 11)) were dissolved in deionized water, the pH value was adjusted to 9.0 by adding 0.1 M NaOH solution, and the mixture was stirred until completely dissolved.

[0032] (2) The preparation of the organic phase solution, membrane preparation and post-treatment steps are the same as those in Example 1-6.

[0033] The biomaterial-based salicin composite nanofiltration membranes prepared in Examples 1-11 were subjected to pure water flux tests, separation performance tests for trace heavy metal ions, separation performance tests for antibiotics, and chlorine resistance tests.

[0034] The separation performance test of biomaterial-based salicin composite nanofiltration membrane for trace heavy metal ions includes the following steps: (1) Prepare the lead (Pb 2+ ), cadmium (Cd 2+ ), chromium (Cr 6+ ) and other heavy metal ions in a simulated wastewater solution with a concentration of 20 mg / L; (2) The biomass-based salicin composite nanofiltration membrane prepared in Example 1-11 was installed in a nanofiltration membrane testing device, and a separation test was performed at an operating pressure of 0.2 MPa; (3) The concentrations of heavy metal ions in the influent and effluent were determined using an inductively coupled plasma mass spectrometer (ICP-MS), and the retention rates of the nanofiltration membrane for different heavy metal ions were calculated.

[0035] The separation performance test of the biomaterial-based salicin composite nanofiltration membrane for antibiotics includes the following steps: (1) Prepare a simulated mixed wastewater solution containing sodium chloride and antibiotics such as sulfonamides and tetracyclines, with a salt solution concentration of 1000 mg / L and an antibiotic concentration of 50 mg / L; (2) The biomass-based salicin composite nanofiltration membrane prepared in Example 1-11 was installed in a nanofiltration membrane testing device, and a separation test was performed at an operating pressure of 0.2 MPa; (3) The concentrations of antibiotics in the inlet and outlet water were measured using an ultraviolet spectrophotometer (UV), and the retention rate of antibiotics by the biomass-based salicin composite nanofiltration membrane was calculated.

[0036] The chlorine resistance test of the biomaterial-based salicin composite nanofiltration membrane includes the following steps: (1) Prepare a chlorine solution containing 1000 ppm sodium hypochlorite (NaClO); (2) The biomass-based salicin composite nanofiltration membranes prepared in Examples 1-11 were immersed in a chlorine solution for 24 hours, and were taken out every hour during the immersion period and washed with deionized water; (3) The separation performance (pure water flux and Na2SO4 retention rate) of the biomaterial-based salicin composite nanofiltration membrane before and after immersion was tested to evaluate the chlorine resistance of the nanofiltration membrane.

[0037] Comparative Example 1 A method for preparing a conventional petroleum-based polyamide nanofiltration membrane, comprising: This comparative example aims to prepare a conventional petroleum-based polyamide nanofiltration membrane as a reference. The method comprises: (1) Dissolve 0.1 wt% piperazine (PIP) in deionized water and stir until completely dissolved to obtain an aqueous solution; (2) Dissolve 0.1 wt% TMC in n-hexane and stir until completely dissolved to obtain an organic phase solution; (3) Immerse the polyethersulfone (PES) ultrafiltration membrane in the aqueous solution prepared in step (1) for 10 minutes, remove it, and remove excess water from the surface with filter paper; (4) Immerse the soaked ultrafiltration membrane in the organic phase solution prepared in step (2) and react for 10 minutes; (5) Take out the film after reaction and place it in an oven at 60°C for heat treatment for 10 minutes; (6) The membrane surface was cleaned with deionized water to remove unreacted monomers, and a traditional petroleum-based polyamide nanofiltration membrane was obtained, which was recorded as M0.

[0038] Comparative Example 2 Preparation of salicin-free biomaterial-based nanofiltration membrane This comparative example aims to evaluate the contribution of salicin to membrane performance. The method comprises: (1) Preparation of aqueous solution: Weigh 1.5 wt% PIP and dissolve it in deionized water. Adjust the pH to 9.0 by adding 0.1 M NaOH solution and stir until completely dissolved.

[0039] (2) The subsequent organic phase solution preparation, membrane preparation and post-treatment steps are the same as those in Example 3.

