Hydrophobic modified molecular sieve / manganese sand functional material as well as preparation method and application thereof

Abstract

The invention belongs to the field of environmental governance materials, and particularly discloses a hydrophobic modified molecular sieve / manganese sand functional material and a preparation method and application thereof.The functional material is of a core-shell structure and comprises natural manganese sand located in an inner core and a molecular sieve shell growing on the surface of the natural manganese sand in situ; the hydrophobicity from the core natural manganese sand to the shell molecular sieve is gradually enhanced, so that directional discharge of water molecules is realized, and meanwhile, a transmission channel of ozone is maintained. The hydrophobic molecular sieve-natural manganese sand material prepared by the invention can relieve corrosion of a humid environment by improving hydrophobicity and stability of a hydrothermal environment of the molecular sieve, can show excellent catalytic activity in a high-humidity environment, and can be widely applied to systems in the fields of air purification, water treatment and the like.

Description

Technical Field

[0001] The present invention belongs to the field of materials for air and water pollution environmental governance, and particularly relates to a hydrophobic modified molecular sieve / manganese sand functional material, a preparation method thereof, and an application thereof. Background Art

[0002] Ultra-low concentration ozone (such as 0.02 - 0.05 ppm) may stimulate the respiratory tract, may cause minor headaches, dizziness, inattention and other discomforts, and long-term exposure may affect sleep quality and make people feel fatigued. The treatment methods for ultra-low concentration ozone (<0.1 ppm) mainly include physical, chemical, and catalytic degradation technologies. The activated carbon adsorption method has a large specific surface area and a rich pore structure, can capture ozone through physical adsorption, and catalytically decompose ozone through its surface functional groups. The adsorption capacity of activated carbon is limited, and it needs to be replaced or regenerated regularly, and the treatment efficiency is greatly affected by air humidity and temperature. The catalytic decomposition method uses catalysts (such as MnO2, CuO, TiO2, Co3O4, etc.) to accelerate the decomposition of ozone into oxygen. The catalyst can be coated on carriers (such as honeycomb ceramics, activated carbon, alumina, etc.) to improve the treatment efficiency, but the catalyst is sensitive to humidity and pollutants, which may affect the degradation efficiency. Therefore, it is crucial to prepare a material that can recognize, adsorb, catalyze, and has hydrophobicity for ultra-low concentration ozone.

[0003] Natural mineral catalysts have large reserves and low prices, and have unparalleled advantages in terms of use cost compared with other catalysts. Natural manganese sand is widely distributed in nature, has rich reserves, and is easy to obtain. Compared with some synthetic catalysts or noble metal catalysts, it has lower costs, has better economy, and is suitable for large-scale applications. Natural manganese sand contains metal elements such as manganese, and the metal active sites on its surface can adsorb ozone molecules and catalyze the decomposition of ozone into oxygen to a certain extent, and has a removal effect on ozone. However, the catalytic decomposition effect of natural manganese sand on low-concentration ozone is limited, especially in outdoor atmospheric environments and high-humidity conditions, the catalytic effect is lower. Summary of the Invention

[0004] Object of the Invention: The technical problem to be solved by the present invention is to provide a hydrophobic modified molecular sieve / manganese sand functional material in view of the deficiencies of the prior art, to improve the problem of efficient catalytic decomposition of low-concentration ozone by natural manganese sand, especially to show good catalytic effects in outdoor atmospheric environments and high-humidity conditions, and to show good water tolerance and long-term catalytic stability during the catalytic process, and to be able to maintain a high catalytic efficiency after long-term use.

[0005] In order to achieve the above object of the invention, the technical solutions adopted by the present invention are as follows:

[0006] A hydrophobic modified molecular sieve / manganese sand functional material has a core-shell structure, including natural manganese sand located in the inner core and a molecular sieve shell in-situ grown on the surface of the natural manganese sand; the hydrophobicity gradually increases from the inner core natural manganese sand to the outer shell molecular sieve to achieve the directional discharge of water molecules while maintaining the ozone transmission channel.

[0007] Among them, molecular sieves have become popular materials for adsorbing and catalyzing ozone due to their high adsorption and catalytic performance, good stability and renewable properties. Molecular sieves have uniform pore sizes and large specific surface areas, and can selectively adsorb ozone molecules according to the size and shape of the molecules. That is, by adjusting the pore size of the molecular sieve, it can selectively adsorb molecules of a specific size, such as ozone, thereby improving the catalytic efficiency. Its pore size is usually between 3 and 15 angstroms, which is comparable to the size of ozone molecules, so ozone molecules can smoothly enter the pore channels of the molecular sieve and be adsorbed. In addition, molecular sieves have a high affinity for polar molecules, and ozone molecules have a certain polarity, which also promotes their adsorption on the molecular sieve.

[0008] Natural manganese sand is widely distributed in nature, with rich reserves and easy access. Compared with some synthetic catalysts or noble metal catalysts, it has a lower cost, better economy, and is suitable for large-scale applications. Natural manganese sand contains metal elements such as manganese, and the metal active sites on its surface can adsorb ozone molecules and catalyze the decomposition of ozone into oxygen to a certain extent, having a removal effect on ozone.

