Preparation method of cationic and amphiphilic quaternized magnetic nanoparticles

Abstract

This invention discloses a method for preparing cationic and amphiphilic quaternized composite magnetic nanoparticles, comprising the following steps: Step S1, preparing magnetic iron oxide nanoparticles using a hydrothermal method; Step S2, preparing silica-coated magnetic iron oxide nanoparticles using the Stober method; Step S3, preparing cationic and amphiphilic quaternized composite magnetic nanoparticles using an electrostatic self-assembly method. This invention uses low-cost alkane quaternary ammonium salts as functional monomers to achieve a three-layer core-shell structure comprising an iron oxide magnetic core, a silica intermediate bridging layer, and an alkane quaternary ammonium salt functional outer layer. The alkane quaternary ammonium salt is stably loaded onto the silica surface through a non-covalent grafting mechanism of electrostatic self-assembly, thereby achieving mild and efficient grafting. The resulting composite magnetic nanoparticles can achieve efficient separation of emulsified oily wastewater at room temperature and exhibit excellent recyclability, salt tolerance, and wide pH adaptability.

Description

Technical Field

[0001] This invention relates to the field of functionalized magnetic nanomaterials and oil-water emulsion separation technology, specifically to a method for preparing cationic and amphiphilic quaternized composite magnetic nanoparticles. Background Technology

[0002] With rapid industrialization, the discharge of oily wastewater has increased significantly. A large amount of this wastewater originates from industries such as oil extraction, coal mining, metal processing, textile printing and dyeing, and food processing, causing severe water and soil pollution and disrupting the ecological balance. In industrial production, oil-in-water (O / W) emulsions constitute a large proportion of oily wastewater. Due to their small oil droplet size, negatively charged surface, and high stability, O / W emulsions are among the most difficult types of oily wastewater to treat. Traditional treatment methods include adsorption, electrochemistry, flocculation, and flotation, but these methods generally suffer from drawbacks such as high cost, low efficiency, complex equipment, high energy consumption, and the potential for secondary pollution.

[0003] In recent years, functionalized magnetic nanoparticles have become a research hotspot in the field of oil-water separation due to their advantages such as ease of operation, high demulsification efficiency, and magnetic recycling. Studies have shown that the amphiphilicity and cationicity of magnetic nanoparticles are crucial to their demulsification performance. Specifically, the amphiphilicity allows them to interact with both water and oil simultaneously, while the cationicity enables them to efficiently capture negatively charged oil droplets through electrostatic attraction.

[0004] Currently, cationic functionalization is usually achieved by introducing amino groups, but the protonation effect of amino groups is significantly affected by pH, and the cationic properties are significantly weakened under alkaline conditions. Quaternary ammonium salts, on the other hand, have a persistent, significant, and stable positive charge that is unaffected by pH changes. This not only broadens their acid-base adaptability but also enables highly efficient oil-water emulsion separation.

[0005] A review of existing technologies reveals reports of using siloxane-based quaternary ammonium salts or polyquaternary ammonium salts to modify magnetic nanoparticles. For example, Chinese patent CN109052596A, entitled "Preparation Method and Application of Magnetic Nanoflocculant for Emulsified Oil Wastewater Treatment," discloses a magnetic nanoflocculant that forms a silica shell containing both quaternary ammonium groups and hydrophobic groups on the surface of iron oxide using a one-step sol-gel method. However, this method has the following drawbacks: First, the use of siloxane-based quaternary ammonium salt monomers results in expensive raw materials and high costs; second, the sol-gel chemical bonding process is complex, with harsh reaction conditions, making large-scale production difficult; furthermore, the resulting demulsifier often requires high temperatures (typically 40–60°C) and long times to achieve effective demulsification. The high demulsification temperature is mainly due to the high temperature dependence of the flocculant's shell structure (rigid silica), thus resulting in high energy consumption.

[0006] Therefore, developing a magnetic nano-demulsifier that uses widely available raw materials, is inexpensive, has a simple preparation process, and can efficiently demulsify at room temperature has significant industrial application value. The preparation method of the cationic and amphiphilic quaternized composite magnetic nanoparticles of this invention is of great significance for the research and development of functionalized magnetic nanomaterials and oil-water emulsion separation technologies. Summary of the Invention

[0007] 1. The technical problem that the invention aims to solve

[0008] This invention aims to overcome the shortcomings of existing technologies and provide a method for preparing cationic and amphiphilic quaternized ammonium composite magnetic nanoparticles. The invention utilizes low-cost alkane quaternary ammonium salts as functional monomers to achieve a three-layer core-shell structure comprising a magnetite magnetic core, a silica intermediate bridging layer, and an alkane quaternary ammonium salt functional outer layer. The alkane quaternary ammonium salt is stably loaded onto the silica surface via a non-covalent grafting mechanism using electrostatic self-assembly, achieving mild and efficient grafting. The resulting composite magnetic nanoparticles can achieve efficient separation of emulsified oily wastewater at room temperature (20–25°C) and exhibit excellent recyclability, salt tolerance, and wide pH adaptability. This simplifies the preparation process, reduces costs, shortens demulsification time, and allows for recycling.

[0009] 2. Technical Solution

[0010] To achieve the above objectives, this invention provides a method for preparing cationic and amphiphilic quaternized magnetic nanoparticles, which involves coating magnetic iron oxide (Fe3O4) with silica, which is negatively charged due to the presence of silicon-oxygen anion groups on its surface. Composite nanoparticles are dispersed in an alcohol-water mixture, and alkane quaternary ammonium salts are added. The silica is then used to coat magnetic iron oxide (Fe3O4). The electrostatic attraction between the negatively charged groups on the surface of the silica and the quaternary ammonium ions in the alkane quaternary ammonium salt molecules allows the alkane quaternary ammonium salt to be physically grafted onto the silica-coated magnetic iron(III) oxide through electrostatic self-assembly. On the surface, the cationic and amphiphilic quaternized magnetic nanoparticles were obtained, and the expression of the particle is as follows: The cationic and amphiphilic quaternized magnetic nanoparticles are used as demulsifiers; the preparation process does not contain siloxane quaternary ammonium salts, and the grafting of alkane quaternary ammonium salts does not form chemical covalent bonds.

