Manganese dioxide and activated carbon nano composite material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of environment-friendly materials, and particularly relates to a manganese dioxide-activated carbon nanocomposite and a preparation method and application thereof. Activated carbon, an acidic potassium permanganate solution and a reducing agent are mixed for a reduction reaction, and a reduction reaction solution is obtained; and dropwise adding a hydrogen peroxide solution into the reduction reaction solution for oxidation reaction to obtain the manganese dioxide-activated carbon nano composite material. The prepared manganese dioxide and activated carbon composite material has the advantages of good formaldehyde removal performance, high formaldehyde removal rate, large clean air amount, excellent cycle performance, simple preparation process, low cost, wide application environment, safety, high efficiency and stable performance. Results of the embodiment show that the 1h removal rate of the manganese dioxide and activated carbon provided by the invention on formaldehyde reaches 92.5%, the clean air amount can reach 700m < 3 > / h, and after five purification-thermal regeneration cycles, the removal rate on formaldehyde is still 90% or above, and the clean air amount is 660m < 3 > / h or above.

Description

Technical Field

[0001] The invention belongs to the technical field of environmentally friendly materials, and specifically relates to a manganese dioxide@activated carbon nanocomposite material and a preparation method and application thereof. Background Art

[0002] Formaldehyde is a colorless gas with a strong pungent odor. Indoor formaldehyde mainly comes from artificial boards, such as particleboard, medium-density fiberboard and plywood. The adhesives used in the manufacturing process of these boards contain formaldehyde. Other sources include paint, varnish, certain types of carpets, and some furniture and decorations. Formaldehyde is listed as a Class I carcinogen by the International Agency for Research on Cancer. Long-term exposure to high concentrations of formaldehyde can cause irritation to the eyes, nose and throat, and even cause chronic respiratory diseases.

[0003] Therefore, in order to protect human health, it is necessary to develop corresponding technologies to remove formaldehyde. At present, the treatment methods used for indoor air purification mainly include biological purification, photocatalytic degradation, adsorption and catalytic oxidation.

[0004] Biological purification refers to the use of the characteristics of plants or microorganisms that use organic matter as a carbon source to capture and transform formaldehyde. However, the biological activity is significantly affected by the environment, and the formaldehyde removal efficiency is low. Photocatalytic degradation relies on photocatalysts and often requires light, especially ultraviolet light. When ultraviolet light conditions are poor, the formaldehyde removal efficiency is low. The adsorption method is a treatment technology with low energy consumption, simple operation, and strong environmental adaptability. However, the current adsorbents have average adsorption performance and low formaldehyde removal efficiency. The catalytic oxidation method is a technology that uses catalysts to oxidize formaldehyde into carbon dioxide and water, but catalysts with better catalytic effects at room temperature often require the addition of precious metals, which are more expensive.

[0005] In summary, the current formaldehyde removal has the disadvantages of low removal efficiency and high cost. Summary of the invention

[0006] The object of the present invention is to provide a manganese dioxide@activated carbon nanocomposite material and a preparation method and application thereof. The manganese dioxide@activated carbon nanocomposite material provided by the present invention has good formaldehyde removal performance, high formaldehyde removal rate and clean air volume, wide application occasions, low preparation cost, can be regenerated and recycled, has high cycle stability and stable formaldehyde removal performance.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a manganese dioxide@activated carbon nanocomposite material, comprising the following steps:

[0009] The activated carbon, the acidic potassium permanganate solution and the reducing agent are mixed to carry out a reduction reaction to obtain a reduction reaction liquid;

[0010] A hydrogen peroxide solution is added dropwise to the reduction reaction solution to carry out an oxidation reaction, thereby obtaining a manganese dioxide@activated carbon nanocomposite material.

[0011] Preferably, the activated carbon includes one or more of fruit shell activated carbon, coal activated carbon and wood activated carbon; the mesh size of the activated carbon is 30 to 60 meshes;

[0012] The activated carbon is pretreated activated carbon, and the moisture content of the pretreated activated carbon is 0.1-30wt%; the pretreated activated carbon is obtained by washing the activated carbon with water and then drying it; the drying temperature is 40-150°C and the drying time is 4-48h.

[0013] Preferably, the molar concentration of potassium permanganate in the acidic potassium permanganate solution is 2.5×10 -3 ~2.5×10 - 1 mol / L; the pH value of the acidic potassium permanganate solution is 3-5.

