Modified graphene oxide film packaged slow-release fertilizer and preparation method thereof

Abstract

The invention discloses a modified graphene film packaged slow-release fertilizer and a preparation method thereof, and belongs to the technical field of fertilizers. Specific monomers including maleic anhydride, acrylamide and methyl methacrylate are adopted as raw materials for emulsion polymerization, graphene oxide is added in situ for reaction in the polymer emulsion preparation process, and graphene oxide is further reduced to prepare the modified graphene film packaging material. After the potassium nitrate fertilizer is coated, the fertilizer with a slow release function is finally obtained. The product has comprehensive properties such as swelling property, water solubility, mechanical property and the like through the technical means, so that the finally prepared modified graphene oxide film packaged slow-release fertilizer has an ideal slow-release effect.

Description

Technical Field

[0001] The invention belongs to the technical field of fertilizers, and in particular relates to a slow-release fertilizer encapsulated by using modified graphene as a film and a preparation method thereof. Background Art

[0002] To maintain crop yields, fertilizers must be applied to the soil to provide plants with essential nutrients. Conservative estimates suggest that 30-50% of crop yields are attributable to natural or synthetic commercial fertilizers. As modern agriculture becomes increasingly dependent on non-renewable fertilizer resources, future production of related minerals may result in lower quality products at higher prices. Some of the nutrients in these non-renewable fertilizers are not absorbed by plants and therefore seep into groundwater or surface water, causing eutrophication and posing a huge risk to ecosystems. In order to improve fertilizer quality and protect the environment and ecosystems, more and more research is aimed at developing new technologies to deliver plant nutrients in water or soil in a slow or controlled manner.

[0003] The application of film-encapsulated fertilizers can improve nutrient utilization efficiency. The encapsulation film coated on the fertilizer particles acts as a physical barrier, slowing down the release of nutrients, thereby reducing the loss of fertilizer nutrients in the environment. Release duration, that is, the time required for the coated fertilizer to release a specified percentage (e.g. 80%), is an important indicator for evaluating slow-release characteristics. Generally speaking, for encapsulated fertilizers with a certain amount of encapsulation material, a longer release duration indicates that the fertilizer has better slow-release performance.

[0004] In the past few years, graphene has attracted great research interest due to its unique two-dimensional structure, high surface area, and excellent structural, mechanical, thermal, optical and electrical properties required for many applications. The prior art has reported the use of graphene oxide as an encapsulation material to prepare slow-release fertilizers (Zhang M, Gao B, Chen J, et al. Slow-release fertilizer encapsulated by graphene oxide films [J]. Chemical Engineering Journal, 2014, 255: 107–113. DOI: 10.1016 / j.cej.2014.06.023.). However, as an ultra-thin carbon material, graphene oxide has high mechanical strength and high surface area, but lacks flexibility and film-forming properties. The coating effect is poor in the actual application process, and thus the ideal slow-release performance cannot be obtained.

[0005] In the prior art, graphene oxide is compounded with aqueous polymer emulsion to make up for this defect, combining the advantages of polymer emulsion film-forming property and viscosity and graphene oxide mechanical properties, such as patent CN107324901A graphene oxide modified polymer composite film controlled release fertilizer and preparation method thereof, polyacrylate emulsion and graphene oxide are compounded as film materials, but it is only to blend and compound the prepared polymer emulsion with graphene oxide, and the dispersion effect and coating effect of graphene oxide are limited. In addition, polymer emulsion itself has certain hydrophilicity, and graphene has a large number of hydrophilic groups such as hydroxyl and carboxyl after oxidation. After the two are compounded, the swelling degree is difficult to control as a film encapsulation material, and it is difficult to ensure long-term fertilizer release. Summary of the invention

[0006] The present invention provides a slow-release fertilizer encapsulated by a modified graphene oxide film and a preparation method thereof, so as to solve the problems existing in the above-mentioned prior art.

