A sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder and its preparation method and application

Abstract

The present invention provides a sludge-based organic matter coupled with perfluorooctanoic acid coated nano-aluminum powder and a preparation method and application thereof, belonging to the technical field of material modification. The present invention first utilizes sludge-based organic matter rich in protein and polysaccharide to coat nano-aluminum powder in an aqueous solution to obtain nano-aluminum powder particles coated with a sludge-based organic interface layer, and then mixes the nano-aluminum powder particles coated with the sludge-based organic interface layer with a perfluorooctanoic acid solution and coats them during a heating and ultrasonic treatment process to obtain sludge-based organic matter coupled with perfluorooctanoic acid coated nano-aluminum powder. The sludge-based organic matter coupled with perfluorooctanoic acid coated nano-aluminum powder effectively coats the sludge-based organic matter interface layer in an aqueous solution and is successfully doped with fluorine element, which can theoretically effectively improve the combustion performance of the nano-aluminum powder. The method is simple and easy to operate and is more convenient for industrial application.

Description

Technical Field

[0001] The present invention belongs to the technical field of material modification, and in particular relates to a sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder, a preparation method thereof, and an application thereof. Background Art

[0002] Aluminum powder has the characteristics of high energy, low oxygen consumption, low toxicity and low cost, and is widely used in engine fuel. Reducing the particle size of aluminum powder from micron to nanometer can increase its combustion rate and significantly reduce the ignition delay time. Therefore, the application of nano aluminum powder has received widespread attention. However, there are still some key difficulties in the application of nano aluminum powder: (1) Nano aluminum powder has a large specific surface area and is easy to agglomerate. First, the agglomerated nano aluminum powder is not conducive to subsequent processing. Second, the agglomeration phenomenon of nano aluminum powder will also affect its combustion performance. (2) The surface of aluminum powder is in contact with air and is easily oxidized, forming a dense Al2O3 layer, which reduces the combustion rate of nano aluminum powder and reduces the energy release during the combustion process.

[0003] To address the challenges in the application of nano-aluminum powders in existing technologies, the idea of ​​coating the nano-aluminum powder surface with an organic interface layer has been proposed. In research both domestically and internationally, a number of organic materials have been used to coat nano-aluminum powders, including polydopamine, tea polyphenols, and tannic acid. While coating the nano-aluminum powder surface with an organic interface layer can reduce its agglomeration and isolate oxygen from the aluminum powder, inhibiting further oxidation and achieving nano-aluminum powder granulation, these coating materials currently suffer from complex processes, high costs, and high pollution levels during preparation, hindering the industrial application of nano-aluminum powder coating technology. Furthermore, existing organic interface layers primarily serve to provide anchor points for subsequent coating materials and isolate the aluminum powder from oxygen. These layers fail to consider the relatively low energy content of the organic interface layer components, which can impact the energy density of propellants based on nano-aluminum powders coated with organic interface layers. Further research is needed to address this issue.

[0004] Existing research indicates that fluorine, as a strong oxidant, can react with aluminum to form AlF3. The reaction releases approximately 56.10 kJ / g of energy, nearly twice the energy released by the reaction of Al with oxygen (30.98 kJ / g). Furthermore, AlF3 exhibits stronger gasification properties than Al2O3, generating a higher pressure differential, significantly increasing mass transfer rates and improving energy release and combustion reaction kinetics. Existing attempts at fluorine-containing materials include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluorotetradecanoic acid (PFTD), perfluorosebacic acid (PFS), perfluoropentanoic acid (PFPA), perfluoropolyether (PFPE), fluorographene (GF), polyfluorodopamine (PF), 3-(perfluoro-n-hexyl)propylene oxide (PFHP), and fluororubber F2311. However, a key difficulty with existing fluorine-doping schemes is that the organic fluorine must be dissolved before coating can be achieved, and the preparation methods are relatively complex, limiting their industrial application. Therefore, it is necessary to provide a method that is simple, low-cost and can effectively improve the combustion performance of nano-aluminum powder. Summary of the Invention