[0009] In this invention, a molecular sieve-natural manganese sand hydrophobic material is prepared by assembling a molecular sieve and natural manganese sand. MnOx in natural manganese sand serves as the active center, and the adsorbed ozone is catalytically decomposed by using its redox cycle. The molecular sieve layer provides a large number of pore channels to enrich ozone molecules; at the same time, the surface of the molecular sieve has certain acid-base and polar functional groups, which can have weak non-covalent interactions (such as van der Waals, dipole-dipole interactions) with ozone, helping to capture ozone. After hydrophobic modification, the water on the catalyst surface is reduced, further ensuring that ozone molecules are more likely to contact the active sites in a dry state, improving the overall adsorption and catalytic efficiency. Finally, this invention intends to optimize the residence time of ultra-low concentration ozone on the material surface by regulating the pore size, surface functional groups and hydrophobic / hydrophilic properties of the molecular sieve-natural manganese sand catalyst, further improving the degradation efficiency and long-term stability of ultra-low concentration ozone.

[0010] Furthermore, this invention also provides a preparation method of the above-mentioned hydrophobic modified molecular sieve / manganese sand functional material, including the following steps:

[0011] S1: Pretreatment of natural manganese sand

[0012] Take natural manganese sand and wash it alternately with deionized water and absolute ethanol to remove surface dust and organic impurities; then immerse the manganese sand in an acid solution and stir at room temperature to remove unstable impurities and some carbonates on the surface, and then wash it repeatedly with deionized water until neutral; finally, dry the washed manganese sand;

[0013] S2: In-situ growth of molecular sieve shell

[0014] Mix deionized water, a silicon source, aluminum nitrate, and a structure-directing agent evenly and adjust the pH value to obtain a precursor solution. Disperse the manganese sand obtained in step S1 in the above precursor solution and allow the precursor solution to fully penetrate the surface of the manganese sand particles; then, after hydrothermal reaction, wash the solid product repeatedly with deionized water to remove the residual precursor solution and unreacted substances on the surface; finally, calcine it in an inert atmosphere to remove the structure-directing agent and form the pore structure of the outer shell molecular sieve;

[0015] S3: Hydrophobic surface modification

[0016] Prepare a hydrophobizing agent solution, then immerse the product obtained in step S2 in the hydrophobizing agent solution and stir at room temperature to allow the hydrophobic functional groups to fully react with the surface of the molecular sieve to form a stable organic hydrophobic layer, and obtain the product after vacuum drying.

[0017] Through the method of in-situ growth, the present invention in-situ grows a molecular sieve on the surface of natural manganese sand, and a core-shell structure can be formed, that is, the molecular sieve wraps the natural manganese sand core as the outer shell. This structure combines the shape selectivity and high specific surface area of the molecular sieve with the catalytic activity or redox characteristics of natural manganese sand, and shows unique advantages in the fields of catalysis, adsorption, energy storage, etc.

[0018] The present invention modifies the material to be hydrophobic. The composite material with a gradually changing hydrophobicity from the inner core to the outer shell can achieve the directional discharge of water molecules while maintaining the efficient transmission of ozone. At the same time, the material of the present invention has a wider application range. Different gradients of hydrophobicity can be designed for the outer shell and the core body, which can be used not only for the removal of ozone in the air in a high-humidity environment, but also for the removal of ozone in water.

[0019] Specifically, in step S1, ultrasonic-assisted cleaning is used when the natural manganese sand is cleaned with deionized water and absolute ethanol, and the ultrasonic cleaning time is 1 - 12 h; the acid solution is a dilute hydrochloric acid aqueous solution with a concentration of 0.1 - 5 mM, and it is stirred at room temperature for 1 - 24 h.

[0020] Specifically, in step S2, the silicon source is tetraethyl orthosilicate or sodium silicate; the structure-directing agent is selected from any one of tetrapropylammonium hydroxide, cetyltrimethylammonium bromide, and sodium diacetate.

[0021] Specifically, in step S2, the mass ratio of the treated manganese sand, silicon source, aluminum nitrate, and structure-directing agent is 10:(1 - 5):(1 - 5):(0.1 - 2), and the pH value of the precursor solution is adjusted to 9 - 11.

[0022] Specifically, in step S2, the temperature of the hydrothermal reaction is 100 - 400 °C, and the time is 12 - 72 h.

[0023] Specifically, in step S2, calcination is carried out in a tubular furnace under a nitrogen atmosphere, the calcination temperature is 300 - 800 °C, and the time is 12 - 24 h.

[0024] Specifically, in step S3, a silane coupling agent is added to anhydrous toluene or ethanol, stirred to form a homogeneous solution, and formulated into a hydrophobic agent solution; the silane coupling agent is octamethylsilane or trifluoromethylsilane; the mass ratio of the silane coupling agent to the product of step S2 is (0.1 - 2):1.

[0025] Specifically, in step S3, the temperature of the vacuum drying is 80 - 200 °C, and the time is 2 - 24 h.

[0026] Furthermore, the present invention also claims the application of the above-mentioned hydrophobic modified molecular sieve / manganese sand functional material in the catalytic decomposition of low-concentration ozone, and the concentration of the low-concentration ozone is not higher than 0.05 ppm.

[0027] Beneficial effects:

[0028] (1) The present invention improves the problem of efficient catalytic decomposition of low-concentration ozone by natural manganese sand, especially shows good catalytic effects in outdoor atmospheric environments and high-humidity conditions, and shows good water tolerance and long-term catalytic stability during the catalytic process, and can maintain a high catalytic efficiency after long-term use. And it can regulate the oxidation state of manganese sand through redox reactions, form abundant oxygen vacancies and active sites, and improve the adsorption and decomposition efficiency of ozone. In addition, the molecular sieve-natural manganese sand catalyst has good stability and catalytic activity under various environmental conditions (such as different humidities, high-speed airflows, etc.), and can cope with the complex changes in the atmospheric environment. Finally, the molecular sieve-natural manganese sand catalyst prepared by the present invention can achieve efficient catalytic decomposition in an extremely low-concentration ozone environment, solving the problem of the failure of traditional catalysts under low-concentration ozone.

