Flame-retardant aerogel capable of catalytically purifying formaldehyde at room temperature as well as preparation method and application of flame-retardant aerogel

Abstract

The invention discloses a preparation method of flame-retardant aerogel capable of catalytically purifying formaldehyde at room temperature, and the preparation method comprises the following steps: firstly, carrying out acid-alkali treatment on solid wastes in the planting industry to obtain cellulose with higher purity, and then loading manganese oxide on the cellulose to obtain the flame-retardant aerogel. Finally, sodium alginate, boric acid and aluminum chloride hexahydrate are combined to be matched with a specific aerogel preparation method to prepare the flame-retardant aerogel capable of catalytically purifying formaldehyde at room temperature. The cellulose is extracted by taking solid wastes in the planting industry as raw materials, so that the method is environment-friendly and low in cost; the manganese oxide is loaded on the cellulose, so that the problems that traditional catalyst powder is difficult to recover and dust pollution is easily caused can be solved; the prepared aerogel material has excellent flame retardance, heat resistance, heat preservation, heat insulation and room-temperature formaldehyde catalytic purification performance, and has positive practical application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cellulose aerogel, more particularly, to a flame-retardant aerogel capable of catalyzing and purifying formaldehyde at room temperature, and a preparation method and application thereof. BACKGROUND

[0002] At present, the traditional building insulation materials in China are mainly foaming materials such as polyurethane and polystyrene, which are flammable and produce a large amount of toxic smoke during combustion, and have safety hazards. The frequency of fire accidents related to building insulation materials is also increasing year by year. Fire is one of the main disasters that threaten public safety and social development, and it has a high frequency and is widespread. There are often a large number of flammable materials in people's homes, and once a fire occurs, the fire can spread rapidly, and a large amount of toxic smoke is produced, which poses a great threat to people's life and property safety.

[0003] Aerogel is a material with a three-dimensional porous network structure, which has the characteristics of low density, low thermal conductivity and high porosity, and has the potential to become a substitute for building insulation materials. Agricultural solid waste refers to solid waste generated during agricultural production, among which solid waste from planting includes waste bamboo, wood chips, straw, wheat straw, and bagasse, which contains rich cellulose. However, the utilization rate of such waste is very low, and it is often used as fuel or fertilizer. Since cellulose is one of the excellent raw materials for preparing aerogel materials, and it can be combined with other materials to prepare composite aerogel materials with excellent flame-retardant and thermal insulation properties, cellulose-based aerogel materials have the potential to develop into new green building insulation materials.

[0004] On the other hand, formaldehyde is a toxic gas that seriously endangers human health, and is often hidden in indoor furniture and decoration materials. Long-term exposure to formaldehyde can cause serious harm to the human body. In addition, formaldehyde is colorless and odorless, and is not easily detected by the human body at low concentrations. When the human body feels the irritation caused by formaldehyde, it has often exceeded several times the safety standard.

[0005] δ-Manganese oxide (δ-MnOx) is a transition metal oxide with abundant oxide morphologies, diverse and controllable structural types, and unique catalytic oxidation activity. It can spontaneously catalytically oxidize formaldehyde gas into non-toxic carbon dioxide and water at room temperature, and is characterized by reusability, low cost, and low-cost processing. Current research on δ-MnOx is quite mature, but the catalysts are often in powder form, which presents many limitations in practical applications, such as difficulty in recycling and easy dust pollution. Finding a support with a high specific surface area for δ-MnOx to expand the application range of catalyst powder is one of the current directions for catalyst material improvement. Cellulose, with its high specific surface area and abundant active hydroxyl content, is very suitable as a catalyst support material. Preparing cellulose loaded with δ-MnOx into an aerogel material can significantly improve the practical application range of δ-MnOx.

[0006] Chinese patent CN116651340A discloses a method for preparing a graphene composite aerogel for formaldehyde removal and sterilization at room temperature. This patent prepares a silver-manganese dioxide-supported graphene composite aerogel by dispersing silver-modified delta-type manganese dioxide in graphene oxide. This method enables the loading of catalysts on a macroscopic carrier, overcoming the problems of harsh application scenarios and difficulty in recycling traditional powder catalysts after use. It can also degrade formaldehyde and sterilize and fight viruses at room temperature.