[0014] Preferably, the mass ratio of the activated carbon to the potassium permanganate in the acidic potassium permanganate solution is (10:1) to (30:1).

[0015] Preferably, the reducing agent is ethanol, and the molar ratio of the reducing agent to the potassium permanganate in the acidic potassium permanganate solution is 1 to 5:1.

[0016] Preferably, the mass content of the hydrogen peroxide solution is 1-5%, and the molar ratio of the hydrogen peroxide in the hydrogen peroxide solution to the potassium permanganate in the acidic potassium permanganate solution is (5:2)-(0.5:1).

[0017] Preferably, the temperature of the reduction reaction and the oxidation reaction are independently 10-50°C, and the time is independently 6-18h; the reduction reaction and the oxidation reaction are carried out under stirring conditions, and the stirring speed of the reduction reaction and the oxidation reaction is independently 600-1500rpm.

[0018] The present invention provides a manganese dioxide@activated carbon nanocomposite material prepared by the preparation method described in the above technical solution, comprising activated carbon and manganese dioxide nanosheets in-situ grown on the surface of the activated carbon.

[0019] The present invention provides the use of the manganese dioxide@activated carbon nanocomposite material described in the above technical solution in the catalytic oxidation of formaldehyde.

[0020] Preferably, the application comprises the following steps:

[0021] The manganese dioxide@activated carbon nanocomposite material is used for catalytic oxidation of formaldehyde;

[0022] The used manganese dioxide@activated carbon nanocomposite material is regenerated in hot air and then reused; the temperature of the hot air is 100-105° C., and the regeneration time is 0.5-10 hours.

[0023] The present invention provides a method for preparing a manganese dioxide @ activated carbon nanocomposite material, comprising the following steps: mixing activated carbon, an acidic potassium permanganate solution and a reducing agent to carry out a reduction reaction to obtain a reduction reaction liquid; and dripping a hydrogen peroxide solution into the reduction reaction liquid to carry out an oxidation reaction to obtain a manganese dioxide @ activated carbon nanocomposite material. The present invention adopts an in-situ synthesis method to prepare the manganese dioxide @ activated carbon nanocomposite material, wherein the activated carbon provides support for the manganese dioxide, while increasing the contact area between the manganese dioxide and formaldehyde, thereby increasing the mass transfer and reaction rate of formaldehyde and improving the utilization rate of the catalytic sites of the manganese dioxide. In addition, the present invention adopts a reduction-oxidation two-step method to prepare manganese dioxide, wherein potassium permanganate is first reduced by a reducing agent to generate loose flaky δ-MnO 2 Then, hydrogen peroxide is used to oxidize the Mn generated by the over-reduction reaction in the first step. 3+ , improve its oxidation state. The preparation method provided by the present invention is conducive to the slow nucleation and growth of manganese dioxide to form delta crystal MnO 2 On the other hand, it can increase its oxidation state, ensuring a stronger catalytic oxidation performance. In addition, the manganese dioxide generated by the preparation method provided by the present invention can exist stably without causing damage to the product.

[0024] At the same time, the preparation method provided by the present invention loads manganese dioxide on activated carbon, does not require high temperature and high pressure, is simple to operate, has low energy consumption, low requirements on equipment conditions, and is highly safe. In addition, the in-situ grown manganese dioxide nanosheets are firmly bonded to the surface of the activated carbon and are not easy to fall off during production and use, making it easy to realize industrial production.

[0025] The present invention provides a manganese dioxide @ activated carbon nanocomposite material prepared by the preparation method described in the above technical solution, comprising activated carbon and manganese dioxide nanosheets grown in situ on the surface of the activated carbon. The manganese dioxide @ activated carbon composite material provided by the present invention has good formaldehyde removal performance, high formaldehyde removal rate, large clean air volume, excellent circulation performance, simple preparation process and low cost, wide application environment, safety and high efficiency, and stable performance. The results of the embodiment show that the 1h formaldehyde removal rate of the manganese dioxide @ activated carbon provided by the present invention reaches 92.5%, and the clean air volume can reach 700m 3 / h, and after five purification-heat regeneration cycles, the formaldehyde removal rate is still above 90%, and the clean air volume is 660m 3 / h or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a morphology diagram of manganese dioxide prepared in Comparative Example 5 of the present invention;

