CN115400699A - Preparation Method and Application of Reduced Graphene Oxide/Phosphated Polyvinyl Alcohol Composite Airgel - Google Patents

Abstract

The invention provides a preparation method of reduced graphene oxide/phosphated polyvinyl alcohol composite aerogel, the composite aerogel is prepared by utilizing the polycondensation reaction between phosphated polyvinyl alcohol and graphene oxide, the super-hydrophilicity of the phosphated polyvinyl alcohol, the excellent optical property and the higher specific surface area of the graphene oxide can be fully utilized, and the reduced graphene oxide/phosphated polyvinyl alcohol composite aerogel with strong mechanical property, super-hydrophilicity, low thermal conductivity and high photothermal conversion efficiency is prepared. The reduced graphene oxide/phosphated polyvinyl alcohol composite aerogel prepared by the method provided by the invention can be applied to water molecule evaporation in brine, actual seawater, black and odorous water or heavy metal dye wastewater.

Description

Preparation Method of Reduced Graphene Oxide/Phosphated Polyvinyl Alcohol Composite Airgel and its application

technical field

The invention relates to the technical field of photothermal water evaporation materials, in particular to a preparation method and application of a reduced graphene oxide/phosphated polyvinyl alcohol composite airgel.

Background technique

With the development of human society and economy, the problems of energy shortage and water pollution have become increasingly prominent. In order to reduce pollution to the environment, the use of clean energy is the only way for human development. Traditional water purification technologies, such as reverse osmosis and membrane distillation technologies, have the characteristics of high energy consumption, centralized and large-scale infrastructure. Inspired by natural evaporation, a solar-driven interface evaporation technology is proposed. As a clean and sustainable energy source, solar energy can convert the absorbed light energy into heat, which can be used to heat water molecules at the water/air interface. Therefore, solar-driven interfacial evaporation technology is considered as one of the promising alternatives to alleviate freshwater resources and reduce carbon footprint.

In solar-driven interfacial evaporation technology, photothermal absorbing materials are the focus, among which graphene oxide (GO) is the rational design of solar evaporator due to its excellent solar light absorption rate, high chemical stability and light density. and utilization offer great opportunities and are widely used in interfacial evaporation. In the existing technology, the application number is 202210251817.0, and the publication date is April 29, 2022. The invention patent named "a cellulose nanofiber airgel photothermal interface water evaporation material and its preparation method" has passed a certain amount of The dispersion containing cellulose nanofibers, polyvinyl alcohol, graphene oxide, cross-linking agent and catalyst is poured into a mold and frozen, then freeze-dried into an airgel, and the airgel is cross-linked at high temperature, and then reduced , A chemically crosslinked cellulose nanofiber/polyvinyl alcohol/reduced graphene oxide airgel photothermal interface water evaporation material was prepared. Although the nanofiber airgel can be prepared in the above technical solution, the preparation process is complicated, the preparation process is long, the cost is high, and it is not friendly to the environment; in addition, in the above technical solution, the poly The cross-linking method of vinyl alcohol and graphene oxide makes it difficult to control the internal structure of the airgel, and the water transfer rate is slow, which affects the evaporation efficiency of the composite airgel in the interface evaporation application.

In view of this, it is necessary to design an improved superabsorbent high-performance three-dimensional reduced graphene oxide/phosphated polyvinyl alcohol composite airgel preparation method and its application to solve the above problems.

Contents of the invention

The object of the present invention is to provide a preparation method and application of reduced graphene oxide/phosphated polyvinyl alcohol composite airgel.