[0040] Comparative Example 3 Preparation of salicin composite nanofiltration membrane based on biomaterials containing salicin but using n-hexane This comparative example is intended to evaluate the advantages of Isopar G as a green solvent. The method comprises: (1) Preparation of organic phase solution: Weigh 0.18 wt% TMC and dissolve it in n-hexane. Stir until completely dissolved to obtain an organic phase solution.

[0041] (2) The subsequent aqueous solution preparation, membrane preparation and post-processing steps are the same as those in Example 3.

[0042] Comparative Example 4 A method for preparing a cellulose-based nanofiltration membrane, comprising: (1) A certain amount of N-methylmorpholine-N-oxide (NMMO) was dissolved in deionized water to prepare an NMMO aqueous solution with a water content of 13.3%; (2) Add cellulose to the NMMO aqueous solution in step (1) and stir until it is completely dissolved and gradually becomes a uniform viscous solution; (3) The solution prepared in step (2) is vacuum degassed and coated on PES to form a film, which is then quickly immersed in deionized water to solidify; (4) The membrane was washed with deionized water to remove the residual NMMO solvent in the membrane, and then dried naturally for later use; (5) Prepare 1 mol / L NaOH solution and immerse the membrane prepared in step (4) in the 30°C NaOH solution for hydrolysis for 30 minutes; (6) Soak in deionized water to wash away the unreacted NaOH solution to obtain a cellulose-based nanofiltration membrane.

[0043] Test example: Comprehensive comparison of membrane separation performance The nanofiltration membranes prepared in Examples 1-11 and Comparative Examples 1-4 were subjected to cross-flow filtration using a self-made filtration device and tested for separation performance at 0.2 MPa. The test results are shown in Table 1. In the table, PWP is pure water flux; R(Pb 2+ )、R(Cd 2+ )、R(Cr 6+ ) are the retention rates of lead, cadmium, and chromium, respectively; R(NaCl), R(CHL), R(TC), and R(ADR) are the retention rates of NaCl, chloramphenicol (CHL), tetracycline hydrochloride (TC), and doxorubicin hydrochloride (ADR), respectively.

[0044]

[0045] As shown in Table 1, the biomaterial-based salicin composite nanofiltration membrane prepared in the present invention exhibits significant performance advantages compared with Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4. Specifically, 1. The effect of aqueous pH on membrane performance: The results of Examples 1-6 show that aqueous pH has a significant effect on membrane performance. As the pH value increases from 7 to 10, the pure water flux of the membrane gradually increases and reaches a peak value of 161.3 L / m at pH 10. 2h bar), and the rejection of heavy metal ions and antibiotics remained high. When the pH value was further increased to 11 and 12, the membrane flux and rejection decreased. This suggests that there is an optimal pH range (e.g., pH 8-10) that can effectively control the extent of interfacial polymerization and the pore structure of the separation layer, thereby optimizing the membrane's separation performance.

[0046] 2. Nonlinear Effect of Salicin Concentration on Membrane Filtration Properties: The results of Examples 7-11 clearly demonstrate the nonlinear effect of salicin concentration on membrane performance. Within the salicin concentration range of 0.1 wt% to 0.5 wt%, pure water flux and heavy metal rejection rates initially increased and then decreased. For example, at salicin concentrations of 0.2 wt% (Example 8, identical to the data from Example 3 at pH 9.0) and 0.3 wt% (Example 9), the membranes exhibited the best overall performance, with high pure water flux and high retention rates for heavy metals and antibiotics. Excessively low salicin concentrations may result in insufficient separation layer density, while excessively high concentrations may increase membrane thickness or form defects, both of which are detrimental to optimal performance. This demonstrates that the present invention can achieve an optimal balance of membrane performance by precisely controlling salicin concentration.

[0047] 3. The introduction of salicin imparts multifunctionality to the membrane (compared with Comparative Example 2): Compared with Comparative Example 2 without salicin, the pure water flux of the membrane of the present invention (e.g., Example 3) increased from 75.8 L / m to 2 h bar significantly increased to 145.3 L / m 2 h bar, and the retention rate of heavy metal ions and antibiotics is also greatly improved. For example, 2+ The retention rate of salicin increased from 85.0% to 99.7%, and the retention rate of CHL increased from 70.0% to 85.1%. This clearly shows that the introduction of salicin not only significantly improved the flux and retention efficiency of the membrane, but also may have given the membrane additional antibacterial and anti-fouling properties, realizing the multifunctionality of the membrane.

