A composite oxide particle filter medium and its preparation method

Abstract

The present invention discloses a composite oxide particle filter material and a preparation method thereof, specifically relating to the technical field of oxide particle filter materials. The filter material uses a ternary composite oxide of cerium dioxide-cobalt tetroxide-nickel oxide as the core material, has a hierarchical pore structure, and is coated with a pH-responsive coating on the surface. The preparation method includes S1, biological template pretreatment, S2, sol-gel synthesis, S3, hierarchical pore construction, and S4, surface modification. The present invention takes the ternary composite oxide of cerium dioxide-cobalt tetroxide-nickel oxide as the core, and with the help of hierarchical pores, surface copper nanoparticles, and internal upconversion nanoparticles, efficiently degrades pollutants under visible light and infrared light. The quaternary ammonium salt compounds grafted on the surface have good antibacterial properties, can inhibit the growth of microorganisms, and extend the service life of the filter material. The overall preparation process is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of oxidation granular filter materials, and more specifically, to a composite oxidation granular filter material and a preparation method thereof. Background Art

[0002] In the field of environmental pollution control, water purification and air purification have always been key problems that need to be urgently solved. When traditional filter materials are faced with increasingly complex pollution situations, many limitations are exposed. Common single-component filter materials, due to their single function, are difficult to meet the requirements of efficiently removing multiple pollutants at the same time. For example, activated carbon filter materials, although having a certain adsorption capacity, have poor treatment effects on certain organic pollutants and microorganisms;

[0003] Higher requirements are put forward for the performance of filter materials. On the one hand, there are often various pollutants in water bodies, such as heavy metal ions, organic compounds, and pathogenic microorganisms, etc., and it is required that the filter materials can effectively adsorb and degrade these pollutants at the same time. On the other hand, for harmful gases and particulate matters in the air, a multifunctional filter material is also urgently needed to achieve purification;

[0004] In the structural and compositional design of existing filter materials, advanced technologies such as photocatalysis cannot be fully utilized to improve the purification efficiency. At the same time, during the long-term use of filter materials, microorganisms are likely to grow on their surfaces, resulting in filter material blockage, a decline in purification performance, and even secondary pollution.

[0005] In view of the above situation, the present invention provides a composite oxidation granular filter material and a preparation method thereof. Summary of the Invention

[0006] In order to overcome the above-mentioned defects of the prior art, the present invention provides a composite oxidation granular filter material and a preparation method thereof to solve the problems raised in the above background art.

[0007] To achieve the above object, the present invention provides the following technical solution: A composite oxidation granular filter material, the filter material particles are in a regular spherical shape, and the particle size distribution is between 0.5 - 2 mm. The filter material uses a ternary composite oxide of cerium dioxide - cobalt tetroxide - nickel oxide as the core material, has a hierarchical pore structure, and is coated with a pH-responsive coating on the surface;

[0008] Among them, the molar ratio of cerium dioxide, cobalt tetroxide, and nickel oxide in the ternary composite oxide is 5:3:2;

[0009] The hierarchical pore structure includes macropores, mesopores, and micropores. Among them, the macropore aperture is 50 - 500 nm, the mesopore aperture is 2 - 50 nm, the micropore aperture is less than 2 nm, and the specific surface area of the filter material ≥ 200 m² / g;

[0010] The pH-responsive coating is composed of the composite of polymethacrylic acid and graphene oxide.

[0011] Preferably, the filter medium surface is loaded with copper nanoparticles, the particle size of the copper nanoparticles is 5-10 nm, and the loading amount is 5 wt%.

[0012] Preferably, the thickness of the pH-responsive coating is 50-100 nm.

[0013] Preferably, carbon nanotubes are uniformly dispersed inside the filter medium, and the mass of the carbon nanotubes accounts for 1%-3% of the total mass of the filter medium, which is used to enhance the mechanical strength and electron conduction ability of the filter medium and improve the catalytic reaction efficiency.

[0014] Preferably, upconversion nanoparticles are doped inside the filter medium, which are used to convert infrared light into visible light, improve the degradation ability of the filter medium to pollutants under visible light and infrared light, and the doping amount is 0.5 wt%-2 wt%.

[0015] Preferably, a quaternary ammonium salt compound with antibacterial properties is grafted on the surface of the filter medium, and the grafting rate is 0.2 mmol / g-0.5 mmol / g, which is used to endow the filter medium with antibacterial function while purifying pollutants and inhibit the growth of microorganisms on the surface of the filter medium.

