CN112121774A

CN112121774A - Preparation method of hydrophilic graphene film

Info

Publication number: CN112121774A
Application number: CN202010939040.8A
Authority: CN
Inventors: 童逸杰
Original assignee: Hangzhou Vocational and Technical College
Current assignee: Hangzhou Vocational and Technical College
Priority date: 2020-09-09
Filing date: 2020-09-09
Publication date: 2020-12-25

Abstract

The invention discloses a preparation method of a hydrophilic graphene film, which takes graphene oxide as a precursor of graphene as a raw material, modifies the graphene oxide by using different functional molecules aiming at different heavy metals, wherein the functional molecules have at least one amino group and can be combined with carboxyl in the graphene oxide, the effect of adjusting the distance between graphene oxide layers is realized according to the difference of small molecular structures, and meanwhile, the functional small molecules have a certain complexing effect on heavy metal ions and are also beneficial to the adsorption of the heavy metals. In order to improve the hydrophilicity of the graphene film, the graphene oxide is sulfonated, and finally the graphene oxide is reduced, so that the excellent performance of the graphene film is achieved. The graphene film is modified through functional molecules, and the fact that different molecules are adopted for modification of different heavy metal ions to achieve obvious difference in adsorption effect is found, so that targeted and selective micromolecules can be used for modifying the graphene oxide film according to different heavy metal ions.

Description

Preparation method of hydrophilic graphene film

Technical Field

The invention relates to the technical field of graphene films, in particular to a preparation method of a water-based graphene film.

Background

In recent years, with the rapid development of industry, the discharge of heavy metal wastewater (such as cadmium, lead, copper, mercury and the like) is increasing. Heavy metal pollution in wastewater has become one of the most serious environmental problems at present, and therefore, the removal and enrichment of heavy metal ions in recovered wastewater has become a hot spot of global sewage treatment research. The existing treatment method for the heavy metal ion polluted water body mainly comprises the following steps: chemical precipitation, electrochemical methods, exchange resin methods, adsorption methods, membrane separation methods, and photocatalytic methods. Chemical precipitation methods are mostly adopted in industry, but the chemical precipitation methods easily cause secondary pollution, are not thorough in treatment of low-concentration heavy metal ions, and are difficult to be applied to treatment of flowing water bodies; the electrochemical method has large power consumption and is not suitable for large-scale treatment; the ion exchange resin method can transfer heavy metal ions to the resin, but the resin and the heavy metal ions are difficult to separate, and the cyclic utilization of the resin and the heavy metal ions cannot be realized; although the membrane separation method has high treatment efficiency, the treatment cost of the membrane material is high; the photocatalysis method is an environment-friendly treatment method, but has higher cost and lower efficiency; the adsorption method is a method for treating heavy metal wastewater in common use, and compared with other methods, the method has the advantages of simple process, convenient operation and high efficiency in treating heavy metal ion pollution of water bodies, and is more and more concerned by people.

Graphene oxide can be considered a non-traditional soft material with properties of polymers, colloids, films, and amphiphilic molecules. Due to its unique mechanical properties, thermal properties and high specific surface area, graphene oxide has received great attention in the fields of chemistry, physics, materials, energy, environment and the like in recent years. The graphite oxide has many carboxyl, hydroxyl, epoxy and other groups, and thus has powerful complexing capacity on heavy metal and low cost. However, since it is generally present in powder form, it is not easy to use, and it has disadvantages such as limited heavy metal adsorption performance and poor mechanical properties. Graphene oxide has long been considered as a hydrophilic substance because of its superior dispersibility in water, but related experimental results show that graphene oxide is actually amphiphilic, exhibiting a distribution of hydrophilic to hydrophobic properties from the edge to the center of a graphene sheet. The hydrophobic property inside the graphene oxide is not beneficial to the circulation of water, so that the adsorption effect is reduced, and therefore, the graphene film is processed into the hydrophilic property, which is very important in the field of water treatment. In addition, for different types of heavy metals, the adsorption effect of the treated graphene oxide is greatly different. For a specific industry, heavy metal species are fixed, and a polluted water body with high concentration needs to be subjected to targeted treatment on the graphene oxide film, so that an excellent adsorption effect can be achieved.