[0029] (2) The hydrophobic molecular sieve-natural manganese sand material prepared by the present invention can alleviate the corrosion in a humid environment by improving the hydrophobicity and the stability of the hydrothermal environment of the molecular sieve, and can exhibit excellent catalytic activity in a high-humidity environment, and can be widely applied to the systems in the fields of air purification and water treatment. In this composite catalyst, MnOx in natural manganese sand serves as the active center, and uses its redox cycle to catalytically decompose the adsorbed ozone. The molecular sieve layer provides a large number of pores to enrich ozone molecules. At the same time, the surface of the molecular sieve has certain acid-base and polar functional groups, which can have a weak non-covalent interaction with ozone, contributing to the capture of low-concentration ozone, and can be applicable to the catalytic decomposition of low-concentration ozone (ppm level or ppb level) to meet the daily air and water treatment requirements. Description of the Drawings

[0030] The following further specifically describes the present invention in conjunction with the drawings and specific embodiments, and the above and / or other advantages of the present invention will become clearer.

[0031] Figure 1 Water contact angle test for ten groups of embodiments of the present invention.

[0032] Figure 2 Ozone removal efficiency of ten groups of embodiments with an ozone concentration of 0.01 ppm, a relative humidity of 65%, and a reaction time of 48 h.

[0033] Figure 3 Ozone removal efficiency of ten groups of embodiments with an ozone concentration of 0.03 ppm, a relative humidity of 80%, and a reaction time of 96 h.

[0034] Figure 4 Ozone removal efficiency of ten groups of embodiments with an ozone concentration of 0.05 ppm, a relative humidity of 85%, and a reaction time of 120 h.

[0035] Figure 5 Verification effect of the functional materials of Example 10 and the comparative example in removing ozone in water.

[0036] Figure 6 Scanning electron microscope image of the hydrophobic modified molecular sieve / manganese sand functional material prepared in Example 10. Detailed Description of the Invention

[0037] According to the following embodiments, the present invention can be better understood.

[0038] Example 1

[0039] In this example, the specific preparation method of the molecular sieve-natural manganese sand hydrophobic material is as follows:

[0040] (1) Ultrasonically clean 5 g of natural manganese sand with deionized water for 1 h, and then clean it with anhydrous ethanol to remove surface dust and organic impurities. Then immerse the treated manganese sand in 50 ml of 1 mM dilute hydrochloric acid solution and stir at room temperature for 6 h. Subsequently, wash it repeatedly with deionized water until the solution is neutral. Place the washed manganese sand in an oven and dry it at 100 °C to constant weight to obtain the treated manganese sand;

[0041] (2) Add 2.5 g of tetraethyl orthosilicate, 2.3 g of aluminum nitrate, and 0.3 g of tetrapropylammonium hydroxide to 50 ml of deionized water, and adjust the pH to 10 with NaOH solution to make the solution homogeneous. Then disperse the treated manganese sand obtained in step (1) in the above precursor solution and ultrasonically vibrate for 5 h. Transfer the mixed system to a high-pressure reaction kettle, with a hydrothermal reaction temperature of 100 °C and a time of 12 h. After the reaction is completed, cool it to room temperature, take out the solid product, and wash it repeatedly with deionized water. Finally, calcine it in a tube furnace under a nitrogen atmosphere at a temperature of 300 °C for 12 h to obtain the molecular sieve-natural manganese sand composite;

[0042] (3) Add 5 g of octamethylsilane to 100 ml of anhydrous ethanol and stir to form a homogeneous solution. Then immerse the molecular sieve-natural manganese sand composite obtained in step (2) in the above solution and stir at room temperature for 24 h. After the reaction is completed, wash it with anhydrous ethanol and then vacuum dry it at 80 - 200 °C for 2 - 24 h. Finally, form the molecular sieve-natural manganese sand hydrophobic material.

[0043] Use the prepared molecular sieve-natural manganese sand hydrophobic material in the ozone pollutant system in a humid environment to improve the removal ability of low-concentration ozone.

[0044] Example 2

[0045] (1) Ultrasonically clean 10 g of natural manganese sand with deionized water for 1 h, and then clean it with anhydrous ethanol to remove surface dust and organic impurities. Then immerse the treated manganese sand in 50 ml of 1 mM dilute hydrochloric acid solution and stir at room temperature for 6 h. Subsequently, wash it repeatedly with deionized water until the solution is neutral. Place the washed manganese sand in an oven and dry it at 100 °C to constant weight to obtain the treated manganese sand;

[0046] (2) Add 5.6 g of sodium silicate, 5.8 g of aluminum nitrate, and 0.9 g of sodium diacetate to 50 ml of deionized water, and adjust the pH to 9 with NaOH solution to make the solution homogeneous. Then disperse the treated manganese sand obtained in step (1) in the above precursor solution and ultrasonically oscillate for 5 h. Transfer the mixed system to a high-pressure reaction kettle, with a hydrothermal reaction temperature of 180 °C and a time of 24 h. After the reaction is completed, cool to room temperature, take out the solid product, and wash it repeatedly with deionized water. Finally, calcine in a tubular furnace under a nitrogen atmosphere at a temperature of 300 - 800 °C for 12 - 24 h to obtain a molecular sieve-natural manganese sand composite;

[0047] (3) Add 5 g of trifluoromethylsilane to 100 ml of absolute ethanol and stir to form a homogeneous solution. Then immerse the molecular sieve-natural manganese sand composite obtained in step (2) in the above solution, stir at room temperature for 24 h, wash with absolute ethanol after the reaction is completed, and then vacuum dry at 100 °C for 6 h. Finally, a molecular sieve-natural manganese sand hydrophobic material is formed.

