Preparation method of nanoparticles

Abstract

The invention discloses a preparation method of nanoparticles, which comprises the following steps: mixing raw materials and a first batch of precipitant in reaction equipment, enabling the materials in the reaction equipment to react at the required reaction temperature to obtain first slurry containing the nanoparticles, and performing first concentration treatment on the first slurry to obtain first clear liquid and first concentrated liquid; mixing the first clear liquid with a second batch of precipitant, reacting at the required reaction temperature to obtain a second slurry containing nanoparticles, and performing second concentration treatment on a mixture formed by the second slurry and the first concentrated liquid to obtain a second clear liquid and a second concentrated liquid; repeating the step until the (N-1) th clear liquid reacts with the Nth batch of precipitant at the required reaction temperature to obtain Nth slurry containing nanoparticles, and performing Nth concentration treatment on a mixture formed by the Nth slurry and the (N-1) th concentrated liquid to obtain Nth clear liquid and Nth concentrated liquid; and washing the Nth concentrated solution to obtain the nano-particle dispersion liquid.

Description

Technical Field

[0001] The present invention relates to the technical field of nanoparticle preparation, and more particularly, to a method for preparing nanoparticles. Background Art

[0002] Nanoparticles, also known as ultrafine powders or superfine powders, generally refer to particles with a particle size below 100 nm. They are a kind of solid particle material in an intermediate physical state between atoms, molecules and macroscopic objects, and have specific surface effects, small size effects, volume effects, quantum size effects and macroscopic quantum tunneling effects, and are widely used. The preparation methods of nanoparticles can be classified into physical methods, chemical methods and physicochemical methods according to whether a chemical reaction occurs, and can be divided into three categories: solid phase method, liquid phase method and gas phase method according to the state of materials in the reaction process.

[0003] The liquid phase method is a method widely used in laboratories and industries for preparing nanoparticles. Nanoparticles can be prepared through a simple solution process without the need for complex instruments. Precipitation method, hydrothermal method, solution evaporation method, solution gel method, radiation chemical synthesis method, etc. are all common liquid phase methods.

[0004] Among them, the precipitation method has a simple process and the obtained nanoparticles have good properties. It is the most widely used method for liquid phase chemical synthesis of high-purity nanoparticles. The precipitation method is to add a precipitant to a raw material solution containing the target element for a precipitation reaction, collect the precipitate and wash it to obtain nanoparticles or further heat and decompose to obtain nanoparticles. However, there are still many problems to be solved in preparing nanoparticles by the precipitation method. For example, the particle size uniformity, purity and stability of nanoparticles need to be further improved. Summary of the Invention

[0005] The main object of the present invention is to provide a reaction unit, a concentration unit, a washing unit, a nanoparticle production system, a nanoparticle preparation method, a pretreatment method for sodium silicate, a sodium silicate pretreatment unit, a method for preparing nano-silica and a nano-silica production system to solve the technical problems of poor particle size uniformity, purity and stability of nanoparticles in the prior art.

[0006] To achieve the above object, according to the first aspect of the present invention, a reaction unit is provided, and the technical solution is as follows:

[0007] Reaction unit, used to react raw materials and precipitants to generate a slurry containing nanoparticles, including: a reaction device, used to react the mixed raw materials and precipitants at a certain temperature to generate a slurry containing nanoparticles; a mixing device, used to mix the raw materials and precipitants and then flow them into the reaction device; the mixing device includes a dispersion membrane, and the precipitant is dispersed by the dispersion membrane and then mixed with the raw materials flowing along the surface of the dispersion membrane; wherein, the mixing device includes: a dispersion membrane cylinder, which is formed by rolling up the dispersion membrane, and a raw material flow channel is formed inside the dispersion membrane cylinder; a dispersion membrane support cylinder, and an annular precipitant flow gap is formed between the inner wall of the dispersion membrane support cylinder and the outer wall of the dispersion membrane cylinder.

[0008] As a further improvement of the above reaction unit: the dispersion membrane is a microfiltration membrane.

[0009] As a further improvement of the above reaction unit: the dispersion membrane is a microfiltration membrane with a filtration pore size of 4 - 6 μm.

[0010] As a further improvement of the above reaction unit: the precipitant inlet of the precipitant flow gap is located at the lower part of the precipitant flow gap; a precipitant feed pump is provided on the precipitant feed pipe.

[0011] As a further improvement of the above reaction unit: the ratio of the diameter of the raw material flow channel to the thickness of the precipitant flow gap is (4 - 10):1.

[0012] As a further improvement of the above reaction unit: the mixing device further includes: a mixing feed pipe, the inlet of which is connected to the bottom of the reaction device, and the outlet is connected to the bottom of the raw material flow channel; a mixing discharge pipe, the inlet of which is connected to the top of the raw material flow channel, and the outlet is connected to the upper part of the reaction device; before mixing is completed, the raw materials circulate in the reaction device, the mixing feed pipe, the raw material flow channel and the mixing discharge pipe.

[0013] As a further improvement of the above reaction unit: a raw material circulation pump is provided on the mixing feed pipe.

[0014] As a further improvement of the above reaction unit: a liquid level gauge, a stirrer and a clarity detector are provided inside the reaction device.

[0015] As a further improvement of the above reaction unit: it further includes a heating device for heating the reaction device.

[0016] The reaction unit of the present invention is not only simple in structure and convenient to use, but also the mixing device disperses the precipitant into droplet form through the dispersion membrane, significantly improving the mixing effect of the precipitant and the raw materials, thereby helping to improve the particle size uniformity and stability of the nanoparticles.

[0017] To achieve the above object, according to the second aspect of the present invention, a concentration unit is provided, and the technical solution is as follows:

[0018] The concentration unit is used for concentrating the slurry containing nanoparticles, and includes: a concentration intermediate tank for receiving the slurry containing nanoparticles and temporarily storing the concentrated thick liquid; a concentration device for concentrating the slurry in the concentration intermediate tank; the concentration device includes a concentration membrane, and after the slurry is filtered through the concentration membrane, a thick liquid and a clear liquid are obtained, and the thick liquid flows back into the concentration intermediate tank; wherein, the concentration device includes: a concentration membrane cylinder, which is formed by winding the concentration membrane, and a slurry flow channel is formed inside the concentration membrane cylinder; a concentration membrane support cylinder, and an annular clear liquid flow gap is formed between the inner wall of the concentration membrane support cylinder and the outer wall of the concentration membrane cylinder.

[0019] As a further improvement of the above concentration unit: the filtration pore diameter of the concentration membrane is 3-5 nm.

[0020] As a further improvement of the above concentration unit: the clear liquid outlet of the clear liquid flow gap is located at the upper part of the clear liquid flow gap.

[0021] As a further improvement of the above concentration unit: the clear liquid outlet is connected to a first three-way valve, one outlet is connected to the reaction device for generating the slurry through a clear liquid return pipe, and the other outlet is connected to a wastewater treatment unit.

[0022] As a further improvement of the above concentration unit: the ratio of the diameter of the slurry flow channel to the thickness of the clear liquid flow gap is (2-6):1.

[0023] As a further improvement of the above concentration unit: the concentration device further includes: a concentration feed pipe, the inlet of the concentration feed pipe is connected to the bottom of the concentration intermediate tank, and the outlet is connected to the bottom of the slurry flow channel; a concentration discharge pipe, the inlet of the concentration discharge pipe is connected to the top of the slurry flow channel, and the outlet is connected to the upper part of the concentration intermediate tank; before the concentration is completed, the slurry circulates in the concentration intermediate tank, the concentration feed pipe, the slurry flow channel and the concentration discharge pipe.

[0024] As a further improvement of the above concentration unit: a slurry circulation pump is provided on the concentration feed pipe.

[0025] As a further improvement of the above concentration unit: a liquid level gauge and a stirrer are provided in the concentration intermediate tank.

[0026] The structure of the concentration unit of the present invention is simple and convenient to use. On the one hand, the slurry is concentrated by the concentration membrane to reduce the processing volume of the subsequent washing unit, improve the washing efficiency, and thus improve the purity of the nanoparticles. On the other hand, the clear liquid passing through the concentration membrane can be refluxed to the reaction equipment for continuous reaction, which not only makes the particle size of the nanoparticles in the reaction equipment more uniform and the particle diameter smaller, but also can improve the raw material utilization rate.

