Silica sol purification method

Abstract

The invention discloses a silica sol purification method, belongs to the technical field of silica sol purification, and aims at solving the technical problem that in the prior art, in application of an existing silica sol purification process, it is still found that the silica sol purification effect improvement space exists. The silica sol purification method comprises the following steps: preparing equipment raw materials: preparing raw materials: a silica sol coarse solution, deionized water and ion exchange resin; preparing equipment: a plurality of reaction vessels, an ion exchange resin bed, a centrifugal machine, a thickener, a pH meter and a thermometer; diluting, carrying out first ion exchange, carrying out centrifugal separation, carrying out second ion exchange and concentrating. According to the silica sol purification method, the technological process of first ion exchange, then centrifugal separation, and then ion exchange and concentration is adopted, and compared with a traditional technological process of first ion exchange, then centrifugal separation and direct concentration, the effect of removing mechanical impurities in silica sol is improved, and silica sol with higher purity can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of silica sol purification, and particularly relates to a silica sol purification method. Background Art

[0002] Silica sol is a special colloidal solution, a colloidal solution in which colloidal particles of silicon dioxide (SiO2) are dispersed in water. It can also be called silica sol or silica hydrosol. Silica sol is mostly milky white or light blue transparent solution, mostly stable alkaline, a few are acidic. The concentration of SiO2 in silica sol is generally 10% to 35%. It is a colloidal solution, odorless, non-toxic, and has low viscosity. When the water molecules of silica sol are evaporated, the colloidal particles can be firmly attached to the surface of the object, and silicon-oxygen bonds are formed between the particles, showing good adhesive properties. Due to its unique properties, it is widely used in many fields such as refractory binders, coatings industry, precision casting, catalysts and carriers, papermaking industry, textile industry, etc. It is a colloidal solution with broad application prospects.

[0003] As an inorganic polymer compound formed by highly dispersed nano-scale silicon dioxide particles in water, silica sol has shown a wide range of application prospects and huge market potential in modern industry and scientific research due to its unique physical and chemical properties. With the continuous advancement of technology and the continuous growth of market demand, the silica sol market is ushering in unprecedented development opportunities, especially in high-tech and high-end manufacturing fields such as electronics, aerospace, heavy machinery, construction, and aviation. The purity, particle size, stability and other performance requirements of silica sol are getting higher and higher, which has promoted the continuous development of silica sol purification technology. New purification methods, new equipment and processes are constantly emerging, which improves the purification efficiency and product quality of silica sol. For example, the purity of silica sol can be improved by using ion exchange method, direct acidification method, ultrafiltration concentration and other methods. However, in the application of existing silica sol purification process, it is still found that there is still room for improvement in the purification effect of silica sol. For this reason, this application proposes a silica sol purification method. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a silica sol purification method, aiming to solve the technical problem that there is still room for improvement in the silica sol purification effect during application of the existing silica sol purification process under the prior art.

[0005] Technical Solution

[0006] In order to solve the above technical problems, the present invention provides a method for purifying silica sol, comprising the following steps:

[0007] Step 1: Equipment and raw material preparation, including:

[0008] Prepare raw materials: silica sol crude solution, deionized water and ion exchange resin;

[0009] Prepare equipment: several reaction vessels, ion exchange resin beds, centrifuges, concentrators, pH meters, and thermometers;

[0010] Step 2: diluting the silica sol crude solution with deionized water;

[0011] Step 3: the first ion exchange, the diluted silica sol is passed through an ion exchange resin bed for ion exchange;

[0012] Step 4: Purification, including:

[0013] Centrifugal separation: using a centrifuge to centrifuge the silica sol after the first ion exchange to remove mechanical impurities therein;

[0014] In the second ion exchange, the silica sol after centrifugal separation is passed through an ion exchange resin bed for ion exchange to further remove impurities;

[0015] Step 5: Concentrating the purified silica sol to a desired SiO2 content;

[0016] Step 6: Testing and quality control, including:

[0017] SiO2 content detection: use chemical analysis method or instrumental analysis method to detect the SiO2 content in silica sol to ensure that the SiO2 content meets the production requirements;

[0018] pH value detection: use a pH meter to detect the pH value of silica sol;

[0019] Particle size distribution detection: Use laser particle size analyzer or electron microscope equipment to detect the particle size distribution of silica sol to ensure that its particle size meets production requirements;

[0020] Step 7: Post-processing and storage, including:

[0021] Post-treatment: filter the concentrated silica sol using a microporous filter membrane or a precision filter to ensure the purity of the silica sol, and use acid or alkali to adjust the pH value of the silica sol to obtain purified silica sol;

[0022] Storage: Put the purified silica sol into a clean, dry, sealed container and store it in a cool, ventilated and light-proof environment. Check the sealing of the storage container regularly.