[0007] The present invention provides a method for preparing a slow-release fertilizer encapsulated by a modified graphene oxide film, which is characterized by comprising the following preparation steps: (1) Add 30g of surfactant to a 1000mL four-necked flask, add 250mL of deionized water to the four-necked flask, and stir to obtain a mixture; add maleic anhydride, acrylamide and methyl methacrylate to a 500mL beaker in sequence and mix to obtain a monomer solution, add the monomer solution to the four-necked flask, and stir at a speed of 300-500rpm for 30min to obtain an oil-water mixture; add 10g of graphene oxide deionized water dispersion to the oil-water mixture, and stir at a speed of 300-500rpm for 30min; put the four-necked flask into a water bath, heat it and keep it at 70-80℃, adjust the stirring speed to 500-700rpm, add the initiator solution dropwise, the adding time is 2h, and after the addition is completed, continue to stir and react for 2h to obtain a polymer composite graphene oxide solution; (2) dropping a reducing agent solution into the polymer composite graphene oxide solution, stirring for 30 min-60 min, reflux reacting in an oil bath at 90° C. for 80-120 min, and filtering to obtain a modified graphene oxide solution; (3) 200 g of potassium nitrate fertilizer particles are placed in a fluidized bed coating machine for full fluidization, and the modified graphene oxide solution is pumped into a nozzle by a peristaltic pump and atomized into droplets, and the droplets are sprayed on the surface of the potassium nitrate fertilizer in the fluidized bed, and after being dehydrated by the fluidized bed gas, a dense modified graphene oxide film is formed on the surface of the potassium nitrate fertilizer particles after coating 3-5 times, thereby preparing a slow-release fertilizer encapsulated by the modified graphene oxide film; (4) The slow-release fertilizer encapsulated by the modified graphene oxide film is placed in an oven at 60-80° C. and dried for 48 hours to obtain a final product.

[0008] The mass ratio of maleic anhydride, acrylamide and methyl methacrylate is 1:1:4-6.

[0009] Preferably, the mass ratio of maleic anhydride, acrylamide and methyl methacrylate is 1:1:5.

[0010] The mass ratio of the net weight of graphene oxide in the deionized water dispersion of graphene oxide to the monomer solution is 1:50-200.

[0011] The surfactant is a mixed solution of OP-10 and sodium dodecyl sulfate, and the mass ratio of OP-10 to sodium dodecyl sulfate is 1:2.

[0012] The reducing agent solution is a hydrazine hydrate solution.

[0013] The atomization pressure of the atomization process in the step (3) is 0.05-0.3 MPa.

[0014] The present invention also provides a slow-release fertilizer encapsulated in a modified graphene oxide film prepared by the method for preparing the slow-release fertilizer encapsulated in a modified graphene oxide film, and uses the slow-release fertilizer in the agricultural field.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: the present invention adds graphene oxide during the preparation of polyacrylate emulsion, adopts maleic anhydride, acrylamide and methyl methacrylate as the three specific polymerization monomers, and the monomers undergo a polymerization process, wherein maleic anhydride can undergo an esterification reaction with the hydroxyl groups in the graphene oxide, thereby realizing in-situ bonding of the graphene oxide with the polyacrylate emulsion, thereby improving the dispersibility and binding force of the graphene oxide with the polymer emulsion, and also improving the dispersion between the graphene oxide sheets, thereby giving full play to the adsorption and sustained-release functions of the graphene oxide.

[0016] In addition to maleic anhydride, the acrylamide selected by the present invention also contains a hydrophilic group, which can also interact with graphene oxide in the preparation process to improve the binding force. By selecting maleic anhydride and acrylamide, the two monomers can improve the binding force of polymer emulsion and graphene oxide on the one hand, and can also achieve the water solubility of slow-release fertilizer on the other hand. In addition, the hydrophobic monomer methyl methacrylate is selected to control the swelling degree of polymer emulsion. By adjusting the three monomers of maleic anhydride, acrylamide and methyl methacrylate in a specific ratio range, after being compounded with graphene oxide, it can ensure that the film encapsulation material has a certain swelling degree, and improve the mechanical properties and film-forming properties, so as to achieve the effect of slow release of fertilizer. In addition, after the present invention reduces the graphene oxide after the polymer compound, the swelling degree is further controlled. The test results show that the slow-release fertilizer encapsulated by the modified graphene oxide film prepared has an ideal slow-release effect. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; the technical features designed in the different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0018] In the description of the present invention, it should be noted that all terms used in the present invention (including technical terms and scientific terms) have the same meanings as those generally understood by ordinary technicians in the field to which the present invention belongs, and cannot be understood as limiting the present invention; it should be further understood that the terms used in the present invention should be understood to have the same meanings as these terms in the context of this specification and in the relevant fields, and should not be understood in an idealized or overly formal sense, unless explicitly defined in the present invention.