[0007] Chinese patent CN112694638A discloses a flexible flame-retardant aerogel, its preparation method, and its application. This patent uses cellulose nanofibers, cellulose nanowires, and sodium alginate as the main raw materials. After cross-linking modification with silanol, boric acid, and calcium ions, the flame-retardant properties of cellulose aerogel are improved by utilizing the inherent flame-retardant properties of sodium alginate and the synergistic flame-retardant properties of boron-based flame retardants. This solves the problem that the aerogel prepared from pure cellulose cannot meet the product use standards due to the inherent flammability of cellulose.

[0008] Current research on aerogel materials is relatively singular. Aerogel materials focusing on room-temperature catalytic formaldehyde purification haven't been considered for application in building insulation materials; similarly, research on flame-retardant and heat-insulating aerogel materials hasn't considered endowing them with room-temperature catalytic formaldehyde purification properties to improve indoor environmental safety. Therefore, there is an urgent need for a multifunctional aerogel material that possesses excellent flame-retardant, heat-resistant, and thermal insulation properties while also exhibiting room-temperature catalytic formaldehyde purification capabilities. Summary of the Invention

[0009] The primary objective of this invention is to overcome the aforementioned problems in the prior art and provide a method for preparing a flame-retardant gel capable of catalytically purifying formaldehyde at room temperature. By stably loading manganese oxide onto cellulose and combining it with boric acid, sodium alginate, and aluminum chloride hexahydrate, along with a specific aerogel preparation method, an aerogel material with flame-retardant and heat-resistant properties, thermal insulation properties, and room-temperature formaldehyde catalytic purification performance is obtained, which has positive practical application value in the field of building environmental health and safety.

[0010] The second objective of this invention is to provide a flame-retardant gel that can catalytically purify formaldehyde at room temperature.

[0011] The above-mentioned objective of this invention is achieved through the following technical solution:

[0012] A method for preparing a flame-retardant gel capable of catalytically purifying formaldehyde at room temperature, characterized in that the method comprises the following steps:

[0013] S1. Extract cellulose from agricultural solid waste to obtain cellulose powder;

[0014] S2. Manganese oxide is loaded onto the cellulose powder obtained in step S1 to obtain manganese oxide-loaded cellulose powder;

[0015] S3. The manganese oxide-loaded cellulose powder obtained in step S2 is uniformly dispersed with sodium alginate in a solvent to obtain a dispersion. The dispersion is freeze-dried to obtain a precursor aerogel. The precursor aerogel is completely immersed in a mixed solution containing boric acid and aluminum chloride hexahydrate for crosslinking. After crosslinking is completed, it is freeze-dried to obtain the flame-retardant gel that can catalytically purify formaldehyde at room temperature.

[0016] Preferably, the solid waste from the agricultural industry mentioned in step S1 includes one of the following: sawdust, waste bamboo, rice straw, wheat straw, corn stalks, sugarcane bagasse, rice husks, peanut shells, and coconut shells.

[0017] Agricultural solid waste contains cellulose, hemicellulose, lignin, and some small molecules. After acid treatment with sodium chlorite and glacial acetic acid and alkali treatment with sodium hydroxide, a large amount of hemicellulose, lignin, and small molecules in agricultural solid waste will be removed, and the hydroxyl groups will be fully exposed, resulting in cellulose with high purity and high reactivity.

[0018] Preferably, the cellulose extraction method in step S1 is as follows:

[0019] S11. The solid waste powder from the agricultural industry is placed in a mixed aqueous solution of sodium chlorite and glacial acetic acid and reacted. After the reaction is completed, it is washed with deionized water until the pH of the washing solution is neutral to obtain the cellulose powder precursor.

[0020] S12. The cellulose powder precursor obtained in step S11 is placed in an aqueous solution of sodium hydroxide for reaction. After the reaction is completed, it is washed with deionized water until the pH of the washing solution is neutral, and then dried to obtain cellulose powder.

[0021] More preferably, the mass percentage concentration of sodium chlorite and the mass percentage concentration of glacial acetic acid in the mixed aqueous solution in step S11 is 2% to 6%.

