A graphite carbon modified silicon dioxide-carbon nitride core-shell nanosphere material, graphene oxide-based composite film, and preparation method and application thereof

Abstract

This invention discloses a graphite-carbon modified silica-carbon nitride core-shell nanosphere material, a graphene oxide-based composite membrane, its preparation method, and its applications. The preparation method is as follows: 1) preparing nano-silica spheres according to a modified Stöber method; 2) obtaining a graphite-carbon modified silica nanosphere template by high-temperature calcination under nitrogen; 3) calcining melamine with the graphite-carbon modified silica nanosphere template in a muffle furnace to prepare the final product. The material obtained in this invention is crosslinked onto the surface of a graphene oxide-based membrane obtained by filtration to obtain a synergistic catalytic separation graphene oxide-based composite membrane. This invention uses a template method to obtain graphite-carbon modified silica-carbon nitride core-shell nanospheres, successfully achieving modification of carbon nitride through morphology control and surface modification, improving visible light photocatalytic efficiency, and can be applied to the degradation of antibiotics in water. The resulting composite membrane further enhances the removal effect of antibiotics in water through a surface confinement strategy.

Description

Technical Field

[0001] This invention belongs to the field of catalytic membrane material preparation technology, specifically relating to a graphite carbon-modified silica-carbon nitride core-shell nanosphere material, an oxide graphene-based composite membrane, its preparation method, and its application. Background Technology

[0002] In recent years, antibiotics, as a novel type of trace organic pollutant, have attracted much attention due to their ability to promote the emergence and spread of drug-resistant bacteria in the environment, as well as their direct acute or chronic biotoxic effects on various organisms and their alteration of species distribution. Among various synthetic antibiotics, sulfamethoxazole is the most commonly used sulfonamide drug, and its presence has been detected in various water bodies. Therefore, efficient wastewater treatment technologies have become a focus of researchers. To date, many mature technologies have been explored and developed, such as biofilm processes, activated sludge processes, adsorption, ion exchange, membrane technology, coagulation sedimentation, electrochemical technology, Fenton process, and photocatalysis. Among these, membrane technology has been widely used in water purification due to its advantages of low chemical consumption, good separation effect, ease of maintenance, and minimal environmental impact; semiconductor photocatalysis technology, which can utilize solar energy, a clean and renewable energy source, has also provided new possibilities for the remediation of water pollution.

[0003] Most common membrane technologies used for removing pollutants from water are pressure-driven and can be classified according to their pore size. Nanofiltration technology, in particular, has been widely studied in drinking water purification and wastewater treatment due to its advantages such as low energy consumption, simple operation, space saving, and high efficiency. Graphene oxide (GO) is an important derivative of graphene. Due to its rapid and selective nanochannels, as well as good mechanical strength and flexibility, graphene oxide-based membranes assembled from graphene oxide sheets are ideal materials for wastewater treatment. However, a single GO membrane can only separate pollutants from water but cannot remove them. Therefore, as separation proceeds, pollutant accumulation inevitably occurs on the membrane surface, clogging the membrane pores, reducing flux, and affecting the normal operation of the membrane.

[0004] As a novel semiconductor photocatalyst, carbon nitride's relatively narrow band gap (2.7 eV) and suitable light absorption wavelength (460 nm) can significantly improve its utilization of sunlight. Furthermore, carbon nitride possesses numerous advantages, including abundant and easily synthesized raw materials, excellent thermal stability, and chemical stability. However, despite its excellent overall performance, the practical application of raw carbon nitride is limited by inherent drawbacks such as rapid photogenerated electron-hole recombination rates, small specific surface area, difficulty in separating from water, low quantum efficiency, and insufficient light absorption. To overcome these shortcomings, researchers have proposed various strategies to enhance the photocatalytic activity of carbon nitride, such as nanostructure engineering, constructing heterojunctions, elemental doping, and introducing defects. However, current research on the modification of carbon nitride remains insufficient, making the development of a simple modification method to obtain a highly efficient and inexpensive catalyst essential.

[0005] To fully utilize the excellent photocatalytic performance of photocatalysts, existing photocatalysts are often applied in photocatalytic reactors in the form of nanoparticles with large specific surface areas. However, separating nanoparticle photocatalysts from water is very difficult, resulting in low catalyst recovery and reuse rates, and their size toxicity may also cause secondary pollution. In recent years, photocatalytic membrane technology, which couples photocatalysis with membrane separation, has attracted increasing attention. Under light irradiation, photocatalytic membranes can degrade pollutants in the feed solution through reactive oxygen species generated by the photocatalyst, thereby preventing the formation of a cake layer on the membrane surface that would cause membrane pore blockage, reducing membrane fouling to a certain extent, and extending membrane lifespan. At the same time, the membrane substrate can serve as both a selective barrier for the removed substances and a support for the photocatalyst, solving the problem of subsequent catalyst separation. In short, photocatalytic membrane technology, to a certain extent, compensates for the shortcomings of single membrane separation and photocatalysis, greatly expanding their application scenarios in the field of water pollution remediation. Summary of the Invention

[0006] To address the insufficient photocatalytic activity and technical problems in the catalytic application of current carbon nitride catalysts, the present invention aims to provide a graphite carbon-modified silica-carbon nitride core-shell nanosphere material, an oxide graphene-based composite film, its preparation method, and its application.

