Preparation method and application of nano silicon dioxide based on dilute fine silica

Abstract

The invention belongs to the technical field of material preparation, and particularly relates to a preparation method and application of nano silicon dioxide based on thin and fine silica, and the preparation method comprises the following steps: crushing thin and fine silica ore to obtain coarse particles; soaking the coarse particles in an acid solution, performing low-frequency hammering type pulping after soaking, and performing coarse filtration on the slurry to obtain a filter residue intermediate; soaking the intermediate in an alkaline solution, and performing secondary pulping in a high-frequency microwave treatment environment after soaking; adding a surfactant, heating, pressurizing and catalyzing, and then carrying out molecular extrusion and multi-frequency ultrasonic pulping; and centrifugally separating impurities, and extracting and purifying to obtain the nano silicon dioxide. Compared with the prior art, the preparation method provided by the invention has the effect of preparing silicon dioxide with the diameter of 1-3nm from thin and fine silica, and is applied to preparation of a new energy battery, so that the energy density of the lithium battery is improved, the charging speed is accelerated, and the electric leakage risk is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation, and particularly relates to a method for preparing nano-silica based on dilute fine silica and its application. Background Art

[0002] Dilute fine silica is a fibrous mineral composed of irregularly arranged small rods. There are irregular structures between the small rods. The diameters of these small rods are between 1 and 3 nanometers, and they contain multiple micropores, and the content of natural silica is more than 70%, so it is called dilute fine silica. Dilute fine silica is a magnesium-rich fibrous mineral, whose main component is silica, and at the same time contains alumina and other oxide impurities such as calcium oxide and sodium oxide. In the natural environment, dilute fine silica presents as a white or grayish-white lumpy powder with a delicate texture.

[0003] Dilute fine silica is a mineral mainly composed of silicates and oxides. Its main components are aluminum silicate and magnesium silicate, and at the same time it also contains a certain amount of silica and iron oxide. In addition, dilute fine silica also contains mineral elements such as copper, iron, manganese, potassium, and sodium. The theoretical chemical composition of dilute fine silica also includes SiO2, MgO, Al2O3, Fe2O3, and H2O. Dilute fine silica has a special layer-chain structure, which is a hydrated magnesium-aluminum silicate mineral formed by components such as MgO, Al2O3, and SiO2 in a certain proportion under high alkaline conditions. This mineral has a special layer-chain structure, and when heated to about 700 to 800 °C, its hardness will increase significantly.

[0004] By analyzing the composition and molecular structure of dilute fine silica, its possible formation process is speculated as follows: Dilute fine silica evolved from marine biological sedimentary rock substances over hundreds of thousands of years. Perhaps it was formed when land animals and plants became the sea due to crustal movements, and then evolved from marine sediments into land. The fat proteins, cellulose oils, and various elements such as iron, zinc, magnesium, and aluminum in organisms, animals, and plants, under the action of the environment and time, gradually evolved into silica nanorods, while protein oils evolved into the adhesion substances between the nanorods.

[0005] Dilute fine silica not only has a simple chemical composition, but also has a certain adsorption capacity, which makes it widely used in industries, pharmaceutical and chemical industries, feeds, etc. In industry, it can be used to manufacture products such as ceramics, enamels, abrasives, coatings, and fillers. In feeds, dilute fine silica can adsorb harmful substances, improve the digestive tract health of animals, and at the same time increase the viscosity of feeds, improve the appetite of animals, thereby promoting the gastrointestinal health of animals and the quality and growth rate of laying hens.

[0006] Since fine silica was discovered relatively recently, its applications have been relatively limited so far. They are mainly some simple applications, and no deep processing or extensive high-quality applications have been carried out. Therefore, it is still necessary to conduct more in-depth research and application development on this fine silica with a natural silica nanorod fiber structure, in order to expand its application fields and enhance its application value. Summary of the Invention

[0007] (1) Technical Problems to be Solved

[0008] The purpose of the present invention is to provide a nano-silica derived from fine silica, its preparation method and application to solve at least one of the above problems, so as to solve the problem that the technology for extracting nano-silica from natural materials in the prior art is limited, and nano-silica with finer particle size cannot be obtained, and the application of fine silica is still relatively limited. The effect is to prepare silica with a diameter of 1 - 3 nm from fine silica and apply it to the preparation of new energy batteries and thermoelectric materials, so as to improve the energy density of lithium batteries, accelerate the charging speed, and reduce the risk of leakage.

