A composite membrane with catalytic and nanofiltration dual functions and a preparation method and application thereof

Abstract

The present application relates to the technical field of water treatment materials, in particular to a composite membrane with catalysis and nanofiltration dual functions and a preparation method and application thereof. The preparation method of the composite membrane comprises the following steps: (1) preparation of a metal catalyst to obtain a Ni-Co@carbon nanocomposite material; (2) preparation of a composite membrane to obtain a dual-function layered Ni-Co@carbon nanocomposite material@MXene catalysis-nanofiltration membrane, namely a composite membrane with catalysis and nanofiltration dual functions. The dual-function composite membrane can simultaneously achieve efficient interception and catalytic degradation of pollutants, and has important scientific value and broad application prospects for improving the separation-catalysis synergistic performance of water treatment membranes, ensuring the safety of drinking water and treating complex industrial wastewater.

Description

Technical Field

[0001] This invention relates to the field of water treatment materials technology, specifically to a composite membrane with dual functions of catalysis and nanofiltration, its preparation method, and its application. Background Technology

[0002] With the rapid development of global industrialization and urbanization, the detection rate of emerging organic pollutants in water bodies is constantly increasing. Among them, antibiotic residues, due to their high detection rate, high toxicity, difficulty in natural degradation, and ease of inducing the spread of drug resistance genes, have become a hot topic of great concern in the field of environmental science. Tetracycline (TC) has been used as an antibacterial agent in human and veterinary pharmaceuticals; however, more than 70% of TC cannot be completely absorbed by humans and animals, and these substances are released into the aquatic environment, causing enormous damage to ecosystems. Therefore, developing efficient, stable, and environmentally friendly antibiotic removal technologies has significant practical and academic value.

[0003] Existing processes for antibiotic removal, including advanced oxidation, photocatalysis, adsorption, and membrane separation, have been applied to treat antibiotic-containing wastewater. Among these, membrane separation stands out due to its inherent advantages in continuous flow operation, high separation efficiency, relatively low energy consumption, and ease of operation, making it a cornerstone of separation technology in industrial applications. Among various membrane materials, two-dimensional (2D) materials have attracted considerable attention in molecular sieve applications due to their unique layered structure and tunable interlayer spacing. MXenes, in particular, have garnered significant interest due to their unique physicochemical properties.

[0004] However, pure MXene nanosheets tend to aggregate tightly during film formation, leading to excessively small interlayer spacing and increased mass transfer resistance, thus posing the classic "permeability-selectivity" trade-off in membrane separation. This is further compounded by poor stability and weak antifouling ability, severely limiting their separation performance and practical applications. Therefore, it is necessary to develop and design a composite membrane with dual catalytic and nanofiltration functions, along with its preparation method and applications, to achieve synergistic coupling of multiple components and functions such as size sieving, adsorption enrichment, and catalytic degradation, thereby improving their practical application value in water treatment. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a composite membrane with dual functions of catalysis and nanofiltration, as well as its preparation method and application. The aim is to achieve synergistic coupling of multiple components and functions, including size sieving, adsorption enrichment, and catalytic degradation, and to create a composite membrane that can effectively treat organic wastewater containing antibiotics.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: In a first aspect, a method for preparing a composite membrane with dual functions of catalysis and nanofiltration includes the following steps: (1) Preparation of metal catalyst: Cobalt source, surfactant and carbon nanomaterial are dissolved in organic solution to obtain solution A; organic ligand is dissolved in organic solution to obtain solution B; solution B is added dropwise to solution A to carry out the first reaction to obtain ZIF-67 / carbon nanocomposite material; The ZIF-67 / carbon nanocomposite material was dispersed with a nickel source in an organic solvent and a second reaction was carried out to obtain the Ni-ZIF-67 / carbon nanocomposite material precursor. The Ni-ZIF-67 / carbon nanocomposite precursor was placed in an inert atmosphere and subjected to high-temperature pyrolysis treatment to obtain Ni-Co@carbon nanocomposite material. (2) Preparation of composite membrane: The dispersion containing the Ni-Co@ carbon nanocomposite material, MXene and polyvinylpyrrolidone is mixed evenly and vacuum filtered to obtain a bifunctional layered Ni-Co@ carbon nanocomposite material@MXene catalytic-nanofiltration membrane, that is, a composite membrane with dual functions of catalysis and nanofiltration.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, the cobalt source mentioned in step (1) includes at least one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, and cobalt sulfate heptahydrate; The surfactant mentioned in step (1) includes at least one of polyvinylpyrrolidone, CTAB, and sodium dodecyl sulfate; The carbon nanomaterials mentioned in step (1) include at least one of graphene, carbon nanotubes (CNTs), and fullerene; The organic ligands mentioned in step (1) include at least one of citric acid, 2-methylimidazole, and ethylenediaminetetraacetic acid; The nickel source mentioned in step (1) includes at least one of nickel nitrate hexahydrate, nickel chloride hexahydrate, and nickel sulfate heptahydrate; The organic solution mentioned in step (1) includes at least one of methanol, ethanol, and ethyl acetate; The inert gas used in step (1) is at least one of nitrogen and argon.

