CN115364788B

CN115364788B - Method for preparing rare earth oxide nano particles based on microfluidic technology

Info

Publication number: CN115364788B
Application number: CN202211175945.8A
Authority: CN
Inventors: 廖伍平; 洪勇健; 关芳
Original assignee: Ganjiang Innovation Academy of CAS
Current assignee: Ganjiang Innovation Academy of CAS
Priority date: 2022-09-26
Filing date: 2022-09-26
Publication date: 2024-03-22
Anticipated expiration: 2042-09-26
Also published as: CN115364788A

Abstract

The embodiment of the application discloses a method for preparing rare earth oxide nano particles based on a microfluidic technology, which comprises the following steps: inputting the disperse phase and the continuous phase into a microreactor, and dispersing the disperse phase in the continuous phase by using the microreactor to form micro-droplets; the disperse phase comprises rare earth nitrate, a dispersing agent, a disperse phase solvent, water and a precipitating agent, wherein the boiling point of the disperse phase solvent is above 150 ℃, and the disperse phase solvent has hydrophilicity; the continuous phase comprises a carrier liquid and optionally a nonionic surfactant, the carrier liquid having a boiling point above 180 ℃ and being immiscible with the dispersed phase solvent; heating the micro-droplets to generate rare earth oxide nano-particles; separating the rare earth oxide nanoparticles. The method can be used for continuous production, has higher production efficiency, and the prepared rare earth oxide nano particles have higher dispersity and uniformity and excellent product quality.

Description

Method for preparing rare earth oxide nano particles based on microfluidic technology

Technical Field

The embodiment of the application relates to the technical field of rare earth materials, in particular to a method for preparing rare earth oxide nano particles based on a microfluidic technology.

Background

Rare earth is a generic name of 15 elements of lanthanoid and 17 elements of scandium (Sc) and yttrium (Y) of the same group iii B as lanthanoid, and is called industrial vitamin. The rare earth nanomaterial has unique properties such as magnetism, optics, electricity, mechanics and the like due to unique 4f electron orbit, surface effect and quantum size effect, is widely applied to the key fields such as national defense, aviation, catalysts, new energy sources, electrons, chemical industry, metallurgy, light industry, ceramics, medicine and the like, and has important scientific and application values.

At present, rare earth nano materials are generally synthesized by adopting traditional methods such as a coprecipitation method, a hydrothermal method, a thermal decomposition method and the like, but the traditional methods have the defects of poor nano particle dispersibility, low repetition rate, discontinuous reaction, uneven quality of the prepared nano materials and the like.

In recent years, a microfluidic method based on droplets has received a lot of attention as an alternative way to synthesize nanomaterials and have a potential for mass production. Compared with the traditional method, the nano particles prepared based on the microfluidic technology have the advantages of good dispersibility, energy conservation, environmental protection, high reproducibility and the like, and an ideal scheme is provided for solving the problems.

However, in the process of converting the nano material synthesis from the batch reactor to the micro-droplet reactor, the flow channel is blocked easily due to narrow microfluidic flow channel and easy deposition of scale, and the continuity is difficult to realize. Therefore, how to achieve "serialization" is the first problem to be solved when the microfluidic technology is successfully applied to rare earth nanomaterials.

Disclosure of Invention

The inventors have carefully examined the process of preparing rare earth oxide nanoparticles using microfluidic technology and found that in the case of conventional use of water as a dispersion solvent, when the dispersion phase contacts the continuous phase at the T-port of the microfluidic chip, the laminar interface forms corresponding scale which accumulates over time resulting in clogging. For this reason, the inventors have made intensive studies and repeated experiments, and finally found that the problem of product deposition can be solved if the reaction for forming rare earth oxide nanoparticles can be performed after the dispersed phase enters the carrier liquid to form micro-droplets (i.e., the reaction for forming rare earth oxide nanoparticles does not substantially occur before the micro-droplets are formed), and the reaction condition that the reactant and the flow channel are not in direct contact. Therefore, the embodiment of the application provides a method for preparing rare earth oxide nano particles based on a microfluidic technology, which is not easy to block a flow channel, can continuously prepare the rare earth oxide nano particles, and has excellent product quality.

The technical scheme provided by the embodiment of the application is as follows:

a method for preparing rare earth oxide nanoparticles based on microfluidic technology, comprising:

inputting the disperse phase and the continuous phase into a microreactor, and dispersing the disperse phase in the continuous phase by using the microreactor to form micro-droplets; the disperse phase comprises rare earth nitrate, a dispersing agent, a disperse phase solvent, water and a precipitating agent, wherein the boiling point of the disperse phase solvent is above 150 ℃, and the disperse phase solvent has hydrophilicity; the continuous phase comprises a carrier liquid and optionally a nonionic surfactant, the carrier liquid having a boiling point above 180 ℃ and being immiscible with the dispersed phase solvent;

heating the micro-droplets to generate rare earth oxide nano-particles;

separating the rare earth oxide nanoparticles.

In some embodiments, the dispersed phase solvent is selected from the group consisting of ethylene glycol, dimethyl sulfoxide.

In some embodiments, the dispersant is selected from polyvinylpyrrolidone K30, cetyltrimethylammonium bromide.

In some embodiments, the precipitant is ammonium hydroxide.