In order to achieve the above-mentioned purpose of the invention, the invention provides a method for preparing a reduced graphene oxide/phosphated polyvinyl alcohol composite aerogel, comprising the steps of:

S1. Add a predetermined amount of polyvinyl alcohol, N,N-dimethylformamide and phosphorus pentoxide into the reaction container, and after mixing evenly, react the reaction container in an oil bath; after the reaction is completed , the product is washed and dried to obtain phosphated polyvinyl alcohol;

S2, using improved Hummers method to prepare graphene oxide;

S3. Disperse the graphene oxide prepared in step S2 in deionized water, add a predetermined amount of urea, and mix uniformly to obtain a graphene oxide solution; then add the phosphated polyvinyl alcohol prepared in step S1 into the graphene oxide solution, and after mixing evenly, transfer the mixed solution to an autoclave for hydrothermal reaction to form a cylindrical three-dimensional composite hydrogel; finally, take out the cylindrical three-dimensional composite hydrogel , after washing and freeze-drying, the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel is prepared.

Preferably, in step S1, the mass ratio of the polyvinyl alcohol, the N,N-dimethylformamide and the phosphorus pentoxide is (1-3): (10-100): (1~3).

Preferably, in step S1, the reaction temperature of the reaction is 100-200° C., and the reaction time is 1-5 h.

Preferably, in step S3, the mass ratio of the graphene oxide, the urea and the phosphated polyvinyl alcohol is (1-3):(10-100):(1-3).

Preferably, in step S3, the reaction temperature of the hydrothermal reaction is 100-200°C, and the reaction time is 1-5h; preferably, the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel The height is 0.5-3cm.

Preferably, in step S2, the specific preparation process of the graphene oxide is as follows: under the condition of magnetic stirring, graphite powder is mixed with sulfuric acid, then sodium nitrate and potassium permanganate are added in sequence, and the above-mentioned mixture is filled with The container is transferred to an oil bath for oil bath reaction. During the reaction process, deionized water is added for temperature rise reaction, and then deionized water and hydrogen peroxide are added for reaction. After the reaction, the product is washed and dried to obtain graphene oxide.

Preferably, the mass ratio of the graphite powder, the sulfuric acid, the sodium nitrate, the potassium permanganate and the hydrogen peroxide is (1～3):(10～50):(1～3):( 1~10): (10~50).

Preferably, the reaction temperature of the oil bath reaction is 10-100° C., and the reaction time is 100-200 min; the washing process is carried out with hydrochloric acid and deionized water, and the washing times are 3-5 times.

In particular, the present invention also provides the application of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel, which is carried out in the following manner: the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel is placed In the water body to be treated, under simulated sunlight, the temperature and humidity of the environment are kept at a constant value, and the water body and the reduced graphene oxide/phosphated polyvinyl alcohol composite aircondensation monitored by an electronic analytical balance The change of the sum of the masses of the glue is used to calculate the photothermal evaporation rate driven by sunlight.

Preferably, the water body is brine, actual sea water, black and odorous water body or heavy metal dye wastewater.

The beneficial effects of the present invention are:

1. The preparation method of the reduced graphene oxide/phosphorylated polyvinyl alcohol composite airgel provided by the present invention is to prepare superhydrophilic phosphated polyvinyl alcohol first, and then compound it with graphene oxide to finally produce A reduced graphene oxide/phosphated polyvinyl alcohol composite airgel with strong mechanical properties, superhydrophilicity, low thermal conductivity and high photothermal conversion efficiency was obtained. Through the above method, the problems of complex preparation process, long preparation process and high cost in the process of using nanofibers to prepare photothermal interfacial water evaporation materials in the prior art are effectively solved, and the preparation can be widely used in salt water, actual sea water, black water, etc. Reduced graphene oxide/phosphorylated polyvinyl alcohol composite aerogels evaporated from water molecules in odorous water or heavy metal dye wastewater.