[0007] The specific technical solution adopted in this invention is as follows:

[0008] A method for preparing graphite-carbon modified silica-carbon nitride core-shell nanospheres includes the following steps:

[0009] 1) Based on the improved Organic carbon-doped silica nanospheres were prepared by a method, then washed several times with ethanol and dried.

[0010] 2) Take the solid powder dried in step 1) and place it in a quartz boat, then transfer it to a tube furnace and heat it in an ultrapure nitrogen atmosphere. The organic carbon on the nano silica spheres is converted into graphite carbon in a high-temperature nitrogen environment. After cooling to room temperature, the graphite carbon modified nano silica sphere template is obtained.

[0011] 3) Melamine and the graphite carbon modified silica nanosphere template described in step 2) are mixed at a mass ratio of 5 to 20:1 and ground evenly. Then, the mixture is placed in a covered ceramic crucible and calcined in a muffle furnace. After cooling to room temperature, it is ground and sieved to obtain graphite carbon modified silica-carbon nitride core-shell nanospheres.

[0012] Further, the improvement described in step 1) The method for preparing organic carbon-doped silica nanospheres is as follows: hexadecyltrimethylammonium bromide is dissolved in a deionized water-ethanol mixture and stirred at 30-40°C for 20-60 min. Then, ammonia water is added and stirred thoroughly. Tetraethyl silicate is then quickly added and stirred for 20-30 h. The mass fraction of ammonia water is 25-30%, the solid-liquid ratio of hexadecyltrimethylammonium bromide to tetraethyl silicate is 0.1-0.3 g:1 mL, preferably 0.15 g:1 mL, and the volume ratio of ammonia water to tetraethyl silicate is 0.8-1.2:1, preferably 0.9-1.0:1.

[0013] Furthermore, the volume ratio of deionized water to ethanol in the mixture is 1.2 to 2.0:1, and the volume fraction of tetraethyl silicate added to the deionized water-ethanol mixture is 1 to 2%, preferably 1.2 to 1.5%.

[0014] Furthermore, in step 2), the calcination temperature is 650-750℃, preferably 700℃, and the calcination holding time is 2-4h, preferably 3h.

[0015] Furthermore, in step 3), the mass ratio of melamine to graphite carbon modified nano-silica sphere template is 10-12:1, the calcination temperature in step 3) is 500-600℃, preferably 550℃, and the calcination holding time is 2-4h, preferably 3h.

[0016] This invention also provides the application of the graphite carbon-modified silica-carbon nitride core-shell nanosphere material in the photocatalytic degradation of antibiotics in water. The application method is as follows: the pH of the antibiotic wastewater is adjusted to 6-7, the graphite carbon-modified silica-carbon nitride core-shell nanosphere material is added to it, the mixture is stirred in the dark to reach adsorption-desorption equilibrium, and then the light source is turned on to carry out the photocatalytic degradation reaction, wherein the light wavelength is greater than 420nm.

[0017] Furthermore, the antibiotic is sulfamethoxazole, the concentration of the antibiotic wastewater is below 10 ppm, and the concentration of the graphite carbon-modified silica-carbon nitride core-shell nanosphere material in the antibiotic wastewater is 0.2-0.6 g / L, preferably 0.4 g / L.

[0018] Furthermore, the light source is illuminated by a xenon lamp with a luminous power of 100–300 mW / cm². 2 The preferred value is 200-300mW / cm. 2 .

[0019] The preparation method of the graphene oxide-based composite membrane for synergistic catalytic separation includes the following steps:

[0020] S1: The graphene oxide solution is filtered through a support membrane as a substrate to form a film, which is then dried to form a graphene oxide-based film on the surface of the support membrane.

[0021] S2: The graphite carbon-modified silica-carbon nitride core-shell nanosphere material of the present invention is dispersed in glutaraldehyde solution to form a suspension. Then, the graphite carbon-modified silica-carbon nitride core-shell nanosphere material is filtered onto the surface of a graphene oxide-based membrane and dried to obtain a graphene oxide-based composite membrane for synergistic catalytic separation.

[0022] Preferably, in step S1, the supporting membrane is a commercial PES membrane with an average pore size of 0.1–0.2 μm, preferably 0.1 μm; the concentration of the graphene oxide solution is 0.05–0.2 g / L, preferably 0.1 g / L, and the loading on the membrane is 0.01–0.02 mg / cm³. 2 The preferred value is 0.0175 mg / cm³. 2 .

[0023] Preferably, in step S2, the ratio of the loading amount of graphite carbon-modified silica-carbon nitride core-shell nanosphere photocatalyst on the film to the loading amount of graphene oxide on the film is 1:1-3:1, preferably 2:1; the mass concentration of the glutaraldehyde solution is 5-20%, preferably 10%.