[0011] As a further improvement of the present invention, the silica-coated magnetic iron oxide composite nanoparticles are prepared using the Stober method. Specifically, the magnetic iron oxide nanoparticles are dispersed in an alcohol-water mixed solution, tetraethyl orthosilicate and an alkaline catalyst are added, and a hydrolysis-condensation reaction is carried out. The surface is coated with a silicon dioxide layer, resulting in a surface containing silicon-oxygen anions (…). ) group and negatively charged silicon dioxide coated with magnetic iron oxide (Fe3O4) The composite nanoparticles; the alcohol-water mixed solution has an alcohol-water volume ratio of (3-5):1; the alkaline catalyst is ammonia water, used to adjust the pH value of the reaction system to ≥9; the hydrolysis-condensation reaction temperature is 40-60℃, and the reaction time is 4-6h.

[0012] As a further improvement of the present invention, the magnetic iron oxide nanoparticles are prepared by a hydrothermal method, specifically, by preparing ferric chloride hexahydrate (… Anhydrous sodium acetate ( ) and polyethylene glycol-4000 (PEG-4000) were dissolved in ethylene glycol (EG) and subjected to a hydrothermal reaction to obtain magnetic iron oxide nanoparticles. The hydrothermal reaction temperature was 180-220℃, the hydrothermal reaction time was 6-12h, the weight ratio of ferric chloride hexahydrate to anhydrous sodium acetate was 1:(2.5-3.0), the weight ratio of ferric chloride hexahydrate to PEG-4000 was 1:(0.7-1.0), and the amount of ferric chloride hexahydrate to ethylene glycol was 25-35mL of ethylene glycol per gram of ferric chloride hexahydrate.

[0013] As a further improvement of the present invention, the hydrothermal reaction temperature in step S1 is 180-220°C, the hydrothermal reaction time is 6-12 hours, and the ferric chloride hexahydrate (… ) and anhydrous sodium acetate ( The weight ratio of ferric chloride hexahydrate to ferric chloride is 1:(2.5-3.0). The weight ratio of ferric chloride hexahydrate to polyethylene glycol-4000 (PEG-4000) is 1:(0.7~1.0). The ratio of ferric chloride hexahydrate to ethylene glycol (EG) is 1 gram per gram of ferric chloride hexahydrate. This corresponds to 25-35 mL of ethylene glycol (EG).

[0014] As a further improvement of the present invention, in step S2, the volume ratio of alcohol to water in the alcohol-water mixed solution is (3-5):1; the alkaline catalyst is ammonia water, used to adjust the pH value of the reaction system to ≥9; the temperature of the hydrolysis-condensation reaction is 40-60℃, and the reaction time is 4-6h.

[0015] As a further improvement of the present invention, in step S3, the alkane quaternary ammonium salt is dodecyltrimethylammonium chloride; the silica-coated magnetic iron(III) oxide (… The mass ratio of composite nanoparticles to alkane quaternary ammonium salts is 1:(0.2~1.0); the electrostatic self-assembly reaction temperature is 70~90℃, the reaction time is 1~3h, and mechanical stirring is carried out under inert gas protection; the grafting driving force of the electrostatic self-assembly method is electrostatic attraction, and no chemical covalent bonds are formed; the alkane quaternary ammonium salts are physically adsorbed onto silica-coated magnetic iron oxide (Fe3O4). )surface.

[0016] The present invention also provides cationic and amphiphilic quaternized magnetic nanoparticles, which are prepared by any of the above preparation methods.

[0017] As a further improvement of the present invention, the composite magnetic nanoparticles have a core-shell structure, wherein the core is iron(II,III) oxide, the middle layer is silicon dioxide, and the outer shell is alkane quaternary ammonium salt molecules physically adsorbed through electrostatic self-assembly; the surface zeta potential of the composite magnetic nanoparticles is positive in the pH range of 3 to 11, and the saturation magnetization is not less than 25 emu / g.

[0018] The present invention also provides the application of the aforementioned cationic and amphiphilic quaternized magnetic nanoparticles in oil-water emulsion separation.

[0019] A method for separating oil-water emulsions includes the following steps:

[0020] The above-mentioned cationic and amphiphilic quaternized magnetic nanoparticles ( The cationic and amphiphilic quaternized magnetic nanoparticles ( ) are mixed with the oil-in-water emulsion oily wastewater to be treated, so that the cationic and amphiphilic quaternized magnetic nanoparticles ( ) It is attracted to the negatively charged surface of oil droplets by electrostatic attraction, which disrupts the stability of the emulsion interface film and promotes the aggregation of oil droplets;

[0021] An external magnetic field is applied to the cationic and amphiphilic quaternized composite magnetic nanoparticles adsorbed with oil droplets. ) Magnetic separation from the aqueous phase yields purified water;

[0022] The separation process is completed at room temperature (20–25°C) without the need for additional demulsifiers or pH adjustments.

[0023] As a further improvement of the present invention, the oil phase in the water-in-oil emulsion oily wastewater is selected from one or more of toluene, n-hexane, chloroform, or corn germ oil; the cationic and amphiphilic quaternized composite magnetic nanoparticles ( The dosage of the product is 0.2-2 g / L of wastewater, the demulsification time is no more than 15 min, and the demulsification rate is no less than 95% in one go.

[0024] As a further improvement of the present invention, the method is applicable to high-salt emulsified oily wastewater with a sodium chloride (NaCl) concentration not exceeding 5 g / L, and can achieve demulsification within a pH range of 3 to 11.

[0025] As a further improvement of the present invention, the cationic and amphiphilic quaternized magnetic nanoparticles ( After magnetic separation and recovery, it can be reused directly without regeneration; after being reused 8 times, the demulsification rate for the same emulsified oily wastewater is still not less than 90%.

[0026] 3. Beneficial effects

[0027] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0028] (1) The present invention has significant structural innovation. The present invention adopts a three-layer core-shell structure consisting of a magnetic core of iron oxide, a silicon dioxide intermediate bridge layer, and an alkane quaternary ammonium salt functional outer layer. The silicon dioxide intermediate layer is covalently grafted onto the surface of iron oxide through hydrolysis condensation, while the alkane quaternary ammonium salt functional outer layer is non-covalently grafted onto the silicon dioxide intermediate layer through electrostatic self-assembly. The present invention introduces an independent silicon dioxide interface adjustment layer and a novel alkane quaternary ammonium salt functional layer. This three-layer structure not only improves the grafting stability of alkane quaternary ammonium salt, but also retains its cationic and amphiphilic properties, providing a structural basis for subsequent demulsification.

