Composite material with graphene coupled with trace elements as well as preparation method and application of composite material

Abstract

The invention discloses a graphene coupled trace element composite material as well as a preparation method and application thereof. The composite material comprises graphene oxide, sugar alcohol and a metal salt hydrate, the metal salt hydrate is selected from at least one of CuSO4. 5H2O, Mn (NO3) 2.4 H2O and Zn (NO3) 2.6 H2O. The preparation method of the composite material is simple, energy consumption is low, the problems of energy waste and environmental pollution in the agricultural production process are solved, and the composite material not only has efficient absorption and utilization performance, but also has excellent water retention performance for preventing and treating soil hardening, and has a good application prospect. The soil resource utilization rate and the crop yield can be further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of agricultural production, and relates to a composite material of graphene coupled with trace elements, a preparation method thereof, and an application thereof. Background Art

[0002] China is a traditional agricultural country with a large planting area of crops, and a large amount of chemical fertilizers are required in the process of agricultural production every year. Traditional fertilizers are prone to problems such as soil compaction and acidification. Therefore, the research, development and use of new fertilizers are imminent.

[0003] Generally, in weakly acidic and alkaline soils, metal ions are easily precipitated and difficult to be absorbed and utilized by crops. Chelates formed by the reaction of chelating agents with metal ions have stronger acid-base adaptability and can well solve this problem. Traditional inorganic trace element fertilizers generally have problems such as antagonism, difficult absorption by crops, and low utilization rate. Currently, EDTA, citric acid, amino acids, etc. are commonly used as chelating agents to react with trace elements. Among them, the EDTA chelate has a large stability constant and the chelate is stable (CN112021111A). EDTA itself has no nutritional value for crops, and has high costs, difficult degradation, and is easy to cause environmental pollution. Organic acid chelating agents such as citric acid, their chelated fertilizers are easy to decompose, the chelating ability is weak, and it is easy to generate precipitation when reacting with calcium and magnesium ions, resulting in a decrease in fertility. Therefore, their application is also greatly limited. Chinese patent document CN112552111A discloses a medium element water-soluble fertilizer and a preparation method thereof. Although this invention solves the problem that the water-soluble fertilizer is easy to generate precipitation, the addition amount of poly-peptide chelated potassium is small, and the concentration of the chelate cannot be guaranteed. Chinese patent document CN102408347A discloses a preparation method of L-aspartic acid chelated potassium dihydrate. This chelated potassium uses aspartic acid to react with potassium carbonate / potassium hydroxide. The weight-volume ratio of the reactant L-aspartic acid to deionized water is 0.1-0.3:1, and the reaction adjusts the pH to 6.0-8.0. This method uses amino acids as chelating agents, the product is not clear, the cost of amino acids is high, and the chelate is easy to decompose. To sum up, there is an urgent need to develop chelating agents with low prices and moderate chelating abilities to improve the performance of trace element fertilizers. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0005] A composite material, the composite material includes graphene oxide, sugar alcohol, and metal salt hydrate.

[0006] According to an embodiment of the present invention, the metal salt hydrate is selected from at least one of CuSO4·5H2O, Mn(NO3)2·4H2O, Zn(NO3)2·6H2O.

[0007] According to an embodiment of the present invention, in the composite material, the metal hydrate includes CuSO4·5H2O, Mn(NO3)2·4H2O, and Zn(NO3)2·6H2O, and their mass ratio is 1:(0.1-5):(1-10), and an example is 1:1:4.

[0008] According to an embodiment of the present invention, the mass fraction of the metal hydrate in the composite material is 1-60%, for example, 2-50%, and examples are 5%, 7%, 10%, 20%, 25%.

[0009] According to an embodiment of the present invention, the graphene oxide is selected from graphene oxide solutions.

[0010] According to an embodiment of the present invention, the graphene oxide solution serves as a solvent material and a chelation reaction promoter material. Preferably, the surface of the graphene oxide has a large number of hydrophilic groups such as hydroxyl groups and carboxyl groups, which can form hydrogen bond bonding with sugar alcohol molecules, causing the spatial structure of the sugar alcohol molecules to rearrange.