Disclosure of Invention

The invention discloses a preparation method of a hydrophilic graphene film, which takes graphene oxide as a precursor of graphene as a raw material, modifies the graphene oxide by using different functional molecules aiming at different heavy metals, wherein the functional molecules have at least one amino group and can be combined with carboxyl in the graphene oxide, the effect of adjusting the distance between graphene oxide layers is realized according to the difference of small molecular structures, and meanwhile, the functional small molecules have a certain complexing effect on heavy metal ions and are also beneficial to the adsorption of the heavy metals. In order to improve the hydrophilicity of the graphene film, the graphene oxide is sulfonated, and finally the graphene oxide is reduced, so that the excellent performance of the graphene film is achieved.

The invention realizes the purpose through the following technical scheme:

a preparation method of a hydrophilic graphene film comprises the following steps:

(1) modifying graphene oxide by using a functional molecule containing at least one amino group, and adjusting the interlayer spacing of the graphene oxide;

(2) sulfonating the graphene oxide modified by functional molecules, namely firstly using NaBH₄Pre-reducing the graphene oxide modified by the functional molecules, and then treating the graphene oxide with a sulfonating reagent;

(3) deep reduction, namely deeply reducing the product treated in the step (2) to ensure that the content of oxygen-containing functional groups is less than 1%;

(4) and (3) forming a graphene film, namely fully mixing the product processed in the step (3) with film-forming resin, and then preparing the hydrophilic graphene film by using a spin-coating method.

Graphene is a novel nano carbon material with excellent comprehensive performance discovered at the present stage, and has wonderful application in many aspects, and the graphene has great application potential in the field of sewage treatment through modification on the monoatomic film. Because of the inevitable agglomeration effect between graphene sheets, pure graphene cannot be directly compounded with a polymer, and unlike graphene, graphene oxide has numerous oxygen-containing functional groups, such as hydroxyl (-OH), carboxyl (-COOH), carbonyl (C-O), epoxide and the like, and the oxygen-containing groups have many characteristics superior to those of graphene, and graphene oxide has very strong plasticity, and can be modified by various molecules to realize different functions.

The purpose in this application is for being used for adsorbing the heavy metal with graphite alkene film, and the design thinking is to decorate oxidation graphite alkene with functional molecule earlier to adjust oxidation graphite alkene's interlamellar spacing, be used for the absorption of different heavy metals. And then sulfonating to ensure that the graphene oxide has strong hydrophilicity. Although graphene oxide molecules have very strong plasticity, so that other molecules can modify graphene oxide, and the graphene oxide molecules can realize better horizontal dispersion in a polymer solvent, the mechanical property and the conductivity of the graphene oxide are much lower than those of graphene or reduced graphene oxide, so that the graphene oxide needs to be reduced finally, and the excellent performance of the graphene is kept.

In the reduction process of graphene oxide, if the reduction is not complete, namely other structures are introduced into the graphene film, the residual oxygen-containing functional groups can influence the comprehensive performance of the graphene film, so that deep reduction of the graphene oxide is necessary₄Pre-reducing graphene oxide, and then deeply reducing poly (diallyldimethylammonium chloride) to enable the content of oxygen-containing functional groups to be less than 1%.

When the graphene film is applied to heavy metal adsorption in wastewater, the mechanical property of the material is very important, the modified graphene film has certain difference in tensile strength and elastic modulus compared with a high-molecular composite film, and researches show that a small amount of high-molecular polymer is mixed in the graphene film, so that the excellent performance of the graphene film can be kept, and the tensile strength and the elastic modulus can be obviously improved.

Further, the specific process of the step (1) is as follows: dispersing graphene oxide in a solvent, performing ultrasonic treatment for 5-10 min, adding functional molecules, performing reflux reaction at 60-100 ℃ for 24-60 h, standing for 1-3 h, removing supernatant, cleaning the lower-layer mixture with purified water for several times, and drying in a vacuum drying oven at 50-100 ℃ for 12-24 h to obtain the functional molecule modified graphene oxide, wherein the solvent is one of water, N-dimethylformamide, ethylene glycol, ethanol and isopropanol.

