Nano formaldehyde-removing anion purification liquid and preparation method thereof

Abstract

The invention discloses a nanometer formaldehyde-removing anion purifying liquid and a preparation method thereof, and relates to the technical field of formaldehyde purifying agents. The nanometer formaldehyde removal negative ion purification liquid is prepared from the following raw materials in percentage by mass: 3 to 6 percent of silicon-cerium co-doped nanometer titanium dioxide, 3 to 6 percent of cerium-doped manganese oxide nanometer composite material, 20 to 30 percent of natural plant extract, 1 to 3 percent of deodorant, 0.6 to 0.1 percent of surfactant and the balance of deionized water, the natural plant extract is extracted from machilus megaphylla, pseudolarix amabilis and pinus massoniana; the mass ratio of the machilus nigrum to the pseudolarix amabilis to the pinus massoniana is 1: (0.6-1.2): (0.8-1.4). The nanometer formaldehyde removal anion purification liquid provided by the invention has excellent formaldehyde removal effect and antibacterial property.

Description

Technical Field

[0001] The present application relates to the field of formaldehyde purifier technology, and in particular to a nanometer formaldehyde-removing negative ion purification liquid and a preparation method thereof. Background Art

[0002] Volatile organic compounds (VOCs) such as formaldehyde, acetaldehyde, and toluene emitted from furniture and decorative materials have become major indoor air pollutants. Formaldehyde is the most common and toxic indoor air pollutant, and its release is long-lasting and persistent, making it difficult to completely remove through simple ventilation or adsorption. Long-term exposure to excessive formaldehyde levels can cause serious harm to human health, including damage to the respiratory mucosa and eyes, and may even cause cancer. Therefore, developing efficient, safe, and sustainable formaldehyde purification methods is crucial for improving indoor air quality and protecting human health.

[0003] Nano-formaldehyde-removing negative ion purification liquid is a composite air purification product that combines nanotechnology, formaldehyde removal technology, and negative ion technology. Through the efficient adsorption and catalytic effects of nanomaterials, it decomposes harmful gases like formaldehyde. Simultaneously, negative ion technology ionizes the air to generate negative ions, which bind to formaldehyde molecules and break them down into non-toxic carbon dioxide and water.

[0004] For related technology, please refer to Chinese invention patent application number CN115253638A, which discloses a nanometer formaldehyde-removing negative ion liquid for air purification and its preparation method. The liquid mainly comprises the following raw materials by weight: 0.5-5.0 parts of nano-metal oxide, 0.5-3.0 parts of nano-titanate, 1.0-5.0 parts of bio-based formaldehyde remover, 0.1-0.3 parts of deodorant, 0.1-0.3 parts of surfactant, 0.1-0.5 parts of antiseptic and fungicide, and 86-92 parts of deionized water. It has good formaldehyde and odor removal effects.

[0005] Regarding the aforementioned related technologies, nano-metal oxides commonly used in existing technologies are nano-titanium dioxide. Nano-titanium dioxide is a photocatalyst whose photocatalytic activity primarily relies on ultraviolet light. However, the intensity of ultraviolet light in indoor environments is typically low, limiting its effectiveness in removing formaldehyde in low-light conditions. This limitation significantly restricts the formaldehyde removal efficiency of nano-titanium dioxide in practical applications. Summary of the Invention

[0006] In order to solve the problem of limited formaldehyde removal effect of nano-formaldehyde-removing negative ion purification liquid containing nano-titanium dioxide, the present application provides a nano-formaldehyde-removing negative ion purification liquid and a preparation method thereof.

[0007] The present application provides a nanometer formaldehyde removal negative ion purification liquid, which adopts the following technical solution:

[0008] A nanometer formaldehyde-removing negative ion purification liquid comprises the following raw materials by mass percentage: 3-6% of silicon-cerium co-doped nanometer titanium dioxide, 3-6% of cerium-doped manganese oxide nanometer composite material, 20-30% of natural plant extract, 1-3% of deodorant, 0.6-0.1% of surfactant, and the balance is deionized water.