In some embodiments, the volume ratio of dispersed phase solvent to water in the dispersed phase is 3 to 10:1.

In some embodiments, the dispersed phase is formulated as follows:

dissolving rare earth nitrate and a dispersing agent in the disperse phase solvent to form a first standby liquid;

preparing an aqueous solution of a precipitant as a second standby liquid;

and mixing the first standby liquid and the second standby liquid in a volume ratio of 3-10:1 to form the disperse phase.

In some embodiments, the concentration of rare earth ions in the first stock solution is 0.01mol/L to 0.15mol/L, and the concentration of the dispersing agent is 10g/L to 50g/L; and/or

The concentration of the precipitant in the second standby liquid is 0.05mol/L-0.50mol/L.

In some embodiments, the flow ratio of the dispersed phase to the continuous phase in the microreactor is from 1:3 to 1:10.

In some embodiments, the carrier fluid is selected from silicone oils, fluorinated oils.

In some embodiments, the nonionic surfactant is selected from the group consisting of triton X-100 and tween-20.

In some embodiments, the nonionic surfactant is present in the continuous phase at a volume concentration of 0.01 to 0.50%.

In some embodiments, the microreactor comprises a converging portion comprising a first flow passage and a second flow passage with an outlet connected in the middle of the first flow passage, the first flow passage and the second flow passage being arranged in a T-shape;

the inputting the disperse phase and the continuous phase into a microreactor, dispersing the disperse phase in the continuous phase by the microreactor to form micro-droplets, comprising:

the continuous phase is input into the first flow channel from the inlet of the first flow channel, and the disperse phase is input into the second flow channel from the inlet of the second flow channel, so that the disperse phase is converged with the continuous phase at the intersection of the first flow channel and the second flow channel and dispersed in the continuous phase to form the micro-droplets.

In some embodiments, the microdroplet is heated by microwaves or by passing the microdroplet through a high temperature environment.

In some embodiments, the temperature of the high temperature environment is 130-180 ℃, and the heating time is controlled to be more than 10 min; the microwave heating power is controlled to be 100W-1500W, and the heating time is controlled to be more than 10 s.

In some embodiments, the temperature of the high temperature environment is 150-180 ℃ and the heating time is controlled between 30min and 90min; the microwave heating power is controlled to be 300W-1000W, and the heating time is controlled to be 1 min-5 min.

In some embodiments, the microfluidic technology-based method of preparing rare earth oxide nanoparticles according to the present invention may further include the step of washing and drying the rare earth oxide nanoparticles.

According to the method for preparing the rare earth oxide nano particles based on the microfluidic technology, the disperse phase solvent with a higher boiling point is selected for preparing the disperse phase, so that the reaction of rare earth ions and precipitant at normal temperature can be effectively inhibited, the precipitation and precipitation in the flow channel of the microreactor are avoided, the flow channel of the microreactor is further prevented from being blocked, and uniform micro-droplets can be formed by the disperse phase in the system under the action of the microreactor. When the micro-droplets are heated, the specific surface area of the micro-droplets is large, and the heat and mass transfer efficiency is high, so that the micro-droplets can rapidly act on rare earth ions and a precipitator, and the rare earth ions and the precipitator are accelerated to precipitate out, so that rare earth oxide nano-particles are generated. The method can not only obtain high-quality rare earth nano oxide nano particles with good dispersity and uniformity, but also realize continuous production and has higher production efficiency.

Drawings

Other features, objects and advantages of the present application will become more apparent upon reading of the detailed description of non-limiting embodiments, made with reference to the following drawings, in which:

FIG. 1 is a flow chart of a method of preparing rare earth oxide nanoparticles according to an embodiment of the present application;

FIG. 2 is a schematic view of a flow channel structure of a microreactor employed in one embodiment of the present application;

FIG. 3 is a microscopic image of a confluence section in the microreactor of FIG. 2;

FIGS. 4a and 4b are, respectively, microscopic images of microdroplets formed in a microreactor according to embodiments of the present application;

FIG. 5a is a scanning electron microscope image of rare earth oxide nanoparticles prepared in example 1 of the present application;

FIG. 5b is a transmission electron microscope image of rare earth oxide nanoparticles prepared in example 3 of the present application;

fig. 6 is an analytical spectrum of a spectrometer of rare earth oxide nanoparticles prepared in example 1 of the present application.

Detailed Description

The present application is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.

It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

Fig. 1 is a schematic diagram illustrating a method for preparing rare earth oxide nanoparticles according to an embodiment of the present application, and referring to fig. 1, the method for preparing rare earth oxide nanoparticles according to an embodiment of the present application may specifically include the following steps S110 to S130.

S110, inputting the disperse phase and the continuous phase into a microreactor, and dispersing the disperse phase in the continuous phase by using the microreactor to form micro-droplets.

Disperse phase

The disperse phase comprises rare earth nitrate, a dispersing agent, a disperse phase solvent, water and a precipitating agent.

The method of preparing the dispersed phase is not particularly limited as long as the components are uniformly dispersed and the rare earth nitrate is substantially unreactive with the precipitant. For example, the method of formulating the dispersed phase may include the following steps S011-S013.