[0009] (2) Technical Solutions

[0010] The purpose of the present invention is achieved through the following technical solutions:

[0011] The first aspect of the present invention discloses a preparation method of nano-silica based on fine silica, including the following steps:

[0012] S1: Crush the fine silica ore to obtain coarse particles A;

[0013] S2: Immerse the coarse particles A in an acidic solution, perform low-frequency hammering pulping after immersion, and roughly filter the pulp to obtain filter residue intermediate B;

[0014] S3: Immerse the intermediate B in an alkaline solution, perform secondary pulping in a high-frequency microwave treatment environment to obtain intermediate C;

[0015] S4: Add a surfactant to the intermediate C, perform molecular extrusion and multi-frequency ultrasonic pulping after heating and pressurizing catalysis to obtain intermediate D;

[0016] S5: Centrifuge to separate impurities in the intermediate D, and extract and purify to obtain the nano-silica.

[0017] Furthermore, the fine silica is crushed by any one of a jaw crusher, a hammer crusher, and a roll crusher to obtain coarse particles A with a particle size of 100 - 500 μm.

[0018] Further, the acidic solution is a composite acid solution of hydrochloric acid and sulfuric acid with a pH value of 2 - 4; the alkaline solution is a mixed solution of sodium hydroxide and potassium hydroxide with a pH value of 10 - 12; the surfactant contains 0.5% - 1.2% by mass of sodium dodecylbenzenesulfonate and 0.3% - 0.8% of polyethylene glycol octyl phenyl ether.

[0019] Further, the mass ratio of the coarse particle A to the acidic solution is 1:(3 - 5), preferably 1:5.

[0020] Further, the coarse particle A is soaked in the acidic solution and left to soak at 25 - 40°C for 12 - 15 days.

[0021] Low - frequency hammer - type beating can change the particle size and morphology of the ore, remove impurities on the ore surface and improve the leaching rate. Specifically: through the action of mechanical force, the ore particles are further broken and refined, and at the same time, the morphology of the particles is changed to make them more uniform and regular, which is beneficial to subsequent processing and treatment; during the beating process, the mutual friction and collision between ore particles may remove some impurities and attachments on the ore surface, improving the purity of the ore; at the same time, through low - frequency hammer - type beating, the specific surface area of the ore particles can be increased, enabling the acidic solution to better penetrate into the interior of the ore, thereby improving the leaching efficiency and leaching rate of impurities.

[0022] Further, the vibration frequency of the low - frequency hammer - type beating is 20 - 50 Hz, and the frequency of the high - frequency microwave is 10 - 15 MHz.

[0023] Further, the particle size of the filter residue intermediate B obtained by filtration after low - frequency hammer - type beating is 50 - 100 μm.

[0024] Further, the intermediate B is soaked in the alkaline solution and soaked at 40 - 60°C for 10 - 15 days.

[0025] Further, the treatment time of the secondary beating in the high - frequency microwave treatment environment is 30 - 60 minutes; the role of the high - frequency microwave treatment is to change the ore structure, improve the reaction uniformity and remove impurities. The microwave energy may affect the crystal structure of the ore. Through the collision and energy transfer of small molecules, the crystal structure of the ore is damaged to make it more porous, which is beneficial to subsequent processing and treatment; during the beating process, the collision of high - frequency microwave small molecules can make the ore particles and the alkaline solution mix more evenly, ensuring that each particle can fully contact the reaction medium, improving the uniformity and consistency of the reaction; the collision of small molecules may help to remove impurities on the surface or inside of the ore. Through physical collision and energy action, the impurities are more easily separated and removed, thereby improving the purity of the preparation.

[0026] Further, the conditions for high-temperature and high-pressure catalysis are catalysis under the conditions of a pressure of 0.5 - 2 MPa and a temperature of 80 - 150 °C. Heating and pressurizing catalysis can accelerate the chemical reaction rate and promote the transformation and nanocrystallization of the silica component in the ore.