[0009] Furthermore, in step (1), the mass ratio of the cobalt source, the surfactant, and the carbon nanomaterial is 20:5:1 to 10:5:1; the concentration of the cobalt source is 0.01 g / mL to 0.05 g / mL. In step (1), the mass ratio of the cobalt source to the organic ligand is 1:1 to 1:5; the concentration of the organic ligand is 0.10 g / mL to 0.15 g / mL. The mass ratio of the ZIF-67 / carbon nanocomposite material to the nickel source in step (1) is 1:1 to 1:4.

[0010] Furthermore, the preparation of the composite membrane in step (2) includes the following specific steps: The dispersions of the Ni-Co@carbon nanocomposite material, MXene, and polyvinylpyrrolidone were mixed evenly and then vacuum filtered using an aqueous filter membrane as a substrate to obtain a bifunctional layered Ni-Co@carbon nanocomposite material@MXene catalytic-nanofiltration membrane, which is a composite membrane with both catalytic and nanofiltration functions. The concentration of the dispersion of the Ni-Co@carbon nanocomposite material is 1~5 mg / mL; The concentration of the MXene dispersion is 1~5 mg / mL; The concentration of the polyvinylpyrrolidone dispersion is 1~5 mg / mL; The mass ratio of MXene to the Ni-Co@carbon nanocomposite material is 1:1 to 1:5; The mass ratio of MXene to polyvinylpyrrolidone is 5:1 to 2:1; The vacuum filtration conditions are: vacuum degree of 0.05~0.2 MPa; The aqueous filter membrane is at least one of MCE membrane, PVDF membrane, PES membrane, and Nylon membrane; the membrane pore size is 0.22~0.45μm; It also includes drying, with the following drying conditions: natural drying at room temperature for 24-48 hours.

[0011] Furthermore, the conditions for the first reaction in step (1) are: standing at room temperature for 12~36 hours; The conditions for the second reaction in step (1) are: stirring at room temperature for 2-6 hours; The high-temperature pyrolysis treatment conditions in step (1) are: temperature of 600~900℃ and reaction time of 2~3h.

[0012] Furthermore, the MXene mentioned in step (2) is prepared through the following steps: Using the MAX phase as a precursor, the MAX phase is dispersed in an acidic etching solution containing fluoride salt. The reaction is heated to achieve selective etching and layered stripping of the MAX phase. After centrifugation and washing, the pH of the washing solution is stabilized at neutral. The lower precipitate is collected and freeze-dried to obtain MXene powder.

[0013] Furthermore, the MAX includes at least one of V3AlC2, Ti3AlC2, and Ti3GeC2; The fluoride salt includes at least one of LiF, NaF, and NH4F; The heating conditions are: temperature 40~80℃, reaction time 24~48h; The mass ratio of MAX to the fluoride salt is 1:1.5 to 1:2; The acidic etching solution is at least one of hydrochloric acid, nitric acid, and sulfuric acid, and the concentration of the acidic etching solution is 3~9 mol / L.

[0014] Secondly, a composite membrane with dual functions of catalysis and nanofiltration is prepared by the aforementioned preparation method.

[0015] The composite membrane of this invention, which has dual functions of catalysis and nanofiltration, uses MXene as a substrate and disperses Ni-Co / carbon nanocomposite materials (such as Ni-Co / CNTs) within the membrane layers, resulting in a layered stacked membrane structure; the water flux of this composite membrane is not less than 95 L·m －2 ·h －1 ·bar －1 The retention rate of antibiotics in water is no less than 95%, and the retention rate remains above 80% even after more than 5 cycles; the composite membrane achieves 100% degradation of antibiotics within 30 minutes; and the degradation rate remains above 90% even after more than 5 cycles.

[0016] Thirdly, the application of a composite membrane with dual functions of catalysis and nanofiltration, wherein the composite membrane with dual functions of catalysis and nanofiltration is used in the treatment of antibiotic pollutants in water.

[0017] Furthermore, the antibiotic includes at least one of tetracycline (TC), oxytetracycline (OTC), doxycycline hydrochloride (DC), sulfamethoxazole (SMX), and ciprofloxacin (CIP).