[0048] Use the prepared molecular sieve-natural manganese sand hydrophobic material in the ozone pollutant system in a humid environment to improve the removal ability of low-concentration ozone.

[0049] Example 3

[0050] (1) Ultrasonically clean 5 g of natural manganese sand with deionized water for 1 h, and then wash it with absolute ethanol to remove surface dust and organic impurities. Then immerse the treated manganese sand in 50 ml of 1 mM dilute hydrochloric acid solution and stir at room temperature for 6 h. Subsequently, wash it repeatedly with deionized water until the solution is neutral, and place the washed manganese sand in an oven at 100 °C to dry to constant weight to obtain the treated manganese sand;

[0051] (2) Add 3 g of tetraethyl orthosilicate, 2 g of aluminum nitrate, and 0.5 g of tetrapropylammonium hydroxide to 50 ml of deionized water, and adjust the pH to 10 with NaOH solution to make the solution homogeneous. Then disperse the treated manganese sand obtained in step (1) in the above precursor solution and ultrasonically oscillate for 5 h. Transfer the mixed system to a high-pressure reaction kettle, with a hydrothermal reaction temperature of 200 °C and a time of 36 h. After the reaction is completed, cool to room temperature, take out the solid product, and wash it repeatedly with deionized water. Finally, calcine in a tubular furnace under a nitrogen atmosphere at a temperature of 400 °C for 16 h to obtain a molecular sieve-natural manganese sand composite;

[0052] (3) Add 10 g of octamethylsilane to 100 ml of absolute ethanol and stir to form a homogeneous solution. Then immerse the molecular sieve-natural manganese sand composite obtained in step (2) into the above solution, stir at room temperature for 24 h, wash with absolute ethanol after the reaction, and then dry in vacuum at 100 °C for 6 h. Finally, a molecular sieve-natural manganese sand hydrophobic material is formed.

[0053] Use the prepared molecular sieve-natural manganese sand hydrophobic material in the ozone pollutant system in a humid environment to improve the removal ability of low-concentration ozone.

[0054] Example 4

[0055] (1) Ultrasonically clean 15 g of natural manganese sand with deionized water for 1 h, and then wash with absolute ethanol to remove surface dust and organic impurities. Then immerse the treated manganese sand into 50 ml of 3 mM dilute hydrochloric acid solution and stir at room temperature for 6 h. Subsequently, wash repeatedly with deionized water until the solution is neutral, and place the washed manganese sand in an oven to dry to constant weight at 100 °C to obtain the treated manganese sand;

[0056] (2) Add 10 g of tetraethyl orthosilicate, 5 g of aluminum nitrate, and 2 g of cetyltrimethylammonium bromide to 50 ml of deionized water, and adjust the pH to 11 with NaOH solution to make the solution homogeneous. Then disperse the treated manganese sand obtained in step (1) into the above precursor solution and ultrasonically oscillate for 5 h. Transfer the mixed system to a high-pressure reaction kettle, and the hydrothermal reaction temperature is 280 °C for 48 h. After the reaction, cool to room temperature, take out the solid product, and wash repeatedly with deionized water. Finally, calcine in a tube furnace under a nitrogen atmosphere at 550 °C for 18 h to obtain a molecular sieve-natural manganese sand composite;

[0057] (3) Add 15 g of octamethylsilane to 100 ml of absolute ethanol and stir to form a homogeneous solution. Then immerse the molecular sieve-natural manganese sand composite obtained in step (2) into the above solution, stir at room temperature for 24 h, wash with absolute ethanol after the reaction, and then dry in vacuum at 90 °C for 13 h. Finally, a molecular sieve-natural manganese sand hydrophobic material is formed.

[0058] Use the prepared molecular sieve-natural manganese sand hydrophobic material in the ozone pollutant system in a humid environment to improve the removal ability of low-concentration ozone.

[0059] Example 5

[0060] (1) Ultrasonically clean 5 g of natural manganese sand with deionized water for 1 h, and then wash it with anhydrous ethanol to remove surface dust and organic impurities. Then immerse the treated manganese sand in 50 ml of 0.5 mM dilute hydrochloric acid solution and stir at room temperature for 6 h. Subsequently, wash it repeatedly with deionized water until the solution is neutral. Place the washed manganese sand in an oven and dry it at 100 °C to constant weight to obtain the treated manganese sand;

[0061] (2) Add 2.5 g of sodium silicate, 2.3 g of aluminum nitrate, and 0.3 g of cetyltrimethylammonium bromide to 50 ml of deionized water, and adjust the pH to 10 with NaOH solution to make the solution homogeneous. Then disperse the treated manganese sand obtained in step (1) in the above precursor solution and ultrasonically vibrate for 5 h. Transfer the mixed system to a high-pressure reaction kettle, with a hydrothermal reaction temperature of 180 °C and a time of 12 h. After the reaction, cool to room temperature, take out the solid product, and wash it repeatedly with deionized water. Finally, calcine it in a tube furnace under a nitrogen atmosphere at a temperature of 300 °C for 12 h to obtain the molecular sieve-natural manganese sand composite;

[0062] (3) Add 5 g of trifluoromethylsilane to 100 ml of anhydrous ethanol and stir to form a homogeneous solution. Then immerse the molecular sieve-natural manganese sand composite obtained in step (2) in the above solution and stir at room temperature for 24 h. After the reaction, wash it with anhydrous ethanol and then vacuum dry it at 80 °C for 2 h. Finally, form the molecular sieve-natural manganese sand hydrophobic material.