2. The reduced graphene oxide/phosphorylated polyvinyl alcohol composite airgel prepared by the present invention can not only endow the composite airgel with superhydrophilicity by introducing superhydrophilic phosphated polyvinyl alcohol, but also make it When used for water evaporation, it can transport water to the evaporation interface more quickly, ensuring efficient evaporation of water under concentrated light intensity; it can also use the network formed between phosphated polyvinyl alcohol and graphene oxide The interaction between the structure and water activates the water molecules, reduces the energy required for water evaporation, thereby increasing the evaporation rate of water; the low thermal conductivity of the composite airgel can concentrate the heat in the process of photothermal conversion on the evaporation interface, The heat exchange with the environment is reduced, which is more conducive to the evaporation process; due to the three-dimensional structure of the composite airgel itself, its evaporative cooling effect during the evaporation process makes the temperature on the side of the composite airgel lower than the ambient temperature, In this way, additional energy can be absorbed from the environment to evaporate water molecules in the water body; in addition, the superhydrophilicity and fast water transport of the composite airgel can construct a dynamic balance between salt crystallization and salt release, avoiding seawater evaporation During the evaporation process, the salt plugs the internal pores of the airgel to ensure the continuous evaporation process.

3. The method for preparing the reduced graphene oxide/phosphorylated polyvinyl alcohol composite airgel proposed by the present invention utilizes the polycondensation reaction between phosphated polyvinyl alcohol and graphene oxide, which can make full use of the excellent properties of graphene oxide itself. The optical properties and three-dimensional environmental enhancement effect of phosphated polyvinyl alcohol are combined with the superhydrophilicity and low evaporation enthalpy, which endows the composite airgel with high evaporation rate and energy utilization efficiency. At the same time, phosphated polyvinyl alcohol and oxidation The reaction between graphene effectively enhances the mechanical strength of the composite airgel and improves the practical application performance in water purification technology.

Description of drawings

Fig. 1 is the preparation schematic diagram of the preparation method of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel of the present invention;

Fig. 2 is the SEM picture of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel that embodiment 1 of the present invention makes;

Fig. 3 is the XRD figure of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel that embodiment 1 of the present invention makes;

Fig. 4 is the FTIR figure of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel that the embodiment of the present invention 1 makes;

Fig. 5 is the XPS figure of the reduced graphene oxide/phosphorylated polyvinyl alcohol composite airgel prepared in Example 1 of the present invention;

Fig. 6 is the absorbance intensity diagram of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel prepared in Example 1 of the present invention;

Fig. 7 is the Raman spectrum of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel prepared in Example 1 of the present invention;

Fig. 8 is the DSC figure of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel prepared in Example 1 of the present invention;

Fig. 9 is a comparison chart of the evaporation rate of pure water of reduced graphene oxide/phosphated polyvinyl alcohol composite airgel with different thicknesses prepared in the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Here, it should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only the structures and/or processing steps closely related to the solution of the present invention are shown in the drawings, and the steps related to the present invention are omitted. Invent other details that don't really matter.

Additionally, it should be noted that the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or apparatus comprising a set of elements includes not only those elements, but also Other elements not expressly listed, or inherent to the process, method, article, or apparatus are also included.

Please refer to shown in Figure 1, the preparation method of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel proposed by the present invention comprises the following steps:

S1. Preparation of phosphated polyvinyl alcohol: Add a predetermined amount of polyvinyl alcohol, N,N-dimethylformamide and phosphorus pentoxide into the reaction vessel, mix well, and transfer the reaction vessel to an oil bath environment The reaction is carried out in; after the reaction is finished, the product is washed with deionized water and dried to obtain phosphated polyvinyl alcohol;

S2, preparation of graphene oxide: the improved Hummers method is used to prepare graphene oxide, the specific preparation process is as follows: under the condition of magnetic stirring, graphite powder is mixed with sulfuric acid, then sodium nitrate and potassium permanganate are added successively, and then the The container of the above mixture is transferred to an oil bath for oil bath reaction. During the reaction, deionized water is added for temperature rise reaction, and then deionized water and hydrogen peroxide are added for reaction. After the reaction, the solution is washed with hydrochloric acid and deionized water for 3 to 5 times, and then dried to obtain graphene oxide;

S3. Prepare reduced graphene oxide/phosphated polyvinyl alcohol composite airgel;