[0022] More preferably, the mass percentage concentration of the sodium hydroxide aqueous solution in step S12 is 4% to 10%.

[0023] More preferably, the average particle size of the agricultural solid waste powder in step S11 is 60-200 mesh.

[0024] More preferably, the temperature of the reaction in step S11 is 70–90°C.

[0025] More preferably, the reaction time in step S11 is 3 to 6 hours.

[0026] More preferably, the temperature of the reaction in step S12 is 60–80°C.

[0027] More preferably, the reaction time in step S12 is 1 to 4 hours.

[0028] More preferably, the drying temperature in step S12 is 40–60°C.

[0029] Cellulose has abundant hydroxyl groups on its surface, which can provide sites for loading manganese oxides. Loading manganese oxides onto cellulose avoids the problems of easy agglomeration of manganese oxide particles, dust pollution during use, and difficulty in recycling.

[0030] Preferably, the method for preparing the manganese oxide-supported cellulose in step S2 is as follows:

[0031] After the cellulose powder obtained in step S1 is fully soaked in manganese sulfate monohydrate, potassium permanganate aqueous solution is added to react. After the reaction is completed, the powder is washed and dried to obtain manganese oxide-loaded cellulose powder.

[0032] More preferably, the mass percentage concentration of the manganese sulfate monohydrate aqueous solution in step S2 is 1% to 4%, and the mass percentage concentration of the potassium permanganate aqueous solution is 0.5% to 2%.

[0033] More preferably, the temperature of the reaction in step S2 is 40–80°C.

[0034] More preferably, the reaction time in step S2 is 2 to 6 hours.

[0035] Boric acid can act as a crosslinking agent to crosslink with the hydroxyl groups on sodium alginate and cellulose. Aluminum chloride hexahydrate can induce sodium alginate to form a gel. The combination of boric acid and aluminum chloride hexahydrate produces a double crosslinking effect, which strengthens the crosslinking strength of the sodium alginate and cellulose system. The resulting aerogel material has a good three-dimensional network structure and excellent flame retardant and thermal insulation properties.

[0036] Preferably, the mass percentage of cellulose loaded with manganese oxide in the dispersion in step S3 is 1% to 3%.

[0037] More preferably, the mass percentage of cellulose loaded with manganese oxide in the dispersion in step S3 is 1.9%.

[0038] Preferably, the mass percentage of sodium alginate in the dispersion in step S3 is 0.5% to 1.5%.

[0039] More preferably, the mass percentage of sodium alginate in the dispersion in step S3 is 1%.

[0040] Preferably, the mass percentage of aluminum chloride hexahydrate in the mixed solution in step S3 is 0.3% to 1%.

[0041] More preferably, the mass percentage of aluminum chloride hexahydrate in the mixed solution in step S3 is 0.5%.

[0042] Preferably, the mass percentage of boric acid in the mixed solution in step S3 is 0.1% to 0.5%.

[0043] More preferably, the mass percentage of boric acid in the mixed solution in step S3 is 0.2%.

[0044] All chemical reagents used in the above preparation methods were commercially available and were not further purified.

[0045] A flame-retardant gel capable of catalytically purifying formaldehyde at room temperature is prepared by the above-described method.

[0046] The above-mentioned flame-retardant gel, which can catalytically purify formaldehyde at room temperature, is used in flame-retardant materials, heat insulation materials, and formaldehyde purification materials.

[0047] Compared with the prior art, the beneficial effects of the present invention are:

[0048] (1) This invention uses solid waste from agricultural production as raw material to extract cellulose, which is green, environmentally friendly, and low-cost, and has good prospects for production and application. Furthermore, compared with existing technologies, this invention uses only three relatively common chemicals—sodium chlorite, acetic acid, and sodium hydroxide—to extract cellulose with high purity, giving it a greater advantage in terms of environmental friendliness. By stably loading manganese oxide onto cellulose, the problems of catalyst powder agglomeration, difficulty in recycling in practical applications, and dust pollution are solved.

