Slow-release activated carbon-plant essential oil composite deodorizing material and preparation method thereof

Abstract

The invention belongs to the technical field of air purification materials, and provides a slow-release activated carbon-plant essential oil composite deodorizing material and a preparation method thereof. The preparation method comprises the following steps: firstly, carrying out chemical oxidation treatment on an activated carbon substrate to introduce an oxygen-containing functional group on the surface, and then depositing a conductive polymer film on the surface of activated carbon through an in-situ chemical oxidation polymerization method; secondly, alkoxy silane is subjected to hydrolytic condensation on the surface of the material through a sol-gel method, and a layer of inorganic oxide thin shell is constructed; finally, a functional solution composed of plant essential oil and an organic solvent is efficiently loaded in the porous structure of the carrier by adopting a vacuum impregnation technology; in order to effectively regulate and control the release rate of the essential oil, the outermost layer of the material is coated with a layer of water-soluble high-molecular polymer in an atomizing and spraying manner to obtain the slow-release activated carbon-plant essential oil composite odor removal material, and the characteristics of long-acting slow release and lasting odor removal are realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of air purification materials, and relates to a slow-release activated carbon-plant essential oil composite odor removal material and a preparation method thereof. BACKGROUND

[0002] With the continuous improvement of the requirement for the quality of life, odor pollution problems reduce the comfort of the environment. Traditional odor removal methods, such as simple ventilation, are limited by environmental conditions and have a short-term effect; and most fragrance products mainly rely on odor masking, which cannot fundamentally eliminate pollution molecules. Physical adsorption is one of the widely used technologies at present, and activated carbon becomes a kind of efficient and inexpensive broad-spectrum adsorbent due to its large specific surface area and developed pore structure, which can effectively capture various odor molecules in the air. However, traditional activated carbon adsorption has inherent defects, that is, the adsorption process is a reversible physical process, and when the environmental temperature rises or the pressure changes, the adsorbed pollution molecules are easily desorbed and released into the air again, causing secondary pollution. In addition, the adsorption capacity of activated carbon is limited, and it will be invalid after saturation.

[0003] In order to overcome the above-mentioned deficiencies, researchers try to compound plant essential oil with natural aroma and certain chemical decomposition capacity with activated carbon. However, the conventional compounding method, such as simple physical impregnation, on the one hand, will greatly reduce the physical adsorption capacity of activated carbon due to the blockage of the micropores of activated carbon by essential oil, and on the other hand, essential oil itself is volatile and has a short action period, and is easy to be inactivated in the preparation process of the composite material due to harsh conditions such as high temperature and strong acid and alkali. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the present application is to provide a slow-release activated carbon-plant essential oil composite odor removal material and a preparation method thereof. The surface of activated carbon is first chemically modified and coated with a multi-layer functional shell, an inner layer of conductive polymer and an outer shell of inorganic oxide are sequentially constructed, and a porous carrier with stable structure is formed; then plant essential oil is loaded in the inner part of the carrier by a vacuum-assisted impregnation method, and a layer of polymer material is coated on the surface of the material, so as to meet the needs of actual production.

[0005] To achieve this purpose, the following technical solutions are adopted in the present application:

[0006] In a first aspect, the present application provides a preparation method of a slow-release activated carbon-plant essential oil composite odor removal material, which comprises:

[0007] S1, adding activated carbon into a nitric acid solution for reflux oxidation to obtain oxidized activated carbon, dispersing the oxidized activated carbon in a hydrochloric acid solution, adding aniline and ammonium persulfate for stirring and polymerization to obtain polyaniline-activated carbon;

[0008] S2, the polyaniline-activated carbon is added to the aqueous solution of polyethyleneimine, stirred, washed and dried, and then placed in a mixed solution, and tetraethoxysilane is added to react, to obtain SiO2-coated activated carbon, the mixed solution is a mixed solution of anhydrous ethanol, deionized water and ammonia water;

[0009] S3, the SiO2-coated activated carbon is immersed in a plant essential oil ethanol solution and vacuumed, then placed in an atomized polyvinyl alcohol aqueous solution, and dried at room temperature to obtain a slow-release activated carbon-plant essential oil composite deodorization material.

