Ionic liquid-based magnetic fluid and preparation method thereof

Abstract

The application discloses an ionic liquid-based magnetic liquid and a preparation method thereof. The ionic liquid-based magnetic liquid comprises a magnetic mesoporous material, a functionalized ionic liquid and a base carrier liquid. The cation of the functionalized ionic liquid is R1R2R3R4N + , wherein R1 is C8-C 20 alkylcarboxylic acid group, R2 is C1-C8 alkyl, R3 is C1-C8 alkyl, and R4 is C1-C8 alkyl. The anion of the functionalized ionic liquid is any one of F ‑ , Cl ‑ , Br ‑ , and I ‑ . The application further provides the preparation method of the ionic liquid-based magnetic liquid. The ionic liquid-based magnetic liquid has good stability, is not easy to volatilize, is not flammable, can be applied to a wide temperature range, and the preparation method is simple and has low requirements on equipment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of materials, and particularly relates to an ionic liquid-based magnetic liquid and a preparation method thereof. BACKGROUND

[0002] Magnetic liquid is a new type of smart material, which is widely used in aerospace, electronic technology, mechanization, energy metallurgy, instruments, biomedicine and many other high-tech fields. Generally, magnetic liquid is a colloidal liquid composed of nanoscale magnetic particles highly dispersed in a base carrier liquid (usually an organic solvent or water). The interaction between the base carrier liquid and the nanoscale magnetic particles makes the magnetic liquid have both the fluidity of a liquid and the magnetism of a solid. Generally, in order to prevent the magnetic particles from agglomerating together under the action of gravity, inter-particle magnetic force or Van der Waals force, each nanoscale particle surface needs to be coated with some long-chain molecules of a surfactant or modified with charged ions to provide sufficient repulsive force.

[0003] In the existing magnetic liquid preparation technology, the preparation methods and applications of ester-based, kerosene-based, gasoline-based and water-based magnetic liquids are relatively mature. However, these magnetic liquids have problems such as narrow temperature range for use, large volatile amount at high temperature, flammability and decomposition, which seriously limit their application range. SUMMARY

[0004] The present application aims to at least solve one of the technical problems in the related art. To this end, the present application provides an ionic liquid-based magnetic liquid, which comprises a magnetic mesoporous material, a functionalized ionic liquid and a base carrier liquid; the cation of the functionalized ionic liquid is R1R2R3R4N + , wherein R1 is C8-C 20 alkyl carboxylic acid group, R2 is C1-C8 alkyl, R3 is C1-C8 alkyl, and R4 is C1-C8 alkyl; and the anion of the functionalized ionic liquid is any one of F - , Cl - , Br - , I - .

[0005] The ionic liquid-based magnetic liquid of the present application has the functionalized ionic liquid as a surfactant, which improves the dispersibility and stability of the magnetic mesoporous material in the base carrier liquid and can be applied in a wide temperature range. Moreover, the ionic liquid-based magnetic liquid of the present application is not easy to volatilize and flammable at high temperature, has good magnetism and stability, and has a wide range of applications.

[0006] In some embodiments, the cation of the functionalized ionic liquid is R1R2R3R4N + , wherein R1 is preferably C8-C 15alkylcarboxylic acid group, R2 is preferably C1-C3 alkyl, R3 is preferably C1-C3 alkyl, and R4 is preferably C1-C3 alkyl; the anion of the functionalized ionic liquid is preferably Cl - or Br - .

[0007] In some embodiments, the base ionic liquid is a quaternary ammonium ionic liquid, the cation of the quaternary ammonium ionic liquid is R1'R2'R3'R4'N + , wherein R1' is C1-C 20 alkyl, preferably C8-C 15 alkyl; R2' is C1-C8 alkyl, preferably C1-C3 alkyl; R3' is C1-C8 alkyl, preferably C1-C3 alkyl; R4' is C1-C8 alkyl, preferably C1-C3 alkyl; and the anion of the quaternary ammonium ionic liquid is any one of Cl - (chloride ion), Br - (bromide ion), [HSO4] - (hydrogen sulfate ion), [BF4] - (tetrafluoroborate ion), [PF6] - (hexafluorophosphate ion), [Tf2N] - (bistrifluoromethanesulfonylimide ion), [HSO4] - (hydrogen sulfate ion), or Br - (bromide ion). -

[0008] In some embodiments, the magnetic mesoporous material is a mesoporous core-shell magnetic nanoparticle, the mesoporous core-shell magnetic nanoparticle comprises an inner core and a shell, the material forming the inner core is a magnetic nanoparticle, the shell is coated on at least part of the outer surface of the inner core, and the shell has a mesoporous structure.

[0009] In some embodiments, the material of the inner core is any one of Fe3O4, γ-Fe2O3 or CoFe2O4; and the material of the shell is SiO2.