[0011] According to an embodiment of the present invention, in the graphene oxide solution, the mass concentration of graphene oxide is 0.1-2%, for example, 0.7%.

[0012] According to an embodiment of the present invention, the solvent in the graphene oxide solution is selected from water.

[0013] According to an embodiment of the present invention, the sugar alcohol is selected from at least one of sorbitol, xylitol, mannitol, etc.

[0014] According to an embodiment of the present invention, in the composite material, the mass ratio of the graphene oxide solution, sugar alcohol, and metal hydrate is preferably (15-1):(0.1-10):1, and examples are 15:3:1, 9:3:1, 9:0.1:1, 1:3:1, 1:2:1.

[0015] According to an embodiment of the present invention, the chelation rate of the composite material is not less than 45%, for example, the chelation rate is 45-90%, and an example is 90%.

[0016] The present invention also provides a method for preparing the above composite material, and the preparation method includes: mixing sugar alcohol, graphene oxide solution, and metal hydrate to obtain a mixed solution, and performing a chelation reaction under hydrothermal conditions to obtain the composite material.

[0017] According to an embodiment of the present invention, the mass ratio of the graphene oxide solution, sugar alcohol, and metal hydrate is preferably (15-1):(0.1-10):1, and examples are 15:3:1, 9:3:1, 9:0.1:1, 1:3:1, 1:2:1.

[0018] According to an embodiment of the present invention, in the graphene oxide solution, the mass concentration of graphene oxide is 0.1-2%, for example, 0.7%.

[0019] According to an embodiment of the present invention, the solvent in the graphene oxide solution is selected from water.

[0020] According to an embodiment of the present invention, the graphene solution can be prepared by a method known in the art. Preferably, the preparation method of the graphene oxide solution includes: preparing an aqueous solution of graphene oxide by using the high-frequency alternating current pulse method according to Patent Document CN106587018B. For example: First, put the anode and cathode plates of high-purity graphite with a size of 600×300×80 into the electrolytic oxidation tank, and the distance between the anode and cathode plates is 70 mm. Then pour 0.09% sulfuric acid electrolyte into the tank, turn on the power supply, and carry out electrolytic oxidation to prepare a graphene aggregate sol. The anode and cathode plates are separated by a plastic mesh, and the effective current density is controlled at 100 A / m 2 ; the power pulse frequency is 60 Hz; the effective voltage is 20 V; the temperature is controlled at 60 °C. After reacting for 200 hours, when the concentration of the graphene sol reaches 0.7%, the oxidation reaction ends, and the solution in the tank is the graphene oxide solution.

[0021] According to an embodiment of the present invention, the preparation method of the mixed solution specifically includes: adding sugar alcohol to the graphene oxide solution to obtain a sugar alcohol graphene oxide solution, and then adding a metal hydrate to the sugar alcohol graphene oxide solution, and sealing and heating and stirring to obtain the mixed solution.

[0022] Preferably, the aqueous solution of graphene oxide is preheated, and sugar alcohol is added to the aqueous solution of graphene oxide and continuously stirred until the sugar alcohol is completely dissolved to obtain the sugar alcohol graphene oxide solution.

[0023] Preferably, the temperature of the preheating treatment is 30-50 °C, for example, 40 °C. Preferably, the time of the preheating treatment is 1-5 hours, and exemplarily, it is 1 hour.

[0024] Preferably, when the sugar alcohol is dissolved under stirring conditions, the stirring conditions known in the art can be selected; for example, the stirring time is 1-5 hours, and exemplarily, it is 1 hour.

[0025] According to an embodiment of the present invention, the hydrothermal conditions in the present invention can be selected by a device known in the art. For example, it is carried out in a stainless steel hydrothermal reaction kettle.

[0026] According to an embodiment of the present invention, the preparation method further includes stirring the mixed solution. Preferably, the stirring can be carried out under conditions known in the art. For example, the stirring time is 0.1-6 hours, and exemplarily, it is 1 hour.