In the selection of the solvent, the functional molecule is dissolved in the solvent, and the graphene oxide is dispersed in the solvent, and the preferred solvent is water, for example, when the functional molecule is N, N' -dimethylethylenediamine, water can be used as the solvent, and the post-treatment step can be reduced.

Further, the functional molecule containing at least one amino group is one or a mixture of N, N' -dimethylethylenediamine, 1, 8-octanediamine, N-tert-butyloxycarbonyl-1, 4-butanediamine, 1-aminopropyl-3-methylimidazole chloride, anthranilic ether-4-sulfonic acid and 2-imino-4-thiobiuret. The functional molecule contains at least one amino group, and can form an amide bond with a carboxyl group in graphene oxide, and the interlayer distance between graphene molecules is determined according to the structure of the functional molecule, while the degree of crosslinking between graphene oxide molecules is increased.

Further, the specific process of reduction in the step (2) is as follows: dispersing the graphene product obtained in the step (1) into pure water by using an ultrasonic device, and adding NaBH₄Reacting for 2-3 hours at 50-100 ℃ while stirring, and after the reaction is finished, washing and centrifuging to obtain reduced graphene, wherein NaBH is₄The weight of (a) is 2-3 times of that of graphene.

Further, the sulfonating reagent in the step (2) is one of 4-sulfonic-group-fluorobenzoic acid diazobenzene and sulfanilic acid diazonium salt.

Further, the reducing agent in the step (3) is poly diallyl dimethyl ammonium chloride, the poly diallyl dimethyl ammonium chloride solution is dripped into the graphene dispersion liquid in the reaction process, the temperature is kept at 80-90 ℃, the reaction is carried out for 5-6 hours under stirring, and after the reaction is finished, the reduced graphene is obtained through washing and centrifuging. In the prior art, the graphene oxide is deeply reduced by adopting hydrazine hydrate, the hydrazine hydrate is a strong reducing agent, has strong corrosivity and belongs to a high-toxicity compound, and hydrazine hydrate steam is inhaled to stimulate the nose and the upper respiratory tract. The liquid or vapor can cause irritation to the eye and can cause permanent damage to the eye. It is irritating to skin; can be absorbed through skin to cause poisoning after repeated contact with skin for a long time. The applicant finds that the poly (diallyldimethylammonium chloride) can reduce the graphene oxide by reacting under mild conditions, and the poly (diallyldimethylammonium chloride) is easily soluble in water, non-toxic, non-combustible and non-explosive, and is a green and safe reducing agent.

Further, the film-forming resin is one of polyimide, cellulose acetate, polyvinyl acetate and polyamide. The film used for adsorbing heavy metals in wastewater needs to have good mechanical property in water and be stable, and the loss of a medium in water can cause the reduction of the film property, so that a high polymer material which has excellent mechanical property and is insoluble in water needs to be selected and mixed with graphene, the above film-forming resins are all high-performance multifunctional materials, have excellent thermal stability, good mechanical property, dielectric property, chemical resistance and irradiation resistance, and have good molding processability and excellent electrical stability, so that the film can be used as a substrate of a plurality of polymers to be widely used for various film materials.

Further, the weight ratio of the film-forming resin to the graphene is 0.2-0.5: 1. the weight ratio of the film-forming resin to the graphene is important for the performance of the graphene film, the specific gravity of the film-forming resin is too high, the key performances such as the hydrophilicity of the graphene and the adsorption capacity of heavy metals can be reduced, and the mechanical property can be obviously improved. The film-forming resin has an excessively low specific gravity, and thus the film-forming effect of the film is reduced and the mechanical properties thereof are insufficient. Therefore, it is necessary to obtain the optimal weight ratio of the film-forming resin to the graphene through a plurality of tests.