[0063] Use the prepared molecular sieve-natural manganese sand hydrophobic material in the ozone pollutant system in a humid environment to improve the removal ability of low-concentration ozone.

[0064] Example 6

[0065] (1) Ultrasonically clean 18 g of natural manganese sand with deionized water for 1 h, and then wash it with anhydrous ethanol to remove surface dust and organic impurities. Then immerse the treated manganese sand in 50 ml of 1 mM dilute hydrochloric acid solution and stir at room temperature for 6 h. Subsequently, wash it repeatedly with deionized water until the solution is neutral. Place the washed manganese sand in an oven and dry it at 100 °C to constant weight to obtain the treated manganese sand;

[0066] (2) Add 5.6 g of sodium silicate, 5.8 g of aluminum nitrate, and 0.9 g of sodium diacetate to 50 ml of deionized water, and adjust the pH to 9 with NaOH solution to make the solution homogeneous. Then disperse the treated manganese sand obtained in step (1) in the above precursor solution and ultrasonically vibrate for 5 h. Transfer the mixed system to a high-pressure reaction kettle, with a hydrothermal reaction temperature of 180 °C and a time of 24 h. After the reaction is completed, cool to room temperature, take out the solid product, and wash it repeatedly with deionized water. Finally, calcine in a tube furnace under a nitrogen atmosphere at a temperature of 300 - 800 °C for 12 - 24 h to obtain the molecular sieve-natural manganese sand composite;

[0067] (3) Add 5 g of trifluoromethylsilane to 100 ml of absolute ethanol and stir to form a homogeneous solution. Then immerse the molecular sieve-natural manganese sand composite obtained in step (2) in the above solution, stir at room temperature for 24 h, wash with absolute ethanol after the reaction is completed, and then vacuum dry at 100 °C for 6 h. Finally, a molecular sieve-natural manganese sand hydrophobic material is formed.

[0068] The prepared molecular sieve-natural manganese sand hydrophobic material is used in the ozone pollutant system in a humid environment to improve the removal ability of low-concentration ozone.

[0069] Example 7

[0070] (1) Ultrasonically clean 6 g of natural manganese sand with deionized water for 1 h, and then wash it with absolute ethanol to remove surface dust and organic impurities. Then immerse the treated manganese sand in 50 ml of 3 mM dilute hydrochloric acid solution and stir at room temperature for 6 h. Subsequently, wash it repeatedly with deionized water until the solution is neutral, and place the washed manganese sand in an oven at 100 °C and dry to constant weight to obtain the treated manganese sand;

[0071] (2) Add 2.5 g of tetraethyl orthosilicate, 2.3 g of aluminum nitrate, and 0.8 g of cetyltrimethylammonium bromide to 50 ml of deionized water, and adjust the pH to 9 with NaOH solution to make the solution homogeneous. Then disperse the treated manganese sand obtained in step (1) in the above precursor solution and ultrasonically vibrate for 5 h. Transfer the mixed system to a high-pressure reaction kettle, with a hydrothermal reaction temperature of 250 °C and a time of 36 h. After the reaction is completed, cool to room temperature, take out the solid product, and wash it repeatedly with deionized water. Finally, calcine in a tube furnace under a nitrogen atmosphere at a temperature of 500 °C for 16 h to obtain the molecular sieve-natural manganese sand composite;

[0072] (3) Add 6 g of trifluoromethylsilane to 100 ml of absolute ethanol and stir to form a homogeneous solution. Then immerse the molecular sieve-natural manganese sand composite obtained in step (2) into the above solution, stir at room temperature for 24 h, wash with absolute ethanol after the reaction, and then vacuum dry at 120 °C for 15 h. Finally, a molecular sieve-natural manganese sand hydrophobic material is formed.

[0073] Use the prepared molecular sieve-natural manganese sand hydrophobic material in the ozone pollutant system in a humid environment to improve the removal ability of low-concentration ozone.

[0074] Example 8

[0075] (1) Ultrasonically clean 8 g of natural manganese sand with deionized water for 1 h, and then wash it with absolute ethanol to remove surface dust and organic impurities. Then immerse the treated manganese sand into 50 ml of 2 mM dilute hydrochloric acid solution and stir at room temperature for 6 h. Subsequently, wash it repeatedly with deionized water until the solution is neutral, and place the washed manganese sand in an oven at 100 °C to dry to constant weight to obtain the treated manganese sand;

[0076] (2) Add 4 g of sodium silicate, 3 g of aluminum nitrate, and 1 g of sodium diacetate to 50 ml of deionized water, and adjust the pH to 9 with NaOH solution to make the solution homogeneous. Then disperse the treated manganese sand obtained in step (1) into the above precursor solution and ultrasonically vibrate for 5 h. Transfer the mixed system to a high-pressure reaction kettle, and the hydrothermal reaction temperature is 180 °C and the time is 12 h. After the reaction, cool to room temperature, take out the solid product, and wash it repeatedly with deionized water. Finally, calcine it in a tube furnace under a nitrogen atmosphere at a temperature of 400 °C for 15 h to obtain a molecular sieve-natural manganese sand composite;

[0077] (3) Add 15 g of trifluoromethylsilane to 100 ml of absolute ethanol and stir to form a homogeneous solution. Then immerse the molecular sieve-natural manganese sand composite obtained in step (2) into the above solution, stir at room temperature for 24 h, wash with absolute ethanol after the reaction, and then vacuum dry at 120 °C for 8 h. Finally, a molecular sieve-natural manganese sand hydrophobic material is formed.