[0005] In view of the shortcomings of the modified nano-aluminum powder in the prior art, such as high cost and single function, the present invention provides a sludge-based organic matter coupled with perfluorooctanoic acid coated nano-aluminum powder and its preparation method and application; the present invention first uses sludge-based organic matter rich in protein and polysaccharide to coat nano-aluminum powder in an aqueous solution to obtain nano-aluminum powder particles coated with a sludge-based organic interface layer, and then mixes the nano-aluminum powder particles coated with the sludge-based organic interface layer with a perfluorooctanoic acid solution and coats them during a heating and ultrasonic treatment process to obtain sludge-based organic matter coupled with perfluorooctanoic acid coated nano-aluminum powder; the sludge-based organic matter coupled with perfluorooctanoic acid coated nano-aluminum powder effectively coats the sludge-based organic matter interface layer in an aqueous solution and is successfully doped with fluorine element, which can theoretically effectively improve the combustion performance of the nano-aluminum powder; the method is simple and easy to operate and is more convenient for industrial application.

[0006] The present invention first provides a sludge-based organic matter coupled with perfluorooctanoic acid coated nano-aluminum powder, wherein the sludge-based organic matter coupled with perfluorooctanoic acid coated nano-aluminum powder is a spherical particle with a smooth surface; in the sludge-based organic matter coupled with perfluorooctanoic acid coated nano-aluminum powder, the sludge-based organic interface layer is dense and uniform in thickness, and perfluorooctanoic acid is uniformly coated on the outside of the sludge-based organic interface layer; the sludge-based organic matter coupled with perfluorooctanoic acid coated nano-aluminum powder is a spherical shell structure with an inner layer of aluminum, a middle layer of sludge-based organic matter, and an outer layer of perfluorooctanoic acid.

[0007] The present invention also provides a method for preparing the above-mentioned sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder, the preparation method comprising:

[0008] (1) Dissolution and cross-linking of sludge-based organic matter:

[0009] The sludge-based organic matter is added to an aqueous solution and ultrasonically dissolved in a water bath until a clear solution is obtained. Then, citric acid is added and ultrasonic cross-linked at the same temperature to obtain an organic interface layer solution.

[0010] (2) Preparation of nano-aluminum powder particles coated with organic interface layer:

[0011] Adding nano-aluminum powder to the organic interface layer solution and mixing thoroughly to obtain a mixed solution, mechanically stirring the mixed solution at a certain temperature for coating, washing and drying after the coating is completed to obtain nano-aluminum powder particles coated with the organic interface layer;

[0012] (3) Preparation of sludge-based organic matter coupled with perfluorooctanoic acid-coated nanoaluminum powder:

[0013] The nano-aluminum powder particles coated with the organic interface layer are mixed with a perfluorooctanoic acid solution at a certain temperature for reaction for 60 to 120 minutes, and ultrasonically treated for 20 to 60 minutes after the reaction, and then washed and dried to obtain sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder.

[0014] Furthermore, in step (1), the method for extracting sludge-based organic matter includes: mixing the sludge with a low eutectic agent (DES) solution and stirring the mixture at room temperature until the mixture is completely dissolved to obtain a mixture, then filtering the mixture to obtain a filtrate, and then filtering the filtrate to obtain a DES solution and a sludge-based organic matter solution respectively, recovering the DES solution, drying the sludge-based organic matter solution and ball milling it for 30 to 60 minutes, and passing it through a 200-mesh sieve to obtain sludge-based organic matter.

[0015] Furthermore, the mass ratio of the sludge to the DES solution is 1:1 to 1:3;

[0016] The sludge includes one or both of the sludges from a municipal sewage treatment plant or a liquor factory after mechanical filtration;

[0017] The DES is a binary or multicomponent mixture composed of a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD) having a melting point lower than that of its single component. In the present invention, the hydrogen bond donor of the DES includes one or more of ChCl, NaOH, Na2CO3, KOH or K2CO3; the hydrogen bond acceptor includes one or more of urea, oxalic acid, glycerol or lactic acid.

[0018] Furthermore, the water content of the sludge is 80% to 85%;

[0019] The concentration of the hydrogen bond donor is 1-3.5 mol / L; the concentration of the hydrogen bond acceptor is 0.5-1 mol / L.