[0010] Specifically includes:

[0011] S1, the activated carbon is added to a nitric acid solution, the temperature is adjusted to a first temperature for reflux oxidation, and then filtered, washed and dried to obtain oxidized activated carbon, the oxidized activated carbon is dispersed in a hydrochloric acid solution, aniline is added at a second temperature, nitrogen atmosphere, ammonium persulfate is added for stirring polymerization, and then filtered, washed and dried to obtain polyaniline-activated carbon;

[0012] S2, the polyaniline-activated carbon is added to the aqueous solution of polyethyleneimine, stirred at a third temperature, washed and dried, and then placed in a mixed solution, and tetraethoxysilane is added to react, and then washed and dried to obtain SiO2-coated activated carbon, the mixed solution is a mixed solution of anhydrous ethanol, deionized water and ammonia water;

[0013] S3, the SiO2-coated activated carbon is immersed in a plant essential oil ethanol solution and vacuumed, then placed in an atomized polyvinyl alcohol aqueous solution, and dried at room temperature to obtain a slow-release activated carbon-plant essential oil composite deodorization material.

[0014] In S1, the activated carbon is placed in a high-temperature nitric acid solution for reflux treatment. In this strong oxidative acidic environment, the unsaturated carbon atoms on the surface of the activated carbon and the defect sites on the edge will undergo oxidation reactions to generate oxygen-containing functional groups: carboxyl and hydroxyl groups. The introduction of these functional groups changes the chemical properties of the activated carbon surface from hydrophobic to hydrophilic, improving its dispersibility in aqueous systems. More importantly, it provides active sites for subsequent chemical grafting or physical adsorption of functional layers. The subsequent polyaniline polymerization is a process of initiating aniline monomer polymerization in an acidic medium provided by hydrochloric acid, using ammonium persulfate as an oxidizing agent. The mechanism is as follows: aniline monomers are first protonated to form aniline cations, ammonium persulfate decomposes to produce highly active sulfate radicals, which abstract electrons from aniline cations to generate aniline cation radicals as active intermediates, which undergo coupling reactions through head-to-tail connection to gradually grow into long polyaniline chains. Due to the negative charge on the surface of the oxidized activated carbon (carboxyl dissociation) and its hydrophilicity, positively charged aniline monomers and cation radicals will be preferentially adsorbed on its surface through electrostatic attraction / π-π interactions, resulting in in-situ polymerization of the polymerization reaction at the activated carbon-solution interface, thereby forming a layer of polyaniline conductive layer that is tightly bound to the substrate.

[0015] In S2, the first step is the surface adsorption modification of polyethyleneimine, which is a high-molecular-weight polymer containing a large number of primary, secondary, and tertiary amine groups. In aqueous solution, the amine groups will be protonated and carry a large number of positive charges. When the activated carbon loaded with polyaniline is immersed in the solution, the long chains of polyethyleneimine will be firmly adsorbed and coated on the surface of the material through electrostatic attraction and van der Waals forces, thereby changing the Zeta potential of the entire composite particle from weakly positive or neutral to strongly positive. The next step is silica coating, which is carried out in a mixed solvent of ethanol, water, and ammonia. Tetraethoxysilane is used as the silicon source, and ammonia is used as the catalyst to provide an alkaline environment, which can significantly catalyze the hydrolysis of tetraethoxysilane to generate silicic acid or its oligomers with hydroxyl groups. These negatively charged silicon species will be preferentially adsorbed on the surface of the activated carbon particles with strong positive charges treated by polyethyleneimine through strong electrostatic attraction. This directional adsorption promotes heterogeneous nucleation on the particle surface and reduces homogeneous nucleation in the solution. With continuous hydrolysis and condensation of silicon species on the particle surface, a dense and uniform amorphous silica shell is finally formed.

