MSG-C3N5 / SC composite photocatalytic membrane as well as preparation method and application thereof

Abstract

The invention discloses an MSG-C3N5 / SC composite photocatalytic membrane and a preparation method and application thereof, and belongs to the technical field of environmental functional materials and water pollution governance, the preparation method comprises the following steps: dissolving straw cellulose in water, adding C3N5 and sodium glutamate with a preset addition amount, and carrying out constant-temperature ultrasonic treatment to obtain a membrane casting solution; coating a substrate with the membrane casting solution, and drying to form a membrane to obtain a precursor composite membrane; and carrying out temperature programming heat treatment on the precursor composite membrane to obtain the MSG-C3N5 / SC composite photocatalytic membrane. The MSG is added, the MSG is converted into a nitrogen-doped carbon material in situ in the heat treatment process, an efficient electron transmission channel is constructed between C3N5 and SC, the photocatalytic efficiency is improved, meanwhile, a three-dimensional structure with rich pores is created, the prepared membrane can stably float on the surface of a water body, and the photocatalytic performance of the membrane is improved. Under illumination, peculiar smell gas above the water surface and organic pollutants in the water body can be synchronously and efficiently degraded.

Description

Technical Field

[0001] This invention relates to an MSG-C3N5 / SC composite photocatalytic membrane, its preparation method, and its application, belonging to the field of environmental functional materials and water pollution control technology. Background Technology

[0002] The treatment of black and odorous water bodies is a key focus and challenge in current water environment management. These water bodies not only contain persistent organic pollutants from livestock and poultry farming and domestic sewage, but the anaerobic decomposition of bottom sediments also produces malodorous gases such as hydrogen sulfide and ammonia, forming a typical water-air composite pollution scenario.

[0003] Existing treatment technologies mainly include physical adsorption, chemical methods, and biological treatment, but all have certain limitations. Physical adsorption is prone to saturation and has high regeneration costs; chemical methods typically consume large amounts of materials and energy and are prone to producing toxic byproducts; biological treatment has a long cycle and is limited by environmental conditions. More importantly, existing technologies are mostly aimed at a single medium and lack effective means to simultaneously and in-situ treat water-air two-phase complex pollution.

[0004] Photocatalysis, as an advanced oxidation process, can utilize solar energy to drive reactions and degrade various pollutants, offering advantages such as being green, low-consumption, and widely adaptable. Among these, C3N5, as a novel non-metallic photocatalyst, exhibits excellent visible light response performance; however, its powder morphology presents challenges such as easy agglomeration, difficulty in recovery, and high recombination rates of photogenerated electron-hole pairs. Immobilizing C3N5 on a support is an effective way to improve its catalytic performance and operability.

[0005] Straw cellulose (SC), as a natural polymeric film-forming material, is widely available and environmentally friendly, and is extremely common in rural environments. Converting agricultural waste into a photocatalytic carrier is one of the ideal strategies for achieving ecological restoration of rural water bodies. However, simple physical blending often leads to uneven dispersion of C3N5 in the membrane and weak interfacial bonding, resulting in low catalytic efficiency of the prepared photocatalyst. Summary of the Invention

[0006] The purpose of this invention is to provide an MSG-C3N5 / SC composite photocatalytic membrane, its preparation method, and its application, thereby improving the photocatalytic efficiency of photocatalysts in the prior art.

[0007] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a method for preparing an MSG-C3N5 / SC composite photocatalytic membrane, comprising: The straw cellulose was dissolved in water, and the preset amounts of C3N5 and sodium glutamate were added. The casting solution was obtained by constant temperature ultrasound. The casting solution is coated onto the substrate and dried to form a film, thus obtaining the precursor composite film. The precursor composite membrane was subjected to programmed temperature heat treatment in an inert gas atmosphere to obtain a lightweight, self-supporting MSG-C3N5 / SC composite photocatalytic membrane.

[0008] Furthermore, the mass ratio of C3N5, straw cellulose, and monosodium glutamate is 1:(5~10):(1~5).