[0020] Furthermore, in step (1), the water bath heating temperature is 30 to 90°C;

[0021] The amount of citric acid added is 30-65% of the mass of the sludge-based organic matter;

[0022] The ultrasonic cross-linking time is 30 to 90 minutes.

[0023] Furthermore, in step (2), the mass of the nano-aluminum powder is 10 to 30 times the mass of the sludge-based organic matter in the organic interface layer solution;

[0024] The mechanical stirring speed is 200-500 r / min, and the temperature is 30-60°C.

[0025] Furthermore, in step (3), the perfluorooctanoic acid is slowly added dropwise to the aqueous solution of the nano-aluminum powder particles coating the sludge-based organic interface layer;

[0026] The mass of the nano-aluminum powder particles coating the sludge-based organic interface layer is 0.1 to 0.4 of the mass of deionized water;

[0027] The perfluorooctanoic acid addition temperature is 55-90°C, and the reaction temperature is the same as the addition temperature;

[0028] The amount of perfluorooctanoic acid added is 0.1 to 0.2 times the mass of the nano-aluminum powder.

[0029] The present invention also provides the use of the sludge-based organic matter coupled with perfluorooctanoic acid-coated nano-aluminum powder in engine fuel.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] In the present invention, DES solution is first used to efficiently extract organic matter from sludge. The obtained sludge-based organic matter is ultrasonically dissolved in an aqueous solution, and then mixed with citric acid and then heated and ultrasonicated in a water bath. This is mainly to promote the cross-linking of the sludge extract and citric acid, which is conducive to the subsequent organic coating of nano-aluminum powder. The cross-linked mixed organic solution is mixed with nano-aluminum powder, and the nano-aluminum powder is coated by mechanical stirring. The main purpose of mechanical stirring is to promote uniform dispersion of aluminum powder, which is conducive to uniform coating of sludge-based organic matter, thereby obtaining sludge-based organic-coated nano-aluminum powder. The sludge-based organic-coated nano-aluminum powder is then mixed with a perfluorooctanoic acid solution for reaction. After sufficient mixing at a certain temperature, ultrasonication is performed at the same temperature to promote the firm bonding of perfluorooctanoic acid and the sludge-based organic interface coating layer, ultimately obtaining a nano-aluminum powder material coated with a fluorine-containing organic interface layer. The obtained coated nano-aluminum powder material effectively coats the sludge-based organic interface layer and is successfully doped with fluorine. In theory, it can effectively improve the combustion performance of the nano-aluminum powder.

[0032] In addition, the advantages of this method are: (1) the solvents used in the preparation of sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder are all deionized water, and no organic solvents are involved, so the preparation process is less costly and more suitable for industrial production.

[0033] (2) The sludge-based organic interface layer in the sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder is denser than other organic interface layers, and can effectively intercept the contact and reaction of water molecules with the nano-aluminum powder.

[0034] (3) The doping method of fluorine element in sludge-based organic matter coupled with perfluorooctanoic acid-coated nano-aluminum powder is simple and has lower cost; at the same time, the fluorine atoms are evenly distributed and the doping amount is large, which can provide more fluorine atoms to generate AlF3 during the reaction process, and theoretically can improve the combustion performance of nano-aluminum powder.

[0035] (4) The surface of the sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder is smooth and the thickness of the particle coating layer is uniform.

[0036] (5) The sludge-based organic matter coupled with perfluorooctanoic acid-coated nano-aluminum powder comes from the sludge after mechanical filtration in municipal sewage treatment plants or liquor factories, which can effectively reduce the raw material cost of the prepared materials and provide a high-value-added resource utilization method for sludge treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic structural diagram of the sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder prepared in the present invention.

[0038] Figure 2 A scanning electron microscope photograph of the nano-aluminum powder particles coated with a sludge-based organic interface layer prepared in Example 1 of the present invention.

[0039] Figure 3 This is a transmission electron microscope photograph of the nano-aluminum powder particles coated with the sludge-based organic interface layer prepared in Example 1 of the present invention.

[0040] Figure 4 This is a scanning electron microscope photograph of the nano-aluminum powder particles coated with the sludge-based organic interface layer prepared in Example 2 of the present invention.