[0016] In S3, the activated carbon carrier with the shell layer is subjected to vacuum treatment to form a negative pressure environment, and liquid is efficiently pressed into the deep part of the evacuated channel. Ethanol, as a low-boiling-point and high-volatility benign solvent, can reduce the viscosity of essential oil, improve the fluidity and penetration ability of essential oil, and can be removed in the subsequent drying process, leaving only pure plant essential oil physically confined in the channel structure. In the final sealing step, an atomized polyvinyl alcohol aqueous solution is sprayed. Polyvinyl alcohol is a water-soluble polymer containing a large number of hydroxyl groups. When the aqueous solution is atomized into small droplets and contacts the material surface and dries, the polyvinyl alcohol molecular chains will cross-link with each other through hydrogen bonds and other forces, and form a non-covalently bound transparent film on the surface of the outermost silica shell. This polymer film is not completely dense and allows smaller essential oil molecules to diffuse out at a slower rate, significantly reducing the initial evaporation rate and achieving slow release. At the same time, due to the presence of a large number of hydrophilic hydroxyl groups on the polyvinyl alcohol molecular chain, the film is sensitive to environmental humidity and will swell when the humidity is high, increasing the molecular chain spacing and pore size, which may lead to a corresponding increase in the release rate of essential oil.

[0017] As a preferred technical solution of the present application, in S1, the mass ratio of the activated carbon to the nitric acid solution is (100-110):1000, for example, it can be (100, 101, 102, 103, 104, 105, 106, 107, 108, 109 or 110):1000, but not limited to the listed values, other values not listed in this range are also applicable.

[0018] In some optional embodiments, the concentration of the nitric acid solution is 2M.

[0019] In some optional embodiments, the first temperature is 80-90°C, for example, it can be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, but not limited to the listed values, other values not listed in this range are also applicable.

[0020] In some optional embodiments, the reflux oxidation time is 2-4h, for example, it can be 2.0h, 2.2h, 2.4h, 2.6h, 2.8h, 3.0h, 3.2h, 3.4h, 3.6h, 3.8h or 4.0h, but not limited to the listed values, other values not listed in this range are also applicable.

[0021] In some optional embodiments, the mass ratio of the oxidized activated carbon, the hydrochloric acid solution, the aniline, and the ammonium persulfate is (100-110):3000:(10-11):(25-27), for example, it can be (100, 101, 102, 103, 104, 105, 106, 107, 108, 109, or 110):3000:(10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, or 11.0):(25, 25.2, 25.4, 25.6, 25.8, 26.0, 26.2, 26.4, 26.6, 26.8, or 27), but is not limited to the listed values, and other values not listed in the range are also applicable.

[0022] In some optional embodiments, the concentration of the hydrochloric acid solution is 1M.

[0023] In some optional embodiments, the second temperature is 0-5℃, for example, it can be 0℃, 0.5℃, 1℃, 1.5℃, 2℃, 2.5℃, 3℃, 3.5℃, 4℃, 4.5℃, or 5℃, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0024] In some optional embodiments, the stirring polymerization time is 4-6h, for example, it can be 4.0h, 4.2h, 4.4h, 4.6h, 4.8h, 5.0h, 5.2h, 5.4h, 5.6h, 5.8h, or 6.0h, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0025] As a preferred technical solution of the present application, in S2, the mass ratio of the polyaniline-activated carbon, the polyethyleneimine aqueous solution, the mixed solution, and the tetraethoxysilane is (100-110):1000:2050:(4-5), for example, it can be (100, 101, 102, 103, 104, 105, 106, 107, 108, 109, or 110):1000:2050:(4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5.0), but is not limited to the listed values, and other values not listed in the range are also applicable.

[0026] In some optional embodiments, the mass fraction of the polyethyleneimine aqueous solution is 1.5wt.%.

[0027] In some alternative embodiments, the third temperature is 40-60°C, for example, it can be 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C or 60°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0028] In some optional embodiments, the stirring time is 1-2 hours, for example, 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2.0 hours, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0029] In some optional embodiments, the mass ratio of anhydrous ethanol, deionized water and ammonia in the mixed solution is 36:4:1, and the mass fraction of ammonia is 25 wt.%.

