Reversed microemulsion composition, iron oxide magnetic particle reversed microemulsion, and preparation method and application thereof, core-shell type iron oxide magnetic particle and preparation method thereof

Abstract

The present application relates to the technical field of magnetic material, in particular to a kind of reverse microemulsion composition, iron oxide magnetic particle reverse microemulsion and its preparation method and application, core-shell type iron oxide magnetic particle and its preparation method.The composition contains iron salt reverse microemulsion component and alkaline reverse microemulsion component;The iron salt reverse microemulsion component contains the following components independently stored or more than two mixed storage: cationic surfactant A, anionic surfactant A, soluble iron source, organic solvent A, water;The alkaline reverse microemulsion component contains the following components independently stored or more than two mixed storage: cationic surfactant B, anionic surfactant B, soluble alkali, organic solvent B, water.The reverse microemulsion composition of anion / cation complex surfactant is proposed in the present application, and relatively small size reverse microemulsion droplet can be prepared.

Description

Technical Field

[0001] This invention relates to the field of magnetic materials technology, specifically to a reverse microemulsion composition, a reverse microemulsion of iron oxide magnetic particles and its preparation method and application, and core-shell type iron oxide magnetic particles and their preparation method. Background Technology

[0002] Iron oxide magnetic nanoparticles have become a research hotspot in many disciplines, particularly in magnetohydrodynamics, catalysis, biotechnology, nuclear magnetic resonance imaging, data storage, and environmental protection. A series of synthetic methods have been developed to synthesize magnetic nanoparticles that can exist stably under different environments, and these methods have been successfully applied to the aforementioned fields. In most anticipated applications, the magnetic particles perform well when their size is smaller than a critical value, which is related to the intrinsic properties of the material and is typically between 10 and 20 nm. When the temperature exceeds the blocking temperature, each particle becomes an individual magnetic domain, exhibiting superparamagnetic behavior. These individual nanoparticles possess a large magnetic moment, and neglecting remanence and coercivity (the strength of the external magnetic field that converts magnetism to zero), they behave like a giant paramagnetic atom, rapidly responding to changes in the external magnetic field. These properties make superparamagnetic nanoparticles highly promising for applications in biomedicine, especially if particle aggregation at room temperature can be overcome.

[0003] Extensive research has been conducted on the synthesis of magnetic nanoparticles in recent decades. Particularly in recent years, numerous articles have been published on the synthesis of controllable-shape, highly stable, monodisperse magnetic nanoparticles. Many popular methods, including co-precipitation, thermal decomposition, micelle synthesis, hydrothermal synthesis, and laser pyrolysis techniques, have been used to synthesize high-quality magnetic nanoparticles. Among these, the reverse microemulsion technique offers unique advantages in the synthesis of core-shell iron oxide magnetic nanoparticles.

[0004] The common process for synthesizing core-shell magnetite nanoparticles using the reverse microemulsion method is as follows: Microemulsion A is prepared using a compound surfactant, an aqueous solution of iron salt, and an oily solvent (such as cyclohexane or liquid paraffin). Then, a compound surfactant, an alkaline aqueous solution, and an oily solvent (the same as microemulsion A) are used. Microemulsion A is then mixed with microemulsion B. The iron salt in the microdroplets of the iron salt aqueous solution will form nanoparticles under alkaline conditions. The size of the microdroplets directly affects the size of the nanoparticles. To effectively control the nanoparticle size below 15 nm, the combination of the compound surfactant and the oily solvent needs to be optimized for the specific system. After the reaction is complete, an oily solution of a silane coupling agent is added to the reaction solution. The silane coupling agent will gradually hydrolyze the magnetite nanoparticles deposited in the water droplets, forming a protective shell with different coupling groups (amino, silanol, or epoxy). To control the shell thickness and uniformity, the concentration of the silane coupling agent in the oily solution, the reaction temperature, and possibly the stirring rate all need to be optimized in detail.

[0005] The key to the success of this technical approach lies in the preparation of reverse microemulsions in both aqueous and alkaline solutions of iron salts. According to the literature, commonly used reverse microemulsion systems include quaternary ammonium salt cationic surfactant / 1-hexanol / kerosene, AOT / 1-hexanol / cyclohexane, and Span 85 / Tween 80 / kerosene. Although reverse microemulsion systems using cationic, anionic, or nonionic surfactants combined with nonionic co-emulsifiers are well-established and have been extensively studied, they still have limitations in practical applications: in some systems, the curvature of the ordered molecular film at the water / oil interface is small. To synthesize small nanoparticles, the concentration of iron salts in the aqueous phase needs to be reduced, which may affect the concentration of the target product in the reaction solution.

[0006] The critical packing parameter model is an important model for the morphology of surfactant micelles in aqueous solutions. According to this model, the morphology of surfactant micelles is determined by the volume of the hydrated head group and the tail chain. When the volume of the hydrated head group is less than 1 / 3 of the tail chain, the resulting micelle shape is spherical. Significantly reducing the volume of the hydrated head group can rapidly adjust the curvature of the ordered film at the water / oil interface, thereby changing the size and shape of the entire micelle particle. Based on the common types of surfactant head groups (cationic, anionic, and nonionic), the combination of cationic and anionic surfactants results in the smallest hydrated portion in the composite head group, making it the most effective method. Other combinations, due to their larger hydrated portions, show less reduction in hydrated head group volume after combination. To modify the surfactant micelle morphology, the tail chain volume needs to be significantly increased. However, simply increasing the tail chain volume has limited effect on changing the curvature of the interfacial film. Summary of the Invention

[0007] As mentioned above, cationic or anionic reverse microemulsions have relatively large droplet sizes. When using such reverse microemulsions, the concentration of soluble iron source is low, resulting in a low yield of the target product. The inventors of this invention propose using anionic / cationic surfactant-based reverse microemulsions to easily formulate micelles with specified shapes and sizes. This eliminates the need to reduce the concentration of soluble iron source during nanoparticle synthesis, thus maintaining the concentration of the target product in the reaction solution. Furthermore, the ordered molecular film thickness at the water / oil interface within the micelles is small. When preparing iron oxide magnetic nanoparticles, small molecules can more easily cross the water / oil interface, resulting in a faster reaction rate and a higher degree of reaction. This composition can also produce smaller reverse microemulsion droplets and offers the advantages of simplicity and environmental friendliness.

[0008] Based on this, the first aspect of the present invention provides a reverse microemulsion composition comprising an iron salt reverse microemulsion component and an alkaline reverse microemulsion component; wherein the iron salt reverse microemulsion component comprises the following components, which are stored independently or in combination: cationic surfactant A, anionic surfactant A, soluble iron source, organic solvent A, and water; wherein the alkaline reverse microemulsion component comprises the following components, which are stored independently or in combination: cationic surfactant B, anionic surfactant B, soluble alkali, organic solvent B, and water.

[0009] The second aspect of the present invention provides a method for preparing an iron oxide magnetic particle reverse microemulsion, the method comprising: preparing an iron salt reverse microemulsion and an alkaline reverse microemulsion respectively using each component of the iron salt reverse microemulsion component and the alkaline reverse microemulsion component described in the present invention, and then contacting the iron salt reverse microemulsion and the alkaline reverse microemulsion together.

[0010] The third aspect of the present invention provides an iron oxide magnetic particle reverse microemulsion prepared by the preparation method of the second aspect of the present invention.

[0011] The fourth aspect of this invention provides the application of the iron oxide magnetic particle reverse microemulsion described in the third aspect of this invention in crude oil emulsion demulsifiers or in the preparation of superparamagnetic nanoparticles.

[0012] The fifth aspect of the present invention provides a method for preparing core-shell type iron oxide magnetic particles, the method comprising: contacting a shell precursor with a reverse microemulsion of iron oxide magnetic particles of the present invention under acidic conditions, and then precipitating under alkaline conditions.

[0013] The sixth aspect of the present invention provides core-shell type iron oxide magnetic particles prepared by the preparation method of the fifth aspect of the present invention.

[0014] Through the above technical solution, the present invention proposes a reverse microemulsion composition using anionic / cationic compound surfactants, which can be used to prepare reverse microemulsion droplets with smaller size, and can increase the content of the target product in the composition, while having a short reaction time and a high degree of reaction. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] It should be noted that, in this invention, the cationic surfactant A in the iron salt reverse microemulsion component and the cationic surfactant B in the alkaline reverse microemulsion component serve only as identifiers to distinguish the cationic surfactants in the iron salt reverse microemulsion component and the alkaline reverse microemulsion component. They do not have a limiting effect and are still cationic surfactants. Similarly, the A and B in anionic surfactant A and anionic surfactant B, and organic solvent A and organic solvent B, are also only for identification purposes.

[0017] In all aspects of the invention, the same components in each aspect are described only once in one aspect and not repeatedly, and this should not be construed as a limitation of the invention by those skilled in the art.

