Composite membrane with functions of adsorption separation and catalytic degradation of new pollutants as well as preparation method and application of composite membrane

Abstract

The invention discloses a composite membrane with adsorption separation and catalytic degradation functions as well as a preparation method and application of the composite membrane. The composite membrane is supported by a porous base membrane, a polyamide separation layer formed by reaction of a 3, 4-dihydroxyphenylethylamine and 2, 3-diaminophenol comonomer and acyl chloride is constructed on the surface of the porous base membrane through interfacial polymerization, and FeCo-g-C3N4 nanosheets are anchored in situ; the membrane can efficiently activate peroxymonosulfate (PMS) to generate free radicals under the nearly neutral condition, efficient interception and catalytic degradation of organic pollutants (such as antibiotics) are synchronously achieved, and heavy metal ions (such as Pb < 2 + > and Cd < 2 + >) are adsorbed through a functional monomer structure; the invention provides an interfacial polymerization preparation method of the membrane. The composite membrane breaks through the limitation of'only interception but not degradation 'of a traditional membrane, realizes integration of'separation-adsorption-degradation', can remarkably reduce the volume of concentrated water and reduce the toxicity of the concentrated water, and is suitable for advanced treatment of wastewater containing composite pollutants in the industries of pharmacy, printing and dyeing and the like.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of separation membrane technology and advanced oxidation catalysis technology, specifically relating to a composite membrane constructed by integrating a Fenton-like catalytic material and a separation layer through interfacial polymerization, and its preparation method. Background Technology

[0002] With the rapid development of industries such as pharmaceuticals, chemicals, and electronics, a large number of emerging pollutants (CECs) have been detected in wastewater, such as tetracycline antibiotics, bisphenol A (BPA), and perfluorinated compounds. These substances are biotoxic, persistent, and pose potential ecological risks, and are difficult to remove effectively using conventional biological treatment methods.

[0003] Traditional, simple membrane separation technologies (such as nanofiltration and reverse osmosis) can efficiently retain CECs, but they only achieve "contaminant transfer" (e.g., Chinese invention patent CN 116059981 B), resulting in higher toxicity of the concentrate, greater difficulty in treatment, and even secondary pollution. Fenton-like technologies utilize transition metals to activate permonosulfate (PMS) to generate strong oxidizing free radicals, which can efficiently degrade organic matter under near-neutral conditions, but homogeneous catalysts are difficult to recover, and heterogeneous catalysts have insufficient activity. In recent years, coupled processes such as "membrane + advanced oxidation" (CN 114345139 B, CN 120664678 A) and "membrane + electrochemical catalysis" (CN 120058163 A, CN118183948 A, CN 120192001 A) have become research hotspots. For example, photocatalysts such as TiO2, g-C3N4, and SiO2@TiO2 are loaded onto the membrane surface (CN 115839035 B, CN 118811932 A, CN 110860218 B, CN 106186171B, CN 104383821 A, CN 118374977 A) to achieve effective separation and degradation of new pollutants. For example, Chinese invention patent CN 108502969 A discloses a wastewater treatment system using photocatalytic degradation membrane separation. The outer surface of the inner membrane and the inner surface of the outer membrane are equipped with photocatalysts. Under ultraviolet light irradiation, hydrogen peroxide undergoes a photo-Fenton reaction under the action of the catalyst, generating a large number of hydroxyl radicals, thereby degrading pollutants. CN 114042387 A discloses a multilayer composite membrane for photocatalytic degradation of dye wastewater separation, its preparation method, and its application, utilizing an organic porous support layer, a three-dimensional graphene oxide separation layer, a tannic acid crosslinking transition layer, and an iron-based catalytic degradation layer. CN 114538597 A discloses a membrane catalytic contactor for enhanced ozone oxidation of novel pollutants in water. CN 118598270 A discloses a method for efficiently removing antibiotics and resistance genes based on a Co3O4-ZIF@CNT catalytic membrane and UV irradiation. CN 114452818 A discloses an ultrafiltration membrane based on a separation-photocatalytic sequence and its preparation method. CN 119327285 A discloses a method for preparing a ceramic membrane with both high-efficiency separation and catalytic functions, using transition metal oxide nanofibers as raw materials, as well as the resulting product and its application, thereby achieving a simultaneous improvement in the separation efficiency and catalytic degradation efficiency of the ceramic membrane. CN 115105976 B discloses a method for preparing a carbon quantum dot photocatalytic multi-layer composite nanofiltration membrane. CN 117299133 A discloses a catalytic separation membrane, its preparation method, its application, and a method for degrading pollutants in water, utilizing cobalt and titanium sources. However, it suffers from problems such as low visible light utilization, the need for an ultraviolet light source, and easy catalyst detachment.However, nano / micron-scale powdered catalysts are prone to loss during use, and the catalysts after the reaction face the challenge of separation and recovery. If the powdered catalysts remaining in the water cannot be completely separated, there is a risk of secondary pollution to the water.