[0027] Figure 2 The surface morphology of coconut shell activated carbon used in Example 2 of the present invention;

[0028] Figure 3 This is the surface morphology of manganese dioxide@activated carbon prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0029] The present invention provides a method for preparing a manganese dioxide@activated carbon nanocomposite material, comprising the following steps:

[0030] The activated carbon, the acidic potassium permanganate solution and the reducing agent are mixed to carry out a reduction reaction to obtain a reduction reaction liquid;

[0031] A hydrogen peroxide solution is added dropwise to the reduction reaction solution to carry out an oxidation reaction, thereby obtaining a manganese dioxide@activated carbon nanocomposite material.

[0032] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0033] The invention mixes activated carbon, acidic potassium permanganate solution and a reducing agent to carry out a reduction reaction to obtain a reduction reaction liquid.

[0034] In the present invention, the activated carbon preferably includes one or more of fruit shell activated carbon, coal activated carbon and wood activated carbon. The mesh size of the activated carbon is preferably 30 to 60 meshes. The specific surface area of ​​the activated carbon is preferably 700 to 2000 m 2 / g, more preferably 900 to 1800 m 2 / g, the average pore size is preferably 0.15 to 5 nm, more preferably 1 to 4 nm, and the total pore volume is preferably greater than 0.35 cm 3 / g.

[0035] In the present invention, the activated carbon is preferably pretreated activated carbon. The moisture content of the pretreated activated carbon is preferably 0.1 to 30wt%, more preferably 0.5 to 25wt%. The pretreated activated carbon is preferably obtained by washing the activated carbon with water and then drying it (hereinafter referred to as the first drying). The water used for the water washing is preferably distilled water. The number of water washings is preferably 1 to 20 times, more preferably 3 to 10 times. The temperature of the first drying is preferably 40 to 150°C, more preferably 60 to 120°C. The time of the first drying is preferably 4 to 48h, more preferably 8 to 36h. The present invention preferably uses the pretreated activated carbon obtained by washing the activated carbon with water and then drying it as the raw material for the reduction reaction. The present invention can remove a large amount of dust and water-soluble impurities contained on the surface of the activated carbon by water washing, avoid the clogging of the pore structure of the activated carbon by dust and impurities, release the surface active sites, and at the same time facilitate the loading of manganese dioxide in the subsequent steps.

[0036] In the present invention, the molar concentration of potassium permanganate in the acidic potassium permanganate solution is preferably 2.5×10 -3 ~2.5×10 -1 mol / L, more preferably 10 -2 ~5×10 -2 mol / L, in the embodiment, it can be 2.5×10 -2 mol / L or 12.5×10 -2 mol / L. The pH value of the acidic potassium permanganate solution is 3 to 5. The acidic potassium permanganate solution preferably comprises potassium permanganate, glacial acetic acid and water. The present invention preferably uses glacial acetic acid to adjust the pH value of the acidic potassium permanganate solution to 3 to 5, which can be 3.5 or 4 in the embodiment. The present invention can maintain a strong oxidizing property of potassium permanganate by controlling the pH value of the acidic potassium permanganate to 3 to 5, and the generated manganese dioxide is more stable.

[0037] In the present invention, the mass ratio of the activated carbon to the potassium permanganate in the acidic potassium permanganate solution is preferably (10:1) to (30:1), more preferably (15:1) to (20:1), and in the embodiments it can be 15:1 or 20:1.

[0038] In the present invention, the reducing agent is preferably ethanol. The present invention uses ethanol as a reducing agent to slowly oxidize potassium permanganate through ethanol to generate loose flaky δ-MnO 2 The present invention uses ethanol as a reducing agent, which is more conducive to the slow nucleation and generation of manganese dioxide to form delta crystal MnO 2 δ-MnO 2It is the crystal form with the best formaldehyde catalytic oxidation effect. Thus, the efficiency of removing formaldehyde by the obtained manganese dioxide@activated carbon nanocomposite material is improved. The present invention uses ethanol as a reducing agent, and acetic acid is generated after the reduction reaction, which does not generate additional processing costs.

[0039] In the present invention, the molar ratio of the reducing agent to the potassium permanganate in the acidic potassium permanganate solution is preferably 1 to 5:1, and in the embodiment it can be 2:1.

