Preparation method of room temperature aldehyde removal and sterilization graphene composite aerogel

Abstract

The application provides a preparation method of a composite aerogel with room-temperature aldehyde-removing and sterilization functions, and the aerogel is a graphene composite aerogel loaded with silver-manganese dioxide. The composite aerogel has a three-dimensional porous structure, which provides a physical adsorption space for capturing gaseous formaldehyde. The loading of silver-manganese dioxide provides a chemical oxidation site for catalytic degradation of formaldehyde. The composite aerogel not only realizes the function of efficiently degrading gaseous formaldehyde at room temperature, but also has good antibacterial and sterilization effects. In the application, divalent manganese salt and persulfate are reacted under alkaline conditions to obtain manganese dioxide (delta type), which is used as a carrier. Silver ions are in-situ generated into silver particles under the action of a reducing agent citrate, and then silver-modified manganese dioxide is obtained. The obtained silver-manganese dioxide is fully mixed in a graphene oxide dispersion liquid, and a composite hydrogel is obtained after hydrothermal reaction. The graphene composite aerogel loaded with silver-manganese dioxide can be obtained after freeze-drying.

Description

Technical Field

[0001] This invention patent relates to the field of graphene aerogel technology, and more particularly to a method for preparing a graphene composite aerogel for room temperature formaldehyde removal and sterilization. Background Technology

[0002] As people's living standards improve, they are paying increasing attention to the air quality of their living environment. Formaldehyde is a common pollutant in the environment, possesses a certain degree of toxicity, and can cause cancer. Common formaldehyde removal methods include physical adsorption, low-temperature plasma decomposition technology, plant absorption, and photocatalysis. Currently, most purification methods on the market use activated carbon for physical adsorption, but it becomes ineffective after adsorption saturation. Studies have shown that manganese dioxide has the highest formaldehyde removal activity at room temperature and can efficiently catalyze the degradation of formaldehyde.

[0003] Graphene aerogel, as a three-dimensional graphene-like material, possesses an ultra-high specific surface area (2630 m²). 2 The g / g ratio is much larger than that of commonly used activated carbon on the market (500-1500 mg / g). 2 / g). At the same weight, the adsorption capacity of graphene aerogel can be increased by more than 100%. Nano-silver possesses small size, large specific surface area, and excellent antibacterial properties. Its mechanism of action is that after silver ions enter the bacterial cell membrane, they randomly interfere with cell wall synthesis, inhibit cross-linking between polysaccharide chains, causing the cell wall to lose its integrity and reducing its protective effect against osmotic pressure. Simultaneously, silver ions undergo a polysaccharide reaction with the bacterial cell wall, preventing oxygen transport into the cell, inhibiting bacterial activity, and causing the bacteria to lose activity and die naturally. Therefore, loading nano-silver and manganese dioxide onto graphene sheets and assembling them into a three-dimensional graphene composite material can fully combine the unique advantages of all three, overcoming the limitations of conventional materials with single functions, and obtaining a composite material that can both efficiently adsorb and degrade formaldehyde and kill bacteria and viruses. However, such inventions are currently rarely reported. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art and provide a method for preparing a graphene aerogel material that removes formaldehyde and kills bacteria.

[0005] The technical solution of the present invention is as follows, including the following steps:

[0006] Step 1: Slowly add sodium hydroxide solution to manganese sulfate solution, stir thoroughly, then add ammonium persulfate as an oxidant. React at room temperature. After the reaction is complete, collect by centrifugation, wash, and dry thoroughly in an oven to obtain a brownish-black powder, which is active manganese dioxide. The molar ratio of manganese sulfate, sodium hydroxide, and ammonium persulfate is 1:24:1.