[0048] 4. Advantages of green solvent Isopar G (compared with comparative example 3): Compared with comparative example 3 using n-hexane as the organic phase solvent, the membrane prepared using Isopar G (such as example 3) of the present invention showed better performance. The pure water flux increased from 55.2 L / m 2 h bar increased significantly to 145.3 L / m 2 h bar, and generally higher retention rates for heavy metals and antibiotics. This demonstrates that Isopar G, as an environmentally friendly solvent, not only reduces the environmental risks and toxicity of the preparation process, but its unique solubility and diffusion properties also facilitate the formation of a thinner, more uniform separation layer with fewer defects and improved mass transfer performance.

[0049] 5. Superior overall performance: Overall, the biomaterial-based salicin composite nanofiltration membrane prepared by the present invention, especially the optimized examples (such as Examples 3, 4, and 9), exhibited excellent overall performance in terms of pure water flux, heavy metal ion retention rate, and antibiotic desalination, generally outperforming traditional petroleum-based polyamide nanofiltration membranes (Comparative Example 1) and cellulose-based nanofiltration membranes (Comparative Example 4). For example, the pure water flux of Example 4 was as high as 161.3 L / m 2 h bar, far exceeding all comparable membranes while still maintaining efficient retention of target pollutants, demonstrating its great potential in a variety of water treatment applications.

[0050] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a biomaterial-based salicin composite nanofiltration membrane, characterized in that: The following steps are involved: (1) Preparation of aqueous solution: dissolve the natural active monomer in deionized water, and adjust the pH value to the desired range using sodium hydroxide solution to obtain aqueous solutions with different pH values; (2) Preparation of organic phase solution: dissolve the acyl chloride in Isopar G as the organic phase solution; (3) Preparation of biomaterial-based salicin composite nanofiltration membrane: immerse the biomaterial-based support membrane in the aqueous solution prepared in step (1), remove excess water from the membrane surface after taking it out, and then immediately immerse it in the organic solution prepared in step (2) to carry out interfacial polymerization reaction; after the reaction is completed, take out the composite membrane and place it in an oven for heat treatment; thoroughly wash the membrane surface with deionized water to remove unreacted monomers and by-products, thereby obtaining a biomaterial-based salicin composite nanofiltration membrane.

2. The method for preparing the biomaterial-based salicin composite nanofiltration membrane according to claim 1, characterized in that: The natural active monomer in step (1) is salicin; The concentration of salicin in the aqueous solution of step (1) is 0.1-0.5 wt%; The pH value of the aqueous phase solution in step (1) is 7-12.

3. The method for preparing the biomaterial-based salicin composite nanofiltration membrane according to claim 1, characterized in that: The acyl chloride in step (2) is trimesoyl chloride; The concentration of acyl chloride in the organic phase solution in step (2) is 0.1-0.2 wt%.

4. The method for preparing the biomaterial-based salicin composite nanofiltration membrane according to claim 1, characterized in that: The biomaterial-based support membrane in step (3) is a polylactic acid membrane.

5. The method for preparing the biomaterial-based salicin composite nanofiltration membrane according to claim 1, characterized in that: The reaction time of the biomaterial-based support membrane in the aqueous solution in step (3) is 10-12 minutes; The reaction time of the organic phase solution in step (3) is 5-8 minutes.

6. The method for preparing the biomaterial-based salicin composite nanofiltration membrane according to claim 1, characterized in that: The oven temperature in step (3) is 60-80°C; The heat treatment time in step (3) is 20-30 minutes.

7. The method for preparing the biomaterial-based salicin composite nanofiltration membrane according to claim 1, characterized in that: Before immersing the biomaterial-based support membrane in the aqueous solution in step (3), the biomaterial-based support membrane is also pretreated. Specifically, the biomaterial-based support membrane is immersed in an ethanol solution at 70°C for 30-40 minutes for hydrophilization pretreatment, and then fully washed with deionized water.

8. A biomaterial-based salicin composite nanofiltration membrane prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the biomaterial-based salicin composite nanofiltration membrane according to claim 8 in the separation of trace heavy metal ions.

10. Use of the biomaterial-based salicin composite nanofiltration membrane according to claim 8 in antibiotic desalination.

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