[0040] In the present invention, the temperature of the reduction reaction is preferably 10 to 50°C, more preferably 15 to 30°C, and in the embodiment, it can be room temperature; the time of the reduction reaction is preferably 6 to 18 hours, more preferably 8 to 12 hours. The reduction reaction is carried out under stirring, and the stirring speed of the reduction reaction is preferably 600 to 1500 rpm, more preferably 900 to 1200 rpm.

[0041] After obtaining the reduction reaction liquid, the present invention drips a hydrogen peroxide solution into the reduction reaction liquid to carry out an oxidation reaction, thereby obtaining the manganese dioxide@activated carbon nanocomposite material.

[0042] In the present invention, the mass content of the hydrogen peroxide solution is preferably 1 to 5%, and in the embodiment it can be 3%. The hydrogen peroxide solution is an aqueous hydrogen peroxide solution. The molar ratio of the hydrogen peroxide in the hydrogen peroxide solution to the potassium permanganate in the acidic potassium permanganate solution is preferably (5:2) to (0.5:1), more preferably (2:1) to (1:1), and in the embodiment it can be 0.8:1. The present invention has no special requirements for the dripping speed of the hydrogen peroxide solution, as long as no large amount of bubbles are generated.

[0043] In the present invention, the temperature of the oxidation reaction is preferably 10 to 50°C, more preferably 15 to 30°C, and in the embodiment, it can be room temperature; the time of the oxidation reaction is preferably 6 to 18 hours, more preferably 8 to 12 hours. The time of the oxidation reaction is calculated after the dropwise addition is completed. The oxidation reaction is carried out under stirring, and the stirring speed of the oxidation reaction is preferably 600 to 1500 rpm, more preferably 900 to 1200 rpm, and in the embodiment, it can be 1000 rpm.

[0044] In the present invention, the oxidation reaction liquid is directly obtained after the oxidation reaction is completed. The present invention preferably performs solid-liquid separation, water washing and drying (hereinafter referred to as the second drying) on ​​the oxidation reaction liquid in sequence to obtain the manganese dioxide @ activated carbon nanocomposite material. In the present invention, the solid-liquid separation is preferably filtration. The second drying temperature is preferably 40 to 120°C, more preferably 70 to 110°C, the second drying time is preferably 4 to 48h, more preferably 8 to 24h, and in the embodiment it can be 12h; after drying is completed, cool to room temperature; the moisture content of the manganese dioxide @ activated carbon composite material obtained after drying is preferably 0.1 to 30wt%, more preferably 0.5 to 25wt%.

[0045] The present invention provides a manganese dioxide@activated carbon nanocomposite material prepared by the preparation method described in the above technical solution, comprising activated carbon and manganese dioxide nanosheets in-situ grown on the surface of the activated carbon.

[0046] The manganese dioxide@activated carbon nanocomposite provided by the present invention includes activated carbon. In the present invention, the activated carbon provides support for manganese dioxide nanosheets, while increasing the contact area between manganese dioxide and formaldehyde, increasing the mass transfer and reaction rate of formaldehyde, and improving the utilization rate of manganese dioxide catalytic sites.

[0047] The manganese dioxide@activated carbon nanocomposite provided by the present invention comprises manganese dioxide nanosheets grown in situ on the surface of the activated carbon. The manganese dioxide nanosheets are δ-crystalline MnO 2 The nanosheets have excellent formaldehyde catalytic oxidation performance. At the same time, the manganese dioxide nanosheets are in-situ grown on the surface of the activated carbon. The manganese dioxide nanosheets are firmly combined with the surface of the activated carbon, are not easy to fall off during production and use, and have a long service life.

[0048] The manganese dioxide@activated carbon nanocomposite material provided by the invention has the advantages of simple preparation method, low energy consumption, good formaldehyde removal performance, high formaldehyde removal rate and excellent cycle performance.

[0049] The present invention provides the use of the manganese dioxide@activated carbon nanocomposite material described in the above technical solution in the catalytic oxidation of formaldehyde. The present invention has no special requirements for the method of the application, and the application can be carried out by a method well known to those skilled in the art. In a specific embodiment of the present invention, the application preferably includes the following steps: using the manganese dioxide@activated carbon nanocomposite material for the catalytic oxidation of formaldehyde.