[0009] Furthermore, the isothermal ultrasonic casting solution includes: The casting solution is obtained by ultrasonication at a temperature of 60~80 ℃ for 20~40 min.

[0010] Furthermore, the casting solution is coated onto the substrate by a casting method.

[0011] Furthermore, the drying film formation includes: drying at 40~60 ℃ for 12~24 h to form a film.

[0012] Furthermore, the process of subjecting the precursor composite film to programmed temperature heat treatment in an inert gas atmosphere includes: In a nitrogen or argon atmosphere, the temperature is increased from room temperature to 450-550 ℃ at a rate of 2-5 ℃ / min, and held at 450-550 ℃ for 1-3 h.

[0013] Furthermore, the substrate is a nickel foam pad, the length of which is 5-10 cm, the width of which is 5-10 cm, and the thickness of which is 1-2 mm.

[0014] In a second aspect, the present invention provides an MSG-C3N5 / SC composite photocatalytic membrane, which is prepared by any of the preparation methods described in the first aspect.

[0015] Secondly, the present invention provides an application of the MSG-C3N5 / SC composite photocatalytic membrane described in the second aspect, comprising: laying the MSG-C3N5 / SC composite photocatalytic membrane on the surface of polluted water, and simultaneously degrading organic pollutants in the polluted water and odorous gases above the polluted water under light irradiation.

[0016] Furthermore, the organic pollutant is a sulfonamide antibiotic and / or a phenolic compound, and the odorous gas is one or more of hydrogen sulfide, ammonia, and methanethiol.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are: 1. An efficient electron transport channel was constructed. During the programmed temperature heat treatment, MSG (monosodium glutamate) formed a nitrogen-doped carbon layer in situ, which built a stable electron bridge between C3N5 and SC (straw cellulose), greatly promoting the separation and transport of photogenerated charges, thereby significantly improving the efficiency of photocatalytic reaction.

[0018] 2. A porous composite structure is formed. The small molecules released during the thermal decomposition of MSG (monosodium glutamate) create multi-level pores inside the membrane, which not only increases the specific surface area and exposes more active sites, but also optimizes the mass transfer pathway of pollutants and improves the mass transfer rate.

[0019] 3. It achieves synergistic treatment of water and air phases. The prepared MSG-C3N5 / SC composite photocatalytic membrane is a lightweight self-supporting structure that can float stably on the water surface, providing a reaction interface for the coexistence of odorous gases on the water surface and recalcitrant organic pollutants underwater, thus achieving efficient in-situ purification.

[0020] 4. Environmentally friendly and easy to recycle, simple to prepare and low in cost, the membrane material is mainly composed of C3N5, SC (straw cellulose) and MSG (monosodium glutamate), which are widely available, have good environmental compatibility, and the membrane form is easy to recycle and reuse, avoiding secondary pollution. The entire process adopts low-temperature casting and inert atmosphere pyrolysis technology, which does not require precious metals or complex templates, and has the potential for large-scale preparation and engineering applications. Attached Figure Description

[0021] Figure 1 This is a schematic diagram illustrating the application scenarios of the MSG-C3N5 / SC composite photocatalytic membrane provided by the present invention; Figure 2 This is a scanning electron microscope image of the MSG-C3N5 / SC composite photocatalytic membrane prepared in Example 2; Figure 3 The graph shows the degradation effect of the MSG-C3N5 / SC composite photocatalytic membrane prepared in Example 1 on hydrogen sulfide, sulfamethoxazole, phenol and ammonia. Figure 4 The graph shows the degradation effect of the MSG-C3N5 / SC composite photocatalytic membrane prepared in Example 2 on hydrogen sulfide, sulfamethoxazole, phenol and ammonia. Figure 5 The graph shows the degradation effect of the C3N5 / SC composite photocatalytic membrane prepared in Comparative Example 1 on hydrogen sulfide, sulfamethoxazole, phenol and ammonia. Figure 6 The graph shows the degradation effect of the C3N5 / SC composite photocatalytic membrane prepared in Comparative Example 2 on hydrogen sulfide, sulfamethoxazole, phenol and ammonia. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0023] Example 1

