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

Abstract

The application discloses modified graphene as a thin film encapsulated slow-release fertilizer and a preparation method thereof, and belongs to the technical field of fertilizers. The application adopts specific monomers maleic anhydride, acrylamide and methyl methacrylate as raw materials for emulsion polymerization, adds graphene oxide in situ during the preparation of the polymer emulsion, and further reduces and prepares graphene oxide to obtain a modified graphene thin film encapsulation material. After the potassium nitrate fertilizer is coated, a fertilizer with a slow-release function is finally obtained. The product has the comprehensive properties of swelling performance, water solubility, mechanical properties and the like through the above technical means, and therefore the modified graphene oxide thin film encapsulated slow-release fertilizer prepared finally has ideal slow-release effect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fertilizers, in particular relates to a modified graphene as a thin film encapsulated slow-release fertilizer and a preparation method thereof. BACKGROUND

[0002] In order to maintain crop yield, it is necessary to apply fertilizer to the soil to provide plants with essential nutrients. Conservative estimates show that 30-50% of crop yield is attributed to natural or synthetic commercial fertilizers. As modern agriculture relies more and more on non-renewable fertilizer resources, the future production of related minerals may produce lower quality products at higher prices. Part of the nutrients in these non-renewable fertilizers will not be absorbed by plants, so they will seep into groundwater or surface water, causing eutrophication and posing a huge risk to the ecosystem. In order to improve the quality of fertilizers and protect the environment and ecosystem, more and more research aims to develop new technologies to deliver plant nutrients in water or soil in a slow or controlled manner.

[0003] Applying thin film encapsulated fertilizers can improve nutrient use efficiency. The encapsulation film coated on the fertilizer particles acts as a physical barrier to slow down the release of nutrients, thereby reducing the loss of fertilizer nutrients in the environment. The release duration, i.e. the time required for a coated fertilizer to release a specified percentage (e.g. 80%) of its content, is an important indicator for evaluating the slow-release properties. In general, for encapsulated fertilizers with a certain amount of encapsulation material, a longer release duration indicates better slow-release performance of the fertilizer.

[0004] In the past few years, graphene has attracted great research interest due to its unique two-dimensional structure, high surface area, and outstanding structural, mechanical, thermal, optical, and electrical properties required for many applications. It has been reported in the prior art that graphene oxide is used 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, although has high mechanical strength and high surface area, lacks flexibility and film-forming properties, and the coating effect is not good during actual application, so it cannot achieve ideal slow-release performance.

[0005] The prior art has graphene oxide and water-based polymer emulsion composite to make up for this defect, combining the film-forming property and viscosity of the polymer emulsion and the mechanical property of graphene oxide, for example, patent CN107324901A graphene oxide modified polymer composite film controlled-release fertilizer and its preparation method, polyacrylate emulsion is compounded with graphene oxide as a film material, however, 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, the polymer emulsion itself has a certain hydrophilicity, graphene has a large number of hydrophilic groups such as hydroxyl and carboxyl groups after oxidation, and the swelling degree of the two after compounding as a film packaging material is difficult to control, and it is difficult to ensure long-term fertilizer release. SUMMARY

[0006] The application provides a modified graphene oxide film packaged slow-release fertilizer and a preparation method thereof to solve the problems in the prior art.

[0007] The application provides a preparation method of a modified graphene oxide film packaged slow-release fertilizer, characterized by comprising the following preparation steps,

[0008] (1) 30 g of a surfactant is added into a 1000 mL four-necked flask, 250 mL of deionized water is added into the four-necked flask, and the mixture is obtained after uniform stirring; 500 mL of a beaker is sequentially added with maleic anhydride, acrylamide and methyl methacrylate, and the mixture is uniformly mixed to obtain a monomer solution, the monomer solution is added into the four-necked flask, and stirring is performed at a rotation speed of 300-500 rpm for 30 min to obtain an oil-water mixture; 10 g of a deionized water dispersion solution of graphene oxide is added into the oil-water mixture, and stirring is performed at a rotation speed of 300-500 rpm for 30 min; the four-necked flask is placed in a water bath kettle and heated and kept at 70-80℃, the stirring speed is adjusted to 500-700 rpm, an initiator solution is added dropwise, the dropwise adding time is 2 h, and after the dropwise adding is completed, the stirring reaction is continuously performed for 2 h to obtain a polymer composite graphene oxide solution;