[0016] The present invention also provides a preparation method for preparing the above-mentioned composite oxide particle filter medium, which specifically includes the following preparation steps:

[0017] S1. Biological template pretreatment,

[0018] S1.1. Immerse bacterial cellulose in a mixed solution of cerium nitrate, cobalt nitrate and nickel nitrate with a concentration of 0.1-0.5 mol / L, and stir for 24 h to load metal ions into the pores of the template;

[0019] S1.2. Before the biological template pretreatment, perform surface hydrophilization treatment on bacterial cellulose. Immerse it in an aqueous solution of silane coupling agent with a mass fraction of 3%-5% for 3-5 h, then rinse it with deionized water and dry it;

[0020] S2. Sol-gel synthesis,

[0021] S2.1. Add citric acid and ethylene glycol with a molar ratio of 1:1-1:3 to the solution in step S1.1, and adjust the pH to 6-7 to form a sol;

[0022] S2.2. At the same time, add the carbon nanotube suspension after ultrasonic dispersion treatment to the sol. The addition amount of the carbon nanotubes is controlled according to the final proportion of 1%-3% of the total mass of the filter medium. The ultrasonic dispersion frequency of the carbon nanotube suspension is 30-50 kHz, and the time is 20-40 min;

[0023] S2.3. Subsequently, microwave heating is carried out at a power of 500 W for 10 min to promote gelation and form a precursor;

[0024] S2.4. After the sol-gel synthesis is completed, the formed precursor is subjected to spray drying. The inlet air temperature is controlled at 180 - 220 °C, and the outlet air temperature is controlled at 80 - 100 °C to form spherical particles with uniform particle size. Particles with a particle size in the range of 0.3 - 0.8 mm are screened out through a vibrating sieve;

[0025] S3. Hierarchical pore structure construction

[0026] S3.1. The precursor in step S2.3 is freeze-dried and calcined at 600 °C for 4 h in a nitrogen atmosphere to remove the biological template and form a hierarchical porous structure;

[0027] S3.2. Then, the hierarchical porous structure is immersed in a solution containing upconversion nanoparticles. The solution concentration is adjusted according to the final doping amount of upconversion nanoparticles of 0.5 wt% - 2 wt%. The immersion temperature is maintained at 40 - 60 °C for 8 - 12 h to uniformly dope the upconversion nanoparticles into the filter material and endow the filter material with photothermal conversion function;

[0028] S3.3. After the hierarchical pore structure construction is completed, the hierarchical porous structure is subjected to pulsed electric field treatment. The electric field strength is 1 - 3 kV / cm, the pulse frequency is 10 - 20 Hz, and the treatment time is 5 - 10 min;

[0029] S3.4. The hierarchical porous structure is subjected to vacuum annealing treatment. The vacuum degree is 10 -3 -10 -2 Pa, the annealing temperature is 400 - 500 °C, and the time is 2 - 3 h;

[0030] S4. Surface modification

[0031] S4.1. Copper nanoparticles are loaded on the particle surface by chemical reduction method. The reducing agent is sodium borohydride, and the molar ratio of sodium borohydride to copper ions is 2:1 - 4:1;

[0032] S4.2. Then, layer-by-layer self-assembly treatment is carried out. Before coating the composite coating of polymethacrylic acid and graphene oxide, positively charged polyelectrolytes and negatively charged functional nanoparticles are alternately adsorbed on the surface of the filter material. The adsorption time for each layer is 10 - 20 min to form a multilayer composite structure;

[0033] S4.3. After completing layer-by-layer self-assembly, immerse the filter media in a grafting solution containing quaternary ammonium salt compounds. The concentration of the grafting solution is 0.5 - 1.5 mol / L, the reaction temperature is 50 - 70 °C, and the reaction time is 3 - 5 h, so that the grafting rate on the surface of the filter media reaches 0.2 mmol / g - 0.5 mmol / g, endowing the filter media with antibacterial properties;

[0034] S4.4. Finally, coat a composite coating of polymethacrylic acid and graphene oxide through electrospinning technology to form a pH-responsive coating. The electrospinning voltage is 10 - 20 kV, the electrospinning distance is 10 - 15 cm, and the flow rate of the electrospinning solution is 0.5 - 1.5 mL / h. During the process of electrospinning and coating the composite coating of polymethacrylic acid and graphene oxide, add titanium dioxide nanoparticles with a mass fraction of 0.5% - 2% to the electrospinning solution. After electrospinning is completed, perform ultraviolet curing treatment on the filter media coated with the pH-responsive coating. The ultraviolet wavelength is 254 nm, and the irradiation time is 15 - 30 min.