[0007] Step 2: Add the synthesized active manganese dioxide from Step 1 to deionized water. After thorough dispersion, add silver nitrate and sodium citrate. The mass ratio of active manganese dioxide:water:silver nitrate:sodium citrate is 1:200:0.16:2.4. Mix and stir at room temperature, then place in an oil bath for stirring and reaction. After the reaction is complete, collect by centrifugation, wash, and vacuum dry to obtain silver-modified active manganese dioxide powder.

[0008] Step 3: Silver-modified active manganese dioxide powder obtained in Step 2 was added to the graphene oxide dispersion at a mass ratio of 3.5:1. After ultrasonic dispersion, the mixture was placed in a stainless steel-PTFE reactor for reaction. After the reaction, the mixture was pre-frozen in a refrigerator and then freeze-dried in a freeze dryer to obtain silver-manganese dioxide-supported graphene aerogel.

[0009] Furthermore, the crystal structure of the active manganese dioxide described in step 1 is δ crystal form.

[0010] Preferably, the concentration of the manganese sulfate solution in step 1 is 50 mmol / L, the concentration of the sodium hydroxide solution is 1.2 mol / L, and the concentration of the ammonium persulfate solution is 50 mmol / L.

[0011] Preferably, the reaction is carried out at room temperature for 10 hours in step 1.

[0012] Preferably, in step 2, the mixture is stirred at room temperature for 1 hour and then placed in an oil bath at 120°C for 4 hours of stirring and reaction.

[0013] Preferably, the concentration of the graphene oxide dispersion in step 3 is 2 mg / mL.

[0014] Preferably, the reaction conditions in step 3 are hydrothermal at 180°C for 12 hours.

[0015] Preferably, the pre-freezing temperature in step 3 is -20°C and the time is 3 hours; the freeze-drying temperature is -60°C and the freeze-drying time is 24 hours.

[0016] The beneficial effects of this invention are:

[0017] (1) Compared with the prior art, the present invention prepares δ-crystal manganese dioxide under milder synthesis conditions. Using it as a carrier, silver ions are generated in situ into silver particles under the action of reducing agent citrate, and then silver-modified manganese dioxide is obtained. The obtained silver-manganese dioxide is fully mixed in graphene oxide dispersion, and a composite hydrogel is obtained after hydrothermal reaction. After freeze-drying, the graphene composite aerogel supported by silver-manganese dioxide can be obtained.

[0018] (2) The synthesis conditions of the present invention are mild, and formaldehyde can be removed at room temperature, with a catalytic formaldehyde conversion rate of over 80%.

[0019] (3) The graphene composite aerogel prepared according to the method of the present invention can both efficiently adsorb and degrade formaldehyde and kill bacteria and viruses.

[0020] (4) The graphene composite aerogel loaded with silver-manganese dioxide prepared by this invention has a stable structure and can be reused. It can be used for indoor air purification. Attached Figure Description

[0021] Figure 1 The image shows a 4000X SEM image of the silver-manganese dioxide-supported graphene aerogel prepared in Example 1.

[0022] Figure 2 The image shows a 300X SEM image of the silver-manganese dioxide-supported graphene aerogel prepared in Example 1.

[0023] Figure 3 This is an energy dispersive spectroscopy (EDS) scan of the silver-manganese dioxide-supported graphene aerogel prepared in Example 1.

[0024] Figure 4 This is a comparison chart of formaldehyde detection in silver-manganese dioxide-supported graphene aerogel prepared in Example 1, and in pure graphene aerogel and activated carbon.

[0025] Figure 5 This is a comparison diagram of the silver-manganese dioxide-supported graphene aerogel prepared in Example 1, pure graphene aerogel, and the blank control group after sterilization. Detailed Implementation

[0026] To make the technical means, creative features, achieved objectives, and effects of this invention readily understandable, the technical solution of this invention will be further explained and described below with reference to specific embodiments and accompanying drawings. However, the following embodiments are merely preferred embodiments of this invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments described herein without creative effort are all within the protection scope of this invention.

[0027] In the embodiments of this invention, all chemical reagents used are commercially available products, and no special purification treatment is required unless otherwise specified.