[0049] (2) The aerogel described in this invention is prepared by combining cellulose loaded with manganese oxide with sodium alginate, boric acid and aluminum chloride hexahydrate using a specific preparation method. It has a good three-dimensional network structure inside, and the cellulose aerogel has excellent flame retardancy, heat resistance, thermal insulation and room temperature formaldehyde catalytic purification performance. It can meet people's needs for building environment health and safety and has positive practical application value.

[0050] (3) The synthesis conditions of the present invention are mild and can achieve spontaneous catalytic purification of formaldehyde at room temperature without other additional conditions. The formaldehyde purification rate reaches more than 80% within 3 hours.

[0051] (4) Existing building insulation materials have relatively simple functions and rarely have the ability to improve the safety of the indoor environment. This invention can provide research ideas for the subsequent development of new multifunctional building insulation materials. Attached Figure Description

[0052] Figure 1 This is a physical image of Example 1 (MPSAB).

[0053] Figure 2 The following are the FTIR spectra of the aerogels of Example 1 (MPSAB), Comparative Example 1 (PC), Comparative Example 2 (MPC), and Comparative Example 3 (MPS).

[0054] Figure 3 Thermogravimetric analysis (TGA) diagrams of the aerogels of Example 1 (MPSAB) and Comparative Example 3 (MPS) under nitrogen atmosphere.

[0055] Figure 4 Limiting oxygen index diagrams for aerogels of Example 1 (MPSAB) and Comparative Example 3 (MPS).

[0056] Figure 5 The graph shows the thermal conductivity of the aerogels of Example 1 (MPSAB) and Comparative Example 3 (MPS).

[0057] Figure 6 Infrared thermal images of the aerogels of Example 1 (MPSAB) and Comparative Example 3 (MPS) after being heated on a heating plate at 75°C for 1 hour.

[0058] Figure 7 This is a schematic diagram of a self-made formaldehyde purification performance testing device.

[0059] Figure 8 The graphs show the formaldehyde purification effect of Example 1 (MPSAB), Comparative Example 3 (MPS), and Comparative Example 4 (PSAB) over time. Detailed Implementation

[0060] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0061] Example 1

[0062] This invention provides a method for preparing a room-temperature catalytic formaldehyde-retardant gel (MPSAB), which includes the following steps:

[0063] S1. Cellulose is extracted from agricultural solid waste to obtain cellulose powder:

[0064] Commercially available pine sawdust powder was passed through an 80-mesh sieve. 10g of the powder was dispersed in 325mL of deionized water, and 12g of sodium chlorite and 10mL of glacial acetic acid were added. The mixture was reacted at 75℃ with magnetic stirring for 4 hours. After the reaction, the powder was washed with deionized water until the pH value was neutral. Then, deionized water was added to bring the total volume to 225mL. 17g of sodium hydroxide was added, and the mixture was reacted at 70℃ with magnetic stirring for 2 hours. After the reaction, the powder was washed with deionized water until the pH value was neutral. The product was dried in a 55℃ forced-air drying oven to constant weight to obtain cellulose powder.

[0065] S2. Manganese oxide is loaded onto the cellulose powder obtained in step S1 to obtain manganese oxide-loaded cellulose powder:

[0066] Take 1.5g of cellulose from step S1 and disperse it thoroughly in 80mL of deionized water. Add 1.313g of manganese sulfate monohydrate and stir until dissolved. Then add 70mL of aqueous solution containing 0.817g of potassium permanganate. React for 3h under magnetic stirring at 60℃. After the reaction is complete, wash several times with deionized water. Dry the product in a forced-air drying oven at 55℃ to constant weight to obtain manganese oxide-loaded cellulose powder.

[0067] S3. Preparation of a flame-retardant gel capable of catalytically purifying formaldehyde at room temperature:

[0068] 1g of manganese oxide-loaded cellulose from step S2 was dispersed in 50mL of deionized water. 0.5g of sodium alginate was added and stirred until fully dissolved. The mixture was poured into a mold and frozen into a solid ice block at -18℃. The mixture was then dried in a vacuum freeze dryer for 24h to obtain a preliminary aerogel material. The aerogel was then completely immersed in a mixed solution of aluminum chloride hexahydrate (0.5% by mass) and boric acid (0.2% by mass). The mixture was crosslinked at 80℃ for 2h. After the crosslinking was completed, the mixture was frozen again into a solid ice block at -18℃ and dried again in a vacuum freeze dryer for 24h to obtain a flame-retardant gel (MPSAB) that can catalytically purify formaldehyde at room temperature.

