Nitrogen-doped carbon geopolymer / metal mesh composite membrane and method of making same

Abstract

This invention discloses a nitrogen-doped carbon geopolymer / metal mesh composite membrane. Using amino acids as both nitrogen and carbon sources, the amino acids are loaded onto the membrane through immersion. The alkalinity of the geopolymer is used as an activator, and the nitrogen-doped carbon geopolymer / metal mesh composite membrane is prepared by high-temperature carbonization. This invention uses green and low-cost amino acids as both carbon and nitrogen sources, allowing the amino acids to coordinate with metal ions to obtain nitrogen-doped carbon with a higher specific surface area. This improves the membrane's surface structure, increases active sites, and effectively enhances the membrane's catalytic degradation performance for organic pollutants, achieving, in some cases, complete removal.

Description

Technical Field

[0001] This invention relates to a method for preparing composite films, specifically to a nitrogen-doped carbon geopolymer / metal mesh composite film and its preparation method. Background Technology

[0002] With the acceleration of industrialization and changes in modern lifestyles, emerging organic pollutants (OPCs), as a new class of environmental pollutants, are being released into environmental systems at an alarming rate. These pollutants include pharmaceuticals and personal care products (PPCPs), industrial chemicals, and plastic additives, characterized by complex chemical structures, high degradation difficulty, and persistence and bioaccumulation in the environment. Recent studies have found that these pollutants not only pose a serious threat to aquatic ecosystems but may also potentially harm human health through bioaccumulation within the food chain.

[0003] Catalytic membrane technology, as an emerging water treatment method, can simultaneously separate and degrade pollutants, showing broad application prospects in the treatment of novel organic pollutants. Metal mesh, with its flexible processing, high thermal stability, and high mechanical strength, is a good choice for catalytic membrane substrates. However, metal mesh as a catalytic membrane substrate suffers from problems such as excessively large pore sizes leading to low pollutant retention efficiency, and easy corrosion of the metal surface causing metal ion leaching and secondary pollution. Furthermore, the insufficient chemical activity of metal mesh itself makes it difficult to directly trigger the deep degradation of pollutants. Therefore, it is necessary to further regulate the pore structure and surface morphology of metal mesh to suppress secondary pollution during application and optimize its filtration and catalytic performance.

[0004] Geopolymers exhibit unique application potential to address the performance limitations of metal meshes. Geopolymers are prepared from low-cost, silica-alumina-rich raw materials such as metakaolin, slag, and fly ash under alkaline activation conditions. They possess excellent hydrophilicity and a negative surface charge, making them excellent adsorbent materials for water treatment and also suitable for curing on metal surfaces as corrosion inhibitors. Furthermore, geopolymers consist of cyclic molecular chains with a "crystal-like" structure, forming closed cage-like cavities that facilitate the fixation of metal ions within these cavities and inhibit leaching. Coating geopolymers onto metal meshes holds promise for effectively controlling the membrane pore structure and surface morphology, effectively addressing secondary pollution issues. However, geopolymers themselves have relatively weak catalytic activity, hindering the efficient degradation of organic pollutants. Introducing highly active catalytic components is necessary to compensate for this shortcoming. Nitrogen-doped carbon-based catalytic materials, with their excellent electron transport and redox capabilities, often possess higher activity and selectivity. Loading nitrogen-doped carbon onto membranes promises to significantly improve membrane catalytic degradation performance. Therefore, effectively combining these three materials to prepare catalytic membranes for the efficient treatment of novel organic pollutants in water remains a pressing technical challenge. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a nitrogen-doped carbon geopolymer / metal mesh composite membrane and its preparation method. The geopolymer-metal mesh composite membrane is prepared by loading a geopolymer onto a metal mesh. The aim is to obtain a membrane that can effectively improve the hydrophilicity and pore structure of the membrane surface and inhibit the leaching of metal ions from the metal mesh; as well as improve the surface structure of the membrane, increase active sites, and effectively enhance the catalytic degradation performance of the membrane.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0007] A nitrogen-doped carbon geopolymer / metal mesh composite membrane was prepared by using amino acids as both nitrogen and carbon sources. The amino acids were loaded onto the membrane through immersion, and the alkalinity of the geopolymer was used as an activator. The membrane was then prepared by high-temperature carbonization.

[0008] The method for preparing nitrogen-doped carbon geopolymer / metal mesh composite films as described above includes the following steps:

[0009] (1) Cut and pre-treat the metal mesh. The cutting of the metal mesh can be carried out according to the actual application and the shape is not fixed.

[0010] (2) Take the metal mesh obtained in step (1), immerse it in the geopolymer slurry, take it out, use a brush to remove the excess slurry, so that a certain mass of geopolymer slurry is evenly coated on the upper and lower surfaces of the metal mesh, put it in an oven, cure and dry it to obtain a geopolymer / metal mesh composite film.