[0035] Preferably, after adding the carbon nanotube suspension in step S2.2, perform high-speed centrifugation on the sol. The centrifugation speed is 8000 - 12000 revolutions per minute, and the centrifugation time is 5 - 10 min.

[0036] Preferably, when soaking in the upconversion nanoparticle solution in step S3.2, use ultrasonic assistance for soaking. The ultrasonic frequency is 40 - 60 kHz, and the ultrasonic power is 100 - 200 W.

[0037] Preferably, during the layer-by-layer self-assembly process in step S4.2, introduce electric field-assisted adsorption, and apply a DC electric field with an intensity of 0.5 - 1.5 kV / cm on the surface of the filter media to promote the faster and more uniform adsorption of polyelectrolytes and functional nanoparticles on the surface of the filter media, shorten the adsorption time of each layer by 3 - 5 min, and improve the stability of the multi-layer composite structure by 40% - 50%.

[0038] The technical effects and advantages of the present invention:

[0039] 1. The filter media of the present invention has a cerium dioxide-cobalt ferrite-nickel oxide ternary composite oxide as the core. The unique hierarchical pore structure provides a large specific surface area. The macropores are conducive to the rapid entry of pollutants, and the mesopores and micropores increase the adsorption sites. At the same time, the surface-loaded copper nanoparticles can catalyze the decomposition of pollutants, and the internally doped upconversion nanoparticles can convert infrared light into visible light, broadening the spectral range of photocatalysis and greatly enhancing the degradation ability of the filter media for pollutants under visible light and infrared light;

[0040] 2. The surface of the filter material of the present invention is grafted with a quaternary ammonium salt compound having antibacterial properties. During the process of purifying pollutants, the quaternary ammonium salt compound can effectively inhibit the growth of microorganisms on the surface of the filter material, ensuring the hygienic safety of the filter material during use, preventing secondary pollution, extending the service life of the filter material, and maintaining its stable purification effect;

[0041] 3. During the preparation process of the present invention, bacterial cellulose is used as a biological template and soaked in a mixed solution of cerium nitrate, cobalt nitrate, and nickel nitrate, so that metal ions are accurately loaded into the pores of the template. In the sol-gel synthesis stage, the molar ratio of citric acid to ethylene glycol and the pH value are reasonably controlled, and carbon nanotubes dispersed by ultrasonic are added to enhance the mechanical strength and electron conduction ability of the filter material. During the construction of the hierarchical pore structure, freeze-drying, high-temperature calcination, pulsed electric field, and vacuum annealing treatments are carried out to accurately regulate the pore structure. In the surface modification step, processes such as loading copper nanoparticles by chemical reduction method, layer-by-layer self-assembly combined with electric field-assisted adsorption, and electrospinning to coat a pH-responsive coating act synergistically to endow the filter material with various excellent properties. Moreover, the entire preparation process has mature technology and strong operability, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is the overall flowchart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0043] Example 1

[0044] This example provides a composite oxide particle filter material. The filter material particles are regular spherical in shape, and the particle size distribution is between 0.5 - 2 mm. The filter material uses a ternary composite oxide of cerium dioxide - cobalt tetroxide - nickel oxide as the core material, has a hierarchical pore structure, and is coated with a pH-responsive coating on the surface; wherein, the molar ratio of cerium dioxide, cobalt tetroxide, and nickel oxide in the ternary composite oxide is 5:3:2; the hierarchical pore structure includes macropores, mesopores, and micropores. Among them, the macropore diameter is 50 - 500 nm, the mesopore diameter is 2 - 50 nm, the micropore diameter is less than 2 nm, and the specific surface area of the filter material ≥ 200 m² / g; the pH-responsive coating is composed of polymethacrylic acid and graphene oxide.