[0069] Example 2

[0070] This embodiment provides a method for preparing a flame-retardant aerogel (MPSAB) that can catalytically purify formaldehyde at room temperature. The preparation process steps S1 and S2 are the same as steps S1 and S2 in Example 1, except that in step S3, after the aerogel material is initially obtained, the aerogel is completely immersed in a mixed solution with a mass percentage of 0.3% aluminum chloride hexahydrate and a mass percentage of 0.1% boric acid, and the rest are the same.

[0071] Example 3

[0072] This embodiment provides a method for preparing a flame-retardant aerogel (MPSAB) that can catalytically purify formaldehyde at room temperature. The preparation process steps S1 and S2 are the same as steps S1 and S2 in Example 1. The difference is that in step S3, after the aerogel material is initially obtained, the aerogel is completely immersed in a mixed solution with a mass percentage of 1% aluminum chloride hexahydrate and a mass percentage of 0.5% boric acid. The rest are the same.

[0073] Example 4

[0074] This embodiment provides a method for preparing a flame-retardant aerogel (MPSAB) that can catalytically purify formaldehyde at room temperature. The preparation process steps S1 and S2 are the same as steps S1 and S2 in Example 1. The difference is that in step S3, after the aerogel material is initially obtained, the aerogel is completely immersed in a mixed solution with a mass percentage of 0.3% aluminum chloride hexahydrate and a mass percentage of 0.5% boric acid. The rest are the same.

[0075] Comparative Example 1

[0076] This comparative example provides a method for preparing natural cellulose aerogel (PC), the preparation process of which is as follows:

[0077] S1. Extract cellulose from agricultural solid waste to obtain cellulose powder.

[0078] S2. Preparation of natural cellulose aerogel (PC): Add 1g of cellulose obtained in step S1 to 50mL of deionized water and stir until it is evenly dispersed to obtain a dispersion. Pour the dispersion into a mold and freeze it into a solid ice block in a -18℃ freezer. Finally, dry it in a vacuum freeze dryer for 24h to obtain natural cellulose aerogel material (PC).

[0079] The steps and conditions for extracting cellulose in step S1 are the same as those in step S1 of the example.

[0080] Comparative Example 2

[0081] This comparative example provides a method for preparing manganese oxide-supported natural cellulose aerogel (MPC). Steps S1 and S2 are the same as those in Example 1, except for step S3, which is detailed below:

[0082] S3. Preparation of manganese oxide-supported natural cellulose aerogel (MPC): 1g of manganese oxide-supported cellulose obtained in step S2 was added to 50mL of deionized water and stirred until it was evenly dispersed to obtain a dispersion. The dispersion was poured into a mold and frozen into a solid ice block in a -18℃ freezer. Finally, it was dried in a vacuum freeze dryer for 24h to obtain manganese oxide-supported natural cellulose aerogel (MPC).

[0083] Comparative Example 3

[0084] This comparative example provides a method for preparing manganese oxide-supported natural cellulose composite aerogel (MPS). Steps S1 and S2 are the same as those in Example 1, except for step S3, which is detailed below:

[0085] S3. Preparation of manganese oxide-supported natural cellulose composite aerogel (MPS): 1g of manganese oxide-supported cellulose obtained in step S2 was added to 50mL of deionized water and stirred until evenly dispersed. 0.5g of sodium alginate was added and stirred until completely dissolved to obtain a mixed solution. The mixed solution was poured into a mold and frozen into a solid ice block in a -18℃ freezer. Finally, it was dried in a vacuum freeze dryer for 24h to obtain manganese oxide-supported natural cellulose composite aerogel material (MPS).

[0086] Comparative Example 4

[0087] This comparative example provides a method for preparing natural cellulose composite aerogel (PSAB), including the following steps:

[0088] S1. Extract cellulose from agricultural solid waste to obtain cellulose powder.