[0009] Preferably, the natural plant extract is extracted from Machilus thunbergii, Pleistocene chinensis, and Pinus massoniana; the mass ratio of Machilus thunbergii, Pleistocene chinensis, and Pinus massoniana is 1:(0.6-1.2):(0.8-1.4).

[0010] Preferably, the method for preparing the natural plant extract comprises the following steps:

[0011] S1. The black shell Nan, golden pine and masson pine raw materials were washed, dried and crushed, then added to an ethanol solution, flash extracted 2-10min, filtered to obtain a residue and a filtrate;

[0012] S2. The filtrate is filtered through a microporous membrane and then eluted with deionized water to obtain an eluate;

[0013] S3. After the eluate is subjected to reduced pressure distillation to recover the solvent, a natural plant extract is obtained.

[0014] Preferably, the raw materials of Machilus nigra, Pine Pinus gmelinii and Pinus massoniana are Machilus nigra leaves, Pine Pinus gmelinii seeds and Pinus massoniana needles.

[0015] Preferably, the silicon-cerium co-doped nano-titanium dioxide is prepared from the following raw materials in parts by weight: 20-30 parts of deionized water, 40-60 parts of ethanol, 5-10 parts of acetic acid, 0.3-0.6 parts of tetraethyl silicate, 0.018-0.036 parts of cerium nitrate hexahydrate, and 2.48-4.96 parts of tetrabutyl titanate.

[0016] Preferably, the method for preparing silicon-cerium co-doped nano-titanium dioxide comprises the following steps:

[0017] Deionized water, ethanol and acetic acid are mixed and stirred evenly at room temperature. Tetraethyl silicate and cerium nitrate hexahydrate are added in sequence and stirred continuously until completely dissolved. Stirring is continued and tetrabutyl titanate is added dropwise to obtain a mixed solution. The mixed solution is transferred to a hydrothermal reactor and heated at 160-180° C. for 12-16 hours. After the reaction is completed, the mixture is naturally cooled to room temperature. The solid product is collected by centrifugation. The solid product is then washed alternately with deionized water and ethanol for several times and then dried in a vacuum at 60-70° C. for 12-16 hours to obtain silicon-cerium co-doped nano-titanium dioxide.

[0018] Preferably, the cerium-doped manganese oxide nanocomposite material is prepared from the following raw materials in parts by weight: 2-5 parts of potassium permanganate, 4.8-12 parts of cerium nitrate hexahydrate, 0.3-0.75 parts of glucose, and 215-430 parts of pure water.

[0019] Preferably, the method for preparing the cerium-doped manganese oxide nanocomposite material comprises the following steps:

[0020] Add 2-5 parts of potassium permanganate to 200-400 parts of pure water and stir until completely dissolved to obtain a potassium permanganate solution;

[0021] Add 4.8-12 parts of cerium nitrate hexahydrate to 10-20 parts of pure water and stir until completely dissolved to obtain a cerium nitrate solution;

[0022] Add 0.3-0.75 parts of glucose to 5-10 parts of pure water and stir until completely dissolved to obtain a glucose solution;

[0023] A cerium nitrate solution and a glucose solution are added dropwise to a potassium permanganate solution, and the mixture is stirred for 20-30 minutes to obtain a mixed solution; the mixed solution is reacted for 30-60 minutes under the conditions of an ultrasonic power of 800-1000W, a microwave power of 600-800W, and a reaction temperature of 75-85°C; after the reaction is completed, a solid product is collected by centrifugation, and the solid product is washed alternately with deionized water and ethanol several times, and then vacuum dried at 60-70°C for 10-12 hours to obtain a cerium-doped manganese oxide nanocomposite material.

[0024] Preferably, the deodorant is one of plant essential oil, zinc ricinoleate, and soybean ethyl sulfate.

[0025] The present application also provides a method for preparing a nanometer formaldehyde-removing negative ion purification liquid, which adopts the following technical solution:

[0026] A method for preparing a nanometer formaldehyde-removing negative ion purification liquid comprises the following steps:

[0027] Silicon-cerium co-doped nano titanium dioxide, cerium-doped manganese oxide nanocomposite material, natural plant extract, deodorant and surfactant are added into deionized water, and mixed and stirred at 300-600 rpm for 10-20 minutes to obtain nano formaldehyde-removing negative ion purification liquid.