[0027] To achieve the above object, according to the third aspect of the present invention, a washing unit is provided, and the technical solution is as follows:

[0028] The washing unit is used for washing the concentrated liquid containing nanoparticles, and includes: a washing intermediate tank for receiving the washing pulp composed of washing water and the concentrated liquid; a filtering device for filtering the washing pulp in the washing intermediate tank; the filtering device includes a filtering membrane, and after the washing pulp is filtered by the filtering membrane, a nanoparticle dispersion liquid and washing water are obtained; wherein, the filtering device includes: a filtering membrane cylinder formed by winding the filtering membrane, and a washing pulp flow channel is formed inside the filtering membrane cylinder; a filtering membrane support cylinder, and an annular washing water flow gap is formed between the inner wall of the filtering membrane support cylinder and the outer wall of the filtering membrane cylinder.

[0029] As a further improvement of the above washing unit: the filtering aperture of the concentration membrane is 2 - 4 nm.

[0030] As a further improvement of the above washing unit: the washing water outlet of the washing water flow gap is located at the upper part of the washing water flow gap; the washing water outlet is connected to the wastewater treatment unit.

[0031] As a further improvement of the above washing unit: the ratio of the diameter of the washing pulp flow channel to the thickness of the washing water flow gap is (4 - 7):1.

[0032] As a further improvement of the above washing unit: the outlet of the washing pulp flow channel is connected to a second three-way valve, one outlet is connected to the washing intermediate tank, and the other outlet is connected to the nanoparticle dispersion liquid storage tank.

[0033] As a further improvement of the above washing unit: an inlet valve is provided on the washing water inlet pipe, an ion detector is provided on the washing water discharge pipe, the inlet valve opens and closes according to the detection value of the ion detector, and the two outlets of the second three-way valve are switched according to the detection value of the ion detector.

[0034] As a further improvement of the above-mentioned washing unit: the filtration device further includes: a filtration feed pipe, the inlet of the filtration feed pipe is connected to the bottom of the washing intermediate tank, and the outlet is connected to the bottom of the pulp washing flow channel; a filtration discharge pipe, the inlet of the filtration discharge pipe is connected to the top of the pulp washing flow channel, and the outlet is connected to the second three-way valve; before the washing is completed, the pulp being washed circulates in the washing intermediate tank, the filtration feed pipe, the pulp washing flow channel and the filtration discharge pipe.

[0035] As a further improvement of the above-mentioned washing unit: a pulp washing circulation pump is provided on the filtration feed pipe.

[0036] As a further improvement of the above-mentioned washing unit: a liquid level gauge and a stirrer are provided in the washing intermediate tank.

[0037] The structure of the washing unit of the present invention is simple and convenient to use. By circulating and filtering the pulp being washed in a flowing state through the filter membrane, the amount of washing water used can be reduced, the washing efficiency can be improved, thereby improving the purity of the nanoparticles. Moreover, the filter membrane can also concentrate the nanoparticle dispersion after the washing is completed, reducing the efficiency of subsequent nanoparticle powder making.

[0038] In order to achieve the above object, according to the fourth aspect of the present invention, a production system for nanoparticles is provided, and the technical solution is as follows:

[0039] The first production system for nanoparticles includes any several of the reaction unit described in the first aspect above, the concentration unit described in the second aspect, and the washing unit described in the third aspect above.

[0040] The second production system for nanoparticles includes: a reaction unit for reacting a raw material and a precipitant to generate a slurry containing nanoparticles; a concentration unit for concentrating the slurry to output a clear liquid and a concentrated liquid; a washing unit for washing the concentrated liquid to output a nanoparticle dispersion; wherein, the reaction unit includes: a reaction device for reacting the mixed raw material and precipitant at a certain temperature to generate a slurry containing nanoparticles; a mixing device for mixing the raw material and the precipitant and then flowing them into the reaction device; the mixing device includes a dispersion membrane, and the precipitant is dispersed by the dispersion membrane and then mixed with the raw material flowing along the surface of the dispersion membrane.

[0041] As a further improvement of the above-mentioned second production system for nanoparticles: the mixing device includes: a dispersion membrane cylinder formed by winding a dispersion membrane, and a raw material flow channel is formed inside the dispersion membrane cylinder; a dispersion membrane support cylinder, and an annular precipitant flow gap is formed between the inner wall of the dispersion membrane support cylinder and the outer wall of the dispersion membrane cylinder.

[0042] As a further improvement to the production system of the second type of nanoparticles described above: The mixing device further includes: a mixing feed pipe, the inlet of the mixing feed pipe is connected to the bottom of the reaction device, and the outlet is connected to the bottom of the raw material flow channel; a mixing discharge pipe, the inlet of the mixing discharge pipe is connected to the top of the raw material flow channel, and the outlet is connected to the upper part of the reaction device; the raw materials circulate in the reaction device, the mixing feed pipe, the raw material flow channel, and the mixing discharge pipe.

[0043] As a further improvement to the production system of the second type of nanoparticles described above: The concentration unit includes: a concentration intermediate tank for receiving the slurry in the reaction device and temporarily storing the concentrated thick liquid; a concentration device for concentrating the slurry in the concentration intermediate tank; the concentration device includes a concentration membrane, and after the slurry is filtered through the concentration membrane, a thick liquid and a clear liquid are obtained, and the thick liquid flows back into the concentration intermediate tank.

[0044] As a further improvement to the production system of the second type of nanoparticles described above: A clear liquid return pipe is provided between the clear liquid outlet of the concentration device and the reaction device; a feeding pipe for adding an additive and / or dilution water to prevent nanoparticle aggregation into the concentration intermediate tank is also included.

[0045] As a further improvement to the production system of the second type of nanoparticles described above: The concentration device includes: a concentration membrane cylinder formed by winding a concentration membrane, and a slurry flow channel is formed inside the concentration membrane cylinder; a concentration membrane support cylinder, and an annular clear liquid flow gap is formed between the inner wall of the concentration membrane support cylinder and the outer wall of the concentration membrane cylinder.

[0046] As a further improvement to the production system of the second type of nanoparticles described above: The washing unit includes: a washing intermediate tank for receiving the washing pulp composed of washing water and thick liquid; a filtering device for filtering the washing pulp in the washing intermediate tank; the filtering device includes a filtering membrane, and after the washing pulp is filtered through the filtering membrane, a nanoparticle dispersion liquid and washing water are obtained.

[0047] As a further improvement to the production system of the second type of nanoparticles described above: The filtering device includes: a filtering membrane cylinder formed by winding a filtering membrane, and a washing pulp flow channel is formed inside the filtering membrane cylinder; a filtering membrane support cylinder, and an annular washing water flow gap is formed between the inner wall of the filtering membrane support cylinder and the outer wall of the filtering membrane cylinder.

[0048] As a further improvement to the production system of the second type of nanoparticles described above: A liquid level gauge and a stirrer are provided in the reaction device, the concentration intermediate tank, and the washing intermediate tank.

[0049] The production system of the third type of nanoparticles includes: a reaction unit for reacting raw materials and a precipitant to generate a slurry containing nanoparticles; a concentration unit for concentrating the slurry and outputting a supernatant and a concentrated liquid; a washing unit for washing the concentrated liquid and outputting a nanoparticle dispersion; wherein, the reaction unit includes reaction equipment; the concentration unit includes concentration equipment; a slurry feed pipe for flowing the slurry into the concentration equipment is provided between the reaction equipment and the concentration equipment; a supernatant return pipe for returning the supernatant to the reaction equipment is provided between the reaction equipment and the concentration equipment; a clarity detector is provided on the reaction equipment, the concentration equipment or the slurry feed pipe; a return valve is provided on the supernatant return pipe; the feed valve and / or the return valve are opened and closed according to the detection value of the clarity detector.

[0050] As a further improvement of the production system of the third type of nanoparticles described above: the supernatant outlet of the concentration equipment is connected to a first three-way valve, one outlet is connected to the reaction equipment through the supernatant return pipe, and the other outlet is connected to a wastewater treatment unit.

[0051] As a further improvement of the production system of the third type of nanoparticles described above: the reaction unit further includes a mixing device for mixing the raw materials and the precipitant and then flowing them into the reaction equipment.

[0052] As a further improvement of the production system of the third type of nanoparticles described above: the mixing device includes: a dispersion membrane cylinder formed by rolling a dispersion membrane, and a raw material flow channel is formed inside the dispersion membrane cylinder; a dispersion membrane support cylinder, and an annular precipitant flow gap is formed between the inner wall of the dispersion membrane support cylinder and the outer wall of the dispersion membrane cylinder.

[0053] As a further improvement of the production system of the third type of nanoparticles described above: the mixing device further includes: a mixing feed pipe, the inlet of which is connected to the bottom of the reaction equipment and the outlet is connected to the bottom of the raw material flow channel; a mixing discharge pipe, the inlet of which is connected to the top of the raw material flow channel and the outlet is connected to the upper part of the reaction equipment; before mixing is completed, the raw materials circulate in the reaction equipment, the mixing feed pipe, the raw material flow channel and the mixing discharge pipe.