[0029] (2) The preparation process of this invention is simple, mild and environmentally friendly. This invention adopts a non-covalent grafting strategy of electrostatic self-assembly, which avoids complex chemical bonding steps. The raw materials are widely available and inexpensive. The reaction is carried out at room temperature or 80°C in aqueous phase. The reaction conditions are mild and no toxic organic solvents are required, which meets the requirements of green chemistry.

[0030] (3) The present invention has excellent demulsification performance and can be efficiently separated at room temperature (20-25℃). It uses cationic and amphiphilic quaternized magnetic nanoparticles as demulsifiers to treat wastewater. The demulsification time is no more than 15 minutes and the demulsification rate is no less than 95% in one step. The present invention achieves rapid and efficient room temperature demulsification.

[0031] (4) The present invention has good salt resistance. Conventional demulsifiers are prone to salt precipitation or activity reduction in high-salt environments. The cationic and amphiphilic quaternized magnetic nanoparticles prepared by the present invention can maintain a demulsification efficiency of more than 96% in emulsified oil wastewater with NaCl concentration as high as 5 g / L due to the high charge density and salt resistance of alkane quaternary ammonium salts. The improved salt resistance expands its application prospects in the treatment of industrial high-salt emulsified oil wastewater.

[0032] (5) The present invention has strong magnetic responsiveness, is easy to recycle and has good recyclability. After the cationic and amphiphilic quaternized magnetic nanoparticles of the present invention are magnetically separated and recycled, they can be reused directly without regeneration treatment. After being reused 8 times, the demulsification rate of the same emulsified oily wastewater is still not less than 90%. Attached Figure Description

[0033] Figure 1 for ( ), )and ( Scanning electron microscope (SEM) and ( ), )and ( Transmission electron microscopy (TEM);

[0034] Figure 2 for , , Magnetic Hysteresis Loop (VSM);

[0035] Figure 3 for , 2. Zeta potential analysis diagram;

[0036] Figure 4 for For water ( Toluene ) and corn germ oil ( The contact angle diagram and For water ( Toluene ) and corn germ oil ( Contact angle diagram;

[0037] Figure 5 Demulsifier Comparison of demulsification performance under different dosages;

[0038] Figure 6 Demulsifier Performance graph for reusable recycling. Detailed Implementation

[0039] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings and embodiments.

[0040] Example 1

[0041] like Figures 1 to 6As shown, the preparation method of cationic and amphiphilic quaternized magnetic nanoparticles in this embodiment includes the following steps:

[0042] Step S1: Prepare magnetic iron oxide nanoparticles using a hydrothermal method, specifically by preparing ferric chloride hexahydrate (Fe3O4) nanoparticles. Anhydrous sodium acetate ( ) and polyethylene glycol-4000 (PEG-4000) were dissolved in ethylene glycol (EG) and subjected to a hydrothermal reaction to obtain magnetic iron oxide nanoparticles.

[0043] Step S2: Prepare silica-coated magnetic iron(III) oxide (Fe3O4) using the Stober method. Magnetic nanoparticles, specifically, magnetic iron(III) oxide (Fe3O4) Nanoparticles were dispersed in an alcohol-water mixture, and tetraethyl orthosilicate and an alkaline catalyst were added to carry out a hydrolysis-condensation reaction in the presence of iron(III) oxide. The surface is coated with a silicon dioxide layer, resulting in a surface containing silicon-oxygen anions (…). ) group and negatively charged silicon dioxide coated with magnetic iron oxide (Fe3O4) Composite nanoparticles;

[0044] Step S3: Prepare cationic and amphiphilic quaternized magnetic nanoparticles using an electrostatic self-assembly method. Specifically, the silicon dioxide is coated with magnetic iron oxide (Fe3O4). Composite nanoparticles are dispersed in an alcohol-water mixture, and alkane quaternary ammonium salts are added. The silica is then used to coat magnetic iron oxide (Fe3O4). The electrostatic attraction between the negatively charged groups on the surface of the silica and the quaternary ammonium ions in the alkane quaternary ammonium salt molecules allows the alkane quaternary ammonium salt to be physically grafted onto the silica-coated magnetic iron(III) oxide through electrostatic self-assembly. On the surface of the ) the cationic and amphiphilic quaternized magnetic nanoparticles were obtained. Demulsifier;

[0045] In step S3, no siloxane quaternary ammonium salts are used, and the grafting of the alkane quaternary ammonium salts does not form chemical covalent bonds. The specific method for preparing magnetic iron oxide nanoparticles in step S1 is the scheme adopted in this embodiment; other methods for obtaining magnetic iron oxide nanoparticles should also fall within the protection scope of this invention. Furthermore, in step S2, other methods besides those in this embodiment are used to prepare nanoparticles with a surface containing silicon-oxygen anions (…). ) group and negatively charged silicon dioxide coated with magnetic iron oxide (Fe3O4) The technical solution of composite nanoparticles should also be included in the scope of protection of this invention.

[0046] In this embodiment, the hydrothermal reaction temperature in step S1 is 180℃, and the hydrothermal reaction time is 6 hours. The ferric chloride hexahydrate (… ) and anhydrous sodium acetate ( The weight ratio of ferric chloride hexahydrate to ferric chloride is 1:2.5. The weight ratio of ferric chloride hexahydrate to polyethylene glycol-4000 (PEG-4000) is 1:0.7. The ratio of ferric chloride hexahydrate to ethylene glycol (EG) is 1 gram per gram of ferric chloride hexahydrate. This corresponds to 25 mL of ethylene glycol (EG).

[0047] In step S2, the volume ratio of alcohol to water in the alcohol-water mixed solution is 3:1; the alkaline catalyst is ammonia water, used to adjust the pH value of the reaction system to ≥9; the temperature of the hydrolysis-condensation reaction is 40℃, and the reaction time is 4h.

[0048] In step S3, the alkane quaternary ammonium salt is dodecyltrimethylammonium chloride; the silica-coated magnetic iron(III) oxide (… The mass ratio of composite nanoparticles to alkane quaternary ammonium salts is 1:0.2; the electrostatic self-assembly reaction temperature is 70℃, the reaction time is 1h, and mechanical stirring is carried out under inert gas protection; the grafting driving force of the electrostatic self-assembly method is electrostatic attraction, and no chemical covalent bonds are formed; the alkane quaternary ammonium salts are physically adsorbed onto silica-coated magnetic iron oxide (Fe3O4). )surface.