[0010] Another aspect of the embodiments of the present application further provides a preparation method of the above-mentioned ionic liquid-based magnetic liquid, comprising the following steps:

[0011] S1, mixing a tertiary amine with a haloalkyl acid and then heating and stirring to obtain a functionalized ionic liquid;

[0012] The general structure of the tertiary amine is R1''R2''R3''N, wherein R1'' is C1-C8 alkyl, R2'' is C1-C8 alkyl, and R3'' is C1-C8 alkyl; and the general structure of the haloalkyl acid is X​m R1'''COOR2''', wherein X is any one of -F, -Cl, -Br, -I, m = 1-3, R1''' is C1-C 18 alkylene; R2''' is -H or C1-C2 alkyl;

[0013] S2, dispersing the functionalized ionic liquid in ethanol, adding the magnetic mesoporous material, mixing and stirring, modifying the magnetic mesoporous material, and obtaining the modified magnetic mesoporous material;

[0014] S3, dispersing the modified magnetic mesoporous material in a base carrier liquid, and obtaining the ionic liquid-based magnetic liquid.

[0015] The preparation method of the ionic liquid-based magnetic liquid provided by the embodiment of the application uses a halogenated alkyl acid and a tertiary amine as raw materials to prepare an ionic liquid with a surface activity function, and uses the ionic liquid to modify a magnetic mesoporous material; then the modified magnetic mesoporous material is dispersed in a base carrier liquid to obtain an ionic liquid-based magnetic liquid. The preparation method is simple, easy to operate, has low requirements on equipment, and is low in cost.

[0016] In some embodiments, in step S1, the tertiary amine has a general structure of R1''R2''R3''N, wherein R1'' is C1-C8 alkyl, R2'' is C1-C8 alkyl, and R3'' is C1-C8 alkyl; and the halogenated alkyl acid has a general structure of X m R1'''COOR2''', wherein X is any one of -Cl, -Br, -I, m = 1-3, R1''' is C1-C 18 alkylene; and R2''' is -H or C1-C2 alkyl.

[0017] In some embodiments, in step S1, the temperature of the heating and stirring is 80-150 DEG C, and the time is 5-12 h.

[0018] In some embodiments, in step S2, the mass ratio of the magnetic mesoporous material to the functionalized ionic liquid is 1:0.5-1:3, and the modification time is 10-20 h.

[0019] In some embodiments, in step S3, the quaternary amine ionic liquid is prepared by mixing and heating a tertiary amine and a halogenated alkane, and then exchanging anions by an ion exchange method; wherein the tertiary amine has a general structure of R1''R2''R3''N, wherein R1'' is C1-C8 alkyl, R2'' is C1-C8 alkyl, and R3'' is C1-C8 alkyl; and the halogenated alkane has a general structure of RX, wherein X is -Cl or -Br, and R is C1-C 20 alkyl.

[0020] In some embodiments, in step S2, the preparation method of the magnetic mesoporous material comprises the following steps: 1) preparing magnetic nanoparticles, then adding a pore-forming agent into a mixed solution of ethanol and water, and then adding ammonia water, and then adding an ethanol solvent containing a silicon source dropwise to perform a sol-gel reaction to obtain magnetic nanoparticles coated with silicon dioxide; and 2) removing the pore-forming agent in the magnetic nanoparticles coated with silicon dioxide obtained in step 1) to obtain the magnetic mesoporous material.

[0021] In some embodiments, the pore-forming agent is hexadecyl trimethyl ammonium bromide, which can be removed by direct calcination or by heating and refluxing in an ethanol solution of ammonium nitrate, and the removal method is simple and easy to operate.

[0022] The present application has the advantages and beneficial effects that:

[0023] (1) The ionic liquid-based magnetic liquid of the embodiments of the present application is modified by using a functionalized ionic liquid as a surfactant for the magnetic mesoporous material, and a quaternary amine ionic liquid similar in structure to the functionalized ionic liquid is used as a base carrier liquid, which can improve the dispersibility of the magnetic mesoporous material in the base carrier liquid, so that the magnetic mesoporous material is uniformly distributed and does not agglomerate. The ionic liquid-based magnetic liquid of the embodiments of the present application has good stability and can be applied in a wide temperature range. Meanwhile, the ionic liquid-based magnetic liquid also inherits the characteristics of the ionic liquid itself, such as non-volatility and non-flammability.

[0024] (2) The ionic liquid-based magnetic liquid of the embodiments of the present application uses mesoporous silica-coated magnetic nanoparticles as the magnetic mesoporous material. The mesoporous silica can increase the specific surface area of the magnetic nanoparticles and increase the active sites, so that more surfactants can be adsorbed, thereby increasing the contact area between the magnetic mesoporous material and the base carrier liquid and effectively improving the stability of the magnetic mesoporous material.