Add the graphene oxide obtained in step S2 into deionized water, mix uniformly, add a predetermined amount of urea, and mix uniformly to obtain a graphene oxide solution; then add the phosphated polyvinyl alcohol obtained in step S1 to the graphene oxide In the solution, after mixing evenly, transfer the above mixed solution to a high-pressure reactor for hydrothermal reaction, and react at 100-200°C for 1-5h. During this process, polycondensation reaction between phosphated polyvinyl alcohol and graphene oxide occurs, A cylindrical three-dimensional composite hydrogel is formed; finally, after the composite hydrogel is washed with deionized water for 3 to 5 times, the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel is obtained through freeze-drying treatment.

Preferably, in step S1, the mass ratio of polyvinyl alcohol, N,N-dimethylformamide and phosphorus pentoxide is (1-3):(10-100):(1-3).

Preferably, in step S1, the reaction temperature is 100-200° C., and the reaction time is 1-5 h.

Preferably, in step S2, the mass ratio of graphite powder, sulfuric acid, potassium permanganate, sodium nitrate and hydrogen peroxide is (1～3):(10～50):(1～3):(1～10): (10-50).

Preferably, in step S2, the reaction temperature of the oil bath reaction is 10-100° C., and the reaction time is 100-200 min.

Preferably, in step S3, the mass ratio of graphene oxide, urea and phosphated polyvinyl alcohol is (1-3):(10-100):(1-3).

Preferably, in step S3, the reaction temperature is 100-200° C., and the reaction time is 1-5 h.

Preferably, in step S3, the prepared composite airgel has a height of 0.5-3 cm, and the height of the composite airgel is determined by the added volume of the solution during the hydrothermal reaction.

Preferably, in step S3, the freeze-drying time is 48 hours.

In particular, the present invention also provides an application method of graphene oxide/phosphated polyvinyl alcohol composite airgel, comprising the following steps: placing a composite airgel with a diameter of 2 cm and a height of 0.5 to 3 cm in the water body to be treated In the process, when the temperature and humidity of the environment are kept at a constant value, using simulated sunlight irradiation, the change of the sum of the mass of the water body and the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel monitored by the electronic analytical balance, Calculate the solar-driven photothermal evaporation rate; the solar intensity in the above process is 50-300mW cm ^-2 , the wind speed is 1.5-2.5ms ^-1 , and the above-mentioned water body is salt water, actual sea water, black and odorous water or heavy metal dye wastewater.

The preparation method and application of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel proposed by the present invention will be further described below in conjunction with specific examples:

Example 1

In this embodiment, a reduced graphene oxide/phosphated polyvinyl alcohol composite airgel is prepared, which includes the following preparation steps:

S1. Preparation of phosphated polyvinyl alcohol: Add polyvinyl alcohol and N, N-dimethylformamide to a five-necked flask, and then add phosphorus pentoxide and mix evenly. Among them, polyvinyl alcohol, N, N- The mass ratio of dimethylformamide to phosphorus pentoxide is 1.25:50:1; transfer the five-neck flask to an oil bath environment at 130°C for 4 hours; after the reaction is complete, wash the product with deionized water, and dry it Prepare phosphated polyvinyl alcohol;

S2. Preparation of graphene oxide: graphene oxide was prepared by the improved Hummers method. The specific preparation process was as follows: under magnetic stirring conditions, graphite powder and sulfuric acid were added to a five-necked flask and mixed evenly, and then sodium nitrate and high manganese were added in turn. Potassium acid, and then transfer the five-necked flask containing the above mixture to an oil bath at 35°C for reaction for 2 hours, add deionized water, then heat up the reaction, then add deionized water and hydrogen peroxide to react, after the reaction, the solution is washed with hydrochloric acid Wash with deionized water for 3 to 5 times, and then dry to obtain graphene oxide; wherein, the mass ratio of graphite powder, sulfuric acid, sodium nitrate, potassium permanganate and hydrogen peroxide is 1:46:1:6: 20;