[0045] This example also provides a preparation method for preparing the composite oxide particle filter material of this example, which specifically includes the following steps:

[0046] S1. Pretreatment of the biological template

[0047] S1.1. Weigh an appropriate amount of bacterial cellulose, completely soak it in a mixed solution of cerium nitrate, cobalt nitrate, and nickel nitrate with a concentration of 0.1 mol / L each, place it on a magnetic stirrer, and stir at a speed of 150 revolutions per minute for 24 h to promote the full loading of metal ions into the pores of the template;

[0048] S1.2. Prior to S1.1, the bacterial cellulose is soaked in an aqueous solution of silane coupling agent with a mass fraction of 3% for 3 h, then rinsed repeatedly with deionized water three times, 3 min each time, and then placed in an oven at 60 °C for drying for 2 h;

[0049] S2. Sol-gel synthesis

[0050] S2.1. Transfer the mixed solution soaked with bacterial cellulose in S1.1 to a three-necked flask. Under stirring, slowly add citric acid and ethylene glycol mixed in a molar ratio of 1:1, and adjust the pH to 6 using 0.1 mol / L sodium hydroxide solution and 0.1 mol / L hydrochloric acid solution to form a sol;

[0051] S2.2. Weigh carbon nanotubes accounting for 1% of the total mass of the final filter material, add them to 150 mL of absolute ethanol, and perform ultrasonic dispersion treatment at an ultrasonic frequency of 30 kHz for 20 min to make a uniform carbon nanotube suspension. Slowly drip this suspension into the above sol. After the dripping is completed, perform high-speed centrifugation on the sol, with a centrifugation speed of 8000 revolutions per minute and a centrifugation time of 5 min;

[0052] S2.3. Place the three-necked flask in a microwave oven and heat it at a power of 500 W for 10 min to promote gelation and obtain a precursor;

[0053] S2.4. Transfer the precursor to a spray dryer, set the inlet air temperature to 180 °C and the outlet air temperature to 80 °C for spray drying treatment to obtain spherical particles with uniform particle size. Use a vibrating sieve to screen out particles with a particle size in the range of 0.3 - 0.8 mm and collect them;

[0054] S3. Hierarchical pore structure construction

[0055] S3.1. Put the screened spherical particles into a freeze dryer and freeze-dry them at -50 °C for 10 h, then transfer them to a tube furnace and calcine them at 600 °C for 4 h in a nitrogen atmosphere to remove the biological template and form a hierarchical porous structure;

[0056] S3.2. Weigh an appropriate amount of upconversion nanoparticles, add them to 80 mL of deionized water to prepare a solution, and adjust the solution concentration according to the final doping amount of upconversion nanoparticles of 0.5 wt%. Immerse the hierarchical porous structure in this solution and soak it in a constant temperature water bath at 40 °C for 8 h, while using ultrasonic assistance for soaking, with an ultrasonic frequency of 40 kHz and an ultrasonic power of 100 W, to uniformly dope the upconversion nanoparticles into the filter material;

[0057] S3.3. Place the doped hierarchical porous structure in a pulsed electric field device, apply a pulsed electric field with an electric field strength of 1 kV / cm and a pulse frequency of 10 Hz, and process for 5 min;

[0058] S3.4. Transfer the hierarchical porous structure treated by the pulsed electric field to a vacuum annealing furnace, and anneal for 2 h under the conditions of a vacuum degree of 10 -3 Pa and an annealing temperature of 400 °C;

[0059] S4. Surface modification

[0060] S4.1. Prepare 80 mL of a copper sulfate solution with a concentration of 0.1 mol / L, take 40 mL and add it to the above-mentioned hierarchical porous structure. Under stirring, slowly add 20 mL of an aqueous solution containing 0.2 mol / L sodium borohydride (the molar ratio of sodium borohydride to copper ions is 2:1), and react for 25 min to load copper nanoparticles onto the particle surface;

[0061] S4.2. Immerse the filter material loaded with copper nanoparticles in a 0.05 mol / L positively charged polyelectrolyte solution, apply a DC electric field with a strength of 0.5 kV / cm on the surface of the filter material, take it out after adsorption for 7 min, rinse it 3 times with deionized water, 2 min each time. Then immerse it in a 0.05 mol / L negatively charged functional nanoparticle dispersion liquid, apply the same electric field, take it out after adsorption for 7 min, and rinse it 3 times with deionized water again. Alternately adsorb 4 times in this way to form a multi-layer composite structure, and the stability of this structure is increased by 40% compared with that without electric field assistance;

[0062] S4.3. Immerse the filter material that has completed layer-by-layer self-assembly in a 0.5 mol / L quaternary ammonium salt compound grafting solution, and react in a water bath at 50 °C for 3 h to make the grafting rate on the surface of the filter material reach 0.2 mmol / g;