[0023] Preferably, in step 2, the crude silica sol solution is diluted with deionized water to a SiO2 content of 10% to 15%.

[0024] Preferably, after each ion exchange, the ion exchange resin bed is washed with deionized water until no impurity ions are detected in the washing liquid.

[0025] Preferably, in step three, the speed of the centrifuge during the centrifugal separation process is 3000-5000 r / min, and the centrifugation time is 1-2 h.

[0026] Preferably, the flow rate of silica sol flowing through the ion exchange resin bed is 0.25 to 0.35 ml / cm 2 ·min.

[0027] Preferably, the method for concentrating the purified silica sol in step 5 includes vacuum evaporation concentration method and ultrafiltration concentration method.

[0028] Vacuum evaporation concentration method: pour the purified silica sol into a vacuum evaporator, set the vacuum degree to 0.01-0.1MPa, and the heating temperature to 60-80℃ for vacuum evaporation concentration. During the concentration process, continuous stirring is required to avoid local overheating of the silica sol and gelation. After concentrating to the required SiO2 content, stop heating and vacuum extraction, and cool the silica sol to room temperature;

[0029] Ultrafiltration concentration method, the purified silica sol is concentrated through an ultrafiltration membrane. The pressure during the ultrafiltration process is 0.25 ~ 0.40MPa, and the membrane flux is 60 ~ 200L / m^2·h. After concentrating to the required SiO2 content, the ultrafiltration is stopped and the silica sol is collected.

[0030] Preferably, in step six, the pH value of the silica sol should be between 8.5 and 10, and in step seven, NaOH solution or dilute sulfuric acid is used to adjust the pH value.

[0031] Preferably, during the purification process of silica sol, the temperature is controlled between 20 and 30° C., and the temperature is monitored regularly, with a frequency of once every 0.5 to 1 hour.

[0032] Preferably, during the silica sol purification process, the stirrer is selected from one or more of an anchor stirrer, a paddle stirrer, and a turbine stirrer, and the stirring speed is 200 to 400 r / min.

[0033] Beneficial Effects

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention can significantly purify silica sol by adopting the process flow of dilution, ion exchange, centrifugal separation, ion exchange, concentration, and detection separation, so that silica sol can meet the use requirements of high-tech and high-end manufacturing fields such as electronics, aerospace, heavy machinery, construction, and aviation. By adopting the process flow of first ion exchange, then centrifugal separation, and then ion exchange and concentration, compared with the traditional process flow of first ion exchange, then centrifugal separation and direct concentration, the effect of removing mechanical impurities in silica sol is improved, and silica sol with higher purity can be obtained; by controlling the reaction temperature, membrane flux, pressure, and pH, the stability of the silica sol purification process is ensured, and a silica sol product with better quality can be prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0037] Figure 1 is a process flow chart of the present invention;

[0038] Figure 2 is a process flow chart of step 1 in the present invention;

[0039] Figure 3 This is a process flow chart of step 4 in the present invention;

[0040] Figure 4 This is a process flow chart of step six in the present invention;

[0041] Figure 5 It is the process flow chart of step seven in the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] This embodiment provides a method for purifying silica sol, and its structural schematic diagram is as follows Figure 1-Figure 5 As shown, the following steps are included:

[0044] Step 1: Equipment and raw material preparation, including:

[0045] Prepare raw materials: silica sol crude solution, deionized water and ion exchange resin;

[0046] Prepare equipment: several reaction vessels, ion exchange resin beds, centrifuges, concentrators, pH meters, and thermometers;

[0047] Step 2: diluting the silica sol crude solution with deionized water. Specifically, diluting the silica sol crude solution with deionized water to a SiO2 content of 10% to 15% for subsequent treatment. For example, taking 100L of silica sol crude solution (SiO2 content of 25%), adding 50 to 75L of deionized water, diluting to a SiO2 content of 10% to 15%;

[0048] Step 3: the first ion exchange, the diluted silica sol is passed through an ion exchange resin bed for ion exchange;

[0049] Step 4: Purification, including:

[0050] Centrifugal separation: using a centrifuge to centrifuge the silica sol after the first ion exchange to remove mechanical impurities therein;

[0051] The second ion exchange is to pass the silica sol after centrifugal separation through an ion exchange resin bed for ion exchange to further remove impurities. Multiple ion exchanges are performed to obtain silica sol with higher purity.

