Preparation method of antibacterial ozone-removing nano titanium oxide

Abstract

The invention discloses a preparation method of antibacterial ozone-removing nano titanium oxide, which comprises the following steps: dissolving tetraisopropyl titanate in absolute methanol, adding into a reaction kettle, adding N-Ag ZIF-8-C composite powder, stirring, injecting a hydrochloric acid solution, continuously stirring to form a sol system, dropwise adding deionized water to induce gelation, drying, and removing a solvent to obtain the antibacterial ozone-removing nano titanium oxide. Calcining in a tubular furnace, and naturally cooling to obtain the antibacterial ozone-removing nano titanium oxide. According to the antibacterial ozone-removing nano titanium oxide, the photon-generated carrier separation efficiency is greatly improved, the visible light response range is widened, meanwhile, the pollutant adsorption capacity is enhanced through the hierarchical pore structure, and compared with the defects that in the prior art, the photocatalytic activity is limited by the inherent wide-band gap characteristic of titanium dioxide, and only ultraviolet light is responded, the photocatalytic activity of the nano titanium oxide is greatly improved. The composite material realizes higher degradation efficiency through a concerted catalysis-adsorption mechanism, and especially has better performance in low-concentration pollutant treatment and complex water quality environments.

Description

Technical Field

[0001] The present invention belongs to the technical field of powder materials, and particularly relates to a preparation method of antibacterial and ozone-removing nano titanium oxide. Background Art

[0002] Nano titanium oxide is titanium dioxide particles existing in the nano scale, and has three crystal structures of rutile type, anatase type and brookite type. Among them, the anatase type is widely used in the field of environmental treatment due to its high photocatalytic activity; this material generates electron-hole pairs through photoexcitation, can efficiently decompose organic pollutants and kill microorganisms, and at the same time has strong ultraviolet shielding ability, and is commonly used in photocatalytic sewage treatment, self-cleaning coatings and sunscreen products.

[0003] Chinese Patent Application CN112044423B discloses that graphite can be formed into tiny lamellae after ball milling and uniformly distributed on the surface of titanium dioxide particles, which can effectively become a carrier for rapid separation of electron holes, broaden the spectral response range of the photocatalyst, and improve the photocatalytic activity. However, in the application of sewage treatment, the photocatalytic activity of the above patent is limited by the inherent wide bandgap characteristic of titanium dioxide, and can only respond to the ultraviolet light band, resulting in low utilization rate of visible light, thus promoting low antibacterial performance. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of antibacterial and ozone-removing nano titanium oxide. By in-situ growing ZIF-8 crystals on the surface of silver nanoparticles to construct a porous framework, using KOH activation and high-temperature carbonization to convert ZIF-8 into a nitrogen-doped porous carbon matrix while maintaining the dispersion state of silver, and then loading nano titanium dioxide by the sol-gel method, it is expected to solve the technical problem that in the prior art, the photocatalytic activity is limited by the inherent wide bandgap characteristic of titanium dioxide, only responds to ultraviolet light, resulting in low utilization rate of visible light, thus promoting low antibacterial performance.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A preparation method of antibacterial and ozone-removing nano titanium oxide, comprising the following steps:

[0007] Step 1. Add Ag@ZIF-8 composite powder, KOH, and urea into a reaction kettle, then add deionized water, and then magnetically stir at 550 - 650 rpm for 25 - 30 h. Then raise the temperature to 80 - 85 °C and continue stirring for 3 - 4 h to complete pre-activation. Subsequently, evaporate and concentrate to 1 / 5 of the original volume under a vacuum degree of -0.095 to -0.100 MPa and a temperature of 70 - 75 °C. Transfer the obtained concentrated solution into a quartz boat of a tubular furnace. Under argon protection, heat it to 800 - 805 °C at a rate of 5 - 5.5 °C / min, keep it at a constant temperature for carbonization for 2 - 3 h, and naturally cool it to room temperature. Finally, wash the obtained powder with hydrochloric acid solution 2 - 3 times, perform suction filtration, wash the filter cake with deionized water until the last washing solution is neutral, dry it under vacuum, and grind it to obtain N-Ag@ZIF-8-C composite powder with a particle size of 3 - 4 μm.