[0054] As a further improvement of the production system of the third type of nanoparticles described above: the concentration unit further includes a concentration intermediate tank for receiving the slurry in the reaction equipment and temporarily storing the concentrated liquid, and the concentration equipment is used for concentrating the slurry in the concentration intermediate tank.

[0055] As a further improvement to the production system of the third type of nanoparticles described above: The concentration device includes: a concentration membrane cylinder, which is formed by winding a concentration membrane, and a slurry flow channel is formed inside the concentration membrane cylinder; a concentration membrane support cylinder, and an annular clear liquid flow gap is formed between the inner wall of the concentration membrane support cylinder and the outer wall of the concentration membrane cylinder.

[0056] As a further improvement to the production system of the third type of nanoparticles described above: The washing unit includes: a washing intermediate tank for receiving the pulp to be washed composed of washing water and thick liquid; a filtering device for filtering the pulp to be washed in the washing intermediate tank; the filtering device includes a filtering membrane, and after the pulp to be washed is filtered through the filtering membrane, a nanoparticle dispersion and washing water are obtained.

[0057] As a further improvement to the production system of the third type of nanoparticles described above: The filtering device includes: a filtering membrane cylinder, which is formed by winding a filtering membrane, and a pulp to be washed flow channel is formed inside the filtering membrane cylinder; a filtering membrane support cylinder, and an annular washing water flow gap is formed between the inner wall of the filtering membrane support cylinder and the outer wall of the filtering membrane cylinder.

[0058] As a further improvement to the production system of the third type of nanoparticles described above: The outlet of the pulp to be washed flow channel is connected to a second three-way valve, one outlet is connected to the washing intermediate tank, and the other outlet is connected to the nanoparticle dispersion storage tank; the washing water outlet of the washing water flow gap is connected to the wastewater treatment unit.

[0059] In addition to having the advantages of the reaction unit described in the first aspect, the concentration unit described in the second aspect, and the washing unit described in the third aspect above, the production system of the third type of nanoparticles of the present invention can significantly improve the concentration effect and stability by controlling the concentration degree and the clear liquid return flow rate through the numerical value of the clarity detector, which not only prevents excessive nanoparticles from remaining in the reaction equipment and continuing to grow in subsequent reactions, resulting in uneven particle size distribution of the nanoparticle product, but also enables as much raw material as possible to return to the reaction equipment for reaction to improve the raw material utilization rate. The above three production systems of nanoparticles are particularly suitable for producing nano-silica.

[0060] To achieve the above object, according to the fifth aspect of the present invention, a method for preparing nanoparticles is provided, and the technical solution is as follows:

[0061] A method for preparing nanoparticles, comprising the following steps:

[0062] Calculate the precipitant required according to the complete precipitation of the target element in the raw material, and add the precipitant in N batches, where N≥2;

[0063] Mix the raw materials with the first batch of precipitant in a reaction device, and react the materials in the reaction device at the required reaction temperature to obtain a first slurry containing nanoparticles. Perform a first concentration treatment on the first slurry to obtain a first clear liquid and a first concentrated liquid.

[0064] Mix the first clear liquid with the second batch of precipitant, and react at the required reaction temperature to obtain a second slurry containing nanoparticles. Perform a second concentration treatment on the mixture composed of the second slurry and the first concentrated liquid to obtain a second clear liquid and a second concentrated liquid; repeat this step until the (N - 1)th clear liquid reacts with the Nth batch of precipitant at the required reaction temperature to obtain the Nth slurry containing nanoparticles, and perform the Nth concentration treatment on the mixture composed of the Nth slurry and the (N - 1)th concentrated liquid to obtain the Nth clear liquid and the Nth concentrated liquid.

[0065] Perform a washing treatment on the Nth concentrated liquid to obtain a nanoparticle dispersion liquid.

[0066] As a further improvement of the above method for preparing nanoparticles: Add the corresponding batch of precipitant in a dispersed state to the materials when the materials are in a circulating flow state.

[0067] As a further improvement of the above method for preparing nanoparticles: The flow rate of the materials is 1.5 - 8 m / s, each batch of precipitant is added within 5 - 20 minutes, a dispersion membrane is used to disperse the precipitant, and the direction in which the precipitant passes through the dispersion membrane is perpendicular to the flow direction of the materials.

[0068] As a further improvement of the above method for preparing nanoparticles: For the first to (N - 1)th concentration treatments, the slurry in the reaction device flows into the concentration device at a certain flow rate, and the clear liquid output from the concentration device continuously flows back to the reaction device until the clarity of the slurry in the reaction device reaches the required level and then the concentration stops; for the Nth concentration, the clear liquid output from the concentration device does not flow back to the reaction device.

[0069] As a further improvement of the above method for preparing nanoparticles: It also includes adding an additive and / or dilution water to prevent nanoparticle aggregation to the reaction device once or in batches after mixing the raw materials with the first batch of precipitant, and then heating to the reaction temperature.

[0070] As a further improvement of the above method for preparing nanoparticles: The volume of the dilution water is 0.58 - 0.63 times the volume of the raw materials.

[0071] As a further improvement of the above method for preparing nanoparticles: The feeding speed of the previous batch of precipitant is greater than that of the next batch of precipitant.

[0072] As a further improvement of the above method for preparing nanoparticles: N = 3.

[0073] As a further improvement to the method for preparing the above-mentioned nanoparticles: Addition amount: The second batch of precipitant > the first batch of precipitant > the third batch of precipitant.

[0074] As a further improvement to the method for preparing the above-mentioned nanoparticles: The total amount of the precipitant consists of 30 - 40% of the first batch of precipitant, 40 - 50% of the second batch of precipitant, and the remaining amount of the third batch of precipitant.

[0075] In the method for preparing the nanoparticles of the present invention, by adding the precipitant in batches, the target elements in the raw materials also nucleate and grow in batches, thereby significantly improving the uniformity of the nanoparticles and enhancing the stability of the reaction process. After the slurry is concentrated in batches and iteratively and then washed, the amount of washing water can be significantly reduced, and a good washing effect can be ensured, improving the purity of the nanoparticles. The above-mentioned method for preparing nanoparticles is particularly suitable for producing nano-silica.

[0076] To achieve the above object, according to the sixth aspect of the present invention, a pretreatment method and a pretreatment unit for water glass are provided, and the technical solution is as follows:

[0077] The pretreatment method for water glass includes the following steps:

[0078] (1) Dilute concentrated water glass with water to obtain dilute water glass;

[0079] (2) Add pasty calcium peroxide to the diluted glass to obtain a mixture;

[0080] (3) Perform heat treatment on the mixture to obtain a solid-liquid mixture;

[0081] (4) Perform cooling treatment on the solid-liquid mixture;

[0082] (5) Perform solid-liquid separation treatment on the cooled solid-liquid mixture, and water glass is obtained.

[0083] As a further improvement to the above-mentioned pretreatment method for water glass: In step (1), the concentrated water glass is prepared using soda ash and has a mass dispersion of 27 - 30%.

[0084] As a further improvement to the above-mentioned pretreatment method for water glass: In step (2), first heat the dilute water glass to 55 - 65 °C, and then add pasty calcium peroxide.

[0085] As a further improvement to the above-mentioned pretreatment method for water glass: In step (2), the pasty calcium peroxide is prepared according to a ratio of containing 500 - 1000 g per liter of water.

[0086] As a further improvement of the above pretreatment method of sodium silicate: in step (2), the dosage of calcium peroxide in each liter of dilute sodium silicate is 0.5 - 1.5 g.

[0087] As a further improvement of the above pretreatment method of sodium silicate: in step (3), the heat treatment is stirring at 85 - 95 °C for 3 - 7 min.

[0088] As a further improvement of the above pretreatment method of sodium silicate: in step (4), the cooling treatment is adding cooling water to the solid-liquid mixture to cool down after the heat treatment is completed.

[0089] As a further improvement of the above pretreatment method of sodium silicate: in step (4), add cooling water until the temperature of the solid-liquid mixture drops to 35 - 45 °C.

[0090] As a further improvement of the above pretreatment method of sodium silicate: in step (5), the mass fraction of sodium silicate is 5 - 15%.

[0091] The sodium silicate pretreatment unit includes: an alkali reaction vessel; a concentrated sodium silicate feeding pipe for inputting concentrated sodium silicate into the alkali reaction vessel; a paste calcium peroxide feeding pipe for inputting paste calcium peroxide into the alkali reaction vessel; a first water adding pipe for inputting dilution water into the alkali reaction vessel; a second water adding pipe for inputting cooling water into the alkali reaction vessel; a heating device for heating the alkali reaction vessel; and a filtering device for filtering the solid-liquid mixture generated in the alkali reaction vessel to obtain sodium silicate.