Compared with the prior art, the invention has the following beneficial effects:

1. the graphene film is modified through functional molecules, and the fact that different molecules are adopted for modification of different heavy metal ions to achieve obvious difference in adsorption effect is found, so that targeted and selective micromolecules can be used for modifying the graphene oxide film according to different heavy metal ions.

2. The graphene film has strong hydrophilicity, and can overcome the defects that the edge of a graphene sheet is hydrophilic and the inside of the graphene sheet is hydrophobic due to the introduction of a sulfonic functional group. And the obtained film keeps the excellent performance of the graphene by reducing the graphene oxide.

3. A small amount of water-insoluble film-forming resin is mixed into graphene, so that the film has excellent mechanical properties, good stability and good molding processability, and can be applied to various devices for treating various waste water.

4. The hydrophilic graphene film has the advantages of good stability, high specific surface area, good mechanical strength and good adsorption effect on heavy metal ions.

Detailed Description

firstly, dispersing graphene oxide in a solvent, performing ultrasonic treatment for 5-10 min, adding functional molecules, performing reflux reaction at 60-100 ℃ for 24-60 h, standing for 1-3 h, removing supernatant, cleaning the lower-layer mixture for several times with purified water, and drying in a vacuum drying oven at 50-100 ℃ for 12-24 h to obtain the functional molecule modified graphene oxide, wherein the solvent is one of water, N-dimethylformamide, ethylene glycol, ethanol and isopropanol. The functional molecule is one or a mixture of N, N' -dimethylethylenediamine, 1, 8-octanediamine, N-tert-butyloxycarbonyl-1, 4-butanediamine, chlorinated 1-aminopropyl-3-methylimidazole, anthranilic ether-4-sulfonic acid and 2-imino-4-sulfurated biuret.

Second, with NaBH₄Pre-reducing graphene oxide, dispersing the product obtained in the step (1) in pure water by using ultrasound, preferably, dispersing the product in an ultrasonic cleaner for 30-40 min to avoid the graphene oxide solution from agglomeration, and after the ultrasound is finished, adding NaBH into the graphene oxide solution₄And heating the solid powder to 50-100 ℃, stirring for 2-3 hours to enable the mixture to fully react, and finally washing and centrifuging to obtain the pre-reduced graphene oxide. In which NaBH is present₄The weight of (a) is 2-3 times of that of graphene. Preferably, NaBH₄The solid powder can also be added in several portions, compared with adding all NaBH at one time₄The solid is added for multiple times, which is beneficial to improving the reduction effect.

Preparing a sulfonating reagent which is 4-sulfo-fluoboric acid diazobenzene or sulfanilic acid diazonium salt, wherein the detailed synthesis steps of the sulfanilic acid diazonium salt are as follows: deionized water is used as a solvent, and 200g of a solution with the mass fraction of 30-40% of sulfanilic acid is prepared. 200mL of 1mol/l hydrochloric acid is measured and slowly mixed with sulfanilic acid solution at the temperature of-10-5 ℃ for 30-40 minutes. And then weighing 25g of potassium nitrite, adding the potassium nitrite into 100ml of deionized water to prepare a potassium nitrite solution, slowly and dropwise adding the potassium nitrite solution into a beaker which is stirring, keeping the solution in the beaker at a constant temperature, and reacting for 3 hours to obtain the sulfanilic acid diazonium salt containing sulfonic acid groups. And filtering and cleaning the obtained product, and freeze-drying to obtain powdery sulfanilic acid diazonium salt. Dispersing the prepared reduced graphene in 200ml of distilled water, carrying out ultrasonic treatment for 30 minutes, then adding 6.3g of sulfanilic acid diazonium salt into the ultrasonic reduced graphene aqueous dispersion under the ice bath condition of 0 ℃, carrying out stirring reaction in an ice bath for 1 hour, and then carrying out centrifugal washing to obtain the sulfonated reduced graphene oxide.