[0018] The ZIF-67 (zeolite imidazole ester framework-67) in the ZIF-67 / carbon nanocomposite material of this invention is a metal-organic framework (MOF) material constructed with cobalt ions as metal nodes and organic ligands. It has a periodic pore structure and extremely high specific surface area. Using it as a template, after nickel ion exchange and high-temperature pyrolysis, Ni-Co bimetallic nanoparticles with good dispersibility can be derived. At the same time, the introduction of carbon nanomaterials (such as carbon nanotubes) further enhances the conductivity and structural stability of the catalyst. The Ni-Co bimetals have a synergistic catalytic effect, which can efficiently activate persulfate (PMS) to generate sulfate radicals (SO4•-). － ), hydroxyl radicals (•OH) and singlet oxygen ( 1It utilizes reactive oxygen species such as O2 to achieve efficient catalytic degradation of organic pollutants. Simultaneously, Ni-Co@carbon nanomaterials and MXene nanosheets are mixed and vacuum filtered to form a membrane. The Ni-Co@carbon nanomaterial catalyst (such as Ni-Co / CNTs) is uniformly distributed between the MXene layers. The Ni-Co@carbon nanomaterial bimetallic catalyst acts as a "rigid pillar" between the MXene layers, physically opening and stabilizing the interlayer channels to form larger two-dimensional confined nanochannels, significantly reducing water transport resistance and greatly increasing water flux. In addition, during membrane separation, the layered structure of MXene nanosheets selectively retains antibiotic molecules of different molecular weights and charges through size sieving and electrostatic interactions. Among them, the conjugated skeleton of carbon nanomaterials can generate strong π-π interactions with the aromatic rings of antibiotic molecules (such as tetracycline), and the Ni-Co bimetallic sites can coordinate or hydrogen bond with the functional groups such as hydroxyl, carbonyl, and amino groups of antibiotic molecules. These interactions cause antibiotic molecules to be rapidly enriched in the interlayer or on the catalyst surface after entering the membrane, resulting in a sharp drop in the concentration of free state, thus showing a synergistic improvement in retention rate and degradation efficiency. Thus, this invention achieves the synergistic coupling of three functions: size sieving, adsorption enrichment, and catalytic degradation, effectively overcoming the shortcomings of traditional separation membranes that can only retain but not degrade, easily generate concentrated waste liquid, and cause membrane fouling.

[0019] The beneficial effects of this invention are: (1) This invention utilizes a combination of bimetallic catalyst and MXene material, and introduces rigid pillars into the MXene interlayer through "interlayer engineering" to effectively control the interlayer spacing. At the same time, the catalytic function is integrated into the membrane structure to obtain a layered MXene composite membrane. This composite membrane selectively retains antibiotic molecules of different molecular weights and charges through size sieving and electrostatic interaction. It utilizes the high specific surface area and abundant active sites of MXene and bimetallic catalyst to adsorb and enrich antibiotics, and achieves in-situ catalytic degradation under the catalytic action of Ni-ZIF-67 / carbon nanocomposite material. Thus, physical separation, adsorption concentration and chemical degradation are coupled into the same membrane separation process.

[0020] (2) This invention overcomes the shortcomings of traditional separation membranes, which can only retain pollutants but cannot completely degrade them, and are prone to producing concentrated waste liquid and membrane fouling. It significantly improves the treatment efficiency and mineralization degree of antibiotic wastewater, reduces the tendency of membrane fouling, and achieves efficient removal and purification of various antibiotic components. It provides an innovative solution for antibiotic wastewater treatment that is multifunctional, stable in operation and easy to scale up. Attached Figure Description

[0021] Figure 1 A schematic diagram of the preparation process of a bifunctional layered Ni-Co / CNTs@MXene catalytic nanofiltration composite membrane; Figure 2 Digital photographs and SEM images of layered Ni-Co / CNTs@MXene catalytic nanofiltration composite membranes are shown. Among them, (a-c) are digital photographs and SEM images of pure MXene membranes from different perspectives, (d-f) are digital photographs and SEM images of M-20 membranes from different perspectives, and (g-i) are digital photographs and SEM images of M-40 membranes from different perspectives. Figure 3 The structural characterization spectra of the composite membranes are shown below; (a) shows the XRD patterns of MXene, M-10, M-20, M-30, M-40 and M-50 membranes, and (b) shows the FTIR patterns of MXene, M-10, M-20, M-30, M-40 and M-50 membranes. Figure 4 Water flux tests were conducted at 1 bar for MXene (M), M-10, M-20, M-30, M-40 and M-50 composite membranes using deionized water as feed. Figure 5 For MXene(M), M-10, M-20, M-30, M-40, and M-50 composite membranes, tetracycline (TC) was used as the feed for water flux and rejection rate at 1 bar. Figure 6 The graph shows the degradation efficiency of composite membranes; (a) represents the degradation efficiency of PVDF membrane, PMS, M-40, M-40 / PMS, and MXene membranes using tetracycline (TC) as the pollutant at different time points; (b) represents the degradation efficiency of MXene (M), M-10, M-20, M-30, M-40, and M-50 composite membranes using tetracycline (TC) as the pollutant at different time points. Figure 7 The degradation efficiency of M-40 composite membrane for tetracycline (TC) at different time points after 5 cycles of degradation. Figure 8 The graph shows the degradation efficiency of the M-40 composite membrane for different antibiotics, including tetracycline (TC), oxytetracycline (OTC), doxycycline hydrochloride (DC), and sulfamethoxazole (SMX). Detailed Implementation