[0027] According to an embodiment of the present invention, the temperature of the chelation reaction is 60-100 °C, for example, 80 °C.

[0028] According to an embodiment of the present invention, the time of the chelation reaction is 0.1-2 hours, for example, 1 hour.

[0029] According to an embodiment of the present invention, the pH of the chelation reaction is 4-7, exemplarily pH = 7.

[0030] According to an embodiment of the present invention, the chelation reaction is carried out under sealed conditions. Preferably, the sealing pressure is 0-10 MPa, exemplarily 5 MPa.

[0031] According to an embodiment of the present invention, after the chelation reaction, heat preservation is optionally carried out.

[0032] According to an embodiment of the present invention, the temperature of the heat preservation is 60-80 °C, exemplarily 80 °C; the time of the heat preservation is 1-6 hours, exemplarily 2 hours.

[0033] The present invention also provides the application of the above composite material in the field of fertilizers, for example, for compound fertilizers.

[0034] The present invention also provides a compound fertilizer, which comprises the above composite material.

[0035] The present invention also provides the application of the above composite material in the agricultural field.

[0036] Beneficial effects

[0037] Under the combined action of the excellent properties of graphene oxide such as high specific surface area, good water absorption, and the excellent conduction performance of sugar alcohols in plants, the chelate formed by metal hydrate salts and sugar alcohols is more easily absorbed by plants, and its fertilizer efficiency is higher than that of ordinary fertilizers, showing a more prominent application value. In view of this, the present invention applies graphene oxide and sugar alcohols to trace element fertilizers and designs and synthesizes a graphene-coupled trace element compound fertilizer with prominent water retention performance and stable absorption and transportation of trace elements.

[0038] Specifically:

[0039] In the present invention, sugar alcohol is used as a chelating agent and graphene oxide is used as a chelating promoter. Since the surface of graphene oxide has a large number of hydrophilic groups such as hydroxyl groups and carboxyl groups, which can form hydrogen bonds with sugar alcohol molecules, the spatial structure of the sugar alcohol molecules is rearranged. At this time, a large number of chelating groups on the sugar alcohol molecules are fully exposed, thereby effectively improving the contact probability between the sugar alcohol molecules and the metal trace elements in the metal salt hydrate, increasing the chelating ability and the stability of the chelate. At the same time, the sugar alcohol in the composite material can also provide more nutrients for crops as a ligand, which is beneficial to the growth of crops.

[0040] The graphene-coupled trace element compound fertilizer of the present invention utilizes a graphene oxide solution as a plant root growth promoter and a liquid reaction environment for fertilizer synthesis, and utilizes sugar alcohols and metal salt hydrates for chelation, thereby producing the graphene-coupled trace element compound fertilizer. This graphene-coupled trace element compound fertilizer material not only exhibits efficient absorption and utilization properties but also possesses excellent water retention properties, preventing soil compaction. The compound fertilizer provided by the present invention facilitates the full utilization of land resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a scanning electron microscope photograph of the compound fertilizer prepared in Example 2 of the present invention.

[0042] Figure 2 These are photos of crops before and after using the compound fertilizer prepared by the present invention. DETAILED DESCRIPTION

[0043] The technical solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection that the present invention is intended to protect.

[0044] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0045] In the preparation process of graphene-coupled trace element compound fertilizer, homemade graphene oxide solution is used as an example of graphene, sorbitol is used as an example of sugar alcohol, and CuSO4·5H2O, Mn(NO3)2·4H2O, and Zn(NO3)2·6H2O are used as examples of metal salt hydrates.

[0046] The performance test process of each compound fertilizer in the following examples:

[0047] First, fully chelate the graphene-coupled trace element compound fertilizer. After the reaction is completed, conduct a fertilization test. The growth temperature of all plants is maintained at 22 °C, and the photoperiod is 16 / 8 h (day / night). In the first 4 weeks of plant growth, water, apply no graphene trace element fertilizer (diluted 300 times), and apply graphene-coupled trace element compound fertilizer (diluted 300 times) once every 5 days, 60 mL each time. After the 5th week, water once every 3 days, 100 mL each time. Measure and analyze various data on the 30th day of plant growth.