[0018] The first aspect of the present invention provides a reverse microemulsion composition comprising an iron salt reverse microemulsion component and an alkaline reverse microemulsion component; wherein the iron salt reverse microemulsion component comprises the following components, which are stored independently or in combination: cationic surfactant A, anionic surfactant A, a soluble iron source, an organic solvent A, and water; wherein the alkaline reverse microemulsion component comprises the following components, which are stored independently or in combination: cationic surfactant B, anionic surfactant B, a soluble alkali, an organic solvent B, and water.

[0019] This invention proposes a reverse microemulsion using anionic / cationic compound surfactants, which can increase the content of the target product in the final reaction solution, while also achieving a short reaction time and high reaction degree. Furthermore, the composition of this invention can be used to formulate smaller reverse microemulsion droplets.

[0020] According to a preferred embodiment of the present invention, in the iron salt reverse microemulsion, based on the total mass of the iron salt reverse microemulsion components, the content of the cationic surfactant A is 0.0001 wt% to 20 wt%, for example, 0.0001 wt%, 0.1 wt%, 0.3 wt%, 2.7 wt%, 3 wt%, 5 wt%, 6 wt%, 8 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, or any combination of two of the above values, preferably 2 wt% to 16 wt%. The compositions of the foregoing embodiments can be formulated to produce smaller-sized reverse microemulsion droplets. When used to prepare iron oxide nanoparticles or modified products, higher yields of low-particle-size target products and reduced reaction time can be obtained.

[0021] According to a preferred embodiment of the present invention, in the iron salt reverse microemulsion, based on the total mass of the iron salt reverse microemulsion components, the content of the anionic surfactant A is 0.0001 wt% to 20 wt%, for example, 0.0001 wt%, 0.1 wt%, 0.3 wt%, 2.7 wt%, 3 wt%, 5 wt%, 6 wt%, 8 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, or any combination of two of the above values, preferably 2 wt% to 16 wt%. The compositions of the aforementioned embodiments can be formulated to produce smaller-sized reverse microemulsion droplets. When used to prepare iron oxide nanoparticles or modified products, higher yields of low-particle-size target products and reduced reaction time can be obtained.

[0022] In this invention, the preparation of reverse microemulsions using a combination of anionic and cationic surfactants effectively controls the size of surfactant micelles. The use of a high concentration of soluble iron source also enables the synthesis of target products with small-sized nanoparticles, resulting in a high content of the target product. Preferably, in the iron salt reverse microemulsion, based on the total mass of the iron salt reverse microemulsion components, the content of the soluble iron source is 0.0001 wt% to 60 wt%, for example, 0.0001 wt%, 1 wt%, 5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 48 wt%, 50 wt%, 55 wt%, 60 wt%, or any combination of two of the above values, preferably 10 wt% to 50 wt%.

[0023] According to a more preferred embodiment of the present invention, in the iron salt reverse microemulsion component, the value of the content of cationic surfactant A*a1 + the content of anionic surfactant A*a2 is 1.4-15, for example, 1.4, 1.9, 2.3, 3.0, 3.2, 4.0, 5.6, 5.8, 5.9, 6.0, 6.2, 6.5, 6.7, 7.6, 7.9, 8.0, 9.0, 10, 11, 12, 14, 15, or any combination of the above two values, preferably 1.8-12, more preferably 1.9-8.0, where a1 is the number of carbon atoms in the long-chain alkyl group with the most carbon atoms in cationic surfactant A, and a2 is the number of carbon atoms in the long-chain alkyl group with the most carbon atoms in anionic surfactant A. The composition of the foregoing embodiment can be formulated to produce smaller-sized reverse microemulsion droplets. When used to prepare iron oxide nanoparticles or modified products, it can better obtain higher yields of low-particle-size target products and reduce reaction time.

[0024] According to a preferred embodiment of the present invention, in the iron salt reverse microemulsion, based on the total mass of the iron salt reverse microemulsion components, the content of the organic solvent A is 10wt% to 80wt%, for example, 10wt%, 12wt%, 14wt%, 16wt%, 17wt%, 20wt%, 25wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, or any combination of two of the above values, preferably 12wt% to 60wt%. The composition of the foregoing embodiment can be formulated to produce smaller reverse microemulsion droplets. When used to prepare iron oxide nanoparticles or modified products, it can better obtain higher yields of low-particle-size target products and reduce reaction time.

[0025] According to the present invention, the water content in the iron salt reverse microemulsion is not particularly limited as long as the purpose of the present invention can be achieved. Generally, the water content is sufficient to dissolve the soluble iron source. Preferably, the water content is based on the total mass of the iron salt reverse microemulsion components: the water content is 10wt% to 50wt%, for example, 10wt%, 18wt%, 30wt%, 40wt%, 50wt%, 60wt%, or any two of the above values, preferably 10wt% to 40wt%.

[0026] According to a preferred embodiment of the present invention, in the alkaline reverse microemulsion, based on the total mass of the alkaline reverse microemulsion components, the content of the cationic surfactant B is 0.0001 wt% to 20 wt%, for example, 0.0001 wt%, 0.1 wt%, 0.3 wt%, 2.7 wt%, 3 wt%, 5 wt%, 6 wt%, 8 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, or any combination of two of the above values, preferably 2 wt% to 16 wt%. The compositions of the foregoing embodiments can be formulated to produce smaller-sized reverse microemulsion droplets. When used to prepare iron oxide nanoparticles or modified products, higher yields of low-particle-size target products and reduced reaction time can be obtained.

[0027] According to a preferred embodiment of the present invention, in the alkaline reverse microemulsion, based on the total mass of the alkaline reverse microemulsion components, the content of the anionic surfactant B is 0.0001% to 20 wt%, for example, 0.0001 wt%, 0.1 wt%, 0.3 wt%, 2.7 wt%, 3 wt%, 5 wt%, 6 wt%, 8 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, or any combination of two of the above values, preferably 2 wt% to 16 wt%. The compositions of the aforementioned embodiments can be formulated to produce smaller-sized reverse microemulsion droplets. When used to prepare iron oxide nanoparticles or modified products, higher yields of low-particle-size target products and reduced reaction time can be obtained.

[0028] According to a preferred embodiment of the present invention, the value of the content of cationic surfactant B * b1 + the content of anionic surfactant B * b2 is 1.5-15, for example, 1.5, 2.2, 2.6, 3.1, 3.3, 4.0, 5.6, 5.8, 5.9, 6.0, 6.2, 6.5, 6.7, 7.6, 7.9, 8.0, 9.0, 10, 11, 12, 14, 15, or any combination of the above values, preferably 1.8-12, more preferably 1.9-8.0; wherein, b1 is the number of carbon atoms in the long-chain alkyl group with the most carbon atoms in the cationic surfactant B, and b2 is the number of carbon atoms in the long-chain alkyl group with the most carbon atoms in the anionic surfactant B. The composition of the aforementioned embodiment can be formulated to produce smaller-sized reverse microemulsion droplets. When used to prepare iron oxide nanoparticles or modified products, it can better obtain higher yields of low-particle-size target products and reduce reaction time.

[0029] According to a preferred embodiment of the present invention, in the alkaline reverse microemulsion, based on the total mass of the alkaline reverse microemulsion components, the content of the soluble alkali is 0.0001 wt% to 60 wt%, for example, 0.0001 wt%, 0.1 wt%, 10 wt%, 14 wt%, 24 wt%, 30 wt%, 35 wt%, 40 wt%, 50 wt%, 60 wt%, and preferably a range of any two of the above values, from 10 wt% to 40 wt%. The compositions of the foregoing embodiments can be formulated to produce smaller-sized reverse microemulsion droplets. When used to prepare iron oxide nanoparticles or modified products, it is possible to obtain higher yields of low-particle-size target products and reduce reaction time.

[0030] According to a preferred embodiment of the present invention, in the alkaline reverse microemulsion, based on the total mass of the alkaline reverse microemulsion components, the content of the organic solvent B is 10wt% to 80wt%, for example, 10wt%, 15wt%, 20wt%, 40wt%, 50wt%, 60wt%, or 80wt%, preferably 15wt% to 60wt%.

[0031] According to a preferred embodiment of the present invention, in the alkaline reverse microemulsion, based on the total mass of the alkaline reverse microemulsion components, the water content is 10wt% to 60wt%, preferably 10wt% to 50wt%.

[0032] According to the present invention, as long as the purpose of the present invention can be achieved, the specific types of ionic surfactant A and cationic surfactant B in the present invention are not particularly limited. According to a preferred embodiment of the present invention, cationic surfactant A and cationic surfactant B are each independently selected from at least one of alkyl quaternary ammonium salt cationic surfactants, alkyl pyridinium salt cationic surfactants and alkylamine salt cationic surfactants.

[0033] According to a particularly preferred embodiment of the present invention, the cationic surfactant A and the cationic surfactant B are each independently selected from alkyl quaternary ammonium salt type cationic surfactants.