[0022] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they should be performed according to the techniques or conditions described in the literature in this field, or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0023] Examples 1 to 6 This embodiment provides a method for preparing a bifunctional layered Ni-Co / CNTs@MXene catalytic-nanofiltration composite membrane, comprising the following steps: Step 1: Cobalt(II) nitrate hexahydrate (Co(NO3)2·6H2O, 3.492 g) and polyvinylpyrrolidone (PVP, 0.25 g) were dissolved in 75 mL of methanol and sonicated for 10 minutes. Then, multi-walled carbon nanotubes (CNTs, 0.25 g) were added to the prepared solution, designated as solution A. Next, 2-methylimidazole (C4H6N2, 10.26 g) was dissolved in 75 mL of methanol, designated as solution B. Solution B was introduced into solution A with stirring, and the two solutions were stirred for 2 hours to mix. The final mixture was then kept in the dark for 24 hours; the solution was filtered through a vacuum filter to collect the precipitate. Finally, the sample was dried at 60 °C for 12 hours to obtain ZIF-67 / CNT powder.

[0024] Step 2: The prepared ZIF-67 and Ni(NO3)2·6H2O were added to 200 mL of ethanol at a weight ratio of 1:1.5. The mixture containing Ni(NO3)2·6H2O and ZIF-67 / CNTs was then continuously stirred for 2 hours to promote Ni deposition on the ZIF-67 template. The resulting precipitate was then collected using a centrifuge and washed six times with ethanol and deionized water. The collected precipitate was dried at 60°C for 24 hours. Finally, the Ni-modified ZIF-67 was heated in a tube furnace at 700°C under a N2 atmosphere for 2 hours to obtain Ni-Co / CNTs powder.

[0025] Step 3: Dissolve 2.4g of LiF completely in a certain amount of 9M hydrochloric acid. Add Ti3AlC2 powder in three portions, 0.5g each time. After complete addition, stir in a 50℃ water bath for 48 hours. After the reaction is complete, wash the precipitate 2-3 times with 3M HCl, centrifuge at 3500 rpm for 3 minutes, retain the lower precipitate, and continue until the upper liquid phase is clear. Wash several times with deionized water until the pH of the supernatant is neutral. Then, collect the obtained multilayer Ti3C2T x After sonicating in an ice bath for 4 hours, centrifuge and collect the lower precipitate, then freeze-dry for 48 hours to obtain MXene powder.

[0026] Step 4: Prepare a 1 mg / mL MXene dispersion. Then, mix the MXene, Ni-Co / CNTs, and PVP at the set mass ratios (mg: 1:0:0, 1:1:1, 1:2:1, 1:3:1, 1:4:1, 1:5:1, see Table 1) and sonicate for 30 min to ensure homogeneity. Transfer the mixture to a vacuum filtration apparatus and use a PVDF membrane with a pore size of 0.22 μm and a diameter of 50 mm as the substrate for filtration. After filtration, carefully transfer the composite membrane to a clean petri dish and allow it to air dry at room temperature for 24 hours. This process yields pure MXene, M-10, M-20, M-30, M-40, and M-50 composite membranes.

[0027] Table 1 A schematic diagram of the preparation process of the composite membrane of the present invention is shown below. Figure 1 As shown, the complete preparation process is fully demonstrated, starting from the MAX phase precursor, removing the aluminum atomic layer by LiF / HCl etching, obtaining MXene nanosheets by ice bath ultrasonic exfoliation, and finally self-assembling them on a PVDF substrate after mixing with a bimetallic catalyst and vacuum filtration.

[0028] Figure 2 Digital photographs and SEM images of layered Ni-Co / CNTs@MXene catalytic-nanofiltration composite membranes; among which, [the membrane is composed of...]. Figure 2 As shown in (a), (d), and (g), all three composite membranes completely cover the substrate surface without cracks, curling, or peeling. Pure MXene exhibits a uniform bluish-black color with a metallic luster and is relatively smooth and flat; M-20 and M-40 membranes are dark black. Figure 2 As shown in (b), (e), and (h), the pure MXene membrane exhibits a typical uniform wrinkled morphology, with multiple layers of tightly stacked sheets forming a continuous and dense surface structure. The M-20 composite membrane displays a distinctly rough surface structure, with Ni-Co@CNTs fillers distributed in uniformly dispersed clusters within the MXene sheets, showing no obvious agglomeration or exposure, indicating good dispersion of the filler in the matrix. Compared to the M-20, the M-40 composite membrane has a denser surface covering of nanoparticle aggregates and higher roughness, but the particle size is more uniform, and they are uniformly anchored on the MXene substrate. Figure 2 As shown in (c), (f), and (i), the cross-section of the pure MXene film exhibits a clear layered stacked structure with no obvious gaps between the layers, and the layers are wavy / wrinkled. After introducing Ni-Co@CNTs, the cross-section still has a layered structure, but the overall thickness increases. Columnar / fibrous materials are visible interspersed between the layers, acting as "pillars" and widening the interlayer spacing. The structure is relatively loose, and the interlayer spacing increases with increasing mass.