And S011, dissolving rare earth nitrate and a dispersing agent in a disperse phase solvent to form a first standby liquid.

The rare earth may include various rare earth elements including lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, and scandium, wherein light rare earth refers to lanthanum, cerium, praseodymium, and neodymium; the middle rare earth refers to samarium, europium and gadolinium; the heavy rare earth refers to terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium and yttrium. For example, the rare earth nitrate includes lanthanum nitrate, cerium nitrate, praseodymium nitrate, …, scandium nitrate, yttrium nitrate, and the like. Alternatively, the rare earth nitrate may be a hydrated rare earth nitrate. Taking cerium nitrate and yttrium nitrate as examples, the rare earth nitrate may be Ce (NO ₃ ) ₃ ·6H ₂ O or Y (NO) ₃ ) ₃ ·6H ₂ O。

The dispersant may be selected from: polyvinylpyrrolidone K30 (PVP-K30), cetyltrimethylammonium bromide (CTAB). Preferably, the dispersant may be polyvinylpyrrolidone K30 (PVP-K30). PVP-K30 not only has stronger viscosity and better dispersing effect, but also can be coated on the surface of the nano particles, increases the steric hindrance, reduces the surface energy and controls the secondary growth of the nano particles.

The boiling point of the disperse phase solvent is above 150 ℃, thereby having thermal stability. The dispersed phase solvent also has hydrophilicity. Therefore, the rare earth nitrate and the dispersing agent can be dissolved, and the rare earth nitrate and the precipitating agent can not react or react slowly in the disperse phase solvent at normal temperature.

In particular, the dispersed phase solvent may be selected from ethylene glycol, dimethyl sulfoxide (DMSO), and the like. With these dispersed phase solvents, the rare earth nitrate and precipitant do not substantially react prior to heating. The disperse phase solvents have higher boiling point and good thermal stability, and can effectively solve the problem of deposition of the sediment in the flow channel of the micro-reactor, thereby avoiding blockage in the flow channel of the micro-fluidic chip. In addition, the disperse phase solvents have stronger viscosity and have the effect of dispersing agents, thereby being beneficial to improving the dispersibility and the uniformity of the formed rare earth oxide nano particles.

The ratio of the dispersant to the rare earth nitrate is not particularly limited, and may be determined for the specific dispersant employed using conventional experimental methods. For example, using PVP-K30 as the dispersant, the mass ratio of rare earth nitrate to PVP-K30 may be 1:5-1:100, such as 1:10, 1:15, 1:20, 1:25, 1:30, 1:40, 1:50, 1:60, etc. Preferably, the mass ratio of the rare earth nitrate to PVP-K30 can be 1:10-1:20. In the proportion range, not only can a better dispersing effect be formed, but also the use amount and the use cost of PVP-K30 can be considered.

Alternatively, the rare earth ion concentration in the first standby liquid is 0.01mol/L to 0.15mol/L, for example, 0.02mol/L, 0.03mol/L, 0.04mol/L, 0.05mol/L, 0.06mol/L, 0.07mol/L, 0.08mol/L, 0.09mol/L, 0.10mol/L, 0.11mol/L, 0.12mol/L, 0.13mol/L, 0.14mol/L, etc.

Optionally, the concentration of dispersant in the first stock solution is from 10g/L to 50g/L, such as 15g/L, 20g/L, 30g/L, 40g/L, 45g/L, etc.

After adding the rare earth nitrate and the dispersing agent to the dispersed phase solvent, any method for accelerating the dissolution rate of the rare earth nitrate and the dispersing agent can be adopted, for example, ultrasonic treatment or stirring treatment is carried out on the mixture to improve the production efficiency.

S012, preparing an aqueous solution of a precipitant as a second standby solution.

The precipitant may be a compound capable of reacting with the rare earth ions to form a precipitate, and may be, for example, a base or oxalic acid. The base may include, among others, substances that can generate hydroxyl groups in aqueous solution, such as ammonium hydroxide, urea, and the like. For example, the second standby liquid may be ammonia water.

Optionally, the concentration of the precipitant in the second standby liquid is 0.05mol/L to 0.50mol/L, for example, 0.10mol/L, 0.12mol/L, 0.15mol/L, 0.20mol/L, 0.25mol/L, 0.30mol/L, 0.35mol/L, 0.40mol/L, 0.45mol/L, etc. Therefore, the method can effectively react with rare earth nitrate to prepare rare earth oxide nano particles, and can avoid the excessively high reaction speed, thereby avoiding the formation of sediment in a flow channel of the microfluidic chip as much as possible.

And S013, mixing the first standby liquid and the second standby liquid to form the disperse phase.

Optionally, after the first stock solution and the second stock solution are mixed, the mixture of the first stock solution and the second stock solution may be stirred. Alternatively, the stirring speed during mixing can be 300-600 r/min, and the stirring time period is 5-10 min.

Optionally, the ratio of the first standby liquid to the second standby liquid is aimed at promoting the sufficient reaction of rare earth ions and compromising the production cost. For example, taking the second standby liquid as ammonia water, the molar ratio of the rare earth ions in the first standby liquid to the hydroxyl ions in the ammonia water can be 1:3-1:10, such as 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, etc.