[0050] The present invention provides the application of the manganese dioxide @ activated carbon nanocomposite material described in the above technical solution in the removal of formaldehyde. The present invention has no special requirements for the method of the application, and can be applied by methods familiar to those skilled in the art. In the present invention, the application preferably includes the following steps: preparing the manganese dioxide @ activated carbon nanocomposite material into a filter element, assembling it into an air purifier for use. The present invention has no special requirements for the specific structure of the air purifier, and can use an air purifier with a structure familiar to those skilled in the art.

[0051] The present invention also provides the application of the manganese dioxide @ activated carbon nanocomposite material of the above technical solution in the field of indoor air purification. The present invention has no special requirements for the method of the application, and can be applied by methods familiar to those skilled in the art. In the present invention, the application preferably includes the following steps: preparing the manganese dioxide @ activated carbon nanocomposite material into a filter element, assembling it into an air purifier for use. The present invention has no special requirements for the specific structure of the air purifier, and can use an air purifier with a structure familiar to those skilled in the art.

[0052] In the present invention, the application preferably also includes:

[0053] The used manganese dioxide@activated carbon nanocomposite material is regenerated in hot air and reused. The temperature of the hot air is 100-105°C, and the regeneration time is 0.5-10 hours. The present invention desorbs moisture, formaldehyde and reaction intermediates in the pores of manganese dioxide@activated carbon by regeneration in hot air, and the regenerated manganese dioxide@activated carbon is reused.

[0054] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0055] Example 1

[0056] The coal-based activated carbon with a particle size of 40 mesh (specific surface area of ​​1450 m 2 / g, the average pore diameter is 2.5nm, and the total pore volume is 0.53m 3 / g) was washed once with distilled water and then dried in an oven at 120°C for 36 h to a moisture content of 2 wt %, to obtain pretreated activated carbon.

[0057] Under stirring, adjust the pH of 400 mL of water to 4.0 with glacial acetic acid, add potassium permanganate (2.5 × 10 -2mol / L) as a manganese source, add pretreated activated carbon in a ratio of activated carbon to potassium permanganate of 15:1, then add anhydrous ethanol (the molar ratio of ethanol to potassium permanganate is 2:1) as a reducing agent, and stir at 1000rpm for 8h; according to the molar ratio of hydrogen peroxide to potassium permanganate of 0.8:1, dilute 30wt% hydrogen peroxide solution to 3wt%, add dropwise to the solution, and then continue to stir at 1000rpm for 8h; filter the product suspension, wash with water, and dry at 80℃ for 12h to obtain a manganese dioxide@activated carbon nanocomposite material.

[0058] The manganese dioxide @ activated carbon is used for catalytic oxidation of formaldehyde, and the used manganese dioxide @ activated carbon is regenerated and reused. The regeneration method of manganese dioxide @ activated carbon is: the used manganese dioxide @ activated carbon is treated under hot air at 105°C for 3 hours.

[0059] According to the test requirements of GB / T 18801-2015 "Air Purifier", the clean air volume (CADR formaldehyde) of manganese dioxide @ activated carbon was tested and the formaldehyde removal rate was calculated. The results showed that the one-hour formaldehyde removal rate of manganese dioxide @ activated carbon reached 88.6%, and the clean air volume could reach 675m 3 / h. After five purification-heat regeneration cycles, the formaldehyde removal rate was 85.4% and the clean air volume was 630m 3 / h.

[0060] Example 2

[0061] Coconut shell activated carbon with a particle size of 50 mesh (electron microscope photo as shown in Figure 2 As shown, the specific surface area is 1750m 2 / g, the average pore diameter is 3.2nm, and the total pore volume is 0.59m 3 / g) was washed 13 times with distilled water and then dried in an oven at 105°C for 24 h to a moisture content of 2% to obtain pretreated activated carbon.

[0062] Under stirring, adjust the pH of 400 mL of water to 3.5 with glacial acetic acid, add potassium permanganate (2.5 × 10 -2mol / L) as a manganese source, add pretreated activated carbon according to the ratio of activated carbon: potassium permanganate mass ratio of 15:1, then add 1mL of anhydrous ethanol (the molar ratio of ethanol to potassium permanganate is 2:1) as a reducing agent, and stir at 1000rpm for 12h; according to the molar ratio of hydrogen peroxide: potassium permanganate of 0.8:1, dilute 30wt% hydrogen peroxide solution to 3wt%, add dropwise to the solution, and then continue to stir at 1000rpm for 12h; filter the product suspension, wash with water, and dry at 110℃ for 12h to obtain a manganese dioxide@activated carbon nanocomposite material. The electron microscope photograph of the manganese dioxide@activated carbon nanocomposite material prepared in this embodiment is shown in Figure 3 shown.