[0089] S2. Preparation of natural cellulose composite aerogel (PSAB): 1g of cellulose powder from step S1 was added to 50mL of deionized water and stirred until evenly dispersed. 0.5g of sodium alginate was added and stirred until fully dissolved to obtain a mixed solution. The mixed solution was poured into a mold and frozen into a solid ice block at -18℃. It was then dried in a vacuum freeze dryer for 24h to obtain the preliminary aerogel material. The aerogel was then completely immersed in a mixed solution containing 0.5% aluminum chloride hexahydrate and 0.2% boric acid by mass. Crosslinking was performed at 80℃ for 2h. After crosslinking, it was again frozen into a solid ice block at -18℃ and dried again in a vacuum freeze dryer for 24h to obtain the natural cellulose composite aerogel (PSAB).

[0090] The steps and conditions for extracting cellulose in step S1 are the same as those in step S1 of the example.

[0091] Performance testing

[0092] (1) Measurement of material mass and density

[0093] Five flame-retardant aerogels (Example 1 (MPSAB)) capable of catalytically purifying formaldehyde at room temperature were selected, with relatively good appearance and different shapes, for density measurement. The average density of the aerogels was calculated. The density (ρ) of the aerogel was determined by the formula (ρ = m / v), where m is the mass and v is the volume of the composite aerogel, and the mass was measured using an electronic balance. The volume of the relatively well-shaped cuboid sample was calculated using the geometric equation (v = a * b * h), where a is the length of the cuboid, b is the width of the cuboid, and h is the height of the cuboid.

[0094] Example 1: A physical example of manganese oxide-supported natural cellulose composite aerogel (MPSAB) is shown below. Figure 1 As shown. By calculating the sample density using the formula and taking the average value, the average density of the composite aerogel material can be calculated to be 35.53 mg / cm³. 3 .

[0095] (2) Infrared spectroscopy test

[0096] The aerogel materials of Example 1 (MPSBC), Comparative Example 1 (PC), and Comparative Example 2 (MPC) were tested using Fourier transform infrared spectroscopy (FTIR) with the KBr pellet method. Changes in functional groups or chemical bonds were determined after chemical treatment of cellulose, loading with manganese oxide, and preparation of composite aerogels. The test results are as follows: Figure 2 As shown.

[0097] Depend on Figure 2 It can be seen that, after being loaded with manganese oxide, Comparative Example 2 (MPC) showed a higher 518 cm⁻¹ in its FTIR image compared to Comparative Example 1 (PC). -1The presence of Mn-O bonds indicates that manganese oxides were successfully loaded onto cellulose, while Comparative Example 2 (MPC) showed similar results at 1633 cm⁻¹. -1 C=O, 1427cm -1 CH, 1168cm -1 CO, 1056cm -1 COC, 895cm -1 The C and C bonds were all preserved, indicating that the structure of cellulose was not destroyed after loading manganese oxide. The FTIR spectra of Example 1 (MPSBC) and Comparative Example 3 (MPS) at 518 cm⁻¹ -1 The Mn-O bonds were preserved, indicating that the structure of manganese oxides was not damaged during the preparation of the flame-retardant gel that can catalytically purify formaldehyde at room temperature.

[0098] (3) Thermogravimetric analysis test

[0099] The thermal stability of the aerogels of Example 1 (MPSBC) and Comparative Example 3 (MPS) was tested using a thermogravimetric analyzer. The measurement temperature range for the thermogravimetric analysis was from room temperature to 700°C, the heating rate was 20°C / min, and the atmosphere was nitrogen. The measurement results are as follows: Figure 3 As shown.

[0100] Depend on Figure 3 It can be seen that Comparative Example 3 (MPS) exhibits significant thermal weight loss between 250℃ and 350℃, with only 36.5% of the initial mass remaining at 700℃. Example 1 (MPSBC) is based on Comparative Example 3 (MPS) by simultaneously introducing boric acid and aluminum chloride hexahydrate as crosslinking agents. At 700℃, 43.9% of the initial mass remains, and the peak of thermal weight loss is delayed to 300℃-350℃, indicating that the thermal stability of the composite aerogel is significantly improved by simultaneously adding boric acid and aluminum chloride hexahydrate.

