Silica sol is a dispersion of nano-sized silica particles in water or a solvent. Since the SiO2 in silica sol contains a large amount of water and hydroxyl groups, silica sol can also be expressed as mSiO2.nH2O.
The particle size of silica sol is at the nanometer level, featuring high uniformity and stability. It also has advantages such as a large specific surface area, high dispersion, and high adsorption capacity.
Uses of Silica Sol
Silica sol is widely used in industries such as fibers, textiles, rubber, coatings, and ceramics. It can be used as a binder and a film-forming agent. When manufacturing inorganic polymer building coatings, it exhibits outstanding performance advantages, such as resistance to dirt and fire. In practical applications, it has excellent water resistance and durability.
Silica sol can be used in the precision manufacturing industry. It has good casting properties, simple process, good strength and high finish. It is widely recognized. When used in ceramics and refractory materials, silica sol is also used as a high-temperature binder due to its excellent refractory and thermal insulation properties. It performs well in refractory materials and refractory fibers, with the highest temperature resistance reaching 1200℃ and strong bonding force.
Nano-sized silica gel particles can be filled into photosensitive paper, increasing the exposure rate and resulting in high-resolution images with vivid colors. Silica sol is also widely used in color picture tubes with silicon steel sheets as raw materials, wine clarifiers, floor wax-resistant and adhesive bonding agents, gel solidifiers for batteries, catalysts for petrochemical carrier materials, and other applications.
Method for preparing silica sol
There are various methods for preparing silica sol. The most commonly used ones include ion exchange method, one-step hydrolysis of silica powder, and silane hydrolysis method, etc.
Silica sol separation and purification
After the silica sol is prepared, it needs to be separated and purified to remove small molecules and be concentrated.
Ultrafiltration membrane concentration and classification: This method is a concentration method for the physical dehydration process of solutions. When the particle size of the silica sol reaches a certain level, a physical dehydration process is carried out using an ultrafiltration device made of polymer membranes. Through the sieving effect of the membranes, different particle sizes of silica sol are separated.
2. Atmospheric pressure (decompression) constant liquid level evaporation and concentration: By heating to evaporate the water in the solution, the purpose of concentration is achieved. Additionally, during the concentration process, the small particles of silica sol continuously grow into large particles of silica colloids. This method has high energy consumption and low concentration efficiency.
3. Combined method of ultrafiltration and evaporation concentration: First, the dilute solution is dehydrated using the ultrafiltration method to remove a large amount of water. Then, the remaining water is removed using the evaporation method. During the dehydration process, the particle size of the silica sol can also be further increased. This concentration process can not only prepare high-concentration silica sol but also further increase the particle size of the silica sol, thereby achieving a better concentration effect and having certain production application value.
Membrane concentration process
There are various methods for preparing silica sol. The most commonly used ones include ion exchange method, one-step hydrolysis of silica powder, and silane hydrolysis method, etc. The silica sol prepared by the ion exchange method has a very low concentration and cannot be applied industrially. It must be concentrated to reach a certain concentration before it can be used industrially. Currently, the most commonly used concentration methods for producing high-concentration silica sol in China and abroad are atmospheric (or reduced pressure) constant liquid level evaporation concentration, ultrafiltration concentration method, as well as the method combining ultrafiltration and evaporation.
In addition to concentrating the silica sol, the separation of silica sols of different particle sizes can also be achieved through membrane filtration.
Advantages of membrane concentration
It can achieve high-level concentration, reducing the silica sol to over 50%.
2. Through the sieving effect of membrane pore size, large-sized silica sol particles are retained while small-sized silica sol particles pass through, thereby achieving the separation of silica sol particles of different sizes.
3. The equipment has a large throughput, fast filtration speed, and high production efficiency.
4. The initial investment is small, the maintenance and operation are simple, and the operating cost is low.
Over the years, Wuhan Bona has been client-oriented and has been dedicated to the development of application processes for membrane separation technology. By integrating processes, membranes and equipment, it has accumulated rich experience in product purification and engineering-scale expansion. It not only solves manufacturing challenges but also improves product quality, thereby jointly enhancing the technical level of the industry with its clients.