[0027] Further, after adding a surfactant to the intermediate C, it is catalyzed for 6 - 8 hours under the conditions of a pressure of 0.5 - 2 MPa and a temperature of 80 - 150 °C.

[0028] Adding a surfactant can improve the dispersibility of ore particles in the solution, prevent particle agglomeration, and facilitate uniform reaction in subsequent processing.

[0029] Further, molecular extrusion is achieved by high-frequency microwave treatment, specifically, high-frequency microwave treatment at 1.5 - 2.0 MHz for 30 - 60 minutes.

[0030] Further, the multi-frequency ultrasonic treatment includes the combined action of longitudinal ultrasonic waves with a frequency of 20 kHz and radial ultrasonic waves with a frequency of 40 kHz, and the treatment time is 60 - 90 minutes.

[0031] Further, the centrifugation speed is 3000 - 10000 rpm, and the centrifugation time is 10 - 30 minutes.

[0032] Further, the organic solvent used in the extraction process is ethanol, which is used to remove impurities and leave pure nano-silica.

[0033] Further, the finally prepared nano-silica fiber has a diameter of 1 - 3 nm and a purity of 95% - 99%.

[0034] Further, the soaking time of the coarse particle A and the intermediate B is 10 - 15 days.

[0035] The present invention extracts nano-silica by a method combining physical grinding and chemical dissolution, which combines the advantages of physical extraction and chemical extraction. There is no need to adopt the traditional extraction method of extracting nano-silica by chemical sintering.

[0036] The second technical solution of the present invention lies in providing an application of nano-silica based on dilute fine silica soil, and the nano-silica is used for doping with graphene to prepare a lithium battery anode material.

[0037] Graphene has strong conductivity. Nano-silica realizes a storage mechanism of one silicon - four lithium ions by buffering the volume change during lithium insertion / extraction through micropores, and solves the problems of poor conductivity and volume expansion of a single-material electrode.

[0038] Furthermore, when preparing the anode material of the lithium battery by doping nano-silica and graphene, the battery performance of the lithium battery is better than that of the battery with a pure graphite anode, including the improvement of specific capacity and energy density, and the acceleration of the charging speed.

[0039] Silica nanoparticles with a particle size less than 100 nm can shorten the lithium ion diffusion path and improve the reaction kinetics. The nano-porous structure can buffer the volume expansion and prevent the electrode from pulverization. As a conductive skeleton, the high conductivity of graphene compensates for the insulation of nano-silica and improves the electron transport efficiency. Moreover, the flexible layered structure of graphene can wrap nano-silica and inhibit the volume expansion during charge and discharge.

[0040] (III) Beneficial effects

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] (1) The present invention extracts nano-silica by a method combining physical grinding and chemical dissolution, which combines the advantages of physical extraction and chemical extraction, and obtains nano-silica with a diameter of 1-3 nm, which is much smaller than that in the prior art. The nano-silica with a smaller diameter can be used as a material for electrode preparation, thereby improving the performance of the electrode material.

[0043] (2) The nano-silica prepared by the present invention can be used for doping graphene to prepare the anode in a lithium ion battery. The nano-scale silica particles can shorten the lithium ion diffusion path, improve the lithium ion migration speed, and enhance the reaction kinetics. The porous structure of nano-silica can buffer the volume expansion and prevent the electrode from pulverization. The specific capacity of the lithium ion battery anode made of the nano-silica prepared by the present invention is better than that of a pure graphene anode. The energy density of the full battery is improved, and the charging speed is accelerated. Moreover, the nano-silica can buffer the volume expansion during charge and discharge through the core-shell structure and three-dimensional porous network design, which is beneficial to reducing electrode pulverization and active material shedding, thereby reducing the internal short circuit caused by material fragmentation and reducing the leakage risk. The silica fiber with a diameter of 1-3 nm and a length of 10 nm - 100 nm has an improved storage capacity in the same space by arranging, so as to improve the capacitance. Because the diameter of the particles in the prior art is 80-100 nm and the storage capacity in the same space is not high, the charging capacity is limited.