When mixing, the volume ratio of the first standby liquid to the second standby liquid may be 3 to 10:1, for example, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc., but not limited thereto, the volume ratio may also be a non-integer ratio between these volume ratios. Thus, the volume ratio of the dispersed phase solvent to water in the dispersed phase may be 3 to 10:1.

It should be noted that the above-mentioned dispersing agent, precipitant and disperse phase solvent are exemplary, and other functional similar substances may be used in the case of satisfying the reaction requirement, and should not be construed as being limited to the specific substances.

Continuous phase

The continuous phase comprises a carrier liquid and optionally a nonionic surfactant. That is, the continuous phase may consist of the carrier liquid alone, or of the carrier liquid and a nonionic surfactant. In addition, the continuous phase may also contain other ingredients, such as ingredients that promote separation of the dispersed phase from the continuous phase, stabilizers, and the like.

The carrier liquid has a boiling point above 180 ℃ which may facilitate heating of the dispersed phase to promote nanoparticle formation. In addition, the carrier liquid is not miscible with the dispersed phase solvent, so that the dispersed phase can form micro-droplets in the carrier liquid, and the size of the formed nano-particles is ensured.

In particular, the carrier liquid may be, for example, silicone oil, fluorinated oil, or the like. Silicone oils such as dimethicone; fluorinated oils are also referred to as fluorooils, PFPEs, and refer to amphiphobic liquids such as perfluoropolyethers, although other liquids may be used in the practice. Of course, immiscible as referred to herein is not to be understood as absolute mutual insolubility, but rather as poorly soluble or substantially insoluble.

In particular, the nonionic surfactant may be selected from: triton X-100 and TWeen-20 (TWeen-20), but is not limited thereto. Wherein the component of triton X-100 (Triton X-100) is polyoxyethylene-8-octyl phenyl ether, also called polyethylene glycol p-isooctyl phenyl ether. Tween-20 is a mixture of polyoxyethylene sorbitan monolaurate and a portion of polyoxyethylene dianhydrosorbitol monolaurate.

Alternatively, the volume concentration of the nonionic surfactant in the continuous phase is 0.01 to 0.50%, for example, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.10%, 0.20%, 0.30%, 0.40%, 0.50%, etc., but is not limited thereto.

When the nonionic surfactant exists, under the action of the nonionic surfactant, the disperse phase solvent, the rare earth ions dissolved in the disperse phase solvent and the precipitant can be contracted to the core of the micro-droplets, the periphery of the micro-droplets is mainly wrapped by the dispersing agent, the stability of the micro-droplets can be improved, the micro-droplets are prevented from being broken, the Ostwald process is inhibited, the uniformity of the formed micro-droplets is improved, and the uniformity of the prepared rare earth oxide nanoparticles is further improved. In addition, the rare earth ion and precipitant water-oil interface adsorption can be inhibited, the rare earth oxide precipitation is inhibited from forming on the surface of the micro-droplet, and the separation difficulty of the rare earth oxide nano particles and the continuous phase is further reduced, so that the recovery rate of the continuous phase is improved, and the raw material consumption and the production cost are reduced.

Microreactor

Optionally, the flow ratio of the dispersed phase and the continuous phase in the microreactor is from 1:3 to 1:10, e.g., 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, etc. In the above ratio range, not only a good dispersing effect can be obtained, but also the use amount of the continuous phase can be considered, which is beneficial to improving the utilization rate of the continuous phase.

The micro reactor (or micro fluidic reactor (Microfluidic reactor)) may be, for example, a micro fluidic chip prepared from silicon wafer, glass, PDMS, or a micro reactor configured as a T-shaped or similar-shaped sink by, for example, a capillary, so long as it is capable of forming pL-nL (picoliter to nanoliter) micro droplets, and thus forming rare earth oxide nanoparticles.

Alternatively, the microreactor includes a confluence part 230, and the confluence part 230 includes a first flow path 231 and a second flow path 232 having an outlet connected to a middle portion of the first flow path 231. The first flow channel 231 and the second flow channel 232 may be arranged in a T-shape or the like. Of course, the structure of the microreactor is merely exemplary and is not limited in its implementation. Fig. 2 is a schematic view of a flow channel structure of a microreactor, and fig. 3 is a microscopic image of a confluence part 230.

On this basis, step S110, the inputting the dispersed phase and the continuous phase into a microreactor, and dispersing the dispersed phase in the continuous phase to form micro droplets by using the microreactor, may include:

the continuous phase is fed into the first flow channel 231 from the inlet of the first flow channel 231 and the dispersed phase is fed into the second flow channel 232 from the inlet of the second flow channel 232 such that the dispersed phase merges with the continuous phase at the intersection of the first flow channel 231 and the second flow channel 232 and disperses in the continuous phase to form the microdroplets.