[0092] As a further improvement of the above sodium silicate pretreatment unit: a temperature detector is provided inside the alkali reaction vessel.

[0093] As a further improvement of the above sodium silicate pretreatment unit: a first valve is provided on the second water adding pipe, and the first valve closes according to the detection data of the temperature detector.

[0094] As a further improvement of the above sodium silicate pretreatment unit: a second valve is provided on the paste calcium peroxide feeding pipe, and the second valve closes according to the detection data of the temperature detector.

[0095] As a further improvement of the above sodium silicate pretreatment unit: a liquid level gauge is provided inside the alkali reaction vessel.

[0096] As a further improvement of the above sodium silicate pretreatment unit: a stirrer is provided inside the alkali reaction vessel.

[0097] As a further improvement of the above sodium silicate pretreatment unit: the filtering device includes a plate and frame filter press and a precision filter connected in sequence.

[0098] As a further improvement of the above sodium silicate pretreatment unit: it further includes a sodium silicate storage tank for storing sodium silicate.

[0099] As a further improvement of the above sodium silicate pretreatment unit: it further includes a stirring tank, and the stirring tank is used for stirring calcium peroxide and water to form a paste-like calcium peroxide.

[0100] The pretreatment method and pretreatment unit of sodium silicate of the present invention can purify sodium silicate, reduce impurities, and thus effectively improve the purity of sodium silicate.

[0101] In order to achieve the above object, according to the seventh aspect of the present invention, a method for preparing nano-silica and a production system for nano-silica are provided, and the technical solutions are as follows:

[0102] The first method for preparing nano-silica includes the following steps:

[0103] Calculate the required acid solution according to the complete precipitation of silicon elements in the raw materials, and add the acid solution in three batches; the raw materials include sodium silicate;

[0104] Mix the raw materials with the first batch of acid solution in a reaction device, and make the materials in the reaction device react at the required reaction temperature to obtain a first slurry;

[0105] Mix the first slurry with the second batch of acid solution and react at the required reaction temperature to obtain a second slurry;

[0106] Mix the second slurry with the third batch of acid solution and react at the required reaction temperature to obtain a third slurry;

[0107] Wash the third slurry to obtain a nano-silica dispersion.

[0108] The first method for preparing nano-silica includes the following steps:

[0109] Calculate the required acid solution according to the complete precipitation of silicon elements in the raw materials, and add the acid solution in three batches; the raw materials include sodium silicate;

[0110] Mix the raw materials with the first batch of acid solution in a reaction device, and make the materials in the reaction device react at the required reaction temperature to obtain a first slurry, and perform a first concentration treatment on the first slurry to obtain a first clear liquid and a first concentrated liquid;

[0111] Mix the first clear liquid with the second batch of acid solution and react at the required reaction temperature to obtain a second slurry, and perform a second concentration treatment on the mixture composed of the second slurry and the first concentrated liquid to obtain a second clear liquid and a second concentrated liquid;

[0112] Mix the second supernatant with the acid solution of the third batch and react at the required reaction temperature to obtain the third slurry. Perform a third concentration treatment on the mixture composed of the third slurry and the second concentrated solution to obtain the third supernatant and the third concentrated solution;

[0113] Wash the third concentrated solution to obtain the nano-silica dispersion.

[0114] As a further improvement of the above two methods for preparing nano-silica: the total amount of the acid solution consists of 30 - 40% of the acid solution of the first batch, 40 - 50% of the acid solution of the second batch, and the remaining acid solution of the third batch.

[0115] As a further improvement of the above two methods for preparing nano-silica: the acid solution includes sulfuric acid and oxalic acid.

[0116] As a further improvement of the above two methods for preparing nano-silica: the acid solution is prepared by containing 3 - 10 g of oxalic acid in 5 - 15% by mass of dilute sulfuric acid per liter.

[0117] As a further improvement of the above two methods for preparing nano-silica: the reaction temperature after the addition of each batch of acid solution is 85 - 95 °C, and the reaction time is 10 - 30 minutes.

[0118] As a further improvement of the above two methods for preparing nano-silica: add dilution water to the reaction equipment at one time after mixing the raw materials with the acid solution of the first batch, and then heat to the reaction temperature.

[0119] As a further improvement of the above two methods for preparing nano-silica: the volume of the dilution water is 0.58 - 0.63 times the volume of the raw materials.

[0120] As a further improvement of the above two methods for preparing nano-silica: the raw materials are obtained by pretreating concentrated water glass with a mass fraction of 27 - 30%.

[0121] As a further improvement of the above two methods for preparing nano-silica: treat concentrated water glass with calcium peroxide and dilute to obtain water glass with a mass fraction of 5 - 15%.

[0122] Production system of nano-silica, comprising: a water glass pretreatment unit for purifying concentrated water glass and outputting water glass; a reaction unit for reacting water glass with acid solution to generate a slurry containing nano-silica; a washing unit for washing the slurry to obtain a nano-silica dispersion; wherein, the washing unit includes: a washing intermediate tank for receiving a pulp wash composed of washing water and the slurry; a filtering device for filtering the pulp wash in the washing intermediate tank; the filtering device includes a filter membrane, and after the pulp wash is filtered through the filter membrane, a nano-particle dispersion and wash water are obtained.

[0123] As a further improvement of the above production system of nano-silica: it further includes an acid solution pretreatment unit for treating sulfuric acid and oxalic acid to obtain acid solution; the acid solution pretreatment unit includes: an acid reaction container; a concentrated sulfuric acid feeding pipe for inputting concentrated sulfuric acid into the acid reaction container; an oxalic acid feeding pipe for inputting oxalic acid into the acid reaction container; a third water adding pipe for inputting dilution water into the acid reaction container.

[0124] As a further improvement of the above production system of nano-silica: a liquid level gauge and a stirrer are provided in the acid reaction container; it further includes an acid solution storage tank for storing the acid solution.

[0125] As a further improvement of the above production system of nano-silica: the water glass pretreatment unit includes: an alkali reaction container; a concentrated water glass feeding pipe for inputting concentrated water glass into the alkali reaction container; a pasty calcium peroxide feeding pipe for inputting pasty calcium peroxide into the alkali reaction container; a first water adding pipe for inputting dilution water into the alkali reaction container; a second water adding pipe for inputting cooling water into the alkali reaction container; a heating device for heating the alkali reaction container; a filtering device for filtering the solid-liquid mixture generated in the alkali reaction container to obtain water glass.

[0126] As a further improvement of the above production system of nano-silica: a temperature detector, a liquid level gauge and a stirrer are provided in the alkali reaction container.

[0127] As a further improvement of the above production system of nano-silica: a first valve is provided on the second water adding pipe, and the first valve closes according to the detection data of the temperature detector; and / or, a second valve is provided on the pasty calcium peroxide feeding pipe, and the second valve closes according to the detection data of the temperature detector.

[0128] As a further improvement of the above production system of nano-silica: the filtering device includes: a filter membrane cylinder formed by winding a filter membrane, and a pulp wash flow channel is formed inside the filter membrane cylinder; a filter membrane support cylinder, and an annular wash water flow gap is formed between the inner wall of the filter membrane support cylinder and the outer wall of the filter membrane cylinder.

[0129] As a further improvement of the above production system of nano-silica: the filtering device further comprises: a filtering feed pipe, the inlet of which is connected to the bottom of the washing intermediate tank, and the outlet is connected to the bottom of the pulp washing flow channel; a filtering discharge pipe, the inlet of which is connected to the top of the pulp washing flow channel, and the outlet is connected to the second three-way valve; before the washing is completed, the pulp to be washed circulates in the washing intermediate tank, the filtering feed pipe, the pulp washing flow channel and the filtering discharge pipe.

[0130] As a further improvement of the above production system of nano-silica: a liquid level gauge and a stirrer are provided in the washing intermediate tank.

[0131] As a further improvement of the above production system of nano-silica: the stirrer comprises an ultrasonic dispersion device and a high-speed homogenizer; and a chelating agent feed pipe is further included.

[0132] The preparation method and production system of nano-silica of the present invention can have the advantages of the preparation method and production system of the nano-particles described in the above fifth aspect and the advantages of the pretreatment method and pretreatment unit of water glass described in the sixth aspect. It has been verified that the particle size distribution of the obtained nano-silica is in the range of 5 to 20 nanometers, the particles are in a regular spherical structure and are uniform, and the purity is as high as 99.8%.