[0008] Step 2. Dissolve tetra-isopropyl titanate in anhydrous methanol and add it into a reaction kettle. Then add N-Ag@ZIF-8-C composite powder and stir at 200 - 500 rpm for 15 - 20 min. Then inject 0.3 mol / L hydrochloric acid solution and continuously stir for 3 - 4 h to form a sol system. Then gradually add deionized water to induce gelation, dry for 12 - 14 h to remove the solvent, and calcine in a tubular furnace at 250 - 255 °C for 3 - 4 h, and naturally cool it to obtain antibacterial and ozone-removing nano-titanium oxide.

[0009] Further, the Ag@ZIF-8 composite powder is prepared through the following steps:

[0010] Step 1. Add a methanol solution of zinc nitrate with a concentration of 12.5 - 13.5 mM and a methanol solution of 2-methylimidazole with a concentration of 25 - 26 mM into a reaction kettle and stir and mix. Subsequently, add silver nanoparticles with a particle size of 20 - 25 nm, ultrasonically disperse for 10 - 15 min, and statically react at 23 - 27 °C for 20 - 24 h to promote the directional growth of ZIF-8 crystals on the surface of silver nanoparticles to form a shell layer of 20 - 40 nm. After the reaction ends, centrifuge the reaction solution at 8000 - 9000 rpm for 10 - 15 min to separate the precipitate. Then ultrasonically resuspend the precipitate with anhydrous methanol and repeat centrifugal washing 2 - 3 times to remove unreacted substances. Vacuum dry the remaining precipitate at 58 - 62 °C for 12 - 14 h and grind it to obtain Ag@ZIF-8 composite powder with a ZIF-8 coating structure.

[0011] Further, the dosage ratio of the zinc nitrate methanol solution, 2-methylimidazole methanol solution, and silver nanoparticles in the step is 45 - 50 mL : 45 - 50 mL : 0.05 - 0.25 g.

[0012] Further, the dosage ratio of the Ag@ZIF-8 composite powder, KOH, urea and deionized water in the step is 5-7 g: 5-7 g: 10-12 g: 250-270 mL.

[0013] Further, the dosage ratio of tetra-isopropyl titanate, anhydrous methanol, N-Ag@ZIF-8-C composite powder, hydrochloric acid solution and deionized water in the step is 8-10 g: 40-60 mL: 2-4 g: 1-2 mL: 2-2.1 mL.

[0014] Advantages of the present invention:

[0015] In the present invention, ZIF-8 crystals are in-situ grown on the surface of silver nanoparticles to form a core-shell structure, and then the silver nanoparticles are fixed through the coordination of the metal-organic framework and a porous skeleton is constructed; subsequently, KOH activation and high-temperature carbonization are used to convert ZIF-8 into a nitrogen-doped porous carbon matrix while retaining the dispersed state of silver; finally, nano-titanium dioxide is loaded by the sol-gel method, the plasma effect of silver is used to enhance light absorption, and the porous structure provides a high specific surface area and a mass transfer channel, thereby obtaining antibacterial and ozone-removing nano-titanium dioxide.

[0016] This antibacterial and ozone-removing nano-titanium dioxide not only improves the separation efficiency of photo-generated carriers, but also broadens the visible light response range. At the same time, the hierarchical pore structure enhances the pollutant adsorption capacity. Compared with the prior art, this composite material achieves a higher degradation efficiency through a synergistic catalytic-adsorption mechanism, and the antibacterial performance is also greatly improved, especially in the treatment of low-concentration pollutants and complex water quality environments. Specific embodiments

[0017] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0018] Example 1: A preparation method of antibacterial and ozone-removing nano-titanium dioxide, comprising the following steps:

[0019] S1. Add 45 mL of a zinc nitrate methanol solution with a concentration of 12.5 mM and 45 mL of a 2-methylimidazole methanol solution with a concentration of 25 mM to a reaction kettle, stir and mix them. Subsequently, add 0.05 g of silver nanoparticles with a particle size of 20 nm, ultrasonically disperse for 10 min, and allow to stand and react at 23 °C for 20 h to promote the directional growth of ZIF-8 crystals on the surface of the silver nanoparticles to form a 20-nm shell layer. After the reaction, centrifuge the reaction solution at 8000 rpm for 10 min to separate the precipitate. Then, ultrasonically resuspend the precipitate with anhydrous methanol and repeat the centrifugation and washing twice to remove the unreacted substances. Vacuum dry the remaining precipitate at 58 °C for 12 h and grind it to obtain Ag@ZIF-8 composite powder with a ZIF-8 coating structure.

[0020] In the ZIF-8 structure, the nitrogen atoms of 2-methylimidazole coordinate with silver ions to achieve chemisorption, promoting the loading of silver ions on the ZIF-8 structure. In the Ag@ZIF-8 composite material, silver cooperates with titanium dioxide to expose more active sites, thereby enhancing the antibacterial performance.

[0021] S2. Add 5 g of Ag@ZIF-8 composite powder, 5 g of KOH, and 10 g of urea to a reaction kettle, then add 250 mL of deionized water, and then magnetically stir at 550 rpm for 25 h. Then, raise the temperature to 80 °C and continue stirring for 3 h to complete pre-activation. Subsequently, evaporate and concentrate the reaction system to 1 / 5 of the original volume under a vacuum degree of -0.095 MPa and a temperature of 70 °C. Transfer the obtained concentrated solution to a quartz boat in a tubular furnace. Under argon protection, heat it to 800 °C at a rate of 5 °C / min, keep it at a constant temperature for carbonization for 2 h, and naturally cool to room temperature. Finally, wash the obtained powder twice with a hydrochloric acid solution, filter it by suction, wash the filter cake with deionized water until the last washing liquid is neutral, vacuum dry it, and grind it to obtain N-Ag@ZIF-8-C composite powder with a particle size of 3 μm.

[0022] The organic ligands of ZIF-8 undergo pyrolytic carbonization in a high-temperature argon atmosphere, releasing nitrogen-containing gases to form a nitrogen-doped carbon skeleton. At the same time, urea decomposes and releases ammonia under alkaline conditions, further providing a nitrogen source, which is integrated into the carbon matrix through C-N bonds to enhance the uniformity of nitrogen doping. The N-Ag@ZIF-8-C composite enables the slow-release effect of silver nanoparticles and the antibacterial activity of nitrogen-doped carbon to form a dual antibacterial mechanism, extending the service life of the material.

[0023] S3. Dissolve 8 g of titanium isopropoxide in 40 mL of anhydrous methanol and add it to the reaction kettle. Then add 2 g of N-Ag@ZIF-8-C composite powder, stir at 200 rpm for 15 min, then inject 1 mL of 0.3 mol / L hydrochloric acid solution and continue stirring for 3 h to form a sol system. Then gradually add 2 mL of deionized water to induce gelation, dry for 12 h to remove the solvent, and calcine in a tube furnace at 250 °C for 3 h, and cool naturally to obtain antibacterial and ozone-removing nano-titanium oxide.

[0024] The hydrolysis product of titanium isopropoxide bonds with the surface active sites of the N-Ag@ZIF-8-C composite powder to achieve uniform coating. The carbonized ZIF-8 framework and the titanium dioxide network jointly construct hierarchical pores, significantly increasing the specific surface area and enhancing the adsorption capacity for reactants or pollutants.