[0024] This embodiment provides a method for preparing an MSG-C3N5 / SC composite photocatalytic film, including the following steps: Step 1: Accurately weigh 1.0 g of SC into a beaker, add 50 mL of deionized water, and magnetically stir at 60 ℃ and 400 rpm for 2 h until the powder is completely dissolved, obtaining a clear SC solution. While maintaining stirring, add 0.1 g of C3N5 and 0.1 g of MSG sequentially, and continue stirring at 60 ℃ for 6 h to obtain a uniform casting solution.

[0025] Step two: After the casting solution is allowed to stand and degas, it is evenly coated onto a nickel foam pad using a casting knife. The thickness of the nickel foam pad is controlled to be 1.5 mm, and the length and width are both 7.5 cm. Then, it is transferred to a 40 ℃ forced-air drying oven for horizontal and static drying for 12 h. After drying, it is peeled off from the nickel foam pad to obtain a lightweight, self-supporting precursor composite membrane.

[0026] Step 3: Place the precursor composite membrane in a tube furnace and purge air with high-purity nitrogen. Under nitrogen atmosphere protection, the temperature is programmed to rise to 500 °C at a rate of 3 °C / min and held at 500 °C for 2 h. After the program is complete, allow it to cool naturally to room temperature, and the resulting MSG-C3N5 / SC composite photocatalytic membrane is obtained.

[0027] The prepared MSG-C3N5 / SC composite photocatalytic membrane was cut into 5 cm × 5 cm samples and floated in 100 mL of black and odorous water. (The scene can be referenced.) Figure 1 Then, a simulated sunlight source (xenon lamp, light intensity density 100 mW / cm²) was used. 2 Irradiate for 3 days (10 hours of light per day). Figure 3 The test results showed that the removal rate of hydrogen sulfide reached 92.5%, the degradation rate of sulfamethoxazole reached 72.0%, the removal rate of phenol reached 71.3%, and the removal rate of ammonia reached 91.8%.

[0028] In this embodiment, the test methods and test conditions for the concentrations of hydrogen sulfide, sulfamethoxazole, phenol, and ammonia are as follows: Hydrogen sulfide concentration determination: Referencing standard GB / T 14678-1993, a gas chromatograph equipped with a GDX-101 packed column was used, with nitrogen as the carrier gas (flow rate 30 mL / min), column temperature 80 ℃, detector temperature 200 ℃, and detection using a flame photometric detector (FPD). The sample was injected through a six-way injection valve.

[0029] Determination of sulfamethoxazole concentration: Refer to standard HJ 1398-2024, use a high performance liquid chromatograph equipped with a C18 column, use acetonitrile-phosphate buffer (25:75 v / v) as the mobile phase, flow rate 1.0 mL / min, column temperature 30 ℃, and detect at a wavelength of 268 nm, and inject directly with a syringe.

[0030] Phenol concentration determination: Referencing standard GB / T 5750.8, a high-performance liquid chromatograph equipped with a C18 column was used, with methanol-0.1% phosphoric acid aqueous solution (volume ratio 40:60) as the mobile phase, flow rate 1.0 mL / min, column temperature 30 ℃, and detection at a wavelength of 270 nm. The sample was directly injected using a syringe.

[0031] Ammonia concentration: Referring to standard HJ 812-2016, gaseous ammonia was absorbed with 0.05 mol / L H2SO4 solution and then determined by ion chromatography. An IonPac CS12A cation exchange column was used, with 20 mmol / L methanesulfonic acid solution as the eluent, a flow rate of 1.0 mL / min, and a conductivity detector. The sample was injected through a six-way injection valve using a syringe.