[0133] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. The additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0134] The accompanying drawings forming a part of the present invention are used to assist in understanding the present invention. The content provided in the accompanying drawings and the related description in the present invention can be used to explain the present invention, but do not constitute an improper limitation to the present invention. In the accompanying drawings:

[0135] Figure 1 It is a schematic structural diagram of an embodiment of the reaction unit of the present invention.

[0136] Figure 2 It is a schematic structural diagram of the mixing device in the embodiment of the reaction unit of the present invention.

[0137] Figure 3 It is a schematic structural diagram of an embodiment of the concentration unit of the present invention.

[0138] Figure 4 It is a schematic structural diagram of the concentration device in the embodiment of the concentration unit of the present invention.

[0139] Figure 5Schematic structural diagram of the first embodiment of the washing unit of the present invention.

[0140] Figure 6 Schematic structural diagram of the filtering device in the first embodiment of the washing unit of the present invention.

[0141] Figure 7 Schematic structural diagram of the second embodiment of the washing unit of the present invention.

[0142] Figure 8 Schematic structural diagram of the first embodiment of the production system of the nanoparticles of the present invention.

[0143] Figure 9 Schematic structural diagram of the second embodiment of the production system of the nanoparticles of the present invention.

[0144] Figure 10 Schematic structural diagram of the third embodiment of the production system of the nanoparticles of the present invention.

[0145] Figure 11 Schematic structural diagram of the sodium silicate pretreatment unit of the present invention.

[0146] Figure 12 Schematic structural diagram of the acid solution pretreatment unit in the embodiment of the production system of the nano-silica of the present invention.

[0147] The relevant marks in the above-mentioned drawings are as follows:

[0148] 110 - Reaction equipment, 120 - Mixing equipment, 121 - Dispersion membrane cylinder, 122 - Raw material flow channel, 123 - Dispersion membrane support cylinder, 124 - Precipitant flow gap, 125 - Precipitant inlet, 130 - Mixing feed pipe, 131 - Raw material circulation pump, 140 - Mixing discharge pipe, 150 - Precipitant feed pipe, 151 - Precipitant feed pump, 210 - Concentration intermediate tank, 220 - Concentration equipment, 221 - Concentration membrane cylinder, 222 - Slurry flow channel, 223 - Concentration membrane support cylinder, 224 - Clear liquid flow gap, 225 - Clear liquid outlet, 230 - Concentration feed pipe, 231 - Slurry circulation pump, 240 - Concentration discharge pipe, 250 - First three - way valve, 260 - Slurry feed pipe, 261 - Slurry feed pump, 270 - Clear liquid return pipe, 310 - Washing intermediate tank, 311 - Ultrasonic dispersion device, 312 - High - speed homogenizer, 320 - Filtration equipment, 321 - Filtration membrane cylinder, 322 - Wash pulp flow channel, 323 - Filtration membrane support cylinder, 324 - Wash water flow gap, 325 - Wash water outlet, 330 - Filtration feed pipe, 331 - Wash pulp circulation pump, 340 - Filtration discharge pipe, 350 - Second three - way valve, 360 - Washing water inlet pipe, 370 - Chelating agent feeding pipe, 380 - Concentrated liquid feed pipe, 381 - Concentrated liquid feed pump, 410 - Alkali reaction vessel, 420 - Concentrated sodium silicate feeding pipe, 430 - Pasty calcium peroxide feeding pipe, 440 - First water adding pipe, 450 - Second water adding pipe, 460 - Filtration device, 470 - Sodium silicate storage tank, 510 - Acid reaction vessel, 520 - Concentrated sulfuric acid feeding pipe, 530 - Oxalic acid feeding pipe, 540 - Third water adding pipe, 550 - Acid liquid storage tank. Detailed implementation mode

[0149] The present invention will be described clearly and completely below with reference to the accompanying drawings. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. Before describing the present invention with reference to the accompanying drawings, it should be particularly noted that:

[0150] The technical solutions and technical features provided in each part including the following description in the present invention can be combined with each other without conflict.

[0151] In addition, the embodiments of the present invention involved in the following description are usually only part of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0152] Regarding the terms and units in the present invention. The terms "including", "having" and any variations thereof in the description, claims and relevant parts of the present invention are intended to cover non - exclusive inclusion.

[0153] Figure 1 This is a schematic structural diagram of an embodiment of the reaction unit of the present invention. Figure 2 This is a schematic structural diagram of the mixing device 120 in the embodiment of the reaction unit of the present invention.

[0154] As Figure 1-2 shown, the reaction unit for reacting a raw material and a precipitant to generate a slurry containing nanoparticles includes a reaction device 110, a mixing device 120, and a heating device (not shown in the figure). The reaction device 110 is used to react the mixed raw material and precipitant at a certain temperature to generate a slurry containing nanoparticles. The mixing device 120 is used to mix the raw material and the precipitant and then flow them into the reaction device 110. The mixing device 120 includes a dispersion membrane. After the precipitant is dispersed by the dispersion membrane, it is mixed with the raw material flowing along the surface of the dispersion membrane. The heating device is used to heat the reaction device 110 after mixing is completed to reach the temperature required for the reaction of the raw material and the precipitant.

[0155] The mixing device 120 includes a dispersion membrane cylinder 121, a dispersion membrane support cylinder 123, a mixing feed pipe 130, and a mixing discharge pipe 140. The dispersion membrane cylinder 121 is formed by winding a dispersion membrane, and a raw material flow channel 122 is formed inside the dispersion membrane cylinder 121. An annular precipitant flow gap 124 is formed between the inner wall of the dispersion membrane support cylinder 123 and the outer wall of the dispersion membrane cylinder 121. The inlet of the mixing feed pipe 130 is connected to the bottom of the reaction device 110, and the outlet is connected to the bottom of the raw material flow channel 122. A raw material circulation pump 131 is provided on the mixing feed pipe 130. The inlet of the mixing discharge pipe 140 is connected to the top of the raw material flow channel 122, and the outlet is connected to the upper part of the reaction device 110. Before mixing is completed, the raw material circulates in the reaction device 110, the mixing feed pipe 130, the raw material flow channel 122, and the mixing discharge pipe 140. Thus, the raw material is mixed with the precipitant during the circulation process, which can significantly improve the mixing effect. The raw material flow channel 122 is vertically arranged, so that the direction of the precipitant passing through the dispersion membrane is perpendicular to the material flow direction, thereby further improving the mixing effect.

[0156] The dispersion membrane is a microfiltration membrane, specifically a microfiltration membrane with a filtration pore diameter of 4 - 6 μm. Thus, it can achieve a good dispersion effect without requiring a high pressure.

[0157] The precipitant inlet 125 of the precipitant flow gap 124 is located at the lower part of the precipitant flow gap 124; the ratio of the diameter of the raw material flow channel 122 to the thickness of the precipitant flow gap 124 is (4 - 10):1. Thus, a fast mixing speed and mixing effect can be ensured.

[0158] A precipitant feed pump 151 is provided on the precipitant feed pipe 150. Thus, it is convenient to control the flow rate of the precipitant.

[0159] A liquid level gauge and a stirrer are provided inside the reaction device 110.

[0160] Figure 3 It is a schematic structural diagram of an embodiment of the concentration unit of the present invention. Figure 4 It is a schematic structural diagram of the concentration device 220 in the embodiment of the concentration unit of the present invention.

[0161] As Figure 3-4 The concentration unit for concentrating the slurry containing nanoparticles shown in the figure includes a concentration intermediate tank 210, a concentration device 220, and a slurry feed pipe 260. The concentration intermediate tank 210 is used to receive the slurry containing nanoparticles and temporarily store the concentrated thick liquid. The concentration device 220 is used to concentrate the slurry in the concentration intermediate tank 210. The concentration device 220 includes a concentration membrane. After the slurry is filtered through the concentration membrane, a thick liquid and a clear liquid are obtained. The thick liquid flows back into the concentration intermediate tank 210. The slurry feed pipe 260 is used to input the slurry into the concentration intermediate tank 210.

[0162] The concentration device 220 includes a concentration membrane cylinder 221, a concentration membrane support cylinder 223, a concentration feed pipe 230, and a concentration discharge pipe 240. The concentration membrane cylinder 221 is formed by winding the concentration membrane, and a slurry flow channel 222 is formed inside the concentration membrane cylinder 221. An annular clear liquid flow gap 224 is formed between the inner wall of the concentration membrane support cylinder 223 and the outer wall of the concentration membrane cylinder 221. The inlet of the concentration feed pipe 230 is connected to the bottom of the concentration intermediate tank 210, and the outlet is connected to the bottom of the slurry flow channel 222. A slurry circulation pump 231 is provided on the concentration feed pipe 230. The inlet of the concentration discharge pipe 240 is connected to the top of the slurry flow channel 222, and the outlet is connected to the upper part of the concentration intermediate tank 210. Before the concentration is completed, the slurry circulates in the concentration intermediate tank 210, the concentration feed pipe 230, the slurry flow channel 222, and the concentration discharge pipe 240. Thus, the slurry is filtered in a circulating flow manner, which is convenient to control the concentration degree and prevent the surface of the concentration membrane from being blocked. The concentration device 220 is placed vertically to reduce the deposition surface of nanoparticles and further prevent the surface of the concentration membrane from being blocked.