[0009] (2) a reducing agent solution is added dropwise into the polymer composite graphene oxide solution, stirring is performed for 30 min-60 min, and reflux reaction is performed at 90℃ under oil bath conditions for 80-120 min, and a modified graphene oxide solution is obtained by filtration;

[0010] (3) Put 200g of potassium nitrate fertilizer particles into a fluidized bed coater and fluidize them thoroughly, use a peristaltic pump to pump the modified graphene oxide solution into a nozzle and atomize it into droplets, the droplets are sprayed onto the surface of the potassium nitrate fertilizer in the fluidized bed, and after 3-5 times of coating, a dense modified graphene oxide film is formed on the surface of the potassium nitrate fertilizer particles, thereby preparing the modified graphene oxide film encapsulated slow-release fertilizer;

[0011] (4) Dry the modified graphene oxide film encapsulated slow-release fertilizer in an oven at 60-80℃ for 48h to obtain the final product.

[0012] The mass ratio of maleic anhydride, acrylamide and methyl methacrylate is 1:1:4-6.

[0013] Preferably, the mass ratio of maleic anhydride, acrylamide and methyl methacrylate is 1:1:5.

[0014] 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.

[0015] The surfactant is a mixture of OP-10 and sodium dodecyl sulfate, and the mass ratio of OP-10 to sodium dodecyl sulfate is 1:2.

[0016] The reducing agent solution is a hydrazine hydrate solution.

[0017] The atomization pressure of the atomization process in step (3) is 0.05-0.3MPa.

[0018] The application also provides a modified graphene oxide film encapsulated slow-release fertilizer prepared by the preparation method of the modified graphene oxide film encapsulated slow-release fertilizer, and the application of the modified graphene oxide film encapsulated slow-release fertilizer in the field of agriculture.

[0019] Compared with the prior art, the application has the following advantages and technical effects: by adding graphene oxide in the preparation process of polyacrylate emulsion, using maleic anhydride, acrylamide and methyl methacrylate as the three specific polymerization monomers, and polymerizing the monomers, the esterification reaction between maleic anhydride and the hydroxyl groups in graphene oxide is realized, the in-situ bonding of graphene oxide and polyacrylate emulsion is realized, the dispersibility and bonding force of graphene oxide and polymer emulsion are improved, and the dispersion between graphene oxide layers is also improved, so that the adsorption and slow-release functions of graphene oxide are fully exerted.

[0020] In addition to maleic anhydride, the acrylamide selected by the present application also contains a hydrophilic group, which can interact with graphene oxide during preparation and improve the binding force. By selecting maleic anhydride and acrylamide, the binding force between the polymer emulsion and graphene oxide is improved, and the water solubility of the slow-release fertilizer is also realized. In addition, methyl methacrylate, a hydrophobic monomer, is selected to control the swelling degree of the polymer emulsion. By adjusting the specific ratio of maleic anhydride, acrylamide and methyl methacrylate, the composite of graphene oxide can ensure a certain swelling degree of the film packaging material, improve the mechanical properties and film forming properties, and achieve the slow release effect of the fertilizer. In addition, the modified graphene oxide after reduction treatment can further control the swelling degree. The test results prove that the modified graphene oxide film packaging slow-release fertilizer has ideal slow-release effect. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The technical features designed in different embodiments of the present application can be combined with each other as long as they do not conflict with each other. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0022] In the description of the present application, it should be noted that all the terms (including technical terms and scientific terms) used in the present application have the same meaning as that generally understood by those skilled in the art to which the present application belongs, and should not be understood as a limitation of the present application; it should be further understood that the terms used in the present application should be understood as having the same meaning as the terms in the context of the present application and the related field, and should not be understood in an idealized or overly formal sense, unless defined explicitly in the present application.