[0025] Example 2: A preparation method of antibacterial and ozone-removing nano-titanium oxide, comprising the following steps:

[0026] S1. Add 47 mL of a 13 mM zinc nitrate methanol solution and 47 mL of a 25.5 mM 2-methylimidazole methanol solution to the reaction kettle and stir to mix. Then add 0.1 g of silver nanoparticles with a particle size of 22 nm, ultrasonically disperse for 12 min, and stand and react at 23 °C for 22 h to promote the oriented growth of ZIF-8 crystals on the surface of the silver nanoparticles to form a 22 nm shell layer. After the reaction is completed, centrifuge the reaction solution at 8500 rpm for 12 min to separate the precipitate. Then resuspend the precipitate with anhydrous methanol by ultrasonic and repeat the centrifugation and washing 2 times to remove the unreacted substances. Vacuum dry the remaining precipitate at 60 °C for 13 h and grind to obtain Ag@ZIF-8 composite powder with a ZIF-8 coating structure.

[0027] S2. Add 6 g of Ag@ZIF-8 composite powder, 6 g of KOH, and 11 g of urea to the reaction kettle, then add 260 mL of deionized water, and then magnetically stir at 600 rpm for 27 h. Then raise the temperature to 82 °C and continue stirring for 3.5 h to complete pre-activation. Subsequently, evaporate and concentrate to 1 / 5 of the original volume under a vacuum degree of -0.097 MPa and a temperature of 72 °C. Transfer the obtained concentrated solution to a quartz boat in a tube furnace, and under argon protection, heat it to 802 °C at a rate of 5.2 °C / min, keep it at a constant temperature for carbonization for 2.5 h, and cool naturally to room temperature. Finally, wash the obtained powder with hydrochloric acid solution 2 times, filter by suction, wash the filter cake with deionized water until the last washing solution is neutral, vacuum dry, grind and crush to obtain N-Ag@ZIF-8-C composite powder with a particle size of 3.5 μm.

[0028] S3. Dissolve 9 g of titanium tetraisopropoxide in 50 mL of anhydrous methanol and add it to the reaction kettle. Then add 3 g of N-Ag@ZIF-8-C composite powder and stir at 350 rpm for 17 min. Then inject 1.5 mL of 0.3 mol / L hydrochloric acid solution and continue stirring for 3.5 h to form a sol system. Then gradually add 2.05 mL of deionized water to induce gelation, dry for 13 h, remove the solvent, calcine in a tube furnace at 252 °C for 3.5 h, and cool naturally to obtain antibacterial and ozone-removing nano-titanium oxide.

[0029] Example 3: A preparation method of antibacterial and ozone-removing nano-titanium oxide, comprising the following steps:

[0030] S1. Add 50 mL of zinc nitrate methanol solution with a concentration of 13.5 mM and 50 mL of 2-methylimidazole methanol solution with a concentration of 26 mM to the reaction kettle, stir and mix. Then add 0.25 g of silver nanoparticles with a particle size of 25 nm, ultrasonically disperse for 15 min, and stand and react at 27 °C for 24 h to promote the directional growth of ZIF-8 crystals on the surface of silver nanoparticles to form a 40-nm shell layer. After the reaction, centrifuge the reaction solution at 9000 rpm for 15 min to separate the precipitate. Then ultrasonically resuspend the precipitate with anhydrous methanol and repeat centrifugation and washing 3 times to remove the unreacted substances. Vacuum dry the remaining precipitate at 62 °C for 14 h and grind to obtain Ag@ZIF-8 composite powder with a ZIF-8 coating structure.

[0031] S2. Add 7 g of Ag@ZIF-8 composite powder, 7 g of KOH, and 12 g of urea to the reaction kettle, then add 270 mL of deionized water, and then magnetically stir at 650 rpm for 30 h. Then raise the temperature to 85 °C and continue stirring for 4 h to complete pre-activation. Then evaporate and concentrate to 1 / 5 of the original volume under a vacuum of -0.100 MPa and a temperature of 75 °C. Transfer the obtained concentrated solution to a quartz boat in a tube furnace, and under argon protection, heat it to 805 °C at a rate of 5.5 °C / min, keep it at a constant temperature for 3 h, and cool naturally to room temperature. Finally, wash the obtained powder with hydrochloric acid solution 3 times, filter by suction, wash the filter cake with deionized water until the last washing solution is neutral, vacuum dry, grind and crush to obtain N-Ag@ZIF-8-C composite powder with a particle size of 4 μm.