[0078] Use the prepared molecular sieve-natural manganese sand hydrophobic material in the ozone pollutant system in a humid environment to improve the removal ability of low-concentration ozone.

[0079] Example 9

[0080] (1) Ultrasonically clean 8 g of natural manganese sand with deionized water for 2 h, and then wash it with absolute ethanol to remove surface dust and organic impurities. Then immerse the treated manganese sand in 50 ml of 2 mM dilute hydrochloric acid solution and stir at room temperature for 8 h. Subsequently, wash it repeatedly with deionized water until the solution is neutral. Place the washed manganese sand in an oven and dry it at 100 °C to constant weight to obtain the treated manganese sand;

[0081] (2) Add 2.4 g of sodium silicate, 2.4 g of aluminum nitrate, and 0.4 g of sodium diacetate to 50 ml of deionized water, and adjust the pH to 10 with NaOH solution to make the solution homogeneous. Then disperse the treated manganese sand obtained in step (1) in the above precursor solution and ultrasonically vibrate for 5 h. Transfer the mixed system to a high-pressure reaction kettle, with a hydrothermal reaction temperature of 220 °C and a time of 30 h. After the reaction is completed, cool it to room temperature, take out the solid product, and wash it repeatedly with deionized water. Finally, calcine it in a tube furnace under a nitrogen atmosphere at a temperature of 450 °C for 18 h to obtain the molecular sieve-natural manganese sand composite;

[0082] (3) Add 6 g of trifluoromethylsilane to 100 ml of absolute ethanol and stir to form a homogeneous solution. Then immerse the molecular sieve-natural manganese sand composite obtained in step (2) in the above solution and stir at room temperature for 24 h. After the reaction is completed, wash it with absolute ethanol and then vacuum dry it at 110 °C for 10 h. Finally, form the molecular sieve-natural manganese sand hydrophobic material.

[0083] Example 10

[0084] (1) Ultrasonically clean 5 g of natural manganese sand with deionized water for 1 h, and then wash it with absolute ethanol to remove surface dust and organic impurities. Then immerse the treated manganese sand in 50 ml of 1 mM dilute hydrochloric acid solution and stir at room temperature for 6 h. Subsequently, wash it repeatedly with deionized water until the solution is neutral. Place the washed manganese sand in an oven and dry it at 100 °C to constant weight to obtain the treated manganese sand;

[0085] (2) Add 2 g of sodium silicate, 2 g of aluminum nitrate, and 1 g of tetrapropylammonium hydroxide to 50 ml of deionized water, and adjust the pH to 11 with NaOH solution to make the solution homogeneous. Then disperse the treated manganese sand obtained in step (1) in the above precursor solution and ultrasonically vibrate for 5 h. Transfer the mixed system to a high-pressure reaction kettle, with a hydrothermal reaction temperature of 200 °C and a time of 72 h. After the reaction is completed, cool it to room temperature, take out the solid product, and wash it repeatedly with deionized water. Finally, calcine it in a tube furnace under a nitrogen atmosphere at a temperature of 600 °C for 14 h to obtain the molecular sieve-natural manganese sand composite;

[0086] (3) Add 10 g of octamethylsilane to 100 ml of absolute ethanol and stir to form a homogeneous solution. Then immerse the molecular sieve-natural manganese sand composite obtained in step (2) into the above solution, stir at room temperature for 12 h, wash with absolute ethanol after the reaction, and then vacuum dry at 180 °C for 17 h. Finally, a molecular sieve-natural manganese sand hydrophobic material is formed.

[0087] Control Example 1

[0088] (1) Ultrasonically clean 5 g of natural manganese sand with deionized water for 1 h, and then wash with absolute ethanol to remove surface dust and organic impurities. Then immerse the treated manganese sand into 50 ml of 1 mM dilute hydrochloric acid solution and stir at room temperature for 6 h. Subsequently, wash repeatedly with deionized water until the solution is neutral, and place the washed manganese sand in an oven at 100 °C to dry to constant weight to obtain the treated manganese sand;

[0089] (2) Add 2.5 g of tetraethyl orthosilicate and 0.3 g of tetrapropylammonium hydroxide to 50 ml of deionized water, adjust the pH to 10 with NaOH solution to make the solution homogeneous. Then disperse the treated manganese sand obtained in step (1) in the precursor solution and ultrasonically vibrate for 5 h. Transfer the mixed system to a high-pressure reaction kettle, and the hydrothermal reaction temperature is 100 °C for 12 h. After the reaction, cool to room temperature, take out the solid product, and wash repeatedly with deionized water. Finally, calcine at 300 °C for 12 h in a nitrogen atmosphere to obtain a molecular sieve-natural manganese sand composite;

[0090] (3) Add 10 g of octamethylsilane to 100 ml of absolute ethanol and stir to form a homogeneous solution. Then immerse the molecular sieve-natural manganese sand composite obtained in step (2) into the above solution, stir at room temperature for 12 h, wash with absolute ethanol after the reaction, and then vacuum dry at 180 °C for 17 h. Finally, a molecular sieve-natural manganese sand hydrophobic material is formed.