[0028] In summary, this application includes at least one of the following beneficial technical effects:

[0029] 1. By adopting the above technical solution, this application uses a composite material of silicon-cerium co-doped nano-titanium dioxide and cerium-doped manganese oxide nanocomposite as the main material for catalytic degradation of formaldehyde gas. Manganese oxide can show excellent activity in the catalytic removal of VOCs. Therefore, even in a lightless environment, it can continuously catalytically degrade formaldehyde gas, effectively improving the formaldehyde removal effect of the nano-formaldehyde removal negative ion purification liquid;

[0030] 2. By adopting the above technical solution, the present application uses a flash extraction method to extract natural plant extracts from Phoebe maculatum, Pine Pine, and Pinus massoniana, which have excellent inhibitory effects on airborne microorganisms. At the same time, the released VOCs can promote air ionization and form a large number of negative ions, thereby significantly improving the formaldehyde purification rate;

[0031] 3. By adopting the above technical solution, the present application uses silicon-cerium co-doped titanium dioxide. The introduction of silicon effectively increases the surface area and pore structure of nano-silica, provides more active sites for catalytic reactions, and increases the surface hydroxyl content of the catalyst, thereby achieving a more efficient photocatalytic degradation effect; the addition of cerium introduces additional energy levels, effectively reducing the energy gap of nano-titanium dioxide, allowing it to absorb light in a wider band, thereby improving its utilization of visible light. DETAILED DESCRIPTION

[0032] The present application is further described in detail below with reference to the embodiments.

[0033] The chemical reagents used in the preparation examples, embodiments and comparative examples provided in the present invention are all commercially available products.

[0034] Preparation Example 1 Preparation of natural plant extracts

[0035] Preparation Example 1.1

[0036] S1. 10g of Phoebe chinensis leaves, 6g of golden pine seeds and 8g of Pinus massoniana needles were washed with water, dried and crushed, then added to 228g of a 20% aqueous ethanol solution, flash-extracted for 2min, and filtered to obtain a residue and a filtrate;

[0037] S2. The filtrate was filtered through a 0.22 μm microporous membrane and then eluted with deionized water to obtain an eluate;

[0038] S3. The eluate was distilled under reduced pressure at 2.67 kPa and 40°C for 1 h. After recovering the solvent, the natural plant extract was obtained.

[0039] Preparation Example 1.2

[0040] S1. 10g of black shell nanmu leaves, 9g of golden pine seeds and 11g of masson pine needles were washed with water, dried and crushed, and then added to 285g of a 20% ethanol aqueous solution by mass fraction, flash extracted for 6min, and filtered to obtain a residue and a filtrate;

[0041] S2. The filtrate was filtered through a 0.22 μm microporous membrane and then eluted with deionized water to obtain an eluate;

[0042] S3. The eluate was distilled under reduced pressure at 4 kPa and 45°C for 1.5 h. After recovering the solvent, the natural plant extract was obtained.

[0043] Preparation Example 1.3

[0044] S1. 10g of black shell nanmu leaves, 12g of golden pine seeds and 14g of masson pine needles were washed with water, dried and crushed, and then added to 342g of a 20% ethanol aqueous solution by mass fraction, flash extracted for 10min, and filtered to obtain a residue and a filtrate;

[0045] S2. The filtrate was filtered through a 0.22 μm microporous membrane and then eluted with deionized water to obtain an eluate;

[0046] S3. The eluate was distilled under reduced pressure at 6.67 kPa and 50°C for 1 h. After recovering the solvent, the natural plant extract was obtained.

[0047] Preparation Example 2 Preparation of Silicon-Cerium Co-doped Nano-Titanium Dioxide

[0048] Preparation Example 2.1

[0049] 20 g of deionized water, 40 g of ethanol and 5 g of acetic acid were mixed and stirred evenly at room temperature. 0.3 g of tetraethyl silicate and 0.018 g of cerium nitrate hexahydrate were added successively, and the mixture was stirred continuously until completely dissolved. 2.48 g of tetrabutyl titanate was added dropwise with continued stirring to obtain a mixed solution. The mixed solution was transferred to a hydrothermal reactor and heated at 160° C. for 12 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The solid product was collected by centrifugation, and the solid product was then washed alternately with deionized water and ethanol for 3 times, and then dried in a vacuum at 60° C. for 16 h to obtain silicon-cerium co-doped nano-titanium dioxide.