And thirdly, carrying out deep reduction on sulfonated reduced graphene oxide, wherein a reducing agent is poly (diallyldimethylammonium chloride), and the reaction process comprises the steps of dripping a poly (diallyldimethylammonium chloride) solution with the mass fraction of 20-30% into the graphene dispersion liquid at the speed of 1-2 drops/second, keeping the temperature at 80-90 ℃, reacting for 5-6 hours under stirring, and after the reaction is finished, washing and centrifuging to obtain the reduced graphene. After deep reduction, the content of oxygen-containing functional groups is less than 1%, and the reduced graphene oxide has the excellent performance of graphene.

And (4) forming a graphene film, namely mixing the product obtained in the step (3) with a high polymer to prepare the graphene film, wherein the high polymer is one of polyimide, cellulose acetate, polyvinyl acetate and polyamide, and the method comprises the following specific steps: and (3) mixing the product obtained in the step (3) with a high molecular polymer, dissolving the high molecular polymer in 100ml of a solvent, stirring for 10-30 min, adding the high molecular polymer, and stirring for 50-120 min at 60-80 ℃ until a homogeneous solution is formed. And cooling the obtained homogeneous solution to room temperature, dripping the solution in the middle of glass on a rotatable glass substrate by using a rubber head dropper, and preparing a composite film by spin coating. Finally, the film is placed in an oven to be dried for 24 hours at the temperature of 50 ℃ to obtain an experimental product.

The embodiment of the invention adopts the following method to determine the adsorption capacity of heavy metal ions: putting a certain mass of film into a conical flask, respectively adding a certain volume of heavy metal ion solution, oscillating for a certain time at a constant temperature of 25 ℃ in a constant-temperature oscillator, and calculating the adsorption capacity of the film adsorbent according to the change of the concentration of the heavy metal ions in the feed liquid. The concentration of the heavy metal ions is measured by using a UV2450 type ultraviolet-visible spectrophotometer, the adsorption capacity is the mass of the heavy metal in the filtered liquid after a certain period of time is subtracted from the initial mass of the heavy metal in the liquid, namely the adsorption amount of the heavy metal in the film, and the adsorption amount of the adsorbed heavy metal is divided by the mass of the film to obtain the adsorption capacity of the heavy metal ions. Wherein the mass of the heavy metal in the liquid is the concentration of the heavy metal multiplied by the volume of the liquid.

Example 1

In this example, the functional molecule is N, N' -dimethylethylenediamine, the film-forming resin is polyimide, and the preparation process is as follows:

carrying out ultrasonic treatment on 100mL of 2.0mg/mL graphene oxide aqueous solution for 10min, adding 30g of N, N '-dimethylethylenediamine, carrying out reflux reaction at 60 ℃ for 48h, standing for 1h, removing supernatant, washing the lower-layer mixture for 2 times with purified water, drying in a vacuum drying oven at 50 ℃ for 12 h to obtain N, N' -dimethylethylenediamine modified graphene oxide,

dispersing the obtained product in an ultrasonic cleaner for 30min, and after the ultrasonic treatment is finished, adding 4g of NaBH into the graphene oxide solution₄And heating the solid powder to 80 ℃, stirring for 3 hours to ensure that the mixture fully reacts, and finally washing and centrifuging to obtain the pre-reduced graphene oxide.

6.3g of sulfanilic acid diazonium salt is added into the ultrasonic reduced graphene water dispersion, and the sulfonated reduced graphene oxide can be obtained by stirring in an ice bath for reaction for 1 hour and then centrifuging and washing.

And (2) dripping a polydiallyldimethylammonium chloride solution with the mass fraction of 20% into the graphene dispersion liquid at the speed of 1 drop/second, keeping the temperature at 80 ℃, reacting for 5 hours under stirring, and after the reaction is finished, washing with water and centrifuging to obtain the reduced graphene.

Dissolving 0.1g of polyimide in 100ml of solvent, stirring for 30min, adding the reduced graphene, and stirring for 120min at 60 ℃ until a homogeneous solution is formed. And cooling the obtained homogeneous solution to room temperature, dripping the solution in the middle of glass on a rotatable glass substrate by using a rubber head dropper, and preparing a composite film by spin coating. Finally, the film is placed in an oven to be dried for 24 hours at the temperature of 50 ℃ to obtain an experimental product.