[0052] Step 5: Concentrating the purified silica sol to a desired SiO2 content;

[0053] Step 6: Testing and quality control, including:

[0054] SiO2 content detection: use chemical analysis methods (such as weight method, titration method, etc.) or instrumental analysis methods (such as spectroscopy, chromatography, etc.) to detect the SiO2 content in silica sol to ensure that the SiO2 content meets production requirements;

[0055] pH value detection: use a pH meter to detect the pH value of silica sol;

[0056] Particle size distribution detection: Use laser particle size analyzer or electron microscope equipment to detect the particle size distribution of silica sol to ensure that its particle size meets production requirements;

[0057] Step 7: Post-processing and storage, including:

[0058] Post-treatment: Use a microporous filter membrane or precision filter to filter the concentrated silica sol. The concentrated silica sol may contain some tiny impurity particles, so it is necessary to further remove these impurities by filtering to ensure the purity of the silica sol. Use acid or alkali to adjust the pH value of the silica sol to obtain purified silica sol.

[0059] For storage, put the purified silica sol into a clean, dry, sealed container to avoid contamination and water evaporation, and store it in a cool, ventilated, light-proof condition, avoiding high temperature and direct sunlight. Check the sealing of the storage container regularly to ensure that the silica sol will not be lost due to volatilization.

[0060] Furthermore, in this embodiment, in step 2, the crude silica sol solution is diluted with deionized water to a SiO2 content of 10% to 15%.

[0061] Furthermore, in this embodiment, after each ion exchange, the ion exchange resin bed is washed with deionized water until no impurity ions are detected in the washing liquid.

[0062] Furthermore, in this embodiment, in step three, the speed of the centrifuge during the centrifugal separation process is 3000-5000 r / min, and the centrifugation time is 1-2 h.

[0063] Furthermore, in this embodiment, the flow rate of the silica sol flowing through the ion exchange resin bed is 0.25-0.35 ml / cm 2 ·min, the greater the flow rate of silica sol flowing through the resin bed, the shorter the time for the metal impurity ions (such as sodium ions) in it to exchange with the exchange ions (such as hydrogen ions) in the resin, which may lead to incomplete exchange, thereby increasing the concentration of metal impurity ions in the silica sol and reducing the purity. When the flow rate of silica sol (or its precursor solution, such as polysilicic acid solution or sodium silicate solution) flowing through the resin bed increases, the contact time between ions therein is shortened, which may lead to incomplete self-polymerization reaction, thereby reducing the particle size of the obtained product. However, when the flow rate is too small, although the exchange reaction can be more complete, it will lead to reduced production efficiency. Therefore, the flow rate of silica sol flowing through the ion exchange resin bed is controlled at 0.25-0.35ml / cm 2 Within the range of min.

[0064] Furthermore, in this embodiment, the method for concentrating the purified silica sol in step 5 includes vacuum evaporation concentration method and ultrafiltration concentration method.

[0065] Vacuum evaporation concentration method: pour the purified silica sol into a vacuum evaporator, set the vacuum degree to 0.01-0.1MPa, and the heating temperature to 60-80℃ for vacuum evaporation concentration. During the concentration process, continuous stirring is required to avoid local overheating of the silica sol and gelation. After concentrating to the required SiO2 content, stop heating and vacuum extraction, and cool the silica sol to room temperature;

[0066] Ultrafiltration concentration method, the purified silica sol is concentrated through an ultrafiltration membrane. The pressure during the ultrafiltration process is 0.25 ~ 0.40MPa, and the membrane flux is 60 ~ 200L / m^2·h. After concentrating to the required SiO2 content, the ultrafiltration is stopped and the silica sol is collected.

[0067] Furthermore, in this embodiment, in step six, the pH value of the silica sol should be between 8.5 and 10, and in step seven, NaOH solution or dilute sulfuric acid is used to adjust the pH value.

[0068] Furthermore, in this embodiment, during the silica sol purification process, the temperature is controlled between 20 and 30°C to ensure the stability of the reaction and the purification effect, and the temperature is monitored regularly, with a temperature monitoring frequency of once every 0.5 to 1 hour. When the temperature is too high (such as exceeding 40°C), the water in the silica sol is easy to evaporate, resulting in excessive concentration, affecting its fluidity and stability. When the stirring temperature is too low (such as below 0°C), the molecular movement slows down, and it is not easy to form a uniform dispersion system, which also affects its performance.

[0069] Furthermore, in this embodiment, during the purification process of the silica sol, the agitator is selected from one or more of an anchor agitator, a paddle agitator, and a turbine agitator, and the stirring speed is 200 to 400 r / min. Too fast a stirring speed may cause local overheating or excessive shear force, affecting the stability of the silica sol, while too slow a stirring speed may cause uneven mixing.