[0032] S3. Dissolve 10 g of titanium tetraisopropoxide in 60 mL of anhydrous methanol and add it to the reaction kettle. Then add 4 g of N-Ag@ZIF-8-C composite powder and stir at 500 rpm for 20 min. Then inject 2 mL of 0.3 mol / L hydrochloric acid solution and continue stirring for 4 h to form a sol system. Then gradually add 2.1 mL of deionized water to induce gelation, dry for 14 h, remove the solvent, calcine in a tube furnace at 255 °C for 4 h, and cool naturally to obtain antibacterial and ozone-removing nano-titanium oxide.

[0033] Comparative Example 1: Based on Example 3, silver nanoparticles were omitted in step S1, and the remaining steps remained unchanged to prepare antibacterial and ozone-removing nano-titanium oxide.

[0034] Comparative Example 2: Based on Example 3, zinc nitrate methanol solution and 2-methylimidazole methanol solution were omitted in step S1, and the remaining steps remained unchanged to prepare antibacterial and ozone-removing nano-titanium oxide.

[0035] Comparative Example 3: Based on Example 3, KOH and urea were omitted in step S2, and the remaining steps remained unchanged to prepare antibacterial and ozone-removing nano-titanium oxide.

[0036] Performance tests were carried out on Examples 1 - 3 and Comparative Examples 1 - 3:

[0037] 1. Take the electroplating wastewater from a certain factory. The pH of this electroplating wastewater is 3.3, and its main chemical composition is: CN: 23 mg / L, Cu: 30 mg / L, Zn: 51 mg / L. After adjusting the pH to 7, the urban sewage treatment agents prepared in Examples 1 - 3 and Comparative Examples 1 - 3 were added respectively, with the addition amount of 18 g / L. After standing and adsorbing for 24 h, it was filtered to obtain the test solution. The test solution was used to measure the concentrations of CN, Cu, and Zn in the solution with an atomic absorption spectrophotometer, and the ion adsorption rates for CN ions and heavy metal ions were calculated. The calculation formula is as follows:

[0038] Ion adsorption rate (%) = (Initial ion concentration of this ion - Concentration of this ion after treatment) / Initial ion concentration of this ion × 100%.

[0039] 2. The antibacterial test can be carried out according to the standard test method for determining the antibacterial activity of a fixed antibacterial agent under dynamic contact conditions in ASTM E2149 - 2013a.

[0040] The results are shown in Table 1:

[0041] Table 1

[0042]

[0043] As can be seen from Table 1, the urban sewage treatment agents prepared in Examples 1 - 3 of the present invention have significantly better adsorption rates for heavy metal ions and CN ions in sewage and antibacterial rates against Escherichia coli than the comparative examples.

[0044] In Comparative Example 1, since silver nanoparticles were omitted, the overall antibacterial performance of the material may be reduced. Silver nanoparticles themselves also have high antibacterial effects and can enhance the antibacterial effect by destroying the bacterial cell membrane or interfering with its metabolic pathway. Therefore, its performance is slightly worse than that of Examples 1 - 3.

[0045] In Comparative Example 2, since the zinc nitrate methanol solution and the 2-methylimidazole methanol solution were omitted, the specific surface area and porosity of the material decreased, which might affect the photocatalytic efficiency of nano-titanium dioxide and the antibacterial activity of silver nanoparticles. Therefore, the adsorption rate of ions in sewage was worse than that of Examples 1 to 3.

[0046] In Comparative Example 3, since KOH and urea were omitted, lacking the nitrogen-doped carbon structure and optimized metal active sites, the antibacterial performance of the material would decrease significantly, and it could not effectively inhibit or kill bacteria, resulting in a lower role played in sewage treatment than Examples 1 to 3.

