System and method for preparing superparamagnetic ferrite nanoparticles by using supercritical composite solvent

Abstract

The invention relates to the technical field of production of nano composite materials, in particular to a system and a method for preparing superparamagnetic ferrite nano particles by using a supercritical composite solvent. The system comprises a CO2 compression and liquefaction module, an ethanol pretreatment module, a metering pump, a precursor storage tank, a high-pressure pump, a preheater, a mixing reactor, a high-pressure reaction kettle, a temperature and pressure joint control module, an in-situ modification injection system, an online coating reactor, a supercritical decompression separator and a magnetic separation and purification module. The preparation method has the advantages that the requirements of magnetization intensity, hydrophilicity, particle size distribution, coating thickness and biocompatibility for preparing the hydrophilic superparamagnetic ferrite nano-particles are met, the hydrophilicity is simpler to realize, the particle size is more uniform to control, no organic residue exists, and the biological safety is higher.

Description

Technical Field

[0001] This invention relates to the field of nanocomposite material production technology, specifically to a system and method for preparing superparamagnetic ferrite nanoparticles using supercritical composite solvents. Background Technology

[0002] High-temperature thermal decomposition can be used to prepare superparamagnetic ferrite nanoparticles, which exhibit low defect rates and excellent crystallinity. However, preparing hydrophilic superparamagnetic ferrite nanoparticles requires the decomposition of organometallic precursors such as iron acetylacetonate at 250–380 °C in an inert atmosphere to form highly crystalline Fe3O4 cores, followed by hydrophilicity through ligand exchange with citric acid or polyethylene glycol. The preparation process involves a series of complex steps, including high-temperature reaction, gradient cooling, centrifugal washing, surface modification, and drying, under strict process conditions. When high requirements are placed on the particle size distribution and biocompatibility of the hydrophilic superparamagnetic ferrite nanoparticles, the control of the cooling process and the purity of the modifiers is extremely critical.

[0003] Supercritical media refer to a special state of matter above its critical temperature and critical pressure, possessing characteristics of both gases and liquids, including high diffusivity, low viscosity, and adjustable solubility. -5 m 2 / s) and liquid (10 -9 m 2 The diffusion coefficient of supercritical CO2 (SC-CO2) is between 10 / s and 10 / s. -7 m 2 Supercritical fluids (SC-CO2) can efficiently penetrate porous materials, and their solubility can be adjusted by pressure / temperature. The solubility of non-polar substances in SC-CO2 increases exponentially with increasing pressure. Supercritical fluids are environmentally friendly, non-toxic, and non-flammable, and can be rapidly recovered by depressurization, replacing traditional organic solvents (such as benzene and chloroform) and reducing VOC emissions. Current technologies use supercritical water (SCW) as a medium to prepare hydrophilic superparamagnetic ferrite nanoparticles. However, the high reactivity of supercritical water easily induces hydroxylation on the particle surface, leading to a wider particle size distribution and a large fluctuation range in magnetization. Using supercritical ethanol (SCEtOH) as a medium to prepare hydrophilic superparamagnetic ferrite nanoparticles results in excessively strong reducing properties, causing compositional deviations and affecting Fe... 3+ Excessive reduction to FeO presents a contradiction between surface hydrophobicity and hydrophilicity, requiring additional modification with citric acid or PEG, increasing process complexity. Supercritical water or supercritical ethanol alone cannot simultaneously meet the requirements of low temperature, low reducing power, and hydrophilicity. Particles synthesized using only one medium often require high-temperature annealing to repair crystal defects, which may lead to secondary agglomeration.