[0004] Integrating membrane separation with advanced oxidation not only avoids the cumbersome subsequent catalyst separation process but also endows membrane materials with the ability to oxidatively degrade small-molecule organic pollutants and reduce irreversible fouling, allowing PS-AOPs to function better in membrane systems. For example, Chinese invention patent CN 119015904 A discloses a catalytic separation membrane that generates singlet oxygen through efficient activation of persulfate, simultaneously performing retention and efficient degradation of organic pollutants. However, current separation membranes cannot achieve effective contact with persulfate and pollutants, resulting in poor degradation of organic micropollutants. Furthermore, they lack the ability to synergistically remove coexisting heavy metals. Therefore, there is an urgent need to develop an integrated functional membrane that can simultaneously achieve organic pollutant retention-degradation and heavy metal adsorption. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the object of the present invention is to provide a composite membrane that combines adsorption separation and catalytic degradation of new pollutants, as well as its preparation method and application. To achieve the above object and other related objects, the present invention provides a composite membrane that combines adsorption separation and catalytic degradation of new pollutants, comprising: a porous organic base membrane and a polyamide separation layer formed on the surface of the porous organic base membrane through interfacial polymerization; The polyamide separation layer is composed of a polyamide network formed by reacting a comonomer containing 3,4-dihydroxyphenylethylamine and 2,3-diaminophenol with an acyl chloride monomer, and the separation layer contains iron-cobalt bimetallic doped carbon nitride nanosheets (FeCo-g-C3N4).

[0006] Preferably, in the comonomer, the mass ratio of 3,4-dihydroxyphenylethylamine to 2,3-diaminophenol is (1~2):1.

[0007] Preferably, the FeCo-g-C3N4 nanosheets in the separation layer have a mass fraction of 0.05% to 0.15%.

[0008] Preferably, the iron-cobalt bimetallic doped carbon nitride nanosheets (FeCo-g-C3N4) have a specific surface area ≥80 m² / g and a molar ratio of C:Fe:Co of 100:(1~3):1.

[0009] Preferably, the porous organic-based membrane is a polysulfone (PSf), polyethersulfone (PES), or polyvinylidene fluoride (PVDF) ultrafiltration membrane with a molecular weight cutoff of 50~100 kDa.

[0010] On the other hand, the present invention provides a method for preparing the composite membrane, the method comprising the following steps: S1. Immerse the porous organic base membrane in an aqueous solution containing 3,4-dihydroxyphenylethylamine and 2,3-diaminophenol for 40-90 seconds, and remove it to remove excess droplets from the surface. S2, the membrane treated by S1 is immersed in an oil phase solution containing acyl chloride monomer and FeCo-g-C3N4 nanosheets for 20-60 seconds to carry out interfacial polymerization reaction; S3. The reacted membrane is heat-treated and cured at 55~75℃ for 3~7 minutes, then cleaned and dried to obtain the composite membrane.

[0011] Preferably, the total monomer concentration of the aqueous solution in S1 is 1.5~2.5 wt%, and the solvent is a buffer solution with pH 8.0~9.0.

[0012] Preferably, the acyl chloride monomer in the oil phase solution in S2 is trimesoyl chloride with a concentration of 0.08~0.18wt%; the oil phase solvent is n-hexane or cyclohexane.

[0013] In another aspect, the present invention provides the application of the composite membrane in the treatment of wastewater from the pharmaceutical, chemical or electronics industries.

[0014] Preferably, the method for treating wastewater is as follows: First, add 0.5~2.0 mM permonosulfate (PMS) to the wastewater to be treated. Then, the wastewater obtained in step one is subjected to cross-flow filtration on the surface of the composite membrane; the cross-flow filtration is carried out under the conditions of pH 5~8, operating pressure 0.4~1.2 MPa, and 25~40℃. The wastewater to be treated contains emerging pollutants and heavy metals; the emerging pollutants include at least one of antibiotics and endocrine disruptors; the heavy metals include Pb. 2+ Cd 2+ Cu 2+ Cr 6+ At least one of them. Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] (1) The first "catechol / o-aminophenol comonomer + FeCo-g-C3N4" synergistic system: The catechol structure not only participates in interfacial polymerization to form a stable polyamide network, but also provides abundant coordination sites, which can efficiently adsorb Pb 2+ Cd 2+ Heavy metals; (2) FeCo bimetallic doped g-C3N4 exhibits excellent Fenton-like activity: it efficiently activates PMS at near-neutral pH, generating active free radicals (SO42-). - · / ·OH), which degrades organic pollutants trapped on the membrane surface in situ, preventing the accumulation of concentrated water; (3) Achieve “triple function integration”: separation (retention of CECs) + adsorption (enrichment of heavy metals) + catalysis (degradation of organic matter), breaking through the limitation of traditional membranes that “only block but do not remove”; (4) No external light source required: The catalytic reaction is carried out at room temperature and without the need for an external light source, which can be adapted to actual wastewater conditions; (5) FeCo-g-C3N4 is covalently anchored to the separation layer to prevent leakage of nanoparticles and ensure long-term operational stability. Attached Figure Description

[0016] Figure 1 A schematic diagram of a method for preparing a composite membrane that combines adsorption separation and catalytic degradation of novel pollutants; Figure 2 A diagram illustrating the mechanism by which composite membranes adsorb and separate trace heavy metal ions and catalytically degrade new pollutants. Detailed Implementation

[0017] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and appendices, but the scope of protection of the present invention is not limited thereto.

[0018] To ensure the accuracy and comparability of the composite membrane performance evaluations in all embodiments and comparative examples, this section uniformly specifies the following standard test methods and calculation methods.