[0041] Figure 5 This is a transmission electron microscope photograph of the nano-aluminum powder particles coated with the sludge-based organic interface layer prepared in Example 2 of the present invention.

[0042] Figure 6 This is a scanning electron microscope photograph of the sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder prepared in Example 2 of the present invention.

[0043] Figure 7This is a transmission electron microscope photograph of the sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder prepared in Example 2 of the present invention.

[0044] Figure 8 This is the EDS elemental analysis diagram of the sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder prepared in Example 2 of the present invention.

[0045] Figure 9 This is the XPS test data chart of the sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0046] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0047] Example 1:

[0048] (1) Sludge-based organic matter extraction:

[0049] 0.5 mol / L HCl, 0.5 mol / L NaOH and 1 mol / L urea were prepared into a DES solution, and then the sludge and DES solution were mixed in a mass ratio of 1:3, stirred thoroughly, and dissolved at room temperature for 24 hours. After the dissolution was completed, the filtrate in the mixture was taken and filtered to obtain a DES solution and a sludge-based organic matter solution. The DES solution was reused, and the sludge-based organic matter solution was dried and ball-milled for 60 minutes to obtain sludge organic matter.

[0050] (2) Dissolution and cross-linking of sludge-based organic matter:

[0051] The sludge-based organic matter was added to the aqueous solution and ultrasonically dissolved in a water bath at 60°C for 60 minutes. After the dissolution was completed, citric acid was added and ultrasonic cross-linking was performed at the same temperature for 60 minutes to obtain a sludge-based organic interface layer solution.

[0052] (3) Preparation of nano-aluminum powder particles coated with sludge-based organic interface layer:

[0053] Nano-aluminum powder with a mass 20 times that of the sludge-based organic matter was added to the sludge-based organic interface layer solution and mixed thoroughly. The mixture was heated in a water bath at 60°C and mechanically stirred for coating. After coating, the mixture was subjected to solid-liquid separation. The obtained solid was washed with deionized water multiple times and dried at 40°C to obtain nano-aluminum powder particles coating the sludge-based organic interface layer.

[0054] (4) Preparation of sludge-based organic matter coupled with perfluorooctanoic acid-coated nanoaluminum powder:

[0055] The nano-aluminum powder particles coated with the sludge-based organic interface layer were mixed with a perfluorooctanoic acid solution at 90° C. for 90 minutes, and after the reaction, ultrasonic treatment was performed for 30 minutes, and then the particles were washed with deionized water multiple times and dried at 40° C. to obtain sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder.

[0056] Figure 1 This is a structural schematic diagram of the sludge-based organic matter coupled perfluorooctanoic acid-coated nano aluminum powder prepared by the present invention. As can be seen from the figure, the sludge-based organic matter coupled perfluorooctanoic acid-coated nano aluminum powder is spherical particles with smooth surfaces; in the sludge-based organic matter coupled perfluorooctanoic acid-coated nano aluminum powder, the sludge-based organic interface layer is dense and uniform in thickness, and perfluorooctanoic acid is uniformly coated on the outside of the sludge-based organic interface layer; the sludge-based organic matter coupled perfluorooctanoic acid-coated nano aluminum powder is a spherical shell structure with an inner layer of aluminum, a middle layer of sludge-based organic matter, and an outer layer of perfluorooctanoic acid.

[0057] Figure 2 The scanning electron microscope photograph of the nano-aluminum powder particles coated with the sludge-based organic interface layer prepared in this embodiment shows that the nano-aluminum powder particles coated with the sludge-based organic interface layer are evenly dispersed, without obvious agglomeration, and have a frosted surface, indicating that the sludge-based organic matter is successfully coated on the surface of the nano-aluminum powder particles.

[0058] Figure 3 This is a transmission electron microscope photograph of the nano-aluminum powder particles coated with the sludge-based organic interface layer prepared in this embodiment. It can be seen from the figure that the coating layer thickness of the nano-aluminum powder particles coated with the sludge-based organic interface layer is uniform, and the thickness of the organic interface layer is about 3.5nm.