[0004] Therefore, providing a method for preparing hydrophilic superparamagnetic ferrite nanoparticles that is simpler to achieve hydrophilicity, has more uniform particle size control, leaves no organic residue, and offers higher biocompatibility is of great significance. To meet the requirements of low reducing power, hydrophilicity, and superparamagnetism in hydrophilic superparamagnetic ferrite nanoparticles, it is necessary to provide a system and method for preparing superparamagnetic ferrite nanoparticles using supercritical composite solvents. By controlling the temperature, pressure, ratio, flow rate, and residence time of the supercritical fluid, the requirements for magnetization, hydrophilicity, particle size distribution, coating thickness, and biocompatibility in the preparation of hydrophilic superparamagnetic ferrite nanoparticles can be met. Summary of the Invention

[0005] To address the problems mentioned in the background art, this invention provides a system and method for preparing superparamagnetic ferrite nanoparticles using a supercritical composite solvent. Ethanol and CO2 are used as a mixed fluid, and the target hydrophilic superparamagnetic ferrite nanoparticles are prepared by controlling the ratio, flow rate, and residence time of the composite solvent within the critical parameter window of the ethanol / CO2 mixed fluid.

[0006] To achieve the above objectives, a first aspect of the present invention provides a system for preparing superparamagnetic ferrite nanoparticles using supercritical composite solvents, comprising: a CO2 compression and liquefaction module, an ethanol pretreatment module, a metering pump, a precursor storage tank, a high-pressure pump, a preheater, a mixing reactor, a high-pressure reactor, a temperature and pressure control module, an in-situ modification injection system, an online coating reactor, a supercritical vacuum separator, and a magnetic separation and purification module. The CO2 compression and liquefaction module and the ethanol pretreatment module are connected to the inlet of the mixing reactor via metering pump pipelines. The precursor storage tank is connected to the high-pressure pump and the preheater sequentially via pipelines to the inlet of the mixing reactor. The outlet pipeline of the mixing reactor is connected to the inlet of the high-pressure reactor. The in-situ modification injection system is connected to the inlet of the high-pressure reactor. The online coating reactor is disposed within the high-pressure reactor and connected to both the inlet and outlet of the high-pressure reactor. The outlet pipeline of the high-pressure reactor is connected to the inlet of the supercritical vacuum separator. The outlet pipeline of the supercritical vacuum separator is connected to the inlet of the magnetic separation and purification module. The temperature and pressure control module is electrically connected to the CO2 compression and liquefaction module, the ethanol pretreatment module, the high-pressure pump, the preheater, and the high-pressure reactor, respectively.

[0007] Preferably, the CO2 compression and liquefaction module is a low-temperature high-pressure pump, and the ethanol pretreatment module is a high-pressure liquid phase pump and a preheater.

[0008] Preferably, the mixing reactor is a static mixer and / or a dynamic eddy current generator.

[0009] Preferably, the high-pressure reactor is a titanium alloy high-pressure reactor that integrates a multi-stage stirring and ultrasonic dispersion module.

[0010] Preferably, the in-situ modification injection system is a high-pressure injection pump.

[0011] Preferably, the online coating reactor is a series-connected microchannel device.

[0012] Preferably, the supercritical pressure reducing separator is a back pressure valve staged pressure reducing device.

[0013] Preferably, the magnetic separation and purification module is a high-gradient magnetic separator combined with a centrifuge.

[0014] Preferably, the supercritical vacuum separator is further provided with a CO2 recovery port, which is connected to a CO2 compressor and then to a CO2 compression and liquefaction module via a CO2 recovery port pipeline. The magnetic separation and purification module is further provided with an ethanol recovery port, which is connected to an ethanol distillation column and then to an ethanol pretreatment module via an ethanol recovery port pipeline.

[0015] A second aspect of the present invention provides a method for preparing superparamagnetic ferrite nanoparticles using a supercritical composite solvent, comprising:

[0016] S1, supercritical fluid generation, compresses CO2 to the supercritical state and pressurizes and heats ethanol to the supercritical state;

[0017] S2, composite supercritical fluid mixing, which mixes supercritical CO2 and supercritical ethanol at a flow ratio of [1:3, 1:5].

[0018] S3, precursor decomposition, injecting homogeneous composite fluid into high-pressure reactor, and regulating reaction conditions of temperature and pressure through temperature and pressure control module;

[0019] S4, in-situ modification injection, the hydrophilic ligand solution is injected into the high-pressure reactor by controlling the flow rate;

[0020] S5, online wrapping, controlling dwell time;

[0021] S6, Supercritical pressure reduction separation, controls the pressure of the supercritical pressure reduction separator to perform pressure reduction separation;

[0022] S7, magnetic separation and purification, performs magnetic separation and purification through the magnetic separation and purification module.