[0163] The filtration pore size of the concentration membrane is 3-5 nm. Thus, a better concentration speed can be achieved without the need for a high pressure.

[0164] The clear liquid outlet 225 of the clear liquid flow gap 224 is located at the upper part of the clear liquid flow gap 224. Thus, by using the natural sedimentation effect of the clear liquid flow gap 224, the content of nanoparticles in the clear liquid can be further reduced. A drain port can be provided at the lower part of the clear liquid flow gap 224 to discharge the internal residual liquid.

[0165] The clear liquid outlet 225 is connected to the first three-way valve 250. One of the outlets is connected to the reaction device 110 for generating the slurry through the clear liquid return pipe 270, and the other outlet is connected to the wastewater treatment unit. Thus, when there is still a large amount of unreacted raw materials in the clear liquid, it can be refluxed to the reaction device 110 for continuous reaction. When the raw materials are basically completely involved in the precipitation reaction, it can be directly discharged to the wastewater treatment unit for treatment and then discharged or reused.

[0166] The ratio of the diameter of the slurry flow channel 222 to the thickness of the clear liquid flow gap 224 is (2 - 6):1. Thus, a relatively fast concentration speed and concentration effect can be ensured.

[0167] A liquid level gauge and a stirrer are provided in the concentration intermediate tank 210. In order to avoid adverse effects of the reduction of the clear liquid temperature on the precipitation reaction, the concentration intermediate tank 210 is provided with a heat preservation device or a heating device. A slurry feed pump 261 is provided on the slurry feed pipe 260. Thus, it is convenient to control the flow rate of the slurry.

[0168] Figure 5 It is a schematic structural diagram of the first embodiment of the washing unit of the present invention. Figure 6 It is a schematic structural diagram of the filtration device 320 in the first embodiment of the washing unit of the present invention.

[0169] As Figure 5-6 The washing unit for washing the concentrated liquid containing nanoparticles shown in the figure includes a washing intermediate tank 310, a filtration device 320, a washing water inlet pipe 360, and a concentrated liquid feed pipe 380 (or a slurry feed pipe 260). The washing intermediate tank 310 is used to receive the pulp formed by the washing water and the concentrated liquid. The filtration device 320 is used to filter the pulp in the washing intermediate tank 310; the filtration device 320 includes a filter membrane, and after the pulp is filtered through the filter membrane, a nanoparticle dispersion liquid and washing water are obtained. The washing water inlet pipe 360 is used to input washing water into the washing intermediate tank 310. The concentrated liquid feed pipe 380 is used to input the concentrated liquid into the washing intermediate tank 310.

[0170] The filtering device 320 includes a filtering membrane cylinder 321, a filtering membrane support cylinder 323, a filtering feed pipe 330, and a filtering discharge pipe 340. The filtering membrane cylinder 321 is formed by winding a filtering membrane, and a pulp washing flow channel 322 is formed inside the filtering membrane cylinder 321. An annular washing water flow gap 324 is formed between the inner wall of the filtering membrane support cylinder 323 and the outer wall of the filtering membrane cylinder 321. The inlet of the filtering feed pipe 330 is connected to the bottom of the washing intermediate tank 310, and the outlet is connected to the bottom of the pulp washing flow channel 322. A pulp washing circulation pump 331 is provided on the filtering feed pipe 330. The inlet of the filtering discharge pipe 340 is connected to the top of the pulp washing flow channel 322, and the outlet is connected to the second three-way valve 350. Before the washing is completed, the pulp to be washed circulates in the washing intermediate tank 310, the filtering feed pipe 330, the pulp washing flow channel 322, and the filtering discharge pipe 340. Thus, the pulp to be washed is filtered and washed during the flowing process, which is convenient for controlling the washing degree, reducing the amount of washing water used, and preventing the surface of the filtering membrane from being blocked. The pulp washing flow channel 322 is vertically arranged to reduce the deposition surface of nanoparticles and further prevent the surface of the filtering membrane from being blocked.

[0171] The filtering pore diameter of the concentration membrane is 2-4 nm. Thus, a good filtering speed can be achieved without requiring a high pressure.

[0172] The washing water outlet 325 of the washing water flow gap 324 is located at the upper part of the washing water flow gap 324; thus, by utilizing the natural sedimentation effect of the washing water flow gap 324, the content of nanoparticles in the washing water can be further reduced. A liquid discharge port can be provided at the lower part of the washing water flow gap 324 to discharge the internal residual liquid.

[0173] The washing water outlet 325 is connected to the wastewater treatment unit, and the washing water is discharged or recycled after being treated by the wastewater treatment unit.

[0174] The ratio of the diameter of the pulp washing flow channel 322 to the thickness of the washing water flow gap 324 is (4-7):1. Thus, a relatively fast filtering speed and filtering effect can be ensured.

[0175] The outlet of the pulp washing flow channel 322 is connected to the second three-way valve 350. One outlet is connected to the washing intermediate tank 310, and the other outlet is connected to the nanoparticle dispersion liquid storage tank. Thus, before the washing is completed, the pulp to be washed is washed during the circulating flow process, and after the washing is completed, it is discharged into the storage tank, so as to carry out the washing of the next concentrated liquid.

[0176] The water inlet pipe 360 for washing water is provided with a water inlet valve, and an ion detector is provided on the washing water discharge pipe. The water inlet valve opens and closes according to the detection value of the ion detector, and the two outlets of the second three-way valve 350 are switched according to the detection value of the ion detector. Thus, by detecting the concentration of target elements or impurity elements in the washing water with the ion detector, the washing degree is controlled, and the purity of the nanoparticles is significantly improved. The ion detector is a conductivity meter, and the higher the ion concentration, the higher the conductivity.

[0177] A liquid level gauge and a stirrer are provided in the washing intermediate tank 310. A concentrated liquid feed pump 381 is provided on the concentrated liquid feed pipe 380, thereby facilitating the control of the flow rate of the concentrated liquid.

[0178] Figure 7 It is a schematic structural diagram of the second embodiment of the concentration unit of the present invention.

[0179] Compared with the first embodiment, the difference of the washing unit in this embodiment is that as Figure 7 shown, there is also a chelating agent feeding pipe 370. By adding a chelating agent, it is possible to remove inorganic salts that are prone to precipitation and adsorbed and wrapped by nanoparticles during the chemical precipitation reaction. In order to wash away the chelating agent during the washing process, the stirrer includes an ultrasonic dispersion device 311 and a high-speed homogenizer 312. When the nanoparticles are nano-silica, the chelating agent is preferably but not limited to disodium ethylenediaminetetraacetate.

[0180] Figure 8 It is a schematic structural diagram of the first embodiment of the production system of the nanoparticles of the present invention.

[0181] As Figure 8 shown, the production system of nanoparticles includes the above-mentioned Figure 1-2 shown reaction unit and Figure 7 shown washing unit.

[0182] Figure 9 It is a schematic structural diagram of the second embodiment of the production system of the nanoparticles of the present invention.

[0183] As Figure 9 shown, the production system of nanoparticles includes the above-mentioned Figure 1-2 shown reaction unit, Figure 3-4 shown concentration unit and Figure 5-6 shown washing unit. Among them, the volumes of the concentration intermediate tank 210 and the washing intermediate tank 310 are one-third of the volume of the reaction equipment 110, and the volume of the reaction equipment 110 is 3000 - 10000 liters. Compared with the first embodiment, by further setting a concentration unit, the amount of washing water can be reduced.

[0184] Figure 10Schematic structural diagram of the third embodiment of the production system of the nanoparticles of the present invention.

[0185] Compared with the second embodiment, the difference of the production system of the nanoparticles in the third embodiment is that, as Figure 10 shown, a slurry feed pipe 260 for allowing the slurry to flow into the concentration device 220 is provided between the reaction device 110 and the concentration device 220; a clear liquid return pipe 270 for returning the clear liquid to the reaction device 110 is provided between the reaction device 110 and the concentration device 220; a clarity detector is provided on the reaction device 110, the concentration device 220 or the slurry feed pipe 260, and the clarity detector is a turbidimeter; a return valve is provided on the clear liquid return pipe 270; the feed valve and / or the return valve are opened and closed according to the detection value of the clarity detector. Compared with the second embodiment, by controlling the reflux and iterative concentration through the clarity detector, the uniformity of the nanoparticles can be improved, and the raw material utilization rate and process stability can be enhanced.