[0048] Example 1

[0049] A preparation method of a graphene-coupled trace element composite material, comprising the following steps:

[0050] 1) Prepare graphene oxide solution: Prepare graphene oxide solution using the high-frequency alternating current pulse method according to patent document CN106587018B; first, place an anode and a high-purity graphite cathode plate of high-purity graphite with dimensions of 600 mm × 300 mm × 80 mm into an electrolytic oxidation tank, and the distance between the anode and cathode plates is 70 mm. Then pour 0.09% sulfuric acid electrolyte (i.e., 0.09% sulfuric acid aqueous solution) into the tank, turn on the power supply, and conduct electrolytic oxidation to prepare graphene aggregate sol. The anode and cathode plates are separated by a plastic mesh, and the effective current density is controlled at 100 A / m 2 ; the power pulse frequency is 60 Hz; the effective voltage is 20 V; the temperature is controlled at 60 °C. After reacting for 200 hours, when the concentration of graphene sol reaches 0.7%, the oxidation reaction ends, and the solution in the tank is the graphene oxide solution.

[0051] 2) Prepare sorbitol graphene oxide solution: Preheat the graphene oxide solution to 40 °C for 1 hour, add sorbitol material powder to the graphene oxide solution, and continuously stir until the sorbitol powder is completely dissolved. The mass ratio of sorbitol material powder to graphene oxide solution is 1:5.

[0052] 3) Dissolve metal hydrates CuSO4·5H2O, Mn(NO3)2·4H2O, and Zn(NO3)2·6H2O in the sorbitol graphene oxide solution according to a mass ratio of 1:1:4, keeping the mass ratio of metal hydrate, sorbitol, and graphene oxide solution as 1:3:15. Add ammonia water to adjust the pH to 7, stir and mix, seal the hydrothermal reaction kettle, and conduct a stirring chelation reaction at 80 °C for 1 hour. After the reaction, keep it at 80 °C for 2 hours to prepare the composite material, which is the compound fertilizer. Chelation rate = (content of chelated metal elements / total amount of metal elements) × 100%; the chelation rate is measured to be 80% by inductively coupled plasma optical emission spectrometry (ICP-OES) method.

[0053] Comparative Example 1

[0054] The method for preparing the comparative fertilizer in this comparative example is specifically as follows: Dissolve metal hydrate salts CuSO4·5H2O, Mn(NO3)2·4H2O, and Zn(NO3)2·6H2O in water according to a mass ratio of 1:1:4, add ammonia water to adjust the pH to 7, stir and mix. Seal the hydrothermal reaction kettle and carry out stirring reaction at 80°C for 1 hour. After the reaction, keep it warm at 80°C for 2 hours to prepare the comparative composite material, which is the comparative fertilizer.

[0055] Example 2

[0056] A method for preparing a graphene-coupled trace element compound fertilizer includes the following steps:

[0057] 1) Prepare graphene oxide solution: Use the high-frequency alternating current pulse method to prepare graphene oxide solution according to Patent CN106587018B; First, place the anode and cathode plates of high-purity graphite with dimensions of 600mm×300mm×80mm into the electrolytic oxidation tank, and the distance between the anode and cathode plates is 70mm. Then pour 0.09% sulfuric acid electrolyte into the tank, connect the power supply, and carry out electrolytic oxidation to prepare graphene aggregate sol. The anode and cathode plates are separated by a plastic mesh, and the effective current density is controlled at 100A / m 2 ; The power pulse frequency is 60Hz; The effective voltage is 20V; Control the temperature at 60°C. After reacting for 200 hours, when the concentration of graphene sol reaches 0.7%, the oxidation reaction ends, and the solution in the tank is the graphene oxide solution.

[0058] 2) Prepare sorbitol graphene oxide solution: Preheat the graphene oxide solution to 40°C for 1 hour, add sorbitol material powder to the graphene oxide solution according to a mass ratio of 1:3, and continuously stir until the sorbitol powder is completely dissolved.