S3. Prepare reduced graphene oxide/phosphated polyvinyl alcohol composite airgel;

Add the graphene oxide obtained in step S2 into deionized water, mix uniformly, add a predetermined amount of urea, and mix uniformly to obtain a graphene oxide solution; then add the phosphated polyvinyl alcohol obtained in step S1 to the graphene oxide solution, after mixing evenly, transfer the above mixed solution to an autoclave for hydrothermal reaction, and react at 160°C for 3 hours to prepare a cylindrical three-dimensional reduced graphene oxide/phosphated polyvinyl alcohol composite hydrogel glue; after washing the composite hydrogel with deionized water for 3 times, the reduced graphene oxide/phosphorylated polyvinyl alcohol composite airgel was prepared by freeze-drying for 48 hours, in which graphene oxide, urea and phosphated polyvinyl alcohol The mass ratio of polyvinyl alcohol is 1:30:1.

The obtained composite airgel is characterized, and the obtained spectra of the characterization are shown in Figures 2 to 8, wherein Figure 2 is the SEM image of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel, as can be seen from the figure The reduced graphene oxide/phosphated polyvinyl alcohol hybrid airgel has a self-assembled three-dimensional interconnected structure, including randomly distributed internal gaps and micron channels. Figure 3 is the XRD pattern of the reduced graphene oxide/phosphorylated polyvinyl alcohol composite airgel. The reduced graphene oxide airgel has a characteristic diffraction peak at 25.1°, and the phosphated polyvinyl alcohol appears near 22.0°. A broad characteristic peak was found, and the reduced graphene oxide/phosphated polyvinyl alcohol hybrid airgel showed a broad peak around 25.0°, which was the superposition of the characteristic peaks of phosphorylated polyvinyl alcohol and reduced graphene oxide. Figure 4 is the FTIR figure of the reduced graphene oxide/phosphorylated polyvinyl alcohol composite airgel. The FTIR spectrum of graphene oxide shows that there is a stretching vibration peak of -OH at 3412cm- ¹ , and C= at 1733cm ^-1 O stretching vibration, C=C bending vibration and CO stretching vibration at 1617cm ^-1 and 1050cm ^-1 respectively. In the FTIR spectrum of reduced graphene oxide, the peak of C=O at 1733 cm ^-1 almost disappeared, and the peak of -OH still existed but became weaker. The peaks of phosphated polyvinyl alcohol at 1210, 1080 and 935 cm ^-1 are P=O, POC and P-OH respectively, which proves that polyvinyl alcohol has been phosphorylated. Functional groups such as C=C, P=O, POC, and P-OH exist in the FTIR spectrum of the reduced graphene oxide/phosphated polyvinyl alcohol hybrid airgel, which proves that the material was successfully prepared. Figure 5 is the XPS image of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel. In the XPS spectrum, P exists, indicating that the reduced graphene oxide/phosphated polyvinyl alcohol hybrid airgel is successfully composited. Fig. 6 is an absorption spectrum diagram of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel, and the absorbance is above 94%. Figure 7 is the Raman spectrum of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel, which can be divided into free water and intermediate water. The intermediate water is more likely to evaporate from the polymer network into steam, so the intermediate water Presence can reduce the energy required for evaporation. Figure 8 is the DSC chart of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel. The evaporation enthalpy of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel is 1512J g ^-1 , much lower than that of pure Enthalpy of evaporation of water (2422J g ^-1 ).

In particular, the present invention also explores the photothermal evaporation performance of the above-mentioned reduced graphene oxide/phosphated polyvinyl alcohol composite airgel. The specific operation steps are as follows: The 2cm composite airgel is placed in pure water. Under the simulated sunlight with an intensity of 100mW cm ^-2 , the evaporation of pure water is shown in Figure 9, and the evaporation rates are 2.49, 3.27, 4.10, and 4.89kg m ^{- 2} h ^-1 , the results show that the photothermal evaporation rate is the highest at the height of 3cm.