[0024] The present invention relates to the application of a synergistic catalytic separation graphene oxide-based composite membrane in the photocatalytic degradation of antibiotics in water. The application method is characterized by: under illumination, dead-end filtration is used to retain and degrade antibiotics in water, allowing the pollutant solution to pass through the graphene oxide-based composite membrane under a pressure of 1-2 bar; the antibiotic is preferably sulfamethoxazole.

[0025] Compared with existing technologies, the present invention has the following advantages:

[0026] 1) The method for preparing graphite carbon-modified silica nanosphere templates of the present invention is mature and can be used for large-scale production. The present invention uses a template method to obtain graphite carbon-modified silica-carbon nitride core-shell nanospheres. The modification of carbon nitride is successfully achieved through morphology control and surface modification. The preparation process is simple and easy to operate. The modification operation optimizes the band structure of the catalyst, promotes the separation and migration of photogenerated carriers, and improves the visible light photocatalytic efficiency. It can be applied to the degradation of antibiotics in water.

[0027] 2) The graphite carbon-modified silica-carbon nitride core-shell nanospheres of the present invention have a wide range of raw material sources, are inexpensive and readily available, and have a simple synthesis process, making them suitable for large-scale production.

[0028] 3) The graphite carbon-modified silica-carbon nitride core-shell nanospheres prepared by the method of the present invention have a more suitable band structure, stronger visible light absorption capacity, and higher photogenerated electron-hole pair separation and migration efficiency compared with unmodified carbon nitride.

[0029] 4) The graphite carbon-modified silica-carbon nitride core-shell nanospheres prepared by the method of the present invention exhibit a significantly higher initial reaction rate than unmodified carbon nitride when used to degrade sulfamethoxazole in water, under the same catalyst addition amount.

[0030] 5) The graphite-carbon modified silica-carbon nitride core-shell nanospheres prepared by the method of the present invention can achieve efficient degradation of sulfamethoxazole in water and have excellent photochemical stability.

[0031] 6) The graphene oxide-based composite membrane prepared by the method of the present invention can effectively retain and catalytically degrade sulfamethoxazole. Attached Figure Description

[0032] Figure 1 The following are scanning electron microscope (SEM) images of unmodified carbon nitride BCN (Fig. a), g-C3N4 / SiO2 core-shell nanospheres SCN (Fig. b) with original nano-SiO2 spheres as templates, g-C3N4 / C-SiO2 core-shell nanospheres SCCN (Fig. c) with graphite carbon-modified nano-SiO2 spheres as templates, and transmission electron microscope (TEM) images of original nano-SiO2 spheres (Fig. d), graphite carbon-modified nano-SiO2 spheres (Fig. e), and g-C3N4 / SiO2 core-shell nanospheres SCN (Fig. f) with original nano-SiO2 spheres as templates, in Example 1 of the present invention.

[0033] Figure 2 The XRD patterns of BCN, SCN, and SCCN are shown in Example 1.

[0034] Figure 3 The FTIR plots of BCN, SCN, and SCCN in Example 1 are shown.

[0035] Figure 4 XPS plots of BCN, SCN, and SCCN in Example 1;

[0036] Figure 5 This is a comparison chart of the photocatalytic degradation efficiency of sulfamethoxazole by BCN, SCN, and SCCN under different light irradiation powers in Example 2.

[0037] Figure 6 This is a comparison of the first-order apparent rate constants of BCN, SCN, and SCCN for the photocatalytic degradation of sulfamethoxazole under different light irradiation powers in Example 2.

[0038] Figure 7 This is a graph showing the cyclic degradation efficiency of SCCN under relatively weak light power in Example 2.

[0039] Figure 8 This is a comparison chart of the photocatalytic degradation efficiencies of BCN, SCN, and hollow carbon nitride nanospheres HSCN for Rhodamine B in Example 4. Detailed Implementation

[0040] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0041] The present invention discloses a method for preparing a graphene oxide-based composite membrane for synergistic catalytic separation, comprising the following steps:

[0042] 1) Based on the improved Method for preparing nano-silica spheres;

[0043] 2) After the reaction is complete, the resulting suspension is filtered and washed three times with ethanol; after washing, the resulting white solid is placed in a 60°C oven and dried overnight.

[0044] 3) Take the dried white powder in a quartz boat, place it in a tube furnace, heat and calcine it in an ultrapure nitrogen atmosphere, and cool it to room temperature to obtain a graphite carbon modified nano-silica sphere template.

[0045] 4) Mix 1g of melamine with 0.1g of graphite carbon modified silica nanosphere template and grind evenly. Then place it in a covered ceramic crucible and calcine it in a muffle furnace. After cooling to room temperature, grind it through a 300-mesh sieve to obtain graphite carbon modified silica-carbon nitride core-shell nanospheres.

[0046] 5) Take a mixture containing 0.35 mg of graphene oxide, and filter it using a commercial PES membrane (with an average pore size of approximately 0.1 μm) at 1 bar. The filtration area of ​​the commercial PES membrane is 20 cm². 2The film is then dried overnight at room temperature to obtain a graphene oxide-based film.