[0063] S4.4. Dissolve polymethacrylic acid and graphene oxide in dimethylformamide according to a mass ratio of 2:1 to prepare a spinning solution with a concentration of 0.08 g / mL, add 0.5% by mass of nano-titanium dioxide, and ultrasonically disperse for 20 minutes. Through an electrospinning device, under the conditions of a spinning voltage of 10 kV, a spinning distance of 10 cm, and a spinning solution flow rate of 0.5 mL / h, coat a polymethacrylic acid and graphene oxide composite coating to form a pH-responsive coating. After electrospinning, place the filter material under a UV lamp with a wavelength of 254 nm and irradiate for 15 min for curing treatment.

[0064] Performance test:

[0065] 1. Structure and morphology: The surface morphology and pore structure of the filter media were observed using a scanning electron microscope. It was found that the filter media particles were regular spherical in shape, with a particle size distribution between 0.5 - 2 mm. The hierarchical pore structure was obvious, and the distribution of macropores, mesopores, and micropores met the requirements.

[0066] 2. Composition analysis: The crystal structure of the filter media was analyzed using an X-ray diffractometer to determine the presence of the cerium dioxide-cobalt tetroxide-nickel oxide ternary composite oxide, and the molar ratio of cerium dioxide, cobalt tetroxide, and nickel oxide was 5:3:2. The surface elemental composition and chemical state of the filter media were analyzed using an X-ray photoelectron spectrometer to verify the loading of copper nanoparticles, grafting of quaternary ammonium salt compounds, etc.

[0067] 3. Specific surface area and pore size distribution: Through nitrogen adsorption-desorption tests, the specific surface area of the filter media was measured to be 205 m² / g. The macropore diameter was between 50 - 500 nm, the mesopore diameter was between 2 - 50 nm, and the micropore diameter was less than 2 nm.

[0068] 4. Photothermal conversion performance: An infrared thermal imager was used to monitor the temperature change of the filter media under simulated sunlight (including infrared light) irradiation to verify its photothermal conversion function. By degrading organic pollutants such as methyl orange, the degradation ability of the filter media to pollutants under visible light and infrared light was tested, and the degradation rate reached 82%.

[0069] 5. Antibacterial performance: Antibacterial tests were carried out using Escherichia coli and Staphylococcus aureus. The filter media was mixed and cultured with the bacterial solution, and the antibacterial rate was calculated by the plate counting method. The results showed that the antibacterial rate was 86%, indicating that the filter media had good antibacterial performance.

[0070] Example 2

[0071] This example provides a composite oxide particle filter media. The filter media particles are regular spherical in shape, with a particle size distribution between 0.5 - 2 mm. The filter media uses the cerium dioxide-cobalt tetroxide-nickel oxide ternary composite oxide as the core material, has a hierarchical pore structure, and is coated with a pH-responsive coating on the surface. Among them, the molar ratio of cerium dioxide, cobalt tetroxide, and nickel oxide in the ternary composite oxide is 5:3:2. The hierarchical pore structure includes macropores, mesopores, and micropores. Among them, the macropore diameter is 50 - 500 nm, the mesopore diameter is 2 - 50 nm, the micropore diameter is less than 2 nm, and the specific surface area of the filter media is ≥200 m² / g. The pH-responsive coating is composed of polymethacrylic acid and graphene oxide.

[0072] This example also provides a preparation method for preparing the composite oxide particle filter media of this example, which specifically includes the following steps:

[0073] S1. Biological template pretreatment

[0074] S1.1: Weigh an appropriate amount of bacterial cellulose and soak it completely in a mixed solution of cerium nitrate, cobalt nitrate, and nickel nitrate, each with a concentration of 0.5 mol / L. Place it on a magnetic stirrer and stir at a speed of 250 revolutions per minute for 24 hours to fully load metal ions into the pores of the template.

[0075] S1.2: Before performing S1.1, first soak the bacterial cellulose in an aqueous solution of 5% silane coupling agent for 5 hours, then rinse it repeatedly with deionized water 4 times, 5 minutes each time, and then place it in an oven at 70 °C for drying for 3 hours.