At the same time, the present invention also explores the photothermal conversion of composite airgel with a height of 3 cm and a diameter of 2 cm under different test conditions, specifically, simulated sunlight with an intensity of 50, 100, 200 and 300 mW cm ^-2 The evaporation rates of pure water are 2.74, 4.89, 7.10, 9.21kg m ^-2 h ^-1 respectively; when the wind speed is 1.5, 2.0 and 2.5ms ^-1 , the evaporation rates of pure water are 12.84, 15.07, 16.22kg m ^-2 h ^-1 ; in the brine with a concentration of 3.5wt% and 15wt%, under simulated sunlight with an intensity of 100mW cm ^-2 , the evaporation rates in brine are 4.69, 4.38kg m ^-2 h ^-1 respectively; When the wind speed is 1.5, 2.0 and 2.5ms ^-1 , the evaporation rates of pure water are 12.84, 15.07, 16.22kg m ^-2 h ^-1 respectively, and the evaporation rates of 3.5wt% brine are 12.59, 14.04, 15.41kg m ^-2 h ^-1 .

The results show that the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel prepared by the present invention has higher evaporation efficiency and good salt resistance characteristics when applied to salt water evaporation; this is because the composite airgel The introduction of phosphated polyvinyl alcohol can endow the composite airgel with superhydrophilicity, which is beneficial to transport the brine to the evaporation interface and then convert the light energy into heat energy with the help of the optical properties of graphene oxide, and then make the water in the brine evaporate. During the process of evaporation, transportation and evaporation, the salt crystallization and salt dissolution in the brine reach a dynamic balance, so the pore structure of the airgel will not be blocked and the brine will not be transported to the evaporation interface. The interaction between the network structure formed between vinyl alcohol and graphene oxide and water activates water molecules and reduces the energy required for water evaporation, thereby increasing the evaporation rate of water molecules.

Examples 2 to 3

The difference between embodiments 2 to 3 and embodiment 1 is only: in step S1, the mass ratio of polyvinyl alcohol, N,N-dimethylformamide, phosphorus pentoxide is different, other steps are basically the same as embodiment 1 , which will not be repeated here. The settings of the mass ratio of polyvinyl alcohol, N, N-dimethylformamide, and phosphorus pentoxide in Examples 2 to 3 are shown in Table 1, and the results show that the evaporation rate of the composite airgel is affected by the phosphated poly In the vinyl alcohol preparation process, the influence of the mass ratio of polyvinyl alcohol, N, N-dimethylformamide, phosphorus pentoxide, when the quality of polyvinyl alcohol, N, N-dimethylformamide, phosphorus pentoxide When the ratio is 1.25:50:1, the evaporation rate of the composite airgel is the highest.

The setting of the mass ratio of polyvinyl alcohol, N, N-dimethylformamide, phosphorus pentoxide and the evaporation rate of the composite airgel obtained when preparing phosphated polyvinyl alcohol in Table 1 embodiment 1 to 3

Examples 4 to 5

The difference between Embodiments 4 to 5 and Embodiment 1 is only that in step S1, the reaction temperature is different, and other steps are basically the same as in Embodiment 1, and will not be repeated here. The setting of the reaction temperature in Examples 4 to 5 is shown in Table 2. The results show that the evaporation rate of the prepared composite airgel decreases when the reaction temperature is 100°C and 200°C.

The setting of reaction temperature and the evaporation rate of the composite airgel when preparing phosphated polyvinyl alcohol in Table 2 embodiment 1 and embodiment 4 to 5

project temperature reflex Evaporation rate (kgm^-2h^-1) Example 1 130 4.89 Example 4 100 2.24 Example 5 200 3.11

Examples 6 to 7

The difference between Embodiments 6 to 7 and Embodiment 1 is only that in step S1, the reaction time is different, and other steps are basically the same as Embodiment 1, and will not be repeated here. The setting of reaction time in embodiment 6 to 7 is as shown in table 3, and the result shows, the performance of composite airgel is affected by the reaction time when preparing phosphated polyvinyl alcohol, and under certain reaction time, obtained The composite airgel has the highest evaporation rate.