[0047] 6) The prepared graphite-modified silica-carbon nitride core-shell nanospheres were dispersed in a 10% glutaraldehyde solution to form a suspension (the concentration of the graphite-modified silica-carbon nitride core-shell nanospheres was 0.1 g / L). Then, a suspension containing 0.7 mg of catalyst was taken and further filtered under 20 psi using the prepared graphene oxide-based membrane as a support. The graphite-modified silica-carbon nitride core-shell nanosphere photocatalyst was pressed onto the surface of the graphene oxide-based membrane. The pressed membrane was dried overnight at room temperature to obtain the synergistic catalytic separation graphene oxide-based composite membrane.

[0048] Example 1

[0049] In this embodiment, the preparation steps of the graphite carbon-modified silica-carbon nitride core-shell nanosphere material are as follows:

[0050] 1) First, based on the improved The original and modified nano-SiO2 sphere templates were prepared by a specific method. The preparation method is as follows: 1.45 g of hexadecyltrimethylammonium bromide (CTAB) was dissolved in a mixed solution containing 478 mL of deionized water and 290.5 mL of ethanol. The solution was placed in a 35°C water bath and stirred for 30 min. Then, 9.5 mL of ammonia water (27 wt%) was added and the mixture was stirred for 5 min. Subsequently, 9.64 mL of tetraethyl orthosilicate (TEOS) was rapidly added, and the mixture was stirred for 24 h. After the reaction was complete, the resulting suspension was filtered and washed three times with ethanol. After washing, the resulting white solid was dried overnight in a 60°C oven.

[0051] 2) Take an appropriate amount of the dried white powder from step 1) into a quartz boat, place it in a tube furnace, heat it to 700°C in an ultrapure nitrogen atmosphere and keep it at that temperature for 3 hours. After cooling to room temperature, you will obtain a graphite carbon modified nano-SiO2 sphere template.

[0052] Meanwhile, in this embodiment, a raw nano-SiO2 sphere template without graphite carbon modification was also prepared. The specific preparation method is as follows: Take an appropriate amount of the dried white powder from step 1) into a 50mL covered ceramic crucible, place it in a muffle furnace, heat it to 550℃ in air and keep it at that temperature for 6 hours, and then cool it to room temperature to obtain the raw nano-SiO2 sphere template.

[0053] 3) Weigh 1g of melamine and 0.1g of the graphite carbon-modified nano-SiO2 sphere template obtained in step 2), mix and grind them evenly, then place them in a 50mL covered ceramic crucible. Heat the crucible in a muffle furnace to 550℃ at a heating rate of 10℃ / min and hold for 3h. After cooling to room temperature, yellow g-C3N4 / C-SiO2 core-shell nanospheres are obtained. After grinding, they are passed through a 300-mesh sieve and stored at room temperature, named SCCN. Simultaneously, g-C3N4 / SiO2 core-shell nanospheres using the original nano-SiO2 spheres as templates were also prepared in this embodiment, named SCN. The specific preparation method of SCN is the same as that of SCCN described above, except that "0.1g of the graphite carbon-modified nano-SiO2 sphere template obtained in step 2)" is replaced with "0.1g of the original nano-SiO2 sphere template obtained in step 2)".

[0054] 4) In addition, this embodiment also includes an experimental control group, namely unmodified carbon nitride, denoted as BCN. The specific preparation method is as follows: Weigh 10g of melamine into a 50mL covered ceramic crucible, place it in a muffle furnace, heat it to 550℃ at a heating rate of 10℃ / min and hold it at that temperature for 4h. After cooling to room temperature, grind it and pass it through a 300-mesh sieve, then store it at room temperature.

[0055] After preparation, the morphology of the three materials SCCN, SCN, and BCN was characterized. A GeminiSEM300 field emission scanning electron microscope was used to observe the three materials separately. A JEM-1010 transmission electron microscope was used to observe the original nano-SiO2 sphere template, the graphite carbon-modified nano-SiO2 sphere template, and SCN. A Bruker D8 Advance X-ray diffractometer equipped with Cu Kα radiation was used to determine the crystal structure of the three materials. A NICOLET6700 Fourier transform infrared spectrometer was used to determine the functional groups contained in the three materials. A Thermo Scientific K-Alpha X-ray photoelectron spectrometer was used to determine the elemental composition of the three materials. The test and analysis results obtained through the above characterization methods are as follows: Figures 1-4 As shown below, a detailed explanation follows:

[0056] exist Figure 1 middle, Figure 1 (a) is a SEM image of BCN. Figure 1 (b) is the SEM image of SCN. Figure 1 (c) is the SEM image of SCCN. Figure 1 (d) is a TEM image of the original nano-SiO2 sphere template. Figure 1 (e) is a TEM image of the graphite-carbon modified nano-SiO2 sphere template. Figure 1 (f) is the TEM image of SCN.