[0019] (1) Pure water flux test The membrane permeation performance was tested in a cross-flow filtration apparatus. Specifically, an ultrafiltration cup (model: XFUF04701, Millipore, USA) with an effective membrane area of ​​A (m²) was used as the test cell. The test system was connected to a 500 mL feed container and a high-pressure nitrogen cylinder to provide operating pressure. All membrane samples were pre-pressurized with ultrapure water at an operating pressure of 0.5 MPa for 30 minutes before testing until the water flux reached a steady state. During the formal testing, the stirring speed of the ultrafiltration cup was set to 600 rpm to simulate cross-flow conditions and minimize concentration polarization effects on the membrane surface.

[0020] Membrane pure water flux (L·m) -2 ·h -1 ·bar -1 Calculate using the following formula ,in: The volume of the permeate during the test period (L); Effective membrane area (m²) 2 ); The test runtime (h); The applied operating pressure (bar).

[0021] The standard test conditions are: operating pressure 0.4 MPa, temperature 25 ± 1°C, and feed liquid is ultrapure water.

[0022] (2) Pollutant separation and catalytic degradation performance test

[0023] This test is used to evaluate the membrane's ability to retain emerging organic pollutants and its in-situ catalytic degradation capabilities.

[0024] Test solution preparation: Using ultrapure water as solvent, prepare simulated wastewater containing a specific concentration of target organic pollutant (such as 10 mg / L tetracycline) and 1.0 mM permonosulfate (PMS), and adjust the pH to 7.0 ±0.2 with dilute hydrochloric acid or sodium hydroxide solution.

[0025] Test procedure: Using the cross-flow filtration device described above, the prepared test solution was used as the feed liquid. The system was run continuously for 2 hours at 0.4 MPa and 25 ± 1°C, during which permeate and retentate samples were collected at specific time points (e.g., 0, 30, 60, 90, 120 min).

[0026] Sample analysis and evaluation indicators: Pollutant concentration determination: The concentration of organic pollutants in each sample was determined using high performance liquid chromatography (HPLC) or ultraviolet-visible spectrophotometry.

[0027] Retention rate (R, %): Calculated according to the following formula, it reflects the membrane's ability to physically sieve and retain pollutants.

[0028]

[0029] in, and These represent the concentrations of organic pollutants in the permeate and the initial feed liquid, respectively.

[0030] Degradation rate (D, %): To eliminate the influence of simple retention and objectively evaluate the contribution of catalytic degradation, it was calculated using the material balance algorithm.

[0031]

[0032] in, This represents the concentration of organic pollutants in the retrieval solution at the end of operation. , , These represent the volumes of permeate, retentate, and initial feed liquid, respectively.

[0033] (3) Heavy metal adsorption performance test This test is used to evaluate the membrane's ability to adsorb and enrich trace heavy metal ions.

[0034] Dynamic adsorption rate test: In the aforementioned "(2) Pollutant separation and catalytic degradation performance test", if the feed liquid also contains specific heavy metal ions (such as 10 mg / L Pb) 2+ If the concentration of heavy metal ions in each sample is high, inductively coupled plasma mass spectrometry (ICP-MS) or atomic absorption spectrometry (AAS) is used to determine the concentration. Dynamic adsorption rate ( Calculate using the following formula:

[0035] in, , , These represent the concentrations of heavy metal ions in the permeate, retentate, and feed liquid, respectively.

[0036] Saturated adsorption capacity test: A static adsorption experiment was conducted. Accurately weigh ( A dry film sample of g was immersed in a certain volume ( (L) Known concentration ( The membrane was immersed in a heavy metal ion solution (mg / L) and shaken in a constant-temperature shaker in the dark until adsorption equilibrium was reached (usually 24 h). The saturated adsorption capacity per unit mass of membrane was calculated by the concentration difference of the solution before and after adsorption. (mg / g):

[0037] in, This represents the concentration (mg / L) of heavy metal ions in the solution at adsorption equilibrium.

[0038] Example 1 A composite membrane that combines adsorption separation and catalytic degradation of novel pollutants, and its preparation method, are disclosed in this embodiment. The specific preparation method of the composite membrane includes the following steps: 1. FeCo-g-C3N4 nanosheets were prepared, and aqueous and oil-phase monomer solutions were prepared. The specific procedures are as follows: (1) Preparation of FeCo-g-C3N4 nanosheets Melamine, ferric nitrate hexahydrate, and cobalt nitrate hexahydrate were accurately weighed in a molar ratio of C:Fe:Co = 100:2:1 and thoroughly ground and mixed in an agate mortar for 30 minutes. The homogeneous mixture was transferred to a covered alumina crucible and placed in a tube furnace. Under an air atmosphere, the temperature was increased to 550°C at a rate of 5°C / min and calcined at this temperature for 4 hours. After the process was completed, the mixture was allowed to cool naturally to room temperature, yielding a pale yellow blocky solid. This solid was ground into powder to obtain iron-cobalt bimetallic doped carbon nitride nanosheets (FeCo-g-C3N4).

[0039] (2) Prepare aqueous and oil phase monomer solutions

[0040] a. Preparation of the aqueous solution: Accurately weigh 3,4-dihydroxyphenylethylamine (dopamine) and 2,3-diaminophenol, and mix them in a 1:1 mass ratio. Dissolve them in a 10 mM Tris-HCl buffer solution at pH 8.5 to prepare a homogeneous aqueous solution with a total concentration of 2.5 wt%. This buffer system is used to provide a suitable weakly alkaline environment for interfacial polymerization while inhibiting the oxidative self-polymerization of dopamine, ensuring the effective utilization of its amino and catechol groups.