[0011] (3) Take the geopolymer / metal mesh composite membrane obtained in step (2), immerse it in an amino acid solution and heat it in a water bath. After taking it out, put it in an oven to dry it and calcine it in a tube furnace under a protective atmosphere to obtain a nitrogen-doped carbon geopolymer / metal mesh composite membrane.

[0012] In step (1), the metal mesh is one of molybdenum mesh, nickel mesh, titanium mesh, copper mesh or stainless steel mesh.

[0013] In step (1), the pretreatment of the metal mesh is either acid treatment or alkali treatment. The acid pretreatment involves sequentially immersing the shaped metal mesh in acetone, isopropanol, ethanol, and deionized water, and then sonicating it for 1-30 minutes to remove oil. Finally, it is soaked in HCl aqueous solution for 1-60 minutes to remove the oxide layer. The alkali pretreatment involves immersing the shaped metal mesh in a mixed solution for 1-60 minutes, then removing it and rinsing it with deionized water. The mixed solution is a mixture of ammonium persulfate, sodium hydroxide, and deionized water.

[0014] The concentration of the HCl aqueous solution is 1~5 mol / L; the mass ratio of ammonium persulfate: sodium hydroxide: deionized water in the mixed solution is 0.1~1:0.1~5:1~50.

[0015] In step (2), the curing and drying temperature is 20~120 ℃ and the curing time is 1~12 h. The preparation method of the geopolymer slurry in step (2) is to weigh each raw material according to the mass ratio of metakaolin, slag, modified water glass and deionized water of 1~10:1~10:1~10:1~10, mix the metakaolin and slag evenly, add the modified water glass and deionized water, and then mechanically stir to mix evenly to obtain the geopolymer slurry.

[0016] The modified water glass is obtained by adding NaOH or KOH to industrial sodium water glass or potassium water glass to obtain a modified water glass with a modulus of 1.0 to 2.4; the mechanical stirring speed is 500 to 3000 r / min and the time is 0.5 to 5 min.

[0017] In step (3), the amino acid solution is obtained by dissolving amino acids in deionized water; the amino acid is one of D-glutamic acid, L-glutamic acid, L-histidine, L-lysine, L-arginine or L-cysteine; the mass concentration of the amino acid solution in step (3) is 0.1% to 10%; the water bath temperature in step (3) is 20 to 95 ℃, and the water bath heating time is 1 to 12 h; the drying temperature in the oven in step (3) is 50 to 120 ℃.

[0018] In step (3), the calcination temperature is 400~1000℃, the heating rate is 1~10℃ / min, and the calcination time is 1 h~5 h; the protective atmosphere is nitrogen or argon.

[0019] In step (3), the amino acid solution is an L-histidine solution with a mass concentration of 1%; the calcination temperature in step (3) is 500℃ and the calcination time is 2h.

[0020] As described above, the application of nitrogen-doped carbon geopolymer / metal mesh composite membranes in the catalytic degradation of organic pollutants in water.

[0021] The organic pollutant is one of bisphenol A, methylene blue, or the antibiotic tetracycline.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] This invention loads geopolymers onto a metal mesh, which improves the hydrophilicity and pore structure of the membrane surface, giving it better membrane separation performance. It also acts as an "armor" to inhibit the leaching of metal ions from the metal mesh, while the entry of metal ions into the geopolymer enhances the membrane's catalytic degradation performance. Furthermore, this invention uses green, low-cost amino acids as carbon and nitrogen sources loaded onto the membrane. The coordination of amino acids with metal ions results in nitrogen-doped carbon with a higher specific surface area, improving the membrane's surface structure, increasing active sites, and effectively enhancing the membrane's catalytic degradation performance for organic pollutants, potentially achieving complete removal. Attached Figure Description

[0024] Figure 1 This is a scanning electron microscope image of the nitrogen-doped carbon geopolymer / metal mesh composite film 1%L-His-NC@GM / CM prepared with L-histidine in Example 4.

[0025] Figure 2 This is a scanning electron microscope image of the geopolymer / metal mesh composite film p-GM / CM prepared at high temperature and calcined as Comparative Example 1.

[0026] Figure 3 This is a scanning electron microscope image of the copper mesh p-CM prepared by high-temperature calcination in Comparative Example 2.

[0027] Figure 4 This is a pore size distribution diagram of the nitrogen-doped carbon geopolymer / metal mesh composite membrane 1%L-His-NC@GM / CM prepared with L-histidine in Example 4.

[0028] Figure 5 The images show the XRD patterns of the geopolymer / copper mesh p-GM / CM prepared in Comparative Example 1, the copper mesh p-CM prepared in Comparative Example 2, and the nitrogen-doped carbon geopolymer / metal mesh composite film 1%L-His-NC@GM / CM prepared in Example 4.