[0034] The cationic surfactant A in this invention may be the same as or different from the specific type of cationic surfactant, but preferably the cationic surfactant A is the same as the specific type of cationic surfactant.

[0035] In this invention, the alkyl group in "alkyl quaternary ammonium salt cationic surfactant" can be a single long-chain alkyl group or a double long-chain alkyl group. As long as the purpose of this invention is achieved, the specific type of alkyl ammonium salt cationic surfactant is not limited. According to a preferred embodiment of this invention, the alkyl quaternary ammonium salt cationic surfactant is selected from C6-C22 alkyl quaternary ammonium salts and / or dialkyl C6-C22 alkyl quaternary ammonium salts. The compositions of the foregoing embodiments can be formulated to produce smaller-sized reverse microemulsion droplets. When used to prepare iron oxide nanoparticles or modified products, it is possible to obtain higher yields of low-particle-size target products and reduce reaction time.

[0036] In this invention, the C6-C18 alkyl group in the C6-C22 alkyl quaternary ammonium salt or the dialkyl C6-C18 alkyl quaternary ammonium salt can be a branched alkyl group or a branched alkyl group, preferably a branched alkyl group. Preferably, the alkyl quaternary ammonium salt type cationic surfactant is selected from C8-C18 alkyl quaternary ammonium salts and / or dialkyl C8-C18 alkyl quaternary ammonium salts.

[0037] The alkyl quaternary ammonium salt type cationic surfactants used in this invention include, but are not limited to, at least one of hexyltrimethylammonium chloride, dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, bis(octadecyl)dimethylammonium chloride, and bis(octadecyl)dimethylammonium bromide. The advantages of this invention are illustrated using several specific cationic surfactants in the embodiments of this invention, and should not be construed as limiting the invention.

[0038] According to a preferred embodiment of the present invention, the anionic surfactant A and the anionic surfactant B are each independently selected from at least one of carboxylate anionic surfactants, sulfonate anionic surfactants, sulfate anionic surfactants, and phosphate anionic surfactants.

[0039] According to a particularly preferred embodiment of the present invention, the anionic surfactant A and the anionic surfactant B are each independently selected from at least one of carboxylate anionic surfactants, sulfonate anionic surfactants, and sulfate anionic surfactants.

[0040] The anionic surfactant A in this invention may be the same as or different from the specific type of anionic surfactant. Preferably, the anionic surfactant A is the same as the specific type of anionic surfactant.

[0041] According to the present invention, there are no special restrictions on the specific type of carboxylate-type anionic surfactant as long as the purpose of the present invention can be achieved. Preferably, the carboxylate-type anionic surfactant includes at least one of alkyl carboxylates, alkyl polyoxyethylene ether carboxylates and alkylphenol polyoxyethylene ether carboxylates. More preferably, the carboxylate-type anionic surfactant includes at least one of C4-C18 alkyl carboxylates, C12-C18 alkyl polyoxyethylene ether carboxylates and C12-C18 alkylphenol polyoxyethylene ether carboxylates.

[0042] In this invention, C4-C18 alkyl carboxylates refer to alkyl carboxylates whose alkyl chains contain 4-18 carbon atoms. The C4-C18 alkyl chains in this invention can be straight chains or branched chains, preferably straight chains, such as C4 alkyl carboxylates (specifically, sodium butyrate), C6 alkyl carboxylates (specifically, sodium hexanoate), C8 alkyl carboxylates (specifically, sodium octanoate), C12 alkyl carboxylates (specifically, sodium laurylate), C16 alkyl carboxylates (specifically, sodium palmitate), and C18 alkyl carboxylates (specifically, sodium stearate).

[0043] In this invention, C12-C18 alkyl polyoxyethylene ether carboxylates refer to alkyl polyoxyethylene ether carboxylates whose alkyl chains contain 12-18 carbon atoms, such as alkyl polyoxyethylene ether carboxylates with 12 carbon atoms (specifically, sodium dodecyl polyoxyethylene ether (n=2)carboxylate) and alkyl polyoxyethylene ether carboxylates with 18 carbon atoms (specifically, sodium octadecyl polyoxyethylene ether (n=2)carboxylate).

[0044] In this invention, C12-C18 alkylphenol polyoxyethylene ether carboxylates refer to alkylphenol polyoxyethylene ether carboxylates whose alkyl chains contain 12-18 carbon atoms, such as alkylphenol polyoxyethylene ether carboxylates with 12 carbon atoms (specifically, sodium dodecylphenol polyoxyethylene ether (n=2)carboxylate) and alkylphenol polyoxyethylene ether carboxylates with 18 carbon atoms (specifically, sodium octadecylphenol polyoxyethylene ether (n=2)carboxylate).

[0045] In a preferred embodiment of the present invention, the sulfonate-type anionic surfactant includes aliphatic diester sulfonates.

[0046] In this invention, the aliphatic dicarboxylic acid ester sodium sulfonate refers to the ester obtained by ester bonding of an aliphatic dicarboxylic acid with a 2-molecule saturated aliphatic alcohol.

[0047] In a preferred embodiment of the present invention, the sulfonate-type anionic surfactant includes C4-C6 alkyl diacid bis(C8-C13) alkyl ester sulfonate.

[0048] In this invention, the C4-C6 alkyl diacid bis(C8-C13) ester sulfonates that can be listed include C4 alkyl diacid bis(C8) ester sulfonates (specifically, sodium bis(2-ethylhexyl)succinate sulfonate) and C4 alkyl diacid bis(C13) ester sulfonates (specifically, sodium bis(tetranyl)succinate sulfonate).

[0049] According to a preferred embodiment of the present invention, the sulfate-type anionic surfactant includes alkyloxyethylene ether sulfate salts.

[0050] According to a particularly preferred embodiment of the present invention, the sulfate-type anionic surfactant includes C12 to C18 alkyl polyoxyethylene ether sulfates, such as C12 alkyl polyoxyethylene ether sulfates (specifically, sodium dodecyl polyoxyethylene ether (n=2) sulfate) and C18 alkyl polyoxyethylene ether sulfates (specifically, sodium octadecyl polyoxyethylene ether (n=2) sulfate).

[0051] The alkyl carboxylates, alkyl polyoxyethylene ether carboxylates, alkylphenol polyoxyethylene ether carboxylates, aliphatic diester sulfonates, and alkyloxyethylene ether sulfates in this invention can be salts conventional in the art, such as sodium salts and potassium salts. The embodiments of this invention use sodium salts as an example to illustrate the advantages of this invention, but should not be construed as limiting the invention.

[0052] According to the present invention, the specific ratio of the iron salt reverse microemulsion component to the alkaline reverse microemulsion component can be set according to a ratio that allows the soluble iron source to precipitate completely. Preferably, in the composition, the soluble iron source is calculated as iron ions, and the soluble base is calculated as hydroxide and / or ammonium ions. The molar ratio of the soluble iron source to the soluble base is (0.05-5):1, for example, 0.05:1, 0.15:1, 0.25:1, 0.35:1, 0.45:1, 0.55:1, 0.65:1, 0.75:1, 0.85:1, 0.95:1, 1:1, 3:1, 4:1, 5:1, preferably (0.15-1):1.

[0053] According to a preferred embodiment of the present invention, the mass ratio of the iron salt reverse microemulsion component to the alkaline reverse microemulsion component is (0.1-5):1, preferably (0.2-1.2):1.

[0054] In this invention, the soluble iron source refers to an iron source that can dissolve in water, preferably including ferric salts and ferrous salts. Using the aforementioned embodiments, when preparing iron oxide nanoparticles or modified products, it is possible to obtain higher yields of the target product with low particle size and reduce reaction time.

[0055] According to a particularly preferred embodiment of the present invention, the mass ratio of the ferric salt to the ferrous salt is (1-3):1, for example, 1:1, 2:1, 2.7:1, 2.8:1, or 3:1, preferably (1.2-2.8):1. The compositions of the foregoing embodiments can be formulated to produce smaller-sized reverse microemulsion droplets. When used to prepare iron oxide nanoparticles or modified products, higher yields of low-particle-size target products and reduced reaction time can be achieved.

[0056] According to the present invention, a soluble base refers to a substance that is soluble in water and forms an alkaline solution in water. Generally, alkaline substances that can provide hydroxide ions or ammonium ions are suitable for the system of the present invention. Examples of soluble bases include at least one of ammonia, dimethylamine, trimethylamine, aniline, lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, and cesium hydroxide. Sodium hydroxide is used as an example in the embodiments of the present invention to illustrate the advantages of the present invention, but it should not be construed as a limitation of the present invention.