[0063] The manganese dioxide @ activated carbon is used for catalytic oxidation of formaldehyde, and the used manganese dioxide @ activated carbon is regenerated and reused. The regeneration method of the manganese dioxide @ activated carbon is: the used manganese dioxide @ activated carbon is treated in hot air at 105°C for 6 hours.

[0064] The removal rate and clean air volume of the obtained manganese dioxide @ activated carbon were tested according to the method in Example 1. The results showed that the one-hour removal rate of formaldehyde by manganese dioxide @ activated carbon reached 92.5%, and the clean air volume could reach 700m 3 / h. After five purification-heat regeneration cycles, the formaldehyde removal rate is still as high as 90.2%, and the clean air volume is 664m 3 / h.

[0065] Comparative Example 1

[0066] The other conditions were the same as those in Example 2, except that the step of adjusting the pH was omitted, and the reactants were directly added to load the activated carbon.

[0067] The removal rate and clean air volume of manganese dioxide @ activated carbon obtained in comparative example 1 were tested according to the method in example 1. The results showed that the one-hour removal rate of formaldehyde by manganese dioxide @ activated carbon was 60%, and the clean air volume was 450m 3 / h. After five purification-heat regeneration cycles, the formaldehyde removal rate is 55% and the clean air volume is 380m 3 The results show that the present invention controls the pH of the reaction system within the acidic range, which is beneficial to enhancing the oxidizability of potassium permanganate and increasing the loading amount of manganese dioxide nanosheets on the surface of activated carbon, thereby improving the formaldehyde removal ability.

[0068] Comparative Example 2

[0069] The other conditions were the same as those in Example 2, except that hydrogen peroxide was not added and stirring was continued directly.

[0070] The removal rate and clean air volume of manganese dioxide @ activated carbon obtained in comparative example 2 were tested according to the method in example 1. The results showed that the one-hour removal rate of formaldehyde by manganese dioxide @ activated carbon was 78%, and the clean air volume was 530m 3 / h. After five purification-heat regeneration cycles, the formaldehyde removal rate is 70% and the clean air volume is 500m 3 The results show that in the reduction-oxidation two-step method adopted by the present invention, the addition of hydrogen peroxide is beneficial to further improve the oxidation state of manganese, increase the lattice oxygen content in the manganese dioxide nanosheets, and thus enhance its catalytic oxidation ability for formaldehyde.

[0071] Example 3

[0072] The other conditions were the same as those in Example 2, except that the mass ratio of activated carbon to potassium permanganate was adjusted to 20:1.

[0073] The removal rate and clean air volume of manganese dioxide @ activated carbon obtained in Example 3 were tested according to the method in Example 1. The results showed that the one-hour removal rate of formaldehyde by manganese dioxide @ activated carbon was 85%, and the clean air volume was 650m 3 / h. After five purification-heat regeneration cycles, the formaldehyde removal rate was 82.4% and the clean air volume was 625m 3 / h.

[0074] Example 4

[0075] The other conditions were the same as those in Example 2, except that the amounts of potassium permanganate and activated carbon were increased by 5 times, that is, the potassium permanganate concentration was 12.5×10 -2 mol / L, the mass ratio of activated carbon to potassium permanganate was maintained at 15:1, and the rotation speed was appropriately increased to 1200rpm.

[0076] The removal rate and clean air volume of manganese dioxide @ activated carbon obtained in Example 4 were tested according to the method in Example 1. The results showed that the one-hour removal rate of formaldehyde by manganese dioxide @ activated carbon was 90.7%, and the clean air volume was 680m 3 / h. After five purification-heat regeneration cycles, the formaldehyde removal rate was 88.6% and the clean air volume was 650m 3 / h.