[0186] The embodiment of the preparation method of the nanoparticles of the present invention uses the above-mentioned production system of the nanoparticles, and specifically includes the following steps:

[0187] Calculate the precipitating agent required according to the complete precipitation of the target element in the raw material, and divide the precipitating agent into N batches for feeding, N≥2;

[0188] Mix the raw material with the first batch of precipitating agent in the reaction device 110, and react the materials in the reaction device 110 at the required reaction temperature to obtain a first slurry containing nanoparticles, and perform a first concentration treatment on the first slurry to obtain a first clear liquid and a first concentrated liquid;

[0189] Mix the first clear liquid with the second batch of precipitating agent, and react at the required reaction temperature to obtain a second slurry containing nanoparticles, and perform a second concentration treatment on the mixture composed of the second slurry and the first concentrated liquid to obtain a second clear liquid and a second concentrated liquid; repeat this step until the (N-1)th clear liquid reacts with the Nth batch of precipitating agent at the required reaction temperature to obtain an Nth slurry containing nanoparticles, and perform an Nth concentration treatment on the mixture composed of the Nth slurry and the (N-1)th concentrated liquid to obtain an Nth clear liquid and an Nth concentrated liquid;

[0190] Perform a washing treatment on the Nth concentrated liquid to obtain a nanoparticle dispersion.

[0191] Wherein, the precipitating agent can be a substance that directly reacts with the target element in the raw material to form a precipitate, or a regulator that changes the pH of the raw material environment to generate a precipitate.

[0192] The mixing of the raw materials with the first batch of precipitant and the mixing of the (N-1)th supernatant with the Nth batch of precipitant are carried out in the mixing device 120, the material flow rate is 1.5 - 8 m / s, and each batch of precipitant is added within 5 - 20 minutes.

[0193] For the 1st to (N-1)th concentration treatments, the slurry in the reaction device 110 flows into the concentration device 220 at a certain flow rate, and the supernatant output from the concentration device 220 continuously flows back to the reaction device 110 until the clarification degree of the slurry in the reaction device 110 reaches the requirement and then the concentration stops; for the Nth concentration, the supernatant output from the concentration device 220 does not flow back to the reaction device 110.

[0194] It also includes adding an additive and / or dilution water to prevent nanoparticle aggregation into the reaction device 110 once or in batches after the mixing of the raw materials and the first batch of precipitant. Adding the additive and / or dilution water after the mixing of the raw materials and the precipitant can improve the mixing speed of the raw materials and the precipitant. Preferably, the volume of the dilution water is 0.58 - 0.63 times the volume of the raw materials.

[0195] The feeding speed of the previous batch of precipitant is greater than that of the next batch of precipitant. Since the content of the target element in the raw materials gradually decreases, by reducing the feeding speed of the precipitant, the mixing of the raw materials and the precipitant can be made more uniform.

[0196] Most preferably, N = 3, and the addition amounts are: the second batch of precipitant > the first batch of precipitant > the third batch of precipitant. Since after the first batch of reaction is completed, the first supernatant has a certain temperature and also has a small amount of crystal seeds, therefore, making the dosage of the second batch of precipitant the highest can significantly improve the production efficiency. Since after the second batch of reaction is completed, the content of the target element in the second supernatant is less, therefore, the addition amount of the third batch of precipitant is the least. Preferably, the total dosage of the precipitant consists of 30 - 40% of the first batch of precipitant, 40 - 50% of the second batch of precipitant, and the remaining third batch of precipitant.

[0197] The embodiment of the pretreatment method of the sodium silicate of the present invention includes the following steps:

[0198] (1) Dilute the concentrated sodium silicate with water to obtain dilute sodium silicate; the concentrated sodium silicate is prepared with soda ash and has a mass fraction of 27 - 30%.

[0199] (2) Heat the dilute sodium silicate to 55 - 65 °C, and then add pasty calcium peroxide to the dilute glass to obtain a mixture; the pasty calcium peroxide is prepared according to the ratio of containing 500 - 1000 g per liter of water; the dosage of calcium peroxide per liter of dilute sodium silicate is 0.5 - 1.5 g.

[0200] (3) Heat-treat the mixture to obtain a solid-liquid mixture; the heat treatment is to stir at 85-95 °C for 3-7 min.

[0201] (4) Cool the solid-liquid mixture; the cooling treatment is to add cooling water to the solid-liquid mixture after the heat treatment to lower the temperature, and add cooling water until the temperature of the solid-liquid mixture drops to 35-45 °C.

[0202] (5) Perform solid-liquid separation on the cooled solid-liquid mixture to obtain water glass.

[0203] Figure 11 It is a schematic structural diagram of the water glass pretreatment unit of the present invention.

[0204] As Figure 11 The shown water glass pretreatment unit includes an alkali reaction vessel 410, a concentrated water glass feeding pipe 420, a pasty calcium peroxide feeding pipe 430, a first water adding pipe 440, a second water adding pipe 450, a heating device (not shown in the figure), a filtering device 460, a water glass storage tank 470, and a stirring tank (not shown in the figure). The concentrated water glass feeding pipe 420 is used to input concentrated water glass into the alkali reaction vessel 410. The pasty calcium peroxide feeding pipe 430 is used to input pasty calcium peroxide into the alkali reaction vessel 410. The first water adding pipe 440 is used to input dilution water into the alkali reaction vessel 410. The second water adding pipe 450 is used to input cooling water into the alkali reaction vessel 410. The heating device is used to heat the alkali reaction vessel 410. The filtering device 460 is used to filter the solid-liquid mixture generated in the alkali reaction vessel 410 to obtain water glass. The water glass storage tank 470 is used to store the pretreated water glass. The stirring tank is used to stir calcium peroxide and water to form pasty calcium peroxide.

[0205] A temperature detector, a liquid level gauge, and a stirrer are provided in the alkali reaction vessel 410. A first valve is provided on the second water adding pipe 450, and the first valve closes according to the detection data of the temperature detector. A second valve is provided on the pasty calcium peroxide feeding pipe 430, and the second valve closes according to the detection data of the temperature detector.

[0206] The filtering device 460 includes a filter press and a precision filter connected in sequence.

[0207] The first embodiment of the production system of nano-silica of the present invention includes a water glass pretreatment unit, an acid solution pretreatment unit, and Figure 8 The shown production system of nano-particles. The water glass pretreatment unit adopts Figure 11 The shown water glass pretreatment unit.

[0208] The second embodiment of the production system of nano-silica of the present invention includes a sodium silicate pretreatment unit, an acid solution pretreatment unit, and Figure 9 the production system of the nano-particles shown. The sodium silicate pretreatment unit adopts Figure 11 the sodium silicate pretreatment unit shown.

[0209] The third embodiment of the production system of nano-silica of the present invention includes a sodium silicate pretreatment unit, an acid solution pretreatment unit, and Figure 10 the production system of the nano-particles shown. The sodium silicate pretreatment unit adopts Figure 10 the sodium silicate pretreatment unit shown.

[0210] Figure 12 is a schematic structural diagram of the acid solution pretreatment unit in the embodiment of the production system of nano-silica of the present invention.

[0211] As Figure 12 shown, in the production systems of nano-silica in the above two embodiments, the acid solution pretreatment unit is used to process sulfuric acid and oxalic acid to obtain an acid solution, and includes an acid reaction vessel 510, a concentrated sulfuric acid feeding pipe 520, an oxalic acid feeding pipe 530, a third water adding pipe 540, and an acid solution storage tank 550. A liquid level gauge and a stirrer are provided in the acid reaction vessel 510. The concentrated sulfuric acid feeding pipe 520 is used to input concentrated sulfuric acid into the acid reaction vessel 510. The oxalic acid feeding pipe 530 is used to input oxalic acid into the acid reaction vessel 510. The third water adding pipe 540 is used to input dilution water into the acid reaction vessel 510. The acid solution storage tank 550 is used to store the acid solution.

[0212] The first embodiment of the preparation method of nano-silica of the present invention adopts the production system of nano-particles in the above first embodiment, and specifically includes the following steps:

[0213] Calculate the required acid solution according to the complete precipitation of silicon elements in the raw materials, and divide the acid solution into three batches for feeding; the raw materials include sodium silicate;

[0214] Mix the raw materials with the first batch of acid solution in the reaction device 110, and make the materials in the reaction device 110 react at the required reaction temperature to obtain the first slurry;

[0215] Mix the first slurry with the second batch of acid solution and react at the required reaction temperature to obtain the second slurry;

[0216] Mix the second slurry with the third batch of acid solution and react at the required reaction temperature to obtain the third slurry;

[0217] Use the washing unit to wash the third slurry, and then the nano-silica dispersion liquid is obtained.