[0019] Example 1 Slow-release fertilizer encapsulated by modified graphene oxide film and preparation method thereof: (1) Add 10g OP-10 and 20g sodium dodecyl sulfate to a 1000mL four-necked flask, add 250mL deionized water to the four-necked flask, and stir to obtain a mixture; add 20g maleic anhydride, 20g acrylamide and 120g methyl methacrylate to a 500mL beaker in sequence and mix to obtain a monomer solution, add the monomer solution to the four-necked flask, and stir at a speed of 300-500rpm for 30min to obtain an oil-water mixture; add 10g of graphene oxide deionized water dispersion to the oil-water mixture, and stir at a speed of 500rpm for 30min; put the four-necked flask into a water bath, heat it and keep it at 80°C, adjust the stirring speed to 700rpm, add 3g potassium sulfate deionized water solution dropwise, and the dropping time is 2h. After the dropping is completed, continue to stir and react for 2h to obtain a polymer composite graphene oxide solution; (2) adding 25 g of reducing agent solution to the polymer composite graphene oxide solution, stirring for 60 min, refluxing for 100 min in an oil bath at 90° C., and filtering to obtain a modified graphene oxide solution; (3) 200 g of potassium nitrate fertilizer granules were placed in a fluidized bed coating machine for full fluidization, and the modified graphene oxide solution was pumped into a nozzle by a peristaltic pump and atomized into droplets, with an atomization pressure of 0.1 MPa. The droplets were sprayed on the surface of the potassium nitrate fertilizer in the fluidized bed, and after being dehydrated by the fluidized bed gas, a dense modified graphene oxide film was formed on the surface of the potassium nitrate fertilizer granules after coating three times, thereby preparing a slow-release fertilizer encapsulated by the modified graphene oxide film; (4) The slow-release fertilizer encapsulated by the modified graphene oxide film is placed in an oven at 80° C. and dried for 48 hours to obtain a final product.

[0020] Example 2 Slow-release fertilizer encapsulated by modified graphene oxide film and preparation method thereof: (1) Add 10g OP-10 and 20g sodium dodecyl sulfate to a 1000mL four-necked flask, add 250mL deionized water to the four-necked flask, and stir to obtain a mixture; add 20g maleic anhydride, 20g acrylamide and 80g methyl methacrylate to a 500mL beaker in sequence and mix to obtain a monomer solution, add the monomer solution to the four-necked flask, and stir at a speed of 300-500rpm for 30min to obtain an oil-water mixture; add 10g of deionized water dispersion of graphene oxide to the oil-water mixture, and stir at a speed of 500rpm for 30min; put the four-necked flask into a water bath, heat it and keep it at 80°C, adjust the stirring speed to 700rpm, add 3g potassium sulfate deionized water solution dropwise, and the dropping time is 2h. After the dropping is completed, continue to stir and react for 2h to obtain a polymer composite graphene oxide solution; (2) adding 25 g of reducing agent solution to the polymer composite graphene oxide solution, stirring for 60 min, refluxing for 100 min in an oil bath at 90° C., and filtering to obtain a modified graphene oxide solution; (3) 200 g of potassium nitrate fertilizer granules were placed in a fluidized bed coating machine for full fluidization, and the modified graphene oxide solution was pumped into a nozzle by a peristaltic pump and atomized into droplets, and the atomization pressure was 0.1 MPa. The droplets were sprayed on the surface of the potassium nitrate fertilizer in the fluidized bed, and after being dehydrated by the fluidized bed gas, a dense modified graphene oxide film was formed on the surface of the potassium nitrate fertilizer granules after coating three times, thereby preparing a slow-release fertilizer encapsulated by the modified graphene oxide film; (4) The slow-release fertilizer encapsulated by the modified graphene oxide film is placed in an oven at 80° C. and dried for 48 hours to obtain a final product.