[0041] b. Preparation of the oil phase solution: Accurately weigh the FeCo-g-C3N4 nanosheets prepared in step (1) to a mass fraction of 0.08 wt% in the oil phase, add them to n-hexane, and ultrasonically disperse for 60 minutes to form a uniform and stable dispersion. Then add trimesoyl chloride (TMC) to the dispersion to a concentration of 0.10 wt%, and gently shake to obtain the oil phase solution. 2. Interface aggregation process:

[0042] S1: Take a commercial polyethersulfone (PES) ultrafiltration membrane (molecular weight cutoff approximately 100 kDa, effective area approximately 20 cm²) and fix it onto a polypropylene frame. Immerse it completely in the above aqueous solution for 80 seconds to ensure the membrane surface is fully wetted. After removal, gently roll it with lint-free paper along the vertical direction of the membrane surface to remove excess droplets and keep the membrane pores and surface moist.

[0043] S2: Immediately immerse the membrane treated in S1 into the oil phase solution for 50 seconds. During this period, the amine monomers in the aqueous phase and the TMC in the oil phase undergo a rapid interfacial condensation reaction at the membrane-oil interface to form a polyamide separation layer, while FeCo-g-C3N4 nanosheets are anchored in situ within the polymer network.

[0044] S3: After polymerization, remove the composite film and place it in a 75°C forced-air oven for 6 minutes to allow the polyamide network to fully crosslink and cure.

[0045] S4: The heat-treated membrane is successively immersed in anhydrous ethanol for 5 minutes and rinsed 3 times in deionized water to thoroughly remove unreacted monomers and solvents. Finally, the membrane is dried in a vacuum drying oven at 40°C for 12 hours to obtain the composite membrane with adsorption separation-catalytic degradation functions. 3. Membrane performance characterization:

[0046] The performance of the obtained composite membrane was tested according to the aforementioned “(I) Comprehensive Testing and Evaluation Method for Membrane Performance”:

[0047] Pure water flux (J): Measured at an operating pressure of 0.4 MPa, the value is 106 L·m. -2 ·h -1 .

[0048] Pollutant separation and degradation performance: (with samples containing 10 mg / L tetracycline and 10 mg / L Pb) 2+ A 1 mM PMS solution (pH≈7.0) was used as the feed liquid, and the mixture was cross-flowed at 0.4 MPa and 25°C for 2 hours. The tetracycline rejection rate (R) was 99% and the tetracycline degradation rate (D) was 55% (calculated based on material balance).

[0049] Heavy metal adsorption performance: Pb was measured 2+ Dynamic adsorption rate (single run): 85%; Pb 2+ Saturated adsorption capacity (Qe): 20 mg / g, determined by static adsorption experiments.

[0050] Examples 2-4: Examples 2-4 provide specific preparation methods for the composite membrane, the steps of which are exactly the same as those in Example 1, the only difference being: In step S1 of the interfacial polymerization process, the time for immersing the polyethersulfone porous base membrane in the aqueous solution was adjusted to 70 seconds, 60 seconds, and 50 seconds (as recorded in Table 1), while the remaining operating parameters, material formulations, and subsequent steps remained unchanged.

[0051] Comparative Example 1:

[0052] A commercially available polyethersulfone (PES) nanofiltration membrane without any functional modification was selected as the performance comparison benchmark. This comparative membrane is a commercial product, and its preparation method does not involve the interfacial polymerization and functional material doping processes of this invention.

[0053] Comparative Example 2:

[0054] To investigate the necessity of 2,3-diaminophenol in the comonomer, this comparative example provides a method for preparing a comparative membrane. The main difference between this method and Example 1 is that: In the preparation of the aqueous monomer solution, only 3,4-dihydroxyphenylethylamine (dopamine) was used as the single amine monomer, and 2,3-diaminophenol was not added. The concentration of dopamine in Tris-HCl buffer (pH=8.5) was maintained at 2.5 wt%. The preparation of the oil phase solution and all subsequent interfacial polymerization and post-treatment steps were exactly the same as in Example 1.

[0055] Comparative Example 3:

[0056] To investigate the contribution of FeCo-g-C3N4 nanosheets to catalytic function, this comparative example provides a method for preparing a comparative film. The main difference between this method and Example 1 is that: In the preparation of the oil phase monomer solution, FeCo-g-C3N4 nanosheets were not added. Only trimesoyl chloride (TMC) was dissolved in n-hexane at a concentration of 0.10 wt% to prepare the oil phase solution. The preparation of the aqueous phase solution and all subsequent interfacial polymerization and post-treatment steps were exactly the same as in Example 1.

[0057] Comparative Example 4:

[0058] To investigate the synergistic effect of functional monomers and catalytic nanosheets, this comparative example provides a method for preparing a comparative film. The steps are exactly the same as in Example 1, i.e., the formulations of the aqueous and oil phases, and all process parameters are identical. The only difference is: This comparative example directly uses a commercial polyethersulfone ultrafiltration membrane without any pretreatment as the base membrane, without undergoing the interfacial polymerization treatments such as fixation and impregnation described in Example 1. This membrane only possesses the characteristics of the base membrane itself, and is used to compare and illustrate that the multifunctional separation layer formed by interfacial polymerization is the core of this invention.