As shown in fig. 2 and 3, an inlet 210 is provided at one end of a first flow channel 231 of the microfluidic chip, the inlets of a second flow channel 232 are respectively connected with the communicated outlets of two third flow channels 233, the two third flow channels 233 are arranged in a V shape, the other ends of the two third flow channels 233 are respectively provided with an inlet 220, a dispersed phase can be input into the third flow channels 233 through the inlet 220, and the dispersed phases in the two third flow channels 233 are converged at the inlet of the second flow channel 232 and flow into the second flow channel 232. The outlet of the second flow channel 232 is connected with the middle part of the first flow channel 231, and the first flow channel 231 and the second flow channel 232 are arranged in a T shape, and the disperse phase is converged into the first flow channel 231 through the outlet of the second flow channel 232. Immediately after the dispersed phase flows into the first flow channel 231, the dispersed phase flows close to the inner wall of the first flow channel 231, but as the dispersed phase accumulates, micro droplets are formed under the double action of surface tension and viscous force, and flow away with the continuous phase. As shown in the microscopic images in fig. 4a and 4b, continuous and uniform micro-droplets can be formed in the flow channel. In fact, as shown in fig. 4a, the darker portion a of the periphery of the microdroplet is a dispersant, and the lighter portion B of the core of the microdroplet is mainly a rare earth ion, a precipitant and a dispersed phase solvent.

Optionally, as shown in fig. 2, the microreactor may further include a mixing runner 240, where the mixing runner 240 is connected to the first runner 231, and a liquid outlet of the microreactor of the mixing runner 240. The mixing channel 240 is used to mix the fluid, so that the uniformity of the reactant in the microdroplet is further improved, and the rare earth oxide nanoparticles formed later can be more uniform.

And S120, heating the micro-droplets to generate rare earth oxide nano-particles.

The reaction of rare earth ions in the micro-droplets and the precipitant and the growth of rare earth oxide nano-particles can be promoted by heating the micro-droplets.

The method of heating the microdroplet is not particularly limited, and any suitable method may be selected as long as it can promote the reaction of the rare earth ions in the microdroplet with the precipitant and the growth of the rare earth oxide nanoparticles. Alternatively, the microdroplets may be heated by microwaves, or the microdroplets may be heated by passing the microdroplets through a high temperature environment (e.g., an oil bath).

The heating temperature and time are not particularly limited, and those skilled in the art can determine by routine experiments according to the desired nanoparticle particle size and the like. In some embodiments, the temperature of the high temperature environment may be 130 ℃ to 180 ℃, preferably 150 ℃ to 180 ℃, and the heating time may be controlled to be more than 10 minutes, for example, 10 minutes to 5 hours, 30 minutes to 90 minutes, etc. In the case of heating the micro-droplets by microwaves, the heating power can be controlled to be 100W-1500W, such as 300W-1000W, 700W; the heating time can be controlled to be 10s to 1h, for example, 10s to 10min, 1min to 5min, etc. Fig. 5a is a scanning electron microscope image of rare earth oxide nanoparticles formed using oil bath heating, and fig. 5b is a transmission electron microscope image of rare earth oxide nanoparticles formed using microwave heating.

Because the particle size of the micro-droplets is smaller, the specific surface area is large, the mass transfer and heat transfer efficiency is extremely high, and the micro-droplets can be directly heated by microwaves or indirectly heated by a high-temperature environment mode, so that a good heating effect can be formed, rare earth ions and precipitants can be promoted to react rapidly to generate rare earth oxides, and the production efficiency is relatively high. In the specific implementation, the micro-droplets may be directly or indirectly heated by various processes, so long as the effect of effectively heating the micro-droplets can be achieved, and the method is not limited to the microwave or oil bath method.

S130, separating the rare earth oxide nano particles.

The method for separating the rare earth oxide nanoparticles is not particularly limited, and any suitable method, such as filtration, centrifugation, etc., may be employed as long as the rare earth oxide nanoparticles can be separated from the dispersed phase solvent and the continuous phase.

Optionally, the separating the rare earth oxide nanoparticles may include the following steps S131 to S132.

S131 centrifuging a mixture comprising the continuous phase, the dispersed phase solvent, and the rare earth oxide nanoparticles. Alternatively, the centrifugation speed can be controlled between 6000 and 10000r/min.

S132, obtaining rare earth oxide nano particles positioned at the bottom layer.

In practice, centrifugation enables the formation of a three-layer structure, the material at the bottom layer being mainly rare earth oxide nanoparticles, the material at the middle layer being mainly a dispersed phase, and the material at the top layer being mainly a continuous phase. Thus, rare earth oxide nanoparticles can be obtained from the bottommost layer, from which the continuous phase is recovered.

It will be appreciated that in particular implementations, the rare earth oxide nanoparticles may be separated from the mixture by a variety of processes, not limited to separation of the rare earth oxide nanoparticles using a centrifugal process.

The method for preparing rare earth oxide nanoparticles based on the microfluidic technology according to the present invention may further include a step S140 of washing the rare earth oxide nanoparticles and a step S150 of drying.

And S140, cleaning the separated rare earth oxide nano particles to remove impurities.

The method of cleaning the rare earth oxide nanoparticles is not particularly limited, and any suitable method may be employed as long as impurities can be removed.

Optionally, the rare earth oxide nanoparticles may be washed, for example, with deionized water and/or absolute ethanol, to remove impurities such as dispersants, precipitants, dispersed phase solvents, and continuous phase impurities, which may be beneficial to improve the purity of the rare earth oxide nanoparticles. For example, each pair of rare earth oxide nanoparticles may be washed three times with deionized water and absolute ethanol, respectively.

And S150, drying the cleaned rare earth oxide nano particles.