[0044] (3) The present invention prepares nano-silica from fine silica by the method of physical grinding + solvent decomposition. By combining various physical and chemical treatment means, such as soaking in acidic solution, low-frequency hammering pulping, high-frequency microwave treatment, etc., the reaction efficiency between the ore and the acidic solution and the alkaline solution can be effectively improved, the dissolution of the target components in the ore and the removal of impurities can be accelerated, the efficiency of extracting nano-silica from the ore is increased, and time is saved.

[0045] (4) In the process of preparing nano-silica by the present invention, steps such as multiple pulping, filtration, centrifugal separation, and extraction and purification are carried out, which can effectively remove impurities in the ore, improve the purity of the final product nano-silica, and make it meet the requirements of high-quality standards. From the preliminary crushing of the ore to the final multi-frequency ultrasonic pulping, the particle size of the ore particles is precisely controlled throughout the process, ensuring that the finally obtained nano-silica has a uniform particle size and good dispersibility. Moreover, through steps such as multi-frequency ultrasonic pulping and centrifugal separation, the agglomeration of nano-silica particles can be effectively prevented, ensuring the quality stability and performance consistency of the product, and meeting the requirements of different application fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0047] Figure 1 It is a schematic diagram of the raw material dilute fine silica for nano-silica based on dilute fine silica of the present invention.

[0048] Figure 2 It is a SEM electron micrograph of nano-silica based on dilute fine silica of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0050] The following specific examples illustrate the implementation manners of the present application. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of them. The present application can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope of protection of the present application.

[0051] It should be noted that the following description relates to various aspects of embodiments within the scope of the appended claims. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement a device and / or practice a method. Additionally, this device can be implemented and this method can be practiced using other structures and / or functionality in addition to one or more of the aspects set forth herein.

[0052] In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the examples can be practiced without these specific details.

[0053] The following describes the technical solutions provided by the embodiments of the present application in conjunction with the accompanying drawings.

[0054] Embodiment 1

[0055] Refer to Figure 1 - Figure 2 , the present invention provides a method for preparing nano-silica based on rare fine silica, comprising the following steps:

[0056] S1: Crushing the rare fine silica ore as shown in Figure 1 to obtain coarse particles A with a particle size of 300 μm by a jaw crusher;

[0057] S2: Immersing the coarse particles A in an acidic solution with a pH value of 2 - 4, the mass ratio of the coarse particles A to the acidic solution being 1:5, standing and soaking at 25°C for 15 days, and then performing low-frequency hammering pulping after soaking, with a vibration frequency of 45 Hz, and coarsely filtering the pulp to obtain filter residue intermediate B with a particle size of 50 μm;

[0058] S3: Immersing the intermediate B in an alkaline solution with a pH value of 10 - 12, soaking at 40°C for 15 days, and then performing secondary pulping for 60 minutes in a high-frequency microwave treatment environment, with the frequency of the high-frequency microwave being 10 MHz, to obtain intermediate C;

[0059] S4: Adding a surfactant to the intermediate C, the surfactant containing 0.8% by mass of sodium dodecylbenzenesulfonate and 0.5% by mass of polyethylene glycol octyl phenyl ether, catalyzing for 6 hours under the conditions of a pressure of 1.5 MPa and a temperature of 100°C, and performing molecular extrusion and multi-frequency ultrasonic pulping to obtain intermediate D;

[0060] S5: Centrifuge at 7000 rpm for 10 minutes to separate the impurities in Intermediate D, and extract and purify using the organic solvent ethanol to obtain the nano-silica described above.

[0061] Molecular extrusion is achieved by high-frequency microwave treatment, specifically, high-frequency microwave treatment at 1.5 MHz for 40 minutes.

[0062] The multi-frequency ultrasonic treatment includes the combined action of longitudinal ultrasonic waves with a frequency of 20 kHz and radial ultrasonic waves with a frequency of 40 kHz, and the treatment time is 60 minutes.

[0063] Refer to Figure 2 , and finally the prepared nano-silica fibers have a diameter of 1 - 3 nm and a purity of 95% - 99%.