[0059] Test Example 1:

[0060] The composite membranes prepared by Examples 1-4 and Comparative Examples 1-4 were tested according to the aforementioned performance test conditions. The results are shown in Table 1 below: Table 1 Performance test characterization of Test Example 1 serial number Contact time of aqueous solution (s) <![CDATA[J H2O (L·m -2 ·h -1 ·MPa -1 )]]> Tetracycline retention rate (%) Tetracycline degradation rate (%) <![CDATA[Pb 2+ Adsorption rate (%) <![CDATA[Pb 2+ Saturated adsorption capacity (mg / g) Example 1 80 106 99 55 85 20 Example 2 70 147 99 61 90 18 Example 3 60 181 99 65 99 22 Example 4 50 191 99 45 85 16 Comparative Example 1 / 95 98 0 0 0 Comparative Example 2 80 101 95 0 0 0 Comparative Example 3 80 105 94 30 0 0 Comparative Example 4 80 99 96 0 75 18 The results of Examples 1-4 and Comparative Examples 1-4 show that, compared with commercial nanofiltration membranes and composite nanofiltration membranes without aqueous and oil phase modification, the strategy proposed in this invention can effectively improve the flux and new pollutant rejection rate of composite nanofiltration membranes, while also adsorbing trace heavy metal ions. More importantly, the introduction of FeCo-g-C3N4 nanosheets overcomes the defect of traditional nanofiltration membranes that only retain but do not remove pollutants. FeCo-g-C3N4 activates permonosulfate (PMS) under near-neutral conditions, generating sulfate radicals (SO42-) in situ. -The composite nanofiltration membrane utilizes hydroxyl radicals (·OH) to catalytically degrade trapped pollutants. Furthermore, the performance of the composite nanofiltration membrane is affected by the contact time with the aqueous solution; optimal performance is achieved when the contact time is 60 seconds. Specifically, the degradation rate of tetracycline is 66%, and Pb... 2+ The adsorption rate is 99%, and Pb 2+ The saturated adsorption capacity is as high as 22 mg / g.

[0061] Example 5: A composite membrane combining adsorption separation and catalytic degradation of novel pollutants and its preparation method, wherein the preparation method comprises the steps described in Example 1, with the difference being:

[0062] In step S1 of the interfacial polymerization process, the immersion time in the aqueous solution is adjusted to 60 seconds. In step S2 of the interfacial polymerization process, the immersion time in the oil solution after the membrane is wetted by the aqueous phase is adjusted to 20 seconds. All other operating parameters, material formulations and subsequent steps remain unchanged.

[0063] Examples 6-8:

[0064] Examples 6-8 provide specific preparation methods for the composite membrane, the steps of which are exactly the same as those in Example 5, the only difference being:

[0065] In step S2 of the interfacial polymerization process, the time for immersing the membrane after being wetted in the aqueous phase into the oil phase solution is adjusted to 30 seconds, 40 seconds, and 45 seconds (as recorded in Table 2), while the remaining operating parameters, material formulations, and subsequent steps remain unchanged. Comparative Example 5:

[0066] To investigate the necessity of comonomers at the optimal oil phase contact time, this comparative example provides a method for preparing a comparative film. The main difference between this method and Example 5 is that:

[0067] In the preparation of the aqueous monomer solution, only 3,4-dihydroxyphenylethylamine (dopamine) was used as the single amine monomer, and 2,3-diaminophenol was not added. The concentration of dopamine in Tris-HCl buffer (pH=8.5) was maintained at 2.5 wt%. The preparation of the oil phase solution and all subsequent interfacial polymerization and post-treatment steps were exactly the same as in Example 5.

[0068] Comparative Example 6: To investigate the contribution of FeCo-g-C3N4 nanosheets to catalytic function under optimal oil phase contact time, this comparative example provides a method for preparing a comparative film. The main difference between this method and Example 5 is that:

[0069] In the preparation of the oil phase monomer solution, FeCo-g-C3N4 nanosheets were not added. Only trimesoyl chloride (TMC) was dissolved in n-hexane at a concentration of 0.10 wt% to prepare the oil phase solution. The preparation of the aqueous phase solution and all subsequent interfacial polymerization and post-treatment steps were exactly the same as in Example 5.

[0070] Comparative Example 7: To investigate the synergistic film-forming effect of functional monomers and catalytic nanosheets on a substrate film under optimal oil phase contact time, this comparative example provides a method for preparing a comparative film. The steps are exactly the same as in Example 5, with the only difference being:

[0071] This comparative example directly uses a commercial polyethersulfone ultrafiltration membrane without any pretreatment as the base membrane, without performing the interfacial polymerization treatments such as fixation and impregnation as described in Example 5.