[0057] from Figure 1 It can be observed that the prepared original SiO2 nanospheres exhibit a uniform nanosphere morphology, with a particle size of approximately 500 nm, smooth surfaces, and aggregates formed through mutual contact. The introduction of graphite carbon has no significant effect on the morphology of the SiO2 nanospheres. Among the three carbon nitride materials, the BCN sample exhibits an irregular blocky structure overall, with a typical lamellar structure inside, composed of a large number of g-C3N4 particles aggregated together. SCN and SCCN have similar morphological characteristics, but show significant changes compared to BCN. Lamellar g-C3N4 curls and covers the surface of the SiO2 nanospheres, forming core-shell nanospheres with a rough surface and obvious wrinkles, and the g-C3N4 is tightly bound to SiO2. It is noteworthy that due to the presence of a large number of melamine molecules in the initial system, layered stacked g-C3N4 inevitably forms along with the core-shell nanospheres.

[0058] Figure 2 These are XRD patterns of three materials: BCN, SCN, and SCCN. Figure 2 It can be observed that all samples exhibit similar diffraction patterns, with two characteristic diffraction peaks at 2θ = 13.1° and 27.4°, corresponding to the in-plane periodic triazine structure (100) and the interlayer stacking of conjugated six-membered rings (002) of g-C3N4, respectively. No obvious diffraction peaks of other phases or impurities were detected, indicating that the introduction of SiO2 and graphitic carbon does not change the crystal structure of g-C3N4. SCN and SCCN show a weak and broad peak around 2θ = 22°, corresponding to the amorphous structure of SiO2. Compared with BCN, the intensity of the (002) peak of SCN is significantly weakened, indicating a reduction in interlayer stacking, consistent with the morphological evolution from bulk to core-shell structure. At the same time, the intensity of the (100) peak of SCN is also weakened, indicating that the in-plane order of the sample is disrupted. Compared with SCN, the diffraction peak intensity of SCCN is further weakened.

[0059] Figure 3 These are the FIIR spectra of three materials: BCN, SCN, and SCCN. Figure 3 It can be observed that in the FTIR spectra of SCN and SCCN samples, in addition to the characteristic peak of g-C3N4, the peak at 1100 cm⁻¹ is also present. -1 The nearby absorption peak corresponds to the antisymmetric tensile vibration of Si-O-Si, at 970 cm⁻¹. -1 The nearby absorption peaks correspond to the bending vibrations of Si-OH, indicating that the formation of a tightly bonded composite material by g-C3N4 encapsulating on the surface of nano-SiO2 spheres is a physical process rather than a chemical reaction.

[0060] Figure 4 These are XPS plots for three materials: BCN, SCN, and SCCN. Figure 4It can be observed that, in addition to the characteristic peaks corresponding to the nuclear energy of g-C3N4, two new peaks and a significantly enhanced O1s peak appear in SCN and SCCN. The two peaks at 103.7 eV and 159.2 eV correspond to Si 2p and Si 2s, respectively, while the enhanced O1s peak is related to the O lattice oxygen in SiO2. 2- The corresponding oxidation state indicates the physical composite of g-C3N4 and nano-SiO2 spheres.

[0061] Example 2

[0062] The three materials prepared in Example 1 were used for the degradation of sulfamethoxazole in water.

[0063] A 100 ppm stock solution was prepared by dissolving sulfamethoxazole solid in 0.1 M NaOH, followed by pH adjustment to approximately 6.5 with 0.1 M hydrochloric acid and 0.1 M NaOH solution. The solution was then stored at 5°C for later use. A 300 W xenon lamp (λ > 420 nm) was used as the light source, with optical power of 242 and 159 mW / cm². 2 .

[0064] Specifically, a magnetic stir bar, 50 mL of 5 ppm sulfamethoxazole solution, and 20 mg of catalyst were added to a 100 mL beaker and ultrasonically dispersed for 1 min. The beaker was then placed on a magnetic stirrer at 400 rpm. Before light exposure, the suspension was stirred in a dark room for 30 min to reach adsorption-desorption equilibrium, and then the light source was turned on to initiate the photocatalytic reaction. Throughout the catalytic reaction, 1 mL of the reaction liquid was transferred every 20 min, filtered through a 0.22 μm aqueous membrane, and then transferred to a liquid chromatography vial for analysis. Air cooling was used for temperature control during the reaction.

[0065] In addition, a cyclic degradation experiment was conducted to test the stability of the SCCN prepared in Example 1.

[0066] The concentration of sulfamethoxazole aqueous solution was determined using an Agilent 1200 series ultra-high performance liquid chromatograph. The chromatographic conditions were set as follows: column temperature 30℃, mobile phase 30% acetonitrile and 70% deionized water (v / v), flow rate 0.8 mL / min, injection volume 20 μL, UV detection wavelength 265 nm, and detection time 8 min.

[0067] The experimental results are as follows Figure 5 As shown, Figure 5 (a) is under relatively strong illumination conditions (optical power of 242mW / cm²). 2 Degradation experiment of ) Figure 5 (b) is under relatively weak lighting conditions (optical power of 159mW / cm²). 2 Degradation experiment of ).