[0050] Preparation Example 2.2

[0051] 25 g of deionized water, 50 g of ethanol and 7.5 g of acetic acid were mixed and stirred evenly at room temperature. 0.45 g of tetraethyl silicate and 0.027 g of cerium nitrate hexahydrate were added successively, and the mixture was stirred continuously until completely dissolved. The mixture was then stirred continuously and 3.72 g of tetrabutyl titanate was added dropwise to obtain a mixed solution. The mixed solution was transferred to a hydrothermal reactor and heated at 170° C. for 14 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The solid product was collected by centrifugation, and the solid product was then washed alternately with deionized water and ethanol for 4 times, and then dried in a vacuum at 65° C. for 14 h to obtain silicon-cerium co-doped nano-titanium dioxide.

[0052] Preparation Example 2.3

[0053] 30 g of deionized water, 60 g of ethanol and 10 g of acetic acid were mixed and stirred at room temperature. 0.6 g of tetraethyl silicate and 0.036 g of cerium nitrate hexahydrate were added successively, and the mixture was stirred continuously until completely dissolved. 4.96 g of tetrabutyl titanate was added dropwise thereto to obtain a mixed solution. The mixed solution was transferred to a hydrothermal reactor and heated at 180° C. for 18 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The solid product was collected by centrifugation. The solid product was then washed alternately with deionized water and ethanol for 5 times, and then dried in a vacuum at 70° C. for 12 h to obtain silicon-cerium co-doped nano-titanium dioxide.

[0054] Preparation Example 3 Preparation of Cerium-doped Manganese Oxide Nanocomposite Material

[0055] Preparation Example 3.1

[0056] Add 2 g of potassium permanganate to 200 g of pure water and stir until completely dissolved to obtain a potassium permanganate solution;

[0057] Add 4.8 g of cerium nitrate hexahydrate to 10 g of pure water and stir until completely dissolved to obtain a cerium nitrate solution;

[0058] Add 0.3 g of glucose to 5 g of pure water and stir until completely dissolved to obtain a glucose solution;

[0059] A cerium nitrate solution and a glucose solution were added dropwise to a potassium permanganate solution, and the mixture was stirred for 20 minutes to obtain a mixed solution; the mixed solution was reacted for 30 minutes under the conditions of an ultrasonic power of 800 W, a microwave power of 600 W, and a reaction temperature of 75°C; after the reaction, a solid product was collected by centrifugation, and the solid product was washed alternately with deionized water and ethanol several times, and then vacuum dried at 60°C for 12 hours to obtain a cerium-doped manganese oxide nanocomposite material.

[0060] Preparation Example 3.2

[0061] Add 3.5 g of potassium permanganate to 300 g of pure water and stir until completely dissolved to obtain a potassium permanganate solution;

[0062] 8.4 g of cerium nitrate hexahydrate was added to 15 g of pure water and stirred until completely dissolved to obtain a cerium nitrate solution;

[0063] Add 0.475 g of glucose to 7.5 g of pure water and stir until completely dissolved to obtain a glucose solution;

[0064] A cerium nitrate solution and a glucose solution were added dropwise to a potassium permanganate solution, and the mixture was stirred for 25 minutes to obtain a mixed solution; the mixed solution was reacted for 45 minutes under the conditions of an ultrasonic power of 900 W, a microwave power of 700 W, and a reaction temperature of 80°C; after the reaction, the solid product was collected by centrifugation, and the solid product was washed alternately with deionized water and ethanol several times, and then vacuum dried at 65°C for 11 hours to obtain a cerium-doped manganese oxide nanocomposite material.