[0025] (3) The preparation method of the ionic liquid-based magnetic liquid proposed in the embodiments of the present application is simple, easy to operate and efficient. The ionic liquid-based magnetic liquid prepared by the method has good magnetic and stability performance. Meanwhile, the method has low requirements for equipment and low production cost, and is easy to realize application in various fields. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The XRD pattern of the Fe3O4@mSiO2 magnetic mesoporous material prepared in Embodiment 1 of the present application.

[0027] Figure 2 The TEM pattern of the Fe3O4@mSiO2 magnetic mesoporous material prepared in Embodiment 1 of the present application under different magnifications. DETAILED DESCRIPTION

[0028] Embodiments of the present application are described in detail below, which are exemplary and intended to explain the present application, and cannot be understood as a limitation of the present application.

[0029] The ion liquid-based magnetic liquid according to an embodiment of the present application comprises a magnetic mesoporous material, a functionalized ion liquid and a base liquid. + , R1 is a C8-C 20 alkyl carboxylic acid group, R2 is a C1-C8 alkyl group, R3 is a C1-C8 alkyl group, and R4 is a C1-C8 alkyl group. - , Cl - , Br - , or I - .

[0030] The ion liquid-based magnetic liquid according to an embodiment of the present application uses a functionalized ion liquid as a surfactant, which can improve the dispersibility and stability of the magnetic mesoporous material in the base liquid, and the ion liquid-based magnetic liquid according to the embodiment of the present application can be applied in a wide temperature range, and is not volatile, non-flammable, and has good magnetic properties and stability.

[0031] In some embodiments, the cation of the functionalized ion liquid is R1R2R3R4N + , wherein R1 is preferably a C8-C 15 alkyl carboxylic acid group, R2 is preferably a C1-C3 alkyl group, R3 is preferably a C1-C3 alkyl group, and R4 is preferably a C1-C3 alkyl group. - , or Br - .

[0032] In some embodiments, the base liquid is a quaternary amine ion liquid, which has a structure similar to that of the functionalized ion liquid, the cation of the quaternary amine ion liquid is R1'R2'R3'R4'N + , wherein R1' is a C1-C 20 alkyl group, preferably a C8-C 15 alkyl group; R2' is a C1-C8 alkyl group, preferably a C1-C3 alkyl group; R3' is a C1-C8 alkyl group, preferably a C1-C3 alkyl group; and R4' is a C1-C8 alkyl group, preferably a C1-C3 alkyl group. - (chloride ion), Br - (bromide ion), [HSO4] - (hydrogen sulfate ion), [BF4] - (tetrafluoroborate ion), [PF6] - (hexafluorophosphate ion), [Tf2N] -Any one of [Tf2N] (bistrifluoromethanesulfonylimide ion), preferably [Tf2N] - [HSO4] (hydrogen sulfate ion) or Br - (bromide ion). - (bromide ion).

[0033] In some embodiments, the magnetic mesoporous material is a mesoporous core-shell magnetic nanoparticle, comprising an inner core and an outer shell, the material forming the inner core is a magnetic nanoparticle, the outer shell is coated on at least part of the outer surface of the inner core, and the outer shell has a mesoporous structure.

[0034] In some embodiments, the material of the inner core is any one of Fe3O4, γ-Fe2O3 or CoFe2O4, and the material of the outer shell is SiO2. SiO2 is widely available, low in price, and easy to operate in experiments. Finally, a magnetic mesoporous composite material with a core-shell structure is formed, which has a magnetic nanoparticle as a core and a mesoporous silica shell. The magnetic mesoporous composite material has a large specific surface area and can adsorb more surfactants. The magnetic liquid prepared by using the core-shell structure magnetic mesoporous material has a high saturation magnetization and good use performance, so as to meet the use requirements of some special conditions and equipment.

[0035] Another aspect of the embodiment of the present application also provides a preparation method of the above-mentioned ionic liquid-based magnetic liquid, comprising the following steps:

[0036] S1, preparing a functionalized ionic liquid: mixing a tertiary amine with a haloalkyl acid and then heating and stirring to obtain the functionalized ionic liquid;

[0037] The general structure of the tertiary amine is R1″R2″R3″N, wherein R1″ is C1-C8 alkyl, R2″ is C1-C8 alkyl, and R3″ is C1-C8 alkyl; the general structure of the haloalkyl acid is X m R1″′COOR2″, wherein X is any one of -F, -Cl, -Br and -I, m = 1-3, R1″′ is C1-C 18 alkylene; and R2″′ is -H or C1-C2 alkyl.