[0068] from Figure 5 As can be seen from the data, among the three materials BCN, SCN, and SCCN, the graphite carbon-modified silica-carbon nitride core-shell nanosphere material SCCN exhibits the highest degradation rate for sulfamethoxazole. Under relatively strong light conditions (LI1 = 242 mW·cm⁻¹), the degradation rate is highest. -2 Both modified SCN and SCCN exhibited enhanced photocatalytic degradation effects. SCN achieved a degradation rate of 80.9% for SMX within 60 min and 96.4% within 120 min; furthermore, SCCN achieved a degradation rate of 93.4% for SMX within 60 min and 99.8% within 100 min. In contrast, BCN achieved a degradation rate of 71.2% for SMX within 60 min and 89.0% within 120 min. Under relatively weak light conditions (LI2 = 159 mW·cm²), the degradation was achieved. -2 Consistent results were obtained. SCCN achieved a degradation rate of 84.5% for SMX within 60 minutes and 92.5% within 80 minutes; SCN achieved a degradation rate of 70.6% for SMX within 60 minutes and 90.3% within 120 minutes; in contrast, BCN achieved a degradation rate of 46.3% for SMX within 60 minutes and 69.9% within 120 minutes.

[0069] The experimental results were fitted with a pseudo-first-order kinetic equation, and the fitting results are as follows: Figure 6 As shown. From Figure 6 It can be seen from this that under relatively strong illumination conditions (optical power of 242mW / cm²), 2 The first-order apparent rate constant for the degradation of sulfamethoxazole by graphite carbon-modified silica-carbon nitride core-shell nanospheres (SCCN) is 2.9 times that of unmodified carbon nitride (BCN); under relatively weak illumination conditions (optical power of 159 mW / cm²), the degradation rate is significantly higher than that of unmodified BCN. 2 This ratio increased to 3.5 times.

[0070] The experimental results of the three-cycle degradation experiment of material SCCN are as follows: Figure 7 As shown. From Figure 7 It can be seen from this that under relatively weak lighting conditions (optical power of 159mW / cm²), 2 The graphite-carbon modified silica-carbon nitride core-shell nanosphere material SCCN exhibits excellent photochemical stability, with a degradation rate of up to 70% after three cycles.

[0071] Example 3

[0072] In this embodiment, the preparation method of hollow carbon nitride nanospheres is as follows:

[0073] 1) First, based on the improved The original and modified nano-SiO2 sphere templates were prepared by a specific method. The preparation method is as follows: 1.45 g of hexadecyltrimethylammonium bromide (CTAB) was dissolved in a mixed solution containing 478 mL of deionized water and 290.5 mL of ethanol. The solution was placed in a 35°C water bath and stirred for 30 min. Then, 9.5 mL of ammonia water (27 wt%) was added and the mixture was stirred for 5 min. Subsequently, 9.64 mL of tetraethyl orthosilicate (TEOS) was rapidly added, and the mixture was stirred for 24 h. After the reaction was complete, the resulting suspension was filtered and washed three times with ethanol. After washing, the resulting white solid was dried overnight in a 60°C oven.

[0074] 2) Take an appropriate amount of the dried white powder from step 1) into a 50 mL covered ceramic crucible, place it in a muffle furnace, heat it in air to 550 °C and keep it at that temperature for 6 h, and then cool it to room temperature to obtain the original nano-SiO2 sphere template.

[0075] 3) Weigh 1g of melamine and 0.1g of the graphite carbon-modified nano-SiO2 sphere template obtained in step 2), mix and grind them evenly, then place them in a 50mL covered ceramic crucible. Heat the crucible in a muffle furnace to 550℃ at a heating rate of 10℃ / min and hold for 3h. After cooling to room temperature, yellow g-C3N4 / C-SiO2 core-shell nanospheres are obtained, named SCN.

[0076] 4) Take an appropriate amount of the yellow powder from step 3) into a beaker, and add 50 mL of 1 mol·L⁻¹ powder. -1 The Na2CO3 solution was heated to 60℃ in a water bath and kept at that temperature for 24 hours to remove the internal nano-SiO2 sphere template. After the reaction was complete, the resulting suspension was filtered and washed three times with deionized water. After washing, the resulting yellow solid was dried overnight in a 60℃ oven to obtain hollow g-C3N4 nanospheres, named HSCN.

[0077] 5) In addition, this embodiment also includes an experimental control group, namely unmodified carbon nitride, denoted as BCN. The specific preparation method is as follows: Weigh 10g of melamine into a 50mL covered ceramic crucible, place it in a muffle furnace, heat to 550℃ at a heating rate of 10℃ / min and hold at that temperature for 4h. After cooling to room temperature, grind and pass through a 300-mesh sieve, and store at room temperature.

[0078] Example 4

[0079] The three materials prepared in Example 3 were used for the degradation of Rhodamine B in water.

[0080] A 100 ppm stock solution of Rhodamine B solid was prepared by dissolving it in deionized water and stored at room temperature in the dark. A 300 W xenon lamp (λ>420 nm) was used as the light source, with a light power of 159 mW / cm². 2 .