[0028] This invention proposes a method for preparing a graphene composite aerogel for formaldehyde removal and sterilization at room temperature. The aerogel is a graphene composite aerogel loaded with silver-manganese dioxide. This composite aerogel has a three-dimensional porous structure, providing physical adsorption space for capturing gaseous formaldehyde. The loading of silver-manganese dioxide provides chemical oxidation sites for the catalytic degradation of formaldehyde, achieving not only efficient degradation of gaseous formaldehyde at room temperature but also exhibiting good antibacterial and bactericidal effects. This invention obtains manganese dioxide (δ-type) by reacting divalent manganese salt and persulfate under alkaline conditions. Using manganese dioxide as a carrier, silver ions are in situ converted into silver particles under the action of the reducing agent citrate, thus obtaining silver-modified manganese dioxide. The obtained silver-manganese dioxide is thoroughly mixed in a graphene oxide dispersion, and a composite hydrogel is obtained after hydrothermal reaction. After freeze-drying, the silver-manganese dioxide-loaded graphene composite aerogel is obtained.

[0029] This invention includes the following steps:

[0030] 1) Slowly add 1.2 mol / L sodium hydroxide solution (alkali) to 50 mmol / L manganese sulfate solution (manganese source), stir thoroughly, and then add 50 mmol / L ammonium persulfate (oxidant). The volume ratio of the three solutions is 1:1:1. Stir at room temperature for 10 h. After the reaction is complete, centrifuge at 8000 rpm to collect the solution, wash it four times with deionized water, and dry it thoroughly in an oven at 60℃ to obtain a brownish-black powder, which is active manganese dioxide.

[0031] The amount of alkali used in the reaction system is closely related to the crystal form of manganese dioxide, and the amount of OH in the reaction system is also closely related to the crystal form of manganese dioxide. - and Mn 2+ A molar ratio ≥ 5 makes it easier to form purer δ-type manganese dioxide. Reaction temperatures controlled at 20-30℃ yield crystals with better crystallinity; excessively high temperatures (above 50℃) result in excessively fast reaction rates, rapid growth, and poor crystallinity. Oxidizing agents include ammonium persulfate and Mn. 2+ A molar ratio of 1:1 yields purer manganese dioxide. Too small a ratio of oxidant will produce byproducts such as manganese trioxide and manganese tetroxide. Centrifugation speed, number of washes, and drying temperature do not affect the crystal form of manganese dioxide.

[0032] 2) The synthesized active manganese dioxide was added to deionized water and fully dispersed. Then, silver nitrate and sodium citrate were added in a mass ratio of 1:200:0.16:2.4. The mixture was stirred at room temperature for 1 hour, then placed in an oil bath at 120°C and stirred for 4 hours. After the reaction, the silver-modified active manganese dioxide powder was collected by centrifugation at 10,000 rpm, washed four times with deionized water, and vacuum dried in an oven at 60°C for 12 hours. Sodium citrate acts as both a stabilizer and a reducing agent, initially stably adsorbing citrate and silver ions onto the surface of the manganese dioxide particles at low temperatures.

[0033] Increasing the concentration of silver nitrate will lead to an increase in the size of silver particles. At the same time, excessive silver nitrate will reduce the exposed area of ​​the carrier manganese dioxide, thereby reducing the ability of manganese dioxide to catalyze formaldehyde.

[0034] Under a fixed silver nitrate concentration, increasing the amount of sodium citrate as a reducing agent will reduce the particle size of silver nanoparticles, but it will also increase the probability of homogeneous nucleation of silver particles, thus reducing the probability of silver particles adhering to manganese dioxide particles. Centrifugation speed, number of washing cycles, and drying temperature are unaffected.