[0029] Figure 3 The structural characterization spectrum of the composite membrane is shown; among which, by Figure 3 As shown in (a), the (002) diffraction peak of the pure MXene film is located at 2θ=6.9°, corresponding to an interlayer spacing of 1.53 nm. After introducing different amounts of Ni-Co@CNTs, the (002) peak of the M-10 film shifts significantly to 5.22°, corresponding to an interlayer spacing of 1.69 nm, and the (002) peak of the M-20 film shifts significantly to 5.18°, corresponding to an interlayer spacing of 1.71 nm. With the increase of catalyst, the characteristic peaks of MXene gradually disappear, which is because the increase of metal content shields the 002 peak of MXene. Furthermore, various composite films show characteristic peaks on the (111), (200), and (220) crystal planes, belonging to the cubic fcc-Ni and fcc-Co of Ni-Co@CNTs. The above results collectively demonstrate that the introduction of the bimetallic catalyst Ni-Co@CNTs preserves the crystal structure of MXene, and the variation in interlayer spacing is due to the intercalation effect of each component, which is consistent with the crystallographic characteristics of Ni, Co, and MXene, proving that the composite system has good structural compatibility.

[0030] Figure 3 (b) shows the FTIR spectrum of the corresponding composite membrane; pure MXene at 3440 cm⁻¹ －1 (O-H stretching vibration), 1400cm －1 (O-H bending vibration) 1630 cm －1 (Ti-O vibration) and 550 cm －1 A characteristic peak appears at the (Ti-C bond); 1580 cm⁻¹ －1 The C=C framework vibration of graphitic carbon is a key characteristic of the conjugated structure of carbon materials (CNTs and ZIF-67-derived porous carbon), demonstrating that Ni-Co@CNTs physically intercalate between the layers without altering the main chemical composition of the membrane. These two characterizations together verify the successful implementation of Ni-Co@CNTs intercalation with MXene.

[0031] Experimental Example 1. Water flux detection: The permeability of the membrane was investigated using a vacuum filtration device under a certain pressure. The volume V (L) of water permeating through the membrane over time was measured. Before testing the water flux, the membrane was pre-pressurized with deionized water until the water permeability reached a stable value (≈0.09 MPa). The flux J (L·m⁻¹) of pure water was tested by vacuum filtration. －2 ·h －1 Then, calculate the permeation flux using the formula: J = V / (A × t × ΔP), where V, A, t, and ΔP are the volume of deionized water (L), the effective filtration area (m²), and the effective filtration area, respectively. 2), permeation time (h) and transmembrane pressure (bar).

[0032] Figure 4 Water flux tests were conducted at 1 bar for MXene(M), M-10, M-20, M-30, M-40, and M-50 composite membranes using deionized water as feed; the water fluxes were 19.99 L·m⁻¹, respectively. －2 ·h －1 ·bar －1 48.66 L·m －2 ·h －1 ·bar －1 58.93 L·m －2 ·h －1 ·bar －1 101.03 L·m －2 ·h －1 ·bar －1 99.57 L·m －2 ·h －1 ·bar －1 and 101.37 L·m －2 ·h －1 ·bar －1 Therefore, M-30, M-40, and M-50 exhibit superior water flux. This is because Ni-Co / CNTs act as rigid pillars interspersed between MXene layers, physically expanding and stabilizing the interlayer channels to form larger two-dimensional confined nanochannels. The increased effective height between layers significantly reduces water transport resistance, thereby enhancing flux. Specifically, CNTs expand and stabilize the interlayer channels, while Ni-Co bimetallic nanoparticles anchor and strengthen the interfacial structure, facilitating the formation of hydroxylated / oxidized layers on the surface. These layers synergize with the abundant oxygen-containing end groups (-OH, -O) of MXene, maintaining the hydrophilicity of the composite membrane and ultimately providing water molecules with more, wider, and more stable transmembrane transport pathways.

[0033] 2. Antibiotic Retention Rate Test: The membrane retention performance was investigated using a vacuum filtration apparatus under a certain pressure. A 10 mL solution of 20 mg / L tetracycline was used as the feed solution to evaluate the membrane separation performance. The antibiotic rejection rate was tested by vacuum filtration and calculated using the formula R = 1 - C. p / C0, where C p C0 and C0 represent the concentrations of antibiotics in the permeate solution and the original feed solution, respectively.

[0034] Figure 5 The antibiotic flux and rejection rate of MXene(M), M-10, M-20, M-30, M-40 and M-50 composite membranes were tested using tetracycline as feed; the antibiotic fluxes were 11.64 L·m⁻¹, respectively.－2 ·h －1 ·bar －1 72.18 L·m －2 ·h －1 ·bar －1 79.40 L·m －2 ·h －1 ·bar －1 84.28 L·m －2 ·h －1 ·bar －1 110.92 L·m －2 ·h －1 ·bar －1 and 139.04 L·m －2 ·h －1 ·bar －1 The antibiotic rejection rates were 35%, 78.08%, 75.55%, 86.79%, 96.91%, and 86.47%, respectively. Therefore, M-40 was selected as the membrane with the best rejection efficiency, and thus it was chosen as the target composite membrane for subsequent degradation experiments. M-40 exhibited excellent rejection efficiency mainly due to the following factors: firstly, the strong π-π interaction between the conjugated framework of CNTs and the aromatic ring of tetracycline; secondly, the coordination or hydrogen bonding adsorption of the hydroxyl, carbonyl, and amino groups of tetracycline by the Ni-Co bimetallic sites; and thirdly, the Co... 2+ Initiating PMS pyrolysis, Ni 3+ / Ni 2+ The electron transfer cycle is promoted, i.e., the synergistic effect of Ni-Co bimetallic sites in PMS activation; finally, the negatively charged end groups on the MXene surface generate electrostatic repulsion and electrostatic attraction with tetracycline under different pH conditions. These effects cause tetracycline to be rapidly enriched in the interlayer or on the catalyst surface after entering the membrane, the free state concentration drops sharply, the number of molecules penetrating the membrane is greatly reduced, and the retention rate increases.