[0076] S2. Sol - gel synthesis

[0077] S2.1: Transfer the mixed solution containing the soaked bacterial cellulose in S1.1 to a three - necked flask. Under stirring, slowly add citric acid and ethylene glycol mixed in a molar ratio of 1:3, and use 0.1 mol / L sodium hydroxide solution and 0.1 mol / L hydrochloric acid solution to adjust the pH to 7 to form a sol.

[0078] S2.2: Weigh carbon nanotubes accounting for 3% of the total mass of the final filter material, add them to 250 mL of absolute ethanol, and perform ultrasonic dispersion treatment at an ultrasonic frequency of 50 kHz for 40 minutes to make a uniform carbon nanotube suspension. Slowly drip this suspension into the above - mentioned sol. After the dripping is completed, perform high - speed centrifugation on the sol at a centrifugation speed of 12,000 revolutions per minute for 10 minutes.

[0079] S2.3: Place the three - necked flask in a microwave oven and heat it at a power of 500 W for 10 minutes to promote gelation and obtain a precursor.

[0080] S2.4: Transfer the precursor to a spray dryer, set the inlet air temperature to 220 °C and the outlet air temperature to 100 °C for spray - drying treatment to obtain spherical particles with uniform particle size. Use a vibrating sieve to screen out and collect the particles with a particle size in the range of 0.3 - 0.8 mm.

[0081] S3. Hierarchical pore structure construction

[0082] S3.1: Put the screened spherical particles into a freeze - dryer and freeze - dry them at - 50 °C for 14 hours, then transfer them to a tubular furnace and calcine them at 600 °C for 4 hours in a nitrogen atmosphere to remove the biological template and form a hierarchical porous structure.

[0083] S3.2. Weigh an appropriate amount of upconversion nanoparticles and add them to 120 mL of deionized water to prepare a solution. The solution concentration is adjusted according to the final doping amount of upconversion nanoparticles being 2 wt%. Immerse the hierarchical porous structure in this solution and soak it in a constant temperature water bath at 60 °C for 12 h. At the same time, use ultrasonic assistance for soaking. The ultrasonic frequency is 60 kHz and the ultrasonic power is 200 W to uniformly dope the upconversion nanoparticles into the filter medium.

[0084] S3.3. Place the doped hierarchical porous structure in a pulsed electric field device and apply a pulsed electric field with an electric field strength of 3 kV / cm and a pulse frequency of 20 Hz for 10 min.

[0085] S3.4. Transfer the hierarchical porous structure treated with the pulsed electric field to a vacuum annealing furnace and anneal it for 3 h under the conditions of a vacuum degree of 10 -2 Pa and an annealing temperature of 500 °C.

[0086] S4. Surface modification

[0087] S4.1. Prepare 120 mL of a copper sulfate solution with a concentration of 0.1 mol / L. Take 60 mL and add it to the above-mentioned hierarchical porous structure. Under stirring, slowly add 30 mL of an aqueous solution containing 0.2 mol / L sodium borohydride (the molar ratio of sodium borohydride to copper ions is 4:1) and react for 35 min to load copper nanoparticles onto the particle surface.

[0088] S4.2. Immerse the filter medium loaded with copper nanoparticles in a 0.08 mol / L positively charged polyelectrolyte solution. Apply a DC electric field with a strength of 1.5 kV / cm on the surface of the filter medium, take it out after adsorption for 15 min, and rinse it 4 times with deionized water, 4 min each time. Then immerse it in a 0.08 mol / L negatively charged functional nanoparticle dispersion liquid, apply the same electric field, take it out after adsorption for 15 min, and rinse it 4 times with deionized water again. Alternately adsorb in this way 6 times to form a multilayer composite structure, and the stability of this structure is increased by 50% compared with that without electric field assistance.

[0089] S4.3. Immerse the filter medium that has completed layer-by-layer self-assembly in a 1.5 mol / L quaternary ammonium salt compound grafting solution and react in a water bath at 70 °C for 5 h to make the grafting rate on the surface of the filter medium reach 0.5 mmol / g.

[0090] S4.4. Dissolve polymethacrylic acid and graphene oxide in dimethylformamide according to a mass ratio of 4:1 to prepare a spinning solution with a concentration of 0.12 g / mL, add nano-titanium dioxide with a mass fraction of 2%, and ultrasonically disperse for 40 min; through an electrospinning device, under the conditions of a spinning voltage of 20 kV, a spinning distance of 15 cm, and a spinning solution flow rate of 1.5 mL / h, coat a composite coating of polymethacrylic acid and graphene oxide to form a pH-responsive coating. After electrospinning is completed, place the filter material under a UV lamp with a wavelength of 254 nm and irradiate for 30 min for curing treatment.