[0038] S2, modifying the magnetic mesoporous material with the functionalized ionic liquid: dispersing the functionalized ionic liquid in ethanol, then adding the magnetic mesoporous material and mixing and stirring to modify the magnetic mesoporous material, so as to obtain the modified magnetic mesoporous material;

[0039] S3, preparing the ionic liquid-based magnetic liquid: dispersing the modified magnetic mesoporous material in a base carrier liquid to obtain the ionic liquid-based magnetic liquid.

[0040] The preparation method of the ion liquid-based magnetic liquid provided by the embodiment of the application uses halogenated alkyl acid and tertiary amine as raw materials to prepare ion liquid with surface activity function, and uses the ion liquid to modify the surface of the magnetic mesoporous material; then the modified magnetic mesoporous material is dispersed in a base carrier liquid to obtain the ion liquid-based magnetic liquid, and the preparation method has a simple process flow and low requirement on equipment.

[0041] In some embodiments, in step S1, the general structure of the tertiary amine is R1″R2″R3″N, wherein R1″ is C1-C8 alkyl, R2″ is C1-C8 alkyl, and R3″ is C1-C8 alkyl; the general structure of the halogenated alkyl acid is X m R1″′COOR2″′, wherein X is any one of -F, -Cl, -Br, and -I, m = 1-3, R1″′ is C1-C 18 alkylene; and R2″′ is -H or C1-C2 alkyl.

[0042] In some embodiments, in step S1, the temperature of the heating and stirring is 80-150 ℃, for example, 80 ℃, 90 ℃, 95 ℃, 120 ℃, 136 ℃, 140 ℃, 150 ℃, etc.; and the time is 5-12 h, for example, 5 h, 6 h, 6.5 h, 7 h, 9 h, 10 h, 10.6 h, 11 h, 12 h, etc.

[0043] In some embodiments, in step S2, the mass ratio of the magnetic mesoporous material to the functionalized ion liquid is 1:0.5-1:3, for example, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.7, 1:3, etc.; and the modification time is 10-20 h, for example, 10 h, 11 h, 12 h, 14 h, 15 h, 16.5 h, 18 h, 20 h, etc.

[0044] In some embodiments, in step S3, the quaternary amine-based ion liquid is prepared by mixing and heating a tertiary amine and a halogenated alkane, and then exchanging anions by an ion exchange method; wherein the general structure of the tertiary amine is R1″R2″R3″N, wherein R1″ is C1-C8 alkyl, R2″ is C1-C8 alkyl, and R3″ is C1-C8 alkyl; and the general structure of the halogenated alkane is RX, wherein X is -Cl or -Br, and R is C1-C 20 alkyl.

[0045] In some embodiments, in step S2, the preparation method of the magnetic mesoporous material comprises the following steps: 1) preparing magnetic nanoparticles, then adding a pore-forming agent to a mixed solution of ethanol and water, mixing with ammonia water, and then adding an ethanol solvent containing a silicon source dropwise to perform a sol-gel reaction to obtain magnetic nanoparticles coated with silicon dioxide; and 2) removing the pore-forming agent in the magnetic nanoparticles coated with silicon dioxide obtained in step 1) to obtain the magnetic mesoporous material.

[0046] In some embodiments, the pore-forming agent is cetyltrimethylammonium bromide, which is removed simply by heating to reflux in an ethanol solution of ammonium nitrate or by direct calcination, and there is no residue after the removal process is complete.

[0047] It is understood that the term "alkyl" or "alkyl group" as used herein includes saturated straight chain or branched chain groups, for example, examples of the term "C1-C8 alkyl" include, but are not limited to, methyl (-CH3), ethyl (-CH2CH3), n-propyl (-CH2CH2CH3), isopropyl (-CH(CH3)2), n-butyl (-CH2CH2CH2CH3), isobutyl (-CH2CH(CH3)2), sec-butyl (-CH(CH3)CH2CH3), t-butyl (-C(CH3)3), n-pentyl (-CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), and the like.

[0048] The ionic liquid-based magnetic liquid and the preparation method thereof of the present application are described in further detail below through specific examples.

[0049] Example 1

[0050] This example provides an ionic liquid-based magnetic liquid, which comprises a magnetic mesoporous material, a functionalized ionic liquid, and a base carrier liquid, wherein the magnetic mesoporous material is Fe3O4@mSiO2; the cation of the functionalized ionic liquid is R1R2R3R4N + , wherein R1 is a C8 alkyl carboxylic acid group, R2 is a C2 alkyl group, R3 is a C2 alkyl group, and R4 is a C2 alkyl group; the anion of the functionalized ionic liquid is Br - .