[0057] According to the present invention, the specific type of organic solvent is not particularly limited as long as the purpose of the present invention can be achieved. Preferably, the organic solvent is immiscible with water, such as at least one of cyclohexane, benzene, toluene, xylene, ethyl acetate, paraffin, kerosene, petroleum ether and white oil, preferably at least one of cyclohexane, kerosene and white oil. The embodiments of the present invention use several specific organic solvents as examples to illustrate the advantages of the present invention, but should not be construed as limiting the present invention.

[0058] According to the present invention, the reverse microemulsion composition of the present invention can form an iron oxide magnetic particle reverse microemulsion. Iron oxide is prepared using the iron oxide magnetic particle reverse microemulsion. As long as the purpose of the present invention can be achieved, the preparation method of the iron oxide magnetic particle reverse microemulsion is not particularly limited. Preferably, the second aspect of the present invention provides a method for preparing an iron oxide magnetic particle reverse microemulsion, the preparation method comprising: preparing an iron salt reverse microemulsion and an alkaline reverse microemulsion respectively using each component of the iron salt reverse microemulsion component and the alkaline reverse microemulsion component described in the present invention, and then contacting the iron salt reverse microemulsion and the alkaline reverse microemulsion.

[0059] In this invention, there are no special limitations on the method for preparing the iron salt reverse microemulsion. The components in the iron salt reverse microemulsion can be mixed evenly. The components can be mixed together, or they can be divided into several groups, mixed separately, and then the mixtures from each group can be combined. For example, soluble iron salts can be dissolved in water to form an iron salt aqueous solution (the method and conditions of dissolution are not special, as long as the soluble iron salts are completely dissolved, such as stirring at 50-70°C). A cationic surfactant A, anionic surfactant A, and organic solvent A are mixed to obtain a compound surfactant solution. Then, the iron salt aqueous solution and the compound surfactant solution are mixed to form the iron salt reverse microemulsion. In this invention, there are no special limitations on the method of mixing the iron salt aqueous solution and the compound surfactant solution. For example, the iron salt aqueous solution can be added to the compound surfactant solution dropwise. Those skilled in the art can choose the addition rate as needed, for example, 0.1–5 ml / min.

[0060] In this invention, there are no particular limitations on the method for preparing the alkaline reverse microemulsion. The components in the alkaline reverse microemulsion can be mixed evenly. The components can be mixed together, or they can be divided into several groups, mixed separately, and then the mixtures of the groups can be combined. For example, a soluble alkali can be dissolved in water to form an alkaline aqueous solution. A cationic surfactant B, anionic surfactant B, and organic solvent B can be mixed to obtain a compound surfactant solution. The alkaline aqueous solution and the compound surfactant solution can then be mixed to form the alkaline reverse microemulsion. In this invention, there are no particular limitations on the mixing method between the alkaline aqueous solution and the compound surfactant solution. For example, the alkaline aqueous solution can be added dropwise to the compound surfactant solution. Those skilled in the art can choose the appropriate rate of addition, such as 0.1–5 ml / min.

[0061] According to the present invention, there are no special limitations on the contact conditions in the preparation of the reverse microemulsion of iron oxide magnetic particles, as long as the present invention can be realized. The preferred contact temperature is 5°C to 95°C, and the preferred contact time is 5 mins to 24 mins.

[0062] The third aspect of the present invention provides an iron oxide magnetic particle reverse microemulsion prepared by the preparation method of the second aspect of the present invention.

[0063] The iron oxide magnetic particle reverse microemulsion prepared by the preparation method of the present invention has small-sized reverse microemulsion droplets, and can ultimately obtain a high content of the target product and a low particle size of the target product.

[0064] The fourth aspect of this invention provides the application of the iron oxide magnetic particle reverse microemulsion described in the third aspect of this invention in crude oil emulsion demulsifiers or in the preparation of superparamagnetic nanoparticles.

[0065] The iron oxide magnetic particle reverse microemulsion of this invention has small-sized reverse microemulsion droplets and high target product yield. When used as a crude oil emulsion demulsifier, it has excellent demulsification effect. At the same time, it can be used to prepare superparamagnetic nanoparticles with high yield and low particle size of the target product.

[0066] The fifth aspect of this invention provides a method for preparing core-shell type iron oxide magnetic particles, the method comprising:

[0067] Under acidic conditions, the shell precursor is contacted with the iron oxide magnetic particle reverse microemulsion described in this invention, and then precipitation is carried out under alkaline conditions.

[0068] In this invention, under acidic conditions, the shell precursor diffuses into the reverse microemulsion of iron oxide magnetic particles for hydrolysis, and then deposits on the surface of the iron oxide magnetic particles under alkaline conditions to form core-shell structured iron oxide magnetic particles. These core-shell type iron oxide magnetic particles have a small particle size and also have high yield.

[0069] According to the present invention, there are no special restrictions on the specific type of shell precursor as long as the purpose of the present invention can be achieved. Preferably, the shell precursor includes a coupling agent.

[0070] According to a particularly preferred embodiment of the present invention, the coupling agent is selected from silane coupling agents. In the first ten embodiments, the silane coupling agent can form a siloxane shell on the surface of the iron oxide magnetic particles.

[0071] There are no special limitations on the types of silane coupling agents used in this invention. The embodiments of this invention use silane coupling agents as examples to illustrate the advantages of this invention, but should not be construed as limiting the invention.

[0072] According to the present invention, the amount of coupling agent is not particularly limited as long as the purpose of the present invention can be achieved. Preferably, the mass of the coupling agent is 2-5 wt% of the mass of the iron oxide magnetic particle reverse microemulsion.

[0073] According to the present invention, the contact method is not particularly limited as long as the purpose of the present invention can be achieved, as long as the coupling agent can be fully introduced into the iron oxide magnetic particle reverse microemulsion. For example, the coupling agent can be dropped into the iron oxide magnetic particle reverse microemulsion for contact. The preferred contact conditions are: temperature of 40-70°C and time of 1-5 hours. The preferred contact is static contact.

[0074] In the invention, acidic conditions can be achieved by adding an acid (e.g., hydrochloric acid) to the system to adjust the reverse microemulsion of iron oxide magnetic particles to acidic conditions (e.g., adjusting the pH to 4-5).

[0075] According to the present invention, a typical shell precursor, such as a coupling agent, is an oily solvent. In order to enable it to better enter the system, it is preferred to use an alkaline reverse microemulsion in the composition of the present invention to control the system under alkaline conditions, preferably controlling the pH value of the system to be 8 to 9.

[0076] According to the present invention, after precipitation, the system still contains water and surfactants. Preferably, after precipitation, the water in the reaction solution is removed, followed by the removal of the liquid phase, and finally washing is performed. The method for removing water from the reaction solution can be conventional reflux to remove water. The removal of the liquid phase and washing are both conventional methods in the art, and the present invention has no special limitations on them.

[0077] The sixth aspect of the present invention provides core-shell type iron oxide magnetic particles prepared by the preparation method of the fifth aspect of the present invention.

[0078] In this invention, the core-shell type iron oxide magnetic particles prepared by the preparation method of the core-shell type iron oxide magnetic particles of this invention have a small particle size. Preferably, the particle size of the core-shell type iron oxide magnetic particles is 2-30 nm, for example, 2 nm, 7 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 25 nm, or 30 nm.

[0079] The present invention will be described in detail below through examples. Unless otherwise specified, the alkyl chains involved in the raw materials used in the following examples and comparative examples are all straight chains. Unless otherwise limited, the raw materials are all disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art, for example, but not limited to:

[0080] Octadecyltrimethylammonium chloride AR (Shanghai test); AOT Solvay (bis(2-ethylhexyl)succinate sodium sulfonate); n-hexanol AR (Shanghai test); cyclohexane AR (Shanghai test); No. 0 kerosene (Sinopec); No. 7 white oil (Wuxi Lanxing); ferric chloride AR (Shanghai test); ferrous chloride AR (Shanghai test); ammonia water AR (Shanghai test); deionized water (self-made, 18.2 MΩ).

[0081] Example 1

[0082] At 60°C, 96.2 g of ferric chloride hexahydrate and 35.2 g of ferrous chloride tetrahydrate were dissolved in 48.78 g of deionized water and stirred until homogeneous to obtain an aqueous solution of ferric salt. 33.8 g of octadecyltrimethylammonium chloride and 16.2 g of sodium octanoate were added to 39 g of cyclohexane and stirred until homogeneous. Then, at 60°C, the aqueous solution of ferric salt was added dropwise to the above solution at a rate of approximately 0.5 ml / min, and stirred to form a transparent reverse microemulsion of ferric salt.

[0083] Add 60 g of sodium hydroxide to 100 g of water and stir until homogeneous to form an alkaline aqueous solution. Add 33.8 g of linear octadecyltrimethylammonium chloride and 16.2 g of linear sodium octanoate to 39 g of cyclohexane and stir until homogeneous. Then, add the alkaline aqueous solution dropwise to the above solution at a rate of about 0.5 ml / min and stir to form a transparent alkaline reverse microemulsion.