[0059] Example 2:

[0060] (1) Sludge-based organic matter extraction:

[0061] 3.5 mol / L HCl, 3.5 mol / L KOH and 0.6 mol / L urea were prepared into a DES solution, and then the sludge and DES solution were mixed in a mass ratio of 1:3, stirred thoroughly, and dissolved at room temperature for 24 hours. After the dissolution was completed, the filtrate in the mixture was taken and filtered to obtain a DES solution and a sludge-based organic matter solution. The DES solution was reused, and the sludge-based organic matter solution was dried and ball-milled for 60 minutes to obtain sludge organic matter.

[0062] (2) Dissolution and cross-linking of sludge-based organic matter:

[0063] The sludge-based organic matter was added to the aqueous solution and ultrasonically dissolved in a water bath at 90°C for 60 minutes. After the dissolution was completed, citric acid was added and ultrasonic cross-linking was performed at the same temperature for 60 minutes to obtain a sludge-based organic interface layer solution.

[0064] (3) Preparation of nano-aluminum powder particles coated with sludge-based organic interface layer:

[0065] Nano-aluminum powder with a mass 25 times that of the sludge-based organic matter was added to the sludge-based organic interface layer solution and mixed thoroughly. The mixture was heated in a water bath at 90°C and mechanically stirred for coating. After coating, the mixture was subjected to solid-liquid separation. The obtained solid was washed with deionized water multiple times and dried at 40°C to obtain nano-aluminum powder particles coated with the sludge-based organic interface layer.

[0066] (4) Preparation of sludge-based organic matter coupled with perfluorooctanoic acid-coated nanoaluminum powder:

[0067] The nano-aluminum powder particles coated with the sludge-based organic interface layer were mixed with a perfluorooctanoic acid solution at 60° C. for 90 minutes, and ultrasonically treated at the same temperature for 30 minutes after the reaction. The particles were then washed with deionized water multiple times and dried at 40° C. to obtain sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder.

[0068] Figure 4 This is a scanning electron microscope photograph of the nano-aluminum powder particles coated with the sludge-based organic interface layer prepared in this embodiment. It can be seen from the figure that the nano-aluminum powder particles coated with the sludge-based organic interface layer prepared in this embodiment are evenly dispersed, without obvious agglomeration, and have a frosted surface, indicating that the sludge-based organic matter is successfully coated on the surface of the nano-aluminum powder particles.

[0069] Figure 5 This is a transmission electron microscope photograph of the nano-aluminum powder particles coated with the sludge-based organic interface layer prepared in this embodiment. It can be seen from the figure that the thickness of the nano-material coating coated with the organic interface layer prepared in this embodiment is uniform, and the thickness of the organic interface layer is about 4.5nm.

[0070] Figure 6 This is a scanning electron microscope photograph of the sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder prepared in this embodiment. It can be seen from the figure that the sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder prepared in this embodiment is uniform and has a frosted surface, indicating that a sludge-based coating layer has been formed on the surface of the nano-aluminum powder.

[0071] Figure 7 This is a transmission electron microscope photograph of the sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder prepared in this embodiment. It can be seen from the figure that the coating layer thickness of the sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder prepared in this embodiment is uniform, and the thickness of the fluorine-containing sludge-based organic interface layer is about 3.9 nm. The decrease in the thickness of the organic interface layer is mainly due to the increase in the dehydration reaction of the sludge-based organic interface layer during the perfluorooctanoic acid coating process.

[0072] Figure 8This is the EDS elemental analysis diagram of the sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder prepared in this embodiment. It can be seen from the figure that the fluorine element on the surface of the sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder prepared in this embodiment is successfully fixed on the surface of the nano-aluminum powder particles coated with the sludge-based organic interface layer, and its distribution is uniform.

[0073] Figure 9 This is the XPS test data diagram of the sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder prepared in this embodiment. It can be seen from the figure that the fluorine element is successfully doped into the coating layer of the nano-aluminum powder.

[0074] The embodiments described are preferred implementations of the present invention, but the present invention is not limited to the above implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention are within the scope of protection of the present invention.