[0030] In some optional embodiments, the reaction time for adding tetraethoxysilane is 1-3 hours, for example, 1.0 hours, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2.0 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, or 3.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0031] As a preferred technical solution of the present invention, in S3, the mass ratio of the SiO2-coated activated carbon to the plant essential oil ethanol solution is (20-30):150, for example, it can be (20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30):150, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] In some optional embodiments, the mass ratio of plant essential oil to anhydrous ethanol in the plant essential oil ethanol solution is 1:10.

[0033] In some optional embodiments, the vacuum holding time is 1-3 hours, for example, it can be 1.0 hours, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2.0 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0034] In some optional embodiments, the time for standing at room temperature is 1-2 hours, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0035] In some optional embodiments, the polyvinyl alcohol aqueous solution has a mass fraction of 0.3 wt.%.

[0036] Secondly, the present invention provides a slow-release activated carbon-plant essential oil composite deodorizing material prepared by the preparation method described in the first aspect.

[0037] Compared with existing technologies, the beneficial effects of this invention are as follows: By adopting a technical route of first constructing a carrier and then loading essential oils, the thermal degradation, chemical denaturation, or volatilization loss of plant essential oils during the preparation process is avoided; by sequentially constructing a conductive polymer layer and a dense inorganic oxide shell on the surface of the activated carbon substrate, a structurally stable and firmly adhered multi-layer coating system is formed, which not only provides a physical barrier for the subsequent slow release of essential oils, but also effectively protects the internal pore structure of activated carbon, avoiding the problem of essential oils directly clogging micropores in traditional impregnation methods; by spraying a layer of high-molecular polymer on the outermost layer of the material, the initial burst release effect of essential oils is reduced, their action period is extended, and long-term slow release is achieved. Detailed Implementation

[0038] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0039] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0040] Example 1

[0041] This embodiment provides a slow-release activated carbon-plant essential oil composite deodorizing material and its preparation method. The preparation method specifically includes the following steps:

[0042] S1, 100g of activated carbon was added to 1000g of 2M nitric acid solution, the temperature was adjusted to 90℃ and refluxed for 2h, filtered, washed and dried to obtain oxidized activated carbon, 110g of oxidized activated carbon was dispersed in 3000g of 1M hydrochloric acid solution, 10g of aniline was added at 5℃, and 26g of ammonium persulfate was added under nitrogen atmosphere and stirred for 6h to polymerize, filtered, washed and dried to obtain polyaniline-activated carbon;

[0043] S2, 100g of polyaniline-activated carbon was added to 1000g of a 1.5wt.% polyethyleneimine aqueous solution, stirred at 40℃ for 1.5h, washed and dried, and then placed in 2050g of a mixed solution, wherein the mixed solution was a mixture of anhydrous ethanol, deionized water and ammonia water, wherein the mass ratio of anhydrous ethanol, deionized water and ammonia water was 36:4:1, and the mass fraction of ammonia water was 25wt.%, 5g of tetraethoxysilane was added and reacted for 1h, and after washing and drying, SiO2-coated activated carbon was obtained;

[0044] S3, 30g of SiO2-coated activated carbon was immersed in 150g of plant essential oil ethanol solution and kept under vacuum for 3h. The mass ratio of plant essential oil to anhydrous ethanol in the plant essential oil ethanol solution was 1:10. After releasing the gas and returning to normal pressure, the free oil was decanted and the solution was left to stand at room temperature for 1h. Then, it was placed in a 0.3wt.% polyvinyl alcohol aqueous solution for atomization and dried at room temperature to obtain a slow-release activated carbon-plant essential oil composite deodorizing material.

[0045] Example 2

[0046] This embodiment provides a slow-release activated carbon-plant essential oil composite deodorizing material and its preparation method. The preparation method specifically includes the following steps:

[0047] S1, 110g of activated carbon was added to 1000g of 2M nitric acid solution, the temperature was adjusted to 80℃ and refluxed for 4h, filtered, washed and dried to obtain oxidized activated carbon, 100g of oxidized activated carbon was dispersed in 3000g of 1M hydrochloric acid solution, 11g of aniline was added at 0℃, and 25g of ammonium persulfate was added under nitrogen atmosphere and stirred for 4h to polymerize, filtered, washed and dried to obtain polyaniline-activated carbon;