[0035] 3) Silver-modified active manganese dioxide powder was added to a 2 mg / mL graphene oxide dispersion at a mass ratio of 3.5:1. After ultrasonic dispersion for two hours, the mixture was placed in a 100 mL stainless steel-PTFE reactor and hydrothermally heated at 180°C for 12 hours. After the reaction, the mixture was pre-frozen at -20°C for 3 hours, and then freeze-dried at -60°C for 24 hours to obtain silver-manganese dioxide-supported graphene aerogel.

[0036] The method for preparing silver-manganese dioxide-supported graphene composite aerogels of this invention features a controllable preparation process, resulting in silver-modified manganese dioxide nanoparticles with uniform size, small particle size, and high dispersion in a three-dimensional porous structure. Figures 1 to 3 As shown, this invention is the first to achieve the assembly of nano-silver, activated manganese dioxide, and graphene into an aerogel with a three-dimensional porous network structure. This aerogel is a multifunctional material that can not only effectively adsorb formaldehyde in the air and catalytically degrade formaldehyde, but also has excellent antibacterial and bactericidal properties, thus showing broad application prospects in air purification and other fields.

[0037] Example 1

[0038] 1) Slowly add 100 mL of 1.2 mol / L sodium hydroxide solution (alkali) to 100 mL of 50 mmol / L manganese sulfate solution (manganese source), stir thoroughly, then add 100 mL of 50 mmol / L ammonium persulfate (oxidant), stir at room temperature for 10 h, collect by centrifugation at 8000 rpm after the reaction is complete, wash 4 times with deionized water by centrifugation, and dry thoroughly in an oven at 60 °C to obtain a brownish-black powder, which is active manganese dioxide.

[0039] 2) 0.5 g of synthetic active manganese dioxide was added to 100 mL of deionized water and dispersed thoroughly. Then, 80 mg of silver nitrate and 1.2 g of sodium citrate were added, and the mixture was stirred at room temperature for 1 h. After that, the mixture was placed in an oil bath and stirred at 120 °C for 4 h. After the reaction was completed, the silver-modified active manganese dioxide powder was collected by centrifugation at 10,000 rpm, washed four times with deionized water, and vacuum dried in an oven at 60 °C for 12 h.

[0040] 3) Measure 70 mL of graphene oxide dispersion with a concentration of 2 mg / mL and add 40 mg of silver-modified active manganese dioxide powder. After ultrasonic dispersion for two hours, place it in a 100 mL stainless steel-PTFE reactor and hydrothermally heat at 180℃ for 12 hours. After the reaction, place it in a -20℃ freezer for 3 hours, and then freeze-dry it at -60℃ for 24 hours to obtain silver-manganese dioxide-supported graphene aerogel.

[0041] Comparative Example 1: The preparation method of pure graphene aerogel is the same as step 3 of Example 1, except that silver-modified active manganese dioxide powder is not added.

[0042] like Figure 1 and Figure 2 As shown, Figure 1 This is a SEM image of the silver-manganese dioxide-supported graphene aerogel prepared in Example 1, magnified 4000 times. Figure 1 The medium-sized particles are silver-modified active manganese dioxide. Figure 2 This is a SEM image of the silver-manganese dioxide-supported graphene aerogel prepared in Example 1, magnified 300 times. It can be seen that the aerogel contains a large number of silver-manganese dioxide particles.

[0043] Figure 3 This is an energy dispersive spectroscopy (EDS) scan of the silver-manganese dioxide-supported graphene aerogel prepared in Example 1.

[0044] Figure 4 This is a comparison chart of the formaldehyde removal rates of the silver-manganese dioxide-supported graphene aerogel prepared in Example 1, the pure graphene aerogel prepared in Comparative Example 1, and activated carbon. The tests were conducted according to Appendix E of GB / T 18801-2022, with an initial formaldehyde concentration of 1.66 mg / m³. 3 The test chamber is 3m 3 Under the same conditions and after 10 hours of operation, the formaldehyde removal rate of the silver-manganese dioxide-loaded graphene aerogel reached over 80%, while that of pure graphene aerogel was approximately 60%, and that of activated carbon was less than 40%. Both activated carbon and pure graphene aerogel physically adsorb formaldehyde, but the silver-manganese dioxide-loaded graphene composite aerogel of this invention can catalytically degrade formaldehyde into carbon dioxide and water.