[0084] At 60°C, all the above-mentioned iron salt reverse microemulsions were transferred to a 500ml four-necked flask. Under magnetic stirring at 300rpm, all the above-mentioned basic reverse microemulsions were slowly added dropwise. The temperature of the reaction solution was controlled to not exceed 60°C by adjusting the dropping rate. After the addition was complete, the mixture was kept at 60°C with stirring for 1 hour to obtain an iron oxide magnetic particle reverse microemulsion.

[0085] Hydrochloric acid was added dropwise to a reverse microemulsion of iron oxide magnetic particles at 60°C to adjust the pH of the aqueous phase to 4.5. Then, 20 g of aminosilane coupling agent KH540 was added dropwise at a rate of approximately 0.5 ml / min. After the addition was completed, the mixture was kept at 60°C for 3 hours to stop the reaction. Next, an alkaline reverse microemulsion (prepared according to the above method) was added dropwise to adjust the pH of the reverse microemulsion to approximately 8.5. The temperature of the entire system was increased to 90°C, and the mixture was refluxed to remove water from the reaction solution. The nanoparticles and sodium chloride particles in the reaction system precipitated out of the system. After complete precipitation, the liquid phase of the reaction solution was discarded. 100 ml of cyclohexane was added, stirred for 4 minutes, and allowed to stand to precipitate. The clear cyclohexane supernatant was then discarded. The washing process was repeated three times to obtain 120 g of crude product, of which approximately 60 g were coupling agent-modified iron oxide magnetic nanoparticles, and the remaining 80 g were NaCl particles. A small sample was observed using a scanning electron microscope, revealing that the magnetic nanoparticles had a diameter of approximately 10 nm.

[0086] Example 2

[0087] At 60°C, 96.2 g of ferric chloride hexahydrate and 35.2 g of ferrous chloride tetrahydrate were dissolved in 48.78 g of deionized water and stirred until homogeneous to obtain an aqueous solution of ferric salts. 39 g of bis(octadecyl)trimethylammonium chloride and 11 g of sodium octanoate were added to 39 g of 0# kerosene and stirred until homogeneous. Then, at 60°C, the aqueous solution of ferric salts was added dropwise to the above solution at a rate of approximately 0.5 ml / min, and stirred to form a transparent reverse microemulsion of ferric salts.

[0088] Add 60 g of sodium hydroxide to 100 g of water and stir until homogeneous to form an alkaline aqueous solution. Add 39 g of bis(octadecyl)trimethylammonium chloride and 11 g of sodium octanoate to 39 g of cyclohexane and stir until homogeneous. Then, add the alkaline aqueous solution dropwise to the above solution at a rate of about 0.5 ml / min and stir to form an alkaline reverse microemulsion.

[0089] At 60°C, all the above-mentioned iron salt reverse microemulsions were transferred to a 500ml four-necked flask. Under magnetic stirring at 300rpm, all the above-mentioned basic reverse microemulsions were slowly added dropwise. The temperature of the reaction solution was controlled to not exceed 60°C by adjusting the dropping rate. After the addition was complete, the mixture was kept at 60°C with stirring for 1 hour to obtain an iron oxide magnetic particle reverse microemulsion.

[0090] Hydrochloric acid was added dropwise to a reverse microemulsion of iron oxide magnetic particles at 60°C to adjust the pH of the aqueous phase to 4.5. Then, 20 g of aminosilane coupling agent KH540 was added dropwise at a rate of approximately 0.5 ml / min. After the addition was completed, the mixture was kept at 60°C for 3 hours to stop the reaction. Next, an alkaline reverse microemulsion (prepared according to the above method) was added dropwise to adjust the pH of the reverse microemulsion to approximately 8.5. The temperature of the entire system was increased to 100°C, and the mixture was refluxed to remove water from the reaction solution. The nanoparticles and sodium chloride particles in the reaction system precipitated out of the system. After complete precipitation, the liquid phase in the reaction solution was discarded. 100 ml of cyclohexane was added, stirred for 4 minutes, and allowed to stand to precipitate. The clear cyclohexane supernatant was then discarded. The washing process was repeated three times to obtain 120 g of crude product, of which approximately 60 g were coupling agent-modified iron oxide magnetic nanoparticles, and the remaining 80 g were NaCl particles. A small sample was observed using a scanning electron microscope, revealing that the magnetic nanoparticles had a diameter of approximately 8 nm.

[0091] Example 3

[0092] At 60°C, 96.2 g of ferric chloride hexahydrate and 35.2 g of ferrous chloride tetrahydrate were dissolved in 48.78 g of deionized water and stirred until homogeneous to obtain an aqueous solution of ferric salts. 34 g of sodium di(2-ethylhexyl)succinate sulfonate and 16 g of octyltrimethylammonium chloride were added to 39 g of No. 7 white oil and stirred until homogeneous. Then, at 60°C, the aqueous solution of ferric salts was added dropwise to the above solution at a rate of approximately 0.5 ml / min, and stirred to form a transparent reverse microemulsion of ferric salts.

[0093] Add 60 g of sodium hydroxide to 100 g of water and stir until homogeneous to form an alkaline aqueous solution. Add 34 g of sodium di(2-ethylhexyl)succinate sulfonate and 16 g of octyltrimethylammonium chloride to 39 g of cyclohexane and stir until homogeneous. Then, add the alkaline aqueous solution dropwise to the above solution at a rate of about 0.5 ml / min and stir to form a transparent alkaline reverse microemulsion.

[0094] At 60°C, all the above-mentioned iron salt reverse microemulsions were transferred to a 500ml four-necked flask. Under magnetic stirring at 300rpm, all the above-mentioned basic reverse microemulsions were slowly added dropwise. The temperature of the reaction solution was controlled to not exceed 60°C by adjusting the dropping rate. After the addition was complete, the mixture was kept at 60°C with stirring for 1 hour to obtain an iron oxide magnetic particle reverse microemulsion.

[0095] Hydrochloric acid was added dropwise to a reverse microemulsion of iron oxide magnetic particles at 60°C to adjust the pH of the aqueous phase to 4.5. Then, 20 g of aminosilane coupling agent KH540 was added dropwise at a rate of approximately 0.5 ml / min. After the addition was completed, the mixture was kept at 60°C for 3 hours to stop the reaction. Next, an alkaline reverse microemulsion (prepared according to the above method) was added dropwise to adjust the pH of the reverse microemulsion to approximately 8.5. The temperature of the entire system was increased to 100°C, and the mixture was refluxed to remove water from the reaction solution. The nanoparticles and sodium chloride particles in the reaction system precipitated out of the system. After complete precipitation, the solution was discarded. 100 ml of cyclohexane was added, stirred for 4 minutes, and allowed to stand to precipitate. The clear cyclohexane supernatant was then discarded. The washing process was repeated three times to obtain 120 g of crude product, of which approximately 60 g were iron oxide magnetic nanoparticles and the remaining 80 g were NaCl particles. A small sample was observed under a scanning electron microscope, revealing that the magnetic nanoparticles had a diameter of approximately 8 nm.

[0096] Example 4

[0097] At 60°C, 96.2 g of ferric chloride hexahydrate and 35.2 g of ferrous chloride tetrahydrate were dissolved in 48.78 g of deionized water and stirred until homogeneous to obtain an aqueous solution of the iron salt. 36.9 g of sodium di(tridecyl)succinate sulfonate and 13.1 g of octyltrimethylammonium chloride were added to 39 g of cyclohexane and stirred until homogeneous. Then, at 60°C, the aqueous solution of the iron salt was added dropwise to the above solution at a rate of approximately 0.5 ml / min, and stirred to form an iron salt reverse microemulsion.

[0098] Add 60 g of sodium hydroxide to 100 g of water and stir until homogeneous to form an alkaline aqueous solution. Add 36.9 g of sodium di(tridecyl)succinate sulfonate and 13.1 g of octyltrimethylammonium chloride to 39 g of cyclohexane and stir until homogeneous. Then, add the alkaline aqueous solution dropwise to the above solution at a rate of about 0.5 ml / min and stir to form a transparent alkaline reverse microemulsion.

[0099] At 60°C, all the above-mentioned iron salt reverse microemulsions were transferred to a 500ml four-necked flask. Under magnetic stirring at 300rpm, all the above-mentioned basic reverse microemulsions were slowly added dropwise. The temperature of the reaction solution was controlled to not exceed 60°C by adjusting the dropping rate. After the addition was complete, the mixture was kept at 60°C with stirring for 1 hour to obtain an iron oxide magnetic particle reverse microemulsion.