[0023] Beneficial effects: The technical solution of this application has the following technical effects:

[0024] 1. Supercritical CO2 reduces the dielectric constant of supercritical ethanol and enhances the solubility of the precursor. At the same time, the rapid diffusion of supercritical CO2 inhibits particle aggregation and improves the dispersibility by no less than 40% compared with the dispersibility under single supercritical medium conditions and the dispersibility of ligand exchange after high-temperature thermal decomposition.

[0025] 2. The preparation of hydrophilic superparamagnetic ferrite nanoparticles using supercritical composite solvents can achieve in-situ coating, avoiding post-processing steps, and ensuring potential and magnetic stability.

[0026] 3. Compared with traditional organic solvent methods, the composite solvent of supercritical CO2 and supercritical ethanol has low toxicity and is recyclable. Attached Figure Description

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 This is a schematic diagram of the system in Embodiment 1 of the present invention.

[0029] Figure 2 This is a flowchart of the method in Embodiment 2 of the present invention.

[0030] In the diagram: 1. CO2 compression and liquefaction module, 2. Ethanol pretreatment module, 3. Metering pump, 4. Precursor storage tank, 5. High-pressure pump, 6. Preheater, 7. Mixing reactor, 8. High-pressure reactor, 9. Temperature and pressure control module, 10. In-situ modification injection system, 11. Online coating reactor, 12. Supercritical vacuum separator, 13. Magnetic separation and purification module. Detailed Implementation

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] Example 1

[0033] like Figure 1As shown, the system for preparing superparamagnetic ferrite nanoparticles using supercritical composite solvents according to the present invention includes: a CO2 compression and liquefaction module 1, an ethanol pretreatment module 2, a metering pump 3, a precursor storage tank 4, a high-pressure pump 5, a preheater 6, a mixing reactor 7, a high-pressure reactor 8, a temperature and pressure control module 9, an in-situ modification injection system 10, an online coating reactor 11, a supercritical vacuum separator 12, and a magnetic separation and purification module 13. The system is characterized in that the outlets of the CO2 compression and liquefaction module 1 and the ethanol pretreatment module 2 are connected to the inlet of the mixing reactor 7 via the metering pump 3, and the precursor storage tank 4 is sequentially connected to the high-pressure reactor 7 via pipelines. Pump 5 and preheater 6 are connected to the inlet of mixing reactor 7. The outlet pipeline of mixing reactor 7 is connected to the inlet of high-pressure reactor 8. The pipeline of in-situ modification injection system 10 is connected to the inlet of high-pressure reactor 8. Online coating reactor 11 is set inside high-pressure reactor 8 and connected to the inlet and outlet of high-pressure reactor 8. The outlet pipeline of high-pressure reactor 8 is connected to the inlet of supercritical vacuum separator 12. The outlet pipeline of supercritical vacuum separator 12 is connected to the inlet of magnetic separation and purification module 13. The temperature and pressure control module 9 is electrically connected to CO2 compression and liquefaction module 1, ethanol pretreatment module 2, high-pressure pump 5, preheater 6, and high-pressure reactor 8, respectively.

[0034] The system begins operation. The CO2 compression and liquefaction module 1 compresses CO2 to a supercritical state, with a critical point of 31.1℃ and 7.38 MPa. The ethanol pretreatment module 2 pressurizes and preheats the ethanol to a supercritical state, with a critical point of 241℃ and 6.14 MPa. The precursor storage tank 4 injects the precursor solution into the high-pressure pump 5, pressurizing the solution to a supercritical reaction pressure of 20–30 MPa. The solution is then directly pumped into the preheater 6 through the high-pressure pump 5. Once the precursor solution is preheated to 250–300℃, the metering pump 3, controlling a fixed flow rate ratio, injects supercritical CO2 and supercritical ethanol into the mixing reactor 4. Simultaneously, the pressurized and preheated precursor solution is injected into the mixing reactor 4, causing the supercritical CO2 and supercritical ethanol to form a homogeneous composite fluid and a co-solvent system with the precursor solution. The co-solvent system is injected into the high-pressure reactor 8, and the hydrophilic ligand solution injected by the in-situ modification injection system 10 is used in the online coating reactor 11 to achieve monolayer coating by utilizing the high diffusivity of supercritical fluid. The residence time of the hydrophilic ligand solution and the co-solvent system in the online coating reactor 11 is controlled to be less than 30 minutes by controlling the flow rate. The supercritical composite liquid is injected into the supercritical vacuum separator 12. Through staged depressurization, supercritical CO2 is vaporized and separated, and the hydrophilic superparamagnetic ferrite nanoparticles are dispersed in the ethanol phase. The hydrophilic superparamagnetic ferrite nanoparticles dispersed in the ethanol phase are injected into the magnetic separation and purification module 13 for magnetic separation and centrifugation to remove unreacted precursors and large particle agglomerates, thereby obtaining the target hydrophilic superparamagnetic ferrite nanoparticles.