[0032] Example 2

[0033] This embodiment provides a method for preparing an MSG-C3N5 / SC composite photocatalytic film, including the following steps: Step 1: Accurately weigh 1.0 g of SC into a beaker, add 50 mL of deionized water, and magnetically stir at 60 ℃ and 400 rpm for 2 h until the powder is completely dissolved to obtain a clear SC solution. While maintaining stirring, add 0.1 g of C3N5 and 0.5 g of MSG sequentially, and continue stirring at 60 ℃ for 6 h to obtain a uniform casting solution.

[0034] Step two: After the casting solution is allowed to stand and degas, it is evenly coated onto a nickel foam pad using a casting knife. The thickness of the nickel foam pad is controlled to be 1.5 mm, and the length and width are both 7.5 cm. Then, it is transferred to a 40 ℃ forced-air drying oven for horizontal and static drying for 12 h. After drying, it is peeled off from the nickel foam pad to obtain a lightweight, self-supporting precursor composite membrane.

[0035] Step 3: Place the precursor composite membrane in a tube furnace and purge air with high-purity nitrogen. Under nitrogen atmosphere protection, the temperature is programmed to rise to 500 °C at a rate of 3 °C / min and held at 500 °C for 2 h. After the program is complete, allow it to cool naturally to room temperature, and the resulting MSG-C3N5 / SC composite photocatalytic membrane is obtained.

[0036] The prepared MSG-C3N5 / SC composite photocatalytic membrane was cut into 5 cm × 5 cm samples and floated in 100 mL of black and odorous water (the same samples obtained by equal division from the same water body as in Example 1). The scenario can be referred to as [example missing]. Figure 1 Then, a simulated sunlight source (xenon lamp, light intensity density 100 mW / cm²) was used. 2 Irradiate for 3 days (10 hours of light per day). Figure 4 The test results showed that the removal rate of hydrogen sulfide reached 93.7%, the degradation rate of sulfamethoxazole reached 76.0%, the removal rate of phenol reached 74.0%, and the removal rate of ammonia reached 91.5%.

[0037] In this embodiment, the testing methods and conditions for the concentrations of hydrogen sulfide, sulfamethoxazole, phenol, and ammonia are consistent with those in Example 1, and will not be repeated here.

[0038] Figure 2 The scanning electron microscope (SEM) microstructure of the MSG-C3N5 / SC composite photocatalytic membrane prepared in Example 2 is shown. MSG and C3N5 are uniformly loaded on the SC surface, exhibiting a distinct lamellar stacked structure with numerous voids and pores between the layers, forming a loose and porous structure. This structure can significantly increase the specific surface area of ​​the material, which is beneficial for pollutant mass transfer and photocatalytic activity.

[0039] Comparative Example 1 This comparative example provides a method for preparing a C3N5 / SC composite photocatalytic membrane, which differs from Example 1 in that the composite photocatalytic membrane material consists only of C3N5 and SC, and does not contain MSG. The method includes the following steps: Step 1: Accurately weigh 1.0 g of SC powder into a beaker, add 50 mL of deionized water, and magnetically stir at 60 ℃ and 400 rpm for 2 h until the powder is completely dissolved to obtain a clear SC solution. While stirring, add 0.1 g of C3N5 and continue stirring at 60 ℃ for 6 h to obtain a uniform casting solution.

[0040] Step two: After the casting solution is allowed to stand and degas, it is evenly coated onto a nickel foam pad using a casting knife, controlling the thickness to be 1.5 mm and the length and width to be 7.5 cm. Then, it is transferred to a 40 ℃ forced-air drying oven for horizontal and static drying for 12 h. After drying, it is peeled off from the nickel foam pad to obtain a lightweight, self-supporting precursor composite membrane.

[0041] Step 3: Place the precursor composite membrane in a tube furnace and purge air with high-purity nitrogen. Under nitrogen atmosphere protection, the temperature is programmed to rise to 500 °C at a rate of 3 °C / min and held at this temperature for 2 h. After the program is complete, allow it to cool naturally to room temperature, and the C3N5 / SC composite photocatalytic membrane is obtained.