[0101] (4) Limiting Oxygen Index Test

[0102] The flammability of Example 1 (MPSBC) and Comparative Example 3 (MPS) aerogels was tested using a fully automated oxygen index analyzer. The test standard was based on GB / T 2406.2-2009, "Determination of flammability by oxygen index method for plastics – Part 2: Room temperature test". The test was conducted using a top-side flammation method, with sample dimensions of 100×10×10 mm. The test results are as follows: Figure 4 As shown.

[0103] Depend on Figure 4It can be seen that the limiting oxygen index of Comparative Example 3 (MPS) is only 20.4, indicating that it is a flammable material. Example 1 (MPSBC) is based on Comparative Example 3 (MPS) by simultaneously introducing boric acid and aluminum chloride hexahydrate, and the limiting oxygen index is increased to 28.1, indicating that the addition of aluminum chloride hexahydrate and boric acid can significantly improve the flame retardant properties of aerogel.

[0104] (5) Thermal insulation performance test

[0105] The thermal insulation performance of Example 1 (MPSBC) and Comparative Example 3 (MPS) aerogels was tested using a TC3000E thermal conductivity meter and an infrared thermal imager. For thermal conductivity testing, the ambient temperature was 25℃, and the sample size was 40×60×5mm. After placing the experimental samples, the test began when the temperature fluctuation was ≤±0.1 within 10 minutes. Each test consisted of three trials, with a 3-minute interval between each trial. Five sets of data were collected using different samples, and the average value was calculated. For infrared thermal imaging testing, the ambient temperature was 25℃, and the sample size was 20×40×5mm. The temperature change of the material surface was measured after heating in a 75℃ heating plate for 1 hour. The thermal conductivity test results are shown below. Figure 5 As shown, the results of the infrared thermal imaging test are as follows: Figure 6 As shown.

[0106] Depend on Figure 5 It can be seen that the thermal conductivity of Example 1 (MPSBC) and Comparative Example 3 (MPS) are 33.2 mW / mK and 35.1 mW / mK, respectively. Figure 6 It is known that after heating in a 75°C heating plate for 1 hour, the surface of the aerogel remained at a relatively low temperature (43.8-44.6°C). Due to the excellent thermal insulation properties of the aerogel material's three-dimensional porous network structure, there was no significant difference in the thermal conductivity of the aerogels in the examples and comparative examples, meaning that the aerogels in the examples and comparative examples all exhibited excellent thermal insulation properties.

[0107] (6) Formaldehyde purification performance test

[0108] The formaldehyde purification performance test was conducted in a self-made experimental apparatus (the structure of the experimental apparatus is as follows). Figure 7 As shown, the main body of the experimental setup is a sealed box with a volume of approximately 10L. Inside the box, there is a formaldehyde detector that can display the formaldehyde concentration in real time, a small fan that promotes gas flow inside the box, and a device for storing aerogel material. This device for storing aerogel material has good sealing properties, which can prevent the aerogel material from coming into contact with formaldehyde before the test begins. At the start of the test, the lid of the device can be slowly opened with a thin thread, allowing the aerogel material inside the experimental setup to come into full contact with the formaldehyde in the sealed box. During the test, the environment inside the sealed box is not affected by external factors.

[0109] Before the experiment, the formaldehyde detector was placed and the fan was turned on. Approximately 0.1g of the aerogel material to be tested was placed in the aerogel material storage device and sealed. A certain amount of formaldehyde solution was dripped into the sealed box to stabilize the formaldehyde concentration in the sealed box at approximately 0.5mg / m³. 3 Then, the lid of the aerogel material storage device is opened to allow the aerogel material inside the device to fully contact the formaldehyde in the box. The changes in the formaldehyde detector reading are observed, and the trend of formaldehyde concentration change in the sealed box is recorded over 2 hours.

[0110] The formaldehyde removal efficiency of the sample is evaluated using the following formula: D = (C0 - C) / C0 * 100%

[0111] In the formula: D is the formaldehyde removal efficiency (%); C0 is the initial mass concentration of formaldehyde (mg / m³). 3 C represents the mass concentration of formaldehyde (mg / m³) after different reaction times. 3 ).