[0218] The second embodiment of the preparation method of the nano-silica of the present invention uses the production system of the nano-particles of the above-mentioned second embodiment, and specifically includes the following steps:

[0219] Calculate the required acid solution according to the complete precipitation of silicon elements in the raw materials, and add the acid solution in three batches; the raw materials include water glass;

[0220] Mix the raw materials with the first batch of acid solution in the reaction device 110, and make the materials in the reaction device 110 react at the required reaction temperature to obtain the first slurry;

[0221] Mix the first slurry with the second batch of acid solution and react at the required reaction temperature to obtain the second slurry;

[0222] Mix the second slurry with the third batch of acid solution and react at the required reaction temperature to obtain the third slurry;

[0223] Use the concentration unit to concentrate the third slurry to obtain a concentrated solution;

[0224] Use the washing unit to wash the concentrated solution, and then the nano-silica dispersion is obtained.

[0225] The third embodiment of the preparation method of the nano-silica of the present invention uses the production system of the nano-particles of the above-mentioned third embodiment, and specifically includes the following steps:

[0226] Calculate the required acid solution according to the complete precipitation of silicon elements in the raw materials, and add the acid solution in three batches; the raw materials include water glass;

[0227] Mix the raw materials with the first batch of acid solution in the reaction device 110, and make the materials in the reaction device 110 react at the required reaction temperature to obtain the first slurry. Use the concentration unit to perform the first concentration treatment on the first slurry and obtain the first clear liquid and the first concentrated liquid;

[0228] Mix the first clear liquid with the second batch of acid solution and react at the required reaction temperature to obtain the second slurry. Use the concentration unit to perform the second concentration treatment on the mixture composed of the second slurry and the first concentrated liquid and obtain the second clear liquid and the second concentrated liquid;

[0229] Mix the second clear liquid with the third batch of acid solution and react at the required reaction temperature to obtain the third slurry. Use the concentration unit to perform the third concentration treatment on the mixture composed of the third slurry and the second concentrated liquid and obtain the third clear liquid and the third concentrated liquid;

[0230] Use the washing unit to wash the third concentrated liquid, and then the nano-silica dispersion is obtained.

[0231] In the preparation methods of nano-silica in the above three embodiments, the acid solution serves as the precipitant. The acid solution can be dilute sulfuric acid with a mass fraction of 5 - 15%, or a mixture of sulfuric acid and oxalic acid, prepared by adding 3 - 10 g of oxalic acid to each liter of dilute sulfuric acid with a mass fraction of 5 - 15%.

[0232] The total amount of the acid solution consists of 30 - 40% of the first batch of acid solution, 40 - 50% of the second batch of acid solution, and the remaining third batch of acid solution. The feeding rate of the first batch of acid solution is 350 - 400 L / h, the feeding rate of the second batch of acid solution is 300 - 350 L / h, and the feeding rate of the third batch of acid solution is 180 - 240 L / h.

[0233] The reaction temperature after the addition of each batch of acid solution is 85 - 95 °C, and the reaction time is 10 - 30 minutes.

[0234] After the raw materials are mixed with the first batch of acid solution, dilution water is added to the reaction device 110 at one time, and then heated to the reaction temperature. The volume of the dilution water is 0.58 - 0.63 times the volume of the raw materials.

[0235] The raw materials include water glass with a mass fraction of 5 - 15%, which is obtained by treating and diluting concentrated water glass with a mass fraction of 27 - 30% with calcium oxide.

[0236] The above nano-silica dispersion is dried to obtain nano-silica powder, and the drying method is preferably spray drying.

[0237] Application examples:

[0238] (1) The process parameters for the pretreatment of water glass are as follows: the mass fraction of concentrated water glass is 27 - 30%; the dilute water glass is heated to 60 °C, and then pasty calcium peroxide is added to the dilute glass. The pasty calcium peroxide is prepared according to the ratio of 800 g per liter of water, and the dosage of calcium peroxide per liter of dilute water glass is 1 g; the heat treatment is stirring at 90 °C for 5 min; after the heat treatment is completed, cooling water is added to the solid-liquid mixture until the temperature of the solid-liquid mixture drops to 40 °C. By controlling the amount of dilution water, water glass with a mass fraction of 10% is obtained.

[0239] (2) The process for obtaining the acid solution is as follows: concentrated sulfuric acid with a mass fraction of 98% is diluted with water to form dilute sulfuric acid with a mass fraction of 10%, and 8 g of oxalic acid is added to each liter of the dilute sulfuric acid.

[0240] (3) The process parameters of the precipitation reaction are as follows: the raw material is 3300 L; the total amount of acid solution is 650 L, which consists of 37% of the first batch of acid solution, 49% of the second batch of acid solution, and 14% of the third batch of acid solution; the feeding rate of the first batch of acid solution is 380 L / h, the feeding rate of the second batch of acid solution is 320 L / h, and the feeding rate of the third batch of acid solution is 200 L / h; the amount of dilution water is 2000 L; the precipitation reaction temperature is 90 °C, the reaction time of the first batch is 15 minutes, the reaction time of the second batch is 20 minutes, and the reaction time of the third batch is 10 minutes.

[0241] The particle sizes of the nano-silica prepared by using the preparation methods of nano-silica in the above three embodiments are all distributed in the range of 5 - 20 nanometers, with a narrow particle size distribution. The particles are in a regular spherical structure and are uniform. The purity of the products obtained from multiple productions is greater than or equal to 99.8%.

[0242] The above has described the relevant content of the present invention. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. Based on the above content of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing nanoparticles, characterized in that: It includes the following steps: Calculate the precipitant required for complete precipitation of the target element in the raw material, and divide the precipitant into N batches for feeding, where N≥2; Mix the raw material with the first batch of precipitant in a reaction device, and react the materials in the reaction device at the required reaction temperature to obtain a first slurry containing nanoparticles. Perform the first concentration treatment on the first slurry to obtain a first clear liquid and a first concentrated liquid; Mix the first clear liquid with the second batch of precipitant and react at the required reaction temperature to obtain a second slurry containing nanoparticles. Perform the second concentration treatment on the mixture composed of the second slurry and the first concentrated liquid to obtain a second clear liquid and a second concentrated liquid; Repeat this step until the (N - 1)th clear liquid reacts with the Nth batch of precipitant at the required reaction temperature to obtain the Nth slurry containing nanoparticles. Perform the Nth concentration treatment on the mixture composed of the Nth slurry and the (N - 1)th concentrated liquid to obtain the Nth clear liquid and the Nth concentrated liquid; Perform a washing treatment on the Nth concentrated liquid to obtain a nanoparticle dispersion.

2. The method for preparing nanoparticles according to claim 1, characterized in that: Add the corresponding batch of precipitant in a dispersed state to the materials in a state where the materials are in a circulating flow state.

3. The method for preparing the nanoparticles according to claim 2, wherein: The flow rate of the materials is 1.5 - 8 m / s, and each batch of precipitant is added within 5 - 20 minutes. The precipitant is dispersed by a dispersion membrane, and the direction in which the precipitant passes through the dispersion membrane is perpendicular to the direction of material flow.

4. The preparation method of the nanoparticles according to claim 1, characterized in that: For the first to (N - 1)th concentration treatments, the slurry in the reaction device flows into the concentration device at a certain flow rate, and the clear liquid output from the concentration device continuously flows back to the reaction device until the clarification degree of the slurry in the reaction device reaches the requirement and then the concentration stops; For the Nth concentration, the clear liquid output from the concentration device does not flow back to the reaction device.

5. The preparation method of the nanoparticles according to claim 1, characterized in that: It also includes adding an additive and / or dilution water to prevent nanoparticle aggregation to the reaction device once or in batches after mixing the raw material with the first batch of precipitant, and then heating to the reaction temperature.

6. The preparation method of the nanoparticles according to claim 5, characterized in that: The volume of the dilution water is 0.58 - 0.63 times the volume of the raw material.

7. The method for preparing the nanoparticles according to claim 1, wherein: The feeding speed of the previous batch of precipitant is greater than that of the next batch of precipitant.

8. The method for preparing nanoparticles according to claim 1, characterized in that: N＝3。 9. The method for preparing the nanoparticles according to claim 8, characterized in that: Dosage: The second batch of precipitant > the first batch of precipitant > the third batch of precipitant.

10. The preparation method of the nanoparticles according to claim 9, wherein: The total amount of the precipitant is composed of 30 - 40% of the first batch of precipitant, 40 - 50% of the second batch of precipitant, and the remaining third batch of precipitant.

Images