[0029] Figure 6 XPS images of the geopolymer / copper mesh p-GM / CM prepared in Comparative Example 1, the copper mesh p-CM prepared in Comparative Example 2, and the nitrogen-doped carbon geopolymer / metal mesh composite film 1%L-His-NC@GM / CM prepared in Example 4.

[0030] Figure 7 This is a graph showing the degradation effect of bisphenol A on nitrogen-doped carbon geopolymer / metal mesh composite membrane 1%L-His-NC@GM / CM prepared with L-histidine at different pH levels in Example 4.

[0031] Figure 8This is a graph showing the bisphenol A degradation effect of nitrogen-doped carbon geopolymer / metal mesh composite membrane 1%L-His-NC@GM / CM prepared with L-histidine under different bisphenol A concentrations in Example 4.

[0032] Figure 9 This is an experimental result of the nitrogen-doped carbon geopolymer / metal mesh composite film prepared with L-histidine (1% L-His-NC@GM / CM) degrading the dye methylene blue, as shown in Example 4.

[0033] Figure 10 This is a diagram showing the experimental results of the nitrogen-doped carbon geopolymer / metal mesh composite membrane (1% L-His-NC@GM / CM) prepared with L-histidine in Example 4, which degrades the antibiotic tetracycline. Detailed Implementation

[0034] The following detailed description, in conjunction with the accompanying drawings, outlines specific embodiments. However, it should be understood that the scope of protection of this invention is not limited to these specific embodiments. Unless otherwise specified, all raw materials and reagents used in the examples are commercially available.

[0035] Example 1

[0036] The preparation method of nitrogen-doped carbon geopolymer / metal mesh composite film includes the following steps:

[0037] (1) Cut the copper mesh into a circle with a radius of 2 cm. Place the cut copper mesh into acetone, isopropanol, ethanol and deionized water in sequence and sonicate for 15 min to remove oil. Then soak it in HCl aqueous solution with a concentration of 2 mol / L for 30 min to remove the oxide layer. This completes the pretreatment.

[0038] (2) Add 17.94 g NaOH to 100 g of industrial sodium water glass with a modulus of 3.37 M to make modified sodium water glass with a modulus of SiO2 / Na2O=1.3 for later use; weigh metakaolin, slag, modified water glass and deionized water in a mass ratio of 2:2:3:2, then mix the weighed metakaolin and slag evenly, add modified sodium water glass with a modulus of 1.3 or deionized water, and keep the speed at 2000 r / min for 2 min to mix evenly to obtain geopolymer slurry; take the metal copper mesh obtained after pretreatment in step (1), immerse it in the above-mentioned prepared geopolymer slurry, take it out, use a brush to remove excess slurry, so that 0.09 g of geopolymer slurry is evenly coated on the upper and lower surfaces of the metal mesh, put it in an oven, cure and dry at 60 ℃ for 5 h to obtain a geopolymer / metal mesh composite film;

[0039] (3) Weigh 3 g of L-histidine into a beaker, add 100 g of deionized water, and sonicate to completely dissolve it to prepare an L-histidine solution with a mass concentration of 3.0 wt% for later use; take the geopolymer / metal mesh composite membrane obtained in step (2) and immerse it in the above-prepared L-histidine solution, cover it with plastic wrap and place it in a 90 ℃ water bath for 4 h, take it out and dry it in a 60 ℃ oven, and then place it in a tube furnace under argon gas, maintain the heating rate at 5 ℃ / min, and calcine at 500 ℃ for 2 h to obtain L-histidine nitrogen-doped carbon geopolymer / metal mesh composite membrane (3%L-His-NC@GM / CM).

[0040] Example 2

[0041] In step (3), “L-histidine” is replaced with “D-glutamic acid”, and the rest of the operation is the same as in Example 1, to obtain a nitrogen-doped carbon geopolymer / metal mesh composite film of D-glutamic acid (3%D-Glu-NC@GM / CM).

[0042] Example 3

[0043] In step (3), “L-histidine” is replaced with “L-arginine”, and the rest of the operation is the same as in Example 1, to obtain a nitrogen-doped carbon geopolymer / metal mesh composite film of L-arginine (3%L-Arg-NC@GM / CM).

[0044] Example 4

[0045] (3) Weigh 1 g of L-histidine into a beaker, add 100 g of deionized water, and sonicate to completely dissolve it to prepare an L-histidine solution with a mass concentration of 1.0 wt% for later use; take the geopolymer / metal mesh composite membrane obtained in step (2) and immerse it in the above-prepared L-histidine solution, cover it with plastic wrap and place it in a 90 ℃ water bath for 4 h, take it out and dry it in a 60 ℃ oven, and then place it in a tube furnace under argon gas, maintain the heating rate at 5 ℃ / min, and calcine it at 500 ℃ for 2 h to obtain an L-histidine nitrogen-doped carbon geopolymer / metal mesh composite membrane (1%L-His-NC@GM / CM); the rest of the operation is the same as in Example 1.