[0077] Comparative Example 3

[0078] Under stirring, adjust the pH of 400 mL of water to 3.5 with glacial acetic acid, add potassium permanganate (2.5 × 10 -2mol / L) as a manganese source, then add 1 mL of anhydrous ethanol (the molar ratio of ethanol to potassium permanganate is 2:1) as a reducing agent, and stir at 1000 rpm for 12 h; according to the molar ratio of hydrogen peroxide to potassium permanganate of 0.8:1, dilute 30% hydrogen peroxide solution to 3%, add dropwise to the solution, and then continue to stir at 1000 rpm for 12 h; filter the product suspension, wash with water, and dry at 110°C for 12 h to obtain a manganese dioxide material. The morphology of the manganese dioxide prepared in this comparative example is as follows Figure 1 As shown. Figure 1 It can be seen that the pure manganese dioxide prepared in this comparative example without adding activated carbon has a flower-like morphology.

[0079] From the above examples, it can be seen that the present invention adopts a room temperature oxidation-reduction two-step method to prepare manganese dioxide, and loads layered manganese dioxide on the surface of activated carbon by in-situ growth to obtain a manganese dioxide @ activated carbon nanocomposite material. The obtained manganese dioxide @ activated carbon material has good formaldehyde removal performance, high formaldehyde removal rate and clean air volume, wide application occasions, low preparation cost, regeneration and recycling, high cycle stability, and stable formaldehyde removal performance. The results of the examples show that the 1h formaldehyde removal rate of the manganese dioxide @ activated carbon provided by the present invention reaches 92.5%, and the clean air volume can reach 700m 3 / h, and after five purification-heat regeneration cycles, the formaldehyde removal rate is still above 90%, and the clean air volume is 660m 3 / h or more.

[0080] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a manganese dioxide@activated carbon nanocomposite material, characterized in that: The following steps are involved: The activated carbon, the acidic potassium permanganate solution and the reducing agent are mixed to carry out a reduction reaction to obtain a reduction reaction liquid; A hydrogen peroxide solution is added dropwise to the reduction reaction solution to carry out an oxidation reaction, thereby obtaining a manganese dioxide@activated carbon nanocomposite material.

2. The preparation method according to claim 1, characterized in that: The activated carbon includes one or more of fruit shell activated carbon, coal-based activated carbon and wood-based activated carbon; the mesh size of the activated carbon is 30 to 60 meshes; The activated carbon is pretreated activated carbon, and the moisture content of the pretreated activated carbon is 0.1-30wt%; the pretreated activated carbon is obtained by washing the activated carbon with water and then drying it; the drying temperature is 40-150°C and the drying time is 4-48h.

3. The preparation method according to claim 1, characterized in that: The molar concentration of potassium permanganate in the acidic potassium permanganate solution is 2.5×10 -3 ~2.5×10 -1 mol / L; the pH value of the acidic potassium permanganate solution is 3-5.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The mass ratio of the activated carbon to the potassium permanganate in the acidic potassium permanganate solution is (10:1) to (30:1).

5. The preparation method according to claim 1 or 3, characterized in that: The reducing agent is ethanol, and the molar ratio of the reducing agent to the potassium permanganate in the acidic potassium permanganate solution is 1 to 5:

1.

6. The preparation method according to claim 1 or 3, characterized in that: The mass content of the hydrogen peroxide solution is 1-5%, and the molar ratio of the hydrogen peroxide in the hydrogen peroxide solution to the potassium permanganate in the acidic potassium permanganate solution is (5:2)-(0.5:1).

7. The preparation method according to claim 1 is characterized in that: The temperature of the reduction reaction and the oxidation reaction are independently 10-50°C, and the time is independently 6-18h; the reduction reaction and the oxidation reaction are carried out under stirring conditions, and the stirring speed of the reduction reaction and the oxidation reaction is independently 600-1500rpm.

8. The manganese dioxide@activated carbon nanocomposite material prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The invention comprises activated carbon and manganese dioxide nanosheets in-situ grown on the surface of the activated carbon.

9. Use of the manganese dioxide@activated carbon nanocomposite material according to claim 8 in catalytic oxidation of formaldehyde.

10. The use according to claim 9, characterized in that: The application comprises the following steps: The manganese dioxide@activated carbon nanocomposite material is used for catalytic oxidation of formaldehyde; The used manganese dioxide@activated carbon nanocomposite material is regenerated in hot air and then reused; the temperature of the hot air is 100-105° C., and the regeneration time is 0.5-10 hours.

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