[0059] 3) Dissolve metal hydrate salts CuSO4·5H2O, Mn(NO3)2·4H2O, and Zn(NO3)2·6H2O in the sorbitol graphene oxide solution, keeping the mass ratio of the metal hydrate salt to sorbitol and the graphene oxide solution as 1:3:9. Add ammonia water to adjust the pH to 7, stir and mix. Seal the hydrothermal reaction kettle and carry out stirring chelation reaction at 80°C for 1 hour. After the reaction, keep it warm at 80°C for 2 hours to prepare the compound fertilizer. The chelation rate is measured to be 90% by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0060] When using the compound fertilizer of Example 2, the leaf area of sunflower seedlings increased significantly by 305.5%, and the plant height increased significantly by 37.17%.

[0061] Example 3

[0062] Preparation method of graphene-coupled trace element compound fertilizer, comprising the following steps:

[0063] 1) Preparation of graphene oxide solution: Prepare graphene oxide solution using the high-frequency alternating current pulse method according to Patent CN106587018B; First, place the anode and cathode plates of high-purity graphite with dimensions of 600×300×80 into the electrolytic oxidation tank, and the distance between the anode and cathode plates is 70 mm. Then pour 0.09% sulfuric acid electrolyte into the tank, turn on the power supply, and carry out electrolytic oxidation to prepare graphene aggregate sol. The anode and cathode plates are separated by a plastic mesh, and the effective current density is controlled at 100 A / m 2 ; The power pulse frequency is 60 Hz; The effective voltage is 20 V; Control the temperature at 60 °C. After reacting for 200 hours, when the concentration of graphene sol reaches 0.7%, the oxidation reaction ends, and the solution in the tank is the graphene oxide solution.

[0064] 2) Preparation of sorbitol graphene oxide solution: Preheat the graphene oxide solution to 40 °C for 1 hour, add sorbitol material powder to the graphene oxide solution according to a mass ratio of 0.1:9, and continuously stir until the sorbitol powder is completely dissolved.

[0065] 3) Dissolve metal hydrate salts CuSO4·5H2O, Mn(NO3)2·4H2O, Zn(NO3)2·6H2O in the sorbitol graphene oxide solution according to a mass ratio of 1:1:4, keeping the mass ratio of the metal hydrate salt, sorbitol, and graphene oxide solution at 1:0.1:9. Add ammonia water to adjust the pH to 7, stir and mix, seal the hydrothermal reaction kettle, and carry out a stirring chelation reaction at 80 °C for 1 hour. After the reaction, keep it warm at 80 °C for 2 hours to prepare the compound fertilizer. The chelation rate is measured to be 47% by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0066] Example 4

[0067] Preparation method of graphene-coupled trace element compound fertilizer, comprising the following steps:

[0068] 1) Preparation of graphene oxide solution: Prepare graphene oxide solution using the high-frequency alternating current pulse method according to Patent CN106587018B; First, place the anode and cathode plates of high-purity graphite with dimensions of 600×300×80 into the electrolytic oxidation tank, and the distance between the anode and cathode plates is 70 mm. Then pour 0.09% sulfuric acid electrolyte into the tank, turn on the power supply, and carry out electrolytic oxidation to prepare graphene aggregate sol. The anode and cathode plates are separated by a plastic mesh, and the effective current density is controlled at 100 A / m 2; The power pulse frequency is 60 Hz; the effective voltage is 20 V; the controlled temperature is 60 °C. After reacting for 200 hours, when the concentration of the graphene sol reaches 0.7%, the oxidation reaction ends, and the solution in the tank is the graphene oxide solution.

[0069] 2) Preparation of sugar alcohol graphene oxide solution: Preheat the graphene oxide solution to 40 °C for 1 hour, add the sorbitol material powder to the graphene oxide solution at a mass ratio of 3:1, and continuously stir until the sorbitol powder is completely dissolved.