The method for drying the rare earth oxide nanoparticles is not particularly limited, and any suitable method, such as drying, spray drying, freeze drying, and the like, may be employed.

Optionally, the washed rare earth oxide nanoparticles may be dried, for example, by an oven at 60-80 ℃, to remove water and/or absolute ethanol to form the final product. As shown in fig. 6, the spectrum distribution of the spectrum of the prepared rare earth oxide nanoparticle is very concentrated, and the prepared rare earth oxide nanoparticle has higher purity. Of course, in the specific implementation, the washed rare earth oxide nanoparticles may also be dried by using, for example, a flow-type drying process.

According to the preparation method of the rare earth oxide nano particles, before the disperse phase is input into the microreactor, the disperse phase solvent with a higher boiling point is selected to prepare the disperse phase, so that the rare earth nitrate and the precipitant are dissolved in the disperse phase solvent, the disperse phase solvent can effectively inhibit the reaction of rare earth ions and the precipitant at normal temperature, the precipitation in a runner of the microreactor is avoided, and further, the blockage in the runner of the microreactor is avoided, uniform micro droplets can be formed by the disperse phase in the system through the action of the microreactor, the micro droplets are heated, and the specific surface area of the micro droplets is large, so that the heat transfer and mass transfer efficiency is high, the rare earth nitrate and the precipitant can be rapidly acted on, the reaction of the rare earth ions and the precipitant and the growth of the rare earth oxide nano particles are promoted, and the precipitation is accelerated. Not only can obtain high-quality rare earth nano oxide with better dispersity and uniformity, but also can realize continuous production, and has higher production efficiency.

Examples

The following describes the preparation method of the rare earth oxide nanoparticle according to the embodiment of the present application in detail with reference to specific examples and experimental results.

Reagents and apparatus

Unless otherwise indicated, all reagents used were commercially available analytically pure reagents.

Polyvinylpyrrolidone (PVP) is PVP K30M W from the exploration platform in the open sea: 40000

The microfluidic chip is manufactured by the chemical industry Co.Ltd.of Wuhan Jian Mizhi control technology, the structure of which is shown in figures 2-3, the front flow channel in the microfluidic chip is in a side K shape, the continuous phase and the disperse phase are contacted at the intersection, the disperse phase is sheared into micro-droplets, and the micro-droplets enter the PTFE capillary after the mixing action of the rear S-shaped flow channel.

Microscope is ZESIS Primotech, germany

The scanning electron microscope was ZESIS Sigma 300, germany

The transmission electron microscope was JEOL JEM 2100F

The energy spectrometer is oxford X-MaxN 80T IE250 in England

Example 1

Preparation of Y (NO) with concentration of 0.12mol/L by using ethylene glycol as disperse phase solvent ₃ ) ₃ 50mL of solution, polyvinylpyrrolidone (PVP) with a concentration of 48g/L was added to the solution, stirred until completely dispersed, and the solution was clear as a first stock solution.

50mL of aqueous ammonia having a concentration of 0.30mol/L was prepared as a second stock solution.

Taking 5mL of the first standby liquid into a clean beaker, placing the clean beaker on a stirrer to stir at the speed of 500r/min, and simultaneously injecting 1mL of the second standby liquid into the beaker by using an injection pump for 10min to obtain a disperse phase.

50mL of silicone oil was taken and 0.20mL of triton X-100 was ultrasonically dispersed into the silicone oil as the continuous phase.

The continuous phase and the disperse phase are injected into the microfluidic chip, wherein the flow rate Vc of the continuous phase is=300 mu L/h, the disperse phase is input in two paths, and the flow rate Vd is=30 mu L/h.

The liquid outlet of the microfluidic chip is externally connected with a Polytetrafluoroethylene (PTFE) capillary tube with an inner diameter of 800 mu m and a length of 10 mu m. The emulsified microdroplets were heated by placing the capillary in an oil bath at 160 ℃ for 60 minutes and collected into a centrifuge tube.

Centrifuging at 8000r/min for 5min, and recovering the upper clear continuous phase.

Collecting the lower precipitate, washing with deionized water and absolute ethanol for 3 times, oven drying at 80deg.C, and storing to obtain pure yttrium oxide nanoparticles, which are similar to spherical yttrium oxide nanoparticles with average particle diameter of about 100nm as shown in figure 5 a. In the embodiment, the cut-off experiment is finished for 121 hours, the flow channel of the microfluidic chip is not obviously blocked, and the analysis spectrogram of the prepared yttrium oxide nano-particles by an energy spectrometer is shown in fig. 6, so that the yttrium oxide nano-particles have higher purity.

Example 2

Preparation of Ce (NO) with concentration of 0.04mol/L by using dimethyl sulfoxide as disperse phase solvent ₃ ) ₃ 50mL of solution, polyvinylpyrrolidone (PVP) with a concentration of 32g/L was added to the solution, stirred until completely dispersed, and the solution was clear as a first stock solution.

50mL of aqueous ammonia having a concentration of 0.3mol/L was prepared as a second stock solution.

Taking 5mL of the first standby liquid into a clean beaker, placing the clean beaker on a stirrer to stir at the speed of 600r/min, and simultaneously injecting 1mL of the second standby liquid into the beaker by using an injection pump for 10min to obtain a disperse phase.