[0064] The nano-silica prepared in Example 1 is doped with graphene to prepare the negative electrode of a lithium battery. Specifically, after synthesizing nano-silica particles, a graphene shell is coated on the outer surface to form a core-shell structure. Finally, the nano-silica / graphene composite powder is prepared into a slurry and coated on a copper foil current collector to form the negative electrode of the battery.

[0065] Comparative example

[0066] The comparative example selected in the present invention is a commercially available pure graphite negative electrode and a lithium battery equipped with a commercially available pure graphite negative electrode.

[0067] The negative electrode of the lithium battery prepared in Example 1 and the lithium battery equipped with the negative electrode of Example 1 are subjected to performance testing. The results are shown in Table 1. In the table, Example 1* is the measurement data after 100 cycles of Example 1.

[0068] Table 1: Graphene-doped nano-silica negative electrode

[0069]

[0070] As shown in Table 1, for the negative electrode of the lithium battery, with the addition of graphene and nano-silica, the energy density is increased by 30 - 50%, and it supports fast charging at 5C (charged to 80% in 12 minutes), and the charging speed is 10 - 15 minutes. Compared with the graphene negative electrode, the battery performance is improved.

[0071] For the same and similar parts among the various embodiments in this specification, reference can be made to each other. Each embodiment focuses on the differences from other embodiments.

[0072] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing nano-silica based on rare fine silica, characterized in that, It includes the following steps: S1: Crushing the dilute silica ore to obtain coarse particles A; S2: Immersing the coarse particles A in an acidic solution, performing low-frequency hammering-type beating after immersion, and coarsely filtering the slurry to obtain the filter residue intermediate B; S3: Immersing the intermediate B in an alkaline solution, performing secondary beating in a high-frequency microwave treatment environment after immersion to obtain intermediate C; S4: Adding a surfactant to the intermediate C, performing molecular extrusion and multi-frequency ultrasonic beating after heating and pressurizing catalysis to obtain intermediate D; S5: Centrifugally separating the impurities in the intermediate D and extracting and purifying to obtain the nanosilica.

2. The preparation method of nano-silica based on rare fine silica according to claim 1, characterized in that, The acidic solution is a composite acid solution of hydrochloric acid and sulfuric acid with a pH value of 2 - 4; the alkaline solution is a mixed solution of sodium hydroxide and potassium hydroxide with a pH value of 10 - 12; the surfactant contains 0.5% - 1.2% by mass of sodium dodecylbenzenesulfonate and 0.3% - 0.8% of polyethylene glycol octylphenyl ether.

3. The preparation method of nano-silica based on rare fine silica according to claim 2, characterized in that, The mass ratio of the coarse particles A to the acidic solution is 1:(3 - 5).

4. The preparation method of nano-silica based on rare fine silica according to claim 3, characterized in that, The vibration frequency of the low-frequency hammering-type beating is 20 - 50 Hz, and the frequency of the high-frequency microwave is 10 - 15 MHz.

5. The preparation method of nano-silica based on rare fine silica according to claim 4, characterized in that, The conditions for high-temperature and high-pressure catalysis are catalysis under a pressure of 0.5 - 2 MPa and a temperature of 80 - 150 °C.

6. A method for preparing nano-silica based on rare fine silica according to claim 5, characterized in that, The molecular extrusion adopts a three-stage gradient pressurization mode with pressures of 10 MPa, 30 MPa, and 50 MPa in sequence, and the holding time for each stage of pressure is 8 - 12 minutes.

7. A method for preparing nano-silica based on rare fine silica according to claim 6, characterized in that, The multi-frequency ultrasonic treatment includes the combined action of longitudinal ultrasonic waves with a frequency of 20 kHz and radial ultrasonic waves with a frequency of 40 kHz.

8. A method for preparing nano-silica based on rare fine silica according to claim 7, characterized in that, The finally prepared nanosilica fiber has a diameter of 1 - 3 nm.

9. A method for preparing nano-silica based on rare fine silica according to claim 8, characterized in that, The immersion time of the coarse particles A and the intermediate B is 10 - 15 days.

10. An application of nano-silica based on dilute fine silica as described in claim 1, characterized in that, The nanosilica is used for doping with graphene to prepare the anode material of a lithium battery.

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