[0051] The preparation method of the ionic liquid-based magnetic liquid comprises the following steps:

[0052] S1, preparation of magnetic nanoparticles: 11 g of FeCl3·6H2O and 9.7 g of FeCl2·4H2O were weighed and dissolved in 513 mL of deionized water, stirred at 45°C for 10 min, and a mixed salt solution was obtained; 17 g of concentrated ammonia was then added dropwise into the mixed salt solution while maintaining heating and stirring for 40 min, and it was observed that the mixed solution rapidly changed from yellow to black; after magnetic separation, the black Fe3O4 magnetic nanoparticles were repeatedly washed with deionized water;

[0053] S2, preparation of magnetic mesoporous material: in a 500 mL three-necked flask, 1 g of Fe3O4 magnetic nanoparticles, 70 mL of water, 280 mL of ethanol, 1 g of cetyltrimethylammonium bromide (CTAB) were added, and ultrasonic stirring was carried out for 30 min, then 10 mL of ammonia water was added, and 4.5 mL of tetraethyl orthosilicate (TEOS) was dissolved in 20 mL of ethanol and slowly added to the mixture, and after stirring for 4 h, magnetic separation was carried out, and after vacuum drying, Fe3O4@SiO2 magnetic nanoparticles were obtained; the Fe3O4@SiO2 magnetic nanoparticles were dispersed in 200 mL of an ethanol solution of ammonium nitrate with a concentration of 10 mg / L, and refluxed at 80°C for 1 h, repeated twice, and the pore-forming agent CTAB was removed to obtain a magnetic mesoporous material of Fe3O4 coated with mesoporous silica, i.e., Fe3O4@mSiO2 magnetic mesoporous material.

[0054] S3, preparation of functionalized ionic liquid: 20 mL of triethylamine and 27 mL of 9-bromononanoic acid were placed in a 100 mL round-bottom flask, and heated and stirred at 120°C for 8 h under the protection of a nitrogen atmosphere, and after cooling, a carboxylic acid functionalized ionic liquid was obtained;

[0055] S4, modification of magnetic mesoporous material with functionalized ionic liquid: the obtained carboxylic acid functionalized ionic liquid was dispersed in ethanol, and freshly prepared Fe3O4@mSiO2 magnetic mesoporous material (the mass ratio of carboxylic acid functionalized ionic liquid to Fe3O4@mSiO2 magnetic mesoporous material was 1:1) was added, and the mixture was stirred at room temperature for 12 h under the protection of a nitrogen atmosphere to modify the Fe3O4@mSiO2 magnetic mesoporous material; then, excess carboxylic acid functionalized ionic liquid was removed with ethyl acetate, and after vacuum drying, the modified Fe3O4@mSiO2 magnetic mesoporous material was obtained;

[0056] S5, preparation of base carrier liquid: 20 mL of triethylamine and 27.5 mL of 1-bromononane were placed in a 100 mL round-bottom flask, and heated and stirred at 120°C for 8 h under the protection of a nitrogen atmosphere, and after cooling, 20 mL of distilled water was added; then, 0.05 g (0.01 mol) of LiNTf2 was dissolved in 10 mL of distilled water; then, the two solutions were mixed and stirred at room temperature for 3 h, and finally, the oily ionic liquid phase and the aqueous phase were separated with a separatory funnel, and the obtained oily ionic liquid phase was washed twice with distilled water, and vacuum dried at 80°C for 48 h to obtain a quaternary amine ionic liquid.

[0057] S6, preparation of ionic liquid-based magnetic liquid: the modified Fe3O4@mSiO2 magnetic mesoporous material was ground in a mortar and placed in a beaker, and then the quaternary amine ionic liquid was added, and ultrasonic stirring was carried out for 3 h to form a stable Fe3O4@mSiO2 ionic liquid-based magnetic liquid.

[0058] The Fe3O4@mSiO2 magnetic mesoporous material in this embodiment was subjected to XRD testing, and its XRD pattern is shown below. Figure 1 As shown, by Figure 1 It can be seen that the Fe3O4@mSiO2 magnetic mesoporous material was effectively synthesized. The microstructure of the Fe3O4@mSiO2 magnetic mesoporous material was analyzed using transmission electron microscopy (TEM), and the TEM images at different magnifications are shown below. Figure 2 As shown, it can be observed that the magnetic mesoporous material has a relatively uniform particle size and is relatively dispersed. It is also uniformly distributed in the carrier liquid, without agglomeration or sedimentation. In addition, the Fe3O4@mSiO2 ionic liquid-based magnetic liquid prepared in this embodiment can remain stable at 25-200℃, has extremely low volatility, and a saturation magnetization of 154 Gs, demonstrating excellent performance.

[0059] Example 2

[0060] This embodiment provides an ionic liquid-based magnetic liquid, comprising a magnetic mesoporous material, a functionalized ionic liquid, and a carrier liquid. The magnetic mesoporous material is γ-Fe₂O₃@mSiO₂; the functionalized ionic liquid has cations R₁R₂R₃R₄N. + Wherein, R1 is a C8 alkyl carboxylic acid group, R2 is a C2 alkyl group, R3 is a C2 alkyl group, and R4 is a C2 alkyl group; the anion of the functionalized ionic liquid is Br. - .