[0046] Example 5

[0047] (3) Weigh 0.5 g of L-histidine into a beaker, add 100 g of deionized water, and sonicate to completely dissolve it to prepare an L-histidine solution with a mass concentration of 0.5 wt% for later use; take the geopolymer / metal mesh composite membrane obtained in step (2) and immerse it in the prepared L-histidine solution, cover it with plastic wrap and place it in a 90 ℃ water bath for 4 h, take it out and dry it in a 60 ℃ oven, and then place it in a tube furnace under argon gas, maintain the heating rate at 5 ℃ / min, and calcine it at 500 ℃ for 2 h to obtain an L-histidine nitrogen-doped carbon geopolymer / metal mesh composite membrane (0.5% L-His-NC@GM / CM); the rest of the operation is the same as in Example 1.

[0048] Example 6

[0049] (3) Weigh 1 g of L-histidine into a beaker, add 100 g of deionized water, and sonicate to completely dissolve it to prepare an L-histidine solution with a mass concentration of 1.0 wt% for later use; take the geopolymer / metal mesh composite membrane obtained in step (2) and immerse it in the above-prepared L-histidine solution, cover it with plastic wrap and place it in a 90 ℃ water bath for 4 h, take it out and dry it in a 60 ℃ oven, and then place it in a tube furnace under argon gas, maintain the heating rate at 5 ℃ / min, and calcine at 400 ℃ for 2 h to obtain the L-histidine nitrogen-doped carbon geopolymer / metal mesh composite membrane (1%L-His-NC@GM / CM) obtained by calcination at 400 ℃; the rest of the operation is the same as in Example 1.

[0050] Example 7

[0051] (3) Weigh 1 g of L-histidine into a beaker, add 100 g of deionized water, and sonicate to completely dissolve it to prepare an L-histidine solution with a mass concentration of 1.0 wt% for later use; take the geopolymer / metal mesh composite membrane obtained in step (2) and immerse it in the above-prepared L-histidine solution, cover it with plastic wrap and place it in a 90 ℃ water bath for 4 h, take it out and dry it in a 60 ℃ oven, and then place it in a tube furnace under argon gas, maintain the heating rate at 5 ℃ / min, and calcine at 800 ℃ for 2 h to obtain the L-histidine nitrogen-doped carbon geopolymer / metal mesh composite membrane (1%L-His-NC@GM / CM) obtained by calcination at 800 ℃; the rest of the operation is the same as in Example 1.

[0052] Comparative Example 1

[0053] Step (1) is the same as step (1) in Example 1;

[0054] Step (2) is the same as step (2) in Example 1;

[0055] (3) The geopolymer / metal mesh composite membrane obtained in step (2) is placed in a tube furnace under argon gas, and the heating rate is maintained at 5℃ / min. It is calcined at 500℃ for 2 h to obtain a geopolymer / metal mesh composite membrane (p-GM / CM) calcined at high temperature.

[0056] Comparative Example 2

[0057] (1) Cut the copper mesh into a circle with a radius of 2 cm. Place the cut copper mesh into acetone, isopropanol, ethanol and deionized water in sequence and sonicate for 15 min to remove oil. Then soak it in HCl aqueous solution with a concentration of 2 mol / L for 30 min to remove the oxide layer. This completes the pretreatment.

[0058] (2) Placed in a tube furnace under argon gas, the heating rate was maintained at 5℃ / min, and calcined at 500℃ for 2 h to obtain a high-temperature calcined copper mesh (p-CM).

[0059] The nitrogen-doped carbon geopolymer / metal mesh composite films prepared in Examples 1-4 and the films prepared in Comparative Examples 1-2 were tested and characterized.

[0060] Scanning electron microscopy (SEM) images were acquired using field emission scanning electron microscopy to characterize the microstructure of the membrane.

[0061] The pore size distribution of the membrane was acquired using a high-performance fully automated mercury porosimeter, and the pore size distribution of the membrane was characterized.

[0062] X-ray diffraction (XRD) patterns were acquired using an X-ray diffractometer to characterize the crystal structure of the film.

[0063] X-ray photoelectron spectroscopy (XPS) was used to collect data and analyze the elements on the film surface.