[0035] 3. Antibiotic degradation test: The degradation of TC by PMS activated by the catalytic membrane was tested in a 250 mL Erlenmeyer flask at room temperature with continuous magnetic stirring. In a typical batch experiment, the target catalytic membrane M-40 was added to 100 mL of TC solution with a TC concentration of 20 mg / L. The initial pH was set at 0.1 mol·L⁻¹. －1 HCl and 0.1 mol·L －1Adjusted with NaOH. Before adding PMS, the suspension was continuously stirred for 30 minutes to maintain adsorption-desorption equilibrium. At predetermined time intervals, 1 mL of the reaction solution was taken and filtered through a 0.22 μm membrane into centrifuge tubes containing 2 μL of methanol for later use. The residual concentration of TC (λ_max = 357 nm) during degradation was determined using a UV-Vis spectrophotometer. The degradation process of TC by the catalytic membrane was calculated using a pseudo-first-order kinetic equation: ln C / C0 = -k obs ·t, where C is the initial concentration of the pollutant, C0 is the concentration of the pollutant within a certain reaction time, and K obs This represents the pseudo-first-order rate constant for pollutant degradation.

[0036] Depend on Figure 6 As shown in (a), when PMS is added alone, the degradation efficiency of TC within 30 minutes is only 35.84%, and the adsorption rates of the PVDF substrate membrane and the M-40 composite membrane are 11.32% and 46.44%, respectively. The removal rates of pure MXene and M-40 tetracycline are close to 49.61% and 100%, respectively. This may be because the surface groups of pure MXene cannot effectively activate PMS, resulting in similar adsorption and degradation capabilities of the pure MXene membrane. However, after introducing Ni-Co / CNTs, the Ni-Co bimetallic efficiently activates PMS, and the adsorption and enrichment of CNTs are combined with the interlayer confinement of MXene. The adsorption rate of M-40 is 46.44%, and the adsorbed TC does not penetrate the membrane but is catalytically mineralized in situ, simultaneously undergoing deep oxidation of TC in the solution and on the membrane surface. Therefore, the total removal rate can reach 100%.

[0037] Depend on Figure 6 As shown in (b), the degradation efficiencies are 83.15%, 96.12%, 99.29%, 100%, and 99.13%, respectively. This indicates that the degradation efficiency of TC gradually increases within 30 minutes with increasing catalyst dosage. This is due to the increase in Ni-Co bimetallic sites, improved PMS activation efficiency, and reduced ROS (•OH, SO4•) concentration. － , 1 O2 production increased significantly, and CNTs and Ni-Co nanoparticles promoted charge transfer between MXene and the catalyst, improving redox cycle efficiency. However, further increasing Ni-Co / CNTs did not improve efficiency and even slightly decreased it. This was mainly because excessive Ni-Co / CNTs agglomerated in the MXene interlayer, causing the outer particles to encapsulate the inner particles. The Ni-Co active sites were physically shielded and could not contact PMS / TC. At the same time, the high concentration of metal sites may lead to ROS self-quenching, resulting in reduced degradation efficiency.

[0038] 4. Antibiotic degradation cycle test: The test method was the same as that in Experiment 3. At room temperature, the degradation experiment of TC by PMS activated by the catalytic membrane was tested in a 250 mL conical flask under continuous magnetic stirring. The difference was that after each cycle, the surface of the catalytic membrane was washed with a certain amount of deionized water or ethanol, and the next degradation experiment was conducted after the membrane was completely dry. Five consecutive degradation cycles were performed. In each cycle, equal amounts of antibiotic solution and PMS were added. The degradation process of TC by the catalytic membrane was calculated using the pseudo-first-order kinetic equation: ln C / C0 = -k obs ·t, where C is the initial concentration of the pollutant, C0 is the concentration of the pollutant within a certain reaction time, and K obs This represents the pseudo-first-order rate constant for pollutant degradation.

[0039] Figure 7 The degradation efficiency of the M-40 composite membrane for tetracycline (TC) was measured at different time points after five cycles. This indicates that the degradation efficiency of the M-40 catalytic membrane for tetracycline remained at 94.54% after five consecutive degradation cycles, demonstrating that the Ni-Co bimetallic active sites possess excellent structural stability and resistance to dissolution. This effectively solves the common problems of traditional powder catalysts, such as easy loss, agglomeration, and difficulty in recovery, as well as the common problems of pure MXene membranes, such as easy oxidation and collapse.