[0045] Figure 5 This is a comparison diagram of the silver-manganese dioxide-supported graphene composite aerogel prepared in Example 1, the pure graphene aerogel of Comparative Example 1, and the sterilization of the blank control group. Figure 5 The results show that the silver-manganese dioxide-supported graphene composite aerogel exhibits excellent antibacterial properties. Antibacterial activity was assessed using liquid culture (OD value measurement). *E. coli* DH5α was cultured in LB medium at 220 rpm and 37°C until the OD value reached [value missing]. 600It is around 0.6, corresponding to 10 8 Dilute the bacterial culture to a final concentration of 10 CFU / mL using a dilution ratio of 1:1000. 5 CFU / mL, the same mass of sterilized test samples (graphene aerogel and silver-manganese dioxide supported graphene composite aerogel) were added to 3 mL of bacterial solution (two parallel replicates were set for each group, and the samples were completely immersed in the bacterial solution), and incubated at 37℃ and 220 rpm for 24 h, during which the OD value was measured.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Therefore, it cannot be used to limit the scope of the present invention. For those skilled in the art, modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a graphene composite aerogel for formaldehyde removal and sterilization at room temperature, characterized in that, Includes the following steps: Step 1: Slowly add sodium hydroxide solution to manganese sulfate solution, stir thoroughly, then add ammonium persulfate, react at room temperature, collect by centrifugation after the reaction is complete, wash, and dry thoroughly in an oven to obtain a brownish-black powder, which is active manganese dioxide; wherein, the molar ratio of manganese sulfate, sodium hydroxide, and ammonium persulfate is 1:24:1; the crystal structure of the active manganese dioxide is δ crystal form; Step 2: Add the active manganese dioxide synthesized in Step 1 to deionized water, disperse it thoroughly, then add silver nitrate and sodium citrate. The mass ratio of active manganese dioxide:water:silver nitrate:sodium citrate is 1:200:0.16:2.

4. Mix and stir at room temperature, then place in an oil bath and stir to react. After the reaction is complete, centrifuge, collect, wash and vacuum dry to obtain silver-modified active manganese dioxide powder. Step 3: Silver-modified active manganese dioxide powder prepared in step 2 is added to the graphene oxide dispersion at a mass ratio of 3.5:

1. After ultrasonic dispersion, the mixture is placed in a stainless steel-polytetrafluoroethylene reactor for reaction. The reaction conditions are 180℃ hydrothermal for 12 hours. After the reaction, the mixture is pre-frozen in a refrigerator and then freeze-dried in a freeze dryer to obtain silver-manganese dioxide-loaded graphene aerogel.

2. The method for preparing graphene composite aerogel according to claim 1, characterized in that, In step 1, the concentration of the manganese sulfate solution is 50 mmol / L, the concentration of the sodium hydroxide solution is 1.2 mol / L, and the concentration of the ammonium persulfate solution is 50 mmol / L.

3. The method for preparing graphene composite aerogel according to claim 1, characterized in that, In step 1, the reaction is carried out at room temperature for 10 hours.

4. The method for preparing graphene composite aerogel according to claim 1, characterized in that, In step 2, the mixture is stirred at room temperature for 1 hour and then placed in an oil bath at 120°C for 4 hours of stirring and reaction.

5. The method for preparing graphene composite aerogel according to claim 1, characterized in that, The concentration of the graphene oxide dispersion in step 3 is 2 mg / mL.

6. The method for preparing graphene composite aerogel according to claim 1, characterized in that, The pre-freezing temperature in step 3 is -20℃ and the time is 3 hours; the freeze-drying temperature is -60℃ and the freeze-drying time is 24 hours.

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