[0049] This embodiment features significant structural innovation. It employs a three-layer core-shell structure consisting of a magnetite magnetic core, a silica intermediate bridging layer, and an alkane-based quaternary ammonium salt functional outer layer. The silica intermediate layer is covalently grafted onto the magnetite surface via hydrolysis-condensation polymerization, while the alkane-based quaternary ammonium salt functional outer layer is non-covalently grafted onto the silica intermediate layer via electrostatic self-assembly. This embodiment introduces an independent silica interface regulation layer and a novel alkane-based quaternary ammonium salt functional layer. This three-layer structure not only improves the grafting stability of the alkane-based quaternary ammonium salt but also retains its cationic and amphiphilic properties, providing a structural basis for subsequent demulsification.

[0050] The preparation process in this embodiment is simple, mild, and environmentally friendly. This embodiment adopts a non-covalent grafting strategy of electrostatic self-assembly, which avoids complex chemical bonding steps. The raw materials are widely available and inexpensive. The reaction conditions are mild and do not require toxic organic solvents, which meets the requirements of green chemistry.

[0051] This embodiment demonstrates excellent demulsification performance, achieving efficient separation at room temperature (20-25°C). In this embodiment, efficient separation is achieved at room temperature of 20°C. Using cationic and amphiphilic quaternized magnetic nanoparticles as demulsifiers to treat wastewater, the demulsification time does not exceed 15 minutes, and the one-time demulsification rate is not less than 95%. This embodiment achieves rapid and efficient room temperature demulsification.

[0052] The cationic and amphiphilic quaternized magnetic nanoparticles prepared in this embodiment have improved salt tolerance and expanded their application prospects in the treatment of industrial high-salt emulsified oil wastewater due to the high charge density and salt resistance of alkane quaternary ammonium salts.

[0053] This embodiment exhibits strong magnetic responsiveness, is easy to recycle, and has good recyclability. The cationic and amphiphilic quaternized magnetic nanoparticles in this embodiment can be directly reused after magnetic separation and recovery without regeneration. After being reused 8 times, the demulsification rate for the same emulsified oily wastewater is still not less than 90%.

[0054] Example 2

[0055] like Figures 1 to 6 As shown, the preparation method of cationic and amphiphilic quaternized magnetic nanoparticles in this embodiment is basically the same as that in Example 1, and preferably includes the following steps:

[0056] Step S1: Prepare magnetic iron oxide nanoparticles using a hydrothermal method, specifically by preparing ferric chloride hexahydrate (Fe3O4) nanoparticles. Anhydrous sodium acetate ( ) and polyethylene glycol-4000 (PEG-4000) were dissolved in ethylene glycol (EG) and subjected to a hydrothermal reaction to obtain magnetic iron oxide nanoparticles.

[0057] Step S2: Prepare silica-coated magnetic iron(III) oxide (Fe3O4) using the Stober method. Magnetic nanoparticles, specifically, are dispersed in an alcohol-water mixture, and tetraethyl orthosilicate and an alkaline catalyst are added to carry out a hydrolysis-condensation reaction. The surface is coated with a silicon dioxide layer, resulting in a surface containing silicon-oxygen anions (…). ) group and negatively charged silicon dioxide coated with magnetic iron oxide (Fe3O4) Composite nanoparticles;

[0058] Step S3: Prepare cationic and amphiphilic quaternized magnetic nanoparticles using an electrostatic self-assembly method. Specifically, the silicon dioxide is coated with magnetic iron oxide (Fe3O4). Composite nanoparticles are dispersed in an alcohol-water mixture, and alkane quaternary ammonium salts are added. The silica is then used to coat magnetic iron oxide (Fe3O4). The electrostatic attraction between the negatively charged groups on the surface of the silica and the quaternary ammonium ions in the alkane quaternary ammonium salt molecules allows the alkane quaternary ammonium salt to be physically grafted onto the silica-coated magnetic iron(III) oxide through electrostatic self-assembly. On the surface of the ) the cationic and amphiphilic quaternized magnetic nanoparticles were obtained. );

[0059] In step S3, there is no siloxane quaternary ammonium salt, and the grafting of the alkane quaternary ammonium salt does not form a chemical covalent bond.

[0060] In this embodiment, the hydrothermal reaction temperature in step S1 is 220℃, and the hydrothermal reaction time is 12h. The ferric chloride hexahydrate (… ) and anhydrous sodium acetate ( The weight ratio of ferric chloride hexahydrate to ferric chloride is 1:3.0. The weight ratio of ferric chloride hexahydrate to polyethylene glycol-4000 (PEG-4000) is 1:1.0. The ratio of ferric chloride hexahydrate to ethylene glycol (EG) is 1 gram per gram of ferric chloride hexahydrate. This corresponds to 35 mL of ethylene glycol (EG).

[0061] In step S2, the volume ratio of alcohol to water in the alcohol-water mixed solution is 5:1; the alkaline catalyst is ammonia water, used to adjust the pH value of the reaction system to ≥9; the temperature of the hydrolysis-condensation reaction is 60℃, and the reaction time is 6h.

[0062] In step S3, the alkane quaternary ammonium salt is dodecyltrimethylammonium chloride; the silica-coated magnetic iron(III) oxide (… The mass ratio of composite nanoparticles to alkane quaternary ammonium salts is 1:1.0; the electrostatic self-assembly reaction temperature is 90℃, the reaction time is 3h, and mechanical stirring is carried out under inert gas protection; the grafting driving force of the electrostatic self-assembly method is electrostatic attraction, and no chemical covalent bonds are formed; the alkane quaternary ammonium salts are physically adsorbed onto silica-coated magnetic iron oxide (Fe3O4). )surface.

[0063] This embodiment uses low-cost alkane quaternary ammonium salts as functional monomers to achieve a three-layer core-shell structure comprising a magnetite magnetic core, a silica intermediate bridging layer, and an alkane quaternary ammonium salt functional outer layer. The alkane quaternary ammonium salt is stably loaded onto the silica surface via a non-covalent grafting mechanism using electrostatic self-assembly, thus achieving mild and efficient grafting. Under room temperature (20-25℃) conditions, this embodiment can achieve efficient separation of emulsified oil wastewater at room temperature (25℃), and has excellent recycling performance, salt tolerance and wide pH adaptability. It simplifies the preparation process, reduces costs, shortens demulsification time, and can be recycled.