[0048] S2, 110g of polyaniline-activated carbon was added to 1000g of a 1.5wt.% polyethyleneimine aqueous solution, stirred at 60℃ for 2h, washed and dried, and then placed in 2050g of a mixed solution, wherein the mixed solution was a mixture of anhydrous ethanol, deionized water and ammonia water, wherein the mass ratio of anhydrous ethanol, deionized water and ammonia water was 36:4:1, and the mass fraction of ammonia water was 25wt.%, 4g of tetraethoxysilane was added and reacted for 3h, and after washing and drying, SiO2-coated activated carbon was obtained;

[0049] S3, 20g of SiO2-coated activated carbon was immersed in 150g of plant essential oil ethanol solution and kept under vacuum for 1h. The mass ratio of plant essential oil to anhydrous ethanol in the plant essential oil ethanol solution was 1:10. After releasing the gas and returning to normal pressure, the free oil was decanted and the mixture was left to stand at room temperature for 2h. Then, it was placed in a 0.3wt.% polyvinyl alcohol aqueous solution for atomization and dried at room temperature to obtain a slow-release activated carbon-plant essential oil composite deodorizing material.

[0050] Example 3

[0051] This embodiment provides a slow-release activated carbon-plant essential oil composite deodorizing material and its preparation method. The preparation method specifically includes the following steps:

[0052] S1, 105g of activated carbon was added to 1000g of 2M nitric acid solution, the temperature was adjusted to 85℃ and refluxed for 3h, filtered, washed and dried to obtain oxidized activated carbon, 105g of oxidized activated carbon was dispersed in 3000g of 1M hydrochloric acid solution, 10.5g of aniline was added at 2℃, and 27g of ammonium persulfate was added under nitrogen atmosphere and stirred for 5h to polymerize, filtered, washed and dried to obtain polyaniline-activated carbon;

[0053] S2, 105g of polyaniline-activated carbon was added to 1000g of a 1.5wt.% aqueous solution of polyethyleneimine, stirred at 50℃ for 1h, washed and dried, and then placed in 2050g of a mixed solution, wherein the mixed solution was a mixture of anhydrous ethanol, deionized water and ammonia water, wherein the mass ratio of anhydrous ethanol, deionized water and ammonia water was 36:4:1, and the mass fraction of ammonia water was 25wt.%, 4.5g of tetraethoxysilane was added and reacted for 2h, and after washing and drying, SiO2-coated activated carbon was obtained;

[0054] S3, 25g of SiO2-coated activated carbon was immersed in 150g of plant essential oil ethanol solution and kept under vacuum for 2h. The mass ratio of plant essential oil to anhydrous ethanol in the plant essential oil ethanol solution was 1:10. After releasing the gas and returning to normal pressure, the free oil was decanted and the mixture was left to stand at room temperature for 1.5h. Then, it was placed in a 0.3wt.% polyvinyl alcohol aqueous solution for atomization and dried at room temperature to obtain a slow-release activated carbon-plant essential oil composite deodorizing material.

[0055] Example 4

[0056] This embodiment provides a slow-release activated carbon-plant essential oil composite deodorizing material and its preparation method. The preparation method specifically includes the following steps:

[0057] S1, 102g of activated carbon was added to 1000g of 2M nitric acid solution, the temperature was adjusted to 82℃ and refluxed for 2.5h, filtered, washed and dried to obtain oxidized activated carbon, 108g of oxidized activated carbon was dispersed in 3000g of 1M hydrochloric acid solution, 10.8g of aniline was added at 3℃, and 25.5g of ammonium persulfate was added under nitrogen atmosphere and stirred for polymerization for 5.5h, filtered, washed and dried to obtain polyaniline-activated carbon;

[0058] S2, 108g of polyaniline-activated carbon was added to 1000g of a 1.5wt.% polyethyleneimine aqueous solution and stirred at 55℃ for 1.8h. After washing and drying, it was placed in 2050g of a mixed solution, which was a mixture of anhydrous ethanol, deionized water and ammonia water, wherein the mass ratio of anhydrous ethanol, deionized water and ammonia water was 36:4:1 and the mass fraction of ammonia water was 25wt.%. 4.8g of tetraethoxysilane was added and reacted for 2.5h. After washing and drying, SiO2-coated activated carbon was obtained.