[0042] The prepared C3N5 / SC composite photocatalytic membrane was cut into 5 cm × 5 cm samples and floated in 100 mL of black and odorous water (the same samples obtained by equal division from the same water body as in Example 1). The scenario can be referred to as [example description needed]. Figure 1 Then, a simulated sunlight source (xenon lamp, light intensity density 100 mW / cm²) was used. 2 Irradiate for 3 days (10 hours of light per day). Figure 5 The test results showed that the removal rate of hydrogen sulfide was 52.5%, the degradation rate of sulfamethoxazole was only 61.4%, the removal rate of phenol reached 69.6%, and the removal rate of ammonia reached 78.9%.

[0043] In this comparative example, the test methods and conditions for the concentrations of hydrogen sulfide, sulfamethoxazole, phenol, and ammonia are the same as in Example 1, and will not be repeated here.

[0044] Comparative Example 2 This comparative example provides a method for preparing a C3N5 / SC composite photocatalytic membrane, which differs from Example 2 in that the composite photocatalytic membrane material consists only of C3N5 and SC, without MSG, and includes the following steps: Step 1: Accurately weigh 1.0 g of SC powder into a beaker, add 50 mL of deionized water, and magnetically stir at 60 ℃ and 400 rpm for 2 h until the powder is completely dissolved to obtain a clear SC solution. While stirring, add 0.5 g of C3N5 and continue stirring at 60 ℃ for 6 h to obtain a uniform casting solution.

[0045] Step two: After the casting solution is allowed to stand and degas, it is evenly coated onto a foamed nickel fiber pad using a casting knife, controlling the thickness to be 1.5 mm and the length and width to be 7.5 cm. Then, it is transferred to a 40 ℃ forced-air drying oven for horizontal and static drying for 12 h. After drying, it is peeled off from the substrate to obtain a lightweight, self-supporting precursor composite film.

[0046] Step 3: Place the precursor composite membrane in a tube furnace and purge air with high-purity nitrogen. Under nitrogen atmosphere protection, the temperature is programmed to rise to 500 °C at a rate of 3 °C / min and held at this temperature for 2 h. After the program is complete, allow it to cool naturally to room temperature, and the C3N5 / SC composite photocatalytic membrane is obtained.

[0047] The prepared C3N5 / SC composite photocatalytic membrane was cut into 5 cm × 5 cm samples and floated in 100 mL of black and odorous water (the same samples obtained by equal division from the same water body as in Example 1). The scenario can be referred to as [example description needed]. Figure 1 Then, a simulated sunlight source (xenon lamp, light intensity density 100 mW / cm²) was used. 2 Irradiate for 3 days (10 hours of light per day). Figure 6 The test results showed that the degradation rate of sulfamethoxazole reached 69.8%, the removal rate of phenol reached 73.8%, and the removal rate of ammonia reached 80.1%.

[0048] In this comparative example, the test methods and conditions for the concentrations of hydrogen sulfide, sulfamethoxazole, phenol, and ammonia are the same as in Example 1, and will not be repeated here.

[0049] Below, in conjunction with Figures 3 to 6 The photocatalytic membranes prepared in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 were analyzed respectively.

[0050] Figure 3 The degradation effects of the MSG-C3N5 / SC composite photocatalytic membrane prepared in Example 1 on sulfamethoxazole, phenol, and hydrogen sulfide were demonstrated. The results showed that, using a material ratio of 0.1 g C3N5 and 0.1 g MSG, the removal rate of hydrogen sulfide reached 92.5% under simulated sunlight irradiation, the degradation rate of sulfamethoxazole reached 72.0%, the removal rate of phenol reached 71.3%, and the removal rate of ammonia reached 91.8%. Meanwhile... Figure 4 The degradation effects of the MSG-C3N5 / SC composite photocatalytic membrane prepared in Example 2 on sulfamethoxazole, phenol, and hydrogen sulfide are shown. The results indicate that, under the same illumination conditions, using a material ratio of 0.1 g C3N5 and 0.5 g MSG, the removal rate of hydrogen sulfide reached 93.7%, the degradation rate of sulfamethoxazole reached 76.0%, the removal rate of phenol reached 74.0%, and the removal rate of ammonia reached 91.5%. These data demonstrate that when the material ratio of C3N5, straw cellulose, and monosodium glutamate is adjusted within the range of 1:(5~10):(1~5), the resulting MSG-C3N5 / SC composite photocatalytic membrane can maintain excellent, stable, and repeatable synergistic remediation performance for both water and air phase pollutants.