[0064] Example 3

[0065] like Figures 1 to 6 As shown, the preparation method of cationic and amphiphilic quaternized magnetic nanoparticles in this embodiment is basically the same as that in Example 1, and preferably includes the following steps:

[0066] Step S1: Prepare magnetic iron oxide nanoparticles using a hydrothermal method, specifically by preparing ferric chloride hexahydrate (Fe3O4) nanoparticles. Anhydrous sodium acetate ( ) and polyethylene glycol-4000 (PEG-4000) were dissolved in ethylene glycol (EG) and subjected to a hydrothermal reaction to obtain magnetic iron oxide nanoparticles.

[0067] Step S2: Prepare silica-coated magnetic iron(III) oxide (Fe3O4) using the Stober method. Magnetic nanoparticles, specifically, are dispersed in an alcohol-water mixture, and tetraethyl orthosilicate and an alkaline catalyst are added to carry out a hydrolysis-condensation reaction. The surface is coated with a silicon dioxide layer, resulting in a surface containing silicon-oxygen anions (…). ) group and negatively charged silicon dioxide coated with magnetic iron oxide (Fe3O4) Composite nanoparticles;

[0068] Step S3: Prepare cationic and amphiphilic quaternized magnetic nanoparticles using an electrostatic self-assembly method. Specifically, the silicon dioxide is coated with magnetic iron oxide (Fe3O4). Composite nanoparticles are dispersed in an alcohol-water mixture, and alkane quaternary ammonium salts are added. The silica is then used to coat magnetic iron oxide (Fe3O4). The electrostatic attraction between the negatively charged groups on the surface of the silica and the quaternary ammonium ions in the alkane quaternary ammonium salt molecules allows the alkane quaternary ammonium salt to be physically grafted onto the silica-coated magnetic iron(III) oxide through electrostatic self-assembly. On the surface of the ) the cationic and amphiphilic quaternized magnetic nanoparticles were obtained. );

[0069] In step S3, there is no siloxane quaternary ammonium salt, and the grafting of the alkane quaternary ammonium salt does not form a chemical covalent bond.

[0070] In this embodiment, the hydrothermal reaction temperature in step S1 is 200℃, and the hydrothermal reaction time is 10h. The ferric chloride hexahydrate (… ) and anhydrous sodium acetate ( The weight ratio of ferric chloride hexahydrate to ferric chloride is 1:2.8. The weight ratio of ) to polyethylene glycol-4000 (PEG-4000) is 1:0.85, and the ferric chloride hexahydrate ( The ratio of ferric chloride hexahydrate to ethylene glycol (EG) is 1 gram per gram of ferric chloride hexahydrate. This corresponds to 30 mL of ethylene glycol (EG).

[0071] In step S2, the volume ratio of alcohol to water in the alcohol-water mixed solution is 4:1; the alkaline catalyst is ammonia water, used to adjust the pH value of the reaction system to ≥9; the temperature of the hydrolysis-condensation reaction is 50℃, and the reaction time is 5h.

[0072] In step S3, the alkane quaternary ammonium salt is dodecyltrimethylammonium chloride; the silica-coated magnetic iron(III) oxide (… The mass ratio of composite nanoparticles to alkane quaternary ammonium salts is 1:0.6; the electrostatic self-assembly reaction temperature is 80℃, the reaction time is 2h, and mechanical stirring is carried out under inert gas protection; the grafting driving force of the electrostatic self-assembly method is electrostatic attraction, and no chemical covalent bonds are formed; the alkane quaternary ammonium salts are physically adsorbed onto silica-coated magnetic iron oxide (Fe3O4). )surface.

[0073] This embodiment uses low-cost alkane quaternary ammonium salts as functional monomers to achieve a three-layer core-shell structure comprising a magnetite magnetic core, a silica intermediate bridging layer, and an alkane quaternary ammonium salt functional outer layer. The alkane quaternary ammonium salt is stably loaded onto the silica surface via a non-covalent grafting mechanism using electrostatic self-assembly, thus achieving mild and efficient grafting. Under room temperature (20-25℃) conditions, this embodiment achieves efficient separation of emulsified oil wastewater at 22℃, and has excellent recyclability, salt tolerance and wide pH adaptability. It simplifies the preparation process, reduces costs, shortens demulsification time, and can be recycled.

[0074] Example 4

[0075] like Figures 1 to 6As shown, the preparation method of the cationic and amphiphilic quaternized magnetic nanoparticles in this embodiment is basically the same as any of the embodiments 1 to 3. Preferably, the preparation of the magnetite magnetic particles in this embodiment is as follows: 1.35g of ferric chloride hexahydrate (FeCl3⋅6H2O), 3.6g of anhydrous sodium acetate (CH3COONa), and 1g of polyethylene glycol (PEG-4000) are dissolved in 40mL of ethylene glycol (EG), and sonicated for 30min to form a homogeneous mixed solution. The above mixed solution is transferred to a 100mL reaction vessel and placed in a vacuum drying oven. The reaction temperature is 200℃ and the reaction time is 8h. After the reaction is completed, the mixture is naturally cooled to room temperature and washed three times with deionized water and anhydrous ethanol, respectively. After vacuum drying at 70℃ for 12h, magnetic magnetite nanoparticles are obtained. Preparation of nanoparticles: 0.5 g of Fe3O4 nanoparticles were added to a mixed solution of 80 mL ethanol and 20 mL deionized water, and sonicated for 30 min to disperse them evenly. 2 mL of ammonia (NH3·H2O) was added to adjust the pH of the mixed solution to ≥9. Then, 2 mL of tetraethyl orthosilicate (TEOS) was added. A solution containing >28.4% of a certain concentration was added to the above mixed solution, and the reaction was carried out at 50°C with mechanical stirring for 5 hours. The solution was washed three times alternately with ethanol and water, and finally dried under vacuum at 70°C for 12 hours to obtain the final product. Nanoparticles.

[0076] In this embodiment, cationic and amphiphilic quaternized composite magnetic nanoparticles ( Preparation of Fe3O4@SiO2 nanoparticles: Under nitrogen protection, 0.5 g of the above Fe3O4@SiO2 nanoparticle sample was added to 25 ml of a mixture of ethanol and water (4:1), and ultrasonically treated for 15 min to ensure uniform dispersion. Subsequently, 0.4 g of dodecyltrimethylammonium chloride (DTAC) was added to the mixed solution. The reaction was mechanically stirred at 80 °C for 2 h. After the reaction, the sample was cooled to room temperature, the lower precipitate was collected by centrifugation, washed three times with ethanol, and finally vacuum dried at 70 °C for 12 h to obtain cationic and amphiphilic quaternized magnetic nanoparticles. ).