[0023] Example 1: Modified graphene oxide film packaging slow-release fertilizer and its preparation method:

[0024] (1) In a 1000 mL four-necked flask, 10 g of OP-10 and 20 g of sodium dodecyl sulfate were added, 250 mL of deionized water was added in the four-necked flask, and after stirring uniformly, a mixture was obtained; in a 500 mL beaker, 20 g of maleic anhydride, 20 g of acrylamide and 120 g of methyl methacrylate were sequentially added and uniformly mixed to obtain a monomer solution, the monomer solution was added to the four-necked flask, and stirring was performed at a rotation speed of 300-500 rpm for 30 min to obtain an oil-water mixture; 10 g of a deionized water dispersion of graphene oxide was added to the oil-water mixture, and stirring was performed at a rotation speed of 500 rpm for 30 min; the four-necked flask was placed in a water bath and heated to 80°C, the stirring speed was adjusted to 700 rpm, 3 g of a deionized water solution of potassium sulfate was added dropwise, the dropwise addition time was 2 h, and after the dropwise addition was completed, the stirring reaction was continued for 2 h, to obtain a polymer composite graphene oxide solution;

[0025] (2) 25 g of a reducing agent solution was added dropwise to the polymer composite graphene oxide solution, stirring was performed for 60 min, and reflux reaction was performed at 90°C under oil bath conditions for 100 min, to obtain a modified graphene oxide solution after filtration;

[0026] (3) 200 g of potassium nitrate fertilizer particles were placed in a fluidized bed coater and fluidized, a peristaltic pump was used to pump the modified graphene oxide solution into a nozzle and atomize it into droplets, 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 coating for 3 times, a dense modified graphene oxide film was formed on the surface of the potassium nitrate fertilizer particles, thereby preparing the modified graphene oxide film encapsulated slow-release fertilizer;

[0027] (4) The modified graphene oxide film encapsulated slow-release fertilizer was placed in an oven at 80°C and dried for 48 h, to obtain a final product.

[0028] Example 2 modified graphene oxide film encapsulated slow-release fertilizer and a preparation method thereof:

[0029] (1) In a 1000 mL four-necked flask, 10 g of OP-10 and 20 g of sodium dodecyl sulfate were added, 250 mL of deionized water was added in the four-necked flask, and after stirring uniformly, a mixture was obtained; in a 500 mL beaker, 20 g of maleic anhydride, 20 g of acrylamide and 80 g of methyl methacrylate were sequentially added and uniformly mixed to obtain a monomer solution, the monomer solution was added to the four-necked flask, and stirring was performed at a rotation speed of 300-500 rpm for 30 min to obtain an oil-water mixture; 10 g of a deionized water dispersion of graphene oxide was added to the oil-water mixture, and stirring was performed at a rotation speed of 500 rpm for 30 min; the four-necked flask was placed in a water bath and heated to 80°C, the stirring speed was adjusted to 700 rpm, 3 g of a deionized water solution of potassium sulfate was added dropwise, the dropwise addition time was 2 h, and after the dropwise addition was completed, the stirring reaction was continued for 2 h, to obtain a polymer composite graphene oxide solution;

[0030] (2) 25 g of a reducing agent solution was added dropwise to the polymer composite graphene oxide solution, stirring was performed for 60 min, and reflux reaction was performed at 90°C under oil bath conditions for 100 min, to obtain a modified graphene oxide solution after filtration;

[0031] (3) 200 g of potassium nitrate fertilizer particles were placed in a fluidized bed coater and fluidized, a peristaltic pump was used to pump the modified graphene oxide solution into a nozzle and atomize it into droplets, 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 coating for 3 times, a dense modified graphene oxide film was formed on the surface of the potassium nitrate fertilizer particles, thereby preparing the modified graphene oxide film encapsulated slow-release fertilizer;

[0032] (4) The modified graphene oxide film encapsulated slow-release fertilizer was placed in an oven at 80°C and dried for 48 h, to obtain a final product.