[0040] 5. Degradation test of different antibiotics: The degradation of TC by PMS activated by the catalytic membrane was tested in a 250 mL Erlenmeyer flask at room temperature with continuous magnetic stirring. In a typical batch experiment, the target catalytic membrane M-40 was added to 100 mL of different antibiotic solutions: tetracycline (TC), oxytetracycline (OTC), doxycycline hydrochloride (DC), and sulfamethoxazole (SMX), all at a concentration of 20 mg / L. The initial pH was set at 0.1 mol·L⁻¹. －1 HCl and 0.1 mol·L －1 Adjust with NaOH. Before adding PMS, continuously stir the suspension for 30 minutes to maintain adsorption-desorption equilibrium. At predetermined time intervals, take 1 mL of the reaction solution and filter it through a 0.22 μm membrane into a centrifuge tube containing 2 μL of methanol for later use. Use a UV-Vis spectrophotometer to determine the residual concentrations of TC (=357 nm), OTC (=352 nm), DC (=276 nm), and SMX (262 nm) during the degradation process.

[0041] Figure 8The graph shows the degradation efficiency of the M-40 composite membrane for different antibiotics, including tetracycline (TC), oxytetracycline (OTC), doxycycline hydrochloride (DC), and sulfamethoxazole (SMX). It can be seen that the degradation efficiencies of the target catalytic membrane for TC, OTC, DC, and SMX within 30 minutes are 100%, 96.54%, 98.09%, and 60.54%, respectively. The M-40 target catalytic membrane exhibits strong degradation efficiency for tetracycline antibiotics, indicating its broad potential applications in this field. However, its degradation efficiency for SMX is significantly lower. This is because tetracycline antibiotics contain multiple -OH, -CONH2, and enol O groups that can react with Ni. 2＋ / Co 2＋ Chelation occurs, but SMX can only weakly coordinate with aniline-NH2 and isoxazole N, while its coordination ability with SO2NH- is extremely weak, resulting in a short residence time of SMX adsorbed at Ni-Co sites. Therefore, the removal of SMX is limited by its structural flexibility, electronic stability, and leakage of intermediate products, leading to significantly low efficiency.

[0042] In summary, this invention combines a bimetallic catalyst (Ni-Co / CNTs) with MXene materials, introducing rigid supports into the MXene interlayer through "interlayer engineering" to effectively control the interlayer spacing and integrate catalytic function into the membrane structure, resulting in a layered MXene composite membrane. The MXene nanosheets are obtained using the MAX phase as a precursor through in-situ etching, interlayer exfoliation, and freeze-drying. The composite catalytic membrane is obtained by ultrasonically mixing a nickel-modified ZIF-67(Co)MOF-derived bimetallic catalyst (Ni-Co / CNTs) with an MXene solution, combining the advantages of heterogeneous catalysis and membrane separation, thereby enhancing their practical application value in water treatment. The CNTs expand and stabilize the interlayer channels, while the Ni-Co bimetallic nanoparticles anchor and strengthen the interfacial structure, facilitating the formation of hydroxylated / oxidized layers on the surface. These layers synergistically with the abundant oxygen-containing end groups (-OH, -O) of MXene, maintaining the hydrophilicity of the composite membrane and thus increasing water flux. Secondly, the strong π-π interaction between the conjugated framework of CNTs and the aromatic ring of tetracycline, along with the coordination or hydrogen bonding adsorption of tetracycline's hydroxyl, carbonyl, and amino groups at the Ni-Co bimetallic sites, leads to the rapid enrichment of tetracycline in the interlayer or on the catalyst surface after entering the membrane. This results in a sharp drop in the concentration of free tetracycline and a significant reduction in the number of molecules penetrating the membrane, manifested as increased retention rate and degradation efficiency. The composite membrane prepared by this invention exhibits high retention rate, high degradation rate, long-term stability, and wide applicability, demonstrating excellent application potential in the field of antibiotic wastewater treatment.

[0043] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a composite membrane with dual functions of catalysis and nanofiltration, characterized in that, Includes the following steps: (1) Preparation of metal catalyst: Cobalt source, surfactant and carbon nanomaterial are dissolved in organic solution to obtain solution A; organic ligand is dissolved in organic solution to obtain solution B; solution B is added dropwise to solution A to carry out the first reaction to obtain ZIF-67 / carbon nanocomposite material; The ZIF-67 / carbon nanocomposite material was dispersed with a nickel source in an organic solvent and a second reaction was carried out to obtain the Ni-ZIF-67 / carbon nanocomposite material precursor. The Ni-ZIF-67 / carbon nanocomposite precursor was placed in an inert atmosphere and subjected to high-temperature pyrolysis treatment to obtain Ni-Co@carbon nanocomposite material. (2) Preparation of composite membrane: The dispersion containing the Ni-Co@ carbon nanocomposite material, MXene and polyvinylpyrrolidone is mixed evenly and vacuum filtered to obtain a bifunctional layered Ni-Co@ carbon nanocomposite material@MXene catalytic-nanofiltration membrane, that is, a composite membrane with dual functions of catalysis and nanofiltration.