[0035] Example 2

[0036] like Figure 1 As shown, the system for preparing superparamagnetic ferrite nanoparticles using supercritical composite solvents of the present invention includes a supercritical vacuum separator 12 with a CO2 recovery port, which is connected to a CO2 compressor and then to a CO2 compression and liquefaction module 1 via a CO2 recovery port pipeline. The magnetic separation and purification module 13 is also equipped with an ethanol recovery port, which is connected to an ethanol distillation column and then to an ethanol pretreatment module 2 via an ethanol recovery port pipeline.

[0037] The CO2 is recovered and reused by connecting the CO2 recovery port pipeline to the CO2 compressor and then to the CO2 compression and liquefaction module 1. The ethanol is recovered and reused by connecting the ethanol recovery port pipeline to the ethanol distillation column and then to the ethanol pretreatment module 2.

[0038] Example 3

[0039] like Figure 1 As shown, the method for preparing superparamagnetic ferrite nanoparticles using supercritical composite solvents of the present invention includes: S1, supercritical fluid generation, compressing CO2 to a supercritical state, and pressurizing and heating ethanol to a supercritical state;

[0040] S2, Composite supercritical fluid mixing, involves mixing supercritical CO2 and supercritical ethanol at a flow ratio of [1:3, 1:5] to form a homogeneous composite fluid;

[0041] S3, precursor decomposition, involves injecting a homogeneous composite fluid into a high-pressure reactor and controlling the reaction conditions of temperature and pressure through a temperature and pressure control module to carry out precursor decomposition.

[0042] S4, in-situ modification injection, the hydrophilic ligand solution is injected into the high-pressure reactor at a controlled flow rate to complete the carboxylation or hydroxylation of the surface of hydrophilic superparamagnetic ferrite nanoparticles in supercritical fluid.

[0043] S5, online coating, controlling residence time, utilizes the high diffusivity of supercritical composite solvent fluid to achieve monolayer coating in an online coating reactor;

[0044] S6, supercritical depressurization separation, uses a supercritical depressurization separator for depressurization separation. The depressurization pressure is set to 5MPa and atmospheric pressure, respectively, so that supercritical CO2 is vaporized and separated, and hydrophilic superparamagnetic ferrite nanoparticles are dispersed in the ethanol phase.

[0045] S7, Magnetic Separation and Purification: Magnetic separation is performed using the magnetic separation and purification module. The magnetic field strength is set to 0.5–1.5T, and the centrifuge speed is set to 8000–12000 rpm. This magnetic separation and purification removes unreacted precursors and large particle aggregates, yielding the target product.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0047] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the system can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above-described wireless terminal can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0048] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0049] In the embodiments provided by this invention, it should be understood that the illustrated system / terminal device and method can be implemented in other ways. For example, the system / terminal device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling or direct coupling or communication connection may be through some interfaces; the indirect coupling or communication connection of the system or unit may be electrical, mechanical, or other forms.