[0072] Test Example 2: The composite membranes prepared by Examples 5-8 and Comparative Examples 1 and 5-7 were tested according to the aforementioned performance test conditions. The results are shown in Table 2 below:

[0073] Table 2 Performance test characterization of Test Example 2 serial number Oil phase solution contact time (s) <![CDATA[J H2O (L·m -2 ·h -1 ·MPa -1 )]]> Tetracycline retention rate (%) Tetracycline degradation rate (%) <![CDATA[Pb 2+ Adsorption rate (%) <![CDATA[Pb 2+ Saturated adsorption capacity (mg / g) Example 5 20 146 99 55 85 20 Example 6 30 168 99 60 91 23 Example 7 40 191 99 64 99 26 Example 8 45 181 99 45 95 24 Comparative Example 1 / 95 98 0 0 0 Comparative Example 5 20 141 90 0 0 0 Comparative Example 6 20 135 93 20 0 0 Comparative Example 7 20 140 94 0 0 18 As shown in Examples 5-8, Comparative Examples 1, and Comparative Examples 5-7, compared to commercial nanofiltration membranes and composite nanofiltration membranes without aqueous and oil phase modification, the strategy proposed in this invention can effectively improve the flux and rejection rate of new pollutants in composite nanofiltration membranes, while also adsorbing trace heavy metal ions. More importantly, the introduction of FeCo-g-C3N4 nanosheets overcomes the defect of traditional nanofiltration membranes that only retain but do not remove pollutants. FeCo-g-C3N4 activates permonosulfate (PMS) under near-neutral conditions, generating sulfate radicals (SO42-) in situ. - The composite nanofiltration membrane utilizes hydroxyl radicals (·OH) to catalytically degrade trapped pollutants. Furthermore, the performance of the composite nanofiltration membrane is affected by the contact time with the oil phase solution; optimal performance is achieved when the contact time is 40 seconds. Specifically, the degradation rate of tetracycline is 64%, and Pb... 2+ The adsorption rate is 99%, and Pb 2+ The saturated adsorption capacity is as high as 26 mg / g.

[0074] Example 9: A composite membrane that combines adsorption separation and catalytic degradation of novel pollutants and its preparation method are disclosed in this embodiment. The specific preparation method of the composite membrane is exactly the same as that in Example 5, with the only difference being:

[0075] In step S2 of the interfacial polymerization process, the immersion time of the membrane after being wetted in the aqueous phase into the oil phase solution is adjusted to 40 seconds. In step S3 of the interfacial polymerization process, the thermosetting temperature is adjusted to 55 °C. All other operating parameters, material formulations and subsequent steps remain unchanged.

[0076] Examples 10-12: They are exactly the same, the only difference is:

[0077] In step S3 of the interface polymerization process, the thermosetting temperature is adjusted to 60 ℃, 65 ℃, and 70 ℃ (as recorded in Table 3), while the remaining operating parameters, material formulation, and subsequent steps remain unchanged.

[0078] Comparative Example 8: To investigate the necessity of comonomers at a preferred curing temperature, this comparative example provides a method for preparing a comparative film. The main difference between this method and Example 9 is that 2,3-diaminophenol is not added to the aqueous phase; otherwise, the methods are the same as in Example 9.

[0079] Comparative Example 9: To investigate the contribution of FeCo-g-C3N4 nanosheets to catalytic function at a preferred curing temperature, this comparative example provides a method for preparing a comparative film. The main difference between this method and Example 9 is that FeCo-g-C3N4 nanosheets are not added to the oil phase; otherwise, the methods are the same as in Example 9.

[0080] Comparative Example 10: To investigate the necessity of interfacial polymerization at a preferred curing temperature, this comparative example provides a method for preparing a comparative membrane. The steps are exactly the same as in Example 9 (curing temperature 55°C), the only difference being that a pristine commercial polyethersulfone ultrafiltration membrane that has not undergone interfacial polymerization treatment is used as the base membrane.

[0081] Test Example 3: Effect of Curing Temperature on Composite Film Properties

[0082] The composite membranes prepared by Examples 9-12, Comparative Examples 1, and Comparative Examples 8-10 were tested according to the aforementioned performance test conditions. The results are shown in Table 3 below.

[0083] Table 3 Performance test characterization of Test Example 3 serial number Curing temperature (°C) <![CDATA[J H2O (L·m -2 ·h -1 ·MPa -1 )]]> Tetracycline retention rate (%) Tetracycline degradation rate (%) <![CDATA[Pb 2+ Adsorption rate (%) <![CDATA[Pb 2+ Saturated adsorption capacity (mg / g) Example 9 55 156 99 56 85 21 Example 10 60 178 99 61 91 24 Example 11 65 199 99 67 99 28 Example 12 70 181 99 55 95 23 Comparative Example 1 / 95 98 0 0 0 Comparative Example 8 55 151 92 0 0 0 Comparative Example 9 55 155 96 21 0 0 Comparative Example 10 55 147 95 0 0 19 As shown in Examples 9-12, Comparative Examples 1, and Comparative Examples 8-10, compared with commercial nanofiltration membranes and composite nanofiltration membranes without aqueous and oil phase modification, the strategy proposed in this invention can effectively improve the flux and new pollutant rejection rate of composite nanofiltration membranes, while also adsorbing trace heavy metal ions. More importantly, the introduction of FeCo-g-C3N4 nanosheets overcomes the defect of traditional nanofiltration membranes that only retain but do not remove pollutants. FeCo-g-C3N4 activates permonosulfate (PMS) under near-neutral conditions, generating sulfate radicals (SO42-) in situ. - The composite nanofiltration membrane utilizes hydroxyl radicals (·OH) to catalytically degrade trapped pollutants. Furthermore, the performance of the composite nanofiltration membrane is affected by the curing temperature, with optimal performance observed at 65 °C. Specifically, the degradation rate of tetracycline is 67%, and Pb... 2+ The adsorption rate is 99%, and Pb 2+ The saturated adsorption capacity is as high as 28 mg / g.