[0061] The preparation method of this ionic liquid-based magnetic liquid includes the following steps:

[0062] S1, Preparation of magnetic nanoparticles: Weigh 11g of FeCl3·6H2O and 9.7g of FeCl2·4H2O, dissolve them in 513mL of deionized water, and stir for 10min in a water bath at 45℃ to obtain a mixed salt solution; then weigh 17g of concentrated ammonia water and add it dropwise to the mixed salt solution, keep heating and stirring for 40min, and observe that the mixed solution quickly changes from yellow to black; after magnetic separation, wash repeatedly with deionized water to obtain black Fe3O4 magnetic nanoparticles;

[0063] S2, Preparation of magnetic mesoporous material: In a 500 mL three-necked flask, 1 g of Fe3O4 magnetic nanoparticles, 70 mL of water, 280 mL of ethanol, 1 g of cetyltrimethylammonium bromide (CTAB) were added, and ultrasonic stirring was performed for 30 min, then 10 mL of ammonia water was added, and 4.5 mL of tetraethyl orthosilicate (TEOS) was dissolved in 20 mL of ethanol and slowly added to the mixture, and after stirring for 4 h, magnetic separation was performed, and after vacuum drying, Fe3O4@SiO2 magnetic nanoparticles were obtained; then the Fe3O4@SiO2 magnetic nanoparticles were placed in a muffle furnace and calcined at 350°C for 3 h in air, and the pore-forming agent CTAB was removed, and Fe3O4 was oxidized in air to obtain γ-Fe2O3, and finally a magnetic mesoporous material of mesoporous silica coated γ-Fe2O3, namely γ-Fe2O3@mSiO2 magnetic mesoporous material, was obtained.

[0064] S3, Preparation of functionalized ionic liquid: 20 mL of triethylamine and 27 mL of 9-bromononanoic acid were placed in a 100 mL round-bottom flask, and heated and stirred at 120°C for 8 h under nitrogen atmosphere protection, and after cooling, a carboxylic acid functionalized ionic liquid was obtained;

[0065] S4, Modification of magnetic mesoporous material with functionalized ionic liquid: The obtained carboxylic acid functionalized ionic liquid was dispersed in ethanol, and freshly prepared γ-Fe2O3@mSiO2 magnetic mesoporous material (the mass ratio of carboxylic acid functionalized ionic liquid to γ-Fe2O3@mSiO2 magnetic mesoporous material was 1:1) was added, and the mixture was stirred at room temperature for 12 h under nitrogen atmosphere protection to modify the γ-Fe2O3@mSiO2 magnetic mesoporous material; then excess carboxylic acid functionalized ionic liquid was removed with ethyl acetate, and after vacuum drying, the modified γ-Fe2O3@mSiO2 magnetic mesoporous material was obtained;

[0066] S5, Preparation of base liquid: 20 mL of triethylamine and 27.5 mL of 1-bromononane were placed in a 100 mL round-bottom flask, and heated and stirred at 120°C for 8 h under nitrogen atmosphere protection, and after cooling, 20 mL of distilled water was added; then 0.05 g (0.01 mol) of LiNTf2 was dissolved in 10 mL of distilled water; then the two solutions were mixed and stirred at room temperature for 3 h, and finally the oily ionic liquid phase and the aqueous phase were separated with a separatory funnel, and the obtained oily ionic liquid phase was washed twice with distilled water and vacuum dried at 80°C for 48 h to obtain a quaternary ammonium ionic liquid.

[0067] S6, Preparation of ionic liquid-based magnetic liquid: The modified γ-Fe2O3@mSiO2 magnetic mesoporous material was ground in a mortar and placed in a beaker, then the quaternary ammonium ionic liquid was added, and ultrasonic stirring was performed for 3 h to form a stable γ-Fe2O3@mSiO2 ionic liquid-based magnetic liquid.

[0068] The γ-Fe2O3@mSiO2 ionic liquid-based magnetic liquid obtained in the embodiment can be stable at 25-200℃, has extremely low volatility, has a saturation magnetization of 103 Gs, has a high saturation magnetization, the γ-Fe2O3@mSiO2 magnetic mesoporous material has uniform particle distribution and does not agglomerate or settle, and the magnetic liquid has excellent performance.

[0069] Example 3

[0070] The embodiment provides an ionic liquid-based magnetic liquid, which comprises a magnetic mesoporous material, a functionalized ionic liquid and a base carrier liquid, wherein the magnetic mesoporous material is CoFe2O4@mSiO2; the cation of the functionalized ionic liquid is R1R2R3R4N + , wherein R1 is a C8 alkyl carboxylic acid group, R2 is a C2 alkyl group, R3 is a C2 alkyl group, and R4 is a C2 alkyl group; and the anion of the functionalized ionic liquid is Br - .