[0050] The units described as separate components may or may not be physically separate. Components displayed as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0051] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A system for preparing superparamagnetic ferrite nanoparticles using supercritical composite solvents, comprising: The system comprises a CO2 compression and liquefaction module, an ethanol pretreatment module, a metering pump, a precursor storage tank, a high-pressure pump, a preheater, a mixing reactor, a high-pressure reactor, a temperature and pressure control module, an in-situ modification injection system, an online coating reactor, a supercritical vacuum separator, and a magnetic separation and purification module. The CO2 compression and liquefaction module and the ethanol pretreatment module outlets are connected to the mixing reactor inlet via metering pump pipelines. The precursor storage tank is connected to the mixing reactor inlet via pipelines sequentially connecting the high-pressure pump and the preheater. The mixing reactor outlet pipeline is connected to the high-pressure reactor inlet. The in-situ modification injection system pipeline is connected to the high-pressure reactor inlet. The online coating reactor is located inside the high-pressure reactor and connected to both the high-pressure reactor inlet and outlet. The high-pressure reactor outlet pipeline is connected to the inlet of the supercritical vacuum separator. The supercritical vacuum separator outlet pipeline is connected to the inlet of the magnetic separation and purification module. The temperature and pressure control module is electrically connected to the CO2 compression and liquefaction module, the ethanol pretreatment module, the high-pressure pump, the preheater, and the high-pressure reactor, respectively.

2. The system for preparing superparamagnetic ferrite nanoparticles using a supercritical composite solvent according to claim 1, characterized in that, The CO2 compression and liquefaction module is a low-temperature high-pressure pump, the ethanol pretreatment module is a high-pressure liquid phase pump and a preheater, and the mixing reactor is a static mixer and / or a dynamic eddy current generator.

3. The system for preparing superparamagnetic ferrite nanoparticles using a supercritical composite solvent according to claim 1, characterized in that, The high-pressure reactor is a titanium alloy high-pressure reactor that integrates multi-stage stirring and ultrasonic dispersion modules.

4. The system for preparing superparamagnetic ferrite nanoparticles using a supercritical composite solvent according to claim 1, characterized in that, The in-situ modification injection system is a high-pressure injection pump.

5. The system for preparing superparamagnetic ferrite nanoparticles using a supercritical composite solvent according to claim 1, characterized in that, The online coating reactor is a series-connected microchannel device.

6. The system for preparing superparamagnetic ferrite nanoparticles using a supercritical composite solvent according to claim 1, characterized in that, The supercritical pressure reducing separator is a back pressure valve staged pressure reducing device.

7. The system for preparing superparamagnetic ferrite nanoparticles using a supercritical composite solvent according to claim 1, characterized in that, The magnetic separation and purification module is a combination of a high-gradient magnetic separator and a centrifuge.

8. The system for preparing superparamagnetic ferrite nanoparticles using a supercritical composite solvent according to claim 1, characterized in that, The supercritical pressure reducing separator is also equipped with a CO2 recovery port, which is connected to a CO2 compressor and then to a CO2 compression and liquefaction module via a CO2 recovery port pipeline.

9. The system for preparing superparamagnetic ferrite nanoparticles using a supercritical composite solvent according to claim 1, characterized in that, The magnetic separation and purification module is also equipped with an ethanol recovery port, which is connected to an ethanol distillation column and then to an ethanol pretreatment module via a pipeline.

10. A method for preparing superparamagnetic ferrite nanoparticles using a supercritical composite solvent, applied to the system for preparing superparamagnetic ferrite nanoparticles using a supercritical composite solvent as described in any one of claims 1-9, comprising: S1, supercritical fluid generation, compresses CO2 to the supercritical state and pressurizes and heats ethanol to the supercritical state; S2, composite supercritical fluid mixing, which mixes supercritical CO2 and supercritical ethanol at a flow ratio of [1:3, 1:5]. S3, precursor decomposition, injecting homogeneous composite fluid into high-pressure reactor, and regulating reaction conditions of temperature and pressure through temperature and pressure control module; S4, in-situ modification injection, the hydrophilic ligand solution is injected into the high-pressure reactor by controlling the flow rate; S5, online wrapping, controlling dwell time; S6, Supercritical pressure reduction separation, controls the pressure of the supercritical pressure reduction separator to perform pressure reduction separation; S7, magnetic separation and purification, performs magnetic separation and purification through the magnetic separation and purification module.

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