[0070] 3) Dissolve metal hydrate salts CuSO4·5H2O, Mn(NO3)2·4H2O, and Zn(NO3)2·6H2O in the sorbitol graphene oxide solution at a mass ratio of 1:1:4, keeping the mass ratio of the metal hydrate salt, sorbitol, and graphene oxide solution as 1:3:1. Add ammonia water to adjust the pH to 7, stir and mix, seal the hydrothermal reaction kettle, and carry out a stirring chelation reaction at 80 °C for 1 hour. After the reaction, keep it warm at 80 °C for 2 hours to prepare the compound fertilizer. The chelation rate is measured to be 56% by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0071] Example 5

[0072] A method for preparing a graphene-coupled trace element compound fertilizer, comprising the following steps:

[0073] 1) Preparation of graphene oxide solution: Use the high-frequency alternating current pulse method to prepare graphene oxide solution according to Patent CN106587018B; first, place the anode and cathode plates of high-purity graphite with dimensions of 600×300×80 in the electrolytic oxidation tank, and the distance between the anode and cathode plates is 70 mm. Then pour 0.09% sulfuric acid electrolyte into the tank, turn on the power supply, and carry out electrolytic oxidation to prepare graphene aggregate sol. The anode and cathode plates are separated by a plastic mesh, and the effective current density is controlled at 100 A / m 2 ; The power pulse frequency is 60 Hz; the effective voltage is 20 V; the controlled temperature is 60 °C. After reacting for 200 hours, when the concentration of the graphene sol reaches 0.7%, the oxidation reaction ends, and the solution in the tank is the graphene oxide solution.

[0074] 2) Preparation of sugar alcohol graphene oxide solution: Preheat the graphene solution to 40 °C for 1 hour, add the sorbitol material powder to the graphene oxide solution at a mass ratio of 2:1, and continuously stir until the sorbitol powder is completely dissolved. The chelation rate is measured to be 45% by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0075] 3) Dissolve metal hydrate salts CuSO4·5H2O, Mn(NO3)2·4H2O, and Zn(NO3)2·6H2O in a sorbitol graphene oxide solution at a mass ratio of 1:1:4, maintaining the mass ratio of metal hydrate salts to sorbitol and graphene oxide solution at 1:2:1. Add ammonia water to adjust the pH to 7, stir and mix. Seal the hydrothermal reaction kettle and carry out a stirring chelation reaction at 80°C for 1 hour. After the reaction, keep it at 80°C for 2 hours to prepare the compound fertilizer.

[0076] Test Example 1

[0077] Use the compound fertilizers of Examples 1 - 5 and the comparative fertilizer of Comparative Example 1 for fertilizing sunflower seedlings to test their performance. Additionally, set up a control group that only uses distilled water as the fertilizer for sunflower seedlings; it is learned that:

[0078] Compared with the control group (only adding distilled water), when using the comparative fertilizer of Comparative Example 1, the leaf area of sunflower seedlings increased significantly by 173.2% and the plant height increased significantly by 24.91%;

[0079] Compared with the control group (only adding distilled water), when using the compound fertilizer of Example 1, the leaf area of sunflower seedlings increased significantly by 239.56% and the plant height increased significantly by 38.29%.

[0080] Compared with the control group (only adding distilled water), when using the compound fertilizer of Example 2, the leaf area of sunflower seedlings increased significantly by 305.5% and the plant height increased significantly by 37.17%.

[0081] Compared with the control group (only adding distilled water), when using the compound fertilizer of Example 3, the leaf area of sunflower seedlings increased significantly by 209.37% and the plant height increased significantly by 36.32%.

[0082] Compared with the control group (only adding distilled water), when using the compound fertilizer of Example 4, the leaf area of sunflower seedlings increased significantly by 181.26% and the plant height increased significantly by 27.41%.

[0083] Compared with the control group (only adding distilled water), when using the compound fertilizer of Example 5, the leaf area of sunflower seedlings increased significantly by 185.13% and the plant height increased significantly by 29.33%.

[0084] Figure 1 Scanning electron microscope photograph of the compound fertilizer prepared for Example 2. It can be seen from Figure 1 that the obvious lamellar porous structure exhibited by graphene oxide, and no other particles were observed.