[0100] Hydrochloric acid was added dropwise to the reverse microemulsion system at 60℃ to adjust the pH of the aqueous phase to 4.5. Then, 20 g of aminosilane coupling agent KH540 was added dropwise at a rate of approximately 0.5 ml / min. After the addition was completed, the mixture was kept at 60℃ for 3 hours to stop the reaction. Next, an alkaline reverse microemulsion was added dropwise to adjust the pH of the reverse microemulsion to approximately 8.5. The temperature of the entire system was increased to 90℃, and the mixture was refluxed to remove water from the reaction solution. The nanoparticles and sodium chloride particles in the reaction system precipitated out of the system. After complete precipitation, the solution was discarded. 100 ml of cyclohexane was added, stirred for 4 minutes, and allowed to stand to precipitate. The clear cyclohexane supernatant was then discarded. The washing process was repeated three times to obtain 120 g of crude product, of which approximately 60 g were coupling agent-modified iron oxide magnetic nanoparticles, and the remaining 80 g were NaCl particles. A small sample was observed using a scanning electron microscope, revealing that the magnetic nanoparticles had a diameter of approximately 7 nm.

[0101] Example 5

[0102] At 60°C, 96.2 g of ferric chloride hexahydrate and 35.2 g of ferrous chloride tetrahydrate were dissolved in 48.78 g of deionized water and stirred until homogeneous to obtain an aqueous solution of ferric salt. 8.6 g of octadecyltrimethylammonium chloride and 11.4 g of sodium hexanoate were added to 39 g of cyclohexane and stirred until homogeneous. Then, at 60°C, the aqueous solution of ferric salt was added dropwise to the above solution at a rate of approximately 0.5 ml / min, and stirred to form a transparent reverse microemulsion of ferric salt.

[0103] Add 60 g of sodium hydroxide to 100 g of water and stir until homogeneous to form an alkaline aqueous solution. Add 8.6 g of octadecyltrimethylammonium chloride and 11.4 g of sodium hexanoate to 39 g of cyclohexane and stir until homogeneous. Then, add the alkaline aqueous solution dropwise to the above solution at a rate of about 0.5 ml / min and stir to form a transparent alkaline reverse microemulsion.

[0104] At 60°C, all the above-mentioned iron salt reverse microemulsions were transferred to a 500ml four-necked flask. Under magnetic stirring at 300rpm, all the above-mentioned basic reverse microemulsions were slowly added dropwise. The temperature of the reaction solution was controlled to not exceed 60°C by adjusting the dropping rate. After the addition was complete, the mixture was kept at 60°C with stirring for 1 hour to obtain an iron oxide magnetic particle reverse microemulsion.

[0105] Hydrochloric acid was added dropwise to the reverse microemulsion system at 60℃ to adjust the pH of the aqueous phase to 4.5. Then, 20 g of aminosilane coupling agent KH540 was added dropwise at a rate of approximately 0.5 ml / min. After the addition was completed, the mixture was kept at 60℃ for 3 hours to stop the reaction. Next, an alkaline reverse microemulsion (prepared according to the above method) was added dropwise to adjust the pH of the reverse microemulsion to approximately 8.5. The temperature of the entire system was increased to 90℃, and the mixture was refluxed to remove water from the reaction solution. The nanoparticles and sodium chloride particles in the reaction system precipitated out of the system. After complete precipitation, the solution was discarded. 100 ml of cyclohexane was added, stirred for 4 minutes, and allowed to stand to precipitate. The clear cyclohexane supernatant was then discarded. The washing process was repeated three times to obtain 120 g of crude product, of which approximately 60 g were iron oxide magnetic nanoparticles and the remaining 80 g were NaCl particles. A small sample was observed under a scanning electron microscope, revealing that the magnetic nanoparticles had a diameter of approximately 12 nm.

[0106] Example 6

[0107] At 60°C, 96.2 g of ferric chloride hexahydrate and 35.2 g of ferrous chloride tetrahydrate were dissolved in 48.78 g of deionized water and stirred until homogeneous to obtain an aqueous solution of iron salts. 42.6 g of sodium di(tridecyl)succinate sulfonate and 7.43 g of hexyltrimethylammonium chloride were added to 39 g of cyclohexane and stirred until homogeneous. Then, at 60°C, the aqueous solution of iron salts was added dropwise to the above solution at a rate of approximately 0.5 ml / min, and stirred to form a transparent reverse microemulsion of iron salts.

[0108] Add 60 g of sodium hydroxide to 100 g of water and stir until homogeneous to form an alkaline aqueous solution. Add 42.6 g of sodium di(tridecyl)succinate sulfonate and 7.43 hexyltrimethylammonium chloride to 39 g of cyclohexane and stir until homogeneous. Then, add the alkaline aqueous solution dropwise to the above solution at a rate of about 0.5 ml / min and stir to form a transparent alkaline reverse microemulsion.

[0109] At 60°C, all the above-mentioned iron salt reverse microemulsions were transferred to a 500ml four-necked flask. Under magnetic stirring at 300rpm, all the above-mentioned basic reverse microemulsions were slowly added dropwise. The temperature of the reaction solution was controlled to not exceed 60°C by adjusting the dropping rate. After the addition was complete, the mixture was kept at 60°C with stirring for 1 hour to obtain an iron oxide magnetic particle reverse microemulsion.

[0110] Hydrochloric acid was added dropwise to the reverse microemulsion system at 60℃ to adjust the pH of the aqueous phase to 4.5. Then, 20 g of aminosilane coupling agent KH540 was added dropwise at a rate of approximately 0.5 ml / min. After the addition was completed, the reaction was stopped after 3 hours of incubation. Next, an alkaline reverse microemulsion (prepared according to the above method) was added dropwise to adjust the pH of the reverse microemulsion to approximately 8.5. The temperature of the entire system was increased to 100℃, and the mixture was refluxed to remove water from the reaction solution. The nanoparticles and sodium chloride particles in the reaction system precipitated out of the system. After complete precipitation, the solution was discarded. 100 ml of cyclohexane was added, stirred for 4 minutes, and allowed to stand to precipitate. The clear cyclohexane supernatant was then discarded. The washing process was repeated three times to obtain 120 g of crude product, of which approximately 60 g were coupling agent-modified iron oxide magnetic nanoparticles, and the remaining 80 g were NaCl particles. A small sample was observed under a scanning electron microscope, revealing that the magnetic nanoparticles had a diameter of approximately 13 nm.

[0111] Example 7

[0112] At 60°C, 96.2 g of ferric chloride hexahydrate and 35.2 g of ferrous chloride tetrahydrate were dissolved in 48.78 g of deionized water and stirred until homogeneous to obtain an aqueous solution of iron salts. 42.6 g of sodium di(2-ethylhexyl)succinate sulfonate and 1 g of hexyltrimethylammonium chloride were added to 46.5 g of cyclohexane and stirred until homogeneous. Then, at 60°C, the aqueous solution of iron salts was added dropwise to the above solution at a rate of approximately 0.5 ml / min, and stirred to form a translucent reverse microemulsion of iron salts.

[0113] Add 60 g of sodium hydroxide to 100 g of water and stir until homogeneous to form an alkaline aqueous solution. Add 42.6 g of sodium di(2-ethylhexyl)succinate sulfonate and 1 g of hexyltrimethylammonium chloride to 46.5 g of cyclohexane and stir until homogeneous. Then, add the alkaline aqueous solution dropwise to the above solution at a rate of about 0.5 ml / min and stir to form a translucent alkaline reverse microemulsion.

[0114] At 60°C, all the above-mentioned iron salt reverse microemulsions were transferred to a 500ml four-necked flask. Under magnetic stirring at 300rpm, all the above-mentioned basic reverse microemulsions were slowly added dropwise. The temperature of the reaction solution was controlled to not exceed 60°C by adjusting the dropping rate. After the addition was complete, the mixture was kept at 60°C with stirring for 1 hour to obtain an iron oxide magnetic particle reverse microemulsion.

[0115] Hydrochloric acid was added dropwise to the reverse microemulsion system at 60℃ to adjust the pH of the aqueous phase to 4.5. Then, 20 g of aminosilane coupling agent KH540 was added dropwise at a rate of approximately 0.5 ml / min. After the addition was completed, the mixture was kept at 60℃ for 3 hours to stop the reaction. Next, an alkaline reverse microemulsion (prepared according to the above method) was added dropwise to adjust the pH of the reverse microemulsion to approximately 8.5. The temperature of the entire system was increased to 90℃, and the mixture was refluxed to remove water from the reaction solution. The nanoparticles and sodium chloride particles in the reaction system precipitated out of the system. After complete precipitation, the solution was discarded. 100 ml of cyclohexane was added, stirred for 4 minutes, and allowed to stand to precipitate. The clear cyclohexane supernatant was then discarded. The washing process was repeated three times to obtain 120 g of crude product, of which approximately 60 g were coupling agent-modified iron oxide magnetic nanoparticles, and the remaining 80 g were NaCl particles. A small sample was observed using a scanning electron microscope, revealing that the magnetic nanoparticles had a diameter of approximately 37 nm.