[0065] Preparation Example 3.3

[0066] Add 5 g of potassium permanganate to 400 g of pure water and stir until completely dissolved to obtain a potassium permanganate solution;

[0067] Add 12 g of cerium nitrate hexahydrate to 20 g of pure water and stir until completely dissolved to obtain a cerium nitrate solution;

[0068] Add 0.75g of glucose to 10g of pure water and stir until completely dissolved to obtain a glucose solution;

[0069] A cerium nitrate solution and a glucose solution were added dropwise to a potassium permanganate solution, and the mixture was stirred for 30 minutes to obtain a mixed solution; the mixed solution was reacted for 60 minutes under the conditions of an ultrasonic power of 1000 W, a microwave power of 800 W, and a reaction temperature of 85°C; after the reaction, a solid product was collected by centrifugation, and the solid product was washed alternately with deionized water and ethanol several times, and then vacuum dried at 70°C for 10 hours to obtain a cerium-doped manganese oxide nanocomposite material.

[0070] Example 1

[0071] 3 g of the silicon-cerium co-doped nano-titanium dioxide prepared in Preparation Example 2.1, 3 g of the cerium-doped manganese oxide nanocomposite prepared in Preparation Example 3.1, 30 g of the natural plant extract prepared in Preparation Example 1.1, 1 g of a deodorant, and 0.6 g of a surfactant were added to 62.4 g of deionized water, and the mixture was stirred at 300 rpm for 20 min to obtain a nano-formaldehyde-removing negative ion purification liquid;

[0072] The deodorant used in this embodiment is eucalyptus essential oil; the surfactant used is Triton X-100.

[0073] Example 2

[0074] 4 g of the silicon-cerium co-doped nano-titanium dioxide prepared in Preparation Example 2.1, 4 g of the cerium-doped manganese oxide nanocomposite prepared in Preparation Example 3.1, 28 g of the natural plant extract prepared in Preparation Example 1.1, 1.5 g of a deodorant, and 0.7 g of a surfactant were added to 61.8 g of deionized water, and the mixture was stirred at 400 rpm for 12 min to obtain a nano-formaldehyde-removing negative ion purification liquid;

[0075] The deodorant used in this embodiment is eucalyptus essential oil; the surfactant used is Triton X-100.

[0076] Example 3

[0077] 4.5 g of the silicon-cerium co-doped nano-titanium dioxide prepared in Preparation Example 2.1, 4.5 g of the cerium-doped manganese oxide nanocomposite prepared in Preparation Example 3.1, 25 g of the natural plant extract prepared in Preparation Example 1.1, 2 g of a deodorant, and 0.8 g of a surfactant were added to 63.2 g of deionized water, and the mixture was stirred at 450 rpm for 15 min to obtain a nano-formaldehyde-removing negative ion purification liquid;

[0078] The deodorant used in this embodiment is eucalyptus essential oil; the surfactant used is Triton X-100.

[0079] Example 4

[0080] 5 g of the silicon-cerium co-doped nano-titanium dioxide prepared in Preparation Example 2.1, 5 g of the cerium-doped manganese oxide nanocomposite prepared in Preparation Example 3.1, 22 g of the natural plant extract prepared in Preparation Example 1.1, 2.5 g of a deodorant, and 0.9 g of a surfactant were added to 64.6 g of deionized water, and the mixture was stirred at 500 rpm for 18 min to obtain a nano-formaldehyde-removing negative ion purification liquid;

[0081] The deodorant used in this embodiment is eucalyptus essential oil; the surfactant used is Triton X-100.

[0082] Example 5

[0083] 6 g of the silicon-cerium co-doped nano-titanium dioxide prepared in Preparation Example 2.1, 6 g of the cerium-doped manganese oxide nanocomposite prepared in Preparation Example 3.1, 20 g of the natural plant extract prepared in Preparation Example 1.1, 3 g of a deodorant, and 1 g of a surfactant were added to 64 g of deionized water, and the mixture was stirred at 600 rpm for 20 min to obtain a nano-formaldehyde-removing negative ion purification liquid;

[0084] The deodorant used in this embodiment is eucalyptus essential oil; the surfactant used is Triton X-100.

[0085] Example 6

[0086] The difference between Example 6 and Example 1 is that the natural plant extract used in Example 6 comes from Preparation Example 1.2.

[0087] Example 7

[0088] The difference between Example 7 and Example 1 is that the natural plant extract used in Example 7 comes from Preparation Example 1.3.