[0021] Comparative Example 1 Slow-release fertilizer encapsulated by modified graphene oxide film and preparation method thereof: (1) Add 10g OP-10 and 20g sodium dodecyl sulfate to a 1000mL four-necked flask, add 250mL deionized water to the four-necked flask, and stir to obtain a mixture; add 20g maleic anhydride, 20g acrylamide and 65g methyl methacrylate to a 500mL beaker in sequence and mix to obtain a monomer solution, add the monomer solution to the four-necked flask, and stir at a speed of 300-500rpm for 30min to obtain an oil-water mixture; add 10g of graphene oxide deionized water dispersion to the oil-water mixture, and stir at a speed of 500rpm for 30min; put the four-necked flask into a water bath, heat it and keep it at 80°C, adjust the stirring speed to 700rpm, add 3g potassium sulfate deionized water solution dropwise, and the dropping time is 2h. After the dropping is completed, continue stirring and reacting for 2h to obtain a polymer composite graphene oxide solution; (2) adding 25 g of reducing agent solution to the polymer composite graphene oxide solution, stirring for 60 min, refluxing for 100 min in an oil bath at 90° C., and filtering to obtain a modified graphene oxide solution; (3) 200 g of potassium nitrate fertilizer granules were placed in a fluidized bed coating machine for full fluidization, and the modified graphene oxide solution was pumped into a nozzle by a peristaltic pump and atomized into droplets, with an atomization pressure of 0.1 MPa. The droplets were sprayed on the surface of the potassium nitrate fertilizer in the fluidized bed, and after being dehydrated by the fluidized bed gas, a dense modified graphene oxide film was formed on the surface of the potassium nitrate fertilizer granules after coating three times, thereby preparing a slow-release fertilizer encapsulated by the modified graphene oxide film; (4) The slow-release fertilizer encapsulated by the modified graphene oxide film is placed in an oven at 80° C. and dried for 48 hours to obtain a final product.

[0022] Comparative Example 2 Slow-release fertilizer encapsulated by modified graphene oxide film and preparation method thereof: (1) Add 10g OP-10 and 20g sodium dodecyl sulfate to a 1000mL four-necked flask, add 250mL deionized water to the four-necked flask, and stir to obtain a mixture; add 20g maleic anhydride, 20g acrylamide and 125g methyl methacrylate to a 500mL beaker in sequence and mix to obtain a monomer solution, add the monomer solution to the four-necked flask, and stir at a speed of 300-500rpm for 30min to obtain an oil-water mixture; add 10g of deionized water dispersion of graphene oxide to the oil-water mixture, and stir at a speed of 500rpm for 30min; put the four-necked flask into a water bath, heat it and keep it at 80°C, adjust the stirring speed to 700rpm, add 3g potassium sulfate deionized water solution dropwise, the dropping time is 2h, and after the dropping is completed, continue to stir and react for 2h to obtain a polymer composite graphene oxide solution; (2) adding 25 g of reducing agent solution to the polymer composite graphene oxide solution, stirring for 60 min, refluxing for 100 min in an oil bath at 90° C., and filtering to obtain a modified graphene oxide solution; (3) 200 g of potassium nitrate fertilizer granules were placed in a fluidized bed coating machine for full fluidization, and the modified graphene oxide solution was pumped into a nozzle by a peristaltic pump and atomized into droplets, with an atomization pressure of 0.1 MPa. The droplets were sprayed on the surface of the potassium nitrate fertilizer in the fluidized bed, and after being dehydrated by the fluidized bed gas, a dense modified graphene oxide film was formed on the surface of the potassium nitrate fertilizer granules after coating three times, thereby preparing a slow-release fertilizer encapsulated by the modified graphene oxide film; (4) The slow-release fertilizer encapsulated by the modified graphene oxide film is placed in an oven at 80° C. and dried for 48 hours to obtain a final product.

[0023] Comparative Example 3: Slow-release fertilizer encapsulated by modified graphene oxide film and preparation method thereof: (1) Add 10g OP-10 and 20g sodium dodecyl sulfate to a 1000mL four-necked flask, add 250mL deionized water to the four-necked flask, and stir to obtain a mixture; add 20g maleic anhydride, 20g acrylamide and 120g methyl methacrylate to a 500mL beaker in sequence and mix to obtain a monomer solution, add the monomer solution to the four-necked flask, and stir at a speed of 300-500rpm for 30min to obtain an oil-water mixture; add 10g of graphene oxide deionized water dispersion to the oil-water mixture, and stir at a speed of 500rpm for 30min; put the four-necked flask into a water bath, heat it and keep it at 80°C, adjust the stirring speed to 700rpm, add 3g potassium sulfate deionized water solution dropwise, and the dropping time is 2h. After the dropping is completed, continue to stir and react for 2h to obtain a polymer composite graphene oxide solution; (2) 200 g of potassium nitrate fertilizer granules are placed in a fluidized bed coating machine for full fluidization, and the modified graphene oxide solution is pumped into a nozzle by a peristaltic pump and atomized into droplets, and the atomization pressure is 0.1 MPa. The droplets are sprayed on the surface of the potassium nitrate fertilizer in the fluidized bed, and after being dehydrated by the fluidized bed gas, a dense modified graphene oxide film is formed on the surface of the potassium nitrate fertilizer granules after coating three times, thereby preparing a slow-release fertilizer encapsulated by the modified graphene oxide film; (3) The slow-release fertilizer encapsulated by the modified graphene oxide film is placed in an oven at 80° C. and dried for 48 hours to obtain a final product.