[0051] Furthermore, a comparative analysis was conducted using only C3N5 loaded onto the SC surface under the same treatment conditions. The C3N5 / SC composite photocatalytic film prepared according to the method provided in Comparative Example 1 showed the following degradation efficiency for water-gas two-phase pollutants under the same illumination conditions: Figure 5 As shown. The degradation efficiency of the C3N5 / SC composite photocatalytic membrane prepared according to the method provided in Comparative Example 2 for water-air two-phase pollutants under the same illumination conditions is as follows. Figure 6 As shown in the figure, the results indicate that without MSG modification, the degradation efficiency of the composite photocatalytic membrane for sulfamethoxazole, phenol, and hydrogen sulfide is significantly reduced. Therefore, this invention demonstrates high degradation efficiency in the simultaneous removal of water-air two-phase pollutants and is suitable for typical complex pollution scenarios such as black and odorous water bodies.

[0052] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an MSG-C3N5 / SC composite photocatalytic membrane, characterized in that, include: The straw cellulose was dissolved in water, and the preset amounts of C3N5 and sodium glutamate were added. The casting solution was obtained by constant temperature ultrasound. The casting solution is coated onto the substrate and dried to form a film, thus obtaining the precursor composite film. The precursor composite membrane was subjected to programmed temperature heat treatment in an inert gas atmosphere to obtain a lightweight, self-supporting MSG-C3N5 / SC composite photocatalytic membrane.

2. The method for preparing the MSG-C3N5 / SC composite photocatalytic membrane according to claim 1, characterized in that, The mass ratio of C3N5, straw cellulose and monosodium glutamate is 1:(5~10):(1~5).

3. The method for preparing the MSG-C3N5 / SC composite photocatalytic membrane according to claim 1, characterized in that, The isothermal ultrasonic casting solution includes: The casting solution is obtained by ultrasonication at a temperature of 60~80 ℃ for 20~40 min.

4. The method for preparing the MSG-C3N5 / SC composite photocatalytic membrane according to claim 1, characterized in that, The casting solution is coated onto the substrate by a casting method.

5. The method for preparing the MSG-C3N5 / SC composite photocatalytic membrane according to claim 1, characterized in that, The drying and film formation process includes drying at 40-60°C for 12-24 hours to form a film.

6. The method for preparing the MSG-C3N5 / SC composite photocatalytic membrane according to claim 1, characterized in that, The process of subjecting the precursor composite film to programmed temperature heat treatment in an inert gas atmosphere includes: In a nitrogen or argon atmosphere, the temperature is increased from room temperature to 450-550 ℃ at a rate of 2-5 ℃ / min, and held at 450-550 ℃ for 1-3 h.

7. The method for preparing the MSG-C3N5 / SC composite photocatalytic membrane according to claim 1, characterized in that, The substrate is a nickel foam pad, which has a length of 5-10 cm, a width of 5-10 cm, and a thickness of 1-2 mm.

8. An MSG-C3N5 / SC composite photocatalytic membrane, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 7.

9. An application of the MSG-C3N5 / SC composite photocatalytic membrane according to claim 8, characterized in that, include: The MSG-C3N5 / SC composite photocatalytic membrane is laid on the surface of polluted water, and under light irradiation, it simultaneously degrades organic pollutants in the polluted water and odorous gases above the polluted water.

10. The application according to claim 9, characterized in that, The organic pollutant is a sulfonamide antibiotic and / or a phenolic compound, and the odorous gas is one or more of hydrogen sulfide, ammonia, and methanethiol.

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