[0081] Specifically, a magnetic stir bar, 50 mL of 20 ppm Rhodamine B solution, and 20 mg of catalyst were added to a 100 mL beaker and ultrasonically dispersed for 1 min. The beaker was then placed on a magnetic stirrer at 400 rpm. Before light exposure, the suspension was stirred in a dark room for 30 min to reach adsorption-desorption equilibrium, and then the light source was turned on to initiate the photocatalytic reaction. Throughout the catalytic reaction, 4 mL of the reaction liquid was transferred every 10 min, filtered through a 0.22 μm aqueous membrane, and then transferred to a 5 mL centrifuge tube for analysis. Air cooling was used to control the temperature during the reaction.

[0082] The concentration of Rhodamine B aqueous solution was determined by a SHIMADZU UV-2600i UV-Vis spectrophotometer with a UV detection wavelength of 553 nm.

[0083] The experimental results are as follows Figure 8 As shown. From Figure 8 As can be seen, among the three materials BCN, SCN, and HSCN, the g-C3N4 / SiO2 core-shell nanospheres SCN exhibited the highest degradation rate for Rhodamine B. SCN achieved a degradation rate of 95.6% for Rhodamine B within 60 minutes, while BCN achieved 46.3% within the same timeframe. In contrast, HSCN showed a degradation rate of less than 20% within 60 minutes. This indicates that the photocatalyst obtained after desilication using Na2CO3 solution exhibits significantly reduced catalytic performance, possibly because the alkaline solution used for desilication disrupts the chemical structure of carbon nitride, causing it to lose most of its catalytic activity. Therefore, the method proposed in this invention for constructing g-C3N4 / SiO2 core-shell nanospheres without desilication has significant advantages.

[0084] Example 5

[0085] The following steps were taken to prepare a graphene oxide-based composite membrane and use a dead-end filtration system to retain sulfamethoxazole in water:

[0086] Dilute an appropriate amount of graphene oxide solution to 0.1 g / L. Then, take a mixture containing 0.35 mg of graphene oxide and filter it using a commercial PES membrane (with an average pore size of approximately 0.1 μm) at 1 bar. The filtration area of ​​the PES membrane is 20 cm². 2 The film is then dried overnight at room temperature to obtain a graphene oxide-based film.

[0087] The prepared graphene-modified silica-carbon nitride core-shell nanospheres were dispersed in a 10% glutaraldehyde solution to form a suspension (concentration of 0.1 g / L). Then, a suspension containing x mg of catalyst was further filtered under 20 psi using the previously prepared graphene oxide-based membrane as a support. The graphene-modified silica-carbon nitride core-shell nanosphere photocatalyst was pressed onto the surface of the graphene oxide-based membrane, where x was 0.35 or 0.7. The pressed membrane was dried overnight at room temperature to obtain the synergistic catalytic separation graphene oxide-based composite membrane.

[0088] Next, dead-end filtration was employed under illumination for the retention and degradation of sulfamethoxazole in water. An aqueous solution of sulfamethoxazole (5 mg / L) was passed through a graphene oxide-based composite membrane for synergistic catalytic separation at 20 psi. During this process, due to the retention effect of the graphene oxide membrane, sulfamethoxazole in the water was retained on the surface and came into contact with the carbon nitride photocatalyst also located on the membrane surface. The removal of sulfamethoxazole from the water by the photocatalyst was achieved through a surface confinement strategy.

[0089] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the protection scope of the present invention should not be considered as being limited to the specific forms described in the embodiments.

Claims

1. A method for preparing graphite-carbon modified silica-carbon nitride core-shell nanospheres, characterized in that, Includes the following steps: 1) Organic carbon-doped silica nanospheres were prepared according to the improved Stöber method, then washed several times with ethanol and dried; 2) Take the solid powder dried in step 1) and place it in a quartz boat, then transfer it to a tube furnace and heat it in an ultrapure nitrogen atmosphere. The organic carbon on the nano silica spheres is converted into graphite carbon in a high-temperature nitrogen environment. After cooling to room temperature, the graphite carbon modified nano silica sphere template is obtained. 3) Melamine and the graphite carbon modified silica nanosphere template described in step 2) are mixed at a mass ratio of 5 to 20:1 and ground evenly. Then, the mixture is placed in a covered ceramic crucible and calcined in a muffle furnace. After cooling to room temperature, it is ground and sieved to obtain graphite carbon modified silica-carbon nitride core-shell nanospheres.

2. The method for preparing graphite-carbon modified silica-carbon nitride core-shell nanospheres as described in claim 1, characterized in that, Step 1) The improved Stöber method for preparing organic carbon-doped silica nanospheres is as follows: hexadecyltrimethylammonium bromide is dissolved in a deionized water-ethanol mixture and stirred at 30-40°C for 20-60 min. Then, ammonia is added and stirred thoroughly. Tetraethyl silicate is then quickly added and stirred for 20-30 h. The mass fraction of ammonia is 25-30%, the solid-liquid ratio of hexadecyltrimethylammonium bromide to tetraethyl silicate is 0.1-0.3 g:1 mL, and the volume ratio of ammonia to tetraethyl silicate is 0.8-1.2:

1.