[0024] Comparative Example 4: Slow-release fertilizer encapsulated by modified graphene oxide film and preparation method thereof: (1) Add 10g OP-10 and 20g sodium dodecyl sulfate to a 1000mL four-necked flask, add 250mL deionized water to the four-necked flask, and stir to obtain a mixture; add 20g maleic anhydride, 20g acrylamide and 120g methyl methacrylate to a 500mL beaker in turn and mix to obtain a monomer solution, add the monomer solution to the four-necked flask, and stir at a speed of 300-500rpm for 30min to obtain an oil-water mixture; put the four-necked flask into a water bath and heat it to 80°C, adjust the stirring speed to 700rpm, add 3g potassium sulfate deionized water solution dropwise, the dropping time is 2h, and continue stirring and reacting for 2h after the dropping is completed to obtain a polymer emulsion. Add 10g of graphene oxide deionized water dispersion to the polymer emulsion, stir at a speed of 500rpm for 30min to obtain a polymer composite graphene oxide solution; (2) adding 25 g of reducing agent solution to the polymer composite graphene oxide solution, stirring for 60 min, refluxing for 100 min in an oil bath at 90° C., and filtering to obtain a modified graphene oxide solution; (3) 200 g of potassium nitrate fertilizer granules were placed in a fluidized bed coating machine for full fluidization, and the modified graphene oxide solution was pumped into a nozzle by a peristaltic pump and atomized into droplets, with an atomization pressure of 0.1 MPa. The droplets were sprayed on the surface of the potassium nitrate fertilizer in the fluidized bed, and after being dehydrated by the fluidized bed gas, a dense modified graphene oxide film was formed on the surface of the potassium nitrate fertilizer granules after coating three times, thereby preparing a slow-release fertilizer encapsulated by the modified graphene oxide film; (4) The slow-release fertilizer encapsulated by the modified graphene oxide film is placed in an oven at 80° C. and dried for 48 hours to obtain a final product.

[0025] The present invention uses the following test means to evaluate the performance of Examples 1-2 and Comparative Examples 1-4.

[0026] Swelling degree test: The water resistance of the sample is characterized by testing the swelling degree of the slow-release fertilizer encapsulated by the modified graphene oxide film in water. Theoretically, under the same other conditions, the lower the swelling degree, the better the water resistance and the corresponding slow-release effect. The swelling degree is defined as: ((W2-W1) / W1)×100%.

[0027] The sample was immersed in 50 mL of deionized water at 25°C, placed in a 50 mL wide-mouth bottle, and the mass of the sample before immersion (w1) and after immersion (w2) was weighed. The sample was weighed every three days until the weight was constant.

[0028] Table 1 Product swelling degree test results: project Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Swelling degree / % 39.54 41.32 50.12 40.05 55.89 53.76 Slow-release performance test: According to the national standard "Slow-release Fertilizer" (GB / T 23348-2009), the smaller the initial nutrient release rate and the 28-day cumulative nutrient release rate of the slow-release fertilizer after immersion in still water at 25°C for 24 hours, the better the slow-release effect.