[0116] Example 8

[0117] At 60°C, 96.2 g of ferric chloride hexahydrate and 35.2 g of ferrous chloride tetrahydrate were dissolved in 48.78 g of deionized water and stirred until homogeneous to obtain an aqueous solution of ferric salt. 42.6 g of sodium di(tridecyl)succinate sulfonate and 7.43 g of tetramethylammonium chloride were added to 46.5 g of cyclohexane and stirred until homogeneous. Then, at 60°C, the aqueous solution of ferric salt was added dropwise to the above solution at a rate of approximately 0.5 ml / min, and stirred to form a milky white reverse microemulsion of ferric salt.

[0118] Add 60 g of sodium hydroxide to 100 g of water and stir until homogeneous to form an alkaline aqueous solution. Add 42.6 g of sodium di(tridecyl)succinate sulfonate and 7.43 g of tetramethylammonium chloride to 46.5 g of cyclohexane and stir until homogeneous. Then, add the alkaline aqueous solution dropwise to the above solution at a rate of about 0.5 ml / min and stir to form a milky white alkaline reverse microemulsion.

[0119] At 60°C, all the above-mentioned iron salt reverse microemulsions were transferred to a 500ml four-necked flask. Under magnetic stirring at 300rpm, all the above-mentioned basic reverse microemulsions were slowly added dropwise. The temperature of the reaction solution was controlled to not exceed 60°C by adjusting the dropping rate. After the addition was complete, the mixture was kept at 60°C and stirred for 1 hour to obtain an iron oxide magnetic particle reverse microemulsion.

[0120] Hydrochloric acid was added dropwise to the reverse microemulsion system at 60℃ to adjust the pH of the aqueous phase to 4.5. Then, 20 g of aminosilane coupling agent KH540 was added dropwise at a rate of approximately 0.5 ml / min. After the addition was completed, the mixture was kept at 60℃ for 3 hours to stop the reaction. Next, an alkaline reverse microemulsion (prepared according to the above method) was added dropwise to adjust the pH of the reverse microemulsion to approximately 8.5. The temperature of the entire system was increased to 90℃, and the mixture was refluxed to remove water from the reaction solution. The nanoparticles and sodium chloride particles in the reaction system precipitated out of the system. After complete precipitation, the solution in the reaction solution was discarded. 100 ml of cyclohexane was added, stirred for 4 minutes, and allowed to stand to precipitate. The clear cyclohexane supernatant was then discarded. The washing process was repeated three times to obtain 120 g of crude product, of which approximately 60 g were coupling agent-modified iron oxide magnetic nanoparticles, and the remaining 80 g were NaCl particles. A small sample was observed under a scanning electron microscope, revealing that the magnetic nanoparticles had a diameter of approximately 52 nm.

[0121] Example 9

[0122] At 60°C, 96.2 g of ferric chloride hexahydrate and 35.2 g of ferrous chloride tetrahydrate were dissolved in 48.78 g of deionized water and stirred until homogeneous to obtain an aqueous solution of iron salts. 7.43 g of sodium di(tridecyl)succinate sulfonate and 42.6 g of hexyltrimethylammonium chloride were added to 39 g of cyclohexane and stirred until homogeneous. Then, at 60°C, the aqueous solution of iron salts was added dropwise to the above solution at a rate of approximately 0.5 ml / min, and stirred to form a transparent reverse microemulsion of iron salts.

[0123] Add 60 g of sodium hydroxide to 100 g of water and stir until homogeneous to form an alkaline aqueous solution. Add 7.43 g of sodium di(tridecyl)succinate sulfonate and 42.6 g of hexyltrimethylammonium chloride to 39 g of cyclohexane and stir until homogeneous. Then, add the alkaline aqueous solution dropwise to the above solution at a rate of about 0.5 ml / min and stir to form a transparent alkaline reverse microemulsion.

[0124] At 60°C, all the above-mentioned iron salt reverse microemulsions were transferred to a 500ml four-necked flask. Under magnetic stirring at 300rpm, all the above-mentioned basic reverse microemulsions were slowly added dropwise. The temperature of the reaction solution was controlled to not exceed 60°C by adjusting the dropping rate. After the addition was complete, the mixture was kept at 60°C with stirring for 1 hour to obtain an iron oxide magnetic particle reverse microemulsion.

[0125] Hydrochloric acid was added dropwise to the reverse microemulsion system at 60℃ to adjust the pH of the aqueous phase to 4.5. Then, 20 g of aminosilane coupling agent KH540 was added dropwise at a rate of approximately 0.5 ml / min. After the addition was completed, the reaction was stopped after 3 hours of incubation. Next, an alkaline reverse microemulsion (prepared according to the above method) was added dropwise to adjust the pH of the reverse microemulsion to approximately 8.5. The temperature of the entire system was increased to 100℃, and the mixture was refluxed to remove water from the reaction solution. The nanoparticles and sodium chloride particles in the reaction system precipitated out of the system. After complete precipitation, the solution was discarded. 100 ml of cyclohexane was added, stirred for 4 minutes, and allowed to stand to precipitate. The clear cyclohexane supernatant was then discarded. The washing process was repeated three times to obtain 120 g of crude product, of which approximately 60 g were coupling agent-modified iron oxide magnetic nanoparticles, and the remaining 80 g were NaCl particles. A small sample was observed under a scanning electron microscope, revealing that the magnetic nanoparticles had a diameter of approximately 44 nm.

[0126] Comparative Example 1

[0127] At 60°C, 9.6 g of ferric chloride hexahydrate and 3.5 g of ferrous chloride tetrahydrate were dissolved in 166.9 g of deionized water and stirred until homogeneous to obtain an aqueous solution of ferric salt. 38.1 g of octadecyltrimethylammonium chloride and 11,4-hexanol were added to 39 g of cyclohexane and stirred until homogeneous. Then, at 60°C, the aqueous solution of ferric salt was added dropwise to the above solution at a rate of approximately 0.5 ml / min, and stirred to form a transparent reverse microemulsion of ferric salt.

[0128] Add 6 g of sodium hydroxide to 152 g of water and stir until homogeneous to form an alkaline aqueous solution. Add 38.1 g of octadecyltrimethylammonium chloride and 11.4 g of 1-hexanol to 39 g of cyclohexane and stir until homogeneous. Then, add the alkaline aqueous solution dropwise to the above solution at a rate of about 0.5 ml / min and stir to form a transparent alkaline reverse microemulsion.

[0129] At 60°C, all the above-mentioned iron salt reverse microemulsions were transferred to a 500ml four-necked flask. Under magnetic stirring at 300rpm, all the above-mentioned basic reverse microemulsions were slowly added dropwise. The temperature of the reaction solution was controlled to not exceed 60°C by adjusting the dropping rate. After the addition was complete, the mixture was kept at 60°C with stirring for 1 hour to obtain an iron oxide magnetic particle reverse microemulsion.

[0130] Hydrochloric acid was added dropwise to a reverse microemulsion of iron oxide magnetic particles at 60°C to adjust the pH of the aqueous phase to 4.5. Then, 20 g of aminosilane coupling agent KH540 was added dropwise at a rate of approximately 0.5 ml / min. After the addition was completed, the mixture was kept at 60°C for 3 hours to stop the reaction. Next, an alkaline reverse microemulsion (prepared according to the above method) was added dropwise to adjust the pH of the reverse microemulsion to approximately 8.5. The temperature of the entire system was increased to 90°C, and the mixture was refluxed to remove water from the reaction solution. The nanoparticles and sodium chloride particles in the reaction system precipitated out of the system. After complete precipitation, the solution was discarded. 100 ml of cyclohexane was added, stirred for 4 minutes, and allowed to stand to precipitate. The clear cyclohexane supernatant was then discarded. The washing process was repeated three times to obtain 12 g of crude product, of which approximately 6 g were iron oxide magnetic nanoparticles modified with the coupling agent, and the remaining 8 g were NaCl particles. A small sample was observed using a scanning electron microscope, revealing that the magnetic nanoparticles had a diameter of approximately 9 nm.

[0131] Comparative Example 2

[0132] At 60°C, 96.2 g of ferric chloride hexahydrate and 35.2 g of ferrous chloride tetrahydrate were dissolved in 48.78 g of deionized water and stirred until homogeneous to obtain an aqueous solution of the iron salt. 38.1 g of octadecyltrimethylammonium chloride and 11,4-hexanol were added to 39 g of cyclohexane and stirred until homogeneous to obtain a cyclohexane solution containing a compound surfactant. Then, at 60°C, the aqueous solution of the iron salt was added dropwise to the cyclohexane solution containing the compound surfactant at a rate of approximately 0.5 ml / min, and stirred to form a transparent reverse microemulsion A.

[0133] Add 60 g of sodium hydroxide to 100 g of water and stir until homogeneous to form an alkaline aqueous solution. Add 38.1 g of octadecyltrimethylammonium chloride and 11.4 g of 1-hexanol to 39 g of cyclohexane and stir until homogeneous to form a cyclohexane solution containing the surfactant. Then, add the alkaline aqueous solution dropwise to the cyclohexane solution containing the surfactant at a rate of approximately 0.5 ml / min and stir to form a transparent reverse microemulsion B.