Table 3 Example 1 and Examples 6 to 7 when preparing phosphated polyvinyl alcohol, the setting of reaction time and the evaporation rate of the composite airgel made

project Reaction time Evaporation rate (kgm^-2h^-1) Example 1 4 4.89 Example 6 1 1.56 Example 7 5 3.67

Comparative example 1

The difference between Comparative Example 1 and Example 1 is that in the process of preparing the composite airgel, polyvinyl alcohol is directly used to replace the phosphated polyvinyl alcohol in Example 1 to prepare the composite airgel, and Comparative Example 1 is in the mold Freezing, the embodiment is to carry out self-condensation reaction in high temperature reactor. In order to compare the light-to-heat conversion efficiency of the polyvinyl alcohol/graphene oxide airgel prepared in Comparative Example 1 and the composite airgel prepared in Example 1, the two were subjected to a photothermal water evaporation test under the same conditions, and the results It shows that the evaporation rate of polyvinyl alcohol/graphene oxide airgel is lower than that of composite airgel, because the moisture transport in polyvinyl alcohol/graphene oxide airgel is slow and the airgel network The energy required for water molecules to evaporate is higher than for composite aerogels.

Comparative example 2

The difference between comparative example 2 and comparative example 1 is: in step S3, after polyvinyl alcohol is added in the graphene oxide solution, also continue to add nanofiber dispersion liquid, butane tetracarboxylic acid and sodium hypophosphite, wherein, The mass ratio of polyvinyl alcohol and the nanofibers in the nanofiber dispersion liquid is 3:10, and the quality of butane tetracarboxylic acid and sodium hypophosphite is identical with polyvinyl alcohol; Subsequent steps are all consistent with comparative example 1, not here Let me repeat.

The composite airgel obtained in Comparative Example 2 and the composite airgel obtained in Example 1 were evaporated under the same conditions, and the evaporation rate of the composite airgel obtained in this comparative example was 2.28 kg m ^-2 h ^-1 , which is significantly lower than the evaporation rate of Example 1, 4.89kg m ^-2 h ^-1 , and the results show that the composite airgel prepared by the method proposed in the present invention can achieve excellent light absorption, superhydrophilicity, and low evaporation The effective combination of enthalpy and environmental enhancement shows more excellent light-to-heat conversion.

In summary, the method for preparing the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel proposed by the present invention utilizes the polycondensation reaction between the phosphorylated polyvinyl alcohol and graphene oxide to prepare the composite airgel, It can make full use of the superhydrophilicity of phosphated polyvinyl alcohol and the excellent optical properties and high specific surface area of graphene oxide itself to obtain strong mechanical properties, superhydrophilicity, low thermal conductivity and high photothermal conversion efficiency. The reduced graphene oxide/phosphorylated polyvinyl alcohol composite airgel; the introduction of phosphated polyvinyl alcohol can not only endow the composite airgel with superhydrophilicity, but also make it easier for the water body to evaporate when it is used for water evaporation. Transported to the evaporation interface, the interaction between the network structure formed between phosphated polyvinyl alcohol and graphene oxide and water can also be used to activate water molecules, reduce the energy required for water evaporation, and combine graphene oxide Excellent light-to-heat conversion performance, effectively improving the water evaporation rate. The reduced graphene oxide/phosphated polyvinyl alcohol composite airgel prepared by the method proposed in the present invention can be applied to the evaporation of water molecules in salt water, actual seawater, black and odorous water or heavy metal dye wastewater to obtain clean water resource.

The above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced. Without departing from the spirit and scope of the technical solution of the present invention.