[0071] The preparation method of the ionic liquid-based magnetic liquid comprises the following steps:

[0072] S1, preparing magnetic nanoparticles: 9.7 g of CoCl2·6H2O and 9.7 g of FeCl2·4H2O are weighed and dissolved in 513 mL of deionized water, stirred at 45℃ under water bath for 10 min to obtain a mixed salt solution; 17 g of concentrated ammonia water is then added dropwise into the mixed salt solution, and heating and stirring are maintained for 40 min; after the reaction is completed, the reaction product is subjected to magnetic separation, and is repeatedly washed with deionized water until the conductivity σ of the washing liquid is ≤100 μs / cm, to obtain CoFe2O4 magnetic nanoparticles;

[0073] S2, preparing magnetic mesoporous material: 1 g of CoFe2O4 magnetic nanoparticles, 70 mL of water, 280 mL of ethanol and 1 g of cetyltrimethylammonium bromide (CTAB) are added into a 500 mL three-necked flask, and are ultrasonically stirred for 30 min; then 10 mL of ammonia water is added, 4.5 mL of tetraethyl orthosilicate (TEOS) is dissolved in 20 mL of ethanol, and the solution is slowly added dropwise into the mixed solution; after stirring for 4 h, magnetic separation is performed, and vacuum drying is performed to obtain CoFe2O4@SiO2 magnetic nanoparticles; the CoFe2O4@SiO2 magnetic nanoparticles are dispersed in 200 mL of an ethanol solution of ammonium nitrate with a concentration of 10 mg / L, and are refluxed at 80℃ for 1 h; the process is repeated twice to remove the pore-forming agent CTAB, and a magnetic mesoporous material of CoFe2O4 coated with mesoporous silica, i.e., CoFe2O4@mSiO2 magnetic mesoporous material, is obtained.

[0074] S3, preparation of functionalized ionic liquid: 20 mL of triethylamine and 27 mL of 9-bromononanoic acid were placed in a 100 mL round-bottom flask, heated and stirred at 120°C for 8 h under the protection of nitrogen atmosphere, and a carboxylic acid functionalized ionic liquid was obtained after cooling;

[0075] S4, modification of magnetic mesoporous material with functionalized ionic liquid: the prepared carboxylic acid functionalized ionic liquid was dispersed in ethanol, and then fresh CoFe2O4@mSiO2 magnetic mesoporous material was added (the mass ratio of carboxylic acid functionalized ionic liquid to CoFe2O4@mSiO2 magnetic mesoporous material was 1:1), and the mixture was stirred at room temperature for 12 h under the protection of nitrogen atmosphere to modify the CoFe2O4@mSiO2 magnetic mesoporous material; then, excess carboxylic acid functionalized ionic liquid was removed with ethyl acetate, and the modified CoFe2O4@mSiO2 magnetic mesoporous material was obtained after vacuum drying;

[0076] S5, preparation of base carrier liquid: 20 mL of triethylamine and 27.5 mL of 1-bromononane were placed in a 100 mL round-bottom flask, heated and stirred at 120°C for 8 h under the protection of nitrogen atmosphere, and then 20 mL of distilled water was added after cooling; 0.05 g (0.01 mol) of LiNTf2 was dissolved in 10 mL of distilled water; then the two solutions were mixed and stirred at room temperature for 3 h, and finally the oily ionic liquid phase and the aqueous phase were separated with a separatory funnel, the obtained oily ionic liquid phase was washed with distilled water twice, and vacuum dried at 80°C for 48 h to obtain a quaternary amine ionic liquid.

[0077] S6, preparation of ionic liquid-based magnetic liquid: the modified CoFe2O4@mSiO2 magnetic mesoporous material was ground in a mortar and then placed in a beaker, and then the quaternary amine ionic liquid was added, and the mixture was ultrasonicated for 3 h to form a stable CoFe2O4@mSiO2 ionic liquid-based magnetic liquid.

[0078] The CoFe2O4@mSiO2 ionic liquid-based magnetic liquid obtained in this example can remain stable at 25-200°C, has extremely low volatility, has a saturation magnetization of 132 Gs, and the CoFe2O4@mSiO2 magnetic mesoporous material particles are uniformly distributed and do not agglomerate or settle, and the magnetic liquid has excellent performance.

[0079] In this disclosure, the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" mean that a particular feature, structure, material, or characteristic is included in at least one embodiment or example of the present disclosure. The illustrative appearances of the above-mentioned terms in various places in the specification are not necessarily referred to the same embodiment or example. Moreover, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. Furthermore, the terminology "comprising" is used in the disclosure as comprising but not limited to, that is, it is open-ended and does not exclude the presence of additional features, structures, materials, or characteristics.