[0091] Control Example 2

[0092] (1) Ultrasonically clean 5 g of natural manganese sand with deionized water for 1 h, and then wash with absolute ethanol to remove surface dust and organic impurities. Then immerse the treated manganese sand into 50 ml of 1 mM dilute hydrochloric acid solution and stir at room temperature for 6 h. Subsequently, wash repeatedly with deionized water until the solution is neutral, and place the washed manganese sand in an oven at 100 °C to dry to constant weight to obtain the treated manganese sand;

[0093] (2) Add 5.8 g of aluminum nitrate and 0.9 g of sodium diacetate to 50 ml of deionized water, and adjust the pH to 9 with NaOH solution to make the solution uniform. Then disperse the treated manganese sand obtained in step (1) in the above precursor solution and ultrasonically vibrate for 5 h. Transfer the mixed system to a high-pressure reactor, with a hydrothermal reaction temperature of 180 °C and a time of 24 h. After the reaction, cool to room temperature, take out the solid product, and wash it repeatedly with deionized water. Finally, calcine it in a tubular furnace under a nitrogen atmosphere at a temperature of 300 °C for 12 h to obtain the molecular sieve-natural manganese sand composite;

[0094] (3) Add 10 g of octamethylsilane to 100 ml of absolute ethanol and stir to form a uniform solution. Then immerse the molecular sieve-natural manganese sand composite obtained in step (2) in the above solution, stir at room temperature for 12 h, wash with absolute ethanol after the reaction, and then vacuum dry at 180 °C for 17 h. Finally, a molecular sieve-natural manganese sand hydrophobic material is formed.

[0095] Figure 1 The following are the water contact angle test data of the molecular sieve-natural manganese sand hydrophobic materials prepared in the above ten groups of examples. The test method is to measure the water contact angle of the membrane through a dynamic contact angle measuring instrument, and take the average value after measuring several test points on each membrane. The results are shown in Figure 1 , it can be seen that Example 10 has the best effect. Through the mesoporous structure of the silica-aluminum molecular sieve, the hydrophobic silane (octamethylsilane in Example 10) is directionally anchored on the surface of the manganese sand to form a hydrophobic layer, reducing the competitive adsorption of water molecules. The hydrophobic layer only covers the non-catalytic area, and the manganese active sites (such as the Mn³⁺ / Mn 4 ⁺ redox pair) are still exposed inside the pores, realizing an intelligent response structure of "hydrophobic shell + hydrophilic catalytic core".

[0096] Use the molecular sieve-natural manganese sand hydrophobic materials prepared in the above ten groups of examples in the ozone pollutant system in a humid environment to improve the removal ability of low-concentration ozone. The specific method is to use a gas chromatograph (equipped with an electron capture detector ECD) to analyze the ozone concentration before and after degradation and calculate the degradation rate.

[0097] Figure 2 The following is the ozone degradation efficiency after 48 h of reaction with an ozone concentration of 0.01 ppm and a relative humidity of 65%.

[0098] Figure 3 The following is the ozone degradation efficiency after 96 h of reaction with an ozone concentration of 0.03 ppm and a relative humidity of 80%.

[0099] Figure 4 The following is the ozone degradation efficiency after 120 h of reaction with an ozone concentration of 0.05 ppm and a relative humidity of 85%.

[0100] It can be seen that the degradation effect of Example 10 is optimal under various conditions. Through the optimization of the molecular sieve loading structure, the regulation of active sites, and the hydrophobic-catalytic synergistic mechanism, the present invention significantly improves the ozone degradation efficiency of the material under various environmental conditions, and is significantly superior to traditional manganese sand and single molecular sieve materials in terms of ozone degradation rate, environmental adaptability, and long-term stability, especially with prominent advantages under high humidity and low concentration conditions.

[0101] Figure 5 This is the experimental result of the verification effect of removing ozone in water:

[0102] The indigo disulfonate sodium (IDS) spectrophotometry was adopted. By detecting the change in the dissolved ozone concentration in water before and after the treatment with the material, the removal efficiency was calculated. A blank control group, a control group with activated carbon added, and experimental groups with the materials prepared according to Example 10, Comparative Example 1, and Comparative Example 2 of this patent were set up. The results showed that compared with pure silicon molecular sieve and pure aluminum molecular sieve, the silicon-aluminum composite molecular sieve prepared in Example 10 had a more complete structure, a larger specific surface area, and a stronger catalytic effect. Compared with activated carbon, the silicon-aluminum mixed molecular sieve effectively avoided the competitive adsorption of water molecules and internal manganese active sites. After being reused 5 times, the efficiency only decreased by 0.7%, and the stability was better than that of activated carbon (attenuation of 26.5%).