Claims

1. A method for preparing sludge-based organic matter coupled with perfluorooctanoic acid-coated nano-aluminum powder, characterized in that: include: (1) Dissolution and cross-linking of sludge-based organic matter: The sludge-based organic matter is added to an aqueous solution and ultrasonically dissolved in a water bath until a clear solution is obtained. Then, citric acid is added and ultrasonic cross-linked at the same temperature to obtain an organic interface layer solution. (2) Preparation of nano-aluminum powder particles coated with organic interface layer: Adding nano-aluminum powder to the organic interface layer solution and mixing thoroughly to obtain a mixed solution, mechanically stirring the mixed solution at a certain temperature for coating, washing and drying after the coating is completed to obtain nano-aluminum powder particles coated with the organic interface layer; (3) Preparation of sludge-based organic matter coupled with perfluorooctanoic acid-coated nanoaluminum powder: The nano-aluminum powder particles coated with the organic interface layer are mixed with a perfluorooctanoic acid solution at a certain temperature for reaction for 60 to 120 minutes, and ultrasonically treated for 20 to 60 minutes after the reaction, and then washed and dried to obtain sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder.

2. The method for preparing sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder according to claim 1, characterized in that: In step (1), the method for extracting sludge-based organic matter comprises: mixing the sludge with a low eutectic solution and stirring the mixture at room temperature until the mixture is completely dissolved, filtering the mixture to obtain a filtrate, and then filtering the filtrate to obtain a low eutectic solution and a sludge-based organic matter solution, respectively, and drying and ball-milling the sludge-based organic matter solution to obtain sludge-based organic matter.

3. The method for preparing sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder according to claim 2, characterized in that: The mass ratio of the sludge to the eutectic solution is 1:1 to 1:3; The sludge includes one or both of the sludges from a municipal sewage treatment plant or a liquor factory after mechanical filtration; The hydrogen bond donor of the eutectic agent includes one or more of ChCl, NaOH, Na2CO3, KOH or K2CO3; the hydrogen bond acceptor includes one or more of urea, oxalic acid, glycerol or lactic acid.

4. The method for preparing sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder according to claim 3, characterized in that: The water content of the sludge is 80% to 85%; The concentration of the hydrogen bond donor is 1-3.5 mol / L; the concentration of the hydrogen bond acceptor is 0.5-1 mol / L.

5. The method for preparing sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder according to claim 1, characterized in that: In step (1), the water bath is heated at a temperature of 30-90°C; The amount of citric acid added is 30-65% of the mass of sludge-based organic matter; The ultrasonic cross-linking time is 30 to 90 minutes.

6. The method for preparing sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder according to claim 1, characterized in that: In step (2), the mass of the nano-aluminum powder is 10 to 30 times the mass of the sludge-based organic matter in the organic interface layer solution; The mechanical stirring speed is 200-500 r / min, and the temperature is 30-60°C.

7. The method for preparing sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder according to claim 1, characterized in that: In step (3), the perfluorooctanoic acid is slowly added dropwise to the aqueous solution of the nano-aluminum powder particles coating the sludge-based organic interface layer; The mass of the nano-aluminum powder particles coating the sludge-based organic interface layer is 0.1 to 0.4 of the mass of deionized water.

8. The method for preparing sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder according to claim 1, characterized in that: In step (3), the feeding temperature of the perfluorooctanoic acid is 55-90° C., and the reaction temperature is the same as the feeding temperature; the amount of the perfluorooctanoic acid added is 0.1-0.2 times the mass of the nano-aluminum powder.

9. The sludge-based organic matter-coupled perfluorooctanoic acid-coated nano-aluminum powder prepared by the method according to any one of claims 1 to 8, characterized in that: The sludge-based organic matter coupled with perfluorooctanoic acid coated nano-aluminum powder is a spherical particle with a smooth surface; in the sludge-based organic matter coupled with perfluorooctanoic acid coated nano-aluminum powder, the sludge-based organic interface layer is dense and uniform in thickness, and perfluorooctanoic acid is uniformly coated on the outside of the sludge-based organic interface layer; the sludge-based organic matter coupled with perfluorooctanoic acid coated nano-aluminum powder is a spherical shell structure with an inner layer of aluminum, a middle layer of sludge-based organic matter, and an outer layer of perfluorooctanoic acid.

10. Use of the sludge-based organic matter coupled perfluorooctanoic acid-coated nano-aluminum powder according to claim 9 in engine fuel.

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