Example 2

In this example, the functional molecule is 1, 8-octanediamine, the film-forming resin is polyimide, and the preparation process and experimental conditions are the same as those of example 1.

Example 3

In this example, the functional molecule is N-t-butoxycarbonyl-1, 4-butanediamine, the film-forming resin is polyimide, and the preparation process and experimental conditions are the same as those in example 1.

Example 4

In this example, the functional molecule is 1-aminopropyl-3-methylimidazole chloride, the film-forming resin is polyimide, and the preparation process and experimental conditions are the same as those in example 1.

Example 5

In this example, the functional molecule was anthranilate-4-sulfonic acid, the film-forming resin was polyimide, and the preparation process and experimental conditions were the same as those of example 1.

Example 6

In this example, the functional molecule was 2-imino-4-thiobiuret, the film-forming resin was polyimide, and the preparation process and experimental conditions were the same as those of example 1.

The heavy metal adsorption test was performed on the films obtained in examples 1 to 6.

And (3) taking the graphene film with the same mass, carrying out a heavy metal adsorption test, measuring the solution with the same volume, wherein the concentration of heavy metal ions in the solution is 300mg/L, adsorbing by using the graphene film, detecting the concentration of heavy metal in the filtrate, and calculating the adsorption quantity of the film.

TABLE 1 comparison of adsorption Properties of films of different examples for different metal ions

Adsorption capacity (mg/g film)	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6
							Hg²⁺	130	90	62	78	75	86
Cd³⁺	89	120	73	62	84	91
							Pb²⁺	110	102	96	250	150	180
Cr³⁺	150	120	240	201	136	98
							Cu²⁺	65	68	71	56	73	86
Fe³⁺	57	69	89	76	105	80

As can be seen from the above table, the films of examples 1-6 have different adsorption effects for different heavy metal ions, wherein the graphene film of example 1 has different adsorption effects for Hg²⁺Has good adsorption effect, and can be used for mainly using Hg as pollutant²⁺The wastewater treatment of (3). Film of example 2 for Cd³⁺Has better adsorption effect and can be used for the main pollutant Cd³⁺The wastewater treatment of (3). Film of example 3 for Pb²⁺Has good adsorption effect, and can be used for mainly polluting Pb²⁺The wastewater treatment of (3). Film of example 4 for Cr³⁺Has good adsorption effect, and can be used for the main pollutant Cr³⁺The wastewater treatment of (3). Film of example 5 for Cu²⁺Has better adsorption effect and can be used for the main pollutant Cu²⁺The wastewater treatment of (3). Film of example 6 for Fe³⁺Has better adsorption effect and can be used for the main pollutant Fe³⁺The wastewater treatment of (3).

Example 7

Under the same other conditions, the performance of the films prepared by different weight ratios of the film-forming resin to the graphene is examined. The film of this example was prepared as follows: the functional molecule is chlorinated 1-aminopropyl-3-methylimidazole, the film-forming resin is cellulose acetate, and the preparation process comprises the following steps:

performing ultrasonic treatment on 100mL of 2.0mg/mL graphene oxide aqueous solution for 10min, adding 15g of 1-aminopropyl-3-methylimidazole chloride, performing reflux reaction at 50 ℃ for 24h, standing for 1h, removing supernatant, cleaning the lower-layer mixture for 2 times by using purified water, drying in a vacuum drying oven at 50 ℃ for 12 h to obtain 1-aminopropyl-3-methylimidazole chloride modified graphene oxide,

dispersing the product in an ultrasonic cleaner for 30min, and after the ultrasonic treatment is finished, adding 4g of NaBH into the graphene oxide solution₄And heating the solid powder to 80 ℃, stirring for 3 hours to ensure that the mixture fully reacts, and finally washing and centrifuging to obtain the pre-reduced graphene oxide.

And adding 5.0g of sulfanilic acid diazonium salt into the ultrasonic reduced graphene aqueous dispersion, stirring in an ice bath, reacting for 1 hour, and centrifuging and washing to obtain the sulfonated reduced graphene oxide.