[0103] Figure 6 This is the scanning electron microscope image of the hydrophobic modified molecular sieve / manganese sand functional material prepared in Example 10. It can be seen that the material presents a clear core-shell stratification, the interface between the inner core and the outer shell is tightly combined, without peeling or cracks, indicating that the preparation process can stably construct the composite structure. The thickness of the outer shell is uniform and the coating is complete. It is verified that the controllable growth outer shell layer of the molecular sieve on the surface of manganese sand shows a uniform porous structure, which conforms to the typical characteristics of the molecular sieve and provides an enrichment and transmission channel for ozone molecules. The dense area on the surface (possibly related to hydrophobic modification) shows no pore blockage phenomenon, indicating that the hydrophobic treatment does not damage the pore channels of the molecular sieve and maintains the functionality of the material. The porous outer shell structure can significantly improve the adsorption capacity of ozone (compared with activated carbon). The inner core manganese sand transfers active sites to the outer shell through interface contact. Combining with the shape-selective enrichment effect of the molecular sieve, the catalytic decomposition efficiency of low-concentration ozone is enhanced. The gradient hydrophobicity of the core-shell structure (from the inner core to the outer shell) is indirectly reflected by the surface morphology, supporting the stable performance of the material under high humidity (see Figure 2 - 5 experimental data).

[0104] The molecular sieve structure formed in this application is a mixed structure of silicon ions and aluminum ions. The silicon-aluminum molecular sieve has no hydrophilic acidic sites in its framework and is naturally hydrophobic. The composite material with a gradually changing hydrophobicity from the inner core to the outer shell can achieve the directional discharge of water molecules while maintaining the efficient transmission of ozone.

[0105] The present invention provides a hydrophobic modified molecular sieve / manganese sand functional material, its preparation method and application ideas and methods. There are many ways to specifically implement this technical solution. The above description is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention. Each component not clearly defined in this embodiment can be realized by the prior art.

Claims

1. A hydrophobic modified molecular sieve / manganese sand functional material, characterized in that, It has a core-shell structure, including natural manganese sand located in the core and a molecular sieve shell in-situ grown on the surface of the natural manganese sand; the hydrophobicity gradually increases from the core natural manganese sand to the shell molecular sieve to achieve the directional discharge of water molecules while maintaining the transmission channel of ozone.

2. The preparation method of the hydrophobic modified molecular sieve / manganese sand functional material according to claim 1, characterized in that It includes the following steps: S1: Pretreatment of natural manganese sand Take natural manganese sand and alternately wash it with deionized water and absolute ethanol to remove surface dust and organic impurities; then immerse the manganese sand in an acid solution and stir at room temperature to remove surface unstable impurities and part of the carbonates, and then repeatedly wash it with deionized water until neutral; finally, dry the washed manganese sand. S2: In-situ growth of molecular sieve shell layer Mix deionized water, a silicon source, aluminum nitrate, and a structure-directing agent evenly and adjust the pH value to obtain a precursor solution. Disperse the manganese sand obtained in step S1 in the above precursor solution and make the precursor solution fully penetrate to the surface of the manganese sand particles; then after hydrothermal reaction, repeatedly wash the solid product with deionized water to remove the residual precursor solution and unreacted substances on the surface; finally, calcine it in an inert atmosphere to remove the structure-directing agent and form the pore structure of the shell molecular sieve. S3: Hydrophobic surface modification Prepare a hydrophobic agent solution, then immerse the product obtained in step S2 in the hydrophobic agent solution and stir at room temperature to make the hydrophobic functional groups fully react with the surface of the molecular sieve to form a stable organic hydrophobic layer, and obtain it after vacuum drying.

3. The preparation method of the hydrophobic modified molecular sieve / manganese sand functional material according to claim 2, characterized in that, In step S1, ultrasonic-assisted cleaning is used when the natural manganese sand is washed with deionized water and absolute ethanol, and the ultrasonic cleaning time is 1 - 12 h; the acid solution is a dilute hydrochloric acid aqueous solution with a concentration of 0.1 - 5 mM, and stir at room temperature for 1 - 24 h.

4. The preparation method of the hydrophobic modified molecular sieve / manganese sand functional material according to claim 2, wherein In step S2, the silicon source is tetraethyl orthosilicate or sodium silicate; the structure-directing agent is selected from any one of tetrapropylammonium hydroxide, cetyltrimethylammonium bromide, and sodium diacetate.

5. The preparation method of the hydrophobic modified molecular sieve / manganese sand functional material according to claim 2, characterized in that, In step S2, the mass ratio of the treated manganese sand, silicon source, aluminum nitrate, and structure-directing agent is 10:(1 - 5):(1 - 5):(0.1 - 2), and the pH value of the precursor solution is adjusted to 9 - 11.

6. The preparation method of the hydrophobic modified molecular sieve / manganese sand functional material according to claim 2, characterized in that, In step S2, the temperature of the hydrothermal reaction is 100 - 400 °C, and the time is 12 - 72 h.

7. The preparation method of the hydrophobic modified molecular sieve / manganese sand functional material according to claim 2, characterized in that, In step S2, calcination is carried out in a tubular furnace in a nitrogen atmosphere, the calcination temperature is 300 - 800 °C, and the time is 12 - 24 h.

8. The preparation method of the hydrophobic modified molecular sieve / manganese sand functional material according to claim 2, characterized in that, In step S3, add a silane coupling agent to anhydrous toluene or ethanol, stir to form a homogeneous solution, and prepare a hydrophobic agent solution; the silane coupling agent is octamethylsilane or trifluoromethylsilane; the mass ratio of the silane coupling agent to the product of step S2 is (0.1 - 2):

1.

9. The preparation method of the hydrophobic modified molecular sieve / manganese sand functional material according to claim 2, characterized in that, In step S3, the temperature of the vacuum drying is 80 - 200 °C, and the time is 2 - 24 h.

10. Use of the hydrophobic modified molecular sieve / manganese sand functional material according to claim 1 in catalytic decomposition of low-concentration ozone, characterized in that, The concentration of the low-concentration ozone is not higher than 0.05 ppm.

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