[0089] Example 8

[0090] The difference between Example 8 and Example 1 is that the silicon-cerium co-doped nano-titanium dioxide used in Example 8 comes from Preparation Example 2.2.

[0091] Example 9

[0092] The difference between Example 9 and Example 1 is that the silicon-cerium co-doped nano-titanium dioxide used in Example 9 comes from Preparation Example 2.3.

[0093] Example 10

[0094] The difference between Example 10 and Example 1 is that the cerium-doped manganese oxide nanocomposite material used in Example 10 comes from Preparation Example 3.2.

[0095] Example 11

[0096] The difference between Example 11 and Example 1 is that the cerium-doped manganese oxide nanocomposite material used in Example 10 comes from Preparation Example 3.3.

[0097] Example 12

[0098] The difference between Example 12 and Example 1 is that the deodorant used in Example 12 is zinc ricinoleate.

[0099] Example 13

[0100] The difference between Example 13 and Example 1 is that the deodorant used in Example 13 is soy ethyl sulfate.

[0101] Comparative Example 1

[0102] The difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, an equal amount of unmodified nano-titanium dioxide is used instead of silicon-cerium co-doped nano-titanium dioxide.

[0103] Comparative Example 2

[0104] The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, silicon-cerium co-doped nano-titanium dioxide is not added, and an equal amount of deionized water is used instead.

[0105] Comparative Example 3

[0106] The difference between Comparative Example 3 and Example 1 is that in Comparative Example 3, no cerium-doped manganese oxide nanocomposite material is added, and an equal amount of deionized water is used instead.

[0107] Comparative Example 4

[0108] The difference between Comparative Example 4 and Example 1 is that no natural plant extract is added in Comparative Example 4, and an equal amount of deionized water is used instead.

[0109] Performance testing

[0110] 1. Referring to the JC / T 1074-2021 "Purification Performance of Indoor Air Purification Functional Coating Materials" standard, the formaldehyde purification rate and formaldehyde purification durability of the nano formaldehyde-removing negative ion purification liquid prepared in Examples 1-13 and Comparative Examples 1-4 were tested. The results are shown in Table 1.

[0111] 2. Referring to the standard HG / T 4109-2009 "Negative Ion Functional Coatings", the air negative ion induction amount of the nano-formaldehyde-removing negative ion purification liquid prepared in Examples 1-13 and Comparative Examples 1-4 was tested. The results are shown in Table 1.

[0112] 3. Referring to the HG / T 3950-2007 Antibacterial Coatings standard, the antibacterial rates of Escherichia coli and Staphylococcus aureus of the nano-formaldehyde-removing negative ion purification liquids prepared in Examples 1-13 and Comparative Examples 1-4 were tested. The results are shown in Table 1.

[0113] The specific test results are as follows:

[0114] Table 1 Performance test results

[0115]

[0116]

[0117] It can be seen from the test results in Table 1 that the nano formaldehyde removal negative ion purification liquid provided by the present application has a significant formaldehyde removal effect and can efficiently remove formaldehyde; and the formaldehyde removal effect is long-lasting and stable, which can ensure that good formaldehyde removal performance can be maintained after long-term use; its negative ion induction effect is excellent, and it can effectively release negative ions and improve air quality; the nano formaldehyde removal negative ion purification liquid provided by the present application also has excellent antibacterial properties, which can significantly reduce bacterial growth.

[0118] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A nanometer formaldehyde-removing negative ion purification liquid, characterized in that: The raw materials include, by mass percentage, 3-6% of silicon-cerium co-doped nano titanium dioxide, 3-6% of cerium-doped manganese oxide nano composite material, 20-30% of natural plant extract, 1-3% of deodorant, 0.6-0.1% of surfactant, and the balance being deionized water.

2. A nanometer formaldehyde-removing negative ion purification liquid according to claim 1, characterized in that: The natural plant extract is extracted from Machilus thunbergii, Pleistocene chinensis and Pinus massoniana; the mass ratio of Machilus thunbergii, Pleistocene chinensis and Pinus massoniana is 1:(0.6-1.2):(0.8-1.4).