[0064] Figure 1 The image shown is a scanning electron microscope image of the nitrogen-doped carbon geopolymer / metal mesh composite film prepared with L-histidine in Example 4. It can be observed that the dense amorphous geopolymer coating is effectively attached to the copper mesh surface and carbon fibers are attached to the surface of the geopolymer, indicating the generation of nitrogen-doped carbon and the effective preparation of the nitrogen-doped carbon geopolymer / metal mesh composite film.

[0065] Figure 2 The image shown is a scanning electron microscope image of the geopolymer / metal mesh composite film calcined at high temperature in Comparative Example 1. It can be seen that the well-dense geopolymer completely covers the surface of the copper mesh, and the pores are reduced.

[0066] Figure 3 The image shown is a scanning electron microscope image of the copper mesh calcined at high temperature in Comparative Example 2. It is observed that the surface of the copper mesh is smooth and the pores are relatively large.

[0067] Figure 4 This is a pore size distribution diagram of the nitrogen-doped carbon geopolymer / metal mesh composite membrane prepared with L-histidine in Example 4. The average pore size of 1%L-His-NC@GM / CM is 964.09 nm, and the porosity is 44.39%.

[0068] Figure 5 The XRD patterns of the nitrogen-doped carbon geopolymer / metal mesh composite films prepared in Examples 1-4 and the films prepared in Comparative Examples 1-2 show that the intensity of the peaks gradually decreases, indicating that the geopolymer and nitrogen-doped carbon were successfully loaded onto the copper mesh during the preparation process.

[0069] Figure 6 The XRD patterns of the nitrogen-doped carbon geopolymer / metal mesh composite film prepared in Example 4 and the films prepared in Comparative Examples 1-2 show that the C and N contents in 1%L-His-NC@GM / CM both increased, while the contents of Al and Si both decreased, indicating that nitrogen-doped carbon with amino acids as the carbon and nitrogen sources was successfully loaded onto the film.

[0070] Application Example 1

[0071] Degradation tests on nitrogen-doped carbon geopolymer / metal mesh composite films prepared with different amino acids.

[0072] Catalytic degradation experiments of bisphenol A were conducted using the nitrogen-doped carbon geopolymer / metal mesh composite membranes prepared in Examples 1-3. Hydrogen peroxide (H₂O₂) was used as the oxidant to catalytically degrade simulated bisphenol A wastewater. The methods are as follows:

[0073] The nitrogen-doped carbon geopolymer / metal mesh composite membranes prepared in Examples 1-3 were added to conical flasks containing 100 mL of bisphenol A solution (20 mg / L), along with 1 mL of H2O2. The flasks were placed in a shaker (40 ℃, 180 r / min) for reaction. Samples were taken at regular intervals, quenched with an equal volume of methanol, and filtered through a 0.22 μm mixed cellulose MCE filter to obtain the sample solution. The concentration of the bisphenol A solution was calculated using high-performance liquid chromatography (HPLC). The bisphenol A degradation results are shown in Table 1: The nitrogen-doped carbon geopolymer / metal mesh composite membranes prepared in Examples 1-3 of this invention can completely remove the organic pollutant bisphenol A from water. The nitrogen-doped carbon geopolymer / metal mesh composite membrane prepared in Example 1 required 60 min to remove 100% of the bisphenol A from water, significantly less than the composite membranes in Examples 2 and 3.

[0074] Table 1: Nitrogen-doped carbon geopolymer / metal mesh composite films prepared with different amino acids for the degradation of bisphenol A

[0075] Group Composite membrane <![CDATA[Dosage of H2O2 in mL]]> Bisphenol A concentration (mg / L) Removal rate / % Time / min Example 1 3%L-His-NC@GM / CM 1 20 100 60 Example 2 3%D-Glu-NC@GM / CM 1 20 100 80 Example 3 3%L-Arg-NC@GM / CM 1 20 100 100

[0076] Application Example 2

[0077] Degradation tests on nitrogen-doped carbon geopolymer / metal mesh composite films prepared with different histidine concentrations.

[0078] The nitrogen-doped carbon geopolymer / metal mesh composite membranes prepared in Examples 1, 4, and 5 were used to conduct catalytic degradation experiments on bisphenol A. Hydrogen peroxide (H2O2) was used as the oxidant to carry out catalytic degradation experiments on simulated bisphenol A wastewater. The methods are as follows:

[0079] The nitrogen-doped carbon geopolymer / metal mesh composite membranes prepared in Examples 1, 4, and 5 were added to conical flasks containing 100 mL of bisphenol A solution (20 mg / L), along with 1 mL of H₂O₂. The flasks were placed in a shaker (40 °C, 180 r / min) for reaction. Samples were taken at regular intervals, quenched with an equal volume of methanol, and filtered through a 0.22 μm mixed cellulose MCE filter to obtain the sample solution. The concentration of the bisphenol A solution was calculated using high-performance liquid chromatography (HPLC). The degradation results of bisphenol A are shown in Table 2. Under the condition that the removal time is 40 min, the nitrogen-doped carbon geopolymer / metal mesh composite membrane prepared by Example 4 with a mass fraction of 1 wt% histidine can completely remove the organic pollutant bisphenol A from the water. In contrast, the 3% L-His-NC@GM / CM in Example 1 has a bisphenol A removal rate of 63.75% after 40 min, and the 0.5% L-His-NC@GM / CM in Example 5 has a bisphenol A removal rate of 81.46% after 40 min.