[0080] Although the embodiments of the present disclosure have been shown and described above, it is understood that the above-described embodiments are exemplary, and are not to be interpreted as limiting the present disclosure, and the ordinary skilled in the art can make changes, modifications, replacements, and variations to the above-described embodiments within the scope of the present disclosure.

Claims

1. A method of preparing an ionic liquid-based magnetic fluid, characterized by, The method comprises the following steps: S1, heating and stirring a tertiary amine and a haloalkyl acid after mixing to obtain a functionalized ionic liquid; The tertiary amine has a general structure of R1 '' R2 '' R3 '' N, wherein R1 '' is a C1-C8 alkyl group, R2 '' is a C1-C8 alkyl group, and R3 '' is a C1-C8 alkyl group; and the haloalkyl acid has a general structure of X m R1 ''' COOR2 ''' , wherein X is any one of -F, -Cl, -Br, and -I, m = 1-3, R1 ''' is a C1-C 18 alkylene group, and R2 ''' is -H or a C1-C2 alkyl group. S2, dispersing the functionalized ionic liquid in ethanol, adding and stirring a magnetic mesoporous material to modify the magnetic mesoporous material, and obtaining a modified magnetic mesoporous material. S3, dispersing the modified magnetic mesoporous material in a base carrier liquid to obtain the ionic liquid-based magnetic liquid; the ionic liquid-based magnetic liquid comprises the magnetic mesoporous material, the functionalized ionic liquid, and the base carrier liquid; the cation of the functionalized ionic liquid is R1R2R3R4N + , wherein R1 is C8-C 20 alkyl, R2 is C1-C8 alkyl, R3 is C1-C8 alkyl, and R4 is C1-C8 alkyl; the anion of the functionalized ionic liquid is any one of F - , Cl - , Br - , and I - .

2. The method for preparing ionic liquid-based magnetic liquid according to claim 1, characterized in that, In step S1, the temperature of the heating and stirring is 80-150 DEG C, and the time is 5-12 h.

3. The method for preparing ionic liquid-based magnetic liquid according to claim 1, characterized in that, In step S2, the mass ratio of the magnetic mesoporous material to the functionalized ionic liquid is 1:0.5-1:3, and the modification time is 10-20 h.

4. The method for preparing ionic liquid-based magnetic liquid according to claim 1, characterized in that, The preparation method of the magnetic mesoporous material comprises the following steps: 1) preparing magnetic nanoparticles, then adding a pore-forming agent to a mixed solution of ethanol and water, adding ammonia water, then adding an ethanol solvent containing a silicon source dropwise to perform a sol-gel reaction to obtain silica-coated magnetic nanoparticles; and 2) removing the pore-forming agent in the silica-coated magnetic nanoparticles obtained in step 1) to obtain the magnetic mesoporous material.

5. The method for preparing ionic liquid-based magnetic liquid according to claim 1, characterized in that, said R1is C8-C 15 alkylcarboxylic acid group, said R2is C1-C3alkyl, said R3is C1-C3alkyl, said R4is C1-C3alkyl; the anion of said functionalized ionic liquid is Cl - or Br - .

6. The method for preparing ionic liquid-based magnetic liquid according to claim 1, characterized in that, The base carrier liquid is a quaternary amine ionic liquid, the cation of the quaternary amine ionic liquid is R1 ' R2 ' R3 ' R4 ' N + , wherein R1 ' is C1-C 20 alkyl, R2 ' is C1-C8 alkyl, R3 ' is C1-C8 alkyl, R4 ' is C1-C8 alkyl; the anion of the quaternary amine ionic liquid is any one of Cl - , Br - , [HSO4] - , [BF4] - , [PF6] - , [Tf2N] - .

7. The method for preparing ionic liquid-based magnetic liquid according to claim 6, characterized in that, The cation of the quaternary ammonium ionic liquid is R1 ' R2 ' R3 ' R4 ' N + , wherein R1 ' is C8-C 15 alkyl, R2 ' is C1-C3 alkyl, R3 ' is C1-C3 alkyl, and R4 ' is C1-C3 alkyl; and the anion of the quaternary ammonium ionic liquid is one of [HSO4] - , [Tf2N] - , or Br - .

8. The method of preparing an ionic liquid-based magnetic fluid according to claim 1 or 4, characterized by, The magnetic mesoporous material is a mesoporous core-shell magnetic nanoparticle, which comprises an inner core and an outer shell, the material of the inner core is a magnetic nanoparticle, the outer shell is coated on at least part of the outer surface of the inner core, and the outer shell has a mesoporous structure.

9. The method for preparing an ionic liquid-based magnetic liquid according to claim 8, characterized in that, The material of the inner core is any one of Fe3O4, gamma-Fe2O3 or CoFe2O4; and the material of the outer shell is SiO2.

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