3. The method for preparing graphite-carbon modified silica-carbon nitride core-shell nanospheres as described in claim 2, characterized in that, The solid-liquid ratio of hexadecyltrimethylammonium bromide to tetraethyl silicate is 0.15 g : 1 mL, and the volume ratio of ammonia to tetraethyl silicate is 0.9~1.0:

1.

4. The method for preparing graphite-carbon modified silica-carbon nitride core-shell nanospheres as described in claim 2, characterized in that, The volume ratio of deionized water to ethanol in the mixture is 1.2 to 2.0:1, and the volume fraction of tetraethyl silicate added to the deionized water-ethanol mixture is 1 to 2%.

5. The method for preparing graphite-carbon modified silica-carbon nitride core-shell nanospheres as described in claim 4, characterized in that, The volume fraction of tetraethyl silicate added to the deionized water-ethanol mixture is 1.2-1.5%.

6. The method for preparing graphite-carbon modified silica-carbon nitride core-shell nanospheres as described in claim 1, characterized in that, In step 2), the calcination temperature is 650-750℃ and the calcination holding time is 2-4h; in step 3), the mass ratio of melamine to graphite carbon modified nano-silica sphere template is 10~12:1, the calcination temperature in step 3) is 500-600℃ and the calcination holding time is 2-4h.

7. The method for preparing graphite-carbon modified silica-carbon nitride core-shell nanospheres as described in claim 6, characterized in that, In step 2), the calcination temperature is 700℃ and the calcination holding time is 3h; in step 3), the calcination temperature is 550℃ and the calcination holding time is 3h.

8. A graphite-carbon modified silica-carbon nitride core-shell nanosphere material prepared by any one of the methods described in claims 1-7.

9. The application of the graphite carbon-modified silica-carbon nitride core-shell nanosphere material as described in claim 8 in the photocatalytic degradation of antibiotics in water, characterized in that... The pH of the antibiotic wastewater was adjusted to 6-7, and the graphite carbon modified silica-carbon nitride core-shell nanosphere material was added into it. The mixture was first stirred in the dark to reach adsorption-desorption equilibrium, and then the light source was turned on to carry out the photocatalytic degradation reaction, wherein the light wavelength was greater than 420 nm.

10. The application as described in claim 9, characterized in that... The antibiotic is sulfamethoxazole, and the concentration of the antibiotic wastewater is below 10 ppm. The concentration of the graphite carbon-modified silica-carbon nitride core-shell nanospheres in the antibiotic wastewater is 0.2~0.6 g / L. The light source is a xenon lamp with a light power of 100~300 mW / cm². 2 .

11. The application as described in claim 10, characterized in that... The concentration of the graphite-carbon modified silica-carbon nitride core-shell nanospheres in the antibiotic wastewater was 0.4 g / L; the light source was a xenon lamp with a light power of 200-300 mW / cm². 2 .

12. A graphene oxide-based composite membrane for synergistic catalytic separation, characterized in that... The method for preparing the composite membrane includes the following steps: S1: The graphene oxide solution is filtered through a support membrane as a substrate to form a film, which is then dried to form a graphene oxide-based film on the surface of the support membrane. S2: The graphite carbon-modified silica-carbon nitride core-shell nanosphere material described in claim 5 is dispersed in a glutaraldehyde solution to form a suspension. Then, the graphite carbon-modified silica-carbon nitride core-shell nanosphere material is filtered onto the surface of a graphene oxide-based membrane and dried to obtain a graphene oxide-based composite membrane for synergistic catalytic separation.

13. The graphene oxide-based composite membrane for synergistic catalytic separation as described in claim 12, characterized in that... In step S1, the supporting membrane is a commercial PES membrane with an average pore size of 0.1–0.2 μm; the concentration of the graphene oxide solution is 0.05–0.2 g / L, and the loading on the membrane is 0.01–0.02 mg / cm³. 2 ; In step S2, the ratio of the loading amount of graphite carbon-modified silica-carbon nitride core-shell nanospheres on the film to the loading amount of graphene oxide on the film is 1:1-3:1; the mass concentration of the glutaraldehyde solution is 5-20%.

14. The graphene oxide-based composite membrane for synergistic catalytic separation as described in claim 13, characterized in that... In step S2, the ratio of the loading amount of graphite carbon-modified silica-carbon nitride core-shell nanospheres on the membrane to the loading amount of graphene oxide on the membrane is 2:

1.

15. The application of the graphene oxide-based composite membrane for synergistic catalytic separation as described in claim 12 in the photocatalytic degradation of antibiotics in water, characterized in that... The application method is as follows: under light irradiation, dead-end filtration is used to intercept and degrade antibiotics in water, allowing the pollutant solution to pass through the graphene oxide-based composite membrane under a pressure of 1~2 bar.

16. The application as described in claim 15, characterized in that... The antibiotic is sulfamethoxazole.

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