2. The method for preparing a composite membrane with dual catalytic and nanofiltration functions according to claim 1, characterized in that, The cobalt source mentioned in step (1) includes at least one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, and cobalt sulfate heptahydrate; The surfactant mentioned in step (1) includes at least one of polyvinylpyrrolidone, CTAB, and sodium dodecyl sulfate; The carbon nanomaterials mentioned in step (1) include at least one of graphene, carbon nanotubes, and fullerene; The organic ligands mentioned in step (1) include at least one of citric acid, 2-methylimidazole, and ethylenediaminetetraacetic acid; The nickel source mentioned in step (1) includes at least one of nickel nitrate hexahydrate, nickel chloride hexahydrate, and nickel sulfate heptahydrate; The organic solution mentioned in step (1) includes at least one of methanol, ethanol, and ethyl acetate; The inert gas used in step (1) is at least one of nitrogen and argon.

3. The method for preparing a composite membrane with dual catalytic and nanofiltration functions according to claim 1, characterized in that, In step (1), the mass ratio of the cobalt source, the surfactant, and the carbon nanomaterial is 20:5:1 to 10:5:1; the concentration of the cobalt source is 0.01 g / mL to 0.05 g / mL. In step (1), the mass ratio of the cobalt source to the organic ligand is 1:1 to 1:5; the concentration of the organic ligand is 0.10 g / mL to 0.15 g / mL. The mass ratio of the ZIF-67 / carbon nanocomposite material to the nickel source in step (1) is 1:1 to 1:

4.

4. The method for preparing a composite membrane with dual catalytic and nanofiltration functions according to claim 1, characterized in that, The preparation of the composite membrane in step (2) includes the following specific steps: The dispersions of the Ni-Co@carbon nanocomposite material, MXene, and polyvinylpyrrolidone were mixed evenly and then vacuum filtered using an aqueous filter membrane as a substrate to obtain a bifunctional layered Ni-Co@carbon nanocomposite material@MXene catalytic-nanofiltration membrane, which is a composite membrane with both catalytic and nanofiltration functions. The concentration of the dispersion of the Ni-Co@carbon nanocomposite material is 1~5 mg / mL; The concentration of the MXene dispersion is 1~5 mg / mL; The concentration of the polyvinylpyrrolidone dispersion is 1~5 mg / mL; The mass ratio of MXene to the Ni-Co@carbon nanocomposite material is 1:1 to 1:5; The mass ratio of MXene to polyvinylpyrrolidone is 5:1 to 2:1; The vacuum filtration conditions are: vacuum degree of 0.05~0.2 MPa; The aqueous filter membrane is at least one of MCE membrane, PVDF membrane, PES membrane, and Nylon membrane; the pore size of the aqueous filter membrane is 0.22~0.45μm.

5. The method for preparing a composite membrane with dual catalytic and nanofiltration functions according to claim 1, characterized in that, The conditions for the first reaction in step (1) are: standing at room temperature for 12-36 hours; The conditions for the second reaction in step (1) are: stirring at room temperature for 2-6 hours; The high-temperature pyrolysis treatment conditions in step (1) are: temperature of 600~900℃ and reaction time of 2~3h.

6. A method for preparing a composite membrane with dual catalytic and nanofiltration functions according to any one of claims 1 to 5, characterized in that, The MXene mentioned in step (2) is prepared through the following steps: Using the MAX phase as a precursor, the MAX phase is dispersed in an acidic etching solution containing fluoride salt. The reaction is heated to achieve selective etching and layered stripping of the MAX phase. After centrifugation and washing, the pH of the washing solution is stabilized at neutral. The lower precipitate is collected and freeze-dried to obtain MXene powder.

7. The method for preparing a composite membrane with dual catalytic and nanofiltration functions according to claim 6, characterized in that, The MAX includes at least one of V3AlC2, Ti3AlC2, and Ti3GeC2; The fluoride salt includes at least one of LiF, NaF, and NH4F; The heating conditions are: temperature 40~80℃, reaction time 24~48h; The mass ratio of MAX to the fluoride salt is 1:1.5 to 1:2; The acidic etching solution is at least one of hydrochloric acid, nitric acid, and sulfuric acid, and the concentration of the acidic etching solution is 3~9 mol / L.

8. A composite membrane with dual functions of catalysis and nanofiltration, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. An application of a composite membrane with dual functions of catalysis and nanofiltration, characterized in that, The composite membrane with dual functions of catalysis and nanofiltration as described in claim 8 is used for the treatment of antibiotic pollutants in water.

10. The application of the composite membrane with dual functions of catalysis and nanofiltration according to claim 9, characterized in that, The antibiotics include at least one of tetracycline, sulfamethoxazole, amoxicillin, and ciprofloxacin.

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