[0080] Table 2: Nitrogen-doped carbon geopolymer / metal mesh composite films prepared with different histidine concentrations for bisphenol A degradation

[0081] Group Composite membrane <![CDATA[Dosage of H2O2, mL]]> Bisphenol A concentration (mg / L) Removal rate / % Time / min Example 1 3%L-His-NC@GM / CM 1 20 63.75 40 Example 4 1%L-His-NC@GM / CM 1 20 100 40 Example 5 0.5% L-His-NC@ GM / CM 1 20 81.46 40

[0082] Application Example 3

[0083] Degradation tests on nitrogen-doped carbon geopolymer / metal mesh composite films prepared at different calcination temperatures.

[0084] Catalytic degradation experiments of bisphenol A were conducted using the nitrogen-doped carbon geopolymer / metal mesh composite membranes prepared in Examples 4, 6, and 7. Hydrogen peroxide (H₂O₂) was used as the oxidant to catalytically degrade simulated bisphenol A wastewater. The methods are as follows:

[0085] The nitrogen-doped carbon geopolymer / metal mesh composite membranes prepared in Examples 4, 6, and 7 were added to conical flasks containing 100 mL of bisphenol A solution (20 mg / L), along with 1 mL of H2O2. The flasks were placed in a shaker (40 °C, 180 r / min) for reaction. Samples were taken at regular intervals, quenched with an equal volume of methanol, and filtered through a 0.22 μm mixed cellulose MCE filter to obtain the sample solution. The concentration of the bisphenol A solution was calculated using high-performance liquid chromatography (HPLC). The bisphenol A degradation results are shown in Table 3: Under a removal time of 40 min, the nitrogen-doped carbon geopolymer / metal mesh composite membrane prepared in Example 4 at a calcination temperature of 500 °C completely removed the organic pollutant bisphenol A from the water, while the composite membrane prepared in Example 6 at a calcination temperature of 400 °C showed a bisphenol A removal rate of 71.52% after 40 min. It is worth noting that in Example 7, the composite membrane prepared at a calcination temperature of 800°C had a bisphenol A removal rate of only 23.44% after 40 min, which was a significant decrease in performance. This may be because the excessively high calcination temperature caused nitrogen-doped carbon to clump together on the membrane surface, affecting the catalytic performance.

[0086] Table 3: Nitrogen-doped carbon geopolymer / metal mesh composite films prepared at different calcination temperatures for bisphenol A degradation

[0087] Group Calcination temperature (°C) <![CDATA[Dosage of H2O2 in mL]]> Bisphenol A concentration (mg / L) Removal rate / % Time / min Example 4 500 1 20 100 40 Example 6 400 1 20 71.52 40 Example 7 800 1 20 23.44 40

[0088] Application Example 4

[0089] The nitrogen-doped carbon geopolymer / metal mesh composite membrane prepared in Example 4 and the membranes prepared in Comparative Examples 1-2 were used to conduct catalytic degradation experiments on bisphenol A. Hydrogen peroxide (H2O2) was used as the oxidant to carry out catalytic degradation experiments on simulated bisphenol A wastewater. The method is as follows:

[0090] The nitrogen-doped carbon geopolymer / metal mesh composite membrane prepared in Example 4 and the membranes prepared in Comparative Examples 1-2 were added to conical flasks containing 100 mL of bisphenol A solution (20 mg / L), 1 mL of H2O2 was added, and the flasks were placed in a shaker (40 ℃, 180 r / min) for reaction. Samples were taken at regular intervals, quenched with an equal volume of methanol, and filtered through a 0.22 μm mixed cellulose MCE filter to obtain the sample solution. The concentration of bisphenol A solution was calculated by high performance liquid chromatography. The degradation results of bisphenol A are shown in Table 2: The nitrogen-doped carbon geopolymer / metal mesh composite membrane prepared in Example 4 of this invention can completely degrade 100 mL of bisphenol A solution (20 mg / L) within 40 min, with a removal rate of 100%. In contrast, the geopolymer / metal mesh composite membrane prepared in Comparative Example 1 without nitrogen-doped carbon showed a removal rate of only 18.80% of bisphenol A within 40 min. Furthermore, in Comparative Example 2, the membrane after direct calcination of the pretreated metal mesh showed a removal rate of only 28.59% for bisphenol A within 40 min, indicating that the nitrogen-doped carbon geopolymer / metal mesh composite membrane prepared using amino acids as carbon and nitrogen sources can significantly improve the removal rate of organic pollutants in water.