[0077] In this embodiment, the above-mentioned cationic and amphiphilic quaternized magnetic nanoparticles ( When added to emulsified oil wastewater at a dosage of 2 g / L, with a demulsification time of 5 min, the demulsification efficiency can reach 96.7%. After washing with ethanol and water respectively, it can be recycled up to 8 times, and the demulsification efficiency still remains above 95.9%.

[0078] Example 5

[0079] like Figures 1 to 6As shown, the preparation method of the cationic and amphiphilic quaternized magnetic nanoparticles in this embodiment is basically the same as that in Example 1. Preferably, in this embodiment, under nitrogen protection, 0.5g of the above-mentioned... The nanoparticle sample was added to a mixture of 25 ml ethanol and water (4:1) and then sonicated for 15 min to ensure uniform dispersion. Subsequently, 0.1 g of dodecyltrimethylammonium chloride (DTAC) was added to the mixture. The reaction was stirred at 80 °C for 2 h. After the reaction, the sample was cooled to room temperature, centrifuged to collect the lower precipitate, washed three times with ethanol, and finally vacuum dried at 70 °C for 12 h to obtain cationic and amphiphilic quaternized magnetic nanoparticles. ).

[0080] In this embodiment, the above-mentioned cationic and amphiphilic quaternized magnetic nanoparticles ( When added to emulsified oil wastewater, the dosage is 2 g / L, the demulsification time is 5 min, and the demulsification efficiency can reach 92.4%.

[0081] Example 6

[0082] like Figures 1 to 6 As shown, the preparation method of the cationic and amphiphilic quaternized magnetic nanoparticles in this embodiment is basically the same as that in Example 1. Preferably, in this embodiment, under nitrogen protection, 0.5g of the above-mentioned... The nanoparticle sample was added to a mixture of 25 ml ethanol and water (4:1) and then sonicated for 15 min to ensure uniform dispersion. Subsequently, 0.2 g of dodecyltrimethylammonium chloride (DTAC) was added to the mixture. The reaction was stirred at 80 °C for 2 h. After the reaction, the sample was cooled to room temperature, centrifuged to collect the lower precipitate, washed three times with ethanol, and finally vacuum dried at 70 °C for 12 h to obtain cationic and amphiphilic quaternized magnetic nanoparticles. ).

[0083] In this embodiment, the above-mentioned cationic and amphiphilic quaternized magnetic nanoparticles ( When added to emulsified oil wastewater at a dosage of 2 g / L, with a demulsification time of 5 min, the demulsification efficiency can reach 95.2%.

[0084] Example 7

[0085] like Figures 1 to 6As shown, the preparation method of the cationic and amphiphilic quaternized composite magnetic nanoparticles in this embodiment is basically the same as that in Example 1. Preferably, in this embodiment, under nitrogen protection, 0.5 g of the above Fe3O4@SiO2 nanoparticle sample is added to a mixture of 25 ml of ethanol and water (4:1), and then ultrasonically treated for 15 min to disperse it evenly. Subsequently, 0.3 g of dodecyltrimethylammonium chloride (DTAC) is added to the mixed solution. The reaction is stirred at 80 °C for 2 h. After the reaction is completed, the sample is cooled to room temperature, the lower precipitate is collected by centrifugation, washed three times with ethanol, and finally vacuum dried at 70 °C for 12 h to obtain the cationic and amphiphilic quaternized composite magnetic nanoparticles.

[0086] In this embodiment, the above-mentioned cationic and amphiphilic quaternized magnetic nanoparticles ( When added to emulsified oil wastewater at a dosage of 2 g / L, with a demulsification time of 5 min, the demulsification efficiency can reach 95.9%.

[0087] Example 8

[0088] like Figures 1 to 6 As shown, the preparation method of the cationic and amphiphilic quaternized magnetic nanoparticles in this embodiment is basically the same as that in Example 1. Preferably, in this embodiment, under nitrogen protection, 0.5g of the above-mentioned... The nanoparticle sample was added to a mixture of 25 ml ethanol and water (4:1) and then sonicated for 15 min to ensure uniform dispersion. Subsequently, 0.5 g of dodecyltrimethylammonium chloride (DTAC) was added to the mixture. The reaction was stirred at 80 °C for 2 h. After the reaction, the sample was cooled to room temperature, centrifuged to collect the lower precipitate, washed three times with ethanol, and finally vacuum dried at 70 °C for 12 h to obtain cationic and amphiphilic quaternized magnetic nanoparticles. ).

[0089] In this embodiment, the above-mentioned cationic and amphiphilic quaternized magnetic nanoparticles ( When added to emulsified oil wastewater, the dosage is 2 g / L, the demulsification time is 5 min, and the demulsification efficiency can reach 95.6%.

[0090] Example 9

[0091] like Figures 1 to 6 As shown, the preparation method of the cationic and amphiphilic quaternized composite magnetic nanoparticles in this embodiment is basically the same as any of the embodiments 1 to 8. Preferably, this embodiment also provides a cationic and amphiphilic quaternized composite magnetic nanoparticle, which is prepared by any of the above-mentioned embodiment methods.

[0092] The composite magnetic nanoparticles described in this embodiment have a core-shell structure, wherein the core is iron(II,III) oxide, the middle layer is silicon dioxide, and the outer shell is alkane quaternary ammonium salt molecules physically adsorbed through electrostatic self-assembly; the surface zeta potential of the composite magnetic nanoparticles is positive in the pH range of 3 to 11, and the saturation magnetization is not less than 25 emu / g.

[0093] This embodiment uses low-cost alkane quaternary ammonium salts as functional monomers to achieve a three-layer core-shell structure comprising a magnetic core of iron oxide, a silica intermediate bridging layer, and an outer functional layer of alkane quaternary ammonium salts. The alkane quaternary ammonium salts are stably loaded onto the silica surface through a non-covalent grafting mechanism of electrostatic self-assembly, thereby achieving mild and efficient grafting. The resulting composite magnetic nanoparticles can achieve efficient separation of emulsified oil wastewater at room temperature (23°C) and exhibit excellent recyclability, salt tolerance, and wide pH adaptability. This simplifies the preparation process, reduces costs, shortens demulsification time, and allows for recycling.

[0094] Example 10

[0095] like Figures 1 to 6 As shown, the preparation method of the cationic and amphiphilic quaternized magnetic nanoparticles in this embodiment is basically the same as any one of the embodiments 1 to 8. Preferably, this embodiment also provides the application of the cationic and amphiphilic quaternized magnetic nanoparticles in oil-water emulsion separation.