[0134] At 60°C, all the above-mentioned iron salt reverse microemulsions were transferred to a 500ml four-necked flask. Under magnetic stirring at 300rpm, all the above-mentioned basic reverse microemulsions were slowly added dropwise. The temperature of the reaction solution was controlled to not exceed 60°C by adjusting the dropping rate. After the addition was complete, the mixture was kept at 60°C with stirring for 1 hour to obtain an iron oxide magnetic particle reverse microemulsion.

[0135] Hydrochloric acid was added dropwise to the reverse microemulsion system at 60℃ to adjust the pH of the aqueous phase to 4.5. Then, 20 g of aminosilane coupling agent KH540 was added dropwise at a rate of approximately 0.5 ml / min. After the addition was completed, the reaction was stopped after 3 hours of incubation. Next, an alkaline reverse microemulsion (prepared according to the above method) was added dropwise to adjust the pH of the reverse microemulsion to approximately 8.5. The temperature of the entire system was increased to 90℃, and the mixture was refluxed to remove water from the reaction solution. The nanoparticles and sodium chloride particles in the reaction system precipitated out. After complete precipitation, the mixture was decanted to remove the compound surfactant and organic solvent. 100 ml of cyclohexane was added, stirred for 3–5 minutes, and allowed to stand to precipitate. The clear cyclohexane supernatant was then decanted. The washing process was repeated three times to obtain 120 g of crude product, of which approximately 60 g were iron oxide magnetic nanoparticles and the remaining 80 g were NaCl particles. A small sample was observed under a scanning electron microscope, revealing that the magnetic nanoparticles had a diameter of approximately 60 nm.

[0136] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A reverse microemulsion composition, characterized in that, The composition contains an iron salt reverse microemulsion component and an alkaline reverse microemulsion component; The iron salt reverse microemulsion component contains the following components, which are stored independently or in combination: cationic surfactant A, anionic surfactant A, soluble iron source, organic solvent A, and water. The alkaline reverse microemulsion contains the following components, which may be stored independently or in combination: cationic surfactant B, anionic surfactant B, soluble alkali, organic solvent B, and water.

2. The reverse microemulsion composition according to claim 1, wherein, In the iron salt reverse microemulsion, the total mass of the iron salt reverse microemulsion components is used as a basis: The content of the cationic surfactant A is 0.0001 wt% to 20 wt%, preferably 2 wt% to 16 wt%; and / or The content of the anionic surfactant A is 0.0001 wt% to 20 wt%, preferably 2 wt% to 16 wt%; and / or The value of the content of cationic surfactant A * a1 + the content of anionic surfactant A * a2 is 1.4-15, preferably 1.8-12, more preferably 1.9-8.0, where a1 is the number of carbon atoms in the long-chain alkyl group with the most carbon atoms in cationic surfactant A, and a2 is the number of carbon atoms in the long-chain alkyl group with the most carbon atoms in anionic surfactant A; and / or The content of the soluble iron source is 0.0001 wt% to 60 wt%, preferably 10 wt% to 50 wt%; and / or The content of organic solvent A is 10 wt% to 80 wt%, preferably 12 wt% to 60 wt%; and / or The water content is 10wt% to 50wt%, preferably 10wt% to 40wt%.

3. The reverse microemulsion composition according to claim 1 or 2, wherein, In the basic reverse microemulsion, the total mass of the basic reverse microemulsion components is used as a basis: The content of the cationic surfactant B is 0.0001 wt% to 20 wt%, preferably 2 wt% to 16 wt%; and / or The content of the anionic surfactant B is 0.0001% to 20 wt%, preferably 2 wt% to 16 wt%; and / or The value of the content of cationic surfactant B * b1 + the content of anionic surfactant B * b2 is 1.5-15, preferably 1.8-12, more preferably 1.9-8.0, wherein b1 is the number of carbon atoms in the long-chain alkyl group with the most carbon atoms in the cationic surfactant B, and b2 is the number of carbon atoms in the long-chain alkyl group with the most carbon atoms in the anionic surfactant B; and / or The content of the soluble alkali is 0.0001 wt% to 60 wt%, preferably 10 wt% to 40 wt%; and / or The content of the organic solvent B is 10 wt% to 80 wt%, preferably 15 wt% to 60 wt%; and / or The water content is 10wt% to 60wt%, preferably 10wt% to 50wt%.

4. The reverse microemulsion composition according to any one of claims 1 to 3, wherein, The cationic surfactant A and the cationic surfactant B are each independently selected from at least one of alkyl quaternary ammonium salt cationic surfactants, alkyl pyridinium salt cationic surfactants, and alkylamine salt cationic surfactants, preferably alkyl quaternary ammonium salt cationic surfactants; Preferably, the alkyl quaternary ammonium salt type cationic surfactant is selected from C6-C22 alkyl quaternary ammonium salts and / or dialkyl C6-C22 alkyl quaternary ammonium salts, and more preferably at least one of alkyltrimethylammonium chloride, dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, bis(octadecyl)dimethylammonium chloride, and bis(octadecyl)dimethylammonium bromide.

5. The reverse microemulsion composition according to any one of claims 1 to 4, wherein, The anionic surfactant A and anionic surfactant B are each independently selected from at least one of carboxylate anionic surfactants, sulfonate anionic surfactants, sulfate anionic surfactants, and phosphate anionic surfactants, preferably selected from at least one of carboxylate anionic surfactants, sulfonate anionic surfactants, and sulfate anionic surfactants; Preferably, The carboxylate-type anionic surfactant comprises at least one of alkyl carboxylates, alkyl polyoxyethylene ether carboxylates, and alkylphenol polyoxyethylene ether carboxylates, preferably at least one of C4-C18 alkyl carboxylates, C12-C18 alkyl polyoxyethylene ether carboxylates, and C12-C18 alkylphenol polyoxyethylene ether carboxylates; and / or The sulfonate-type anionic surfactant includes aliphatic diester sulfonates, preferably including C4-C6 alkyl diacid bis(C8-C13) alkyl ester sulfonates; and / or The sulfate-type anionic surfactant includes alkyloxyethylene ether sulfates, preferably C12 to C18 alkyl polyoxyethylene ether sulfates.

6. The reverse microemulsion composition according to any one of claims 1 to 5, wherein, In the composition, the soluble iron source is calculated as iron ions, and the soluble base is calculated as hydroxide and / or ammonium ions; the molar ratio of the soluble iron source to the soluble base is (0.05–5):1, preferably (0.15–1):1; and / or The mass ratio of the iron salt reverse microemulsion component to the alkaline reverse microemulsion component is (0.1–5):1, preferably (0.2–1.2):1; and / or The soluble iron source includes ferric salts and ferrous salts, preferably with a mass ratio of ferric salt to ferrous salt of (1-3):1, more preferably (1.2-2.8):1; and / or The soluble base includes at least one selected from ammonia, dimethylamine, trimethylamine, aniline, lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, and cesium hydroxide; and / or The organic solvent is immiscible with water, and preferably the organic solvent includes at least one of cyclohexane, benzene, toluene, xylene, ethyl acetate, paraffin, kerosene, petroleum ether, and white oil.

7. A method for preparing a reverse microemulsion of iron oxide magnetic particles, characterized in that, The preparation method includes: preparing iron salt reverse microemulsion and alkaline reverse microemulsion using each component of the iron salt reverse microemulsion component and the alkaline reverse microemulsion component as described in any one of claims 1 to 6, and then contacting the iron salt reverse microemulsion and the alkaline reverse microemulsion together. Preferably, the contact conditions include: a temperature of 5°C to 95°C, and / or a time of 5 mins to 24 mins.

8. The iron oxide magnetic particle reverse microemulsion prepared by the preparation method according to claim 7.

9. The application of the iron oxide magnetic particle reverse microemulsion according to claim 8 in crude oil emulsion demulsifier or in the preparation of superparamagnetic nanoparticles.

10. A method for preparing core-shell type iron oxide magnetic particles, characterized in that, The preparation method includes: Under acidic conditions, the shell precursor is contacted with the iron oxide magnetic particle reverse microemulsion of claim 8, and then precipitation is carried out under alkaline conditions. Preferably, The shell precursor includes a coupling agent, preferably selected from silane coupling agents; and / or The coupling agent is present in an amount of 2-5 wt% of the iron oxide magnetic particle reverse microemulsion; and / or The contact conditions are: a temperature of 40-70°C and / or a time of 1-5 hours; The alkaline conditions are controlled by the alkaline reverse microemulsion as described in claim 7.

11. A core-shell type iron oxide magnetic particle prepared by the preparation method of claim 10; Preferably, the core-shell type iron oxide magnetic particles have a particle size of 2-30 nm.