[0029] Table 2 Test results of product sustained release performance: project Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Nutrient release rate within 24 hours 12.86% 11.67% 15.97% 19.86% 15.68% 23.70% Cumulative nutrient release rate in 28 days 44.56%% 49.45% 66.32% 77.84% 78.11% 73.85% It can be seen from the test results in Table 1 and Table 2 that the present invention adopts specific monomers of maleic anhydride, acrylamide and methyl methacrylate as raw materials for emulsion polymerization, and in-situ adds graphene oxide to react during the preparation of the polymer emulsion. By regulating the monomers of maleic anhydride, acrylamide and methyl methacrylate within a specific ratio range, and further reducing the graphene oxide therein, it can ensure that the film packaging material has a low swelling degree, and can also take into account the good dispersion of graphene oxide and give full play to the adsorption and sustained release properties and mechanical properties, and the film packaging material also has good film-forming properties and adhesion. The improvement of the above comprehensive properties makes the product obtained after the modified graphene oxide film packaging material finally prepared is coated with potassium nitrate fertilizer has excellent swelling degree and sustained release performance.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a slow-release fertilizer encapsulated by a modified graphene oxide film, characterized in that: The method comprises the following preparation steps: (1) Add 30g of surfactant to a 1000mL four-necked flask, add 250mL of deionized water to the four-necked flask, and stir to obtain a mixture; add maleic anhydride, acrylamide and methyl methacrylate to a 500mL beaker in sequence and mix to obtain a monomer solution, add the monomer solution to the four-necked flask, and stir at a speed of 300-500rpm for 30min to obtain an oil-water mixture; add 10g of graphene oxide deionized water dispersion to the oil-water mixture, and stir at a speed of 300-500rpm for 30min; put the four-necked flask into a water bath, heat it and keep it at 70-80℃, adjust the stirring speed to 500-700rpm, add the initiator solution dropwise, the adding time is 2h, and after the addition is completed, continue to stir and react for 2h to obtain a polymer composite graphene oxide solution; (2) dropping a reducing agent solution into the polymer composite graphene oxide solution, stirring for 30 min-60 min, reflux reacting in an oil bath at 90° C. for 80-120 min, and filtering to obtain a modified graphene oxide solution; (3) 200 g of potassium nitrate fertilizer particles are placed in a fluidized bed coating machine for full fluidization, and the modified graphene oxide solution is pumped into a nozzle by a peristaltic pump and atomized into droplets, and the droplets are sprayed on the surface of the potassium nitrate fertilizer in the fluidized bed, and after being dehydrated by the fluidized bed gas, a dense modified graphene oxide film is formed on the surface of the potassium nitrate fertilizer particles after coating 3-5 times, thereby preparing a slow-release fertilizer encapsulated by the modified graphene oxide film; (4) The slow-release fertilizer encapsulated by the modified graphene oxide film is placed in an oven at 60-80° C. and dried for 48 hours to obtain a final product.

2. A method for preparing a slow-release fertilizer encapsulated by a modified graphene oxide film as claimed in claim 1, characterized in that: The initiator solution is a potassium persulfate deionized water solution, and the concentration of the potassium persulfate deionized water solution is 0.02-0.05 g / mL.

3. A method for preparing a slow-release fertilizer encapsulated by a modified graphene oxide film as claimed in claim 1, characterized in that: The mass ratio of maleic anhydride, acrylamide and methyl methacrylate is 1:1:4-6.

4. A method for preparing a slow-release fertilizer encapsulated by a modified graphene oxide film as claimed in claim 3, characterized in that: The mass ratio of maleic anhydride, acrylamide and methyl methacrylate is 1:1:

5.

5. A method for preparing a slow-release fertilizer encapsulated by a modified graphene oxide film as claimed in claim 1, characterized in that: The mass ratio of the net weight of graphene oxide in the deionized water dispersion of graphene oxide to the monomer solution is 1:50-200.

6. A method for preparing a slow-release fertilizer encapsulated by a modified graphene oxide film as claimed in claim 1, characterized in that: The surfactant is a mixed solution of OP-10 and sodium dodecyl sulfate, and the mass ratio of OP-10 to sodium dodecyl sulfate is 1:

2.

7. A method for preparing a slow-release fertilizer encapsulated by a modified graphene oxide film as claimed in claim 1, characterized in that: The reducing agent solution is a hydrazine hydrate solution.

8. A method for preparing a slow-release fertilizer encapsulated by a modified graphene oxide film as claimed in claim 1, characterized in that: The atomization pressure of the atomization process in the step (3) is 0.05-0.3 MPa.

9. A slow-release fertilizer encapsulated by a modified graphene oxide film, characterized in that: The slow-release fertilizer is prepared by the preparation method of the modified graphene oxide film encapsulated by any one of claims 1 to 8.

10. Use of the slow-release fertilizer encapsulated by the modified graphene oxide film as claimed in claim 9 in the agricultural field.