[0096] This embodiment uses low-cost alkane quaternary ammonium salts as functional monomers to achieve a three-layer core-shell structure comprising a magnetic core of iron oxide, a silica intermediate bridging layer, and an outer functional layer of alkane quaternary ammonium salts. The alkane quaternary ammonium salts are stably loaded onto the silica surface through a non-covalent grafting mechanism of electrostatic self-assembly, thereby achieving mild and efficient grafting. The resulting composite magnetic nanoparticles can achieve efficient separation of emulsified oil wastewater at room temperature and have excellent recyclability, salt tolerance, and wide pH adaptability. This simplifies the preparation process, reduces costs, shortens demulsification time, and allows for recycling.

[0097] Example 11

[0098] like Figures 1 to 6 As shown, this embodiment of the method for separating oil-water emulsions is basically the same as any of the embodiments 1 to 10, and preferably includes the following steps:

[0099] The above-mentioned cationic and amphiphilic quaternized magnetic nanoparticles ( The cationic and amphiphilic quaternized magnetic nanoparticles ( ) are mixed with the oil-in-water emulsion oily wastewater to be treated, so that the cationic and amphiphilic quaternized magnetic nanoparticles ( ) It is attracted to the negatively charged surface of oil droplets by electrostatic attraction, which disrupts the stability of the emulsion interface film and promotes the aggregation of oil droplets;

[0100] An external magnetic field is applied to the cationic and amphiphilic quaternized composite magnetic nanoparticles adsorbed with oil droplets. ) Magnetic separation from the aqueous phase yields purified water;

[0101] The separation process is completed at room temperature without the need for additional demulsifiers or pH adjustments.

[0102] In this embodiment, the oil phase in the water-in-oil emulsion oily wastewater is selected from one or more of toluene, n-hexane, chloroform, or corn germ oil; the cationic and amphiphilic quaternized composite magnetic nanoparticles ( The dosage was 0.2 g / L of wastewater, the demulsification time was 5 min, and the demulsification rate was 95% in one step.

[0103] The method described in this embodiment is applicable to high-salt emulsified oily wastewater with a sodium chloride (NaCl) concentration not exceeding 5 g / L, and can achieve demulsification within a pH range of 3 to 11.

[0104] The cationic and amphiphilic quaternized magnetic nanoparticles described in this embodiment ( After magnetic separation and recovery, it can be reused directly without regeneration; after being reused 8 times, the demulsification rate of the same emulsified oily wastewater is 90%.

[0105] This embodiment uses low-cost alkane quaternary ammonium salts as functional monomers to achieve a three-layer core-shell structure comprising a magnetic core of iron oxide, a silica intermediate bridging layer, and an outer functional layer of alkane quaternary ammonium salts. The alkane quaternary ammonium salts are stably loaded onto the silica surface through a non-covalent grafting mechanism of electrostatic self-assembly, thereby achieving mild and efficient grafting. The resulting composite magnetic nanoparticles can achieve efficient separation of emulsified oil wastewater at room temperature and have excellent recyclability, salt tolerance, and wide pH adaptability. This simplifies the preparation process, reduces costs, shortens demulsification time, and allows for recycling.

[0106] Example 12

[0107] like Figures 1 to 6 As shown, this embodiment of the method for separating oil-water emulsions is basically the same as any of the embodiments 1 to 10, and preferably includes the following steps:

[0108] The above-mentioned cationic and amphiphilic quaternized magnetic nanoparticles ( The cationic and amphiphilic quaternized magnetic nanoparticles ( ) are mixed with the oil-in-water emulsion oily wastewater to be treated, so that the cationic and amphiphilic quaternized magnetic nanoparticles ( ) It is attracted to the negatively charged surface of oil droplets by electrostatic attraction, which disrupts the stability of the emulsion interface film and promotes the aggregation of oil droplets;

[0109] An external magnetic field is applied to the cationic and amphiphilic quaternized composite magnetic nanoparticles adsorbed with oil droplets. ) Magnetic separation from the aqueous phase yields purified water;

[0110] The separation process is completed at room temperature without the need for additional demulsifiers or pH adjustments.

[0111] In this embodiment, the oil phase in the water-in-oil emulsion oily wastewater is selected from one or more of toluene, n-hexane, chloroform, or corn germ oil; the cationic and amphiphilic quaternized composite magnetic nanoparticles ( The dosage was 2 g / L of wastewater, the demulsification time was 15 min, and the demulsification rate was 96% in one step.

[0112] The method described in this embodiment is applicable to high-salt emulsified oily wastewater with a sodium chloride (NaCl) concentration not exceeding 5 g / L, and can achieve demulsification within a pH range of 3 to 11.

[0113] The cationic and amphiphilic quaternized magnetic nanoparticles described in this embodiment ( After magnetic separation and recovery, it can be reused directly without regeneration; after being reused 8 times, the demulsification rate for the same emulsified oily wastewater is 95.9%.

[0114] This embodiment uses low-cost alkane quaternary ammonium salts as functional monomers to achieve a three-layer core-shell structure comprising a magnetic core of iron oxide, a silica intermediate bridging layer, and an outer functional layer of alkane quaternary ammonium salts. The alkane quaternary ammonium salts are stably loaded onto the silica surface through a non-covalent grafting mechanism of electrostatic self-assembly, thereby achieving mild and efficient grafting. The resulting composite magnetic nanoparticles can achieve efficient separation of emulsified oil wastewater at room temperature and have excellent recyclability, salt tolerance, and wide pH adaptability. This simplifies the preparation process, reduces costs, shortens demulsification time, and allows for recycling.

[0115] Example 13

[0116] like Figures 1 to 6 As shown, this embodiment of the method for separating oil-water emulsions is basically the same as any of the embodiments 1 to 10, and preferably includes the following steps:

[0117] The above-mentioned cationic and amphiphilic quaternized magnetic nanoparticles ( The cationic and amphiphilic quaternized magnetic nanoparticles ( ) are mixed with the oil-in-water emulsion oily wastewater to be treated, so that the cationic and amphiphilic quaternized magnetic nanoparticles ( ) It is attracted to the negatively charged surface of oil droplets by electrostatic attraction, which disrupts the stability of the emulsion interface film and promotes the aggregation of oil droplets;

[0118] An external magnetic field is applied to the cationic and amphiphilic quaternized composite magnetic nanoparticles adsorbed with oil droplets. ) Magnetic separation from the aqueous phase yields purified water;

[0119] The separation process is completed at room temperature without the need for additional demulsifiers or pH adjustments.