[0084] Example 13:

[0085] A composite membrane that combines adsorption separation and catalytic degradation of novel pollutants and its preparation method are disclosed in this embodiment. The specific preparation method of the composite membrane is exactly the same as that in Example 11, with the only difference being: In step S3 of the interface polymerization process, the thermosetting temperature is adjusted to 65°C and the thermosetting time is adjusted to 3 minutes, while the remaining operating parameters, material formulation and subsequent steps remain unchanged. Examples 14-16:

[0086] Examples 14-16 provide specific methods for preparing the composite membrane, the steps of which are exactly the same as those in Example 13, the only difference being: In step S3 of the interface polymerization process, the thermosetting time is adjusted to 4 minutes, 5 minutes, and 7 minutes (as recorded in Table 4), while the remaining operating parameters, material formulation, and subsequent steps remain unchanged. Comparative Example 11:

[0087] To investigate the necessity of comonomers at an optimal curing time, this comparative example provides a method for preparing a comparative film. The main difference between this method and Example 13 is that 2,3-diaminophenol is not added to the aqueous phase; otherwise, the methods are the same as in Example 13. Comparative Example 12:

[0088] To investigate the contribution of FeCo-g-C3N4 nanosheets to catalytic function under an optimal curing time, this comparative example provides a method for preparing a comparative film. The main difference between this method and Example 13 is that FeCo-g-C3N4 nanosheets are not added to the oil phase; otherwise, the methods are the same as in Example 13. Comparative Example 13:

[0089] To investigate the necessity of interfacial polymerization at a preferred curing temperature, this comparative example provides a method for preparing a comparative membrane. The steps are identical to those in Example 13, except that a pristine commercial polyethersulfone ultrafiltration membrane that has not undergone interfacial polymerization is used as the base membrane.

[0090] Test Example 4: Effect of Curing Time on Composite Film Performance

[0091] The composite membranes prepared by Examples 13-16 and Comparative Examples 1 and 11-13 were tested according to the aforementioned performance test conditions. The results are shown in Table 4 below: Table 4 Performance test characterization of Test Example 4 serial number Curing time (min) <![CDATA[J H2O (L·m -2 ·h -1 ·MPa -1 )]]> Tetracycline retention rate (%) Tetracycline degradation rate (%) <![CDATA[Pb 2+ Adsorption rate (%) <![CDATA[Pb 2+ Saturated adsorption capacity (mg / g) Example 13 3 166 99 56 85 20 Example 14 4 188 99 63 91 23 Example 15 5 210 99 70 99 30 Example 16 7 192 99 65 92 24 Comparative Example 1 / 95 98 0 0 0 Comparative Example 11 3 131 93 0 0 0 Comparative Example 12 3 135 94 23 0 0 Comparative Example 13 3 146 91 0 0 16 As shown in Examples 13-16, Comparative Examples 1, and Comparative Examples 11-13, compared with commercial nanofiltration membranes and composite nanofiltration membranes without aqueous and oil phase modification, the strategy proposed in this invention can effectively improve the flux and new pollutant rejection rate of composite nanofiltration membranes, while also adsorbing trace heavy metal ions. More importantly, the introduction of FeCo-g-C3N4 nanosheets overcomes the defect of traditional nanofiltration membranes that only retain but do not remove pollutants. FeCo-g-C3N4 activates permonosulfate (PMS) under near-neutral conditions, generating sulfate radicals (SO42-) in situ. - The composite nanofiltration membrane utilizes hydroxyl radicals (·OH) to catalytically degrade trapped pollutants. Furthermore, the performance of the composite nanofiltration membrane is affected by the curing time, with optimal performance observed at a curing time of 5 minutes. Specifically, the degradation rate of tetracycline is 70%, and Pb... 2+ The adsorption rate is 99%, and Pb 2+ The saturated adsorption capacity is as high as 30 mg / g. Application Examples:

[0092] To evaluate the comprehensive performance and advantages of the composite membrane of this invention in the actual treatment of complex high-salt wastewater, the following simulation comparison experiment was conducted. 1. Membrane sample

[0093] Experimental group: The composite membrane prepared in Example 15 was used, which has a complete integrated function of "separation-adsorption-degradation".

[0094] Control group: The control membrane prepared in Comparative Example 3 was used. This membrane has the same polyamide separation layer and heavy metal adsorption sites, but FeCo-g-C3N4 nanosheets were not added to the oil phase, and therefore it does not have the catalytic function to activate PMS. 2. Test methods and test conditions

[0095] Prepare 1 L of simulated high-salinity wastewater containing 20 mg / L bisphenol A (BPA), 30 mg / L diethyl phthalate (DEP), and Cd. 2+ 10 mg / L, Cu 2+ 15 mg / L NaCl and 20 g / L NaCl were added, and the pH was adjusted to 7.0. A flat-sheet membrane module with an effective membrane area of ​​0.014 m² was used for cross-flow circulation concentration at an operating pressure of 1.2 MPa for 4 hours. 1.0 mM PMS was continuously added to the feed solution of the experimental group to activate the membrane's catalytic function; the control group did not add PMS, simulating traditional nanofiltration process conditions. 3. Test Results and Analysis

[0096] (1) Effect of water recovery and concentrate reduction: After the operation, the experimental group produced 810 mL of water and 190 mL of concentrate; the control group produced 715 mL of water and 285 mL of concentrate. The water recovery rate of the experimental group (81%) was significantly higher than that of the control group (71.5%), resulting in a 33.3% reduction in the final concentrate volume. This is directly attributed to the effective mitigation of membrane fouling and concentration polarization caused by organic pollution by catalytic degradation.