Dissolving a certain mass of cellulose acetate in 100ml of solvent, stirring for 30min, adding the reduced graphene, and stirring for 120min at 60 ℃ until a homogeneous solution is formed. And cooling the obtained homogeneous solution to room temperature, dripping the solution in the middle of glass on a rotatable glass substrate by using a rubber head dropper, and preparing a composite film by spin coating. Finally, the film is placed in an oven to be dried for 24 hours at the temperature of 50 ℃ to obtain an experimental product.

TABLE 2 film Performance parameters prepared from film-forming resins in different proportions

From the above table, it is found that the mechanical strength of the thin film can be effectively improved by adding a small amount of film-forming resin to the graphene. When the content of the film forming resin is more than 0.5, the water permeability of the film is reduced, and when the content of the film forming resin is less than 0.2, the mechanical strength of the film is remarkably reduced, so that the weight ratio of the film forming resin to the graphene is preferably 0.2-0.5: 1. More preferably, the weight ratio of the film-forming resin to the graphene is 0.3-0.4: 1.

The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed.

Claims

1. A preparation method of a hydrophilic graphene film is characterized by comprising the following steps:

modifying graphene oxide by using a functional molecule containing at least one amino group, and adjusting the interlayer spacing of the graphene oxide;

sulfonating the graphene oxide modified by functional molecules, namely firstly using NaBH₄Pre-reducing the graphene oxide modified by the functional molecules, and then treating the graphene oxide with a sulfonating reagent;

deep reduction, namely deeply reducing the product treated in the step (2) to ensure that the content of oxygen-containing functional groups is less than 1%;

and (3) forming a graphene film, namely fully mixing the product processed in the step (3) with film-forming resin, and then preparing the hydrophilic graphene film by using a spin-coating method.

2. The preparation method according to claim 1, wherein the specific process of the step (1) is as follows: dispersing graphene oxide in a solvent, performing ultrasonic treatment for 5-10 min, adding functional molecules, performing reflux reaction at 60-100 ℃ for 24-60 h, standing for 1-3 h, removing supernatant, cleaning the lower-layer mixture with purified water for several times, and drying in a vacuum drying oven at 50-100 ℃ for 12-24 h to obtain the functional molecule modified graphene oxide, wherein the solvent is one of water, N-dimethylformamide, ethylene glycol, ethanol and isopropanol.

3. The method according to claim 1, wherein the functional molecule having at least one amino group is one or a mixture of N, N' -dimethylethylenediamine, 1, 8-octanediamine, N-t-butoxycarbonyl-1, 4-butanediamine, 1-aminopropyl-3-methylimidazole chloride, anthranilic ether-4-sulfonic acid, and 2-imino-4-thiobiuret.

4. The preparation method according to claim 1, wherein the reduction in the step (2) is carried out by the following specific process: dispersing the graphene product obtained in the step (1) into pure water by using an ultrasonic device, and adding NaBH₄Reacting for 2-3 hours at 50-100 ℃ while stirring, and after the reaction is finished, washing and centrifuging to obtain reduced graphene, wherein NaBH is₄The weight of (a) is 2-3 times of that of graphene.

5. The preparation method according to claim 1, wherein the sulfonating agent in the step (2) is one of 4-sulfo-fluorobenzoic acid diazobenzene and sulfanilic acid diazonium salt.

6. The preparation method according to claim 1, wherein the reducing agent in the step (3) is poly diallyl dimethyl ammonium chloride, the reaction process is to drop poly diallyl dimethyl ammonium chloride solution into the graphene dispersion liquid, the temperature is kept at 80-90 ℃, the reaction is carried out for 5-6 hours under stirring, and after the reaction is finished, the reduced graphene is obtained through washing and centrifugation.

7. The method according to claim 1, wherein in the step (4), the film-forming resin is one of polyimide, cellulose acetate, polyvinyl acetate, and polyimide.

8. The preparation method according to claim 1, wherein in the step (4), the weight ratio of the film-forming resin to the graphene is 0.2-0.5: 1.