[0059] S3, 22g of SiO2-coated activated carbon was immersed in 150g of plant essential oil ethanol solution and kept under vacuum for 2.5h. The mass ratio of plant essential oil to anhydrous ethanol in the plant essential oil ethanol solution was 1:10. After releasing the gas and returning to normal pressure, the free oil was decanted and the mixture was allowed to stand at room temperature for 1.2h. Then, it was placed in a 0.3wt.% polyvinyl alcohol aqueous solution for atomization and dried at room temperature to obtain a slow-release activated carbon-plant essential oil composite deodorizing material.

[0060] Comparative Example 1

[0061] This comparative example provides a slow-release activated carbon-plant essential oil composite deodorizing material and its preparation method. The difference between this and Example 1 is that the polyaniline polymerization step is not performed in S1, only the nitric acid oxidation step in S1 is performed, and oxidized activated carbon is used for step S2. Other process parameters and operating conditions are exactly the same as in Example 1.

[0062] Comparative Example 2

[0063] This comparative example provides a slow-release activated carbon-plant essential oil composite deodorizing material and its preparation method. The difference between this and Example 1 is that step S2 is omitted, and polyaniline-activated carbon is used instead of the SiO2-coated activated carbon in S3. Other process parameters and operating conditions are exactly the same as in Example 1.

[0064] Comparative Example 3

[0065] This comparative example provides a slow-release activated carbon-plant essential oil composite deodorizing material and its preparation method. The difference between this and Example 1 is that the polyvinyl alcohol aqueous solution atomization step is not performed in S3, while other process parameters and operating conditions are exactly the same as in Example 1.

[0066] The performance of the slow-release activated carbon-plant essential oil composite deodorizing materials prepared in Examples 1-4 and Comparative Examples 1-3 was tested, and the specific process is as follows:

[0067] The sustained-release effect test method was as follows: 2.000g of the composite material sample was evenly spread on the bottom of an open glass weighing bottle that had been pre-equilibrated in a constant temperature and humidity chamber at 25℃ and 50% relative humidity (RH) for 12 hours and had already been weighed. The initial total mass m0 was quickly weighed and recorded. The sample bottle was then placed open in the constant temperature and humidity chamber at 25℃ and 50% RH for 48 hours. After the test, the sample bottle was quickly removed, and its final total mass m1 was recorded on an analytical balance. The mass loss rate of the sample was calculated as [(m0-m1) / m0]×100%. At the same time, 2.000g of blank carrier without volatile components was placed in another weighing bottle with the same treatment as a calibration.

[0068] Odor removal effect test method: A 10L dry, clean, sealed glass test chamber was evacuated and then filled with high-purity nitrogen to replace the air three times. A small fan was pre-installed inside the chamber. Ammonia water or standard ammonia gas was injected to bring the initial ammonia concentration inside the chamber to 100ppm. The fan was turned on for circulation for 5-10 minutes, and the initial concentration was measured and recorded using a gas detection tube or online sensor. A 10.0g sample of the composite material to be tested was spread evenly in a petri dish, quickly placed in the test chamber, and immediately sealed. The mixture was statically placed at 25℃ and 50%RH for 2 hours. After completion, the fan was turned on for circulation for 2-3 minutes to ensure uniform gas mixing inside the chamber, and the endpoint concentration was measured and recorded. Purification rate = [(initial concentration - endpoint concentration) / initial concentration] × 100%.

[0069] The test results are shown in Table 1.