[0097] (2) Pollutant removal and resource utilization effects: Heavy metals: Two sets of membranes for Cd 2+ and Cu 2+ The retention rates were all >99.5%, indicating that the present invention did not sacrifice the high efficiency of separation / adsorption performance of heavy metals when introducing catalytic function.

[0098] Organic pollutants: The total residual BPA and DEP in the concentrated water of the experimental group was only 6.8 mg, while that in the control group was as high as 47.2 mg. According to material balance calculations, the experimental group removed a total of 43.2 mg of organic pollutants during operation.

[0099] (3) Assessment of mineralization degree and toxicity of concentrated water: Total organic carbon (TOC) analysis showed that the TOC removal rate of the experimental group's effluent reached 93%, consistent with the above calculation results. Further LC-MS analysis of the experimental group's concentrated water revealed no detection of the original target pollutants BPA and DEP, only trace amounts of small-molecule acidic intermediates. This indicates that approximately 92.8% of the removed organic matter was mineralized into CO2 and H2O, achieving deep degradation and significantly reducing the ecotoxicity of the concentrated water. The concentrated water of the control group, however, was rich in the original pollutants. 4. Conclusion

[0100] This application example demonstrates that, compared to traditional nanofiltration membranes (or materials) lacking catalytic function, the composite membrane of this invention, when treating high-salt, complex-polluted wastewater, not only simultaneously and efficiently retains heavy metals but also achieves efficient degradation and mineralization of organic pollutants through in-situ activation of the PMS. This integrated "separation-adsorption-degradation" function brings three core benefits: significantly improved system water recovery rate (reducing concentrate volume by 33%), thoroughly reduced organic toxicity load in the concentrate (mineralization rate >92%), and significantly reduced difficulty and cost of subsequent concentrate treatment, providing a highly competitive key technology for "zero-discharge" treatment of industrial wastewater.

[0101] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection of the present invention. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of the present invention, or equivalent structural or procedural transformations made using the content of the present invention's specification and drawings, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of patent protection of the present invention.

Claims

1. A composite membrane that combines adsorption separation and catalytic degradation functions, characterized in that, include: A porous organic base membrane and a polyamide separation layer formed on the surface of the porous organic base membrane by interfacial polymerization; The polyamide separation layer is composed of a polyamide network formed by reacting a comonomer containing 3,4-dihydroxyphenylethylamine and 2,3-diaminophenol with an acyl chloride monomer, and the separation layer contains iron-cobalt bimetallic doped carbon nitride nanosheets (FeCo-g-C3N4).

2. The composite membrane according to claim 1, characterized in that, In the comonomer, the mass ratio of 3,4-dihydroxyphenylethylamine to 2,3-diaminophenol is (1~2):

1.

3. The composite membrane according to claim 1, characterized in that, The FeCo-g-C3N4 nanosheets have a mass fraction of 0.05% to 0.15% in the separation layer.

4. The composite membrane according to claim 1, characterized in that, The iron-cobalt bimetallic doped carbon nitride nanosheets (FeCo-g-C3N4) have a specific surface area ≥80 m² / g and a molar ratio of C:Fe:Co of 100:(1~3):

1.

5. The composite membrane according to claim 1, characterized in that, The porous organic-based membrane is a polysulfone (PSf), polyethersulfone (PES), or polyvinylidene fluoride (PVDF) ultrafiltration membrane with a molecular weight cutoff of 50~100 kDa.

6. A method for preparing a composite membrane according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Immerse the porous organic base membrane in an aqueous solution containing 3,4-dihydroxyphenylethylamine and 2,3-diaminophenol for 40-90 seconds, and remove it to remove excess droplets from the surface. S2, the membrane treated by S1 is immersed in an oil phase solution containing acyl chloride monomer and FeCo-g-C3N4 nanosheets for 20-60 seconds to carry out interfacial polymerization reaction; S3. The reacted membrane is heat-treated and cured at 55~75℃ for 3~7 minutes, then cleaned and dried to obtain the composite membrane.

7. The preparation method according to claim 6, characterized in that, The total monomer concentration of the aqueous solution in S1 is 1.5~2.5 wt%, and the solvent is a buffer solution with pH 8.0~9.

0.

8. The preparation method according to claim 6, characterized in that, The acyl chloride monomer in the oil phase solution in S2 is trimesoyl chloride, with a concentration of 0.08~0.18 wt%; the oil phase solvent is n-hexane or cyclohexane.

9. The composite membrane according to any one of claims 1 to 5 or the composite membrane prepared by any one of claims 6 to 8, and its application in treating wastewater from the pharmaceutical, chemical or electronic industries.

10. The application according to claim 9, characterized in that, The method for treating wastewater is as follows: First, add 0.5~2.0 mM permonosulfate (PMS) to the wastewater to be treated. Then, the wastewater obtained in step one is subjected to cross-flow filtration on the surface of the composite membrane; the cross-flow filtration is carried out under the conditions of pH 5~8, operating pressure 0.4~1.2 MPa, and 25~40℃. The wastewater to be treated contains emerging pollutants and heavy metals; the emerging pollutants include at least one of antibiotics and endocrine disruptors; the heavy metals include Pb. 2+ Cd 2+ Cu 2+ Cr 6+ At least one of them.

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