[0120] In this embodiment, the oil phase in the water-in-oil emulsion oily wastewater is selected from one or more of toluene, n-hexane, chloroform, or corn germ oil; the cationic and amphiphilic quaternized composite magnetic nanoparticles ( The dosage of the product is 1.0 g / L of wastewater, the demulsification time is no more than 10 min, and the demulsification rate is 95.5% in one go.

[0121] The method described in this embodiment is applicable to high-salt emulsified oily wastewater with a sodium chloride (NaCl) concentration not exceeding 5 g / L, and can achieve demulsification within a pH range of 3 to 11.

[0122] The cationic and amphiphilic quaternized magnetic nanoparticles described in this embodiment ( After magnetic separation and recovery, it can be reused directly without regeneration; after being reused 8 times, the demulsification rate for the same emulsified oily wastewater is still not less than 95.6%.

[0123] This embodiment uses low-cost alkane quaternary ammonium salts as functional monomers to achieve a three-layer core-shell structure comprising a magnetite core, a silica intermediate bridging layer, and an alkane quaternary ammonium salt functional outer layer. The alkane quaternary ammonium salt is stably loaded onto the silica surface via a non-covalent grafting mechanism using electrostatic self-assembly, thus achieving mild and efficient grafting. The resulting cationic and amphiphilic quaternized composite magnetic nanoparticles (… It can achieve efficient separation of emulsified oil wastewater at room temperature and has excellent recycling performance, salt resistance and wide pH adaptability. It simplifies the preparation process, reduces costs, shortens demulsification time, and can be recycled.

[0124] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for the preparation of cationic and amphiphilic quaternized complex magnetic nanoparticles, characterized in that, Magnetic magnetite composite nanoparticles coated with silica, which are negatively charged due to the presence of silicon-oxygen anion groups on their surface, are dispersed in an alcohol-water mixture. Alkane quaternary ammonium salts are added, and the quaternary ammonium ions in the quaternary ammonium salt molecules are physically grafted onto the silica-coated magnetic magnetite surface by electrostatic self-assembly, utilizing the electrostatic attraction between the negatively charged groups on the silica-coated magnetic magnetite surface and the quaternary ammonium ions in the quaternary ammonium salt molecules, to obtain the cationic and amphiphilic quaternized magnetic composite nanoparticles.

2. The method for preparing cationic and amphiphilic quaternized composite magnetic nanoparticles according to claim 1, characterized in that, The silica-coated magnetic iron oxide composite nanoparticles were prepared using the Stober method. Specifically, iron oxide nanoparticles were dispersed in an alcohol-water mixed solution, tetraethyl orthosilicate and an alkaline catalyst were added, and a hydrolysis-condensation reaction was carried out to coat the iron oxide surface with a silica layer, resulting in silica-coated magnetic iron oxide composite nanoparticles with a negatively charged surface due to the presence of silicon-oxygen anion groups. The alcohol-water volume ratio of the alcohol-water mixed solution was (3-5):

1. The alkaline catalyst was ammonia water, used to adjust the pH value of the reaction system to ≥9. The hydrolysis-condensation reaction was carried out at a temperature of 40-60℃ for 4-6 hours.

3. The method for preparing cationic and amphiphilic quaternized composite magnetic nanoparticles according to claim 2, characterized in that, The magnetic iron oxide nanoparticles were prepared by a hydrothermal method. Specifically, ferric chloride hexahydrate, anhydrous sodium acetate, and polyethylene glycol-4000 were dissolved in ethylene glycol and subjected to a hydrothermal reaction to obtain magnetic iron oxide nanoparticles. The hydrothermal reaction temperature was 180–220°C, and the hydrothermal reaction time was 6–12 h. The weight ratio of ferric chloride hexahydrate to anhydrous sodium acetate was 1:(2.5–3.0), the weight ratio of ferric chloride hexahydrate to polyethylene glycol-4000 was 1:(0.7–1.0), and the amount of ferric chloride hexahydrate to ethylene glycol was 25–35 mL of ethylene glycol per gram of ferric chloride hexahydrate.

4. The method for preparing cationic and amphiphilic quaternized composite magnetic nanoparticles according to claim 1 or 3, characterized in that, The alkane quaternary ammonium salt is dodecyltrimethylammonium chloride; the mass ratio of the silica-coated magnetic iron oxide composite nanoparticles to the alkane quaternary ammonium salt is 1:(0.2-1.0); the electrostatic self-assembly reaction temperature is 70-90℃, and the reaction time is 1-3h.

5. Cationic and amphiphilic quaternized magnetic nanoparticles, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 4.

6. The cationic and amphiphilic quaternized composite magnetic nanoparticles according to claim 5, characterized in that, The composite magnetic nanoparticles have a core-shell structure, wherein the core is iron(II,III) oxide, the middle layer is silicon dioxide, and the outer shell is alkane quaternary ammonium salt molecules physically adsorbed through electrostatic self-assembly.

7. The application of the cationic and amphiphilic quaternized magnetic nanoparticles according to claim 5 or 6 in oil-water emulsion separation.

8. A method for separating oil-water emulsions, characterized in that, Includes the following steps: The cationic and amphiphilic quaternized magnetic nanoparticles as described in claim 5 or 6 are mixed with the oil-in-water emulsion oily wastewater to be treated, so that the composite magnetic nanoparticles are adsorbed onto the surface of negatively charged oil droplets by electrostatic attraction, thereby disrupting the stability of the emulsion interface film and promoting the aggregation of oil droplets. An external magnetic field is applied to magnetically separate the composite magnetic nanoparticles adsorbed with oil droplets from the aqueous phase, thus obtaining purified water.

9. The method for separating oil-water emulsions according to claim 8, characterized in that, The oil phase in the water-in-oil emulsion oily wastewater is selected from one or more of toluene, n-hexane, chloroform, or corn germ oil; the dosage of the composite magnetic nanoparticles is 0.2-2 g / L of wastewater, the demulsification time is no more than 15 min, and the one-time demulsification rate is no less than 95%.

10. The method for separating oil-water emulsions according to claim 9, characterized in that, The method is applicable to high-salt emulsified oily wastewater with a sodium chloride concentration not exceeding 5 g / L, and can achieve demulsification within a pH range of 3 to 11.

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