Claims (10)

1. a preparation method of reduced graphene oxide/phosphorylated polyvinyl alcohol composite airgel, is characterized in that, comprises the steps: S1. Add a predetermined amount of polyvinyl alcohol, N,N-dimethylformamide and phosphorus pentoxide into the reaction container, and after mixing evenly, react the reaction container in an oil bath; after the reaction is completed , the product is washed and dried to obtain phosphated polyvinyl alcohol; S2, using improved Hummers method to prepare graphene oxide; S3. Disperse the graphene oxide prepared in step S2 in deionized water, add a predetermined amount of urea, and mix uniformly to obtain a graphene oxide solution; then add the phosphated polyvinyl alcohol prepared in step S1 into the graphene oxide solution, and after mixing evenly, transfer the mixed solution to an autoclave for hydrothermal reaction to form a cylindrical three-dimensional composite hydrogel; finally, take out the cylindrical three-dimensional composite hydrogel , after washing and freeze-drying, the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel is prepared. 2. the preparation method of reduced graphene oxide/phosphorylated polyvinyl alcohol composite airgel according to claim 1, is characterized in that, in step S1, described polyvinyl alcohol, described N, N-di The mass ratio of methyl formamide and the phosphorus pentoxide is (1-3):(10-100):(1-3). 3. The preparation method of reduced graphene oxide/phosphated polyvinyl alcohol composite airgel according to claim 1, characterized in that, in step S1, the reaction temperature of the reaction is 100-200°C, and the reaction The time is 1 to 5 hours. 4. the preparation method of reduced graphene oxide/phosphorylated polyvinyl alcohol composite airgel according to claim 1, is characterized in that, in step S3, described graphene oxide, described urea and described phosphoric acid The mass ratio of the esterified polyvinyl alcohol is (1-3):(10-100):(1-3). 5. The method for preparing reduced graphene oxide/phosphated polyvinyl alcohol composite airgel according to claim 1, characterized in that, in step S3, the reaction temperature of the hydrothermal reaction is 100-200°C , the reaction time is 1-5 hours; preferably, the height of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel is 0.5-3 cm. 6. the preparation method of reduced graphene oxide/phosphorylated polyvinyl alcohol composite airgel according to claim 1, is characterized in that, in step S2, the specific preparation process of described graphene oxide is as follows: Under stirring conditions, mix graphite powder with sulfuric acid, then add sodium nitrate and potassium permanganate in sequence, then transfer the container containing the above mixture to an oil bath for oil bath reaction, add deionized water during the reaction process for temperature rise reaction , then add deionized water and hydrogen peroxide to react, and after the reaction, wash and dry the product to prepare graphene oxide. 7. the preparation method of reduced graphene oxide/phosphorylated polyvinyl alcohol composite airgel according to claim 6, is characterized in that, described graphite powder, described sulfuric acid, described sodium nitrate, described permanganese The mass ratio of the potassium chloride to the hydrogen peroxide is (1-3):(10-50):(1-3):(1-10):(10-50). 8. The preparation method of reduced graphene oxide/phosphated polyvinyl alcohol composite airgel according to claim 6, characterized in that the reaction temperature of the oil bath reaction is 10-100°C, and the reaction time is 100°C. ~200 min; the washing process is carried out with hydrochloric acid and deionized water, and the number of washings is 3 to 5 times. 9. An application of the reduced graphene oxide/phosphorylated polyvinyl alcohol composite aerogel obtained in claims 1 to 8, characterized in that, the following method is adopted: the reduced graphene oxide/phosphorylated polyvinyl alcohol The polyvinyl alcohol composite airgel is placed in the water body to be treated, and the temperature and humidity of the environment are kept at a constant value under simulated sunlight, and the water body and the reduced graphene oxide/phosphoric acid monitored by the electronic analytical balance The change of the mass sum of esterified polyvinyl alcohol composite airgel was used to calculate the photothermal evaporation rate driven by sunlight. 10. The application of the reduced graphene oxide/phosphated polyvinyl alcohol composite airgel according to claim 9, wherein the water body is salt water, actual seawater, black and odorous water body or heavy metal dye wastewater.

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