[0033] Comparative Example 1: Modified graphene oxide film encapsulated slow-release fertilizer and a preparation method thereof

[0034] (1) In a 1000 mL four-necked flask, 10 g of OP-10 and 20 g of sodium dodecyl sulfate were added, 250 mL of deionized water was added in the four-necked flask, and after stirring uniformly, a mixture was obtained; in a 500 mL beaker, 20 g of maleic anhydride, 20 g of acrylamide and 65 g of methyl methacrylate were sequentially added and uniformly mixed to obtain a monomer solution, the monomer solution was added to the four-necked flask, and stirring was performed at a rotation speed of 300-500 rpm for 30 min to obtain an oil-water mixture; 10 g of a deionized water dispersion of graphene oxide was added to the oil-water mixture, and stirring was performed at a rotation speed of 500 rpm for 30 min; the four-necked flask was placed in a water bath and heated to 80°C, the stirring speed was adjusted to 700 rpm, 3 g of a deionized water solution of potassium sulfate was added dropwise, the dropwise addition time was 2 h, and after the dropwise addition was completed, the stirring reaction was continued for 2 h, to obtain a polymer composite graphene oxide solution;

[0035] (2) 25 g of a reducing agent solution was added dropwise to the polymer composite graphene oxide solution, stirring was performed for 60 min, and reflux reaction was performed at 90°C under oil bath conditions for 100 min, to obtain a modified graphene oxide solution after filtration;

[0036] (3) 200 g of potassium nitrate fertilizer particles were placed in a fluidized bed coater and fluidized, a peristaltic pump was used to pump the modified graphene oxide solution into a nozzle and atomize it into droplets, 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 coating for 3 times, a dense modified graphene oxide film was formed on the surface of the potassium nitrate fertilizer particles, thereby preparing the modified graphene oxide film encapsulated slow-release fertilizer;

[0037] (4) The modified graphene oxide film encapsulated slow-release fertilizer was placed in an oven at 80°C and dried for 48 h, to obtain a final product.

[0038] Comparative Example 2: Modified graphene oxide film encapsulated slow-release fertilizer and preparation method thereof

[0039] (1) In a 1000 mL four-necked flask, 10 g of OP-10 and 20 g of sodium dodecyl sulfate were added, 250 mL of deionized water was added in the four-necked flask, and after stirring uniformly, a mixture was obtained; in a 500 mL beaker, 20 g of maleic anhydride, 20 g of acrylamide and 125 g of methyl methacrylate were sequentially added and uniformly mixed to obtain a monomer solution, the monomer solution was added to the four-necked flask, and stirring was performed at a rotation speed of 300-500 rpm for 30 min to obtain an oil-water mixture; 10 g of a deionized water dispersion of graphene oxide was added to the oil-water mixture, and stirring was performed at a rotation speed of 500 rpm for 30 min; the four-necked flask was placed in a water bath and heated to 80°C, the stirring speed was adjusted to 700 rpm, 3 g of a deionized water solution of potassium sulfate was added dropwise, the dropwise addition time was 2 h, and after the dropwise addition was completed, the stirring reaction was continued for 2 h, to obtain a polymer composite graphene oxide solution;

[0040] (2) 25 g of a reducing agent solution was added dropwise to the polymer composite graphene oxide solution, stirring was performed for 60 min, and reflux reaction was performed at 90°C under oil bath conditions for 100 min, to obtain a modified graphene oxide solution after filtration;

[0041] (3) 200 g of potassium nitrate fertilizer particles were placed in a fluidized bed coater and fluidized, a peristaltic pump was used to pump the modified graphene oxide solution into a nozzle and atomize it into droplets, 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 coating for 3 times, a dense modified graphene oxide film was formed on the surface of the potassium nitrate fertilizer particles, thereby preparing the modified graphene oxide film encapsulated slow-release fertilizer;

[0042] (4) The modified graphene oxide film encapsulated slow-release fertilizer was placed in an oven at 80°C and dried for 48 h, to obtain a final product.