[0091] Table 4: Membranes prepared in Example 4 and Comparative Examples 1-2 used for the degradation of bisphenol A

[0092] Group Composite membrane <![CDATA[Dosage of H2O2 in mL]]> Bisphenol A concentration (mg / L) Time / min Removal rate / % Example 4 1%L-His-NC@GM / CM 1 20 40 100 Comparative Example 1 p-GM / CM 1 20 40 18.80 Comparative Example 2 p-CM 1 20 40 28.59

[0093] Application Example 5

[0094] Degradation tests of nitrogen-doped carbon geopolymer / metal mesh composite films under different conditions

[0095] 1. Degradation test of nitrogen-doped carbon geopolymer / metal mesh composite film at different pH values

[0096] The nitrogen-doped carbon geopolymer / metal mesh composite membrane prepared in Example 4 was used to conduct bisphenol A degradation experiments. The pH of 100 mL of bisphenol A solution (20 mg / L) was adjusted to 3, 5, 7, 9, and 11, respectively, and placed in conical flasks. 1 mL of H₂O₂ and the membrane obtained in Example 4 were added, and the mixture was placed in a shaker (40 ℃, 180 r / min) for reaction. Samples were taken at regular intervals, quenched with an equal volume of methanol, and filtered through a 0.22 μm mixed cellulose MCE filter to obtain the sample solution. The concentration of the bisphenol A solution was calculated by high-performance liquid chromatography (HPLC). The bisphenol A degradation results are as follows: Figure 7As shown, the degradation results revealed that the pH value of the reaction solution within a wide range of 3-9 had little impact on the catalytic degradation performance of the system. The removal rate of bisphenol A could reach 100% within 60 min, indicating that the nitrogen-doped carbon geopolymer / metal mesh composite membrane has good stability under environmental changes.

[0097] 2. Degradation tests of nitrogen-doped carbon geopolymer / metal mesh composite films at different bisphenol A concentrations:

[0098] The nitrogen-doped carbon geopolymer / metal mesh composite film prepared in Example 4 was used to conduct a bisphenol A degradation experiment:

[0099] The nitrogen-doped carbon geopolymer / metal mesh composite membrane prepared in Example 4 was added to conical flasks containing 100 mL of solutions with different bisphenol A concentrations (10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, and 50 mg / L), respectively. 1 mL of H₂O₂ was added, and the flasks were placed in a shaker (40 °C, 180 r / min) for reaction. Samples were taken at regular intervals, quenched with an equal volume of methanol, and filtered through a 0.22 μm mixed cellulose MCE filter to obtain the sample solution. The bisphenol A concentration was calculated using high-performance liquid chromatography (HPLC). The bisphenol A degradation results are as follows: Figure 8 As shown: The degradation results showed that the nitrogen-doped carbon geopolymer / metal mesh composite film could degrade 10-50 mg / L bisphenol A solution to 100% within 50 min, and the complete degradation of 10 mg / L solution took only 30 min.

[0100] Application Example 6

[0101] The nitrogen-doped carbon geopolymer / metal mesh composite film prepared in Example 4 was used to conduct a methylene blue degradation experiment:

[0102] The obtained composite membrane was added to an Erlenmeyer flask containing 100 mL of methylene blue solution (20 mg / L), along with 1 mL of H2O2. The flask was placed in a shaker (40 ℃, 180 r / min) for reaction. Samples were taken at regular intervals, quenched with an equal volume of methanol, and filtered through a 0.22 μm mixed cellulose MCE filter to obtain the sample solution. The concentration of the methylene blue solution was calculated using a UV spectrophotometer. The methylene blue degradation results are as follows: Figure 9 As shown, nitrogen-doped carbon geopolymer / metal mesh composite membranes with amino acids as carbon source and carbon source can also effectively remove methylene blue dye from water, with a removal rate of 98.48% within 100 min.

[0103] Application Example 7

[0104] The nitrogen-doped carbon geopolymer / metal mesh composite film prepared in Example 4 was used to conduct a tetracycline degradation experiment:

[0105] The obtained composite membrane was added to an Erlenmeyer flask containing 100 mL of tetracycline solution (20 mg / L), along with 1 mL of H₂O₂. The flask was placed in a shaker (40 ℃, 180 r / min) for reaction. Samples were taken at regular intervals, quenched with an equal volume of methanol, and filtered through a 0.22 μm mixed cellulose MCE filter to obtain the sample solution. The tetracycline solution concentration was calculated using a UV spectrophotometer. The tetracycline degradation results are shown below. Figure 10 As shown, nitrogen-doped carbon geopolymer / metal mesh composite membranes using amino acids as carbon sources and nitrogen doped carbon geopolymers as carbon sources can also effectively remove tetracycline antibiotics from water. Tetracycline can be 100% removed within 40 minutes, demonstrating the effectiveness of this composite membrane in removing various organic pollutants.

