Silica gel is comprised of randomly linked spherical polymerized silicate particles , the primary particles. The properties of silica gels are a result of the size and state of aggregation of the primary particles and their surface chemistry.
Modern silica gel technology enables the production of highly pure gels that are composed of nearly 100% SiO2 with tailor-made pore systems and surface properties.
Silica gels can be produced from different raw materials. However, the synthesis from mineral acids, e.g. sulfuric acid, and aqueous sodium silicate is the only industrial relevant process today.
Sulfuric acid and sodium silicate are mixed under controlled conditions to build the primary particles of the desired size, which polymerize and form the raw gel from which all types of silica gels are made.
This glass-like gel is broken down into granules and then washed, aged, and dried to produce the highly porous materials.
By controlling the washing, ageing, and drying conditions, the important physical parameters such as porosity, pore size, and surface area can be adjusted to produce a range of different silica gel types .
Silica gels are available in a wide range of particle sizes, each type having a well-defined particle size distribution. The type of mill applied during the grinding step and the use of a classifier allow for the manufacturing of fine-sized products with a cut coarse tail.