[0043] Comparative Example 3: Modified graphene oxide film encapsulated slow-release fertilizer and a preparation method thereof

[0044] (1) In a 1000 mL four-necked flask, 10 g of OP-10 and 20 g of sodium dodecyl sulfate were added, 250 mL of deionized water was added to the four-necked flask, and the mixture was stirred uniformly; 20 g of maleic anhydride, 20 g of acrylamide and 120 g of methyl methacrylate were sequentially added to a 500 mL beaker and mixed uniformly to obtain a monomer solution, the monomer solution was added to the four-necked flask, and the oil-water mixture was obtained by stirring at a speed of 300-500 rpm for 30 min; 10 g of a deionized water dispersion of graphene oxide was added to the oil-water mixture, and the mixture was stirred at a speed of 500 rpm for 30 min; the four-necked flask was placed in a water bath and heated to 80°C, the stirring speed was adjusted to 700 rpm, 3 g of potassium sulfate deionized water solution was added dropwise, the dropwise addition time was 2 h, and the stirring reaction was continued for 2 h after the dropwise addition was completed to obtain a polymer composite graphene oxide solution;

[0045] (2) The 200 g of potassium nitrate fertilizer particles were placed in a fluidized bed coater and fluidized, the modified graphene oxide solution was pumped into a nozzle by using a peristaltic pump and atomized into droplets, the atomization pressure was 0.1 MPa, the droplets were sprayed on the surface of the potassium nitrate fertilizer in the fluidized bed, and the modified graphene oxide film was formed on the surface of the potassium nitrate fertilizer particles after being coated for 3 times through the dehydration of the fluidized bed gas, thereby preparing the modified graphene oxide film encapsulated slow-release fertilizer;

[0046] (3) The modified graphene oxide film encapsulated slow-release fertilizer was dried in an oven at 80°C for 48 h to obtain the final product.

[0047] Comparative Example 4: Modified graphene oxide film encapsulated slow-release fertilizer and preparation method thereof

[0048] (1) In a 1000 mL four-necked flask, 10 g of OP-10 and 20 g of sodium dodecyl sulfate were added, 250 mL of deionized water was added to the four-necked flask, and the mixture was stirred uniformly; 20 g of maleic anhydride, 20 g of acrylamide and 120 g of methyl methacrylate were sequentially added to a 500 mL beaker and mixed uniformly to obtain a monomer solution, the monomer solution was added to the four-necked flask, and the oil-water mixture was obtained by stirring at a speed of 300-500 rpm for 30 min; the four-necked flask was placed in a water bath and heated to 80°C, the stirring speed was adjusted to 700 rpm, 3 g of potassium sulfate deionized water solution was added dropwise, the dropwise addition time was 2 h, and the stirring reaction was continued for 2 h after the dropwise addition was completed to obtain a polymer composite graphene oxide solution;

[0049] (2) 25 g of a reducing agent solution was added dropwise to the polymer composite graphene oxide solution, stirred for 60 min, and refluxed at 90°C for 100 min in an oil bath, and a modified graphene oxide solution was obtained by filtration;

[0050] (3) 200 g of potassium nitrate fertilizer particles were placed in a fluidized bed coater and fluidized, the modified graphene oxide solution was pumped into a nozzle using a peristaltic pump and atomized into droplets, the atomization pressure was 0.1 MPa, the droplets were sprayed onto the surface of the potassium nitrate fertilizer in the fluidized bed, and the potassium nitrate fertilizer particles were coated 3 times to form a dense modified graphene oxide film on the surface of the potassium nitrate fertilizer particles, thereby preparing the modified graphene oxide film encapsulated slow-release fertilizer;

[0051] (4) The modified graphene oxide film encapsulated slow-release fertilizer was dried in an oven at 80°C for 48 h to obtain the final product.

[0052] The following test methods were used to evaluate the performance of Examples 1-2 and Comparative Examples 1-4.

[0053] Swelling degree test: The water resistance of the sample was characterized by testing the swelling degree of the modified graphene oxide film encapsulated slow-release fertilizer in water. In theory, under the same conditions, the lower the swelling degree, the better the water resistance and the better the slow-release effect. The swelling degree is defined as: ((W2-W1) / W1) x 100%.

[0054] The sample was immersed in 50 mL of deionized water at 25°C in a 50 mL jar, and the mass of the sample before immersion (w1) and after immersion (w2) was measured. The sample was weighed every three days until the weight was constant.