The continuous phase and the disperse phase are injected into the microfluidic chip, wherein the flow rate Vc of the continuous phase is=1.60 mL/h, the disperse phase is input in two paths, and the flow rate Vd is=0.08 mL/h.

The liquid outlet of the microfluidic chip is externally connected with a Polytetrafluoroethylene (PTFE) capillary tube with an inner diameter of 800 mu m and a length of 5 mu m. The emulsified microdroplets were heated by placing the capillary in an oil bath at 170 ℃ for 60 minutes and collected into a centrifuge tube.

Collecting the sediment at the lower layer, washing with deionized water and absolute ethyl alcohol for 3 times, putting into a baking oven, and drying and preserving at 80 ℃ to obtain the pure cerium oxide nano particles. In the embodiment, the cut-off experiment is finished for 200 hours in a co-continuous reaction mode, the flow channel of the microfluidic chip is not obviously blocked, the prepared cerium oxide nano particles are approximately spherical, and the average particle size is about 70nm.

Example 3

Preparation of Ce (NO) with concentration of 0.04mol/L by using glycol as disperse phase solvent ₃ ) ₃ 50mL of solution, polyvinylpyrrolidone (PVP) with a concentration of 32g/L was added to the solution, stirred until completely dispersed, and the solution was clear as a first stock solution.

Taking 5mL of the first standby liquid into a clean beaker, placing the clean beaker on a stirrer to stir at the speed of 700r/min, and simultaneously injecting 1mL of the second standby liquid into the beaker by using an injection pump for 10min to obtain a disperse phase.

The continuous phase and the disperse phase are injected into the microfluidic chip, wherein the flow rate Vc of the continuous phase is=1.20 mL/h, the disperse phase is input in two paths, and the flow rate Vd is=0.08 mL/h.

The liquid outlet of the microfluidic chip is externally connected with a Polytetrafluoroethylene (PTFE) capillary tube with an inner diameter of 800 mu m and a length of 5 mu m. And (3) placing the capillary tube in a microwave oven to heat the emulsified micro-droplets by microwaves with the power of 700W and the heating time of 3min, and collecting the micro-droplets into a centrifuge tube.

Collecting the sediment at the lower layer, washing with deionized water and absolute ethyl alcohol for 3 times, putting into a baking oven, and drying and preserving at 80 ℃ to obtain the pure cerium oxide nano particles. In this embodiment, the end of the cut-off experiment is completed for 160 hours, no obvious blocking phenomenon occurs in the flow channel of the microfluidic chip, and the prepared cerium oxide nanoparticles are approximately cubic, and have an average particle diameter of about 20nm, as shown in fig. 5 b.

Example 4

Preparation of Ce (NO) with concentration of 0.08mol/L by using glycol as disperse phase solvent ₃ ) ₃ 50mL of a solution, cetyltrimethylammonium bromide (PVP) at a concentration of 32g/L was added to the solution, stirred until completely dispersed, and the solution was clear as a first stock solution.

Taking 5mL of the first standby liquid into a clean beaker, placing the clean beaker on a magnetic stirrer to stir at the speed of 600r/min, and simultaneously injecting 1mL of the second standby liquid into the beaker by using an injection pump for 10min to obtain a disperse phase.

50mL of silicone oil was taken and 0.20mL of Tween-20 was ultrasonically dispersed into the silicone oil as the continuous phase.

Centrifuging the product for 5min at 8000r/min, and recovering the upper clear continuous phase. Collecting the sediment at the lower layer, washing with deionized water and absolute ethyl alcohol for 3 times, putting into a baking oven, and drying and preserving at 70 ℃ to obtain the pure cerium oxide nano particles. In the embodiment, the ending of the cut-off experiment is carried out for 168 hours in a co-continuous way, and no obvious blocking phenomenon occurs in the flow channel of the microfluidic chip. The cerium oxide nano particles are approximately spherical, have high uniformity and have an average particle size of about 80nm.

Example 5

50mL of Ce (NO 3) 3 solution with the concentration of 0.04mol/L is prepared by taking ethylene glycol as a disperse phase solvent, polyvinylpyrrolidone (PVP) with the concentration of 32g/L is added into the solution, and the solution is stirred until the mixture is completely dispersed and clarified to be used as a first standby liquid.

Taking 5mL of the first standby liquid into a clean beaker, placing the clean beaker on a stirrer to stir at the speed of 800r/min, and simultaneously injecting 1mL of the second standby liquid into the beaker by using an injection pump for 10min to obtain a disperse phase.

50mL of silicone oil was taken as the continuous phase.

The liquid outlet of the microfluidic chip is externally connected with a Polytetrafluoroethylene (PTFE) capillary tube with an inner diameter of 800 mu m and a length of 5 mu m. The emulsified microdroplets were heated by placing the capillary in an oil bath at 160 ℃ for 60 minutes and collected into a centrifuge tube.

Centrifuging at 8000r/min for 8min, and recovering the upper clear continuous phase.

Collecting the sediment at the lower layer, washing with deionized water and absolute ethyl alcohol for 3 times, putting into a baking oven, and drying and preserving at 80 ℃ to obtain the pure cerium oxide nano particles. In this embodiment, the cut-off time is finished and is continuously performed for 120 hours, and no obvious blocking phenomenon occurs in the flow channel of the microfluidic chip. The prepared cerium oxide nano particles are approximately spherical, and the average particle size is about 260nm.