3. A nanometer formaldehyde-removing negative ion purification liquid according to claim 2, characterized in that: The preparation method of the natural plant extract comprises the following steps: S1. The black shell Nan, golden pine and masson pine raw materials were washed, dried and crushed, then added to an ethanol solution, flash extracted 2-10min, filtered to obtain a residue and a filtrate; S2. The filtrate is filtered through a microporous membrane and then eluted with deionized water to obtain an eluate; S3. After the eluate is subjected to reduced pressure distillation to recover the solvent, a natural plant extract is obtained.

4. The method for preparing a nanometer formaldehyde-removing negative ion purification liquid according to claim 3, wherein: The raw materials of Machilus nigra, Pine Pine and Pinus massoniana are Machilus nigra leaves, Pine Pine seeds and Pinus massoniana needles.

5. The nanometer formaldehyde-removing negative ion purification liquid according to claim 1, characterized in that: The silicon-cerium co-doped nano-titanium dioxide is prepared from the following raw materials in parts by weight: 20-30 parts of deionized water, 40-60 parts of ethanol, 5-10 parts of acetic acid, 0.3-0.6 parts of tetraethyl silicate, 0.018-0.036 parts of cerium nitrate hexahydrate, and 2.48-4.96 parts of tetrabutyl titanate.

6. A nanometer formaldehyde-removing negative ion purification liquid according to claim 5, characterized in that: The preparation method of silicon-cerium co-doped nano-titanium dioxide comprises the following steps: Deionized water, ethanol and acetic acid are mixed and stirred evenly at room temperature. Tetraethyl silicate and cerium nitrate hexahydrate are added in sequence and stirred continuously until completely dissolved. Stirring is continued and tetrabutyl titanate is added dropwise to obtain a mixed solution. The mixed solution is transferred to a hydrothermal reactor and heated at 160-180° C. for 12-16 hours. After the reaction is completed, the mixture is naturally cooled to room temperature. The solid product is collected by centrifugation. The solid product is then washed alternately with deionized water and ethanol for several times and then dried in a vacuum at 60-70° C. for 12-16 hours to obtain silicon-cerium co-doped nano-titanium dioxide.

7. The nanometer formaldehyde-removing negative ion purification liquid according to claim 1, characterized in that: The cerium-doped manganese oxide nanocomposite material is prepared from the following raw materials in parts by weight: 2-5 parts of potassium permanganate, 4.8-12 parts of cerium nitrate hexahydrate, 0.3-0.75 parts of glucose, and 215-430 parts of pure water.

8. A nanometer formaldehyde-removing negative ion purification liquid according to claim 7, characterized in that: The preparation method of the cerium-doped manganese oxide nanocomposite material comprises the following steps: Add 2-5 parts of potassium permanganate to 200-400 parts of pure water and stir until completely dissolved to obtain a potassium permanganate solution; Add 4.8-12 parts of cerium nitrate hexahydrate to 10-20 parts of pure water and stir until completely dissolved to obtain a cerium nitrate solution; Add 0.3-0.75 parts of glucose to 5-10 parts of pure water and stir until completely dissolved to obtain a glucose solution; A cerium nitrate solution and a glucose solution are added dropwise to a potassium permanganate solution, and the mixture is stirred for 20-30 minutes to obtain a mixed solution; the mixed solution is reacted for 30-60 minutes under the conditions of an ultrasonic power of 800-1000W, a microwave power of 600-800W, and a reaction temperature of 75-85°C; after the reaction is completed, a solid product is collected by centrifugation, and the solid product is washed alternately with deionized water and ethanol several times, and then vacuum dried at 60-70°C for 10-12 hours to obtain a cerium-doped manganese oxide nanocomposite material.

9. The nanometer formaldehyde-removing negative ion purification liquid according to claim 1, characterized in that: The deodorant is one of plant essential oil, zinc ricinoleate and soybean ethyl sulfate.

10. The method for preparing a nanometer formaldehyde-removing negative ion purification liquid according to any one of claims 1 to 9, characterized in that: The following steps are involved: Silicon-cerium co-doped nano titanium dioxide, cerium-doped manganese oxide nanocomposite material, natural plant extract, deodorant and surfactant are added into deionized water, and mixed and stirred at 300-600 rpm for 10-20 minutes to obtain nano formaldehyde-removing negative ion purification liquid.

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