[0091] Performance testing:

[0092] 1. Structure and morphology. By observing the surface morphology and pore structure of the filter material through a scanning electron microscope, it can be seen that the filter material particles are regular spherical shapes, with a particle size distribution between 0.5 - 2 mm, the hierarchical pore structure is clear, and the distribution of macropores, mesopores, and micropores meets the requirements.

[0093] 2. Composition analysis. Use an X-ray diffractometer to analyze the crystal structure of the filter material to determine the presence of a cerium dioxide-cobalt tetroxide-nickel oxide ternary composite oxide, and the molar ratio of cerium dioxide, cobalt tetroxide, and nickel oxide is 5:3:2. Use an X-ray photoelectron spectrometer to analyze the surface element composition and chemical state of the filter material to verify the loading of copper nanoparticles, the grafting of quaternary ammonium salt compounds, etc.

[0094] 3. Specific surface area and pore size distribution. Through nitrogen adsorption-desorption testing, the specific surface area of the filter material is measured to be 230 m² / g, the macropore diameter is between 50 - 500 nm, the mesopore diameter is between 2 - 50 nm, and the micropore diameter is less than 2 nm.

[0095] 4. Photothermal conversion performance. Use an infrared thermal imager to monitor the temperature change of the filter material under simulated sunlight (including infrared light) irradiation to verify its photothermal conversion function. By degrading organic pollutants such as methyl orange, test the degradation ability of the filter material to pollutants under visible light and infrared light, and the degradation rate reaches 91%.

[0096] 5. Antibacterial performance. Conduct antibacterial tests using Escherichia coli and Staphylococcus aureus. Mix the filter material with the bacterial solution and culture it, and calculate the antibacterial rate by the plate counting method. The result shows that the antibacterial rate is 96%, indicating that the filter material has good antibacterial performance.

[0097] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite oxidized particle filter material, characterized in that: The filter material particles are regular spherical, with a particle size distribution between 0.5-2 mm, with a ternary composite oxide of cerium dioxide-cobalt tetraoxide-nickel oxide as the core material, having a hierarchical pore structure, and coated with a pH responsive coating with a thickness of 50-100 nm on the surface; The molar ratio of cerium dioxide, cobalt oxide and nickel oxide in the ternary composite oxide is 5:3:2; The graded pore structure includes macropores, mesopores and micropores, wherein the pore size of macropores is 50-500nm, the pore size of mesopores is 2-50nm, the pore size of micropores is less than 2nm, and the specific surface area of ​​the filter material is ≥200m² / g; The pH-responsive coating is a composite of polymethacrylic acid and graphene oxide; The filter material surface is loaded with copper nanoparticles, the particle size of the copper nanoparticles is 5-10nm, and the loading amount is 5wt%; Carbon nanotubes are evenly dispersed inside the filter material, accounting for 1%-3% of the total mass of the filter material. They are used to enhance the mechanical strength and electronic conductivity of the filter material and improve the efficiency of the catalytic reaction. The filter material is doped with upconversion nanoparticles to convert infrared light into visible light, thereby improving the filter material's ability to degrade pollutants under visible and infrared light. The doping amount is 0.5wt%-2wt%; The surface of the filter material is grafted with a quaternary ammonium salt compound with antibacterial properties, with a grafting rate of 0.2mmol / g-0.5mmol / g. The filter material has antibacterial function while purifying pollutants and inhibiting the growth of microorganisms on the surface of the filter material. The above filter material specifically includes the following preparation steps: S1. Biological template pretreatment, S1.1, immersing bacterial cellulose in a mixed solution of cerium nitrate, cobalt nitrate and nickel nitrate with a concentration of 0.1-0.5 mol / L, stirring for 24 hours, so that the metal ions are loaded into the pores of the template; S1.