[0070] Table 1. Test results of the slow-release activated carbon-plant essential oil composite deodorizing materials prepared in Examples 1-4 and Comparative Examples 1-3

[0071] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Mass loss rate (%) 2.4 2.8 2.3 2.7 3.7 4.6 4.3 Purification rate (%) 90 87 91 88 82 93 87

[0072] As shown in Table 1, compared to Example 1, Comparative Example 1 showed an increased mass loss rate and decreased purification rate; Comparative Example 2 showed an increased mass loss rate and increased purification rate; and Comparative Example 3 showed an increased mass loss rate and decreased purification rate. This is because Comparative Example 1 did not perform the polyaniline polymerization step. The lack of a PANI layer leads to more structural defects in the subsequent SiO2 shell, easily forming an incomplete shell with pinholes or microcracks, which becomes a channel for the rapid release of essential oil molecules, reducing the material's sustained-release performance, thus decreasing the mass loss rate. Comparative Example 2 did not perform the S2 step and used polyaniline-activated carbon to replace the SiO2-coated activated carbon in S3. The lack of a sustained-release barrier and the absence of a SiO2 layer reduced the resistance to diffusion of small molecule gases into the internal activated carbon core, improving the purification rate. Comparative Example 3 did not perform the polyvinyl alcohol aqueous solution atomization step, lacking a "sealing" effect, thus decreasing the mass loss rate.

[0073] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a slow-release activated carbon-plant essential oil composite deodorizing material, characterized in that, The preparation method includes: S1, Activated carbon is added to nitric acid solution and refluxed to obtain oxidized activated carbon. The oxidized activated carbon is dispersed in hydrochloric acid solution, and aniline and ammonium persulfate are added and stirred to polymerize, resulting in polyaniline-activated carbon. S2, add polyaniline-activated carbon to a polyethyleneimine aqueous solution and stir. After washing and drying, place it in a mixed solution and add tetraethoxysilane to react, thereby obtaining SiO2-coated activated carbon. The mixed solution is a mixture of anhydrous ethanol, deionized water and ammonia. S3. SiO2-coated activated carbon is immersed in a plant essential oil ethanol solution and kept under vacuum, and then placed in a polyvinyl alcohol aqueous solution for atomization to obtain a slow-release activated carbon-plant essential oil composite deodorizing material.

2. The preparation method of the slow-release activated carbon-plant essential oil composite deodorizing material according to claim 1, characterized in that, In S1: The mass ratio of activated carbon to nitric acid solution is (100-110):1000; The concentration of the nitric acid solution is 2M.

3. The preparation method of the slow-release activated carbon-plant essential oil composite deodorizing material according to claim 1, characterized in that, In S1: The mass ratio of the oxidizing activated carbon, hydrochloric acid solution, aniline and ammonium persulfate is (100-110):3000:(10-11):(25-27). The concentration of the hydrochloric acid solution is 1M.

4. The preparation method of the slow-release activated carbon-plant essential oil composite deodorizing material according to claim 1, characterized in that, In S2: The mass ratio of the polyaniline-activated carbon, polyethyleneimine aqueous solution, mixed solution and tetraethoxysilane is (100-110):1000:2050:(4-5).

5. The preparation method of the slow-release activated carbon-plant essential oil composite deodorizing material according to claim 1, characterized in that, In S2: The mass fraction of the polyethyleneimine aqueous solution is 1.5 wt.%.

6. The preparation method of the slow-release activated carbon-plant essential oil composite deodorizing material according to claim 1, characterized in that, In S2: The mass ratio of anhydrous ethanol, deionized water and ammonia in the mixed solution is 36:4:1, and the mass fraction of ammonia is 25 wt.%.

7. The preparation method of the slow-release activated carbon-plant essential oil composite deodorizing material according to claim 1, characterized in that, In S3: The mass ratio of the SiO2-coated activated carbon to the plant essential oil ethanol solution is (20-30):

150.

8. The preparation method of the slow-release activated carbon-plant essential oil composite deodorizing material according to claim 1, characterized in that, In S3: The mass ratio of plant essential oil to anhydrous ethanol in the plant essential oil ethanol solution is 1:

10.

9. The preparation method of the slow-release activated carbon-plant essential oil composite deodorizing material according to claim 1, characterized in that, In S3: The polyvinyl alcohol aqueous solution has a mass fraction of 0.3 wt.%.

10. A slow-release activated carbon-plant essential oil composite deodorizing material obtained by the preparation method according to any one of claims 1-9.