Comparative example 1

Preparation of Ce (NO) with concentration of 0.08mol/L by using water as solvent ₃ ) ₃ 50mL of solution, polyvinylpyrrolidone (PVP) with a concentration of 32g/L was added to the solution, stirred until completely dispersed, and the solution was clear as a first stock solution.

The liquid outlet of the microfluidic chip is externally connected with a Polytetrafluoroethylene (PTFE) capillary tube with an inner diameter of 800 mu m and a length of 5 mu m.

And when the reaction is carried out for 13min, the interior of the flow channel of the microfluidic chip is blocked, and the reaction cannot be continued.

Comparative example 2

Preparation of Ce (NO) with concentration of 0.08mol/L by using glycol as solvent ₃ ) ₃ 50mL of solution, polyvinylpyrrolidone (PVP) with a concentration of 32g/L was added to the solution, stirred until completely dispersed, and the solution was clear as a first stock solution.

And injecting the continuous phase and the disperse phase into the microfluidic chip, wherein the flow rate Vd=300 mu L/h of the continuous phase, and the first standby liquid and the second standby liquid are input in two paths, and the flow rates Vd=30 mu L/h.

As a result, the reaction was continued for 220 minutes, and the interior of the flow channel of the microfluidic chip was blocked, and the reaction could not be continued.

The experimental results of the above examples and comparative examples are shown in the following table.

TABLE 1

As can be seen from the table, the application adopts ethylene glycol and dimethyl sulfoxide as the disperse phase solvents, the disperse phase is mixed before the disperse phase solvents are input into the microfluidic chip, and the reaction of rare earth ions and precipitants is inhibited by the disperse phase solvents, so that continuous reaction can be realized. Comparative example 1 uses water as the solvent of the dispersed phase, and the reaction lasts only 13min, failing to achieve continuous reaction. In the comparative example 2, the volume ratio of the glycol to the water is 1:1, so that the reaction of rare earth ions and the precipitant cannot be effectively inhibited by the disperse phase solvent, and the final reaction only lasts for 220 minutes, so that the flow passage of the microfluidic chip is blocked and cannot be continued.

In addition, it should be noted that, the application selects two rare earth elements of cerium and yttrium from light rare earth and heavy rare earth respectively for experiment, from the experimental results, continuous production can be realized, and rare earth oxide nano particles with uniform particle size can be formed, so the preparation method is applicable to various rare earth elements (including light rare earth and heavy rare earth).

The above embodiments are only exemplary embodiments of the present application and are not intended to limit the present application, the scope of which is defined by the claims. Various modifications and equivalent arrangements may be made to the present application by those skilled in the art, which modifications and equivalents are also considered to be within the scope of the present application.

Claims

1. A method for preparing rare earth oxide nano particles based on a microfluidic technology, which is characterized by comprising the following steps:

heating the micro-droplets to generate rare earth oxide nano-particles;

separating the rare earth oxide nanoparticles.

2. The method of claim 1, wherein the step of determining the position of the substrate comprises,

the disperse phase solvent is selected from ethylene glycol and dimethyl sulfoxide; and/or

The dispersing agent is selected from polyvinylpyrrolidone K30 and cetyltrimethylammonium bromide; and/or

The precipitant is ammonium hydroxide; and/or

The volume ratio of the disperse phase solvent to water in the disperse phase is 3-10:1; and/or

The carrier fluid is selected from silicone oil and fluorinated oil; and/or

The nonionic surfactant is selected from the group consisting of triton X-100 and tween-20; and/or

The volume concentration of the nonionic surfactant in the continuous phase is 0.01-0.50%.

3. The method of claim 1, wherein the dispersed phase is formulated as follows:

preparing an aqueous solution of a precipitant as a second standby liquid;

4. The method of claim 3, wherein the step of,

the concentration of rare earth ions in the first standby liquid is 0.01mol/L-0.15mol/L, and the concentration of the dispersing agent is 10g/L-50g/L; and/or

5. The method of claim 1, wherein the flow ratio of the dispersed phase to the continuous phase in the microreactor is from 1:3 to 1:10.

6. The method of claim 1, wherein the microreactor comprises a confluence portion comprising a first flow channel and a second flow channel with an outlet connected in the middle of the first flow channel, the first flow channel and the second flow channel being arranged in a T-shape;

7. The method of claim 1, wherein the microdroplet is heated by microwaves or by passing the microdroplet through a high temperature environment.

8. The method of claim 7, wherein the step of determining the position of the probe is performed,

the temperature of the high-temperature environment is 130-180 ℃, and the heating time is controlled to be more than 10 min;

the microwave heating power is controlled to be 100W-1500W, and the heating time is controlled to be more than 10 s.

9. The method of claim 7, wherein the step of determining the position of the probe is performed,

the temperature of the high-temperature environment is 150-180 ℃, and the heating time is controlled to be 30-90 min;

the microwave heating power is controlled to be 300W-1000W, and the heating time is controlled to be 1 min-5 min.

10. The method of claim 1, further comprising the step of washing and drying the rare earth oxide nanoparticles.