[0070] The present invention can significantly purify silica sol by adopting the process flow of dilution, ion exchange, centrifugal separation, ion exchange, concentration, and detection separation, so that silica sol can meet the use requirements of high-tech and high-end manufacturing fields such as electronics, aerospace, heavy machinery, construction, and aviation. By adopting the process flow of first ion exchange, then centrifugal separation, and then ion exchange and concentration, compared with the traditional process flow of first ion exchange, then centrifugal separation and direct concentration, the effect of removing mechanical impurities in silica sol is improved, and silica sol with higher purity can be obtained; by controlling the reaction temperature, membrane flux, pressure, and pH, the stability of the silica sol purification process is ensured, and a silica sol product with better quality can be prepared.

[0071] All technical features in this embodiment can be freely combined according to actual needs.

[0072] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for purifying silica sol, characterized in that: The following steps are involved: Step 1: Equipment and raw material preparation, including: Prepare raw materials: silica sol crude solution, deionized water and ion exchange resin; Prepare equipment: several reaction vessels, ion exchange resin beds, centrifuges, concentrators, pH meters, and thermometers; Step 2: diluting the silica sol crude solution with deionized water; Step 3: the first ion exchange, the diluted silica sol is passed through an ion exchange resin bed for ion exchange; Step 4: Purification, including: Centrifugal separation: using a centrifuge to centrifuge the silica sol after the first ion exchange to remove mechanical impurities therein; In the second ion exchange, the silica sol after centrifugal separation is passed through an ion exchange resin bed for ion exchange to further remove impurities; Step 5: Concentrating the purified silica sol to a desired SiO2 content; Step 6: Testing and quality control, including: SiO2 content detection: use chemical analysis method or instrumental analysis method to detect the SiO2 content in silica sol to ensure that the SiO2 content meets the production requirements; pH value detection: use a pH meter to detect the pH value of silica sol; Particle size distribution detection: Use laser particle size analyzer or electron microscope equipment to detect the particle size distribution of silica sol to ensure that its particle size meets production requirements; Step 7: Post-processing and storage, including: Post-treatment: filter the concentrated silica sol using a microporous filter membrane or a precision filter to ensure the purity of the silica sol, and use acid or alkali to adjust the pH value of the silica sol to obtain purified silica sol; Storage: Put the purified silica sol into a clean, dry, sealed container and store it in a cool, ventilated and light-proof environment. Check the sealing of the storage container regularly.

2. A silica sol purification method according to claim 1, characterized in that: In step 2, the crude silica sol solution is diluted with deionized water to a SiO2 content of 10% to 15%.

3. A silica sol purification method according to claim 1, characterized in that: After each ion exchange, the ion exchange resin bed was washed with deionized water until no impurity ions were detected in the washing liquid.

4. A silica sol purification method according to claim 1, characterized in that: In step 3, the speed of the centrifuge during the centrifugal separation process is 3000-5000 r / min, and the centrifugation time is 1-2 h.

5. A silica sol purification method according to claim 1, characterized in that: The flow rate of silica sol flowing through the ion exchange resin bed is 0.25~0.35ml / cm 2 ·min.

6. A method for purifying silica sol according to claim 1, characterized in that: The method for concentrating the purified silica sol in step 5 includes vacuum evaporation concentration method and ultrafiltration concentration method. Vacuum evaporation concentration method: pour the purified silica sol into a vacuum evaporator, set the vacuum degree to 0.01-0.1MPa, and the heating temperature to 60-80℃ for vacuum evaporation concentration. During the concentration process, continuous stirring is required to avoid local overheating of the silica sol and gelation. After concentrating to the required SiO2 content, stop heating and vacuum extraction, and cool the silica sol to room temperature; Ultrafiltration concentration method, the purified silica sol is concentrated through an ultrafiltration membrane. The pressure during the ultrafiltration process is 0.25 ~ 0.40MPa, and the membrane flux is 60 ~ 200L / m^2·h. After concentrating to the required SiO2 content, the ultrafiltration is stopped and the silica sol is collected.

7. A method for purifying silica sol according to claim 5, characterized in that: In step six, the pH value of the silica sol should be between 8.5 and 10, and in step seven, NaOH solution or dilute sulfuric acid is used to adjust the pH value.

8. A method for purifying silica sol according to claim 1, characterized in that: During the purification process of silica sol, the temperature is controlled between 20 and 30°C and monitored regularly at a frequency of once every 0.5 to 1 hour.

9. A method for purifying silica sol according to claim 5, characterized in that: During the purification process of silica sol, the agitator is selected from one or more of an anchor agitator, a paddle agitator, and a turbine agitator, and the stirring speed is 200 to 400 r / min.

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