[0112] The formaldehyde purification performance of the aerogels of Example 1 (MPSAB), Comparative Example 3 (MPS), and Comparative Example 4 (PSAB) was tested at room temperature using a self-made experimental apparatus. The test results are as follows: Figure 8 As shown. By Figure 8 It can be seen that the aerogel materials of Example 1 (MPSAB), Comparative Example 3 (MPS), and Comparative Example 4 (PSAB) can purify 83.0%, 84.7%, and 30.6% of formaldehyde, respectively, within three hours under the experimental conditions. The test results of Comparative Example 4 (PSAB) indicate that the physical adsorption of the aerogel material and the natural degradation of formaldehyde under these experimental conditions cause a 30.6% decrease in the formaldehyde concentration inside the homemade container. Example 1 (MPSAB) and Comparative Example 3 (MPS), both loaded with manganese oxide, exhibited high formaldehyde purification performance, indicating that the addition of boric acid and aluminum chloride hexahydrate during the preparation of the composite aerogel material has no significant impact on the formaldehyde purification performance.

[0113] The flame-retardant, heat-resistant, heat-insulating, and room-temperature formaldehyde catalytic purification performance of the flame-retardant gels (MPSAB) prepared in Examples 2-4 are similar to those in Example 1.

[0114] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a flame-retardant gel capable of catalytically purifying formaldehyde at room temperature, characterized in that, The preparation method includes the following steps: S1. Extract cellulose from agricultural solid waste to obtain cellulose powder; S2. Manganese oxide is loaded onto the cellulose powder obtained in step S1 to obtain manganese oxide-loaded cellulose powder; S3. The manganese oxide-loaded cellulose powder obtained in step S2 is uniformly mixed with sodium alginate in water to obtain a dispersion, and the precursor aerogel is obtained by freeze-drying. The precursor aerogel is completely immersed in a mixed solution containing boric acid and aluminum chloride hexahydrate for cross-linking. After the cross-linking is completed, it is freeze-dried to obtain the flame-retardant gel that can catalytically purify formaldehyde at room temperature.

2. The preparation method according to claim 1, characterized in that, The solid waste from the agricultural industry mentioned in step S1 includes one of the following: sawdust, waste bamboo, rice straw, wheat straw, corn stalks, sugarcane bagasse, rice husks, peanut shells, and coconut shells.

3. The preparation method according to claim 1, characterized in that, The cellulose extraction method described in step S1 is as follows: S11. The solid waste powder from the agricultural industry is placed in a mixed aqueous solution of sodium chlorite and glacial acetic acid and reacted. After the reaction is completed, it is washed with deionized water until the pH of the washing solution is neutral to obtain the cellulose powder precursor. S12. The cellulose powder precursor obtained in step S11 is placed in an aqueous solution of sodium hydroxide for reaction. After the reaction is completed, it is washed with deionized water until the pH of the washing solution is neutral, and then dried to obtain cellulose powder.

4. The preparation method according to claim 1, characterized in that, The method for preparing manganese oxide-supported cellulose in step S2 is as follows: The cellulose powder obtained in step S1 was fully soaked in a manganese sulfate monohydrate solution, and then a potassium permanganate solution was added to react. After the reaction was completed, the powder was washed and dried to obtain manganese oxide-loaded cellulose powder.

5. The preparation method according to claim 1, characterized in that, The mass percentage of cellulose loaded with manganese oxide in the dispersion in step S3 is 1% to 3%.

6. The preparation method according to claim 1, characterized in that, The mass percentage of sodium alginate in the dispersion in step S3 is 0.5% to 1.5%.

7. The preparation method according to claim 1, characterized in that, The mass percentage of aluminum chloride hexahydrate in the mixed solution described in step S3 is 0.3% to 1%.

8. The preparation method according to claim 1, characterized in that, The mass percentage of boric acid in the mixed solution in step S3 is 0.1% to 0.5%.

9. A flame-retardant gel capable of catalytically purifying formaldehyde at room temperature, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

10. The application of the flame-retardant gel capable of catalytically purifying formaldehyde at room temperature as described in claim 9 in flame-retardant materials, heat-insulating materials, and formaldehyde-purifying materials.

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