[0055] Table 1 Product swelling degree test results:

[0056] Item 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

[0057] Slow-release performance test: According to the national standard for 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 in 25°C static water for 24 hours, the better the slow-release effect.

[0058] Table 2 Product slow-release performance test results:

[0059] Item 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 for 28 days 44.56%% 49.45% 66.32% 77.84% 78.11% 73.85%

[0060] It can be seen from the test results in Table 1 and Table 2 that, by using specific monomers maleic anhydride, acrylamide and methyl methacrylate as raw materials for emulsion polymerization, and adding graphene oxide in situ during the preparation of the polymer emulsion, by controlling the specific ratio range of maleic anhydride, acrylamide and methyl methacrylate monomers, and further reducing the graphene oxide, the film packaging material can not only have low swelling degree, but also have good dispersion of graphene oxide, fully play the adsorption and slow-release performance, mechanical properties, and the film packaging material also has good film-forming property and adhesion. The improvement of the above comprehensive performance makes the product obtained by coating the modified graphene oxide film packaging material on the potassium nitrate fertilizer have excellent swelling degree and slow-release performance.

[0061] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a modified graphene oxide film encapsulated slow release fertilizer, characterized in that, It comprises the following preparation steps, (1) 30 g of a surfactant is added into a 1000 mL four-necked flask, 250 mL of deionized water is added into the four-necked flask, and a mixture is obtained after stirring uniformly; 500 mL of a beaker is sequentially added with maleic anhydride, acrylamide and methyl methacrylate, and a monomer solution is obtained after mixing uniformly, the monomer solution is added into the four-necked flask, and an oil-water mixture is obtained after stirring at a rotating speed of 300-500 rpm for 30 min; 10 g of a deionized water dispersion of graphene oxide is added into the oil-water mixture, and stirring is performed at a rotating speed of 300-500 rpm for 30 min; the four-necked flask is placed into a water bath and heated and kept at 70-80 ℃, the stirring speed is adjusted to 500-700 rpm, and an initiator solution is added dropwise, the dropwise adding time is 2 h, and continuous stirring reaction is performed for 2 h after the dropwise adding is completed, and a polymer composite graphene oxide solution is obtained; the mass ratio of maleic anhydride, acrylamide and methyl methacrylate in the monomer solution is 1:1:4-6, and the initiator solution is a potassium persulfate deionized water solution; (2) a reducing agent solution is added dropwise into the polymer composite graphene oxide solution, stirring is performed for 30 min-60 min, reflux reaction is performed at 90 ℃ under oil bath conditions for 80-120 min, and a modified graphene oxide solution is obtained after filtration; (3) 200 g of potassium nitrate fertilizer particles are placed into a fluidized bed coater and fully fluidized, a peristaltic pump is used to pump the modified graphene oxide solution into a nozzle and atomize into droplets, the droplets are sprayed onto the surface of the potassium nitrate fertilizer in the fluidized bed, dehydration is performed through the fluidized bed gas, and a dense modified graphene oxide film is formed on the surface of the potassium nitrate fertilizer particles after coating for 3-5 times, so that the modified graphene oxide film encapsulated slow-release fertilizer is prepared; (4) the modified graphene oxide film encapsulated slow-release fertilizer is placed into an oven at 60-80 ℃ and dried for 48 h, and a final product is obtained.

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

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

5.

4. A method of preparing a modified graphene oxide film encapsulated slow release fertilizer according to 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.

5. A method of preparing a modified graphene oxide film encapsulated slow release fertilizer according to 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.

6. A method of preparing a modified graphene oxide film encapsulated slow release fertilizer according to claim 1, characterized in that, The reducing agent solution is a hydrazine hydrate solution.

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

8. A modified graphene oxide film encapsulated slow release fertilizer, characterized in that, The modified graphene oxide film encapsulated slow-release fertilizer is prepared by the preparation method of any one of claims 1-7.

9. Application of the modified graphene oxide film encapsulated slow-release fertilizer of claim 8 in the field of agriculture.