[0085] Figure 2 Performance test of the graphene-coupled trace element compound fertilizer prepared for Example 2, photographs of crops before and after use. Among them, Figure a is the control group,Figure 2 In b-f, all are compound fertilizers of Application Example 2. The specific differences are as follows: the compound fertilizers of Example 2 are diluted 300, 200, 150, and 100 times respectively; Figure 2 the concentration of the compound fertilizer corresponding to f in is 0.03%. From Figure 2 it can be clearly seen that the leaf area and plant height of sunflower seedlings using the graphene-coupled trace element compound fertilizer of Example 2 are significantly increased compared with those of sunflower seedlings using the control group.

[0086] Adjustments are made according to the process parameters recorded in the present invention, and the preparation of the graphene-coupled trace element composite material can be realized, and it exhibits basically the same performance as the composite material of Example 2.

[0087] The above describes the exemplary embodiments of the present invention. However, the protection scope of this application is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A composite material, characterized in that, The composite material includes graphene oxide, sugar alcohol, and metal salt hydrate; The metal salt hydrate is selected from at least one of CuSO4·5H2O, Mn(NO3)2·4H2O, and Zn(NO3)2·6H2O.

2. The composite material according to claim 1, characterized in that, In the composite material, the metal salt hydrate includes CuSO4·5H2O, Mn(NO3)2·4H2O, and Zn(NO3)2·6H2O, and their mass ratio is: 1:(0.1 - 5):(1 - 10). Preferably, the mass fraction of the metal salt hydrate in the composite material is 1 - 60%.

3. The composite material according to claim 1 or 2, characterized in that, The graphene oxide is selected from graphene oxide solutions. Preferably, the graphene oxide solution serves as a solvent material and a chelation reaction promoter material. Preferably, in the graphene oxide solution, the mass concentration of graphene oxide is 0.1 - 2%. Preferably, the solvent in the graphene oxide solution is selected from water.

4. The composite material according to any one of claims 1 to 3, characterized in that, The sugar alcohol is selected from at least one of sorbitol, xylitol, and mannitol. Preferably, in the composite material, the mass ratio of the graphene solution, sugar alcohol, and metal salt hydrate is (15 - 1):(0.1 - 10):

1. Preferably, the chelation rate of the composite material is not less than 45%.

5. A method for preparing the composite material according to any one of claims 1-4, characterized in that, The preparation method includes: mixing sugar alcohol, graphene oxide solution, and metal salt hydrate to obtain a mixed solution, and performing a chelation reaction under hydrothermal conditions to obtain the composite material.

6. The preparation method according to claim 5, characterized in that, The mass ratio of the graphene oxide solution, sugar alcohol, and metal salt hydrate is (15 - 1):(0.1 - 10):

1. Preferably, in the graphene oxide solution, the mass concentration of graphene oxide is 0.1 - 2%. Preferably, the solvent in the graphene oxide solution is selected from water. Preferably, the specific preparation method of the mixed solution includes: adding sugar alcohol to the graphene oxide solution to obtain a sugar alcohol - graphene oxide solution, and then adding the metal salt hydrate to the sugar alcohol - graphene oxide solution, and sealing and heating and stirring to obtain the mixed solution.

7. The preparation method according to claim 5 or 6, characterized in that, The preparation method further includes stirring the mixed solution. Preferably, the temperature of the chelation reaction is 60 - 100°C. Preferably, the time of the chelation reaction is 0.1 - 2 hours. Preferably, the pH of the chelation reaction is 4 - 7. Preferably, the chelation reaction is carried out under sealed conditions. Preferably, the sealing pressure is 0 - 10 MPa. Preferably, after the chelation reaction, heat preservation is optionally carried out. Preferably, the temperature of the heat preservation is 60 - 80°C; the time of the heat preservation is 1 - 6 hours.

8. Application of the composite material according to any one of claims 1 - 4 in the field of fertilizers.

9. A compound fertilizer, characterized in that, The compound fertilizer includes the composite material according to any one of claims 1 - 4.

10. Application of the composite material according to any one of claims 1 - 4 in the agricultural field.

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