[0106] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A nitrogen-doped carbon geopolymer / metal mesh composite film, characterized in that: Using amino acids as both nitrogen and carbon sources, the amino acids were loaded onto the membrane through immersion. The alkalinity of the geopolymer was used as an activator, and a nitrogen-doped carbon geopolymer / metal mesh composite membrane was prepared by high-temperature carbonization.

2. The method for preparing the nitrogen-doped carbon geopolymer / metal mesh composite film as described in claim 1, characterized in that, The operation includes the following steps: (1) Cut and pre-treat the metal mesh; (2) Take the metal mesh obtained in step (1), immerse it in the geopolymer slurry, take it out, cure and dry it to obtain a geopolymer / metal mesh composite film; (3) Take the geopolymer / metal mesh composite membrane obtained in step (2), immerse it in an amino acid solution and heat it in a water bath. After taking it out, dry it and calcine it under a protective atmosphere to obtain a nitrogen-doped carbon geopolymer / metal mesh composite membrane.

3. The method for preparing the nitrogen-doped carbon geopolymer / metal mesh composite film according to claim 2, characterized in that: The metal mesh in step (1) is one of molybdenum mesh, nickel mesh, titanium mesh, copper mesh or stainless steel mesh.

4. The method for preparing the nitrogen-doped carbon geopolymer / metal mesh composite film according to claim 2, characterized in that: In step (1), the pretreatment of the metal mesh is either acid treatment or alkali treatment; the acid pretreatment involves sequentially immersing the cut metal mesh in acetone, isopropanol, ethanol, and water, and then sonicating it for 1-30 minutes to remove oil, followed by soaking it in an HCl aqueous solution for 1-60 minutes to remove the oxide layer; the alkali pretreatment involves immersing the cut metal mesh in a mixed solution for 1-60 minutes, then removing it and rinsing it with water; the mixed solution is a mixture of ammonium persulfate, sodium hydroxide, and water; the concentration of the HCl aqueous solution is 1-5 mol / L; in the mixed solution...

5. The method for preparing the nitrogen-doped carbon geopolymer / metal mesh composite film according to claim 2, characterized in that: The curing and drying temperature in step (2) is 20~120 ℃, and the curing time is 1~12 h; the preparation method of the geopolymer slurry in step (2) is to weigh each raw material according to the mass ratio of metakaolin, slag, modified water glass and water of 1~10:1~10:1~10:1~10, mix the metakaolin and slag evenly, add the modified water glass and water, and then mechanically stir to mix evenly to obtain the geopolymer slurry; the modified water glass is obtained by adding NaOH or KOH to industrial sodium water glass or potassium water glass to obtain modified water glass with a modulus of 1.0~2.4; the mechanical stirring speed is 500~3000 r / min, and the time is 0.5~5 min.

6. The method for preparing the nitrogen-doped carbon geopolymer / metal mesh composite film according to claim 2, characterized in that: The amino acid solution in step (3) is obtained by dissolving amino acids in water; the amino acid is one of D-glutamic acid, L-glutamic acid, L-histidine, L-lysine, L-arginine or L-cysteine; the mass concentration of the amino acid solution in step (3) is 0.1% ~ 10%; the water bath temperature in step (3) is 20~95 ℃, and the water bath heating is 1~12 h; the drying temperature in step (3) is 50~120℃.

7. The method for preparing the nitrogen-doped carbon geopolymer / metal mesh composite film according to claim 2, characterized in that: The calcination temperature in step (3) is 400~1000℃, the heating rate is 1~10℃ / min, and the calcination time is 1 h~5 h; the protective atmosphere is nitrogen or argon.

8. The method for preparing the nitrogen-doped carbon geopolymer / metal mesh composite film according to claim 2, characterized in that: The amino acid solution mentioned in step (3) is an L-histidine solution with a mass concentration of 1%; the calcination temperature mentioned in step (3) is 500℃ and the calcination time is 2h.

9. The application of the nitrogen-doped carbon geopolymer / metal mesh composite membrane as described in claim 1 or the nitrogen-doped carbon geopolymer / metal mesh composite membrane prepared by any of the methods in claims 2-8 in the catalytic degradation of organic pollutants in water.

10. The application according to claim 9, characterized in that: The organic pollutant is one of bisphenol A, methylene blue, or the antibiotic tetracycline.

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