[0047] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0048] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing antibacterial and deozonating nano titanium oxide, characterized in that: The method comprises the following steps: dissolving tetraisopropyl titanate in anhydrous methanol and adding the mixture into a reaction kettle, adding N-Ag@ZIF-8-C composite powder, stirring at 200-500 rpm for 15-20 minutes, injecting 0.3 mol / L hydrochloric acid solution and continuously stirring for 3-4 hours to form a sol system, adding deionized water dropwise to induce gelation, drying for 12-14 hours, removing the solvent, calcining in a tubular furnace at 250-255° C. for 3-4 hours, and cooling naturally to obtain antibacterial and deozonizing nano titanium oxide.

2. The method for preparing an antibacterial and deozonating nano titanium oxide according to claim 1, characterized in that: The dosage ratio of tetraisopropyl titanate, anhydrous methanol, N-Ag@ZIF-8-C composite powder, hydrochloric acid solution and deionized water is 8-10 g: 40-60 mL: 2-4 g: 1-2 mL: 2-2.1 mL.

3. The method for preparing an antibacterial and deozonating nano titanium oxide according to claim 2, characterized in that: The N-Ag@ZIF-8-C composite powder is prepared by the following steps: Ag@ZIF-8 composite powder, KOH and urea are added to the reactor, and then deionized water is added, and then magnetic stirring is carried out at 550-650rpm for 25-30h, and then the temperature is raised to 80-85℃ and stirring is continued for 3-4h to complete pre-activation, and then evaporated and concentrated to 1 / 5 of the original volume at a vacuum degree of -0.095 to -0.100MPa and a temperature of 70-75℃. The concentrated solution is transferred to a tubular furnace quartz boat, and under argon protection, the temperature is raised to 800-805℃ at a rate of 5-5.5℃ / min, and carbonized at a constant temperature for 2-3h, and naturally cooled to room temperature. Finally, the obtained powder is washed with hydrochloric acid solution for 2-3 times, filtered, and the filter cake is washed with deionized water until the last washing liquid is neutral, vacuum dried, and ground to obtain N-Ag@ZIF-8-C composite powder with a particle size of 3-4μm.

4. The method for preparing an antibacterial and deozonating nano titanium oxide according to claim 3, characterized in that: The usage ratio of the Ag@ZIF-8 composite powder, KOH, urea and deionized water is 5-7 g: 5-7 g: 10-12 g: 250-270 mL.

5. The method for preparing an antibacterial and deozonating nano titanium oxide according to claim 4, characterized in that: The Ag@ZIF-8 composite powder is prepared by the following steps: A zinc nitrate methanol solution and a 2-methylimidazole methanol solution are added to a reaction kettle and stirred and mixed, and then silver nanoparticles with a particle size of 20-25 nm are added, ultrasonically dispersed for 10-15 minutes, and allowed to stand for reaction at 23-27° C. for 20-24 hours to promote the directional growth of ZIF-8 crystals on the surface of the silver nanoparticles to form a 20-40 nm shell layer. After the reaction is completed, the reaction solution is centrifuged at 8000-9000 rpm for 10-15 minutes to separate the precipitate, and then the precipitate is ultrasonically resuspended with anhydrous methanol and repeatedly centrifuged and washed 2-3 times to remove unreacted products. The remaining precipitate is vacuum dried at 58-62° C. for 12-14 hours and ground to obtain an Ag@ZIF-8 composite powder with a ZIF-8 coating structure.

6. The method for preparing an antibacterial and deozonating nano titanium oxide according to claim 5, characterized in that: The dosage ratio of the zinc nitrate methanol solution, the 2-methylimidazole methanol solution and the silver nanoparticles is 45-50 mL: 45-50 mL: 0.05-0.25 g.

7. The method for preparing an antibacterial and deozonating nano titanium oxide according to claim 6, characterized in that: The concentration of the zinc nitrate methanol solution is 12.5-13.5 mM, and the concentration of the 2-methylimidazole methanol solution is 25-26 mM.

Images