2. Before the pretreatment of the bio-template, the bacterial cellulose is subjected to surface hydrophilization treatment by soaking it in a 3%-5% by mass silane coupling agent aqueous solution for 3-5 hours, then rinsed with deionized water and dried; S2, sol-gel synthesis, S2.1, adding citric acid and ethylene glycol in a molar ratio of 1:1-1:3 to the solution in step S1.1, adjusting the pH to 6-7, and forming a sol; S2.2, at the same time, adding the carbon nanotube suspension treated with ultrasonic dispersion to the sol, the amount of carbon nanotubes added is controlled to account for 1%-3% of the total mass of the filter material, the ultrasonic dispersion frequency of the carbon nanotube suspension is 30-50kHz, and the time is 20-40min; S2.3, then microwave heating at a power of 500 W for 10 min to promote gelation and form a precursor; S2.4, after the sol-gel synthesis is completed, the formed precursor is spray dried, the air inlet temperature is controlled at 180-220°C, and the air outlet temperature is controlled at 80-100°C, so that the precursor forms spherical particles with uniform particle size, and the particles with a particle size in the range of 0.3-0.8 mm are screened out by a vibrating screen; S3, hierarchical channel construction, S3.1, freeze-drying the particles screened in step S2.4, and calcining them at 600°C for 4 hours in a nitrogen atmosphere to remove the biological template and form a hierarchical porous structure; S3.2, then, immersing the hierarchical porous structure in a solution containing upconversion nanoparticles, wherein the concentration of the solution is adjusted according to the final doping amount of the upconversion nanoparticles of 0.5wt%-2wt%, and the immersion temperature is maintained at 40-60°C for 8-12h, so that the upconversion nanoparticles are uniformly doped into the filter material, giving the filter material a photothermal conversion function; S3.3, after the hierarchical pores are constructed, the hierarchical porous structure is subjected to pulse electric field treatment, with an electric field strength of 1-3 kV / cm, a pulse frequency of 10-20 Hz, and a treatment time of 5-10 min; S3.4, vacuum annealing treatment is performed on the hierarchical porous structure, and the vacuum degree is 10 -3 -10 -2 Pa, annealing temperature is 400-500℃, time is 2-3h; S4. Surface modification, S4.1, using a chemical reduction method to load copper nanoparticles on the particle surface, the reducing agent is sodium borohydride, wherein the molar ratio of sodium borohydride to copper ions is 2:1-4:1; S4.2, then a layer-by-layer self-assembly treatment is performed, before coating the composite coating of polymethacrylic acid and graphene oxide, firstly, a positively charged polyelectrolyte and a negatively charged functional nanoparticle are alternately adsorbed on the surface of the filter material, and the adsorption time of each layer is 10-20 minutes, so as to form a multi-layer composite structure; S4.3, after completing the layer-by-layer self-assembly, immerse the filter material in a grafting solution containing a quaternary ammonium salt compound, the concentration of the grafting solution is 0.5-1.5 mol / L, the reaction temperature is 50-70°C, the reaction time is 3-5h, so that the grafting rate on the filter material surface reaches 0.2mmol / g-0.5mmol / g, giving the filter material antibacterial properties; S4.

4. Finally, the polymethacrylic acid and graphene oxide composite coating is coated by electrospinning technology to form a pH responsive coating. The spinning voltage is 10-20 kV, the spinning distance is 10-15 cm, and the flow rate of the spinning solution is 0.5-1.5 mL / h. In the process of electrospinning to coat the polymethacrylic acid and graphene oxide composite coating, 0.5%-2% of nano-titanium dioxide is added to the spinning solution. After the electrospinning is completed, the filter material coated with the pH responsive coating is subjected to ultraviolet curing treatment. The ultraviolet wavelength is 254 nm and the irradiation time is 15-30 min.

2. The method for preparing the composite oxidized particle filter material according to claim 1, characterized in that: After the carbon nanotube suspension is added in step S2.2, the sol is subjected to high-speed centrifugation at a speed of 8000-12000 rpm for 5-10 min.

3. The method for preparing the composite oxidized particle filter material according to claim 1, characterized in that: When soaking the upconversion nanoparticle solution in step S3.2, ultrasound-assisted soaking is used, with an ultrasound frequency of 40-60kHz and an ultrasound power of 100-200W.

4. The method for preparing the composite oxidized particle filter material according to claim 1, characterized in that: During the layer-by-layer self-assembly process in step S4.2, electric field-assisted adsorption is introduced, and a DC electric field with an intensity of 0.5-1.5 kV / cm is applied to the filter material surface to promote faster and more uniform adsorption of polyelectrolytes and functional nanoparticles on the filter material surface, shortening the adsorption time of each layer by 3-5 minutes and improving the stability of the multilayer composite structure by 40%-50%.

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